Of the many problems facing the jet engine designer, lubrication was considered to be one of the least important. But as engine development progressed, it was quickly realized that lubrication could become a limiting factor unless improved lubricants were forthcoming. The arduous operating conditions imposed on the lubricant plus the need to achieve increasingly better engine performance, reliability and economic operation, virtually eliminated mineral-based oils, and a new type of lubricant was introduced. Developed from non-petroleum sources, these synthetic lubricants, as they are now known, have given excellent performance in both subsonic and supersonic planes over the last 30 years, and without their timely introduction, development of the jet engine could have been severely retarded. Recently developed turbofan engines of 18-20,000 1b thrust, high performance engines for the SST, the "Jumbo Jets" and high-speed military aircraft have posed further problems to the lubricant supplier. These problems have been met by developing a range of high-temperature synthetic lubricants. A number of carried out performance trials indicate that these should meet all the requirements of the jet engine designer and operator.
Exercise 15. Put all types of questions to the texts above.
