Numerical Evaluation of a New Strategy of Emissions Reduction by Urea Direct Injection for Heavy Duty Diesel Engines

The effect of ammoniac deoxidizing agent (Urea) on the reduction of NOx produced in the Diesel engine was investigated numerically. Urea dissolved in water was directly injected into the engine cylinder during the expansion stroke. The NOx deoxidizing process was described using a simplified chemical kinetic model coupled with the comprehensive kinetics of Diesel oil surrogate combustion. If the technology of DWI (Direct Water Injection) with the later injection timing was used, the deoxidizing reactants could be delivered in a controlled amount directly into the flame plume zones, where NOx formed. Numerical simulations for the Isotta Fraschini DI Diesel engine were carried out using the KIVA-3V code, modified to account for the “co-fuel” injection and reaction with combustion products. The results showed that the amount of NOx could be substantially reduced up to 80% with the injection timing and the fraction of Urea in the solution optimized

Performance and emissions of renewable blends with OME3-5 and HVO in heavy duty and light duty compression ignition engines

Interest in poly(oxymethylene)dimethyl ether (OME3-5) as an alternative to fossil fuels in compression ignition engines has increased owing to its potential for soot reduction. The high oxygen content of the polymer and lack of carbon–carbon bonds and aromatic structures can help to reduce engine out soot emissions. However, OME3-5 is potentially damaging to engine components, and thus engine modifications are required when using neatOME3-5.In the present study, OME3-5 was blended with hydrotreated vegetable oil (HVO), rapeseed methyl ester and the C8-alcohol 2-ethylhexanol (an isomer of n-octanol) to ensure miscibility. Three blends were designed with an oxygen content of 6.4, 12.8 and 17.8% by mass. Performance and emissions were compared to the reference fuels fossil diesel and HVO in a single cylinder light duty and heavy duty compression ignition engine at different loads.Evaluation of the combustion in both engines showed similar trends: The indicated thermal efficiency was slightly higher for the oxygenated fuel and the combustion duration shorter compared to diesel. Due to the lower heating value of the blends, the indicated specific fuel combustion increased with increasing share of OME3-5 in the blend.For both engines, engine out soot emissions were decreased strongly, whereas NOx emissions were slightly increased. Analysis of the particle size distribution showed a decrease in the particle number of agglomerated particles (>30 nm) for the blends. For the heavy duty engine, an increase in nucleation mode particles (<30 nm) was measured

Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine

The effect of two thermal barrier coatings and their surface roughness on heat transfer, combustion, and emissions has been investigated in a single-cylinder light-duty diesel engine. The evaluated thermal barrier coating materials were plasma-sprayed yttria-stabilized zirconia and hard anodized aluminum, which were applied on the piston top surface. The main tool for the investigation was cylinder pressure analysis of the high-pressure cycle, from which the apparent rate of heat release, indicated efficiency, and heat losses were derived. For verification of the calculated wall heat transfer, the heat flow to the piston cooling oil was measured as well. Application of thermal barrier coatings can influence engine operating conditions like charge temperature and ignition delay. Therefore, extra attention was paid to choosing stable and repeatable engine operating points. The experimental data were modeled using multiple linear regression to isolate the effects of the coatings and of the surface roughness. The results from this study show that high surface roughness leads to increased wall heat losses and a delayed combustion. However, these effects are less pronounced at lower engine loads and in the presence of soot deposits. Both thermal barrier coatings show a reduction of cycle-averaged wall heat losses, but no improvement in indicated efficiency. The surface roughness and thermal barrier coatings had a significant impact on the hydrocarbon emissions, especially for low-load engine operation, while their effect on the other exhaust emissions was relatively small

Alcohol flexible HD single cylinder diesel engine tests with separate dual high pressure direct fuel injection

Both greenhouse gas (GHG) emissions and local emissions from heavy duty (HD) Diesel engines must be greatly reduced to make transportation sustainable and comply with increasingly stringent emissions regulations. The fuel flexible engine concept for HD Diesel engines uses a dual fuel direct injection system in which ignition of the main alcohol fuel, either methanol or ethanol, is induced by a small Diesel pilot injection delivered via a separate direct injector. The objective of this investigation was to find ways to combine the advantages of conventional Diesel engines with the advantages of low carbon fuels and to thereby bypass the soot-NOx-trade-off. Experiments were conducted using a modified single-cylinder HD engine and three fuels (methanol, ethanol, and a reference Diesel fuel) to determine how the choice of fuel affected the engine\u27s combustion behaviour, emissions and fuel efficiency. Injection pressures on the alcohol side were varied up to 1500 bar and the investigation was carried out at low, medium and high speed-load points. The alcohol fuels significantly outperformed Diesel fuel under all tested conditions (with and without exhaust gas recirculation (EGR)). Indicated thermal efficiency was increased by up to 3.5%-points and simultaneously soot emissions were lowered by a factor of 40 or more and NOx by 20%. Combustion stability and emissions were in the same range as for Diesel but replacing more than 95 % of the fossil Diesel with an alcohol fuel

