scholarly journals The Effect of Fuel Injection Location on Supersonic Hydrogen Combustion in a Cavity-Based Model Scramjet Combustor

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 193 ◽  
Author(s):  
Eunju Jeong ◽  
Sean O’Byrne ◽  
In-Seuck Jeung ◽  
A. F. P. Houwing
Keyword(s):  
Equivalence Ratio ◽  
Fuel Injection ◽  
Flow Direction ◽  
Flame Structure ◽  
Flow Characteristics ◽  
Supersonic Combustion ◽  
Reacting Flow ◽  
Total Enthalpy ◽  
Scramjet Combustor ◽  
Injection Location

Supersonic combustion experiments were performed using three different hydrogen fuel-injection configurations in a cavity-based model scramjet combustor with various global fuel–air equivalence ratios. The configurations tested were angled injection at 15° to the flow direction upstream of the cavity, parallel injection from the front step, and upstream injection from the rear ramp. Planar laser-induced fluorescence of the hydroxyl radical and time-resolved pressure measurements were used to investigate the flow characteristics. Angled injection generated a weak bow shock in front of the injector and recirculation zone to maintain the combustion as the equivalence ratio increased. Parallel and upstream injections both showed similar flame structure over the cavity at low equivalence ratio. Upstream injection enhanced the fuel diffusion and enabled ignition with a shorter delay length than with parallel injection. The presence of a flame near the cavity was determined while varying the fuel injection location, the equivalence ratio, and total enthalpy of the air flow. The flame characteristics agreed with the correlation plot for the stable flame limit of non-premixed conditions. The pressure increase in the cavity for reacting flow compared to non-reacting flow was almost identical for all three configurations. More than 300 mm downstream of the duct entrance, averaged pressure ratios at low global equivalence ratio were similar for all three injection configurations.

Experimental study on the effect of air throttling on supersonic combustion

2016 ◽  
Vol 232 (3) ◽  
pp. 472-480 ◽  
Author(s):  
Ye Tian ◽  
Shunhua Yang ◽  
Baoguo Xiao ◽  
Jialing Le
Keyword(s):  
Experimental Study ◽  
Mass Flux ◽  
Equivalence Ratio ◽  
Flame Stabilization ◽  
Wall Pressure ◽  
Supersonic Combustion ◽  
Reacting Flow ◽  
Flux Rate ◽  
Shock Train ◽  
Scramjet Combustor

The effect of air throttling on supersonic combustion was investigated by experiments in the present paper. Our results indicated that, in the non-reacting flow, a shock train could be generated in the scramjet combustor due to the increased backpressure caused by air throttling, and the wall pressure increased obviously. But when the mass flux rate of air throttling was not large enough, the shock train would oscillate with the flow. In the reacting flow, the flame stabilization was achieved in the combustor without air throttling when the equivalence ratio of kerosene was 0.2 and 0.31, but the flame was blown off when the equivalence ratio of kerosene was 0.45. On the contrary, the kerosene (equivalence ratio: 0.45) was ignited successfully in the combustor with air throttling, and it kept burning all the time in the cases with air throttling −5% (the flux of air throttling was 5% of the inflow flux) and with air throttling −14% (the flux of air throttling was 14% of the inflow flux), but the flame was blown off in the case with air throttling −1.1% after kerosene had burnt 70 ms. The flux of air throttling should be large enough to achieve flame stabilization, and the hydrogen and air throttling should both exist all the time in order to keep the flame burning steadily.

Transverse Injection Experiments within an Axisymmetric Scramjet Combustor

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Shan M. Assis ◽  
Jeyakumar Suppandipillai ◽  
Jayaraman Kandasamy
Keyword(s):  
High Speed ◽  
Fuel Injection ◽  
Flow Direction ◽  
Reacting Flow ◽  
Rear Wall ◽  
Cross Sectional ◽  
Scramjet Combustor ◽  
Transverse Injection ◽  
Downstream Flow ◽  
Injection Pressures

Abstract Investigations on the performance of a rear wall angled cavity with upstream transverse fuel injection in a Mach 1.8 flow field is experimentally studied in a non-reacting flow facility. The high speed flow is directed to a circular cross sectional supersonic combustor and proceeded towards the cavities having two consecutive angles being inclined towards the downstream flow direction. Wall mounted injector is positioned at a distance of 10 mm upstream from the cavity. Air is used as the injectant to simulate the gaseous fuel. The experiments are performed to explore the effect of the increase in injection pressures within various rear wall angled cavities by comparing with the ‘no-injection’ case and to finally assess the mixing performance of the flow. Transverse injection through upstream wall orifice of the cavities outlines a more uniform mixing compared to ‘no-injection’ configuration. Increase in injection pressures enhances mixing and stagnation pressure loss values.

