Part 1: A Swirl Vane Generation Code for Fuel Spray Nozzles

Achieving an optimal level of flow swirl is required for efficient mixing of air and fuel in order to realise lean combustion. A novel method is devised to achieve a necessary level of swirl, using NACA airfoil profiles as the baseline for swirl stator blades. Formulas for achieving a required level of swirl have been derived and implemented in a computer program that generates aerodynamic vanes which meet the specified swirl. The usability of the program over a broad range of Reynolds numbers is verified. A curve fitting method has been developed, taking into account the trailing edge angles and blade solidity, in order to speed up the iterative process. A significant computational speed-up is achieved from this approach, and an excellent initial preliminary vane design can be obtained, which can later be introduced inside an automated optimisation process.

Experimental Study on Flow Patterns of Decaying Swirling Gas-Liquid Flow in a Horizontal Pipe

Swirling flow is one of the well-recognized techniques to control the working process. This special flow is widely adopted in swirl vane separators in nuclear steam generator (SG) for water droplet separation and the fission gas removal system in Thorium Molten Salt Reactor (TMSR) for gas bubble separation. Since the parameters such as separation efficiency, pressure drop and mass and heat transfer rate are strongly dependent on the flow pattern, the accurate prediction of flow patterns and their transitions is extremely important for the proper design, operation and optimization of swirling two-phase flow systems. In this paper, using air and water as working fluids, a visualization experiment is carried out to study the gas-liquid flow in a horizontal pipe containing a swirler with four helical vanes. The test pipe is 5 m in length and 30 mm in diameter. Firstly, five typical flow patterns of swirling gas-liquid flow at the outlet of the swirler are classified and defined, these being spiral chain, swirling gas column, swirling intermittent, swirling annular and swirling ribbon flow. Being affected by the different gas and liquid flow rate of non-swirling flow, it is found that the same non-swirling flow can change into different swirling flow patterns. After that, the evolution of various swirling flow patterns along the streamwise direction is analyzed considering the influence of swirl attenuation. The results indicate that the same swirling flow pattern can transform into a variety of swirling flow patterns and subsequent non-swirling flow patterns. Finally, the flow pattern maps at different positions downstream of the swirler are presented.