Exhaust Emission Levels Research Articles

Cold start emissions of an ethanol-fuelled engine with heated intake air and fuel

This works presents the exhaust emission levels from a flexible fuel engine with heated intake air and fuel during cold start operation. A vehicle powered by an ethanol-fuelled flexible fuel engine was used in the experiments, following the US FTP-75 test schedule. The conventional gasoline injection system for cold start assistance was removed. Heating of intake air and fuel was provided by electric resistances. The results demonstrate that intake air and fuel heating can attend cold start expectations and simultaneously reduce exhaust hydrocarbon and carbon monoxide emissions.

The effect of a low ambient temperature on the cold-start emissions and fuel consumption of passenger cars

This paper examines the cold-start-up events of spark and compression ignition engines in the context of transient operation and emissions control. When the temperatures of the oil, coolant and engine block are equal or close to the ambient temperature, start-up can be difficult to achieve without significant excess levels of exhaust emissions and fuel consumption. In general, the lower the ambient temperature, the more significant these problems are. The physical processes responsible for this phenomenon are briefly discussed. Excess emission factors from a pool of Euro 4 and Euro 5 petrol vehicles and three Euro 5 diesel vehicles are presented, as tested over the Urban Drive Cycle at 24 °C and at −7 °C. A full modal emissions analysis was also conducted at 24 °C and at −7 °C on one petrol vehicle and one diesel vehicle over the New European Drive Cycle. The most problematic emissions are identified for both engine types, and recommendations are made to legislators regarding cold-start emissions.

Experimental Study of Transient Nitric Oxide, Smoke, and Combustion Noise Emissions during Acceleration of an Automotive Turbocharged Diesel Engine

The control of transient emissions from turbocharged diesel engines is an important objective for automotive manufacturers, since newly produced engines must meet the stringent criteria concerning exhaust emissions levels as dictated by the legislated Transient Cycles Certification. In the current study, experimental tests are conducted on an automotive, turbocharged diesel engine in order to investigate the formation mechanism of nitric oxide, smoke, and combustion noise emissions under various acceleration schedules experienced during daily driving conditions. To this aim, a fully instrumented test bed was set up in order to capture the development of key engine and turbocharger variables during the transient events. Analytical diagrams are provided to explain the behaviour of emissions development in conjunction with turbocharger and governor/fuel pump response. Turbocharger lag was found to be the main cause for the emission spikes during all test cases examined, with the engine calibration playing a vital role. The analysis was extended with a quasi-steady approximation of transient emissions using steady-state maps, in order to highlight the effect of dynamic engine operation on pollutants and combustion noise emissions.

Investigating the emissions during acceleration of a turbocharged diesel engine operating with bio-diesel or n-butanol diesel fuel blends

Abstract Control of transient emissions from turbocharged diesel engines is an important objective for automotive manufacturers, since stringent criteria for exhaust emission levels must be met as dictated by the legislated transient cycles. On the other hand, bio-fuels are getting impetus today as renewable substitutes for conventional fuels (diesel fuel or gasoline), especially in the transport domain. In the present work, experimental tests are conducted on a turbocharged truck diesel engine in order to investigate the formation mechanism of NO (nitric oxide) and smoke under various accelerating schedules experienced during daily driving conditions. To this aim, a fully instrumented test bed was set up in order to capture the development of key engine and turbocharger variables during the transient events using ultra-fast response instrumentation for the instantaneous measurement of the exhaust NO and smoke opacity. Apart from the baseline diesel fuel, the engine was operated with a blend of diesel fuel with 30% bio-diesel, and a blend of diesel fuel with 25% n-butanol. Analytical diagrams are provided to explain the behavior of emissions development in conjunction with turbocharger and fueling response. Unsurprisingly, turbocharger lag was found to be the main culprit for the emissions spikes during all test cases examined. The differences in the measured exhaust emissions of the two bio-fuel/diesel fuel blends, both leading to serious smoke reductions but also NO increases compared with the baseline operation of the engine were determined and compared. The differing physical and chemical properties of bio-diesel and n-butanol against those of the diesel fuel, together with the formation mechanisms of NO and soot were used for the analysis and interpretation of the experimental findings concerning transient emissions.

