they are shown the spinning cylinder (it is from a Honda C-50), the spinning crankshaft (you can see its main journal spinning about a stationary axis, you can also see the crankpin of the crankshaft holding the piston rod that holds the piston head (which is also from a Honda C-50) that reciprocates inside the spinning cylinder.
In the following GIF_video_animation:
the piston have been removed to show the spinning crankshaft and the spinning cylinder.
The only orbiting thing in this video is the crankpin.
About packaging an exhaust system, I expect you could mount a turbine co-axial to the crank,
& /or perhaps do an aero-shaped variant of an expansion-chamber to suit.
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
You write:
"About packaging an exhaust system, I expect you could mount a turbine co-axial to the crank,
& /or perhaps do an aero-shaped variant of an expansion-chamber to suit."
I think the best packaging for small airplanes is to eliminate the exhaust system and the scavenging pump.
The following animations are for a more compact version of the PatRon 2-stroke direct injection Diesel for small airplanes etc, mentioned in previous posts.
For the same bore (120mm) and piston stroke (60mm) the maximum dimesnion of the rotating cylinder is only 280mm (11 inches).
The cylinder head to cylinder head distance is 240mm.
The piston crown to piston crown distance is 180mm.
In such an engine for small airplanes (and the similar) the only compromises are the induction of unfiltered air and the noise from the exhaust (which is lower than the noise from the propeller the engine drives).
Hi Manolis, I think you may be a bit too quick in dismissing the useful gains to be had from 2T exhaust energy,
even the simple fixed dimension expansion chamber offers a 'boost' of ~0.3 bar over ambient atmosphere..
&, pertaining to driving a propeller, the air-filtration aspect also, with foreign object detritus being fanned up...
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
This system is transfer port based, different from the BRP/Rotax dual DFI/throttle body type as used on snowcraft...
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
You write:
“Hi Manolis, I think you may be a bit too quick in dismissing the useful gains to be had from 2T exhaust energy,
even the simple fixed dimension expansion chamber offers a 'boost' of ~0.3 bar over ambient atmosphere..”
The reasonable choice for a 2-stroke is the compression ignition because, by definition, a Diesel engine runs well from extra lean (idling), to lean, to slightly lean (at peak torque, peak power).
Besides, with the direct injection the fuel has not the chance to escape to the exhaust before participating in a combustion.
In comparison, a spark ignition 2-stroke has to operate at “strange conditions” wherein the residual gas causes unstable combustion and varies periodically the conditions the fuel is burnt at (this was what the Honda Radical Combustion was trying to fix).
One more advantage of an efficient direct injection Diesel is the low temperature and pressure of the exhaust gas. With more energy of the fuel going to the crankshaft as mechanical energy, the thermal loss on the exhaust gas reduces.
The sooner the combustion completes, the better. We talk for progressive and not impact combustion.
With a longer piston dwell around the combustion Dead Center (say, TDC), more fuel is burnt at higher expansion ratios.
The efficiency at which a fuel droplet (or more correctly a fuel molecule) is burnt depends on the instant expansion ratio.
For instance, in a conventional Diesel (red curve) with, say, 15:1 compression ratio (which correspond to a dead volume of 7% of the cylinder capacity)
a molecule of the fuel burnt at 15 degrees after the TDC (wherein the piston has covered only 2% of its stroke downwards) “sees” an expansion ratio of 107/(2+7)=12:1, while a molecule burnt at 30 degrees after the TDC (the piston has covered 8% of its stroke downwards) “sees” an expansion ratio of only 7:1.
The overall thermal efficiency results by calculating the partial thermal efficiency at which each molecule was burnt,
The more efficient the burning of the fuel, the less energy is left to the exhaust gas and the quieter the exhaust.
This is what the OPRE and PatOP prototype engines do.
Listen the sound of the exhaust in the following videos.
I think there are no 2-stroke Diesels using expansion box for tuned exhaust.
The gain of using a well exhausted (literally speaking) gas to “boost”, by an expansion chamber, a high efficiency di Diesel is questionable.
Without any exhaust system (the PatRon 2-stroke di Diesel of the animations), the noise from the relatively quiet exhaust is covered by the noise from the rotating propeller.
You write:
“KTM announces Euro 4 compliant EFI 2T Enduro machines for 2018. http://www.racerxonline.com/2017/03/15/ ... ng-in-2018
This system is transfer port based, different from the BRP/Rotax dual DFI/throttle body type as used on snowcraft..”
With indirect injection, they achieve Euro 4 compliance. Great news for the 2-strokes.
I suppose the injection in the transfer port is “late” (to prevent unburned gas from escaping to the exhaust).
Do they use some kind of “stratified” charge?
By the way,
besides the GB 2,528,748 UK patent granted to the PatAT / PatATi system of pattakon (asymmetric transfer and exhaust in the 2-stroke engines), a “Notice of Allowance” for the same patent was received last week from the USPTO (the US patent is, officially, to be granted in a couple of months).
If KTM with conventional design makes Euro 4 compliant 2-stroke engines, I wonder what Euro class compliant a KTM with a PatATi will be.
Well done with the patent grant Manolis, & should KTM take up your ideas to your advantage, even better..
