turbo vs super charging

[itchybum]

It's been a long time.

Can anyone give me a quick run-down on the fundamental difference(s) between turbo-charging and super-charging?

And what about turbo-super-charging (eg the TSIO-540 engine).

Thanks in advance.

[Jet_A_Knight]

Here ya go fella............

http://www.avweb.com/news/columns/182102-1.html

Then follow your nose.:ok:

[DirectAnywhere]

A Turbo-Supercharger is the correct name for a Turbo-Charger, or simply turbo.

A supercharger uses an impeller geared off the crankshaft to provide additional manifold inlet pressure.

Turbosuperchargers use an exhaust gas driven turbine to power an impeller, as opposed to a gearing system.

Both systems provide the ability to either increase power at low altitudes or maintain sea level rated power to higher altitudes.

TSIO-540 stands for a Turbo Supercharged Fuel Injected Horizontally Opposed 540 Cubic Inch engine.

P.S. That's a good background article for anyone doing CPL AGK.

[OZBUSDRIVER]

Further to Direct Anywhere's post, it is worth remembering that supercharging requires engine power to turn the supercharger, resulting in a net gain.Whilst turbo chargers derive power from expanding waste gases in the exhaust system therefore scavenging extra energy from wasted heat.

And if you realy want to twist your brain. Supercharged and Turbo compound as on old radial engines.

Regards

Mark

[Spodman]

Not to mention power recovery turbines that sit in the exhaust and help drive the engine...

[1McLay]

Also woth noting

A supercharger compresses the fuel/air mixture before it enters the cylinders where a turbocharger compresses only the air before it enters the cylinders.

The advantage of a super charger is there is no lag in the system i.e. if you need power it's there when you open the throttle where as with a turbo there is a slight lag while the turbine spools up to an efficient speed. Turbo's are usually run at a ratio of between 7:1 and 13:1 of engine speed.

The problem with charging is the rapid increase in temperature of the air can lead to high CHT, EGT and TIT which can invoke detonation which will wreck an engine in no time. i.e. usually high mixture settings are required to keep the temps down.

But it is very effective in turning a normally aspirated engine in to a high altitude performer!

Just out of interest I know of a TIO-540 that has an insatiable thrist for 140 litres of fuel an hour at full power! Hard case when an IO-540 does about 60-70L/hr at full power! No wonder the worlds oil supply is running out!

1M:ok:

[always inverted]

a supercharger surely only has instant power because it is bolted to the crank, so on the other end of the unit the compressor rotates faster because it has to- fixed shaft,
Surely the increased air flow through the metering system is relayed to the the injection system which dumps more fuel to make the fuel air ratio the same and therefore increasing the power.

Just out of curiosity, which is more common on light a/c and which is more efficient.

[nzmarty]

hello everyone. i'm a new member, work in a/c engineering, but have seen the light and are in the process of doing PPL/CPL, so i can dance around the sky all day :)

turbocharging is more common on production aircraft. i'm guessing for a few reasons, 1. the engine is running at a (reasonably) constant speed, so doesn't need the instant acceleration of the (crank driven) supercharger, 2. the profile of a supercharger is somewhat high, causing engine cowling to be larger than desirable - a turbo is 'hidden' in the exhaust system and 3. a turbo is relatively simple. if it breaks, the engine will still run, just at reduced horsepower. the supercharger is a much more integral part of the engine, and if it breaks, it is more likely to cause collateral damage

the only aircraft i can think of that are crank driven supercharged are WW2 high performace fighters - no doubt someone will enlighten me though.....

