U.S. patent application number 10/487893 was filed with the patent office on 2004-12-09 for piston compressor.
Invention is credited to Coney, Michael Willoughby Essex, Cross, Andrew Mark.
Application Number | 20040244580 10/487893 |
Document ID | / |
Family ID | 9921343 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040244580 |
Kind Code |
A1 |
Coney, Michael Willoughby Essex ;
et al. |
December 9, 2004 |
Piston compressor
Abstract
A compressor comprising a cylinder (1) with an axially
reciprocating piston (5) which compresses gas in the cylinder. At
least two circumferential rows of flat fan spray nozzles (10) spray
water into the cylinder during compression. Each nozzle is arranged
such that the spray is in a plane substantially parallel to the
axis (4) of the cylinder and is directed towards a central region
of the cylinder.
Inventors: |
Coney, Michael Willoughby
Essex; (Swindon, GB) ; Cross, Andrew Mark;
(Malmesbury, GB) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
9921343 |
Appl. No.: |
10/487893 |
Filed: |
February 26, 2004 |
PCT Filed: |
August 30, 2002 |
PCT NO: |
PCT/GB02/03974 |
Current U.S.
Class: |
92/174 |
Current CPC
Class: |
F04B 39/062
20130101 |
Class at
Publication: |
092/174 |
International
Class: |
F01B 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2001 |
GB |
0121180.4 |
Claims
1: A compressor comprising a cylinder having an axis, a piston
reciprocally moveable along the cylinder axis to compress gas in
the cylinder and at least two circumferential rows of spray nozzles
to spray water into the cylinder during compression, wherein the
nozzles are flat fan spray nozzles each of which is arranged such
that the spray is in a plane substantially parallel to the axis of
the cylinder and is directed towards a central region of the
cylinder.
2: A compressor according to claim 1, wherein the plane of the
nozzles is inclined at less than 10.degree. to the axis of the
cylinder.
3: A compressor according to claim 1, where a nozzle plane is
inclined at an angle of less than 5.degree. with respect to the
axis of the cylinder.
4: A compressor according to any one of claim 1 wherein the nozzles
are directed substantially at the axis of the cylinder.
5: A compressor according to claim 1, wherein an offset of one half
of the nozzle pitch is introduced between nozzles in adjacent
rows.
6: A compressor according to claim 1, wherein the angle of
divergence of the fan spray of each row of nozzles decreases
towards the cylinder head.
7: A compressor according to claim 1, wherein the nozzles are
inclined such that the lower extremity of the spray from the row of
nozzles furthest from the cylinder head is at a smaller angle with
respect to the cylinder wall than for nozzles closer to the
cylinder head.
8: A compressor according to claim 1, wherein the nozzles are
mounted with their central axis inclined downwardly with respect to
the cylinder axis.
9: A compressor according to claim 8, wherein the top part of the
cylinder wall in which the nozzles are mounted is tapered inwardly
towards the cylinder head, and the piston is provided with a
complementary taper.
10: A compressor according to claim 1, wherein the nozzles extend
to a distance from the cylinder head of at least 20%, preferably at
least 25% and more preferably at least 30% of the piston
stroke.
11: A compressor according to claim 1, wherein the piston rings are
offset from the top of the piston such that they remain below the
lowermost nozzles at top dead centre.
12: A compressor according to claim 1, further comprising a
pre-compressor to compress the gas upstream of the cylinder to a
pressure of 2 to 5 bar.
13: A compressor according to claims claim 1, wherein the cylinder
is capable of withstanding a peak pressure of at least 20 bar,
preferably at least 40 bar and most preferably at least 60 bar.
14: A compressor according to claim 1 further comprising means to
control the profile of flow rate versus time to the rows of nozzles
to allow different profiles for different rows of nozzles during
the compression stroke.
Description
[0001] The present invention relates to a compressor comprising a
cylinder having an axis, a piston reciprocally movable along the
cylinder axis to compress gas in the cylinder and at least two
circumferential rows of spray nozzles to spray water into the
cylinder during compression. Such a compressor will subsequently be
referred to as "of the kind described".
[0002] A compressor of the kind described is disclosed in our
earlier application WO 98/16741. This discloses the use of swirl
nozzles which impart a rotary motion to the liquid being injected
to produce a hollow cone spray pattern of fine droplets. The
nozzles are arranged circumferentially and are placed close enough
to each other so that the cones intersect one another to fill the
empty space within each cone with droplets from an adjacent nozzle.
