A numerical study is presented of the effects of changes in simplex nozzle geometry on its performance. A computational model based on the arbitrary-Lagrangian-Eulerianmethod with an adaptive grid-generation scheme is used. Three nondimensional geometric parameters are studied: the length-to-diameter ratio of the swirl chamber L s /D s and ori ce l o /d o and the swirl-chamber-diameter-to-exit-ori ce-diameter ratio D s /d o . The variations in the atomizer performance, caused by the changes in the geometric parameters, are presented in terms of the lm thickness at the exit of the ori ce, the spray cone angle, and the discharge coef cient. Results indicate that these geometric parameters have a signi cant effect on the internal ow and performance of simplex nozzles. With a constant mass ow through the nozzle over the range of parameters considered, an increase in L s /D s produces an increase in the lm thickness at the ori ce exit, a decrease in the spray cone half-angle, and a slight decrease followed by an increase in the discharge coef cient. Conversely, increasing l o /d o decreases lm thickness, spray cone angle, and discharge coef cient. An increase in D s /d o results in a decrease in lm thickness and discharge coef cient and a decrease in spray cone angle.
Nomenclaturechamber diameter, m d o = exit-ori ce diameter, m K = atomizer geometric constant, A p / ( D s d o ) L s = swirl-chamber length, m l o = ori ce length, m m = vertex mass Çm = mass-ow rate, kg/s p = mean pressure, N/m 2 p 1 = ambient pressure, N/m 2 R 1 , R 2 = radii of curvature, m r = radial coordinate, m t = time, s t s = lm thickness, m t ¤ s = dimensionless lm thickness, t s / (d o / 2) u = axial velocity, m/s v = radial velocity, m/s w = swirl velocity, m/s x = axial coordinate, m D p = pressure differential, N/m 2 h = spray cone half-angle, deg l = dynamic viscosity, kg m/s l t = turbulent dynamic viscosity, kg m/s q = uid density, kg/m 3 r = surface tension, N/m