Health Monitoring of an Auxiliary Power Unit Using a Classification Tree
The objective of this work is to present a method to monitor the health of Auxiliary Power Units (APU) using a Dynamic Computational Model, Gas Path Analysis and Classification and Regression Trees (CART). The main data used to train the CART consists of measurements of the exhaust gas temperature, the bleed pressure and the fuel flow. The proposed method was tested using actual APU data collected from a prototype aircraft. The method succeeded in classifying several relevant fault conditions. The few misclassification errors were found to be due to the insufficiency of the information content of the measurement data. *
Aircraft APU failure rate prediction based on improved Weibull-based GRP
Auxiliary Power Unit (APU) is an essential component of civil aircraft. In order to meet demands for aircraft APU maintenance, failure rate of aircraft APU should be predicted. Since aircraft APU is a repairable system, its performance degradation can be considered as a Generalized Renewal Process (GRP). Therefore, aircraft APU failure rate prediction can be implemented by utilizing Weibull-based GRP. However, Aircraft APU maintenance effect which is required in Weibull-based GRP is difficult to quantify. In order to solve this problem, an improved Weibull-based Generalized Renewal Process (IWGRP) model is proposed in this work. To be specific, utilizing some key test parameters after repairs, aircraft APU maintenance effect is estimated. Based on aircraft APU maintenance effect, conditional failure rate and hazard rate of aircraft APU can be obtained. Then, conditional failure rate and hazard rate are utilized to predict aircraft APU failure rate. Finally, the performance of IWGRP is validated by real data from China Southern Airlines (CSA). Experiment results demonstrate that IWGRP is suitable for aircraft APU failure rate prediction.
A Low Cost, On-Site Performance Monitoring System
A simple thermodynamic analysis for on-site performance monitoring of shaft power gas turbines is described. The method is simple, requires minimal extra instrumentation, yet permits the operator to determine the critical cycle parameters of turbine inlet temperature and airflow. Computing requirements can be handled by a programmable calculator at minimum cost. Experimental verification of the system showed very good agreement with engine tests.Copyright © 1979 by ASME