A Systematic Way of Choosing Driveline Configuration and Sizing Components in Hybrid Vehicles

Our way of life is on a collision course with geological limitations. Ever since petroleum geologist M. King Hubbard correctly predicted in l956 that U.S. oil production would reach a peak in l973 and then decline (1), scientists and engineers have known that worldwide oil production would follow a similar trend. Today, the only question is when the world peak will occur.The U.S. transportation system depends almost entirely (∼97%) on oil (2), and foreign imports have risen steadily since l973 as the demand increased and domestic supplies decreased. Today, more than 60% of U.S. oil consumption is imported and the dependence on foreign oil is bound to increase. There is no question that once the world peak is reached and oil production begins to drop, either alternative fuels will have to be supplied to make up the difference between demand and supply, or the cost of fuel will increase precipitously and create an unprecedented social and economic crisis for our entire transportation system.Among energy analysts the above scenario is not in dispute. There is, however, uncertainty about the timing. Bartlett (3) has developed a predictive model based on a Gaussian curve similar in shape to the data used by Hubbard as shown in Fig. 1. The predictive peak in world oil production depends only on the assumed total amount of recoverable reserves. According to a recent analysis by the Energy Information Agency (4), world ultimately recoverable oil reserves are between 2.2×1012 barrels (bbl) and 3.9×1012bbl with a mean estimate of the USGS at 3×1012bbl. But changing the total available reserve from 3×1012bbl to 4×1012bbl increases the predicted time of peak production by merely 11yr, from 2019 to 2030. The present trend of yearly increases in oil consumption, especially in China and India, shortens the window of opportunity for a managed transition to alternative fuels even further. Hence, irrespective of the actual amount of oil remaining in the ground, peak production will occur soon and the need for starting to supplement oil as the primary transportation fuel is urgent because an orderly transition to develop petroleum substitutes will take time and careful planning.Some analysts claim that hydrogen can take the place of petroleum in a future transportation system (56). But in previous publications, the authors have shown that hydrogen is inferior as an energy carrier to electricity (7) and that the energy efficiency of hydrogen vehicles, especially if the hydrogen were produced by the electrolysis of water, is considerably less than the efficiency of hybrid electric vehicles or fully electric battery vehicles (7). The results of these analyses have subsequently been confirmed by other studies, particularly those by Hammererschlag and Mazza (8) and Mazza and Hammerschlag (9).Before hydrogen could become a useful automotive fuel, an entirely new system of energy production and distribution on twice the scale of today’s electric power generating stations and distribution grid would have to be built. It has been estimated that a hydrogen transmission and storage system to fuel only 50% of the automotive fleet by the year 2020 would cost at least $600 billion (10) and that to make the hydrogen by electrolysis would require doubling the electric power generation rate (11). There is no question that a paradigm shift in fuel for worldwide transportation is imperative, and before embarking on such a huge investment, it is prudent to compare the hydrogen option with alternative ways to provide the energy and/or fuel needed by the transportation system.This paper presents and analyzes two generic approaches to meet the future demand of the U.S. ground transportation systems that do not require hydrogen, can use existing transmission infrastructure, and can eventually reduce CO2 emission drastically with a renewable energy system. Both these pathways are examined from an energetic and environmental perspective and are shown to be superior to the hydrogen economy on both these criteria. The first approach is a demand-side strategy based on the use of electric hybrid vehicles, an energy-efficient vehicle configuration, combined with a liquid fuel. This approach could use the existing liquid-fuel distribution system, but would need an expanded and robust electric-transmission system, albeit on a smaller and much more economical scale than a hydrogen fuel-cell infrastructure. The second approach is a supply-side strategy, based on synthetic fuel generation that can use initially coal or natural gas as the energy source, but can eventually transition to renewable biomass sources. The two pathways are not mutually exclusive, but can be combined into a secure and efficient future transportation system as will be shown in this paper.Cradle-to-grave energy efficiency is an important criterion for comparing energy-source utilization pathways because if a pathway is less efficient than another pathway that accomplishes the same final goal from the same amount of primary energy, then the less efficient pathway requires more primary energy to accomplish the same end. Hence, if the primary energy source is nonrenewable, then the less efficient pathway leaves less of the energy source for the future. It also means that more pollution is produced and the cost for the final end use is likely higher. However, if the primary energy source is renewable, then the efficiency does not change the amount of primary energy available in the future and energy efficiency does not have the same significance for renewable energy sources as for nonrenewable sources. Efficiency is, of course, important because the cost of delivering the energy is usually strongly influenced by the system efficiency. But a comparison between renewable and nonrenewable pathways should be based on economic and environmental criteria, such as cost and CO2 generation.In order to demonstrate the urgency for initiating a plan to supplement oil as soon as possible, we have made calculations to predict the potential gasoline savings based on the very optimistic scenario that, at an arbitrary starting time, all new light vehicles sold in the U.S. would be either hybrid or electric vehicles. The term “light vehicles” as used here includes all automobiles, family vans, sports utility vehicles, motorcycles, and pickup trucks. This scenario is an extreme case to show that because of the slow turnover of the light-vehicle fleet, it takes a long time for a significant impact on gasoline consumption to occur. The following cases are considered: (i) All new vehicles sold are gasoline-electric hybrid vehicles (HEV); (ii) all new vehicles sold are plug-in, gasoline-electric hybrids with a 20mil electric-only range (PHEV20); (iii) all new vehicles are diesel-electric hybrids (DHEV) with diesel fuel from coal or biomass; (iv) all new vehicles are plug-in, diesel hybrids with a 20mil all-electric range (PDHEV20); or (v) all new vehicles are all-electric vehicles (EV).The calculations use a rate of new vehicle sales of 7% of the fleet per year, a retirement rate of 5%/y, and a resulting net increase in total vehicles of 2%/y. These numbers represent an approximate fit to the light-vehicle sales and total number data for the years 1966 to 2003 reported by the U.S. government (12). All calculated results are presented in percentages and are therefore independent of the time at which all new vehicle sales switch to hybrids or EVs. When new car sales begin to be all hybrids or all EVs, it is assumed that the future rate of retirement of vehicles from the all-gasoline fleet is 5%/y of the remaining gasoline vehicles. The all-gasoline fleet is therefore completely retired 20 years later. The yearly rate of retirement of hybrid or EV vehicles is then 5% of the total number of vehicles at the beginning of that year, less 5% of the number of gasoline vehicles at the beginning of year zero. Thus, in year zero, no hybrid or EVs are retired.The following average vehicle mileage values were used: gasoline fleet, 21mpg (miles per gallon); gasoline HEV, 41mpg; gasoline PHEV 20, 56mpg of gasoline (13). A mileage is not needed for the EVs, or the diesels, since neither use gasoline, and we assume that the diesel fuel will be derived from nonpetroleum sources, as discussed in Secs. 34.The results of these calculations are presented in Figs. 234. Figure 2 shows the ratio of the total number of vehicles in the fleet, the number of all-gasoline vehicles in the fleet, and the number of hybrid or EV vehicles in the fleet to the total number in the fleet as a function of time. The total number of vehicles increases by over 60% in 25 years at the assumed 2%/y net increase while the number of all-gasoline vehicles decreases linearly from 100% initially to 0% after 20y. The number of hybrid or EV vehicles increases from 0% initially to 58% in 10y and 100% in 20y. This graph emphasizes how long it takes for the introduction of a new vehicle type to show a significant impact on the composition of the vehicle fleet, even when only the new vehicle types are sold after a starting point. This slow turnover of the fleet is the fundamental reason that the effects on gasoline consumption show up so slowly.Figure 3 shows the annual reduction in gasoline consumption as a function of time. Note that for HEVs the annual savings in gas consumption is 29% of the gasoline consumption for a conventional fleet in the tenth year and becomes constant at 49% in the twentieth year. Figure 3 also shows that the plug-in gasoline hybrid scenario saves 41% of the usage in the tenth year and increasing to 64% in the twentieth year and thereafter. Clearly, 10y after starting to sell only hybrid or EV vehicles, the impact of the HEV or PHEV20 scenarios on gasoline consumption is still rather small. After 20yr, the impact becomes significant, but gasoline consumption still remains high for gasoline hybrids. The total number of vehicles and the consumption (with the assumption of no efficiency improvement) by an all-gasoline fleet will have increased by more than 60%, but even the PHEV20 savings is only 40% of the zero-time annual-rate of gasoline consumption. The DHEV, DPHEV20, and EV scenarios show 59% annual savings in the tenth year and 100% in the twentieth year and thereafter. As would be expected, the nongasoline vehicles have a much greater impact on gasoline usage than gasoline-using HEVs, and the impact occurs more rapidly.Figure 4 gives the cumulative gasoline savings for the various scenarios compared to an all-gasoline fleet. HEVs save cumulatively 16% after 10yr and 20% after 20 years. Because of the cumulative savings, HEVs would use in 28yr the same amount of gasoline as an all-gasoline fleet would use in 20yr. PHEV20s save 21% after 10yr and 38% after 20yr. These results emphasize the relatively small effect on gasoline consumption that these highly optimistic scenarios have in the first decade after implementation. DHEVs, DPHEV20s, and EVs, the options without any gasoline use, save cumulatively as much as 32% after 10yr and 59% after 20yr.A 2004 report of the Committee on Alternatives and Strategies for Future Hydrogen Production and Use (14), prepared under the auspices of the National Research Council (NRC), concluded that the vision of a hydrogen economy is based on the expectation that hydrogen can be produced from domestic energy sources in a manner that is “both affordable and environmentally benign.” An analysis of currently available technologies for achieving this goal (7) showed that irrespective of whether fossil fuels, nuclear fuels or renewable technologies are used as the primary energy source, hydrogen is inefficient compared to using the electric power or heat from any of these sources directly. Given these facts, it is important to note that the NRC report also stated that “If battery technology improves dramatically, all-electric vehicles might become the preferred alternative (to fuel cell electric vehicles).” The report also noted that “Hybrid vehicle technology is commercially available today and can therefore be realized immediately.” If synthetic fuels made from coal, natural gas, or biomass were used in place of gasoline in hybrid vehicles, the consumption of oil could be reduced immediately and eventually eliminated. In the light of these observations, it is therefore important to examine what the current state of battery technology is, what can be expected in the near future, and how these developments affect the potential of hybrid vehicle performance and economics.To assess the performance of a battery for electric vehicles, the following characteristics have to be considered: Specific energy, a measure of the battery weight in units of watt hours per kilogramEnergy density, a measure of the space the battery occupies in watt hours per cubic meterCapacity, the total quantity of energy a battery can