Development and Testing of Techniques for Oscillating Pressure Measurements Especially Suitable for Experimental Work in Turbomachinery

Abstract

Strong pressure oscillations of high frequencies and high amplitudes occur in the region of turbomachine rotors. The measurement of the average pressures resulting from these oscillations is one of the most important measuring problems in turbomachinery, because the pneumatic measuring systems usually used in such tests yield average pressures which normally do not agree with the true time-integrated values. This paper deals with an investigation aimed at the development of techniques, which permit the measurement of well-defined average values of oscillating pressures. Three different methods developed and tested at DFVLR are described. Two of them—a hydraulic and a mechanical one—are able to measure the true time-averaged pressures with an accuracy better than 0.5 percent of the acting pressure amplitude. The third procedure is based on an evaluation method by means of which the average pressures indicated by special pneumatic measuring systems can be correlated to the true time-weighted values. Experimental and computed results are presented showing a very good agreement.