h a l f b a k e r yPoof of concept
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This submission summarizes an engine that reduces
emissions of lawn tools, off-road vehicles, scooters,
generators, range extenders, and light aircraft
collectively
responsible for millions of tons of annual emissions.
The engine is designed for full time operation of
Homogeneous Charge
Compression Ignition (HCCI) in the
Low Temperature Combustion (LTC) regime for improved
efficiency and reduced emissions when fueled by canola
oil, (bio)diesel or JP-8. The key design decisions and
features are listed below:
• Radial configuration eliminates cold end cylinders,
reduces temperature variance
• Plethora of small bore pistons tolerate extreme loads
of
explosive combustion
• Variable compression for stable ignition delay over load
and temperature
• Cam drive allows rapid compression with pause at peak
for chemical kinetics
• Opposed pistons reduce combustion chamber surface
area and heat loss
• Two stroke operation for large port area in small bores
• Separately timed scavenge pump moves air at low
pressure
• Rotor facilitates later incorporation of an integral
motor/generator
• Centrifugal force recovers oil leaving ports (issue in
opposed-piston two-strokes)
• Highly polished steel cams and followers with Diamond
Like Coating
• Radial with opposing cylinders yield harmonic balance
of
complex forces
• Six cylinder sets, four cycles per rotation, 24 power
strokes per revolution
• Cams enable four power strokes per revolution yielding
a
4:1 reduction gear
• Centrifugal force replaces discrete pumps for fuel, oil,
and coolant.
• Cam driven fuel injectors eliminate single point
failures
in fuel system
• Only a simple two-way exhaust catalyst required (no
soot
filter or NOx adsorber)
• Cam radius, contact area, and surface speed increase
with engine displacement
• Excess compression for cold start allows sustained
performance at altitude
An affordable 9.2 cc prototype is planned to demonstrate
performance. Math model predictions summarized in the
figures compare favorably to a Honda 50 cc engine. The
performance shown is associated with operation at sea
level, compression ratio of 29:1, 10 bar BMEP, peak
combustion pressure of 220 bar (preventing ignition of
lubricating oil), and peak combustion temperature of
2150K (inhibiting NOx production).
The engine concept and design are complex and subtle,
yet
the accompanying video shows the mechanical apparatus
and its operation to be simple and elegant. The
manufacturing cost is expected to be low due to high
reuse
of comparatively few unique components.
2 Patents Allowed, 3rd is pending.
Learn more by viewing my Create The Future Contest
entry at https://bit.ly/3pSVlBu . Please like my entry or,
better yet, register and vote for it !
[Rotary]'s Rotary engine idea
Perfect_20Engine_20...omotive_20X_20PRIZE
// Better crack the enigmatic assembly of this idea fast before the bionic Sphinx is brought from her half-life! // [sninctown, Jun 14 2021]
US 10,590,845
https://patents.goo...ent/US10590845B1/en
RodRico's patent [xaviergisz, Jun 15 2021]
US 2017/0328277
https://patents.goo.../US20170328277A1/en
cited by the US examiner during the examination of RodRico's patent [xaviergisz, Jun 15 2021]
[link]
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Welcome to the halfbakery, [RodRico]! |
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It looks like the linear motion of the piston is converted
to rotary motion using a cam mechanism. How is this
cam lubricated? |
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This reminds me of [rotary]'s rotary-engine concept
many years ago. I hope [rotary] is ok these days. |
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I have an idea for a new genre of romance novel. The
Engine Romance. It would be like a romance novel
except the only character is an engine and the plot is
describing how the engine works. |
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I like that genre idea, [sninctown]. I've sometimes thought
about writing a
variation on that, where the plot is the process of solving an
interesting technical problem, but with teasing references to
some human interest things happening in the background, but
handled in such a way as to make clear that they're really not
what's important in this story. The "unreliable narrator"
would keep forgetting other characters' names (and maybe
sometimes their own), but would be absolutely reliable on all
technical details. |
