Experimental and numerical investigations are performed to clarify the flowfield in a model scramjet combustor with a backward-step in case of injecting fuel perpendicularly behind the step. The airflow total temperature is 1, 800 K and the Mach number is 2.0. The backward-step, which generates high Damkohler number (Da) region, is expected to work as a flame-holder. However, when the precombustion shock wave (PSW) is absent, the recirculation zane behind the step and the region downstream the fuel injector are divided by low Da region, and the reaction in the recirculation zone and that downstream the fuel injector occur independentiy, therefore, the recirculation zone cannot work as fiarne-holding region. The presence of the PSW enlarges the recirculation zone and connects the above two regions by relatively high Da region, and allows the step to work as a flame-holder. Therefore, for the design of the backward step, not only the proper arrangement of the step and the fuel injector but the use of PSW is essential particularly in the low airflow total temperature.
This paper discusses a feedback controller for the planar space robot's attitude and hand position. Two types of feedback controllers are investigated for a robot with a two degrees of freedom arm: control with a sliding plane and control with time-variant terms. The characteristics of the closed system under these controllers are studied using the derived anatytical solutions of the state variables. The effects of the estimation error in the robot's mass parameter are also discussed. Numerical simulations are given to show the validity of the controllers.
The near-field pressure distributions, which are needed to predict the far-field sonic-boom signatures, are measured experimentally with use of the wind tunnel of Mach number 2.0 for the supersonic aircraft models having different wing planforms and nose configurations in the cases with and without lift. The overall boom characteristics are also discussed in the basis of visualization of the flow patterns around the aircraft model with use of Schlieren technique and pressure measurement at off-centerline region by changing the model roll angle. The major results are as follows: As for the wing planform, the near-field peak pressures by an arrow wing and a cranked arrow wing are smaller than that of a delta wing, which suggests that they will give smaller sonic boom intensity. As for the nose configuration, a blunt nose is considered to be effective for sonic boom reduction, but because of a noticeable increase of drag, a careful shaping of nose has to be needed.
This paper describes laboratory experiments of effect of wall catalysis on aerodynamic heating in high- temperature gases. Heat fluxes on two kinds of catalytic material, stainless steel and alumina ceramic, were measured in an arc-heated wind tunnel. Stainless steel was considered as near fully catalytic material whereas alumina ceramic was selected as non-catalytic material. In order to investigate the effect of wall catalysis, heat fluxes were measured in three different arc-keated gases, argon, nitrogen and air. Measured results showed that the stainless steel to alumina ceramic heat flux ratios for air were 38% larger than those for argon and nitrogen. This implies that the recombination of oxygen atoms on the wall due to catalysis of wall material partly controls heat flux.
An apparatus for flow visualization around oscillating wing was designed and assembled. To validate the modern CFD. the experimental data not only about the pressure distributions on the wing surfaces but also the flow patterns around the wing are needed. The present system aims to offer the experimental information on the flow patterns around oscillating 2-D wings. In this report, the outlines of the driving mechanism for the 2-D wing and the smoke generator are presented together with the related other devices. It is shown that the system works well in the low-turbulence wind tunnel at NAL and expected that it can be used for the research of low speed unsteady aerodynamics and aeroelasticity.
Low speed wind tunnel measurements were done on a 50° delta wing with rounded leading-edge vortex flaps in order to assess the benefits of the rounded leading-edge vortex flaps. Deflecting the rounded leading-edge vortex flap improves the lift/drag ratio at relatively higher lift coefficients, when compared with the sharp edged vortex flap.