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Old 14th Jan 2011, 19:21   #1 (permalink)
 
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Gemini diesel engine

Is the Gemini Diesel project still afloat. Any recent news on progress would be appreciated.
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Old 15th Jan 2011, 03:36   #2 (permalink)
 
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The last available news on the Gemini appears to be from around late 2009. There's no substantial developments to report. Tim Archer talks up the Gemini at a 2009 expo in the video below... but the bottom line is...

1. The Gemini isn't radical enough to be able to claim a serious advancement in engine technology, weight saving, and fuel efficiency.

2. Just fiddling with a WW2 Junkers Jumo design, only produces the same problems that saw the Jumo development abandoned.
There's no way of building a substantially lighter weight, water-cooled, highly fuel efficient diesel, using the opposed piston design.

The last news was that Power Plant Developments were doing "fuel mapping" in late 2009. I would suspect that this engine is going nowhere.
The company is probably at the stage of looking for more money... as many of these "new engine" companies burn up money faster than they can get people to invest.

Thus we have most of these so-called "revolutionary" aircraft diesels, all stalled at the point of progress, of about 5-6 years ago.
Some have fallen by the wayside, most are stalled on age-old problems of keeping weight down... reliability at a high level... sealing... cost at satisfactory levels... and a failure to offer SUBSTANTIAL advances in technology.

Even the so-called, fabulous Rand-Cam engine has stalled... on the age-old problem with all rotary-style engines, of massive problems with sealing.
The Rand Cam engine has now morphed into the RadMax, after the Rand Cam engine failed to live up to all its claims.. but the RadMax engine is still not a runner, either.
These perpetual sealing problems were the downfall of the Sarich Orbital engine... it was a major problem with the Wankel engines... and it haunts every rotary engine developer.

The Raptor Turbo diesel has nothing to offer over anything else available. A convential 4 cyl engine placed horizontally, is only inventing the wheel again.. but with a different hubcap, to try and convince people it's a radical development.

Gemini Diesel interview - Tim Archer .. Gemini Diesel 100 HP aircraft engine, PPD Gemini aircraft engine manufacturer, Lightsport Aircraft Pilot Video newsmagazine.

Raptor Turbo diesel .. Raptor Turbo Diesel

RadMax engine .. RadMax Technologies, Inc.
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Old 15th Jan 2011, 09:15   #3 (permalink)
 
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Well its not revolutionary technology that impresses me, rather simplicity and reliability, and the ability to use diesel fuel.
So the stated installed weight of the 100hp Gemini is less than my 80hp Limbach. If the Gemini turns out to be as reliable and burns jetA1 fuel I would certainly want one.
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Old 15th Jan 2011, 10:48   #4 (permalink)
 
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V-T-1 - You're never going to get a "new" diesel aircraft engine that is a model of simplicity.
To reach the required level of technological advancement, to produce high HP from low weight, there will have to be a degree of complexity.
Complexity in itself is not a bad thing, it's excessive complexity is where the problems start.

The reason the likelihood of any of the above engines getting "off the ground", so to speak, is low... is that not only do they not offer serious advances in engine technology... but that the companies themselves are not necessarily well-focussed, or well-organised.

For any new diesel aircraft engine to succeed, it will need to have...

1. Wide appeal... to as many markets as possible... to assist with lowering the cost base...
2. Serious technological advances in metallurgy, combustion principles, and a sizeable leap in advancement of IC diesel engine design...
3. A company behind it, that is well funded... has an MD or CEO that "drives" the development process, and who can convince buyers that the engine has major advantages over anything else available...
4. A development program that is mappable, and has "waypoints" of development and proving, that are laid out in a concrete manner.. and largely met, on time, and on-budget.

Of course, having a potential military buyer to tap into, is often of very great assistance... as the military is often prepared to spend vast sums of money on promising projects, that many civilian operators would recoil from, in horror.

I don't see where any of the current crop of "new" diesel aircraft engine suppliers/companies are focussed enough, funded enough, or have enough "drive" behind them... to produce a viable diesel aircraft engine, that would make 99% of potential buyers/users, rush to outlay a serious deposit on one.

The problems behind the design and production of a highly satisfactory diesel aircraft engine, are many and varied.
They range from the much higher combustion pressures of a diesel (requiring serious strength in pistons and cylinders .. to serious vibration problems, created by the greater combustion impact of a diesel stroke.

The simplicity of a diesel is offset by many of these other inherent problems, that can only be overcome by advances in technology and improved design.

