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RNDDUDE
User Rank
Platinum
Re: not very Likely
RNDDUDE   9/26/2011 12:03:39 PM
NO RATINGS
Amclaussen, good summary of Turbo vs. Supercharger. You said:

 The idea is that the pressure boost needed by the cylinder-piston is not really well met by both devices; thus the concept shown could well be a better match for the cylinder charging needs, maybe better than the traditional Otto cycle.

However, the piston-driven compressor in the prototype is mechanically matched to the engine rpm,  and it's volumetric output is thus rpm dependent, and has parasitic power draw, which is the same as a supercharger. The qualitative issue is whether it is a more eficient air pump across all rpm ranges than a external supercharger. Also, I tend to surmise that the gains are from what is essentially a two-stage forced induction, turbocharger and then internal compressor. Seems I have seen people trying this with external turbo pumping into external supercharger into engine with encouraging results.

DON KEMP 1
User Rank
Iron
SPLIT-CYCLE ENGINE
DON KEMP 1   9/26/2011 11:57:10 AM
NO RATINGS
IF I AM NOT MISTAKEN ,THIS HAS BEEN IN PRODUCTION BY A MOTORCYCLE COMPANY( STEYR,DAIMLER,PUCH )FOR MANY YEARS.IT IS A 2 STROKE VERSION.WHCH EXECPT FOR IT BEING A BALANCE NIGHTMARE , WAS QUITE SUCCESSFUL

REGARDS DON

Amclaussen
User Rank
Platinum
Re: Split cycle engine= two stroke? Not at all...
Amclaussen   9/26/2011 11:51:17 AM
NO RATINGS
A two-Stroke is VERY different... and it's Specific Fuel Consumption (efficiency) is lower than in a 4-Stroke.  By optimizing the charging cylinder to perform a charging task only, and then making the power cylinder optimum for producing the downstroke better,  can suspect this concept couls have advantages.  But is is definitely NOT a two-stroke. (the better eficiency Two-strokers are those that burn diesel and have an integral blower to sweep the burnt gasses out of the combustion chamber, but the ubiquitous gasoline two-strokers are notably less efficient and produce a lot more contaminant gasses in their operation.  Please analize in detail the article's drawing, then the alleged advantages can be visualized. Anyway, the idea of using a crankshaft driven compressor in order to handle the air, and a power cylinder to drive the same crankshaft, with both relative sizes optimized to match the volumetric needs of the engine, always working at the same exac RPM, looks like an elegant solution to me. It needs to be built and througly tested before anyone can claim it a success.  But the idea looks like a good one.  Other elegant engineering ideas were not as sucessful as desired, like the variable compresion engine from Volvo (If I remember correctly), that was so difficult to run in practice or expensive to produce so that today none are seen in the streets.

Kevin
User Rank
Platinum
Better than many / still mainly hype
Kevin   9/26/2011 11:50:03 AM
I've followed and studied alternative engines for many years.  Many are pure scams, such as the MYT engine and quasiturbine.  The split-cycle concept has some merit, but in the end has only a tiny advantage over conventional technology, and some large disadvantages.  For example, conv. engines benefit from doing all 4 cycles in one cylinder, because the avg. temperature is lowered.  The split-cycle will have a very hot power cylinder.  The "one power cycle per revolution" is no advantage, if you view the mechanism as two pistons (which it actually is).  In the end, it is just running a rather conventional 4-stroke process with a different mechanism.  A better use of research dollars is to figure out how to clean-up turbodiesels (with proven superior efficiency), or incrementally improve conventional engines (reduce friction, direct injection, eliminate throttling losses, downsizing, hybrids).  These approaches can give as much or actually more efficiency improvements.  And...I need to mention that lower weight and better aerodynamics are probably the best path to better efficiency, as the Edison2 car has proven in actual results in the Automotive X-Prize competition (>100mpg, good real-world performance).