Modeling of the Thermal Characteristics of an Eccentric Multi-Stage Inverse Jet Diffusion Flame Burner

2014 ◽  
Author(s):  
Sherif Amin ◽  
Ahmed Emara ◽  
Adel Hussien ◽  
Ibrahim Shabaka
Keyword(s):  
Thermal Structure ◽  
Flame Structure ◽  
Flow Characteristics ◽  
Thermal Characteristics ◽  
Maximum Temperature ◽  
Reacting Flow ◽  
Free Jet ◽  
Multi Stage ◽  
Flame Burner ◽  
Dissipation Model

The objective of this paper is to study the effect of eccentricity on the thermal characteristics and flow field of a triple-concentric free jet burner. The investigation concerns three values of eccentricity (1.25, 1.88, and 2.5 times the inner-jet diameter); and in addition to the normal centric jet (no eccentricity). Prediction of the reacting flow characteristics and the planar flow visualization for all burners’ configurations is simulated with the CFD k-ε turbulence of “ANSYS-CFX”. In addition, the finite rate and eddy dissipation model is utilized to simulate the interaction between the chemical reaction and turbulence. The temperature, velocity and turbulence intensity are investigated to simulate the thermal-structure interaction. The results are obtained at a constant momentum rate. It showed significant changes in the coherent structures shed from the annular jets. By increasing the eccentricity, the maximum temperature will be attained more rapidly than centric case. In addition, the mixing point become nearer the burner rim, which increased the flame size and shifted the flame structure.

Effect of Axial Swirl Vane Location on Combustion Dynamics

1999 ◽  
Author(s):  
Douglas L. Straub ◽  
Geo A. Richards
Keyword(s):  
Air Temperature ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Time Lag ◽  
Fixed Time ◽  
Air Velocity ◽  
Combustion Dynamics ◽  
Premix Combustion ◽  
Swirl Vane ◽  
Injection Location

This paper reports the effect of changing the location of axial swirl vanes on premix combustion dynamics. Tests are conducted in a specially designed single-injector combustor operating at a pressure of 7.5 atmospheres and an inlet air temperature of 588K (600F). All of the tests are conducted using natural gas as the fuel. The air velocity and equivalence ratio are varied over an operating map for four different axial swirl vane positions in the premix nozzle. In contrast to earlier studies reported from this combustor, the fuel injection location is fixed. The results confirm the importance of the convective fuel time lag for the different swirl vane locations, but also show that changing the vane location at a fixed time lag can significantly affect the magnitude of the combustion oscillations.

scholarly journals Direct Measurements of Skin Friction in Supersonic Combustion Flow Fields

1992 ◽  
Author(s):  
K. M. Chadwick ◽  
D. J. Deturris ◽  
J. A. Schetz
Keyword(s):  
Skin Friction ◽  
Fuel Injection ◽  
Force Measurement ◽  
Tangential Force ◽  
Transverse Component ◽  
Supersonic Combustion ◽  
Quartz Tube ◽  
Hydrogen Fuel ◽  
Sensor Head ◽  
Scramjet Combustor

