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I'm familiar with the wikipedia-standard can/can-annular/annular style combustors, but I've found a design that don't seem to fit into any of these categories, used in a number of engines such as the Turbomeca Makila and Ariel, and General Electric's H-series.

Turbomeca Arriel Cutaway

It looks like an annular design but According to GE, there's no fuel nozzles... I think fuel gets sprayed in through ports on the turbine shaft? Beyond that I haven't been able to find anything, I can't even find a name to refer to it by.

I'd love to know more about this setup, like what it's called and what it's advantages and disadvantages are, i.e. why did Turbomeca/GE's engieers go with this design instead of one of the more common setups?

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2 Answers 2

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This is a typical engine used where space is at a premium, that explains its particular layout.

From left to right we find:

  • An axial compressor with one single stage; this is used as the beginning of the engine since axial compressors are more stable in respect to asymmetries in the input airflow; anyway they give a relatively small jump of pressure; that's why it is followed by
  • A centrifugal compressor which gives a high compression rate in a relatively small space;
  • They are followed by an annular combustion chamber which in this case is "curled up" giving it a "C" shape; this is again done in order to optimise the used space and reduce as much as possible its length; compressed air enters from the left through the holes, mixes up with fuel, ignites and burns towards the right; a second set of holes on the right part of the chamber let "fresh" compressed air in in order to cool down a bit the combustion products before impelling on;
  • The first turbine, which drives the centrifugal compressor;
  • A second turbine follows, driving the axial compressor;
  • And finally the turbine extracting the power delivered to the output shaft of the turboshaft is found, closing the engine setup.
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    $\begingroup$ A very concise and easy to follow description. Thanks! $\endgroup$ Commented Mar 26 at 15:25
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    $\begingroup$ @WayneConrad: thanks 🤗 $\endgroup$
    – sophit
    Commented Mar 26 at 15:47
  • $\begingroup$ That is amazing! What is the typical power output of this jobber? And is there a typical aircraft application you can mention... $\endgroup$ Commented Mar 26 at 15:54
  • $\begingroup$ @ThomasPerry: the Turbomeca Arriel in the picture is used on many helicopters around the world and delivers some 700shp. According to Wikipedia 10'000 of them have been built in 50 years, i.e. 200 per year. $\endgroup$
    – sophit
    Commented Mar 26 at 16:56
  • $\begingroup$ Once again proof that aviation. is the only decent "SE" site. Bravo. $\endgroup$
    – Fattie
    Commented Mar 27 at 12:36
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The combustor appears to bhe the orange part about 1/3 from the left. It is perforated.

Flow exits the blue centrifugal compressor to the left and makes a 90 deg turn into the chamber surrounding the combustor. Flow goes through the holes in the combustor, snakes around, and enters the first stage of the turbine.

On the top of the far side of the combustor, we see a black thing. I think it is either the injector and/or igniter. Likewise, there is a boss on the direct top of the case above the combustor, that looks like an access point for another 'injector'.

If this engine has four injectors, it would appear that one is out of view on the bottom of the engine and one was removed in constructing the cutaway.

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