Combustion test of afterburner for pre-cooled turbo jet engine (PCTJ) is carried out. A sub-scaled combustor is installed at the end of a high enthalpy wind tunnel. The airflow is heated by a pebble-type heater up to 1000K, which is equivalent to the exhaust gas of the core engine. Gas hydrogen is injected as fuel in the hot air and burnt. Seven injectors are tested to investigate the effect of fuel injection method on combustion efficiency. For normal alignment injectors, the combustion efficiency increases with increase in the equivalence ratio, but when the equivalence ratio is higher than four, the combustion efficiency does not increase. On the other hand, for a zigzag alignment injector, the combustion efficiency increases steadily and is almost 100% when the equivalence ratio is five. There is a good correlation between vertical component of fuel jet momentum and combustion efficiency.
It has been investigated that a battery of an electric-powered airplane is charged with a propeller used as a windmill during a descending flight. In case of the propeller used in the present paper, the maximum efficiency of the windmill is about 10%. For the maximum efficiency, the pitch angle of the windmill at any spanwise positions, which is measured from the rotational plane, is smaller than that of the propeller by 13--14deg. With the charged battery, the airplane can make a horizontal flight with its distance of about 60% of the descending distance. Furthermore, when the pitch angle of the windmill is same as that of the propeller, the airplane can make a horizontal flight with its distance of about 30% of the descending distance.
The purpose of this study is to propose a new landing point determination method for autonomous lunar/planetary landers. To decide a target point for safety landing, the proposed method utilizes image processing algorithms that use brightness value for detecting flat and horizontal regions. In addition, the proposed method applies fractal dimension analysis for judging scientifically interesting regions. The proposed method is evaluated by image processing simulations using a CG image generated by DEM that is produced by fractal modeling method to express natural geometry, based on observed data.
Aerodynamic characteristics of a cylinder with a fineness ratio 1.68 in axial flow were examined experimentally using a magnetic suspension and balance system. Sting support interferences were also estimated by use of a dummy sting located at the back of the cylinder. Flow field structures were measured using particle image velocimetry. There were little influences of the rear sting on a drag coefficient for the Reynolds numbers from 6.7 × 104 to 1.9 × 105. In addition, over the entire measurement range, the drag and base pressure coefficient depended little on the Reynolds number. On the other hand, it was revealed that the rear sting made the flow field non-axisymmetric. In the case with the sting, the streamwise velocity at the rear of the cylinder was a little slower with the distance from the sting, while the turbulence intensity became much stronger. The similar features were observed near the cylinder side surface. Furthermore, high values of the turbulent fluctuation perpendicular to the freestream direction were observed near the trailing edge of the cylinder. It suggested that the rear sting had stronger influences on the flow away from the sting and the effects spread upstream.
Lift-off height and flame curvature of a triple flame formed with methane-air and propane-air mixture are investigated experimentally in various fuel concentration gradients and sound pressures. Burning velocity of the triple flame has strong correlation with fuel concentration gradient, and lift-off height is determined by balanced position between the burning velocity and unburned gas velocity just ahead of the leading edge of triple flame. Therefore, to investigate the influence of acoustic oscillation on fuel concentration gradient, multi slot burner which can make mixing layer with uniform distribution of streamwise flow velocity is employed. Fuel concentration gradient is calculated by numerical simulation in various sound pressures. The lift-off height decreases and the flame curvature is slightly changed by increase in sound pressure. It is thought that the acoustic oscillations change the fuel concentration gradient and flame moves to upstream where the fuel concentration gradient is steep originally without sound. The flame curvature slightly changes by sound, whereas it is thought that the influence of change in the flame curvature by acoustic oscillation does not dominate the change in the lift-off height.