Pre-cooled Turbojet Engine Research Articles

Development of Supersonic Vehicle for Demonstration of a Precooled Turbojet Engine

JAXA is developing Mach 5 hypersonic turbojet engine technology that can be applied in a future hypersonic transport. Now, Jet Engine Technology Research Center of JAXA conducts the experimental study using a 1 / 10 scale-model engine. In parallel to engine development activities, a new supersonic flight-testing vehicle for the hypersonic turbojet engine is under development since 2004. In this paper, the system configuration of the flight-testing vehicle is outlined and development status is reported.

矩形ならびに軸対称プラグノズルから放出される超音速ジェット騒音の予測

Effects of nozzle geometry, and total temperature on supersonic jet noise radiated from rectangular and axi-symmetric plug nozzles are investigated, experimentally. In JAXA (Japan Aerospace Exploration Agency), a pre-cooled turbojet engine for an HST (Hypersonic transport) is under development. In the present study, three kinds of subscale nozzle models are employed, namely two kinds of rectangular plug nozzles (RPN1 and RPN2) and an axi-symmetric plug nozzle (APN), and the jet noise data are acquired at aft angles of the jets by use of 1/4 inch high frequency microphones. The total pressure is set at 0.3MPa(a), which corresponds to the take-off condition of the vehicle, and the total temperature is varied from 290K to 860K. The jet noise spectra obtained are reduced to normalized spectra by use of a scaling law of heated jets (AU n law). It is shown that the normalized spectra collapse onto two lines according to each nozzle geometry, regardless of the total temperature. For APN, the peak SPL is smaller by about 8 to 14 dB when compared with that for RPN1 and RPN2, which implies that the axi-symmetric plug nozzle could be much quieter than rectangular plug nozzle.

矩形プラグノズルからの排気騒音に及ぼす空力タブの効果

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.

空力タブのノズル形状ならびに間欠噴射が超音速噴流騒音に及ぼす効果

Effects of the nozzle geometry and intermittent injection of aerodynamic tabs on exhaust noise from a rectangular plug nozzle were investigated experimentally. In JAXA (Japan Aerospace Exploration Agency), a pre-cooled turbojet engine for an HST (Hypersonic transport) is planned. A 1/100-scaled model of the rectangular plug nozzle is manufactured, and the noise reduction performance of aerodynamic tabs, which is small air jet injection from the nozzle wall, was investigated. Compressed air is injected through the rectangular plug nozzle into the atmosphere at the nozzle pressure ratio of 2.7, which corresponds to the take-off condition of the vehicle. Aerodynamic tabs were installed at the sidewall ends, and 4 kinds of round nozzles and 2 kinds of wedge nozzles were applied. Using a high-frequency solenoid valve, intermittent gas injection is also applied. It is shown that, by use of wedge nozzles, the aerodynamic tab mass flow rate, necessary to gain 2.3dB reduction in OASPL (Overall sound pressure level), decreases by 29% when compared with round nozzles. It is also shown that, by use of intermittent injection, the aerodynamic tab mass flow rate, necessary to gain 2.3dB reduction in OASPL, decreases by about 40% when compared with steady injection. By combination of wedge nozzles and intermittent injection, the aerodynamic tab mass flow rate significantly decreases by 57% when compared with the conventional strategy.

予冷ターボジェットエンジンにおけるジェット噴射を用いた熱交換器の除霜

An innovative defrosting method for precooled turbojet engines are presented, and validated in this study using experimental methods. High speed gas jet was impinged on the cooling tubes of a heat exchanger for the purpose of defrosting. The coolant of the heat exchanger was liquid nitrogen, and whose temperature was 83K. The air flow speed, the air temperature and the air humidity were 1.0m/s, 23oC and 59%, respectively. The effects of the jet duration, jet intervals and humidity of the jet gas on the heat exchange were assessed. As a result, we found that the presenting defrosting method is valid for the defrosting of the precooler.

Trajectory Optimization and Conceptual Study of Small Test Vehicles for a Hypersonic Engine Using a High-Altitude Balloon

The Japan Aerospace Exploration Agency, JAXA, announced a long-term vision recently. In the vision, JAXA aims to develop hypersonic aircrafts. A pre-cooled turbojet engine has great potential as one of newly developed hypersonic airbreathing engines. We also expect the engine to be installed in space transportation vehicles in the future. For combustion test in the real flight conditions of the engines, JAXA has an experimental plan where a small test vehicle is released from a high-altitude balloon. This paper applies numerical analysis and optimization techniques to conceptual designs of the test vehicle in order to obtain the best configuration and trajectory for the flight test. The results show helpful knowledge for designing prototype vehicles.

Precooled turbojet engine flight experiment using balloon-based operation vehicle

Development of the Balloon-based Operation Vehicle (BOV) is currently in progress for the first flight scheduled in 2006. In a series of BOV experiments, a vehicle in a wing-body configuration is lifted by a high-altitude balloon and dropped, after which the microgravity experiments will be performed onboard the vehicle under favor of the quasi-free-fall environments. Although the BOV is originally designed for the microgravity experiments, various types of experiments can also be performed in a hypersonic flight at lower altitudes. One candidate currently under review is a flight experiment of a precooled turbojet engine in reduced dimension. In this article, an overview of the BOV experiment is introduced, and the current development status of the BOV and a flight model of the precooled turbojet engine is presented. The aerodynamic load and the aerodynamic characteristics of the BOV are obtained by computational fluid-dynamic analyses and wind-tunnel experiments.

高高度気球を用いた極超音速エンジン小型実験機に対する軌道最適化と概念検討

Japan Aerospace Exploration Agency, JAXA announced a long-term vision recently. In the vision, JAXA aims to develop hypersonic aircrafts. A pre-cooled turbojet engine has great potential as one of newly developed hypersonic air-breathing engines. We also expect the engine to be installed in space transportation vehicles in future. For combustion test in real flight condition of the engines, JAXA has an experimental plan with a small test vehicle falling from a high-altitude balloon. This paper applies numerical analysis and optimization techniques to conceptual designs of the test vehicle in order to obtain the best configuration and trajectory that can achieve the flight test. The results show helpful knowledge when we design prototype vehicles.