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  #1  
Old 02-22-2021, 08:32 PM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
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Default Are you ready for...... Liquid Piston

Here is the latest and greatest......

Let's see how long it takes to power anything of value. Maybe this will be the one.

https://www.youtube.com/watch?v=bfQu8zgpgwg

.
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  #2  
Old 02-22-2021, 09:29 PM
lawnboy lawnboy is offline
 
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I've lost hope for anything new that actually takes off. (pun intended)
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  #3  
Old 02-23-2021, 06:08 AM
PhatRV PhatRV is offline
 
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Location: Buena Park, California
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Quote:
Originally Posted by gasman View Post
Here is the latest and greatest......

Let's see how long it takes to power anything of value. Maybe this will be the one.

https://www.youtube.com/watch?v=bfQu8zgpgwg

.
I've been following the development of this Liquid Piston design for a while. While I can see its utility in powering the smaller UAVs at its current design iteration, anything as large as an RV will require a huge scale up effort which isn't trivial, and swing a big propeller at low RPM will require a gearbox. Due to its natural diminutive size, perhaps they can create a gasoline-electric hybrid propulsion to solve the gearing engineering problem while maintaining the efficiency claimed by the factory. There will be a weight penalty for the gasoline-electric hybrid package but it is probably not as bad as battery powered electric airplane. Just pure conjecture.
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  #4  
Old 02-23-2021, 06:48 AM
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airguy airguy is offline
 
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It's a modified Wankel. I believe we've done that and been there.
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  #5  
Old 02-23-2021, 06:53 AM
BillL BillL is online now
 
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Location: Central IL
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Great for a hybrid electric drone. Us the module to get to altitude then fuel is gone, and eject it for the weight savings. Completely disposable. Perfect for a military project with cubic dollars but a strict mission profile.

Climate change initiatives will kill all military excesses of emissions.

I do say a clever design to address some of the issues if the wankel style rotary engine. This is really no different except valving, and component locations, but still very clever. Not really efficient either, thermally.

Rotaries are too limiting. As soon as it is tooled, then somebody wants more power, and the design is tooling constrained to the dimensions. No stroke or bore tweaks like the piston recip. No valving changes, just so inflexible to application demands.

I designed a wankel style 18 hp from scratch, sourced the components and it ran very well (natural gas), but in the process found why they are so limited in a constantly evolving production environment.
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  #6  
Old 02-23-2021, 08:06 AM
PhatRV PhatRV is offline
 
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The original Wankel design definitely has a lot of mechanical constraints compare to the reciprocating design. I am not sure if the Liquid Piston company put some thought into solving these other than curing the vexing apex oil seal problem by creating a reverse Wankel design. The original rotary also suffered from poor fuel efficiency and some argued the real reason was due to the strict emission standards.
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  #7  
Old 02-23-2021, 08:33 AM
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airguy airguy is offline
 
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Quote:
Originally Posted by PhatRV View Post
The original Wankel design definitely has a lot of mechanical constraints compare to the reciprocating design. I am not sure if the Liquid Piston company put some thought into solving these other than curing the vexing apex oil seal problem by creating a reverse Wankel design. The original rotary also suffered from poor fuel efficiency and some argued the real reason was due to the strict emission standards.
Didn't they also run up against very high EGT and problems with the turbo as a result of the heat?
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #8  
Old 03-04-2021, 03:19 PM
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HAL Pilot HAL Pilot is offline
 
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Quote:
Originally Posted by airguy View Post
Didn't they also run up against very high EGT and problems with the turbo as a result of the heat?
curious

Who is "They" Liquid piston or Mazda?

One of the ways liquid piston claims to save fuel is to shut down 1 of the 3 cylinders per rotation when at cruise, and rotating the location of which cylinder is off to the next cylinder on the second revolution. This results in:

"Cycle-skipping power modulation allows high efficiencies at low power settings while simultaneously cooling the engine’s walls internally and providing partial heat recovery.

Water may be injected to internally cool the engine. Some of this cooling energy is recuperated, as the water turns to steam, increasing the chamber pressure."

I don't know if the water injection is on the "off" cylinder or all of them.

I think the hybrid model would be awesome, but I do not see it anytime soon unless there are some Drone engine developments that are under NDAs at the moment.
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  #9  
Old 02-23-2021, 08:34 AM
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Carl Froehlich Carl Froehlich is offline
 
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Yep - rotary engines can be problematic. I however am thrilled someone is putting money into alternative aviation Diesel engines - beyond a traditional four stroke, heavy diesel variant of a Lycoming or Continental engine, or following the “never really worked before” path of adopting an automotive engine.

Considering back in the day big piston engines all had something along the lines of a planetary reduction gear, we know how to build propeller reduction units - other than belt drive.

Carl
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