Dynamics of a Prescribed Mixing Ratio Variable Fuel Flow Automatic Valve

The production of emulsions on board of engines in real time with the fuel needs for the actual loading requires the development of a mixer that is capable to give the right volumetric ratio between the dispersed phase (water or ethanol) and the continuous phase (fuel). A Prescribed Mixing Device (PMD) has been developed to follow in real time the fuel request of a Gas Turbine or other engines. Previous investigations have demonstrated the stable steady state behavior at the various fuel flow rates ranging from idle to full load. Moreover, the influence of fuel viscosity variations (due to fuel temperature and quality changes) on the PMD response has been studied. This paper deals with the dynamic behavior of such a PMD. A physical model has been developed and accordingly, an amply series of tests have been carried on to check the PMD response to step and sinusoidal changes in the fuel request. A stable behavior has been evidenced thus the water content of the emulsion produced does not show significant drift in its value versus time.