Engineers reveal concept for detonative propulsion

Detonation is a supersonic combustion wave, characterized by a shock wave driven by the energy release from closely coupled chemical reactions. It is a typical form of pressure gain combustion, converting chemical energy into thrust efficiently. The concept of harnessing detonation to improve thermodynamic cycle efficiency and enhance the performance of aerospace propulsion systems has been a subject of interest for many years.

Since the 1950s, various types of detonation engines have been proposed, including pulse detonation engines, oblique detonation engines, and rotating detonation engines. However, these three types of detonation engines encounter challenges such as poor thrust continuity, high starting Mach numbers, and insufficient performance gains, which limit the widespread application of detonation propulsion technology.

In a recent article featured in the Chinese Journal of Aeronautics, Dr. Haocheng Wen and Prof. Bing Wang from Tsinghua University proposed a new concept for detonative propulsion, called the Ram-Rotor Detonation Engine, which is expected to break through the limitations of the above-mentioned detonation engines.

“The original intention of developing this new engine was to improve the structures of rotating detonation engines,” said Dr. Wen. “This concept is also inspired by the ram-rotor compressor.”

The ram-rotor detonation engine, abbreviated as RRDE, mainly consists of a rotating rotor with blades, and a stationary casing. The blades on the rotor are distributed in a helical symmetric manner. The combustible mixture undergoes compression, detonation combustion, and expansion within the variable cross-sectional channels between the blades.

The authors performed primary theoretical and numerical investigation on the RRDE. They established a theoretical model to analyze the relationship between the propulsion performance and parameters such as inlet velocity, rotor rim velocity, and equivalence ratio. It is indicated that for the stoichiometric hydrogen/air mixture, the total pressure gain of RRDE can exceed 3.

Furthermore, they also conducted numerical simulations on the typical structure of RRDE and obtained the characteristic flow field and propulsion performance of the engine. Their simulation results demonstrate that the detonation wave can stabilize and remain stationary within the blades by the given configuration, and can adapt to the variations in parameters such as the equivalence ratio within a certain range.

“Our study primarily verifies the performance benefits and operation feasibility of the RRDE,” said Dr. Wen.

The authors believe that the RRDE has several advantages, including a simple and compact structure, high efficiency, and adaptability to a wide-range of flight Mach number. However, they also candidly acknowledge that the realization of the RRDE is confronted with numerous challenges that demand resolution, such as the stabilization mechanism of detonation wave, supersonic boundary layer interference, implementation of high-speed rotor, as well as thermal protection, etc.

“Our team is conducting ongoing research on key scientific and engineering issues in RRDE,” said Prof. Wang. They expect the RRDE can provide high-performance propulsion for supersonic vehicles in the future.

Provided by
Tsinghua University Press