The StarRotor engine
11-25-2005, 10:09 PM
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The StarRotor engine
The StarRotor engine is a Brayton cycle engine (think: jet engines, as opposed to the otto and diesel cycle engines in today's vehicles) invented at Texas A&M. It seems that it would have the advantages of a conventional turbine, only with good throttle response, cheaper manufacturing costs, and a broader powerband--three things conventional turbines don't do very well. The quasiturbine looks nice, but this one already has working models. Apparently they're making progress, as they've just finished their 3rd generation design.
* The StarRotor engine is projected to be very efficient (45-60%).
By simply replacing conventional engines (15-20% efficiency) with a StarRotor engine, fuel economy will double or triple. For example, a conventional luxury car getting about 25 mpg on the highway would get about 75 mpg. A conventional economy car getting 40 mpg would get about 120 mpg.
* It should produce very low pollution.
Advanced combustor technology reduces pollution, including unburned hydrocarbons, carbon monoxide, and nitrogen oxides.
* It has multi-fuel capability.
Any liquid or gaseous fuel can be burned, including gasoline, kerosene, jet fuel, diesel, alcohol, methane, hydrogen, and even vegetable oil.
* It should be inexpensive to mass produce.
The parts count of the engine is about 10% of a conventional automobile engine, and the majority of parts do not require complex machining.
* There should be no vibrations.
All moving components are in pure rotation; there are no oscillating components therefore it is in balance.
* It should be quiet.
Because the gas is fully expanded, there is low exhaust noise.
* The engine is expected to have a long life and low maintenance.
The compressor and expander of the StarRotor engine have a slight clearance between the rotors, resulting in no friction or wear. Also, it should require very infrequent oil changes, perhaps every 100,000 miles. Because it has very few moving parts, it is expected to be very reliable and require very little maintenance.
* The engine should be smaller than conventional internal combustion engines.
The StarRotor engine volume and mass are about half that of a conventional internal combustion engine. A 130-hp engine will occupy approximately 2 cubic feet.
* It should have a high turn-down ratio.
The engine is efficient over a wide range of speeds and torques.
* The StarRotor engine should be easily scalable.
Designs from 50 W to 50 MW are possible. (Please visit this DARPA White Paper for added details.)
By simply replacing conventional engines (15-20% efficiency) with a StarRotor engine, fuel economy will double or triple. For example, a conventional luxury car getting about 25 mpg on the highway would get about 75 mpg. A conventional economy car getting 40 mpg would get about 120 mpg.
* It should produce very low pollution.
Advanced combustor technology reduces pollution, including unburned hydrocarbons, carbon monoxide, and nitrogen oxides.
* It has multi-fuel capability.
Any liquid or gaseous fuel can be burned, including gasoline, kerosene, jet fuel, diesel, alcohol, methane, hydrogen, and even vegetable oil.
* It should be inexpensive to mass produce.
The parts count of the engine is about 10% of a conventional automobile engine, and the majority of parts do not require complex machining.
* There should be no vibrations.
All moving components are in pure rotation; there are no oscillating components therefore it is in balance.
* It should be quiet.
Because the gas is fully expanded, there is low exhaust noise.
* The engine is expected to have a long life and low maintenance.
The compressor and expander of the StarRotor engine have a slight clearance between the rotors, resulting in no friction or wear. Also, it should require very infrequent oil changes, perhaps every 100,000 miles. Because it has very few moving parts, it is expected to be very reliable and require very little maintenance.
* The engine should be smaller than conventional internal combustion engines.
The StarRotor engine volume and mass are about half that of a conventional internal combustion engine. A 130-hp engine will occupy approximately 2 cubic feet.
* It should have a high turn-down ratio.
The engine is efficient over a wide range of speeds and torques.
* The StarRotor engine should be easily scalable.
Designs from 50 W to 50 MW are possible. (Please visit this DARPA White Paper for added details.)
Last edited by BaronVonBigmeat; 11-25-2005 at 10:11 PM.
11-26-2005, 09:39 AM
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If it is so great, why aren't there any starrotor compressors? This concept has been used in hydraulic (oil) pumps for decades:
http://www.timgilles.com/photogaller...lpumprotor.jpg
I'm sure thousands of engineer must have thought about using this concept to compress air instead of liquid. How come there aren't even any used to compress air?
But this is way more challenging not only do they want to use the former liquid pump as a compressor they also want to use it as a turbine.
I see:
* cooling issues (the turbine part is constantly exposed to hot temperatures).
* lubrication issues
* friction (a gasturbine in comparison is not in contact with the housing).
* it will definitely have a lower power to weight ratio than a gas turbine.
* also, you definitely don't want to drive the outer wheel with the inner wheel (friction) - you'd need a gear like the wankel engine has.