As for the exhaust system, yes a CI engine can certainly benefit, you wont find many sans turbo these days..
Technically, the exhaust pulse sound-wave will add 'volume' to the level perceived as 'noise',
-unless you can get it to function on a particular frequency - to effectively 'cancel' the prop 'noise'?
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
Manolis, re: harnessing the exhaust energy otherwise wasted as inconvenient emissions of noise/fumes,
perhaps something along these lines could be utilized for a 180`/flat - single crank 2T twin,
- or the radially disposed rotary, with dimensionally correct design?
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
You write:
“harnessing the exhaust energy otherwise wasted as inconvenient emissions of noise/fumes, perhaps something along these lines could be utilized for a 180`/flat - single crank 2T twin,
- or the radially disposed rotary, with dimensionally correct design?
Something like this ?
The exhaust is secured on the rotating cylinder and spins with it.
It could have even a catalyst inside.
The two chambers have 180 degrees phase difference (measured on the rotating cylinder).
The cylinder is spinning at a specific direction; so, it would be better the intake and exhaust of the one cylinder of the PatRon of the drawing to turn “upside-down”.
In the PatRoVa rotary valve web page they have been added he following animations:
They show a single disk PatRoVa compressor.
The single disk rotary valve is secured on the crankshaft.
The design is of the cross-head type.
Depending on the orientation of the exhaust ports, such an expansion chamber could be shaped in aero-form,
to reduce drag, &/or direct the fumes into a static/concentric pipe extension - fitted with a rotary seal..
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
MotoGP rookie Jack Miller is feeling the effects of what his Honda engine “wants.”
By Kevin Cameron posted Nov 29th, 2014 at 10:00pm
I noted that MotoGP rookie Jack Miller, describing his recent test at Malaysia’s Sepang International Circuit, spoke of the “smoother, more controlled power delivery” of the pneumatic-valve Honda RC213V-RS.
I like to emphasize that pneumatic springs have value other than the raw ability to reach high rpm. What pneumatics do best is make the valves follow short-duration, high-lift cams that metal springs cannot. Engines with metal springs must be given longer duration and reduced lift if they are to reach competitive rpm, and both of these changes compromise performance. Yamaha was behind this 8-ball in 2006.
Increasing duration (valve open time) to give metal springs longer time in which to accelerate/decelerate valves has two harmful effects:
1) Keeping the intakes open longer after bottom center (BDC) allows the piston, rising on its compression stroke at low- and mid-rpm, to push out part of the fresh charge it has just pumped in (at higher revs, the inertia of the faster-moving intake flow prevents this). Less charge retained in the cylinder equals less engine torque.
2) Beginning to open the intakes earlier before top center (TDC) extends the overlap period during which the exhausts are not yet closed yet the intakes have begun to open. This creates a window through which exhaust pipe waves act to create a deep flat spot just before peak torque. (This occurs at mid-rpm when the returning pipe wave is positive and pushes exhaust gas back into the cylinder and possibly even fills the intake pipes and airbox with exhaust. The torque-weakening effect of all this exhaust gas in the cylinder produces the flat spot.)
The result of the above is both weak torque in the low- and midrange, and a steeper, more abrupt torque rise from the flat spot to the torque peak just above it. The rider finds it tricky to exit corners smoothly when his engine has to accelerate through such a steep torque rise.
The third effect is reduced intake flow even on top end, caused by the reduction in valve lift required if a metal-spring engine is to reach higher revs.
In sum, what pneumatic springs really do is allow valve motion to more closely approximate what the engine and its airflow “want.”
END OF QUOTE
It seems the poppet valves have reached their limit in the MotoGP racing engines.
For even more power at higher revs, they are required even bigger valves and even longer valve lifts.
The metal valve springs cannot follow.
The Desmo of Ducati has reached its limits.
The pneumatic valve springs are better, however the inertia loads increase with rpm square, they also increase proportionally with the valve lift, they also increase proportionally with the mass of the valve (which increases with the cube of the valve diameter).
Here is a PatRoVa Rotary valve with tapered disks (the exhaust exits from the centers):
I find it hard to believe that the potential of the valve springs has been reached.
Whatever force is needed, a suitable spring stiffness can provide it at the required displacement. I agree that the problems posed by the dynamic behaviour of the spring are by no means trivial but they are not unsolvable.
The main reason pneumatic valves are used in motorsport is because the work required to compress the working fluid adiabatically is less than the work required to compress a linear spring by the same amount. Simply put, it takes less power to turn the cams. Yes, it does side step potentially problematic spring dynamics, but that is a secondary effect.
Now for the real questions
1. How do you plan to seal that disk valve ?
2. Don t you think that combustion chamber is going to be atrocious for a high speed engine ?
Harry Ricardo noted the fundamental restrictions of poppet valves with springs, cams, drives,
& what-not, many decades ago..
..the way the poppet valve head obtunds its own port - is one glaring example..
Current F1 engines obtain efficiency via costly F/A complexity, even while constrained to being poppet valve 4Ts.
Toyota tried to utilize their supercharged 4V DOHC experience, & to run it as a 2T..
..but the poppet valve soon showed its limitations - when required to operate at twice usual speed/gas flow..
"Well, we knocked the bastard off!"
Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).
