Performance Prediction on a Partially Admitted Small Axial-Type Turbine

Abstract

A performance prediction model is developed for axial-type turbines that operate at partial admission. Losses generated within the turbine are classified into windage loss, expansion loss and mixing loss. This developed loss model is compared with an experimental result when a turbine operates with a rectangular-type nozzle at a partial admission rate from 22% to 37%. The present predicted results show better agreement with the experimental results than with those predicted by other models, as the expansion loss in this model is developed more closely to the real flow situation. If a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. In this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model is found to be in good agreement with the experimental results. Thus, the developed model could be applied to predict the performance of axial-type turbines that operate at various partial admission rates or with different nozzle shapes.

Investigation of supersonic impulse turbines for application to geothermal binary power stations

“…The model is based upon fitted data between 12% to 100% admission rates However this model seemed to under predict the losses. This was reported by Cho (2006) et al in a paper on the performance prediction on partially admitted turbines. Similar findings were encountered in this study.…”

“…Fridh (2004) et al andCho (2006) et al also experimentally showed this relationship between optimum blade speed and admission rate. Roelke (1994) cites findings reported by Stenning (1953) which investigated the effects of partial admission on axial turbine performance across a range of admission rates for predicting sector losses.…”

A Study of Cycle Analysis and Turbine Design for Obtaining Small-Scaled Power from the Organic Rankine Cycle Using R245fa

“…The rotational speed of the rotor can be decided based on the maximum efficiency operating condition from the relationship of the spouting velocity ( j C ) at the nozzle and the circumferential velocity (U ). Figure 3 shows the velocity ratio which revealed the maximum efficiency operating conditions [11][12][13][14] when the turbine operated in partial admission. It shows the characteristics such that the optimum velocity ratio is reduced when the partial admission rate is decreased.…”

“…(11). Cho [12] Rohlik [13] Cho [14] Partial admissionrate,  In the axial-type turbine, the relative velocities at the inlet and exit are the same for the zero-reaction turbine. However, the radial-type turbine has smaller radius at the exit than that at the inlet.…”

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

“…A performance prediction model was developed for a turbine operating at supersonic flow with the working fluid R113 by selecting better models among known prediction models [16]. 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.…”