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Impact of Demanding Low Temperature Urban Operation on the Real Driving Emissions Performance of Three European Diesel Passenger Cars

Concawe, Belgium-Heather Hamje
Eni SpA, Italy-Corrado Fittavolini, Leonardo Pellegrini
Published 2018-09-10 by SAE International in United States
In Europe, the development and implementation of new regulatory test procedures including the chassis dynamometer (CD) based World Harmonised Light Duty Test Procedure (WLTP) and the Real Driving Emissions (RDE) procedure, has been driven by the close scrutiny that real driving emissions and fuel consumption from passenger cars have come under in recent times. This is due to a divergence between stated certification performance and measured on-road performance, and has been most pointed in the case of NOx (oxides of nitrogen) emissions from diesel cars. The RDE test is certainly more relevant than CD test cycles, but currently certification RDE cycles will not necessarily include the most extreme low speed congested or low temperature conditions which are likely to be more challenging for NOx after-treatment systems. To build understanding of the emissions and fuel consumption performance of the latest available diesel passenger cars, Concawe has conducted a study of the performance of three vehicle types. Two of the vehicles featured urea-dosed Selective Catalytic Reduction (SCR) after-treatment, whilst the third was fitted with a Lean NOx…
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Fuel Factors Affecting the High-Load Limit of a Temperature Stratified Controlled Auto-Ignition Engine

Chevron USA Inc.-William Cannella
MIT-Amir Maria, Wai Cheng, Kenneth Kar
Published 2014-04-01 by SAE International in United States
Factors affecting the pressure rise rate, and consequently the high-load limit, in the sequential ignition of a homogeneous charge in a temperature gradient have been identified. The pressure rise rate decreases with an increase in the magnitude of the temperature gradient and an increase in the sensitivity of the constant volume ignition delay time to temperature. It increases with an increase in the intrinsic reaction rate (i.e., the reaction rate for a charge of uniform composition and temperature). Since the ignition delay time and the intrinsic reaction rate are directly related to fuel properties, the high-load limit is sensitive to fuel selection.The above three factors are used to explain the high-load limit obtained from a knock limited Controlled Auto-Ignition (CAI) engine with a homogeneous charge operating with three different fuels. The fuel comparisons are made with the engine operating at the same combustion phasing. The fuel ignition delay time and intrinsic heat release rate have been characterized in a Rapid Compression Machine (RCM). Depending on the operating condition, the ranking of the fuel is explained…
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Understanding Knock Metric for Controlled Auto-Ignition Engines

SAE International Journal of Engines

Chevron-William Cannella
MIT-Amir Maria, Wai K. Cheng, Kenneth Kar
  • Journal Article
  • 2013-01-1658
Published 2013-04-08 by SAE International in United States
The knock metric for controlled auto-ignition (CAI) engines is assessed by considering the physical processes that establish the pressure wave that contributes to the acoustic radiation of the engine, and by analyzing pressure data from a CAI engine. Data sets from the engine operating with port fuel injection, early direct injection and late direct injection are used to monitor the effect of mixture composition stratification. Thermodynamic analysis shows that the local pressure rise produced by heat release has to be discounted by the work spent in acoustic expansion against the ambient pressure to properly predict the pressure wave amplitude. Based on this analysis, a modified correlation between the pressure wave amplitude and the maximum pressure rise rate (MPRR) is developed by introducing an MPRR offset to account for the expansion work.
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Particulate Matter Emissions from a Direct Injection Spark Ignition Engine under Cold Fast Idle Conditions for Ethanol-Gasoline Blends

