Introduction to Off Design Simulations GasTurb 13 – Tutorial 3 Introduction to Off Design Simulations Copyright © GasTurb GmbH

Off-Design Simulations Let us begin with a jet engine. Select the most simple engine architecture, a Turbojet. Select as Scope Performance and then click Off Design A click on Standard Maps begins the off-design calculation. Copyright © GasTurb GmbH

We Need Some Data… Copyright © GasTurb GmbH

Off-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. Now we calculate the cycle design point as an off-design point Copyright © GasTurb GmbH

Off-Design Point Summary Copyright © GasTurb GmbH The contents of this summary page is identical to that of the cycle design point

Operating Point Details This is the Standard High Pressure Compressor Map file Copyright © GasTurb GmbH On this page those details of the operating point are presented that are not needed for a cycle design calculation. This is the Standard High Pressure Turbine Map file

Compressor Map Copyright © GasTurb GmbH 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. Copyright © GasTurb GmbH

Turbine Map Copyright © GasTurb GmbH 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. Copyright © GasTurb GmbH

Here Turbine Pressure Ratio is shown over Corrected Speed. Turbine 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 Copyright © GasTurb GmbH

Turbine Map Copyright © GasTurb GmbH 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. Copyright © GasTurb GmbH

Thermodynamic Stations 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. Copyright © GasTurb GmbH

Off-Design Input Data Copyright © GasTurb GmbH 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 Let us run a case with 1200 K Burner Exit Temperature. Copyright © GasTurb GmbH

The solution is found by iteration Off-Design Result The solution is found by iteration Copyright © GasTurb GmbH

Compressor operating point for T4=1200K Compressor Map Cycle design point Compressor operating point for T4=1200K Copyright © GasTurb GmbH

Now let us calculate the complete sea level static operating line. Off-Design Iteration 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 variables of the iteration. Betavalues are auxiliary coordinates in component maps. Iteration targets are flow continuity between components and power balances Now let us calculate the complete sea level static operating line. Copyright © GasTurb GmbH

Off-Design Input Operating Line Reset to 1 and enter for the HPC Spool Speed ZXN also 1 Copyright © GasTurb GmbH

Operating Line Input Copyright © GasTurb GmbH Increase the Number of Points to 20, then run the case by clicking the Operating Line button 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. Answer No Copyright © GasTurb GmbH

Compressor Operating Line We will employ a handling bleed to cure that problem. Here the compressor surges Copyright © GasTurb GmbH

Off-Design Input Operating Line Re-run the operating line Enter numbers in all 3 boxes Click Controls to show the controls button group. Then click the Bleed button Copyright © GasTurb GmbH

Repeat the Operating Line Calc Answer this time Yes Copyright © GasTurb GmbH

Switch Automatic Bleed “On” Enter 1 for the second operating line, then click Run Copyright © GasTurb GmbH

Compressor Operating Lines With and Without Bleed Let us have other views on the data Copyright © GasTurb GmbH With bleed the surge problem does not exist.

The Default Plot Copyright © GasTurb GmbH With bleed the surge problem does not exist. However, with bleed the fuel consumption is higher… Copyright © GasTurb GmbH

New Picture Copyright © GasTurb GmbH

New Picture Copyright © GasTurb GmbH

T4 = f(Corrected Spool Speed) With bleed the surge problem does not exist; however, the burner exit temperature is significantly higher Copyright © GasTurb GmbH This slide ends the Introduction to Off-Design Simulations Tutorial