Sensitivity of combustion noise and NOx and soot emissions to pilot injection in PCCI Diesel engines (original) (raw)
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Suitability analysis of advanced diesel combustion concepts for emissions and noise control
Energy, 2011
During the last years, the preservation of the atmospheric environment has played an increasingly important role in society. The Diesel engine can be considered an environmentally friendly engine because of its low consumption and the subsequent carbon dioxide (CO 2 ) emissions reduction. However, in the near future it will face strong restrictive emission standards, which demand that the current nitrogen oxides (NO x ) and soot emissions are halved. To comply with these restrictions new combustion concepts are emerging, such as PCCI (premixed charge compression ignition), in which the fuel burns in premixed conditions. Combustion noise is thus deteriorated and consequently end-users could be reluctant to drive vehicles powered with Diesel engines and their potential for environment preservation could be missed. In this paper, Diesel combustion is addressed through the analysis of performance, emissions and combustion noise in order to evaluate the suitability of PCCI engines for automotive applications. The results show that PCCI combustion offers great possibilities to fulfill future emission restrictions, but the engine noise is strongly deteriorated. The great sensitivity of users to this factor requires vehicle manufacturers to focus their efforts on the optimization of passive solutions for implementing the PCCI concept in passenger car and light-duty engines, even with the subsequent increase in the cost of vehicle. This aspect is less restrictive in heavy-duty engines, since the great benefits in emissions reduction compensate the deterioration of engine noise.
International Journal of Automotive Technology
An experimental investigation has been carried out to highlight the effects of different injection strategies on the performance and emissions of a low compression ratio Euro 5 diesel engine operated with high EGR rates. Rate-shaped main injections, achieved with piezoelectric and solenoid injectors by means of boot and injection fusion, respectively, as well as optimized multiple injection patterns have been compared. The results of the comparisons, performed with reference to a state-of-the-art double pilot-Main (pM) strategy, are presented in terms of engine-out exhaust emissions, combustion noise (CN) and fuel consumption. Rate-shaped main injections, when included in delayed multiple injection patterns, have shown a minor influence on reducing NOx, while a slight deterioration in soot has been found. Both a double pilot and a boot injection schedule have been able to reduce CN at low loads. A higher reduction in CN has been obtained with an injection fusion event. Finally, DoE optimized triple and quadruple injection strategies have led to improved soot-NOx trade-offs, with respect to the pM calibration. In fact, splitting the injection helps to entrain air inside the fuel plumes, thus creating locally leaner mixture (less prone to forming soot) and allowing increasing the EGR rates (reducing NOx formation).
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
In conventional diesel engines (DEs), the auto-ignition and decomposition reactions are considerably dependent on the disintegration of fuel spray and the fuel-air mixing quality. While mixed, localized fuel-rich areas in the combustion chamber also strongly affected the results of the combustion period as well as the emission formation of particulate matters (PM) and nitrogen oxides (NOx). Due to this above-mentioned reason, the combustion of diesel fuel acts as a toxic emission resource released into the environment. It is thus necessary to question that how to use this type of engine with minimizing emissions of PM and NOx without affecting significantly the thermal efficiency of engine. Involving with the use of premixed charge compression ignition (PCCI) mode is considered as an advanced combustion mode for the strategy of NOx and PM emission reduction. In this article, the combination of fuel injection under high pressure applied to PCCI combustion mode was assessed on the basis of the emission characteristics of NOx and PM. The changing trends of NOx and PM emissions were thoroughly analyzed to have a comprehensive overview on the effects of fuel injection pressure (IP) on controlling emissions of NOx and PM when DEs were operated under PCCI combustion conditions. In closing, it is worth mentioning that the increase in fuel IP was demonstrated to improve the engine performance, while the emission control based on PCCI combustion strategy was found to bring several benefits for the control and management of combustion process under lower temperatures compared to conventional DE.
SAE Technical Paper Series, 2007
Homogeneous Charge Compression Ignition (HCCI) combustion is a combustion concept which offers simultaneous reductions in both NO x and soot emissions from internal combustion engines. In light of increasingly stringent diesel emissions limits, research efforts have been invested into HCCI combustion as an alternative to conventional diesel combustion. This paper reviews the implementation of HCCI combustion in direct injection diesel engines using early, multiple and late injection strategies. Governing factors in HCCI operations such as injector characteristics, injection pressure, piston bowl geometry, compression ratio, intake charge temperature, exhaust gas recirculation (EGR) and supercharging or turbocharging are discussed in this review. The effects of design and operating parameters on HCCI diesel emissions, particularly NO x and soot, are also investigated. For each of these parameters, the theories are discussed in conjunction with comparative evaluation of studies reported in the specialised literature.