Evaluation of the effect of engine, load and turbocharger parameters on transient emissions of diesel engine

The vital issue of exhaust emissions during transient operation of diesel engines has been studied so far mainly on an experimental rather than simulation basis, owing to the very high computational times required for the analysis of each transient cycle. The study of transient emissions, however, is extremely important to manufacturers, since newly produced engines must meet the stringent regulations concerning exhaust emissions levels. In the present work, a comprehensive two-zone transient diesel combustion model is used for a preliminary evaluation of the effect of various parameters on nitric oxide (NO) and soot emissions during transient operation after load changes. The parameters are divided into three categories according to the specific sub-system examined, i.e. engine, load and turbocharger. Demonstrative diagrams are provided for the development of NO and soot emissions during the transient event, which depict the effect of each parameter considered. Moreover, the peculiarities of each case are discussed mainly in relation to turbocharger lag effects. For the current engine-load configuration, it is found that exhaust valve opening timing and cylinder wall insulation affect considerably NO and soot emissions. Additionally, load characteristics as well as turbocharger (T/C) mass moment of inertia play an important role on the development of transient NO and soot emissions.

Hydrous ethanol vs. gasoline-ethanol blend: Engine performance and emissions

This work compares the performance and emissions from a production 1.0-l, eight-valve, and four-stroke engine fuelled by hydrous ethanol (6.8% water content in ethanol) or 78% gasoline-22% ethanol blend. The engine was tested in a dynamometer bench in compliance with NBR/ISO 1585 standard. The performance parameters investigated were torque, brake mean effective pressure (BMEP), brake power, specific fuel consumption (SFC), and thermal efficiency. Carbon monoxide (CO), carbon dioxide (CO 2), hydrocarbons (HC) and oxides of nitrogen (NO X ) exhaust emissions levels are also presented. The results showed that torque and BMEP were higher when the gasoline-ethanol blend was used as fuel on low engine speeds. On the other hand, for high engine speeds, higher torque and BMEP were achieved when hydrous ethanol fuel was used. The use of hydrous ethanol caused higher power at high engine speeds, whereas, for low engine speeds, both fuels produced about the same power. Hydrous ethanol produced higher thermal efficiency and higher SFC than the gasoline-ethanol blend throughout all the engine speed range studied. With regard to exhaust emissions hydrous ethanol reduced CO and HC, but increased CO 2 and NO X levels.

Improvement of premixed charge compression ignition-based combustion by two-stage injection

The objective of this study is to find strategies for extending the load range of premixed charge compression ignition-based combustion while improving thermal efficiency and reducing combustion noise and exhaust emission levels. Experiments were performed using a single-cylinder direct-injection diesel engine equipped with a common-rail injection system and a cooled EGR system. First, experiments were carried out with single-stage injection. The results indicated a notable improvement of NO x and smoke emissions by selecting lower EGR rates and later injection timings according to the increase in injection quantity. However, the problems of high pressure rise rates and levels of unburned species emissions developed. To solve these problems, two-stage injection was applied. These additional experiments started with injection and EGR conditions that were based on the results of the single-stage injection tests, and modifications were made to mitigate the increased emissions and decreased thermal efficiency. As a result, judicious selection of injection and EGR conditions for two-stage injection provided a drastic improvement in exhaust emissions with a sufficiently low pressure rise rate to be equivalent to pilot-diesel operation.

The performance characteristics of a hydrogen-fuelled free piston internal combustion engine and linear generator system

A power generation system that utilizes a hydrogen-fuelled free piston engine (FPICE) and a linear generator are under development. A FPICE gives power output more efficiently compared with conventional reciprocating piston engines, because it utilizes many benefits such as low friction loss and inherently variable compression ratio apart from the low emission of hazardous exhaust gases. In addition, if hydrogen fuel is used in an FPICE, it would be possible to make the exhaust emission level almost zero without sacrificing the efficiency. In this study, a prototype FPICE, two-stroke twin-cylinder engine, was developed and a linear generation system was incorporated in between the cylinders to get the electricity and the start of the engine, as well. It was possible to operate the engine at a velocity of 17 Hz. The FPICE was found to give different piston positions at top dead centre, and this irregular piston movement affected significantly both the compression process and the subsequent combustion of the other cylinder of the engine at the same time. Both compressed natural gas and hydrogen were used to the test engine, and the results showed different combustion characteristics with the fuels used. Since the scavenging efficiency easily gets worse in such a low-speed operation of the two-stroke engines, hydrogen fuel has been found to give higher burn rate and resultantly to show improvements in power output and the emissions.

