Three-Dimensional Numerical Simulations of Low Frequency Combustion Instability in a LOX/Methane Rocket Engine

2010 ◽  
Author(s):  
Songjiang Feng ◽  
Wansheng Nie ◽  
Bo He ◽  
Yufeng Cheng
Keyword(s):  
Numerical Simulations ◽  
Rocket Engine ◽  
Combustion Instability ◽  
Three Dimensional ◽  
Low Frequency ◽  
Lox Methane

scholarly journals A physical conjecture for the dipolar–multipolar dynamo transition

2019 ◽  
Vol 874 ◽  
pp. 995-1020 ◽  
Author(s):  
B. R. McDermott ◽  
P. A. Davidson
Keyword(s):  
Numerical Simulations ◽  
Rotation Axis ◽  
Three Dimensional ◽  
Low Frequency ◽  
Rossby Number ◽  
Length Scale ◽  
Inertial Waves ◽  
Rotation Rates ◽  
Rotating Turbulence ◽  
Planetary Dynamos

In numerical simulations of planetary dynamos there is an abrupt transition in the dynamics of both the velocity and magnetic fields at a ‘local’ Rossby number of 0.1. For smaller Rossby numbers there are helical columnar structures aligned with the rotation axis, which efficiently maintain a dipolar field. However, when the thermal forcing is increased, these columns break down and the field becomes multi-polar. Similarly, in rotating turbulence experiments and simulations there is a sharp transition at a Rossby number of ${\sim}0.4$. Again, helical axial columnar structures are found for lower Rossby numbers, and there is strong evidence that these columns are created by inertial waves, at least on short time scales. We perform direct numerical simulations of the flow induced by a layer of buoyant anomalies subject to strong rotation, inspired by the equatorially biased heat flux in convective planetary dynamos. We assess the role of inertial waves in generating columnar structures. At high rotation rates (or weak forcing) we find columnar flow structures that segregate helicity either side of the buoyant layer, whose axial length scale increases linearly, as predicted by the theory of low-frequency inertial waves. As the rotation rate is weakened and the magnitude of the buoyant perturbations is increased, we identify a portion of the flow which is more strongly three-dimensional. We show that the flow in this region is turbulent, and has a Rossby number above a critical value $Ro^{crit}\sim 0.4$, consistent with previous findings in rotating turbulence. We suggest that the discrepancy between the transition value found here (and in rotating turbulence experiments), and that seen in the numerical dynamos ($Ro^{crit}\sim 0.1$), is a result of a different choice of the length scale used to define the local $Ro$. We show that when a proxy for the flow length scale perpendicular to the rotation axis is used in this definition, the numerical dynamo transition lies at $Ro^{crit}\sim 0.5$. Based on this we hypothesise that inertial waves, continually launched by buoyant anomalies, sustain the columnar structures in dynamo simulations, and that the transition documented in these simulations is due to the inability of inertial waves to propagate for $Ro>Ro^{crit}$.

scholarly journals Effects of LOX Particle Diameter on Combustion Characteristics of a Gas-Liquid Pintle Rocket Engine

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Xuan Jin ◽  
Chibing Shen ◽  
Rui Zhou ◽  
Xinxin Fang
Keyword(s):  
Rocket Engine ◽  
Oscillation Amplitude ◽  
Three Dimensional ◽  
Particle Diameter ◽  
Low Frequency ◽  
Pressure Oscillation ◽  
Combustion Efficiency ◽  
Combustion Characteristics ◽  
Rocket Engines ◽  
Liquid Rocket

LOX/GCH4 pintle injector is suitable for variable-thrust liquid rocket engines. In order to provide a reference for the later design and experiments, three-dimensional numerical simulations with the Euler-Lagrange method were performed to study the effect of the initial particle diameter on the combustion characteristics of a LOX/GCH4 pintle rocket engine. Numerical results show that, as the momentum ratio between the radial LOX jet and the axial gas jet is 0.033, the angle between the LOX particle trace and the combustor axial is very small. Due to the large recirculation zones, premixed combustion mainly occurs in the injector wake region. As the initial LOX particle diameter increases, the LOX evaporation rate and the combustion efficiency decrease until the combustion terminates with the initial LOX particle diameter greater than 110 μm. The oscillation amplitude of the combustor pressure increases significantly along with the increase of the initial LOX particle diameter, and the low-frequency unstable combustion occurs when the initial LOX particle diameter exceeds 60 μm. The combustor pressure oscillation at about 40 Hz couples with the swinging process of spray and flame, while the unsteady LOX evaporation amplifies the combustor pressure oscillations at 80 Hz and its harmonic frequency.

scholarly journals Three-Dimensional Numerical Simulations of Twisted Stacked Tape Cables

2015 ◽  
Vol 25 (3) ◽  
pp. 1-5 ◽  
Author(s):  
Philipp A. C. Kruger ◽  
Victor M. R. Zermeno ◽  
Makoto Takayasu ◽  
Francesco Grilli
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional
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