Natural Gas Engine - Motor
... methane is a powerful greenhouse gas causing significant emissions concerns...
... conventional internal combustion engines (IC) operated on natural gas
will not likely meet the future severe environmental standards to be implemented...
For gas pipeline pressure energy recovery
using a rotary Quasiturbine expander, see
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Internal combustion engine
The difference between liquid and gaseous fuel in the Quasiturbine ?
Ultimately, all fuels get into gaseous state in the combustion chamber, so one may be at first legitimate to expect little difference,
but looking at the combustion process itself is not where the answer stands.
One needs to look at the details of the specific engine intake and dynamic.
Because engines generally prefer a near stochiometric mixture
(except for non-homogeneous Diesel and homogeneous photo-detonation, which works in excess of air),
the amount of fuel and air should be balanced at intake. Lets consider the gasoline 4 strokes piston engine.
When the intake valve opens, a fix volume is aspirated.
Since the gasoline intaked as liquid droplets does occupy almost no-volume,
most air available can be intaken from the depressurised intake manifold.
In this regard, the gasoline injectors near intake valves are superior to the carburetors
in permitting more liquid droplets and less gasoline atomization (vapor),
which explains why the modern gasoline injector engines have a higher specific power density.
Fortunately with the piston engine, when the intake valve closes, there is plenty of time for the gasoline droplet to atomize
during compression and later even during the combustion stroke,
because optimum pressure is not required until well pass the TDC (top dead centre).
However, this droplets intake technique is not without adverse effect on pollution,
but this slow imperfect combustion saves the engine valves from being torched out !
By opposition, intaking gaseous fuel which occupied a substantial volume, will leave less volume available for air intake,
and the engine specific power density will be diminished.
Let imagine someone using for example a liquid nitrogen gaseous condenser near the intake valve
(not good with hydrogen of course), the gaseous fuel would condense into droplets at intake,
and a more similar situation to liquid gasoline would be observed.
To make it short, it is not easy to produce the same combustion condition by intaking liquid or gaseous fuel,
and those condition differences are further apparent in the front flame velocity (in addition to the specific chemistry characteristics...).
Because of its continuous intake flow and its early and late intake characteristics,
the Quasiturbine is most able to minimize the gaseous fuel intake penalty.
Where does the Quasiturbine photo-detonation mode stands ?
Everyone has experienced that lens sun focalization can lit a fire.
As the compression ratio of an engine increases, not only the gas temperature increases, but also the radiation level.
Combustion goes primarily through at least 3 phases :
Primo, at low compression ratio, a hot spot (spark) is required to start a combustion front flame wave.
This subsonic wave propagate and lit progressively the mixture (this is smooth deflagration use in our gasoline vehicle).
Secundo, higher pressure will provoke thermo-ignition, which is a very non-uniform process liting mixture patches,
and inter-patches combustion being driven +/- by the previous describe front flame wave.
Tertio, still higher compression ratio produces uniform radiation driven liting process,
which is an extremely rapid volumetric combustion.
In this case, there is essentially no front propagation, just a powerful light radiation everywhere...
This is the most severe knocking that the piston cannot stand, but it is the most powerful and perfect way to combust fuel !
In fact, additives used to increase the gasoline octane index
are efficient photon absorbents molecules which prevent this kind of photons build-up,
and such polluting additives are not needed in photo-detonation mode engine.
Even if shock waves do have the potential to lit a fuel mixture,
photo-detonation does not actually make use of a shock wave within the mixture.
However, the rapid chamber pressure increase does generate a shock wave in the engine environment,
which could be substantially moderated by a rapid increase of the combustion volume at that time
(this is what the Quasiturbine does !).
So, why does the piston don't stand the photo-detonation ?
Because it stands high compression near TDC (top dead centre) much too long before producing useful work at mid-stroke.
And why does the Quasiturbine stand it (particularly the QTAC) ?
Because the volume pulse is 15 to 30 times shorter near TDC, and also because its higher surface to volume ratio
is moderating the violence of the photo-detonation process, which is almost independent of the mixture front-wave flame velocity...
Consequently, even if the Quasiturbine can run in conventional Otto mode,
its photo-detonation mode provides the most benefit to fuel efficiency and environment, both for liquid or gaseous fuel...
The Photo-detonation mode :
A necessity for the hydrogen and gaseous engine
In order to do work on a piston, the fuel-air mixture needs to burn at a speed faster than the piston is moving.
Low hydrogen flame speed is a disadvantage shared with most other gaseous fuels.
For comparison, a gasoline-air mixture has a flame front speed
that ranges typically from 70 up to 170 feet/second in IC engines,
while an ideal hydrogen-air mixture has a flame front speed of about 8 feet/second.
An average vehicle engine rotating at 2,000 rpm (33 revolutions per second)
produces piston linear speed of 45 feet/second in the middle-stroke,
which is already 5 times faster than the hydrogen flame front speed !
