Engine Size Research Articles

Computational Approach in Sizing of Pulsejet Engine

<p>Research in pulsejet has intensified recently due to its design simplicity that can be developed into efficient small scale propulsive units for new applications such as UAVs and Unmanned Combat Vehicles (UCAV). A major obstacle for its development is low efficiency of the engine. The objective of this research is to investigate the possibility of using pulsejet in certain applications where the pulsejet can trade its low efficiency with low cost, simple design, and light weight. Numerical analysis is used for analysing the pulsejet engine design. The main results drawn from this research is in increasing efficiency and improving performance of engine by improving size of engine, especially diameter of combustion chamber. The computed results show good resemblance with published data.</p>

An investigation of factors that determine motorcyclists' adoption of an idle-stop system in Taiwan

ABSTRACTTo combat gas emissions produced by idling motorcycles at red lights, the Taiwanese government passed an “idle-stop (IS)” bill that requires manufacturers beginning in 2015 to equip 10% of newly manufactured motorcycles with a microchip enabling the idling engines to automatically shut off. Along with safety concerns over the new but controversial technology, the additional charge would influence riders' decisions to adopt the system. This article specifically studies this matter by using a survey that investigated the contributory factors to motorcyclists' adoption of the system. Probabilistic models were estimated using data gathered from 3,673 motorcyclists in Taoyuan City, Taiwan. Three separate models (by no incentive, purchase support, and annual tax rebate) with mixed logit formulation were estimated to investigate the effects of the variables on respondents' three levels of IS adoption (low, medium, high) and capture potential heterogeneity. Several variables (e.g., female riders) appear to have heterogeneous effects, lending support to the use of mixed logit models in idle-stop research. An annual tax rebate appears to be the most tempting incentive, although it has limited effect on heavy motorcycle users, OAPs (old age pensioners), and those having safety concerns—suggesting that promotional activities (e.g., demonstrations, field operational tests) to enhance market penetration of the technology may be directed toward these groups. Other variables found to be significant determinants of IS adoption include, for example, gender, motorcycle engine size, red-light duration, and when the gasoline price was rising. The policy implications of the results are finally discussed.

Reforming Vehicle Taxes on New Car Purchases Can Reduce Road Transport Emissions -- Ex Post Evidence.

Australia is falling behind the international trend towards low carbon transport to reduce greenhouse gas (GHG) emissions. For instance, in 2012 the Australian Government forecasts that road transport emissions will continue to increase to 2020 and then slow to 2030 because of higher oil prices and the introduction of mandatory CO2 emissions standards. The forecast assumes vehicle efficiencies of petrol and diesel engines will improve, and there will be a gradual shift to alternative technologies. However, in 2007 the European Union found that while advances in vehicle technology had delivered most of the carbon reductions, these advances were offset by new cars that had become significantly more powerful, larger, and heavier. This is the case in Australia. The paper shows how Australia can accelerate the uptake of low carbon technology through reforming existing vehicle taxes into an environmental related tax. The reform will require basing the tax on CO2 emissions from previously being based on the vehicles technical characteristics such as cylinder capacity, engine size and fuel type. The literature supports the reform of vehicle taxes into an environmental tax, which was found to be a powerful instrument in influencing the purchase decisions of consumers. Specifically, the paper examines the literature and reviews the ex post evidence on the successful reform of vehicles taxes. In the case study of Ireland, it was found that the reformed vehicle taxes based on CO2 emissions provided a strong price signal, and consumer response was greater than anticipated. As a result, Irelands ambitious targets in reducing its GHG emissions were met. The paper provides evidence to Australia’s policy makers, consultants and car manufacturers that reforming existing vehicle taxes into an environmental related tax is an effective measure in transitioning Australia into a low carbon transport and reducing road transport emissions.

