# Simplification of Low-Cycle Creep–Fatigue Load Spectrum of Combustion Chamber and Life Assessment for Feature Simulation Specimens

## TL;DR

This study simplifies the load spectrum for combustion chamber fatigue testing and shows that it accurately predicts life with minimal error.

## Contribution

A simplified load spectrum for low-cycle creep–fatigue of combustion chambers was developed and experimentally validated.

## Key findings

- The simplified load spectrum had a 6.13% average life error compared to the original.
- Test results for flat specimens with single or multiple holes were within the double dispersion band of predictions.
- Cooling gas flow improved the low-cycle creep–fatigue life of tubular specimens.

## Abstract

What are the main findings?
A simplified load spectrum for low-cycle creep–fatigue of combustion chambers was developed with experimental validation.Different combustion chamber feature simulation specimens were tested under original and simplified load spectrums.The low-cycle creep–fatigue life of the combustion chamber feature simulation specimens was predicted.

A simplified load spectrum for low-cycle creep–fatigue of combustion chambers was developed with experimental validation.

Different combustion chamber feature simulation specimens were tested under original and simplified load spectrums.

The low-cycle creep–fatigue life of the combustion chamber feature simulation specimens was predicted.

What are the implications of the main findings?
The simplified load spectrum yielded a 6.13% average life error compared to the original spectrum, with both results lying within the double dispersion band.The experimental results of the flat specimens with single or multiple holes were both within the double dispersion band of the predicted results.Internal cooling gas flow reduced temperatures near film-cooling holes in tubular specimens, enhancing their low-cycle creep–fatigue life.

The simplified load spectrum yielded a 6.13% average life error compared to the original spectrum, with both results lying within the double dispersion band.

The experimental results of the flat specimens with single or multiple holes were both within the double dispersion band of the predicted results.

Internal cooling gas flow reduced temperatures near film-cooling holes in tubular specimens, enhancing their low-cycle creep–fatigue life.

Based on the damage equivalence principle, simplification of the low-cycle creep–fatigue original load spectrum of a combustion chamber under multi-stage flight conditions, such as low speed, takeoff, climb, and cruise states, and experimental verification were carried out in this study. The low-cycle creep–fatigue life of the combustion chamber feature simulation specimens was predicted. The results showed that compared with the original load spectrum, the simplified load spectrum had an average life error of 6.13% in the low-cycle creep–fatigue tests of flat-plate specimens with a single hole. The simplified load spectrum test results and the original load spectrum test results were both within the double dispersion band of their average values. The low-cycle creep–fatigue test results of the flat specimens with single or multiple holes were both within the double dispersion band of the predicted results, while the test results of circular tube specimens with multiple holes were basically within the fourfold dispersion band of the predicted results. In addition, after passing cooling gas inside the circular tube test specimens with multiple holes, the temperature near the gas film holes was reduced, thereby improving their low-cycle creep–fatigue test life.