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Mazda’s rotary engine in the age of the electric car

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Re: Mazda’s rotary engine in the age of the electric car

#261

Post by TylerE »

redwall_hp wrote: post #248
ryukoposting wrote: post #225

Earlier quoted context omitted.

>In most applications you can work around this with redundancies and diverse technologies Are you proposing that Mazda should put two engines in their cars? Or am I misreading this? >hard earned decades of learning and be pressing advantages. Not every novel and viable solution ends up being an enhancement. That's precisely what Mazda is doing. They poured decades of R&D into the rotary engine, and are leveraging tha…

Formula 1 cars are also series hybrids, for about a decade now. Electric motors drive the wheels at all times, and power comes from a turbocharged V6.

This is incorrect.

The F1 MGU-K is geared to the crankshaft via the timing gears. The wheels are absolutely NOT electrically driven, it’s working as a torque fill for the conventional powertrain.

Re: Mazda’s rotary engine in the age of the electric car

#262

Post by everybodyknows »

willis936 wrote: post #189
Retric wrote: post #178

Earlier quoted context omitted.

That rate isn’t a deal killer for a plug in hybrid. The engine might see ~1/4th the ware per mile spending the vast majority of its time off. Meanwhile hybrids really want a small and lightweight engine because of all the extra equipment.

Right but then why not use a more efficient and reliable engine? The motors will last hundreds of thousands of miles. The power circuitry should have a similar run if kept cool. Why have an ICE that's more likely to fail with lower thermal efficiency? The engine used in Toyota's most popular cars runs in Atkinson most of the time with a 40% thermal efficiency. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425626/

> The engine uses port and side direct fuel injection systems (PFI/GDI, referred to by Toyota as D-4S); a cooled, external exhaust gas recirculation system (cEGR); and a wide range of authority variable valve timing with electric phasing on the intake camshaft and hydraulic phasing on the exhaust camshaft. Atkinson Cycle is implemented using late intake valve closing (LIVC). Effective compression ratio is varied by varying intake camshaft phasing.

Clever indeed.

Re: Mazda’s rotary engine in the age of the electric car

#263

Post by rootusrootus »

lightedman wrote: post #245
cookiengineer wrote: post #199

Earlier quoted context omitted.

Technically, the Wankel rotary engine design allows much higher power output than an I-4 or even a V-6 engine design due to no strains on the rods, and much less strains on the piston(s) as those literally blow up all the time in I4 engine designs in similar power output ranges. I've seen many very reliable 3 or 4 rotary wankel swaps in RX7 FD3S that output far beyond anything imaginable any V8/V12 could produce. 200…

"The multiple use of hydrogen (e.g. a stove just needs to burn the gas)" Oh, no. You don't want to be cooking over a flame capasble of melting platinum. You will utterly destroy your pots and pans temper. I do jewelry work, hydrogen gas is one of the hardest gases to properly work with. I'd rather let a newbie play with oxy-acetylene than a hydrogen torch.

Could you elaborate on why this is? Naively, the temperature of a simple hydrogen flame is not too much hotter than a methane flame. And in torch form, it seems like MAPP is several hundred degrees (C) hotter? And oxy-acetylene a few hundred more on top of that. Any torch seems to have way more than enough heat to melt platinum (1700C)?

Re: Mazda’s rotary engine in the age of the electric car

#265

Post by Retric »

pfdietz wrote: post #244
Retric wrote: post #223

Earlier quoted context omitted.

Atkinson engines have poor power to weight ratio at maximum efficiency, if you’re going to maintain that 40% then the engine needs to be oversized and under utilized. This is why many hybrids have seemingly much more power than they need. Thus the 194HP Prius vs 75 HP on a CX-90 plug in SUV. Also it’s not just that you can have extra Li+ it’s also pushing around less dead weight when the engine is off. So you can get…

It could make more sense to use a conventional engine, but get extra expansion (the kind an Atkinson/Miller cycle engine gets from the longer expansion stroke) by turbo-compounding. That is, exhaust gases (still at greater than ambient pressure) go through a turbine that is coupled to the output shaft, or to another generator, rather than being used to drive a compressor as in a conventional turbo. Or, attach a motor…

Possibly, but that’s a lot of separate systems.

It might make sense to look into a turbine engine on a hybrid. Though that’s probably been investigated I doubt anyone has invested the kind of time and money needed to make a real shot of it.

Re: Mazda’s rotary engine in the age of the electric car

#266

Post by chipsa »

ryukoposting wrote: post #164
ghostly_s wrote: post #159

Earlier quoted context omitted.

> The Wankel is at its most efficient and its most reliable when operating at a constant RPM. Conveniently, the EV generator application demands a pretty flat RPM band. If I understand the article correctly, the "series" hybrid configuration means precisely that it cannot operate at the ideal rpm when charging the battery, because it is always driving the wheels directly as well.

Exactly the opposite. In a series hybrid, there is no mechanical connection between the engine and the wheels - only an electrical one, with the battery still providing considerable power in most cases, even when it's depleted. No hybrid ever runs its battery all the way to zero, and series hybrids are no exception. The Chevy Volt (the other notable series hybrid in Western markets) keeps its engine at a near-constan…

The Volt is a series/parallel hybrid. It has situations where the motor is directly connected to the wheels. The BMW i3 does has a series only set up, but that’s probably because it also has a BEV only version.

