Supersonic Combustion Chamber Research Articles

Computational study of the coaxial air and fuel jet through a 3-lobe strut injector for efficient fuel mixing in a supersonic combustion chamber

In this article, comprehensive simulations of the compressible air stream inside the combustion chamber are done to disclose the mixing and circulation performance of the 3-lobe injector behind the strut. The computational approach is employed to visualize the jet flow with/without the inner air jet released at supersonic flow. The main focus is the importance of lobe shape nozzle on the fuel diffusion into the main stream behind the strut. The role of the shock waves and their contact with the fuel jet flow is also investigated in the present work. Free stream velocity inside the combustion chamber is Mach = 4 while the hydrogen fuel jet is injected via sonic speed. A comparison of single and 3-lobe nozzles indicates that the lobe configuration of the nozzle increases the circulation behind the nozzle. Besides, the usage of the internal air jet increases the contact of the fuel jet with the shear layer initiated from the edge of the strut.

Fuel mixing and diffusion behind the unswept ramp injector with lobed nozzle at combustor of scramjet engine

-The use of 2-lobe nozzle for efficient fuel mixing behind the ramp injector nozzle is comprehensively investigated in this article. Computational fluid dynamic is applied for the evaluation of the three-dimensional flow behind the strut with annular 2-lobe nozzle at supersonic combustion chamber. In this work, the Mach number of free steam air flow and fuel jet are 2 and 1, respectively. The usage of internal air jet for the fuel mixing improvement is also analyzed to disclose the critical features which improve the fuel diffusion in the combustor. The Mach contour on the horizontal and vertical planes in both injection model is compared to show how induced vortex pair is created and extended behind the strut. The result of computational study shows that the injection of the air jet increases the number of vortex pairs behind the strut and the interaction of the fuel with air jet is increased. However, the circulation strength is decreased by inner air jet. Use of inner jet enhances the fuel mixing more than two times behind the nozzle. Our findings show that the fuel mixing is heightened downstream of strut by coupling inner air jet with annular fuel jet.

The fuel mixing of multi-annular extruded fuel jets in cavity flame holder at supersonic combustion chamber: Computational study

A cavity-flame holder is widely used for the injection of the fuel jet in a supersonic combustor due to high fuel residence time. This paper presents extensive results about the impacts of extruded annular multi-jets for improving fuel mixing inside the cavity flame holder. A three-dimensional model of the cavity with multiple extruded nozzles in different lengths and conditions has been examined in this study to investigate the flow and fuel mixing inside the cavity. In addition, the usage of internal air jets is investigated and extensive comparisons between the elongation of the extruded nozzle and the use of the inner air jets for better fuel distribution are done. The presented results show that the usage of both inner air jet and nozzle elongation significantly enhances the fuel distribution within the cavity flame-holder. The achieved finding confirms that the latter technique is more efficient for the fuel mixing in the combustor of a scramjet engine.

Performance analysis of a planar shaped strut injector based supersonic combustion chamber

Abstract This current work presents the performance analysis of a supersonic combustor interface and flow construction through a scramjet engine with a planar shaped strut injector (PSSI) at the supersonic Mach. An important aspect of this study is discovering the fuel mixing mechanism inside the combustion chamber with PSSI. The novel PSSI configuration can enhance mixing and combustion performance. The scramjet configuration is incorporated with a supersonic inlet air temperature of 1250 K, where the vitiated air follows at Mach 3, and this technique is based on a high accelerating effect of the scramjet propulsion mechanism. Scramjet engines can maintain naturalistic high enthalpy conditions in minimum durations. It is observed that the maximum temperature of 3510 K is attained at the recirculating zones produced because of undulation enlargement and therefore the fuel jet losses concentration whereas the maximum combustion efficiency of 86 % is investigated from the current research work.

