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Physics of Combustion Noise Reduction with Multiple Injections in a DI Diesel Engine - A Computational Study

机译:DI柴油机中多次喷射的燃烧降噪物理 - 计算研究

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With the ability of modern high pressure diesel injectors to deliver accurate, closely coupled multiple pulse injections, it is possible to minimize engine combustion noise without negative effect on exhaust emissions. Literature shows that, splitting the cycle heat release into several parts helps to lower peak heat release rate and combustion noise. The charge cooling caused by fuel vaporization can be effectively used to influence ignition delay and achieve lower noise, emissions and fuel consumption. With the traditional pilot-main injection scheme, researchers have shown that, the injection dwell time between the pilot and main is primarily responsible for noise reduction. The current objective is to analytically explore the fundamental physics behind the experimentally observed noise reduction phenomena with multiple injections. This computational study was conducted at a key part-load operation (2000RPM and 5Bar BMEP) with five injection pulses. In agreement with experimental trends, computational results showed that as the dwell between the third injection pulse and the fourth (main) injection pulse is reduced, combustion noise decreased and, if the dwell is decreased beyond an optimum value, combustion noise started to increase. The heat of vaporization needed for the evaporation of fuel spray in the main (fourth) injection pulse, locally cools the environment and profoundly influences the ignition delay of fuel injected in the first three (smaller) injection pulses. This cooling affects the rate of pressure rise in the cylinder, which in turn affects the combustion noise.
机译:具有现代高压柴油喷射器能够提供精确的,紧密耦合多脉冲注射的能力,可以最大限度地减少发动机燃烧噪音而不会对废气排放产生负面影响。文献表明,将循环热释放分成几个部分有助于降低峰值热释放速率和燃烧噪声。由燃料蒸发引起的电荷冷却可以有效地用于影响点火延迟并实现较低的噪音,排放和燃料消耗。通过传统的飞行员主注射方案,研究人员表明,试点和主要之间的注入停留时间主要负责降噪。目前的目的是分析实验观察降噪现象背后的基本物理,具有多次注射。该计算研究是在具有五个注射脉冲的关键部分负载操作(2000rpm和5ber bmep)的过程中进行。在实验趋势方面,计算结果表明,由于停留第三喷射脉冲和第四(主要)喷射脉冲减小,燃烧噪声降低,如果停留量减少超过最佳值,则燃烧噪声开始增加。在主(第四)喷射脉冲中蒸发燃料喷射所需的蒸发热,局部地冷却环境,并深刻地影响喷射在前三(较小的)喷射脉冲中注入的燃料的点火延迟。该冷却影响圆柱体中的压力升高速率,这反过来影响燃烧噪声。

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