Why ordinary lubricating oil can not meet the LNG engine

LNG vehicles are reliable, economical, can effectively improve emissions, and are environmentally friendly and safe. The development of LNG vehicles is a systematic project. Although the proportion of lubricating oil in the whole project is small, its importance cannot be ignored.

Engine lubricants are designed to meet the normal operation of the engine under various conditions, and are organically balanced according to the structural performance of the engine, the physical properties and composition of the fuel, the combustion characteristics and products, the engine compression ratio and reinforcement factor, the emission standards and exhaust treatment, and the operating environment, among other factors.

Technical upgrades to lubricants inevitably mean significant technical advances in the engines they are designed for, or that environmental standards are being upgraded. Qualified lubricants have to pass rigorous bench and driving tests, step by step, to meet the standards before they can be used.

The difference with gasoline diesel is that gaseous fuels are very pure, thermally efficient, have high gas temperatures and burn cleanly, but their poor lubricity can easily cause wear and tear such as bonding, friction, corrosion and rust. If an unsuitable lubricant is used, the consequences are unthinkable. Therefore, the transformation and updating of LNG vehicle technology is inevitably accompanied by the development and application of LNG engine lubricating oil.

In practical application, the modified or dual-fuel engine can not be in place because of the compression ratio, the calorific value of the mixture is 12% lower than that of gasoline, the inflation efficiency and air volume is reduced by 1-6%, and the air intake is only 89.8% of that when using gasoline, and the total power performance can be reduced by 10-20% when using common engine lubricant; due to the high combustion temperature of the engine, the nitrogen oxide content is high; LNG fuel itself has no LNG fuel itself has no lubricity, which aggravates the wear of engine valve system.

First, the high temperature of combustion chamber is easy to oxidize, accumulate carbon, and affect the emission using ordinary gasoline/diesel engine oil oxidizes too quickly, resulting in oil quality, viscosity decline or lubrication failure, the cylinder temperature is high when the lubricant is easy to produce carbon and lead to early combustion, the spark plug carbon accumulation will cause abnormal engine wear or failure.

Second, the valve components easy to wear. The steam/diesel engine is sprayed into the cylinder in the form of mist droplets, which can play a role in lubrication and cooling of valves and valve seats, while LNG enters the cylinder in a gaseous state and does not have the function of liquid lubrication, which makes the valves and valve seats dry and unlubricated and prone to bonding and wear. Under the action of high temperature, the high ash additive of ordinary engine oil will easily generate hard deposits on the surface of engine parts, prompting abnormal engine wear, spark plug blockage and valve carbon accumulation, causing engine explosion, ignition failure and valve fire; resulting in engine power decline, power instability, etc., and even shorten engine life.

Third, easy to form harmful substances. The use of ordinary engine oil emissions in excess of nitrogen oxides in the exhaust can not be resolved, accelerating the generation of sludge, will cause oil blockage or generation of varnish and other harmful substances. Especially for the engine equipped with EGR device, it is easy to cause oil quality decline, filter clogging, viscosity and acid and alkali values out of control and other trends.

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