Shin-ichi Moriya

Experimental Study on Transitional Phenomena of Extendible Nozzle

An extendible nozzle is considered to be a feasible device to improve the performance of booster engines because it has possibilities to provide altitude compensation and to achieve higher specific impulse. The booster engine with the extendible nozzle has to deploy its nozzle extension on engine firing. For the design of the extendible nozzle including its driving mechanics, it is required to clarify the transitional phenomena during the nozzle deployment. In order to investigate the transitional phenomena, firing tests using a sub-scale model were carried out on a high altitude test stand. In the firing test, the nozzle extension was sustained at a fixed position by supporting rods and the ambient pressure was varied to simulate an altitude change. In order to simulate the nozzle deployment, also the position of nozzle extension was adjusted by replacing the supporting rods. The nozzle extension was sustained at 57%, 67%, 77%, 87%, and 100% deployed positions. The axial load and side load acting on the nozzle extension were evaluated quantitatively by using small load cells installed in each supporting rod, and in addition, the distributions of wall pressure and heat flux along the inner wall of the nozzle extension were measured. Based on the experimental data, the transitional phenomena were investigated in both the mechanical and the thermal aspects. As results, the mechanical and the thermal conditions which can be critical in the design of the extendible nozzle were provided.

Characteristics of Dynamic Loads Acting on an Extendible Nozzle

An extendible nozzle is considered to be a feasible device to improve the performance of booster engines because it has possibilities to provide altitude compensation and to achieve higher specific impulse. The booster engine with the extendible nozzle has to deploy its extendible nozzle during firing. The loads acting on the extendible nozzle vary with a nozzle deployment position as well as an altitude. For the design of the extendible nozzle and its driving mechanics, it is required to clarify the characteristics of dynamic loads acting on the extendible nozzle. In order to investigate the characteristics of dynamic loads, firing tests were carried out on a high altitude test stand. The extendible nozzle was sustained by a nozzle supporting system composed of six rods, and the nozzle deploying position was adjusted at 100%, 76%, and 56% deployed position. In the firing tests, the ambient pressure was varied to simulate an altitude change. The axial load and side load acting on the extendible nozzle were evaluated quantitatively by using small load cells installed in each supporting rod. From the experimental data of dynamic loads acting on the extendible nozzle for 100%, 76%, and 56% deployed position, the effect of nozzle deployment position on the dynamic loads were clarified.

Dynamic Characteristics of an Extendible Nozzle during Deployment

*† ‡ § ** †† An extendible nozzle is considered to be a feasible device to improve the performance of booster engines because it has possibilities to provide altitude compensation and to achieve higher specific impulse. The booster engines with the extendible nozzle have to deploy the extendible nozzle during firing. For the design of the extendible nozzle and its driving mechanics, it is required to clarify the dynamic characteristics of the extendible nozzle. Dynamic characteristics of the loads acting on the extendible nozzle were investigated through the firing tests on a high altitude test stand with varying the ambient pressure to simulate the altitude change. In the firing tests, the extendible nozzle supported by four or six rods was used. The thrust and side loads acting on the extendible nozzle were evaluated quantitatively by using the supporting system consisted of six rods. Using the measured load data and the calculated nozzle pressure distribution data, the estimation of flow separation point were carried out. The effect of deployment position was also clarified.

Numerical Investigations of Heat Transfer Enhancement in a Thrust Chamber with Hot Gas Side Wall Ribs

Heat transfer enhancement due to hot gas side wall ribs in a thrust chamber is discussed in this paper. Three-dimensional Favre-averaged Navier-Stokes simulations conjugating heat conduction simulation were performed for LOX/GH2 calorimeter chambers considering the finite rate chemical reactions. Atomization process of a LOX jet was modeled as LOX droplets by Discrete Phase Model. The computed results reveal the threedimensional combustion flow mechanism inside the chambers, and predict heat transfer enhancement due to hot gas side wall ribs. The computed heat flux agreed well with the experimental values, although some discrepancies were observed. Maximum heat flux and temperature on the hot gas side ribbed cylinder as well as the throat section were predicted.

Experimental and Numerical Study on Performance of Extendible Nozzle for Altitude Compensation

An extendible nozzle for altitude compensation is considered to be a feasible device to improve the performance of booster engines because it can provide higher thrust at sea level and higher specific impulse in vacuum. The booster engine with the extendible nozzle has to deploy its nozzle extension on engine firing. For the design of the extendible nozzle including its driving mechanics, it is required to clarify the transitional phenomena during the nozzle deployment. Based on the experimental results of the firing tests using a sub-scale model, the characteristics of thrust coefficient, the nozzle axial load, and the nozzle side load affected by the nozzle flow transition are examined. The backflow of combustion gas through the gap between the fixed nozzle and the nozzle extension was also examined with use of CFD analysis. As results, disadvantages in the nozzle performance and the nozzle loads in case of improper nozzle deployment condition are clarified.

Wall Thickness Measurements by Ultrasonic Probes in a Liquid Rocket Combustion Chamber

The regenerative cooling combustion chamber of a liquid rocket engine is exposed to a large temperature difference between the combustion gas and the liquid fuel. To estimate the inner wall damage, an evaluation of wall deformations is very important since chamber life is usually related to such deformations. In this study, the ultrasonic thickness measurement technique based on the pulse reflection method was chosen and conducted the measuring tests of ligament thicknesses and the analyses of ultrasonic wave propagations. Two types probe were manufactured which have a polystyrene and a local immersion delay. From the test and the analysis results with a polystyrene delay, it was shown that the b1 echo could not stably obtained in an A-scan graph and measurement accuracy was not sufficient in measuring the thicknesses of a convex and a concave ligaments. From the test results with a local immersion delay, the measurement accuracy within ±50 μm was attained to measure the thicknesses of a convex and a concave ligaments. Nomenclature S1 = First surface echo B1 = First bottom echo B2 = Second bottom echo Vl = Acoustic velocity of longitudinal wave Vs = Acoustic velocity of shear wave

Evaluation of Spark Plasma Sintering (SPS) Forming Method for Liquid Rocket Combustion Chambers

The objective of this study was to investigate new fabrication methods for combustion chambers to potentially reduce fabrication time and cost. For this purpose, the SPS (Spark Plasma Sintering) forming method was applied for bonding the inner cylinder and the outer jacket of combustion chambers. With the SPS forming method, very complicated bonding can be easily achieved while sustaining sufficient bonding strength between the inner cylinder and the outer jacket and providing perfect sealing of coolant channels. The primary task of the present study was to investigate the applicability of SPS bonding to the inner cylinder and the outer jacket in combustion chambers. To confirm the applicability of SPS bonding to combustion chambers, tensile test specimens and simulated combustion chamber specimens were manufactured. For these types of specimens, pressure proof tests using water were conducted to confirm the bonding strength at coolant channel pressure of up to 50 MPa. Furthermore, ultrasonic inspections were conducted before and after the pressure proof tests using an ultrasonic imaging device. From the test results, the applicability of SPS bonding for the inner cylinder and the outer jacket in combustion chambers was confirmed.