Analysis of a new concept in power plants for electric vehicles

This paper reports on growing research efforts in the area of advanced heat engines. In particular, an engine is currently being investigated which operates much as a Stirling engine but uses a working fluid with a phase–changing component, which increases pressure variations for a given temperature difference and thus allows a much higher power for a given engine size. Applications for such an engine range from direct conversion of solar or nuclear energy to powering an artificial heart. This paper discusses how this engine may be applied to replacing the battery/electric motor system of an electric car with a thermal energy storage system and a Stirling engine which utilizes a phase–changing component in the working fluid. As a part of this discussion, the effect on total energy and oil consumption in the US is presented, if all of the cars were to utilize such a method of power. Also, the most recent results of the current research pertaining to the engine is presented, including the effects of water in the working fluid of a Stirling engine and the further effects of modifying the regenerator with a hydrated salt.

Experimental Determination of Liquefied Petroleum Gas–Gasoline Mixtures Knock Resistance

The results of previous experimental researches showed that great advantages can be achieved, both in terms of fuel consumption and pollutant emissions, in bifuel vehicles by means of the double-fuel combustion, i.e., the simultaneous combustion of gasoline and a gaseous fuel, such as liquefied petroleum gas (LPG) or natural gas (NG). The substantial increase in knock resistance pursued by adding LPG to gasoline, which allowed to maintain an overall stoichiometric proportion with air also at full load, is not documented in the scientific literature and induced the authors to perform a proper experimental campaign. The motor octane number (MON) of LPG–gasoline mixtures has been hence determined on a standard cooperative fuel research (CFR) engine, equipped with a double-fuel injection system in order to realize different proportions between the two fuels and electronically control the overall air–fuels mixture. The results of the measurement show a quadratic dependence of the MON of the mixture as function of the LPG concentration evaluated on a mass basis, with higher increase for the lower LPG content. A good linear relation, instead, has been determined on the basis of the evaluated LPG molar fraction. The simultaneous combustion of LPG and gasoline may become a third operative mode of bifuel vehicles, allowing to optimize fuel economy, performances, and pollutant emissions; turbocharged bifuel engines could strongly take advantage of the knock resistance of the fuels mixture thus adopting high compression ratio (CR) both in pure gas and double-fuel mode, hence maximizing performance and reducing engine size. The two correlations determined in this work, hence, can be useful for the design of future bifuel engines running with knock safe simultaneous combustion of LPG and gasoline.

A prospective, multi-institutional study of pediatric all-terrain vehicle crashes.

Pediatric all-terrain vehicle (ATV) injuries have been increasing annually for more than a decade. The purpose of this study was to prospectively evaluate crash circumstances and clinical outcomes resulting from pediatric ATV crashes. Three pediatric trauma centers prospectively collected data from patients during their hospitalization for injuries sustained in ATV crashes from July 2007 through June 2012. Patients completed a 35-item questionnaire describing the crash circumstances (ATV engine size, safety equipment use, and training/experience). Clinical data (injuries, surgical procedures, etc.) were collected for each patient. Eighty-four patients were enrolled, with a mean (SD) age of 13.0 (3.1) years, and were predominantly male (n = 55, 65%). Injuries were musculoskeletal (42%), central nervous system (39%), abdominal (20%), thoracic (16%), and genitourinary (4%). Multisystem injuries were prevalent (27%), and two patients died. Thirty-three patients (43%) required operative intervention. Most children were riding for recreation (96%) and ignored ATV manufacturers' recommendation that children younger than 16 years ride ATVs with smaller (≤90 cc) engines (71%). Dangerous riding practices were widespread: no helmet (70%), no adult supervision (56%), double riding (50%), riding on paved roads (23%), and nighttime riding (16%). Lack of helmet use was significantly associated with head injury (53% vs. 25%, p = 0.03). Rollover crashes were most common (44%), followed by collision with a stationary object (25%) or another vehicle (12%). Half (51%) of children said that they would ride an ATV again. These data demonstrate a relationship between dangerous ATV riding behaviors and severe injuries in children who crash. Children younger than 16 years should not operate ATVs, and legislation that effectively restricts ATV use in children is urgently needed. Epidemiologic study, level III.

