Cha Xiong

One-dimensional unsteady design method for pulsed detonation engine nozzles

A new design method for pulse detonation engines nozzle was developed theoretically. The effects of non-uniform exhaust on the performance of pulse detonation engine were analyzed by constant volume cycle model. The results showed thrust losses induced by the non-uniform exhaust could be decreased by increasing fill pressure ratio. If the fill pressure ratio was larger than 10, the performance losses with a fixed optimal nozzle could be controlled within 3%. The optimal area ratio of the nozzle was obtained when the time-averaged pressure at the nozzle exit equals the ambient pressure. This was also applicable to one-dimensional unsteady frictionless pulse detonation engine model. Thus an optimal area of the nozzle could be calculated by the time-averaged total pressure. Compared with the zero-dimensional results obtained by numerical search technique, the errors of predicted optimal area could be neglected if fill pressure ratio is too large to prevent shock from propagating back to the nozzle. And the errors of predicted optimal area are lower than 5% compared with the results of the one-dimensional unsteady pulse detonation engine model.

Multicycle Detonation Investigation by Emission–Absorption-Based Temperature Diagnostics

In order to analyze and improve the performance of pulse detonation engines (PDEs), detailed detonation processes deserve much more attention. However, the measurements of characteristic parameters are difficult because the flow field in detonation is unsteady, with high pressure and high temperature. A new device based on the emission–absorption principle is developed specially for measuring pulsed temperature in a PDE plume. Experimental results show that the measured pulsed temperature can diagnose the PDE operation, such as multicycle detonation wave formation, operation frequency, and overfilling process. Effects of PDE configuration, operation frequency, and fuel on PDE plume temperature were investigated experimentally. The plume temperature increases with operation frequency. The PDRE average peak plume temperature is much higher than direct-connected PDEs and air-breathing PDEs. The newly developed plume temperature measurement method is simple, cheap, and easy to operate, which provides a useful tool to diagnose PDE multicycle operation and interaction of external flow field and PDE operation.

Experimental Study on DDT Characteristics in Spiral Configuration Pulse Detonation Engines

Abstract This work investigated features of the deflagration to detonation transition in a curved tube. A number of experiments were performed to acquire the transition rule of DDT, which would provide the design data and theoretical basis for the curved detonation chamber. The content of research is as follows: (1) Flow resistance experiments of nine detonation chambers have been explored. The results show that the spiral configuration can reduce the axial length of DC, and the total pressure recovery coefficient increases with the spiral pitch. (2) Single-cycle detonation experiments have been conducted using the 9 tubes in the resistance experiments. Liquid-gasoline/air is used as the detonative mixture in all the experiments. The detonation experimental results indicate that there is no detonation wave formed in the straight tube, but in all the selected spiral tubes fully-developed detonation waves have been obtained; compared to the straight tube case, the DDT time decrease with the decreasing of the radius of curvature (RC) by 6.2%∼19.8% in the spiral detonation tubes.

Experimental Investigations of a Pulsed Detonation Combustor-Turbine Hybrid System

Experimental studies were performed to investigate the interactions of a pulse detonation engine (PDE) tube integrated with a radial flow turbine of a turbo-charger and to examine whether a compressor and turbine could be used in the harsh pulsing flow of a pulse detonation engine. The effect of equivalence ratio on the attenuation of the peak pressure exiting pulse detonation combustor (PDC) through a turbine was also investigated. Liquid C8H16 and air were used as the fuel and oxidizer. The experimental rig can be operated stably under the firing frequency with a range from 1 to 10 Hz. The fully developed detonations are propagating directly into the turbine inlet and yet the turbine still functions despite over 12,000 detonations, showing no visible pitting or discoloration. The air mass flow rate at the exit of the compressor is about 100 kg/h greater than that at the inlet of PDC. The peak pressure exiting PDC firstly increases and then decreases with increasing equivalence ratio from 0.86 to 1.27. The maximum peak pressure exiting PDC is achieved at an equivalence ratio of 1.15. The turbine attenuates the strength of detonation driven shocks about 6.5-7.5 dB. But the attenuation trend is opposite to that of peak pressure.

The Thermodynamic Performance of Ideal Single-tube Air- breathing Pulse Detonation Engine

A new single-tube air-breathing pulse detonation engine (APDE) with bypass air duct is introduced. It is composed of inlet, valve, detonation chamber, bypass air duct and nozzle. Based on the analysis of the operation cycle of the APDE, airstreams flowing into the engine can be separated into three parts: one is flowing out from the engine through the bypass; one is exhausted from the nozzle as purge gas; and the else is mixed with fuel and is combusted. And the concept of cycle factor α that represents the ratio of air quantity for detonation combustion to incoming air quantity is defined to analyze the influence of the mass distribution on the performance of APDE. Although α has no effect on the cycle thermal efficiency of APDE, it influences the engine propulsive performance. When the APDE is full fuel filled and with the equivalent incoming air-flow and fuel-flow rate, the APDE will be superior to ramjet for 0∼5 Mach if α is larger than 0.8. When the APDE and ramjet work with equal mass fuel-air ratio of combustion, the specific fuel consumption of APDE is lower than that of ramjet for 0∼5 Mach. Also, if a is higher than 0.9, the specific thrust of APDE is higher than ramjet for 0∼5 Mach. Further, the operation mode of partial fuel filling can be used to enhance the performance, but it simultaneously decreases the total thermal cycle efficiency.© 2006 ASME

Performance Estimation for Air-breathing Pulse Detonation Engine with Bypass and Mix/Separate Exhaust

Performance model, based on quasi 1-D, unsteady computational fluid dynamics simulations, was developed to estimate the performance of two kinds of single-tube airbreathing pulse detonation engines (APDE) namely (i) APDE with bypass and separate exhaust and (ii) APDE with bypass and mix exhaust. The effect of bypass on the inlet was analyzed first and the results shown that the introduction can weaken the influences of the on-off of valve at head of detonation chamber on the operation performance of inlet and decrease the necessary capacity of acoustic volume at the downstream of the inlet. Then the performances of the two types APDE were researched. If the configuration of APDE is reasonable, the propulsive efficiency of APDE can be greatly enhanced when the flow in the bypass were mixed with the high temperature combustion products.