SAE International Journal of Engines

Massachusetts Institute of Technology-Iason Dimou, Kenneth Kar, Wai Cheng
  • Journal Article
  • 2011-01-1305
Published 2011-04-12 by SAE International in United States
The engine out particular matter number (PN) distributions at engine coolant temperature (ECT) of 0° C to 40° C for ethanol/ gasoline blends (E0 to E85) have been measured for a direct-injection spark ignition engine under cold fast idle condition. For E10 to E85, PN increases modestly when the ECT is lowered. The distributions, however, are insensitive to the ethanol content of the fuel. The PN for E0 is substantially higher than the gasohol fuels at ECT below 20° C. The total PN values (obtained from integrating the PN distribution from 15 to 350 run) are approximately the same for all fuels (E0 to E85) when ECT is above 20° C. When ECT is decreased below 20° C, the total PN values for E10 to E85 increase modestly, and they are insensitive to the ethanol content. For E0, however, the total PN increases substantially. This sharp change in PN from E0 to E10 is confirmed by running the tests with E2.5 and E5. The midpoint of the transition occurs at approximately E5. Because the fuel…
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Using Mass Spectrometry to Detect Ethanol and Acetaldehyde Emissions from a Direct Injection Spark Ignition Engine Operating on Ethanol/Gasoline Blends

Massachusetts Institute of Technology-Kenneth Kar, Wai Cheng
Published 2011-04-12 by SAE International in United States
Ethanol and acetaldehyde emissions from a direct ignition spark ignition were measured using mass spectrometry. Previous methods focused on eliminating or minimizing interference from exhaust species with identical atomic mass and fragment ions created in ionization process. This paper describes a new technique which exploits the fragment ions from ethanol and acetaldehyde. A survey of mass spectra of all major species of exhaust gas was conducted. It was found that ethanol contributes most ions in mass number 31 and that no other gas species produces ions at this mass number. Acetaldehyde detection suffers more interference. Nevertheless, it was estimated that detection at mass number 43 is possible with 10% error from 2-methylbutane.This new technique was validated in an engine experiment. By running the engine with pure gasoline and E85, the validity of the technique can be checked. Two conditions were investigated: idling (1200 rpm, 1.5 bar NIMEP, retarded ignition timing) and medium load (1500 rpm, 3.8 bar NIMEP, MBT ignition timing). The results from both conditions confirmed that ions were only detected when E85 was…
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Speciated Engine-Out Organic Gas Emissions from a PFI-SI Engine Operating on Ethanol/Gasoline Mixtures

SAE International Journal of Fuels and Lubricants

Massachusetts Institute of Technology-Kenneth Kar, Wai K Cheng
  • Journal Article
  • 2009-01-2673
Published 2009-11-02 by SAE International in United States
Engine-out HC emissions from a PFI spark ignition engine were measured using a gas chromatograph and a flame ionization detector (FID). Two port fuel injectors were used respectively for ethanol and gasoline so that the delivered fuel was comprised of 0, 25, 50, 75 and 100% (by volume) of ethanol. Tests were run at 1.5, 3.8 and 7.5 bar NIMEP and two speeds (1500 and 2500 rpm). The main species identified with pure gasoline were partial reaction products (e.g. methane and ethyne) and aromatics, whereas with ethanol/gasoline mixtures, substantial amounts of ethanol and acetaldehyde were detected. Indeed, using pure ethanol, 74% of total HC moles were oxygenates. In addition, the molar ratio of ethanol to acetaldehyde was determined to be 5.5 to 1. The amount (as mole fraction of total HC moles) of exhaust aromatics decreased linearly with increasing ethanol in the fuel, while oxygenate species correspondingly increased. These results suggest that the change in ethanol and aromatics exhaust emissions were due to fuel replacement. It was also found that the oxygenate fraction of total…
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Effects of Ethanol Content on Gasohol PFI Engine Wide-Open-Throttle Operation

SAE International Journal of Fuels and Lubricants

Honda R&D Co. Ltd-Kaoru Ishii
Massachusetts Institute of Technology-Kenneth Kar, Wai Cheng
  • Journal Article
  • 2009-01-1907
Published 2009-06-15 by SAE International in United States
The NOx emission and knock characteristics of a PFI engine operating on ethanol/gasoline mixtures were assessed at 1500 and 2000 rpm with λ =1 under Wide-Open-Throttle condition. There was no significant charge cooling due to fuel evaporation. The decrease in NOx emission and exhaust temperature could be explained by the change in adiabatic flame temperature of the mixture. The fuel knock resistance improved significantly with the gasohol so that ignition could be timed at a value much closer or at MBT timing. Changing from 0% to 100% ethanol in the fuel, this combustion phasing improvement led to a 20% increase in NIMEP and 8 percentage points in fuel conversion efficiency at 1500 rpm. At 2000 rpm, where knocking was less severe, the improvement was about half (10% increase in NIMEP and 4 percentage points in fuel conversion efficiency). Because there was no significant change in the end gas temperature in these experiments, the gasohol knock resistance was attributed solely to the ignition chemistry of the ethanol.
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Measurement of Vapor Pressures and Enthalpies of Vaporization of Gasoline and Ethanol Blends and Their Effects on Mixture Preparation in an SI Engine