Design of fly-eye lens for laser display

It is an important research subject for the optical system of laser display on how to decrease the size of the optical system and improve the lighting effect of the laser source. The optical system design of the laser projector is mainly considered from these two aspects, and it can be found that when the size of the whole fly-eye lens and the focal length of the single fly-eye are certain, more arrays of the fly-eyewill be useful to increase the light effect and decrease the size of the optical engine. The lighting effect of the illumination beams with different numerical apertures and tracing 40 000 light lines of the optimized fly-eye lens show that the transmittance can reach about 92.5% with almost no stray light and scattered light.

The engineering sizing of the packed desorption column of hydrogen isotopes from Pb–17Li eutectic alloy. A rate based model using experimental mass transfer coefficients from a Melodie loop

The model of the desorption of hydrogen isotopes from lead lithium alloy in a packed column is derived from the first principles using the plug flow in the liquid phase either the plug flow or ideal mixing in the gas phases. Sievert's law of non-linear equilibrium is followed. The volumetric mass transfer coefficient kLa and its dependence on the liquid metal flow rate are evaluated on the basis of the Melodie loop experiments.The presented model is used for evaluation of the minimum flow rate of the purge gas for which the concentration of the isotope in the gas leaving the column is at its highest, while the driving force of the interfacial transport of the isotope is still not reduced and the tritium desorption efficiency is therefore retained. The potential effect of the axial dispersion in the gas and liquid phase is evaluated. Highlighted are the issues of the optimum packing geometric surface area, above which the efficiency starts to decrease, and of the role of the surface tension and the contact angle with regard to the wettability of the packing. On the basis of the findings related to these factors, the Mellapak 500Y and Mellapak packings with flat surfaces are recommended for the tests aiming to intensify the tritium desorption efficiency in the packed columns. The models were used for the engineering sizing of the packed columns in two breeding blanket concepts for the DEMO plant – utilizing DCLL (dual coolant lead lithium) and HCLL (helium cooled lithium lead).

Design of fly's-eye lens for LCOS laser display

Design of optical system in laser display has always been an important research topic. From the aspect of decreasing the system volume and improving the light efficiency, it can be found that when the size of fly's-eye lens and the value of f/# are definite, the more fly's-eye arrays there are, the more useful it will be to the decrease of the optical engine size, which means that more honeycombs on fly's-eye lens and better dodging effect can be more beneficial for the decrease of the system size. After the optimal design for the rectangular elements on sub-fly's-eye lens and then doing 4000 ray tracing, the light transmittance turns out to be good with little parasitic light and scattering light.

Flame Structure Effects at High G-Loading

Previous research has been conducted showing significant benefits on combustion efficiency and stability by creating high gravity-loaded combustion environments. Ultracompact combustor systems decrease the size and weight of the overall engine by integrating the compressor, combustor, and turbine stages. In this system, the core flow is split and a portion is routed into a circumferential direction to be burned at a high equivalence ratio. Fuel and air are brought into the cavity and combusted in a high g-loaded environment driven by air injection. Computational research showed that the hole diameter of the air injection jets are directly related to g-loading within the cavity. An experimental rig was built where the air injection rings could be changed to contain one of three different jet hole diameters to verify this result. The smallest air injection diameter achieved the highest g-loading in the cavity, which is consistent with the computational fluid dynamics (CFD) results. However, the flame stability within the cavity was affected by the air injection jet becoming too large or too small for a particular equivalence ratio. Video taken at 8000 Hz was used to capture the flame structure, revealing that the flame was not stable even before lean blow out conditions were achieved. Additionally, the direction that the air jets swirled in the cavity was found to have an impact on the combustion dynamics. When flow swirled counterclockwise and impacted the suction side of the turbine vane, the cavity had a more uniform fully developed flow field, as opposed to the pressure side impact. Finally, liquid fuel testing was done to test the atomization and mixing of JP-8 in a g-loaded environment. The results showed that increasing the cavity g-load increased the residence time the fuel stayed in the cavity.

