On Discharge Capability and Swirl Generation Capability of Swirler
Fuel-air mixing process is one crucial key to determine the performance of a diesel engine, and it is crucially determined by swirl within cylinder. For generating strong swirl within the cylinder, a new device named swirler has been propounded. In the present paper, four swirlers have been employed to experimentally study the performance on both the discharge capability and swirl generation capability. The steady flow test bench was employed to study the both capabilities in macro-level. Then, a water-flow model was employed to observe the flow motion within the cylinder via the tested swirlers. The results indicate that adopting swirler with a suitable configuration could generate strong swirl without remarkable discharge capability loss.
On heat transfer enhancement in swirl pipe flows
Abstract We propose theoretical model of the heat transfer in the axisymmetric swirl pipe flows. The model is used to study influences of the type of vortex symmetry and of the vorticity distribution in the vortex core on the heat transfer enhancement. The study shows that traditional empirical correlations for swirl flows are, in general, insufficient. Indeed, two types of vortex structures can exist in the swirl flows with the same integral characteristics: vortices with left-handed and right-handed helical symmetry. Left-handed helical vortexes generate wake-like swirl flows and increase heat transfer in comparison with the axial flow. Right-handed vortex structures generate jet-like swirl flows and can diminish heat transfer. Two major factors of the heat transfer enhancement have been identified: (i) formation of the swirl flow with left-handed helical vortex; (ii) modification of the near wall velocity profile of the inviscid flow due to the different vorticity distribution in the vortex core.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.