MaxOctane

I know this may not be TSX related, but it is very interesting (trust me...read on):

A company called StarRotor Corp. has been developing a new type of engine called a StarRotor engine. This engine is very different than anything else you have ever seen before. Standard engines today use the Otto thermodynamic cycle, which is extremely inneficient. This new engine uses the Brayton thermodynamic cycle which is 2 to 3 times more efficient than the Otto cycle. The Brayton cycle has never been implemented in auto engines because the only axial or centrifugal compressors can process the large volumes of air required of the Brayton cycle and these compressors require very high speeds in excess of 100K rmp's to work.

StarRotor has designed a new compressor capable of processing the large volumes of air required of the Brayton cycle. This engine will be freaking awesome. A few of the beneifts are:

1. increase in efficiency: 2 to 3 times, which means your gas mileage will double or triple.

2. all moving parts rotate around their respective axis. Inner and outer rotors where the compressing and expanding happen don't touch, which means little to no wear on this engine. This means that this engine will go in the millions of miles with very little maintenance. (fewer and infrequent oil changes)

3. Cheap to mass produce. This engine will have a tenth of the moving parts of a standard internal combustion engine and few of these parts need special machining.

4. It will be very quiet. Standard engines release exploding gasses as exhaust which is very loud. This engine will release exhaust at atmospheric pressure so it will be very quiet.

5. This engine can run on any fuel, including gas, deisel, kerosene, jet fuel, alcohol and it will be very low pollution.

6. Because the engine is so much more efficient, it will also be alot smaller, which means less weight.

StarRotor already has a working compressor (the hard part). They expect to have a working prototype in about a year. I imagine it will go through a series of improvement states and then might be ready for consumer grade production. You can see more about it including neat animations at http://www.starrotor.com

Now, for the performance guys. This engine will be pretty freaking awesome. Engines today are very limited by timing, and have a specific torque and power curve depending on the camshaft. This is extremely inefficient. Because this new engine will be so much more efficient, and because everything works on pure rotation, the torque curve will be perfectly flat. This means that you will get the same torque at any RPM and the total torque will depend on the size of the engine. Horsepower will be linear and will be dependant on the RPM of the engine. The higher the RPM, the more horsepower - but get this - how high can you rev this engine? Theoretically the only thing limiting the RPM of this engine will be how fast can you dump fuel into it. You might be able to get a small efficient 200 torque engine that you can drive like a grandma regularly but as soon as you punch it, it will have like 800 HP at 20K or 30KRPM. Do you see where I am going with this?

Now for the discussion. How will the market react to this new engine? Alot of people seem to think that there is too much invested in hybrids and thus will reject this engine. In addition to scrapping hyrid research money, production lines will need to be changed ect... I am an engineer, and in no way into marketing or economics. Seeing this on the horizon, what do you think will happen?

jiggaman

well if it is everything you say its going to be i sure as hell hope it finds its way into a production car one day!

madmanmax3000

so what does it all mean Basil??

Selanne_2001

So itz gonna be basically the same as an airplane gas turbine engine?? If thatz the case, then they might have a few problems on their hands. Me coming in as a trainin' aircraft engineer, i kno therez a few down side of have a jet engine. First of all, the hotter the expandin' gas, the more efficient the engine will be, so what ultimately decides how powerful the engine isn't how much fuel u dump in but how hot can the engine withstand.No. 2, havin' a gas turbine engine will no doubt give u a lot less vibration and wear but in the event of a failure, say just a turbine blade falls off or having a rock sucked into the engine, there's a good chance of damaging the entire engine.Also jet engines require large amount of airflow in order to keep the engine combustion camber from deforming, not sure how they're gonna archeive that.Thatz all i could think of, i could be wrong tho feel free to correct me

MaxOctane

Those are all good observations, however it is important to understand that although this can be considered a gas turbine engine, it has a very different design than what they use in jet engines. It does indeed use the same thermodynamic cycle but it uses a gerotor type compressor. You also have to understand that this comprssor is not going to be rotating at 100K RPM. This is NOT a jet engine. Don't compare it to one.