Biodiesel B10 – An Alternative Fuel for Diesel Pick-Up Trucks

From the test study of the use of biodiesel B10 in a diesel pick-up truck with an engine size not over 2500 cc, it showed that biodiesel B10 can be effectively used as an alternative fuel giving low polluted emission. On dynamometer performance test of the Isuzu TFR 2500 Di pick-up truck used over 200,000 kilometers, it resulted that the maximum power output from the use of diesel was 60.9 hp@3,630 rpm whereas from the use of biodiesel B10 was 58.1 hp@3,700 rpm which was about 4.6% lower. Considering the heating value of diesel of 35,970 kJ/l, it was 8.4% higher than that of the pure biodiesel (32,940 kJ/l). Since biodiesel B10 is a mixture of 10% pure biodiesel and 90% diesel fuel, and the molecular structure of biodiesel contains 11%wt oxygen gives better combustion. However, biodiesel was more viscous compared to diesel at the same fuel injection pressure of 180 kgf/cm2, therefore, the fuel nozzle injector was changed to a 5-hole nozzle from the original 4-hole nozzle for better fuel spray and atomization in the combustion chamber. The maximum power output of 58.6 hp@3,685 rpm was achieved but the fuel consumption rate and soot emission were lower. Comparing the road test results at the average speed of 90 km/h, the average consumption rate of biodiesel B10 was 16.4 km/l which was about 5.2% higher than that of diesel of 17.3 km/l. When changing to 5-hole fuel injector, the average consumption rate of biodiesel B10 was 18.4 km/l, about 12.2% saver than from the original 4-hole nozzle use. Similarly the average consumption rate of diesel when using the 5-hole nozzle injector was saver to 18.6 km/l. It clearly provided better fuel atomization in the combustion chamber. From the random emission measurements, it showed that there was 33.7% soot from using biodiesel B10 which was lower than the use of diesel of 34.2% for 4-hole fuel injector, and decreased to 31.2% when switching to the 5-hole fuel injector. Keywords: biodiesel, B10, alternative fuel, diesel pick-up truck, fuel nozzle injector

(Invited) High κ/InGaAs for Ultimate CMOS – Interfacial Passivation, Low Ohmic Contacts, and Device Performance

(Invited) High κ/InGaAs for Ultimate CMOS – Interfacial Passivation, Low Ohmic Contacts, and Device Performance

Integrated multifidelity, multidisciplinary evolutionary design optimization of counterrotating compressors

In high-speed air-breathing propulsion, compact turbomachinery is essential to reduce the engine size and weight. Hence, high compression ratios are required in the compressor stages. This paper proposes an optimization-based integrated design approa

Modeling the Impact of Subject and Opponent Vehicles on Crash Severity in Two-Vehicle Collisions

The main goal of this research was to develop models for crash severity prediction in a subject vehicle while taking into account the impact of both vehicles involved (Vehicles V1 and V2). Three binary targets were modeled: FatalSIK (to predict overall severity), FatalSIKV1 (to predict the probability of a serious injury, fatality, or both in Vehicle V1), and FatalSIKV2 (to predict the probability of a serious injury, fatality, or both in Vehicle V2). For the period from 2006 to 2010, 874 collisions involving injuries, fatalities, or both were analyzed. However, the crash sample included few severe events. Because imbalanced data introduce a bias toward the majority class (nonsevere crashes), in predictive modeling, they would result in less accurate predictions of the minority class (severe crashes). For the challenge imposed by small sample size and imbalanced data to be overcome, an important methodology was developed on the basis of a resampling strategy by using 10 stratified random samples for model evaluation. The effect of vehicle characteristics such as weight, engine size, wheelbase, and registration year (age of vehicle) were explored. Logistic regression analysis for FatalSIK suggested that the age of the vehicle and the type of collision were significant predictors (p < .0084 and .0346, respectively). Models FatalSIKV1 and FatalSIKV2 showed that the engine size of the opponent vehicle was statistically significant in predicting severity (p < .0762 and p < .03875, respectively). Models for FatalSIKV1 and FatalSIKV2 yielded satisfactory results when evaluated with the 10 stratified random samples: 61.2% [standard deviation (SD) = 2.4] and 61.4% (SD = 3.1), respectively.

