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“Inside-out Wankel” rotary engine delivers 5X the power of a diesel

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Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#81

Post by 93po »

seabird wrote: post #42
93po wrote: post #30

Earlier quoted context omitted.

A Traxxas 5407 TRX 3.3 engine used in RC cars makes 1.42 horsepower, weighs 305 grams, and fits in the palm of your hand. This is 1hp per 0.46 pounds of engine weight, nearly three times better than the camry engine. Granted an RC engine runs on a mixture of fuel and nitromethane, and doesn't have any reasonable durability compare to a Camry engine. But it also only costs $200.

You can't just make the Traxxas 18x bigger and get linear performance improvement. Trying to compare power/weight between engines with radically different weight constraints is silly.

Ok, a Kawasaki H2R engine makes 326 horsepower and weighs about 160 pounds running regular fuel. That's almost identical to the Traxxas - 1hp for 0.49 pounds.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#82

Post by jabl »

himinlomax wrote: post #13
Gordonjcp wrote: post #9

Earlier quoted context omitted.

They're not great, at all. They have very few moving parts and they are very smooth because there are no reciprocating parts. Other than that, they have emissions like 2-stroke engines because of the incomplete combustion and we have never been able to devise any kind of material to make the apex and side seals last anything like as long as piston rings. Piston engines are a terrible way to power vehicles, but everyt…

Wankel engines are great in one respect, power density. But they have terrible reliability and fuel efficiency. Turbine engines also have great power density and terrible fuel efficiency, but they are very reliable. Diesel engines are reliable and fuel efficient but heavy. This one appears to have improved reliability and fuel efficiency over the Wankel without sacrificing power density.

Large turbines running at close to rated power actually have pretty good efficiency. Turbines are bad at scaling down to smaller sizes due to e.g. boundary layer friction, and also part load efficiency is poor. Recuperators help somewhat, though still not nearly as good as a piston engine.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#83

Post by codeflo »

causi wrote: post #14

Ok, so they're "shooting for" a performance of 1hp per 1.57 lbs of engine weight. A Toyota Camry engine produces 1hp for every 1.41 lbs of engine weight. It produces 1ft-lb of torque for every 1.94 pounds of engine weight, compared to 1.58 for the Camry. How is this revolutionary motor being outdone by a mid-range sedan engine?

I know this is off-topic, but I'm curious. I always had the impression that even in the US, standard units are used for engineering. Reading about "ft-lb" makes me think I was wrong (and my head hurt, tbh). Do you really compute stuff like torque in imperial units? Don't you need weird factors in every formula to make that work?

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#84

Post by m3047 »

elihu wrote: post #78

Kind of weird article that doesn't talk about either the main benefits or design hurdles. The advantage of the LiquidPiston design is that at the time of ignition, the combustion chamber is a roughly round shape, as opposed to a traditional rotary where it's a long crescent. This should theoretically improve the emissions and fuel economy to be more like piston engines. I don't think Liquid Piston was talking about a…

2 stroke has poor unburned emissions because of mix flow-through when ports are open. If air charge / purge is completed before fuel is injected then that doesn't occur; whether that's diesel or something else is irrelevant.

As a bonus, built in EGR if properly managed.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#85

Post by red-iron-pine »

astral303 wrote: post #74
mywittyname wrote: post #10

A non-turbo diesel is an interesting choice of competitor. The big selling point of the Kohler motor is that it's almost silent - even the valve train is belt-driven to reduce noise. Not sure a rotary engine screaming at 6500RPM is comparable here to a diesel with a peak torque at 2000 and peak power at 3600. > LiquidPiston has been working on these X-engines for nearly 20 years now, I'm guessing they will never actu…

rotary engines do not really scream at peak power... this is why Mazda has plans to use rotary at peak power to generate electricity for their hybrid EVs. re 20 years to make a new engine point, compare investment $ in traditional ICE across the car industry vs investment $ into rotary or other alternative engines (the former is order of magnitudes more)

Mazda still holding on to those rotary engines, eh?

Still, call my interest piqued. I'll keep an eye out for their Wankel-EVs

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#86

Post by abfan1127 »

m3047 wrote: post #84
elihu wrote: post #78

Kind of weird article that doesn't talk about either the main benefits or design hurdles. The advantage of the LiquidPiston design is that at the time of ignition, the combustion chamber is a roughly round shape, as opposed to a traditional rotary where it's a long crescent. This should theoretically improve the emissions and fuel economy to be more like piston engines. I don't think Liquid Piston was talking about a…

2 stroke has poor unburned emissions because of mix flow-through when ports are open. If air charge / purge is completed before fuel is injected then that doesn't occur; whether that's diesel or something else is irrelevant. As a bonus, built in EGR if properly managed.

