hardingfv32 wrote: ↑Sun Jun 25, 2017 7:30 am1) Name a chemical that would make a good fuel AND work as a lubricant? The latest lubricants have very high combustion temperatures. As an example they can make it through a CAT without lighting off.
2) Current lubricants provide a big reduction in friction…increase in power. It is going to take a lot of combustion energy to make-up for any loss friction reduction from an inferior lubricant. In other words this is a compromise.
Lube oil is perfect for this, especially in an engine designed for thermal efficiencies with high compression ratio. Lube oil measures high on the Centane number scale and hence has a short ignition delay. So, <speculation starts> if the combustion precess is ultra lean - then spraying lube oil into the combustion chamber before the spark timing, will autoignite via compression ignition and act as multiple ignition source - much in the same way as TJI intends to be. Hence lube oil can be used as an ignition fuel. </speculation ends>
The devil is in the detail and implementation of the technology. I can see holes in my argument as to why they may want to do this or how its done. For example: oil has to be sprayed at a particular time and cannot be inducted from ports - otherwise how will you control when it auto-ignites? Will only lead to pre-ignition. How to spray without using a second injector?
Ofcourse - it could be used in an entirely different way, but to answer the question asked by hardingfv32 - engine oil can has good lubrication property and can be burnt via compression ignition. The underlying physics makes a case for it.