Concept: Heavy-Duty Multi-Fuel Turbine for Class 8 Trucks
26 June 2006
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| A rendering of a 540hp prototype. |
A Florida company, Turbine Truck Engines (TTE), is developing an implementation of a multi-fuel turbine for heavy-duty vehicle applications, and has recently completed the design of a fifth, 540hp prototype.
The Dentonation Cycle Gas Turbine (DCGT), originally developed by Alpha Engines beginning in 1984, promises to consume 30% less fuel; to emit fewer criteria pollutants (NOx, CO, HC); and to emit fewer greenhouse exhaust gasses than current piston engine technology. The turbine operates on all hydrocarbon, hydrogen, and synthetic fuels. The DCGT has Flex-Fuel and mixed-fuel capabilities, as well as cold start capabilities with any fuel.
TTE was formed in 2000 to acquire the engine technology and license rights from Alpha Engines. Alpha Engines Corporation remains as a privately owned research and development company.
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| Cross-section of the DCGT |
The engine includes a turbine rotor contained within a housing. Exhaust ports of paired valveless combustion chambers are located on opposite sides of a rotor, which operates in a manner similar to a water wheel. Combustion gases exit the combustion chambers via nozzles, and spin the turbine rotor.
A valveless manifold fed with fuel and oxidizer connects the combustion chamber pairs. A blower, rather than a compressor, supplies low pressure air via the single manifold. When the air-fuel charge ignites, the back pressure from the detonation shuts off the charge flow to the active chamber and redirects the charge to the opposite chamber for the next detonation. The process repeats cyclically. The rotor shaft can provide mechanical power directly, or be used to generate electricity as a genset in a series-hybrid application.
The engine uses a fuel pump and vaporizers to gasify wet fuels prior to mixing with combustion air in the manifolds. The engine uses a plasma arc ignition (Electromagnetic Isothermal Combustion—EIC), a visibly constant illuminating plasma flame between two electrodes to detonate fuel-air mixtures and does not require critical ignition timing.
TTE claims that the almost instantaneous ignition of the low-pressure air and fuel mixtures produces high velocity shock waves that kinetically compress inert gases resulting in higher working pressures than the pressures produced in constant pressure heating utilized in gas turbine engines, and Otto and Diesel cycle piston engines. The EIC process also produces complete combustion of fuel-oxidizer mixtures in cyclic detonations that reduce emissions, according to the company.
As a result, the company claims, the detonation cycle engine uses less working fluid and produces less exhaust gas per horsepower hour than Brayton cycle turbines and Otto or Diesel cycle piston engines.
The EIC process enables the DCGT to operate with blower air at low static pressure, negating the necessity of compressing and preheating fuel-oxidizer mixtures prior to combustion. By eliminating the compression of fuel-oxidizer mixtures, the DCGT achieves higher thermal efficiencies in a simplified mechanical structure, according to the company.
In addition to the fifth design prototype, Alpha had developed four working prototypes:
1987. The engine consisted of one 8-inch diameter, 26-pound turbine wheel, driven by two horizontally opposed combustion chambers. The engine produced 78 horsepower at 12,500 rpm.
1989. The engine consisted of two 5-inch diameter, 11-pound turbine wheels mounted on a single shaft, driven by four horizontally opposed combustion chambers. The engine produced 130 horsepower at 14,000 rpm.
1991. The engine consisted of two 7-inch diameter, 19.6-pound turbine wheels mounted on a single shaft, driven by four horizontally opposed combustion chambers. The engine produced 256 horsepower at 8,300 rpm.
1997. The engine consists of four 6-inch diameter, 12-pound turbine wheels mounted on a single shaft, driven by eight horizontally opposed combustion chambers. The engine produces 130 horsepower at 8,400 rpm. This engine is currently used for demonstration and can be seen by appointment.
Working prototype #4. 1997.
The fifth design prototype has six 15-inch diameter, 20-pound turbine wheels mounted on a single shaft, driven by 12 horizontally opposed combustion chambers producing 540 hp at 3,000 rpm.
TTE last week announced that it is discussing a potential joint venture with a $5-billion worldwide transportation company to manufacture heavy duty highway truck engines.
Resources:
Videos of earlier prototypes.
- US Patent #6,000,214: Detonation Cycle Gas Turbine Engine System Having Intermittent Fuel and Air Delivery
Hmm! This is unlike anything previously revealed. 20 years in development and no actual picture of a prototype to show to the world. Reminds me of the German pulsejet engine used in the V1 rocket in WWII. As simple as the pulsejet engine, it still requires a valve and compression of air-fuel mixture by virtue of airspeed above 200mph for adequate efficiency. Of course, development of tubojet engine by Von Ohain and Frank Whittle with far greater efficiency put the pulsejet engine out of existence. Recently, there is a resurgent interest in the detonation jet engine which uses compressed air from forward motion into a tube, and a rotary valve to interrupt this flow, and a purposely arranged detonation follows which creates a loudest bang and a powerful kick of thrust forward, and the cycle repeats ad nauseum. Of course, for continous thrust, a bundle of detonation tubes will be needed, resembling the barrels of a gattling gun, in which each tube will detonate at different times. Pretty ingenous device, which recognizes the superior efficiency of the intermittent combustion engine over that of a continous combustion engine as represented by the Brayton cycle. Furthermore, while in a piston engine we try to avoid detonation as much as possible for fear of piston damage, then someone got smart and says, OK, so, let's remove the piston and let this thing detonates all it wants and let's see how much power we can get out of it. (here, I'm afraid that the turbine blades are at risk of being damaged by the massive force of detonation) Well, so much for initial announcement, the detonation jet engine has not been heard of years later.
