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Old 24-10-2012, 22:51   #31
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Re: Article On New Diesel Technology

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I believe the odds of an apex seal failing are lower than throwing a valve or rod.

Want to make a bet? I worked for a monkey in Davis Ca. developing the OEM rotary's for his so called flying car (really a leaf blower). Those engines had to be set up within .0002" (that's 2/10ths of one thousands of an inch) most of the time and those tiny apex's had coming apart parties constantly.
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Old 24-10-2012, 22:55   #32
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Re: Article On New Diesel Technology

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The navy is sitting on an engine from the 70's that uses no fuel. Documentary on you tube convinced me.


.......
But where does the heat source come from? It still needs to be created, and even solar heat has limitations.
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Old 24-10-2012, 23:45   #33
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But where does the heat source come from? It still needs to be created, and even solar heat has limitations.
Did you watch the documentary? They are building engines that run on 20 degrees f. Of difference in temps.
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Old 25-10-2012, 01:40   #34
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Re: Article On New Diesel Technology

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Did you watch the documentary? They are building engines that run on 20 degrees f. Of difference in temps.
TANSTAAFL

With a small difference in temperature, there is a small amount of energy to be obtained from it. The video was talking about using waste heat from industrial plants. It also said it would take 2 years to to break even on building costs, another indication of low amounts of power generated. Everyone in the video was talking about heat pumps, no one was talking about breaking thermodynamic laws. Would these increase efficiency, yes because of less wasted heat from plants.

You could set out solar collectors to heat water to power it. This would be equivalent to solar cells in terms of it being "free power", but now you have water, moving parts, pumps, generator if you want electricity. It would have to have a much higher efficiency than solar panels to make it worthwhile. You still can't get more energy out than the energy put in per square meter by the sun.

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Old 25-10-2012, 03:14   #35
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Re: Article On New Diesel Technology

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Originally Posted by Astrid View Post
The idea was also used in a variety of Napier engines such as the Deltic and in a series of engines pioneered by Hugo Junkers in 1928. Of course the new explorations with new technologies into old ideas can be very worthwhile.
Indeed!

I don't quite grasp why opposed pistons should represent such a great leap forward. I guess it lowers piston speed by half -- a good thing, but piston speed is not a major engineering problem on diesels, AFAIK. You get a really long con rod in exchange, which can't be good - big increase in reciprocating mass.

What's more cool about this engine, as far as I can tell, is that it's a two stroke. Two strokes are really, really cool because you double the volumetric efficiency compared to a four stroke. As far as I can tell, the really key feature of this new engine is that it is a revival of the Detroit Diesel concept of supercharger-scavenging. And here they seem to have done something extremely clever -- maybe really groundbreaking -- they have invented a new supercharger which is both turbocharger (that is, turbo-supercharger), and mechanical supercharger at the same time. Not mechanical, but electrical. So it uses electrical power to spin up the turbine when there's not enough gas flow -- which eliminates the inefficient mechanical supercharger which Detroit Diesels had. Once there's enough exhaust gas flow to spin the turbo, electrical drive tapers off, and here's another cool thing -- when there's excess energy in the exhaust gas flow, this turbo generates electrical power. Now this is really cool! So in this sense it's a Detroit Diesel without the power drag of the mechanical supercharger (remember many Detroit Diesels had turbochargers besides the mechanical supercharger -- they wouldn't run without some overpressure to scavenge the combustion chambers, so a turbo alone wouldn't do it, but a mechanical supercharger drains power, unlike a turbo-supercharger which captures wasted power from the exhaust stream). So this looks to me like a real leap forward, but a technology which doesn't depend on the opposed pistons -- could be used with regular reciprocating piston engines too.

How cool two strokes are can be illustrated by the engine in my snowmobile. It's a Rotax, semi-direct injected. The big advantage of two strokes is volumetric efficiency and mechanical simplicity; the big drawback has always been fuel efficiency and emissions -- because some of the unburned mixture inevitably escapes into the exhaust port -- fresh mixture pours straight in hard on the heels of the outgoing exhaust gas -- there is no way to divide the two gas flows when you don't have separate exhaust and intake strokes.

