Combustion Instability of a Multi-injector Rocket Engine Using the Flamelet Progress Variable Model

TL;DR

This study computationally investigates combustion instability in a multi-injector rocket engine using the flamelet progress variable model, comparing it with one-step-kinetics, and analyzing dominant oscillation modes and resonance effects.

Contribution

It introduces a FPV-based combustion model for rocket engines and compares its results with traditional methods, highlighting differences in instability amplitude predictions.

Findings

Dominant longitudinal mode at 1500 Hz identified

Tangential standing wave at 2500 Hz with larger amplitude in FPV

Resonance effects in injectors linked to chamber oscillations

Abstract

The combustion instability is investigated computationally for a multi-injector rocket engine using the flamelet progress variable (FPV) model. A C++ code is developed based on OpenFOAM 4.0 to apply the combustion model. Flamelet tables are generated for methane/oxygen combustion at the background pressure of $200$ bar using a 12-species chemical mechanism. A power law is determined for rescaling the reaction rate for the progress variable to address the pressure effect. The combustion is also simulated by the one-step-kinetics (OSK) method for comparison with the FPV approach. A study of combustion instability shows that a longitudinal mode of $1500$ Hz and a tangential standing wave of $2500$ Hz are dominant for both approaches. While the amplitude of the longitudinal mode remains almost the same for both approaches, the tangential standing wave achieves a larger amplitude in the FPV simulation. A preliminary study of the resonance in the injectors, which is driven by the longitudinal-mode oscillation in the combustion chamber, is also presented.