Counter Rotating Props ?

[Henning]

yes, the certainly did, however a turbocharger's turbine is spun using exhaust gasses and a supercharger uses a direct drive off the crankshaft, which reduces "turbo lag." i am not sure if the allison 1710-89 powerplants had both, at least in the 38's, but it is possible and not unheard of in other applications.

A "Supercharger" is any device that brings the manifold pressure above what would be available in the ambient atmosphere.. It can be exhaust or otherwise driven. The 20-645-E7 EMD has an interesting setup where the turbo shaft has a sprag clutch to the engine so at low rpm it is mecanically driven and when the exhaust flow goes high enough the turbine spins it out of the sprag clutch.

The Continental engine nomenclature even takes this into consideration labeling the engines with a "TS" for "Turbo Supercharged"

 

[roncachamp]

Dont forget about power recovery turbines.. which are exhaust driven and apply the energy to the driveshaft (in addition to turbochargers and superchargers).. Many of your big WWII engines used these, especially when you consider 45% of the energy in gas goes out the tailpipe as waste heat.

Actually a postwar development of engines introduced during the war.

 

[SCCutler]

Actually a postwar development of engines introduced during the war.

For some reason, I had thought that the B-29s had turbocompound engines with power-recovery; guess I was wrong. It happens...

 

[Henning]

For some reason, I had thought that the B-29s had turbocompound engines with power-recovery; guess I was wrong. It happens...

I think some were retrofitted after the war, but they didn't last for long. It wasn't far into the Korean conflict that the AF retired all the B-29s after they had a major loss to Mig 15s.

 

[roncachamp]

I think some were retrofitted after the war, but they didn't last for long. It wasn't far into the Korean conflict that the AF retired all the B-29s after they had a major loss to Mig 15s.

No Turbo-Compounds on the B-29, which was not completely retired by the USAF until 1959.

 

[airbornejohnny]

For some reason, I had thought that the B-29s had turbocompound engines with power-recovery; guess I was wrong. It happens...

are you thinking of wartime emergency power (WEP)?
not sure what aircraft had it just a thought.

 

[Ted]

are you thinking of wartime emergency power (WEP)?
not sure what aircraft had it just a thought.

War Emergency Power varied from engine to engine, but it typically involved water injection and/or a higher boost rating than for normal takeoff power. I seem to recall seeing on the P-51 it being something like 8-10" more than takeoff power (which already was not exactly low).

The power recovery turbines extracted power from exhaust gasses similar to a turbocharger. However the difference is that the power recovery turbines then used that power to mechanically put more power to the propeller, rather than using that power to force more air into the engine. The R-3350 turbo-compound engine was one of the more well-known for that feature.

 

[denverpilot]

Water injection with modern techniques could be used to "fix" the 100LL problem for the 20% of the fleet that can't use 91UL. Just think outside the box a little...

A lot cheaper (and less political) than finding a new fuel...

But... not cheap for the 20%, and those aircraft are the high-dollar, politically-connected folks.

 

[Ted]

Water injection with modern techniques could be used to "fix" the 100LL problem for the 20% of the fleet that can't use 91UL. Just think outside the box a little...

A lot cheaper (and less political) than finding a new fuel...

But... not cheap for the 20%, and those aircraft are the high-dollar, politically-connected folks.

At the rate that 20% burns fuel, anything that allowed a cheaper fuel for them would pay for itself very, very fast.

 

[Henning]

At the rate that 20% burns fuel, anything that allowed a cheaper fuel for them would pay for itself very, very fast.

Which is why Continental China Engines should bring the 350hp TDI to market sooner rather than later. Not only cheaper but more efficient.

 

[Henning]

Water injection with modern techniques could be used to "fix" the 100LL problem for the 20% of the fleet that can't use 91UL. Just think outside the box a little...

A lot cheaper (and less political) than finding a new fuel...

But... not cheap for the 20%, and those aircraft are the high-dollar, politically-connected folks.

