Recycling heat energy

[Phantom]

Originally Posted by NiHaoMike

What about inject water into the exhaust after the cat and spin a turbine with the mixture of exhaust gas and steam?

Something like this could work but water injection is not needed and would complicate the system and add weight. Mostly what would need to be done is replace the compressor side of a turbocharger with a generator run the wires and adjust the exhaust bypass for efficiency. But I do not think it would help much on a hybrid.

[bwilson4web]

Originally Posted by Bicycle Bob

. . .
One-year-old Alphabet Energy develops “thermoelectrics” for waste heat recovery — semiconductor materials that generate electricity when you make one side hot and the other side cold. The startup says it can create them at a cost 50 times cheaper than existing materials, and at around $1 per watt for industries such as heavy manufacturing, automotive, aerospace and power generation (see our list of 7 Startups Building Green Car Tech for a Pre-Electric World).
. . .

I'm pretty sure their energy yield is still a function of dT between the hot and cold sides. Still, I wouldn't look a 'gift horse in the mouth.'

I'm a little more excited about absorption cycle chillers. IMHO, exhaust temperatures look like they would be a good match for a 2,500-5,000 BTU cooling system. In the volume of a car, it would be a nice way to cool cabins. No moving parts if designed right (and the car isn't rolled.)

Bob Wilson

[cujet]

A recent test of an exhaust driven turbine (on a normally aspirated engine) driving an alternator shows potential gains. Yes, there are additional pumping losses. However, with proper camshaft design (less overlap), the net result is slightly higher overall efficiency.

I don't remember the specifics, but I believe something like 4%. In other words, the weight is worth it.

I suppose this would be for a hybrid car.

[ECONORAM]

Originally Posted by Christ

Nope, because it won't work. The fuel used to keep your engine cool is primarily designed to keep it from knocking, which can't be helped by external cooling. You can help it with water injection, though.

Seriously? So we are all burning more fuel than necessary for engine operations? Would a proper H20 injection setup let you trim some fuel flow?

[gone-ot]

...that's the reason for the "old" MILITARY AVGAS method of rating high-octane with two numbers; the first was the "lean" (max. economy) octane number while the second was the "rich" (max. power) octane number, for instance: 115/145 AVGAS.

...of course, that was when pilots (not computers) adjusted throttle settings and carburetor "richness" to compensate for altitude, cruising or high speed.

...and, many aircraft engines also used water-injection to lessen engine detonation during METO power situations (like war!) and over-loaded take off during hot weather.

[Phantom]

Originally Posted by Old Tele man

...and, many aircraft engines also used water-injection to lessen engine detonation during METO power situations (like war!) and over-loaded take off during hot weather.

The water in that example is injected in the intake path and used to cool the cylinder reducing detonation. What was being suggested was to inject in the exhaust.

[rbrowning]

I have always wondered why a waste heat engine like this:
Cyclone Power Technologies - How It Works
couldn't be scaled to get it's external heat from the engine cooling & exhaust, and eliminate parasitic losses such as alternators, AC and power steering and brakes. If it isn't feasible on a passenger car why not a bus or refrigerated semi-tractor trailer rig?

[Phantom]

Why auto makers do not do this is because it will cut into profits. It's easier and cheaper to use a belt driven generator instead of running a more complex system that needs to be researched developed and tested when they cannot charge any more for adding it.

[Christ]

Originally Posted by Phantom

Why auto makers do not do this is because it will cut into profits. It's easier and cheaper to use a belt driven generator instead of running a more complex system that needs to be researched developed and tested when they cannot charge any more for adding it.

You ever had to change an alternator belt in the rain at night on the side of the freeway?

Yeah, they can charge more for a belt-less system.

[user removed]

Belt less systems are ancient. Think 70 years ago.

regards
Mech