Control of the Formation of a Transonic Region in a Supersonic Flow by using a Throttling Jet and Near-Wall Heat Release

2019 ◽  
Keyword(s):  
Supersonic Flow ◽  
Heat Release ◽  
Transonic Region ◽  
Near Wall

Numerical Study of Vortex/Flame Interaction in Actively Forced Confined Non-Premixed Jets

1999 ◽  
Vol 122 (2) ◽  
pp. 376-380 ◽  
Author(s):  
K. R. Anderson ◽  
S. Mahalingam
Keyword(s):  
Numerical Simulations ◽  
Heat Release ◽  
Numerical Study ◽  
Fixed Level ◽  
Vorticity Production ◽  
Near Wall

Numerical simulations of coplanar reacting jets subjected to near wall confinement have been performed. The primary conclusion is that for a fixed level of heat release, the mechanism of baroclinic vorticity production increases with more severe wall confinement. [S0022-1481(00)00602-2]

scholarly journals Some Effects of Hydrogen Self-Ignition and Combustion in Supersonic Flow

2014 ◽  
Vol 16 (2-3) ◽  
pp. 245
Author(s):  
U. Zhapbasbayev ◽  
V. Zabaykin ◽  
Y. Makashev ◽  
A. Tursynbay ◽  
B. Urmashev
Keyword(s):  
Supersonic Flow ◽  
Heat Release ◽  
Chemical Reactions ◽  
Laboratory Data ◽  
Combustion Process ◽  
Supersonic Combustion ◽  
Low Flow ◽  
Diffusion Combustion ◽  
Maximum Pressure ◽  
Combustion Mode

<p>Results are presented of computational and experimental investigations of the influence of temperature and flow composition on the hydrogen combustion kinetics for a coaxial fuel supersonic flow. Depending on the flow parameters, combustion is shown to occur with an intense heat release governed by the speed of chemical reactions, or a diffusion combustion with heat release governed by mixing. The computational results are in good agreements of with laboratory data and portrays many important features of supersonic combustion. The influence of the gas temperature and composition on the diffusion combustion of a circular hydrogen jet in supersonic coaxial flow at the over expanded exhaust regimes is investigated. It is found that at low flow temperatures (Т<sub>2 </sub>~ 900 K) and in the absence of water vapors in the oxidizer gas composition, the speed of chemical reactions is the determining factor for combustion. An increase in the flow temperature (Т<sub>2</sub> &gt; 1200 K) causes a reduction of the induction time of the reactive mixture, because the mixing of fuel with oxidizer decreases, and a “sluggish” diffusion combustion of non-mixed gases is observed. The presence of water vapor and active radicals in the gas ensures the self-ignition from the start of the mixing, and the diffusion combustion mode is limited by mixing of the hydrogen jet with the coaxial flow (similar to the case with high initial temperatures of the air stream). In the case of the delay combustion process the maximum pressure level on the wall is 10% more than that in the combustion mode with ignition at the start of mixing. A sluggish combustion regime may lead to an incomplete hydrogen burnout.</p>

Effect of a Premixed Pilot Flame on the Velocity-Forced Flame Response in a Lean-Premixed Swirl-Stabilized Combustor

2019 ◽  
Author(s):  
Jihang Li ◽  
Stephen Peluso ◽  
Domenic Santavicca ◽  
James Blust
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Shear Layer ◽  
Heat Release Rate ◽  
Release Rate ◽  
Wall Region ◽  
Rate Fluctuation ◽  
Phase Images ◽  
Flame Response ◽  
Near Wall

Abstract The effect of a fully-premixed pilot flame on the velocity-forced flame response of a fully premixed flame in a single-nozzle lean-premixed swirl combustor operating on natural gas fuel is investigated. Measurements of the flame transfer function show that as the percent pilot is increased there is a decrease in the flame transfer function gain at all frequencies, a decrease in the frequencies at which the gain minima and maxima occurred, and a decrease in the flame transfer function phase at high frequencies. High-speed CH* chemiluminescence flame imaging is used to gain a better understanding of the mechanism(s) whereby the pilot flame affects flame dynamics and thereby the flame transfer function. Time-averaged flame images show that the location of the maximum heat release rate does not change with forcing frequency or percent pilot, although the flame extends further upstream into the inner shear layer with increasing percent pilot. Heat release rate fluctuation images show that significant heat release rate fluctuations occur in the inner shear layer, the outer recirculation zone, and the near wall region and that the primary effect of increasing the forcing frequency or the percent pilot is a shift of the heat release rate fluctuation from the near wall region to the inner shear layer. In addition, an increase in the percent pilot results in lengthening and narrowing of the inner shear layer and the near wall regions. The phase images show that the phase is less uniform as the frequency or percent pilot increase, resulting in greater interference between in phase and out of phase fluctuations which reduces the FTF gain. The phase images also show that the wavelength of the heat release rate perturbation travelling through the inner shear layer decreases with increasing frequency and percent pilot which suggests that the pilot flame alters the recirculation flow field. Flame transfer functions calculated for the heat release rate fluctuations in the inner shear layer, the near wall region and the outer recirculation zone show that the inner shear layer is the largest contributor to the global heat release rate fluctuation in the unpiloted flame and that the primary effect of the pilot flame on the reduction of the global FTF gain is a result of the pilot flame’s effect on the inner shear layer.

Effects of combustor geometry on the combustion process of an RBCC combustor in high-speed ejector mode

2019 ◽  
Vol 33 (27) ◽  
pp. 1950330
Author(s):  
Taiyu Wang ◽  
Zhenguo Wang ◽  
Zun Cai ◽  
Jian Chen ◽  
Mingbo Sun ◽  
...  
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Heat Release ◽  
Reaction Mechanisms ◽  
Total Pressure ◽  
High Speed ◽  
Combustion Process ◽  
Numerical Approach ◽  
Combined Cycle ◽  
Chemical Reaction Mechanisms

The combustion characteristics of high-speed ejector mode in a 2-dimensional strut-based RBCC (rocket-based combined cycle) combustor had been investigated numerically in a Mach 2.5 supersonic flow. The numerical approach had been validated by comparing numerical results with available experimental data. Besides, three different hydrogen-air chemical reaction mechanisms had also been compared. The effect of the combustor geometry on the combustion process was then discussed by analyzing the heat release distribution and flow field. It was found that the wall configuration, closeout angle of the converging location and converging ratio all have significant influences on the heat release distribution and flow field structures. It is demonstrated that a converging–diverging wall configuration is beneficial for the combustion process with significant heat release increase compared to the other wall configurations. In addition, the closeout angle of the converging location is also closely related to the combustion performance, and there exists an optimized closeout angle in a specific combustor geometry. It is also revealed that the major heat release region moves upstream obviously with increase in the converging ratio, leading to an enhanced combustion process. However, the converging ratio is still to be optimized to keep a balance between heat release increase and total pressure loss of the supersonic flow.

Supersonic flow over a cone with heat release in the neighborhood of the apex

1993 ◽  
Vol 28 (2) ◽  
pp. 244-247 ◽  
Author(s):  
V. A. Levin ◽  
L. V. Terent'eva
Keyword(s):  
Supersonic Flow ◽  
Heat Release
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