[Dale Harris]

Hey 1M, if your TIO 540 is running properly, it's probably using 165 per hour. Our's do........... (350 H.P.) NZMarty, you ever seen a Queenair? Geared AND supercharged!!! Pains in the arse to manage properly tho...... and that T.B.O...... ouch!!!!!! Inverted, you kind of missing the point of Turbo/Supercharging. Usually used to boost Take off H.P., and increase cruise manifold pressure, giving altitude and cruise speed increases. Because the a/c engine is usually operated at constant power, supercharging in both forms quite useful in some circumstances. It's a different animal to the car type Turbo or Supercharging

[nzmarty]

did a little bit of work on queenairs and chieftans about 15 years ago, but can't remember the queenairs being both turbo & super charged. i'll have to take your word on that. been a turbine head, and something else, since then.....

[OpsNormal]

1 Mac. Hunt down whoever taught you about forced induction and shake them profusely....

Also woth noting...

A supercharger compresses the fuel/air mixture before it enters the cylinders where a turbocharger compresses only the air before it enters the cylinders.

Sorry, not quite right. Both can either run an air/fuel mixture through them, or conversly can operate dry. Think of a diesel engine. Diesels can use either turbo or supercharging just like a spark ignition engine, but the fuel is injected usually directly into the cylinder for ignition to occur. A similar concept in piston recips in aircraft, but of late the designs have used fuel injection which occurs into the inlet port of the cylinder heads.

Turbo's are usually run at a ratio of between 7:1 and 13:1 of engine speed.

Dunno where you got those figures from, but a turbo only turning at 7 times the speed of the engine is attached to an engine that is idling, nothing more. Turbo chargers are known to exceed 60-120,000 rpm (no, that is not a misprint) in normal engine operation, depandant on air density and temperature. They utilise things like ceramic bearings and very fragile seals to achieve no mean feats of physics.

It matters not how a supercharger is driven, but uses methods such as direct drive from the crankshaft, gearing off the crankshaft and various methods of belt drives to achieve the desired result.

A turbo (or turbo-supercharger if you like), is purely driven by engine exhaust pressure and flow from the engine. For the most part, lag will only usually be a problem from lower rpm, such as advancing the throttles at the beginning of the take-off roll.

The only type of forced induction that one would have an idea of exactly how fast it is turning at any given time is a gear driven or toothed belt driven supercharger, as it is turning at a speed that is regulated by crankshaft rpm (and its either reduction or overdriven gearing).

You are, however, spot on about them being fuel monsters just to keep the temps/detonation buffer down.

Have a good one,

OpsN ;)

[itchybum]

Oh yeeeeeah...... now I remember. Thanks for all the good replies.

But I seem to recall a PAIR of TIO-540s ( I think they were) on a PA31 burning about 150 l/hr in the cruise. Or was that the TSIO-540 on a C402?? Or was THAT the TSIO-520?? Or was that on the C310R....???

Ah the good old days........

I DO know the C210 burnt about 60l/hr, a nice round figure, just like Elizabeth Hurley. But what engine was it??? IO-540??

[Tinstaafl]

No. C210s, C310s, C4xx, Barons*, Bonanzas* have Continental IO-520s, not Lycoming IO540s.



*or did until Beech replaced them with Cont. IO550s

[1McLay]

Ops Normal

Thanks, that makes interesting reading. I stand corrected!
After having a chat with our LAME, he said it would depend on weather the engine was carby or injected to depend on weather the system was dry or fuel/air charged.

That sentence bout the speed ratio should've read super charger not turbo! Cheers mate :D


Dale Harris

Our TIO-540 normally uses no more than 150L per hour at full throttle. Usually about 40" @ 2450 rpm (in a 206!) 350hp

[Tinstaafl]

That twigs a memory. Did Cessna replace the Cont. IO520s with Lyc. IO540s in the restarted C206 line?

[Dale Harris]

Yeah they did tinny, but had a few problems with them initially. Dunno if they fixed them or reverted to Conti's. Unless it's a retrofit, there ain't any 350 hp 206's out there, the new ones are still 300 hp.

1 Mc, 43" map and 2575 RPM L/TIO 540 will get you 350 hp 40" and 2450 doesn't.

Itchy, they had Continental IO 520's, mostly, some 550's as a retrofit, even a turbine or 2 out there as well........

