Influence of Thermal Inertia on Dynamic Characteristics of Gas Turbine Impeller Components

TL;DR

This paper studies how thermal inertia affects the performance of gas turbine components during dynamic operations like startup and shutdown.

Contribution

The study introduces a hybrid simulation method combining CFD and FEM to analyze thermal inertia effects on gas turbine rotor dynamics.

Findings

Thermal inertia causes shifts in the dynamic characteristics of rotor components.

Heat transfer accounts for about 0.1% of total inlet enthalpy, with 6–15% of exchanged heat converting to technical work.

Compressor components exhibit less intense heat transfer compared to turbine components due to smaller temperature differences.

Abstract

Gas turbines in land-based microgrids and shipboard-isolated power grids frequently face operational challenges, such as the startup and shutdown of high-power equipment and sudden load fluctuations, which significantly impact their performance. To examine the dynamic behavior of gas turbines under transitional operating conditions, a three-dimensional computational fluid dynamic simulation is employed to create a model of the gas turbine rotor, incorporating thermal inertia, which is then analyzed in conjunction with three-dimensional finite element methods. The governing equations of the flow field are discretized, providing results for the flow and temperature fields throughout the entire flow path. A hybrid approach, combining temperature differences and heat flux density, is applied to set the thermal boundary conditions for the walls, with the turbine’s operational state determined based on the direction of heat transfer. Additionally, mesh division techniques and turbulence models are selected based on the geometric dimensions and operating conditions of the compressor and turbine. The simulation results reveal that thermal inertia induces a shift in the dynamic characteristics of the rotor components. Under the same heat transfer conditions, variations in rotational speed have a minimal impact on the shift in the characteristic curve. The working fluid temperature inside the compressor components is lower, with a smaller temperature difference from the wall, resulting in less intense heat transfer compared to the turbine components. Overall, heat transfer accounts for only about 0.1% of the total enthalpy at the inlet. When heat exchange occurs between the working fluid and the walls, around 6–15% of the exchanged heat is converted into changes in technical work, with this percentage increasing as the temperature difference rises.

Figures