Approximate theory for the flow through a cascade of cambered airfoils

turbomachinery, cascade theory

Kurosaka, Mitsuru ; Rannie, W. Duncan

University:California Institute of Technology

Department:Engineering and Applied Science

关键词: turbomachinery, cascade theory;   

Others  :  https://thesis.library.caltech.edu/8770/7/Kurosaka_m_1968.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

An approximate theory for steady irrotational flow through acascade of thin cambered airfoils is developed. Isolated thin airfoilshave only slight camber is most applications, and the well knownmethods that replace the source and vorticity distributions of thecurved camber line by similar distributions on the straight chord lineare adequate. In cascades, however, the camber is usually appreciable,and significant errors are introduced if the vorticity and sourcedistributions on the camber line are approximated by the same distributionon the chord line.

The calculation of the flow field becomes very clumsy inpractice if the vorticity and source distributions are not confined to astraight line. A new method is proposed and investigated; in thismethod, at each point on the camber line, the vorticity and sourcesare assumed to be distributed along a straight line tangent to the camberline at that point, and corrections are determined to account forthe deviation of the actual camber line from the tangent line. Hence,the basic calculation for the cambered airfoils is reduced to thesimpler calculation of the straight line airfoils, with the equivalentstraight line airfoils changing from point to point.

The results of the approximate method are compared withnumerical solutions for cambers as high as 25 per cent of the chord.The leaving angles of flow are predicted quite well, even at this highvalue of the camber. The present method also gives the functionalrelationship between the exit angle and the other parameters such asairfoil shape and cascade geometry.