Control of an air siphon nozzle using hydrogen and gases other than air

Air siphon nozzles are a simple device commonly used to transport liquid fuel to a combustor. Recent research in dual fuel combustion demonstrates benefits to using gas and liquid phase fuels in the same system. This paper demonstrates the use of hydrogen and other gases other than air to control liquid fuel flow through the siphon nozzle. It is shown mathematically that the two major variables controlling liquid flow rate are the specific heat ratio and upstream pressure of the gas. Since diatomic gases have similar specific heat ratios (k = 1.4 at 300 K), a mixture of hydrogen and air can control liquid flow using only pressure, regardless of mixture composition. At relevant gas pressures, it is analytically shown that the error from changing k is small for 1.1 < k < 1.67. The analytical work was verified experimentally by measuring the suction pressure on the fuel line. Tests using air, hydrogen, argon and helium showed good agreement between gases. However, the deviation begins to increase with the use of propane. This flexibility with gas selection enables liquid flow control with gas mixtures such as hydrogen rich reformate.