The fact that a hydrogen-air mixture has a flame front speed of about 1/10
that of a gasoline-air mixture contributes to explain why hydrogen engines only run at reduced power and low rpm under load.
However, the photo-detonation mode is extremely rapid and totally removes this limitation.
This is why the photo-detonation mode (not compatible with piston, but with the Quasiturbine)
is so critical for the future of the hydrogen engine.
The Best Current present state of gas technologies: Currently, the most efficient power generator, using natural gas as the fuel, is the Combined Cycle Gas Turbine CCGT. The CCGT is about 55% efficient (58 to 60% according to http://www.fossil.energy.gov/techline/tl_ats_ge1.shtml or http://www.energyusernews.com/eun/cda/articleinformation/coverstory/bnpcoverstoryitem/0,2582,6779,00.html ) because (1) it uses the heat from the gas combustion cycle to turn a turbine and (2) it uses the residual heat to generate steam for a steam turbine cycle. These are quite high tech sophisticated pieces of equipment with limited live span time and further, they are accompanied by high maintenance cost. Fuel cells, operating on steam-reformed natural gas, will have very low emissions, but despite some claims of very high efficiency, their efficiency is only about 35% from raw fuel. Furthermore, they are not readily available for high power output plants yet now a day. An article in Scientific American of June 2001 exposes that combustion uniformity is the key challenge in internal combustion engine. As a matter of fact, Researchers have been looking how to make a uniform combustion in Diesel engine (injectors are not making a uniform combustion) for 40 years. In fact, the Quasiturbine is the solution to this key crucial engine problem, so important to all of us.
Why is the Natural gas Quasiturbine superior to conventional engine?
North American energy policies: In keeping with the announced U.S. policy to reduce dependence on foreign oil sources, natural gas from the U.S. and from Canada is the obvious fuel of choice, given its relative abundance and low cost per BTU.
Environmental concerns: The problem with a conventional internal combustion (IC) engine, running on natural gas, is that methane is a very stable molecule and complete combustion of the methane in the internal combustion IC cylinder is very difficult. Because methane is a powerful greenhouse gas, this causes significant emissions concerns. The conventional internal combustion IC engines operated on natural gas will not likely meet the future severe environmental emission standards. This concern is even more important with syngas and, hythane, etc. used as fuel in internal combustion IC engine, and worse with the low specific energy gas mixture produced by gasifiers and bio-digesters is also a concern. The Quasiturbine operating on natural gas has favorable potential emissions characteristics to meet severe standards, because of very little uncombusted methane or other VOC's (Volatile Organic Compound) from the engine (see the summary of the combustion characteristics below). The Quasiturbine is quite a recent invention, and theoretical emissions characteristics of the natural gas-powered Quasiturbine should be validated by measurement testing as soon as possible...
Quasiturbine and the environment solution: The Quasiturbine pressure pulse is shorter and increased linearly (as opposed to tangentially at the TDC position like the sine wave of the conventional crankshaft). This means that photo-detonation at the TDC is not followed by a long confinement time, responsible for so many broken pistons. Furthermore, because the pressure pulse is 15 to 30 times shorter at the top, photo-detonation invariably occurs there, and the Quasiturbine is not synchronization sensitive. The objective is to operate the Quasiturbine in photo-detonation mode, with compression ratio of 20:1 to 40:1 ! (Polluting with piston, but not with the short and linear Quasiturbine pressure pulse). The radiation is then the triggering source of a volumetric combustion, and will occur for all molecules, including methane. In fact, the lower the octane index is, the better the combustion is, because the octane additive are by nature radiations absorbents. To be able to work under photo-detonation mode required other engine characteristics, and the Quasiturbine has all those requirements. No more sparkplug, just crank it. No more diesel injector, just pulverized at atmospheric air intake. 500 times less NOx because the Quasiturbine has a confinement time too short to allow for the chemistry of the NOx to occur. No more timing synchronization. Conversion in mechanical energy extends early and late compared to piston engine, and for this reason the combustion gas cools down adiabaticaly (no thermal lost) faster than in piston engines, so that the heat flow to the engine block is less than with piston, and this is the reason why the second steam cycle is less required in Combined Cycle Quasiturbine CCQT ... and so on!