Cycle-Controlled Water Injection for Steady-State and Transient Emissions Reduction From a Heavy-Duty Diesel Engine

A system for coinjecting mixtures of diesel fuel and water into a heavy-duty diesel engine has been developed and evaluated at the Southwest Research Institute. This system features prototype Lucas electronically controlled injectors, full electronic control, and can vary the percentage of water in the mixture on a cycle-resolved basis. Tests of this system were conducted on a production Volvo D-12 engine, and have produced reduced NOx and smoke emissions over steady-state and transient conditions. Water-diesel coinjection yielded a considerable improvement in NOx-smoke and NOx-BSFC trade-offs under steady-state engine operation. In addition, control of the water percentage on a cycle-resolved basis was shown to be an effective method for mitigating NOx and smoke emissions over step-load transients. Results from this work show that a combination of aggressive EGR and diesel+water coinjection is very promising for producing very low levels of engine-out exhaust emissions, reducing the water storage requirements, and improving fuel efficiency. Further refinement of this injection technology is in progress.

RME or DME: A preferred alternative fuel option for future diesel engine operation

The twin challenges of fossil fuel depletion and environmental degradation, present engine and vehicle manufacturers with problems focused on future provision of both automotive power plant and conventional hydrocarbon fuels. In the drive to meet more stringent emission controls, many options have been identified, in the investigation of viable alternative fuels, and in the means of meeting the standards. While the operation of spark-ignition engines with natural gas is proven, other fuels are currently being explored for compression-ignition engines. In this study, di-methyl ether and rape-seed methyl ester, together with diesel fuel, were used, both as neat fuels and for pilot injection, in a natural gas dual-fuelled compression-ignition engine, to examine the performance and the levels of exhaust emissions. The merits and shortcomings as alternative fuels for diesel engines are discussed. While the ester performs much like diesel fuel in both modes, the ether produced lower specific oxides of nitrogen in dual-fuel operation.

Studies of Self-Pollution in Diesel School Buses: Methodological Issues

Considerable interest has focused on levels of exhaust emissions in the cabins of diesel-powered school buses and their possible adverse health effects. Significantly different policy and engineering issues would be raised if compelling evidence found that in-c-cabin contamination was due to self-pollution from bus emissions, rather than ambient pollution, neighboring vehicles, and/or re-entrained road dust. We identified 19 reports from 11 studies that measured diesel exhaust particulate in the cabins of 58 school bus of various type. Studies were evaluated in light of their experimental design, their data quality, and their capacity to quantify self-pollution. Only one study had a true experimental design, comparing the same buses with and without emission controls, while four others used intentional tracers to quantify tailpipe and/or crankcase emissions. Although definitive data are still lacking, these studies suggest that currently available control technologies can nearly eliminate particulate self-pollution inside diesel school buses.

An Experimental Study of Rich Premixed Gasoline/O2/Ar Flame with Tunable Synchrotron Vacuum Ultraviolet Photoionization

In this work, a rich premixed gasoline/O2/Ar flame at low pressure (30 Torr) with an equivalence ratio (φ) of 1.73 is investigated and reported. The identification and mole fraction calculation of most flame species, including isomeric intermediates, are performed in this study using the tunable synchrotron photoionization and molecular-beam mass spectrometry techniques, and the flame temperature profile is recorded using a Pt/Pt-13%Rh thermocouple. The possible formation pathways of some flame species, such as 1,3-butadiene, benzene, and naphthalene, are discussed in this paper, along with the comparison between this flame and other premixed hydrocarbon flames. It is concluded that the mole fraction of 1,3-butadiene is strongly related to that of the 1-buten-3-yl radical in the hydrocarbon flames. The decomposition of higher aromatics is found to be more important for benzene formation in this flame than the recombination of small intermediates, while the intermediate reactions are suggested as the dominant formation pathway of naphthalene. The comprehensive experimental data will be helpful for understanding the combustion mechanism of gasoline and pursuing a better control of exhaust emission levels from gasoline-fueled engines.

Environmental Assessment of a Diesel Engine Under Variable Stroke Length and Constant Compression Ratio

In the light of the energy crisis and the stringent environmental regulations, diesel engines are offering good hope for automotive vehicles. However, lot of work is needed to reduce the diesel exhaust emissions and give the way for full utilization of the diesel fuel’s excellent characteristics. This paper presents a theoretical study on the effect of variable stroke length technique on the emissions of a four-stroke, water-cooled direct injections diesel engine with the help of experimentally verified computer software designed mainly for diesel engines. The emission levels were studied over the speed range (1000 rpm to 3000 rpm) and stroke lengths (120 mm to 200 rpm) and were compared with those of the original engine design. The simulation results clearly indicate the advantages and utility of variable stroke technique in the reduction of the exhaust emission levels. A reduction of about 10% to 75% was achieved for specific particulate matter over the entire speed range and bore-to-stroke ratio studied. Further, a reduction of about 10% to 59% was achieved for the same range. As for carbon dioxide, a reduction of 0% to 37% was achieved. On the other hand, a less percent change was achieved for the case of nitrogen dioxide and nitrogen oxides as indicated by the results. This study clearly shows the advantage of VSE over fixed stroke engines. This study showed that the variable stroke technique proved a good way to curb the diesel exhaust emissions and hence helped making these engines more environmentally friendly.

