Papers by Keyword: Low Pressure

Abstract: Low Density and Low Pressure Sheet Molding Compounds (LD-LPMC) were prepared by using magnesium oxide paste and crystalline polyester as thickening system to reduce molding pressure and Hollow Glass Microspheres (HGM) as fillers to reduce the density. The molding pressure of LD-LPMC was investigated. The effects of HGM content (0%, 3.8%, 7.6%, 11.4%, 15.2%, 19.0%) on the density, flexural strength and thermal conductivity of LD-LPMC were studied. The results showed that 2-4Mpa was the best molding pressure for the composite materials. With the increase of HGM content, the density, flexural strength and thermal conductivity of LD-LPMC decreased. The thermal conductivity increased with the increase of temperature. When the molding pressure was 3Mpa and the content of the HGM was 7.6%, the density decreased by 13.6%, the flexural strength only decreased by 23.3% and the thermal conductivity (40°C) also decreased by 11.5%, which reflected the low density, high strength and good thermal insulation performance of LD-LPMC.

Abstract: Flash point and boiling point are the important physical property of the flammable liquids, and are important parameters to evaluate their combustion behavior. In this study, as series of measurement of two mono compound fuels (N-decane and N-hexanol) and two mixture compound fuels (0# diesel and Jet A) at different pressure were carried out by using the flash point (open-closed cup) and boiling point measuring apparatus in an altitude chamber at different sub-atmospheric pressures at 35 KPa, 45 KPa, 55 KPa, 65 KPa, 75 KPa, 85 KPa, 95 KPa and 101 KPa were conducted. Based on the theoretical formula between the flash point (T_F) and the boiling point (T_B) and the atmosphere pressure, the relationship between T_B and T_F has been derived. The experiment results and the theoretical formula all show that the flash point is in linear relationship with the boiling point. The results can provide a more scientific insight into the production, storage, transport and use of fuel and the safety design in aircraft fuel tank.

Abstract: The interaction among heavy interstitial atoms present in metals with bcc structure is studied using anelastic spectroscopy. This technique makes it possible to obtain information on interstitial concentration, precipitation, solubility limit, and diffusion. The diffusion coefficients of nitrogen in niobium were obtained using the relaxation parameters obtained from anelastic spectroscopy measurements for different oscillation frequencies of the system. The results showed the interstitial diffusion of nitrogen present in solid solution in niobium when submitted to different charges of nitrogen at a temperature of 1373 K and a partial pressure in the order of 10^-4 Torr. The exponential variation of the pressure experimentally in function of the time was thus obtained.

Abstract: In the paper, for high-power marine overflow valve of low pressure big traffic problems, the design of the inside leaking mouth leaks in parallel structure ,that is suitable for the different oil and water flow, using additional flow beam, guiding type low pressure large flow overflow valve was developed and the experimental study, obtained the dynamic and static parameters of the valve. Invented the inside leaking and leaked mouth parallel connection structure, inside leaking and leaked mouth parallel connection is established the mathematical model of the overflow valve. Results show that compared with the traditional straight moving type overflow valve, the type overflow valve through a larger flow, has better dynamic and static performance and cavitation resistance.

Abstract: Some parameters, such as cabin pressure and Relative Humidity (RH), in a civil cabin environment, are significantly lower than those at sea level when the civil aircraft is in its cruise conditions at high altitude. The common PMV thermal comfort assessment model is not suit for this environment. Therefore, a Corrected PMV (CPMV) model is adopted to analyze the impact of these two parameters on thermal comfort in a cabin. From the simulations, we can draw conclusions that, within a normal operative range of RH and cabin pressure, the low RH and pressure can lead to a negative deviation and a positive deviation of thermal sensation values, respectively, but their impacts on thermal comfort of passenger are limited. The CPMV model is further applied to assess the thermal comfort of investigated flights.

Abstract: Abstract. Non-depositing critical velocity is an important parameter in project design for low pressure pipeline irrigation system. By using indoor experimental system of water pipeline conveyance, the non-depositing critical velocity with different sediment content has been researched. The results show that the non-depositing critical velocity increases with the increasing of sediment content, but it does not increase substantially with the increasing of sediment content. The empirical formula of non-depositing critical velocity has been drawn, and close agreement between the empirical formula and the measured data exists with a correlation coefficient R2=0.95, which can provide the basic theoretic reference to prevent pipe from being clogged in channel irrigation area.

Abstract: When liquid within short pipe is placed suddenly into low-pressure environment from an atmospheric pressure, the effects of temperature and pressure on occurrence and developing of evaporation wave are studied, the variations of flow patterns are observed. The experimental results show that flow patterns of liquid within short pipe gradually change from bubble rising to blazing bubble flow until annular flow with a decrease in initial environmental pressure. Intensity and moving speed of the evaporation wave increased with a decrease of the diameter of pipe and pressure, and an increase of the fluid temperature. The evaporation wave fronts are in a state of explosive vaporization, instantaneous propagation velocity of evaporation wave fronts is violently fluctuating.

Abstract: Experimental investigation of falling film evaporation on horizontal tubes was carried out in this paper. Tube surface, spray flow rate and coolant flow rate were the factors considered in the experiment. The impact on falling film evaporation performance was obtained as expected. Experimental results are obtained that the heat transfer performances of low finned tubes are better than that of smooth tubes. The increasing of flow rate enhances heat transfer performance of falling film evaporation at first, while the flow rate gets a certain value, it will hinder the improvement of heat transfer performance. It was also found that there is almost no effects on heat transfer coefficient when the flow rate of coolant changes.

Abstract: In this article, for a better understanding of the viscosity changes in LPMC (low pressure sheet molding compounds), the thickening mechanism of crystalline polyesters was studied. And by means of varying the content of crystalline polyester resin, the thickening effect on resin paste was investigated, too. Results gained during experiments showed that there existed three kinds of functions acting in the process of thickening: swelling, hydrogen bonds and induction crystallization. The thickening effect was excellent when the amount of crystalline polyester resin was 3%. This research supports the producing process for LPMC with theory basement.

Abstract: In this study, the high temperature oxidation behavior of polycrystalline MoSi2 in a low-pressure atmosphere was investigated. Polycrystalline MoSi2 was produced by the spark plasma sintering process. Oxidation tests were carried out at 1500°C at either 10Torr or 760Torr in an Ar-20%O2 atmosphere. For both conditions, the weight change peaked at the initial oxidation stage, and then their weights gradually increased with increasing oxidation time. The sample weight became heavier in the ambient pressure than in the low-pressure, but the evaporation oxidation was not significant in the low-pressure condition. After the low-pressure oxidation tests, the formation of Mo5Si3 in the MoSi2 substrate was identified. The oxidation resistance of MoSi2 at 1500°C is discussed based on the obtained results.