Air Turbo Ramjet Research Articles

Overspeeding characteristics of turbomachinery for gas generator cycle air turbo ramjet engine

The main interest in the current study focuses on the possibility of overspeeding for the gas-generator cycle air turbo ramjet (GG-ATR) engine. The authors developed the air turbo ramjet engine and investigated its compressor performance. Based on those data, the authors developed the analytical code for the air turbo ramjet engine, which calculates the performances of turbomachinery, gas-generator, and ram combustor. The previous study described that the rotor overspeeding would not occur in the air turbo rocket engine. However, the current results show that degraded ram combustion can decrease the compressor pressure ratio and the compressor power. This reduced compressor power can cause overspeeding for the air turbo ramjet engine. The experimental results of compressor power and turbine inlet pressure support those analytical results.

Low toxic nitromethane based monopropellant for gas generator cycle air turbo ramjet engine

The present study proposes ethanol-nitromethane mixture as a safe, storable, and low toxic monopropellant for a gas generator cycle air turbo ramjet engine and evaluates its propulsion performance. The present study proposes that nitromethane is mixed with ethanol to adjust gas generator combustion temperature. The author developed the computational code for the present analysis and verified its accuracy. The specific thrust of ethanol-nitromethane is nearly identical to that of ethanol-liquified oxygen and is higher than methanol-hydroxylammonium nitrate aqueous solution and hydrazine. Hydrazine has the highest Isp among the propellants in the present analysis. However, Isp of ethanol-nitromethane is nearly equal to that of ethanol-liquified oxygen and higher than those of methanol-hydroxylammonium nitrate aqueous solution, and hydroxyl terminated polybutadiene-ammonium perchlorate. With the propellant-to-air ratio range in the present study, ethanol-nitromethane has the stoichiometric condition at the ram combustor around the propellant-to-air ratio range from 0.2 to 0.25 and can obtain high ram combustion temperature. This result is favorable for ethanol-nitromethane because it improves the specific thrust and the specific impulse. Therefore, ethanol-nitromethane can be a promising low-toxic liquid monopropellant for the air turbo ramjet engine.

Alcohol and alkane fuel performance for Gas Generator cycle Air Turbo Ramjet Engine

The present study investigates the feasibility of alcohol fuels for a Gas Generator cycle Air Turbo Ramjet (GG-ATR) Engine in comparison with alkane fuels. The alkane and alcohol fuels in the present study range from C1 species (CH4 and CH3OH) to C4 species (n-C4H10 and 1-C4H9OH).The present study analytically evaluates Specific thrust and Specific impulse (Isp) of GG-ATR engine as functions of gas generator combustion temperature. For both alcohols and alkanes, the peak Gas Generator (GG) combustion temperatures exist for specific thrust and ram combustor temperature. Comparing alcohol to alkane in the lower GG combustion temperature, specific thrusts and Isp of alcohol tend to be higher than those of C2H6, C3H8, and 1-C4H10. GG combustion gases for alcohol fuels contain higher mole fractions of H2O and CO2 than those for alkanes. Because of high mole fractions of H2O and CO2, the ratio of GG combustion gas for alcohols to air flow rate is fortunately close to the stoichiometric ratio, resulting in higher ram combustion temperature. The high ram combustion temperature can contribute to the higher specific thrust and Isp. Lower GG combustion temperature is preferable because of a thermal limit of a turbine blade. Thus, alcohols have superiorities to alkanes for the GG-ATR engine application.

Advantage of ethanol fuel for gas generator cycle air turbo ramjet engine

Performance analyses of Gas Generator cycle Air Turbo Ramjet (GG-ATR) engine are conducted to investigate the feasibility of ethanol fuel, as comparing Liquefied Hydrogen (LH2), Liquefied Natural Gas (LNG), and n-C12H26. Liquefied Oxygen (LOX) is considered as an oxidizer. Gas generator combustion temperature and compressor pressure ratio are selected as the analytical parameters, which are varied from 900 to 1700 K and from 2.0 to 4.0, respectively.In general, specific impulses of light molecule weight fuels, such as LH2 and LNG, are higher than those of large molecule weight fuel. For storable fuel, Isp of ethanol is larger than that of n-C12H26 when gas generator temperature is less than 1300 K, although specific heat release of ethanol is only two thirds of n-C12H26 heat release. The main chemical species of n-C12H26 gas generator (GG) combustion gas are CH4 and CO. On the other hand, ethanol GG combustion gas is mainly composed of H2 and CO, resulting in smaller molecular weight than n-C12H26. These characteristics contribute to larger Isp of ethanol than n-C12H26 and indicate the feasibility of ethanol for GG-ATR engine fuel.