This can be almost completely overcome with direct (or semi-direct) injection, where what flows into the cylinder is not a fuel-air mixture but plain air. If the fuel is put into the cylinder separately, it can be controlled in a way so that practically none of it escapes through the exhaust port.

So my snowmobile engine develops 120 horsepower and weighs less than 50 kilos -- the same or even better "power density" (as those guys call it) as the new opposed piston diesel. Maximum horsepower is produced at a leisurely 7000 RPM. And the specific power is huge -- 200 horsepower per liter. Fuel consumption is 30% or more better than a conventional carburetted two stroke snowmobile, and is about the same as a comparable four stroke snowmobile which, however, weighs significantly more (a 120 horsepower four stroke engine weighs more than double).

Look for direct injected two stroke gasoline engines on cars -- I bet they will appear pretty soon.
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Old 25-10-2012, 10:40   #36
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Re: Article On New Diesel Technology

I think the idea was to use two pistons per cylinder, so that you had for instance, twelve pistons in a six cylinder engine, thus cutting down weight, which in the 1920s and 30s was a major consideration, particularly in the Junkers aero diesels.
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Old 25-10-2012, 12:11   #37
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Re: Article On New Diesel Technology

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Originally Posted by Astrid View Post
I think the idea was to use two pistons per cylinder, so that you had for instance, twelve pistons in a six cylinder engine, thus cutting down weight, which in the 1920s and 30s was a major consideration, particularly in the Junkers aero diesels.
The Junkers Jumo engines always fascinated me! I built a model as a child. Practical diesel power for an aircraft - that's got to be a very good thing.

I still don't quite see why extra pistons reduce weight. Maybe I just don't get it (I'm not an engineer). I get the reduced piston speed, but one piston with twice the stroke is surely lighter than two, with an extra con rod, to add insult to injury. Minus the the weight of a cylinder head, but the opposed piston engine will still surely be heavier for a given swept volume (displacement).
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Old 25-10-2012, 12:59   #38
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Re: Article On New Diesel Technology

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Originally Posted by GaryMayo View Post
The navy is sitting on an engine from the 70's that uses no fuel. Documentary on you tube convinced me.

An engine whose total energy input is less than its total energy output is known as a perpetual motion machine. No offense intended.
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Old 12-12-2012, 09:57   #39
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Re: Article On New Diesel Technology

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Originally Posted by Cheechako View Post
If you've ever driven a Wankel Mazda... they aren't lacking out of the hole! Maybe it's a HP/to weight thing... but they come out Fast!
Mazda has stopped making them because of emissions.
The combustion chamber in a rotary isn't ideal compared to pistons, it is long and flat, not a ball shape like a piston engine.
And they require a small amount of oil injected for lubrication.
None of these are issues with boats.

Diesel's are very heavy engines, they must be to withstand the diesel combustion. I don't think four times as heavy seems a good idea in a boat, unless it is a monohull and you use the engine as ballast..
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Old 12-12-2012, 10:03   #40
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Re: Article On New Diesel Technology

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Originally Posted by nimblemotors View Post
Diesel's are very heavy engines, they must be to withstand the diesel combustion. I don't think four times as heavy seems a good idea in a boat, unless it is a monohull and you use the engine as ballast..
Interesting, since 99% of the catamarans made have 2 diesels and run just fine
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Old 12-12-2012, 19:05   #41
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Re: Article On New Diesel Technology

Those interested in opposed piston motors Gooogle Napier deltic & Lister TS3
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Old 12-12-2012, 19:29   #42
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Re: Article On New Diesel Technology

Agree, the direct injected 2-strokes are fantastic.
I read that Dodge was going to put one in the Neon, but didn't get ready in time. While they use much less oil because it isn't mixed with the fuel anymore, they still burn some, so unlikely it will make into cars of today.

My plan is to put the kawasaki jetski direct injected 2 strokes in my cat. The 2-cylinder motors are so simple and light, you can lift them out by yourself.
I can carry a spare engine and parts to rebuild them. My only concern
is that the electronics to control them can fail like electronics do on boats.
But then spares of those too don't weigh anything.

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Originally Posted by Dockhead View Post
Indeed!

I don't quite grasp why opposed pistons should represent such a great leap forward. I guess it lowers piston speed by half -- a good thing, but piston speed is not a major engineering problem on diesels, AFAIK. You get a really long con rod in exchange, which can't be good - big increase in reciprocating mass.

