An Overview of Combustion Instabilities and Rocket Engine Injector Design

2016 ◽  
Author(s):  
Claire Staschus ◽  
Robert A. Frederick
Keyword(s):  
Rocket Engine ◽  
Combustion Instabilities ◽  
Injector Design

scholarly journals Numerical Analysis of Self-Excited Combustion Instabilities in a Small MMH/NTO Liquid Rocket Engine

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Jianxiu Qin ◽  
Huiqiang Zhang
Keyword(s):  
Droplet Size ◽  
Mass Fraction ◽  
Rocket Engine ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Liquid Rocket Engine ◽  
Combustion Instabilities ◽  
Pressure Oscillations ◽  
Two Phase ◽  
Liquid Rocket

Combustion instabilities in a small MMH/NTO liquid rocket engine used for satellite attitude and course control are numerically investigated. A three-dimensional Navier-Stokes code is developed to simulate two-phase spray combustion for cases with five different droplet Sauter Mean Diameters. As the droplet size increases from 30 microns to 80 microns, pressure oscillations are stronger with larger amplitudes. But an increase of the droplet size in the range of 80 microns to 140 microns indicates a reduction in the amplitudes of pressure oscillations. This trend is the same as the Hewitt criterion. The first tangential (1T) mode and the first longitudinal (1L) mode self-excited combustion instabilities are captured in the 60-micron and 80-micron cases. Abrupt spikes occur in the mass fraction of MMH and coincide with abrupt spikes in the mass fraction of NTO at the downstream regions just adjacent to the impinging points. Thus, local combustible high-dense mixtures are formed, which result in quasiconstant volume combustion and abrupt pressure spikes. The propagation and reflection of pressure waves in the chamber stimulate the combustion instability. When the droplet size is too small or too large, it is difficult to form local high-dense premixtures and combustion is stable in the chamber.

scholarly journals Driving and damping mechanisms for transverse combustion instabilities in liquid rocket engines

2017 ◽  
Vol 820 ◽  
Author(s):  
A. Urbano ◽  
L. Selle
Keyword(s):  
Rocket Engine ◽  
Three Dimensional ◽  
Rocket Engines ◽  
Combustion Instabilities ◽  
Time Resolved ◽  
Physical Mechanisms ◽  
Eddy Simulation ◽  
Liquid Rocket Engines ◽  
Large Eddy ◽  
Liquid Rocket

This work presents the analysis of a transverse combustion instability in a reduced-scale rocket engine. The study is conducted on a time-resolved database of three-dimensional fields obtained via large-eddy simulation. The physical mechanisms involved in the response of the coaxial hydrogen/oxygen flames are discussed through the analysis of the Rayleigh term in the disturbance-energy equation. The interaction between acoustics and vorticity, also explicit in the disturbance-energy balance, is shown to be the main damping mechanism for this instability. The relative contributions of Rayleigh and damping terms, depending on the position of the flame with respect to the acoustic field, are discussed. The results give new insight into the phenomenology of transverse combustion instabilities. Finally, the applicability of spectral analysis on the nonlinear Rayleigh and dissipation terms is discussed.

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