Component maps

Turbojet

Copyright © GasTurb GmbH

engine model

changes

map

This is the cycle design point, calculated in off-design mode.

the cycle design point in off-design mode – the yellow square is inside the circle.

Copyright © GasTurb GmbH

Close the result window

The circle marks the cycle design point, the yellow square marks the off-design operating point.

The cycle design point is
Mass Flow W2RStd = 32 kg/s
Pressure Ratio = 12
Efficiency = 0.85

W2RStd = Mass Flow Corrected to Standard Day Conditions

Special Maps

The Standard Maps yield in many cases reasonable trends. However, for accurate simulations the Standard Maps must be replaced by Special Maps.

the appropriate compressor map from file.
To shorten the tutorial we do not read a special map, we stay with the default map.

Peak Efficiency is the highest efficiency found in the scaled map.

The coordinates of the design point in the map (the yellow square) are
Beta,ds = 0.5 and N/sqrt(T),ds = 1

The yellow square marks the cycle design point.

You can either edit the coordinates of the design point or move the design point with the mouse: click it, keep the button pressed, move it.
We will set the cycle design point now to
Beta,ds = 0.4
N/sqrt(T),ds = 1.05

in the scaled map. Previously it was 0.8568, now it is 0.8929.
The reason for that is: the cycle design point efficiency remains always 0.85

Close the map window

Line

The data can only be stored as Engine Model File if all data on the Steady State page are identical to those from the cycle design point and if all the Modifiers are zero.
An Engine Model File contains in addition to a normal data file information about the component maps and how they are scaled.

Next we run a single operating line with the default settings.

Compr

cycle design point has the relative corrected speed value of 1.
The numbers at the other speed lines are those from the un-scaled map, divided by N/sqrt(T),ds = 1.05

Peak Efficiency is the highest efficiency found in the map, it is 0.8929.

If we would use the Standard Map with the default setting of the cycle design point
(i.e. Beta,ds = 0.5 and N/sqrt(T),ds = 1),
then the operating line in the compressor map would look as in the next slide.

cycle design point has the relative corrected speed value of 1.

Peak Efficiency is the highest efficiency found in the map, here it is 0.8568.

With the Default Design Point Coordinates Beta,ds = 0.5 and N/sqrt(T),ds = 1

Standard Map Scaled With the Special Design Point Coordinates Beta,ds = 0.4 and N/sqrt(T),ds = 1.05

This is the cycle design point where both operating lines agree.

Hint:
This slide is made of two pictures which were copied to the clipboard from GasTurb and then pasted into Power Point.

line

Switch back to Standard maps

with measured data

Click Open

Run the Operating Line

Select No

Plot

the isentropic compressor efficiency over the corrected compressor flow

efficiency is higher than in the simulation. For improving the agreement we go for editing the HPC Map.

slider to make the lines pass through the middle of the data points.

This line shows the peak efficiency on each speed line

This line shows the efficiency for beta=0.5

These are the measured efficiency data points

Alternatively to using the slider you could edit the peak efficiency values in this column

Click on Speed to modify the speed-mass flow correlation

Speed-Mass Flow correlation by re-labeling the speed lines in the map.

The new compressor map should be saved after closing the map editor