Combustor Wall Research Articles

The impact of film cooling on the heat release within a rotating detonation combustor

Rotating detonation combustors establish a detonation wave that continuously circulates inside a small annulus. The presence of the detonation wave and the downstream oblique shock within the small annulus coupled with high mass flow induces a high heat load to the combustor wall. Preliminary analysis shows that for higher thermal power, internal air cooling alone is not sufficient to remove the heat out of the walls to maintain them below the maximum temperature of the metal. A possible solution is to use film cooling to reduce the heat flux to the combustor walls. One issue, though, is that the introduction of film cooling provides additional air into the system that can influence the combustion process as well as providing a location for secondary combustion.This paper represents the first investigation to study the secondary implications on combustion of using film cooling in a rotating detonation combustor. The TU Berlin RDC architecture was modified with the introduction of 480 film cooling holes placed in the oblique shock region. High fidelity LES investigations were performed for different coolant plenum pressures to show the benefits of using film cooling. However, due to the presence of unburnt fuel in this post-detonation region, the coolant can result in additional combustion leading to an increase in temperature near the wall. One the one hand, these secondary reactions result in an increase of the overall heat release increasing combustion efficiency, however this also results in higher temperatures and reduced film cooling effectiveness. A simulation performed with nitrogen as a coolant enabled the effects of increased mixing caused by the ejection of coolant gases to be separated from the additional heat release. The simulation with nitrogen shows a reduction of 88% in the local heat release in the post detonation region resulting in similar performance as the uncooled case and significantly cooler walls.

Effects of combustor wall temperature on the outer recirculation zone combustion modes transition in lean premixed DME/air swirling flames

In this study, the effects of wall thermal boundary conditions on the outer recirculation zone (ORZ) combustion modes transition in the DME/air swirling flames were investigated using the Large Eddy Simulation (LES) and Flamelet Generated Manifold (FGM) method. The results show that the ORZ chemistry and temperature are highly sensitive to the wall thermal boundary condition. Based on the correlation between the temperature and species observed in the time-averaged numerical results, the relation between the combustion mode and temperature in the ORZ was discovered. Through temporal analysis of species and heat release rate in the ORZ, the stable Mode II and Mode IV as well as the unstable Mode III were identified. The chemical reaction pathway analysis for typical probe in the ORZ reveals that different combustion modes undergo distinct (low-temperature or high-temperature) chemical reaction pathways. Afterwards, the definition of ORZ combustion modes used in experiments was refined by utilizing the chemical reaction data from the simulations. And it was applied to identify the combustion mode across the entire computational domain. The results confirm the consistency between the combustion modes determined in experiments based on OH and CH2O and those determined in simulations using chemical reaction rates. Finally, this explains the mechanism of the flickering flame in Mode III is the competition between the low-temperature and high-temperature reaction in the ORZ. Whereas the unstable Mode III can be stabilized by changing the wall temperature to reach the stable Mode II or Mode IV.

Thermodynamic and entropy generation analyses of Telsa-valve structured meso-scale combustors fuelled with hydrogen for thermophotovoltaic applications

The present work numerically examed the effects of hydrogen volume flow rates (Qv) and equivalence ratios (Φ) on thermal performances of meso-scale combustors structured with Tesla-vale type flow channels. Four distinct Tesla-valve configurations are implemented and then subsequently compared. The reverse-flow Tesla valve with counter-flow combustor (RC) structure shows a remarkable improvement of 72.6 % to the combustor wall temperature at Qv = 100 mL/min. The diodicity (Di) of the Tesla valve is found to be increased with a higher Qv, and a lower Φ contributes to a higher Di. Besides, Di is decreased when Φ goes up, stabilizing at Φ = 0.9. The reverse-flow Tesla valve exhibits a more uniform pressure distribution and entropy production than the forward-flow Tesla valve. At Φ = 0.9, the hydrogen-to-air ratio maximized heat release, producing the highest entropy. Tesla-valve structured combustors demonstrate near complete combustion before Φ reaching 0.9, the combustion efficiency (ηcombustion) is gradually decreased after Φ getting to 1.0. The RC construction achieved maximum combustion efficiency under conditions of insufficient oxygen. This present study demonstrates the feasibility of enhancing thermal and overall performances of meso-scale combustors structured with Tesla-valve channels, and revealing the key parameters effects on the combustion characteristics in these combustors.