Water, water-meth, NOS injection... will only take care of the problems on take off and a few brief applications per tankful of juice. I used to use NOS a lot to fill in for turbo lag in the pre EFI days and to keep out of detonation on high load hole shots with steep props. Pushy Galore pumped bottle gas all the way to altitude with that, IIRC, O-200. For limited use, it's a good way to add some HP. However even the HP TC big bores would be fine on 91UL if they had modern fuel and ignition control systems. The airframes are another story, most will require some boost pump.

...or switch to diesels.

 

[Ted]

However even the HP TC big bores would be fine on 91UL if they had modern fuel and ignition control systems.

Producing how much power? What makes you believe that the laws of physics that govern combustion and detonation change just because modern fuel and ignition control systems are installed on an engine?

 

[flyingcheesehead]

Water injection with modern techniques could be used to "fix" the 100LL problem for the 20% of the fleet that can't use 91UL. Just think outside the box a little...

A lot cheaper (and less political) than finding a new fuel...

Hey, what's wrong with a new fuel? I'm encouraged by both the Swift and GAMI solutions. At least one of them is capable of being bio-sourced as well, which is politically good. Hey, maybe aviation can be a leader again...

But... not cheap for the 20%, and those aircraft are the high-dollar, politically-connected folks.

Bah. The really high-dollar folks have been burning Jet-A for a long time. The 20% are the folks who are trying to go as fast as possible on a budget... AND the warbirds. Are you going to go tell the CAF that they're "high-dollar, politically connected folks" and need to add "modern" water injection systems to their birds?

 

[kyleb]

The R-3350 turbo-compound engine was one of the more well-known for that feature.

The later 3350's were the only turbo compound engines to see service. They were also a very maintenance intensive solution, and pretty much the piston engine's last gasp before turbines took over. In most cases, the turbo compound varients of various airframes were retired before their non-TC'd bretheren.

 

[Henning]

Producing how much power? What makes you believe that the laws of physics that govern combustion and detonation change just because modern fuel and ignition control systems are installed on an engine?

Pretty much the same power. The difference comes in safety margin requirements to assure staying out of detonation so they will be able to carry higher pressure safely.

 

[Ted]

Pretty much the same power. The difference comes in safety margin requirements to assure staying out of detonation so they will be able to carry higher pressure safely.

I'd invite you to try it for yourself and report back with the results.

 

[airbornejohnny]

What makes you believe that the laws of physics that govern combustion and detonation change just because modern fuel and ignition control systems are installed on an engine?

With the advances in automotive technology that we see today, I would be surprised if very little came out of aviation science. Even if that is the case, with the kind of fuel efficiency advancements that have been made such as those in diesels and more efficient ignition systems in gas there has to be something better that can be applied to aviation. Am I just being ambitious?

Also, so far as corn-for-ethanol goes, does anyone know of similar "green" advances for jet fuel or diesel?

 

[flyingcheesehead]

With the advances in automotive technology that we see today, I would be surprised if very little came out of aviation science. Even if that is the case, with the kind of fuel efficiency advancements that have been made such as those in diesels and more efficient ignition systems in gas there has to be something better that can be applied to aviation. Am I just being ambitious?

Maybe. Aviation engines are much more "on the edge" than automotive engines are. I'm not sure what the car guys are doing for increased efficiency, but at the end of the day, like Ted says, the physics of combustion are the limiting factor, and aviation engines operate much closer to the limits than auto engines do.

Also, so far as corn-for-ethanol goes, does anyone know of similar "green" advances for jet fuel or diesel?

That assumes ethanol is "green" in the first place.

The Air Force has been testing a bio-blend jet fuel, for what that's worth.

 

[airbornejohnny]

Maybe. Aviation engines are much more "on the edge" than automotive engines are. I'm not sure what the car guys are doing for increased efficiency, but at the end of the day, like Ted says, the physics of combustion are the limiting factor, and aviation engines operate much closer to the limits than auto engines do.



That assumes ethanol is "green" in the first place.

The Air Force has been testing a bio-blend jet fuel, for what that's worth.

Heard about the AF blend...seems promising.
What I meant about the automotive stuff (should have ellaborated a bit more) was the computerized control of valve/ignition timing and air/fuel ratios for different performance. Obviously, aircraft have a much broader environment to contend with than the average auto, it just doesn't seem far fetched that its POSSIBLE...whether I personally would trust a computer is potentially another story:wink2:. Im somewhat out of the loop here, just wondering how far piston engines have really advanced.

