Therefore, in order to improve the performance of hydraulic servo valve, it is important to study the mathematical model and distribution of jet flow field.

Needle valve pressure better than other valves, sealing performance, it is generally used for small flow, high pressure gas or liquid sealing medium, also used in conjunction with the pressure gauge.

The experimental results show that the new valve functions to well in testing the rate of gas flow that it can be applied to the performance testing of ventilators.