Milan Banjac

Secondary Flows, Endwall Effects and Stall Detection in Axial Compressor Design

This paper describes a methodology and a fully tested and calibrated mathematical model for the treatment of endwall effects in axial compressor aerodynamic calculations. Additional losses and deviations caused by the clearance and secondary flows are analyzed. These effects are coupled with endwall boundary layer losses (EWBL) and blockage development. Stall/surge detection is included, and mutual interaction of different loss mechanisms is considered. Individual mathematical correlations for different effects have been created or adopted from earlier papers with the aim of forming one integral model that is completely described in this paper. Separate mathematical correlations and calibration measures are discussed in detail in the first part of the paper. The developed overall model is suitable for application in two-dimensional (2D) or mean-line compressor flow calculations. During the development, it was tested, calibrated, and validated using throughflow calculations comparing numerical results with experimental data for a large number of test cases. These test cases include compressors with very different configurations and operating ranges. The data on the compressors were taken from the open literature or obtained from industrial partners.

Development and validation of a new universal through flow method for axial compressors

Abstract This article describes the development of a new through flow method for the analysis of axial multi-stage compressors. The method is based on a stream function approach and a finite-element solution procedure. It includes a high-fidelity loss and deviation model with improved correlations and end-wall boundary layer calculation. A radial distribution model of losses and a new spanwise mixing model are applied to simulate three-dimensional flow effects. The calibration of the models is made by calculating a number of test cases with different configurations with the aim of achieving high accuracy and optimum robustness for each of the test cases considered. The code was applied to flow analysis and performance prediction of a newly developed gas turbine compressor. Comparison of the predicted results and measured test data for the overall compressor performance and a number of parameters under different operating conditions showed good agreement. The results of the validation confirm that this method based on cali-brated correlations can be applied as a reliable tool for flow analysis and parameter variation during the design phase for a wide range of compressor configurations.

Development and Validation of a New Universal Through Flow Method for Axial Compressors

This paper describes the development of a new through flow method for the analysis of axial multistage compressors. The method is based on a stream function approach and a finite element solution procedure. It includes a high-fidelity loss and deviation model with improved correlations and endwall boundary layer calculation. A radial distribution model of losses and a new spanwise mixing model are applied to simulate 3D flow effects. The calibration of the models is made by calculation a number of test cases with different configurations with the aim of achieving high accuracy and optimum robustness for each of the test cases considered. The code was applied to flow analysis and performance prediction of a newly developed gas turbine compressor. Comparison of the predicted results and measured test data for the overall compressor performance and a number of parameters under different operating conditions showed good agreement. The results of the validation confirm that this method based on calibrated correlations can be applied as a reliable tool for flow analysis and parameter variation during the design phase for a wide range of compressor configurations.Copyright

A Simple Model for Thermodynamic Properties of Air and Combustion Gases for Educational Purposes

A new, simple model for the thermodynamic properties of dry air and combustion gases is presented. The model has been developed mainly for educational purposes with the focus on gas turbine cycle calculations included in university courses. The equations used are short and easy to include in a student computer program. This ideal gas model is based on well-known correlations from the open literature and each equation is an approximated fit to an appropriate expression from the original reference. In the new concept, each relation is expressed using a simple algebraic formulation that has an explicit inverse function. Therefore, the numerical result of an inverse function can be obtained directly, without the involvement of any iterative procedure. This simplifies the programming of auxiliary subroutines for thermodynamic properties. It becomes an easy task and the use of complicated models, in basic university courses, is avoided. Long and complex subroutines which are treated as “black boxes” are now excluded from the code, and a program for thermodynamic cycle calculation is then completely written by a student, starting from the very beginning.Copyright