| Aeroengine online washing is an effective means of restoring engine performance and extending online time.It has become one of the basic procedures for engine maintenance and is included in the Aircraft Maintenance Manual.At present,the simple washing equipment used by Chinese airlines has a complicated cleaning process and a long operating time.Under the condition of rapid growth of the fleet size,it has gradually failed to meet the requirements,so a new type of washing equipment has came into being.Since the reliability of aeroengine is highly correlated with the recovery of gas path performance after washing,and the previous research is based on the airline’s original washing equipment.Therefore,performing aeroengine online washing and reliability research under the conditions of new washing equipment has become an urgent issue to be solved.This paper first introduces definition,factors and common indicators of reliability basic theories.Combined with the characteristics of aeroengines,respectively describes the reliability analysis methods of historical fault data and performance degradation data.Then based on the historical washing interval of an airline’s CFM56-7 engine under the conditions of the new washing equipment and the original equipment,combined with the statistical methods such as hypothesis testing and parameter estimation,the washing interval prediction model based on the use reliability was established respectively.The maintenance time of the water washing effect of the two sets of equipment and the recommended washing interval are pointed out,and compared with the washing interval recommended by the manufacturer,the results show that the performance of the current two types of water washing equipment cannot meet the requirements of high reliability of the aeroengine under the recommended washing interval.Then,in order to optimize the cleaning effect of the new washing equipment,the CFM56-7 turbofan engine with a similar degree of pollution and service time of about 5 years are used as washing object,and a cleaning fluid configuration optimization experiment based on response surface design is carried out.It is concluded that when the water temperature is85℃,the water quality is deionized water,and the concentration of the cleaning agent is 6%,the EGTM recovers the maximum,reaching 10.013℃.Finally,a data preprocessing methodcombining box plot method and quadratic exponential smoothing method is proposed for the EGTM time series before and after washing.And based on the linear model for trend item extraction,a comparative study of performance degradation reliability was carried out.Through comprehensive comparison,the conclusion that the washing effect is better with the new washing equipment under the same situation is obtained.This paper takes the new washing equipment as the platform,based on the basic theory of reliability and analytical methods,and combines the knowledge of statistics,experimental design,time series and comparative analysis to conduct in-depth research on the reliability of aeroengine online washing under the condition of new washing equipment.This paper can provide reference for improving the water washing technology in China and carrying out scientific water washing plan. |