 

[denverpilot]

Maybe. Aviation engines are much more "on the edge" than automotive engines are. I'm not sure what the car guys are doing for increased efficiency, but at the end of the day, like Ted says, the physics of combustion are the limiting factor, and aviation engines operate much closer to the limits than auto engines do.

Not up here.

It's difficult to get 80% power out of my O-470 up here, and by 1000' AGL I'm below 75% most days.

A little water-injection for you guys "livin' on the edge" at sea level, climb on up to 6500' MSL for cruise and go a little slower, and you're all set!

A little more power management besides WOT and a little H2O, and there's almost no "leaded fuel crisis" at all.

Lots of work for little return on these fuels.

Add computerized ignition and mixture control with appropriate sensors, and the detonation problems caused by having a brain dead set of levers set by us fallible control-freak monkeys, and you've got workable solutions today.

The problem is there's money hiding somewhere that the fuel folks want. A simple obvious solution isn't going to make them a generation-worth of income. *Especially* if they can call it "green" and get tax money for developing it and for every gallon sold.

 

[kyleb]

Heard about the AF blend...seems promising.
What I meant about the automotive stuff (should have ellaborated a bit more) was the computerized control of valve/ignition timing and air/fuel ratios for different performance. Obviously, aircraft have a much broader environment to contend with than the average auto, it just doesn't seem far fetched that its POSSIBLE...whether I personally would trust a computer is potentially another story:wink2:. Im somewhat out of the loop here, just wondering how far piston engines have really advanced.

The issue with aircraft engines is that they turn at low RPM and have large cylinder volumes. That creates perfect conditions for detonation. The flame front doesn't move quickly enough through the large cylinder volume to burn all of the fuel before the unburnt fuel gets hot enough and compressed enough to detonate.

Auto technology (other than the smaller cylinder volume/higher RPM Rotax approach) won't fix that problem.

 

[Ted]

Not up here.

It's difficult to get 80% power out of my O-470 up here, and by 1000' AGL I'm below 75% most days.

A little water-injection for you guys "livin' on the edge" at sea level, climb on up to 6500' MSL for cruise and go a little slower, and you're all set!

A little more power management besides WOT and a little H2O, and there's almost no "leaded fuel crisis" at all.

Lots of work for little return on these fuels.

Add computerized ignition and mixture control with appropriate sensors, and the detonation problems caused by having a brain dead set of levers set by us fallible control-freak monkeys, and you've got workable solutions today.

The problem is there's money hiding somewhere that the fuel folks want. A simple obvious solution isn't going to make them a generation-worth of income. *Especially* if they can call it "green" and get tax money for developing it and for every gallon sold.

That is, quite possibly, the most inaccurate and poorly thought out summary of the fuel issue that I have ever read.

 

[Henning]

I'd invite you to try it for yourself and report back with the results.

The results won't be any different than when we went through the same experiments with heavily boosted big and small block Chevys 2 decades ago when these systems first came out, and they've only improved since.

I still think it's a waste of effort for airplanes as they should be running on diesel fuel.

 

[airbornejohnny]

The issue with aircraft engines is that they turn at low RPM and have large cylinder volumes. That creates perfect conditions for detonation. The flame front doesn't move quickly enough through the large cylinder volume to burn all of the fuel before the unburnt fuel gets hot enough and compressed enough to detonate.

Auto technology (other than the smaller cylinder volume/higher RPM Rotax approach) won't fix that problem.

I understand the difference...the design is similar to diesel engines, which have advanced an awful lot accross the pond as far as emissions and fuel efficiency are concerned (other stuff too). Fuel atomization (from what I have learned from some fiends) is a major factor for more recent diesel advancements by having more accurate fuel/air mixture control for more complete combustion with less fuel. Wouldn't similar measures give similar results in A/C piston engines?

 

[Ted]

The results won't be any different than when we went through the same experiments with heavily boosted big and small block Chevys 2 decades ago when these systems first came out, and they've only improved since.