store and later deliver in watt hoursEfficiency, the ratio of energy that can be extracted from the battery to the initial energy input to change the batterySpecific power, the rate at which the battery can deliver the stored energy per unit weight of battery in watts per kilogramBattery lifecycle, the number of charge and discharge cycles that a battery can sustain during its lifeA significant effort to replace oil as a transportation fuel was undertaken ten years ago in California, when the California Air Resources Board [CARB] mandated that a certain percentage of all vehicles sold in California had to have zero tailpipe emissions (15). At that time the only technology available to meet the mandate was the all battery electric vehicle [BEV], which required no gasoline for its operation. The experiment to mandate the use of BEVs in California failed because the technology was not ready for commercialization. The best battery available in 1995 (fluted-tubular lead acid) had an energy storage density of 35Wh∕kg, a specific power of 100W∕kg, and a life cycle of 600-1000cycles. With these battery characteristics, the maximum range of a BEV was only 50mil, and the battery pack required replacement every 25,000mil at a cost of between $7000 and $8000 for an average BEV (16). Since that time, new batteries have been developed by Panasonic, VARTA, and SAFT, that have twice the energy-storage density, three times the specific power, and two or three times the cycle life of the lead acid batteries sold in California, as shown in Table 1 (13).In addition to the advanced batteries, a new concept has been developed that combines the best qualities of hybrid and battery vehicle technologies. This “plug-in hybrid vehicle” can recharge vehicle batteries during off-peak hours, and since most cars are parked 90% of the time, there are plenty of charging opportunities at both home and the workplace. Furthermore, a large portion of the electric generation infrastructure is only needed for peak demands and lays idle much of the time. Hence, if charging automobile batteries occurred during off-peak hours, they would level out the load of the electric production system and reduce the average cost of electricity (17). Moreover, plug-in hybrid vehicles are not range limited because they have an engine that can refuel at existing gas stations to use when the batteries are low.The efficiency of a PHEV depends on the number of miles the vehicle travels on liquid fuel and electricity, respectively, as well as on the efficiency of the prime movers according to1η=energytowheelsenergyfromprimarysource=f1η1η2+f2η3η4where η1 is the efficiency of the primary source of electricity, η2 is the efficiency of transmitting electricity to the wheels, f1 is the fraction of energy supplied by electricity, f2 is the fraction of energy supplied by fuel =(1−f1), η3 is the efficiency of primary source to fuel, and η4 is the efficiency of fuel to wheels.PHEVs can be designed with different all-electric ranges. The distance, in miles, that a PHEV can travel on batteries alone is denoted by a number after PHEV. Thus, a PHEV20 can travel 20mil on fully charged batteries without using the gasoline engine. According to a study by EPRI (13), on average 1/3 of the annual mileage of a PHEV20 is supplied by electricity and 2/3 by gasoline. The percentage depends, of course, on the vehicle design and the capacity of the batteries on the vehicle. A PHEV60 can travel 60mil on batteries alone, and the percentage of electric miles will be greater as will the battery capacity.The tank-to-wheel (more appropriately, battery-to-wheel) efficiency for a battery all-electric vehicle according to EPRI (13) is 0.82. In a previous analysis by the authors (18), the efficiency in 1993 was only 0.49. Comparing these results shows the enormous improvements in the electric component efficiency (controller 87%, battery 90%, charger 90%, drivetrain 90%;). When these numbers are multiplied by a hybrid-weight-times-idle factor of 1.3 (19), the overall efficiency of an electric hybrid is 82%, the same as that used in the EPRI study (13). It is important to note that currently all-electric vehicles can be nearly twice as efficient as when (18) was published.Given the potentials for plug-in hybrid vehicles, the Electric Power Research Institute (13) conducted a large-scale analysis of the cost, the battery requirements, and the economic competitiveness of plug in vehicles today and within the near term future. Table 2 presents the net present value of life-cycle costs over ten years for a midsized combustion vehicle [CV], hybrid vehicle [HEV] and a plug in electric vehicle with a 20mil electric-only range [PHEV20]. The battery module cost in dollars per kilowatt is the cost at which the total life-cycle costs of all three vehicles would be the Figure presents cost for battery as a function of number of units produced per year. According to this a production of about units per year units would the cost reduction to make both hybrid electric vehicles and plug in electric vehicles 3 presents the electric and plug-in hybrid vehicle battery that would be to make electric vehicles cost for vehicles according to EPRI (13). As shown in Table the characteristics of batteries, and batteries are to meet the required cost and performance The battery characteristics shown in Table 1 and Fig. are years and it is likely that more from would show Furthermore, the EPRI study assumed a current gasoline cost of A of the analysis based on a gasoline cost of that the battery at which the net present values of conventional combustion vehicles and battery vehicles are would up from to for an HEV and from to for a PHEV Figure shows the cost for batteries production for Hence, it that the cost of HEVs and with available batteries is with that of engine The EPRI analysis is because it compared the performance of all battery electric and plug in hybrid vehicles only to currently available combustion as shown in the use of diesel in a hybrid would increase the efficiency of compared to a hybrid with engine and the amount of fuel Hence, it be concluded that the EPRI analysis is it includes advanced batteries, it does not the increased efficiency by using diesel of combustion Furthermore, diesel fuel, as will be shown in can be produced from coal or renewable sources as can the electric power required for charging the The introduction of to the energy is the of this it is and can be as renewable technologies become more cost and fossil fuels more natural gas and biomass can be into liquid the most fossil fuel in the is used almost to In order to make coal into a vehicle fuel, it first be to a gas by a of The of this then be to of that can be used as vehicle fuel. biomass and natural gas can be used of coal or combined with coal to make these and are discussed gas can be used as a vehicle fuel, or it can be with to make gas, which can be used to fuels in the same manner as for The technology is well developed as shown by the recent of of which will natural gas, which is currently to liquid fuel. These and a in of which is diesel in With a with an estimated billion and a diesel with the of with an estimated at The of natural gas to make vehicle fuels was discussed in an paper by the authors (18), and of those results are presented later for comparison with coal as the fuel It should also be noted that biomass can be either alone or in with coal and to liquid fuels by the same as coal, or it can also be and then into vehicle fuels as in is a that is a in the production of synthetic liquid fuels from coal for transportation The coal is shown in Fig. It a such as coal or with to and This gas can be to hydrogen or to make or can be used as a transportation fuel in but this study on diesel fuel because are more the first of the coal is with limited to and The in the coal is to hydrogen gas, and are as In the shift is with to and The and hydrogen are from the and to the or into The that is in this is from the in a for Thus, it can be from the and are the costs when liquid fuel is produced from The estimated time of for a is to years. The depends on the production capacity of the the cost of a with a capacity to barrels of liquid fuel per is estimated to be of the order billion of coal claim that there will be gas pollution from the However, in the future vehicle emissions of can be reduced those of vehicles, by the use of plug-in hybrid electric vehicles and by of the from the fuel production is a synthetic diesel fuel that can be made from coal by of The is first to make which can then be to The is to the and the gas is to electricity for the as shown in Fig. is a gas at but can be under and then can be to other liquid of make it an fuel for It is similar to but has a number The number to the of a fuel to With combustion of the fuel occurs after and emissions are as a of combustion The combustion also in by the need for to the shown in Fig. coal into liquid fuel. The was by scientists before and is used today in by to make diesel fuel gas to make a liquid fuel of synthetic diesel fuel, which is similar to and which is used to make synthetic gasoline (7). The is from the liquid diesel and to the The gas resulting from is to electricity for the can be made from coal by by gas After the hydrogen gas and are from the gas, and hydrogen are The hydrogen can be stored and the can be for electricity and/or to the shift as shown in Fig. store and the hydrogen, it is either to it to or to it at a The efficiency of the first option is while the second is efficient (7). Both and hydrogen have been for fuel storage in a of hydrogen fuel-cell vehicles is in the of coal or natural gas into a vehicle fuel. The energy efficiency of these is important in the overall well to efficiency of these alternative Table 4 presents or efficiency for various fuels from coal or natural and have reported the and energy for with of the and values are used (18) presented for natural gas without and estimated that of CO2 the efficiency of by about two percentage Since natural gas only about as much per unit of energy as coal, it has been assumed that will reduce the efficiency of to fuels by percentage point. Thus, percentage has been from values reported by (18) to the values shown in Table In the of data for the of natural gas to the authors assumed that the ratio of the for natural gas is the same as that for coal to estimate this efficiency as shown in Table 4 that the production of liquid fuels from natural gas is more efficient than from But is in and the technology is not a It is however, for the that is currently into the in gasoline The of of these has been But production is the more for the term and does not require hydrogen as a fuel or energy Today, the of fuel from coal, at the only in The of supplies of such fuels as gasoline, and The economic and of coal have been U.S. and for a fuel in using technology and are to the that will have a capacity to of diesel fuel. has in recent NRC study other technologies that could synthetic fuels from biomass and presents a comparison of the energy on energy for production from and These significant in synthetic But the for synthetic fuel production need to be multiplied before synthetic fuels can make up for the between demand and of gasoline after the peak in oil production is on the analysis presented in this we the following and oil production is expected to peak within the and as is liquid fuel are expected to increase This could lead to a crisis in the U.S. transportation system that on 60% of which is options for a transportation crisis by and/or liquid fuels derived from petroleum with synthetic fuels from natural gas, or coal and by demand by increasing the efficiency and mileage of options to have impact they be at least before hybrid vehicles are a option to reduce the liquid fuel consumption of future transportation hybrid vehicles can the existing infrastructure for electric power transmission by charging batteries during peak hours and use liquid fuels only for a fraction of overall power hybrid vehicles can diesel that can be by synthetic fuels derived from coal, natural gas, or use efficiency is increased efficiency alone will not be to the transportation without the production of large of synthetic liquid number of technologies for synthetic diesel that can be used in diesel and reduce emission of that lead to scale of effort required to provide synthetic fuels will require years to and should therefore be as soon as hybrid or all-electric vehicles with available battery technology in an are compared to gasoline of the of the transportation it is that be by government such as for the of synthetic fuels and CO2 high liquid fuel mileage for automobiles, and for efficient plug-in hybrid scenario in this paper for a secure transportation system can be immediately with available technologies and without hydrogen or authors to for as of an independent study for the of at the of

