Search Results

Abstract An investigation into the pre-ashing of new gasoline particulate filters (GPFs) has demonstrated that the filtration efficiency of such filters can be improved by up to 30% (absolute efficiency improvement) when preconditioned using ash derived from a fuel-borne catalyst (FBC) additive. The additive is typically used in diesel applications to enable diesel particulate filter (DPF) regeneration and can be added directly into the fuel tank of the vehicle. This novel result was compared with ash derived from lube oil componentry, which has previously been shown to improve filtration efficiency in GPFs. The lube oil-derived ash utilized in this work improved the filtration efficiency of the GPF by −30%, comparable to the ash derived from the FBC additive.

Abstract The water droplet erosion (WDE) on high-speed rotating wheels appears in several engineering fields such as wind turbines, stationary steam turbines, fuel cell turbines, and turbochargers. The main reasons for this phenomenon are the high relative velocity difference between the colliding particles and the rotor, as well as the presence of inadequate material structure and surface parameters. One of the latest challenges in this area is the compressor wheels used in turbochargers, which has a speed up to 300,000 rpm and have typically been made of aluminum alloy for decades, to achieve the lowest possible rotor inertia. However, while in the past this component was only encountered with filtered air, nowadays, due to developments in compliance with tightening emission standards, various fluids also collide with the spinning blades, which can cause mechanical damage.

Abstract Dynamic stresses exist in parts of a catalyst muffler caused by the vibration of a moving vehicle, and it is important to clarify and predict the vibration response properties for preventing fatigue failures. Assuming a vibration isolating installation in the vehicle frame, the vibration transmissibility and local dynamic stress of the catalyst muffler were examined through a vibration machine. Based on the measured data and by systematically taking vibration theories into consideration, a new prediction method of the vibration modes and parameters was proposed that takes account of vibration isolating and damping. A lumped vibration model with the six-element and one mass point was set up, and the vibration response parameters were analyzed accurately from equations of motion. In the vibration test, resonance peaks from the hanging bracket, rubber bush, and muffler parts were confirmed in three excitation drives, and local stress peaks were coordinate with them as well.

Abstract Low-Pressure cooled Exhaust Gas Recirculation (LP-cEGR) is proven to be an effective technology for fuel efficiency improvement in turbocharged spark-ignition (SI) engines. Aiming to fully exploit the EGR benefits, new challenges are introduced that require more complex and robust control systems and strategies. One of the most important restrictions of LP-cEGR is the transient response, since long air-EGR flow paths introduce significant transport delays between the EGR valve and the cylinders. High dilution generally increases efficiency, but can lead to cycle-by-cycle combustion variation. Especially in SI engines, higher-than-requested EGR dilution may lead to combustion instabilities and misfires. Considering the long EGR evacuation period, one of the most challenging transient events is throttle tip-out, where the engine operation shifts from a high-load point with high dilution tolerance to a low-load point where EGR tolerance is significantly reduced.

Abstract Uncertainty of fuel reserves, environmental crisis, and health concerns arise from transport demands and reliance on fossil fuels. Downsized gasoline turbocharged direct injection (GTDI) engines have been developed and applied to most modern gasoline vehicles, delivering superior efficiency in high-load operation, reduced friction, and weight. But fuel enrichment and late combustion phasing to mitigate knocking combustion have hindered the efficiency benefits at higher loads with high boost. Furthermore, the wide valve-overlap with a three-cylinder setup for the maximum scavenging efficiency produces bursts of short-circuit (SC) air to cause underestimation of the equivalence ratio by the oxygen sensor, resulting in higher tailpipe nitrogen oxides (NOx) emissions with three-way catalyst (TWC) exhaust aftertreatment. Reducing the valve overlap to limit short-circuiting and enrichment will recover the combustion efficiency and the engine ER, but at the cost of high knock onset.

Abstract In the development of hydrocarbon (HC) traps for E85 fuel vehicle emission control, the addition of palladium (Pd) to BEA zeolite was studied for trapping and decreasing cold-start ethanol emissions. BEA zeolite after a laboratory aging at 750°C for 25 hours released nearly all of the trapped ethanol as unconverted ethanol at low temperature, and some ethene was released at a higher temperature by a dehydration reaction. The addition of Pd to BEA zeolite showed a decrease in the release of unconverted ethanol emissions even after the lab aging. The release of methane (CH4), acetaldehyde (CH3CHO), carbon monoxide (CO), and CO2 from Pd-BEA zeolite during desorption (temperature programmed desorption (TPD)) demonstrated that multiple ethanol reaction mechanisms were involved including dehydrogenation and decomposition reactions.

