Effects of aerodynamic tabs on exhaust noise from a rectangular plug nozzle were investigated experimentally. In JAXA (Japan Aerospace Explanation Agency), a pre-cooled turbojet engine for the 1st stage propulsion of a TSTO (Two stage to orbit) is planned. In the present study, a 1/100-scaled model of the rectangular plug nozzle for the pre-cooled turbojet engine is manufactured and the exhaust noise characteristics were investigated. Compressed air is injected through the rectangular plug nozzle into the atmosphere. The nozzle pressure ratio was set at 2.7, which corresponds to the take-off condition of the vehicle. Aerodynamic tabs were installed at the ramp end (Upper AT), the cowl end (Lower AT) and the sidewall end (Side AT). The SPL (Sound pressure level) was measured with a high-frequency microphone. Without AT, the sound spectrum has a broadband peak at which the SPL is around 105dB. For Lower and Side ATs, the OASPL (Overall SPL) of the exhaust noise decreases, especially around ramp end. At the maximum, the OASPL was reduced by 2.4dB with about 2% loss of the main jet total pressure at the cowl exit. It is shown that the aerodynamic tabs are effective in noise reduction in a rectangular plug nozzle.
The purpose of this paper is to obtain an optimum thickness distribution of an inflatable membrane reflector which consists of two circular membranes attached at their edges. The deflection analysis of the membrane is based on the large deflection theory of plate. In numerical simulation, the finite element method is used. In the optimization, the objective function is the surface profile error between the paraboloid and the inflated shape of membrane, and the discrete distribution of optimum thickness is obtained. In addition, the simulation for experiment is performed under a restricted condition in thickness. Based on this result, a circular membrane with optimized thickness profile is produced and the shape measurement experiment is performed.
Two-stream flow model of ejector including heat and mass transfer was constructed by the comparison of the numerical simulations in the rocket-ramjet combined-cycle engine driven three different rocket gas; cold N2 gas, hot combustion gas and it within excess H2. The analysis of the ejector revealed that the heat and mass transfer from hot rocket plume with supersonic speed to cold airflow induced area change (expansion) of the airflow stream tube and the pressure rise in the constant-area section at the downstream of the rocket base. This pressure rise reduced the pumping performance of the ejector. To absorb the expansion of the airflow, the flowpath was changed from the constant area to the diverging area at the downstream of the rocket base. The numerical simulation in the modified engine demonstrated that the diverging-area section at the downstream of the rocket base improved the pumping performance.
Adhesive bonding structure around a metalic mouthpiece of a cryogenic composite tank was analyzed based on fracture mechanics. Energy release rate was analytically formulated considering difference in strain energies in tension and bending between before and after the crack growth based on a simplified mathematical model. The analytical results were compared with the calculated results by finite element method for five example tanks; they revealed fairly good match. This analysis gives a guideline of the initial optimal design of a cryogenic composite tank based on fracture mechanics.
Pitot impact pressure measurements on the correctly expanded supersonic jet from the axisymmetric nozzle have been performed along the jet centerline and radial direction. The test nozzle was designed by the characteristic method. Also, the flow visualizations have been performed with the three nozzles (these are bell and conical types, and another one is designed by the characteristics method). The design Mach number of these nozzles is 2.4, and the Reynolds number on the correctly expanded condition is 3.5× 106. The total temperature of the jets is equal to the room condition, so we considered only the flow of the cold jet on the effect of temperature. In the present study, the aims are to obtain more knowledge of the mean-flow characteristics and investigate the effect of the nozzle geometry on the correctly expanded supersonic jets. The results are as follows. The progress empirical formulae on the potential core length xcore/De, the spreading rate δη and the spreading parameter σ were proposed by the investigation of present and previous experimental results, respectively. These parameters are important on the understanding of mean-flow characteristics of the correctly expanded supersonic jets. And the flow visualizations showed that the configurations of supersonic jets from these nozzles were different due to the nozzle geometry, even though the pressure ratios on the nozzles are same condition.
We have been investigating a method to accomplish critical operations efficiently and accurately for future spacecraft such as HTV. We are now developing a framework for maintaining operation flow diagrams and operation procedures based on the generation of source descriptions for operating procedures. This framework aims at not only reducing the time and effort required to develop such information, but also acquiring quality and consistency between the diagrams and the procedures. This paper describes the system used to configure the description built on the framework and the effectiveness of the method by applying the system to the spacecraft mission operations.