1 Copyright © 2010 by ASME Proceedings of the ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis ESDA2010 July 12-14, 2010, Istanbul, Turkey ESDA2010-25266 MODELING OF NON-NEWTONIAN FLUID FLOW WITHIN SIMPLEX ATOMIZERS Mohammad Rezaeimoghaddam Graduate student Department of Mechanical Engineering Ferdowsi University Mashhad, Iran, Email:m.rezaei.moghaddam@gmail.com Rasool Elahi* Graduate student Department of Mechanical Engineering Ferdowsi University Mashhad, Iran Email:r.elahi.msc@gmail.com M. R. Modarres Razavi Professor . Department of Mechanical Engineering Ferdowsi University Mashhad, Iran Email:m-razavi@um.ac.ir Mohammad B. Ayani Assistant Professor Department of Mechanical Engineering, Ferdowsi University Mashhad, Iran Email:mbayani@um.ac.ir ABSTRACT In this paper the Volume-of-Fluid (VOF) method is used to simulate Newtonian and non-Newtonian fluid flow within simplex (pressure-swirl) atomizers. The two-dimensional axisymmetric swirl Navier-Stokes equations coupled with the VOF method is employed for accounting the formation mechanism of the liquid film inside the swirl chamber and the orifice hole of the pressure swirl atomizer. For verification of the code, the numerical results were compared with experimental data for large scale prototype injector with water (Newtonian fluid) as injection fluid in various constant inlet mass flow rate. 1By using power-law equation to calculate shear stress terms in the Navier-Stokes equations, the code is extended to compute Newtonian and non-Newtonian fluid flow inside the atomizer. The time-independent purely viscous power-law fluids flow in pressure-swirl atomizers is simulated. The effects of shear-thinning fluids (0.5 < n <1), viscous Newtonian (n = 1) fluids and shear thickening fluids (1< n < 1.5) on atomizers performance (discharge coefficient and spray cone angle) were investigated. Results were shown that with increasing the power-law index the spray cone angle decreases and the discharge coefficient increases. *Graduate student and author of correspondence INTRODUCTION Simplex atomizers are widely used in air-breathing gas turbine and combustion as they provide good spray and also they are relatively simple and inexpensive to manufacture [1]. In spite of widely used simplex atomizers involving Newtonian fluids, there are many applications that use the non-Newtonian fluids as injection liquid in simplex injectors such as pharmaceutical products, paint sprays, spray-drying of food and agriculture sprays. The atomizer‟s principle of operation is simple. It consists of the inlet grooves, swirl chamber and discharge orifice (see Fig. 1). Liquid is fed into the swirl chamber through tangential ports. The liquid is accelerated through the swirl chamber and then enters the orifice hole. The swirl motion of the liquid pushes it close to the wall and creates a zone of low pressure along the center line which results in back flow of air in the injector. The liquid emerges from the orifice as a conical sheet that spreads radially outwards due to centrifugal force.