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#4533809 - 10/04/17 12:45 PM New Diesel design
28oz Offline


Registered: 04/20/17
Posts: 344
Loc: Utah, USA
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#4533830 - 10/04/17 01:05 PM Re: New Diesel design [Re: 28oz]
bigj_16 Offline


Registered: 07/03/17
Posts: 1268
Loc: Douglas County, Colorado
Fairbanks-Morse, Colt-Pielstick and the like have had opposed piston two-strokes around for a while. Seems like the Army could adapt an existing engine, rather than have a new design

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#4533983 - 10/04/17 03:46 PM Re: New Diesel design [Re: 28oz]
A_Harman Offline


Registered: 10/01/10
Posts: 6921
Loc: Michigan
Interesting that Cummins is in a joint venture with Achates to develop a 21st century version of the opposed-piston diesel. There is also the OPOC engine being developed by Ecomotors that is an opposed-piston, opposed-cylinder configuration.

Hopefully the relatively poor combustion characteristics of the OP engine can be improved by new common-rail injection systems. Since it's being developed for the military, the engine is probably exempt from EPA emissions standards. (When I worked on a military engine for Cummins back in the 1990's, it didn't have to meet emissions standards.) The army would only be worried about no observable smoke.

The British had many OP diesels in military service back in the 1960's, made by Leyland and Rolls-Royce, and all based loosely on the German Jumo 205.

And there was the Rootes TS3 Commer that was used in commercial trucks for decades.

And the Napier Deltic in locomotives and torpedo boats.


Edited by A_Harman (10/04/17 03:47 PM)
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#4534083 - 10/04/17 06:08 PM Re: New Diesel design [Re: 28oz]
javacontour Offline


Registered: 06/26/03
Posts: 10306
Loc: Illinois
Seems like there would be more reciprocating mass in an opposed piston engine.

I realize there is no valvetrain. However, it seems like the mass of the valve train is more than made up for in the mass of a second set of pistons and all the assorted hardware that makes that happen.

At least a valve train moves at half the crank speed. Opposed pistons move at the same rate.

What is the advantage of this setup vs more common engines we have today?
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#4534119 - 10/04/17 07:14 PM Re: New Diesel design [Re: 28oz]
Shannow Offline


Registered: 12/12/02
Posts: 39875
Loc: 'Stralia
revolutionary ???

Only in an advertising puff piece.

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#4534120 - 10/04/17 07:17 PM Re: New Diesel design [Re: 28oz]
A_Harman Offline


Registered: 10/01/10
Posts: 6921
Loc: Michigan
Opposed piston engines are 2-strokes, so they have higher power density than 4-strokes. Historically, OP diesels were very fuel-efficient, achieving thermal efficiencies of 40% back in the 1940's. Combined crankshaft strokes are very long, giving a lot of expansion to the combustion gases. The biggest problem to the OP is that since it doesn't have a cylinder head, fuel must be injected from the cylinder walls, which leads to problems with spray impingement on the piston rims and cylinder walls, and poor distribution of fuel in the cylinder if only one injector is used. Two or more injectors could be used, but that adds cost.
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1985 Z51 Corvette track car
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2001 Dodge Ram 2500 diesel
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#4534195 - 10/04/17 09:45 PM Re: New Diesel design [Re: A_Harman]
javacontour Offline


Registered: 06/26/03
Posts: 10306
Loc: Illinois
Originally Posted By: A_Harman
Opposed piston engines are 2-strokes, so they have higher power density than 4-strokes. Historically, OP diesels were very fuel-efficient, achieving thermal efficiencies of 40% back in the 1940's. Combined crankshaft strokes are very long, giving a lot of expansion to the combustion gases. The biggest problem to the OP is that since it doesn't have a cylinder head, fuel must be injected from the cylinder walls, which leads to problems with spray impingement on the piston rims and cylinder walls, and poor distribution of fuel in the cylinder if only one injector is used. Two or more injectors could be used, but that adds cost.


But is this an advantage over a two stroke with a conventional head?

Can't I just build a single piston in cylinder two stroke and not need to carry all the extra reciprocating mass of a second crank (worst case) and rods, pistons, etc? I could use a turbo to blow the cylinder full of air and displace any exhaust that doesn't escape on its own via its own heat and expansion.

Seems like unnecessary and wasteful complication compared to using what would be wasted exhaust energy to provide forced induction.
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#4534280 - 10/05/17 04:41 AM Re: New Diesel design [Re: javacontour]
Shannow Offline


Registered: 12/12/02
Posts: 39875
Loc: 'Stralia
No cylinder head to lose heat to having the gasses "push" on it to oppose the piston...therefore less heat loss, and cooling system load/size.
No head gaskets.
No poppet valves (or sleeves/rotary seeing as this is touted as revolutionary), no cams etc.
Still needs a blower of some style if it's a two stroke, and there's no scavenging without forced induction at cranking speed.
Look at a DOHC set-up for a diesel with near vertical valves, and see how much "stuff" is otherwise above the head gasket.



Could nearly double the capacity with opposed piston for no more floorplan, and not much extra height.

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#4534427 - 10/05/17 09:09 AM Re: New Diesel design [Re: 28oz]
nyumski Offline


Registered: 05/14/15
Posts: 227
Loc: Indonesia
for instance i saw enlightment and breakthrough instead of electric thing engine but i am worried it cant replace inline 6 cyl diesel engine LOL
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#4534531 - 10/05/17 11:23 AM Re: New Diesel design [Re: 28oz]
Claud Offline


Registered: 02/11/14
Posts: 593
Loc: Margate England
I wonder how much mechanical loss there is from the synchronising gears to the transmission input?.
It isn't a new concept, more a re-think of an old idea. Perhaps technology has advanced enough to deal with any inherent shortcomings.

Claud.

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#4534532 - 10/05/17 11:23 AM Re: New Diesel design [Re: 28oz]
Claud Offline


Registered: 02/11/14
Posts: 593
Loc: Margate England
I wonder how much mechanical loss there is from the synchronising gears to the transmission input?.
It isn't a new concept, more a re-think of an old idea. Perhaps technology has advanced enough to deal with any inherent shortcomings.

Claud.

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#4541263 - 10/12/17 02:36 PM Re: New Diesel design [Re: Shannow]
javacontour Offline


Registered: 06/26/03
Posts: 10306
Loc: Illinois
Originally Posted By: Shannow
No cylinder head to lose heat to having the gasses "push" on it to oppose the piston...therefore less heat loss, and cooling system load/size.
No head gaskets.
No poppet valves (or sleeves/rotary seeing as this is touted as revolutionary), no cams etc.
Still needs a blower of some style if it's a two stroke, and there's no scavenging without forced induction at cranking speed.
Look at a DOHC set-up for a diesel with near vertical valves, and see how much "stuff" is otherwise above the head gasket.


Could nearly double the capacity with opposed piston for no more floorplan, and not much extra height.


But can't you do much of that without opposing pistons? If you are using forced induction and this engine is already using ports, can't you have the best of both worlds by not using the opposing piston? Blow enough air in there, inject the fuel at the right time using an injector built into what would normally be the head, but is just part of the closed, cast engine block.

Perhaps I'm not considering the shorter stroke of each individual piston. I.E if two pistons are moving the same distance instead of one moving 2x the individual distance....

What, if anything am I missing here?
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