Research Papers: Gas Turbines: Cycle Innovations

Improved Multiple Point Nonlinear Genetic Algorithm Based Performance Adaptation Using Least Square Method

[+] Author and Article Information
Y.G. Li

M. F. Abdul Ghafir, L. Wang, R. Singh

School of Engineering, Cranfield  University, Cranfield, Bedford MK43 0AL, UK

K. Huang, X. Feng, W. Zhang

 China Aviation Powerplant Research Institute, Aviation Industry Corporation of China, Zhuzhou, Hunan Province, PC 412002, P.R. China

J. Eng. Gas Turbines Power 134(3), 031701 (Dec 30, 2011) (10 pages) doi:10.1115/1.4004395 History: Received April 14, 2011; Revised May 24, 2011; Published December 30, 2011; Online December 30, 2011

At off-design conditions, engine performance model prediction accuracy depends largely on its component characteristic maps. With the absence of actual characteristic maps, performance adaptation needs to be done for good imitations of actual engine performance. A nonlinear multiple point genetic algorithm based performance adaptation developed earlier by the authors using a set of nonlinear scaling factor functions has been proven capable of making accurate performance predictions over a wide range of operating conditions. However, the success depends on searching the right range of scaling factor coefficients heuristically, in order to obtain the optimum scaling factor functions. Such search ranges may be difficult to obtain and in many off-design adaption cases, it may be very time consuming due to the nature of the trial and error process. In this paper, an improvement on the present adaptation method is presented using a least square method where the search range can be selected deterministically. In the new method, off-design adaptation is applied to individual off-design point first to obtain individual off-design point scaling factors. Then plots of the scaling factors against the off-design conditions are generated. Using the least square method, the relationship between each scaling factor and the off-design operating condition is generated. The regression coefficients are then used to determine the search range of the scaling factor coefficients before multiple off-design points performance adaptation is finally applied. The developed adaptation approach has been applied to a model single-spool turboshaft engine and demonstrated a simpler and faster way of obtaining the optimal scaling factor coefficients compared with the original off-design adaptation method.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Scaling of compressor map

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Figure 2

A flow chart of the performance adaptation process [13]

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Figure 3

Increasing trend of number of attempts

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Figure 4

Fitted polynomial line for multiple OD points

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Figure 5

Flow chart of the least square GA searching method

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Figure 6

Model engine configuration

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Figure 7

Scaling factor plot for compressor ETA

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Figure 8

Scaling factor plot for compressor WAC

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Figure 9

Scaling factor plot for compressor PR

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Figure 10

Prediction errors for SP before and after adaptations

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Figure 11

Prediction errors for FF before and after adaptations

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Figure 12

Prediction errors for P3 before and after adaptations

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Figure 13

Prediction errors for P12 before and after adaptations using both heuristic and least square methods

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Figure 14

Prediction errors for SP before and after adaptations using both heuristic and least square methods

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Figure 15

Number of attempts against number of OD points included in adaptation




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