DESIGN SOLUTION REPORT

Design Solution Report

Abstract

Numerical and experimental investigations have been made on the coefficient of discharge Cd and the spray cone angle ? of a swirl spray solid cone pressure nozzle. The theoretical predictions are made from a numerical computation of flow in the nozzle using the standard k- model of turbulence. The values of Cd and ? have been evaluated from the radial distributions of velocity components of liquid flow at the nozzle exit. The experiments have been carried out to measure the values of Cd and ? of a solid cone spray nozzle at different operating conditions to validate the numerical predictions. It has been established, from a fair agreement between the theoretical and experimental results, that the adaptation of the standard k- model for turbulence in nozzle flow serves well the purpose of predictions of Cd and ? within the range of operating parameters studied in the present work. It has been observed that the coefficient of discharge and the spray cone angle remain almost constant with the Reynolds number Re of the flow at inlet to the nozzle. The coefficient of discharge Cd is almost uninfluenced by inlet swirl number S in its lower range, but decreases with S in its higher range. The spray cone angle ?, on the other hand, always increases with an increase in S. For a given Re, an increase in flow ratio qr (the ratio of flow rate through inlet central port to the total flow through the nozzle) increases the value of Cd and decreases the value of ?. However, the influence of qr on Cd is prominent at lower values of D2/D1 (the ratio of the diameters of inlet axial port to the swirl chamber of the nozzle). An increase in the value of Cd takes place with a decrease in D2/D1 mainly in the range of higher qr and for values of D2/D1 less than 0.17. The spray cone angle ?, on the other hand, is almost uninfluenced with D2/D1, except in the situation when ? increases with an increase in D2/D1, from 0.38 to 0.75 mainly in the lower range of flow ratio qr.

Design Solution Report

Introduction

The importance of swirl spray pressure nozzle lies in its widespread industrial applications in combustion, evaporation, drying, humidification, cooling, air-conditioning, sprinkling etc. A unified design approach of nozzle in these fields requires the interrelations between different performance characteristics of the nozzle with pertinent input parameters such as, liquid properties, injection conditions and nozzle geometry. This needs a physical understanding of the flow inside the nozzle and mechanism of spray formation outside the nozzle. The simplest form of a pressure swirl nozzle is the one known as simplex nozzle. There are two basic types of simplex nozzle. In one type, liquid at high pressure is supplied to the nozzle through purely tangential ports and the nozzle produces a hollow cone spray. In another type, a high pressure liquid is fed to the nozzle through both axial and tangential ...