ResearchProject Area D
Subproject D6

Subproject D6 Interaction of combined module variances and influence on the overall system behaviour

Multiphysical systems, such a turbofan engines, require intensive analysis for the regeneration of individual modules to recover performance and ensure operational reliability. In subproject D6, the development of a dynamic digital twin is aimed at, for an exact modelling in the complete operational area. For this purpose, the IFAS research high-bypass jet engine is discretised and modelled in higher order. The aim of the project is to predict and evaluate the effects of deterioration and repair on safety limits and transient loads.


Since the performance of an aircraft is directly and inextricably linked to the performance of the propulsion system, efforts are constantly being deployed to increase both the thrust generation and the fuel efficiency of engines. The continuing demands for increased performance result in working very close to the aerodynamic, thermal and structural limits of the propulsion system. At the same time, the operating limits must be selected in such a way as to ensure safe operation even during transient emergency situations. 

However, the deterioration of isolated or combined components leads to two negative effects:

  1. The distance to the operating safety limits are reduced
  2. Transient loads increase, driving the engine to the limits more quickly.
Figure 1 Impact of deterioration on the compressor performance map

The objective of this subproject is to evaluate the influence of deterioration and repair on the steady-state and transient operating performance of engines. As an example, Figure 1 shows a repaired (green) and deteriorated (red) map of a compressor with a steady-state and transient operating line between the D and A operating points. The deterioration leads to a shift of the map to the lower left and of the operation line to the upper left. The transient operating line in particular thus comes very close to the stability limit.

Figure 2 CAD model and Pseudo-Bond-Graph of the V2500-A1

In order to investigate this influence as accurately as possible, the ASTOR (AircraftEngine Simulation for Transient Operation Research) performance calculation program is being developed in subproject D6, which discretizes the complete propulsion system using a finite difference method (FDM). For this purpose, the quasi 1D conservation equations for flow and energy transport, the dynamics of rotating machinery, friction and radial gap change due to heat transport in the engine are simulated.  The resulting differential equation system is thus able to calculate the dynamic performance of the engine with interdependent interactions, allowing higher accuracies in the prediction of transient operation (compared to ordinary iterative performance synthesis methods). Figure 2 shows the IFAS research engine in the pseudo-bond graph notation representing the algorithm of ASTOR.


In close cooperation with subprojects of the CRC 871 (e.g. A3, B3 and D5), a digital performance twin of the IFAS research engine of the V2500-A1 was created in ASTOR, which contains geometric information as well as the component-specific performance maps. This allowed the influence of deterioration on operational performance to be simulated and evaluated in several studies.

Figure 3 Impact of deterioration on system stability (Goeing et al 2020)

Figure 3 shows the transient operation lines of 5 different engines (Θ) at an acceleration between operation point D and A. The green line represents a new engine. The green line represents a new engine, blue represents an engine with a deteriorated high-pressure turbine, black represents a deteriorated high-pressure compressor, and red/yellow represents a deteriorated turbine and compressor. The right figure shows the distance to stability limit (SM) versus rotational speeds (with dots -transient, dashed -stationary). The left figure depicts the distance between transient and steady-state operating lines. Both figures show that the influence of a deteriorated compressor is much more critical for the stability limits than for the turbine, which was not evident when considering classical performance parameters.


In the upcoming stages of this project, extensive test runs with the IFAS research engine are planned, which are intended on the one hand to validate ASTOR experimentally, and on the other hand to investigate performance degradation caused by specific modifications. Together with subprojects A3 and A6, modifications will be made to the combustor whose influence will be measured at various positions of the engine in order to investigate the influence on the overall engine and to reflect this in ASTOR.

Figure 4 Operation line during surge

Furthermore, the FDM of the engine in ASTOR allows the simulation of highly dynamic effects, such as the deep rotating stall in the high-pressure compressor and the reaction of the overall system. As an example of this, Figure 4 shows the course of the high-pressure compressor during the deep stall. The characteristic curves shown in green represent the stable range of the high-pressure compressor and the engine up to the stability limit. If the compressor is throttled rapidly because the fuel is added too quickly (acceleration in an emergency), it can enter the unstable range, which would have fatal consequences for the turbofan engine.


