1. GasTurb 13 – Tutorial 4
Optimizing a Cycle
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2. For this tutorial we will use a Turbojet.
GasTurb 12 Main Window
For this tutorial we will use a Turbojet.
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3. Select the engine model
We Need Some Data
Select the engine model
Open the engine model
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4. First we run a single cycle
Input Data Page
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First we run a single cycle

5. Starting Point of the Optimization
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6. Optimization Task: Find the Compressor Pressure Ratio for Minimum SFC
A parametric study with Pressure Ratio as the only parameter yields…
The SFC minimum is at pressure ratio 65
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The optimization feature allows finding the SFC minimum without doing a parametric study.

7. Selecting Optimization
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Now we go for Optimize.

8. Optimization Input Window
The Min Value must be lower than the Start Value
The Max Value must be higher than the Start Value
First drag the Optimization Variable to the input grid.
Next enter boundaries for the variables.
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Finally define the Figure of Merit

9. Optimization Input Window
The Figure of Merit can be maximized or minimized. Of course SFC shall be minimized
Drag your Figure of Merit to the box.
Now run the optimization
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10. The Optimization Window
The upper boundary
(Max Value)
for the variable
The lower boundary
(Min Value)
for the variable
Click to run the optimization
Let us have a look at the result.
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11. SFC Optimum Copyright © GasTurb GmbH
This result is somewhat unrealistic for a turbojet - among other reasons because the turbine pressure ratio is almost 24.
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12. Repeating the Optimization
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13. Repeating the Optimization
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14. Introducing Constraints
The Min Value must be lower than the Start Value
The Max Value must be higher than the Start Value
We introduce as Constraint the Turbine Pressure Ratio.
We enter for the upper boundary (Max Value) 4. This is a reasonable limit for a single stage turbine.
The Min Value is of no relevance for this optimization problem.
Then we re-run the optimization.
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15. End of the Constrained Optimization
The value of the optimization variable is within the Min and Max Values
The value of the optimization constraint is equal to the Max Value
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16. Result of the Constrained Optimization
This introduction to optimization was very simple. The problem could have been solved also with a simple parametric study.
Next we go for a more complex task which would require many parametric studies for finding the optimal solution.
Applying numerical optimization leads quickly to the result.
Turbine Pressure Ratio is 4
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17. GasTurb 12 Main Window Copyright © GasTurb GmbH
We will consider a Geared Unmixed Flow Turbofan.
The file opening menu will appear automatically,
read the file
Demo_gtf.CYG
After reading the data, the design input window opens.
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18. First we run a single cycle
Input Data Page
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First we run a single cycle

19. Starting Point of the Optimization
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After closing this window click Optimization.
Then, hit the Optimize button.

20. Optimization Input Copyright © GasTurb GmbH
The Figure of Merit is again SFC
… and three Constraints.
There are five optimization variables…
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21. Optimization Status Copyright © GasTurb GmbH
Status at the end of the optimization
Status at the begining of the optimization
Let us have a look at the optimum
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22. Result of the Optimization
The SFC was previously 16.51,
Optimization has reduced it by 6.3%.
Net Thrust >= 31 kN
T45 <=1300K
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LPT Pressure Ratio <=12
The solution fulfills the Constraints

23. Optimization Input Copyright © GasTurb GmbH
Do all of these constraints really apply to Cruise conditions?
No !
the LPT Inlet Temperature T45 Limit must not be exceeded during a hot day Take-Off.
Next we will show how this can be taken into account.
Go back to the GasTurb Main Window.
When asked to restore the old data, chose “Yes”.
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We have optimized the cycle for minimum SFC at cruise conditions. However, …

24. GasTurb 12 Main Window Copyright © GasTurb GmbH Select Off Design…
…and Standard Maps
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25. Select the Mission Option
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26. In the Design Input Window click Optimization and Run.
Mission Input
Run the Single Point Mission and check if the off-design iteration converges.
Close the Mission Windows and go back to the GasTurb12 Main Window. Switch back to the Calculation Mode Design and select Performance.
In the Design Input Window click Optimization and Run.
Choose a Single Point Mission and enter the Take-Off operating conditions as well as the required thrust of 145kN
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27. Design and Off-Design Constraints
Click Constraints
Select “Case 1” to apply the T45 constraint to the off-design condition.
These dropdown lists are visible only if a mission is defined.
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28. After the Optimization Run
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29. The Cycle Design Point Copyright © GasTurb GmbH
The SFC was previously 16,51.
Single Point Optimization yielded 15,47.
but T45 at Hot Day Take-Off was 1351K.
With additional constraint for Off Design (T45 <= 1300K), SFC is reduced by 5.3%.
Net Thrust >= 31 kN
T45 is not constrained at the cycle design point
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LPT Pressure Ratio <=12

30. Hot Day Sea Level Take-Off
T45 <=1300K
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This slide ends the
Control System Optimization Tutorial