Tuesday, 10 January 2012

Last night I did some investigation on the air system and made some interesting observations. I measured the flow rate more accurately and confirmed that the flow rate was about 1/4 less maintaining 60PSI than at 30PSI, even after taking out the needle valve. I know AC motors should have a constant speed, and Ariel had the good idea of measuring the speed of the compressor (RPM) at low and high pressure. Luckily the compressor shaft was exposed enough to attach a tachometer to and I discovered that, as expected the speed of the compressor was not significantly different at 30 and 60PSI (maybe %1-3 difference). So if the compressor is pumping at the same speed then that means there must be some losses in the system. There are several this could be but Ariel came up with the most likely, which was that the piston ring leaks more at a higher pressure. I am currently running two compressors in parallel, a new one and a quite old one I got second hand. It is probable that the old one leaks more at higher pressure. There are also thermal losses which increase for higher pressure ratios as the air is hotter when its compressed, but then cools down and decreases in volume but these are not significant. Also I discovered when researching the air compressors that I have that they can actually run continuously. I was hesitant to leave my new compressor on incase it overheated so I atached a thermometer to it and found that it stayed at a constant 50 degrees c. This means I have effectively doubled the amount of sparge air I have available.

I also have been designing the plumbing for the peroxide test stand. For the nitrous-ethanol stand I used steel "bundy" tube which was cheap but a huge pain to work with. For peroxide I am going with stainless braided tube with a teflon liner. Since I am buying all the parts from overseas I wanted to make sure I had everything before I ordered them so I did the drawing in detail. It may be difficult for anyone else to read.....

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