Rudolf Diesel produced a workable, patented, diesel engine design in 1896.
It took until the mid-1920's, before the diesel engine was adequately refined to install in a truck. It was a crude effort, compared to later truck diesels.

It took until 1931 before Caterpillar could produce a "lightweight", speed-adjustable diesel engine that was suitable for use in crawler tractors.
Caterpillar expended over US$1,000,000 (in 1928 dollars) between 1928 and 1931 to produce just three, working, prototype engines.

Even then, Caterpillar still had to "sell" their diesel tractor, despite its major fuel efficiency advantage.

Cummins Engine Co ran at a loss, every year, for 17 years (1920 to 1937), before it finally turned a profit, with a diesel truck engine, that offered serious advances in efficiency, reliability, fuel economy, and longevity.
It was extremely fortunate indeed, that Clessie Cummins was fully bankrolled for that entire period, by a banking family that believed in his Cummins diesel dream.

The same kind of intensive effort, research and development is now going to be required, to produce an aircraft diesel engine, that everyone will be flocking to purchase.

Last edited by onetrack; 16th Jan 2011 at 07:22. Reason: sp...
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Old 15th Jan 2011, 10:54   #5 (permalink)
 
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So far I have seen nothing to impress me in the diesel aero engine field, there are all sorts of things that all seem to be ready to fly in the "near future".

So far the three cylinder UK developed engine has flown in a few home builts but it is far from a production engine, my personal feeling is just a way of keeping employed on the back of govenment development grants.

The American Deltahawk looks to be the best of the bunch but this too is always promising certification next year!

I am off to do the manufactures maintenance course on one of the diesels that is flying in a few weeks, may be that will change my opinion?
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Old 15th Jan 2011, 13:03   #6 (permalink)
 
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Quote:
Just fiddling with a WW2 Junkers Jumo design, only produces the same problems that saw the Jumo development abandoned.
There's no way of building a substantially lighter weight, water-cooled, highly fuel efficient diesel, using the opposed piston design.

onetrack, do you consider that common rail injection, solenoid fuel injectors and electronic engine management are 'just fiddling'?

Diesel engines have won the Le Mans 24 hour race and produced VW Golfs with better performance thah the comparable petrol version, so why do you suggest that applying modern levels of monitoring and control, not to mention 70+ years worth of metallurgical and computerised finite element analysis advances to an opposed piston diesel engine won't bear fruit?
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Old 15th Jan 2011, 14:57   #7 (permalink)
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There is a review of a fine looking RV-9A* in the current issue of Flyer. It is powered by the Wilksch 3-cylinder diesel engine. The engine weight is comparable with a similar Lycoming - the RV-9As fitted with the Wilksch engine are all at the lighter end of RV average weights. The performance is comparable with an RV fitted with an O-235 and it cruises at 117 it's IAS burning 16 lts/ hour of jet A1.

Wilksch currently have over 20 engines flying - 7 of them in RV-9s.

The Wilksch is a 2- stroke diesel with mechanical injection - so it's pretty simple engine.

Dave

* it's mine!
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Old 15th Jan 2011, 16:26   #8 (permalink)
 
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In configuration the Wilksch is simple - but the major problem is that is has not been designed for simple production. The 'wrist pin' with a hemi-spherical cup and socket is a nightmare in production terms - and it gives issues in terms of reciprocating weight. A 'clever' idea but one whichhas crippled the engines potential.

The total production of the engine is very modest largely because of this. At the end of the day if really does nothing much better than an O-235 might do with fuel injection and a good ignition system.
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Old 15th Jan 2011, 16:51   #9 (permalink)
 
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Onetrack makes many good points...
But meanwhile some people just quietly get on with viable and simple diesel motors that seem to work really well. The Wilksch is simple and apparently reliable (so long as the installation and cooling requirements are sorted properly).
But the French homebuilt scene is thriving on PSA/Citroen car engine conversions. The successful formula is to build ultra lightweight airframes and use a simple belt drive reduction gear on the lightened car engine.
No homebuilder uses common rail because it is inherently unreliable, as a simple electrical failure will mean loss of the engine.
All the successful engines so far use tried and tested super reliable mechanical injection. Both the Dieselis and Gazaile achieve greater than 80 mpg and endurance of nearly 10 hours. Maybe it's as always the cost of certification is the main obstacle to diesel development for GA.
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Old 15th Jan 2011, 17:08   #10 (permalink)
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Quote:
In configuration the Wilksch is simple - but the major problem is that is has not been designed for simple production. The 'wrist pin' with a hemi-spherical cup and socket is a nightmare in production terms - and it gives issues in terms of reciprocating weight. A 'clever' idea but one whichhas crippled the engines potential
The new "big bore" Wilksch that is currently durabity testing no longer has the spherical cup & socket. The revised combustion system on the big-bore requires a shaped piston crown so will have conventional bearings on the connecting rods.

