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The purpose of this study is to improve the performance of hollow fiber membrane and improve the separation efficiency.

By establishing a mathematical model of hollow fiber membrane gas separation, the influences of parameters such as pressure difference between the inside and outside of the filament, initial oxygen concentration of intake air, intake air flow rate and back pressure outside the filament on the polarization coefficient were analyzed, so as to explore the degree of influence of operating parameters on the concentration polarization, and put forward a technical scheme to reduce the concentration polarization.

Factors such as pressure difference between the inside and outside of the filament, initial oxygen concentration of intake air, intake air flow rate and back pressure outside the filament have a certain effect on the polarization coefficient. Among them, the polarization coefficient is positively correlated with pressure difference inside and outside the filament, initial oxygen concentration of intake air and back pressure outside the filament, and is negatively correlated with intake air flow.

Negative pressure suction on the permeation side can be used to increase the membrane permeation flow rate and reduce the concentration polarization.

The influence of concentration polarization on membrane performance is reduced by controlling various factors.

The objective of this study is to model the propagating front in the interaction of gases in an aircraft fuel tank. To this end, we introduce a nonlinear parabolic operator, for which solutions are shown to be regular.

The authors provide an analytical expression for the propagating front, that shifts any combination of oxygen and nitrogen, in the tank airspace, into a safe condition to avoid potential explosions. The analytical exercise is validated with a real flight.

According to the flight test data, the safe condition, of maximum 7% of oxygen, is given for a time t = 45.2 min since the beginning of the flight, while according to our analysis, such a safe level is obtained for t = 41.42 min. For other safe levels of oxygen, the error between the analytical assessment and the flight data was observed to be below 10%.

The interaction of gases in a fuel tank has been little explored in the literature. Our value consists of introducing a set of nonlinear partial differential equations to increase the accuracy in modeling the interaction of gasses, which has been typically done via algebraic equations.

U.S.S.R. Oxygen and nitrogen in metallised surfaces. One of the most important considerations in the matter of extending the life of units or components under rolling friction conditions or corrosion is the use of different pseudo‐alloys on a steel base, and the chemical composition and nature of these ‘alloys,’ especially in the matter of oxygen and nitrogen content. Electro‐metallising is briefly described. The micro‐structure of a steel metallised pseudo‐alloy is shown and discussed. Characteristic features are porosity and heterogeneity, the former amounting to 10 to 15%. Methods of analysis, especially for oxygen and nitrogen, include anodic solution and separation of non‐metallic inclusions (including oxides) in powder form. Nitrogen content averaged 0.13% and oxygen 2.7% (without manganous oxide). An x‐ray study was made of the phase constitution of non‐metallic inclusions, with tabulated results and x‐ray photographs. Analyses of the pseudo‐alloys for carbon manganese, sulphur, phosphorus and silicon are also tabulated. —(L. V. Krasnichenko et al., Zh. prikl. Khim. (J. Appl. Chem.), 1958, (8), 1170–1174.)

Determining the variation law of the oxygen concentration in the ullage space of the fuel tank is the key to the design of the inert system. Among various factors affecting the oxygen concentration in the ullage space of the fuel tank, the temperature difference between day and night shows particular importance while relevant analysis and calculation are scarce.

This study establishes a theoretical simulation model of the central wing fuel tank of an aircraft according to the relevant provisions of day-night temperature variation in FAR25 airworthiness regulations, verifies the model with the existing experimental data and discusses the corresponding relationship between the oxygen concentration in the ullage space of the fuel tank and the day-night temperature difference. The influence of day and night temperature difference, fuel type, fuel load rate, initial oxygen concentration, dissolved oxygen evolution and other factors on the oxygen concentration in the ullage space of the fuel tank were analyzed, and the limit of initial oxygen concentration of the fuel tank before the shutdown at night meeting the requirements of the airworthiness provisions was proposed.

The results show that the temperature difference between day and night, fuel load rate, initial oxygen concentration and other factors have different effects on the oxygen concentration in the ullage space of fuel tank. The initial oxygen concentration limit before shutdown shall be 2% below the 12% oxygen concentration stipulated by FAA.

The research results in this paper will be of good reference value to the design of the inert system and the calculation of the flammability exposure evaluation time. This paper aims to be good reference of the design of the inert system and the calculation of the flammability exposure evaluation time.

The research results of this paper can provide practical guidance for the current civil airworthiness certification work.

A major drawback of current copper thick‐film technology is the inefficient removal of the organic binder associated with the dielectric material in the low‐oxygen inert gas (N2) atmosphere of the furnace. In processing large area and/or multilayer substrates, the incomplete binder removal causes deleterious effects which have been well documented. Therefore, it is necessary to remove hydrocarbons and residual carbon from the films in the burn‐out section of the furnace before the films begin developing their characteristic microstructures. However, the atmosphere currently employed is not capable of removing all the carbon and hydrogen in the form of gaseous oxides. In literature, in addition to furnace modifications, several atmosphere modifications and manipulations have been proposed to achieve optimum properties for the fired films. With few exceptions, the scientific basis for such atmosphere modifications and manipulations has been left either unaddressed or obscure. With this background, this paper examines the feasibility of using a reactive gas mixture in the furnace to achieve efficient organic binder removal. Phase stability diagrams are presented to illustrate the stability of (i) carbon, (ii) thick film copper ingredients, (iii) active phases of resistors, and (iv) components of glassy and crystalline phases of dielectrics in selected reactive atmospheres. The stability of certain furnace belt constituents is also addressed. Mass balance calculations are shown to demonstrate the extent of carbon removal and copper oxidation in typical nitrogen atmospheres. Based on the interpretation of thermodynamic data and reaction mechanisms involved, a specific H2‐H2O mixture with nitrogen as the carrier gas is recommended. The approach presented here constitutes a general analytical scheme to understand materials‐atmosphere interactions occurring across a temperature range. Several issues in furnace design are also discussed from the standpoint of gas‐solid reaction kinetics. These deal with the design of gas‐flow systems that facilitate removal of organic binders.

