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The purpose of this study is to solve the oil drill pipe joints and casing excessive wear problems and to improve the drill pipe joint-casing wear resistance and anti-friction properties.

On the surface of the drill pipe joints using oxyacetylene flame bead weld (BW) wear-resistant welding wire ARNCO-100XT^TM prepares welding layer, high-velocity oxygen fuel (HVOF) Cr₃C₂75-NiCr25 prepares coating and subsonic flame spray and remelt (SFSR) Ni60 prepares coating, then comparing and analyzing the friction and wear of the three types of wear-resistant layers and the casing under the condition of 1.8 g/cm³ mud drilling fluid lubrication. The wear resistance and anti-friction performance of the drill pipe joints were evaluated based on the wear situation, finally revealing its friction and wear mechanisms.

Three types of wear-resistant layers can improve the surface wear resistance of drill pipe joints, the wear-resistant layer and the substrate are well combined and the welding layers and coating are both dense and uniform. The wear resistance of the HVOF-Cr₃C₂75-NiCr25 coating is 10.9 times that of the BW-ARNCO-100XT^TM weld layer, and the wear resistance of the SFSR-Ni60 weld layer is 2.45 times that of the BW-ARNCO-100XT^TM weld layer. The anti-friction properties of SFSR-Ni60 welding layer is the best, followed by HVOF-Cr₃C₂75-NiCr25 coating, and the anti-friction properties of BW-ARNCO-100XT^TM welding layer is the worst among the three.

The research results of this paper have great practical value in the process and material of improving the wear resistance and anti-friction performance of the drill pipe joint casing.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.

This paper aims to get an in-depth understanding of the fuel spray characteristics to further improve the emission performance of a lean premixed prevaporized (LPP) combustor with staged lean combustion.

In this paper, the fuel spray characteristics in the LPP combustor are experimentally studied by using particle image velocimetry (PIV), and raw data are processed by image-processing technologies for different inlet conditions. The effects of the fuel allocation and pilot atomizer position on fuel spray characteristics are investigated.

Experiment results show that when only the pilot atomizer is operated, the fuel spray characteristics is worsened by increasing fuel flow rate. The fuel spray fields generated by the pilot atomizer are better at the throat than that at the pilot swirler outlet; when the pilot atomizer and primary injector are operated at the same time with the same inlet fuel air ratio, the spray characteristics are improved by increasing the primary fuel flow rate and decreasing the pilot fuel flow rate. Meanwhile, fuel spray fields generated by the pilot atomizer are better at the throat than that at the pilot swirler outlet.

The present results are useful for further development of the LPP combustor.

An LPP combustor with staged lean combustion technology was proposed; to obtain fuel spray characteristics, image-processing program was compiled; the fuel spray characteristics in the LPP combustor were investigated, especially the effects of the fuel allocation and pilot atomizer position.

THE power plant for the Concord supersonic transport has evolved from an optimization study which showed that a medium‐pressure ratio turbojet would be the best compromise for a transatlantic M=2•2 civil aircraft. The detail design of the engine intake and nozzle systems is currently proceeding in the Design Offices of British Aircraft Corporation and Bristol Siddeley Engines in England and S.N.E.C.M.A. in France.

The purpose of this study is to investigate the effect of the injection angle α on the spray structures of an air-blast atomizer and help enhance the understanding of droplet-gas mixing process in such atomizers in the engineering domain.

The phenomena in the air-blast atomizer were numerically modelled using the computational fluid dynamics software Fluent 17.2. The Euler-Lagrange approach was applied to model the droplet tracking and droplet-gas interaction in studied cases. The standard k-ε model was used to simulate the turbulent flow. A model with a modified drag coefficient was used to consider the effects of the bending of the liquid column and its penetration in the primary breakup region. The Kelvin-Helmholtz, Rayleigh-Taylor model was applied to consider the secondary breakup of the droplets.

The basic spatial distribution and spray structures of the droplets corresponding to the angled liquid jet (α = 60°) were similar to those reported in liquid jets injected transversely into a gaseous crossflow studies. The injection angle α did not considerably influence the averaged Sauter to mean diameter (SMD) of the cross-sections. However, the spray structures pertaining to α = 30°, α = 60° and α = 90° were considerably different. In the case of the atomizer with multiple injections, a “collision region” was observed at α = 60° and characterized by a higher ci and larger averaged SMD in the central parts of the cross-sections.

The injection angle α is a key design parameter for air-blast atomizers. The findings of this study can help enhance the understanding of the droplet-gas mixing process in air-blast atomizers. Engineers who design air-blast atomizers and face new challenges in the process can refer to the presented findings to obtain the desired atomization performance. The code has been validated and can be used in the engineering design process of the gas-liquid jet atomizer.

This paper aims to investigate the effects of Cr and Ta additions on the friction performance and corrosion-wear mechanism of Fe90-Al₂O₃ coating in 3.5% NaCl solution.

Cr and Ta reinforced Fe90-Al₂O₃ coatings were prepared on Q235 steel by laser cladding. The effects of Cr and Ta addition on the coefficient of friction (COF) and wear rate of Fe90-Al₂O₃ coating were investigated using a friction tester, and the wear model was established to discuss its corrosion-wear mechanism.