Turbocharged Solid Propellant Ramjet for Tactical Missile

Turbocharged solid propellant ramjet (TSPR) is the combination of solid propellant gas generator air turbo ramjet (ATR)with solid ramjet, is cycle of augmented ATR, the parametric performance calculation were carried out for TSPR, The effects of independent design parameters including parameters of compressor and turbine and propellants were studied and the preferred compressor, turbine and propellants were obtained for TSPR; The operation envelop of TSPR and ATR were obtain under the preferred component limitation, the results shows that TSPR offers wide speed-altitude operation envelope, high specific thrust, high specific impulse, it is combining the advantages of the ATR and solid ramjet, and suitable for tactical missiles application meets potential requirements for boosting and cruising.

4029 エルボ下流に配置した千鳥配列円管群を通過する流れ(G05-6 物体まわりの流れ(1),G05 流体工学)

The Air Turbo Ramjet (ATR) engine is considered to be one of the propulsion systems for space planes. The precooler is one of the heat exchangers and a key technology for the ATR engine. It produces, however, the inlet distortions of total pressure. The tube banks with staggered arrangement are located just downstream of an elbow. The velocity distributions are measured in the downstream of the tube banks. For comparison, the tube banks with straight duct are also examined. The results show that the low spot of an arranging in A-shape in the elbow duct with tube banks. Moreover, a low speed area appears by backward side in the straight duct with yawed tube banks.

タンデム翼列によるファンの高負荷化

For axial flow compressors and fans in the aircraft engines higher pressure ratio is required in order to attain the high thrust engines. In this study, the fan with the tandem cascades was introduced to increase the fan pressure ratio. The use of tandem cascades in the fan allows savings in length and weight and therefore a compact fan could be built. The design of fan with tandem cascades and the fan testing were carried out to develop the high pressure ratio fan for the Air Turbo Ramjet (ATR) propulsion system. The ATR is a combined cycle engine which performs like a turbojet engine at subsonic speeds and a ramjet at supersonic speeds. In particular, high fan pressure ratio contributes to increase the engine thrust during subsonic flight at which the engine does not make use of ram effect. The results of the fan testing indicate that the pressure ratio of 2.2 is achieved in single stage fan.

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.

小型・高推力エアーターボラムエンジン

The Air Turbo Ramjet (ATR) is a combined cycle engine which performs like a turbojet engine at subsonic speeds and a ramjet at supersonic speeds and therefore the ATR is an attractive propulsion system for the wide operation range (e.g. Mach 0 to Mach 4). The ATR can provide a higher specific impulse than a solid fuel rocket engine and a higher thrust per frontal area than a turbojet engine. The major ATR components are the inlet, fan (compressor), turbine, gas generator, combustor and exhaust nozzle. In the ATR, the turbine drive gas is generated by a decomposed liquid or solid fuel gas generator. In order to carry heavier payloads and to attain shorter flight time, the compact and high thrust engine is required. In this study, the ram combustor with the double-staged flameholders and the fan with tandem blade were introduced to shorten the engine length and to increase the fan pressure ratio, respectively. Furthermore, the engine testing was carried out on sea level static condition to confirm the engine component integration technologies for the ATR propulsion system.

Computational Analysis of the Flow Field Near the Boat-tail Region of Annular Plug Nozzles.

Flow fields over annular plug nozzles are computationally simulated and the boat-tail drag characteristics are clarified and discussed based on the simulation results. The plug nozzle configuration is taken from the ATREX (Air Turbo Ramjet) engine under development at the ISAS. The simulations are carried out for the axi-symmetric nozzle configuration using compressible Navier-Stokes equations. The computed result shows that there exists a low pressure region downstream of the Prandtl-Meyer expansion on the boat-tail region and the separation shock wave appears due to the interaction of the main flow and the nozzle plume downstream. The result also shows that the primary cause of the boat-tail drag turns out to be the low pressure region downstream of the Prandtl-Meyer expansion. The flow field with the secondary flow injection is then simulated and the computed result shows that the pressure in the region in front of the separation shock wave increases and the secondary flow injection successfully reduces the boat-tail drag. The effect of the turbulence model used in the computation is discussed to ensure the reliability of the solutions.

