DEVELOPMENT OF A PNEUMATIC-OPTICAL PROBE FOR FLOW FIELD AND WETNESS MEASUREMENT IN STEAM FLOWS

摘要

Normally wetness measurement in steam flows at LP turbines is divided into flow field measurement with pneumatic probes and wetness measurement with thermodynamical or optical probes. This procedure has several disadvantages. In this paper we describe the combination of a pneumatic and an optical probe for measurements in two phase flows. The idea is to measure thermodynamical and fluiddynamical properties of the flow simultaneously. The pneumatic part consists of a four-hole wedge probe and the optical part is a multiwavelength light extinction probe. Investigations about the behavior of the single components and the combined probe were carried out and experiments were performed in a water tunnel, a wind tunnel and a model steam turbine. Especially for the latter test facility the probe should be designed as small as possible, because there is no large space and, furthermore, in order to avoid changes in the flow field due to blockage effects. Therefore we realised two probes. A normal one for measurements at real steam turbine and a small one for measurements at a model steam turbine. The diameter of the probe stem is d = 18 mm and d = 10 mm, respectively.