Identifying optimal location for control of thermoacoustic instability through statistical analysis of saddle point trajectories.

We propose a framework of Lagrangian Coherent Structures (LCSs) to enable passive open-loop control of tonal sound generated during thermoacoustic instability. Experiments were performed in a laboratory-scale bluff-body stabilized turbulent combustor in the state of thermoacoustic instability. We use dynamic mode decomposition on the flow-field to identify dynamical regions where the acoustic frequency is dominant. We find that the separating shear layer from the backward-facing step of the combustor envelops a cylindrical vortex in the outer recirculation zone, which eventually impinges on the top wall of the combustor during thermoacoustic instability. We track the saddle points in this shear layer emerging from the backward-facing step over several acoustic cycles. A passive control strategy is then developed by injecting a steady stream of secondary air targeting the identified optimal location where the saddle points spend a majority of their time in a statistical sense. After implementing the control action, the resultant flow-field is also analyzed using LCS to understand the key differences in flow dynamics. We find that the shear layer emerging from the dump plane is deflected in a direction almost parallel to the axis of the combustor after the control action. This deflection, in turn, prevents the shear layer from enveloping the vortex and impinging on the combustor walls, resulting in a drastic reduction in the amplitude of the sound produced.

Coupling study of onboard power generation system of Magnetohydrodynamics enhanced Brayton Cycle

Closed cycle power generation systems offer a possible solution to meet the high electricity needs of hypersonic vehicles, but the power generation is limited by the finite cold source and cycle temperature. Introducing two-phase flow liquid metal (LM) MHD power generation based on Closed-Brayton-Cycle (CBC) is a potential solution that can enhance the thermal-electricity conversion process at the system level. However, it is difficult to reflect the complex coupling relationship between the power generation system and the vehicles propulsion system and the limitations of finite cold sources by relying only on ideal system analysis, especially the contradiction between the void fraction and the mass flow of working fluid after the introduction of LMMHD power generation. The study utilizes a multi-dimensional model to evaluate the performance of the CBC enhanced by multi-stage LMMHD generators coupled with hydrocarbon fuel scramjet. The multi-stage mixing-separation LMMHD generator is proposed to decouple the void fraction of the MHD channel and the wall cooling process, and control the void fraction by change number of stages. The calculation result indicate that the void fraction significantly affects the overall power generation performance, including output power, performance boundary, etc. Increasing the void fraction is beneficial, and the optimal void fraction is 0.65. At the same Mach number, the fuel cooling capacity available to the system increases with the fuel equivalence ratio, resulting in higher total power output. The maximum Mach number for thermal protection of the combustor walls alone may surpass 9.5. For gas void fractions of 0.35/0.5/0.65, the maximum power generation reaches 182.8/167.1/156.9 kW, respectively. The novel system is compared with other advanced thermal-electricity conversion cycles under nearly the same conditions and demonstrated clear performance advantages.