極超音速空気吸い込み式エンジン用予冷却器（プリクーラ）の開発研究

Here is presented an experimental and analytical study on a precooler for hypersonic air-breathing engines. Precooling of the incoming air breathed by an air-inlet gives extension of the flight envelope and improvement of the thrust and specific impulse. Three precooler models were installed into an air-turbo ramjet engine and tested under the sea level static condition. When the fan inlet temperature was down to 180K, the engine thrust and specific impulse increased by 2.0 and 1.2 times respectively. Thick frost formed on the tube surfaces at the entrance part of the precooler blocked the air-flow passage. On the other hand, very thin frost formed at the exit part because the water vapor included in the air was changed to mist particles due to the low temperature of the air in this part. Parametric studies on the precooler design values and a sizing analysis were also performed. Decrease of tube outer diameters on the precooler is only way to increase heat exchange rates without increase of its weight and pressure loss.

136 3D-C/C複合材製ディスクの回転破壊(OS 耐熱材料)

Cold spin tests of three dimensional fiber-reinforced carbon-carbon composites were conducted for the turbine disk of the air-turbo ram jet engine (ATREX). The fly-out objects were detected at the rotation speed of 12000 r.p.m. and the fly-out behavior was caused by the delamination of the fiber bundles from the surface of the disk. The energy release rate, G, was estimated about 30 J/m2 for this 3D-C/C disk and fine fiber weave structure and large bonding strength between fiber bundle are shown to be effective to increase rotation speed. Gaseous Si conversion and Si infiltration method were examined to increase rotation speed of 3D-C/C disk.

DEVELOPMENT STUDY ON ATREX ENGINE

The study on ATREX engine (Air-Turbo Ramjet engine) development is being been conducted in ISAS since 1986 as a candidate for the propulsion system of the fly-back booster up to Mach 6 on the reusable TSTO space plane. ATREX is a fan-boosted ramjet engine using liquid hydrogen as a fuel and coolant. Sea-level static firing tests of ATREX with precooling were carried out in parallel with the wind tunnel tests on the aerodynamic components such as air intake and plug nozzle. Further studies on precooler have been conducted not only for performance improvement but also for weight reduction to meet flight requirements. In 1998, a new type precooler (Type-III) was designed and tested. Its heat transfer performance could be improved by increasing its compactness using tubes of smaller in diameter as well as its weight could be reduced. On the other hand, some difficulties increased in its manufacturing due to larger number of tubes required. The new precooler performance on heat transfer and pressure loss compared with the old type of precoolers are presented here. The test results of ATREX engine installed with new precooler is presented. Some progress in aerodynamic studies on ATREX engine is also presented here. The control of the axisymmetric air inlet by capturing the terminal shock waves and the reduction on boat tail drag of the plug nozzle were conducted in the wind tunnel.

２Ｄ Ｃ／Ｃ複合材料製ダブテール接合の強度および破壊挙動

In a development study of the air-turbo-ramjet (ATR) engine for a space plane, carbon-carbon (C/C) composites are attempted to be applied to the tip-turbine structure mainly taking advantage of high specific strength at elevated temperature. This disk has rather complicated shape and thus the joining structure is expected to be used. For the joint between fan blades and a fan disk, the dovetail joint is appeared to be useful but it is indispensable to maintain sufficient durability against extremely high centrifugal force to design optimally material property as well as the joint geometry. Tensile tests were carried out on simplified dovetail joint models made of three type of two dimensionally reinforced C/C composites. The effect of stacking pattern and various geometrical parameters was examined so as to fined an optimal structure. The result of the tensile test suggests that fracture of the dovetail joint be controlled by the average stress criterion, which implies stress concentration near the shoulder is almost relaxed during failure process of the C/C composites. It is also shown that AE signals are extremely useful to identify durability limit of the dovetail joint especially when the fracture mode is shear.

