Abstract
The two-phase flow downstream of a production gas-turbine engine combustor fuel injection system (i.e., “swirl cup”) is characterized at atmospheric pressure in the absence of reaction. The swirl cup features a centrally located simplex atomizer, a surrounding liquid filming surface, and counter-swirling air streams. Two-component phase Doppler interferometer is employed to determine the time averaged droplet size and velocity distributions and the time-averaged velocities of the continuous phase (gas-phase in the presence of spray). The time-dependent behavior of both phases is documented with a high-speed video camera. This work represents the first detailed characterization of the two-phase flow field in a production fixture and reveals the complexity of the flow field produced. The interferometric results, for example, reveal an on-axial recirculation zone and show that droplets are entrained as a function of size. Large slip velocities between the gas phase and the droplets are measured in all regions of the flow, indicating the presence of momentum transfer between phases. The magnitude of the slip velocities is correlated with droplet size. High speed photographs (1) reveal the dynamic behavior of the droplet and continuous phase, (2) identify clustering of droplets, and (3) reaffirm a correlation of droplet recirculation with size.
Highlights
Mean QuantitiesA production gas turbine combustor swirl cup and a 3 x -scale model (both/eaturing co-axial, counterswirling air streams) are characterized at atmospheric pressure
A production gas turbine combustor swirl cup and a 3 x -scale model are characterized at atmospheric pressure. Such a study provides an opportunity to assess the effect of scale on the behavior of the continuous phase and droplets by comparing the continuous phase velocity, droplet size, and droplet velocity at geometrically analogous positions
A portion of the droplets convect directly downstream while the remainder impinge onto the inner surface of a primary venturi, form a thin liquid film, and are re-atomized in the shear field produced between the two counterswirling air streams
Summary
A production gas turbine combustor swirl cup and a 3 x -scale model (both/eaturing co-axial, counterswirling air streams) are characterized at atmospheric pressure. Such a study provides an opportunity to assess the effect of scale on the behavior of the continuous phase (gas in the presence of spray) and droplets by comparing the continuous phase velocity, droplet size, and droplet velocity at geometrically analogous positions. Resolved velocity measurements of the continuous phase, droplet size, anddroplet velocity wereacquireddownstream oftheproduction and 3 x-scale swirl cups by using two-component phase-Doppler interferometry in the absence of reaction. More significant differences are noted in droplet size, the presence ofthe swirl cup assemblies substantially reduces the differences in size that are otherwise produced by the two atomizers when operated independent of the swirl cup
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