Supercharging, Turbocharging, Turbo-Supercharging

"ttyymmnn" (ttyymmnn) 08/27/2018 at 11:57 • Filed to: planelopnik

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Help me understand this, Oppo.

I’ve spent much of the morning reading about this topic as it pertains to aircraft engines, and I think I’m close to understanding the basic concepts of what the different terms mean. This is what I’ve got, and I’d appreciate some correction if I’m wrong.

Supercharging: This is a general term that refers to compressed air being forced into the engine to increase manifold pressure and improve performance at high altitude. Supercharging is achieved with a mechanical turbine that is driven by the engine itself.

Turbocharging: The turbocharger is basically a supercharger that is driven by engine exhaust gases rather than directly by the engine. Exhaust gases spin a turbine which takes outside air and compresses it. The air is then cooled by an intercooler before being forced into the engine. The main benefit is that you can use a waste gate to control the amount of supercharging that is taking place. The drawback is that it requires lots of ducting which takes up a lot of space.

Turbo-supercharging: Basically the same thing as turbocharging, but just a different name for the same process. It’s supercharging using a turbine. However, there may be a combination of turbocharging and mechanical supercharging going on at the same time.

I’m going to the grocery store, and will be back in an hour or so. Thanks in advance!

DipodomysDeserti > ttyymmnn 08/27/2018 at 12:02

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Yeah, that’s pretty much it.

RamblinRover Luxury-Yacht > ttyymmnn 08/27/2018 at 12:02

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http://rwebs.net/avhistory/opsman/geturbo/geturbo.htm

Some reading, from 1943.

RamblinRover Luxury-Yacht > ttyymmnn 08/27/2018 at 12:05

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Related to my link, the aeromotive lexical use of turbo-supercharger in GE applications was simply a turbo, but often was seemingly paired with a conventional supercharger, so referring to the engine as being supercharged with the turbo referred to as the turbo-supercharger to avoid confusion... or something like that.

HammerheadFistpunch > ttyymmnn 08/27/2018 at 12:06

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If I remember Turbo-Supercharger was just another name for tur bocharging.

Everything else looks right.  Then there was compounding, which was another form of madness.  Turbocharging but not to compress air, to recover waste heat energy via a turbine to mechanically add HP back to the shaft via gearing.  

Aremmes > ttyymmnn 08/27/2018 at 12:07

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You’ve nailed it. Combining a turbo and a supercharger is usually called twincharging , and was pretty common with Detroit two-stroke engines.

KingT- 60% of the time, it works every time > ttyymmnn 08/27/2018 at 12:07

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Pretty much. Some additional resources to understand the nuances better.

This very cool animated infographic:

https://animagraffs.com/supercharger-vs-turbo/

Engineering Explained Playlist- 20 videos:

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Also related, Volvo’s T6 2.0 engine is Turbocharged AND Supercharged.

whoarder is tellurium > ttyymmnn 08/27/2018 at 12:11

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Just to note:

All types of supercharging/turbocharging can be intercooled in some way for higher efficiency and power.

The two major types of charge air cooling:

Air-to-Air and Air-to-Water

Water/methanol injection can be used to cool intake charge temps as well. (Just as it was used in the past on turbojets/low bypass turbofans)

My bird IS the word > ttyymmnn 08/27/2018 at 12:15

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Not sure how it pertains to airplanes, but typically whennit is both turbocharged and suprrcharged it is called twincharging in cars.

Long_Voyager, Now With More Caravanny Goodness > whoarder is tellurium 08/27/2018 at 12:20

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They can also all be wastegated to control boost.

Long_Voyager, Now With More Caravanny Goodness > HammerheadFistpunch 08/27/2018 at 12:21

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Turbo-Supercharger?:

404 - User No Longer Available > ttyymmnn 08/27/2018 at 12:28

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AFAIK the other downside of Turbos is that it’s also affected by altitude due to atmospheric pressure.

Also Lancia has an engine that combines supercharging AND turbocharging... not sure if that can be called turbo-supercharged.

https://www.roadandtrack.com/car-culture/classic-cars/videos/a29930/lancia-delta-s4-petrolicious/

and 100 more > HammerheadFistpunch 08/27/2018 at 12:30

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This is   how I have come to understand it.

