Transient Behavior in Variable Geometry Industrial Gas Turbines: A Comprehensive Overview of Pertinent Modeling Techniques

Abstract

Generally, industrial gas turbines (IGT) face transient behavior during start-up, load change, shutdown and variations in ambient conditions. These transient conditions shift engine thermal equilibrium from one steady state to another steady state. In turn, various aero-thermal and mechanical stresses are developed that are adverse for engine’s reliability, availability, and overall health. The transient behavior needs to be accurately predicted since it is highly related to low cycle fatigue and early failures, especially in the hot regions of the gas turbine. In the present paper, several critical aspects related to transient behavior and its modeling are reviewed and studied from the point of view of identifying potential research gaps within the context of fault detection and diagnostics (FDD) under dynamic conditions. Among the considered topics are, (i) general transient regimes and pertinent model formulation techniques, (ii) control mechanism for part-load operation, (iii) developing a database of variable geometry inlet guide vanes (VIGVs) and variable bleed valves (VBVs) schedules along with selection framework, and (iv) data compilation of shaft’s polar moment of inertia for different types of engine’s configurations. This comprehensive literature document, considering all the aspects of transient behavior and its associated modeling techniques will serve as an anchor point for the future researchers, gas turbine operators and design engineers for effective prognostics, FDD and predictive condition monitoring for variable geometry IGT.

A General Overview of Combined Cycle Gas Turbine Plants

“…In Ref. [76], the study is founded on the literature based statistical segregation of different phenomena causing transient behavior. It has been clarified that load change transient phenomenon has not been taken into consideration by researchers.…”

“…Investigation into the dynamic performance of these plants requires detailed information of the process. Dynamic simulation is also a cost-efficient tool to sustain unit commissioning and regular operation by estimating component life time and directing maintenance [101]. Modern simulation strategies combine a graphical user interface with detailed models for flow, thermodynamics and heat transfer.…”

“…Proportional-integral-derivative (PID) control scheme has been implemented to capture the entire transient operation in mechanical drive GT power station [103]. However, it emerged as a holistic model and benefitted in monitoring the surging, startup and slow transient operation occurring inside the centrifugal compressor section [101]. Previous control system simulators have based on simple block diagram and generalized type programs [104].…”

“…Moreover, generalized type simulators proved to be time consuming in solving the Jacobian matrix. It is very important to improve the use of more advanced control strategies like fuzzy, neural or predictive optimal control [101]. A new control system is proposed in [105] for the robust decentralized stabilization of multimachine power systems based on linear matrix inequalities(LMI).…”

Experimental Transient Process Analysis of Micro-Turbojet Aviation Engines: Comparing the Effects of Diesel and Kerosene Fuels at Different Ambient Temperatures

“…This process typically lasts a few seconds for an aviation turbo engine. Numerous historical and recent studies have been published to provide a mature understanding of the transient performance of gas turbines [25,26].…”