What If?: The Turbine Had Not Been Invented

[440_Magnum]

Re: What If?: The Turbine Had Not Been Invented

IMHO - All of the variable valve timing, lift, etc., serves great purpose for engines where their application demands performance and efficiency across a broad RPM range. However, aircraft engines operate in a narrow RPM band and are optimized to reliably do just that. What would the advantage be of a technologically advanced valve train?

A fair question. But you have to remember that even though the engine RPM may be constant, the engine loading isn't, therefore the airflow dynamics through the engine can still vary a lot. If you de-couple the valve action from being driven solely by the position of the crankshaft (and therefore camshaft) you can do really neat things like change valve timing events as a function of manifold pressure and mass air flow. That's exactly what modern diesel injection systems have done, and why modern diesels are so much quieter and smoke so much less than pre-90s engines. It used to be that a camshaft activated the injection event solely as a function of crank position with some "tuning" due to throttle position or manifold pressure. First the HEUI engines, and now to an even greater extent the common-rail diesels, allow the injection events to be arbitrary in relation to crank position or even have multiple events per cycle ("pilot" injection to reduce noise, for example). The same revolution is just waiting to happen with intake and exhaust valve actuation, and things like VTEC, VANOS, and MDS are the first small steps in that direction.

Again, since most racers run WFO, it might not be a benefit in that specific application... but the general question was "what if the turbine engine hadn't been invented."

[Paynts]

Re: What If?: The Turbine Had Not Been Invented

I know this is a little off topic but seeing the way things are going with this thread I want to ask a question to the experts here.
Is anyone running advanced ECUs with anti knocksensors electronic timing /wasted spark and the all the other goodies in any of the Reno racers?
If not it strikes me this would be a relitively cheap way to increase the reliability and maybe even the power of these engines

[kiwiracefan]

Re: What If?: The Turbine Had Not Been Invented

HI paynts....

I believe that the blue thunder II guys are in the process of installing the latest Motec ECU for their sport class racer, but im not sure what the unlimited guys use if indeed any of them are using modern ECU's

[Plane Nuts]

Re: What If?: The Turbine Had Not Been Invented

Blue Thunder has been using an ecu controled waste spark system which is based on GM distributorles ignition. They have used a Motec system from day 1.

[Blue Foam]

Re: What If?: The Turbine Had Not Been Invented

I know this is a little off topic but seeing the way things are going with this thread I want to ask a question to the experts here.
Is anyone running advanced ECUs with anti knocksensors electronic timing /wasted spark and the all the other goodies in any of the Reno racers?
If not it strikes me this would be a relatively cheap way to increase the reliability and maybe even the power of these engines

To answer your question directly, no. Not a single air racing team uses current technology ECU's and data acquisition. Blue Thunder has used Motec ECU's "from day one" because this was part of the engine they were sold. No Sport or Unlimited air racer has ever used anti-knock sensors on boosted engines of any type.

Nor have they used modern engine coatings, sequential injection, high-energy tunable ignition, boost control, ECU's, etc.

I realize that I am beating a dead horse in the presence of ostriches here... but you asked.

If the turbine had never been invented, these technologies would be as ubiquitous in air racing as they are in all other forms of motorsports.

[Apteryx]

Re: What If?: The Turbine Had Not Been Invented

I realize that I am beating a dead horse in the presence of ostriches here... but you asked.

If the turbine had never been invented, these technologies would be as ubiquitous in air racing as they are in all other forms of motorsports.

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[First time Juke]

Re: What If?: The Turbine Had Not Been Invented

I realize that I am beating a dead horse in the presence of ostriches here... but you asked.

If the turbine had never been invented, these technologies would be as ubiquitous in air racing as they are in all other forms of motorsports.

I know this feeling. All official sponsors here turned down my pusher prop design that would have flown 1/10 of the fuel compared to most other ultralites and been also faster ( ultralite top speeds are not prohibited here ).

I think the developement of pusher prop designs were stalled when jet engines proved to provide more top speed ( with the cost of higher fuel consumption of course ). Did I mention this already ?

[MRE]

Re: What If?: The Turbine Had Not Been Invented

Merlin engine builders have been useing modern piston coatings for many years.

[AirDOGGe]

Re: What If?: The Turbine Had Not Been Invented

Pusher props aren't common for several reasons.

