Effect of Fuel-Injection Distance and Cavity Rear-Wall Height on the Flameholding Characteristics in a Mach 2.52 Supersonic Flow

Scramjet based on solid propellant has become a potential choice for the development of future hypersonic vehicles. In this paper, a boron-containing solid rocket scramjet based on the central strut injection was proposed, and the ground direct-connect experiment with the equivalence ratios of 0.43 to 2.4 under the flight condition of Mach 6, 25 km was carried out. The pressure and flow rate over time were measured in the experiment. The results show that the engine can realize stable supersonic mode or subsonic mode combustion by changing the gas flow rate. The engine can effectively increase the combustor pressure, reduce the unstable combustion time, and advance the strong combustion position by increasing the gas flow rate. The engine achieved high combustion efficiency when the equivalence ratio was about 1, with a maximum of 88.28%. A numerical simulation analysis was also carried out in this paper. Compared to the experimental results, the pressure error obtained by numerical simulation was less than 4%, and the typical position error was less than 3%, suggesting that the simulation model can be used to predict the behavior of scramjet.

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Solid Rocket Scramjet Based on Central Strut

Zeng,

Wang,

Huang

et al. 2024

“…Kannaiyan [22] conducted a study on the combustion of ethylene fuel under singlestep and multi-step reactions based on the heat release rate parameters at different locations in the combustion chamber. He et al [23] conducted experimental and numerical studies on the flame stability characteristics of ethylene fuel in a scramjet concave cavity combustor. The results show that a shorter injection distance can effectively reduce the lean purge limit of the combustion chamber, while the rear wall expansion chamber and a longer injection distance can effectively increase the rich blowout limit.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Combustion Mechanism with Multi-Position Injection in a Dual-Mode Combustor

Dong³

et al. 2023

To improve the flame propagation, combustion stability, and uniformity of the temperature field, multi-position injection is applied in a dual-mode combustor by controlling heat release in different locations. Using the chemical reaction of the finite rate combustion model and the detailed reaction mechanism of hydrogen combustion as described by Jachimowski, the influence of different multi-position injection patterns in a dual-mode combustor is analyzed. The one-equation Large Eddy Simulation (LES) turbulence model was chosen to define the sublattice turbulent viscous terms in a three-dimensional scramjet model. Based on a combustion chamber, the effect of the injection equivalent ratio (0.35–0.70), the relative position of the nozzle holes, and the injection pressure on the combustion process and flow field characteristics are analyzed with multi-position injection. The combustion efficiency, total pressure recovery coefficients, and pressure distribution under different operation conditions are compared. We observed that the combustion intensity increases and the upstream combustion shock string distance becomes greater with increased equivalent ratios. When the global equivalent ratio of multi-position injection remains unchanged, the arrangement of nozzles with the small injection spacing, i.e., two injection holes arranged face to face on the upper and lower walls, or the setting of multiple injection holes with the same pressure, can effectively increase the stability rate of the combustion flow field. In addition, the combustion efficiency at the outlet and the internal pressure of the combustion chamber in the stable state are also improved, relative to the increased total pressure loss.

“…The concepts of supersonic combustion and scramjets make it possible for aircraft to achieve hypersonic flight in the atmosphere. However, ignition and flame stabilization are challenging issues in a scramjet [1][2][3][4][5]. The residence time of the air in a combustor (t flow ≈ 0.5 ms) is even shorter than the typical self-ignition time of fuel (t ig ≈ 1-2 ms) [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Supersonic Combustion Mode Analysis of a Cavity Based Scramjet

Meng

Sun

et al. 2022

Since flame stability is the key to the performance of scramjets, scramjet combustion mode and instability characteristics were investigated by using the POD method based on a cavity-stabilized scramjet. Experiments were developed on a directly connected scramjet model that had an inlet flow of Mach 2.5 with a cavity stabilizer. CH* chemiluminescence, schlieren, and a wall static pressure sensor were employed to observe flow and combustion behavior. Three typical combustion modes were classified by distinguishing averaged CH* chemiluminescence images of three ethylene fuel jet equivalence ratios. The formation reason was explained using schlieren images and pressure characteristics. POD modes (PDMs) were determined using the proper orthogonal decomposition (POD) of sequential flame CH* chemiluminescence images. The PSD (power spectral density) of the PDM spectra showed large peaks in a frequency range of 100–600 Hz for three typical stabilized combustion modes. The results provide oscillation characteristics of three scramjet combustion modes.