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Study on Prefire Characteristics of Wire Insulation by Overload in Weakly Buoyant Environment

Author: WangKai
Tutor: KongWenJun；WangBaoRui
School: Graduate School,Chinese Academy of Sciences
Course: Thermal Power Engineering
Keywords: Microgravity LV functional simulation Narrow channel analog Fire -front properties Manned spacecraft fire
CLC: TK124
Type: Master's thesis
Year: 2011
Downloads: 12
Quote: 1
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Abstract

With the development of the manned space program, manned aircraft fire safety gradually be taken seriously. Manned aircraft inside the three elements of a fire: the oxidant (oxygen astronauts survive must), combustible materials (non-metallic materials), potential sources of ignition (electrical components overload or short circuit). At the same time, the manned aircraft flying in the microgravity environment of space gas flow law, the internal electronics of the heat exchanger characteristics with ground often gravity environment. So we can not simply apply a ground fire prevention, monitoring and extinguishing solutions. In order to meet the needs of the manned aircraft fire safety, the need to explore the the fire early signs microgravity fire occurred. However, due to the ground to get the microgravity experiments limited time and space flight experiments are expensive, difficult to direct fire early characteristics of various materials microgravity research. Heat exchanger similar principle, using of two implementations weak buoyancy method, weak surface buoyancy experiment station, Fire early characteristics of the materials under simulated microgravity environment: First, reduce the JEM pressure, weak buoyancy environment is defined as low functional simulation \Typical electrical components for manned spacecraft - wire fire early characteristics of experimental research to study the impact of a current-carrying wire insulation under the pressure and the height of the narrow channel pre-ignition characteristics. First, according to the \The results show that the the weak buoyancy provided by the low-pressure function simulation environment, to reflect the rate of temperature rise of the wire insulation in microgravity and the final equilibrium temperature. Secondly, based on this method, the two kinds of overload current analysis of the influence of pressure the size of the single conductor ignition advance characteristics. Finally, in view of the low pressure, the chemical reaction of the insulation of the conductors is restricted, consider raising the oxygen concentration in the experiment. The results showed that the pressure is reduced to within a certain range, the method can overcome the defects of low pressure. In the third chapter of the thesis, wire narrow channel simulation experiments, the results show that the height decreases as the narrow channel, the wire insulation temperature rise rate and the final equilibrium temperature increases. Reduce the channel dimensions can simulate microgravity wire insulation fire early signs. But when the narrow channel size is too small, there are restrictions wall the cold put out the role and transporting oxygen. This paper, the method of reducing the pressure to increase the size of the narrow channel to be resolved. Experimental results show that the modest reduction in pressure after the low-pressure narrow channels, can overcome the narrow channel analog defects. The fourth chapter of the thesis, by the numerical simulation method to study single wire fire early temperature change characteristics. Pressure, gravity, and the narrow channel height of the characteristics of the impact, and comparing the experimental results on the front conductor. The results show that, the the microgravity wire fire pre-temperature characteristics can be simulated by two weak buoyancy in this article. Through this research, a systematic analysis of the validity and scope of application of the ground under simulated microgravity materials ignition advance signs of two experimental methods, and try some improvements. This work provides some useful lessons for the fire performance of the test materials under microgravity.

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Thermal Engineering Theory > Heat Transfer
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