ESsentially, what we call turbo charging today was originally referred to as turbo-super charging, as mechanically-forced induction was around long before the concept of using exhaust-driven forced induction. 

Cé hé sin > ttyymmnn 08/27/2018 at 12:36

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This can get quite complicated. As you said, supercharging involves blowing air into the engine so as to have a gr eater quantity than would be available with normal aspiration and turbocharging (originally turbosupercharging) involves using otherwise waste energy in the exhaust gases to do the blowing. So a turbo is a kind of supercharger but not vice versa.

However a turbo can be driven mechanically. Two stroke diesels can’t operate efficiently without having air blown in so they have a difficulty starting in that if fitted with a turbo they need the turbo to blow sufficiently but at the same time the turbo won’t blow without enough exhaust pressure which isn’t available without the engine actually running. This conundrum is resolved by spinning the turbo mechanically until the engine is running. Just to add some semantics, a two stroke diesel isn’t usually supercharged in the usual sense in that air isn’t blown in under pressure but rather is an approximation of the amount that would be available to a normally aspirated engine.

user314 > ttyymmnn 08/27/2018 at 12:37

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Cé hé sin > 404 - User No Longer Available 08/27/2018 at 12:37

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As did VW, for the Golf twincharge. It wasn’t a success.

HammerheadFistpunch > and 100 more 08/27/2018 at 12:38

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yes.  Thats my understanding too.

Cé hé sin > HammerheadFistpunch 08/27/2018 at 12:40

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You can still get turbocompund engines of course. Merc and Scania use them in trucks, and then there’s F1 with its KERS systems.

HammerheadFistpunch > Cé hé sin 08/27/2018 at 12:41

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Yes, it still exists but its pretty rare. I love it, Its stupid but so cool at the same time.

and 100 more > HammerheadFistpunch 08/27/2018 at 12:44

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Sorry, I was agreeing with you, but the way I worded it sounded like I was correcting you. I see that   now, my apologies. 

HammerheadFistpunch > and 100 more 08/27/2018 at 12:47

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Nah I got your meaning, were all good.

Chariotoflove > ttyymmnn 08/27/2018 at 13:15

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Here you go. You’re welcome.

ttyymmnn > Chariotoflove 08/27/2018 at 13:21

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Thanks. This clears everything up. I should have just asked you first and not wasted all that time reading the Internet. 

ttyymmnn > Cé hé sin 08/27/2018 at 13:24

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So a turbo is a kind of supercharger but not vice versa.

Right, as I said above. All turbochargers are superchargers, but not all superchargers are turbochargers. There’s a Venn diagram to be made.  I’m going to write about an aircraft that used the Allis on V-1710, which led me down this rabbit hole of finally making myself understand the terminology.

ttyymmnn > My bird IS the word 08/27/2018 at 13:25

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I have not come across “twin charging” in my reading as it pertains to aircraft. At least not yet. But there are definitely instances of both being used simultaneously. 

ateamfan42 > ttyymmnn 08/27/2018 at 13:25

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The main benefit is that you can use a waste gate to control the amount of supercharging that is taking place.

I would disagree.  The main benefit of turbocharging is that the energy used to spin the impeller (and therefore the compressor) is thermal and kinetic energy in the exhaust that would tend to just be waste otherwise.  A (conventional) supercharger is a direct load on the motor (like any other accessory), whereas a turbo tends to be a more efficient method of compressing the intake air.

ttyymmnn > KingT- 60% of the time, it works every time 08/27/2018 at 13:26

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This was always one of my favorites.

ttyymmnn > RamblinRover Luxury-Yacht 08/27/2018 at 13:33

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In my reading this morning, I came across the name Sanford Alexander Moss , who worked for GE and won the Collier trophy for his work with the supercharger. So it is perhaps a GE term, and one that stuck with the device that he designed. All of this started because I am beginning to work on what was supposed to be a short piece about a forgotten aircraft. But it’s always important for me to understand what I’m writing about rather than just arranging facts. Virtually every article about a WWII aircraft has some mention of super/turbo/turbo-charging, so it was high time I got my head around it.

Thanks for the link. It’s a long read, but should be worth my time.