You are right in saying that the more heat, the more efficient, but everything else you said is wrong. I originally said that what will limit the SPEED will be how much fuel you can dump in. Each engine will be made to run at a specific heat limit. Obvoiusly the more heat a specific engine has, the more efficient it will be, but it might be too hot for the engine to handle, and thus limiting how much fuel you will be able to dump in. Before I had said that what determines the torque will be the SIZE of the engine, and NOT how much fuel you dump in as you mentioned.

No. 2. I don't claim that this engine will be immune to failure. Although I know a turbine blade CAN'T fall off, primarily because there are no turbine blades. Did you view the website? If you view the animations you will get a better idea of how the engine works. Secondly, if you put an air filter on this engine, a rock is most likely not going to find its way into the engine, as rocks today don't usually find their way into your standard internal combustion engine.

Seriously though, view the website, check out the animations. The combustion chamber will not be at risk of deforming because it won't be producing 10 billion pounds(exaggerated) of force required to fly an airplane.

crfortin

> what do you think will happen?

I think it won't work.

If it does work; I think Big Oil will hire hitmen to kill the developers.

MaxOctane

You're giving yourself alot of credit. By saying that it won't work you are saying that a team of engineers, with PHD's, AND who have been working on this project for 5 years, is wrong.

Don't get me wrong. The Brayton cycle is not new, has been around since the 1800's and has been proven in jet engines. The concept is flawless, the only question is, can you get a compressor that can process the volume of air required of the Brayton cycle? - and the answer is YES! They already have a working compressor and have achieved efficiencies as high as 70%. If you see the compressor, there isn't much more to it for the expandor. I don't understand how you can think that it won't work.

Can I ask that you state your level of education, experience and field? Also can you state your reasoning behind your bold statement? I was with you about 4 years ago when Dr. Holtzapple originally made it known what he was trying to do - Now, 4 years later, with a working compressor, this isn't a matter of if, it's a matter of when. If it doesn't happen, it won't be because of the concept, it will be because of funding or lack thereof.

Also oil companies making hits on an entire company? Buying them out, maybe. Are oil companies making hits on companies producing hybrids? It doesn't appear that way, and these hybrids get really good gas mileage.

This is a discussion. The purpose of this discussion is to not only discuss your opinion, but also to back it up or state your reasonings for believing so. Thanks.

r33p04s

i think he is saying no it wont work as in it wont make it into production...not not it wont work physically...i doubt it will be a big hit if it does make it into production also...

MaxOctane

Again, can you state your reasoning for believing so? A revolutionary new engine that is better than standard IC engines in every way, and yet you don't think it will be a big hit? You must have a good reason to believe so....

crfortin

I have no education. I post using a stolen laptop with pirated WI-FI service from my cardboard box outside the train station.

Good luck pumping your rotary engine stock.

PS. I've read the DARPA report and you'll notice that it only lists efficiencies for a few fixed RPMs. Just like a turbine. You don't think spinning something at 5000+RPM all day long could cause bearing problems ? What exactly happens in that magic box called the combustion chamber ? The technical summary is full of curt little statements that sound like "we can't use oil but a simple coating might work". What about momentum when you change RPM ? Where does heat disipate ? etc, etc.

When they can build a prototype for 10k that puts out 300HP and is half the size of current internal combustion at 2x the efficiency and reliabliity. I'll tune back in.

are you a mechanical engineer ?

MaxOctane

No need for sarcasm. This was meant to be a friendly discussion about how the automotive industry will respond to this engine. It seems that some people are having a hard time believing that the engine will work at all. The DARPA report was written over a year ago, long before they had developed the working compressor. Have you tried to measure efficiencies on a device that hasn't been invented yet? I believe the main reason for the uncertainty was because they were not sure how much leakage would effect the performance of the compressor. Since the inner and outer rotors do not touch, air is able to leak out. At low RPM's this leakage might cause some inefficiency, however now with a working compressor, the output data shows this to not be as much of a factor as originally thought. Ideally this engine's performance will perform linearly, as the compressor already does (you can view the results at their website).