Towards detailed combustor wall kinetics: An experimental and kinetic modeling study of hydrogen oxidation on Inconel

Gas-phase hydrogen combustion is ubiquitous in industrial processes, and the associated surface kinetics on heat-resistant alloys plays a crucial role in designing efficient low-carbon technologies. We conducted new temperature programmed reduction experiments to determine the reducibility of materials following an oxidation cycle. These experiments were modeled using a thermoconsistent multi-site microkinetic model for H2 heterogeneous oxidation on Inconels, which was validated against literature experiments. This competitive adsorption model considers iron bulk content, hydrogen spillover and subsurface oxygen migration on hydrogen surface oxidation kinetics. New X-ray diffraction experiments confirmed the postulated crystallographic structures in the Inconel samples, suggesting their presence on the surface scale. The phenomenological model was coupled with several state-of-the-art gas-phase oxidation mechanisms to assess gas/surface reactions interaction as a function of material and temperature. The results reveal a complex interaction in which surface removes H radicals from the gas-phase, while the Bradford (H2+OH) reaction converts OH into H2O, promoting water adsorption on Inconel. This interaction was found to give rise to gas-phase thermokinetic oscillations. The model predicts a non-monotonous effect of reactor area-to-volume ratio on reactivity and emphasizes the impact of Inconel composition on product selectivity. Overall, the multi-site model provides new insight into the contrasting reactivities among active sites, bridging the gap between material science and heterogeneous combustion modeling.

Numerical analysis of heat transfer and fluid flow structures of jet impingement on a flat plate with different shapes of roughness elements

Jet impingement is a heat transfer technique utilized in different applications in industry. It is used for cooling the turbine blade and the combustor wall because of its high cooling rate. The heat transfer (HT) and flow structure of a circular air-impinging jet over a flat target plate with a circular row of 48 roughness elements are numerically investigated using renormalization group k–ε turbulence model. Different shapes of roughness elements, namely cylindrical roughness elements (CREs), droplet roughness elements (DREs), and hemispherical roughness elements (HREs), are examined. The effects of Reynolds number changed from 7,000 to 35,000, and the roughness elements location relative to jet diameter ( s / d ) of 1.5, 2, 2.5, and 3 at a constant jet-to-target plate distance ( H / d ) of 2 are studied. Temperature distribution, local Nusselt number ( Nu ), average Nusselt number (Nuavg ), average Nusselt number ratio (Nuavg,r ), velocity distribution, turbulence kinetic energy, streamline contours, and static pressure ( p ) over the roughness elements are evaluated and discussed. The results showed that the existence of roughness elements has a significant effect on the thermal and hydraulic characteristics. The Nuavg,r for the CREs, DREs, and HREs is up to 1.61, 2.02, and 1.2, respectively. All roughness element shapes increase the flow velocity in the narrow area between the elements and increase the wetted area. CREs augment the HT rates by increasing the turbulence intensity, while DREs reduce the drag force effects.

Dynamics of elevated dodecane jets in crossflow at supercritical pressure

In advanced aero-engines, kerosene is often transversely injected into the combustor at supercritical pressure, where the shorter jet penetration depth may result in poor mixing and the local hot spots near the combustor wall. Elevating the jet nozzle is proposed to remedy these issues, where the flowfield complexity increases as a result of the intricate interactions among the jet, crossflow, and stack wake. The distinct flow dynamics of elevated dodecane jets in crossflow (EJICF) at supercritical pressure are numerically investigated using large eddy simulation. The effects of various parameters, including ambient pressure, elevation stack thickness, and stack height are studied. The results reveal that, the jet-wake recirculation bubble is prominently evident at low supercritical pressure, attributed to the strong real-fluid effect resulting from significant density stratification in the jet's upstream shear layer. Analysis of streamline patterns and vorticity budgets underscores the role of the real-fluid effect in delaying the shift of the flow pattern from the transitional regime to the jet-dominated regime. Increasing stack thickness mitigates the impact of jet upshear effects and has the potential to eliminate the lock-in phenomena between jet wake and stack wake. A reduction in stack height leads to the diminishment of the stack wake vortex shedding. In contrast to conventional JICF, the EJICF configuration exhibits a heightened tendency for recirculation bubble formation in the jet wake region. An analysis of spatial mixing deficiencies demonstrates that incorporating an elevation stack with proper thickness and height can dramatically improve the jet-crossflow mixing efficiency.

