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

Experimental and numerical investigation of split injections at low load in an hddi diesel engine equipped with a piezo injector

In order to investigate the effects of split injection on emission formation and engine performance,experiments was carried out using a heavy duty single cylinder Diesel engine. Split injections with varied dwell Time and start of injection were investigated and compared with single injection cases. In order to isolate the effect of the parameters selected to investigate,other variables were kept constant. In this investigation no EGR was used. The engine was equipped with a common rail injection system with a piezoelectric injector. To interpret the observed phenomena,engine CFD simulations using the KIVA-3V code were also made. The results show that a reduction in NOx emissions and brake specific fuel consumption was achieved for short dwell times whereas they were increased when the dwell time was prolonged. No EGR was used so the soot levels were already very low in the cases of sinGle injections. The results indicated,however,no increase in soot as a result of splitting the injection in two parts. Both HC and CO emissions were found to increase with split injections.In order to investigate the effects of split injection on emission formation and engine performance, experiments were carried out using a heavy duty single cylinder diesel engine. Split injections with varied dwell time and start of injection were investigated and compared with single injection cases. In order to isolate the effect of the selected parameters, other variables were kept constant. In this investigation no EGR was used. The engine was equipped with a common rail injection system with a piezo-electric injector. To interpret the observed phenomena, engine CFD simulations using the KIVA-3V code were also made. The results show that reductions in NOx emissions and brake specific fuel consumption were achieved for short dwell times whereas they both were increased when the dwell time was prolonged. No EGR was used so the soot levels were already very low in the cases of single injections. The results indicated, however, no increase in soot as a result of splitting the injection in two parts. Both HC and CO emissions were found to increase with split injections. Copyright © 2006 SAE International

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

Performance and Emissions of a DME Diesel Engine - A Simulation Study

In order to investigate DME combustion in a heavy duty diesel engine, a three dimensional CFD study was performed. Following parameters were investigated; injection timing, amount of fuel injected, umbrella angle and EGR amount with respect to combustion efficiency and emissions formation. It can be concluded that a large amount of EGR effectively suppresses NO formation and that the low heating value of DME can be balanced by a larger amount of injected fuel without any penalties in combustion efficiency and CO emissions

Reducing pressure fluctuations at high loads by means of charge stratification in HCCI combustion with negative valve overlap

Not availabl

The effect to knock on the heat transfer in a spark-ignition engines : Cars temperature measurements in the thermal boundary layer combined with heat-flux measurements

The temperature in the thermal boundary layer close to the combustion chamber wall was measured under knocking and non-knocking conditions using dual-broadband rotational coherent anti-Stokes Raman Scattering (CARS). A horseshoe-shaped combustion extension was employed to get an optical access to the region near the combustion chamber wall. Time-resolved measurements of the cylinder pressure (at three different locations in the cylinder chamber) and the heat flux to the wall were conducted simultaneously with the CARS measurements. Knocking and non-knocking conditions were achieved using different mixtures of n-heptane and iso-octane. Results from this measurement series will be used further for comparison with modeling of heat transfer and chemical kinetics close to the cylinder wall

Numerical Evaluation of Direct Injection of Urea as NOx Reduction Method 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 desolved 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 is supposed to be used, the deoxidizing reactants could be delivered in a controlled amount directly into the flame plume zones, where NOx are forming. Numerical simulations for the Isotta Fraschini DI Diesel engine are 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

Heat release in the end-gas prior to knock in lean, rich and stochiometric mixtures with and without EGR

SI Engine knock is caused by autoignition in the unburnt part of the mixture (end-gas) ahead of the propagating flame. Autoignition of the end-gas occurs when the temperature and pressure exceeds a critical limit when comparatively slow reactions - releasing moderate amounts of heat - transform into ignition and rapid heat release. In this paper the difference in the heat released in the end-gas - by low temperature chemistry - between lean, rich, stochiometric, and stoichiometric mixtures diluted with cooled EGR was examined by measuring the temperature in the end-gas with Dual Broadband Rotational CARS. The measured temperature history was compared with an isentropic temperature calculated from the cylinder pressure trace. The experimentally obtained values for knock onset were compared with results from a two-zone thermodynamic model including detailed chemistry modelling of the end-gas reactions