Numerical Study on Regenerative Cooling Characteristics of Kerosene Scramjets

Xuan Jin,Chibing Shen,Xianyu Wu,Li Yan

doi:10.1155/2020/8813929

Xuan Jin, Chibing Shen + Show 2 more

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https://doi.org/10.1155/2020/8813929

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Abstract

The use of kerosene-based regenerative cooling for scramjet has been found widespread attention due to its inherent nature of high energy utilization efficiency and good thermal protection performance. In order to provide a reference for the later design and experiments, three-dimensional turbulence simulations and sensitivity analysis were performed to determine the effects of three operating mode parameters, heat flux, mass flow rate, and outlet pressure, on the regenerative cooling characteristics of kerosene scramjets. A single rectangular-shaped channel for regenerative cooling was assumed. The RNG k-ε turbulence model and kerosene cracking mechanism with single-step global reaction were applied for the supercritical-pressure heat transfer of kerosene flows in the channel. Conclusions can be drawn that as the kerosene temperature rises along the channel, the decrease of fluid density and viscosity contributes to increasing the fluid velocity and heat transfer. When the kerosene temperature is close to the pseudocritical temperature, the pyrolysis reaction results into the rapid increase of fluid velocity. However, the heat transfer deterioration occurs as the specific heat and thermal conductivity experience their turning points. The higher heat flux leads to lower heat transfer coefficient, and the latter stops rising when the wall temperature reaches the pseudocritical temperature. The same rising trend of the heat transfer coefficient is observed under different outlet pressures, but the heat transfer deterioration occurs earlier at smaller outlet pressure for the reason that the corresponding pseudocritical temperature decreases. The heat transfer coefficient increases significantly along with the rise of the mass flow rate, which is mainly attributable to the increase of Reynolds number. Quantitative results indicate that as the main influence factors, the heat flux and mass flow rate are respectively negatively and positively relative to the intensification of heat transfer, but outlet pressure always has little effects on cooling performance.

Highlights

As the vehicle speed moves into supersonic and hypersonic regimes, the supersonic combustion ramjet system must provide higher combustion pressure and larger efficient thrust [1,2,3,4,5]
Based on the analysis of this study, the following conclusions can be made: (1) For the basic case, the kerosene density and viscosity decrease with the increase of the kerosene temperature rises, which leads to the rise of fluid velocity and the intensification of heat transfer
The specific heat and thermal conductivity, respectively, reach the maximum and minimum when the kerosene temperature is close to the pseudocritical temperature (708 K) at 5 MPa, and the heat transfer deterioration occurs the pyrolysis reaction promotes the rapid increase of fluid velocity

Summary

Introduction

As the vehicle speed moves into supersonic and hypersonic regimes, the supersonic combustion ramjet (scramjet) system must provide higher combustion pressure and larger efficient thrust [1,2,3,4,5]. Sorts of thermal protection techniques [6], such as the air-breathing cooling and passive thermal protection techniques, are unable to realize effective thermal protection for high-temperature propulsion components. Confronted with this challenge, the kerosene-based regenerative cooling technology has been proposed to sustain more stable operation for the scramjet system [7,8,9]. The heat-absorbing capacity of kerosene significantly increases by means of pyrolysis [11], which is a nonlinear transformation process with strong coupling effect between heat and mass transfer Many efforts, both experimentally and numerically, have been directed to obtain the fundamental understanding of supercritical-pressure heat transfer characteristics during the above active cooling process. Pu et al [13] developed and validated the CFD code for conjugate heat transfer

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Conclusion