A two-cylinder pulse detonation engine (PDE) with a single converging nozzle connected to an automotive turbocharger system was constructed. Hydrogen and air are injected through solenoid valves into the combustion tubes in which the mixtures are ignited alternatively for a given frequency. In this research, the frequency is selected as 80 and 100Hz. Power output from the turbine was measured by measuring that of co-axial compressor. The output obtained reached to 6kW and a rotational speed of the turbine reached to 105rpm while a thermal efficiency based on the lower heating value of hydrogen was 4% as maximum which was lower than the theoretically expected value. Combustion process was observed and it was elucidated that a turbine inlet peak pressure was not high enough because of decay of the shock wave in downstream of detonation tube and the steady detonation wave have not been established in the combustion tubes.
In recent years, there has been a renewal of interest in the study of supersonic transport (SST). The high speed, economic viability and environmental compatibility are required for the future SST. So, the wing of SST has to be thin as possible in order to minimize the weight and enhance performances. For this reason, the design of lugs between the main wing and body is very important. In structural optimization of lug, topology optimization has been used to determine the optimal structural lay-out. However, topology optimization has the problem that there are several different solutions depending on the analysis data and multiple loads caused by aeroelastic forces on the wing. In this study, in order to search for an optimal solution from topology optimized solutions for several loads, these solutions are classified according to the topological characteristics by using Self-Organizing Map (SOM). In this case, topological characteristics were represented by using model's spatial densities of topology optimized solutions. Through this classification, it is possible to explore to the optimal topology optimized solution within various topology optimized solutions.
This paper proposes a new method to predict an unstart of a supersonic wind tunnel. The pressure loss caused by both of a model and structures in the wind tunnel and cross-sectional area distribution are considered as well as blockage ratio in the conventional method. The prediction based on the proposed method was obtained by using quasi-1D numerical simulation. In order to validate the proposed method, a wind tunnel test was performed. The predicted maximum blockage ratios quite agreed with experimental ones except for a few cases in which strong shock wave-boundary layer interaction was observed. The method is expected to be available for various wind tunnels and it gives us more accurate prediction than that by conventional theory.
In this paper, we propose a new thrust stand measuring not only constant thrust but also wide-frequency-range thrust variation beyond the resonant frequency. The designed thrust stand uses active control, disturbance observer and measurement of acceleration and solenoid current. A controller monitors pendulum motion and adjusts force of a solenoid actuator in such a way that the pendulum deflection angle is kept constant. Spontaneously, disturbance observer evaluates thrusts with variations directly from measures: acceleration and solenoid-actuator current. Thrust is directly determined from the current and acceleration because spring constant and damping factor originating from wires, tubes and the thrust stand can be ignored due to null-position active control. A calibrator, yielding both constant force and sinusoidal force with offset, was also designed to show that the designed thrust stand can evaluate both constant thrust and its variation beyond the resonant frequency. The prototype thrust stand successfully measured thrust with its variation in the frequency range from 0 to 75Hz, whereas conventional null-position method yielded 410-% overestimation of thrust variation with a phase shift of 120deg at a resonant frequency of 30Hz.