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The purpose of this paper is to provide an analytical method of jet flow injection direction and to determine the influence of oil nozzle structure parameters on oil injection direction, thus providing the design method of oil nozzle structure parameters.

A model of oil injection loss is established to analyze the influence of oil nozzle structure parameters on oil injection direction. The computational fluid dynamics method is used to simulate the process of the deviation of jet flow injection direction. The deviation of jet flow injection direction with different oil nozzle structure parameters is calculated and their variations are obtained. Moreover, the deviation of jet flow injection direction with different oil nozzle structure parameters is tested to verify the analysis results.

Results indicate that radial velocity caused the deflection of the oil injection direction. The deviation of jet flow increased as the nozzle slenderness ratio decreased. The design method of the nozzle slenderness ratio (greater than five) is proposed to avoid the deviation of injection direction, and it is necessary to consider the matching between the nozzle slenderness ratio and pipeline pressure. The computational results coincide well with the experimental results.

The research presented here analyzed the influence of oil nozzle structure parameters on oil injection direction via a numerical analysis method. It also leads to a design reference guideline that could be used in jet lubrication, thus controlling the direction of the injection jet accurately.

This paper aims to investigate the influence of oil–air lubrication flow behavior on point contact sliding wear characteristics.

Oil–air lubrication equations between point contact counterparts were established on the basis of volume of fluid model. The effects of oil supply and injection azimuth on oil-phase volume fraction and its pressure distribution were simulated with commercial software Fluent. Characteristics of point contact sliding wear were then tested with an MFT-3000 friction tester under oil–air lubrication condition. The influence of flow behavior on wear characteristic was investigated combined with numerical and experimental results. The wear mechanism was revealed using SEM, EDS and ferrography.

When air supply speed is constant, the oil-phase volume fraction increases with the increase in oil supply, which helps form continuous oil film and decrease the sliding wear evidently. The injection angle and distance considerably influence the oil–air flow behavior. When injecting at a certain distance and angle, the oil-phase volume fraction reaches its maximum, and the abrasion loss is minimal. Under the test conditions in this study, abrasive particles are mainly debris and a few spiral cuttings. The wear mechanism is abrasive wear.

The influence of the behavior of oil–air lubrication flow on the characteristic of point contact sliding wear is analyzed. This work provides guidance for the application of oil–air lubrication technology in point contact friction pairs.

This paper aims to reveal the mechanism of air barrier effect in jet lubrication and to figure out the influence of gear parameters and conditions on air barrier, thus providing guidance to the design of jet lubrication in ultra-high speed gear cooling system.

The computational fluid dynamics method is used to calculate the flow and pressure of ultra-high speed gears. The flow and pressure distributions are obtained under different gear parameters and working conditions, so their variations are obtained. A multiphase flow model is established to simulate the flow regime of oil jet to ultra-high speed gears. Simple experiments are carried out to observe the air barrier effect of high-speed gears.

Air barrier effect exists in the jet lubrication of ultra-high speed spur gears, which could prevent oil jet to reach on the gear surfaces. The results show that the generated pressure has positive relations with gear speed, module and width; however, as the increasing of gear width, their marginal contribution to pressure is decreasing. The computational results coincide well with the experimental results.

The research presented here proposed the air barrier effect of ultra-high speed gears for the first time. It also leads to a design reference guideline that could be used in jet lubrication of ultra-high speed gears, thus preventing lubrication and cooling failures.

This paper aims to improve the cooling performance of the impinging jet to the machining and power transmissions, and provides more parameters to the design of the cooling system.

A multiphase flow model with heat transfer terms is established to calculate the convective heat transfer coefficient. The computational fluid dynamics method is used to simulate the jet flow. The convective heat transfer coefficients with different spray parameters are calculated and their variations are obtained. Temperatures are tested to reflect the cooling performance (convective heat transfer coefficients) with different spray parameters.

The results show that the higher convective heat transfer coefficient can be obtained with the same flow rate by decreasing nozzle diameter while increasing either the number of nozzles or the oil supply pressure. The spray distance was found to have little influence on convective heat transfer; however, the more the spray is directed parallel to the surface, the higher the convective heat transfer coefficient. The computational results coincide well with the experimental results.

The research presented here leads to a design reference guideline that could be used in machining and power transmissions to reduce the temperature, thus improving their quality and efficiency, and preventing failure at high speeds and/or under heavy loads.

This paper aims to investigate the effects of air inlet flow rate on the bearing cavity and operating conditions during the oil-air lubrication.

