Abstract
Turbomachinery has been widely used in the energy systems as an energy conversion device, such as gas turbine and aero-engine. The losses in the turbomachinery, especially in the multi-stage conditions, restrict the energy conversion efficiency and corresponding fuel economy. Previous studies show that non-axisymmetric endwall could be used to decrease the losses in compressors, but the real effects in the rig tests are usually inconsistent with the numerical simulation. In this paper, a shroud profiled endwall optimization method with the strategy of local loss as the objective function is proposed, aiming at reducing the tip loss of an embedded stator under the operating point. The traditional total loss coefficient and four local loss functions are studied to investigate how the objective functions influence the optimization results. Three optimized endwall geometries are tested in the embedded test platform. It showed that the strategy of loss coefficient above 90% span as the objective function was best at decreasing the stator loss in the tip region as well as the whole span. Under this strategy, the loss above 90% span was suppressed by 48.17% and the loss of the whole span decreased 9.27%, which proved the PEW optimization design method with the strategy of local loss as the objective function is potential.
Highlights
Non-axisymmetric endwall is first used in the turbines to make the flow field of stator more uniform and reduce the secondary flow losses [1,2]
The was calculated by the surrogate model in one generation, and the optimum one in this generation surrogate model first selects a set of geometric parameters as one individual that could severely was chosen to conduct the CFD simulation, with the CFD responses adding to the database to further influence the response predicted by the model, followed by a CFD simulation to measure the error train the surrogate model, which sharply decreased the consuming time for each generation
A method for shroud profiled endwall (SPEW) optimization of an embedded stator with the strategy of local loss coefficient as the objective function is proposed and the optimization effects are experimentally confirmed in the multistage condition
Summary
Non-axisymmetric endwall is first used in the turbines to make the flow field of stator more uniform and reduce the secondary flow losses [1,2]. Profiled endwall (PEW) has been widely studied in the compressors and turbines, both numerically and experimentally [1,2,3,4,5,6,7,8,9,10], with its direct effect on the flow field near the endwall region and further influence on the main flow. Experimental study is crucial when applying PEW on the engineering practice as CFD simulation could hardly predict the precise flow fields in the multistage condition. Five optimization schemes are proposed with different objective functions and three of the optimization results are tested It shows that choosing the local loss coefficient from 90% to 100% span as the objective function is better than the traditional total loss coefficient of the whole blade height in reducing the loss of the stator. The mechanism of how the profiled endwall influence the flow field is discussed according to the test results
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