Katsuyoshi Fukiba

New Defrosting Method Using Jet Impingement for Precooled Turbojet Engines

Precooled turbojet engines are effective propulsion systems for hypersonic aircraft. However, a serious problem is that frost forms on the cooling tubes of the precooler, thereby decreasing the engine performance. This paper presents a new method for defrosting the precooler using jet impingement. The validity of the proposed defrosting method was investigated through fundamental experiments. In the experiments, the frost formed on the cooling tubes of the single-row heat exchanger was removed by jet impingement. We used the jet periodically. The jet interval is 10-50 s. In addition, the jet duration is short (about 0.1 s). Therefore, the consumption of the high-pressure air to make the jet flow is small. The coolant temperature and main flow speed influences on the defrosting method effectiveness were assessed. Results show that this defrosting method is effective, especially when the coolant temperature and the main flow speed are low.

Design Study of Hypersonic Components for Precooled Turbojet Engine

Recent studies about variable nozzles, that are a rectangular type nozzle and an axisymmetric type nozzle, of the precooled turbojet engine (S-engine) which are developed for the demonstration of the key technologies for the propulsion system of the hypersonic airplane and the first stage propulsion of the TSTO space plane are described in this paper. For the rectangular nozzle, three types of C-shaped carbon/carbon composite cowls which includes subscale model of the precooled turbojet engine are fabricated and the fine attachment to the ramp is confirmed. For the firing of the S-engine, stainless steel cowl with concrete heat insulator are fabricated and tested for 20 sec. Axisymmetric variable plug nozzle which is made of C/C material is fabricated and pressurized by the cold flow test. The axisymmetric plug nozzle can be operative up to 0.57 MPa of nozzle inlet pressure.

Experimental Study on Aerodynamic Characteristics of Telescopic Aerospikes with Multiple Disks

In this paper, experimental studies on telescopic aerospikes with multiple disks are reported. The telescopic aerospike is useful as an aerodynamic control device; however, changing its length causes a buzz phenomenon,which many researchers have reported. The occurrence of buzzing might be critical to the vehicle because it brings about severe pressure oscillations on the surface. Disks on the shaft produce stable recirculation regions by dividing the single separation flow into several conical cavity flows. Therefore, the telescopic aerospikes with stabilizer disks are useful without being any length constraints. Aerodynamic characteristics of the telescopic aerospikes were investigated using wind tunnel tests. Transition of recirculation/reattachment flow modes of a plain spike causes a large change in the drag coefficient. Because of this hysteresis phenomenon, the plain spike is unsuitable for fine aerodynamic control devices. Adding stabilizer disks is effective for the improved control of aerospikes.

Hypersonic Turbojet Engine Design of a Balloon-Based Flight Testing Vehicle

JAXA is developing Mach 5 hypersonic turbojet engine technology that can be applied in a future hypersonic transport. Now, in Jet Engine Technology Research Center of JAXA, the experimental study, which uses a 1 / 10 scale-model engine, is conducted. 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.

Development of a Small-scale Supersonic Flight Experiment Vehicle as a Flying Test Bed

With the aims of creating and validating innovative fundamental technologies for highspeed atmospheric flights, a small scale supersonic experiment vehicle is designed as a flying test bed. Several aerodynamic configurations are proposed and analyzed by wind tunnel tests. A twin-engine configuration is selected as the baseline. Its flight capability is predicted by point mass analysis on the basis of aerodynamic characterization and propulsion performance estimation. In addition, a prototype vehicle with the equivalent configuration and dimension is designed and fabricated for verification of the subsonic flight characteristics of the experiment vehicle. Its first flight test is carried out and good flight capability is demonstrated.

Numerical Study on the Heat Transfer of the Flow with Endothermic Chemical Reaction

The numerical study on the regenerative cooling method using an endothermic fuel was conducted in this study. We focused on the heat transfer of the flow with the thermal decomposition of the ethane. The flow within heated walls at the temperature of 1200 and 1300 K was investigated by CFD analysis. The results with and without chemical reaction were compared. We found that the heat flux with the thermal decomposition increases remarkably. This increase is caused not only by the temperature decrease attributable to the endothermic reaction, but also by the heat transfer attributable to the diffusion effect and by the increase in the flow speed.