Why not use a Combined Cycle Quasiturbine CCQT in the same way as the Combined Cycle Gas Turbine CCGT? There would be two cycles. In the first cycle, a Quasiturbine would be used as an internal combustion gas engine to generate electric power. The sensible heat from the first cycle would then be run through a heat exchanger to generate steam in a boiler for the second cycle. Because of similar Quasiturbine's unique ability to run on combusted gases and steam, in the second cycle, steam would provide a second Quasiturbine's motive force, thereby increasing overall fuel efficiency. Furthermore, the Quasiturbine center being empty, the internal combustion (IC) and Steam Quasiturbines can be on the same shaft, with a simple ratchet coupling, and the torque will be cumulative on one single electrical generator! The interesting point (from a capital cost standpoint) is that it does not required both different systems as the gas turbine and the steam turbine do with a CCGT. The Quasiturbines would function as both a gas turbine (first cycle) and as a steam turbine (second cycle). Operationally, it would run the Quasiturbine in first cycle mode until steam is built up in the boiler. When the steam pressure is adequate, a computer would start the second Quasiturbine cycle mode. As steam pressure decreases, the computer would return to the first cycle mode only. Thus, in principle, one could have a Combined Cycle Quasiturbine CCQT. The fuel efficiency of the CCQT would probably be less than a true CCGT (55%) but more than the Quasiturbine alone (33%) which can run at higher internal gas temperature because of early adiabatic expansion mechanical conversion. This type of efficiency would actually be more than a fuel cell stack, which, despite some claims to higher efficiency, is only about 35% at most from raw fuel, and quite costly on live for time and maintenance. For small unit, the combustion cycle could be combined with the Quasiturbine-Stirling cycle, which with a spoon of water can also work as a closed circuit steam engine. Details at:
Other Quasiturbine advantages: The Quasiturbine is a very low RPM engine. Internal combustion IC engine idle is under 200 RPM and up to 3000 or more. It does not required a gearbox to direct drive an electric generator. The Quasiturbine natural gas engine can be made very large to drive 10's of megawatts size generator. Low noise, low tech equipments, low maintenance cost, minimum plant personnel qualification required.
Some commercial markets are being the same as the market misappropriately targeted by fuel cells. Fuel cells, operating on steam-reformed natural gas, will have very low emissions. Demonstration that an internal combustion IC Quasiturbine also has low emissions characteristics operating on natural gas would provide a low price alternative for the transition period until further fuel cell developments. For marketing purposes, the Quasiturbine's more favorable emission characteristics will be very important.
High power density applications:
Generally speaking, the commercial market of natural gas Quasiturbine or CCQT is not being the same as the market targeted by fuel cells. On the RAGON diagram, the Quasiturbine is the highest density power plant by weight and volume. Fuel cell chemistry forbids such a specific high power density (which is very appreciated also in the transportation industry). The Quasiturbine is such a recent invention, and already some are not willing to wait longer to test this spectacular high power density...
It is not certain that CCQT could be practically adapted for a hybrid electric vehicle. It might depend on the size of the boiler. But if such a natural gas-powered, hybrid electric vehicle could be engineered, it might well approach the 80 mpg (gasoline equivalent) vehicle that DOE has wanted, especially with a regenerative braking system. For small units, a Quasiturbine-Stirling engine could replace advantageously the second stage steam-Quasiturbine.
Distributed power generation:
Another market for CCQT is distributed power generation and uninterruptible power supplies. The CCQT would have fuel efficiency advantages similar to a CCGT but would be compact enough to be easily located on-site. If the CCQT could be sold for about US$800 per kW installed, it could be a cost-effective option in this market. The Quasiturbine seems like an ideal power generator for these applications with natural gas, syngas, hythane, etc. as the fuels.
The Quasiturbine is quite recent invention, and already some opportunities are presenting themselves for cogeneration projects.
Key Gas Organizations: In the past years, the following key organizations in the world gas community have been regularly informed about the Quasiturbine technology:
AGA - American Gas Association http://www.aga.org
APGA - American Public Gaz Association http://www.apga.org/
National Propane Gas Association mailto:firstname.lastname@example.org
INGAA - Interstate Natural Gas Association of America http://www.ingaa.org/
Natural Gas Supply Association http://www.ngsa.org/
CGA - Canadian Gas Association mailto:email@example.com
AGI - Australian Gas Industry mailto:firstname.lastname@example.org mailto:email@example.com
ENGVA - European Association for Natural Gas mailto:firstname.lastname@example.org
JGA - The Japan Gas Association mailto:email@example.com
WLPGA - World LP Gas Association mailto:firstname.lastname@example.org
... and others ...
Quasiturbine: A technology soon ready for action:
For all the previous reasons, the Quasiturbine is a breakthrough as a natural gas combustion engine. Conventional piston and turbine engine experts are starting to seriously work on it. All the solutions are in front of us. This overview suggests to focus strongly on some engineering efforts on a natural gas-powered Quasiturbine as soon as possible. Some may not, as of now, realized the full fuel efficiency and environmental potential of the Quasiturbine operating on natural gas. At this time, only a few seem to acknowledge the potential of the Quasiturbine for small engine and large electricity generation from natural gas, but more and more experts are looking into this technology and recognize its strategic interest for the future. The Quasiturbine natural gas is getting more and more support every day, and it is now just a matter of time and effort...
For small power needs, natural gas is well suited for the Stirling-Quasiturbine engine at:
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Quasiturbine au Gaz
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