Nobuhiro Tanatsugu

Experimental Study on Restart Control of a Supersonic Air-Breathing Engine

To study the dynamic response of a supersonic airbreathing engine and establish control logic for intake unstart, restart control tests were conducted at Mach 3 using a subscale engine model consisting of an axisymmetric intake (inlet) and a turbojet. Assuming that the combustion flame is blown out by intake unstart, restart control follows a sequence. First, after a flow is started the turbojet engine is ignited. Second, the intake is started while the rotational speed and the combustion gas temperature of the core engine are controlled. Third, the intake spike position and the terminal shock position are controlled, and the intake total pressure recovery achieves the design value (60%). The tests were successful, and engine thrust was recovered at approximately 30-40 s after engine start-up. A sudden increase in combustion gas temperature and rotational speed occurred after intake unstart. To reduce the sudden increase in the gas temperature, a new sequence that involved closing a fuel control valve after detection of intake unstart was implemented, and the increase in gas temperature was reduced. To avoid intake buzz, buzz margin control using a bypass door was successfully implemented.

Applications of carbon-carbon composites to an engine for a future space vehicle

Feasibility studies were carried out aiming at the application of carbon/carbon (C/C) composites to a turbine disk, heat exchangers, and a plug nozzle for an engine intended for use in a future reusable space vehicle. In these applications, the maximum temperature was estimated to be about 1500°C. In order to withstand this high temperature, attempts were made to utilize threedimensionally reinforced C/C composites. The most serious problem encountered in the application of C/Cs to the turbine disk was the loss of fragments of the composite located near the outer periphery due to strong centrifugal force, which resulted in severe vibration due to rotational imbalance. The heat exchangers and plug nozzle have complex shapes in order to realize a large heat exchanging area. Joined structures were explored for these components. The principal effort in these applications has been placed on finding structures requiring low joining strength and developing materials with low gas leakage.

Development study of the ATREX engine for TSTO spaceplane

An expander cycle air-turbo ramjet (ATREX) engine has been developed in the Institute of Space and Astronautical Science (ISAS). The ATREX will be used from lift-off up to Mach 6 as the propulsion system of the fly-back booster of TSTO spaceplane. This report indicates the present status of studies and key technologies to solve on the ATREX. Flight tests using a demonstration engine are necessary in order to get engine data over wide and unsteady flight conditions. The total engine system and components have been re-considered according to current and near term technologies and materials. For example, the turbo machine configuration is changed, namely, the turbine is placed behind the fan instead of the present tip turbine. A ram combustor test was conducted with six mixers for the new flow passage. Catalytic igniters were tried and could make the global combustion when the igniter temperature was more than 450K. Some devices to reduce the frost formation on a precooler were tested. Addition of a small quantity of methanol with the incoming air can effectively restrain the frost formation. Application studies of carbon/ carbon composites to a turbine ring and a heat exchanger has been conducted. Basic studies are continued to make complicated shapes, to protect leakage and oxidization.

DEVELOPMENT STUDY ON AXISYMMETRIC AIR INLET FOR ATREX ENGINE

A development study of variable geometry axisymmetric inlet has been done at IS AS since 1993. Total pressure recovery and mass capture ratio of the inlets are obtained by the wind tunnel tests at ISAS supersonic wind tunnel and NASA GRC 1-by 1-foot supersonic wind tunnel. In Feb 2000, a control test of an inlet is conducted at ONERA S3MA supersonic wind tunnel to accomplish an automatic operation of the inlet. As a result, we succeeded in controlling the inlet automatically and about 90% of the maximum inlet performances are achieved without manual operation. The configuration of the supersonic and subsonic diffuser is modified to increase the mass capture in the subsonic flight without the increase of the total pressure loss in the supersonic flight, and new type of inlet configuration is designed (Type-M). Although, type-M inlet can make 75% of total pressure recovery at Mach 3.5, it is necessary to improve the bleed system of the spike surface. A flyable inlet model whose cowl diameter is 740mm is now on the drawing board.

Optimization of airbreathing propulsion system for the TSTO spaceplane

The Institute of Space and Astronautical Science (ISAS) has proposed a fully reusable Two-Stage-ToOrbit (TSTO) vehicle along the aerodynamic way to LEO. In this paper it is shown TSTO conceptual design methodology. Genetic algorithm (GA) was applied to optimize design parameters of engine, airframe, and trajectory simultaneously. Several types of engine were quantitatively compared using payload ratio as an evaluating function. It was concluded that precooled turbojets is the most promising engine for TSTO among Turbine Based Combined Cycle (TBCC) engines.

