ARTICLE:

• MODELLING OF CAVITATION FLOW IN A NOZZLE AND ITS EFFECT ON SPRAY DEVELOPMENT  download article

Sergey Martynov
3 Ultrasonics Group, Mechanical Engineering Department, UCL, Torrington Place, London, WC1E 7JE, UK

D. Mason
University of Brighton, Brighton, U.K.

Morgan R. Heikal
School of Environment and Technology, Faculty of Science and Engineering, The University of Brighton, Cockcroft Building, Lewes Road, Brighton BN2 4GJ, United Kingdom

Sergei S. Sazhin
Sir Harry Ricardo Laboratories, Internal Combustion Engines Group, School of Environment and Technology, Faculty of Science and Engineering, The University of Brighton, Cockcroft Building, Brighton BN2 4GJ, UK

M. Gorokhovski
CORIA UMR 6614 CNRS University of Rouen, Site Universitaire du Madrillet BP12, 76801 Saint Etienne du Rouvray; and LMFA UMR 5509 CNRS Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69131 Ecully Cedex, France

ABSTRACT

The experimental observations and theoretical models of spray formation due to the effect of cavitation development in injection nozzles are reviewed. Particular attention is focused on the effects of cavitation disturbances on jet and spray break-up. Models of jet and spray break-up which take into account the stochastic character and non-equilibrium spectrum of product droplets are essential when modelling the primary and secondary stages of break-up. Single-fluid models of cavitation are shown to be robust, but contain empirical rate parameters which require adjustments for specific flows. This study addresses the liquid quality and viscous shear stress effects on cavitation flow. In order to account for the liquid quality effect on cavitation a model derived from bubble dynamics theory is developed. The model for the concentration of cavitation nuclei in a liquid is derived by assuming hydrodynamic similarity of cavitation flows. The model accounts for the variation in the number density of cavitation bubbles as a function of liquid tension in the cavitation region. This model was developed using an analogy with the effect of liquid superheat on the number of nuclei in models for nucleate boiling. The model contains a parameter, which describes the liquid quality. This can be adjusted using one set of measurements for a given liquid. The influence of viscous shear stress on the cavitation threshold in high-speed flows, such as those observed in the nozzles of a direct-injection diesel engine, has been clarified. In order to describe this effect on hydrodynamic cavitation in high-speed turbulent flows a model that takes into account the critical vapour pressure was developed. The model was adjusted to describe sub-cavitation and super-cavitation flows in real-scale models of diesel injectors.

 download article

JET-08 pages

« Previous article         Next article »