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Old 12-09-2010, 10:59 AM   #201 (permalink)
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I think we are on the same page Marcus

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Old 12-09-2010, 12:21 PM   #202 (permalink)
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I should've mentioned I do like hybrids, only I like the energy density, "cleanness", and braking regeneration of efficient hydraulics...
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Old 12-09-2010, 02:17 PM   #203 (permalink)
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If you have to brake, hydraulic looks like a good option.

For xmitting power from the engine, there are still many situations where direct drive, and neutral drive, from the engine is substantially better, IMHO.

Though perhaps a hydraulic transformer would be a good fit for a downstream Rankine cycle application, as that will need some "impedance matching" almost constantly, and the series losses will be less (assuming the power recovery from the downstream Rankine cycle is less than the engine)
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Old 12-09-2010, 03:19 PM   #204 (permalink)
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I think we are on the same page, although your book may be "the fundamentals of engineering principles" where mine might be "how to draw funny cartoons".

I don't think series hydraulics have the efficiencies for good highway mpg's. But I see some advantages in brake regen with a parallel hybrid set-up, mostly in being able to undersize (more) the engine. I think there would be very few places where it would make sense to use an ice to charge a hydraulic system to propel a car. Especially if the driver were a hyper-miler type.
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Old 12-09-2010, 04:32 PM   #205 (permalink)
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the other nice thing about onboard hydraulic recovery from the exhaust/brakes, is you can feel less guilty about power steering (and it should work for a looong time with the engine off) Might as well power the brakes w/it too(if/when necessary). I'll stop short of mentioning active suspension But a hydraulic starter and next to no battery might be interesting too.
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Old 12-09-2010, 05:19 PM   #206 (permalink)
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get this,
how about a valve/lever so you can use the clutch and brake pedals to pump up the hydraulic reservoir in an "emergency", or at a stoplight?
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Old 12-09-2010, 07:14 PM   #207 (permalink)
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You may have missed when I said there could be 3 steps to the cogeneration:

Gas turbines making electricity
Heat recovery makes steam to drive turbines to make more electricity
Then use the low grade heat for heating or cooling buildings.

In a car, the engine could turn a generator to make electricity
Heat recovery makes steam to drive a small turbine to make more electricity
Then use the low grade heat for heating when needed.

So, a plug-in serial hybrid, with a cogeneration unit to charge the batteries and heat the car when needed.

The engine could spin the armature, and the steam turbine could spin the stator in the opposite direction, so there would only need to be one generator.
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Old 12-09-2010, 07:22 PM   #208 (permalink)
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serial bad, plug in bad (except in a cost per mile analysis)
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Old 12-09-2010, 07:29 PM   #209 (permalink)
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Hi,

Quote:
Originally Posted by dcb View Post
serial bad, plug in bad (except in a cost per mile analysis)
Why do you say that?

How would you make better use cogeneration in a conventional car or parallel hybrid?
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Old 12-09-2010, 08:22 PM   #210 (permalink)
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I should just get my own thread. But for here mech added some links to a hydraulic hybrid that was %83 efficient in series mode (not including the accumulator). If you have a right sized engine (including what you recover downstream plus some minimal safety margin) then it should be pretty close to bsfc anyway. I expect series electric to be similiar to worse (90% * 90%), but you are leaving about 18% peak efficiency on the table.

With parallel, you can still add or remove from the accumulator to tweak the engine load if it actually nets a gain when the stored power is reused, or if you just need a little more power. But it allows for a direct drive option as well.

If you are trying to make something idiot proof, firstly good luck, secondly it will always be a compromise with what is really achievable. Some things computers are good at, i.e. the timing demands and lack of drastic changes in the combustion chamber between strokes, but some things require intelligence, coordination, predictive skills, superb sensory awareness, experience, and even values, to navigate most efficiently, i.e. driving.

Series is also a way to "automate away" those higher level decisions and dilute our expectations for drivers(and engineers), at the cost of significant efficiency, when the number 1 cost effective (and probably most effective period) mod here is "Adjust the nut behind the wheel".

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