Optimization of Intercooled Turbofan Jet Thermodynamic Cycle Considering Weight Penalty and Pressure Loss of Heat Exchanger

Thermal cycles of a turbofan jet engine equipped with an intercooler are optimized for two different engine sizes to understand the engine characteristics. The optimization tool consists of a thermodynamic cycle analysis module, a weight evaluation module, a heat exchanger model and an optimization routine. It is confirmed that the tool searches for a reasonable design point within a ten-dimensional design space. The pressure ratio of a conventional turbofan is restricted by the compressor exit temperature. In contrast, intercooling enables higher pressure ratios and hence higher core thermal efficiency. The net decrease in fuel consumption is small however, because the thermal efficiency improvement, weight penalty and pressure loss are all at the same order of several percent. The minimum blade height at the compressor exit imposes another restriction on the pressure ratio increase for small intercooled engines, and net fuel consumption in small engines may increase by intercooling. The performance of an intercooled turbofan is determined by a balance between thermal efficiency improvement through the increase in pressure ratio and disadvantages resulting from additional weight and pressure losses. The development of a light, low-pressure-loss heat exchanger and optimization of the thermodynamic cycle are important.

Determinants of US passenger car weight

After a precipitous drop from 1976–1982, the weight of US passenger cars has grown steadily. This article examines multiple conflicting influences on vehicle weight in two categories: technological changes that reduce vehicle weight and improvements in functionality that, ceteris paribus, add to vehicle weight. The widespread adoption of unibody construction, lightweight materials and smaller engines has been offset by growth in vehicle size and feature content. The best estimates from this work indicate that new features and functionality would have added at least 250 kg (550 lbs) to the weight of the average new car between 1975 and 2009, if not for offsetting improvements in technology. Over the same period, it is estimated that alternative materials, more weight-efficient vehicle architectures and reduced engine sizes have taken 790 kg (1700 lbs) out of the weight of the average car. These observable influences do not explain the full extent of the drop and subsequent growth in weight, suggesting that substantial non-observed technological improvements were made from 1976–1982 and that unobserved improvements in areas such as crashworthiness and NVH have added substantially to vehicle weight in the past two decades.

Analysis of Coolant Mass Flow Requirements for Transpiration Cooled Ceramic Thrust Chambers

The long-term development of ceramic rocket engine thrust chambers at the German Aerospace Center (DLR) culminates in compact designs of transpiration-cooled fibre-reinforced ceramic rocket engine chamber structures. Achievable benefits of the transpiration cooled ceramic thrust chamber are the reduction of engine mass and manufacturing cost, as well as an increased reliability and higher lifetime due to thermal cycle stability. The transpiration cooling principle however reduces the engine performance. Due to the transpiration cooling the characteristic velocity decreases with increasing coolant ratio. The goal of the chamber development is therefore to minimize the required coolant mass flow. The wall temperature can be calculated using known heat transfer correlations, for example given by Bartz, and employing a model given in literature for the reduction of the heat transfer coefficient based on coolant mass flow. By this method the required coolant mass flow ratio for different chamber diameters and pressure levels can be calculated. This paper discusses the application potential of DLR’s ceramic thrust chamber technology for high performance engines. Parametric variations of engine sizing (such as chamber pressure and diameter) are performed. For large diameters and high chamber pressures the required coolant ratio is below 1%.

