Abstract
This paper describes the first part of the global work done by the authors aimed at finding the best settings for a numerical model for the calculations of axial uncooled turbines using RANS approach. The authors studied more than 80 papers published over the past 5 years in the examined field. Their analysis did not allow to identify unified recommendations for the creation of numerical models. The selection of model parameters is usually motivated by general considerations of numerical simulation, which follow from the method. In none of the papers the selection of parameters is correlated with the structure of the flow in the turbine. Many specific simulation issues were not covered at all. For the research, more than 1000 models of full-size axial turbines (including multistage turbines) and their elements were created. They differed in the number, size, parameters of the elements of finite volume meshes, in turbulence models, in the degree of simplification. The results were compared with the experimental data. As a result, the following was obtained: 1. A method for developing and optimizing the working process of turbines using numerical simulation based on the RANS approach is proposed. The search for the optimal turbine configuration is carried out using light computational models, which are based on the simplified channel geometry and the finite volume mesh. Their application makes it possible to reliably find the optimal turbine configuration 2.8 times faster. The characteristics of the selected variants are verified with the help of verification models that consider the real geometry of the channels and have a minimum error. 2. Recommendations are given on the selection of parameters for finite volume meshes and the selection of turbulence models for numerical models of the working process of axial turbines designed to perform optimization and verification calculations.
Highlights
The world market of mainline aircraft engines until 2033 is estimated at 7400 pieces with a total cost of $ 1028 billion [1]
Recommendations are given on the selection of parameters for finite volume meshes and the selection of turbulence models for numerical models of the working process of axial turbines designed to perform optimization and verification calculations
Analysis of 80 publications issued in ASME conference proceedings over the last 5 years related to the study and optimization of the working process of axial turbines showed that among all the parameters that are adjusted in the creation of numerical models, the authors pay the greatest attention to the parameters of the finite volume mesh and to the selected turbulence models that is not surprising, since these are the parameters, the selection of which is available to a typical engineer
Summary
௬ಷು ೌೣ ௬ಷು భ maximum cell aspect ratio of the finite volume mesh yFP1 –size of the element of the finite volume mesh closest to the endwall. YB2B1 - size of the element of the finite volume mesh closest to the blade surface. CIAM – Central Institute of Aviation Motors ζPR – profile losses λ – specific velocity β1 – inlet flow angle of the cascade, degree β2 – outlet flow angle of the cascade, degree ߪ୰ଶୣୱ(ߞோ) –residual dispersion F – F-ratio test qMSE – mean square error ܧܵܯݍ(ߞோ) ̢ mean relative square errors ζEXP mean – mean experimental value of profile losses S – calculation speed up ηPR – cascade efficiency ߨТ∗ - gas expansion ration in turbine αOUT – outlet flow angle of the turbine, degree ∗ܣТ - throughflow capacity of the turbine, mଷିܭ.ହିݏଵ n – rotational speed, rpm ܿௌ∗ - isentropic rate of gas expansion in a turbine, m/s Е – efficiency of parallelization of a computational task B2B – two-dimensional blade passage FV – finite volumes
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