To reduce air pollution and avoid petroleum exhaustion problem, many advanced countries, especially Japan installed Hybrid Vehicles (HV). As the use of HV popularizes around the world, there will be a huge amount of End-of-Life HV in the near future, and the proper treatment of these End-of-Life HVs, especially the waste NiMH (Nickel-Metal Hydride) batteries, will become a serious problem. Currently, the recycling of NiMH battery is gaining substantial attention. However, instead of recycling waste NiMH batteries directly, regenerating and reusing a used NiMH battery for a secondhand HV will largely reduce waste battery generation and demand for new NiMH battery. However, the environmental impact of regenerating and reusing a waste NiMH battery was not clear and has not been compared with the situation when using a brand-new NiMH battery. The purpose of this research is to compare the environmental performance (CO2 emission) of regenerated NiMH battery and brand-new NiMH battery in an HV from their production to usage stage and to discuss the validity of using a regenerated NiMH in Japan and in other countries using the Life-Cycle Assessment (LCA) approach. This research analyzed the composition of a NiMH battery and the CO2 emission during the manufacture, transportation, regeneration and usage process of a NiMH battery. The data used in this research was collected from reports and data published by the government of Japan, vehicle makers and previous studies. Original field survey and interview research on battery regeneration operators were also performed. The result showed that there is not a big difference in environmental effect. Moreover, by doing so, a huge amount of resource will be saved from battery manufacturing process while reducing waste generation. It is recommended that waste NiMH battery should be regenerated and reused in HV instead of being recycled directly in the future.