Re: Mazda’s rotary engine in the age of the electric car

#267

Post by topspin »

idontwantthis wrote: post #206
callalex wrote: post #80

Earlier quoted context omitted.

You also have to keep in mind that the average consumer is…quite stupid, or more charitably quite sensitive. There are lots of cars on the market today with CVTs (continuously variable transmissions) that enable the motor to always be driven in the most optimal RPM. However in software, the engines are intentionally driven at less efficient rpm’s so that the driver can feel steps and lurches as the car accelerates wh…

I just bought a car with a CVT and now I’m upset.

No need for that. While it's possible to point out particular "performance" car CVTs that do indeed compromise efficiency for aesthetics, that's not done in most cases, at least not to the degree that efficiency is significantly compromised. The actual reason for not doing as suggested and placing the entire burden of acceleration on the CVT (thus keeping the engine at a constant RPM) is that this would be a foolish design.

Between the precision electronic fuel delivery and ignition, variable valve timing, variable plenums and other features of your ICE, all of which are invariably present today when an ICE is the prime mover, the ICE power curve has wide RPM bands in which its efficiency is high. By taking advantage of these wide bands of efficiency, the CVT can have less size, mass, mechanical loss, cost, etc., than would be the case if the CVT were required to precisely enforce a constant engine RPM.

Minimizing the burden on the CVT is crucial because CVTs are a mechanical compromise: they are inherently not as strong as a conventional transmission and generally have higher mechanical losses.

The manufacturers responsible for these designs aren't actually fools, slavishly beholden to some old fashioned transmission aesthetic. They're responding to a large number of pressures and doing the math. The math says that constraining the ICE to an efficient, yet non-zero, RPM band is better than trying to manufacture miraculously agile CVTs.

Re: Mazda’s rotary engine in the age of the electric car

#268

Post by mattmaroon »

themerone wrote: post #24
mattmaroon wrote: post #15

I have never understood why the Volt Series Hybrid idea never took off. It is more efficient to turn gasoline into electricity and then drive the car with that than to directly connect the engine to the wheels. Is it perhaps that the cost involved is just too much more than a plugin hybrid to make the small extra fuel savings worth it?

Aside from your suggestion violating the laws of physics, that's actually not how the Volt worked. The original concept for the volt was that the engine would only generated electricity, but in production models, the engine was connected to the drivetrain.

It wasn’t my suggestion, but what I read way back in the day, and it may not be accurate but it does not violate the laws of physics. It’s entirely possible that (just as one hypothetical example) being able to keep the engine at optimal RPMs at all times in a series hybrid creates more efficiency even after the extra conversion losses.

Re: Mazda’s rotary engine in the age of the electric car

#269

Post by lightedman »

rootusrootus wrote: post #263
lightedman wrote: post #245

Earlier quoted context omitted.

"The multiple use of hydrogen (e.g. a stove just needs to burn the gas)" Oh, no. You don't want to be cooking over a flame capasble of melting platinum. You will utterly destroy your pots and pans temper. I do jewelry work, hydrogen gas is one of the hardest gases to properly work with. I'd rather let a newbie play with oxy-acetylene than a hydrogen torch.

Could you elaborate on why this is? Naively, the temperature of a simple hydrogen flame is not too much hotter than a methane flame. And in torch form, it seems like MAPP is several hundred degrees (C) hotter? And oxy-acetylene a few hundred more on top of that. Any torch seems to have way more than enough heat to melt platinum (1700C)?

A hydrogen-oxygen flame (this is what happens naturally since you're burning hydrogen in open atmosphere) burns closer to 2800C, and also has the fun property of causing embrittlement (which is especially worsened at higher temperatures where metal expands and becomes more porous.) Your steel pots and pans are essentially toast under a hydrogen flame.

People think "Fire is fire" and no, no it is not.

Re: Mazda’s rotary engine in the age of the electric car

#270

Post by class3shock »

newsclues wrote: post #231
class3shock wrote: post #228

Earlier quoted context omitted.

I would just add that sometimes ideas exceed the technology of their time. So revisiting a design that had deficiencies (weak points, high production costs, bad emissions, etc.) with new tools, materials, etc. can lead to breakthroughs. Not that that's what is happening here, just why some ideas that previously didn't work seem to circle back around.

It’s hard to tell if you can improve technology until it’s good enough (jet engines) or if it’s a futile dead end. Kelly Johnson of Skunkworks had a keen mind for differentiating between them.

It is indeed and sometimes it can go either way depending on the time point. A good example is what eventually became the PW GTF, the PW8000, discussed here:

https://cornponepapers.blogspot.com/2006/04/short-life-and-u...

Just a little bit to early but when they came back to the idea they ended up with a technology that they use on all their new (big) commercial engines.

For anyone that doesn't know the name Kelly Johnson I recommend "Kelly: More Than My Share of It All". A rare person who combined technical genius with an ability to get large scale things done.

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