An experimental investigation was conducted to measure skin friction along the chamber walls of supersonic combustors. A direct force measurement device was used to simultaneously measure an axial and transverse component of the small tangential shear force passing over a non-intrusive floating element. This measurement was made possible with a sensitive piezoresistive deflection sensing unit. The floating head is mounted to a stiff cantilever beam arrangement with deflection due to the flow on the order of 0.00254 mm (0.0001 in). This allowed the instrument to be a non-nulling type. A second gauge was designed with active cooling of the floating sensor head to eliminate non-uniform temperature effects between the sensor head and the surrounding wall. The key to this device is the use of a quartz tube cantilever with piezoresistive strain gages bonded directly to its surface. A symmetric fluid flow was developed inside the quartz tube to provide cooling to the backside of the floating head. Tests showed that this flow did not influence the tangential force measurement. Measurements were made in three separate combustor test facilities. Tests at NASA Langley Research Center consisted of a Mach 3.0 vitiated air flow with hydrogen fuel injection at Pt = 500 psia (3446 kPa) and Tt = 3000 R (1667 K). Two separate sets of tests were conducted at the General Applied Science Laboratory (GASL) in a scramjet combustor model with hydrogen fuel injection in vitiated air at Mach = 3.3, Pt = 800 psia (5510 kPa), and Tt = 4000 R (2222 K). Skin friction coefficients between 0.001–0.005 were measured dependent on the facility and measurement location. Analysis of the measurement uncertainties indicate an accuracy to within ±10–15% of the streamwise component.

Reacting flow analysis of a cavity-based scramjet combustor using a Jacobian-free Newton–Krylov method

2018 ◽  
Vol 122 (1258) ◽  
pp. 1884-1915
Author(s):  
R. Rouzbar ◽  
S. Eyi
Keyword(s):  
Chemical Reaction ◽  
High Speed ◽  
Fuel Injection ◽  
Computational Cost ◽  
Mixing Efficiency ◽  
Reacting Flow ◽  
Flux Vector ◽  
Flux Limiter ◽  
Scramjet Combustor ◽  
Flux Vector Splitting

ABSTRACTThe scramjet is a rather a new technology and there are many issues related to their operation, especially when it comes to the combustion processes. Combustion in high-speed flows causes various problems such as flame instability and poor fuel–air mixing efficiency. One of the methods used to overcome these problems is to recess a cavity in the combustor wall where a secondary flow is generated. In this study, a computational fluid dynamics (CFD) code is developed to analyse the reacting flow passing through the cavity-based scramjet combustor. The developed code is based on three-dimensional coupled Navier–Stokes and finite rate chemistry equations. An ethylene-air reduced chemical reaction model is used as a fuel–air combination. The Spalart–Allmaras model is utilised for turbulence closure. The non-dimensional form of the flow and chemical reaction equations are discretised using a finite volume method. The Jacobian-Free Newton–Krylov (JFNK) method is used to solve the coupled system of non-linear equations. The JFNK is a matrix-free solution method which improves the computational cost of Newton’s method. The parameters that affect the performance of the JFNK method are studied in the analysis of a scramjet combustor. The influence of the forcing term on the convergence of the JFNK method is studied in the analysis of scramjet combustor. Different upwind flux vector splitting methods are utilised. Various flux limiter techniques are employed for the calculations of higher order flux vectors. The effects of flux vector splitting and flux limiter methods on the convergence and accuracy of the JFNK method are evaluated. Moreover, the variations of the mixing efficiency with fuel injection angles are studied.

CFD Analysis of Scramjet Combustor with Non-Premixed Turbulence Model Using Ramp Injector

2014 ◽  
Vol 555 ◽  
pp. 18-25 ◽  
Author(s):  
Krishna Murari Pandey ◽  
Sukanta Roga
Keyword(s):  
Supersonic Combustion ◽  
Maximum Temperature ◽  
Combustion Model ◽  
Inlet Temperature ◽  
Reacting Flow ◽  
Complete Combustion ◽  
Scramjet Combustor ◽  
Air Inlet ◽  
Fuel Jet ◽  
Combustion Of Hydrogen

This paper presents the supersonic combustion of hydrogen using strut injector along with two-dimensional turbulent non-premixed combustion model with air inlet temperature of 750 0k and vitiated Mach number of 2. In this process, a PDF approach is created and this method needs solution to a high dimensional PDF transport equation. As the combustion of hydrogen fuel is injected from the strut injector, it is successfully used to model the turbulent reacting flow field. It is observed from the present work that, the maximum temperature of 2096 0k occurred in the recirculation area which is produced due to shock wave-expansion and the fuel jet losses concentration and after passing successively through such areas, temperature decreased slightly along the axis. From the maximum mass fraction of OH, it is observed that there is very little amount of OH around 0.0017 were found out after combustion. By providing strut injector, expansion wave is created which causes the proper mixing between the fuel and air that results in complete combustion.

