A different Brayton Cycle concept.

  • #1
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3

Main Question or Discussion Point

This is a revisit of a site that we have seen in the past, but there has been some updating and it looks promising. This is definitely not what most have in mind when they talk about the internal combustion (re. Otto/Diesel cycle)engine and list the limitations of it. In fact, it's not even what most of us think of when we think of a Brayton Cycle engine. What do you think?

KM

Starrotor Company
 
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Answers and Replies

  • #2
FredGarvin
Science Advisor
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I don't see a whole lot of innovation in simply replacing the compressor and turbine with gerotors. However, If they can make a better mousetrap, more power to them. I was worried about a couple of their statements on their web site:

There should be no vibrations. All moving components are in pure rotation; there are no oscillating components therefore it is in balance.
They are treading on very thin ice by making that comment in the fashion they did. There will be vibrations. No rotor of any kind is perfectly in balance. Neither is the airflow going through the engine.

The StarRotor engine should be easily scalable.
My company has done a lot of work with scaling and it is not easy and it has limitations. I'm not saying it can't be done, but there are many aspects of a turbine that will not scale or are very difficult to scale. Also, as they will find out, varying reactions to scaling, i.e. vibration responses and speeds, are not scaled linearly with the components.

Hopefully they can produce a new version. Innovation is a great thing.
 
  • #3
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FredGarvin said:
I don't see a whole lot of innovation in simply replacing the compressor and turbine with gerotors.
Here, I think the innovation comes in a configuration that can be produced cheaply for more mundane uses, like autos. My guess is that it will probably never be able to match the mass air-flow capabilities of a turbine.

FredGarvin said:
They are treading on very thin ice by making that comment in the fashion they did. There will be vibrations. No rotor of any kind is perfectly in balance. Neither is the airflow going through the engine.
I suspect that here, they are making the allusion that Otto-cycle engine makers use when comparing say, their twelve cylinder engine to a six. In that context, they refer to the engine being "smooth" when, in reality it is just smoother than the six. Another example is the sign on some busses that extol the use of "clean" natural gas. It isn't clean; just more-so than gasoline. Also I might point out that I asked them about noise emissions about a year ago, and they admitted that there would be some noise from the gerotor teeth, an acknowledgement that there would be vibration to some extent.

On "scaling", we'll just have to wait and see. They seem optimistic.

KM
 
  • #4
FredGarvin
Science Advisor
5,066
7
I agree with the comparrison angle. There will be virutally no vibration when compared to a reciprocating engine. I just wish they would say that plainly.

In regards to scaling, I don't think they'll have the hard issues when scaling up. You are afforded more leeway with space and weight savings when you go larger. However, going smaller is entirely different. They may not need to go smaller than what they already have. I do know that a proper pump gerotor clearance is a biyatch to maintain when you get to a certain level.

The noise attenuation will always be the bane of any turbine. Powerturbines especially since they can't take advantage of mixing cold and hot airstreams like a turbofan does.

My comapny had a successful program about 15 or so years ago for almost the smae thing they discussed...for environmental control in an enclosed vehicle for NBC conditions. Even though it wasn't picked up for production, it was very successful for us.

I'm going to pass that link around to some co-workers. Thanks!
 
  • #5
t92
8
0
Has anyone ever built a subatmospheric brayton-cycle piston engine?
or
a sub-atmospheric open stirling cycle?
 
  • #6
has anyone tried to make a Brayton-cycle to drive say an electrical generator using(adapting) a piston, combustion engine turbo-charger?
 

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