SAE International Journal of Fuels and Lubricants

The University of Auckland-Kenneth Kar, Tristan Last, Clare Haywood, Robert Raine
  • Journal Article
  • 2008-01-0317
Published 2008-04-14 by SAE International in United States
Global ethanol trade is forecast to increase 25-fold by 2020. Most of it will be blended with gasoline to make biofuel. However, blending ethanol with gasoline has a profound effect on the evaporation characteristics of the mixture. In particular, the thermodynamic properties of the blends can be significantly different than the constituents. A clear understanding of the blend's properties is essential for optimizing engine design, e.g. utilizing charge cooling effect.Data available in the literature is very limited, considering ethanol-gasoline blends will be used as a fuel in large scale worldwide. In this work, comprehensive measurements of vapor pressures were carried out. The enthalpies of vaporization were derived from vapor pressure data using the Clausius-Clapeyron equation. Maximum vapor pressure occurs with 20% ethanol-gasoline blend at which a positive azeotrope is formed. The trend is different in enthalpy of vaporization. The results presented here contradict previous claims that the enthalpy of vaporization is a linear function of ethanol content. Such a trend is true up to 20%; the value then decreases a little and appears to flatten…
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Particulate and Hydrocarbon Emissions from a Spray Guided Direct Injection Spark Ignition Engine with Oxygenate Fuel Blends

Shell Global Solutions-Harold Walmsley
University of Auckland-Kenneth Kar
Published 2007-04-16 by SAE International in United States
The blending of oxygenated compounds with gasoline is projected to increase because oxygenate fuels can be produced renewably, and because their high octane rating allows them to be used in substitution of the aromatic fraction in gasoline. Blending oxygenates with gasoline changes the fuels' properties and can have a profound affect on the distillation curve, both of which are known to affect engine-out emissions.In this work, the effect of blending methanol and ethanol with gasoline on unburned hydrocarbon and particulate emissions is experimentally determined in a spray guided direct injection engine. Particulate number concentration and size distribution were measured using a Cambustion DMS500. These data are presented for different air fuel ratios, loads, ignition timings and injection timings. In addition, the ASTM D86 distillation curve was modeled using the binary activity coefficients method for the fuel blends used in the experiments.In general, unburned hydrocarbon emissions were reduced at low load but increased at high load for the alcohol blends. The effect on particulate emissions was dependent on the operating point: for rich mixtures the accumulation…
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Cycle-by-Cycle Variations in Exhaust Temperatures Using Thermocouple Compensation Techniques

University of Auckland-Kenneth Kar, Akshya Swain, Robert Raine
University of Oxford-Stephen Roberts, Richard Stone
Published 2006-04-03 by SAE International in United States
Exhaust gas temperatures in a 1.4 L, sparked ignition engine have been measured using fine wire thermocouples at different loads and speeds. However the thermocouples are not fast enough to resolve the rapid change in exhaust temperature. This paper discusses a new thermocouple compensation technique to resolve the cycle-by-cycle variations in exhaust temperature by segmentation. Simulation results show that the technique can find the lower time constants during blowdown, reducing the bias from 28 to 4%. Several estimators and model structures have been compared. The best one is the difference equation-least squares technique, which has the combined error between -4.4 to 7.6% at 60 dB signal-to-noise ratio. The compensated temperatures have been compared against combustion parameters on a cycle-by-cycle basis. The results show that the cycle-by-cycle variations of the exhaust temperatures and combustion are correlated. For instance, the mass fraction burnt is positively correlated with cycle-averaged temperature. When there is a larger variability in combustion, the exhaust temperature also exhibits higher cycle-by-cycle variations. Overall, the results have confirmed that the segmentation technique has successfully resolved…
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