but I wonder how thick the material would need to be in stainless or inconel to have an equivalent thermal barrier as a ceramic coating would provide?
I am unable to find any real information on the thermal conductivity of ceramic coatings. The websites give info in terms of skin temperature drop when used on exhaust headers, virtually no engineering data or hard numbers. Kinda disappointing for an industry that claims to be high tech...
Inconel has a thermal conductivity of 1/10 that of cast aluminum, depending on the alloy. Thermal conductivity of 356 aluminum alloy (typical cast) is 128 W/m K, inconel is 12 W/m K. It is my belief that most ceramics are aluminum oxide based, ALO has a thermal conductivity of 30W/m K or 2.5 times better (worse?) than inconel. I wish I could find figures for the actual ceramic coating...
Hi
This is indeed an interesting thread...
I did a little research myself into this maybe 6 months ago but I can't remember where I posted.
On thermal conductivity: Al is roughly 210w/m2 /deg K
Steel is approx 50
Granite 2
Glass 0.8
Red brick 0.63
Cement(Lime) 0.3...
So ceramic is probably safely near glass IMO
I argued that ceramic coating would be a good thing but I was shot at by the view that there would be lower volumetric effeciency problems...
I think SHCs of the insulation are a factor in this.
My view point was from the fact that a third of the energy flows round in the coolant and most is from the head and more specifically the prechamber its greatest temperature gradient and large surface area to volume ratio. Then the piston face and main head face with diminishing effects down the walls of the block.
I think I worked out that a 1/4 mm layer gave an insulation of approx 1/3 ... or 2/3 of previous heat passing.
Again someone thought there could be an issue of cold toes in the cab if the main source of heat(the head) was insulated. Hmm... well I think a smaller main radiator could off-set this. :shock:
I feel that quite simply more retained heat in swirl chamber helps combustion and more energy to expand the gasses and so more torque. Thus less fuel needed to reproduce previous heating of gases and hence simply more efficient; with the option of more power.
Of course there is the other third of energy going out of the exhaust; some of which can be recouped by the turbo; but my desire oneday is to utilize the heat to drive a Stirling engine for battery power storage... Ok supplemented with one of those braking energy reclaimers...Dream mode off!!
Anyway that's my 2 pennyworth (4cents
)