h a l f b a k e r yBaker Street Irregulars
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If you could build a stirling engine with enough horsepower, it could potentially be a great racecar engine.
The biggest issue with the use of a stirling engine to power a car is the time needed to warm the engine up; in a racecar this would be a non-issue, since the engine could be heated up before
the race starts -- as early as we desire.
We don't even need to make then engine burn fuel to heat itself up for racing -- we can preheat the engine using an external power supply.
The simplest way would be to build into it an electrical resistance heater.
A much cooler way to preheat the engine would be to use an external, removable, electric motor, which would run the engine backwards, forcing the engine to pump heat from the "cold" side of the engine to the "hot" side of the engine.
A secondary issue is changing speeds, but this can be solved with a CVT or IVT transmission.
We might even be able to perform a limited amount of regenerative braking, by forcing the engine to run backwards when we want to slow down.
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Burn moss peat to heat the engine up, and you have a Stirling Moss racecar. |
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Oh, I'm not planning on removing the fuel from the car *entirely*, merely avoiding using fuel to warm up the car's engine -- a task which could require as much as two or three minutes, starting from a cold engine, using fuel alone. |
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Unfortunately, the biggest issue with using a Stirling engine to power a car is NOT the warm up time (which is actually quite short) but the tiny power output. I've built a Stirling, it takes about 10 seconds to warm up but produces enough power to turn a small fan, from an engine weighing the same as a 1HP internal combustion engine.
Also, heat is a poor energy storage medium. |
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[Twizz]: Don't most modern stirlings have a heat-recapture device between the hot and cold regions? |
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Internal combustion engines replaced external combustion engines a century ago for one simple reason.
The horsepower to weight ratio is a lot better.
And race cars tend to be very demanding about a horsepower to weight ratio.........
Stirling engines tend to be used mainly where there is a large temperature differential and there are no side loads seen at the output shaft.
Examples: A NASA probe that has a small nuclear battery for a hot side and 4 degrees above absolute zero in space for a cold side.
A dessert based electric power utility with a lot of parabolic dish area focused on the regenerator's hot plate. |
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//A dessert based electric power utility// That would be totally awesome. |
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Yes, kind of like having your cake and eating it ... |
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As a motorsport, probably not a big crowd-puller - but as an inter-university competition for ligtweight vehicles - similar to the solar-power challenge - it could be very interesting. |
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// Stirling engines tend to be used mainly where […]
there are no side loads seen at the output shaft. // |
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Surely the allowable side load depends only on the
bearings used on the driveshaft, not the type of engine? |
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That would be the logical assumption. |
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Most of these engines have a large flywheel; that's going to side-load any bearing. If it's a plain journal, then that would cause asymmetric wear to the brasses. |
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Not a problem on a NASA probe as outside planetary gravity fields a lot of these forces are absent. |
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Indeed, but the purpose of rotary bearings is to keep the
shaft steady in place and free to rotate regardless of any
side or axial loads within the expected ranges. If they
don't succeed in that, you didn't specify strong enough
bearings. |
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