Abstract
The latest generation of high-pressure common rail equipment now provides diesel engines possibility to apply as many as eight separate injection pulses within the engine cycle for reducing emissions and for smoothing combustion. With these complicated injection arrangements, optimizations of operating parameters for various driving conditions are considerably difficult, particularly when integrating fuel injection parameters with other operating parameters such as exhaust gas recirculation rate and boost pressure together for evaluating calibration results. Understanding the detailed effects of fuel injection parameters upon combustion characteristics and emission formation is therefore particularly critical. In this article, the results and discussion of experimental investigations on a high-speed direct injection light-duty diesel engine test bed are presented for evaluating and analyzing the effects of main adjustable parameters of the fuel injection system on all regulated emission gases and torque performance. Main injection timing, rail pressure, pilot amount, and particularly pilot timing have been examined. The results show that optimization of each of those adjustable parameters is beneficial for emission reduction and torque improvement under different operating conditions. By exploring the variation in the interval between the pilot injection and the main injection, it is found that the pressure wave in the common rail has a significant influence on the subsequent injection. This suggests that special attentions must be paid for adjusting pilot timing or any injection interval when multi-injection is used. With analyzing the fuel amount oscillation of the subsequent injections to pilot separation, it demonstrates that the frequency of regular oscillations of the actual fuel amount or the injection pulse width with the variation in pilot separation is always the same for a specified fuel injection system, regardless of engine speed, fuel amount, injection pulse, and injection pressure.
Highlights
IntroductionFor high-pressure common rail (HPCR) fuel injection, after piezo-injector and 2500 bar injection pressure, 3000 bar injection pressure is being developed by those main suppliers and will come to market in the several years for meeting the nextstage emission regulations.[1,2]
With the contributions of high-pressure common rail (HPCR) injection system, variable geometry turbocharger (VGT), exhaust gas recirculation (EGR), and diesel particulate filter (DPF) for improving drivability and emissions, high-speed direct injection (HSDI) diesel engines have shared about 50% in European passenger
The operating characteristics of the common rail fuel injection system of high-speed light-duty diesel engine have been explored on a 2.2-L four-cylinder four-valve turbocharged passenger car DI diesel engine
Summary
For HPCR fuel injection, after piezo-injector and 2500 bar injection pressure, 3000 bar injection pressure is being developed by those main suppliers and will come to market in the several years for meeting the nextstage emission regulations.[1,2]. Common rail fuel injection allows to adjust injection pressure, fuel injection amount, and injection timing very flexibly. It can use multiple injections for optimizing combustion and emissions.[3,4,5] Currently, it is possible to have up to eight injection pulses—two pilot, four main, and two post-injection pulses. The efficiency of the catalytic converter is increased as unburned hydrocarbon (HC) is destroyed by the hot exhaust
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