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Old 08-31-2012, 04:17 AM   #1 (permalink)
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Hmm.. hydraulic pulse'n'glide...

I was thinking the other day...

Doing some searches here about hydraulic hybrids, I haven't searched yet for pneumatic hybrids but I imagine things are somewhat similar.

Sole point of a hybrid is using braking energy to accelerate again, not to cruise the car. Several ways to do that.

One advantage of using "pulse and glide" is from what I understand to keep the engine where it is more efficient? Ie - to add energy (increasing speed) while the engine is in a moderate load more efficient state of peak BSFC, then to shut it off completely and coast for a bit, then to restart and accelerate back up again. Almost like a flywheel effect except you are storing energy in the moving car itself. Downsides include other drivers wondering WTF you are doing, higher aerodynamic resistance and exceeding speeding laws at the higher speed you obtain, annoying drivers and needing driving conditions that even allow it.

But why couldn't that be done internally?

I was resuming an old conversation about flywheels in one thread, and another about hit and miss engines in the other thread being a poor way to store energy...

What if a hybrid system were designed that, instead of solely storing energy during braking for acceleration, it stored energy from a pulse of power from the engine?

What if that let you stay a nice slower speed, 50mph or whatever you wanted (or 70mph if you needed to) being able to be used in close in traffic, no annoying other drivers, etc.

What if instead of pulse and glide making the vehicle accelerate and decelerate you simply used the engine on mode to add energy to a battery pack, or pneumatic/hydraulic accumulator, and then shut off the engine, bleeding power back out again to maintain speed, then using the last of pressure to kick the engine back on again into a moderate load condition?

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Old 08-31-2012, 07:50 AM   #2 (permalink)
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My design which is covered by US patent #7677208 is for an in wheel variable displacement hydraulic pump-motor that does exactly what you describe in your post.
It is covered in several threads on this site since I joined in 2008.

The principle is to incorporate pulse and glide into the vehicle. Engine operation is separated from the vehicles speed, allowing the engine to operate in the range of absolutely best efficiency while maintaining a constant vehicle speed.

In wheel drives have an advantage over any other type. The reason is hydraulic drives suffer efficiency losses at higher RPM. Placing the drive in the wheel reduces the RPM. This allows the drive to keep speeds below 1000 RPM where efficiency is highest.

The infinitely variable ratios of the variable displacement drive mean that as pressure drops in the accumulator the precise amount of power may still be applied to the wheels until the pressure has reached the minimum required, at which point the engine starts and replenishes the pressure. This means the stroke position in the drive is constantly changing, as pressure drops the stroke increases. As pressure rises when the engine is running the stroke position decreases. All during the cycle the power applied to the wheels remains constant, providing a constant speed, even though the pressure is constantly changing. You are pulsing the accumulator instead of the vehicle itself, storing energy in the accumulator, versus conventional P&G where energy is stored in the speed of the vehicle itself.

If you search through the thread I have posted here over the last 4 years there is plenty of information. If you have a question please do not hesitate to ask.

regards
Mech

Last edited by user removed; 09-04-2012 at 08:32 PM..
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Old 09-04-2012, 07:23 PM   #3 (permalink)
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Are there any designs we can build them for personal only noncommercial use then to save the earth?

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