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Ed O'Malley
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3kW to provide air conditioning and cab electricity? Or cab heating, cab electricity and main engine block heating? I do not think it is nearly enough. When I was manufacturing diesel APU's we provided 25,000 BTU/hr cooling through a belt-driven compressor and it was barely enough to keep the cab comfortable when parked in 100+ degree sunlight. That took probably 6kW of power all by itself. And they do not mention the price of this APU, but I bet it is way up there. An installed diesel APU, back in 2005-2008 anyway was around $9,000.
Great discussion! A couple points: 1)Surface area to volume ratio: This is not a scalable measurement and therefore cannot be used to compare engines of different sizes. We prefer a dimensionless term of combustion chamber surface area divided by the surface area of a sphere of the same volume. If you compare the Clarke-brayton to a conventional engine of the same power, compare a 159mm bore diesel with a 168mm stroke and a 18:1 compression ratio. How much surface area is there compared to the clarke brayton whose combustion bore is 80mm with an 88mm stroke and about a 12:1 compression ratio (but 56:1 overall)? The clarke-brayton has a lot less surface area for heat loss! 2) Conventional turbocharged diesels do not get anywhere near a 56:1 effective compression ratio. The highest compression diesels out there that I am aware of reach a peak combustion pressure of about 20MPa and the Clarke-Brayton reaches 30MPa. 3)I think there is some confusion about the fuel system being used. The current engine is using a common rail diesel direct injection system. We plan on developing an LNG system in the future. This is not HCCI and it is not spark ignited. 4) Intercooling is of no use on the Clarke-Brayton. Think of the intake cylinder as the compressor on a turbo. The reason you have an intercooler is to reduce the volume of the heated up compressed air so you can get more of it into the cylinder. Our compressed air is forced by the intake piston into the combustion chamber. It must all go in, no matter what (except for a small clearance volume + the volume of the transfer passage). Intercooling would not get any extra air in! 5) We fire every revolution, but it is not a 2-stroke cycle. Thermodynamically it is the same as a 4-stroke cycle(but it takes 5 strokes to work one charge of air all the way through the engine - what should we call this??). It is not a scavenged engine. The transfer ports in and out of the combustion cylinder are valved.
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May 10, 2014