Influence of Nozzle Design Upon the Primary Jet Breakup of High-Viscosity Fuels for Entrained Flow Gasification

Abstract

The research work of the present study is focused on the influence of design parameters of twin-fluid nozzles used for the atomization of high-viscosity fuels with respect to the primary breakup of the liquid jet. Two external mixing twin-fluid nozzles, which have already been investigated in previous studies [1, 2], were chosen as basic design. Based on the previous findings the web thickness between fuel and oxidizer supply was varied. In addition both designs were extended by a channel for internal mixing of gas and liquid with a length to diameter ratio of one. Moreover one of the basic nozzles was scaled by decrease of the effective areas in a way that momentum flux ratio as well as gas to liquid mass flow ratio was kept constant. The newly designed atomizers were subsequently investigated with regard to the influence of the changes upon the primary jet breakup using CFD simulations. The numerical simulations were conducted by means of the open source package OpenFOAM. The Volume of Fluid method was used for the determination of the gas-liquid interface. These simulations were then compared with experimentally validated simulations of the basic nozzle designs with regard to the breakup morphology of the jet and the mode of the primary surface instability. In addition, the liquid structure was examined by comparison of breakup length and frequency. The results of these simulations showed that small changes in the atomizer design heavily influence the primary breakup, which in turn influences the overall performance of the atomizer (e.g. SMD). Moreover, these findings will contribute to a better understanding of the physics of the breakup of high-viscosity liquid jets and as well to create an experimentally validated CFD based tool for future burner development and optimization.

Simulation of the Primary Jet Breakup of Non-Newtonian Fuels: Basic Research for Simulation-Assisted Design of Low-Grade Fuel Burner

“…The analysis showed good agreement with regard to the morphology, the primary instability mode as well as quantitative parameters such as the primary breakup length and frequency. Moreover, a dependence of the morphology upon the primary instability mode was confirmed, which is in good agreement with previous studies [25].…”

“…This finding also is in accordance with previous investigations [25], wherein a change of the primary instability mode was induced by a slight change of the nozzle geometry at constant operating conditions and the same decrease in the liquid breakup length was reported.…”

“…Besides these experiments, numerical simulations were conducted by the authors to investigate the primary breakup of highviscosity liquids in [23][24][25] and validated with the data obtained in the experiments. These results showed good agreement with the measurements with regard to the breakup morphology and the mode of the primary instability as well as the breakup frequency and length.…”

Influence of Reactor Pressure on the Primary Jet Breakup of High-Viscosity Fuels: Basic Research for Simulation-Assisted Design of Low-Grade Fuel Burner

“…Apart from the experimental investigations, numerical simulations were conducted to study the primary breakup of highviscosity liquids [20][21][22]. The data obtained by the simulations was successfully validated with the experiments: For instance, the results showed good agreement with the measurements with regard to the breakup morphology and the mode of the primary instability as well as the breakup frequency and length.…”

Progress in the Smoothed Particle Hydrodynamics Method to Simulate and Post-process Numerical Simulations of Annular Airblast Atomizers

“…Ma et al (2016) performed a LES of a hybrid airblast atomizer with a VOF/Lagrangian spray framework. Müller et al (2017) used OpenFOAM with VOF to investigate the influence of the nozzle design on the breakup of a cylindrical viscous jet. Odier et al (2018) investigated the flapping mechanism of a coaxial liquid jet at a moderate density ratio (10) with the ACLS method from Desjardins et al (2008).…”