Unburned Gas Temperatures in an Internal Combustion Engine. I:Cars Temperature Measurements

Abstract

Broadband,coherent anti-Stokes Raman scattering (CARS) measurements of unburned gas temperatures have been performed in an internal combustion engine.The engine is fueled with n-butane and air and is operated under both knocking and non-knocking conditons.Temperatures are determined by fitting calculated CARS spectra to experimentally obtained,cycle-averaged nitrogen CARS spectra.The accuracy of the fitted temperature depends on a number of factors,including the modeling of collisional narrowing and the response of the intensified diode array detector,the accuracy of nitrogen linewidths and nonresonant susceptibilities used in the CARS fitting code,and the use of the correct laser line shape convolution.The estimated accuracy of the CARS temperatures is 5-9 percent and is presently limited by long-term drift in the broadband dye laser frequency spectrum.The CARS temperatures are compared with the temperature predictions of a heat release model for the engine.The implications of the measurements for modeling the chemic al kinetics of autoignition are discussed.