Countermeasures against the icing problem on the ATREX precooler

Abstract An air-precooling system before compression is indispensable to extend the flight envelope and the improvement of the performance of turbo-based air breathing engines for the space plane. One of the critical problems on a shell-and-tube-type precooler is a deterioration of its heat exchange and pressure recovery performance due to the thick frost formation on its tube surface. An innovative method is proposed to mix a condensable additive like ethanol, methanol, etc. in the airflow as a defrosting system. The defrosting effectiveness and essential factors on the additive were investigated by using a small heat exchanger under two different cooling temperature conditions, that is, lower and higher cooling wall temperatures than the melting point of mixture of the water vapor and the additive. It was cleared in the test that most of the alcohols had good effectiveness with methanol the best. This methanol addition concept was applied in the precooler of the practical ATREX engine. A methanol injection system worked well and the thick frost layer formed on the tube surface at the entrance side of precooler could be eliminated. The required methanol mass along the ATREX engine flight path is estimated to be less than 3% of fuel hydrogen consumption.

Development study on precooler for atrex engine

A review of the development of a precooler for the air-turboramjet expander cycle engine (ATREX) is given. Three types of precooler for the ATREX engine ground test model were designed, manufactured and tested under the sea level static condition. The results suggested two problems affecting the precooler performance such as heat transfer rate and air flow pressure drop. One is non-uniformity of the air flow through the tube banks. The other problem is frost formation on the heat transfer surfaces. Concerning the non-uniformity, the shell configuration was modified based on the analysis by CFD calculation. To improve the precooler performance under frosting condition, the new method to add a condensable gas into the air flow was proposed and.examined by experiments on a subscale heat exchanger model. Addition of a small quantity. of ethanol can be effectively restrain the decline of the precooler performance due to frost formation.

On-orbit experiment plan on solar thermodynamic power system☆

Abstract This paper presents the on-orbit experiment plan of the solar thermodynamic power system operating the space flyer unit (SFU) presently being developed in Japan. The on-orbit experiments will be conducted with four primary objectives. First, to demonstrate the operation of the solar thermodynamic system in space environment. Second, to assess the performance capability of the solar thermodynamic system in space. Third, to verify functions of thermodynamic engine, solar ray collector, thermal storage system and space radiator especially from view point of durability and reliability. Fourth, to examine how vibration and inertia caused by moving parts of thermodynamic engine affect the primary functions of SFU and other mission payloads. The solar thermodynamic power system consists of a free piston-type Stirling engine, a linear synchronous generator, a Cassegrain-type solar ray collector, a thermal storage system and a space radiator. This system produces the continuous electric power of 2.5 kW, 330 V a.c. using 4.3 m dia solar collector. The output power is fed to the MPD thruster experiment. This experiment is proposed for the second SFU mission called “Energy Mission” in the mid 1990s. As a preliminary experiment, the ballistic flight experiment using sounding rocket is also planned.

MULTI-ROW DISK ARRANGEMENT CONCEPT FOR SPIKE OF AXISYMMETRIC AIR INLET

In this paper are presented the advanced concept of air inlet applying for the air breathing propulsion systems of hypersonic flight vehicle like a space plane. It is designated to be the Multi-Row Disk (MRD) inlet. It was devised to give the better inlet performance (mass capture ratio (MCR) and total pressure recovery (TPR)) over the wide flight conditions up to around Mach 6 by improving its off-design performance. The MRD inlet is a kind of axisymmetric air inlet composed of the center conical envelope spike and the cowl. As shown in Fig. 1, the unique structure is employed on the conical envelope spike that is composed of a tip cone and several round disks arranged so as to shape the conical envelope. The space in between the disks can be changed mechanically and thus the overall spike length of the MRD inlet is adjustable to meet the shock on lip condition at the given flight speed independent of the throat area control. The performance of MCR and TPR are governed respectively by the shock on lip condition to reduce a spillage flow and the throat area control and thus the MRD inlet is easier to improve them independent from each other under the off design conditions. It was made clear from the result of wind tunnel tests that the MRD inlet achieves the same ondesign performance as the conventional inlet with the solid surface conical spike and improves TPR by 10% comparing with the conventional ones in case of flow matching with the turbo fan. It was revealed from the result of wind tunnel tests and numerical simulations that the cavities formed in between the disks gave little effect on a boundary layer growth.

Carbon-carbon composite turbine disk for the air turbo ramjet engine (ATREX)

A feasibility study of three-dimensionally fiber-reinforced carbon-carbon composites (3DC/Cs) for application to a turbine disk of ATREX (Air turbo ramjet engine with expander cycle) was carried out. Spin burst tests at room temperature were conducted using 3D-C/C disks, and the fracture behaviors were characterized. A 3D-C/C disk was totally fractured at a peripheral speed of 516 m/s (r = 150 mm), which is sufficient for the ATREX application. However, fiber bundles at the disk periphery prematurely suffered micro-scale damage, and fragments of the fiber bundle unit flew out before total fracture occurred. In order to prevent the fly-out behavior, the disk was impregnated with Si only near its periphery. Although this treatment increased the initiation speed of the flyout behavior, this improvement was considered insufficient for purposes of the ATREX application. Next, a simplified analysis was conducted to characterize the fly-out behavior. Based on this analysis, the following three measures were discussed: (1) decreasing bundle thickness (i.e. using fine fiber texture), (2) increasing toughness of the fiber bundle interface, and (3) minimizing local curvature in waviness of the fiber bundles in the circumferential direction.