Chariotoflove > ttyymmnn 08/27/2018 at 13:34

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I also found this article on the history of the turboencabulator. I know you’re a tech history buff .

ttyymmnn > ateamfan42 08/27/2018 at 13:35

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Right, and perhaps I wasn’t clear in my thinking or writing, and my understanding is, obviously, limited. Somewhere I read about how a mechanical (conventional)  supercharger is beholden to engine RPM, whereas the amount of boost from the turbocharger can be regulated with the waste gate. Perhaps that is an oversimplification. I still have more reading to do.

ttyymmnn > Chariotoflove 08/27/2018 at 13:49

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Be sure to watch it all the way through. The first half is Bud Haggert reviving his original performance. 

RamblinRover Luxury-Yacht > ttyymmnn 08/27/2018 at 13:51

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In fairness to the GE crew, turbo-supercharger is more descriptive. It’s only ubiquitous modern use that has made “turbocharger” a not-silly word. It “super-charges” with air (it provides a charge in excess of natural aspiration), and it’s turbine-driven; there’s a little ambiguity in “turbocharger” whether one is charging a turbine or charging *with* a turbine...

Most correctly, of course, turbine is the correct word only for the outflowing side, and the other side is an impeller or compressor or...

kanadanmajava1 > whoarder is tellurium 08/27/2018 at 13:57

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The intercooler term is wrongly used nearly always. Those that we know as intercoolers are actually aftercoolers.

An aftercooler is a charge air cooler that is located between the compressor and the engine. An intercooler is a charge air cooler that is located between two compressors. So a n intercooler cannot exist unless an engine has at least two compressors. I n a v e r y s pecial case a single turbocharger could have se veral compressors.

One truck brand has used the term aftercooler. B u t e v e n t h e S i s u g u y s d i d n ’ t r e a l l y u n d e r s t a n d w h a t t h e t e r m a c t u a l l y m e a n s . M a y b e t h e e n g i n e e r s d i d b u t t h e m a r k e t i n g g u y s d i d n ’ t . Their engine did have the aftercooler c o r r e c t l y positioned between the compressor and the engine but they were trying to emphasis that the charge air cooler was integrated in their intake manifold.

So the production r o a d vehicle s to actually have an intercooler are very rare. T he first example is Lancia Delta S4 that had a turbocharger and a supercharger accompanied b y two charge air coolers. A b i t o v e r 200 of these were made.

Maybe I’m tired but I cannot remember any other production cars to have an intercooler. Nissan March Super-Turbo and VW’s Twincharger TSI engine did have similar set of turbo-/superchargers but neither had an intercooler. M a y b e s o m e m odern diesel engine might have one.

M a n y p i s t o n e ngined aircraft had these o f c o u r s e .

KingT- 60% of the time, it works every time > Chariotoflove 08/27/2018 at 14:00

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I knew someone would post this

ttyymmnn > RamblinRover Luxury-Yacht 08/27/2018 at 14:08

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As I said to Cé Hé Sin, “A ll turbochargers are superchargers, but not all superchargers are turbochargers.” And now I know that turbo-superchargers is just a more specific name for a device that supercharges with an exhaust-driven  turbine.

ateamfan42 > ttyymmnn 08/27/2018 at 14:08

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Somewhere I read about how a mechanical (conventional) supercharger is beholden to engine RPM, whereas the amount of boost from the turbocharger can be regulated with the waste gate.

Supercharger speeds are tied to engine speed, but that ratio can be adjusted with gearing on the compressor drive. Some compressors use a planetary gear set so that the compressor will “spool up” at lower rpm (like a small turbo), and then use valving to control boost at a set level. As a contrast, s etups with a linear boost curve that rises with RPM are sometimes preferred by autocrossers and road racers that want a throttle response more like a naturally aspirated engine.

ttyymmnn > ateamfan42 08/27/2018 at 14:09

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Thanks!

If only EssExTee could be so grossly incandescent > ttyymmnn 08/27/2018 at 14:30

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With superchargers, the boost doesn’t scale directly with revs so you can actually lose top end power. Higher revs means more mechanical drag on the engine and reduced supercharger efficiency. They’re mostly used to help low range power as a result.

Turbos are the opposite, because their output feeds back into itself. Higher boost means higher exhaust pressure means even higher boost. Turbos are mostly used for mid and top end power bumps, although they can be set up to work with low revs.

