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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.

This paper aims to examine the friction coefficient and wear rate characteristics of SCM 440 bearing steel used in the cylinder block of a tractor engine with gas lubrication and oil lubrication.

Friction tests were performed using a pin-on-disc tester with loads of 2 to 10 N and sliding velocities of 0.06 to 0.34 m/s. The experiment was done with and without nitrogen, and paraffin oil lubricant was used to prevent wear during process.

The nondimensional characteristic number from the Stribeck curves indicated that the lubrication regime is hydrodynamic. As the velocity and load increased, the friction coefficient of the SCM 440 increased and greater applied load resulted in a smaller friction coefficient. The range of the friction coefficient was 0.017001 to 0.092904 with paraffin oil lubrication and 0.01614 to 0.4555 with nitrogen lubrication. Nitrogen is effective in reducing the friction coefficient of materials that are in contact and subjected to a load and velocity.

The experiments confirm that nitrogen is effective for reducing the friction coefficient of SCM 440 materials that are in contact with each other and subjected to a load and velocity.

IN A PAPER ON THE ABOVE SUBJECT presented to The Institute of Petroleum in January by G. A. Dickens and W. B. Broadbent (both of Mobil Oil Co. Ltd.), these authors said that the lubrication problems arising from electrification of railway locomotives are not great and although there may be no entirely new lubrication problems, diesel traction on a large scale is new to the U.K. and in this field, service life between overhauls is very dependent on the quality of crankcase lubricating oil. Dividing diesel traction into three categories, namely shunters, railcars, and main line locomotives, they discussed the differing lubrication requirements of each. Shunting diesel engines are mainly 600/800 r.p.m. units developing up to 4,000 h.p. ; main line and mixed traffic locos utilise diesel units of 600/1200 r.p.m. developing from 800 to 2,000 h.p.; railcar and light weight trains use engines of 1,500/2,000 r.p.m. developing up to 250 h.p.

The ENGINEERING, MARINE, WELDING AND NUCLEAR ENERGY EXHIBITION at Olympia to be opened by Sir Christopher Hinton, F.R.S., M.A., Hon.D.Eng., M.I.C.E., M.I.Mech.E., Managing Director (Industrial Group) U.K. Atomic Energy Authority, on Thursday, 29th August, is held in alternating years and draws both Home and Overseas visitors.

THE Engineering, Marine, Welding and Nuclear Energy Exhibition opens at Olympia on April 16th and runs until April 30. It is open from 10 a.m. to 6 p.m. each day (except Sundays), with the exception of April 27th, 28th, and 29th, when it remains open until 8 p.m. Price of admission is 3s. There are well over 500 stands and of these between 60 and 70 are showing products that should be of interest to most readers of Scientific Lubrication, since they concern some type of lubrication equipment. Amongst these are the following, and the illustrations reproduced here concern items which will be exhibited on the stands. Items in bold type describe new products or products being exhibited for the first time.

THE TERM “synthetic lubricant” has been adopted to designate a variety of fluids, derived from sources other than mineral oils, which have been developed by the technologist in order to satisfy the extreme conditions under which present‐day machinery has to operate : for example, high or low temperatures, or both, often with high bearing loads, and sometimes under conditions which demand resistance to ignition. Although, in fact, modern petroleum oils are prepared to such stringent specifications, and by such carefully controlled processes, that they are almost equally as “tailor‐made”, it is their comparatively limited temperature range that largely brought about the development of the so‐called synthetic product.

A brief comparison of tooling techniques in the automotive and aircraft industries. One problem arising where the same tooling shop is used lies in the difference between the types of engineering drawings. The aircraft drawings are complicated by the fact that engineering changes are not included in the up‐to‐date working drawings.