Computational modeling of the rectangular non-aligned multi-injector for efficient fuel mixing in a supersonic combustion chamber

The present investigation examines the usage of rectangular multi-injectors for fuel injection in a supersonic combustion chamber. To evaluate the fuel jet penetration and distribution, a computational method is applied to model the supersonic compressible flow with cross multi-fuel jets released from annular rectangular nozzles with different nozzle configurations. The main effort of this work is to evaluate the jet interactions in the existence of cross-supersonic flow. Fuel jet penetration and distribution are evaluated for three proposed injector arrangements to attain the more efficient option for better fuel mixing. Our results show that reducing injector space improves fuel mixing inside the combustor via creation of strong vortices. Beside, injection of air from internal nozzle increase fuel interactions and fuel mixing inside combustion chamber.

Enhancing fuel distribution of downward steps in supersonic combustion chambers using shock generators

This study investigates the impact of a shock generator on the fuel distribution of downward step fuel injection in a scramjet engine’s combustor. Computational simulations of CFD are employed to analyze the three-dimensional structure of multi-jets released in a downward-step configuration. The inlet is subjected to a free stream supersonic flow with [Formula: see text], while hydrogen gas is injected at [Formula: see text] through injectors situated on the vertical planes of the downward step. A shock generator with a [Formula: see text] angle is positioned at the top of the domain to induce a bow shock, which significantly affects fuel distribution. The research assesses the influence of free stream and jet pressure on the fuel distribution behind the jets. The results indicate that increasing the free stream flow strengthens the induced bow shock, leading to enhanced fuel jet interactions and improved fuel mixing behind the jets.

The usage of non-aligned multi-circular winding injectors for efficient fuel mixing inside the scramjet engine

The usage of zigzag multi-jet configuration for efficient fuel circulation along the supersonic combustion chamber has been extensively examined in this article. To analyze the flow and fuel jet interactions, computational fluid dynamic is applied as an efficient technique to visualize the flow and fuel jet in the zigzag injection system. Injection via an annular nozzle is compared with coaxial air and fuel jet to find the effective mechanism for well-organized fuel mixing in the combustion chamber of the scramjet engine. The circulation and fuel mixing of the zigzag injection is inspected at a supersonic air stream with Mach = 4. The contour of the Mach value and stream shows that the deflection of the air stream after contact with the core of the upstream jet redirects to the core of the downstream jet and consequently, the fuel mixing is enhanced in the combustion chamber. The usage of an internal air jet expands the performance of fuel mixing of annular jets up to 100 % in the zigzag nozzle arrangement.

Estimation of the fuel mixing of annular extruded fuel multi-jets in cavity flame holder at the supersonic combustion chamber via predictive surrogate model

Cavity flame holder is a well-organized method for fuel mixing inside the combustion chamber of supersonic vehicles. In this study, the combined machine learning technique of proper orthogonal decomposition (POD) combined with Long Short-Term Memory network (LSTM) is used for prediction of fuel jet penetration inside the cavity flame holder at free stream Mach=2.2 is investigated. Computational Fluid Dynamic is applied for the three-dimensional model of a cavity flame holder with extruded multi-nozzles. A comparison of single and extruded multi-nozzles for the fuel mixing at the combustor with cavity configuration is also done. The presented results show that the use of multi-jet efficiently increases the fuel mixing inside the cavity since the vortex structure is enhanced in this configuration. The usage of a shock creator pushes the shear layer into the cavity and limits the fuel penetration inside the cavity. Therefore, the shock creator is not recommended for the fuel mixing of extruded multi-jet injection systems.

Using shock generator for the fuel mixing of the extruded single 4-lobe nozzle at supersonic combustion chamber

The importance of the fuel injection configuration on the propulsion efficiency of high-speed vehicles is apparent. In this article, the use of an annular extruded 4-lobe nozzle for the injection of fuel jet in a supersonic combustor of a scramjet engine in the existence of a shock generator is examined. The main aim of this study is to obtain the efficient jet arrangement for efficient fuel mixing inside the engine of hypersonic vehicles. A numerical approach is used to model the supersonic air stream and cross-jet flow with the SST turbulence model. The role of nozzle altitude and internal air jet on the fuel mixing of the hydrogen within the high-speed domain are disclosed. The importance of the horseshoe vortex and counter-rotating vortex on the fuel distribution is also presented. Our results show that the usage of a coaxial jet instead of an annular jet would increase fuel mixing by more than 40% in the combustion chamber.

