the Doble is 12 volt, the generator has a control box which decides if the generator requires water or heat or both, in an over pressure situation both the burner and pumps are off, so there is no excess steam, however there is a safety valve just in case of extreme overpressure, this should not normally operate.
the whole system is electrically operated, when the ignition is turned on the power goes to the control box and assuming that pressure and temperature are low the switches send the power to the electric motor seen in this post, the motor is driving a fan which blows air through the carburettor and the mixture into the combustion chamber, on the back of the motor you can see an aluminium gear box at 90 degrees, this cross shaft has a set of points at the end and a cam lobe in the middle for a typical ac delco petrol pump. some as soon a the burner is called for the fan starts, the spark in the combustion chamber is also and fuel pumped up to the float chamber.
in between the electric motor and the fan housing is a steam turbine, this is driven by the exhaust from the engine, when creeping along slowly it will do nothing, but should you open her up on the freeway the massive surge of steam from the exhaust spins the turbine up faster than the motor ( times 2 approx.) and extra power is made