I'd appreciate it if anyone can give us more details as to the working principle of this weird new contraption.
Posted by: Roger Pham | 26 June 2006 at 03:56 PM
Roger,
Videos of the working prototypes are available on TTE website here: http://www.turbinetruckengines.com/video.htm
Patent information here: http://www.turbinetruckengines.com/pages/patent.html
Posted by: Mike | 26 June 2006 at 04:10 PM
Thanks, Mike, for the links.
Very ingenious and original concept. This type of engine is best adapted to hybrid electric, as it may not retain its advertised efficiency at less than optimal throttle setting, and may have poor accelerational characteristic typical of that of a turbine engine due to rotational inertia of the turbine wheel.
Looking at the patent, it seems that the shape of the combustion chamber can be improved by having a 3-dimensional hemispherical shape converging at the igniter, and the shape of the manifold should be circular instead of regtangular for better propagation of the pressure shock wave. Furthermore, the quoted efficiency of Otto-cycle engine at 0.6 lb of fuel/hp/hr is plain wrong. Optimized 200hp automobile engines can achieve 0.45 lb of fuel/hp/hr. Likewise, the quoted efficiency of Diesel-cycle engine at 0.55 lb/hp/hr is also plain wrong. A good 200hp Diesel engine can achieve 0.33lb/hp/hr. Therefore, the claimed 0.3 lb of fuel/hp/hr for the Detonation-cycle engine is not much better than that of a good Diesel engine. Likewise, the quoted 1.2 lb of fuel/hp/hr for a Brayton-cycle 200hp gas turbine engine is also plain wrong. A Rolls-Royce Allison 17B gas turbine of ~300hp is rated at 0.65 lb of fuel/hp/hr. But, otherwise, in comparison to a similar-sized gas turbine, this detonation engine is a revolutionary improvement. But, whether it can replaced a rugged and proven diesel engines in big-rig tractor-trailer trucks remain to be seen.
Posted by: Roger Pham | 26 June 2006 at 10:09 PM
I' sorry, but my BS bells have been going off since I read this. Seeing the website made it worse. The numbers are so far off it has to be a scam, no engineer would make those mistakes.
Please notice no engineer on the board or management.
Why no dyno numbers, graphs etc.? No pollution per unit power projections. This will only fool non technical people.
For the record I lost a small amount of money on one of these Florida companies doing electric vehicles years ago. They were able to scam money out of some other wise smart people. I did not invest, I sent a pile of expensive books to the company to prove to them they had made errors after being asked to look at it by a friend that did invest. I though they had made an error and was trying to help. Never saw my books and he never saw the money. Solarmax. They never had a documented instrumented product either.
Real engineers build and test. Then they play with it, put it to some use, not just on a test stand. Then they go ask for money to make a production prototype.
I may be wrong about this, but the next big thing in engineering is not coming from Florida.
Posted by: jPadula | 27 June 2006 at 06:53 AM
If the goal is to put it in Semi trucks, then who cares about HP, what's the torque? :)
Even 540hp is going to have a hard time getting 60,000Lbs moving if it's only making 100ft/lbs
Posted by: Ash | 27 June 2006 at 07:14 AM
Ash -
generally, small gas turbines produce little torque but do so at very high speed. A suitable transmission can perform the conversion. For an example, see
http://www.scania.com/products/newtruckrange/technology/turbocompound/how_does_it_work.asp
Scania uses turbocompunding in addition to turbocharging. Note the hydraulic clutch to protect the turbine against torsional vibration of the crankshaft, induced by the pistons.
I share jPadula's concerns about this engine concept. It's really a single-stage gas turbine with intermittent combustion. The stability and load response dynamics of single-stage turbines are well documented. Even as two-stage systems, turbines are considered unsuitable for prime movers for automobiles:
http://www.4wdonline.com/Rover/GasTurbines.html
http://www.allpar.com/mopar/turbine.html
It is not at all clear how you could achieve higher pressure on the turbine side of the combustion chamber than on the intake side. Pressure waves travel in all directions from a detonation and must be reflected to achieve the deisred effect. The diagram and picture do not indicate the presence of any valves.
Intermittent combustion, regardless of ignition mechanism, involves transient flames that are quenched near the relatively cold walls (premixed charge, cp. gasoline) or that contain very rich zones (late injection, cp. diesel). Either way, you get substantially higher engine-out emissions than with a continous flame. The company claims to use "plasma arc ignition". How, pray tell, is that different from a spark plug?
