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Cyclone Power to Showcase External Combustion Engine at SAE Event

Cyclone Power Technologies will showcase two automotive applications of its external combustion Green Revolution Engine (earlier post) at the upcoming SAE Commercial Vehicle Convention in Chicago. The company will display a 100 hp Automotive Engine and a 330 hp Truck Engine, which will be installed in a full truck chassis for the first time.

Cyclone’s engine is a multi-fuel capable engine that uses an external combustion chamber to heat a separate working fluid, de-ionized water, which expands to create mechanical energy by moving pistons or a turbine.

The engine’s combustion chamber creates a rotating flow that facilitates complete air and fuel mixing and complete combustion. Less heat is also released. Exhausted gases run through a heat exchanger before leaving the engine, lowering the temperature at release.

The company proposes a number of configurations of the engine, including small single-cylinder units; a two-cylinder opposed piston engine; and three-, four- and six-cylinder radial engines.

The company most recently concluded its testing with low octane gasoline. The design of Cyclone’s fuel injector, which works with a primary and secondary air source, maintained a low temperature flame front with an extremely clean burn, according to the company.

As a result of the low temperature burn of the gasoline, the Cyclone engine produced little or no NOx, and kept carbon monoxide levels at a minimum. Additionally, the cylindrical design of the engine’s combustion chamber effectively eliminated much of the unburnt hydrocarbons from the fuel source, according to the company.

Cyclone has also tested a bio-fuel, d-Limonene, made from orange peels; biodiesels produced from palm oil, cotton seed oil and chicken fat; and three grades of ethanol produced from corn.



So... it's a closed-loop steam engine?

Robert Schwartz

"Cyclone’s engine ... uses ... combustion ... to heat a separate ... water, which expands to create mechanical energy ..."

Bring back the Stanley Steamer. My father, of blessed memory, loved them. He loved to tell me about how quite they were and how much torque they could generate at zero speed.

First, Grandma's Baker electric, now the Stanley Steamer. Everything old is new again.


But you had to wait for that Stanley Steamer to head up to boiling point to build up steam pressure before you could go anywhere. I doubt you'd see many of these engines in the average car for just that reason. This is why ICEs won out in the first place.


Unlike old steam locomotives (and the Stanley Steamer) which had to heat a lot of water before starting off, these engines have flash steam boilers which only heat a small amount of water at a time and can warm up in a matter of seconds.

Cool to see that this initiative is still alive and kicking.


So the cyclone engine has high specific power, can run on many different fuels, and has clean(er) emissions.

But the inevitable question is how efficient it is in terms of what percent of the fuel's potential energy is actually realized into mechanical work? Also - how is the engine lubricated, and how does one avoid the oxidation and corrosion caused by the water?

Nate Fairchild

They're using de-ionized water - so no corrosion and oxidation - and I remember reading that its lubricated by water as well.

Roger Pham

Upon reviewing of cyclonepower.com website, it appears that the Cyclone steam engine is of sound design principle and ingenious execution, far more advance than previous steam engines of antiquity.

However, only one thing that remain unproven: How good is lubrication by water? At such high power concentration per displacement (3hp/cid) and at 3200 psi peak pressure, surely the frictional stress on the metal surfaces is much stronger than that of an ICE with peak pressure of ~1000 psi and BMEP ~120psi range. And yet, the ICE piston, cylinder and bearing are supported by a much thicker layer of oil with much higher lubricity. If this water lubrication works, it will open up the way for more efficient ICE with less heat loss to coolant, since the engine (ICE) now with water lubrication can run at much higher temperature and needs much less cooling if at all. Air cooling will be more than sufficient if much less cooling is required, leading to lighter and lower cost ICE.

Thermodynamically speaking, with peak super-heated steam temperature of 1200 F, or 648 C and with a single stage adiabatic expansion, one can expect no more than ~35% thermal efficiency, even with minimum friction loss and heat regeneration. Even the best power plant steam turbines operating at comparable super-heated steam temperature with multiple reheating stages and meticulous attention to heat recycling can achieve ~40-45% thermal efficiency. This, in comparison to a simple truck diesel engine at 42% efficiency, or a power-generating diesel engine at nearly 50% efficiency.

This is perhaps the reason why no listing of thermal efficiency at the Cyclonepower.com website.



I found a mention of thermal efficiency at the back end of Cyclone's PDF:

"Burning a gaseous fuel which is pre-expanded loses a lot of power where as using hydrogen in a cyclone is a plus.

Assume JP-8 @ 6.819 lbs per gal fuel burn at .06 gal per hp per hr
19,810 fuel BTU per lb
.06 X 6.819 =.40914 X 19,810 = 8105.063
2545 / 8105.063 = .314 or 31.4% thermal efficiency ±10%

Whereas, diesel is about 30% to 35% and gasoline is 20% to 25% after a hundred years of development."



I'm a bit confused about thermal efficiency and its importance in regard to the Cyclone. It'll run on many combustible things, so in the event that it gets the same mileage as a current ICE, the ability to use cheaper fuel would be advantageous. It pollutes a very miniscule amount, and it makes 2.5 hp/ cubic inch. So where does thermal efficiency come in? And how unorthodox is the water lubrication? Is there any precedent?

This whole thing seems almost too good to be true. The idea of an "external combustion engine," that runs on anything and can be tied perspectively to steam engines, is more marketable than an electric one. Especially in the US and double especially when it looks like it's straight out of the 60's.




This engine could perhaps be interesting as a range extender for series plug-in electric vehicles. Its characteristics of multi-fuel, low emission and low noise are important for such an application. Instant torque is not important for a range extender. If it also is efficient and can be produced at low cost it will be really interesting. Once the batteries are ready for plug-in vehicles the development of chemical fuel engines will be mostly about creating good range extenders. When these batteries are made it should be quite possible that the ICE will get really tough competition from engines such as the Stirling engine, see http://en.wikipedia.org/wiki/Stirling_heat_engine#Advantages_of_Stirling_engines. I am not an engine expert so I could be wrong on this matter.


Uhhhh, Stirling cycle anyone? I can't see anything novel here other than using water with a phase change to steam....

gavin walsh

it is not stirling cycle, it is a modified Rankine cycle.


I just learned that sterling engines have very low specific power so unless that can be dramatically improved that will disqualify them as range extenders for future plug-in vehicles.


Organic rankine cycle is going to be one of the big, big things this century.

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