Structure effect of wall cooling channel on liquid metal heat transfer in aero-engines

In this study, a model of the cooling channel and an experimental system for heat transfer involving liquid metal are studied, to investigate the influence of the wall cooling channel structure of combustor on the heat transfer process. The error between the experimental and simulated outcomes fall is within 3 %, suggesting that the accuracy of the simulation is satisfactory. The simulation results found that the temperature non-uniformity coefficient can be reduced by 13 % and 7 % through adjusting the aspect ratio under the heat flux of 3 MW/m2 and 1.5 MW/m2 respectively, and the wall temperature of gas side can be reduced by 89 K and 47 K respectively. A smaller aspect ratio is favorable for homogenizing the liquid metal temperature distribution. Longer widths, however, can lead to horizontal thermal stratification, which can be unfavorable for heat transfer. With an aspect ratio and rib thickness of about 0.5 and 0.4 mm, respectively, the cooling channel outlet has the lowest non-uniformity coefficient of temperature and enthalpy, which is conducive to the improvement of the wall energy recovery rate. The optimal cooling channel effectively improves the thermal stratification in channel, and provides theoretical guidance for the suitable application of liquid metal to the combustor wall cooling channel.

Experimental study on the propagation characteristics of non-premixed H2/air flames in a curved micro-combustor

In this study, propagation characteristics of non-premixed H2/air flames in a curved micro-combustor were experimentally investigated. It was found that after cold-state ignition at the combustor exit, flames can propagate upstream and form a stable flame over a wide range of average inlet velocity (Vave,in) and nominal equivalence ratio (φ). The top-wall temperature distribution demonstrated that a flame separation phenomenon occurs when φ ≤ 1. High temperature zone of the combustor wall expanded and shifted downstream with an increasing Vave,in; however, with an increase in φ, it expanded initially and then shrank, and moved toward the air-side. The maximum wall temperature varied non-monotonically with both the Vave,in and φ, and they peaked at Vave,in = 1.5 m/s and φ = 1.6, respectively. Both lower and upper propagation limits (i.e., propagable velocities) exhibited non-monotonic tendencies versus φ. Specifically, the lowest and highest propagation limits are 0.3 m/s and 7.0 m/s, respectively, and they both occur at φ = 1.4. Empirical correlations of the propagation limits and propagable velocity range with φ were obtained. In summary, the present study demonstrated the feasibility of cold-state ignition of non-premixed H2/air for curved micro-combustors, and revealed the main flame propagation characteristics.

Interpreting Heat Flux Measurements in a Vitiated Backward-Facing Step Flow

The investigation of the relative impact of convective and radiative heat flux from vitiated gases to a combustor wall was performed in a backward-facing step combustor. Backward-facing step flows have many flow features of gas turbine combustors (recirculation, impingement, and boundary-layer development), but in a two-dimensional, nonproprietary geometry. Reynolds number, gas temperature, and plate temperature were varied as heat flux was measured in different regions of the flow. Measurements were made using a heat flux sensor and radiometer, which measure total and radiative heat flux, respectively. The highest total heat flux was measured at the impingement location and the lowest in the recirculation zone. Separating the total heat flux into the radiative and convective components is not straightforward and requires simulations of the experiment. Spectrally resolved Monte Carlo ray-tracing simulations are used to scale the radiative heat flux measurements for the separation of convective and radiative heat flux from the total heat flux measurements. These calculations show that only about 30% of incident radiation is captured by the radiometer due to spectral differences between the two sensors. Once the radiation measurement is corrected, experimental results show higher radiative than convective heat transfer at low Reynolds numbers (Reh=2000), highlighting the impact of radiative heat transfer in hot gas environments.

