Engine Model Decks - GasTurb DLLs

GasTurb program libraries (GasTurb DLLs) can be used to perform GasTurb calculations in an automatic way.

The GasTurb program is an independent event-driven software which cannot be controlled by other Windows programs. It simulates the design and performance of a large variety of gas turbines (currently 27 separate gas turbine configurations for jet propulsion and for power generation). They differ regarding the arrangements of compressors and turbines on one or more spools, depending on whether it is a mixed or an unmixed flow turbofan, or whether it is a shaft power producing gas turbine, for example.

GasTurb DLLs (dynamic link libraries) can be used for running the gas turbine performance simulation implemented in GasTurb as part of another Windows program (Excel, MatLab, etc.). The interface functions exported by a DLL can be called from any other Windows program, independently of the programming language of the calling program.

While there is just one GasTurb program, there is a separate DLL for each of the 27 engine configurations.

A GasTurb DLL is a much smaller piece of software than the GasTurb program. The input and output of each of the available DLLs is limited to the input and output data required for the respective engine configuration. There is no graphical user interface and no graphical output.

The structure and the nomenclature used in the GasTurb DLL interface basically follows the SAE Aerospace Recommended Practice ARP755 and the SAE Aerospace Standard AS681. The latter defines the requirements for engine performance representation on digital computers, via computer decks. This term dates back to when computer programs and data were supplied as a 'deck' of cards. Any GasTurb DLL can be regarded as a Computer Deck.

GasTurb DLL + Engine Model File = GasTurb Engine Model Deck

GasTurb DLLs can be used as follows: First, during an initialization process, the data describing engine performance is loaded. This initialization data has been created before, using the GasTurb program, and is stored as an Engine Model File. The Engine Model File contains all data necessary for creating off-design simulations, both for steady state and transient operation. It is advised to check the Engine Model File with GasTurb thoroughly before using it with a DLL, in order to avoid invalid engine operation results (negative surge margin, etc.) and numerical problems caused by inappropriate compressor or turbine maps. Once the initialization is completed, an arbitrary number of steady state and transient operating points can be calculated. 

As a sample, the manual of turbojet deck can be found here.