<div class="htmlview paragraph">Hybrid electric vehicles are seen as a solution to improving fuel economy and reducing pollution emissions from automobiles. By recovering kinetic energy during braking and optimizing the engine operation to reduce fuel consumption and emissions, a hybrid vehicle can outperform a traditional vehicle. In designing a hybrid vehicle, the task of finding optimal component sizes and an appropriate control strategy is key to achieving maximum fuel economy.</div> <div class="htmlview paragraph">In this paper we introduce the application of convex optimization to hybrid vehicle optimization. This technique allows analysis of the propulsion system's capabilities independent of any specific control law. To illustrate this, we pose the problem of finding optimal engine operation in a pure series hybrid vehicle over a fixed drive cycle subject to a number of practical constraints including:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">nonlinear fuel/power maps</div></li> <li class="list-item"><div class="htmlview paragraph">min and max battery charge</div></li> <li class="list-item"><div class="htmlview paragraph">battery efficiency</div></li> <li class="list-item"><div class="htmlview paragraph">nonlinear vehicle dynamics and losses</div></li> <li class="list-item"><div class="htmlview paragraph">drive train efficiency</div></li> <li class="list-item"><div class="htmlview paragraph">engine slew rate limits</div></li> </ul> </div> <div class="htmlview paragraph">We formulate the problem of optimizing fuel efficiency as a nonlinear convex optimization problem. This convex problem is then accurately approximated as a large linear program. As a result, we compute the globally minimum fuel consumption over the given drive cycle. This optimal solution is the lower limit of fuel consumption that any control law can achieve for the given drive cycle and vehicle. In fact, this result provides a means to evaluate a realizable control law's performance.</div> <div class="htmlview paragraph">We carry out a practical example using a spark ignition engine with lead acid (PbA) batteries. We close by discussing a number of extensions that can be done to improve the accuracy and versatility of these methods. Among these extensions are improvements in accuracy, optimization of emissions and extensions to other hybrid vehicle architectures.</div>

<div class="htmlview paragraph">Hybrid vehicles are becoming more and more attractive due to their reduced emissions and their higher fuel efficiency. Storage of electrical energy is the most critical aspect of hybrid automobiles. Therefore, an exact knowledge of the behavior of the battery and further electrical storage elements is mandatory. Their nonlinear characteristics over wide ranges of current magnitude, transient period, temperature and state of charge must be evaluated. Battery aging is another matter of increasing importance.</div> <div class="htmlview paragraph">For this reason, an automated battery test bench has been developed which is capable of reproducing high dynamic loads in both charging and discharging direction. Pulse rise times are in the range of a few microseconds at maximum currents up to 1500 A. The quasi-static charge and discharge power can reach 20 kW. Optimized characterization programs enable a rapid extraction of battery behavior parameters as well as capacitor characteristics.</div> <div class="htmlview paragraph">With this equipment various types of automotive batteries such as lead-acid and nickel-metal hydride batteries and all types of double-layer capacitors can be characterized.</div> <div class="htmlview paragraph">For statistical analysis of several batteries in parallel, a compact version of the test bench with reduced current amplitudes and transient response times was developed. This stand-alone tester can be used for both stimulating aging effects and characterizing the most relevant battery parameters simultaneously.</div> <div class="htmlview paragraph">The battery measurement equipment was successfully used to characterize different types of batteries. Parameterization of a battery model with high transient and amplitude dynamics for automotive applications was reached. This paper will show the complex analog and power electronics as well as the flexible data acquisition and load profile generation. Furthermore, measured data and model responses will be presented together with aging effects of double-layer capacitors.</div>

<div class="htmlview paragraph">In order to supplement the on-going development work aimed at reducing emissions levels, in particular NO, in the exhaust of diesel engines a research programme was initiated to investigate the fundamental nature of NO formation.</div> <div class="htmlview paragraph">A rapid acting sampling valve to obtain gas samples directly from the combustion chamber of a running diesel engine was developed concurrently with a mathematical model for the formation of NO in diesel engines, based on the extended Zeldovich mechanism.</div> <div class="htmlview paragraph">Gas samples were obtained from the following types of diesel engine:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">i)</span> <div class="htmlview paragraph">A single spray sector of a large quiescent direct injection combustion chamber</div> </li> <li class="list-item"> <span class="li-label">ii)</span> <div class="htmlview paragraph">A deep bowl direct injection combustion chamber employing inlet induced swirl</div> </li> <li class="list-item"> <span class="li-label">iii)</span> <div class="htmlview paragraph">A Ricardo Comet V indirect injection combustion system.</div> </li> </ol> </div> <div class="htmlview paragraph">The temporal and spacial distribution of NO and the local air fuel ratio were determined in each case.</div> <div class="htmlview paragraph">The model depended heavily on the information provided by the gas samples which, in conjunction with high speed photography of the combustion process, indicated that NO was formed only in gases exposed to high temperature flame and that any NO found in cooler areas of fresh air or weaker mixture appeared there solely by mixing with the hot gases, despite the high oxygen concentration. In addition the delay between the combustion and the appearance of NO is clearly shown and this allowed considerable simplification of the model in that only the reactions involved in NO formation needed to be considered kinetically in order to give good correlation between experimental and theoretically predicted exhaust NO content over most of the engine operating range.</div> <div class="htmlview paragraph">It is concluded that the gas sampling valve proved to be a valuable tool in understanding the fundamentals of NO formation in particular and combustion problems in general and greatly assisted in the formulation of a mathematical model for prediction of NO emissions from diesel engines.</div> <div class="htmlview paragraph">NITRIC OXIDE (NO) is one of the more undesireable pollutant constituents of vehicle exhaust gas emissions because of its connection with the formation of photochemical smog in certain locations throughout the world (<span class="xref">1</span>)<span class="xref">*</span></div> <div class="htmlview paragraph">As a consequence of this connection, legislation was proposed to progressively reduce the maximum permitted levels of NO in vehicle exhaust. Maximum levels of the other gaseous pollutants, carbon monoxide (CO) and unburned hydrocarbons (HC) were also proposed in the legislation and it was clear that eventually the relatively clean diesel engine would be unable to meet the proposed emissions levels in its normal form.</div>

