11
$\begingroup$

Simple question, and I've always assumed that they are the same thing, but I'd like feedback from someone who knows more than me :)

$\endgroup$
  • $\begingroup$ Definitely not-- important to know when you are adding fuel. I'll let someone else take the honors of making a real answer! $\endgroup$ – quiet flyer Oct 30 at 15:26
  • $\begingroup$ No, just like a turbocharged car is not a jet/turboprop car $\endgroup$ – DeepSpace Oct 30 at 18:32
  • $\begingroup$ You might mind some interest in researching a Turbofan( big commercial airliner engine) vs turboprop(like a turbo fan but there is no outside cover for the main fan) vs a turbojet(fighter jet engine). A turbofan/prop use a jet engine to spin a very big blade to make thrust. A pure turbojet makes thrust just by the action of the jet itself no big propeller in front $\endgroup$ – DatsunZ1 Oct 31 at 15:23
  • $\begingroup$ @DeepSpace it's rather: “no, just like a turbocharged car is not a gas turbine car”. A jet or turboprop car would also have a different means of propulsion, whereas turboprops and turbo-supecharged pistons both have propellers which work essentially in the same way. $\endgroup$ – leftaroundabout Nov 1 at 9:31
38
$\begingroup$

They are both internal combustion engines that have a turbine in their exhaust that is used to power a compressor to pressurize the air before it is used for combustion.

In the turboprop, the turbine also powers the prop. In between the compressor and turbine, the fuel/air mixture is burnt without significant moving parts. Without the turbine and compressor, a turbine engine is essentially a tube with heating element in it.

In a turbocharged piston engine, you have an otherwise normal piston engine which turns the prop. The turbine is in the exhaust from the piston engine and powers the compressor pushing air into the piston engine. The turbine and compressor are not connected to the prop though.

Here they are as diagrams along with some other types of engine.

engine type diagrams

$\endgroup$
  • 2
    $\begingroup$ Could note that "turbosupercharger" and "turbocharger" are often used interchangeably, while "supercharger" is sometimes used to mean "gear-driven supercharger" but really can mean either a gear-driven supercharger or a turbosupercharger (turbocharger). I guess what I'm saying is that the diagram labelled "supercharger" would really be better labelled "gear-driven supercharger". At least is the terminology that is most aligned with the original meaning of these words. Maybe now "supercharger" is universally accepted to mean only the gear-driven variety? Could the basis of another question. $\endgroup$ – quiet flyer Oct 31 at 18:34
  • $\begingroup$ @quietflyer When researching engine stuff for.makimg an Xplane model I have íonly met "supercharchger" to mean the gear-driven one. It was for old engines, though. $\endgroup$ – Vladimir F Oct 31 at 20:17
  • $\begingroup$ @quietflyer I considered adding a note that "turbocharged" is also historically called "turbosupercharged" but the diagram was getting complicated enough as it was. I thought that terminology was effectively dead but if it's still in use somewhere it would make sense to add. $\endgroup$ – smithkm Oct 31 at 20:47
  • $\begingroup$ Probably not a significant issue, see responses to my recently-posted related question. $\endgroup$ – quiet flyer Oct 31 at 20:49
22
$\begingroup$

No, a turboprop is more like a jet engine with a propeller in the front instead of a fan:

enter image description here
Source: Wikimedia

In its simplest form a turboprop consists of an intake, compressor, combustor, turbine, and a propelling nozzle. Air is drawn into the intake and compressed by the compressor.

Many turbo props have a gear box (as shown in the image above, the black part to the left) which drives the prop from the engine.

Whereas a turbo piston is simply a normal piston engine with a turbo charger attached:

enter image description here
Source: BoldMethod

You can learn more about how a turbo piston works on BoldMethod: How a turbocharger system works. The basics is that it uses the exhaust gases from the engine to drive a compressor which increases the pressure (and oxygen content) going into the intake. More oxygen (and fuel) means more power. For turbo-pistons it also means that you can get sea-level performance at altitude.

As far as fuel is concerned, a turboprop runs off of Jet-A (Kerosene) fuels and (most) turbo charged pistons run on av-gas. Some diesel turbo pistons also run off of Jet-A and it is very important that you don't put Jet-A in an av-gas piston or av-gas in a turbo prop.

$\endgroup$
  • $\begingroup$ "Some diesel turbo pistons also run off of Jet-A" -- which diesel turbo pistons don't run on Jet-A? is there another diesel fuel available at airports? $\endgroup$ – Peter Duniho Oct 31 at 0:17
5
$\begingroup$

A turbocharged engine is a common gas engine with pistons

  • The limiting factor on a gas engine is how much air can get into the pistons.
  • It is supercharged - that is, an air pump forces more air into the engine than it would draw naturally. The mechanically driven variety is seen on Mad Max. If you use exhaust flow to spin the pump, it is turbosupercharged.
  • People shorten "turbosupercharge" to "turbocharge".

A turboprop engine is a jet engine. Fullstop.

  • The jet engine makes lots of thrust. They stuck some extra turbine blades in the jet blast, which spin another shaft. That makes it a "turboshaft engine" because it makes rotation instead of thrust. You put something useful on that shaft, like a generator, helicopter rotor, naval screw, air compressor, fan, propfan, or in this case, a prop. That's a turboprop!

The advantage of a jet-based instead of piston-based engine is power-to-weight - after all you have nominally 2 moving parts, the spindle of the jet engine proper and the added turboshaft, and nothing reciprocates.

$\endgroup$
3
$\begingroup$

They are completely different things, a turboprop is similar to a jet engine as it has compressors, the main difference is that there's a shaft that spins a propeller instead of turning a fan.

A turbocharger is device for piston engines, it uses pressure coming from the exhaust manifold of a piston engine to compress air going into the intake manifold. It's the same technology used on car diesel and gasoline engines, and it works the same way. There are vanes that can be adjusted to manage the boost level, on cars these are computer controlled but in many airplanes turbo speeds are have to be manually adjusted by adjusting boost pressure in the exhaust (keyword: wastegate). Recent aero-diesels have modern computer controls though. Turbos on piston aero engines can either be turbochargers, in which case they add extra power to an engine by increasing the compression in the cylinders, or they can be turbo-normalizers, which maintain sea level air pressure to the engine even at higher altitudes.

There are superchargers as well, these are also compressors for piston engines the difference is they use engine power directly to compress the air rather than exhaust pressure.

$\endgroup$
  • 2
    $\begingroup$ I'd like the source for pilot controlled turbo vanes please... turbine housing vanes and wastegate are not the same thing. Both are used for regulating boost pressure, but in a very different way. $\endgroup$ – Jpe61 Oct 30 at 16:37
  • 1
    $\begingroup$ I didn't understand your comment at first, I have edited for clarity. I don't know of any manually controlled vanes, it's manual wastegate control. $\endgroup$ – GdD Oct 30 at 16:47
  • 1
    $\begingroup$ That matches my reality :) $\endgroup$ – Jpe61 Oct 30 at 16:50
  • 1
    $\begingroup$ Probably the only thing today that will! $\endgroup$ – GdD Oct 30 at 16:50
  • $\begingroup$ Well, they are not that completely different things. The turbocharger uses the same principle and has the same function as one spool of a turbine, making a turbocharged engine is kind of a hybrid between reciprocating and turbine engine. $\endgroup$ – Jan Hudec Oct 30 at 22:58
2
$\begingroup$

No, one is https://en.wikipedia.org/wiki/Otto_cycle one is https://en.wikipedia.org/wiki/Brayton_cycle, thermodynamicly extremely different

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.