Experimental investigation of heat transfer to carbon dioxide in parallel rectangular channels under supersonic mainstream

Active cooling using carbon dioxide(CO2) is a promising method for supersonic vehicles' combustion chamber, but few studies have considered CO2 heat transfer under supersonic mainstream conditions. In this paper, the double-wall heat transfer effect of CO2 under supersonic mainstream conditions is investigated by using the direct-connection experimental platform. The double-wall consists of an inner liner and a cooling jacket with parallel rectangular channels. The inlet CO2 parameter conditions range for T (Temperature) = 263.3 ∼ 272.5 K, m (Mass flow rate) = 50 ∼ 205.3 g/s, and P (Pressure) = 3.87 ∼ 8.88 MPa. It has been found that the magnitude of CO2 mass flow rate has a very significant effect on the effectiveness of thermal protection. The CO2 active cooling provides effective thermal protection for the inner liner at inlet parameter m = 199.1 ∼ 205.3 g/s, P = 8.69 ∼ 8.88 MPa, and T = 263.3 ∼ 266.8 K. Moreover, the heat transfer reaches thermal equilibrium quickly. However, it is more effective in thermally protecting the inner liner near the CO2 inlet than near the CO2 outlet at the inlet parameters of m = 50 ∼ 88.6 g/s, P = 3.87 ∼ 7.74 MPa, and T = 263.3 ∼ 272.5 K. In addition, there may be a risk of structural burnout near the CO2 outlet.

Numerical and experimental investigation of streamwise-vortex/fuel-plume interactions in a scramjet combustor

The interaction between streamwise vortices and fuel plumes was investigated through numerical simulations and experiments conducted in a supersonic combustion chamber. Different interactions between vortices and plumes were generated by varying the position of fuel injection on the alternating-wedge struts. This study also involved the development of a reduced-order model to predict the development of fuel plumes and elucidate the mixing mechanism of streamwise vortices. To validate the accuracy of the reduced-order model, Mie scattering and Acetone-PLIF measurements were employed to observe changes in plume morphology downstream of the struts. By utilizing this model, the influence of fuel injection on the development of streamwise vortices can be assessed effectively. Furthermore, the reduced-order model exhibits reasonable predictive capabilities concerning the evolution of streamwise vortices and fuel plumes, thus shedding light on the underlying interaction mechanism between fuel injection and streamwise vortices.

Numerical investigation on the combustion characteristics of boron powder fuel under H2/Air flame in a supersonic cavity-based combustor

To explore the combustion organization rules of powder-fueled scramjets, this study conducted numerical simulations to investigate the combustion characteristics of boron particles in the supersonic combustion chamber, while varying the injection scheme, cavity structure, and hydrogen flow rate. The results demonstrate that the addition of a small flow of hydrogen assists in the ignition and combustion of boron particles when combined with incoming air in a supersonic combustor. Compared to the injection scheme at the wall of the combustor upstream of the cavity, the proposed intra-cavity injection scheme significantly improves the combustion efficiency of boron particles. Moreover, the combustion efficiency of boron particles improves further as the cavity depth increases. Successful ignition and combustion of boron particles occur when the solid-to-gas ratio (SB/GH) of boron powder fuel to hydrogen is below 20 at a constant boron powder fuel mass flow rate. The highest combustion efficiency of boron particles is observed at an SB/GH ratio of approximately 12.5. Further decreasing SB/GH no longer improves the combustion efficiency of boron particles. The findings of this research can provide valuable insights for the engineering application of combustion organization schemes in powder-fueled scramjets utilizing boron powder as fuel.

