Dissertation > Industrial Technology > Machinery and Instrument Industry > Gas compression and transportation machinery > Compressors, compressor

Researches of Loss Mechanisms and Simulation Theory for High-loaded Helium Compressor

Author ChenHang
Tutor ZhengQun
School Harbin Engineering University
Course Power Machinery and Engineering
Keywords helium compressor high-loaded boundary layer similitude theory separationstructure
Type Master's thesis
Year 2013
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As its good inherent safety and economy, high temperature gas-cooled reactor (HTGR)has been one of the most promising fourth generation of advanced nuclear energy systemtechnologies. The stable and efficient work of the helium compressor has importantsignificance for the HTGR. View from the published literatures about the HTGR, only veryfew parts refer to the helium compressor aerodynamic design. Despite the flow conditions ofthe air compressor cascade have made certain achievements, as the quite difference of heliumand air in physical properties, the helium compression mechanism has far way to go,especially the boundary layer flow separation and their characteristics for high-loaded heliumcompressor.In this paper, the two-dimensional plane cascade of the high-loaded helium compressorare taken as the research, its flow characteristics are simulated numerically based on the γ-Reθtransition model under different inlet incidence angles, Reynolds numbers and Mach numbers,combining with the boundary layer calculation procedures, how the flow in the boundarylayer develops with the changing inlet conditions are researched, the flow characteristics andthe loss mechanism of the helium compressor are analyzed; The flow conditions of differentloads and characteristics helium compressor cascades are discussed. The results show that forthe high-loaded helium compressor, with the increasing of the incidence angle and the Machnumber also with the decreasing of the Reynolds number, the location of suction surfacetransition point moves ahead, and the transition process intensified, which makes thethickness of the suction surface boundary layer increases, resulting in the total pressure lossincreases. On the basis of similitude theory study, aerodynamic performances of air andhelium compressors are simulated numerically; flow differences of helium and air under threedifferent loadings are analyzed. The research result shows that with the loading increase, therole of the working fluid viscosity term enhances, the flow difference between the helium andair cascade are more visible. And this paper gives the similitude theory of the differentworking fluid from the theoretical aspects. research result indicates that for the differentworking fluid, as the Mach number increases, the similarities deviation gradually increasesand similarities deviation using the Mach number as a generation of modeling is greater thanthat of the Euler number. At last, the vortex and separation structures of the high-loaded helium compressorrectangular cascade are analyzed. And in this paper, it is pointed out that the endwallboundary layer flows which have different distance from the cascades surface have differentflow momentum, therefore exist different flow characteristics, the research results can furtherdeepen the understanding of fluid motion and development in the high-loaded heliumcompressor; Concerning the conditions of bad flow and great loss at the endwall, this paperanalysis the flow of the bowed blades with different bowed angles and bowed heights. Theresearch result shows that the proper combination of the bowed angle and bowed height canreduce the lower energy accumulation at the endwall, thus the separation shape are moresimpler and the separation area decreases.The results show that with the increase of the cascade loading and incidence angle, theseparation morphology of the high-loaded helium compressor cascade transforms from theopen to the closed separation morphology, proper combination of the bowed angle and bowedheight can reduce the lower energy accumulation in the endwall of high-loaded heliumcompressor, effectively improve the flow conditions there, thus the separation shape are moresimpler and the separation area decreases.

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