<div class="section abstract"><div class="htmlview paragraph">Hybrid and electric vehicles present a promising trade-off between the necessary reductions in emissions and fuel consumption, the improvement in driving pleasure and performance of today's and tomorrow's vehicles. These hybrid vehicles rely primarily on electronics for the control and the coordination of the different sub-systems or components. The number and complexity of the functions distributed over many control units is increasing in these vehicles. Functional safety, defined as absence of unacceptable risk due to the hazards caused by mal-function in the electric or electronic systems is becoming a key factor in the development of modern vehicles such as electric and hybrid vehicles. This important increase in functional safety-related issues has raised the need for the automotive industry to develop its own functional safety standard, ISO 26262.</div><div class="htmlview paragraph">The aim of the paper is to briefly introduce the ISO 26262 standard and the specific hazards associated with hybrid and electric vehicles. The paper will highlight how the risk-based approach of ISO 26262 can influence the safety integrity level of some safety related functions specific to hybrid and electric vehicles. It will also highlight how well established safety related functions, such as torque monitoring of a conventional internal combustion engine can be influenced through vehicle hybridization. A vehicle safety concept for the torque monitoring of an electric vehicle will then be presented. The results of the implementation of this functional safety concept in an electric vehicle developed by the company FEV GmbH will be shown as example. The first measurements made in the vehicle show that the monitoring concept fulfills the reaction time requirement to ensure that unintended torque increase do not lead to uncontrollable vehicle acceleration.</div></div>

<div class="htmlview paragraph">This paper presents a theoretical and experimental study on the possibility of combustion similarity in differently sized diesel engines. Combustion similarity means that the flow pattern and flame distribution develop similarly in differently sized engines. The study contributes to an understanding and correlating of data which are presently limited to specific engine designs.</div> <div class="htmlview paragraph">The theoretical consideration shows the possibility of combustion similarity, and the similarity conditions were identified. To verify the theory, a comparison of experimental data from real engines was performed; and a comparison of results of a three dimensional computer simulation for different engine sizes was also attempted. The results showed good agreement with the theoretical predictions.</div> <div class="htmlview paragraph">THE PURPOSE of this research is to determine the possibility of the existence of combustion similarity in differently sized diesel engines, and to propose conditions for realizing model experiments.</div> <div class="htmlview paragraph">Diesel engine combustion has been widely investigated, but there is no theory of engine size effects. Engine performance in large engines is estimated from experience, without the benefit of model experiments to perform fine optimization. The establishment of a theory of size effects could provide a method for correlation of the vast amount of independent data that is available, and offer significant opportunity for diesel engine research and design.</div> <div class="htmlview paragraph">It should be noted that this study does not try to simply compare large and small engines, which are generally designed with different concepts and have different combustion chamber configurations. The study investigates conditions necessary for the establishment of combustion similarity, even though these conditions might not be practical. An ultimate objective of the research is to determine the reasons why combustion chamber configurations are different for large and small size engines.</div> <div class="htmlview paragraph">The first study of scale effects in engines was reported by Taylor(<span class="xref">1</span>) in 1966. His considerations were based on the fact that the mean effective pressure and mean piston speed are roughly independent of the cylinder size. This relation is very basic, but does not enable an estimation of combustion similarity.</div> <div class="htmlview paragraph">The symposium on “Size effect and similarity theory on diesel engine combustion”, Tokyo, March 1982, was of direct relevance to combustion similarity in diesel engines (<span class="xref">2</span>). The symposium covered similarities in fuel spray, air motion, heat transfer, combustion, lubrication, and engine performance. The main conclusion of the symposium was that the establishment of a similarity theory would be impossible. However, the evaluation of the data presented at the symposium may be expanded with the theory presented here, because the discussion then was based on simple comparisons of experimental data without non-dimensional treatment.</div> <div class="htmlview paragraph">There is a report on similarity in boilers (<span class="xref">3</span>). Here theoretical considerations of flow patterns and combustion rates for burner combustion were presented. In the design of large marine engines, Kawasaki Heavy Industries has produced a number of engines with similar geometry, and has succeeded in obtaining similar combustion patterns, as well as vibration and mechanical stresses (<span class="xref">4</span>,<span class="xref">5</span>).</div> <div class="htmlview paragraph">With this background, the authors first presented a theory on diesel combustion similarity to Transactions of the Japan Society of Mechanical Engineers in 1988 (<span class="xref">6</span>). The theory showed the fundamental equations in appropriate non-dimensional form were similar for differently sized diesel engines. The equations included continuity, momentum, energy, chemical reaction, continuity of species, and state equations.</div> <div class="htmlview paragraph">An English translation of the paper has been published in the International Journal of the Japan Society of Mechanical Engineers in 1990 (<span class="xref">7</span>). Following this report, the authors presented experimental results partially validating the theoretical predictions at the International Symposium COMODIA in 1990 in Kyoto (<span class="xref">8</span>). The paper discussed similarity in the development of fuel jet in a model apparatus, and it compared the thermal efficiency, heat release rate, and emissions of real engines varying from 260 to 400mm in bore diameter.</div> <div class="htmlview paragraph">The authors have also presented a theoretical study on the relationship between optimum swirl and fuel injection systems (<span class="xref">9</span>). This study predicted air entrainment changes in fuel sprays for a variety of engine conditions. It did not evaluate similarity between engines, but contains equations applicable for differently sized engines.</div> <div class="htmlview paragraph">The present report discusses and modifies the theoretical consideration provided in the previous reports (<span class="xref">6</span>,<span class="xref">7</span>,<span class="xref">8</span>) with more precise equations. The paper also discusses similarity in emissions, and factors which may cause deterioration in similarity. Additionally it shows the results of computer simulations of the possibility of similarity. The report also briefly describes the main results of the experiments presented in the previous work.</div>