The role of the shock generator on the mixing performance of hydrogen jet released from the extruded transverse 3-lobe nozzle in a scramjet engine

The role of a shock generator in the fuel distribution of a scramjet engine is highly significant. In this article, the usage of the erected 3-lobe nozzle in the existence of a shock generator for fuel injection inside a supersonic combustion chamber is fully studied. A three-dimensional model of the extruded 3-lobe nozzle with two altitudes of 4 mm and 2 mm is produced to disclose the importance of the produced vortex upstream/downstream by the usage of the extruded injector. Comprehensive computational analysis is done to investigate the mixing efficiency and fuel diffusion of the proposed jet configuration. Impacts of the coaxial inward air jet on the hydrogen dispersion of the annual extruded 3-lobe injector are also revealed in the present research. The results of the flow structure indicate that the produced vortex upstream of the erected nozzle improves the fuel dispersion behind the hydrogen jet. Our findings show that the effects of injector height are more considerable than the use of an inner air jet for advance of the fuel mixing within the combustor of a scramjet engine.

Using extruded circular multi-injectors to improve fuel jet mixing and distribution in combustion chambers of scramjet

An extensive investigation of multi-nozzle with various heights is done for enhancing the fuel mixing and distribution in supersonic combustion chambers of scramjets by using Computational Fluid Dynamics. Fuel injection and mixing play a crucial role in many industries, including automotive. This study examines the mechanism of hydrogen fuel jet mixing when injected through a multi-nozzle with varying heights in the combustion chamber of a scramjet. The impact of different injector height configurations on supersonic cross-flow is analyzed through computational fluid dynamics, and the flow and fuel mixing are evaluated to determine the most efficient fuel injection setup. A comparison is made between the proposed multi-jet configurations and simple multijet configurations to identify the primary hydrodynamic and mixing benefits of multi-jet configuration with different heights. The findings indicate that the use of multi-jet injectors with different heights decreases the circulation factor and improves fuel mixing downstream of four jets by 40 %.

Usage of extruded diamond multi-injectors for improvement of fuel mixing inside the supersonic combustion chamber

The main attention of this work is to investigate the usage of diamond multi extruded injectors on the fuel distribution in combustor of scramjet. This study applied the computational technique to simulate the transverse fuel jets released from extruded nozzles. The main focus is to evaluate the role of induced shock waves on the penetration and distribution of fuel jets. The effects of jet space and usage of annular nozzle for the fuel injection system are revealed. Results of this work shows that the gap of jet would be more efficient for mixing when the inner air jet is also used. Also, injection of the air from the core of annular nozzle significantly increase the fuel mixing.

Effect of shock generator on fuel mixing in an annular single lobe transverse nozzle at the supersonic combustion chamber of a scramjet engine using computational fluid dynamics

This study investigates the influence of a wedge shock generator on hydrogen mixing in an annular single lobe transverse nozzle at the supersonic combustion chamber of a scramjet engine using computational fluid dynamics (CFD). The fuel mixing process is crucial for efficient combustion in scramjet engines, which operate at high speeds and require rapid mixing of fuel and air. The shock generator is a device that generates a shock wave in the flow field, which can enhance mixing by increasing turbulence and promoting the fuel penetration into the air stream. A comparison of three lobe injectors is done to attain the efficient nozzle type for the fuel mixing inside the combustion chamber. CFD simulations were done to analyze the consequence of the shock generator on fuel mixing in the nozzle and assess its potential for improving combustion efficiency. The results show that the usage of shock generator can significantly enhance fuel-air mixing in the nozzle, leading to improved combustion efficiency and reduced emissions. The findings of this study provide valuable insights into the design and optimization of shock generators for scramjet engines, which can contribute to the development of more efficient and sustainable air-breathing propulsion systems.