Abstract Different aftertreatment systems consisting of a combination of selective catalytic reduction (SCR) and SCR catalyst on a diesel particulate filter (DPF) (SCR-F) are being developed to meet future oxides of nitrogen (NOx) emissions standards being set by the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB). One such system consisting of a SCRF® with a downstream SCR was used in this research to determine the system NOx reduction performance using experimental data from a 2013 Cummins 6.7L ISB diesel engine and model data. The contribution of the three SCR reactions on NOx reduction performance in the SCR-F and the SCR was determined based on the modeling work. The performance of a SCR was simulated with a one-dimensional (1D) SCR model. A NO2/NOx ratio of 0.5 was found to be optimum for maximizing the NOx reduction and minimizing NH3 slip for the SCR for a given value of ammonia-to-NOx ratio (ANR).

Abstract The present study evaluates the effect of engine speed, exhaust gas recirculation (EGR), and compression ratio on conventional diesel combustion (CDC) and two isobaric combustion cases, by utilizing multiple injection strategies. The experiments were conducted in a Volvo D13C500 single-cylinder, heavy-duty engine, fuelled with standard European Union (EU) diesel fuel. The engine was operated at three different speeds of 1200, 1500, and 1800 revolutions per minute (rpm). For each engine speed and combustion cases, the EGR rate was varied from 0% to 40%. The low-pressure isobaric combustion (IsoL) and high-pressure isobaric combustion (IsoH) were maintained at peak cylinder pressure (PCP) of 50 and 68 bar, respectively, which was representative of the peak motoring pressure (PMP) and PCP of CDC. This was possible by adjusting the intake air pressure to 1.7 and 2.3 bar—absolute for IsoL and IsoH, respectively, at 1200 rpm.

Abstract TOC

Abstract The impact of technical vehicle conditions on dynamical and emission vehicle characteristics has been of relatively little interest. Therefore, this study focuses on the impact of malfunctions of and unwarranted interferences in the exhaust gas recirculation system, known as EGR, on selected vehicle characteristics. Attention has been paid to the EGR blanking off and its permanent opening, carbon deposition in the engine’s intake manifold, and other malfunctions and interferences commonly occurring during the lifespan of vehicles. The parameters observed have included the composition of the exhaust gases, smoke opacity, engine power and torque, and others. The measurements have been performed with vehicles of different ages, different numbers of kilometers driven, and different levels of engine management.

Abstract An ongoing challenge with Gasoline engines is achieving rapid activation of the three-way catalyst during cold starts in order to minimize pollutant emissions. Retarded combustion is an effective way in achieving rapid light-up of the three-way catalyst and can be facilitated by stratified charge using late fuel injection. This, however, provides insufficient time for fuel entrainment with air, resulting in locally fuel-rich diffusion combustion. Employing a split injection strategy can help tackle these issues. The effects of a split injection strategy, using a high-pressure Solenoid injector, on the in-cylinder charge formation are investigated in the current study. The studies are performed inside an optical Gasoline engine using high-speed particle image velocimetry (PIV) in the central tumble and Omega tumble planes, by means of a high-speed laser and camera operating at a repetition rate of 10 kHz.

Abstract Nitrous oxide (N2O) is both an ozone depleting gas and a potent greenhouse gas (GHG), having a global warming potential (GWP) value nearly 300 times that of carbon dioxide (CO2). While long known to be a trace by-product of combustion, N2O was not considered a pollutant of concern until the introduction of the three-way catalyst (TWC) on light-duty gasoline vehicles in the 1980s. These precious metal-containing catalysts were found to increase N2O emissions substantially. Through extensive research efforts, the effects of catalyst type, temperature, air/fuel ratio, space velocity, and other factors upon N2O emissions became better understood. Although not well documented, N2O emissions from non-catalyst vehicles probably averaged 5-10 mg/mi (on the standard FTP test), while early generation TWC-equipped vehicles exceeded 100 mg/mi. As emissions control systems evolved to meet increasingly stringent criteria pollutant standards, N2O emissions also decreased.

Abstract A major reduction of greenhouse gas emissions, as well as other toxic emissions, is required to reduce the environmental impact of transportation systems. Renewable fuels, in combination with new internal combustion processes, such as reactivity controlled compression ignition (RCCI), are promising measures to enable this reduction. By combining two fuels with different reactivity, RCCI offers high efficiency and low emissions through homogeneous low-temperature combustion. However, a two-fuel RCCI approach leads to an increased number of adjustable operation parameters, such as injection timing. Optimizing these operation parameters to ensure homogenous combustion is challenging. To that end, optical methods provide temporally and spatially resolved information on mixture formation and combustion to analyze the homogeneity of the process. However, established methods, such as OH* imaging, cannot differentiate between multiple fuels.

Abstract In order to meet the emission requirements of the China VI regulations on natural gas (NG) engines, the China VI compliant NG engines generally adopt the equivalent combustion technology route with high-pressure exhaust gas recirculation (HP-EGR). However, the HP-EGR introduction mode heavily relies on engine exhaust pressure, which has negative impact on engine pumping work. In regards to this issue, study on an alternative EGR technology is very important to achieve high EGR introduction ability with low pumping work. In this research, an experimental study on an equivalent-NG engine used in extended-range hybrid vehicles was carried out. The influence of high-low-pressure EGR (HLP-EGR) technology on engine combustion, performance, and emission characteristics was analyzed. The potential of HLP-EGR in improving engine economy and reducing emissions was explored.

