A part-load performance analysis method for gas turbines based on the stage by stages model of the power turbine

Liping Deng; Hu Wu; Qi’an Xie

doi:10.1515/tjj-2024-0065

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A part-load performance analysis method for gas turbines based on the stage by stages model of the power turbine

Liping Deng , Hu Wu and Qi’an Xie

Published/Copyright: March 12, 2025

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From the journal International Journal of Turbo & Jet-Engines Volume 42 Issue 3

Abstract

In existing calculation studies of gas turbine part-load performance, the multi-stage power turbine (PT) is usually considered as an integral whole, and the variation rule of power and efficiency of the PT’s front/rear stage with load cannot be obtained. Therefore, the 6-stage PT of LM2500+ gas turbine is divided into 2 sub-turbines to be investigated by establishing the gas turbine part-load performance model based on the stage by stages method of the power turbine in this paper. The model is used to calculate the part-load performance of the LM2500+ under the fuel flow strategy (FF) and the first sub-turbine variable area nozzle (VAN) strategy. The results show that the relative errors of the mass flow rate, pressure ratio and thermal efficiency calculated by the model compared to the experiment data are all within 3.5 %.Under the FF strategy, the degree of mismatch in PT front/rear stage gradually increases as the load decreases from 100 % to 0.0 %, with the share of the first sub-turbine power increases from 22 % to 130 %, and the second sub-turbine efficiency decreases from 0.876 to −0.126. The adoption of the VAN strategy further exacerbates the degree of mismatch between the PT front/rear stages.

Keywords: gas turbine; variable geometry turbine; part-load performance; stage by stages method

Corresponding author: Hu Wu, School of Power and Energy, Northwestern Polytechnical University, Xi’an, Shaanxi, 710129, China, E-mail: wuhu@nwpu.edu.cn

Acknowledgments

The first author would like to thank Lab Associates for providing many reference on the calculation method of their research achievements.

Research ethics: Not applicable.
Informed consent: Not applicable.
Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Use of Large Language Models, AI and Machine Learning Tools: None declared.
Conflict of interest: The author states no conflict of interest.
Research funding: None declared.
Data availability: Not applicable.

Nomenclature

Abbreviations

C: compressor
I: inlet
CC: combustion chamber
E: exhaust
G: generator
HT: High pressure turbine
PT: power turbine
VAN: variable area nozzle
FF: fuel flow
SFC: specific fuel consumption

Subscripts

cor: corrected
cormap: corrected from map
cd: design point
cr: critical state
g: gas
max: maximum
1S: Power turbine first stage
5S: The rear 5 stages of the power turbine
FG: Fixed geometry

Superscripts

-: relative value

Notations

π: pressure ratio
W: mass flow, kg/s
η: efficiency
Δθ: variable area nozzle angle, degree
η _T: thermal efficiency
T_ti: total temperature. i = Station 0,2,3,4,5,56,6,8
P_ti: total pressure. i = Station 0,2,3,4,5,56,6,8
A _5nb: throat area of the power turbine guide vane
const: constant
C _P: specific heat at constant pressure
k ^′: specific heat ratio
n: rotor speed
a: sound velocity
r: radius
R: gas constant
u: rim speed
λ: speed factor
K_g’: a constant in a flow formula
W_g: gas mass flow
q(λ): flow function
σ _nb: total pressure recovery coefficient from turbine guide inlet to throat

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Received: 2024-07-16

Accepted: 2025-02-18

Published Online: 2025-03-12

Published in Print: 2025-08-26

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Articles in the same Issue

https://doi.org/10.1515/tjj-2024-0065

Keywords for this article

gas turbine; variable geometry turbine; part-load performance; stage by stages method