Prof. Dr.-Ing. Jens Friedrichs
TU Braunschweig
Hermann-Blenk-Strasse 37
38108 Braunschweig
Prof. Dr.-Ing. Jens Friedrichs
TU Braunschweig
Hermann-Blenk-Strasse 37
38108 Braunschweig


Jan Göing
TU Braunschweig
Hermann-Blenk-Strasse 37
38108 Braunschweig
Jan Göing
TU Braunschweig
Hermann-Blenk-Strasse 37
38108 Braunschweig


International Scientific Journal Paper, peer-reviewed

  • Goeing, J.; Seehausen, H.; Vladislav, P.; Lueck, S.; Seume, J. R.; Friedrichs, J. (2020): Influence of combined compressor and turbine deterioration on the overall performance of a jet engine using RANS simulation and Pseudo Bond Graph approachJ. Glob. Power Propuls. Soc. 4:296–308
    DOI: 10.33737/jgpps/131109
  • Gilge, P.; Kellersmann, A.; Friedrichs, J.; Seume, J. R. (2019): Surface roughness of real operationally used compressor blade and bliskProceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 1-10
    DOI: 10.1177/0954410019843438
  • Kellersmann A., Reitz G., and Friedrichs J. (2018): Deterioration effects of coupled blisk bladesJ. Glob. Power Propuls. Soc. 2:465–476
    DOI: 10.22261/JGPPS.CKB8N6
  • Kellersmann, A.; Weiler, S.; Bode, C.; Friedrichs, J.; Städing, J.; Ramm, G (2018): Surface Roughness Impact on Low-Pressure Turbine Performance Due to Operational DeteriorationJ. Eng. Gas Turbines Power 140(6): 062601
    DOI: 10.1115/1.4038246
  • Reitz, G., Kellersmann, A., Schlange, S., & Friedrichs, J. (2018): Comparison of sensitivities to geometrical properties of front and aft high pressure compressor stagesCEAS Aeronautical Journal 9, 135–146
    DOI: 10.1007/s13272-018-0281-8

International Conference Paper, peer-reviewed

  • Göing, J.; Bode, C.; Friedrichs, J. (2021): Performance Simulation of Roughness Induced Module Variations of a Jet Propulsion by Using Pseudo Bond Graph TheoryASME Turbo Expo 2020
    DOI: 10.1115/GT2020-14456
  • Göing J., Kellersmann A., Bode C., Friedrichs J. (2020): System Dynamics of a Single-Shaft Turbojet Engine Using Pseudo Bond GraphIn: Dillmann A., Heller G., Krämer E., Wagner C., Tropea C., Jakirlić S. (eds) New Results in Numerical and Experimental Fluid Mechanics XII. DGLR 2018. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, vol 142. Springer, Cham.
    DOI: 10.1007/978-3-030-25253-3_41
  • Göing, J.; Kellersmann, A.; Bode, C.; Friedrichs, J. (2019): Jet Propulsion Engine Modelling Using Pseudo Bond Graph ApproachASME Turbo Expo 2019
    DOI: 10.1115/GT2019-90420
  • Seehausen, H.; Gilge, P.; Kellersmann, A.; Friedrichs, J.; Herbst, F. (2019): Numerical Study of Stage Roughness Variations in a High Pressure CompressorGas Turbine Society of Japan (Hg.): Proceedings of the International Gas Turbine Congress 2019 Tokyo.

International Conference Paper, not peer-reviewed

  • Göing, Jan; Bode, Christoph; Friedrichs, Jens; Seehausen, Hendrik; Herbst, Florian; Seume, Joerg R (2020): Performance Simulation of Roughness Induced Module Variations of a Jet Propulsion by Using Pseudo Bond Graph TheoryProceedings of ASME Turbo Expo 2020 Turbomachinery Technical Conference and Exposition GT2020
  • Göing, J.; Lück, S.; Bode, Ch.; Friedrichs, J. (2019): Simulation of the Impact of a Deteriorated High-Pressure Compressor on the Performance of a Turbofan Engine Using a Pseudo Bond Graph Modelling ApproachGPPS Peking 2019
All publications of the Collaborative Research Centre