Combustion Dynamics of Ten-injector Rocket Engine Using Flamelet Progress Variable

TL;DR

This study computationally investigates combustion instability in a ten-injector rocket engine using advanced flamelet models and simulations, revealing dominant oscillation modes and coupling mechanisms at high pressure.

Contribution

It introduces a flamelet progress variable model combined with detached eddy simulation for high-pressure rocket combustion analysis, including a pressure scaling law and comparison with one-step kinetics.

Findings

Dominant longitudinal and tangential oscillation modes identified.

Coupling between pressure, flow, and helicity fluctuations analyzed.

Resonance effects in injectors driven by chamber oscillations studied.

Abstract

The combustion instability is investigated computationally for a ten-injector rocket engine using the compressible flamelet progress variable (FPV) model and detached eddy simulation (DES). An C++ code is developed based on OpenFOAM 4.1 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. The flames at this high pressure level are found having similar structures as those at much lower pressures. A power law is determined to rescale the reaction rate for the progress variable to address the pressure effect. The combustion is also simulated by the one-step-kinetics (OSK) model for comparison with the FPV model. Premixed and diffusion flames are identified locally for both the FPV and OSK models. Study of combustion instability shows that a combined first longitudinal and first tangential mode of 3200 Hz is dominant for the FPV model while the OSK model favors a pure first tangential mode of 2600 Hz. The coupling among pressure oscillation, unsteady transverse flow and helicity fluctuation is discussed. A preliminary study of the resonance in the injectors, which is driven by the acoustic oscillation in the combustion chamber, is also presented.