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Exhaust Gas Recirculation (EGR) coolers are widely used on diesel engines to reduce in-cylinder NOx formation. A common problem is the accumulation of a fouling layer inside the heat exchanger, mainly due to thermophoresis that leads to deposition of particulate matter (PM), and condensation of hydrocarbons (HC) from the diesel exhaust. From a recent investigation of deposits from field samples of EGR coolers, it was confirmed that the densities of their deposits were much higher than reported in previous studies. In this study, the experiments were conducted in order to verify hypotheses about deposit growth, especially densification. An experimental set up which included a custom-made shell and tube type heat exchanger with six surrogate tubes was designed to control flow rate independently, and was installed on a 1.9 L L-4 common rail turbo diesel engine.

Exhaust Gas Recirculation (EGR) coolers are commonly used in on-road and off-road diesel engines to reduce the recirculated gas temperature in order to reduce NOx emissions. One of the common performance behaviors for EGR coolers in use on diesel engines is a reduction of the heat exchanger effectiveness, mainly due to particulate matter (PM) deposition and condensation of hydrocarbons (HC) from the diesel exhaust on the inside walls of the EGR cooler. According to previous studies, typically, the effectiveness decreases rapidly initially, then asymptotically stabilizes over time. Prior work has postulated a deposit removal mechanism to explain this stabilization phenomenon. In the present study, five field aged EGR cooler samples that were used on construction machines for over 10,000 hours were analyzed in order to understand the deposit structure as well as the deposit composition after long duration use.

This study experimentally investigates the impact of Miller cycle strategies on the combustion process, emissions, and thermal efficiency in heavy-duty diesel engines. The experiments were conducted at constant engine speed, load, and engine-out NOx (1160 rev/min, 1.76 MPa net IMEP, 4.5 g/kWh) on a single cylinder research engine equipped with a fully-flexible hydraulic valve train system. Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC) timing strategies were compared to a conventional intake valve profile. While the decrease in effective compression ratio associated with the use of Miller valve profiles was symmetric around bottom dead center, the decrease in volumetric efficiency (VE) was not. EIVC profiles were more effective at reducing VE than LIVC profiles. Despite this difference, EIVC and LIVC profiles with comparable VE decrease resulted in similar changes in combustion and emissions characteristics.

With ongoing concerns about the elevated levels of ambient air pollution in urban areas and the contribution from heavy-duty diesel vehicles, hybrid electric vehicles are considered as a potential solution as they are perceived to be more fuel efficient and less polluting than their conventional engine counterparts. However, recent studies have shown that real-world emissions may be substantially higher than those measured in the laboratory, mainly due to operating conditions that are not fully accounted for in dynamometer test cycles. At the U.S. EPA National Fuel and Vehicle Emissions Laboratory (NVFEL) the in-use criteria emissions and energy efficiency of heavy-duty class 8 vehicles (up to 36280 kg) can be evaluated under controlled conditions in the heavy-duty chassis dynamometer test.

This paper presents an experimental investigation of the impact of EGR dilution on the tradeoff between flame and end-gas autoignition heat release in a Spark-Assisted Compression Ignition (SACI) combustion engine. The mixture was maintained stoichiometric and fuel-to-charge equivalence ratio (ϕ′) was controlled by varying the EGR dilution level at constant engine speed. Under all conditions investigated, end-gas autoignition timing was maintained constant by modulating the mixture temperature and spark timing. Experiments at constant intake pressure and constant spark timing showed that as ϕ′ is increased, lower mixture temperatures are required to match end-gas autoignition timing. Higher ϕ′ mixtures exhibited faster initial flame burn rates, which were attributed to the higher laminar flame speeds immediately after spark timing and their effect on the overall turbulent burning velocity.

Combined direct and port fuel injection (i.e., dual injection) in spark ignition engines is of increasing interest due to the advantages for fuel flexibility and the individual merits of each system for improving engine performance and reducing engine-out emissions. Greater understanding of the impact of dual injection will enable deriving the maximum benefit from the two injection systems. This study investigates the effects of dual injection on combustion, especially knock propensity and tolerance to exhaust gas recirculation (EGR) dilution at different levels of EGR. A baseline for comparison with dual injection results was made using direct injection fueling only. A splash blended E20 fuel was used for the direct injection only tests. For the dual injection tests, gasoline, representing 80% by volume of the total fuel, was injected using the direct injector, and ethanol, representing 20% by volume of the total fuel, was injected using the port fuel injector.

