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Posted: 7/11/2016 11:23:20 AM EDT
[#1]
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Great question, and there is a lot of work in that space! The biggest reason you don't see a lot of other devices is that the added cost usually doesn't justify the additional gains. Probably the most common way to recover waste heat is a turbocharger. While many folks see this as just a way to boost power (by adding in more air, and thus more fuel can be burned) it also typically increases thermal efficiency since the engine doesn't have to do extra work to intake that extra air. There are devices like turbo compounding devices that have a turbine that is geared to the crank shaft. There are all sorts of other turbo generator type devices that use exhaust to do useful work. The challenge is that a lot of heat goes into the engine coolant, and recovering that is a bit harder. In some stationary genset applications that waste heat can be used to heat hot water and other things to at least use that heat rather than have to pay for another heat source to make hot water. Quote HistoryQuoted:
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The turbine engine is not the most thermodynamically efficient design out there, and right now a traditional piston reciprocating design is about as good as it gets. Some get close to 50% thermally efficient or higher. Turbines excel in situations where power to weight ratio is more important than fuel economy. Without fully geeking out, it has to do with cycle efficiency...and in very simplest terms, the higher you can compress the intake charge, the more energy you can get out of it once you add the fuel. You seem knowledgable. If most of the efficiency is lost due to heat, then why haven't people figured out a way to extract that heat and turn it into power? Electrical or otherwise. Great question, and there is a lot of work in that space! The biggest reason you don't see a lot of other devices is that the added cost usually doesn't justify the additional gains. Probably the most common way to recover waste heat is a turbocharger. While many folks see this as just a way to boost power (by adding in more air, and thus more fuel can be burned) it also typically increases thermal efficiency since the engine doesn't have to do extra work to intake that extra air. There are devices like turbo compounding devices that have a turbine that is geared to the crank shaft. There are all sorts of other turbo generator type devices that use exhaust to do useful work. The challenge is that a lot of heat goes into the engine coolant, and recovering that is a bit harder. In some stationary genset applications that waste heat can be used to heat hot water and other things to at least use that heat rather than have to pay for another heat source to make hot water. he engine doesn't have to do extra work to intake that extra air. Thermodynamics fail. The work to empty the cylinders increases. There is no free lunch. |
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Posted: 7/11/2016 11:24:22 AM EDT
[#2]
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I'm surprised there isn't a solid state solution which can use temperature differential to generate electricity. Quote HistoryQuoted:
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The turbine engine is not the most thermodynamically efficient design out there, and right now a traditional piston reciprocating design is about as good as it gets. Some get close to 50% thermally efficient or higher. Turbines excel in situations where power to weight ratio is more important than fuel economy. Without fully geeking out, it has to do with cycle efficiency...and in very simplest terms, the higher you can compress the intake charge, the more energy you can get out of it once you add the fuel. You seem knowledgable. If most of the efficiency is lost due to heat, then why haven't people figured out a way to extract that heat and turn it into power? Electrical or otherwise. Great question, and there is a lot of work in that space! The biggest reason you don't see a lot of other devices is that the added cost usually doesn't justify the additional gains. Probably the most common way to recover waste heat is a turbocharger. While many folks see this as just a way to boost power (by adding in more air, and thus more fuel can be burned) it also typically increases thermal efficiency since the engine doesn't have to do extra work to intake that extra air. There are devices like turbo compounding devices that have a turbine that is geared to the crank shaft. There are all sorts of other turbo generator type devices that use exhaust to do useful work. The challenge is that a lot of heat goes into the engine coolant, and recovering that is a bit harder. In some stationary genset applications that waste heat can be used to heat hot water and other things to at least use that heat rather than have to pay for another heat source to make hot water. I'm surprised there isn't a solid state solution which can use temperature differential to generate electricity. There are a couple. The power density is low though. |
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Posted: 7/11/2016 12:47:20 PM EDT
[#3]
Already been tried in the 1960's.
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Posted: 7/11/2016 1:04:48 PM EDT
[#4]
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Already been tried in the 1960's. https://i.kinja-img.com/gawker-media/image/upload/s--TsO-nPOa--/c_scale,fl_progressive,q_80,w_800/1867342cswhcwjpg.jpg Indeed. 
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Posted: 7/11/2016 1:11:10 PM EDT
[#5]
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Not being in an aircraft I would imagine the maintenance interval would be much more forgiving. Quote HistoryQuoted:
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Half a mile per gallon and a rebuild cost (every couple of months) more than the original purchase price of the car. Sign me the fuck up! Not being in an aircraft I would imagine the maintenance interval would be much more forgiving. I doubt it would be enough to make it economically viable. In commercial trucks that run 150,000 miles a year it might be doable but you'll never make a turbine as cheap to run and maintain as a modern gas piston engine for a daily driven personal vehicle. |
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Posted: 7/11/2016 1:28:17 PM EDT
[#6]
fuck pistons. ill keep my spinning doritos
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Posted: 7/11/2016 6:45:49 PM EDT
[#7]
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Not being in an aircraft I would imagine the maintenance interval would be much more forgiving. Quote HistoryQuoted:
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Half a mile per gallon and a rebuild cost (every couple of months) more than the original purchase price of the car. Sign me the fuck up! Not being in an aircraft I would imagine the maintenance interval would be much more forgiving. The MX interval is actually very forgiving on airplanes. It isn't the MX which makes them expensive. It's the Parts. MX would be much more labor intensive down on the ground. Turbines need clean air. The dust and crud down at 0 AGL, is a problem. |
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Posted: 7/11/2016 6:52:50 PM EDT
[#8]
I can rebuild an ICE blow it up and rebuild again and again.
