Experimental Study in a Cascade Row for Improving the Performance of a Partially Admitted Turbo-Expander

Soo-Yong Cho,Chong-Hyun Cho,Sang-Kyu Choi,Chae Rim

doi:10.3390/en81212385

Soo-Yong Cho, Chong-Hyun Cho + Show 2 more

Open Access

https://doi.org/10.3390/en81212385

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Abstract

Turbo-expanders are widely used as power generators in the field of energy conversion such as organic Rankine cycle (ORC) systems. When the available thermal energy is not sufficient to operate the turbo-expander in full admission, it is much better to operate in partial admission instead of stand-down. However, the performance of the turbo-expander greatly depends on the operating conditions. Among many operating conditions, the flow angle at the nozzle and solidity can be major factors affecting the performance of the expander. In order to investigate the optimal operation conditions, experiments were conducted in a linear cascade apparatus simulating the operation of turbo-expander in partial admission. Three different nozzle flow angles of 58°, 65°, and 72° were adopted, and the experiments were conducted with respective solidities of 1.25, 1.38, and 1.67 at each nozzle flow angle. The cross section of the nozzle was rectangular and the chord of the tested blade was 200 mm. The blades moved in a rotational direction, and the forces on the blades were measured with the surface pressure at steady state. The experimental results showed that the rotational force increased for a larger solidity or for a smaller nozzle flow angle.

Highlights

Turbo-expanders have been widely used to generate electricity in power plants and in the field of energy conversion to utilize renewable energy
In order to compare each performance for three different solidities and nozzle flow angles, the operating forces and surface pressures on a linear cascade blade were measured along the admission region
In a linear cascade simulating the operation of a turbo-expander working in a low partial admission rate, the force and surface pressure on a blade were measured with three different nozzle flow angles and solidities

Summary

Introduction

Turbo-expanders have been widely used to generate electricity in power plants and in the field of energy conversion to utilize renewable energy. A prediction model was developed for a single stage axial-type turbine working in partial admission through a circular-type nozzle channel [17] In reviewing these prediction models for partial admission, it is clear that they estimated the turbine performance accurately at the design point. Studies were conducted to investigate the effects of design variables on a partially admitted turbo-expander using a cascade apparatus [18,19,20] Those experimental results were limited to predicting the performance of a turbo-expander employing a circular-type nozzle. In order to compare each performance for three different solidities and nozzle flow angles, the operating forces and surface pressures on a linear cascade blade were measured along the admission region

Linear Cascade

Findings

Conclusions