International Journal of Engine Research, 2019
From the different power plants, the compression ignition diesel engines are considered the best alternative to be used in the transport sector due to its high efficiency. However, the current emission standards impose drastic reductions for the main pollutants, that is, NO x and soot, emitted by this type of engines. To accomplish with these restrictions, alternative combustion concepts as the premixed charge compression ignition are being investigated nowadays. The objective of this work is to evaluate the impact of different fuel injection strategies on the combustion performance and engine-out emissions of the premixed charge compression ignition combustion regime. For that, experimental measurements were carried out in a single-cylinder medium-duty compression ignition diesel engine at low-load operation. Different engine parameters as the injection pattern timing, main injection timing and main injection fuel quantity were sweep. The best injection strategy was determined by m...
Thermal Science, 2015
The use of diesel engines for vehicle has been increasing recently due to its higher thermal efficiency and lower CO2 emission level. However, in the case of diesel engine, NOx increases in a high temperature combustion region and particulate matter is generated in a fuel rich region. Therefore, the technique of PCCI (premixed charge compression ignition) is often studied to get the peak combustion temperature down and to make a better air-fuel mixing. However it also has got a limited operating range and lower engine power produced by the wall wetting and the difficulty of the ignition timing control. In this research, the effect of injection strategies on the injected fuel behavior, combustion and emission characteristics in a PCCI engine were investigated to find out the optimal conditions for fuel injection, and then ethanol blended diesel fuel was used to control the ignition timing. As a result, the combustion pressures and ROHR (rate of heat release) of the blended fuel becam...
2010
Homogeneous Charge Compression Ignition (HCCI) combustion is a combustion concept which offers simultaneous reductions in both NOx and soot emissions from internal combustion engines. In light of increasingly stringent diesel emissions limits, research efforts have been invested into HCCI combustion as an alternative to conventional diesel combustion. This paper reviews the implementation of HCCI combustion in direct injection diesel engines using early, multiple and late injection strategies. Governing factors in HCCI operations such as injector characteristics, injection pressure, piston bowl geometry, compression ratio, intake charge temperature, exhaust gas recirculation (EGR) and supercharging or turbocharging are discussed in this review. The effects of design and operating parameters on HCCI diesel emissions, particularly NOx and soot, are also investigated. For each of these parameters, the theories are discussed in conjunction with comparative evaluation of studies reported in the specialised literature.
2016
In this work a computational model of a single-cylinder optical research engine is used to study the effects of different pilot injection strategies on combustion noise and soot emissions in a lightduty optical diesel engine. The engine is equipped with an optical piston with a conventional re-entrant bowl, which retains all details of the corresponding metal piston. The model is validated against measurements of combusting and non-combusting high-pressure diesel sprays in the Engine Combustion Network constant-volume chamber in terms of jet structure, ignition delay, lift-off length and soot volume fraction distributions, for chamber temperatures of 750 to 1200 K and O2 concentrations of 15% to 21%. Mixture formation in the engine is validated against in-cylinder PLIF measurements from a single injection pulse for a low-load condition, and from a pilot injection. A pilot injection sweep is performed for a moderate load operating condition with a single-pulse, nearTDC injection stra...
International Journal of Engine Research, 2005
Homogeneous charge compression ignition (HCCI) combustion is an alternative to current engine combustion systems and is used as a method to reduce emissions. It has the potential nearly to eliminate engine-out NOx emissions while producing diesel-like engine efficiencies, when a premixture of gas-phase fuel and air is burned spontaneously and entirely by an autoignition process. However, when direct injection is used for diesel fuel mixture preparation in engines, the complex in-cylinder flow field and limited mixing times may result in inhomogeneity of the charge. Thus, in order to minimize non-uniformity of the charge, early injection of the fuel is desirable. However, when fuel is injected during the intake or early compression stroke, the use of high-pressure injection is limited by the relatively low in-cylinder gas pressure because of spray impingement on the cylinder walls. Thus, it is also of interest to consider low-pressure injectors as an alternative. In the present paper...
International Journal of Vehicle Design, 2012
Homogenous charge compression ignition (HCCI) cases are compared for improvements on the combustion chamber design of the engine to achieve near zero particulate matter (PM) and NOx emissions. Therefore combustion simulations of the engine have been performed to fi nd out emission generation in the cylinder. The interaction of air motion with high-pressure fuel spray has also been analyzed. Finally, a comparison has been made considering the performance of the engine for various confi gurations such as compression ratio, injection timing, and cone angle. The results are widely in agreement qualitatively with the previous similar experimental and computational studies in the literature.