Effects of Fuel Flow and Airflow Swirl on Thermal Performance of a Miniature-Scale Combustor for Direct Energy Conversion Systems

Micropower generation and micropropulsion are two emerging fields where micro- and miniature-scale combustors are anticipated to play a significant role. Today, there is a growing interest in combustion-based direct energy conversion modules such as thermoelectric and thermophotovoltaic micropower generators. In this study, the effects of swirl addition to fuel flow and airflow on combustor operational envelope, flame blowout limit, combustion efficiency, exhaust gas temperature, mean outer wall temperature, emitter efficiency, and normalized temperature standard deviation of a miniature-scale (mesoscale) combustor are studied under various equivalence ratios. The findings demonstrate that swirling flows improve the flame blowout limit and operational envelope of the combustor; however, this improvement is more significant for airflow swirl. Besides simultaneous swirling flows of fuel and air result in the highest blowout limit. Additionally, it has been shown that swirl addition improves combustion efficiency and causes a significant amount of heat to be generated, which raises the temperature of the exhaust gas, the mean outer wall temperature, and the emitter efficiency. Furthermore, mean outer wall temperature and emitter efficiency have the highest values for simultaneous swirling flows of fuel and air. It is also observed that increasing the fuel flow swirl number generally lessens the normalized temperature standard deviation (NTSD) and consequently improves the combustor wall temperature uniformity, while for the airflow swirl case, a swirler with 30° vane angle for airstream has a lower NTSD than a 45° vane angle swirler. The results obtained in this study provide useful information for designing a combustion-based direct energy conversion module.

Numerical investigation of premixed methane-ammonia combustion in a mesoscale porous combustor

The present study focuses on the numerical modeling of the premixed methane-ammonia combustion in a mesoscale porous combustor. The primary objective is to reduce carbon dioxide emissions by using ammonia as a carbon-free fuel while maintaining constant the combustor wall temperature compared to pure methane. Ammonia addition in the mixture increases nitrogen oxide compared to pure methane-oxygen combustion, which is undesirable. On the other hand, porous material improves fuel and air mixing and leads to more appropriate fuel distribution which could lower the combustion temperature and as well NOx emission. So, simultaneous using ammonia and porous media in the combustion is the effective combination to reduce the consumption of hydrocarbon fuels. In the current study, porosity of porous media is changed within the range of 50 %–90 %, molar fraction of ammonia is varied from 0.1 to 0.9, and equivalence ratios ranging from 0.8 to 1. Also, to find the optimal combustion parameters, the response surface methodology has been employed. The results indicated that to achieve satisfactory conditions for methane-ammonia-oxygen combustion in contrast to the combustion of pure methane-oxygen, it is the best condition to employ a porosity of 63 %, an ammonia mole fraction of 0.9, and a stoichiometric equivalence ratio. Because of the utilization of porous media, the mean wall temperature reached to 1543 K, indicating a 3.5 % reduction compared to pure methane combustion. Simultaneously, nitrogen oxide emission drops to 2270 ppm, showcasing a 10 % reduction compared to the non-porous media ammonia-methane combustion. Additionally, the use of the 0.9 M fraction of ammonia leads to a noteworthy 75 % decrease in the mass fraction of carbon dioxide emissions compared to pure methane combustion. These findings accelerate the optimal use of carbon-free fuels such as ammonia as alternatives to hydrocarbon fuels.

Effects of wall cavity and fuel injection pressure on the performance of a non-reacting supersonic combustor

