INTRODUCTION TO INTRODUCTION TO OFF DESIGN SIMULATIONSOFF DESIGN SIMULATIONS

GasTurb 12 – Tutorial 3

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Off-Design SimulationsOff-Design Simulations

Let us begin with a jet engine. Select the most simple engine

architecture, a Turbojet.

Let us begin with a jet engine. Select the most simple engine

architecture, a Turbojet.

A click on Standard Maps begins the off-design calculation.

A click on Standard Maps begins the off-design calculation.

Select as ScopePerformance and then click

Off Design

Select as ScopePerformance and then click

Off Design

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We Need Some Data…We Need Some Data…

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Off-Design Input Data PageOff-Design Input Data Page

After reading the file, the cycle design point is calculated. This

happens in the background.

The standard compressor and turbine maps are scaled in such a way that they fit to the cycle

design point.

After reading the file, the cycle design point is calculated. This

happens in the background.

The standard compressor and turbine maps are scaled in such a way that they fit to the cycle

design point.Now we calculate the cycle

design point as an off-design point

Now we calculate the cycle design point as an

off-design point

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Off-Design Point SummaryOff-Design Point Summary

The contents of this summary page is identical to that of the

cycle design point

The contents of this summary page is identical to that of the

cycle design point

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Operating Point DetailsOperating Point Details

This is the Standard High Pressure Compressor Map

file

This is the Standard High Pressure Compressor Map

file

This is the Standard High Pressure Turbine Map fileThis is the Standard High Pressure Turbine Map file

On this page those details of the operating point are presented that are not needed for a cycle

design calculation.

On this page those details of the operating point are presented that are not needed for a cycle

design calculation.

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Compressor MapCompressor Map

The circle marks the cycle design point,

the yellow square marks the off-design operating

point.

The circle marks the cycle design point,

the yellow square marks the off-design operating

point.

In this special case – because we have calculated the cycle design point in off-

design mode – the yellow square is inside the circle.

In this special case – because we have calculated the cycle design point in off-

design mode – the yellow square is inside the circle.

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Turbine MapTurbine Map

The circle marks the cycle design point,

the yellow square marks the off-design operating point.

The circle marks the cycle design point,

the yellow square marks the off-design operating point.

There are six different versions of a turbine map.

The y-axis can be Pressure Ratio or Corrected Work.

Here Turbine Pressure Ratio is shown over the

product of Corrected Flow and Corrected Speed.

There are six different versions of a turbine map.

The y-axis can be Pressure Ratio or Corrected Work.

Here Turbine Pressure Ratio is shown over the

product of Corrected Flow and Corrected Speed.

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Turbine MapTurbine Map

Here Turbine Pressure Ratio is shown over Corrected Speed.

The corrected flow is shown as contour lines in

% of the maximum corrected flow in the map

Here Turbine Pressure Ratio is shown over Corrected Speed.

The corrected flow is shown as contour lines in

% of the maximum corrected flow in the map

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Turbine MapTurbine Map

Here Turbine Pressure Ratio is shown with the

same axes as a compressor map: Turbine

Pressure Ratio over Corrected Mass Flow.

The disadvantage of this format is that all the speed

lines nearly collapse.

Here Turbine Pressure Ratio is shown with the

same axes as a compressor map: Turbine

Pressure Ratio over Corrected Mass Flow.

The disadvantage of this format is that all the speed

lines nearly collapse.

Thermodynamic StationsThermodynamic StationsC

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Here you get all the details at the thermodynamic stations.

The engine geometry - all the flow areas at all stations - is among the results of the cycle

design point calculation.

Here you get all the details at the thermodynamic stations.

The engine geometry - all the flow areas at all stations - is among the results of the cycle

design point calculation.

Off-Design Input DataOff-Design Input DataC

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Here you can choose whether Relative Spool Speed ZXN or

Burner Exit Temperature ZT4 is given.

Here you can choose whether Relative Spool Speed ZXN or

Burner Exit Temperature ZT4 is given.

Enter 2 to make Burner Exit Temperature an input and

use 1200 for it

Enter 2 to make Burner Exit Temperature an input and

use 1200 for it

Let us run a case with 1200 K Burner Exit Temperature.

Let us run a case with 1200 K Burner Exit Temperature.

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Off-Design ResultOff-Design Result

The solution is found by

iteration

The solution is found by

iteration

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Compressor MapCompressor Map

Compressor operating point for T4=1200K

Compressor operating point for T4=1200K

Cycle design point

Cycle design point

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Off-Design IterationOff-Design Iteration

These are the variables of the iteration. Betavalues

are auxiliary coordinates in component maps.

These are the variables of the iteration. Betavalues

are auxiliary coordinates in component maps.

These are the estimated values of the iteration variables. If the

iteration fails to converge, you can try with better estimates for the

variables.

These are the estimated values of the iteration variables. If the

iteration fails to converge, you can try with better estimates for the

variables.

Iteration targets are flow continuity between

components and power balances

Iteration targets are flow continuity between

components and power balances

Now let us calculate the complete sea level static

operating line.

Now let us calculate the complete sea level static

operating line.

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Off-Design InputOff-Design InputOperating LineOperating Line

Reset to 1 and enter for the HPC Spool Speed ZXN also 1Reset to 1 and enter for the

HPC Spool Speed ZXN also 1

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Operating Line InputOperating Line Input

The operating line commences with the single point which was calculated before the operating line window was

opened. A series of points with decreasing gas generator spool speed

will be calculated. The default step size of relative spool speed is 0.025.

The operating line commences with the single point which was calculated before the operating line window was

opened. A series of points with decreasing gas generator spool speed

will be calculated. The default step size of relative spool speed is 0.025.

Increase the Number of Points to 20, then run the case by clicking the

Operating Line button

Increase the Number of Points to 20, then run the case by clicking the

Operating Line button

AnswerNo

AnswerNo

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Compressor Operating LineCompressor Operating Line

Here the compressor

surges

Here the compressor

surges

We will employ a handling bleed to cure

that problem.

We will employ a handling bleed to cure

that problem.

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Off-Design InputOff-Design InputOperating LineOperating Line

Click Controls to show the controls button group.

Then click the Bleed button

Click Controls to show the controls button group.

Then click the Bleed button

Enter numbersin all 3 boxes

Enter numbersin all 3 boxes

Re-run the operating lineRe-run the

operating line

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Repeat the Operating Line CalcRepeat the Operating Line Calc

Answer this timeYes

Answer this timeYes

Switch Automatic Bleed “On”Switch Automatic Bleed “On”C

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Enter 1 for the second operating line, then

click Run

Enter 1 for the second operating line, then

click Run

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Compressor Operating LinesCompressor Operating LinesWith and Without BleedWith and Without Bleed

With bleed the surge problem does not exist.

With bleed the surge problem does not exist.

Let us have other views on the dataLet us have other views on the data

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The Default PlotThe Default Plot

With bleed the surge problem does not exist. However, with bleed the

fuel consumption is higher…

With bleed the surge problem does not exist. However, with bleed the

fuel consumption is higher…

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New PictureNew Picture

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New PictureNew Picture

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T4 = f(Corrected Spool Speed)T4 = f(Corrected Spool Speed)

With bleed the surge problem does not exist; however, the burner exit temperature is significantly higher

With bleed the surge problem does not exist; however, the burner exit temperature is significantly higher

This slide ends the Introduction to Off-Design Simulations

Tutorial

This slide ends the Introduction to Off-Design Simulations

Tutorial