A Study On One-Dimensional Method For Combustion Efficiency Evaluation And Influence Factors Effect Analysis

Combustion efficiency is one of the important parameters to indicate a combustor's performance in scramjet research. Several methods have been developed to estimate combustion efficiency in the past 40 years of scramjet study.Among many methods, One-dimensional method is more practical and rapid in experimental researches to estimate how a combustor or scramjet works. And its results are comparatively reliable when it comes to a combustor under strong combustion regime with a relatively uniform flow (which occurs in the rearward part of a combustor). For purpose of simplicity and practical applications, some factors usually have to be ignored and several assumptions have to be imposed in the one-dimensional method, which limit the generality in applications, though many labs in the world have developed and used it. We aim to develop a one-dimensional method of our own to estimate combustion efficiency in short duration flows and hope the newly developed method has the possibility to be used under wider conditions with better results. To achieve this goal, we studied the influences of several factors experimentally and numerically on the preference of a given combustor and developed a more applicable one-dimensional method.This paper consists of five chapters. In the first chapter, a brief introduction is given of the research background of scramjet and its current situation both at home and abroad.In the second chapter, methods used in this paper to measure the combustor parameters and estimate its performance were introduced and equations for the one-dimensional method were derived and influences of several factors were analyzed. In this chapter are also discussed some definitions of combustion efficiency and a proper one is put forward to be used in the paper.In the third chapter, the facility, experimental procedures and measuring techniques used to get the experimental results and validate the one-dimensional method are introduced. After analyzing the experimental results, we conclude that the flow field of scramjet under strong combustion condition featured a uniform flow at the exit, and the one-dimensional method developed in this paper is applicable in this case.In the forth chapter, ways to get combustion efficiency and to treat the input data in the nearly developed one-dimensional method are introduced. The influence factors on combustion efficiency are studied, including the mean molecular weight, mean specific heat at constant pressure and friction coefficient. On the base of results, a method is recommended for determining the value of mean molecular weight, mean special heat and friction coefficient distributions, and the uncertainties brought by them are also discussed.The fifth chapter is conclusions, including the achievements and the innovative points.