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Recent advances in the development and application of lubricating oils for high efficiency diesel engines (including
impairing oxidation resistance and deposit-forming tendencies. This lubricant has completed some 5000 hours on test beds and 1500 hours flying in Concorde engines.
Recent advances in the development and application of lubricating oils for high efficiency diesel engines (including marine) L. J. Richards (Shell Refining Co Ltd, UK) and J. W. Schrakarnp (Koninklijke/Shell Laboratorium, Netherlands) The need for the closest possible co-operation between those designing and developing diesel engines and the petroleum technologist as early as possible in the life of the projects was stressed. Improved oils are required because of the necessity for engines of high efficiency and high specific output. One factor often forgotten is the rate of chemical reaction between the oil and combustion products in the region of cylinder walls and piston rings. Improvements in viscosity/temperature characteristics are necessary, and may lead to the more general use of deep hydrogenation of selected crude fractions unless serious drawbacks in the use of polymeric thickeners, such as breakdown under shear and the production of excessive carbonaceous deposits in the ring groove areas of highly rated engines, can be eliminated. Whilst synthetic oils may appear to have attractive properties, it is felt that benefits to the user are unlikely to justify their high initial cost. The sixty minutes available allowed little time for a comprehensive discussion. Nevertheless it proved to be interesting, consisting of prepared written questions followed by the author's answers, and subsequently by oral contributions. Highlights which arose from this discussion period included the following: No compatibility problems have arisen from mixing either conventional or hydrofined oils either with themselves or ester-containing oils. The influence of exhaust gas recirculation as a means of reducing nitrogen oxide compounds in the exhaust on lubricating oil performance is being investigated. Mr Colyer agreed that oil thickening is not a problem in Europe (probably because of the greater sump capacity relative to engine swept volume), and tended to play down the extent of troubles experienced in the USA
indicating that action taken was more of a preventative one for the future. Although selection of magnesium as the metal base for detergent additives reduces the ash, and in some instances shows up well in reducing pre-ignition, it has disadvantages in other ways such as poor high-temperature performance. So far, bench tests to reproduce pre-ignition problems have required the introduction of additional oil in the intake air to give an artificially high oil consumption. Mr Tardy drew attention to the differences between European engines and operating conditions and those of US engines operating in the USA, and stressed that many factors important in the USA were not important in Europe. Dr Agius referred to the large number of tests involved in developing an oil for Europe, and asked whether any simplification was possible. Professor Freund instanced the fundamental influence of fuel sulphur content, and stressed that high total base number were only required when the sulphur content of the fuel was high. Dr Anabian proposed a formula for the lubricating oil requirements of an engine, taking into account sulphur content of the fuel, the severity of the running conditions, and the sump capacity, etc. Mr Biske made a plea to manufacturers to simplify methods of changing oil in the sump. In summarizing the Chairman suggested that the papers discussed had indicated the need for development of improved test methods for oil evaluation and the correlation of such methods with service performance; additives to impart improved high-temperature performance; further experience with the new synthetic oils in supersonic aircraft; investigation of the mechanism of additive behaviour in petroleum and synthetic stock. A review of this Panel Discussion would not be complete without paying tribute both to the excellent organization on the part of the Russian hosts, and to the magnificent conference rooms where the good seating and excellent acoustic properties were much appreciated, as was the reliability of the electronic equipment used for simultaneous translation. Those of the World Petroleum Congress delegates who attended Panel Discussion No 17 thought it well worth while. A. Towle
IMPERIAL COLLEGE, LONDON. 12-16 JULY 1971
Limits of lubrication The Limits of Lubrication Conference held under the aegis of Dr A. Cameron certainly lived up to its name, The informal nature of the meetings allowed many quick descriptions of up to the minute research generally by the younger workers in the field, and used them as the basis for stimulating discussions by the more experienced delegates. The subjects covered included turbulence, e.h.l., hydrodynamics, pitting, scuffing, surface coatings and additives, plastics and wear, and metal working. Although some delegates questioned whether turbulence is actually present in oil film bearings it seems likely that it will become important as the speeds of power plants
232
TRIBOLOGY November 1971
increase. It is reassuring to know that much progress has been made in this field by converting the problem to a simple laminar flow situation where Reynolds equation is applicable. This is done by modifying the ideal viscosity according to the ideal Reynolds number based on the film thickness. Advances in hydrodynamic lubrication are nowadays almost exclusively by use of computers. Full solutions of Reynolds equation for journal bearings are becoming possible and confident predictions of practical situations were the order of the day. These included an analysis of multi-bearing flexible rotor systems in which up to eight
