This thesis is concerned with the removal of particulate
material from gases using fibrous filters.
described under three headings:-
(a) The Collision Efficiency The particle fibre collision
efficiency is calculated by computing trajectories in the
Davies and Kuwabara flow fields. Electrostatic and
gravitational field forces are taken into account. The
influence of fibre Knudsen number and Reynolds number on
inertial interception is predicted.
A model is described which takes into account a log normal
distribution of fibre spacing in a filter. It is used to
predict the pressure drop across a random fibre mat and its
mean efficiency of inertial interception both of which are a
factor of two or three less than predicted by the simple
(b) Particle Retention Mechanisms' It is shown that bounce
is the only significant mechanism responsible for particle
non-adhesion in fibrous filters. An equilibrium model is
used to predict the critical particle size above which adhesion
The behaviour of filters in the low adhesion region is
examined by measuring the collection efficiency of model
filters using narrow sized fractions of dust. The efficiency
is a decreasing function of particle size and velocity,
trends which agree with the equilibrium model.
(c) Non-stationary Filtration The behaviour of filters under
load is examined experimentally. The efficiency may either
increase or decrease initially with loading, the characteristics
depending on the same factors which influence the
single fibre efficiency.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University