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Performance Assessment of a New Generation Gas Engine Lubricant- Novel Developmental Screening Methodology

该论文已在赫尔辛基举行的第28届CIMAC大会上发表,论文的版权归CIMAC所有。Recent trends in gas engine design have focused on improving power output and efficiency while reducing emissions. Despite the fact that gas engines may be similar to other engines in their appearance and specifications, lubrication requirement of a gas engine is quite different from the conventional diesel or gasoline engine, owing to their higher combustion temperatures, engine loads and very different engine operation. Gas engines operate at high temperatures greater than 200 °C. At these high temperatures, especially, in a piston environment, lubricating oil is prone to severe thermal oxidation. Nitration is the most common route cause for many maladies of a gas engine lubricant which occurs due to the reaction of the oil with the oxides of nitrogen (NOX) generated during combustion. Several engine operating factors which will contribute to nitration are air to fuel ratio, load, cylinder liner temperatures, blow-by ingress, poor crankcase ventilation etc. Impact of nitration on lubricant would be excessive sludge/varnish formation, premature oil thickening, insoluble increase and ring and liner wear. To sustain these operational eventualities, natural gas engine lubricants are to be robust in nature. This robustness is important to achieve longer drain potentials which is one of the customer demand, as frequent oil changes not only pushes up the oil bill but also will lead to consequential power loss arising out of shut downs. Oils not properly designed specifically for gas engines can reduce head rebuild cycles, filter plugging and accelerate ring and liner wear. Natural Gas Engine Oils are classified according to their ash content- low, medium and high. Ash comes from the detergent additives used in these formulations. While too low an ash leads to valve seat recession, to high an ash leads to valve guttering and torching. Hence optimum balance is to be achieved. Since gaseous fuel per se is much cleaner and devoid of sulphur compared to liquid fuels, low ash (<0.6% Wt) is generally preferred for these oils. Regarding base oils, API Gp. II base oils –hydro-treated, branched paraffinic- are more preferred owing to their higher oxidation stability than Gp. I oils. Gp.III oils, though are more oxidatively stable, may not be suitable because of their lower viscosity. Further, lubricants based on off-the shelf additive packages from various additive suppliers may not be as robust as they ought to be. The present paper describes the development of a new generation, component based, low ash natural gas engine oil for stationary gas engines formulated with API Gp.II base oil. Performance assessment methodology devised involves effective lab screening tests, with each test simulating a condition that the oil would experience in service. Selection of test methods involve adoption of those severe deposit formation tests which are commonly used for passenger car and heavy duty diesel engine segments- where pass/fail criteria and test conditions for these parameters are far more severe. Three types of thermo-oxidation tests – static, bubbling oxygen, dynamic catalytic oxidation tests were used coupled with blotter test to establish the oxidation stability of the oil. A specially designed nitration bench test was employed to assess the oil resistance to degradation from nitration. Friction, wear and film strength characteristics were screened in widely accepted tribological test rigs. All the test data were benchmarked against a very high industry reference oil. The candidate oil delivers better performance than industry reference product in tests related to Nitration, Oxidation, Deposits, Corrosion, TBN Retention, Acid Control, Wear, Film Thickness, Friction and Sludge Dispersancy. Single cylinder engine tests were conducted to demonstrate that the formulation offers superior control of deposits and bearing corrosion protection.
发表在 :
作 者 :Ramakumar Sankara SV
发表日期:2016-06-07

The Benefit of using Group II Base Oils in Medium Speed Engines

论文已在中国上海举行的第27届CIMAC大会上发表。论文的版权归CIMAC所有。Group ll base oils are a category of base oils defined by the American Petroleum Institute as having a sulphur content less than 300ppm,a sat-urates content greater than 90% and a viscosity index of between 80 and 120. Group ll base oils have been used in automotive lubricants for many years. This was driven by the need to improve performanceof the lubricant to meet the demands of new engine technologies. As a consequence, the supply of Group ll base oil has been increasing and the capacity of Group I base oil is forecast to decrease. So far, these trends in base oil capacity have left the lubricants for medium speed marine engines unaffected; such lubricants have historically always used Group I base oils as the diluent for the additive system. With increasing availability of Group ll base oils, there is now a drive to utilise them for medium speed marine engine applications. The current economic climate is a strong motivator for the ship owner/operator to scrutinise their operation and identify where further cost savings can be made. Hence there is a desire for reduced oil consumption and increased power output. Combine this with increasingly poor heavy fuel oil quality, to which medium speed engines are sensitive, and it becomes clear that the demands on the lubricant are increas-ing. This paper discusses whether the use of Group ll base oil can go some way to meeting those demands, by providing improved oxidation resistance, viscosity control and lower volatility. An upgrade of these performance features would extend the time before condemning limits for the oil are reached. The capability of these base oils in comparison to Group I is examined in bench and laboratory engine testing. The deployment of a Group lI based lubricant in the field, and what benefits have been observed, is discussed.
发表在 :CIMAC Congress 2013, Shanghai
作 者 :Laura Gregory
发表日期:2013-06-01

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