Hideo Sunakawa

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.

High-cycle fatigue behavior of Ti-5Al-2.5Sn ELI alloy forging at low temperatures

High-cycle fatigue properties of Ti-5Al-2.5Sn Extra Low Interstitial (ELI) alloy forging were investigated at low temperatures. The high-cycle fatigue strength at low temperatures of this alloy was relatively low compared with that at ambient temperature. The crystallographic orientation of a facet formed at a fatigue crack initiation site was determined by electron backscatter diffraction (EBSD) method in scanning electron microscope (SEM) to understand the fatigue crack initiation mechanism and discuss on the low fatigue strength at low temperature. Furthermore, in terms of the practical use of this alloy, the effect of the stress ratio (or mean stress) on the high-cycle fatigue properties was evaluated using the modified Goodman diagram.

Effect of stress ratio on high-cycle fatigue properties of Ti-6Al-4V ELI alloy forging at low temperature

The effect of the stress ratio R (the ratio of minimum stress to maximum stress) on the high-cycle fatigue properties of Ti-6Al-4V extra-low interstitial (ELI) alloy forging was investigated at 293 and 77 K. At 293 K, the fatigue strength at 107 cycles exhibited deviations below the modified Goodman line in the R=0.01 and 0.5 tests. Moreover, at 77 K, larger deviations of the fatigue strength at 107 cycles below the modified Goodman line were confirmed in the same stress ratio conditions. The high-cycle fatigue strength of the present alloy forging exhibit an anomalous mean stress dependency at both temperatures and this dependency becomes remarkable at low temperature.

An End-to-End High Fidelity Numerical Simulation of the LE-X Engine - Influence of Coolant Leakage on Engine Power Balance -

Risk evaluation is important for the development of new engines. There are many methods for estimating development risk and reliability. Among these high-fidelity numerical simulation is one of the most useful and powerful tools and is sometimes the only method available. A rocket engine is a very complicated and compact system. A single failure in the engine may have a significant influence on other components. Therefore, the influence of component interaction must be considered to evaluate risk appropriately. Further, the combustion chamber for a booster engine is quite large. Thus, it is not easy to perform a combustion test, and, if some hazard occurs, the engine and surrounding facility could be damaged severely. Therefore, a very detailed risk evaluation is quite important. One way to evaluate risk is to carry out a high-fidelity numerical simulation of an entire engine system. In the present report, results of an end-to-end high fidelity numerical simulation of whole engine system were reported and influence of coolant leakage on engine power balance was evaluated.