The rotary steam engine found a niche driving rotary water pumps on early steam fire engines. Such engines were made by Silsby and also Ahrens. These engines were horse-drawn; steam only powered the pump.

Why did it succeed here, and here alone?
The rotary steam engine type used was light, compact, simple and reliable.
A short working life was no drawback- a fire engine spent a very small proportion of its life actually pumping. (In 1937 consultant engineer W E Millington stated that the running time of a London fire engine pump was 5 weeks in a total working life of 15 years)
The high steam consumption was of little interest- the cost of coal must have been a miniscule proportion of the cost of maintaining a fire brigade and turning out to a fire. It is significant that none of the many photos of old steamers show any lagging on the boiler or steam pipes. It was accepted that fire engine boilers had to be driven very hard, with a lot of priming, and that they needed the continuous attention of a skilled and experienced man.

Another possible reason is that if the gear-type rotary engine worked non-expansively- which it certainly appears to do- then there would have been a lot of energy left in the exhaust steam. The exhaust was directed to a blast-pipe in the chimney (just as in a steam loco) to increase the draught. Given the emphasis on raising steam in the shortest possible time, a powerful blast might well have been more important than economy. This notion is backed up by contemporary pictures of steam fire engines in use, with smoke rushing vertically out of the chimney.