It is possible to have both a turbocharger and supercharger on an engine.

ttyymmnn > If only EssExTee could be so grossly incandescent 08/27/2018 at 14:51

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Something I came across in my reading as it pertains to aircraft is that turbo-superchargers were best with high-altitude aircraft like fighters and bombers, while superchargers gave their greatest benefit at middle altitudes. 

Chariotoflove > ttyymmnn 08/27/2018 at 14:56

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Oh yeah, that one’s great too.

“For the purposes of obscurity...”  LOL

Chariotoflove > KingT- 60% of the time, it works every time 08/27/2018 at 14:56

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I used it for something else last week, but I couldn’t resist.

If only EssExTee could be so grossly incandescent > ttyymmnn 08/27/2018 at 15:03

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Makes sense, I guess, because of the compounding boost of a turbo. You can get better intake pressure in the thin air. At high altitude the fuel economy penalty of a supercharger might outweigh the performance gain.

Rusty Vandura - www.tinyurl.com/keepoppo > ttyymmnn 08/27/2018 at 15:58

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You forgot turbonormalizing...

ttyymmnn > Rusty Vandura - www.tinyurl.com/keepoppo 08/27/2018 at 16:00

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??

I like cars: Jim Spanfeller is one ugly motherfucker > ttyymmnn 08/27/2018 at 17:08

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Turbos and Superchargers are both forced induction. SCs work with a pulley from or a direct mount to an output shaft from the engine. Air is forced into the engine at greater pressure than atmospheric pressure by means of some sort of turbine or airscrew. There are multiple ways of executing this. Turbochargers perform the same forced induction with a turbine spun by exhaust gasses. The air that is forced in comes from the atmosphere in either mechanism. Both have benefits, but turbos are generally wider used because they hav e grea ter benefits at high revs, where more exhaust gasses are produced.

Sgt Jmack > HammerheadFistpunch 08/27/2018 at 17:13

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On certain military vehicles, as well as a small number of other vehicles , there is a supercharger and a turbocharger on the engines.

WilliamsSW > ttyymmnn 08/27/2018 at 18:00

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Hehe that’s actually a thing, but it’s really just a turbocharger - managed a bit differently to maintain manifold pressure at altitude (as opposed to increasing manifold pressure).

Rusty Vandura - www.tinyurl.com/keepoppo > ttyymmnn 08/27/2018 at 18:27

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Using a turbocharger to make the engine perform at altitude as though it were really at sea level was how I had it explained to me, applied to a general aviation piston engine, like maybe Uncle Don’s Piper IO-540.

Chan - Mid-engine with cabin fever > ttyymmnn 08/27/2018 at 18:38

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But what is a Hypercharger?

Chan - Mid-engine with cabin fever > If only EssExTee could be so grossly incandescent 08/27/2018 at 18:39

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Turbochargers are wildly inefficient.  They produce VERY poor noise-per-litre.

BoxerFanatic, troublesome iconoclast. > ttyymmnn 08/27/2018 at 18:50

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You are largely correct.

Supercharging, or using a supercharger, is compressing intake air via an engine driven compressor. Has nothing to do with the exhaust, and the rate of compression is tied to engine RPMs.

Turbocharging, or using a turbine-driven supercharger, is compressing intake air via a compressor driven by an exhaust gas turbine, that uses exhaust flow and thermal energy to create pressure differential, and that pressure di fferential at the turbine inlet vs. the turbine outlet, spins said turbine as exhaust rushes to try to equalize, basically go from high pressure to low pressure. This helps utilize some of the waste heat in the exhaust, to generate intake pressure, which in turn generates power in the engine.

Turbo-Supercharging actually is different than turbocharging, it is the combination of supercharging with kinetic turbine compounding.