Various methods of aligning the hollow cone sprays in order to
achieve good overall distribution of droplets within the cylinder
are described.
[0003] A present invention aims to improve the distribution of
droplet in a compressor of the kind described.
[0004] According to the present invention, in a compressor of the
kind described, the nozzles are flat fan spray nozzles each of
which is arranged such that the spray is in a plane substantially
parallel to the axis of the cylinder and is directed towards a
central region of the cylinder.
[0005] The invention provides a spray arrangement which is
particularly suitable for larger compressors which operate at high
speed and pressure. As the size, speed and pressure of the
compressor increases, it has been found that the drag force of the
gas prevents the droplets from penetrating sufficiently far into
the cylinder to cool the gas at further distances from the nozzles
within the time available. Further, it becomes less important to
produce the finest possible droplets such as those produced by
hollow cone spray nozzles as the high drag forces tend to break up
the larger droplets. Under the circumstances, the most important
consideration is to achieve maximum penetration of the water
droplets through the gas space. This aim is considerably assisted
if the hollow cone spray nozzles are replaced by the flat fan
nozzles which are directed towards the central region of the
cylinder but still achieve a sufficiently wide distribution in the
direction parallel to the axis of the cylinder. It has been found
desirable to minimize the interaction between the neighbouring
nozzles in order that the kinetic energy of the water is applied to
achieve a maximum penetration towards the centre axis of the
cylinder and this is achieved by the above arrangement. The spray
nozzles are preferably in a plane which is inclined at less than
10.degree. to the axis of the cylinder and is preferably inclined
at less than 5.degree. to the axis of the cylinder.
[0006] In order to maximise the penetration of the liquid, the flat
fan spray nozzles are preferably directed substantially at the axis
of the cylinder.
[0007] Preferably at least three or four circumferential rows of
spray nozzles are provided. In order to minimise interference
between adjacent rows of nozzles, an offset of one half of the
nozzle pitch is introduced between nozzles in adjacent rows.
[0008] In order to reduce or eliminate water from nozzles closest
to the cylinder head impinging on the cylinder head, the angle of
divergence of the fan spray of each row of nozzles preferably
decreases towards the cylinder head. This also has the advantage
that the sprays become more concentrated towards the end of the
piston stroke, when the rate of heat generation by compression is
at its highest. Effectively, this means that the nozzles closest to
the cylinder head have a less divergent spray than those further
from the cylinder head so that the spray closest to the cylinder
head is concentrated into a smaller axial length of the piston. To
increase the distribution of liquid down the cylinder, the nozzles
are preferably inclined such that the lower extremity of the spray
from the row of nozzles furthest from the cylinder head is at a
smaller angle with respect to the cylinder wall than for nozzles
closer to the cylinder head.
[0009] The nozzles are preferably mounted with their central axes
inclined downwardly with respect to the cylinder axis. One way of
increasing a downward incline of the nozzles with respect to the
cylinder axis is to taper the top part of the cylinder wall in
which the nozzles are mounted inwardly towards the cylinder head.
Under the circumstances, the piston will also need to be provided
with a complementary taper.
[0010] To achieve rapid penetration of the gas at an earlier stage
of compression, it is preferable to allow the nozzles to extend to
a distance from the cylinder head of at least 20%, preferably at
least 25% and more preferably at least 30% of the piston stroke. To
avoid problems of interference between the piston rings and the
nozzles it is advantageous for the piston rings to be offset from
the top of the piston such that they remain below the lowermost
nozzles at top dead centre.
[0011] An example of the compressor constructed in accordance with
the present invention will now be described with reference to the
accompanying drawings, in which:
[0012] FIG. 1 is a schematic perspective view showing the inside of
the compressor cylinder and an arrangement of nozzles;
[0013] FIG. 2A is a side view of a single flat fan spray
nozzle;
[0014] FIG. 2B is a top view of the flat fan spray nozzle of FIG.
2A;
[0015] FIG. 2C shows a typical spray pattern of a flat fan nozzle
of FIGS. 2A and 2B; and
[0016] FIG. 3 is a perspective view showing the construction of one
type of flat fan nozzle suitable for the compressor of the kind
described.