On the Influence of Fuel Distribution on the Flame Structure of Bluff-Body Stabilized Flames

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Jeffery A. Lovett ◽  
Kareem Ahmed ◽  
Oleksandr Bibik ◽  
Andrew G. Smith ◽  
Eugene Lubarsky ◽  
...  
Keyword(s):  
Reaction Zone ◽  
Bluff Body ◽  
Fuel Injection ◽  
Flame Structure ◽  
Reacting Flow ◽  
Oh Radicals ◽  
Fuel Distribution ◽  
Jet In Crossflow ◽  
Wide Range ◽  
Stabilized Flames

This paper describes recent learning on the flame structure associated with bluff-body stabilized flames and the influence of the fuel distribution with nonpremixed, jet-in-crossflow fuel injection. Recent experimental and analytical results disclosing the flame structure are discussed in relation to classical combustion reaction zone regimes. Chemiluminescence and planar fluorescence imaging of OH* radicals as an indicator of the flame zone are analyzed from various tests conducted at Georgia Tech using a two-dimensional vane-type bluff-body with simple wall-orifice fuel injectors. The results described in this paper support the view that combustion occurs in separated flame zones aligned with the nonpremixed fuel distribution associated with the fuel jets that are very stable and contribute to flame stability at low fuel flow rates. The experimental data is also compared with computational reacting flow large-eddy simulations and interpreted in terms of the fundamental reaction zone regimes for premixed flames. For the conditions of the present experiment, the results indicate combustion occurs over a wide range of flame regimes including the broken reaction zone or separated flamelet regimes.

An Investigation of the Effects of Fuel Staging on Flame Structure in a Gas Turbine Model Combustor

2013 ◽  
Author(s):  
J. D. Gounder ◽  
I. Boxx ◽  
P. Kutne ◽  
F. Biagioli ◽  
H. Luebcke
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Laser Diagnostics ◽  
Thermal Power ◽  
Flame Structure ◽  
Operating Conditions ◽  
Fuel Staging ◽  
Turbine Model

Gas turbine (GT) flames at lean operating conditions are susceptible to instabilities that can lead to unsteady operation, flame extinction, and thermoacoustic oscillations. High speed (10 kHz) laser and optical diagnostic techniques have been used to investigate the effect of fuel staging on the mechanisms involved in such instabilities and the overall performance of a gas turbine model combustor. The GT burner used in this study consists of coaxial swirlers which allow for fuel staging capability, where the fuel is varied from 100% to 20% fuel injection in the inner swirler. The burner is equipped with a combustion chamber with large quartz windows, allowing for the application of optical and laser diagnostics. Simultaneous high speed OH Planar Laser Induced Fluorescence (PLIF) and OH* chemiluminescence (CL) imaging, exhaust gas sampling and acoustic measurements were applied to characterize the flames and determine the operability limits of the combustor. Methane air flames at atmospheric pressure have been investigated at a constant thermal power of 58 kW. The global equivalence ratio was kept constant, while the fuel staging was varied. The bulk flow velocity at the exit plane was kept constant at 20 m/s. Simultaneous high speed particle image velocity (PIV) and OH PLIF measurements were performed at a repetition rate of 10 kHz on specifically chosen flames with a fixed staging and equivalence ratio. This paper will present the flame and the flow field structure resolved using the kHz measurement technique. The interaction between the velocity field and the flame front marked by the OH LIF will be presented. The mean PIV image provides the location of the inner and outer recirculation zones. The flame structure presented in this paper will also show the effectiveness of fuel mixing as the staging is varied. The changes in flame shape with variation in fuel staging is determined using the OH* chemiluminescence images. As the fuel flow in the inner swirler is reduced, the NOx and CO emissions also reduce and reach a minimum at a staging of 45% fuel being injected in the inner swirler. As fuel injection in the outer swirler increases beyond 60% the NOx and CO emissions start also increasing.

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