[agurk]

What we call a turbocharger today has two turbines in it - one that is spun by the exhaust gasses and a second one that compresses the incoming air. These two turbines are directly connected.

If you look at super chargers they're all some kind of pump driven by the mechanical energy directly from the crank. If this pump was a turbine, then you'd have a crankshaft driven turbine super charger.

So this is half of a modern turbocharger (the compressor) being driven by the crank rather than the exhaust gasses.

[diarrhea]

> What we call a turbocharger today has two turbines in it - one that is spun by the exhaust gasses and a second one that compresses the incoming air. These two turbines are directly connected.

That's incorrect, a turbocharger has one turbine, and its driving counterpart is the impeller. That impeller/compressor is never referred to as a turbine. Turbines can only ever extract work from a fluid.

Superchargers as well as turbochargers also don't have pumps, those are machines for which the working medium is incompressible (water, ...; density is not a function of pressure, in "engineering precision"). If it is compressible, it's a compressor: it affects not only an increase in pressure but also in density.

A fan also works on compressible media but is only supposed to impose some velocity. For this, it necessarily also increases the medium's pressure, but to a low degree, such that (IIRC) changes in density are negligible.

[usrusr]

Well, you can find the term "bike pump" even on newyorktimes.com and that's not about hydraulic brake levers, so there might be some difference between technical language and common usage even in English.

But I'm posting this to say thank you, I was completely unaware of this detail. In my mind, and likely in GP's mind, the term pump was characterized by the piston principle, not by the medium. And I realize now that the "pumps for air" incorrectness is much less common in English than in German (my home language).

Apparently in engineering German the distinction is exactly the same as in English, but it's completely absent from common usage. German never even adopted a verb for high pressure inflation that is not derived from pump. Other than that, the terms pump and Pumpe are extremely similar in English and in German, which is unlikely due to common Germanic roots but because of something much more recent. I suspect nautical terminology which must have been a strong language unifier before navies became a key element of national separation.

[agurk]

A pump moves a fluid and a compressor reduces the volume of a fluid. If your fluid is compressible, such as air, then moving it will entail some compression. This was the GP's point about a fan.

This means there are not two distinct binary categories of pump or compressor that these things can be neatly classified as. This is compounded a little as fluids are often erroneously thought of as only incompressible fluids like water without realising it's a much bigger category.

Due to my brainfart regarding turbines, I assumed the GP had misunderstood the mechanism of action so I used the simpler word pump to explain. It is not incorrect to describe the action of a turbocharger as pumping more air into the cylinder, especially in my native dialect of English.

[diarrhea]

Interesting!

Agurk has a point as well.

All I know and was saying that in my field (engineering thermodynamics... in some sense the field on this topic), people feel very strongly about "compressor -> compressible fluid" and "pump -> incompressible fluid" (and the "fan" stuff).

[agurk]

You're right I did misspeak about the definition of a impeller/turbine.

Never is a strong word though and there are such things as turbine pumps which are not true turbines[0]. As far as I can tell they've never been used for engine applications.

Regarding pumps they operate on a fluid, of which air is definitely classed as. [1]

[0] https://www.globalspec.com/learnmore/flow_transfer_control/p...

[1] https://en.m.wikipedia.org/wiki/Pump