Experiments in Fluids

, Volume 8, Issue 3, pp 121–128

Initiation of explosive boiling of a droplet with a shock wave

Authors

  • D. L. Frost
    • Mechanical Engineering Dept.McGill University
Originals

DOI: 10.1007/BF00195785

Cite this article as:
Frost, D.L. Experiments in Fluids (1989) 8: 121. doi:10.1007/BF00195785

Abstract

The role of incident shock waves in the initiation of vapor explosions in volatile liquid hydrocarbons has been investigated. Experiments were carried out on single droplets (1–2 mm diameter) immersed in a host fluid and heated to temperatures at or near the limit of superheat. Shocks generated by spark discharge were directed at previously nonevaporating drops as well as at drops boiling stably at high pressure. Explosive boiling is triggered in previously nonevaporating drops only if the drop temperature is above a threshold temperature that is near the superheat limit. Interaction of a shock with a stably boiling drop immediately causes a transition to violent unstable boiling in which fine droplets are torn from the evaporating interface, generating a two-phase flow downstream. On the previously nonevaporating interface between the drop and the host liquid, multiple nucleation sites appear which grow rapidly and coalesce. Overpressures generated in the surrounding fluid during bubble collapse may reach values on the same level as the pressure jump across the shock wave that initiated the explosive boiling. A simple calculation is given, which suggests that shock focusing may influence the location at which unstable boiling is initiated.

List of symbols

c

speed of sound

D

drop diameter

n

index of refraction

p

pressure

R0

initial bubble radius

t0

bubble collapse time

T

temperature

Greek symbols

ρ

density

θ

angle relative to surface normal

Subscripts

i

incident ray

r

refracted ray

sl

superheat limit conditions

v

vapor

f

host fluid

2

test fluid

undisturbed conditions

Copyright information

© Springer-Verlag 1989