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The current paper studies the thermoacoustically unstable combustion, under elevated mean pressure, of a commercial swirl stabilized gas turbine burner fitted with optically accessible windows. We study natural gas flames at mean pressures of 3, 4 and 6 bar which delivered thermal loads equal to 335 kW, 474kW and 685 kW respectively, at constant equivalence ratios and bulk velocities. In the 3 bar case, dynamic pressure bursts were observed amidst a quiescent acoustic background. The flame anchored on the shear layers of the recirculation zone and it periodically expanded in the outer recirculation zone (ORZ). In the 4 and 6 bar cases, the flame was thermoacoustically unstable with seldom requiescent events, with suppressed expansion to the ORZ. Dynamic Mode Decomposition on high speed images from the 3 bar case, showed that said expansion introduced an additional time scale, further to the fundamental acoustic timescale. A physical mechanism is suggested to link dynamics and flame shape differences on adjusting mean pressure. The premixture is characterized by a Lewis number lower than unity, the laminar flame speed increases on decreasing mean pressure and the flow imposed on the flame strain rate oscillated over a period of thermoacoustic instability. This combination resulted in local oscillations of the heat release rate, in the region of the outer shear layers. The phenomenon was pronounced in the 3 bar case, due to higher flow dilatation imposed strain rates than the 4 and 6 bar cases.

The liquid flow inside, and the induced air flow around, a falling droplet in stagnant air was numerically investigated using the Volume of Fluid (VoF) method to describe the droplet interface. The droplet consisted of oil with the same surface tension and with viscosity as parameter. It was injected into stagnant air with an initial velocity of 1m/s; therefore the initial Weber (W e = 0.14), Reynolds (Re = 141) and Bond (Bo=2.4)