发动机故障方程的建立与故障因子的引入

Development of Engine Fault Equation and Introduction of Fault Factors

本文提出了在建立发动机故障方程时应当引入故障因子的概念。文中指出，根据原封不动地保留着部件正常特性方程（即不引入故障因子）的数学模型所得到的线性模型仅仅是小偏差方程而不是故障方程。这种小偏差方程不能适用于故障诊断，并且还会导致用较少测量参数可以诊断出较多的同时发生的独立故障的错误结论。文中给出了建立故障方程的正确方法，并以不可压流的管口出流问题为例加以说明，并且对个别相当有影响的文献在这一问题上的错误观点进行了详细的分析。

A concept that fault factors should be introduced into mathematical model during developing engine fault equation is proposed in the paper. It is indicated that the linear model obtained from the mathematical model with exact original normal characteristic equations of the components (i.e., without introducing fault factors) is only the equations of small changes other than the fault equctions. Such equations of small changes are not applicable to engine fault diagnosis, and would result in a mistaken conclusion that more independent malfunctions occurred simultaneously can be diagnosed with less measurements. The basic principle of developing fault equation is described and an example of imcompressible fluid flows through a nozzle is given to demonstrate the principle of introducing fault factors. A detailed analysis of the mistaken viewpoint on this problem in an influential literature is also made in the paper.