Turbo- Supercharging, in cases like the P38 Lightning aircraft, starts with a supercharged engine, driving the compressor via power taken off the crankshaft to increase dynamic compression in the engine. It then adds a different style of turbine to the engine’s exhaust system, typically called a blow-down turbine. The blow-down turbine is less dependent on pressure, more dependent on gas flow through the turbine, and creates less exhaust back pressure. It typically is used on engines like aircraft, that are typically high-RPM constant use, and relatively steady-state... not a lot of throttle variability, and idling is not generally used in flight. this recovers a bit of pressure and thermal energy, but mostly flow-based kinetic energy in the exhaust to spin the turbine, which turns a gear-set that mixes that kinetic energy back into the crankshaft of the engine, to add that waste energy back into the overall power output, and offset the power draw of the supercharger compressor, and sends that power to the airscrew, or whatever drive or thrust device is being used for propulsion or energy transfer.

Essentially the engine is the center section between the turbine and the compressor, both in an airflow sense, and in a kinetic sense, where turbocharging only places the engine between the compressor and the turbine in an airflow sense, and the kinetic rotation is independent of the engine’s crankshaft.

Turbine-compounding didn’t last long, because it was a short step from that to removal of the piston engine, in favor of a fuel combustor stage between the compressor and the turbine , and then you have a first-generation turbojet, without needing the pistons, rods, valvetrain, and such.

But a few piston warbirds used it, and some other applications have used it for power efficiency and recovery of as much energy as feasible for use... but it does add complexity.

Some have suggested turbo-supercharging, or just turbine-compounding with rotary engines for super- light and experimental personal aircraft, where jet engines, even micro turbines might be too expensive, hot, and less fuel-inefficient at low-altitudes to work as well as a turbo-supercharged wankel rotary at 9000 RPMs, rather than a jet-engine’s 40,000 RPMs.

I could see using twin-charging (a small 1st-stage supercharger to produce initial pressure and anti-lag intake airflow , supplemented by a larger sequential turbocharger, not turbine-compounding), or turbine-compounding on a Wankel or LiquidPiston rotary (if they ever go to production) to create a compact, and power-efficient ICE section for a parallel-series hybrid drive... where the ICE section never has to idle, or lug the vehicle around in stop-and-go traffic with low engine RPMS and low oil pressure under high torque demand, because electric traction motors would take care of that, while the power efficient ICE would act as a compact but high-output generator, and a high-speed cruising direct-kinetic-drive unit, bypassing inefficient and thermally damaging high-current electrical demand.

ttyymmnn > WilliamsSW 08/27/2018 at 19:09

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Makes sense. I had just not come across the term.

ttyymmnn > Rusty Vandura - www.tinyurl.com/keepoppo 08/27/2018 at 19:09

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Makes sense. I had just not come across the term.

WilliamsSW > ttyymmnn 08/27/2018 at 19:16

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It’s somewhat common in high performance GA aircraft - piston singles and twins. Not something the military has used, as far as I know.

As OC said, it’s using a turbo to *maintain* sea level manifold pressure (and power) at higher altitudes.  Usually uses an automated wastegate to limit manifold pressure - in theory reducing reliability/heat issues from boosting pressure, and reducing pilot workload (when there’s an automated wastegate).  

WilliamsSW > ttyymmnn 08/27/2018 at 19:50

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Hmmm, now I’m wondering what aircraft... have a guess but I’ll save it. Looking forward to the writeup!

ttyymmnn > BoxerFanatic, troublesome iconoclast. 08/27/2018 at 21:37

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This is a great explanation, and I thank you for all the words. There are still some bits that I don’t understand fully, mostly a matter of terminology. But I’ll read it a couple more times when it’s quiet around the house.

I was led down this rabbit hole because I’m getting ready to write a short piece about a mostly forgotten Curtiss fighter that was an early application of the Allison V-1710 (which was later used in the P-38). But I can’t really talk about the airplane unless I talk a little bit about the engine, because the airplane was specifically built to fly that particular engine, and the fate of the aircraft was tied to the successes and failures of the engine. Even though I’m not much of a gearhead, it’s not enough for me  to simply say, for example, “the engine was underpowered” without understanding why it was underpowered. And the story of the Allison V-12 itself is a saga of superchargers and turbochargers and turbo-superchargers that all comes down to the Allison getting a bad rap when compared to the remarkable Merlin. And I haven’t even started to figure out why the Merlin was so much better.

Thanks again.

ttyymmnn > WilliamsSW 08/27/2018 at 21:41

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This is what I had to say to BoxerFanatic , who gave me a very good primer on all of this that I will have to read a couple more times.