Bearing problems at 5K rpm all the time? I don't believe jet engines have bearing problems? The combustion chamber will be nothing but a place to burn fuel, just like a jet engine. To see how this is done go to: http://travel.howstuffworks.com/turbine4.htm
The problem about the oil and coating has already been solved in the working compressor. What about momentum when changing RPM? Well, it isn't much of a problem in your car right now. In fact, I can rev from 500RPM to 5000 RPM and there is supposed to be a problem? I don't understand how this is supposed to be a problem? Where does heat dissipate? Since the engine is so much more efficient, it will give off less waste heat than a standard IC engine. I assume if heat is going to be a problem, then a radiator system can be installed.

The problems you list are very minor. The IC engine took over 80 years to significantly develop, and I am sure they ran into many problems along the way. I am in no way saying that this engine will be a breeze and will be designed without problems during development - if this were true, than the engine would have been finished by now. But the point is, is eventually the minor problems will be solved, or solutions will be designed to mitigate the problem and this engine will succeed.

I am a mechanical engineer, and I studied under Dr. Holtzapple as an undergrad.

Selanne_2001

I have to agree with u on the specific engines are designed to run on specific heat, however, as u might've studied for gas turbine engines, 75% of the air is actually used for coolin' the combustion camber and not actually used in the combustion process itself so I'm just wonderin' if they'll be able to create that mass airflow required, otherwise the eingine will be designed to run at a lower heat, hence not as efficient/powerful(not sayin' it'll be as bad a an ic engine tho). Also, how about the maintenance on the engine, since itz basically a turbine engine in principles, with the compressor and expander rotating on it's own axis, the slightest out of round will create a considerable amount of vibration especially on highspeed rotation(which is required for an engine to be efficient).Hey, i'm not sayin' i kno everything, so feel free to correct me and a healthy debate is always good. Oh and btw, yes airplanes do have bearing problems and hence they require special attentions, hence they have a 100 hr inspections and such.

CGTSX2004

iTrader: (1)

The real question is whether or not there will be sufficient fossil fuels left for this engine to burn by the time a truly production ready engine can be fitted into a production car.

And seriously, why is it that if the Brayton cycle has been around so long that someone only just now is looking at the possibility of utilizing it in a car?

TSX Hokie

OK, as a mechanical engineer that works in gas turbine research, let me point out a few things about this engine:

1. All thermodynamic cycles are limited to a maximum theoretical efficiency, the Carnot efficiency. The Carnot efficiency for any cycle is 1-Tc/Th, where Tc is the temperature heat is rejected at (usually ambient) and Th is the combustion temperature in this case, both in absolute (Rankine or Kelvin). Note: Since fuel cells are an electrochemical process, they are not limited by Carnot efficiency. Aircraft engines/industrial turbines achieve very good efficiencies by using lots of tricks to get the turbine inlet temperature up, like actively cooling the turbine stages, using exotic turbine coatings, and having extremely high compression ratios (>30:1). From what I can tell, this engine has no special turbine cooling or coatings, and the compression ratio is 6:1. While this is still good enough to be more efficient than the typical Otto cycle, it isn't even close to even the least efficient industrial or aircraft gas turbines.

2. The reason we haven't seen many Brayton cycle car engines is what someone pointed out earlier: off-design operation. Reciprocating engines aren't terribly efficient, but their efficiency is not strongly dependent on operating condition: they might stall at 500 RPM and blow up at 8000 RPM, but in between the efficiency is fairly constant. Gas turbines need to stay very close to their design RPM, and even getting there typical requires complex mechanisms (like multiple spools, variable stators, and compressor bleed). Unless this engine is coupled with a CVT or hybrid drive system to store energy and allow it to stay at a fairly constant RPM, it won't work very well in automotive applications. The website doesn't explain at all how they intend to handle part-speed operation.

3. These 'gerotor' compressors are just fancy positive-displacement blowers, like the roots superchargers that many cars use. Typically, positive-displacement compressors are not very efficient.

