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This paper aims to provide a reliable and efficient numerical piston–cylinder design method and assess the effect of clearance on the piston-cylinder lubrication.

Numerical analyses of lubrication characteristics were performed for the piston–cylinder interface. The axial piston was numerically modeled, and the film pressure was calculated using the unsteady two-dimensional Reynolds equation. The behavior of the piston was analyzed by calculating the eccentricity satisfying the force and moment balance.

The secondary motion of the piston included numerically simulated several cycles until the piston behavior converged, and contact with the inner wall of the cylinder and friction region was estimated. Results showed that the piston–cylinder clearance affected the contact force, length of the contact region and leakage flow rate.

This result improves the understanding of the piston–cylinder lubrication and suggests considerations in terms of lubrication in clearance design.

OILS and greases are in many ways excellent lubricants. In fact, it is difficult to envisage modern industry without them. There are, however, a number of applications where the presence of oil or other petroleum lubricants, gives rise to serious operational problems. One of these applications is the lubrication of Steam Cylinders.

A free-piston engine (FPE) is an unconventional engine that abandons the crank system. This paper aims to focus on a numerical simulation for the lubricating characteristics of piston rings in a single-piston hydraulic free-piston engine (HFPE).

A time-based numerical simulation program was built using Matlab to define the piston motion of the new engine. And a lubrication mode of piston rings was built which is based on the gas flow equation, hydrodynamic lubrication equation and the asperity contact equation. The piston motion and the lubrication model are coupled, and then the finite difference method is used to obtain the piston rings lubrication performances of the FPE. Meanwhile, the lubrication characteristics of the new engine were compared with those of a corresponding conventional crankshaft-driven engine.

The study results indicate that compared with the traditional engine, the expansion stroke of the HFPE is longer, and the compression stroke is shorter. Lubrication oil film of the new engine is thicker than the traditional engine during the initial stage of compression stroke and the final stage of the power stroke. The average friction force and power of the hydraulic free piston engine are slightly lower than those of the traditional engine, but the peak friction power of the FPE is significantly greater than that of the traditional engine. With an increase in load, the friction loss power and friction loss efficiency decrease, and with a decrease in equivalence ratio, the friction power loss reduces, but the friction loss efficiency decreases first and then increases.

In this paper, only qualitative analysis was performed on the tribological difference between conventional crankshaft engine and HFPE, instead of a quantitative one.

This paper contributes to the tribological design method of HFPE.

No social implications are available now, as the HFPE is under the development phase. However, the authors are positive that their work will be commercialized in the near future.

The main originality of the paper can be introduced as follows: the lubrication and friction characteristics of the new engine (HFPE) were investigated and revealed, which have not been studied before; the effect of the HFPE’s special piston motion on the tribological characteristics was considered in the lubrication simulation. The results show that compared with the traditional crankshaft engine, the new engine shows a different lubrication performance because of its free piston motion.

The SATISFACTORY LUBRICATION OF Diesel engines presents some of the most difficult problems encountered by oil technologists. This is especially true of large marine engines, where, due to low speeds and high loads, it is difficult to establish fluid film lubrication. Cylinder lubrication is particularly difficult due to the high temperatures encountered. This problem is more difficult in two‐stroke engines than in four‐stroke engines as, in the former, there is no non‐working stroke during which it is easier to form an oil film on the cylinder walls. Pressure‐charged two‐stroke engines are the most difficult of all to lubricate satisfactorily. The problem is aggravated in engines operating on residual fuel due to the high sulphur content increasing corrosive wear, and to the abrasive ash forming constituents present in such fuels. In addition, the contaminating influences of partially burnt products of combustion on the crankcase oil have to be considered. The ever‐present risk of water leakage into the crankcase oil, either from condensation, or from leakage of the cooling system, influences and often restricts the use of otherwise beneficial additives.

The purpose of this paper is to investigate the coupling mechanism of the roughness distribution characteristic and surface textures on the cylinder liner.

The cylinder liner-piston ring lubrication model with non-Gaussian roughness distribution surface was proposed in this paper to find the optimum cylinder liner surface. The motored engine tests were carried out to verify the simulation results.

The calculation and experiment results show that the large negative skewness surface has the optimal lubrication performance in the un-textured liner, while in the textured liner, the small negative skewness surface is more appropriate, which means surface textures couple with small negative skewness surface can improve the lubrication performance.

Although there are some works related to liner surface roughness and textures, the combine of roughness distribution and surface textures is not usually taken into account. Therefore, this research is different from others, as the present model considers with real non-Gaussian roughness distribution liners.

A comprehensive series of articles covering the duties and properties required of oil engine lubricants and circulating systems.

There are two principal reasons why it is disadvantageous, and frequently dangerous, to over‐lubricate the cylinders of air compressors, firstly fire risk and secondly contamination of air with oil vapour. Control of oil feed will prevent any likelihood of explosive fires but it may be necessary to incorporate special oil vapour filters to prevent contamination of materials and products coming into contact with the compressed air.

IN A PAPER to The Institute of Marine Engineers on November 24th at London, P. Jackson, M.Sc., M.I.Mech.E., M.I.Mar.E. (Director, William Doxford & Sons (Engineers) Ltd.) gave details of testing experiences with the Doxford J Type opposed piston marine oil engine. The following is an extract from this paper, dealing with piston lubrication and a new type of lubricator distributor which was designed for this particular engine type.

IN CONSIDERING the lubrication problems pertinent to the production machinery in this industry, we must, quite naturally, start with the raw product—iron. In other words, its refinement from the ore, by smelting in the blast furnace, and its subsequent conversion to steel in the Bessemer converter, the open hearth or electric furnace. Each has a place in the industry according to the characteristics or chemical properties of the final product.

Currently, lubrication analysis of piston ring is generally done under engine rated operating condition. However, the engine (such as the vehicle engine) does not always operate in rated operating condition, and its operating condition changes frequently in actual use. In addition, the lubrication status of piston ring is generally assumed as the flooded lubrication or a certain form of poor lubrication in most of the lubrication analysis.

In this paper, based on the equations about the flow rate of lubricating oil and the variation of control volume, the flow model of lubricating oil in the piston ring-cylinder liner conjunction is established. The lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done, in which the lubricating oil at the inlet of piston ring is considered as the lubricating oil attached on the relevant location of cylinder wall after the piston ring moves over at the previous stroke.

There is remarkable difference for the lubrication characteristics of the piston ring under different engine operating conditions. The worst lubrication status of piston ring may not take place under engine rated operating condition.

In this paper, based on the measured engine cylinder pressure, the lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done in which the lubricating oil supply condition at the inlet of piston ring is considered. The results of this paper are helpful for the design and research of engine piston ring-cylinder liner conjunction.