【摘 要】
：
In internal combustion engines,exhaust gas recirculation(EGR)is a common means to reduce nitrogen oxide(NOx)emissions.In diesel engines EGR rates up to 50%are used to lower the combustion temperature
【机 构】
：
Institute of Engineering Thermodynamics(LTT),FAU Erlangen-Nuremberg,Germany;Erlangen Graduate School
【出 处】
：
13th International Conference on Liquid Atomization and Spra
论文部分内容阅读
In internal combustion engines,exhaust gas recirculation(EGR)is a common means to reduce nitrogen oxide(NOx)emissions.In diesel engines EGR rates up to 50%are used to lower the combustion temperature due to lower oxygen content of the ambient gas in the cylinder.In a permanently scavenged high temperature/high pressure injection and combustion vessel(1000 K,10 MPa)the self-ignition and combustion process of diesel under engine relevant conditions can be investigated using optical measurement techniques under constant and repeatable conditions so that isolated parameter influences on spray and combustion processes can be studied.The test bench can be scavenged either by air,nitrogen or any gas mixture.Thus the influence of different EGR rates on the spray,ignition and combustion process of diesel fuel can be examined.The measurements in the investigation were performed at EGR rates of 0,10,20,30 and 40 percent for different temperatures of the ambient gas.The visible integral flame signal in the nonpremixed diesel flame and the chemical luminescence signal of the OH radical(OH*)in premixed parts of the flame were recorded simultaneously.During the radical chain reactions of the self-ignition of hydrocarbons this OH radical occurs early in the reaction mechanism and significantly before the occurrence of visible soot luminosity.Thus it is an indicator for the ignition delay.As the measurements were performed time resolved in discrete steps the temporal occurrence of OH radical luminescence enables the numerical calculation of the ignition delay for diesel fuel under EGR influence.This analysis quantitatively shows the elongation of the ignition delay for rising EGR rates.Furthermore,a significant change of combustion propagation and reaction rate can be examined spatially and temporally resolved for the premixed and the non-premixed flame by analysis of the flame luminosity and derived numerical parameters.A potential to reduce soot by increased EGR rates is derived and explained by ignition delay,locally reduced reaction rates and therefore increased mixing times.
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