Btw you can also make a brayton cycle engine with a wankel engine. It would make more sense to start from there, because a wankel engine as opposed to that 'starrotor' has obviously been tested as an engine and not just to pump oil.
http://www.timgilles.com/photogaller...lpumprotor.jpg
I'm sure thousands of engineer must have thought about using this concept to compress air instead of liquid. How come there aren't even any used to compress air?
But this is way more challenging not only do they want to use the former liquid pump as a compressor they also want to use it as a turbine.
I see:
* cooling issues (the turbine part is constantly exposed to hot temperatures).
* lubrication issues
* friction (a gasturbine in comparison is not in contact with the housing).
* it will definitely have a lower power to weight ratio than a gas turbine.
* also, you definitely don't want to drive the outer wheel with the inner wheel (friction) - you'd need a gear like the wankel engine has.
Btw you can also make a brayton cycle engine with a wankel engine. It would make more sense to start from there, because a wankel engine as opposed to that 'starrotor' has obviously been tested as an engine and not just to pump oil.
11-27-2005, 12:31 AM
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I actually think this makes lots of sense. I don't think asking the question of whether or not it's good based on the fact you don't see any of these out there is a very relevant question. Perhaps no one thought to use one for this application before. Every technology starts somewhere. This is a concept that I would watch. We definitely haven't already discovered everything there is to discover so this has potential. It has alot more potential than the quasiturbine concept. I think the real question that we should be asking is how did such an inferior concept of the piston engine ever gain such widespread use? Just because something is good doesn't necessarily mean we are using it and just because something isn't so good doesn't necessarily mean we aren't using it. We're still using gasoline after all.
11-27-2005, 09:45 AM
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Originally Posted by BaronVonBigmeat
The StarRotor engine is a Brayton cycle engine (think: jet engines, as opposed to the otto and diesel cycle engines in today's vehicles) invented at Texas A&M.
11-27-2005, 11:17 AM
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Originally Posted by terrypk1
where would compression and air/fuel mixture take place though?
This is how the whole engine is supposed to operate: http://www.starrotor.com/Engine.htm (same as a gas turbine).
First they should get the compressor in their air conditioner to work. (Which is peanuts compared to the development of a new engine).
http://www.starrotor.com/AC.htm
Also if this concept was so great it would be used in air motors (air drillers and air hammers). I'm pretty sure the guy that invented the original liquid pump several decades ago must have considered all these applications. And actually I wouldn't be surprised if the original inventor tried to use it as a compressor first but ended up having to use it as an oil pump, since he dealt with all kinds of sealing and friction issues. Mechanical Engineers know that pumps, compressors and turbines are all related in one way or another.
I see way more potential in a compound gasoline rotary engine: Same as this Rolls Royce engine but with a cooling step (intercooler) after the compression stage.
http://www.der-wankelmotor.de/Motore...lls-royce.html
* Isothermal compression as opposed to adiabatic compression increases efficiency.
* Compression ratio can be increased (= higher efficiency)
* Smaller combustion chamber (= better fuel distribution, lower AFR possible, less combustion surface = higher efficiecny)
* Compression ratio can be made smaller than expansion ratio (= higher efficiency)
* Big rotor can be made out of aluminum (lighter)
* More efficient usually means more power as well
* Due to the valves this would not really be feasible with a piston engine (= clear advantage of the rotary engine compared to the piston engine)
11-29-2005, 08:46 PM
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They claim that a brayton cycle engine is easier to seal than an otto cycle engine, but don't really explain it any beyond that. If only there were a big breakthrough in ceramics, so that all-ceramic engines could be produced. Cooling and lubrication systems wouldn't be necessary, and sealing would be much easier since your parts aren't expanding or contracting to any significant degree. Then you could make a lot of these wacky engine designs a reality.
Speaking of wacky engines, has anyone seen the ball piston engine?
Speaking of wacky engines, has anyone seen the ball piston engine?
Last edited by BaronVonBigmeat; 11-29-2005 at 08:49 PM.
11-30-2005, 02:34 PM
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You can find hundreds of new engine concept on the net. If an engine hasn't even been used to compress air or to run as a simple pneumatic motor, you need to be suspicious.
Here's an engine, that looks somewhat more interesting and is more promising than most:
http://www.ericksonmotors.com/
Here's an engine, that looks somewhat more interesting and is more promising than most:
http://www.ericksonmotors.com/
11-30-2005, 08:06 PM
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Engine management could conceivably be a big issue. Multicombustion chamber dynamics could also be tricky to manage from a NVH standpoint - something that current Wankels get away with by using 2 rotors, I suppose.
11-30-2005, 09:05 PM
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There is only 1 combustion chamber. It is stationary between the 2 sections. This is just like a jet engine in terms that this is essentially a burner can. You just inject fuel and ignite it both at a steady state. You wouldn't even need a throttlebody. Just control the amount of fuel such as with a diesel engine. This actually makes it very easy.
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