<div class="htmlview paragraph">The paper reports on a study performed as a joint project between Rhodia, Renault Automobiles and AVL and deals with the application of a sintered metal trap (SMT) whose regeneration is supported by the use of a Ce-based fuel-borne catalyst installed on a delivery van equipped with a conventional IDI/NA diesel engine. For demonstration purpose, a trap protection strategy was developed with the aim to minimize the trap loading and thus the consequent fuel consumption penalty that can be observed for worst-case low speed driving scenarios. Measures to temporarily increase the exhaust gas temperature during inner-city driving and therefore to initiate the start of regeneration were successfully applied.</div> <div class="htmlview paragraph">MAJOR EFFORT IS BEING currently undertaken to develop and apply advanced aftertreatment systems to meet future proposed exhaust gas emission standards for passenger cars, LDT and HD diesel engines.</div> <div class="htmlview paragraph"><span class="xref"><u>Fig. 1</u></span> shows as an example the potential of HSDI engines with respect to achieving different US emission standards depending on vehicle weight. With advanced HSDI diesel engines, the emission standards for NOx and particulate could be met when using electronically controlled EGR and oxidation catalysts up to certain vehicle weights. Further improvements may be expected by new technology elements currently being pursued /<span class="xref">1</span>/ such as improved fuel injection equipment, highly dynamic EGR systems, cooled EGR etc. However, since emission levels generally increase proportional to the vehicle weight, the introduction of advanced exhaust gas aftertreatment systems besides the oxidation catalysts will primarily be a necessity of heavier vehicles.</div> <div class="htmlview paragraph"> <figure id="F1" class="figure"> <div class="graphic-wrapper"><img class="article-figure figure" src="982598_fig0001.jpg" alt="No Caption Available"/></div> </figure> </div> <div class="htmlview paragraph">In addition to the beneficial effects of improved fuel quality on emissions, possible strategies to reduce NOx and particulates (as the main pollutants in diesel exhaust) are summarized in <span class="xref"><u>Fig.2</u></span>.</div> <div class="htmlview paragraph"> <figure id="F2" class="figure"> <div class="graphic-wrapper"><img class="article-figure figure" src="982598_fig0002.jpg" alt="No Caption Available"/></div> </figure> </div> <div class="htmlview paragraph">By the application of electronically controlled EGR together with oxidation catalyst and the further improvement of the combustion process, in some cases the legislative emission targets could be met. However, as emission standards of NOx and particulate will be tightened further in the future, additional measures besides in-cylinder control and oxidation catalyst will be needed.</div> <div class="htmlview paragraph">Both particulate trap system and DENOx catalyst are seriously considered as additional strategies to reduce NOx and particulates /<span class="xref">2</span>/. In order to meet the fictitious emission targets, basically two routes may be adopted:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Reduction of particulate emissions to the target level by measures on the engine (e.g. fuel injection with high pressure) and the application of a DENOx catalyst requested to offer high NOx efficiency (e.g. SCR or NOx storage catalyst with more than 60% reduction. However, such systems are not yet proven to offer such an high efficiency.</div></li> <li class="list-item"><div class="htmlview paragraph">Reduction of NOx emission to the target level by engine measures (e.g. cooled EGR with high rates) and application of particulate trap /<span class="xref">3</span>/.</div></li> </ul> </div> <div class="htmlview paragraph">Which of these strategies could be applied as a serial solution in the future is a currently still open question.</div> <div class="htmlview paragraph">Considering only the use of particulate traps in the following, it is worth noting that it would be beneficial not only for achieving future standards or even current regulations /<span class="xref">4</span>/, but also as a retrofit solution to improve the environmental situation in inner cities - application to busses /<span class="xref">5</span>,<span class="xref">6</span>,<span class="xref">7</span>/ and/or vans transporting goods - resulting in the reduction of visible and therefore disturbing black smoke. However, many problems must be overcome.</div> <div class="htmlview paragraph">Only particulate trap systems which are cost-effective and therefore self-regenerating without any external and costly measures <u>and</u> durable might be used on a large scale.</div> <div class="htmlview paragraph">One of the possible ways how to manage such an application is being described in this paper.</div>

<div class="section abstract"><div class="htmlview paragraph">This paper presents a technical, financial and environmental analysis of four different hybrid buses operated under Buenos Aires driving conditions. A conventional diesel bus is used as reference and three electric hybrids equipped with different energy storage technologies, Li-Ion, NiMH batteries and double layer capacitors (ultracapacitors), are evaluated, along with a hydraulic hybrid platform which uses high-pressure accumulators as its energy buffer. The operating conditions of the buses are set using real driving GPS data collected from various bus routes within the city. The different vehicle platforms are modeled on AUTONOMIE SA and validated by comparing the obtained fuel consumption results to those reported by local transport authorities and values found in the literature. The embedded energy and <i>CO</i><sub>2</sub> emissions of each platform are estimated using GREET and the total cost of ownership of each vehicle is calculated and compared to that of the conventional bus. Furthermore, aging models are proposed to evaluate the life duration of the batteries and ultracapacitors. Results show that, independent of the energy storage technology, the fuel economy performance of all hybrids is highly dependent on the size and configuration of the powertrain and energy storage components. When optimized, all hybrids achieve significant fuel consumption reductions compared to a conventional diesel bus, however, the ultracapacitor based system seems to outperform the other technologies. The battery based electric buses achieve similar fuel consumption reductions, but the NiMH based batteries shows a considerably shorter life expectancy. This has a significant impact on both the economic and environmental performance of this vehicle. The life cycle emission analysis shows that, given the high fuel consumption of a conventional bus, the additional embedded <i>CO</i><sub>2</sub> emissions of the hybrid vehicles are offseted by the achieved reduction of in-service <i>CO</i><sub>2</sub> emissions due to fuel consumption reductions. Regarding the economic performance of the different platforms, results show that the fuel savings achieved by all hybrids displace the higher capital costs required. Overall, all hybrid buses show a strong potential to reduce both <i>CO</i><sub>2</sub> emissions and costs, resulting in negative costs of <i>CO</i><sub>2</sub> abatement.</div></div>

<div class="htmlview paragraph">The modern diesel engine is used around the world to power applications as diverse as passenger cars, heavy-duty trucks, electrical power generators, ships, locomotives, agricultural and industrial equipment. The success of the diesel engine results from its unique combination of fuel economy, durability, reliability and affordability - which drive the lowest total cost of ownership.</div> <div class="htmlview paragraph">The diesel engine has been developed to meet the most demanding on-highway emission standards, through the introduction of advanced technologies such as: electronic controls, high pressure fuel injection, and cooled exhaust gas recirculation. The standards to be introduced in the U.S. in 2007 will see the introduction of the <i>Clean Diesel</i> which will achieve near-zero NO<sub>x</sub> and particulate emissions, while retaining the customer values outlined above. The progress toward near-zero emissions has involved the development of:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Advanced engines using new technologies</div> </li> <li class="list-item"><div class="htmlview paragraph">Advanced aftertreatment systems</div> </li> <li class="list-item"><div class="htmlview paragraph">Availability of ultra-low sulfur diesel fuels</div> </li> </ul> </div> <div class="htmlview paragraph">This paper describes the technology, tools and processes used to develop ultra-low emission diesel engines for on-highway heavy-duty applications. While meeting emissions is an important goal, it is vital to develop engines that retain traditional customer values. The primary purpose of this paper is to provide a set of ideas and practical tools that allow engine design and development to focus on the end-user, while satisfying regulatory requirements. The on-highway heavy-duty (HD) diesel engine is used to illustrate the processes; however the general principles may be applied to other diesel engine applications, such as off-highway, marine or power generation.</div> <div class="htmlview paragraph">The paper underlines the importance of selecting the right technology and system architecture for the application, executing the design of hardware and controls software, and optimizing the performance, fuel economy and emissions through controls calibration using the best available tools. Understanding customer requirements is the fundamental foundation for effective engine design, as is the integration of the engine system with the machine it will drive - be it a truck, a ship or a power generating set.</div> <div class="htmlview paragraph">The paper will describe the modern HD diesel engine, as used in on-highway applications in the US, and will discuss the technologies that make these engines possible. The evolution of emissions requirements in the U.S. and worldwide will be discussed. The important processes of system integration and product definition will be discussed briefly and put in context with the demands of developing new engine systems to meet proposed ultra-low emissions standards. The paper will close with a look forward to advanced technologies that will be candidates for meeting future stringent emission standards.</div>

