The Same Initial Condition of the Optimum Method for All Specifications

Abstract

In the previous study (AJK2015-09034 A meridian profile obtained by no restriction in optimum process), an optimum meridian profile of impeller and guidevane by no restriction was obtained. In case of no restriction, all the design parameters and specifications are variable optimum parameters. As the result, the combination of the best design parameters and specifications were selected. In optimum process, blade number, outlet impeller mid span diameter, rotational speed of impeller and specific speed were also variable optimum parameters. As the variable design parameters need to change gradually, the blade number considering as solidity is used as real number in optimum process. There are two kinds of object functions in previous case study. One object function is composed of efficiency and initiated suction specific speed. The ideal goal of efficiency is 100%. The goal of initiated suction specific speed is 1000. The best specific speed of best efficiency was 680 and 852. The other object function is composed of only efficiency. The best specific speed of best efficiency was 520 and 539. The unit of specific speed is composed of m, min−1 and m3/min. In this case study, the initial conditions of design parameters for all design specifications are born from the best one combination of optimum design parameters obtained by no restriction in the previous case study. In this method, the optimum profile for various specifications are obtained by the optimum profile of the best specific speed in condition of changing the specific speed little by little. In previous study, the suitable initial value of all design parameters for each design specifications was not able to obtain. In this case study, the two optimum meridian profiles of low and high specific speed (200 and 3000) was born from one same meridian profile obtained by no restriction in previous optimum process, that is, it become clear that all design parameters calculated by no restriction produces initial value of all design parameters for all specifications in case study of the two kind of specific speed 200 and 3000. If the ideal goal value of efficiency is 100% and the goal value of the initiated suction specific speed is 1000, the initiated suction specific speed looks like as restriction. If the ideal goal value of the initiated suction specific speed is very large value and the efficiency is not 100% but small value, the efficiency looks like as restriction. The object function contains the efficiency and suction specific speed. The coupling constant combined efficiency and suction specific speed is important constant for the object function. As the result of this case study, one of a meridian profile obtained by no restriction in optimum process was able to become the same initial condition of the optimum method for all specifications.