Research On The Fouling Mechanism And The Effect Of Fouling On Performance Of Axial Flow Compressor

Axial flow compressor is one of the important parts of gas turbine units. Because50%-60%power of unit is consumed by the axial flow compressor, the compressor performance directly affects the efficiency of the whole unit. In many failure modes in the compressor,70%-85%compressor performance degradation is caused by fouling. Therefore, it is very important to study the fouling mechanism. The effect of fouling on the performance of an axial compressor and the monitoring and control strategies of compressor fouling can not be ignored. It has very important practical significance for the safe, efficient and healthy operation of gas turbine. The main achievements in this paper are as follows:(1) Theoretical analysis and numerical simulation of particle transport mechanism and deposition process in compressor are implemented from the microscopic point of view. And then, the relation between the particle deposition mechanism and blade position is established. The fouling in pressure side is due to the inetia effect of larger particles, and the fouling in suction side is due to the turbulent diffusion caused by small particles. Then, the influence of particle size, particle volume concentration, temperature, the initial speed of entrance, rotation speed, surface roughness and humidity on deposit formation were studied.(2) The modelling methods of fouling behavior for a single stage axial flow compressor are analyzed. And then, the shortcoming in the last modelling methods is discussed. In this paper, a new method is presented by using the combining measuring technology applied in reverse engineering with a traditional CFD analysis method to obtain accurate geometrical model of fouled blade. The real state of fouled blade can be effectively characterized by this method. Therefore, it can accurately simulate the effect of fouling on compressor performance.(3) A new performance prediction method of multistage axial flow compressor is put forward which overcome the disadvantages of tradional method. The fouled multistage axial flow compressor is divided into two parts for which a reasonable computing method is respectively chosed. For the fouled stages, the performance is calculated by combining stage stacking method, similarity theory with linear progression model. On the other hand, the performance of non-fouled stages is computed by averaged infinitesimal stage method.(4) The optimizational scheme of compressor fouling monitoring is put forward which deal with the problems existed in monitoring method relyed on single parameter. In the intial operation, the judgement is based on the performance parameters. When they reduced to a certain extent of the performance, the blade profile parameters are monitored so as to accurately evaluate the fouling severity.(5) The compressor cleaning interval is analyzed in order to obtain the optimized mathematical model.