I was led down this rabbit hole because I’m getting ready to write a short piece about a mostly forgotten Curtiss fighter that was an early application of the Allison V-1710 (which was later used in the P-38). But I can’t really talk about the airplane unless I talk a little bit about the engine, because the airplane was specifically built to fly that particular engine, and the fate of the aircraft was tied to the successes and failures of the engine. Even though I’m not much of a gearhead, it’s not enough for me to simply say, for example, “the engine was underpowered” without understanding why it was underpowered. And the story of the Allison V-12 itself is a saga of superchargers and turbochargers and turbo-superchargers that all comes down to the Allison getting a bad rap when compared to the remarkable Merlin. And I haven’t even started to figure out why the Merlin was so much better.

So I won’t give anything away, but there should be enough clues to figure it out for yourself if you want to do a little detective work. I hoped to write today, but spent all my free time reading about superchargers. I’m hoping to have something by Thursday.

WilliamsSW > ttyymmnn 08/27/2018 at 21:57

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Hehe - I missed the Curtiss reference, but I think I’m right. Mostly becaus e I believe you’ve already written about most of the other oddball aircraft that used the V-1710.

ttyymmnn > WilliamsSW 08/27/2018 at 22:05

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Actually, I don’t think I have! I haven’t written for  my “Planes that you (probably) haven’t heard of” series in a long time. I’m having enough trouble keeping up with my TDIAH series and also getting my chores done. But once I get my head around the engine stuff and do a little more reading, this one should come out pretty quickly. I hope.

WilliamsSW > ttyymmnn 08/27/2018 at 22:15

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Maybe I’m wrong then - but my guess happened to be (I think) the first Curtiss aircraft to use the engine.

Either way, I look forward to it! 

BoxerFanatic, troublesome iconoclast. > ttyymmnn 08/27/2018 at 22:35

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I have to lead with this... I was incorrect, after looking back at the P38 specifications, It’s Turbo-Superchargers, were actually not turbine-compounded and supercharged .

The P38's Allison engines were what we describe as “turbocharged”, they were called turbo-superchargers, because turbochargers were still being referred to that way, a “ turbine-driven supercharger.”

Turbine-compounded, aero engines, and other types of engines were rare, such as the Napier Nomad, and the Wright R-3350 radial turbine compounded engine, and a Russian Dobryn in VD-4K. Detroit Diesel has a turbine-compounded DD15 engine for trucking.

There is also the concept of an internal vs. external supercharger, which solely means that an internal supercharger draws air and fuel through the carburetor, and pressurizes the intake manifold, and is plumbed between the two, which can compensate for air pressure at altitude, but can also pre-detonate. Any intercooler also has to be within the intake tract.

An External supercharger intakes ambient air, and discharges pressurized air through an optional intercooler, and a sealed carburetor, and intake manifold. Most superchargers and turbochargers that are commonly used, are considered external, and not plumbed “ behind” the carburetor or air-metering device, between that and the intake port of the cylinder head.

The P38 used big pancake-style external turbochargers that sat exposed through the top of th engine cowling on the boom fuselages, with the turbocharger center axle arranged vertically, as an ‘ external’ compressor.

I was just reading, supposedly some of the early models had some problems with intake air temperature through the carburetor, especially above 50 degrees celsius. There were various attempts, and a redesign of the intercoolers to keep those intake temperatures in check, and maintain maximum power and reliability.

http://www.wwiiaircraftperformance.org/p-38/p-38-wayne.html

ttyymmnn > BoxerFanatic, troublesome iconoclast. 08/27/2018 at 23:27

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This is an excellent read, but I’ll have to finish it tomorrow. Thanks for the link.

BoxerFanatic, troublesome iconoclast. > ttyymmnn 08/27/2018 at 23:39

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Certainly.

I enjoy reading about that sort of thing, too, and it usually takes a couple of passes to really get the details straight.

Chan - Mid-engine with cabin fever > HammerheadFistpunch 08/28/2018 at 13:32

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Yep, this makes perfect sense. I n the original intent of the word, “Supercharging” was just a buzz word for forced induction. Before the idea to use a turbine and exhaust pressure to drive the intake, there was just gear/belt-driven supercharging for 20-3 0 years.

( The exhaust-driven turbine was patented in 1905, according to Wiki. )