Integrated CFD modelling for nozzle design for fog generation

  • Yankang Tian

Student thesis: Doctoral Thesis


Sprays, as dynamic droplet/particle clouds of functional substances, are widely used in industry, agriculture, and our daily lives. Sprays are different depending on the situations in which they are used and are characterized by pattern, capacity, impact, angle and drop size. Each application has its own requirements for spray characteristics and these requirements are demanding continuing development of atomization systems. Improvement of spraying systems which use a nozzle to convert bulk liquid into dispersed droplets requires knowledge of the atomization process. Although great effort has been dedicated to study, describe, and predict spray generation, flow evolution from continuous stream to separated droplets is still beyond full understanding. What is more, internal nozzle flow and initial breakup that decide the characteristics of far-field spray take place inside enclosed injector, this makes it challenging for non-invasive measurement. At the beginning of this study, available nozzle designs and their performances, and commonly used approaches for modelling fluid flows were reviewed. It is emphasised that there is currently a lack of detailed design principles for sprays with a fine droplet and high flow rate, this type has a great potential for wide application. However, this remains a challenge for advanced nozzle design. To overcome difficulties in the nozzle design, a development workflow is planned in detail. Requirement-oriented nozzle optimization and an integrated CFD model establishment are two closely related components in this study. Numerical results help the justification and dimension selection for nozzle design while physical tests on the nozzle help to validate the CFD model. Architecture for integrated CFD modelling is discussed including the steps for bridging the knowledge gap between different numerical theories. CFD-aided advanced nozzle design and optimization actions are conducted. With parametric modelling a large number of nozzle dimensions can be tested numerically, this largely reduces the development cycle and cost compared to real part fabrication and physical testing. The first detailed design of a nozzle is achieved based on the results from CFD modelling. The designed nozzle was fabricated and then tested in a fog dynamic lab. The results of flow rates, spray angles, and droplet sizes were recorded. These results are used to validate the proposed integrated CFD model. Design of the nozzle was improved by requirement-driven optimization. Virtual testing based on valid integrated CFD modelling is used to study the optimized nozzle design. As an important achievement of this study, a multi-fluid fogging nozzle was designed. Numerical evaluation using integrated CFD modelling shown that the nozzle could generate sprays with flow rate up to 0.53 𝐿/𝑠 and droplets ranging mostly from 2 𝜇𝑚 to 5 𝜇𝑚. The designed nozzle was manufactured and tested in laboratory in Spain. Data obtained from experiments successfully validates the performance predicted by simulations. Being capable to generate spray with high flow rate and fine droplets, this multi-fluid nozzle design shows its strong potential for fogging applications such as firefighting, pest management, and dust suppression.
Date of Award17 May 2019
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorYi Qin (Supervisor) & Andrzej Rosochowski (Supervisor)

Cite this