This study numerically investigates the flow field of a non-reacting cavity-configured scramjet (Supersonic Combustion Ramjet) combustor at various fuel injection pressures by solving the 2D Reynolds-Averaged Navier-Stokes (RANS) equations, species transport equations, and Menter SST k-ω model. The aim of this research is to reveal the effects of wall cavity insertion and fuel injection pressure (FIP) on the crucial performance parameters i.e., fuel-air mixing efficiency (MxE), total pressure recovery (TPR), and mass-averaged Mach number (MAMN). Accordingly, two trapezoidal cavities of aspect ratio 7 are introduced on the opposite walls of a rectangular combustor. The combustor entrance is configured with rearward-facing steps and it intakes finite parallel air streams through finite-width inlets. Gaseous hydrogen jets are injected 30 mm downstream from the combustor entrance and 10 mm upstream from the cavity leading edge. FIP is varied according to the fuel-to-freestream pressure ratios (FFPR) of 4.5, 9.0, 13.5, and 18.0. The results of the cavity-configured combustor are then compared with the performance of the combustor in the absence of the wall cavities. The results delineate the change in flow structures with the inclusion of wall cavities and variation in FIP. Insight physics of mixing, total pressure loss, and MAMN in different regions of the combustor are studied and the results are quantified for comparison. MxE in a cavity-configured combustor does not monotonically increase with decreasing FFPR as found in the combustor without wall cavities. The shock-shear layer interactions (SSLIs) play a dominant role in mixing inside the cavity-configured combustor. The results also demonstrate that the insertion of wall cavities can increase fuel-air MxE through the formation of cavity recirculation zones. In the cavity-configured combustor, a maximum of 45% MxE is achieved for FFPR 4.5, which is 4% higher than the value obtained from the combustor without the cavities with an expense of 3% greater total pressure loss.

Experimental verification of rotating detonation engine with film cooling

In this short letter, we report an experimental investigation on the integration of film cooling for thermal protection in a 72-mm cylindrical rotating detonation engine (RDE). The cooling scheme involves injection of cooling air through a series of cat-ear-shaped film cooling holes densely distributed along the outer wall of the cylindrical combustor. Our findings reveal the successful initiation of the RDE and sustained propagation of the rotating detonation wave (RDW) when film cooling is activated, and the outflow reaches a supersonic state. Experimental observations corroborate the numerical simulations, indicating a lateral expansion tendency of the cooling jet under the influence of the high-frequency RDW.

Experimental investigation on combustion and emission characteristics of non-premixed ammonia/hydrogen flame

The use of ammonia and hydrogen as fuels to decarbonise the heavy transport industry has attracted worldwide attention. In this work, a swirl-enhanced combustion test rig has been built to investigate the combustion and emission characteristics of non-premixed ammonia/hydrogen flames. The blowoff limits were first examined to ensure that a range of stable flames could be achieved. Emissions containing nitric oxide (NO), nitrous oxide (NO2), ammonia slip (NH3) and unburnt hydrogen (H2) were then measured with a variety of global equivalence ratios, hydrogen blending ratios, inlet gas temperature, swirl numbers and combustion chamber insulation conditions. The structure of non-premixed ammonia/hydrogen flames and the relationship between excited hydroxyl radicals (OH*) and NO emission were revealed using OH* chemiluminescence profiles. The stable non-premixed ammonia/hydrogen flames were achieved when the hydrogen blending ratio was greater than 20%. The optimal emission performance was achieved under stoichiometric conditions, as determined by combustion efficiency. The insulation conditions of the combustor wall played a key role in the emission results, as significant growth of NO and NO2 as well as a reduction of ammonia slip were found. Although a lower swirl number improved the flame stability range, the increases in NO and NO2 emissions were observed.

Exploring combustion characteristics of a novel micro combustor with a fan swirler for thermophotovoltaic system

The combustion and thermal characteristics of non-premixed methane (CH4)–air flames in a swirl micro combustor are numerically investigated for potential use in a thermophotovoltaic (TPV) system. Swirling flows associated with methane–air combustion are simulated using a Reynolds stress model and detailed chemistry of GRI-Mech 3.0. The optimal condition for improved emission and combustion performance is established by taking into account six blade angles and three fuel-lean equivalence ratios, to consider among other geometric features of the fan swirler and operating conditions.The reactive swirling flows in a micro combustor with a fan swirler are modified by altering the blade angle (θb). For θb = 5°, 10°, and 15°, the swirl micro combustor with a two-vortex structure exhibits a significant enhancement of the fuel–air mixing and thermal performance compared to no-swirl combustor. As θb increases, inner vortices close to the fuel stream and outer vortices near the combustor wall behind the fan blades are developed according to the interaction of swirling flows and recirculating flows due to the blockage effect of the fan blades. For θb = 15°, the strong interaction between two vortex regions maximizes combustion efficiency. The combustion efficiency is highest at θb = 15° and lowest at θb = 75°. For three fuel-lean conditions of θb = 15°, the flame zone is enlarged towards the combustion chamber wall, resulting in a high and uniform wall temperature. The resulting radiant emitter efficiencies for a TPV system are increased by 28.3 %–35.1 % compared to that of the no-swirling micro combustor. The results indicate that the fan swirler has recirculation flows for the best emitter and combustion efficiency unlike vane-type swirlers.