The average COFs of Fe90-Al₂O₃, Fe90-Al₂O₃-10%Cr and Fe90-Al₂O₃-10%Ta coatings in 3.5% NaCl solution are 0.57, 0.42 and 0.75, respectively, and the corresponding wear rates are 9.42 × 10⁻⁷, 5.31 × 10⁻⁷ and 7.02 × 10⁻⁷ mm³ s⁻¹ N⁻¹, respectively. The corrosion-wear resistance of Fe90-Al₂O₃-10%Cr coating is the best among the three kinds of coatings, in which the additions of Cr and Ta play a role in solid solution strengthening.

The Fe90-Al₂O₃ coating was strengthened by the additions of Cr and Ta to improve its corrosion-wear resistance in 3.5% NaCl solution.

Application of cold spray technology may exhibit significant benefits for the additive manufacturing process, particularly for producing intricate objects. To ascertain the feasibility of such an application, this paper aims to present a numerical investigation of the effect of scaling down a convergent-divergent (de Laval) nozzle, which is typically used in the cold spray industry, on the compressible flow parameters and thermal characteristics.

The Navier–Stokes equations and energy equation governing compressible flow are numerically solved using a finite volume method with a coupled solver. The conjugate heat transfer technique is used to couple fluid and solid heat transfer domains and predict the local heat transfer coefficient between the solid and fluid. The use of various RANS turbulence models has also been investigated to quantify the effect of the turbulence model on the simulation.

The numerical results reveal that the flow and thermal characteristics are altered as the convergent-divergent nozzle is scaled down. The static pressure and temperature profiles at any section in the nozzle are shifted toward higher values, while the Mach number profile at any section in the nozzle is shifted toward a lower Mach number. The turbulent kinetic energy at the nozzle exit increases with the scaling down of the nozzle geometry. This study also provides convincing evidence that the adiabatic approach is still suitable even though the temperature of the nozzle wall is extremely high, as required for industrial application. Results indicate that it is feasible to use the available capabilities of the cold spray technology for additive manufacturing after scaling down the nozzle.

The idea of adopting cold spray technology for additive manufacturing is new and innovative. To develop this idea into a viable commercial product, a thorough understanding of the flow physics within a cold spray nozzle is required. The simulation results discussed in this paper demonstrate the effect that scaling down of a convergent-divergent nozzle has on the flow characteristics in the nozzle.

The purpose this experimentation is to study the combustion characteristics of compression ignition engine fuelled with mineral diesel. The reason behind the numerical simulation is to validate the experimental results of the combustion characteristics.

The numerical analysis was carried out in this study using MATLAB Simulink, and the zero dimensional combustion model was applied to predict the combustion parameters such as in cylinder pressure, pressure rise rate and rate of heat release.

Incorporating the dynamic combustion duration with respect to variable engine load in the zero dimensional combustion model using MATLAB Simulink reduced the variation of experimental and numerical outputs between 5.5 and 6 per cent in this analysis.

Validation of the experimental analysis is very limited. Investigations were performed using zero dimensional combustion model, which is the very appropriate for analysing the combustion characteristics.

Existing studies assumed that the combustion duration period as invariant in their numerical analysis, but with the real time scenario occurring in CI engine, that is not the case. In this analysis, mass fraction burnt considering the dynamic combustion duration was incorporated in the heat transfer model to reduce the error variation between experimental and numerical studies.

IN recent years, much attention has been given to spontaneous ignition problems because of the high skin temperatures of aircraft operating at high Mach numbers. The problem is not really new, however, since for many years aircraft engines have been operating with carcase temperatures above the laboratory closed vessel spontaneous ignition temperatures for fuels and lubricants, and installation engineers have collected a good deal of ad hoc data to justify the safety of particular power plants. FIG. 1 indicates the main risk areas for a typical subsonic by‐pass jet installation.

The background of missile costs is discussed. Missiles are new and very costly. Developments in this field have been subjected to political vicissitudes which have often upset long‐term developments. Missile technology is on the frontier of science and there is no background of knowledge to draw on; much basic and expensive research is required. Missile engineering models are complex in detail and assembly, and therefore costly, and constant change occurs while making and testing the model. The complexity and functional requirements of missile parts are running a parallel race with the machines and processes being developed to fabricate the materials required. The usually small runs required in missile production again add to costs. Imposed on all these activities is the requirement that reliability of near 100 per cent is needed and in no case can reliability be allowed to be secondary to cost. The inflight life and shelf conditions for a missile are usually fairly well established and 100 per cent reliability for a short operating life with a long shelf life are the real requirements. There is a considerable tendency to overdesign for reliability. Some costly features of design such as finest finish, closest tolerances and highest strength are carried over by habit from aircraft design and are not always required in missiles. Having examined some causes of high costs, a programme for cost reduction is set out. Costs can be reduced by: (i) earlier freezing of designs making changes only in groups of several changes at wider intervals, (ii) making a more realistic approach to reliability designs, (iii) selecting tolerances in a more analytical manner according to individual needs, (iv) selecting materials on the basis of actual design requirements instead of using the very best materials available even when the short life makes them unnecessary, (v) avoiding tool‐room methods in production engineering, (vi) setting work standards on as many operations as possible and enforcing them to the greatest degree possible, (vii) selecting the best type of workers to make the transition from development models to production missiles as smooth as possible, and (viii) setting up rigid systems and parts designation procedures for handling production parts. Finally, methods of organizing research and development and production for bridging the gap between engineering design and production are proposed.