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Meanwhile, welcome to the bakery, [RodRico]. The fact that you already
have two patents allowed brings some immediate kudos. I'm not qualified
to comment on this particular idea, but I'll await with interest what
[RayfordSteele] has to say. |
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[sninctown] The centrifugal oil pump and rotary motion
flings oil onto the cams. There are holes in the lightly
loaded regions where the cams slide forcing excess oil
back into the oil loop. An easily overlook feature of the
architecture is the speed at which the cams are
operating. Even in the smallest feasible engine (9.2 cc),
the path length of the outer cam profile is about a foot,
so its effective diameter is almost 4 inches, larger than a
V-8 journal bearing with proportionally larger surface
speed. Thus the cam is in the hydrodynamic lubrication
regime from below idle to max RPM. |
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I'm not familiar with [Rotary]'s engine, but mine bears
resemblance to that shown in US patent 593,078 from
1897 as well as the Michel cam engine of 1921 shown in
patent 1,603,969. Mine differs from prior art in being
opposed piston with a third piston dedicated to the role
of air pump so it can be precisely timed to pump only
when needed (thus reducing pumping loss). It also, of
course, reflects modern understanding of HCCI and LTC
that were unknown at the time of relevant prior art. |
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[pertinax] the book you describe sounds a lot like one of my
all time favorites, "The Soul of a New Machine" by Tracy
Kidder. It describes the development of the Data General
Eclipse computer and mixes technology and drama so well
it earned a Pulitzer Prize for non-fiction. |
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Breaking news... My design was just accepted as an entry in
the Create the Future Contest. You can see it at
https://bit.ly/3pSVlBu . Please "like" it or better yet,
register and vote for it ! |
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//the promise of Da Vinci Code// |
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Perhaps but, if so, it was a promise most outrageously broken; I
did say //reliable on all technical details//. |
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//an engine that reduces emissions of lawn tools, off-
road vehicles, scooters, generators, range extenders, and
light aircraft// |
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Hmm. There is a range of engines you're covering, and
they all have good reasons for being used in the
respective applications. I suspect it's educational to work
through them. |
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Lawn tools, there's a couple of engines that are common,
small 2 strokes for strimmers and the like, and the
ubiquitous Briggs & Stratton 4-stroke lawnmower engine.
The main driver here is cost. Can you get a version of
your engine down to ~$100 WITH profit? I doubt it. Your
component count is off the scale, and I suspect the
production will require much better tolerances, which are
expensive. The best way to improve lawn tools is to go
electric, which is happening. |
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off-road vehicles/scooters: Again a few types, but lets go
with a 125cc 2 stroke dirt bike. 40hp, ~20kg, can you do
that? No way. You need much more material to operate at
the compression ratios you need, meaning much heavier.
You can't operate at the high revs of spark ignition
meaning you need more displacement. Then there's the
packaging & handling consequences of a massive spinning
engine block in the middle of the bike. |
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generators: Again, cost is the driver for small generators,
and you're up against established designs that can be had
for a few hundred $. What level of efficiency
improvement will you get over a conventional diesel? |
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Light aircraft: We already know how to improve these
engines. A good start would be modern ignition, EFI and a
turbocharger to offset altitude. All straight out of any old
conventional car. We don't do that because the barrier to
entry here is the levels of certification required in the
aviation world. It's over the top, most agree, essentially
safer modern engines aren't allowed because of safety.
But that's the way it is, and it's the same for your engine.