For one, they tend to be less efficient, mainly due to the disturbed airflow reaching the propeller after having passed around the wings and fuselage. Some racers have done well to get around this issue, but those are small, very slick airframe designs compared to your average bigger and bulkier passenger aircraft.

For another, they can be heavier, more expensive and/or difficult to make if the set-up requires an extension drive-shaft.

Then there's always the safety issue, since a pilot usually cannot see the propeller behind him/her at start-up, so one has to be a bit more careful to make sure the prop is clear when doing so.

-

Finally, and this is just my opinion based on experience, but I believe a tractor set-up is more stable than a pusher.

A prop pushing from the back, to me anyway, is like pushing a shopping cart backwards. The vehicle is always trying to swap ends. Side loads from the prop don't help either. The only thing keeping everything flying in a straight line is the tail-feathers.

A tractor set-up seems naturally more stable, as it's technically towing the plane behind it forward, like a horse pulling a cart. Side motions on the nose would have less effect on the direction of flight, especially at critical low speeds.

Just my observation.

[Blue Foam]

Re: What If?: The Turbine Had Not Been Invented

Merlin engine builders have been useing modern piston coatings for many years.

Not trying to be confrontational here, I really am curious since I actually asked the Doctor about this in 1999 and again in 02:

a) TBC's on the crown?
b) Phenolic bonded TFE-graphite on the skirt?
c) Molybdenum plated ring faces (top and bottom, not sides)?
d) dispersants on the piston backside?
e) some combination?
f) other?

I know that some coating was used on the cylinder sleeves, was this SiN, BN or other?

Each coating type and application has its effects and impacts on other components, some negative. For example, using TBC's without changing bore clearance will result in piston rattle and seizure due to lower-than-normal piston growth. OTOH, if the power level is raised to above the wartime-emergency level, a piston clearance that would normally seize may be correct with TBC's and dispersants. It's complicated and integrated solutions are needed.

I know, "money, money money". My contention has always been that it would be cheaper to put the money into a well planned program of implementing these with EFI than taking the same 50 year old engine apart for the umpteenth time and polishing the same out-of-spec parts again and again. And no, i would not go "whole hog" the first time out and blow 20 engines (or even 5). I would use the mods to increase reliability at current power levels first while experience is built with the systems. Blue Thunder has used EFI for years, why not follow a proven product?

[First time Juke]

Re: What If?: The Turbine Had Not Been Invented

Pusher props aren't common for several reasons.

1.For one, they tend to be less efficient, mainly due to the disturbed airflow reaching the propeller after having passed around the wings and fuselage. Some racers have done well to get around this issue, but those are small, very slick airframe designs compared to your average bigger and bulkier passenger aircraft.

2.For another, they can be heavier, more expensive and/or difficult to make if the set-up requires an extension drive-shaft.

3.Then there's always the safety issue, since a pilot usually cannot see the propeller behind him/her at start-up, so one has to be a bit more careful to make sure the prop is clear when doing so.

-

Finally, and this is just my opinion based on experience, but I believe a tractor set-up is more stable than a pusher.

A prop pushing from the back, to me anyway, is like pushing a shopping cart backwards. The vehicle is always trying to swap ends. Side loads from the prop don't help either. The only thing keeping everything flying in a straight line is the tail-feathers.

A tractor set-up seems naturally more stable, as it's technically towing the plane behind it forward, like a horse pulling a cart. Side motions on the nose would have less effect on the direction of flight, especially at critical low speeds.

Just my observation.

Airdogge,

So far I have appreciated all you say, but now I think we are "divorcing" !

1. I have heard from 2 aviation experts that this is far more efficient way to move aeroplane. History also clearly shows it. LF 2100 was last serious attempt to make it work ( death of Bill Lear stopped the project ).

2. They weigh lot less ( see LF 2100 ).

3. This depends of the design whether the pilot sees the prop or not.

I think only valid comparison to determine how aft mounted prop behaves is a car with front drive or with rear drive.

Like I have stated in my blog there is a strong suction from the prop that works as a power steering ( as long as the prop is runned by the engine at some thrust which is not decelerating the craft ).

I think a test pilot used to front prop tractors cannot see these advantages and acts on the same prejudictions as you do ( unfortunately ).

Best Regards,

Juke