Methods of liquid spraying based on mixing
of liquid flow with gas flow have been known for a long time. The difference
between speed of mixed flows leads to the initiation of aerodynamic forces which
influence from gas flow on liquid flow. These forces slow down or speed liquid
flow which cannot preserve its original form and disintegrates into particles of
different size. As a result a flow of spraying liquid consisting of mixture of
liquid particles with gas is formed.
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The inhomogeneity of the mixture in size and
speed of spraying liquid particles is the peculiarity of such methods. Presence
of particles of different size in the mixture is a disadvantage of numerous
technological processes. For example, during fuel combustion large particles
burn partially. During spraying gun operation small particles scatter in the
environment and do not reach coloured surface.
It possible to improve homogeneity of mixture
by means of removal of “unnecessary” particles of specified size from the
spraying liquid flow. For this purpose a device for selection of specified size
particles in which outer force influences on particles of spraying liquid is
additionally installed. Such force can be represented by electrostatic, magnetic,
centrifugal forces, Earth gravitational force, etc. The outer force arranges
particle movement distributing them according to their size in the spraying
liquid flow. Removal of specified size particles is realized by means of
collection of all the particles from a certain sector in the spraying liquid
flow. An example of such a device for selection of specified size particles is
the cyclone in which input flow twists and begins spiral motion. Centrifugal
forces throw liquid particles away on the cyclone wall preserving only the
smallest liquid particles in output flow. However, the very construction of the
device for particles selection and principles of realization of outer force
result in occurrence of many different disadvantages. In particular, cyclone is
characterized by high aerodynamic resistance to input flow, large size and
materials consumption.
The authors of the article offered an idea
which gives new possibilities in the methods of liquid spraying under
consideration. The idea is to combine in time and space both the process of
liquid spraying and that of the particle distribution according to their size in
the spraying liquid flow. For this purpose aerodynamic forces which lead to
liquid spraying should simultaneously perform the function of outer force that
distributes particles according to their size in the spraying liquid flow. On
the one hand it simplifies the construction of device for selection of specified
size particles making it just a pure particles collector. On the other hand, the
compactness of the device is achieved. Theoretically, the minimum distance
between a spray nozzle and a particles collector is just several diameters of
spraying liquid particles.
Technical realization of the given idea leads
to appearance of a number of new devices. One can distinguish between two
classes of devices according to the character of processes of liquid spraying
and removal of specified size particles: devices of continuous action and that
of impulsive action. Two devices from each class are given as examples. Figure 1
shows a device of continuous working, and figure 3 – that of the impulsive
action.
Fig.1. Device of continuous action
The device of continuous action consists of
the case 1 with the inner channel 2, made in the form of Venturi pipe. In the
narrow part of the channel 2 there is a spray nozzle 3 placed at an angle of 90°
to gas flow direction. Some distance away from the spray nozzle 3 there is a
collector for spraying liquid particles 4, made and placed with possibility to
gather specified size particles. The collector 4 is connected with a pipe for
liquid removal 5.
The working process of said device is the
following. Gas goes through the inner channel 2. In the narrow part of the
channel 2 decompressions takes place making liquid flow through the spray
nozzle 3. Different sectors with large, medium and small particles are formed in
the flow of spraying liquid. See fig. 2.
Fig.2. Different sections in the flow of
spraying liquid
The collector 4 gathers specified size
particles due to its location in a certain sector of the spraying liquid flow.
Gathered liquid goes to the respraying through the pipe 5.
Fig.3. Device of impulsive action
The device of impulsive action consists of a
reservoir with spraying liquid 1, connected with a spray nozzle 4 by means of a
pipe 2 through a pump 3. Some distance away from the spray nozzle 4 there is a
flow distributor 5, made and placed with possibility of impulse switching of
spraying liquid flow to a particles collector 6. The particles collector 6 is
connected with the reservoir 1 by means of a pipe 7. There is a synchronizer 8
which coordinates work of the pump 3 with the flow distributor 5. The flow
distributor is constructed in the form of cutoff plate blade fixed on the shaft.
During rotation the cutoff plate blade directs impulsively the spraying liquid
flow into the collector 6. The collector 6 is made in the form of two truncated
cones, connected with loose bases.
The working process of said device is the
following. Liquid from the reservoir 1 goes to the pump 3 which provides impulse
feed of liquid through the spray nozzle 4. In the spraying liquid flow large
(fast) particles fly towards, outstripping small (slow) particles, see fig.4.
Fig.4. Distribution of small and large
particles in the spraying liquid flow
The flow distributor 5 impulsively switches
the spraying liquid flow into the collector 6 which leads to the removal of
large or small particles. Gathered liquid returns to the reservoir 1 through the
pipe 7. The synchronizer 8 coordinates work of the pump 3 with that of the flow
distributor 5, which provides conditions for removal of specified size particles
from the spraying liquid flow.
Are the offered technical decisions new? Is it
impossible to find descriptions of similar devices among thousands of patents
for inventions in the field of liquid spraying? Do really exist unstudied
possibilities in well known and well studied sphere?
Let’s leave labor-intensive methods of
complete enumeration of known technical decisions for experts from patent
departments. In the given article we provide discussion of statistic character.
As it is widely known, methods of mathematic statistics estimate the whole
population of objects according to sample of objects from this population. If
objects under consideration are absent in the sample, they are absent in the
whole population of objects with certain probability. Besides, let’s use the
peculiarity of science and technical information to occur many times in
different recourses. That is why we can judge upon knowledge in the sphere of
liquid spraying on the basis of small amount of relevant resources. In this
given case scientific literature, textbooks, reference books for engineers can
be used as a source of information. The object for research is any information
which in this or that way correlates with the given idea. For example,
classification of spraying devices, practical recommendations for construction
and exploitation, influence of parameters on the work of device (speed of mixing
flows and angle between them, distance from spray nozzle to particles collector,
recurrence rate and duration of impulses, etc). The authors failed to find such
data that is evidence of the fact that the offered technical decisions are new.