I don't know anything about the tests you did on the Chevy V8s, but the fuel and ignition systems were significantly different to what our engines have, so saying the results won't be any different I don't believe is accurate.

As I said, try it for yourself, report back with the results.

 

[denverpilot]

That is, quite possibly, the most inaccurate and poorly thought out summary of the fuel issue that I have ever read.

Do you have the 100% solution for the fleet?

Just trying to spark comment/thought by folks in a completely new direction with over-the-top comments.

(Maybe five winkies will get the point of the winkies across?)

Serious point: The engines in the fleet are changing. LSAs are mostly MoGas burners. 80% of existing aircraft also can burn it just fine.

91UL meets the 80/20 rule today. Not tomorrow. What's stopping it from being adopted?

Put 91UL on every airport and economically what will happen? -- The 20% will adapt.

80% of the fleet is waiting around burning 100LL waiting for the expensive solution that only 20% need. Doesnt make sense.

Diesel is an interesting next technology step as well, but again... Why? 80/20. 91UL is available today at every refinery...

Your thoughts, Ted?

 

[flyingcheesehead]

Put 91UL on every airport and economically what will happen? -- The 20% will adapt.

Or simply be grounded. Again - Think warbirds here. And, frankly, a whole lot of other airplanes that might not be "worth" spending the $$$ to adapt to a 91UL solution, but that you don't want to see grounded.

We need the 100% solution because we can't afford to alienate the 20%. Aviation is too small as it is.

91UL isn't a "solution" at all. I'd be reluctant to even call it a "kludge." It's a cop-out, nothing more.

 

[Trapper John]

I still think it's a waste of effort for airplanes as they should be running on diesel fuel.

Are there any aviation diesels that have the same power output at the same weight as an air-cooled gasoline aviation engine?

 

[kyleb]

I understand the difference...the design is similar to diesel engines, which have advanced an awful lot accross the pond as far as emissions and fuel efficiency are concerned (other stuff too). Fuel atomization (from what I have learned from some fiends) is a major factor for more recent diesel advancements by having more accurate fuel/air mixture control for more complete combustion with less fuel. Wouldn't similar measures give similar results in A/C piston engines?

We already have the fuel distribution option (GAMI injectors), and there are marginal improvements to be made if you get the injectors properly balanced.

The problem is that we've backed ourselves into a corner with the big cylinder volumes and slow revving engines. It is (arguably) a better option than adding the complexity and weight of a gearbox, but it does come with limitations due to the opportunity for very high cylinder pressures.

 

[JesseD]

I thought the 20% burned more gas than the other 80

Weren't people were aiming for 95-98NL, or even (possibly) 100NL?

As someone that might end up in that 20%, I'd like a single fuel to help keep costs reasonable.

 

[Everskyward]

Put 91UL on every airport and economically what will happen? -- The 20% will adapt.

80% of the fleet is waiting around burning 100LL waiting for the expensive solution that only 20% need. Doesnt make sense.

I know very little about engines and what they need but why couldn't the airplanes that need the higher octane use some kind of additive which could be blended in the same manner as Prist is blended with JetA?

 

[N801BH]

I know very little about engines and what they need but why couldn't the airplanes that need the higher octane use some kind of additive which could be blended in the same manner as Prist is blended with JetA?

Bingo................

 

[Trapper John]

I know very little about engines and what they need but why couldn't the airplanes that need the higher octane use some kind of additive which could be blended in the same manner as Prist is blended with JetA?

I'm not sure if any of the proposed 100LL replacements would allow for field blending or not.

I'd suspect that the refiners/marketers don't want to go back to having 2 aviation fuels given the small market. If I'm a refiner/marketer, I have a responsibility to deliver a fuel that meets the applicable ASTM specs at the point of sale. If the fuel I sell has some important process (like the an additive blended in) to meet that spec being accomplished at hundreds or thousands of dispensing points, my quality assurance job would be much more difficult. I'd have to come up with idiot-proof blending equipment, which probably wouldn't be cheap.

 

[N801BH]

I thought the 20% burned more gas than the other 80

Weren't people were aiming for 95-98NL, or even (possibly) 100NL?