Dave
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Old 15th Jan 2011, 18:10   #11 (permalink)
 
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[[ leaving the original topic to discuss car conversions ]]

@ vee-tail 1 : I agree it is a scary idea to have the ignition depending on the electrical circuit - but is that not the case for a FADEC petrol engine too?

As for the French relying on French car engines: they do, to a certain degree, especially for the diesel. But in Holland, there is a project much like the Gazaile - I actually think it is based upon it - using a (heavily modified?) diesel from an Opel.

For myself I can't stop dreaming of converting the Subaru boxer diesel for aviation use - it is rated at 150 HP for road use, so should be able to power a 4-seater, perhaps not even needing a reduction. But the fact that no-one has yet done this seems to indicate the engine is not really a strong candidate. I wonder why, though.
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Old 15th Jan 2011, 21:21   #12 (permalink)
 
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A road car needs about 15-20% power to cruise at 70mph.

Running a Subaru (or any automotive engine) at 60-70% power settings as aircraft engines need to do is not going to be that popular with its internals....

Regarding O-235s in an RV-9, the Van's figures will be true air speed at 8000ft. I think DBo's figures are more likely UK based 'low level' figures - we don't tend to cuise at 8000ft in the UK.
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Old 15th Jan 2011, 21:36   #13 (permalink)
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Quote:
Regarding O-235s in an RV-9, the Van's figures will be true air speed at 8000ft. I think DBo's figures are more likely UK based 'low level' figures - we don't tend to cuise at 8000ft in the UK.
...and vans use mph not knots... For a fixed power setting our IAS is pretty much constant with altitude. Pull out a calculator & an atmosphere table and you'll see that we're pretty much comparable with an O-235. we tend not to climb with full power (It tends to be a bit smoky - mechanical indirect injection's automotive equivalent is a black cab). But the full-power climbs we did for our initial permit matched Vans book numbers for 120 hp..

Dave
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Old 16th Jan 2011, 07:08   #14 (permalink)
 
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onetrack, do you consider that common rail injection, solenoid fuel injectors and electronic engine management are 'just fiddling'?
Mechta - Basically, yes. Common-rail injection was in production in the late 1920's. The only difference today is finer control with electronics, and higher rail pressures.
The problem with extremely high rail pressures is that any rupture of the rail can be catastrophic... in the form of damage by the burst, or by the initiation of fire.
In one of Caterpillars latest common-rail, new design engines, Caterpillar have taken the step of positioning the extremely-high-pressure rail, inside a low pressure fuel supply tube.
This is an arrangement that is designed to control and mitigate any danger from any rail burst, by dispersing the burst into the low-pressure tubing.

Solenoid injectors, electronically-controlled, are an improvement on mechanical injection, by allowing staggered injection pulses.
However, the total reliability of engine electronics is still in question... and there needs to be backups in case of electronic-control failure.
Electronic engine controls do not do well in the reliability stakes, because of their inherent lack of robustness.

Quote:
Diesel engines have won the Le Mans 24 hour race and produced VW Golfs with better performance thah the comparable petrol version, so why do you suggest that applying modern levels of monitoring and control, not to mention 70+ years worth of metallurgical and computerised finite element analysis advances to an opposed piston diesel engine won't bear fruit?
There is only so much that FEA can do, and electronic controls only add small percentages of gain. I don't have a problem with electronic controls per se... they just need to be robust, foolproof, and have backup.
What the basic problem is here, is that there's no MAJOR advancement in IC engine design, with any of the above-mentioned models. Perhaps it's the basic conservativeness of the aircraft fraternity to stick with the tried-and-true.
However, a major advance in engine design is required, to reduce weight substantially, and increase efficiency substantially.

That is why my money is on engine designs such as the Revetec engine. A design that gets away from the basic inefficiency of the rod-and-crank design, and produces a substantially-improved method of transferring reciprocating movement to rotary movement.