What's more cool about this engine, as far as I can tell, is that it's a two stroke. Two strokes are really, really cool because you double the volumetric efficiency compared to a four stroke. As far as I can tell, the really key feature of this new engine is that it is a revival of the Detroit Diesel concept of supercharger-scavenging. And here they seem to have done something extremely clever -- maybe really groundbreaking -- they have invented a new supercharger which is both turbocharger (that is, turbo-supercharger), and mechanical supercharger at the same time. Not mechanical, but electrical. So it uses electrical power to spin up the turbine when there's not enough gas flow -- which eliminates the inefficient mechanical supercharger which Detroit Diesels had. Once there's enough exhaust gas flow to spin the turbo, electrical drive tapers off, and here's another cool thing -- when there's excess energy in the exhaust gas flow, this turbo generates electrical power. Now this is really cool! So in this sense it's a Detroit Diesel without the power drag of the mechanical supercharger (remember many Detroit Diesels had turbochargers besides the mechanical supercharger -- they wouldn't run without some overpressure to scavenge the combustion chambers, so a turbo alone wouldn't do it, but a mechanical supercharger drains power, unlike a turbo-supercharger which captures wasted power from the exhaust stream). So this looks to me like a real leap forward, but a technology which doesn't depend on the opposed pistons -- could be used with regular reciprocating piston engines too.

How cool two strokes are can be illustrated by the engine in my snowmobile. It's a Rotax, semi-direct injected. The big advantage of two strokes is volumetric efficiency and mechanical simplicity; the big drawback has always been fuel efficiency and emissions -- because some of the unburned mixture inevitably escapes into the exhaust port -- fresh mixture pours straight in hard on the heels of the outgoing exhaust gas -- there is no way to divide the two gas flows when you don't have separate exhaust and intake strokes.

This can be almost completely overcome with direct (or semi-direct) injection, where what flows into the cylinder is not a fuel-air mixture but plain air. If the fuel is put into the cylinder separately, it can be controlled in a way so that practically none of it escapes through the exhaust port.

So my snowmobile engine develops 120 horsepower and weighs less than 50 kilos -- the same or even better "power density" (as those guys call it) as the new opposed piston diesel. Maximum horsepower is produced at a leisurely 7000 RPM. And the specific power is huge -- 200 horsepower per liter. Fuel consumption is 30% or more better than a conventional carburetted two stroke snowmobile, and is about the same as a comparable four stroke snowmobile which, however, weighs significantly more (a 120 horsepower four stroke engine weighs more than double).

Look for direct injected two stroke gasoline engines on cars -- I bet they will appear pretty soon.
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Old 12-12-2012, 20:39   #43
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Re: Article On New Diesel Technology

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Quote from Dockhead:
I don't quite grasp why opposed pistons should represent such a great leap forward. I guess it lowers piston speed by half -- a good thing, but piston speed is not a major engineering problem on diesels, AFAIK. You get a really long con rod in exchange, which can't be good - big increase in reciprocating mass.
Significantly easier to balance and much greater torque at much lower engine speeds. Those are a few that I picked up on. The long con-rod is in one particular design that eliminated the dual crankshafts.
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Old 13-12-2012, 08:05   #44
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Re: Article On New Diesel Technology

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I won't buy one for JUST this reason alone "...with 10 times fewer parts...". How, is that possible? 1 times fewer parts is 0 total parts. So, does it have negative parts?

This assertion that products are "X times less..." is just stupid - and impossible.
They mean that a traditional diesel engine has ten times as many parts as the liquid piston engine. In other words, the liquid piston engine has one tenth as many parts as a traditional diesel. The website says that the liquid piston engine has thirteen parts of which only three are moving parts.
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Old 13-12-2012, 09:37   #45
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Re: Article On New Diesel Technology

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Originally Posted by shakey doug View Post
Those interested in opposed piston motors Gooogle Napier deltic & Lister TS3
At 13.5 hp I think this OPOC (Opposed Piston Opposed Cylinder) diesel has all those other ones beat.
1) No vibration
2) Small
3) Light weight
4) Fewer parts
When have you seen a 5kw generator thats the size of a brief case and light enough to carry.
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