Investigation On Improving Performance Of Aero-valve Pulse Detonation Engine

As a new concept engine the pulse detonation engine (PDE), due to its simple structure andexcellent performance caused by the strong interest of the countries in the world. The content of thisthesis include inversing-rotating aero-valves, thermal jet ignition technology, surface evaporation ofliquid fuel technology using waste heat of detonation tube and initiation and propagation ofdetonation in annular-sector tube, the study results are as follows:1. A new type of aero-valve, called inversing-rotating aero-valve, was advanced by summarizingthe experience of former designers. Experimental results showed that aero-valves with larger swirlnumberS_N, which are fixed straight tubes (1.5D long) ahead of inlet, have more attractive one-wayperformance. The axial inversing-rotating aero-valve shows up more adaptability for PDE with100mm-200mm diameter, while considering pressure loss and one-way performance. Furthermore,the pressure of travelling waves to upstream through valve can be decreased about70%. A series ofnumerical investigation offer a result, that is, the optimum value of swirl number is approximately1.0.2. To take full advantage of the flame accelerated fast in the recirculation region located in thedownstream of the aero-valve and to overcome the shortcomings of Ignition difficulties, the thermaljet ignition technology is used in this paper. Using parallel direct thermal jet ignite the Combustiblemixed gas in a PDE model with internal diameter (ID)114mm and length of1100mm (10D) anddetonation waves in the frequency of50Hz is observed.3. In order to further strengthen the combustion heat release intensity in the head of thedetonation chamber, the central swirling thermal jet ignition technology is used in the PDE. Anintegrated design with double swirl air-blast atomizer and ignition spark plugs, forms a precombustionchamber of PDE. The atomization and ignition performance of precombustion chamber areinvestigated through experimal and numetical method. The results display that the reliable ignitionrange of precombustion room is very wide, and it is efficient to provide ignition energy for PDE. Butit must match the head structure of PDE such as aero-valve and spray device. In this paper,precombustion chamber throat area should be selected between5%-7%of the pneumatic valve throatarea, thus, the best results display.4. The surface temperature distribution of detonation tube with60mm ID is obtained withdifferent work frequency of PDE. A annular evaporator is designed, which is injected with air andkerosene. The characteristic of the kerosene in evaporator are given with PDE operating frequency, airmass flow, kerosene mass flow and the ratio air and oil. 5. Gasous kerosene offerd by evaporator is injected to detonation chamber and ignited,experimental result display the characteristic of initiation and propogation detonation wave areimproved significantly. There is an optimum range about the air mass flow and the proportion ofkeserone in the fuel involved combustion.The PDE detonation wave propagation speed in this rangeclose to the case using the gasous fuel, the detonation wave initiating time and the shortest distance.6. In the study about the detonation propagation characteristics in the annular-sector tube, it isfound that the region in the lower convex of the annular-sector tube is the most intense reaction, themaximum pressure and the first initiation position of the entire cross-section in the detonation. Due tothe variance of the reaction in the entire cross-section of the tube, the detonation cell size changesalong the radial direction, that is the more close to the outer ring of the annular-sector tube, the largersize of the detonation cell. It is also found that the influences of the oxygen content in the air on theaccelerated propagation process of kerosene/air mixture in the detonation tube is very significant.The study results show that the steady-state detonation wave will be produced in the condition, whichoxygen content is greater than31.5%, in the chemical appropriate mixture of gas and air; and theDDT process will be faster accelerated in the little oil-rich mixture condition. The sensitivity of DDTprocess to the oil-rich mixture condition is greater than the oil-poor mixture condition. The initialtemperature of the mixed gas has little effect on the flame acceleration in tubes, when the temperatureof mixed gas is changed in the range of460K~579K. The variation and values of specific impulse ofthe fan ring detonation tube in the kerosene/air mixture circumstances is basically similar with that inthe same-area circular detonation tube.7. It is found that the influence of the resistance of test bench to the measured values of thrustmust be considered in the PDE thrust measurement experiment, and the thrust value, measured by thesteady-state sensor, should be corrected with the bench resistance value. A PDE sample, which isflow-backwards pneumatic valve, rotating jet ignition, detonation chamber diameter of114mm, theignition frequency of40Hz, was invented. We tested the different combination ways of the sheetspoiler blunt and parabolic spoiler blunt, in the PDE sample, and pressure values and thrust valueswere measured in the end of detonation chamber. The results of study show that the maximum thrust,18.4kgf, is acquired when we used three sheet spoiler blunt and a parabolic spoiler blunt.