Test emission characteristics of motorcycles in Central Taiwan

Due to the large population and high levels of motorized-vehicle exhaust emissions, motorcycle emissions make an important contribution to total emissions in Taiwan, ROC. Aiming to reduce the air pollution generated by these motorcycles, the Taiwan Environmental Protection Administration (TEPA) has maintained an enforced inspection and maintenance (I/M) program for in-use motorcycles since 1996. This report explores the effects of engine type, engine size, engine age, and manufacturers of in-use motorcycles on CO/HC emissions in I/M testing data during the period of 1996–2002 in the Central Air Quality Basin of Taiwan. Additionally, geographical characteristics and failure rates of motorcycles are analyzed. The results indicate that the age, size, and type of engine, and the manufacturers of motorcycles all play a significant role in determining I/M emission test results. The findings also show that two-stroke motorcycles emitted approximately ten times greater HC than those of four-stroke motorcycles. CO/HC test emissions increase with a decrease in engine size, HC test emissions contributed by Yamaha and other manufacturers being the highest. Although CO/HC test emissions generally increase with the age of the motorcycle, older motorcycles do not contribute significantly to total emissions due to the small number of older motorcycles. It was observed that CO/HC test emissions depend on driving patterns, geographical location, and inspection rates of motorcycles. The failure rate due to CO is nearly four times greater than that of HC, and the older and smaller-engine-size motorcycles obtain greater failure rates. These statistical findings can also provide the EPA of Taiwan or other Asian countries with useful information for formulating better environmental strategies to manage motorcycles effectively.

Motor Vehicle Exhaust Gas Suicide in Victoria, Australia 1998-2002

Motor vehicle exhaust gas suicide (MVEGS) is the second most frequent method of suicide in Victoria, Australia. It is a highly lethal method of suicide with 1.5 deaths for every hospital admission. Australian regulations require all vehicles manufactured since 1998 to have a maximum carbon monoxide exhaust emission level of 2.1 g/km, reduced from the previous level of 9.6 g/km. Information surrounding all Victorian MVEGS between 1998-2002 was analyzed to determine whether suicides occurred in vehicles with the lower emission levels. Between 1998-2002, 607 suicides by this means were recorded while just 393 hospital admissions were recorded for the same period. Mean carboxyhaemoglobin levels were significantly lower in fatalities using vehicles manufactured from 1998, however suicide still occurred in these vehicles (n = 25). The extent to which the new regulations contributed to the relatively low rate of suicide in vehicles less than 5 years old compared to their frequency in the fleet remains unknown. Based on international experience and the age of the Victorian vehicle fleet, it may take well over a decade until substantial decreases in MVEGS are observed in the absence of active preventive measures.

An experimental investigation of fuel injection timing on NOx emission of marine slow speed engines

At present, air pollution Annex to Marpol 73/78 convention is being compiled to regulate NOx and SOx emission limits. The paper describes the application of a CFD combustion model - KIVAII3v for a large bore, slow speed marine diesel engine and explores the feasibility of using fuel timing injection variables to estimate NOx exhaust emissions levels, at steady running conditions. The correlation analysis between the measured and calculated gaseous emission caused by fuel variable injection timing (VIT) was performed. The analysis is based on experimental data from Wartsila RTA engines test bed trials. Extracted and averaged measured history of NOx, and other gas components emission concentration were used as a comparison basis for calculation results. An examination of the measured and calculated results, particularly NOx concentrations, generally reveals a difference of emission levels associated with engine load and VIT setting.

Exhaust Emissions of Biodiesel, Petrodiesel, Neat Methyl Esters, and Alkanes in a New Technology Engine

