# Approximated Compressor Map by empirical Coefficients - basic compressor in a moist air network (Aircraft Environmental Crontol System)

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David Reimert on 4 May 2021
Commented: David Reimert on 15 Jun 2021
In order to simulate a compressor in a moist air network I found the custom component of a basic compressor in the Aircraft Environmental Crontol System - Example provided by MathWorks.
You can open ssc_aircraft_ecs to see the compressor block with the parameters.
I have a compressor map of the compressor I want to simulate in the model. In the basic compressor block the compressor map is approximated by empirical coefficients that control the shape of the speed lines and scaled based on a known nominal operating condition.
The parameters are
• Coefficient for curve through the bend of the speed lines (default 1.5)
• Coefficient for spacing of speed lines (default 0.7)
• Coefficient for sharpness of the bend of the speed lines (default 0.08)
My question is: How to determine the 3 coefficients with the compressor map?
I couldn't find an answer to my probem. I hope you can help me.
Best regards
David
##### 1 CommentShowHide None
Yifeng Tang on 6 May 2021
Couple things to try:
1. Item 4 in this example allows you to plot the compressor map for the given coefficients. In the actual code, you can see the equations that are using these coefficients. This may allow you to use tools like curve fitting toolboxes to get these coefficients from your map.
2. set up a testing harness around the compressor, using controlled reservoirs. Perform a parameter estimation exercise (Documentation: https://www.mathworks.com/help/sldo/parameter-estimation.html). This requires Simulink Design Optimization. More general info on this topic: https://www.mathworks.com/discovery/parameter-estimation.html
If you don't have access to the toolboxes mentioned, you can always use the sample code from the demo and compare the compressor map manually (ouch)

Yifeng Tang on 14 Jun 2021
Couple things to try:
1. Item 4 in this example allows you to plot the compressor map for the given coefficients. In the actual code, you can see the equations that are using these coefficients. This may allow you to use tools like curve fitting toolboxes to get these coefficients from your map.
2. set up a testing harness around the compressor, using controlled reservoirs. Perform a parameter estimation exercise (Documentation: https://www.mathworks.com/help/sldo/parameter-estimation.html). This requires Simulink Design Optimization. More general info on this topic: https://www.mathworks.com/discovery/parameter-estimation.html
If you don't have access to the toolboxes mentioned, you can always use the sample code from the demo and compare the compressor map manually (ouch)
##### 1 CommentShowHide None
David Reimert on 15 Jun 2021
Than you!! I've chosen the Parameter Estimation. Powerful tool and easy to use.

R2020b

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