THE Nineteenth Salon International de l'Aeronautiquc was principally a British and French affair, although there were notable contributions also from the Netherlands, Italy and the U.S.A. As an exhibition, however, it was patchy and many of the exhibitors showed nothing new; some because of security restrictions, but others undoubtedly because they simply had nothing new to show after two years. The restrictions and economics of today were very much in evidence, and it was even surprising how some of the manufacturers have managed to exist at all since the end of the War.

A device for controlling the fuel supply comprises a valve regulating the admission of fuel to a chamber having in its wall two diaphragms, the first connected to the valve to cause it to close upon an increase in pressure in the chamber and the second actuated by engine suction to cause the valve to close when the engine depression falls below a predetermined valve. An anterior throttle 3, Fig. 1, regulates a fuel valve 6 controlling a passage 4 leading from a chamber 11 into which fuel is admitted from a headed tank or a pump past a valve 14. A diaphragm 20 in the wall of the chamber 11 separates the chamber from a suction chamber 21 communicating with the mixing chamber 1 of the carburetter through a passage 22 opening at the throat of the Venturi 5 adjacent the fuel outlet passage 4. When the engine is running, the diaphragm 20 is held against a stop 27, but when the engine stops, a spring 26 moves the diaphragm downwards bringing a stud 24 into contact with a lever 16 which engages the fuel valve 14 with its other end to close it. On starting the engine, the stud 24 is withdrawn and the spring 11 opens the fuel valve to an extent determined by the engagement of the end 36 of the lever 16 with a hook 35 on a second diaphragm 19 separating the chamber 11 from a chamber 28 at atmospheric pressure or that pressure as modified by a controlled passage 30 leading to the outlet 23 of the suction passage 22. As the pressure in the chamber 11 increases with the inlet of fuel thereto the pressure‐regulating diaphragm 19 is depressed and the hook 35 engages the lever 16 to close the fuel valve 14. In a modification, the shut‐off diaphragm 20 operates the stud 24 through a lever. In the form shown in Fig. 4, the pressure‐regulating diaphragm 19 is connected to one end 49 of a floating lever 50 engaging at its other end 59 with the stem CO of an outwardly opening fuel valve 61. The centre of the lever 50 is joined through rods 52, 54 to a lever 55 actuated by a diaphragm 58 forming one wall of a suction chamber 37. When the engine stops, a spring 39 depresses the diaphragm 58, raising the centre of the floating lever 50 to lift the end 59 off the stud 61 and permit a spring 64 to close the valve 61, the end 49 of the lever engaging a stop 67. When the engine is running, suction holds the diaphragm 58 against a stop 65 and the diaphragm 19 and it spring 33 regulate the fuel pressure in the chamber 11. Equal diaphragms 19, 73, Fig. 6, may be used, the fuel valve 61 being closed by the fuel pressure, a spring 64 and a slight difference in strength between the springs 74, 33 co‐operating with the diaphragms, this form avoiding closure of the valve during sudden acceleration. The suction and air chambers 21, 28 may be disposed side by side and the diaphragms be connected by a two‐armed lever of which the arms may be proportioned to compensate for inequality in the sizes of the diaphragms. As shown in Fig. 9, the air and suction chambers 28, 21 are between intercommunicating fuel chambers 98, 99 and a single spring 108 urges the diaphragms 19, 73 apart, a one‐way connexion 107, 106 between cylinders 103, 105 secured to the diaphragms ensuring lifting of the lower diaphragm to permit a spring 64 to close the fuel valve 61 when the engine stops. Specifications 378,025, 378,038, 382,948, 454,782 and 464,327 are referred to.

MANY problems associated with aircraft investigations involve the accurate measurement of fluctuating fluid pressures. Various types of pickup exist from which choice may be made for this purpose. The suitability of a particular type for a specific application depends on the characteristics of the type and its associated electronic recorder. The fundamental requirements of fluctuating pressure pickups are discussed, and various types are described and typical examples of their application are given. Design data are derived based on experiments conducted on condenser type pickups, from which it is possible to design single diaphragm types for particular frequency and sensitivity requirements.