<div class="htmlview paragraph">Variations in the in cylinder flow field which result from differences in the intake flow are known to have important effects on the performance and emissions behavior of diesel engines. The intake flow and combustion in a heavy duty DI diesel engine with a dual valve port have been simulated using the computational fluid dynamics code KIVA-3. Variation of the in-cylinder flow field has been achieved by varying the intake valve timing. Variations in the in-cylinder flow, including a range of length scales, degrees of inhomogeneity in a number of scalar and vector quantities, and the persistence of various flow structures, are compared, and their significance to combustion and emissions parameters are assessed. The interaction of fuel spray parameters, particularly spray-wall interaction with structures present in the flow field are evaluated.</div> <div class="htmlview paragraph">INCREASINGLY STRICT REQUIREMENTS for NOx and soot emissions continue to drive the effort to improve computational models related to diesel combustion. In recent years, experimental studies and computational modeling work have led to improvements in the emissions performance of diesel engines as well as advancements of the models themselves. One particularly interesting and difficult problem in optimizing diesel engines is the simultaneous reduction of NO and soot emissions. Recently, a number of important advancements have been in areas such as the understanding and modeling of high pressure fuel spray behavior, autoignition, fuel droplet combustion, NOx production, and soot production and oxidation. Researchers have been successful using combined experimental and computational approaches to accurately measure and reproduce trends in emissions behavior [<span class="xref">1</span>]. Further, modeling efforts have been instrumental in suggesting strategies for simultaneously reducing soot and NO emissions [<span class="xref">2</span>].</div> <div class="htmlview paragraph">It has been known for many years that intake flow has important effects on the combustion behavior and emissions performance in diesel engines. For example, in small direct-injected (DI) diesel engines, swirl can increase the rate of fuel-air mixing, reducing the combustion duration at retarded injection timings [<span class="xref">3</span>]. Swirl interaction with compression induced squish flow increases turbulence levels in the combustion bowl, promoting mixing [<span class="xref">4</span>]. On the other hand, it has been shown that there exists a level of swirl beyond which the fuel-air mixing in the piston can actually be diminished due to adverse swirl-squish interaction [<span class="xref">5</span>]. In addition, creation of excess swirl can also diminish engine efficiency due to increased pumping losses. It is now possible to compute intake flow in detail, including the effects of moving intake valves. Examples of such simulations include the modeling of intake flow through a dual valve port in a heavy-duty industrial diesel engine [<span class="xref">6</span>] and of flow in a 4 valve per cylinder direct injected gasoline engine [<span class="xref">7</span>]. Previous work has also focused on the effects on fuel spray of changes in the in-cylinder flow field generated by changes in the piston bowl geometry [<span class="xref">8</span>]. A further step in understanding intake flows through modeling is to study their effect on combustion. The availability of higher performance computers and CFD codes with advanced grid structure has made detailed modeling of intake flow and its effect on fuel-air mixing a reality. In addition, modeling of the effect of intake flow on global combustion parameters, such as heat release rate, average pressure, and average turbulent kinetic energy has been performed in both diesel [<span class="xref">9</span>] and spark ignited engines [<span class="xref">10</span>].</div> <div class="htmlview paragraph">Pollutant formation and oxidation processes are very dependent on local conditions such as temperature and species densities. For this reason, detailed studies of the effect of intake generated in-cylinder flow on emissions performance need to emphasize local flow details in addition to cylinder averaged quantities.</div> <div class="htmlview paragraph">In this work, we attempt to relate the emissions performance of a heavy duty dual port DI diesel engine to changes in the intake flow. <span class="xref">Table 1</span> gives operating parameters for the Caterpillar 3406 single cylinder engine. Differences in the intake flow are accomplished by varying the intake valve lift profiles. Because the formation of pollutants occurs at length scales smaller</div> <div class="htmlview paragraph"> <div class="table-wrap" id="T1"> <div class="graphic-wrapper"><img class="article-image tableFig" src="952430_fig0001.jpg" alt="No Caption Available"/></div> <div/></div> </div> <div class="htmlview paragraph">than the dimensions of the combustion chamber, we compare flow field details at several length scales. Since details of the intake flow field are often dissipated prior to fuel injection, the persistence of structures in the flow field during the compression stroke is also assessed. In the next section, details of the models used as well as the methods used to analyze the flow field details are given.</div>

<div class="htmlview paragraph">Hybrid vehicles have been in the news quite a bit of late given the commercial introduction of a number of hybrid vehicles that sport significant improvements in fuel economy. The improved fuel efficiency of these vehicles can be directly attributable to the hybridized power train on board these internal combustion engine vehicles.</div> <div class="htmlview paragraph">Similarly, hybridization of fuel cell vehicles not only helps improve fuel economy but can also help overcome other technical barriers (start up delays, transients). For fuel cell vehicles, hybridization of on-board fuel cell systems is expected to have the potential to improve the vehicle efficiency largely due to the ability to recover braking energy and via flexibility in designing the system controls. However, the advantages can be offset by the tradeoffs due to added energy losses associated with the DC/DC converter and the battery pack itself. Additional tradeoffs not explicitly addressed in this study include added overall complexity, additional packaging constraints, and potentially higher overall cost.</div> <div class="htmlview paragraph">This report will focus on a quantitative analysis of the performance of the indirect-hydrocarbon (IH, onboard fuel processor using gasoline type fuel), hybrid and load-following fuel cell vehicles (FCVs) from the viewpoint of the energy use throughout the system. Specifically, the vehicle energy use and efficiency will be compared between the load following (non-hybrid) and hybrid vehicle platforms.</div> <div class="htmlview paragraph">Several hybrid component configurations were studied and two representative configurations were investigated in depth. The first (Configuration 1), in which the DC/DC converter is placed in the path of the fuel cell stack current, there does appear to be some benefit, in terms of energy usage, in hybridizing the IH fuel cell vehicle.</div> <div class="htmlview paragraph">Specifically, on the US EPA cycles, the hybrid vehicle outperformed the load following vehicle on the FUDS</div> <div class="htmlview paragraph">sequence but the load following vehicle had slightly better results on the HIWAY cycle. However, if the DC/DC converter is placed in the battery current path only, with the fuel cell stack directly connected to the electric drive train (Configuration 2), the benefits in terms of improved fuel economy are larger than in the first configuration. The results corresponding to both these configurations will be analyzed and discussed in this paper.</div> <div class="htmlview paragraph">Overall, three main factors affect these vehicle results, all of which will be explicitly examined in this study.</div> <div class="htmlview paragraph">These factors are: vehicle weight, fuel cell system efficiency (including the battery), and regenerative braking capabilities. Specifically, the hybrid vehicle fuel economy can be reduced due to a ∼10% heavier vehicle, and a lower overall fuel cell system efficiency (when including the battery and DC/DC converter losses). One important factor is clearly the regenerative braking capability; but the other factor is associated with the ability to improve the efficiency of the fuel cell system itself by taking advantage of the flexibility offered energy storage sub-system and adopting better control strategies.. The real question however is whether these gains outweigh the losses introduced by the additional components needed to hybridize the vehicle.</div>