Characterisation of a low pressure turbine for turbocompounding applications in a heavily downsized mild-hybrid gasoline engine

This paper describes the outcomes of a study carried out on a novel exhaust energy recovery system for a heavily downsized gasoline engine. The investigation was carried out based on a 1.0 L turbocharged gasoline engine offering the same performance as a 2.0 L model, with the aim of reducing CO2 emissions from 169 g/km to 99 g/km. This is to be obtained by the synergistic application of electrified boosting, stop/start technology, regenerative braking, torque assist and exhaust energy recovery systems.The research focussed on the design of a high performance LPT (Low Pressure Turbine) to recover latent energy left in the exhaust gas after expanding in the main turbocharger turbine. The LPT is meant to be coupled to an electric generator whose combination is usually referred as electric turbocompounding. Given the small engine size and therefore the low mass flow rate of the exhaust gas, the design operating conditions were fixed at 50,000 rpm with an optimum pressure ratio of PR ≈ 1.1. Commercially available turbines are not suitable for this purpose due to the very low efficiencies (less than 40%) experienced when operating in such low pressure ratios range. The design was accomplished by following a number of steps which go from meanline loss model development, full 3-D CFD (Computational Fluid Dynamics) analysis (using ANSYS CFX), prototype manufacturing and steady-state testing. The test results, that were conducted by using the Imperial College London cold-flow test facility, showed good agreement with CFD analysis with an efficiency greater than 70%.The steady maps obtained from testing were then input into a 1-D engine model including the electric turbocompounding. Three different arrangements were considered for the turbocompounding: (1) pre-catalyst, (2) post-catalyst and (3) in the wastegate of the main turbocharger. Two different scenarios were investigated in which the extra energy recovered by the turbocompounding unit is either fully regenerated into the engine crankshaft or stored and not re-used. The BSFC (brake specific fuel consumption) and the BMEP (brake mean effective pressure) were calculated and compared with the baseline engine under full and part load conditions. At full load, the analysis was performed for several engine speeds (from 1000 rpm to 6000 rpm at steps of 500 rpm each). The results showed that the extra energy recovered by the turbocompounding device is offering a significant benefit on engine performance; the post-catalyst solution offers the best compromise in terms of BSFC and BMEP with an improvement of 2.41% and 2.21% respectively. At part load engine instead, the analysis was performed for three engine speeds (1500 rpm, 2000 rpm and 4000 rpm) for the post-catalyst position only. Despite the increment in pumping work due to the presence of the LPT, no significant penalty in BSFC was calculated when no energy is returned into the engine whereas an improvement of ≈2.64% was found in the other case.

Size-scaling effect on the velocity field of an internal combustion engine, part II: Turbulence characteristics

Top dead center turbulence characteristics in two geometrically scaled, two-valve, single-cylinder research engines were investigated to study engine size scaling relationships. Velocity data were ...

Size dependence of efficiency at maximum power of heat engine

We perform a molecular dynamics computer simulation of a heat engine model to study how the engine size difference affects its performance. Upon tactically increasing the size of the model anisotropically, we determine that there exists an optimum size at which the model attains the maximum power for the shortest working period. This optimum size locates between the ballistic heat transport region and the diffusive heat transport one. We also study the size dependence of the efficiency at the maximum power. Interestingly, we find that the efficiency at the maximum power around the optimum size attains a value that has been proposed as a universal upper bound, and it even begins to exceed the bound as the size further increases. We explain this behavior of the efficiency at maximum power by using a linear response theory for the heat engine operating under a finite working period, which naturally extends the low-dissipation Carnot cycle model [M. Esposito, R. Kawai, K. Lindenberg, C. Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. The theory also shows that the efficiency at the maximum power under an extreme condition may reach the Carnot efficiency in principle.