I know hot air? Blows through staggered fan blades? Producing power? I think. Very loud too. |
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Posted: 7/12/2016 5:03:06 PM EDT
[#9]
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Thermodynamics fail. The work to empty the cylinders increases. There is no free lunch. Quote HistoryQuoted:
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The turbine engine is not the most thermodynamically efficient design out there, and right now a traditional piston reciprocating design is about as good as it gets. Some get close to 50% thermally efficient or higher. Turbines excel in situations where power to weight ratio is more important than fuel economy. Without fully geeking out, it has to do with cycle efficiency...and in very simplest terms, the higher you can compress the intake charge, the more energy you can get out of it once you add the fuel. You seem knowledgable. If most of the efficiency is lost due to heat, then why haven't people figured out a way to extract that heat and turn it into power? Electrical or otherwise. Great question, and there is a lot of work in that space! The biggest reason you don't see a lot of other devices is that the added cost usually doesn't justify the additional gains. Probably the most common way to recover waste heat is a turbocharger. While many folks see this as just a way to boost power (by adding in more air, and thus more fuel can be burned) it also typically increases thermal efficiency since the engine doesn't have to do extra work to intake that extra air. There are devices like turbo compounding devices that have a turbine that is geared to the crank shaft. There are all sorts of other turbo generator type devices that use exhaust to do useful work. The challenge is that a lot of heat goes into the engine coolant, and recovering that is a bit harder. In some stationary genset applications that waste heat can be used to heat hot water and other things to at least use that heat rather than have to pay for another heat source to make hot water. he engine doesn't have to do extra work to intake that extra air. Thermodynamics fail. The work to empty the cylinders increases. There is no free lunch. You are right, there is no free lunch...but using turbochargers you get back a lot of wasted energy and often SIGNIFICANTLY reduce pumping losses. In non-throttled applications (like diesels) with a good turbo match you actually get a slight amount of positive pumping work as you go higher in boost pressure. I.e. the positive pressure acting on the piston during the intake stroke is more than the pumping work to push the exhaust back out of the cylinder on the exhaust stroke. While it isn't "free" it is using the energy left in the exhaust for useful work. The reason for this is that a turbo isn't working on gas flow and pressure alone, it is actually using the expansion of that gas to extract the energy from it. If intake manifold pressure is > exhaust manifold pressure, you have positive pumping work. Things change a lot when you add an intake throttle and waste-gate or VG turbos where you will still have some pumping losses, which is sometimes intentional to help with cylinder scavenging and EGR for emissions controls. Let me know if we need to break out the P-v curves to diagram the cycle. |
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Posted: 7/12/2016 5:55:22 PM EDT
[#10]
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fuck pistons. ill keep my spinning doritos Heck yeah! Spin those triangles. Several have mentioned using turbines in a hybrid configuration to charge batteries. I also remember reading that Mazda had experimented with a similar set up using a smaller Wankel, possible even using a hydrogen fuel. Like turbines, the rotary could be set up to run in it's peak efficiency range and also minimize emissions if burning conventional gas, which is one of the challenges they have faced in bringing rotary back into production. |
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Posted: 7/12/2016 7:37:34 PM EDT
[#11]
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Turbine-electric. Runs on anything, instant torque, traction control/torque vectoring/etc just software away. This. Turbines run best at constant speed, so using a micro turbine to turn a generator for electric car would be the way to go... Could quickly recharge batteries and provide steady source for high speed cruising. Fuel would be about anything that burns... |
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Posted: 7/12/2016 7:44:22 PM EDT
[#12]
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Chrysler did a testbed series of turbine cars, Jay Leno owns one. They had their advantages but some pretty big issues. Quote HistoryQuoted:
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Always thought that turbine engines are the most efficient platform with the least parts and produce the most power. The internal combustion engine is a product of the industrial age and fairly antiquated as a means to produce a vehicles momentum. It works, but only so well. Much of the energy produced is wasted. Why haven't we produced a turbine style engine to power our automobiles? I would have thought that it would be the next logical step. People smarter than me chime in please Chrysler did a testbed series of turbine cars, Jay Leno owns one. They had their advantages but some pretty big issues. Like this one? 
The guy who owned this actually drove it once in a while and had the only spare turbine for it. Leno didn't even have that. The Henry Ford Museum doesn't even have a turbine in theirs. They tried it and it didn't work out. The owner was telling the group I was in that when they took it apart everything on the inside was hand made and not the same size from one side to the other side which made things more difficult to get it working again. |
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Posted: 7/12/2016 7:45:32 PM EDT
[#13]
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Posted: 7/12/2016 7:47:29 PM EDT
[#14]
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That's the one I had in mind. Posted Via AR15.Com Mobile Quote HistoryQuoted:
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How about a radial? Posted Via AR15.Com Mobile I would like one of these installed in my car. http://www.williammaloney.com/aviation/NewEnglandAirMuseum/AircraftEngines/images/14PrattWhitneyR2800DoubleWasp.jpg That's the one I had in mind. Posted Via AR15.Com Mobile Like this? In a race car? 
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