异辛烷燃烧过程的声场激励调控特性

Acoustic Field Excitation and Regulation Characteristics of Iso-Octane Combustion Process

从宏观与微观层面分析了超声波对异辛烷燃烧的调控作用机理,利用发动机台架试验验证了原机三维燃烧数值模拟模型,基于燃烧室内物理嵌入动网格声源面方法,实现将20 kHz振幅为300μm超声波成功馈入燃烧室.将有、无超声波馈入燃烧室的工作缸压差值作为超声辐射压力扰动,研究了超声场激励对异辛烷的着火延迟期、中间反应组分及敏感性的影响特性.通过对比分析超声馈入方案S_(1)~S_(3)及无超声馈入方案S_(0),结果表明:S_(1)~S_(3)方案均使燃烧相位得以提前,S_(2)和S_(3)中C_(3)H_(6)、IC_(4)H_(8)和C_(2)H_(4)的峰值摩尔分数分别提升42.1%、24.7%、27.5%和21.5%、9.6%、5.3%,且两者异辛烷燃尽时间均提前0.18 s.当量比为1且初始温度分别为1300 K和1700 K时,着火延迟期分别缩短31.8%和6.4%,且均促进了OH自由基的大量生成.

The regulation mechanism of ultrasound on iso-octane combustion was analyzed from the macro and micro levels.The three-dimensional computational fluid dynamics model of the original engine was calibrated using the bench test data.Based on the method of physically embedding the dynamic grid sound source surface in the combustion chamber,the ultrasonic with 20 kHz frequency and 300μm amplitude was successfully fed into the combustion chamber.Taking the difference between the cylinder pressure with and without ultrasonic wave feeding into the combustion chamber as the ultrasonic radiation pressure disturbance,the effects of ultrasonic field excitation on the ignition delay period,intermediate reaction components and sensitivity analysis of iso-octane were studied.By comparing and analyzing the simulation results of three ultrasonic-fed schemes S_(1)—S_(3)with no ultrasonic-fed scheme S_(0),the results show that the S_(1)—S_(3)schemes can advance the combustion phase,and the peak mole fractions of C_(3)H_(6),IC_(4)H_(8)and C_(2)H_(4)in S_(2)and S_(3)are increased by 42.1%,24.7%,27.5%and 21.5%,9.6%,5.3%,respectively and the iso-octane burnout time of both schemes are advanced by 0.18 s.When the equivalence ratio is 1 and the initial temperature is 1300 K and 1700 K,the ignition delay period is shortened by 31.8%and 6.4%,respectively and both promote to produce a large number of OH radicals.