The impact of inner air jet on fuel mixing mechanism and mass diffusion of single annular extruded nozzle at supersonic combustion chamber

In this research, the usage of an extruded annular nozzle for mixing fuel through the combustion chamber is fully studied. The chief focus is to reveal the flow of the fuel jet by three-dimensional simulation of the sonic hydrogen jet with two nozzle heights (1 mm and 2 mm). The main novelty of this study is the connection of mass diffusion mechanism on fuel mixing of jet released from the extruded nozzle in combustion chamber. The computational method is developed for modeling of highly compressible airflow with a cross-fuel jet released from an extruded nozzle. Both annular and coaxial fuel and air jet are investigated to find the efficient mechanism of fuel distribution inside the combustor. The flow parameters and vortex structure near the injector are fully analyzed. RANS equations are used for the modeling of the high-velocity flow. Our results show that the injection of fuel through the extruded nozzle improves the performance of fuel mixing in the combustor. Coaxial fuel and air jets released from extruded nozzle is more efficient for fuel injection system due to formation of strong interactions of the fuel with free air stream.

Comparison of the different shapes of extruded annular nozzle on the fuel mixing of the hydrogen jet at supersonic combustion chamber

The fuel mixing mechanism is a critical aspect of the propulsion system of hypersonic vehicles. This study aimed to comprehensively investigate a novel jet configuration that enhances fuel mixing in the combustion chamber. The primary objective was to analyze the significance of vortexes in fuel distribution within the combustion chamber. Computational fluid dynamics was used to investigate the three-dimensional structure of the transverse fuel jet released from an extruded nozzle in a supersonic free stream. The influence of jet type (circular and lobe structure nozzles) and nozzle height was fully explored in this research. The free stream air jet was supersonic (Mach = 4), and the hydrogen jet was injected using various annular nozzles in sonic condition. The results obtained show that the use of an annular circular nozzle is efficient in fuel mixing behind the extruded nozzle. Additionally, fuel mixing improves by approximately 90% when the height of the extruded 3-lobe injector is increased by twice its original length.

Influence of coaxial fuel–air jets on mixing performance of extruded nozzle at supersonic combustion chamber: Numerical study

Increasing the mixing efficiency of the fuel jet along the combustion chamber is a crucial step for the advancement of the current high-velocity vehicles. In this article, comprehensive computational investigations have been performed to disclose the role of an annular air jet on the fuel mixing of the single extruded nozzle located inside the combustion chamber. This study has tried to offer hydrodynamic insight about the jet flow feature when released from the extruded nozzle in supersonic cross flow. Computational fluid dynamic is used for the visualization of fuel jet interactions with air stream. Effects of nozzle height on the mechanism of fuel jets are extensively analyzed in this investigation. Our results show that the injection of the annular jet would increase the strength of the circulations, and consequently, fuel mixing improves inside the combustion chamber. Our findings display that fuel mixing increases about 100% by the injection of the annular air jet in the combustion chamber.

Experimental Study of the Formation and Evolution of Gas Jets in Supersonic Combustion Chambers

A simple and efficient flow field visualization method (based on shadow imaging) was applied in a direct-connect test to explore the influence of the momentum flux ratio and the jet angle on the formation and evolution of nitrogen jets in supersonic combustion chambers. The test setup adopts a rectangular flow passage to simulate a flight condition with Mach number of 6 and altitude of 25 km. The experimental results showed that (a) the flow field visualization method adopted in this paper can clearly register the formation and evolution of the shock wave structure in the flow field and the windward shear vortex on the jet surface. (b) The evolution process of the windward shear vortex is significantly affected by the jet angle. In particular, the stretching position of the windward shear vortex changed when the jet angle was obtuse. (c) The bow shocks showed local distortion due to the periodic generation of large-scale shear vortexes. (d) Under the working conditions of the test, the largest instability of the flow field was found for a jet angle of 120°. This work provides, on one hand, the experimental basis for clarifying the formation and evolution mechanism of transverse gas jets, and on the other, valuable data that can be used to validate numerical simulations.