Excellent news
The blue/purple area has been hottest , the bronze less hot , checkout the pic of my karts FT after several runs http://www.racketmotorman.turbinebuilde ... =4&pos=102 , the stainless at the outlet end is still silvery but at the primary end with combustion temps up near 2,000 deg C the stainless is purpled from the radiant heat of combustion , this is normal ...................please don't add any holes to try and rectify the colouring , you'll only cause combustion problems .
Further along the FT as the secondary air is injected the gas temps start to drop and theres less radiant heat so the wall only goes a golden colour , when the tertiary air is injected further down the 'tube the temps drop to a point where there is minimal radiant heat easily handled by wall cooling holes ( lotsa little ones) for the inside and the air flow over the outside .
With your combustor top glowing redhot , I need to know if your fuel is being injected "above" the primary holes, nearer the endcap, or further down the flametube opposite the primary holes or slightly further downstream .
If the fuel is injected "above" the primary holes , there will be "recirculation" back up towards the endcap causing flames to hit the endcap and heat it excessively , there will always be some radiant heating of the endcap with that type of design, its unavoidable , ..............some guys have added FT wall holes at the very top of the FT so that air will blow across the endcap to help cool it , but these holes need to be figured into the primary hole area .
As you already have your holes near the top , its probably easiest to displace your LPG injector a little further into the FT , ..................I'll be able to give you a better answer once I see a pic of the FT's colouration which will indicate avenues of development
Congrats again , its getting there
Cheers
John
