Thanks for posting this paper.
I quickly skimmed over the paper to glean for any new discoveries that I might have missed when I did my own research in the mid 1990s. I did not notice what type of engine they were using for their research but it must have been something with very small displacement and without a tuned pipe for it to only make about 3 KW approximately (4 HP) at 4000 RPM.
The engine I used for my research was a 1996 CR 250 (standard bore and stroke) on methanol and made 72 hp at approximately 9000 RPM at the counter shaft. This engine was being developed for shifter kart and micro midget application.
The Indian paper's research goal was to reduce emissions, improve fuel economy and improve power output if possible with their importance in that respective order. The Indians were observing detonation problems at full throttle at 4000 RPM.
My research goal was to find a thermal barrier/coating that would allow the engine's performance level to be raised by protecting the piston from the increased thermal load that increasing the power to even higher levels will bring to the piston and other engine components. We had reached the thermal limits of the OEM piston on gasoline at around 68 Hp. Running the engine on methanol allowed us to raise the power level to a little over 72 hp before reaching the thermal limits of the OEM piston.
The thermal barriers and different thickness of coating we tested all reduced the heat that the piston absorbed but produced severe detonation problems. We could not stop the detonation by reducing ignition timing, lowering the compression, giving the engine more fuel or reducing pipe pressure without reducing the power levels below where we started (approximately 45 hp).
The coating company said they had never experienced reports of detonation from any of their thousands of customers. They said their thermal barriers should stop detonation due to a cooler running piston. I Knew why the thermal barriers were causing detonation, but the company that did our thermal barriers obviously did not understand the basic thermodynamics of how thermal barriers work or insulation of any type. Heat will only move from a hot body to a cooler body. If two surfaces are the same temperature, heat will not flow between them. Coating the power turbines in turbine engines or pistons in diesel engines will protect the components from heat but the surface temperature of the insulated component will remain high and will be carried over to the next engine cycle. The high surface temperature carry over for turbines and diesels does not cause detonation.
We need a thermal barrier that has zero thermal inertia. We want the surface temperature of the piston, combustion chamber and cylinder wall to always be the same as the temperature of the combustion temperature at any instant in time in order to stop heat loss. Using the thermal barriers on four-stroke pistons and valves seems to work on the lower RPM and most low HP engines because twice as much time passes between combustion events as on two-strokes. Low RPM engines give the insulated surfaces more time to cool. Detonation seems to raise its head on the high RPM high HP four-stroke spark ignited engines just like the highly developed two-strokes.
If any engineering, physics or chemistry major is looking for a subject for a Masters or Doctoral thesis, may I suggest developing a thermal barrier that has zero thermal inertia, has close to zero thickness, it is reasonably transparent and will adhere to anything. I am sure our government would supply a lot of grant money for any research project like this and could easily be classified a "Green energy project". A discovery such as suggested would revolutionize our world as we know it and reduce energy consumption by at least a factor of 100 or more. Every process that uses heat or needs to reject heat would benefit. The applications are unlimited.