While we may see a Brayton cycle car someday, it will only be a gimmick once fuel cell technology is fully implemented.

crfortin

notwithstanding, the burden of proof is on Doc AppleHolder to make a working prototype. He can write all the papers in the world or engine "parts" and nobody will respond much untill then. I do wish him luck though.

Ok, based on the animation on the website/wikipedia on this cycle basically compresses air burns it at high temp and decompresses it. But the power has to be delivered on the decompression. & for added fun the exhaust gas is passed by a heat exchanger to pass heat onto and heat the intake air on it's way out the door.* The two rotors spin on the same shaft from the diagram.

*The heat issue is interesting because in a conventional high perf motor you're trying to keep the air cool and use fuel with short molecular chains,etc (octane) to prevent pre'iginition as you fill the cylinder to high compression. Whereas here you're trying to heat it as much as possible + compress before hand to burn it as completely as possible and make sure a higher % of the gas exceeds the activation energy in the combustion chamber.

So the expander is what delivers the power and has to deal with the ultra high temp expanding exhaust gases. This to me is the rub. He's built a high efficiency air compressor but not the part that is going to deal with delivering power and dealing with 1000 degree exhaust fumes. I think there is more to this than turning the compressor phase around. Yes turbines do it but they have typically have larger airflow to mass ratios than this device.

Remember in a conventional gas car the fuel is burning/exploding hotter than the melting point of the cylinder walls. I think it is the compressed air in the blast front that protects it.

This may work perfectly but based on a straw poll of me and the other bums here under the freeway who have PhD's in metalurgy, mechanics and thermodynamics we feel that there is a 80% chance that phase 2 of the engine will turn to molten glue.

Admittedly the clever Dr. Apple has listed a plan for this too, which is building the drive shaft/center turbine elements out of ceramic material. Like space shuttle tiles. So long as you watch out for bumps in the road you should be fine.

MaxOctane

Sufficient fossil fuels left? Anybody who has fully read the original post should already have read that this engine will run on any fuel including alcohol, jet fuel, kerosene, hydrogen and even vegetable oil.

And again, if you read the original post, you would have read that only axial or centrifugal compressors can process the large volumes of air required of the Brayton cycle. These compressors require very high speeds, in excess of 100K RPM - which will not work in a vehicle. That in addition with high temperatures and low turn down ratio. I encourage you to read the entire post, or at least read some of StarRotor's webpage before posting.


1. Turbine cooling is mentioned on the website. Atomized water can be added to the intake to cool the incoming air.

2. One thing I have noticed is that it has been ASSUMED that this engine will only run at one speed as does a jet engine. One of the advantages of this engine will be that it will have a HIGH TURN-DOWN RATIO. It would appear that engineers who work on gas turbine engines have made this assumption. This assumption is FALSE. The StarRotor engine will be efficient over over a wide range of RPM's. Please understand that this is not a jet engine. And the website does explain how it will handle different speeds. A plate over the compressor will obviously have two holes, one for intake and one for exhaust. By rotating where these holes are placed, you can control the compression ratio. By changing the compression ratio, and changing how much fuel is dumped in, you can control the speed of the engine and thus have a high turn-down ratio engine.

3. Typically positive placement compressors arent very efficient, yet the 3rd generation compressor, already built and tested, with output data, shows the compressor to hold efficiencies as high as 70%. Is this not efficient?

TSX Hokie

I couldn't find any mention of turbine cooling. Spraying water in the compressor inlet has been shown to improve efficiency for many Brayton cycle applications, but it doesn't raise the allowable turbine inlet temperature, which is the single most important metric for the performance of any Brayton device.

In the FAQs he even admits that leakage problems hurt part-speed performance. AND he says that the most likely initial application will be stationary power, not automobile engines. I am not disputing the claim that this device (if it is ever produced) will be a good option for small stationary power applications.


What compression ratio is that 70% at? If its 6:1, that is better than any roots blower. State-of-the art axial compressors would require 3 stages for 6:1, for at most 75% efficiency.