Recent advances in the development and application of lubricating oils for high efficiency diesel engines (including marine) L. J. Richards (Shell Refining Co Ltd, UK) and J. W. Schrakarnp (Koninklijke/Shell Laboratorium, Netherlands) The need for the closest possible co-operation between those designing and developing diesel engines and the petroleum technologist as early as possible in the life of the projects was stressed. Improved oils are required because of the necessity for engines of high efficiency and high specific output. One factor often forgotten is the rate of chemical reaction between the oil and combustion products in the region of cylinder walls and piston rings. Improvements in viscosity/temperature characteristics are necessary, and may lead to the more general use of deep hydrogenation of selected crude fractions unless serious drawbacks in the use of polymeric thickeners, such as breakdown under shear and the production of excessive carbonaceous deposits in the ring groove areas of highly rated engines, can be eliminated. Whilst synthetic oils may appear to have attractive properties, it is felt that benefits to the user are unlikely to justify their high initial cost. The sixty minutes available allowed little time for a comprehensive discussion. Nevertheless it proved to be interesting, consisting of prepared written questions followed by the author's answers, and subsequently by oral contributions. Highlights which arose from this discussion period included the following: No compatibility problems have arisen from mixing either conventional or hydrofined oils either with themselves or ester-containing oils. The influence of exhaust gas recirculation as a means of reducing nitrogen oxide compounds in the exhaust on lubricating oil performance is being investigated. Mr Colyer agreed that oil thickening is not a problem in Europe (probably because of the greater sump capacity relative to engine swept volume), and tended to play down the extent of troubles experienced in the USA
indicating that action taken was more of a preventative one for the future. Although selection of magnesium as the metal base for detergent additives reduces the ash, and in some instances shows up well in reducing pre-ignition, it has disadvantages in other ways such as poor high-temperature performance. So far, bench tests to reproduce pre-ignition problems have required the introduction of additional oil in the intake air to give an artificially high oil consumption. Mr Tardy drew attention to the differences between European engines and operating conditions and those of US engines operating in the USA, and stressed that many factors important in the USA were not important in Europe. Dr Agius referred to the large number of tests involved in developing an oil for Europe, and asked whether any simplification was possible. Professor Freund instanced the fundamental influence of fuel sulphur content, and stressed that high total base number were only required when the sulphur content of the fuel was high. Dr Anabian proposed a formula for the lubricating oil requirements of an engine, taking into account sulphur content of the fuel, the severity of the running conditions, and the sump capacity, etc. Mr Biske made a plea to manufacturers to simplify methods of changing oil in the sump. In summarizing the Chairman suggested that the papers discussed had indicated the need for development of improved test methods for oil evaluation and the correlation of such methods with service performance; additives to impart improved high-temperature performance; further experience with the new synthetic oils in supersonic aircraft; investigation of the mechanism of additive behaviour in petroleum and synthetic stock. A review of this Panel Discussion would not be complete without paying tribute both to the excellent organization on the part of the Russian hosts, and to the magnificent conference rooms where the good seating and excellent acoustic properties were much appreciated, as was the reliability of the electronic equipment used for simultaneous translation. Those of the World Petroleum Congress delegates who attended Panel Discussion No 17 thought it well worth while. A. Towle
IMPERIAL COLLEGE, LONDON. 12-16 JULY 1971
Limits of lubrication The Limits of Lubrication Conference held under the aegis of Dr A. Cameron certainly lived up to its name, The informal nature of the meetings allowed many quick descriptions of up to the minute research generally by the younger workers in the field, and used them as the basis for stimulating discussions by the more experienced delegates. The subjects covered included turbulence, e.h.l., hydrodynamics, pitting, scuffing, surface coatings and additives, plastics and wear, and metal working. Although some delegates questioned whether turbulence is actually present in oil film bearings it seems likely that it will become important as the speeds of power plants
232
TRIBOLOGY November 1971
increase. It is reassuring to know that much progress has been made in this field by converting the problem to a simple laminar flow situation where Reynolds equation is applicable. This is done by modifying the ideal viscosity according to the ideal Reynolds number based on the film thickness. Advances in hydrodynamic lubrication are nowadays almost exclusively by use of computers. Full solutions of Reynolds equation for journal bearings are becoming possible and confident predictions of practical situations were the order of the day. These included an analysis of multi-bearing flexible rotor systems in which up to eight