提高高马赫数超燃冲压发动机推力的理论方法

Translated title of the contribution: THE THEORETICAL METHOD TO INCREASE THE THRUST OF HIGH MACH NUMBER SCRAMJETS

Xin Han, Yunfeng Liu, Zijian Zhang, Wenshuo Zhang, Kaifu Ma

Research output: Journal article publicationReview articleAcademic researchpeer-review

Abstract

The oblique detonation engines and shock-induced combustion ramjets have been proved to be practicable for high flight Mach number air-breathing engines in recent years. However, whether the oblique detonation engines and shock-induced combustion ramjets have enough thrust or not is unknown yet. In this paper, the combustion characteristics and propulsive performance of scramjets are discussed theoretically. Firstly, the mechanism of engine unstart of scramjets is discussed from the point of view of shock/shock interaction and deflagration-to-detonation transition. The results show that engine unstart process is very similar to the deflagration-to-detonation transition process. In the combustor of scramjets, the maximum velocity of the deflagration wave is very close to the detonation velocity. Therefore, the C-J detonation velocity is defined as the stable operation boundary of scramjets. Secondly, the formula of thrust produced by the divergent nozzle is put forth and key parameters influencing thrust are obtained. According to the thrust formula, supersonic combustion is beneficial for increasing the thrust. The main way to increase the thrust is to increase the pressure of combustion products. The propulsive performance of scramjets is theoretically analyzed by using C-J detonation theory, which is the critical condition when the engine is thermally choked. Finally, the theoretical method to increase the thrust is discussed. For high flight Mach number scramjets Ma ≥ 12, the velocity in the isolator is much faster than the C-J detonation velocity in the combustor and the problem of engine unstart disappears. Therefore, extra fuel and oxidizer can be injected into the combustor to increase the thrust further as long as the shock wave generated by the high pressure combustion products is slower than the air velocity in the isolator. The theoretical results agree well with the existing experimental and numerical results, which can be used as a baseline for the development of high Mach number scramjets.

Translated title of the contributionTHE THEORETICAL METHOD TO INCREASE THE THRUST OF HIGH MACH NUMBER SCRAMJETS
Original languageChinese (Simplified)
Pages (from-to)633-643
Number of pages11
JournalLixue Xuebao/Chinese Journal of Theoretical and Applied Mechanics
Volume54
Issue number3
DOIs
Publication statusPublished - 18 Mar 2022

Keywords

  • High flight Mach number scramjets
  • Oblique detonation engines
  • Shock-induced combustion ramjets
  • Supersonic combustion
  • The method to increase the thrust

ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanics of Materials
  • Mechanical Engineering
  • Applied Mathematics

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