This guy may have a very good compressor concept. He is far from a working engine prototype though, and even farther from one that would work in an automobile. Fuel cells will be widely adopted by the time a Brayton cycle car is commercially available.

r33p04s

If i remember right the auto industry had experimented with "jet" engines in the 50's or 60's. They never made it out of the show circuit. It was reasons like needing such high rpm to create power it was almost ridiculous to imagine having to rev for 5k to 100k at every stop light. Noise was another major issue, any engine revving to 100k would be very loud among other reasons. I know things may have changed since then but I'm guessing the reasons they didn't venture into it before will keep them from venturing there again, unless the improvements overcome those kinks they ran into before I doubt it will come back. Hybrid technolgy will most likely over shadow and/or destroy any chances of this engine making it into production.
And about being able to burn on any fuel like alchohol, I think if push came to shove the industry could make a hybrid engine to burn on other combustable liquids or be a pure electric motor.

mindshare77

Mazda has something close to this out already in the RX8

http://www.mazdausa.com/MusaWeb/disp...ehicleCode=RX8

See RENESIS Rotary Engine not the exact same thing but I think it is close

Maxboost

Hmm, I've been wondering all year long during my thermo class why no one has put this Brayton into use.
Anyway, to the discussion.
After reading through the StarRotor website I think it's kinda funny that 80% of the claims in that page all starts with a word "should".
One thing that I don't understand is how could this engine cope with the rotating mass of itself. Because according to the picture from the website I see that the compressor is not rotation around its axel, it actually rotates like Mazda rotary engine. Here is the problem, is there going to be any engine mount strong enough to withstand the momentum the compressor creating because you said that it needs to be rotate at a very high RPM.

As for fuel I think it's still hard to speculate anything at this point since different manufactures are moving down their own respective path. For exaple, Japanese rely heavily on Gas/Electric hybrid. Germans are working on Fuel Cell.
If you ask me, I'm more interested in fuel cell. ZERO emission.

Master47

If it's too efficient, the oil companies will buy up the patent faster than you can blink, for more money than any car company could afford.

MaxOctane

No, the fuel burning will increase the expandor inlet temperature.


I don't believe I am reading this. The FAQ says that leakage will occur but will not be much of a factor. Here, I'll post it for you: "Yes, the gas leaks, but not enough to significantly reduce engine efficiency. The gaps are small enough that the amount of gas leaked is very small compared to the amount of gas processed, such as in conventional Brayton cycle engines that employ turbines where there is a gap between the blade tip and housing." This has already been proven in the compressor already built. It also says that the only reason why it will be likely used in stationary power first is because the utility industry is willing to pay more per kilowatt than the automotive industry, NOT because the engine will work better in stationary power.

Dr. Holtzapple believes he will have a working prototype in another year or so. I don't doubt that he can do it. Regardless, you seem to have alot of hope in fuel cells. Although I admit they do have alot more funding, fuel cells have 100,000 times more problems then this engine ever will have. Are you aware of these fuel cell problems? They aren't small ones either! (that subject is for another thread please)

MaxOctane

Sigh...you should research the jet engines they experimented with in the 50's and 60's, and then you should re-read my post. This engine is NOT a freaking jet engine! This engine will turn at a much slower rate than a jet engine and is much different than the ones experimented with before. I'm not going to explain why again, try reading the thread first...

MaxOctane

The RX8 engine is on a different planet than the StarRotor engine. The biggest difference is that the StarRotor engine uses the Brayton thermodynamic cycle. Please read the thread and the webpage a little bit more to learn more.

MaxOctane

Well, it's hard to say that it WILL and not "should" when the thing doesn't exist yet. Engineers have to speculate how things will work based on complex calculations because they cannot take real-life results.

Also, I believe you should take another look at the animations. The rotors do rotate around their respective axis. If you will notice, the inner and outer rotors do not rotate around the SAME axis, but they are still in pure rotation, unlike the Wankel Mazda rotory engine where the motion is eliptical.

There will be no momentum problems because the engine will not be turning THAT fast. Also, the engine itself will be smaller and thus will not have as much mass, so it will not be a problem.