Session: 8.3.2 - Pumping Machinery II

Paper Number: 155329

155329 - Parameter Study of a Classic Impeller Using Previous Method of Optimum Meridian Profile With Additional Design Parameters 

Abstract: 

The meridian profile design of impeller and guidevane is the first action of design procedure. Generally, it is executed referring to the conventional design parameter concerned with specific speed. According to the previous result calculated the efficiency of impeller and guidevane using diffusion loss coefficient, the meridian profile is related closely to blade-to-blade flow conditions. It is obviously the optimum meridian profile is decided by the optimum blade-to-blade flow conditions. That is, the calculation loss between the diffusion coefficient of blade-to-balde flow conditon and hub-tip cylindrical friction loss is executed for the various meridian profile impeller and guidevane. As the result, the best meridian profile is decided. In this study, the method of AJKFLUID2019-4645 is followed and the method, which can be applied to actually a lot of classic impeller and guidevane generally used, is descrived.

 The new three kinds of mixed flow angle and the curve condition parameter of impeller outlet profile are presented in this case study. As the result, arbitrary meridian profile can be expressed accurately by additional above four design parameters.

The relation between the change of design parameters and the efficiency is investigated through the search of design parameters from the meridian profile of the best efficiency in AJKFLUID2019-4645 to classic impeller. It can be understood which design parameter largely influences efficiency. Next, it is shown to be able to execute the optimization od the design parameter of a classical example impeller and to improve its efficiency.

Four design parameters added newly are explained more in detail. Up to now, impeller outlet line was a straight line. The outlet mixed flow angle was set to orthogonal in impeller outlet line. The mixed flow angle of hub outlet is equal to the mixed flow angle of tip outlet. The impeller tip inlet mixed flow angle was defined. The mixed flow angle of hub inlet was equal to the mixed flow angle of tip inlet. Therefore, it was difficult to express arbitrary meridian profile accurately. In this case study, it was possible to optimize the impeller even if the impeller outlet line is not orthogonal to the tip or hub flow line. If the mixed flow angle of hub outlet is not equal to that of tip outlet, it was possible to optimize the impeller. If four new design parameters are added, the amount of the calculation becomes 531441X3⁴ because the design parameter that has been used up to now is followed. The reason for this is that the design parameter with high efficiency of one design parameter is selected for three values of 'Present value', 'Large value' and 'Small value'. The amount of the calculation becomes 3¹²=531441 kinds of every step when the number of design parameters used in AJKFLUIDS2019-4645 is 12. Therefore, the calculation time has been shortened by assuming the impeller blade number and the guidevane blade number etc. to be a constant. As a result, it was shown that efficiency has been improved to classic original impeller.

Presenting Author: Takuji Tsugawa Independent Consultant

Presenting Author Biography: I was graduated Osaka University in 1982.
I am Consultant Engineer of Mechanical Engineering.