Loading...

Experimental Study on Primary Breakup Dynamics and Spray Characteristics of Rotary Atomizers

Rezayat, Sajjad | 2019

1441 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52541 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Farshchi, Mohammad
  7. Abstract:
  8. The liquid breakup analysis and spray characteristics measurement of atomizers are very essential for the numerical modeling of the primary atomization in combustion chambers. The rotary atomizers are used in many applications especially in small gas turbine engines as a fuel injection system. An experimental investigation of primary breakup dynamics and spray characteristics of rotary atomizers with high aspect ratio discharge channels are described. Four different rotary atomizers with round radial, round radial-axial, round radial tangential, and square radial discharge channels are studied. The purposes of this study are to identify the effect of channel orientation and its geometry on the primary breakup and spray characteristics of rotary atomizers. A high-resolution shadow imaging technique with pulsed backlight illumination was used for spray visualization. The droplets size measurements ae conducted using the particle/droplet image analysis (PDIA) technique. The droplet size of different rotary atomizers are compared with each other to obtain the best atomizer in point of smaller droplets size production. In this study, the liquid film formation regime, breakup modes, spray characteristics, and droplet size were obtained. The breakup process was studied with the variation of rotational speed and liquid volume flow rate. Five different breakup modes including, Rayleigh, column, bag, stretched ligament, and shear breakup mode were identified in terms of aerodynamic weber number and liquid to air momentum flux ratio in different atomizers. In a certain region of aerodynamic Weber number, the liquid breakup modes are varied with the momentum flux ratio. The results suggest qualitative similarities between the primary breakup of the present rotary atomizers with a non-turbulent liquid jet and a fan like liquid sheet under a gas cross flow. Among the atomizers, the rotary atomizer with round radial-tangential and square radial discharge channel produce smaller droplets in compare with the other atomizers, respectively. The last part of this study is related to the research which has been down in Lund University. The Laser induced Fluorescents with particle image velocimetry (PIV/PLIF) are used to identify the spray velocity field in different operating conditions. Two high power cavity lasers with the pulse duration of 150 ns and 1 microsecond time delay in 355 nm wavelength are used for the liquid dye excitation. The results indicate that the spray velocity field is highly affected by the rotational speed. The effect of volume flow rate variation on the velocity filed decreases with the increasing rotational speed. The results reveal some differences between the velocity field in the liquid breakup in a gas cross flow with that of in the rotary atomizer. The spray velocity filed is provided for the numerical modeling validation in different operating conditions
  9. Keywords:
  10. Rotary Atomizer ; Particle Image Velocimetery (PIV) ; Sauter Mean Diameter ; Particles/Droplet Image Analysis (PDIA) ; Liquid Sheet Breakup in a Gas Cross Flow ; Particle Image Velocimetry with Plannar Laser Induced Fluorescence (PIV/PLIF)Technique ; Discharge Channeles Orientation Effect

 Digital Object List

 Bookmark

...see more