Numerical Modeling Of The Ignition Initiation In The Scramjet Combustion Chamber Via Detonation

2016 ◽  
Vol 11 (4) ◽  
pp. 33-44
Author(s):  
Igor Bedarev ◽  
Valentin Temerbekov ◽  
Aleksandr Fedorov ◽  
Kristina Rylova
Keyword(s):  
Numerical Modeling ◽  
Detonation Wave ◽  
Combustion Chamber ◽  
Wave Interaction ◽  
Kinetic Scheme ◽  
Reacting Flow ◽  
Mixing Process ◽  
Detonation Tube ◽  
Cellular Detonation ◽  
Air Mixing

The paper studies of the cellular detonation wave interaction with supersonic reacting flow in the scramjet combustion chamber. Comparing the flow fields for the details and the reduced chemical kinetics models is allowed verifying the acceptability of the proposed simplified kinetic scheme. The possibility of using pulsating detonation for the ignition intensification in the scramjet combustion chamber is shown. Calculation of the detonation wave interaction with nonpremixed hydrogenair mixture is made. The ability to influence on the hydrogen-air mixing process by means of detonation tube is detected. The effect of tube sizes to intensification of hydrogen air mixing in the flow at channel with a cavity is calculated.

INITIALIZATION OF SUPERSONIC COMBUSTION BY INJECTING THE TRANSVERSE DETONATION WAVE INTO THE FLOW

2020 ◽  
Author(s):  
S. S. Katsnelson ◽  
◽  
A. A. Litvintseva ◽  
G. A. Pozdnyakov ◽  
◽  
...  
Keyword(s):  
Detonation Wave ◽  
Kinetic Scheme ◽  
Supersonic Combustion ◽  
Third Order ◽  
Mixture Flow ◽  
Hydrogen Mixture ◽  
Detonation Tube ◽  
Single Temperature ◽  
The Mathematical Model ◽  
Transverse Detonation Wave

The work presents the investigation results of the influence on supersonic oxygen- hydrogen mixture flow by the injected flow into it generated by a detonation tube installed in the supersonic channel wall. The goal of this work is to study the processes of chemical reaction initiation and flow reconstruction under such influence. The mathematical model of the combustion initiation in the experimental setup is developed within a continuous medium on the model-based of a chemically nonequilibrium single-temperature gas. For the combustion reaction of the oxygen-hydrogen mixture, the following main reagents were selected: H2O, OH, O, H, H2, O2, HO2, H2O2 and O3. The combustion kinetic scheme involving these reagents contains 27 reactions. The numerical solution of the equation initial system was found using a third-order noncentral difference scheme. The parameters of the flow initiating combustion were determined from the system of one-dimensional conservation laws for a detonation wave in a detonation tube.

Analysis on the Mixing Process in a Heavy-Duty Diesel Engine under Different Conditions of Spray Position

2013 ◽  
Vol 732-733 ◽  
pp. 387-391
Author(s):  
Ye Yuan ◽  
Guo Xiu Li ◽  
Yu Song Yu ◽  
Yang Jie Xu
Keyword(s):  
Combustion Chamber ◽  
Three Dimensional ◽  
Mixing Process ◽  
Heavy Duty ◽  
Power Performance ◽  
Position Change ◽  
Heavy Duty Diesel Engine ◽  
Air Mixing ◽  
Circumferential Distribution ◽  
Heavy Duty Diesel

In order to investigate the influence of spray position on fuel air mixing quality, three-dimensional numerical simulation of the working process of a heavy-duty diesel was conducted. To quantitatively study the mechanism of the effect of spray position on fuel air mixing process, the deviation of spray centroid was introduced to describe the spray position change in combustion chamber. The results show that the gas intake swirl can affect the spatial distribution of spray in combustion chamber under three directions in cylindrical coordinate, in which the circumferential distribution is affected most. It then can be concluded that the spray can be limited to the vicinity of the combustion chamber axis. Better spray position, which is more helpful for the process of fuel air mixing and combustion, can be achieved by using optimal swirl, so that the power performance will be improved.

Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

2020 ◽  
Author(s):  
Γεώργιος Πατεράκης
Keyword(s):  
Experimental Investigation ◽  
Turbulent Flow ◽  
Bluff Body ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Wide Range ◽  
Flow Features ◽  
Air Mixing ◽  
The Impact ◽  
Stratified Flames