<div class="section abstract"><div class="htmlview paragraph">With current and pending regulations-including Corporate Average Fuel Economy (CAFE) 2025 and Tier 3 or LEV III-automakers are under tremendous pressure to reduce fuel consumption while meeting more stringent NOx, PM, HC and CO standards. To meet these standards, many are investing in expensive technologies-to enhance conventional, four-stroke powertrains-and in significant vehicle improvements. However, others are evaluating alternative concepts like the opposed-piston, two-stroke engine.</div><div class="htmlview paragraph">First manufactured in the 1890s-and once widely used for ground, marine and aviation applications-the historic opposed-piston, two-stroke (OP2S) engine suffered from poor emissions and oil control. This meant that its use in on-highway applications ceased with the passage of modern emissions standards.</div><div class="htmlview paragraph">Since then, Achates Power has enhanced the opposed-piston engine and resolved its historic challenges: wrist pin and power cylinder durability, piston and cylinder thermal management, piston ring integrity and oil consumption [<span class="xref">1</span>].</div><div class="htmlview paragraph">An in-depth study on opposed-piston, two-stroke diesel engine performance and emissions in a light-duty truck application is presented here for the first time in a technical paper. The paper includes a: <ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Brief review of the opposed-piston, two-stroke engine's architectural advantages (thermodynamics, pumping work and combustion)</div></li><li class="list-item"><div class="htmlview paragraph">Comprehensive overview of the engine's performance and emissions results, including indicated thermal efficiency, fuel consumption and emissions</div></li><li class="list-item"><div class="htmlview paragraph">Comparison of fuel economy and emissions to the published benchmark, the Cummins 2.8L ATLAS Diesel Engine [<span class="xref">2</span>]</div></li><li class="list-item"><div class="htmlview paragraph">Discussion of an exhaust temperature control strategy that is used to meet the aggressive catalyst light-off requirements of light-duty applications by achieving rapid catalyst light-off after a cold start</div></li><li class="list-item"><div class="htmlview paragraph">Comparison of engine balance of the light-duty truck concept engine and a state-of-the-art gasoline V6 engine</div></li><li class="list-item"><div class="htmlview paragraph">Examination of the packaging options for an opposed-piston, two-stroke engine in a light-duty truck application</div></li></ul></div><div class="htmlview paragraph">The results of this study show that the Achates Power opposed-piston engine benefits-high efficiency, low emissions and reduced cost, mass and complexity-already demonstrated for medium-duty commercial vehicles [<span class="xref">1</span>] are also available for light-duty applications. In fact, to an even greater extent: over 30% fuel economy improvement when compared to an equivalent four-stroke diesel engine.</div><div class="htmlview paragraph">Moreover, this study shows that the final 2025 light-truck CAFE fuel economy regulation not only has the potential to be met but also the potential to be exceeded with a full-size 5,500 lb. pick-up truck by simply applying the Achates Power technology without any hybridization or vehicle improvements.</div></div>

<div class="htmlview paragraph">A Tapered Element Oscillating Microbalance (TEOM) was used to measure transient diesel particulate emissions. Light duty IDI and DI engined vehicles were tested over the LA4 Drive Cycle. One vehicle, a 1.6 litre IDI diesel engined VW Golf (Rabbit), was also tested over the Japanese 10-mode and European ECE-15 Cycles. Transient particulate emissions were also measured from a heavy duty DI diesel engine tested according to the US Federal Heavy Duty Transient Test Procedure. The TEOM proved to be very flexible, permitting continuous particulate measurements to be made at each of the conditions studied. Particulate mass determined by the TEOM over a complete cycle was generally lower, typically by between 13 and 28%, than that measured using conventional gravimetric filtration procedures. A new calibration technique was devised which improved the correlation between TEOM and gravimetric results.</div> <div class="htmlview paragraph">PARTICULATE EMISSION RATES from light duty vehicles powered by diesel engines are currently subject to legislative limits in the United States. The prescribed method for the measurement of particulates involves driving a vehicle over a specific cycle which includes a wide range of engine operating conditions.</div> <div class="htmlview paragraph">During a test the total exhaust from the engine is continuously mixed in a dilution tunnel with ambient air. A portion of the mixture is passed through a filter. Upon completion of a test the filter is weighed and the particulate mass calculated and converted into a mass emission rate. Currently vehicles powered by heavy duty diesel engines are not subject to particulate legislation. However, from 1987 regulations are proposed which will necessitate the collection of particulate emissions from these engines over a transient cycle.</div> <div class="htmlview paragraph">The measurement of particulate in the manner described precludes the identification of the engine conditions which contribute most to the emission during a transient test.</div> <div class="htmlview paragraph">Clearly, in order to achieve a minimum particulate emission rate from an engine in the most economical fashion, it is necessary to identify engine operating conditions which produce high rates of particulate emissions. To accomplish this over a transient cycle requires that the particulate emission rate be continuously measured.</div> <div class="htmlview paragraph">Transient particulate emissions have previously been determined using opacity meters (<span class="xref">1</span>,<span class="xref">2</span> and <span class="xref">3</span>)*, photoacoustic spectrometers (<span class="xref">1</span>,<span class="xref">2</span>,<span class="xref">4</span>,<span class="xref">5</span> and <span class="xref">6</span>) a pressure drop monitor (<span class="xref">7</span>) and a tapered element oscillating microbalance, TEOM, (<span class="xref">8</span>,<span class="xref">9</span>). The relative merits of these instruments have been examined by the Smoke and Particulate Panel of the Diesel Exhaust Composition Program Group of the Co-ordinating Research Council (<span class="xref">10</span>). This paper describes further work on the application of a TEOM to the continuous measurement of diesel particulate emissions. The objectives of the study were twofold.</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1.</span> <div class="htmlview paragraph">To assess the suitability of the TEOM to the quantitative and continuous measurement of particulate from a variety of diesel engines over important test cycles.</div> </li> <li class="list-item"> <span class="li-label">2.</span> <div class="htmlview paragraph">To investigate the accuracy of the TEOM by comparing particulate mass determined by the TEOM with that obtained using conventional gravimetric procedures.</div> </li> </ol> </div> <div class="htmlview paragraph"> <figure id="F1" class="figure"> <div class="graphic-wrapper"><img class="article-figure figure" src="850405_fig0001.jpg" alt="No Caption Available"/></div> </figure> </div>

<div class="section abstract"><div class="htmlview paragraph">Future pollutant emissions legislations are expected to be increasingly stringent. To reduce Nitrogen Oxides (NOx) emissions produced by Diesel engines, advanced combustion technologies - like Low Temperature Combustion (LTC) -, vehicle hybridization and NOx after-treatment systems - such as Selective Catalytic Reduction (SCR) systems - can be considered, leading to a growing demand for NOx models.</div><div class="htmlview paragraph">In this paper, we present a state-of-art of the different existing NOx models, from the black-boxes to the three-dimensional Computational Fluid Dynamics (CFD) codes. A way to classify these models is proposed. The paper also introduces the current applications for each subgroup of models.</div><div class="htmlview paragraph">Then, a black-box and two grey-box NOx models are studied regarding their accuracy and their sensitivity to model inputs. These models are validated for two Diesel engines on steady-state operating points as well as on transient operations. The semi-physical models accurately predict NOx emissions. The static map shows a good match with experimental data for the operating conditions resulting from the engine calibration, but can not detect any variation in these conditions. The high sensitivity of the semi-physical models according to the intake manifold composition shows that these models can not be used directly for all the engine control applications.</div></div>