Mazda Rotary Engine

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Lendo

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Interesting, I will have a look. I know they eliminated overlap for hydrogen use (Naturally), but exactly how I'm unsure.
George
 

rv7charlie

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If I read it correctly, they just delay the H2 injection (directly into the intake chamber) until after the apex seal closes the exhaust port for that chamber. The Renesis has no overlap, so from a HP standpoint, shouldn't be a big deal. The 16X prototype has both port injection & a direct injector. Given the 'unique' cycle characteristics of the rotary, I've wondered whether the direct injection method could be used on the rotary (like they're doing with H2), but with conventional automotive injectors & fuel pressures. The injection point would never see the elevated pressures of combustion; unlike a piston engine. I rather doubt that the rotary would have the intake valve coking issues of DI piston engines, either. ;-) Seriously, feeding the engine 2 stroke 'premix' should function just like it does in the old 13B & Renesis, and keep the apex seals carbon free.
 

Lendo

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rv7charlie, a quick Internet search suggests a strong link between Crighton's engine development and Garside's patent. I just can't put my finger on why. Perhaps Garside designed something for Crighton or Norton and patented it.
Bottom line their from the same stable.
George
 

Lendo

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rv7charlie, your most likely correct, I may have missed that connection.
Delayed fuel injection is something Tracy did as well, also the high pressure DIRECT injection overcome any pressure build-up, as can be seen by the position of the injectors, you would be aware of this but others interested parties may not be. Fresh Air helping exhaust extraction is good;, Fresh Air with fuel, not so good; Fresh Air with Hydrogen - BAD :)
George
 

daveklingler

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Given the 'unique' cycle characteristics of the rotary, I've wondered whether the direct injection method could be used on the rotary (like they're doing with H2), but with conventional automotive injectors & fuel pressures. The injection point would never see the elevated pressures of combustion; unlike a piston engine.
I had the same thought. I have a pile of Sachs and Mazda engines I've planned to use to experiment with DI Real Soon Now. I'd like to try stratified charge and multiple ignitions per cycle to improve BSFC, like the 16X. The plan's been in my brain for a few years but the progress is painfully slow.

I haven't figured out anything conclusive about injector positions and angles, in addition to spark plug positions and angles with regard to the injectors. My thought was to closely copy the geometry of the engine whose injection system I choose, but I've noticed pretty large differences between what Ford and GM do. I would have thought they'd be similar. Still early for my efforts.

I'd also planned to go with Nikasil coatings and ceramic seals. If cast iron seals can have good longevity with Nikasil, that's very, very useful information.
 
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At what rpm on the 13B rew(?) and torque is that 250 HP produced. Can you publish engine dyno curves for us?
Our engine only uses Mazda parts. It is PPorted etc. The dyno sheet I have handy is from 2009 and we were tuning to reach peak HP at 6000. We changed the intake sizes and lengths to get more HP at 7000 and subtracted a tooth from our spur gear. A lot has changed since then. Changed the injection timing and got the EGT down a couple hundred degrees from this chart.
Here is from that test:Screen Shot 2021-11-09 at 4.36.57 PM.png
 

Lendo

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Dave just use the same direct injection site of the RX8, at the very top of the Rotor housing I did a lot of area calculations on this some considerable time back and it give enough time for the complete fuel injection after the inlet is closed and before pressure of the rotating Rotor is raised too high.
It's just a timed balancing act, the injector will be doing multiple pulsed injections during that short period, as I understand it.
George
 

Urquiola

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I had the same thought. I have a pile of Sachs and Mazda engines I've planned to use to experiment with DI Real Soon Now. I'd like to try stratified charge and multiple ignitions per cycle to improve BSFC, like the 16X. The plan's been in my brain for a few years but the progress is painfully slow.

I haven't figured out anything conclusive about injector positions and angles, in addition to spark plug positions and angles with regard to the injectors. My thought was to closely copy the geometry of the engine whose injection system I choose, but I've noticed pretty large differences between what Ford and GM do. I would have thought they'd be similar. Still early for my efforts.