The current work describes an experimental investigation of isothermal and turbulent reacting flow field characteristics downstream of axisymmetric bluff body stabilizers under a variety of inlet mixture conditions. Fully premixed and stratified flames established downstream of this double cavity premixer/burner configuration were measured and assessed under lean and ultra-lean operating conditions. The aim of this thesis was to further comprehend the impact of stratifying the inlet fuelair mixture on the reacting wake characteristics for a range of practical stabilizers under a variety of inlet fuel-air settings. In the first part of this thesis, the isothermal mean and turbulent flow features downstream of a variety of axisymmetric baffles was initially examined. The effect of different shapes, (cone or disk), blockage ratios, (0.23 and 0.48), and rim thicknesses of these baffles was assessed. The variations of the recirculation zones, back flow velocity magnitude, annular jet ejection angles, wake development, entrainment efficiency, as well as several turbulent flow features were obtained, evaluated and appraised. Next, a comparative examination of the counterpart turbulent cold fuel-air mixing performance and characteristics of stratified against fully-premixed operation was performed for a wide range of baffle geometries and inlet mixture conditions. Scalar mixing and entrainment properties were investigated at the exit plane, at the bluff body annular shear layer, at the reattachment region and along the developing wake were investigated. These isothermal studies provided the necessary background information for clarifying the combustion properties and interpreting the trends in the counterpart turbulent reacting fields. Subsequently, for selected bluff bodies, flame structures and behavior for operation with a variety of reacting conditions were demonstrated. The effect of inlet fuel-air mixture settings, fuel type and bluff body geometry on wake development, flame shape, anchoring and structure, temperatures and combustion efficiencies, over lean and close to blow-off conditions, was presented and analyzed. For the obtained measurements infrared radiation, particle image velocimetry, laser doppler velocimetry, chemiluminescence imaging set-ups, together with Fouriertransform infrared spectroscopy, thermocouples and global emission analyzer instrumentation was employed. This helped to delineate a number of factors that affectcold flow fuel-air mixing, flame anchoring topologies, wake structure development and overall burner performance. The presented data will also significantly assist the validation of computational methodologies for combusting flows and the development of turbulence-chemistry interaction models.

Analysis of the Mixing and Emission Characteristics in a Model Combustor

2018 ◽  
Author(s):  
Shan Li ◽  
Shanshan Zhang ◽  
Lingyun Hou ◽  
Zhuyin Ren
Keyword(s):  
Gas Turbines ◽  
Schmidt Number ◽  
Numerical Study ◽  
Flame Temperature ◽  
Scalar Dissipation ◽  
Mixing Process ◽  
Nox Formation ◽  
Turbulent Schmidt Number ◽  
Wide Range ◽  
Air Mixing

Modern gas turbines in power systems employ lean premixed combustion to lower flame temperature and thus achieve low NOx emissions. The fuel/air mixing process and its impacts on emissions are of paramount importance to combustor performance. In this study, the mixing process in a methane-fired model combustor was studied through an integrated experimental and numerical study. The experimental results show that at the dump location, the time-averaged fuel/air unmixedness is less than 10% over a wide range of testing conditions, demonstrating the good mixing performance of the specific premixer on the time-averaged level. A study of the effects of turbulent Schmidt number on the unmixedness prediction shows that for the complex flow field involved, it is challenging for Reynolds-Averaged Navier-Stokes (RANS) simulations with constant turbulent Schmidt number to accurately predict the mixing process throughout the combustor. Further analysis reveals that the production and scalar dissipation are the key physical processes controlling the fuel/air mixing. Finally, the NOx formation in this model combustor was analyzed and modelled through a flamelet-based approach, in which NOx formation is characterized through flame-front NOx and its post-flame formation rate obtained from one-dimensional laminar premixed flames. The effect of fuel/air unmixedness on NOx formation is accounted for through the presumed probability density functions (PDF) of mixture fraction. Results show that the measured NOx in the model combustor are bounded by the model predictions with the fuel/air unmixedness being 3% and 5% of the maximum unmixedness. In the context of RANS, the accuracy in NOx prediction depends on the unmixedness prediction which is sensitive to turbulent Schmidt number.

Mechanics of Plate Fracture from Detonation Wave Interaction

2018 ◽  
Vol 44 (2) ◽  
pp. 188-197 ◽  
Author(s):  
Kefan Zhang ◽  
Minzu Liang ◽  
Fangyun Lu ◽  
Xiangyu Li
Keyword(s):  
Detonation Wave ◽  
Wave Interaction ◽  
Plate Fracture

An Accurate Performance Prediction of Solid Fuel Ramjets Using Coupled Intake-Combustor-Nozzle Simulation

2020 ◽  
Vol 36 (6) ◽  
pp. 933-941
Author(s):  
A. M. Tahsini
Keyword(s):  
Combustion Chamber ◽  
Solid Fuel ◽  
Solid Phase ◽  
Three Dimensional ◽  
Flow Fields ◽  
Reacting Flow ◽  
Computational Domain ◽  
Regression Rate ◽  
Fuel Flow ◽  
Accurate Performance

ABSTRACTThe performance of the solid fuel ramjet is accurately predicted using full part simulation of this propulsion system, where the flow fields of the intake, combustion chamber, and the nozzle are numerically studied all together. The conjugate heat transfer is considered between the solid phase and the gas phase to directly compute the regression rate of the fuel. The finite volume solver of the compressible turbulent reacting flow is utilized to study the axisymmetric three dimensional flow fields, and two blocks are used to discretize the computational domain. It is shown that the combustion chamber's pressure is changed due to the fuel flow rate's increment which must be taken into account in predictions. The results demonstrate that omitting the pressure dependence of the regression rate and also the effect of the combustor's inlet profile on the regression rate, which specially exists when simulating the combustion chamber individually, under-predicts the solid fuel burning rate when the regression rate augmentation technique is applied to improve the performance of the solid fuel ramjets. It is also illustrated that using the inlet swirl to increase the regression rate of the solid fuel augments considerably the thrust level of the considered SFRJ, while the predictions without considering all parts of the ramjet is not accurate.

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