Research on product value of wheel diameter and rotational speed - A new design parameter for micro radial turbines

The physical realizability is the primarily consideration in micro radial turbine design. The determination of realizability mainly depends on the physical size (wheel diameter) and operation condition (rotational speed). In the past design, the product value of wheel diameter (D) and rotational speed (N) was taken as design result, but this value would lead repeating works because it may not appropriate for the realizability of micro radial turbine. This paper takes DN value as a design parameter to help the micro radial turbine design directly. The analysis of matching relationship between stage velocity ratio and degree of reaction was studied firstly. The influence of matching effects was investigated secondly. Then the DN value was presented and the theoretical research for optimal value selection was conducted thirdly. Compared with the other design parameters, the DN value can reflect the effect of efficiency, wheel size, rotational speed and design working condition directly and the effect of wheel material, structure style, shafting and bearings type directly. So the DN value is a highly concentrated and useful parameter for micro radial turbines. Some aerodynamic and structure parameters of micro radial turbine will be facilitated and designed by using the method of this paper.