Experimental Assessment on Exploiting Low Carbon Ethanol Fuel in a Light-Duty Dual-Fuel Compression Ignition Engine

Compression ignition (CI) engines are widely used in modern society, but they are also recognized as a significative source of harmful and human hazard emissions such as particulate matter (PM) and nitrogen oxides (NOx). Moreover, the combustion of fossil fuels is related to the growing amount of greenhouse gas (GHG) emissions, such as carbon dioxide (CO2). Stringent emission regulatory programs, the transition to cleaner and more advanced powertrains and the use of lower carbon fuels are driving forces for the improvement of diesel engines in terms of overall efficiency and engine-out emissions. Ethanol, a light alcohol and lower carbon fuel, is a promising alternative fuel applicable in the dual-fuel (DF) combustion mode to mitigate CO2 and also engine-out PM emissions. In this context, this work aims to assess the maximum fuel substitution ratio (FSR) and the impact on CO2 and PM emissions of different nozzle holes number injectors, 7 and 9, in the DF operating mode. The analysis was conducted within engine working constraints and considered the influence on maximum FSR of calibration parameters, such as combustion phasing, rail pressure, injection pattern and exhaust gas recirculation (EGR). The experimental tests were carried out on a single-cylinder light-duty CI engine with ethanol introduced via port fuel injection (PFI) and direct injection of diesel in two operating points, 1500 and 2000 rpm and at 5 and 8 bar of brake mean effective pressure (BMEP), respectively. Noise and the coefficient of variation in indicated mean effective pressure (COVIMEP) limits have been chosen as practical constraints. In particular, the experimental analysis assesses for each parameter or their combination the highest ethanol fraction that can be injected. To discriminate the effect on ethanol fraction and the combustion process of each parameter, a one-at-a-time-factor approach was used. The results show that, in both operating points, the EGR reduces the maximum ethanol fraction injectable; nevertheless, the ethanol addition leads to outstanding improvement in terms of engine-out PM. The adoption of a 9 hole diesel injector, for lower load, allows reaching a higher fraction of ethanol in all test conditions with an improvement in combustion noise, on average 3 dBA, while near-zero PM emissions and a reduction can be noticed, on the average of 1 g/kWh, and CO2 compared with the fewer nozzle holes case. Increasing the load insensitivity to different holes number was observed

Advanced concepts for future light-duty diesel engines

Future diesel engines for passenger cars will have to meet increasingly stringent exhaust emissions legislation and be more efficient in order to reduce CO2 emissions. The most difficult challenges are to meet US Tier 2 regulations, which will impose limits of 0.07 g/m NOx and 0.01 g/m PM, and the requirements of the US06 Supplemental Federal Test Procedure for low NOx emissions at high load. To cope with the increasingly stringent emissions legislation new technologies must be introduced. The chapter describes possible new technologies, such as new combustion concepts, future fuel injection systems, advanced charging and EGR systems and after-treatment systems needed for meeting the future requirements

Advanced concepts for future light-duty diesel engines

Future diesel engines for passenger cars will have to meet increasingly stringent exhaust emissions legislation and be more efficient in order to reduce CO2 emissions. The most difficult challenges are to meet US Tier 2 regulations, which will impose limits of 0.07 g/m NOx and 0.01 g/m PM, and the requirements of the US06 Supplemental Federal Test Procedure for low NOx emissions at high load. To cope with the increasingly stringent emissions legislation new technologies must be introduced. The chapter describes possible new technologies, such as new combustion concepts, future fuel injection systems, advanced charging and EGR systems and after-treatment systems needed for meeting the future requirements

Comparison of Conventional Diesel and Fischer-Tropsch Diesel Fuels for HCCI Combustion

Engine tests were performed with Swedish low sulfur Diesel, European EN 590 Diesel and two natural gas-derived Fischer-Tropsch Diesel fuels in a light-duty single-cylinder engine to compare their emission, fuel consumption, and combustion characteristics. The engine was operated in HCCI combustion mode with multiple injections and different injection timings. The combustion was phased to a constant CA50 for all operating points by adjusting the amount of EGR. Low soot emissions are expected with HCCI, and no significant differences between the various fuels were detected in this respect. However, NOx emissions were lower for the F-T fuels than the other fuels, due to their high cetane number and higher EGR requirements