A novel steam engine with no separate boiler. Yes, you read that right.

[Kaleb]

Not too long ago I stumbled upon a journal article detailing a liquid-piston steam engine which did away with the need for a boiler in the traditional sense. Following this up led me to some patent documents filed by a group of Japanese engineers working for Denso that details the working principle and basic layout of said engine. Here's a link to one of the patent documents if any of you are interested: https://patents.google.com/patent/US6931852B2/en

The basic layout of this engine can be seen in this patent drawing:

Modus operandii: When the piston 14 moves down, the working fluid (assumed to be water) is displaced upwards in tube 11 until it reaches the heated section at 12, at which point the liquid boils, increasing the pressure and pushing the rest of the water down, which in turn pushes the piston upwards. In doing so the water/steam boundary drops to a point where the steam comes into contact with the cooler at 13 which, since it is kept below the boiling point of water, causes it to condense again, reducing the pressure and allowing the piston at 14 to move down again and repeat the cycle.

This additional patent drawing should hopefully make the working principle clearer.

For those of you who didn't know, the term "adiabatic" in this case basically means that, in theory at least, there is no transfer of heat or matter between the engine and its surroundings, that is to say energy is introduced or dissipated solely as mechanical work. In practice however nothing is perfect; there will always be some heat losses etc; but (hopefully) you get the idea.

Even if the principles still seem clear as mud as you read this, you should hopefully be able to see that this is an incredibly simple way of making an engine; which of course made me think "Can I get this to work? One way to find out, let's build it!". I checked the status of the patent, and it seems to have expired as of 2016, so I'm (hopefully) in the clear.

 

[Hopper]

Interesting. Quite similar in principle to a Stirling engine, moving the fluid between hot and cooler areas to cause expansion and contraction. But in this case the fluid instead of being a gas (air) as in a Stirling, it is fluid that boils and increases pressure much more. Will also take much more (latent) heat to make it boil than a Stirling to simply expand it.

I wonder if a model sized example could be made to work using a liquid other than water so not so much heating and coooling was needed to get the liquid to turn to gas and vice-versa? Maybe one of the low-pressure refrigerants, whatever teh modern substitute for R11 is (lol, that's how long since I worked on fridge gear!)

 

[BaronJ]

Hi Guys,

The problem with using water in this scheme is the amount of time it would take to transfer the heat to the water and to remove the heat transferred. All that will happen is that the water will get hotter until it becomes steam, with the attendant danger of explosion, assuming no safety valve.

I think Hopper has the right idea, an easily volatile liquid that turns into a gas at a relatively low temperature causing expansion and can loose its temperature quite quickly.

 

[fcheslop]

Reminds me of the Naptha launches
https://en.wikipedia.org/wiki/Naphtha_launch#Naphtha_launches