Re: Different fuels and blow backs
Posted by: Nick Howell
Date: October 21, 2015 12:59PM
Er, continuing after accidently posting......
On firing up with straight unleaded petrol the flames were nice and blue on both the pilot and main burner. Changing to straight hexane and after adjusting the main jet,the result was the same so back to petrol. The pilot light vapourising coil was glowing orange for a lot of its length when teh main fire was on and sure enough after ten miles it started to carbon up inside; after twenty miles is was almost blocked up completely with low pressure to the pilot, yelllow and ble flames and from there of course more yellow flames on the main burner because of a weak pilot.
Plan two involved using straight kerosene --if the vapoursor was too hot for petrol I thought it would be fine for kerosen and making up a shorter vapourisor to the pilot and curled a little further away from the flames so as not to get too hot; now one hot spot next to the pilot, glowing orange, but not quite vapourising the kero enough. Plan 3, back to making a longer vapouriser, going around the midddle of the burner to be hot enough. Result, blue flames with a few yellow tips on the pilot when warming up, all blue when the main burner was on which was also nice and blue. But....when the pressure is up and the burner plate is hot and the steam automatic has cut off, when it cuts back in the main jet just keeps blowing back (igniting from the main jet). Adding 25% hexane made no difference.
Something is igniting the fuel vapour before it gets above the burner plate. I now have the burner out and have cleaned out the inside of any rusty flakes, which were very few, filed down a raised speck inside the inlet tube in case that was glowing hot, and there are no breaks in between jets on teh plate that could cause ignition below.
Does anyone have any suggestions as to what can cause ingnition aty the main jet?