Development of an Effervescent Atomizer for Industrial Burners

Abstract

The present work is conducted with the aim of developing an effervescent atomizer for industrial burners that will generate a fine and steady spray in large turn-down ratio. The atomizer is fed with light heating oil (LHO) and uses air as an atomizing medium. First, a basic classification is made of the published design concepts of effervescent atomizers investigated by different researchers. Three distinct types of such atomizers are recognized. A single-hole, plain-orifice atomizer with an "outside-in" gas injection configuration was chosen for this study. The basic geometric parameters that may significantly influence atomizer performance are described. An experimental study of the effervescent atomizer was conducted to evaluate the influence of operational conditions and of several geometric parameters on the drop size in the spray. The Sauter mean diameter of drops was measured using a Phase/Doppler Particle Analyser. The study covers the size and number of aerator holes, their location, and the diameter of the mixing chamber. The influence of these parameters on the spray quality was evaluated at atomizing pressures of 0.1, 0.3 and 0.5 MPa and gas to liquid mass flow-rate ratios (GLR) of 2, 5 and 10 %. The main goal of this work is to develop a new procedure for the design of effervescent atomizers. This procedure is based upon our experimental results and it is also supported by the findings of other authors. It allows for the determination of the key geometric parameters of the atomizer to achieve sprays of minimum mean drop size for defined values of liquid flow rate, air supply pressure and GLR. The article also studies the optimization of the exit orifice size and of other parameters, such as the size of the mixing chamber (internal diameter and length), and the number, size, and position of aeration holes.The present work is conducted with the aim of developing an effervescent atomizer for industrial burners that will generate a fine and steady spray in large turn-down ratio. The atomizer is fed with light heating oil (LHO) and uses air as an atomizing medium. First, a basic classification is made of the published design concepts of effervescent atomizers investigated by different researchers. Three distinct types of such atomizers are recognized. A single-hole, plain-orifice atomizer with an "outside-in" gas injection configuration was chosen for this study. The basic geometric parameters that may significantly influence atomizer performance are described. An experimental study of the effervescent atomizer was conducted to evaluate the influence of operational conditions and of several geometric parameters on the drop size in the spray. The Sauter mean diameter of drops was measured using a Phase/Doppler Particle Analyser. The study covers the size and number of aerator holes, their location, and the diameter of the mixing chamber. The influence of these parameters on the spray quality was evaluated at atomizing pressures of 0.1, 0.3 and 0.5 MPa and gas to liquid mass flow-rate ratios (GLR) of 2, 5 and 10 %. The main goal of this work is to develop a new procedure for the design of effervescent atomizers. This procedure is based upon our experimental results and it is also supported by the findings of other authors. It allows for the determination of the key geometric parameters of the atomizer to achieve sprays of minimum mean drop size for defined values of liquid flow rate, air supply pressure and GLR. The article also studies the optimization of the exit orifice size and of other parameters, such as the size of the mixing chamber (internal diameter and length), and the number, size, and position of aeration holes.