Determination of Design Hole Area at the Cylindrical Throttle Channel Inlet

Abstract

In design and operation of the hydraulic drive a with throttle control it is necessary to know the relationship between the pressure drop in the throttle controller and the flow of the working fluid flowing through it. To define this relationship it is necessary to know the area of hole at the throttling channel inlet and the value of flow rate.

Experience shows that manufacturing process capabilities disable us to provide a completely circular hole at the inlet of a cylindrical throttle channel and exclude having a chamfer. In this case, it is impossible to use a direct method to measure the actual design value of the area obtained as a result of manufacturing the throttle channel. The paper proposes the indirect method to determine a design area. The method is based on the fact that the flow rates at the same Reynolds number, lying in the zone of self-similarity, with fluid flow through the cylindrical channel having a circular cross section in separated state are equal to the flow rate of a sharpedged hole in the thin wall.

In order to assess the correctness of the indirect method are experimentally studied throttle device models with cylindrical throttle channels of different geometric dimensions and models with a sharp-edged hole in the thin wall.

The experimental studies have found that for models with cylinderical throttle channels, design values of the inlet area received by indirect method lie between the values of the area determined by direct measurement of the outer and inner diameters of the chamfer. Graphs of the flow rate as a function of the Reynolds number obtained from the experimentally determined dependence of the flow on the available head and taking into account the value of the hole areas defined by an indirect method coincided for all models with the cylinderical throttle channels and for the model with a circular hole in a thin wall in the range of Reynolds numbers from 104 до 106 .

The assessment results allow us to draw a conclusion that the indirect method to determine the design area of the throttle channel inlet is correct and recommend this method for practical use.