A model of oil-air lubrication of rolling bearings is established using computational fluid dynamics numerical simulation. Moreover, temperature and vibration experiments are carried out for comparisons and validation.

Results suggest that the velocity and pressure distributions of the oil-air flow inside the chamber are not uniform. Moreover, the uniform decreases with increasing air inlet flow rate. The non-uniform oil distribution inside the bearing significantly influences the bearing temperature rise and lubrication effect. Furthermore, the decrease in pressure uniformity enhances the vibration intensity and increases the amplitude of the vibration acceleration by more than 40 per cent. Increasing the air inlet flow rate improves lubrication and cooling efficiency but produces intense vibrations.

A method of establishing rolling bearings model under oil-air lubrication is presented in the paper. The effect of air inlet flow rate on flow uniform under oil-air lubrication has been researched insightfully. The results provide a useful reference to improve the oil-air lubrication system and enhance the operational stability of the motorized spindle.

The purpose of this paper is to design an oil-air lubrication system with low temperature rise, vibration and noise simplifies the spindle configuration. The oil-air lubrication unit is a key component for high-speed grinding machine tools. The development of oil-air lubrication unit suitable for high/ultrahigh rotational speed is a daunting task owing to the lubrication challenges.

This paper emphasizes three main issues: the analysis of oil-air two-phase flow for tradition oil-air lubrication unit with the simulation method; the design of new oil-air lubrication unit for the high/ultrahigh-speed grinding machine tools and the comparative experiment research of tradition and new oil-air lubrication unit. The optimum structure parameters that create the optimum flow pattern and operating conditions resulting in low temperature increase, vibration and noise of oil-air lubricated spindle can be achieved by the simulation method and experiments.

The simulation and experimental results show that new oil-air lubrication unit lubricating a high speed electric spindle has a better performance with a small temperature increase and vibration, which means that our proposed method is an effective design method for oil-air lubrication system.

A design method suitable for high-speed oil-air lubrication unit is proposed. New oil-air lubrication unit is expected to apply for high/ultrahigh rotational speed grinding machine tools.

In the last article in this series we dealt with the methods of applying grease to anti‐friction bearings. In this article we deal with application of lubricating oils.

The purpose of this paper is twofold. First review the relevant literature in machining using minimum quantity lubrication (MQL), contrast the economical, environmental, and technical attributes of this technology to conventional flood‐cooling techniques. Second highlight areas of relevant future research.

The approach consists of describing the essential elements of MQL as a technology, reviewing the relevant research by focusing on the most frequently used machining processes in this industry, highlighting the findings as they compare to flood cooling, and pointing to directions of required research in this technology.

The application of MQL in machining has shown better results in some processes; including in drilling, a cleaner environment, and a more cost‐effective machining technology. Further research is required however to better understand the underlying cause an effect phenomena in machining using microlubrication technology including environmental and health effects of this technology.

The paper provides a body of knowledge required for all stakeholders to better use or design machining systems using microlubrications.

This paper focuses on the state of the art of MQL and how it contrasts with conventional methods of machining.

A NEW 8 ft. × 8 ft. HIGH‐SPEED WIND tunnel recently inaugurated by the Ministry of Supply at the Royal Aircraft Establishment at Bedford is to be used for aerodynamic research on models of aircraft and guided missiles. It is claimed to be the largest and most advanced wind tunnel of its type in Western Europe. Responsibility for the design and construction of this wind tunnel has been a partnership between Ministry of Works engineers and architects, Ministry of Supply scientists and engineers, Lloyds Register of Shipping, the English Electric Company Ltd., and other main contractors and a large number of sub‐contractors. We are interested in the lubrication of this job and in particular, lubrication of the compressor.

This paper aims to provide an analytic technique for determining the convection heat transfer and temperature of oil jet lubricated spur gears.

A multiphase flow model is developed to calculate the convection heat transfer coefficients on different gear faces during different contact conditions. The frictional heat is calculated and a method to distribute between the two gears is developed. A finite element model is established to calculate the temperatures in both meshing and cooling processes.

The convection heat transfer coefficients on different surfaces are obtained successfully. Area-related formulae are developed to calculate the heat distribution coefficients. The gear temperature reaches a maximum at the beginning of meshing, then reduces and gets minimum at pitch point, after that it increases again. The gear temperature descends rapidly to steady temperature during the short time of jet cooling process. The tendency of computational results coincides well with the experimental results.

The research presented here could be used in the design phase of the jet lubricated spur gears. The precise temperature is obtained to assess the thermal capacity of gears, from which the gear parameters and oil supply conditions could be adjusted and designed.