[Jamair]

OpsNormal (g'day Dave) & 1Mclay; whether an operator chooses to use excess FUEL to cool (with a rich mixture) or excess AIR to cool (with a lean mixture) will determine the fuel consumption (along with MAP, density alt etc)....

Chieftains are specifically approved in the POH and Engine Operators Manual to run LoP, as are many others incl Seneca II-IV, some Barons, some 400-Cessnas.....A Chieftain that I run for someone else averages 160l/hr; the LAME owner wants TiT RoP by 75 degrees - his call.

Before you decide which way to run, you need two obligatory inclusions - GAMIjectors and an all-point engine monitor. Running ANY of these big-bores without seeing what is happening in ALL the cylinders is a mugs game.

"But what if I blow the engine running lean?" Same as if you blow it running rich - unless you can prove poor workmanship or materials on the part of the manufacturer or rebuilder, you will cop the bill (and look at the charts in the handbooks - you stand a much greater chance of blowing an engine running RICH than LEAN). Happily, my two expensive IO-540s have data collected every 6 seconds of operation, so I KNOW what is happening all the time, and CAN prove compliance with POH and Engine Operators Handbook.

BTW, if you don't have an Engine Operators Handbook for the engines you're running - GET ONE!! (Call Hawkers).

(steps down off soapbox, mops fevered brow, stumbles away mumbling about BSFCs, detonation margins, CHTs.......):p

[Dale Harris]

Jamair, I know what you are saying, but we were comparing Full throttle outputs and fuel burn. Ain't no lean of peak operation approved there. BTW, the 160 or 165 Lt/hr was for 1 Chieftain engine............

[1McLay]

Hey Dale

We run our engine at 2450rpm & 42". It is rated 350hp and looking and the figures it gets that at 42" and 2575rpm. (maybe a typo, but doubt it)

Hence the slightly reduced fuel consumption. I agree with Jamair bout the engine data managment. Very helpful, for mointoring all cyclinders, good for picking up fouled plugs blocked injectors etc before pouring on the coals. Mixture is usually full rich in the climb and leaned out during descent and ground ops. However its never LOP in our machine.

And Dale, the last time I flew it (bout 10mins ago) it WAS STILL a C206 with a TIO-540 (STC conversion).:ok:

1Mc

[lineboy_nz]

Don't forget that turbo's are lighter.

[Dale Harris]

Yes, but you did notice I said "unless there are retrofits out there". Of course you would agree that you get less fuel burn, because you are making less horsepower, wouldn't you? It's no misprint, to get 350 horses out of the TIO 540, you pretty much need 2575 and 42" You'd be getting something in the region of about 300 to maybe 310 hp at that rpm. Check the lycoming engine handbook that someone mentioned earlier. It'll show you the hp you are producing. If I can find it i'll have a look at it tonight.

[Capt W E Johns]

Seems to me that the TIO-540 needs a lot of inches and a lot of gas for not many extra horses... I fly a Lycoming IO-540 which is benched at over 300 BHP with around 28" and 2700 RPM, using about 100 LPH.

Is the TIO-540 compression ration much lower without supercharging? (forgive the ignorance, I have only flown a couple of types)

[DirectAnywhere]

Capt. Johns, Compression Ratio doesn't change as it's the ratio of the cylinder volume with the piston at BDC compared to cylinder volume with piston at TDC. Turbocharging itself won't change this basic characteristic of the engine.

[Woomera]

The "new" piston engine Cessnas have Lycoming engines. Textron, Lycoming parent company, bought Cessna from General Dynamics in January 1992.

[Jamair]

Jeeez, I dunno Dale; I ain't any sorta expert at all, but 330lt/hr seems AWFUL rich for a Chieftain........I've never seen more than 220 total flow at takeoff - thats full power, full fine, full rich, at SL. I don't have my Chieftain PoH handy, but next time I'm in the thing I'll look those numbers up.:confused:

[1McLay]

Hi Capt W E Johns

Seems to me that the TIO-540 needs a lot of inches and a lot of gas for not many extra horses... I fly a Lycoming IO-540 which is benched at over 300 BHP with around 28" and 2700 RPM, using about 100 LPH.