[0017] As shown in FIG. 1, the compressor comprises a cylinder 1
having a cylinder wall 2, a cylinder head 3 and an axis 4. A piston
5 is axially reciprocable within the cylinder 1. Air introduced
into the cylinder 1 through an inlet valve (not shown) in the
cylinder head. This air will typically have been pre-compressed to
2 to 5 bar. Compressed air is exhausted through an outlet valve
(not shown) in the cylinder head 3. The compressed air will
typically have a pressure of at least 20 bar, preferably at least
40 bar, and more preferably at least 60 bar. The general operation
of the compressor is as described in our earlier application
WO98/16741.
[0018] During compression, water is sprayed into the cylinder 1
through a plurality of flat fan spray nozzles 10 as described
below. The water is supplied under pressure to the nozzles through
nozzle manifolds (not shown) which surround the cylinder. A
suitable arrangement is disclosed in PCT/GB 01/01457. As shown in
that document, different manifolds may be used to supply the
different rows of nozzles, so that different profiles of flow rate
versus time may be supplied to the different rows. The water in the
cylinder is forced out of the cylinder through the outlet valve to
a separator where the water is removed from the compressed air.
[0019] A common design of flat fan spray nozzles are shown in more
detail in FIGS. 2A,2B and 3. The nozzle 10 has a hollow cylindrical
housing. At the end of the nozzle, the internal end face 11 is
hemispherical. A groove 12 is cut across the outer end face of the
nozzle and intersects with the hemispherical end face 11 forming an
orifice 13 which has a generally elliptical shape with tapered
ends. The orifice is typically 3 mm long and 1 mm across. The water
flows along the cylindrical passage until it meets the
hemispherical end face 11 on each size of the groove 12 whereupon
it is diverted towards the opposite side of the groove. The two
halves of the flow impact on each other at the groove and are
forced out of the orifice 13 forming the characteristic spray.
Other designs of flat fan spray nozzles are known in the art and
may also be used in place of those shown in FIG. 3.
[0020] As shown in FIG. 2A-2C the spray 15 has the flat fan shape
which is generally planar in a plane 16 as shown in FIG. 2B. There
is some inevitable divergence of the spray 15 out of the plane 16
resulting in a flow profile 17 having a tapered elliptical shape
corresponding to the shape of the orifice 13.
[0021] The arrangement of the flat fan spray nozzles 10 within the
cylinder 1 will now be described with reference to FIG. 1. In this
figure, the sprays 15 are shown projecting only a very short
distance into the cylinder. This has been done for the purposes of
the clarity of the figure. In practice, the spray will penetrate
into the central region of the cylinder. Also, for clarity, only
the sprays 15 and not the nozzles 10 have been shown in FIG. 1.
[0022] Four circumferential rows of nozzles are shown in FIG. 1.
Each nozzle 10 is arranged such that the plane 16 of each spray 15
is parallel to the axis 4 of the cylinder and is directed towards
this axis. Each of the spray nozzles 10 is mounted such that its
central axis is directed downwardly with respect to the axis 4. The
angle .theta. of divergence of the spray is smallest for the spray
15 adjacent to the piston head 3 and gets progressively larger
further from the piston head 3. This ensures that a narrower spray
is produced closest to the piston head substantially reducing or
eliminating contact between the spray and the piston head and
providing the most concentrated spray to the region closest to the
cylinder head. As a consequence of this, the lowermost sprays
inject water closer to the cylinder wall 2 and the uppermost sprays
ensuring that a wider region within the cylinder is reached by the
spray. Although not shown in FIG. 1, each row of nozzles is
preferably staggered with respect to an adjacent row by an amount
equal to half of the pitch between the adjacent nozzles thereby
reducing further the possibility of interference between the
adjacent rows of nozzles.
[0023] As shown in FIG. 1, the piston rings 18 are positioned
towards the bottom of the piston 5. This is done in order to ensure
that, at top dead centre, the piston rings 18 are still below the
lowermost nozzles. The flow of water is controlled such that only a
little water is injected by a row of nozzles once the top of the
piston has passed the nozzles. The amount of water is preferably
sufficient only to fill the crevice above the piston rings 18 so as
to avoid reducing the efficiency of the compressor.
* * * * *