In addition, the Revetec engine produces peak torque at very low RPM, and doesn't need to reach high RPM for efficiency. This speaks volumes for vastly improved engine lifespan, as well as being ideally suited for light aircraft propulsion.
Add on a Coates Rotary Valve head to a Revetec engine, and we are talking serious advances in engine design... over the conventional IC piston/poppet valve engine, that has hardly altered, in basic design principles, in nearly 120 years.

If a rotary engine such as the RadMax could solve its sealing problems, then it would possibly be a viable contender in the aircraft propulsion market... however, I believe the sealing problems are insurmountable.
I know Ralph Sarich personally, and I know he spent over 20 yrs trying to solve the sealing problems of the Orbital Engine, and he eventually gave up.
He offered the Orbital Engine to more than a dozen major manufacturers, and not one of them was prepared to swap over to Orbital Engine power, because their best engineers could never come up with a satisfactory answer to the rotary engines sealing problems, either.

Last edited by onetrack; 16th Jan 2011 at 07:20.
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Old 16th Jan 2011, 08:17   #15 (permalink)
 
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Speaking of rotary engines, what about the Mistral? They are still around, exhibiting, looking for money, and when I last spoke to them (4/2010) they seemed to have a nice working engine.
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Old 16th Jan 2011, 12:38   #16 (permalink)
 
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Jan, is this be the Opel engined aircraft? Looks good.
DAC Ranger

Onetrack, a common rail rupture in flight sounds like the stuff of nightmares! But I wonder how likely such a failure could be, as presumable it could happen with any fuel injected engine? ... however one would indeed be enough!
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Old 16th Jan 2011, 12:56   #17 (permalink)
 
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Yes, that's the one I was thinking of. As I read their web pages, they put a lot of effort into optimising (sp?) the engine for aviation use.
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Old 16th Jan 2011, 13:23   #18 (permalink)
 
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Onetrack, I can see your concern with the high pressure rail on a common rail engine bursting, and the pipe within a pipe would appear to be the answer. You certainly wouldn't want fuel at the pressures involved being sprayed around under the cowling.
Having dealt with the burst, the next problem is to stop the engine stopping, and the opposed piston engine allows one to have a separate injection pump and injector on each side of the cylinder. Extra complexity, yes, but so is dual ignition on a petrol engine.

I do wonder if we are all hoping for too much by wanting a sudden huge step in efficiency, given the extra hoops a aero engine has to jump through before it can go into use? As with a lot of things in the real world, a small percentage improvement, across lots of components is probably more realistic. It will also only be by getting out and doing it (flying the engines), that engine and airframe manufactures will get the answers. Engines on paper and on dynamometers are not operating in the real world.

Either engines stay in the dark ages for eternity, or one must accept that electronic monitoring and control is the way forward. You can't cut the safety margins in the interests of efficiency without knowing to what you are cutting them. As an example, how far would you be prepared to lean out a Lycoming if you didn't have any indication of cylinder head temperature or exhaust gas temperature?

Your example of common rail being around in the 1920s, is a good example. It has taken until now with modern solenoid injectors to make it a viable proposition for cars. The basic technology was there for common rail, but the control for the injector was not.

If you want efficiency, then precise engine mapping and control is the way to go, if you want simplicity, then compromises must be made and fuel burn goes up. You can't have your cake and eat it.

Last edited by Mechta; 16th Jan 2011 at 13:35.
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Old 17th Jan 2011, 09:10   #19 (permalink)
 
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V-T-1 - Common rail ruptures aren't unknown, and when they rupture, it's extremely dangerous. Fuel spraying everywhere, over a hot engine, at 20,000-30,000 psi, is a guaranteed way to start a major fire.
It's often a catastrophic event on ships and construction equipment, resulting in major fires. On a aircraft, it would immediately be life-threatening.
It's not a problem that is going to stop diesels in aircraft, it just needs to be addressed in the design of the fuel injection equipment, if extremely high pressure common-rail injection is planned to be used.
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Old 17th Jan 2011, 18:23   #20 (permalink)
 
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Double walled fuel lines have been a very common fitment on marine engines for years to eliminate the threat from rupture - although the Australian Navy lost a destroyer or possible something a little larger by replacing the HP fuel line with flexibles..........

To get really high power (over 50hp per litre) from a diesel engine the use of common rail technology is necessary. Look at the evolution of the VW 1.9lt engines - from 75 bhp to now over 180 - quite a development and made possible by precise injection and careful matching to boost.
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