As someone that might end up in that 20%, I'd like a single fuel to help keep costs reasonable.

What amazes me is a national gasoline producer has had the cure to the 100LL problem for years and did not capitalize on the ripe market. This is a well proven product, meets all the specs for avaition applications, has years of on track testing and was not presented for consideration. As with anything else there is the 'economy of scale' costing and with Sunoco's ability to currently produce the product and tooling up to meet the demands of replacing 100LL, the increased volume will drive the cost way down to the end user over the current price they sell to the racing market. All race vehicles have bladders in their fuel cells so compatibility to aircraft stuff should be seamless.

http://www.sunocoinc.com/site/Consumer/RaceFuels/UnleadedFuels/



http://www.sunocoinc.com/Site/Consumer/RaceFuels/UnleadedFuels/Sunoco260GTX.htm


http://www.sunocoinc.com/Site/Consumer/RaceFuels/UnleadedFuels/Sunoco260GTPlus.htm

 

[kyleb]

All race vehicles have bladders in their fuel cells so compatibility to aircraft stuff should be seamless.

I don't understand your comment on bladders and compatability. I don't see how bladders in racing vehicles equates to compatability for that fuel in all of the wet wing aircraft out there...

 

[N801BH]

I don't understand your comment on bladders and compatability. I don't see how bladders in racing vehicles equates to compatability for that fuel in all of the wet wing aircraft out there...

Because one of the main complaints from the industry was any new fuel would attack fuel bladders that are in certain aircraft...

 

[Everskyward]

If I'm a refiner/marketer, I have a responsibility to deliver a fuel that meets the applicable ASTM specs at the point of sale. If the fuel I sell has some important process (like the an additive blended in) to meet that spec being accomplished at hundreds or thousands of dispensing points, my quality assurance job would be much more difficult. I'd have to come up with idiot-proof blending equipment, which probably wouldn't be cheap.

There are many fuel trucks which blend Prist. In addition you can buy it in cans to be dispensed as the fuel comes out of the nozzle and goes into the tank. Granted, the proportion of Prist in the fuel has a pretty wide latitude which may not be the case for an octane additive.

 

[gismo]

What amazes me is a national gasoline producer has had the cure to the 100LL problem for years and did not capitalize on the ripe market. This is a well proven product, meets all the specs for avaition applications, has years of on track testing and was not presented for consideration. As with anything else there is the 'economy of scale' costing and with Sunoco's ability to currently produce the product and tooling up to meet the demands of replacing 100LL, the increased volume will drive the cost way down to the end user over the current price they sell to the racing market. All race vehicles have bladders in their fuel cells so compatibility to aircraft stuff should be seamless.

http://www.sunocoinc.com/site/Consumer/RaceFuels/UnleadedFuels/



http://www.sunocoinc.com/Site/Consumer/RaceFuels/UnleadedFuels/Sunoco260GTX.htm


http://www.sunocoinc.com/Site/Consumer/RaceFuels/UnleadedFuels/Sunoco260GTPlus.htm

If Sunoco260 was a suitable substitute for 100LL I think that it would already be available for that. Keep in mind that the octane ratings of auto fuel are different than AvGas (and typically higher), plus there are other specs that need to be met in terms of shelf life, volatility, and lack of issues with aircraft fuel system components.

 

[Trapper John]

There are many fuel trucks which blend Prist. In addition you can buy it in cans to be dispensed as the fuel comes out of the nozzle and goes into the tank. Granted, the proportion of Prist in the fuel has a pretty wide latitude which may not be the case for an octane additive.

Right, but the Jet-A producer has already done his thing before the Prist gets added. Prist isn't needed for the Jet-A to meet Jet-A specs.

 

[Everskyward]

Right, but the Jet-A producer has already done his thing before the Prist gets added. Prist isn't needed for the Jet-A to meet Jet-A specs.

But some airplanes require Prist or some other anti-icing additive because they don't have fuel heaters. In the same manner, if a lower octane fuel were manufactured for a bulk of the GA fleet couldn't an additive be used for the airplanes which need it?