Thermal Efficiency Discussion

[RobertISaar]

Turbos bring up another question I have. Can a turbo be sized appropriately, and tuned to actually make boost while at a steady state of output. I mean say for instance start with a 2.0L (really I am thinking something around 600cc-1.0L) engine, setup and tune the combination to make 3-5 psi while cruising. Not much but enough to offset the pumping losses, and use the exhaust velocity to do something useful.

what kind of cruise RPM would be desired? around 2,500(with a 2L)? because i can definitely see turbine housings small enough for that to be a reality.

[gregs78cam]

yea, 2000-2500 rpm, 4K-5K with a <1L. Turbos are great at making better than 100%VE at WOT, why not at cruise?

[Playtoy_18]

I am interested and am playing with the ideas of thermal efficiency as well a small bit.
One big issue I see is with all the energy conversions taking place.
From chemical to heat to mechanical etc..
The heat is a necessary evil,as the expansion of the chemical combustion reaction is what transfers to mechanical energy.
I am trying to make those conversion processes more efficient in order to coax more efficient power.
One thing i've been playing with is the use of specialized coatings.
Coating the piston and chamber will help retain heat where it can be used in the cylinder instead of wasting it into the cooling system.
At the same time however,the fuel delivery must also take a new turn.
One big issue with fuel is atomization,fuel will only be consumed in the combustion process from the surface of a droplet of fuel as I have been taught.
So to actually use less fuel,the fuel must be almost completely vaporized or else the rest of the droplet goes right out the exhaust.
Direct injection helps accomplish this,as the ecoboost from Ford has shown.
Offhand I think the v6 twin turbo in the f150's is running about 12psi,10:1cr and over 350hp from a 3.5.
I want to say the sho or one of them is actually running higher boost and cr as well.
I believe it is from some of the benefits of such higher pressures/better atomizatin as well as the excellent effects of controlling cylinder temps.

I'm trying to negate alot of the parasitic effects of the mechanical parts as well using dry film and ceramic coatings as well as thermal transfer and barrier coatings.
Coming up on some actual engine testing,and i'm anxious to see if it is going anywhere.
I have both of smokey books and honestly alot of where my ideas come from,I admire the hell out of him.
Interesting topic,subscribed.

[RobertISaar]

fuel vaporization is a big issue... one reason why i would hesitate to coat the intake valves with anything that would prevent it from heating up. if anything, let that run hotter, the fuel charge spends some significant time sitting on it.

it would be neat if there were some type of coating(catalyst?) that could be applied to the backside of the valve that either reduced the temperature necessary for gasoline to vaporize, or otherwise would help it along.

[Playtoy_18]

http://www.techlinecoatings.com/arti...ve_Article.htm

I used the same product on the inside of a carb manifold,he had to rejet down two sizes and play with the plug gap when tuning it afterwards.
Offhand I would say in general it definately helps keep the fuel in the airflow and off the walls.

*sorry,that covers the front and not so much back of valve.
The dry film product creates a "boundary level turblulence" that promotes flow as well as keeping the fuel suspended and off the port walls.

[1project2many]

if we moved up to 100% oxygen.... would that also significantly alter the stoich ratio for a given fuel? it seems like it would have to.

Yes. The balanced ratio of oxygen to fuel is about 11:1. The end components are primarily CO2 and H20. But 100% oxygen carries it's own set of problems. Oxygen prefers to bond with other atoms such as Hydrogen and Carbon. Given the chance, O2 will quickly break apart to form bonds with these elements. In a warm engine with sharp edges and hot spots, increasing heat from compression is all the chance that O2 needs. Ignition can easily start well before the spark and with no inert gas to inhibit the reaction, fuel quickly burns. Additionally, free oxygen and excess heat can cause internal engine parts to burn or melt which rarely leads to long engine life.

Can a turbo be sized appropriately, and tuned to actually make boost while at a steady state of output.

Yes. That was a major part of Smokey's hot vapor engine.

fuel vaporization is a big issue... one reason why i would hesitate to coat the intake valves with anything that would prevent it from heating up.

But, and this is a big but, fuel that has changed phase and become a gas will expand and force much needed oxygen out of the engine. The turbocharger on the hot vapor engine played a dual role. First, it served as a giant mixer, a homogenizer, to turn fuel and air into a consistent mixture. Second, and more importantly, it kept the gaseous fuel from forcing oxygen back out of the engine.

So to actually use less fuel,the fuel must be almost completely vaporized or else the rest of the droplet goes right out the exhaust.
Direct injection helps accomplish this,as the ecoboost from Ford has shown.

What direct injection really accomplishes best is to move the vaporization phase away from the intake pathway and into the cylinder. Not only does this prevent O2 displacement but it allows the beginning and end of combustion to be better timed to specific positions of the piston and crankshaft.

it would be neat if there were some type of coating(catalyst?) that could be applied to the backside of the valve that either reduced the temperature necessary for gasoline to vaporize, or otherwise would help it along.

You've got the catalyst in your car already. Platinum and Palladium are excellent catalysts for combustion. We just need a binding agent that can be applied to engine parts and will withstand the heat of combustion. Anyone interested in mixing ground up cat ceramic with thermal barrier coatings?

[Playtoy_18]

Don't the platinum and palladium have it's reactions after combustion though?
I thought we were talking about using the fuel more efficiently,after it's burned and needs a catlyst for emissions then the idea pertains more towards controlling emissions versus controlling combustion/fuel efficiency/vaporization etc..