Biodiesel is a renewable, alternative diesel fuel of domestic origin derived from a variety of fats and oils by a transesterification reaction; thus, it consists of the alkyl esters, usually methyl esters, of the fatty acids of the parent oil or fat. An advantage of biodiesel is its potential to significantly reduce most regulated exhaust emissions, including particulate matter (PM), with the exception of nitrogen oxides (NOx). In this work, three fatty acid methyl esters, neat methyl laurate, neat methyl palmitate, and technical grade methyl oleate, were selected for exhaust emissions testing in a heavy-duty 2003 six-cylinder 14 L diesel engine with exhaust gas recirculation. These fuels were compared with neat dodecane and hexadecane as well as commercial samples of biodiesel and low-sulfur petrodiesel as the base fuel, thus establishing for the first time a baseline of the exhaust emissions of neat hydrocarbon (alkane) fuels versus neat methyl esters. All fuels were tested over the heavy-duty diesel transient cycle. PM emissions were significantly reduced with biodiesel and methyl oleate (about 77 and 73%, respectively), while reductions with methyl palmitate and methyl laurate were even greater (82−83%) compared to the petrodiesel fuel. PM emissions with biodiesel only slightly exceeded the upcoming emissions standards, raising the possibility that biodiesel may meet these standards using only a diesel oxidation catalyst without employing a particulate trap. NOx emissions increased with biodiesel (about 12%) and technical grade methyl oleate (about 6%) but decreased (about 4−5%) with methyl palmitate and methyl laurate relative to those of the base fuel. PM emissions decreased (about 45−50%) with both dodecane and hexadecane. NOx emissions were reduced (around 15.5−16%) with dodecane and hexadecane compared to those of the petrodiesel fuel. The methyl ester moiety influences exhaust emissions by reducing particulate matter considerably more than neat straight-chain hydrocarbons, which are enriched in “clean” petrodiesel fuels, while NOx exhaust emissions, which showed little chain-length dependence, are less reduced. Thus, no future “clean” petrodiesel fuel should be able to achieve the low PM exhaust emissions levels of biodiesel without additional additive treatments or support by engine technology. Unsaturated fatty esters show slightly increased NOx and PM emissions compared to their saturated counterparts. The soluble organic fraction of the PM emissions was higher for the ester fuels. Hydrocarbon (HC) and CO exhaust emissions were also determined. Although HC emissions were low, a strong effect of chain length was observed.

Pollution dispersion at an urban motorway tunnel portal: Comparison of the small-scale predictive study with the actual conditions measured on the site

This paper presents a study on the environmental impact of vehicle exhausts at the south portal of the Landy tunnel located north of Paris, France. This study is based on a 1995 dispersion study using a hydraulic model and a 2002 campaign of in situ measurements. The 1995 study, conducted before the motorway covering was built, was aimed at comparing the theoretical NO2 concentrations, obtained with a hydraulic scale model, with the permissible thresholds imposed by French regulations. The NO2 concentrations obtained with the scale model were found to be reasonable, but as a precaution it was decided to retain a contingency option to subsequently install a massive extraction chimney to reduce exhaust emission levels at the portal. The 2002 in situ measurement campaign was aimed at measuring the actual pollution levels in the vicinity of the Landy tunnel south portal. The statistical analysis showed that the NO2 concentrations were higher on the east side of the road than the west, but still 5 to 10 times lower than at the exhaust, and are of the same order of magnitude as alongside other major Paris motorways. The PM10 measurements were in line with regulatory reference values on both sides of the road. Comparing the 1995 study and the 2002 in situ measurements showed a certain consistency but also highlighted the complexity of the phenomena involved and the difficulty of identifying the influence of the tunnel exhaust on the NO2 levels at the roadside.

Emissions Reduction Technologies for Military Gas Turbine Engines

Future military gas turbine engines will have higher performance than current engines, resulting in increased compressor and combustor exit temperatures, combustor pressures, and fuel-air ratios with wider operating limits. These combustor characteristics suggest undesirable exhaust emission levels of nitrogen oxides and smoke at maximum power and higher carbon monoxide and unburned hydrocarbons at low power. To control emission levels while improving performance, durability and cost, requires major advances in combustor technology. Current emissions control approaches as applied to conventional swirl-stabilized combustors include rich- and lean-burn strategies, together with staged combustion. These approaches, even in fully developed form, may not be sufficient to satisfy the projected design requirements. Unconventional combustor configurations may become necessary. Different engine cycles other than the standard Brayton cycle may also be used for special applications in order to avoid the use of excessive combustion temperatures. The paper presents an overview of the currently utilized emissions control approaches, comparing their performances and likely potential for meeting future requirements. Experimental results are presented for two non-conventional combustor configurations that have shown promise for advanced engine applications. A brief discussion is offered on cycle changes that could result in lower peak temperatures while maintaining advanced performance.

Detecting Air Leaks in an Engine Intake Manifold Using Nonlinear PCA

This paper describes the application of nonlinear principal component analysis (NLPCA) for the detection of air leaks in the intake manifold of internal combustion engines. Such faults, if undetected, can lead to inefficient engine operation, result in expensive repairs and cause an increased level of exhaust emissions. Using a VW 1.9L TDI diesel engine, several data sets were recorded that describe normal steady-state behaviour and the influence of air leaks at various speed and pedal positions. These data sets were then analysed using an NLPCA based monitoring scheme. It was found that even small air leaks could be detected.