Another reason for scepticism is that the power conversion element (i.e. the turbine in this case) is never exposed to cold gas. In large jet engines, some of the compressed air is bled through the shaft and out through nozzles on the leading edge of the turbine vanes to produce a shroud of cool protective gas. Below 1.5MW rated power, the turbine vanes are usually too thin for this and you have to make do with the lower process temperature that can be handled by high-temp alloys or ceramics. Pelton turbines such a#the one proposed above cannot be cooled by shrouding regardless of size. Thus, the temperature limits of available turbine material seriously limits the core Carnot efficiency of small units - and in the trucking business, fuel consumption is *everything* (well, almost).
Posted by: Rafael Seidl | 27 June 2006 at 08:16 AM
Rafael,
The above are important points you've raised. I had the same concerns re this engine concept. Upon further examination, I've come to realize that no valve would be needed, nor would be desirable given the violent force of detonation. As one combustion chamber detonates, the pressure wave is sent in both directions, toward the turbine for powering it, and toward the manifold for compressing the fresh air going into the other cylinder (combustion chamber). The exact orifice size and shape of pressure wave receptacles on both ends must be precisely determined in order to optimize power output, timing and compression of the other cylinder. The compression achievable should be high, and the patent quotes a number of 20 bars of compression and 80 bars for peak pressure generated. The pressure wave sending toward the manifold can also send some fresh cool intake air past the cylinder and toward to the turbine blade of the non-detonating cylinder for cooling it. This is the beauty of this intermittent combustion concept that will make this engine much cheaper and simpler than gas turbines, albeit a lot heavier, due to the lack of continous combustion. Gas turbines gets anywhere from 2-4 hp/lb of engine weight, whereas this engine is listed as having 0.5 hp/lb of engine wt, thus reducing its desirability in hi-performance aircraft application. This engine desperately needs hi-pressure fuel injectors in order to inject fuel at precisely the point near maximum compression in the combustion chamber only, in order to prevent escape of raw fuel together with fresh air charge into the turbine blade in the cooling mode.
It appears that the patent attempts to hold back information necessary for optimum functionality of the engine, perhaps for security reason. The overall concept seems workable with significant modification from the diagram in the patent, albeit it would be very critical to get it to run just right, perhaps may require computer monitoring and control in order to synchronize the detonation on one cylinder with the compression wave on the other non-detonating cylinder. The engine probably can't idle with any degree of efficiency as typical of gas turbines, hence must be turned on or off, and hybrid system to take care of the vehicle's accessory needs during idling and restarting. Acceleration will also be a problem, given the necessary sturdy and heavy construction of the turbine wheel to withstand the force of detonation. All these limitations may have been factors in delaying entry of this concept into mainstream acceptance phase.
What remains to be done is testing of the engine prototype by an independent engine testing laboratory in order for the engine design to gain any degree of credibility.
Posted by: Roger Pham | 27 June 2006 at 10:21 AM
The plasma arc ignition is said to facilitate detonation due to greater energy and temperature of the ignition source in comparison to a much weaker spark from a spark plug. For the same reason, fuel injection as I've suggested must be done fairly early and must be very finely atomized in order to promote complete mixing with air to permit detonation. Properly done, the combustion process can be complete due to the high energy of detonation, hence minizing exhaust emission.
Posted by: Roger Pham | 27 June 2006 at 10:58 AM
Meanwhile... back at the ranch,
Somender Singh's Grooves have been dyno tested by random people and every test of any kind supports his claims about improved efficiency, improved torque (especially low-end) , reduced harmful emissions, reduced operating temp and other claims that seem far fetched until you read who is interested in it 'out there'. The Groove can be applied to old engines or incorporated into the head making process for peanuts compared to all the valve limiters and doodads presently being offered. "Tis just a scratch" but feels oh so good to get 23% better mileage, not to mention clean oil!
Posted by: zipper | 18 September 2006 at 06:27 PM
Interesting to know the groove is being discussed ? Singh's website www.somender-singh.com has more in depth case histories of what is happening inside the combustion chamber to do what it is doing.
His theory of combustion highlighting the role of Nitrogen is a real eye opener ? How come nobody ever thought of it ? or they took it for granted !
Posted by: Flamefront | 09 October 2006 at 01:51 AM
Do you guys really think that putting grooves in your cylinder head will give you better fuel economy? This one belongs right up there with the "Tornado" fuel saving device...lol. This guy might really think he has a breakthrough but sorry to say that it is not. I am sure a multitude of different combustion chamber shapes and designs have been tested by the automotive industy that they would have stumbled onto this by now. Another good one for Mythbusters...
Posted by: Brian G | 06 March 2007 at 08:24 AM
Hey People, Somender Singh's grooves certainly do work and changes the way the whole car runs !!! I've been fortunate to have the mod done by the master himself !!! Absolutely fantastic !!!
Read my review "Totally Transformed" on :
http://www.somender-singh.com/
Posted by: Jeevan | 10 March 2007 at 09:23 AM
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