In a diesel engine, propane injection dramatically increases combustion efficiency to near 100%. An open flame is a different situation but I wonder if there would be a benefit to adding propane - more heat, same heat with less fuel, colorful flames, something?
I remember you mentioning this at the Vegas Round, sounds interesting, but what I am thinking is the cost may out weigh the benefits.
Secondly, the injection of a gaseous fuel will have to be well integrated in the diesel fuel cone, so as to not to detract from the existing pattern but only enhance the BTU output of the burner, that may require quit a bit of testing.
I believe the most cost effective way to increase heat rise efficiency on current hot pressure washer designs is to use something that is already in existence on industrial facilities. Waste heat recovery and utilization.
Jim had some interesting ideas about this kind of stuff.
You could rig up a coil around the muffler somehow to kind of pre-heat the water before it goes into the burner or pump to warm it up some, maybe that would give you some more heat?
I wonder if it is a different coil for a larger BTU burner or is it just a larger blower and fuel nozzle?