Probably to some degree that is quite right but the main advantage is the T engine will continue putting out that power for many thousands of feet in an upwards direction. Basically the turbo charged engine will work as though it is at sea level up to around 20,000ft. Obviously somethin' no N/A engine will ever achieve! :8

regards

1M

[nomorecatering]

Everyone should read John Deakins articles on Engine Operation, better still attend the workshop run by Advanced Pilot Seminars, Jointly run by John Deakin.

[Dale Harris]

Jamair, All references to Lycoming Operator's manual, TIO 540.


Full Rated power, (350 h.p) TIO 540 J series, requires 41 U.S. Gal/Hr. X2 = 82 U.S. Hr. = about 320 L/Hr. I would respectfully suggest if your engine is only using 110 L/Hr, it isn't producing 350 h.p. Remember, we are talking about Takeoff power, we average 155 l/hr block time. Remember guys, the TIO 540 series can be had in many different versions, many producing different rated H.P. They vary from 250 rated h.p to 360 rated h.p. The fuel burn at take off and in cruise will obviously vary accordingly. My figures are for your average everyday Chieftain, with the L/TIO 540 J series. As a check last night, on take off, the a/c I flew indicated 42 gal/hr R/h eng and 40 gal/hr on the L/h. Fits nicely with the average I gave above, although given the OAT and Air pressure, I think they are underboosting slightly.

Direct anywhere,
Compression ratio does vary amongst Turbo and Non Turbo charged engines, even amongst the turbo charged varieties. In the TIO 540 series, they vary from as low as 7.2 to 1 up to 8.5 to 1, depending on the amount of boost allowed. A non turbo charged engine usually has higher compression ratio than a turbo.

Just out of interest, I used to fly a Queenair with the original geared supercharged 540's. IGSO 540's to be exact. Rated H.P. was 380. It achieved that at 3400 R.P.M. Or maybe it was 3200? It's been a while. Anyway it also produced 47 " of boost. Required, If i recall correctly, something in the order of 300 L/hr PER ENGINE at that power. Of course, the engine was probably really producing something closer to 450 or 480 H.P. really, as the supercharger is notoriously H.P. hungry, hence the big rpm and boost/fuel flow numbers.

[DirectAnywhere]

Thanks Dale.

I presume this changing of the compression ratio is a design compromise by the manufacturer.

The act of merely bolting a turbocharger onto an engine won't change the compression ratio unless the manufacturer makes a design decision to change the length of the piston/ length of the con rod/ anything else - to change that ratio though will it?

[Dale Harris]

Yes it is a design compromise, DA, usually based on the detonation margins existing for that engine design. Fuel octane, quality etc all have a part to play, plus ultimate output from the engine. Any time you drop compression ratio, you lose power and efficiency. Manufacturers use different "tricks" to change compression ratios, including piston deck heights, but sometimes they will also vary the combustion chamber size too. Another trick is to use "dished" pistons rather than flat topped ones. All methods vary the combustion space available, at TDC, not the actual cylinder volume in any appreciable way. If you want to vary the cylinder volume you either have to change the bore or the stroke. That's much more expensive!!!!!

Cheers.

Actually, that is a bit simplistic. I am of course referring to the static compression ratio. Turbo or Supercharging does change the dynamic compression ratio, it has to, since you are compressing a bigger volume of mixture. In a dynamic sense, the compression ratio in every engine varies somewhat in practice, according to many variables. Static ratio is what is normally quoted as a comparison. That is of course as you said, the comparison of combustion space with the piston at TDC compared with the cylinder volume at BDC.

[Jamair]

Well, like I said Dale, I ain't any sorta expert at all, so next time I'm in the thing I'll check those numbers. Cheers.