Thesis /

ROMDOC-THESIS-2017-1107

Contribuţii la studiul reţelelor de profile în regim subsonic şi supersonic cu aplicaţii la maşinile cu palete

Dinu, Maria-Ramona
2011-09-06

Abstract: Abstract The class of profiles that can be obtained using the conformal mapping transformation usually applied to linear cascade plates, in incompressible and stationary flow, is extended. Thus, the paper develops and validates the conformal mapping on an ellipse. Transformation allows to obtain analytical expressions for the complex potential. The paper presents comparisons with singularities method. The conformal mapping for cascade blades in incompressible flow is extended to cascade of large thickness profiles of given form. The closed analytical expressions for the complex potential of the velocity field are also maintained. To this aim the direct interpretation of the upstream velocity effects as flow singularities in the transformed planes is used. An row of blades attached, to the real one is also defined. To obtain the circle contour the Fast Fourier Transform in complex variable is applied, in combination with Joukowsky transform, to accelerate the convergence speed. Applications to determine the velocity and pressure distribution for turbine profiles are given. The effect of variation of the thermodynamic functions with temperature for the intensity of normal shock waves is important and cannot be neglected for an accurate calculation, as required, for example, in aerospace problems. Because the usual gases specific heat increases with temperature, the real temperature after the shock wave can be smaller with hundreds of Kelvin degrees at higher Mach numbers. The same large differences are in the stagnation temperatures. Big differences exist in the entropy variation leading to much larger pressure losses. The proposed method of calculation was able to preserve the analytical relations from the constant caloric capacities, in terms of new introduced equivalent Mach numbers. At the same time, the calculation is simplified, only one unknown equation having to be solved. Flows accompanied by normal and oblique shock considering the variation with temperature are studied. Applications and comparisons are presented for air in the Mach number interval (1,3; 12).The gas dissociation and/or ionization at very high temperature were, for the moment, neglected. The above model is applied to study supersonic compressor stages.

Keyword(s): Mecanica fluidelor -- Teză de doctorat ; Inginerie aerospaţială -- Teză de doctorat ; Aerodinamică -- Teză de doctorat
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