17-07-2023, 10:10 PM
Looking up the boiling point of petrol, it gives a range of 35 to 70 degrees C as petrol is composed of various hydrocarbons - some boiling at a lower temperature than others. So, if a fuel tank reaches about 50 degrees C, the lighter fractions in the fuel will be ready about to boil, if the aren't already. As the temperature in the carb is similar - just a couple of degrees higher - it seems that not much heat is being added in the fuel lines? However, once vapour has formed and flow stops, then further heating of the stationary fuel will occur e.g. by radiation from the hot manifold. A baffle could help reduce this, but if the tank is so warm, there isn't much margin before problems occur again?
Adding 10% kerosene would mean that 10% of the fuel has quite a high boiling point, the remaining 90% will still contain the light fractions that will boil in the range 35 to 50 degrees C. Therefore, adding 10% kerosene might not help much in avoiding vapour lock occurring?
Running with the bonnet raised or off presumably helps keep the fuel in the tank much cooler on a long run? 50 degrees seems very warm - I also wonder what range of operating temperatures Austin considered, given they were happy to export to places like India. Other than a four-blade fan, were there any other modifications?
Adding 10% kerosene would mean that 10% of the fuel has quite a high boiling point, the remaining 90% will still contain the light fractions that will boil in the range 35 to 50 degrees C. Therefore, adding 10% kerosene might not help much in avoiding vapour lock occurring?
Running with the bonnet raised or off presumably helps keep the fuel in the tank much cooler on a long run? 50 degrees seems very warm - I also wonder what range of operating temperatures Austin considered, given they were happy to export to places like India. Other than a four-blade fan, were there any other modifications?