Hi Guys,
Part one of mini still is now in place...
I pulled off the first exhaust elbow today and replaced it with a 2 1/2" T piece... Took a bit of fancy guestimations in the length department to get it all back together... actually it was no real biggie, just had to thread some custom length pipe nipples to keep exhaust in the right place... there was not too much room for error as the pipes we were mating to have plumbed in heat exchangers for the house... just took a bit more time than I wanted, measure thrice, cut once!
At the end of it all, all I have to show for it is an itchy and scratchy body after unwrapping the fibreglass lagging which is well cooked and brittle by now... its amazing the places you develope itches when that fine stuff blows around....
After we got the T in place, I installed a reducing bush in the top end, at 90 degrees to the exhaust flow, and stuck the pyrometer in to get a feel for the EGT we would be playing with under normal conditions.... At 50% load(10A@220V), the EGT hovers between 350 and 390 C... at near full to full load(20A@220V) we end up at around 550 to 600C.... These measurements were taken at about 10" from the exhaust flange, right where we will position the boiler bottom probably.... The thermocouple was encased in a 6mm steel line and lowered into the gas stream, readings were taken after the temperature stabilised....
While I had the pyrometer going, I looked at the effect of WI on EGT and head temperature... Quite interesting...
Under normal running, 4L per hour or so WI, the above temps were taken. Start heavy flush, 3-400 ml per minute, and a sudden spike in EGT is noted, probably due to better heat conduction and transferring heat from the combustion chamber into the exhaust system. Maintain the hi flow, and EGT starts dropping rapidly as the heat is carried away from the motor internals to the exhaust proper... After going back to 4 to 5 L / hr, the EGT is about 5 to 10 degrees hotter than previous, once stabilised.... After an hour or so, the EGT has declined to the original measurements taken... I surmise that this is due to a small soot boundary layer that forms under normal running conditions... The WI boost is not really long enough to influence the head and coolant temps to any great degree... if I run a medium amount of water through the system, around 8L/hr, sustained for 2 to 3hrs, the head and coolant temp drops by about 10 to 15 degrees and maintains... this is around 125ml per minute if I calculated it out right... EGT climbs initially, then drops down and holds at around 250-300C... This tells me that there is little to no water in the exhaust stream, all is converted to steam in the cleaning process.... (Daytime air temps were around the 20 to 22C for all you purists that want to work out the exhaust energy capacity...)
Another interesting thing I noted, little to zero carbon buildup in the exhaust proper, in that first stage of heat exchanger that I really expected to clog up.... Note: 1700hrs plus, of questionable fuel and varied load conditions.... interestingly, barring the dark colour, the texture of the internal galvanising on the pipes can clearly be seen in the longitudinal weld area... this tells me that there is less than .2mm or so of buildup ... absolutely awesome! With this performance, it is actually a waste of time to make the exhaust that brushes may be inserted for cleaning.... why bother?
Tomorrow I will be doing the itchy and scratchy thing again.... re-lag the header pipe with fibreglass tape..... I wonder if my son is coming to visit.... I am sure I could play waiter and ferry the ales while he lags it..... I wonder if he will catch on to my sly trickery...
Right... enough said....
Keep on scratching....
Regds
Ed
