Analysis Of Critical Problems In The Design Of Low Pressure Stage Of High-Pressure Centrifugal Compressor With Large Flow Rate

The centrifugal compressors play an important role in every field of the national economy, such as aerospace, metallurgy industry, petroleum industry, chemical industry and power plants. As driven machines, the centrifugal compressors consume the power in order to produce the high pressure of working air. In recent years, a big new challenge to the design and research of the domestic compressors with large capacity is posed, especially in the megaton ethylene project and large air separation unit. The study shows that it is very important to enhance the whole design levels of centrifugal compressors with large quantities by expanding the scope of working condition, raising the operating security of sets, increasing the flow efficiency, improving the flow structure, reducing energy loss, and further studying on the internal flow of the centrifugal compressor. These achievements will lead to a realistic and historical significance on the development of our major equipment manufacturing and energy conservation.According to the pneumatic and structure characteristics of the large flow rate centrifugal compressor, such as high hub-tip ratio of the impeller, big relative width ratio between the inlet and outlet of the impeller, high Mach number, small relative axial span and worse structure rigid of the impeller, the correlated investigation is completed in this paper. To begin with, the analysis on the damage of the impeller inlet element in the centrifugal compressor low pressure casing is completed by numerically researching the inner steady flow field across the impeller passages with the commercial software, NUMECA. The investigation includes the performance account of the whole low pressure casing and the reliability certification of physical and mathematical model of the numerical simulation. The main reasons of the accident are revealed through analyzing the relationship between the inner flow field and the impeller structure under the real operating condition. Afterwards, the unsteady flow numerical simulation for the first stage in the low pressure casing is completed in order to find out the extent to which the flow distortion contributing to the impeller damage. As a result, the key point of designing the centrifugal compressor with a large flow rate and high pressure ratio and the accident reasons are further stated.Finally, several improved solutions are proposed based on the steady and unsteady flow numerical investigation. After comparison with the original design, an advanced scheme is achieved which has provided the technical support in the compressor design. Now the compressor is normally operating.