Impact of H2 Blending of Methane on Micro-Diffusion Combustion in a Planar Micro-Combustor with Splitter

An investigation into the non-premixed combustion characteristics of methane in a planar micro-combustor with a splitter was performed. The impact of blending methane with hydrogen on these characteristics was also analyzed. Additionally, the effects of inlet velocity and global equivalence ratio on flame location, flame temperature, combustion efficiency and outer wall temperature were studied for three different fuel compositions: pure methane (MH0), 60% methane with 40% hydrogen (MH40), and 40% methane with 60% hydrogen (MH60)). A heat recirculation analysis of the combustor wall was conducted to determine the amount of heat recirculated into the unburnt gas at various inlet velocities for all three fuel compositions. The results demonstrated that the stability limit of methane in terms of inlet velocity (1–2 m/s) and global equivalence ratio (1.0–1.2) was significantly enhanced to 1–3 m/s and 0.8–1.2, respectively, with the addition of hydrogen. At an inlet velocity of 2 m/s, the flame location of 3.6 mm for MH0 was significantly improved to 2.2 mm for MH60. Additionally, outer wall temperature exhibited a rise of 100 K for MH60 compared to MH0. Furthermore, from heat recirculation analysis, when the ratio of heat recirculated to heat loss exceeded unity, the flame started exhibiting the lift-off phenomenon for all the fuel compositions.

ROLE OF DUAL CAVITY ON THE COMBUSTION PERFORMANCE OF A SPLITTER PLATE–ASSISTED SUPERSONIC COMBUSTOR

An unsteady-state simulation using Reynolds-averaged Navier-Stokes was conducted to explore the performance of an ethylene-fueled scramjet combustor employing a dual cavity floor injection strategy and a splitter plate. The validity of this approach was confirmed by comparing it to experimental data, which showed a reasonable match between the observed experimental results and the simulation. A thorough analysis of the injection system's performance is conducted using variables such as the scramjet combustor's total pressure loss, wall pressures, and combustion efficiency. The findings revealed that the leading edge cavity shock waves' interaction from both the walls created a highpressure area close to the cavities, which forces the fuel jets in the direction of the combustor walls. Fuel distribution into the combustor is thereby prompted by the intense interactions that arise between the cavity's aft walls and fuel jets. Moreover, the recirculation zones within the cavity are significantly expanded, improving both the performance of combustion and mixing within the cavity. The combustion efficiency in the current study has shown a notable increase of 13% compared to our previously investigated configuration involving a splitter plate combined with a single cavity combustor.

Development of fully fiber-coupled phosphor thermometry imaging for combustion applications

Fully fiber-coupled phosphor thermometry imaging was demonstrated in an atmospheric fuel-flexible jet-stabilized combustor operated with methane–hydrogen–air flames. Different fuel-air mixedness and operating conditions ranging from 100% methane to 100% hydrogen were investigated. The phosphor GdAlO3:Cr was excited at 532 nm using a fiber bundle, while an imaging fiber bundle was used for signal detection. The presented setup allowed to cover a temperature range from 400–1100 °C with a precision of 0.2–2%. Temperature maps of the combustor walls for six operating conditions will be presented and the influence of the different flame conditions on the wall temperatures will be discussed.