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When Cummins went "Adiabatic"


kscarbel2
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Being reminded of Isuzu’s ceramic engine causes me to mention Cummins’ adiabatic engine research.

Adiabatic is a thermodynamic term meaning no heat loss. The engine retains virtually all the heat created by the combustion of the fuel, and thereby requires no cooling system.

Cummins and the United States Army experimented with such an engine in a five-ton model M813 6x6.

The Army was interested in the project because it found that 60 percent of its vehicle-related failures involved problems with cooling systems.

The Army’s Tank Automotive Command (TACOM) at Warren, Michigan, and Cummins jointly developed this first generation adiabatic engine by modifying the NHC250 normally found in the M813.

The major changes involved making the pistons, cylinder liners, cylinder head, valves and exhaust manifolds out of a ceramic-metallic mixture which could tolerate temperatures exceeding 2,000 degrees Fahrenheit.

By retaining most of the heat generated by fuel combustion and converting it into energy, the efficiency of the engine was improved almost 100 percent.

A normal engine is only able to convert about one third of the heat created into usable power. The other two thirds is lost through the cooling system or out the exhaust pipe.

Fuel economy was also improved with the adiabatic NHC250 version by almost 30 percent.

Other advantages to the adiabatic NHC250, particularly in military applications, included the ability to install the engine within a vehicle in any position, since there was no requirement for airflow, or the need to be near a radiator for cooling.

Without the need of a radiator, hoses and water pump, a weight savings of 338 pounds was realized with the adiabatic version.

Lastly, because of the adiabatic engine’s very high combustion chamber temperatures, it could run well on a wide variety of fuels.

Related reading:

http://papers.sae.org/830314/

http://papers.sae.org/840428/

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Cummins Adiabatic (1).jpg

Cummins Adiabatic (2).jpg

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These engines require a very expensive oil blend to deal with the high operating heat we learned a lot about these with my friend having one in his garage. The 240 naturally aspirated cummins in the 800 series military truck was taken out and replaced with a turbo charged 290 adiabatic.

Edited by ranchhopper
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Kinda like those rumors from a hundred years ago that the oil companies bought out Stanley Steamer because of its potential effect on their profits! A few years ago 20? Ford designed a ceramic V8 engine block! Never heard any more about it! Got a question for any of you guys who worked in the motor pool in the sixties. I used to see deuce and a half and possibly five ton tractors that were " multi fuel" I assume that would be petroleum based fuels( gasoline,diesel, kerosene,jet fuel etc) I'm thinking some way of changing the compression ratio? Or injected rather than carburated? With adjustable jetting! Anybody work on them? Several automakers have introduced variable compression ratio engines which use a linkage or eccentric on the connecting rods! But they work in conjunction with today's computerized electronic engines which didn't exist  in the sixties! Fascinating!

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7 hours ago, ranchhopper said:

A friend of mine bought one of these experimental five ton 813 military trucks through a GSA auction he has since sold it to a collector in Illinois.

 

6 hours ago, ranchhopper said:

These engines require a very expensive oil blend to deal with the high operating heat we learned a lot about these with my friend having one in his garage. The 240 naturally aspirated cummins in the 800 series military truck was taken out and replaced with a turbo charged 290 adiabatic.

BMT...........Simply the best knowledge base for truck information the world over.

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