EV's are not a panacea anytime soon either, although someday maybe.  I would like to see a renewable-based liquid fuel (biofuel or solar-synthesized fuel) take the place of gasoline.  This could allow the most benefit with the least change to current infastructure and user convenience profiles.

Best of luck to all innovators! 

Amclaussen
User Rank
Platinum
Re: not very Likely
Amclaussen   9/26/2011 11:27:35 AM
NO RATINGS
Not likely: the Mechanically driven Supercharger not only introduce a power drag, but their compression efficiency is not that great (the Turbo driven supercharger is almost always more efficient).  Either won't match the air compression and handling needs of the cylinder-piston over the whole range of RPM's and loads that the auto engine commonly faces.

The thing with a Turbo or Supercharger is that both have performance maps that do not match the performance map of the piston engine entirely.  The Turbocharger produces way too much compressed air at high RPM's, and the mecahnically driven Supercharger does the opposite.  Thus, the Turbo needs a waste gate to avoid overcharging the combustion chamber of the piston-cylinder engine, and presents some lag; the Supercharger has lower overall compression efficiency but does deliver pressure boost inmediately, and then runs off at higher RPM's.  The idea is that the pressure boost needed by the cylinder-piston is not really well met by both devices; thus the concept shown could well be a better match for the cylinder charging needs, maybe better than the traditional Otto cycle.  Please consider that the Otto cycle engine usually operates at very low effective compresion ratios, due to the throttle valve being open completely only when the accelerator pedal is pushed hard!  This concept remainds me of the so called "Turbo-Compound" engines used in  the 50's in the last piston driven airliners like the DC-7 Super and the latter Super Costellations...  but were overly complex and unreliable, and were soon replaced by the jet turbine.

vandamme
User Rank
Silver
Re: Shaking the Automotive Industry.
vandamme   9/26/2011 11:03:59 AM
"We cannot use these in the US becaus of the high combustion pressures and temperatures (the key to efficiency) causes too much NOx"


So, it's purely political? We can fix that.

Ivan Kirkpatrick
User Rank
Platinum
Fossil Fuels are plentiful
Ivan Kirkpatrick   9/26/2011 10:43:47 AM
I suspect that we will be using fossil fuels a lot longer than many people suspect or desire.  Reducing emissions is a laudable goal but the world is going to use up all the fossil fuel we can no matter what the green climate folks would like to see happen.

I would really like to see the EV replace ICE powered ones but the target to beat is still the ICE and the availability of fossile fuels is still good enough.  How good and for how long is difficult to say but we keep finding more and figuring out how to get it in a relatively cost effective manner.  Oil, coal, natural gas, methane hydrates, we are going to use them all.

RNDDUDE
User Rank
Platinum
Re: Very Likely
RNDDUDE   9/26/2011 10:31:01 AM
Isn't this essentially an internal supercharger? Seems a traditional supercharger would have less parasitic loss, no fricton from extra pistons and valve train, and would accomplish exactly the same thing....

wlawson
User Rank
Iron
Re: Shaking the Automotive Industry.
wlawson   9/26/2011 10:29:11 AM
Having a long history of watching these various technologies I am very skeptical until they actually build one and run it on a dyno or an instrumented vehicle.  They need to build it and test it, otherwise it is just another idea that is good on paper but will never materialize.  The world is full of failed attemps.  like the ECOmotor.  So far no one has been able to violate the laws of thermodynamics

Currently the most efficient practical engines are the direct injected European Diesels at over 30% actual dyno efficiency. We cannot use these in the US becaus of the high combustion pressures and temperatures (the key to efficiency) causes too much NOx

vandamme
User Rank
Silver
Re: Shaking the Automotive Industry.
vandamme   9/26/2011 9:26:59 AM
"..at 65 mpg proven via simulation,,,there is talk in the 80 mpg range and a longer view of 100 mpg."

In other words, they haven't built anything that performs, but the investors are dreaming big dreams of selling out and the PR machine is cranked up to 11.

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