This paper aims to improve the previous fuel scrubbing model and find out the relationship between bubble diameter and scrubbing efficiency (ƞ).

A fuel tank scrubbing test bench was established to verify the accuracy of this model. Ullage and dissolved oxygen concentration were measured, and images of bubble size and distribution were collected and analyzed using image analysis software.

The bubble diameter has a great influence on ullage and dissolved oxygen concentration during the fuel scrubbing process. The scrubbing efficiency (ƞ) has an exponential relationship with bubble diameter and decreases rapidly as the bubble diameter increases.

The variation of the ullage and dissolved oxygen concentration predicted by this model is more accurate than that of the previous model. In addition, the study of bubble size can provide a guidance for the design of fuel scrubber.

This study not only improves the previous fuel scrubbing model but also develops a method to calculate scrubbing efficiency (ƞ) based on bubble diameter. In addition, a series of tests and analyses were conducted, including numerical calculation, experiment and image analysis.

To reduce the flammability exposure assessment time and meet the requirements of airworthiness regulations of transport aircraft, inerting system has become the standard configuration of modern civil aircraft. Therefore, airworthiness regulations put forward definite quantitative index requirements for the safety of inerting system, and to obtain the quantitative data of the safety of inerting system, it is necessary to solve the calculation method. As one of the quantitative/qualitative evaluation techniques for system safety, fault tree analysis is recognized by international airworthiness organizations and national airworthiness certification agencies. When fault tree analysis technology is applied to quantitative analysis of the safety of inerted system, there are still some problems, such as heavy margin of constructing fault tree, great difficulty, high requirement for analysts and poor accuracy of solving when there are too many minimum cut sets. However, based on tens of thousands of flight simulation tests, Monte Carlo random number generation method can solve this problem.

In this paper, the fault tree of airborne inerting system is established, and the top event is airborne inerting system losing air separation function. Monte Carlo method based on random number generation is used to carry out system security analysis. The reliability of this method is verified.

The static fault tree analysis method based on Monte Carlo random number generation can not only solve the problem of quantitative analysis of inerting system, but can also avoid the defects of complicated solution and inaccurate solution caused by the large number of minimum cut sets, and its calculation results have good reliability.

The research results of this paper can be used as supporting evidence for airworthiness compliance of airborne inerting system.

The research results of this paper can provide practical guidance for the current civil airworthiness certification work.

The dissimilar welds between AISI 304L and Fe-15.6Cr-8.5Mn were investigated on oxidation at 700°C with the effects of dissolved nitrogen in the welds. This paper aims to clarify the oxidation behaviors to expand the range of application for Fe-Cr-Mn stainless steel.

Dissimilar welds between AISI 304L and Fe-15.6Cr-8.5Mn were fabricated using gas tungsten arc welding to investigate the oxidation behavior of the welds at 700°C. Pure Ar and Ar-4%N₂ shielding gases were used to evaluate the effects of nitrogen gas. The welds were introduced to the cyclic oxidation test. In each cycle, the furnace was heated up to 700°C, and the temperature was kept at 700°C for 8 h, then the mass gain because of oxidation was examined. The scales after oxidation test were investigated by using scanning electron microscopy with EDX and X-ray diffraction analysis.

Addition of 4 per cent nitrogen to Ar shielding gas reduced delta-ferrite content in the weld. Ar-4%N₂ shielding gas resulted in dissolved nitrogen which helped increase the diffusivities of chromium or oxygen vacancies in the oxide to facilitate the chromia formation at the inner part near the steel substrate. This protective layer can help reduce the Fe outward diffusion, thus reducing mass gain because of iron oxide formation.

The oxidation behavior of dissimilar welds between AISI 304L and Fe-15.6Cr-8.5Mn were investigated at 700°C. The evaluation is beneficial for expanding the range of application of Fe-Cr-Mn stainless steel at high temperature.

The purpose of this work is to investigate the performance of non‐contaminating metal cutting environments and investigate the associated tool chip interface conditions. The work benchmarks flood coolant characteristics and considers gaseous cutting environments as possible alternatives.

Cutting trials were undertaken for a range of cutting environments. Flood coolant was investigated as was dry cutting, compressed air, room temperature nitrogen and liquid nitrogen environments. A range of cutting variables was measured in order to document the effect of cutting environment.

The gaseous component of the liquid nitrogen environment limited the adhesion on the tool face to a region along the flank edge of the tool, shifting rake face conditions from seizure to that of sliding. Tighter chip curl, shorter contact lengths, reduced adhesion and lower feed forces are evidence that liquid nitrogen is acting as a “liquid inert barrier” beneath the chip within the tool/chip interface.

Only one tool work combination has been investigated. More tool work combinations will need to be investigated.

The work demonstrated that it is possible to use environmentally safe environments during metal cutting operations. This reduces the exposure of the environment and machine tool operatives to compounds which have been shown to have detrimental effects on the environment and human health.

The work has led to presenting a hypothesis that liquid nitrogen acts as a “liquid inert barrier” beneath the chip within the tool/chip interface.

Ancient and Modern The ability of zeolite granules to act as a molecular sieve has been known to science for many years: now NGL have adapted this age‐old process and by harnessing it to modern electronic technology have created a new concept in aircraft Life Support systems.