Single Point

Off-design simulations deal with the behavior of a gas turbine with a given geometry. This geometry is found by running a single cycle design point.

To prepare for an off-design simulation, the component design points must first be correlated with the component maps. This can be done automatically using the standard GasTurb maps and the standard design point settings in these maps. The maps will be scaled to size before the off-design calculation commences in such a way that they are consistent with the cycle design point.

This approach works well if the primary interest lies in the basic off-design behavior of an engine type. However, if more accurate simulations of a specific engine are required, then special compressor and turbine maps should be used.

GasTurb allows the replacement of standard maps with maps that are more representative for the gas turbine being simulated. GasTurb has an additional ready-made component map collection available, which includes many compressor and turbine maps. Moreover, the Smooth C and Smooth T programs enable compressor and turbine maps to be prepared easily and accurately for performance simulation programs.

Operating Line

In GasTurb an operating line is a full performance curve from maximum power to idle. The distance between the points is defined as equal steps in gas generator spool speed, thrust or shaft power. Many operating lines can be calculated in just one run.


GasTurb can simulate a complete flight mission in one go. It can also be run in batch mode with an unlimited number of points, in which case the output will be written to an excel sheet.

Engine performance can be examined throughout the flight envelope. Various limiters ensure that the engine operates safely in all flight conditions. So, for example, you can plot the spool speed at maximum rating as contour lines, for example…

Flight Envelope

Engine performance can be examined throughout the flight envelope. By setting limiters it is simple to generate maximum ratings, which may be plotted as shown.

Transient Performance

GasTurb can simulate gas turbine acceleration and deceleration processes. Inertia, heat soakage and even changing tip clearance can be taken into account.

Controls and Limiters

Using the options available under Controls it is simple to set up maximum or minimum values for many parameters. Also automatic schedules may be defined for most control parameters and handling bleeds.


It is possible to simulate both pressure and temperature distortion at the inlet. Parallel compressor theory is used to show the effect on the operating conditions on the downstream compressors.