I'd also planned to go with Nikasil coatings and ceramic seals. If cast iron seals can have good longevity with Nikasil, that's very, very useful information.
I own, pending final assembly, this Sachs KM-914, with a directo added peripheral port. As the new port opens later than the standard, it allows an 'Stratified engine', direct port receiving a richer mix than the standard. For those who still deny global warming, I purchased this engine from a member of Hercules Wankel IG, who prepared it for his snowmobile, but it was 9 years without snow when he sold it.
Air cooled housing and rotor work better than oil cooled rotor, liquid cooled housing Wankel, by all parts having an slightly higher temperature, quenching, flame extinction , is less in charge cooled rotor, air cooled housing. The Norton approach, David W Garside, having air and a bit of oil going through rotor, then cooled in an 'intercooler', then going to carb, reduced temperature in mix arriving to working chamber dropping Sachs KM-914 doble admision.jpgfrom 90 centigrades to 50 centigrades, a hughe improvement in BMEP. Who will test this? Blessings +
 

Lendo

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Squish areas are the same in air or oil cooled motors, it's the squished area i.e. lack of space between rotor and housing, which extinguishes the flame front and allows unburnt fuel into the exhaust. As far as I'm aware no other reason, unless you have a some other reason- I'm always willing to listen.
George
 

rv7charlie

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Here in the USA, the term is used differently. Here, it describes the area of the combustion chamber that is pinched to basically nothing at the end of the compression stroke, which causes massive turbulence in the rest of the combustion chamber, which improves fuel-air mixing.
Squish

Urquiola,

Charge cooling has historically had pretty terrible BSFC in rotaries (significantly worse than typical rotary efficiency). The SAE article describes something different; the rotors are cooled by a closed loop of airflow which is in turn cooled by an air>water heat exchanger. They describe the air cooling path being pressurize by what amounts to blowby, which increases its ability to carry heat away from the rotors.

Given the research that's been done into the efficiency gains available when running combustion engines at elevated temperatures (limited by metallurgy & lubricant breakdown), It would be interesting to see whether there'd be more efficiency available if they air-cooled the housings, as well as the rotors. If the seals could survive the same temps as a Lyc cylinder head (350-450 F), it should offset some of the losses from the extreme surface area of the rotary's combustion chamber.

Charlie
 

Urquiola

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Squish is not same as Quenching, quenching is flame extinction. A hotter working chamber wall will reduce flame extinction border, air cooled housings are hotter, charge cooled rotors are hotter. Curtiss-Wright proved exhaust HC is in inverse relation to rotor surface temperature, a hotter rotor reducing exhaust HC.
The issue of low BMEP in air cooled housing, charge cooled rotor Wankel RCE is mix entering working chamber at high temp, usually around 90 centigrades. Norton solved this. If you read the Yanmar Diesel SAE papers about their Wankel, $33 to download for non-members at www.sae.org you'll see they had two different versions of roughly same engine. Fuel economy was slightly better in air cooled version.
Yanmar Diesel made extensive use of Reed Valves in their Wankel.
The Renesis approach, side exhaust ports, combined with an square or rectangular peripheral intake port could totally eliminate port overlap, loss of fresh mix into exhaust, keeping the high MEP of Peripheral intake Port.
The Hot exhaust gas in Wankel comes from the low BMEP, this was what burnt exhaust valves in early ICE, when cause of detonation was unknown, CR was very low. Unburnt mix going through exhaust port adds temp to exhaust, but this could be avoided.
Proposal in YouTube video 'Rotary engine breakthrough' is sound, it can be done with a copper insert in leading plug site.
The new Aixro engines have plug channel pointing to trailing side of Rotor, Kawasaki patented adding a wedge shaped extension to plug hole, pointing to trailing side of rotor, Toyota improved 9% Wankel fuel economy with a glow plug in leading plug hole and Reed-Valve controlled Peripheral intake port. To be continued...
Blessings +RCE bmep percent vs Cooling way E McGovern.jpgWankel cooling system vs performance chart -SAE paper 900035 .jpgWankel RCE cooling systems & performances.jpgWankel RCE cooling ways and mnfg' costs.jpg
 
