Study on the test load for the structural test of the flight-load condition of the external fuel tank for fixed-wing aircraft

In this study, for the purpose of conducting the structural tests for the verification of structural soundness of the flight-load conditions of the external fuel tank for the fixed-wing aircraft, the flight load acting on the external fuel tank was converted to test load and the suitability of the converted loads was verified. The loads imposed on the external fuel tank were expressed as the combination of the inertial load (based on the acceleration in the translational direction) and the tangential direction inertial load (based on the angular acceleration of the moment). To calculate the test load, the transfer function table was generated by calculating the shear load and moment based on the unit load. For this purpose, a transfer function table was established by dividing the external fuel tank into a few sections and calculating the shear load and moment generated by the unit shear load and unit moment in each section. In addition, the test load for each section was calculated by computing the established transfer function table and flight-load conditions. However, in actual structural tests, it is often not possible to impose a load in the same position as the point at which the shear load and moment are calculated. For this reason, the actual test-load positions had to be determined and the calculated test loads were redistributed to those positions. Then, the final test load plan was established by applying a whiffle tree to increase the efficiency of the test while also making it easier to apply the actuators. Finally, the suitability of the established test load plan was confirmed by comparison with the flight-load conditions.

Massive Molecular Gas as a Fuel Tank for Active Galactic Nuclei Feedback In Central Cluster Galaxies

Massive molecular gas has been discovered in giant elliptical galaxies at the centers of galaxy clusters. To reveal its role in active galactic nucleus (AGN) feedback in those galaxies, we construct a semianalytical model of gas circulation. This model especially focuses on the massive molecular gas (interstellar cold gas on a scale of ∼10 kpc) and the circumnuclear disk (≲0.5 kpc). We consider the destruction of the interstellar cold gas by star formation and the gravitational instability for the circumnuclear disk. Our model can reproduce the basic properties of the interstellar cold gas and the circumnuclear disk, such as their masses. We also find that the circumnuclear disk tends to stay at the boundary between stable and unstable states. This works as an “adjusting valve” that regulates mass accretion toward the supermassive black hole. On the other hand, the interstellar cold gas serves as a “fuel tank” in the AGN feedback. Even if the cooling of the galactic hot gas is prevented, the interstellar cold gas can sustain the AGN activity for ≳0.5 Gyr. We also confirm that the small entropy of hot gas (≲30 keV cm2) or the short cooling time (≲1 Gyr) is a critical condition for the existence of massive amounts of molecular gas in the galaxy. The dissipation time of the interstellar cold gas may be related to the critical cooling time. The galaxy behavior is described by a simple relation among the disk stability, the cloud dissipation time, and the gas cooling rate.

Use of the Low-Potential Heat for Heating Helium in Rocket-Carrier Tank Pressurisation Systems

The energy efficiency of new technical developments is a critical issue. It should be noted that today the focus in this issue has seen a major shift to the maximum use of renewable energy sources. The purpose of this research is to reduce the weight of helium heat exchangers of the fuel tank pressurisation systems in modern rocket propulsion systems that use fuel components like liquid oxygen and kerosene-type fuel. This is the first time that the question has been raised about the possibility and advisability of increasing the temperature of helium at the heat exchanger inlet without the use of additional resources. The paper addresses the use of the waste (“low-potential”) heat and ”industrial wastes” present in propulsion systems. Basic laws of complex heat exchange and the retrospective review of applicable heat exchanger structures are applied as a research methodology. Two sources of low-potential heat are identified that have been previously used in the rocket engine building in an inconsistent and piecemeal manner to obtain and heat the pressurisation working fluid. These are the rammedair pressurisation during the motion of the rocket carrier in the atmosphere, and the tank pressurisation as a result of boiling of the top layer of oxidiser which is on the saturation line. This is the first time that the advisability has been substantiated of increasing the temperature of the working fluid at the heat exchanger inlet, first of all due to the use of the low-potential heat. This is also the first time that unemployed sources of low-potential heat and “industrial wastes” are found in modern deep throttling propulsion systems. These are the high-boiling-point fuel in the tank, behind the highpressure pump, at the exit of the combustion chamber cooling duct, and also the fuel tank structures, and the engine plume. A possibility is proved, and an advisability demonstrated of their implementation to increase the efficiency of pressurisation system heat exchangers. This is the first time that the methodology of combustion chamber cooling analysis has been proposed to be adopted for the heating of heat exchanger by the engine plume. This is the first time that a classification of waste heat sources has been developed which can be used to increase the pressurisation working fluid temperature. The identified reserves help to increase the efficiency of the helium heat exchangers of the tank pressurisation systems in the propulsion systems