Analysis and prediction of the spray produced by an internal mixing chamber twin-fluid nozzle

Internal mixing chamber twin-fluid nozzles can advantageously replace traditional Y type nozzles to atomize high viscosity fluids. This is the case of power plants consuming heavy crude oils, where the use of this type of nozzles allows to obtain the smallest possible droplets with reduced gas flow rates. This work, based on previous experiments and new additional results, analyzes the flow in a specific twin-fluid nozzle of our own design and finally proposes some correlations to describe the flow conditions inside the mixing chamber, and subsequently, the characteristics of the final spray, represented by its Sauter mean diameter (SMD). These correlations include all the relevant variables, and the influence of each of them is discussed for different values of the inlet variables. Particular attention is focused on the situation in which the gas entrance to the mixing chamber is choked. The analysis and procedures here described could be easily applied to any twin-fluid nozzle with an internal mixing chamber.