Habeed
July 19, 2015, 1:31pm
1
I’ve read about sterling engine prototypes using helium as a working fluid and some kind of heat source. Well, a steam engine, water boils, steam is at vastly higher pressure than fluid, the high pressure gas drives the engine, and then is condensed back to water.
You aren’t going to reduce helium’s temperature in the condenser of the engine enough to liquify helium, so how do these engines work?
Grey
July 19, 2015, 1:40pm
2
It’s simply extracting work from the expansion/contraction of the helium gas in the two chambers.
In tha case of a closed cycle engine the fluid never leaves the system in question.
Xema
July 19, 2015, 2:35pm
3
Beyond an external heat source and (often) a piston or two, there’s rather little in common between a Sterling engine and a steam engine.
It’s Stirling. Good info here
Stirling Engine Basics — What is a Stirling Engine?
A Stirling engine is a heat engine that works on the basis of an external applied temperature difference. By maintaining a hot and cold temperature difference the engine is able to run and produce mechanical power. It is different from the Internal Combustion Engine (ICE) in that it is a closed cycle; that is, the working gas is enclosed (sealed) inside the engine. This is in contrast to the ICE in which the working gas (air) is drawn in from the environment, combusted with fuel, and expelled as exhaust. In such an engine valves and timing mechanisms are necessary. But in a Stirling engine, no such components are required. In addition, the Stirling engine is not restricted to the type of fuel used. It is indifferent to the source of heat, which opens up many possibilities, including non-polluting solar energy, or the burning of biomass (wood, husks, ethanol, etc), which are carbon-neutral. Carbon-neutral means they absorb as much carbon dioxide (during their growth - due to photosynthesis) as they emit when burned. This is unlike fossil fuels, which add a net amount of carbon dioxide to the atmosphere when burned.
The basic principle of the Stirling engine is this. The engine is filled (under pressure), with a gas such as air, helium, or hydrogen. This is called the “working gas”. Inside the engine the gas is heated. This increases its pressure and moves pistons as a result. The gas is then cooled, lowering its pressure. It is then heated again, and the cycle repeats. In a real engine this typically happens very fast, on the same order of speed as an ICE. The working gas is shuttled back and forth very quickly inside the engine, between the hot and cold ends, continuously gaining and losing heat and producing power as a result.
LSLGuy
July 19, 2015, 7:23pm
5
ETA:Ninja’d pretty thoroughly. And for once my post was the shorter of the two. :o
It’s a Stirling engine with an “i” in the middle. There’s pretty much never a phase change in the working fluid, so any comparison to a steam engine means it’s time to go read this again Stirling engine - Wikipedia