The Fuel Problem in Gas Turbines

Abstract

Accepting the principle that the gas turbine is potentially capable of consuming all fuels, the author proceeds to investigate the range of possible liquid fuels and the fuel characteristics of greatest practical significance. Whilst certain properties of liquid fuels—as for example, ignition characteristics and molecular structure—are so complex that no correlation with gas-turbine combustion behaviour has been possible, yet other properties, mainly but not exclusively physical in nature, do exist for which the reverse is the case. Properties falling in the latter category are those which show relatively little variation as between hydrocarbon types or as between isomers, and include carbon/hydrogen ratio, density, vapour pressure, viscosity, and inflammability limits. The influence of these properties on the combustion process is discussed in detail under the two main heads, ( a) fuel injection and stabilization of flame, and ( b) the burning of the droplets after ignition, and the nature of the exhaust products. A number of new and interesting generalizations emerge from this discussion, and are presented in graphical form. Though no hard and fast conclusions may be drawn, the author indicates that the main fuel characteristics affecting gas turbine operation are viscosity, initial and final volatility, elementary analysis of the organic constituents and physical characteristics of the ash.