Syngas (synthesis gas) aided combustion from various fuel reforming strategies is of increasing interest in boosted lean burn SI engines due to its impact on dilution tolerance and knock resistance. Due to the interest in reformed fuels, more concrete understanding of how to leverage syngas supplementation under various lean conditions is essential to optimize engine performance and derive the most benefit from the availability of syngas in the combustion process. While the impact of syngas supplementation on combustion stability has been studied adequately, detailed understanding of the impact of syngas on knocking is still limited. Hence, this study investigates the effect of syngas (H2/CO) addition on knock tendency under boosted EGR (Exhaust Gas Recirculation) and air diluted conditions. Syngas amount is controlled on an energy basis from 0% to 15% to compare the difference between EGR and air dilution.

The Honda Particulate Matter Index (PMI) is a very helpful tool which provides an indication of a fuel’s sooting tendency. Currently, the index is being used by various laboratories and vehicle OEMs as a metric to understand a fuels impact on automotive engine sooting, in preparation for new global emissions regulations. The calculation of the index involves generating detailed hydrocarbon analysis (hydrocarbon molecular speciation) using gas chromatography laboratory equipment and the PMI calculation requires the exact list of compounds and correct naming conventions to work properly. The analytical methodology can be cumbersome, when the gas chromatography methodology has to be adjusted for new compounds that are not in the method, or if the compounds are not matching the list for quantification. Also, the method itself is relatively expensive, and not easily transferrable between labs.

With increasingly stringent light duty particulate emissions regulations, it is of great interest to better understand particulate matter formation. Helping to build the knowledge base for a thorough understanding of particulate matter formation will be an essential step in developing effective control strategies. It is especially important to do this in such a way as to emulate real driving behaviors, including cold starts and transients. To this end, this study examined particulate emissions during transient operation in a recent model year vehicle equipped with a GDI engine. Three of the major federal test cycles were selected as evaluation schemes: the FTP, the HWFET, and the US06. These cycles capture much of the driving behaviors likely to be observed in typical driving scenarios. Measurements included particle size distributions from a TSI EEPS fast-response particle spectrometer, as well as real-time soot emissions from an AVL MSS soot sensor.

Cooled EGR provides benefits in better fuel economy and lower emissions by reducing knocking tendency and decreasing peak cylinder temperature in gasoline engines. However, GDI engines have high particle emissions due to limited mixing of fuel and air, and these particle emissions can be a major source of EGR cooler fouling. In order to improve our knowledge of GDI engine EGR cooler fouling, the effects of tube geometry and coolant temperature on EGR cooler performance and degradation were studied using a four cylinder 2.0L turbocharged GDI engine. In addition, deposit microstructure was analyzed to explore the nature of deposits formed under GDI engine operation. The results of this study showed that a dented tube geometry was more effective in cooling the exhaust gas than a smooth tube due to its large surface area and turbulent fluid motion. However, more deposits were accumulated and higher effectiveness loss was observed in the dented tube.

This experimental study involves optimization of the scheduling of diesel post injections to reduce soot emissions from a light-duty diesel engine. Previous work has shown that certain post injection schedules can reduce engine-out soot emissions when compared to conventional injection schedules for the same engine load. The purpose of this study is to investigate the impact of post injection scheduling for a range of engine conditions on a light duty multicylinder turbodiesel engine (1.9L GM ZDTH). For each engine operating condition, a test grid was developed so that only two variables (post injection duration and the commanded dwell time between main injection and post injection) were varied, with all other conditions held constant, in order to isolate the effects of the post injection schedule. Results have identified two distinct regimes of post injection schedules that reduce soot emissions.

In this study, the performance and emissions of a 4 cylinder 2.5L light-duty diesel engine with methane fumigation in the intake air manifold is studied to simulate a dual fuel conversion kit. Because the engine control unit is optimized to work with only the diesel injection into the cylinder, the addition of methane to the intake disrupts this optimization. The energy from the diesel fuel is replaced with that from the methane by holding the engine load and speed constant as methane is added to the intake air. The pilot injection is fixed and the main injection is varied in increments over 12 crank angle degrees at these conditions to determine the timing that reduces each of the emissions while maintaining combustion performance as measured by the brake thermal efficiency. It is shown that with higher substitution the unburned hydrocarbon (UHC) emissions can increase by up to twenty times. The NOx emissions decrease for all engine conditions, up to 53%.