EFFECTS OF VARYING LIQUID FUEL AND AIR CO-FLOW RATES ON SPRAY CHARACTERISATION OF AN ANNULAR CO-FLOW SPRAY BURNER R. A. Alsulami 1 , S. Nates 2 , W. Wang 2 , S. H. Won 2 , B. Windom 1 1 Colorado State University, Fort Collins, CO 2 University of South Carolina, Columbia, SC ABSTRACT Development of efficient and clean combustion systems requires the understanding of all the processes experienced by a complex liquid fuel in IC engines, such as atomization, vaporization, turbulent mixing, and combustion. Many of these processes are interconnected; the atomization process, which leads to various droplet sizes can enhance or diminish the vaporization rate of the liquid fuel and consequently impact the energy conversion process. Furthermore, the combustion/flame stability of liquid-fueled gas turbine can be influenced by the fuel and the air co-flow rates delivered in the engine. Increasing the fuel and/or air flow rates can enhance droplet breakup and the turbulence of the flow, and as a result sway the droplet size distribution of the spray. This work focuses on investigating the impact of varying the fuel and air flow rates on the spray atomization (e.g. droplet size distribution) of an Annular Co- Flow Spray Burner. This was explored by measuring droplet sizes and velocities of the spray at different radial and axial positions of n-heptane fuel under nonreacting conditions. In addition, the turbulence intensity and the liquid spray droplet distribution were quantified for different fuel and air flow rate conditions. The measurements were obtained by using a Phase Doppler Particle Analyzer/Laser Doppler Velocimeter (PDPA/LDV) at P = 1 atm and T = 298 K. Moreover, the Sauter Mean Diameters for different flow conditions are predicted, using an established correlations, and compared to PDPA/LDV measurements. The results provided a fair understanding of the influence of varying the fuel and air flow rates on the droplet sizes, velocity, and turbulent intensity. Furthermore, the results presented here will support future work that will focus on unraveling the role of phase change on flame stability. NOMENCLATURE PDPA: Phase Doppler Particle Analyzer LDV: Laser Doppler Velocimeter SMD: Sauter Mean Diameter SMDglobal: Global (overall) Sauter Mean Diameter DSD: Droplet size distribution PDF: Probability density function RMS: Root mean square di: Diameter of fuel nozzle do: Diameter of annular air co-flow  ̇  : Air flow rate  ̇  : Fuel flow rate r: Radial position z: Axial position Do: Initial droplet diameter  30 : Volumetric diameter  20 : Surface diameter : Number of droplets   : Liquid surface tension   : Dynamic liquid viscosity   : Kinematic liquid viscosity ̇  : Liquid mass flow rate ∆: Pressure drop across the spray nozzle   : Surrounding air density INTRODUCTION The optimization of combustion systems is essential, as a result of the current environmental and energy requirements. Therefore, the complex interaction between the processes which govern the combustion of liquid fuel, including atomization, fuel/air loading and mixing, and chemical reactions in multi- phase and turbulent environment, should be understood to achieve optimal performance. This understanding can be achieved by studying each process that liquid fuels experience in a combustion engine individually before any further complex investigation. For example, when the role of atomization, volatility and reactivity of different fuels on flame stability of 1 Copyright © 2019 ASME Proceedings of ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition GT2019 June 17-21, 2019, Phoenix, Arizona, USA GT2019-90989 Downloaded from https://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT2019/58622/V04BT04A005/6439468/v04bt04a005-gt2019-90989.pdf by Colorado State University user on 28 December 2019