Plus, big spinning masses again. Not ideal. |
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How do your sliding friction numbers add up? A single
cylinder engine is 2 piston rings, both ends of the con rod,
crank bearings, cam bearings and 2 cam followers. As far
as I can tell you're at least 6x this, and with smaller
everything you're looking at much greater sliding surface
area Vs combustion chamber size. |
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Also, how are you metering your fuel accurately? Cam
driven injectors is 1930's tech, and extremely fiddly. If
you cam/follower interaction is off (and if it isn't, it will
wear it's way there requiring lash adjustment) then you
loose the sort of super-tight control that you need for
good emissions. The piezoelectric fuel injector is a much
better choice, wide range and on-the-fly adjustment on
each cylinder according to conditions. |
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No idea about your design specifically, but HCCI engines would tend to be heavier (so light aircraft is probably out, unless you're going to save HCCI for cruise) |
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Other than that, I don't think HCCI has been developed for small constant-speed engines (even though it seems obvious in retrospect) : good idea. |
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bs0u0155, your barrage of comments is difficult to
respond to in its entirety, so I'll pick out the major points
and go from there. |
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1) Yes, my engine with be more costly and heavy than a
two-stroke. If the world were OK with high emissions and
low efficiency, two-strokes would rule the world and my
engine wouldn't stand a chance. My analysis indicates I'm
should be competitive with commercial Honda 50 cc
engines in terms of power density in both weight and
volume. I will certainly be more costly, but the high
internal reuse of common components takes me down the
cost learning curve quickly, so the engine shouldn't be as
costly as it may appear at first glance. I do worry about
assembly labor, however. |
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2) Lawn tools *should* be going electric, and those who
do their own yard work have mostly made the transition.
When I watch lawn contractors, however, I see only
gasoline engines. Perhaps they're reluctant to plug into
customer outlets or don't want the risk of not finding a
working outdoor outlet? I don't know, but I see nothing
but gasoline engines. |
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3) Sliding friction is certainly a concern, but it's driven by
many factors (speed, contact area, surface finish and
lubrication) and can't be judged by simply counting parts. |
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4) Fuel metering. I think you're assuming unit injectors
with variable volume pumps. I didn't go that route
precisely because of the issues you raise. I use one cam to
pump over twice the fuel I need under the needle then
use a second cam to release the pressure in order to
modify the inject duration. This is a somewhat binary
process that doesn't depend on cam lash. I use hard
strong materials for the cams and don't expect them to
wear significantly more or less across cylinders. I monitor
AFR via exhaust analysis and modify injection duration
accordingly, so uniform aging of cam surfaces is removed.
The piezo injector is certainly a better choice for in-line
and V cylinder arrangements. It's not so good in a radial
configuration like mine that offers other opportunities. |
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\\If the world were OK with high emissions and low efficiency,\\ |
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I'm bunning this for myriad reasons, but the only realistic way to reduce emissions in the real world is to make motors that are more efficient at a lower cost (including the cost of fuel), all else being equal, such that the market wants them. Furthermore more parts almost always means higher cost and lower efficiency by every measure including by emissions. Not only for the engine itself, but for the mechanisms to build it. |
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Also a video is a terrible way to present text with diagrams. |
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\\ the only realistic way to reduce emissions in the real
world is to make motors that are more efficient at a
lower cost (including the cost of fuel), all else being
equal, such that the market wants them. \\ |
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We didn't reduce automotive emissions over the past 50
years because "the market wants" lower emissions, we did
it through government regulation. Government continues
to push hard on emissions, even going so far as to ban
internal combustion altogether. |
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\\ Furthermore more parts almost always means higher
cost and lower efficiency by every measure including by
emissions. \\ |
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More parts usually does mean greater cost, but the
magnitude of the cost increase for having more machined
parts is strongly correlated to set-up time which is driven
by the number of *unique* parts. My engine will be more
expensive than a two-stroke. It probably won't be as
expensive as a double overhead cam four-stroke with
variable valve timing and four valves per cylinder,
however. |
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More parts most decidedly does not mean higher
emissions. Take out fancy injection systems, variable
valve timing, intake air flow and O2 sensors, EGR, air
pump, and catalytic converter plus the particulate filter
and NOx adsorber in diesels and you'll have a *lot* fewer
parts, but much worse emissions. |
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\\ Also a video is a terrible way to present text with
diagrams \\ |
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Yes, it is. The contest rules limit text to 500 words but
allow a 3 minute video, however, so I used the video to
add more information. Otherwise, the video would have
had only the animation and I would have lost the
opportunity to add context. |
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