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-   -   Are you ready for...... Liquid Piston (https://vansairforce.net/community/showthread.php?t=192633)

gasman 02-22-2021 08:32 PM

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

.

lawnboy 02-22-2021 09:29 PM

I've lost hope for anything new that actually takes off. (pun intended)

PhatRV 02-23-2021 06:08 AM

Quote:

Originally Posted by gasman (Post 1505342)
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.

airguy 02-23-2021 06:48 AM

It's a modified Wankel. I believe we've done that and been there.

BillL 02-23-2021 06:53 AM

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.

PhatRV 02-23-2021 08:06 AM

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.

airguy 02-23-2021 08:33 AM

Quote:

Originally Posted by PhatRV (Post 1505417)
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?

Carl Froehlich 02-23-2021 08:34 AM

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

HAL Pilot 03-04-2021 03:19 PM

Quote:

Originally Posted by airguy (Post 1505427)
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.

airguy 03-04-2021 03:49 PM

The high EGT and turbo problems I'm thinking of were on Mazdas, but the problem, as it was described at the time, was basically a product of the Wankel design. Now that was on gasoline - diesel will burn a lot cooler.


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