Clarification
For the purposes of discussion on this site, when we say Heat Engine, we mean converting heat to motion. There are any number of electronic devices operated and/or affected by heat. Several of those convert heat to electrical energy. Heat affects many physical processes.
While the scope of this site is limited to actual moving engines, let us still say the rules are everywhere the same. 100 units of heat will always end up as 100 units of something, whether its heat, electrical, chemical, potential, or even light energy. You get 100 cents from every energy dollar. Its up to you not to spill it, drop it, or let it fly away.
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The two types of Heat Engine
Engine Type Number One: The Vapor expansion engine. Converts heat to work by the formula Work = Volume time pressure. Converts Work to Heat by the same formula, and hence all vapor expansion engines are "reversible", and all produce work at exactly the same rate, 1 unit of work for 1 unit of heat.
Engine Type Number Two: Uhm. Hold on...
Just a minute. I'm thinking... Well, I guess that's enough rambling.
Just making a point. There is only one type of heat engine.
Note: Turbines are also constrained volume, vapor expansion heat engines. All turbines, including those not in heat engines, like water driven, are doing work with the same formula, volume change times pressure. A turbine allows for the volume change to be a continuous flow. Rockets, jets, all expanding vapor engines.
So all those diagrams trying to be "real general", have been futilely waiting for the 2nd type of heat engine, for 200 years since Sadi Carnot first predicted (paraphrased) "All practical heat engines will be vapor expansion engines. Reason being only matter in the vapor state has a significant change in size due to changes in heat." See...
"Reflections", Pg 48 MOTIVE POWER OF HEAT.
Wherever there exists a difference of temperature,
wherever it has been possible for the equilibrium
of the caloric to be re-established,, it is possible
to have also the production of impelling power.
Steam is a means of realizing this power, but it is
not the only one. All substances in nature can
be employed for this purpose,, all are susceptible of
changes of volume, of successive contractions and
dilatations, through the alternation of heat and cold.
All are capable of overcoming in their changes of
volume certain resistances, and of thus developing
the impelling power. A solid body a metallic
bar for example alternately heated and cooled increases
and diminishes in length, and can move
bodies fastened to its ends. A liquid alternately
heated and cooled increases and diminishes in volume,
and can overcome obstacles of greater or less
size, opposed to its dilatation. An aeriform fluid is
susceptible of considerable change of volume by
variations of temperature. If it is enclosed in an
expansible space, such as a cylinder provided with
a piston, it will produce movements of great extent.
Vapors of all substances capable of passing
into a gaseous condition, as of alcohol, of mercury,
of sulphur, etc., may fulfil the same office as vapor
of water. The latter, alternately heated and
cooled, would produce motive power in the shape.
Pg 49
of permanent gases, that is, without ever returning
to a liquid state. Most of these substances
have been proposed, many even have been tried,
although up to this time perhaps without remarkable
success.
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