Hybrid Wiener model: An on-board approach using post-flight data for gas turbine aero-engines modelling

Abstract On-board modelling of gas turbine aero-engines over the life cycle is a promising solution for engine performance improvement and future aero-propulsion requirements. In this paper, an on-board modelling approach named Hybrid Wiener model (HWM) is proposed for gas turbine aero-engines using post-flight engine monitoring data, which aims at estimating the unmeasured safety-critical control parameters (i.e. thrust, surge margin, and turbine entry temperature) by monitoring the engine degradation effects. Common on-board models for nominal engines, i.e. piecewise linear model, novel generalized describing function, and Wiener model, are systematically tested on a validated turbofan engine aero-thermal model. Simulations demonstrate that Wiener model is the best candidate for nominal engines. HWM is therefore constructed with the integration of on-line Wiener models and an off-line adaptation approach. The on-line part computes the unmeasured safety-critical parameters in a real-time manner. Meanwhile, the off-line adaptation part serves to periodically update the nonlinear static blocks of on-line Wiener models using the post-flight data in order to match the particular degraded engine. Idle to full-power rapid transient simulations of HWM are carried on the turbofan engine aero-thermal model for degradation simulations using publicly available data. Results from the studied turbofan engine at different flight cycles demonstrate that HWM is not only able to guarantee the steady accuracy for thrust, surge margin, and turbine entry temperature, but also ensures that the maximum transient errors for these safety-critical parameters are less than 4.66% during rapid acceleration states. Moreover, the percent errors of peak values for surge margin and turbine entry temperature between HWM and the engine are within 0.50%. The performance of the proposed HWM over the engine life cycle is therefore confirmed.