I thought 2-strokes had poor emissions was the injection of lubrication oil into the air fuel mixture. traditional 2-strokes I'm familiar with pull in air into the crank case (which requires lubrication), then uses a portion of the exhaust stroke to compress the fuel/air creating forced induction. By keeping air out of the crank case and providing lubrication delivery outside of the air/fuel mixture, emissions can be significantly improved. The article claims the design allows external lubrication, but it doesn't say how. I'd like to see how the seals are better than apex seals.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#87

Post by kube-system »

Syonyk wrote: post #76
kube-system wrote: post #47

Earlier quoted context omitted.

IIRC some automakers do test automotive engines at 100% duty cycle (in a test stand configuration). And more than a few automotive engines are used in slightly modified variants for marine and aviation applications. As I understand, the reason a typical car engine can’t sit at 100% duty cycle isn’t the engine itself, but usually the cooling and oiling configuration. Examples: https://youtu.be/GNPB3RtHN2M https://www.…

I'm aware of some auto engine conversions - the 13Bs out of the RX-7s and related could do it, the older Subaru engines (EA81) would do it, but they're just a small aircraft engine in a car, design-wise... Looking over the Viking engines, I don't think it's fair to call those "automotive engines," because my read of the description of what they do means they're pulling it apart and replacing an awful lot of pieces. T…

If changing those minor attributes makes an engine "not a car engine" then the majority of race cars also don't have car engines.

On their About page, they themselves say:

> Companies like Honda and Mitsubishi have spent millions of dollars refining and testing. We don’t claim that we can outsmart either company when it comes to the design of any internal running component of these engines. We don't change vital engine parameters around and claim we have different models. The compression, etc. is all stock. Every part is OEM Honda / Mitsubishi, nothing is new aftermarket from unknown origins.

> We start with the most up to date year engines with super low mileage, derived from fender benders across the US. When customers want the information about where there engine core came from and how many miles it had - we have all that documentation readily available to show.

Literally, every one of these engines came out of a car. I think that plainly qualifies it as a car engine.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#88

Post by abfan1127 »

Syonyk wrote: post #76
kube-system wrote: post #47

Earlier quoted context omitted.

IIRC some automakers do test automotive engines at 100% duty cycle (in a test stand configuration). And more than a few automotive engines are used in slightly modified variants for marine and aviation applications. As I understand, the reason a typical car engine can’t sit at 100% duty cycle isn’t the engine itself, but usually the cooling and oiling configuration. Examples: https://youtu.be/GNPB3RtHN2M https://www.…

I'm aware of some auto engine conversions - the 13Bs out of the RX-7s and related could do it, the older Subaru engines (EA81) would do it, but they're just a small aircraft engine in a car, design-wise... Looking over the Viking engines, I don't think it's fair to call those "automotive engines," because my read of the description of what they do means they're pulling it apart and replacing an awful lot of pieces. T…

those mods sound very similar to typical mods found in drag race cars.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#89

Post by dsr_ »

elihu wrote: post #78

Kind of weird article that doesn't talk about either the main benefits or design hurdles. The advantage of the LiquidPiston design is that at the time of ignition, the combustion chamber is a roughly round shape, as opposed to a traditional rotary where it's a long crescent. This should theoretically improve the emissions and fuel economy to be more like piston engines. I don't think Liquid Piston was talking about a…

The four strokes of a four stroke cylinder are intake, compression, combustion, and exhaust. That's down, up, down, up. Since there's no down or up in any of this engine's combustion chambers, "strokes" is probably inappropriate.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#90

Post by coryrc »

eYrKEC2 wrote: post #61
qbrass wrote: post #49

Earlier quoted context omitted.

It actually happens less on this engine than piston engines because the lobe on the rotor kind of rotates over the combustion chamber for a while instead of moving towards or away from it. On the other hand, it exposes a lot of surface area to heat, which gets absorbed by the rotor but isn't used to turn the engine. It's a problem it shares with wankel engines. The advantage over wankels is the extra time air and fue…

I know this goes towards steam-engine design, but why can't that heat be re-captured as steam? When the engine heat gets above a threshold, inject [distilled?] water instead of fuel.

Water injection is a thing, it gains a little efficiency. Generally not worth the complexity.
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