Toshihiro Nakano

Active Control of Twin-Pulse Combustors

The pressure losses of steady-flow combustors can be overcome with so-called pressure gain or pulse combustors. Higher combustion efficiency and low NO x are the well-known advantages that outweigh the disadvantages of noise, combustor control, and lower operational flexibility. Inlets with variable cross section enable an active control of the combustor as gas generator for turbines. Therefore, a special emphasis is given to the design of the inlet, its control capacity, and its impact on combustor and turbine performance.

Effect of blade surface roughness on performances of axial flow fans with different blade cambers.

In order to clarify the influence of blade camber ratio on the effect of surface roughness on axial flow fan performances, three rotor blades with different camber ratio have been designed for the same fan specification, and performance tests have been conducted by changing sand grain roughness of blade surface. The axial fan rotor with larger camber indicates greater deterioration of performance with increasing surface roughness. In the case of small camber ratio, the torque coefficient of the fan does not change with roughness. Also the effect of blade surface roughness has been investigated from the viewpoint of boundary layer theory.

Studies on Pulse Jet Engine by Wind Tunnel Testing

Simple design and efficiency make pulse jet engines attractive for aeronautical short-term operation applications. An active control system extends the operating range and reduces the fuel consumption considerably so that this old technology might gain a new interest. The results on wind tunnel experiments have been reported together with the impact of combustion mode (pulse or steady) on system performance.

Flow Visualization of Separated Flow in the Wind Tunnel by the Suction from Side Wall

In order to investigate large-scale separated flow in the wind tunnel, surface tuft method was applied to wind tunnel flow which was sucked from side wall. In the region of flow separation, many vortices were observed, which center lines were normal to either side wall or bottom wall.

Study on Pressure Oscillation in a Supersonic Cavity Flow

In recent year, research and development activities for next generation supersonic transport are being car-ried out actively by the world aeronautical community. In a supersonic intake, a cavity plays an important role in the control of shock waves. The study of the supersonic internal flow with the cavity is important not only for resarch on industrial applications but also for basic research in gasdynamics. In the present study, the supersonic internal flow with cavities was investigated experimentally by a schlieren optical method and pressure measurements in the case of the flow Mach number 1.9 at the cavity entrance. The effects of configurations of cavity leading edge and porous wall on the flow-induced pressure oscillation were clarified qualitatively.

Control of Condensation Shock Wave Using Porous Wall with Cavity

Since the concept of passive control of shock-boundary layer interaction was published in 1983, many papers have been reported on the application of this technique to transonic airfoil flows. In the present paper, this technique is applied to condensation shock wave which is caused by rapid expansion of moist air in a supersonic nozzle. The effects of passive control on condensation shock wave have been experimentally investigated by a schlieren optical method and by pressure measurements. As a result, it is found that passive control is the useful technique to suppress the periodic oscillation of condensation shock wave.

Visualization of Flow Patterns around a Cylindrical Protuberance in Supersonic Flow Using the Vapor-Screen Method

A passive boundary-layer control, which consists of porous wall with cavity, may be the useful technique for alleviation of shock oscillations. In order to clarify the effect of the control on flow patterns around a cylindrical protuberance in the supersonic flow, flow visualizations have been carried out using the vapor-screen method.The flow patterns have been shown especially for the three-dimensional shock configurations, and compared with those for solid wall. Results indicate that there appears the distinct difference in shock structures.

THREE-DIMENSIONAL VISUALIZATION OF SHOCK WAVE CONFIGURATION USING VAPOR-SCREEN METHOD

The vapor-screen method, a simple and practical method of flow visualization for high speeds, has been applied to the threedimensional shock waves generated in a supersonic nozzle with the obstacle. The shock wave profiles at each of the cross-sections have been shown clearly. As a result, it has been demonstrated that the vapor-screen method is very useful to visualize the three-dimensional shock wave configuration.

VAPOR-SCREEN METHOD FOR FLOW VISUALIZATION IN AN INDRAFT SUPERSONIC NOZZLE

The vapor-screen method, a simple and practical method of flow visualization for high speeds, has been applied to supersonic flow field generated in an indraft supersonic nozzle. As the result, the condition of visualization has been clarified and it has been demonstrated that this method is very useful to visualize flows in the indraft tunnel.

Visualization of Shock Waves in a Supersonic Nozzle by Vapor-Screen Method

The vapor-screen method is a simple and practical method of flow visualization for high speeds. In the present paper, it has been applied to shock waves generated in a supersonic nozzle, and the photograph has been compared with that of shadowgraph method. As the result, it has been demonstrated that this method is very useful to visualize shock waves.