Development Study on ATREX Engine

This is the status report of the development study on ATREX engine (Air Turbo Ramjet) that is now under way in the Institute of Space and Astronautical Science (ISAS) cooperation with the Ishikawajima Harima Heavy Industries (IHI), the Kawasaki Heavy Industries (KHI), the Mitsubishi Heavy Industries (MHI). ATREX engine will be applied for the propulsion system of fly-back booster of TSTO space plane. ATREX is the combined cycle (a fan-boosted ramjet) engine providing the effective thrust from sea level static to flight Mach number 6. ATREX is worked on the expander cycle with precooling the incoming air as shown in Fig. 1 . ATREX employs the tip turbine configuration which allows the compactness and the light weight of turbo machinery and the variable geometry airintake and plugnozzle which allow the wide range operation conditions.From 1990 to 1992, “ ATREX-500“ has been tested at the sea level static conditions. ATREX-500 is the 1/4-scale model of which fan inlet diameter is 300mm and overall length 2,200mm. From 1992 have been performed the wind tunnel tests on the primary components of ATREX, the axisymmetric variable geometry airintakes, the precoolers and the variable geometry plug nozzles. In parallel to the windtunnel tests, the ram combusters have been tested simulating the hypersonic flight conditions and the application studies on advanced carbon-carbon composite for the tip-turbine and fan assembly has been proceeded.In 1994 initiated the flight test plan in which ATREX will be verified in the practical flight conditions by using an unmanned flying test bench.In 1995 will be tested ATREX-500 installing the precooler under the sea level static conditions to examine the engine performance and the icing on the precooler.The present paper addresses the high loading ram combuster experiment using the mixer with skewed lobes to generate swirl flow and the analytical studies and the designs on the precooler and the precooled ATREX engine and the flight test plan.

Development study on ATREX engine

This is the status report of the development study on ATREX engine (Air Turbo Ramjet) that is now under way in the Instutute of Space and Astronautical Science (ISAS) in cooperation with the Ishikawajima Harima Heavy Industries (IHI), the Kawasaki Heavy Industries (KHI), the Mitsubishi Heavy Industries (MHI). ATREX engine will be applied for the propulsion system of fly-back booster of TSTO space plane. ATREX is the fan-boosted ramjet producing the effective thrust from sea level static to flight Mach number 6. ATREX is worked on the expander cycle with precooling incoming air as shown in Fig.1. ATREX employs the tip turbine configuration which allows compactness and light weight of turbo machinery and the variable geometry airintake and plug nozzle which allows the wide range flight conditions. ATREX development study has been conducted with the sea level static tests since 1990. ATREX engine for tests is the scaled model designated by “ATREX-500” of which fan inlet diameter is 300 mm and overall length 2,200 mm. From 1992 have been performed the wind tunnel tests on the primary aerodynamic components such as the axisymmetric variable geometry air intakes, the precoolers and the variable geometry plug nozzles. The application study on advanced carbon-carbon composite for the tip-turbine and fan assembly has been conducted. This study status is presented in the another session of this IAF congress 1. The flight test of ATREX is now planning to verify the engine performance and functions in the practical flight conditions by using an unmanned flying test bench. In 1995 was tested ATREX-500 installing the precooler under the sea level static conditions to examine the engine performance and the icing problem on the precooler. The present paper addresses primarily the test results of precooled ATREX engine.

96/04309 The basis for a method to integrate work environment in life cycle assessments

This is the status report of the development study on ATREX engine (Air Turbo Ramjet) that is now under way in the Institute of Space and Astronautical Science (ISAS) cooperation with the Ishikawajima Harima Heavy Industries (IHI), the Kawasaki Heavy Industries (KHI), the Mitsubishi Heavy Industries (MHI). ATREX engine will be applied for the propulsion system of fly-back booster of TSTO space plane. ATREX is the combined cycle (a fan-boosted ramjet) engine providing the effective thrust from sea level static to flight Mach number 6. ATREX is worked on the expander cycle with precooling the incoming air as shown in Fig. 1. ATREX employs the tip turbine configuration which allows the compactness and the light weight of turbo machinery and the variable geometry airintake and plugnozzle which allow the wide range operation conditions.From 1990 to 1992, “ ATREX-500“ has been tested at the sea level static conditions. ATREX-500 is the 1/4-scale model of which fan inlet diameter is 300 mm and overall length 2,200 mm. From 1992 have been performed the wind tunnel tests on the primary components of ATREX, the axisymmetric variable geometry airintakes, the precoolers and the variable geometry plug nozzles. In parallel to the windtunnel tests, the ram combusters have been tested simulating the hypersonic flight conditions and the application studies on advanced carbon-carbon composite for the tip-turbine and fan assembly has been proceeded.In 1994 initiated the flight test plan in which ATREX will be verified in the practical flight conditions by using an unmanned flying test bench.In 1995 will be tested ATREX-500 installing the precooler under the sea level static conditions to examine the engine performance and the icing on the precooler.The present paper addresses the high loading ram combuster experiment using the mixer with skewed lobes to generate swirl flow and the analytical studies and the designs on the precooler and the precooled ATREX engine and the flight test plan.

