An Investigation On Six-tube Two-phase Valveless Pulse Detonation Engine

The turbofan and pulse detonation combined engine is a concept propulsion system. In this system, traditional afterbuener of the turbofan may be replaced with multi-tube pulse detonation combustion chamber at the bypass of the turbofan. Compared with single tube PDE, there are many difficulties in coordinate work of each pulse detonation tube. In order to explore design theorys and methods of six-tube two-phase valveless PDE, six-tube valveless PDE was manufactured and several key technology research of PDE was carried out. The main production include:1)The six-tubeφ61mm PDE was designed and machininged. The aero-valve as a one-way valve was optimized to make total pressure loss small and annular passage area was sure to be uniform to make fuel uniform in circle direction. The inlet of single PDE was designed and the center cone was installed to reduce total pressure loss. If inlet of single PDE works normally, the volume of inlet should be as small as possible. The pneumatic atomizer for each PDE was designed and half V blunt body and groove ignition equipment were also designed according to the rule of holding the ignition source. Based on deflagration to detonation transition (DDT) research, combustion strengthen equipments were designed. according to the different process of DDT, different methods were applied.The structure of six-tube PDE was design, such as the common inlet of six-tube PDE, fuel supply system for six-tube PDE et al.2)The relationship between resistance loss in common condition and the peak pressure of detonation wave under different structures was studied and the concept of effective and ineffective pressure loss was defined. It is showed that if the cone reflector assembly was installed downstream the medium shock wave, detonation near the the cone reflector assembly would be triggered and the peak pressure was improved, so total pressure loss caused by the the cone reflector assembly was mainly effective. It should be careful to install blunt body downstream the two-phase fuel because: first, blunt body would improve total pressure loss, reduce the airflow speed so as to increase the SMD of fuel atomization field. Secondly, the fuel particle would knock on the surface of blunt body to form oil film to decrease the peak pressure. The pressure loss of center cone was ineffective because center cone influence the desquamation of eddy under the inducement speed. For spiral obstacle, it can reduce DDT distance, improve the peak pressure of detonation because its surface was benefit for interaction of shock wave and flame. In a word, the performance of spiral obstacle assembly is better than that of circular annular obstacle assembly. 3)The key technologies of six-tube valveless PDE was broken through after several reforms for six-tube PDE. According to the results,the six-tube PDE can work coordinately and continuously at the total operation frequency 90Hz.Based on analyzing the operation theory of six-tube,the isolation part in fuel pipe was used to solve the pressure influedce between detonation tube and oil-supply system. It was helpful to add front evaporator before the spark plug when understanding ignition theory. It was succeedful that improving combustion-strengthen device and increasing the performce of fuel evaporation (adding back evaporator).4)The theory computation model which considers total pressure loss was brought forward. According to the results, the circle time of PDE would enlarge when coefficient of total pressure loss increases. On the other side, average thrust would decrease when coefficient of total pressure loss increases. At subsonic fligh, the working frequency and average thrust would be large as mach number turned large. Otherwise, Specific Fuel Consumption(SFC) decreased as mach number turned large.