Abstract The present work proposes a viable approach to develop single-cylinder diesel engines for the future by implementing regulated intake air boosting (RIAB) and engine downspeeding (ED) along with the well-established low compression ratio (LCR) approach. The investigations were conducted in a mass-production light-duty single-cylinder diesel engine initially equipped with a naturally aspirated (NA) intake system. By lowering the compression ratio (CR) and implementing the intake air boosting (IAB) using a belt-driven supercharger, the maximum brake mean effective pressure (BMEP) of the engine could be increased by 50%. More importantly, the improved performance could be achieved without violating the peak firing pressure (PFP) limits. However, a significant penalty was observed in the brake-specific fuel consumption (BSFC) at low-load operating points due to the additional power consumption of the IAB system.

Abstract In the last few years, reactivity-controlled compression ignition (RCCI) mode combustion has gained researchers’ attention due to its superior performance, combustion, and emission characteristics compared to other low-temperature combustion (LTC) strategies. In this study, RCCI mode combustion investigations were carried out to explore the effects of exhaust gas recirculation (EGR) and intake charge temperature (ICT) on combustion, performance, and emission characteristics of a mineral diesel/methanol-fueled engine. In this study, constant engine speed (1500 rpm) and load (3 bar brake mean effective pressure [BMEP]) were used to perform engine experiments. The premixed ratio (rp) of methanol was varied from rp = 0 to rp = 0.75, where rp = 0 represents the baseline compression ignition (CI) mode combustion. At all rp, EGR rate and ICT were varied from 0 to 30% and 40° to 80°C, respectively.

Abstract Mandated requirements for cleaner and increasingly fuel-efficient vehicles drive innovation in engine technologies and combustion strategies, as well as in emissions control systems. As next-generation technologies are being developed and implemented in the engine and powertrain systems for both SI and CI engine vehicles, engine aftertreatment must meet increasingly specific conditions. As a result, there is an ever-increasing need for the comprehensive use of advanced, multiscale analytical and characterization tools to understand and evaluate the effects of new engine and emissions control technologies, their complex interactions with other subsystems, and overall performance metrics of vehicles. This review focuses on the application of current and future analytical and characterization methods relevant to the emissions control field.

Abstract The mobility landscape changes drastically. Ever-stricter regulation limits lead to extensive efforts in reducing emissions and fuel consumption. While diesel engines are the superior device in on-road transportation in terms of practicality and fuel consumption, they suffer from a distinct trade-off in particulate matter (PM) and nitrogen oxides (NOX) to the nature of the diffusive combustion process. The oxygenated fuel oxymethylene ether (OME) displays great potential to resolve this trade-off in multiple ways. With respect to engine-out emissions, the near soot-free combustion provides great leverage to drastically reduce NOX with little to no penalty in terms of particle emissions. Apart from its benefits in engine applications, OME displays high potential to reduce well-to-tank carbon dioxide (CO2) emissions.

Abstract Powertrain simulations and catalyst studies showed the efficiency credits and feasibility of onboard reforming as a way to recover waste heat from heavy duty vehicles (HDVs) fueled by natural gas (NG). Onboard reforming involves 1) injecting NG into the exhaust gas recycle (EGR) loop of the HDV, 2) reforming NG on a catalyst in the EGR loop to hydrogen and carbon monoxide, and 3) combusting the reformed fuel in the engine. The reformed fuel has increased heating value (4-10% higher LHV) and flame speed over NG, allowing stable flames in spark ignition (SI) engines at EGR levels up to 25-30%. A sulfur-tolerant reforming catalyst was shown to reform a significant amount of NG (15-30% conversion) using amounts of precious metal near the current practice for HDV emissions control (10 g rhodium). Engine simulations showed that the high EGR levels enabled by onboard reforming are used most effectively to control engine load instead of waste-gating or throttling.

Abstract Homogeneous charge with direct injection (HCDI) is a single-fuel low-temperature combustion (LTC) strategy that injects diesel into the intake port and inside the engine cylinder. The present study aims to numerically evaluate various oxides of nitrogen (NOx) mitigation methods such as split injection, exhaust gas recirculation (EGR), and water vapor induction in a single-cylinder diesel engine operated in HCDI mode. Numerical investigations are carried out using a commercial computational fluid dynamics (CFD) code CONVERGE. Experimental data are generated in a light-duty diesel engine operated in HCDI mode at 2.4 bar indicated mean effective pressure (imep) (low load) and 4.6 bar imep (high load) conditions to validate the CONVERGE predictions. The production engine is modified to run in HCDI mode through suitable modifications in the intake system, cylinder head, and fuel injection systems.