96/04311 Biological mine drainage treatment

This is the status report of the development study on ATREX engine (Air Turbo Ramjet) that is now under way in the Institute of Space and Astronautical Science (ISAS) cooperation with the Ishikawajima Harima Heavy Industries (IHI), the Kawasaki Heavy Industries (KHI), the Mitsubishi Heavy Industries (MHI). ATREX engine will be applied for the propulsion system of fly-back booster of TSTO space plane. ATREX is the combined cycle (a fan-boosted ramjet) engine providing the effective thrust from sea level static to flight Mach number 6. ATREX is worked on the expander cycle with precooling the incoming air as shown in Fig. 1. ATREX employs the tip turbine configuration which allows the compactness and the light weight of turbo machinery and the variable geometry airintake and plugnozzle which allow the wide range operation conditions.From 1990 to 1992, “ ATREX-500“ has been tested at the sea level static conditions. ATREX-500 is the 1/4-scale model of which fan inlet diameter is 300 mm and overall length 2,200 mm. From 1992 have been performed the wind tunnel tests on the primary components of ATREX, the axisymmetric variable geometry airintakes, the precoolers and the variable geometry plug nozzles. In parallel to the windtunnel tests, the ram combusters have been tested simulating the hypersonic flight conditions and the application studies on advanced carbon-carbon composite for the tip-turbine and fan assembly has been proceeded.In 1994 initiated the flight test plan in which ATREX will be verified in the practical flight conditions by using an unmanned flying test bench.In 1995 will be tested ATREX-500 installing the precooler under the sea level static conditions to examine the engine performance and the icing on the precooler.The present paper addresses the high loading ram combuster experiment using the mixer with skewed lobes to generate swirl flow and the analytical studies and the designs on the precooler and the precooled ATREX engine and the flight test plan.

Thermal design of a hydrogen heater for an air turboramjet engine

A compact heat exchanger has been designed for an air turboramjet engine proposed for future spacecraft. Hydrogen fuel is heated by the combustion gas of the engine at the heat exchanger. The heat exchanger, called a hydrogen heater when used in an aircraft, has to be compact so that when it is set in an engine duct to enhance heat transfer it will cause a small increase in the pressure loss of the combustion gas. To endure the vibration caused by combustion gas turbulence and the high pressure of hydrogen fuel flowing in the heat exchanger, inline tangential tube banks are adapted. An optimum design point of the heat exchanger is shown that is calculated by use of results of fundamental experiments on the heat transfer of inline tangential tubes. A small heat exchanger is developed and loaded into an ATREX500 type engine, a sea-level static air turboramjet engine used to check the predicted thermal performance of the heat exchanger. Experimental results almost match the engine system requirements and show the possibility of developing a flight-model heat exchanger.

Apparatus for cooling and cleaning raw gases from coal gasifiers

This is the status report of the development study on ATREX engine (Air Turbo Ramjet) that is now under way in the Instutute of Space and Astronautical Science (ISAS) in cooperation with the Ishikawajima Harima Heavy Industries (IHI), the Kawasaki Heavy Industries (KHI), the Mitsubishi Heavy Industries (MHI). ATREX engine will be applied for the propulsion system of fly-back booster of TSTO space plane. ATREX is the fan-boosted ramjet producing the effective thrust from sea level static to flight Mach number 6. ATREX is worked on the expander cycle with precooling incoming air as shown in Fig.1. ATREX employs the tip turbine configuration which allows compactness and light weight of turbo machinery and the variable geometry airintake and plug nozzle which allows the wide range flight conditions.ATREX development study has been conducted with the sea level static tests since 1990. ATREX engine for tests is the scaled model designated by “ATREX-500” of which fan inlet diameter is 300 mm and overall length 2,200 mm. From 1992 have been performed the wind tunnel tests on the primary aerodynamic components such as the axisymmetric variable geometry air intakes, the precoolers and the variable geometry plug nozzles. The application study on advanced carbon-carbon composite for the tip-turbine and fan assembly has been conducted. This study status is presented in the another session of this IAF congress1.The flight test of ATREX is now planning to verify the engine performance and functions in the practical flight conditions by using an unmanned flying test bench. In 1995 was tested ATREX-500 installing the precooler under the sea level static conditions to examine the engine performance and the icing problem on the precooler.The present paper addresses primarily the test results of precooled ATREX engine.