Study of wet-steam flow in the last stage of the LPC of an experimental steam turbine

Abstract

The system for measuring the fractional composition of wet-steam flow in the last stage of the LPC of an experimental steam turbine is presented. Wet-steam flow is a superposition of two fractions: primary moisture (formed by steam condensation during steam expansion in the flow path) and secondary moisture (formed by descending and crushing of water films discharged from the surface of turbine guides and rotor blades in the process of surface condensation). Determination of process moisture parameters (droplet size distribution and volume concentration) is based on measurement of optical transparency of the wet-steam flow. Registration of sizes and velocity of secondary droplets is based on pulse photo registration of the flow. The measuring complex consists of two types of optical probes (for registration of primary and secondary moisture parameters), units of measuring equipment, control computers, software and auxiliary systems. Operation of the complex is controlled remotely from a control panel. The presented system has been used for more than 20 years at the model turbine stand of JSC "NPO CKTI". The present work is devoted to measurements on experimental turbine ETPN-5 of JSC "Power Machines". Probes were installed before and after the last stage to register the parameters of primary moisture, and a probe measuring the parameters of secondary moisture was installed in the rim clearance. Experimental data on the distribution of the droplet size and wetness of the primary moisture along the height of the channel before and after the last stage are obtained. The distributions of erosion-hazardous droplets by size, velocity and direction of movement in the rim clearance are presented.