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Urquiola

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Well, here is a can of worms worthy of a completely new discussion, but let me throw aa few things out-

A long time ago, Mazda did a bunch of testing with various anti-wear/low friction methods other than chrome plating for the rotor housing surface and nitriding for the iron plates. They ended up with a Nikasil coated steel liner and irons as the most practical option, along with a "cermet" treated rotor housings. The problem with the Nikasil and Cermet coatings was the break in. Basically, the housings had to be burnished before the seals were installed, and even then initial wear could be extreme. Now, that was with older materials so that has certainly changed, but neither process is practical in a production car.
In the 2000's forward the UAV industry liked the rotary engine since it ran so smooth and allowed a much more vibration free camera platform. They did a large amount of development and ended up back where Mazda did, with Nikasil or Cermet coatings, along with more modern seals, including ceramics.

In my shop I had a set of worn out rotor housings stripped of thier chrome plating and coated with Nikasil to just over 10thou, and a set of irons surface ground 10 under with Nikasil built back up to standard. I put the motor together with stock apex seals and ran it for 1000miles to break it in/burnish the Nikasil. When I took it apart the seals were abnormally worn. This is because the Nikasil surface is rough and very hard, and where a piston ring wears slightly in a Nikasil bore, the spring pressure and seal construction of the apex and side seals are simply not durable enough. the same thing was noted with CERMET housings that Pineapple did up until about 2010 or so. I re-assembled the engine with new seals and after 100 miles the compression was slightly above average and continued to improve. At 5000 miles I tore the engine down again and there was no wear noted. The apex seals had burnished in slightly but the housings and irons looked the same as they had. I sold the engine to a customer and a few years later at around 60K miles I tore the same engine down with no measurable wear noted again. This is noteworthy because this was an engine fitted to an S4 Turbo 2 that made about 300whp, was driven almost every day, and was abused by its owner. At one point the owner discovered the OMP lines had broken and there was little if any oil being injected into the engine, and he had several overboost events that should have caused major damage, but did not.

So, in reality the technology is out there now to create amazingly durable 13B engines with more modern components, but the cost is somewhat high. Also, I think the fellow in Canada that did the CERMET housings is no longer offering it. Nikasil can be tricky and if not done exactly right it can and will "peel" from the substrate metal.
In an aircraft the added strength and durability might be worth the trouble, or maybe not.
I'm always in doubt about Cermet seals. Old research pointed ferrotic seals gave best results in terms of wear against a nikasil coated housing, but even if ferrotic is a cermet, I can't compare it with the ceramic seals for sale today, because lack of info.
Nikasil coating is better than hard chrome, at some sites, they electroplated the chrome, then reversed current polarity for a while to get a porous surface where lubricating oil attach.
The oil in Mazda three rotor Le Mans endurance race winner had MoS2 as additive, a solid lubricant, reported having saved some reciprocating engines which run having lost oil for 50 km or so.
Suzuki RE-5 had a plating patented by Alfred P Grazen in Canada, their rotor was same as in Comotor two rotor engines, it had ferrotic apex seals.
Users indicate you can change IKA seals to ceramic seals, but once the engine has run with ceramic seals, it must always have this type of apex seals.
As safety, adding some 1% oil directly mixed in fuel is proposed by many.
Blessings +
 

Lendo

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Urquiola, I've been advised that Min Flame front thickness is 0.015" less than (0.381) for gasoline, but could be less with Hythane ( natural Gas (Methane) and Hydrogen). However perhaps the Rotor face of the Mazda Rotary could be modified, so as to not exceed that minimum to get a more complete burn without reducing the compression ratio or cooling design, I have seen recent attempts on the internet. The Hythane does reduce incomplete burn but requires a complex redesign of the fuel system.
 
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