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This is the place to discuss general issues related to the U-boat war or the war at sea in WWII. 
Re: Junkers Free Piston Diesel Compressor.
Posted by: Terry Andrews. ()
Date: October 11, 2003 08:18AM

<HTML>Hi Tom & Ted.
Nice to hear from you guys again!

Here is a description of the Compressor!


The Diesel engine portion is situated in the centre, the compressors are arranged on the outside. The two groups of pistons running in opposite directions are connected with one another swing free outwards and inwards, and thus have no mechanical limitation of stroke. In practice, however a determined maximum stroke is not exceeded due to cushioning, but in the event of a break down copper screws are provided to absorb the impact of the pistons.

Method of Operation.

For starting up, compressed air is directed on the pistons brought into the outside position. The pistons now speed towards the centre and compress in the engine cylinder the combustion air. Where upon fuel is injected into the combustion air heated by high compression. By means of the combustion which occurs the pistons are driven apart. In doing so, a part of the air enclosed in the compressor is pressed into the scavenging air receiver as scavenging air for the engine through the scavenging valves. The remainder of the air, after passing the scavenging valves, is compressed further to the working pressure of the compressor and is pushed out through the delivery valves. The working pressure in the compressor is maintained by means of a pressure retaining valve even when the reservoir pressure fluctuates. At the outer ends of the strokes the scavenger and exhaust ports are uncovered by the engine pistons which are brought to rest by the compressed air. This forces the pistons together again and compresses the air between them in readiness for the next cycle.


Since the pistons have no mechanical limitation of stroke, the stroke of the pistons is controlled automatically by changing the amount of fuel injected. The more fuel there is injected into the engine the quicker the pistons fly apart and the more compressed air is delivered. At "no load" the compressor runs at 810 cycles per minute. When pumping against full pressure, i.e. 205 atms., the speed increases to 850 cycles per minute.

Source: Technical Report on U-570 (HMS Graph) January 1943.

Copys of the above report are available from "little old me".

Hope this helps.
Terry Andrews.
The U-Boat Chronicles.</HTML>

Options: ReplyQuote

Subject Written By Posted
U-505...finally Tom Iwanski 10/10/2003 09:05PM
Re: U-505...finally Ted Agar 10/10/2003 09:39PM
Re: Junkers Free Piston Diesel Compressor. Terry Andrews. 10/11/2003 08:18AM
Re: Junkers Free Piston Diesel Compressor. Rick Pacey 09/12/2020 04:45AM
Re: U-505...finally ROBERT M. 10/11/2003 04:56AM
Re: U-505...finally ROBERT M. 10/12/2003 02:51AM
Thanks for the replies Tom Iwanski 10/12/2003 07:07PM

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