U.S. patent application number 12/094380 was filed with the patent office on 2008-11-20 for helical screw compressor.
This patent application is currently assigned to GHH RAND SCHRAUBENKOMPRESSOREN GMBH. Invention is credited to Carsten Achtelik, Michael Besseling, Norbert Henning, Dieter Hutterman.
Application Number | 20080286129 12/094380 |
Document ID | / |
Family ID | 36763690 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080286129 |
Kind Code |
A1 |
Achtelik; Carsten ; et
al. |
November 20, 2008 |
Helical Screw Compressor
Abstract
The invention relates to a helical screw compressor which
comprises two rotors (7, 9) having ribs (7', 9) which extend a
screw-like manner and grooves which engage with each other in a
combing and sealing manner. The total number of ribs of both rotors
is at least 14, and the height (H) of the grooves is no more than
0.15 times the external diameter (Da) of the rotor profile (7)
and/or (9). The shaft journals of the rotors have a diameter which
is not smaller than half of the external diameter (Da) of the rotor
profile.
Inventors: |
Achtelik; Carsten;
(Dinslaken, DE) ; Hutterman; Dieter; (Hunxe,
DE) ; Besseling; Michael; (Hunxe, DE) ;
Henning; Norbert; (Mulheim, DE) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
100 E WISCONSIN AVENUE, Suite 3300
MILWAUKEE
WI
53202
US
|
Assignee: |
GHH RAND SCHRAUBENKOMPRESSOREN
GMBH
Oberhausen
DE
|
Family ID: |
36763690 |
Appl. No.: |
12/094380 |
Filed: |
June 9, 2006 |
PCT Filed: |
June 9, 2006 |
PCT NO: |
PCT/EP2006/005556 |
371 Date: |
May 20, 2008 |
Current U.S.
Class: |
417/315 |
Current CPC
Class: |
F04C 18/16 20130101;
F04C 18/084 20130101; F04C 23/001 20130101; F04C 2220/40 20130101;
F04C 29/04 20130101 |
Class at
Publication: |
417/315 |
International
Class: |
F04B 37/00 20060101
F04B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 2005 |
DE |
10 2005 058 698.8 |
Claims
1. A screw compressor with two rotatably held rotors (3, 5) that
are rotated in opposite directions, said rotors having a profile
(7, 9) along a section of their length that has screw-shaped ribs
(7', 9') and grooves and meshing with one another via these ribs
and grooves, forming a seal, characterized in that the total number
of screw-shaped ribs (7', 9') of the two rotors is at least 14.
2. A screw compressor according to claim 1, wherein one rotor is
the main rotor (3) and the other rotor is the secondary rotor (5),
and wherein the profile (7) of the main rotor contains six ribs
(7') and the profile (9) of the secondary rotor contains eight ribs
(9').
3. A screw compressor according to claim 1, wherein the rib height
of each rotor (3, 5) is not larger than 0.15 times the outer
diameter of the profile (Da) of the rotor.
4. A screw compressor according to claim 1, wherein each rotor has
shaft pins (7a, 7b, 9a, 9b) next to the profile section,
characterized in that the diameter (D, D') of each shaft pin in the
area adjacent to the profile section (7, 9) is not smaller than
half the outer diameter of the profile (Da).
5. A screw compressor according to claim 2 wherein the rib height
of each rotor (3, 5) is not larger than 0.15 times the outer
diameter of the profile (Da) of the rotor.
6. A screw compressor according to claim 5, wherein each rotor has
shaft pins (7a, 7b, 9a, 9b) next to the profile section,
characterized in that the diameter (D, D') of each shaft pin in the
area adjacent to the profile section (7, 9) is not smaller than
half the outer diameter of the profile (Da).
7. A screw compressor according to claim 2, wherein each rotor has
shaft pins (7a, 7b, 9a, 9b) next to the profile section,
characterized in that the diameter (D, D') of each shaft pin in the
area adjacent to the profile section (7, 9) is not smaller than
half the outer diameter of the profile (Da).
8. A screw compressor according to claim 3, wherein each rotor has
shaft pins (7a, 7b, 9a, 9b) next to the profile section,
characterized in that the diameter (D, D') of each shaft pin in the
area adjacent to the profile section (7, 9) is not smaller than
half the outer diameter of the profile (Da).
Description
[0001] The invention pertains to a screw compressor with two screw
rotors that are rotatably held in a rotor housing with parallel
axes, each of which has a profile section with screw-shaped ribs
and grooves. The ribs and grooves of the rotors mesh together,
forming a seal, and the gas volumes contained between them and the
rotor housing are conveyed and compressed when the rotors are
operated.
[0002] In screw rotors of this type, the design of the profiles has
until now focused on creating the largest possible volumes for the
gas to be compressed, located between the rotors and the rotor
housing, relative to a given outer rotor profile diameter. In other
words, as high a rotor profile volumetric utilization as possible
has been sought.
[0003] In contrast, the aim of the present invention is to provide
a screw compressor that is suitable for the compression of gas to
very high pressures, typically in the 30 to 50 bar range, and that
can be operated primarily as the last stage of a multi-stage
compressor system, in particular a three-stage compressor system.
At such high pressures, the rotors are subjected to high lateral
forces that act to bend the rotors away from each other due to the
gas volume contained between them and the housing under high
pressure. This can negatively affect the seal between the rotors,
and thus to a loss of efficiency. Also, due to the separation of
the rotors, the radial gap between the rotors and the rotor housing
can not be as tightly toleranced as desirable to attain a good seal
and a high efficiency.
[0004] Thus, the object of the invention is to provide a screw
compressor that is suitable primarily for operation at high
compressive pressures. The solution to this objective is indicated
in claim 1. The dependent claims refer to further advantageous
embodiments of the invention.
[0005] It was found that the design of the rotors indicated in the
claims leads to an especially favorable relationship between the
bending stiffness of the rotors on one hand and the volume of the
contained compressed gas, which creates the bending forces, in the
screw notches of the rotors on the other.
[0006] One embodiment of the invention is explained in more detail
below with the help of the drawings. Shown are:
[0007] FIG. 1 a partial sectional view of a screw compressor
according to the invention.
[0008] FIG. 2 a perspective representation of the rotors of the
screw compressor of FIG. 1.
[0009] FIG. 3 The rotor profile of the two rotors in a cross
section perpendicular to the axes.
[0010] The screw compressor shown as an exemplary embodiment in
FIG. 1 has a rotor housing 1, shown in a sectional view, in which
two rotors 3 and 5 are rotatably held with parallel axes. The
rotating axes of the rotors 3, 5 lie in a common vertical plane
that is also the sectional plane used to illustrate the rotor
housing 1. Each rotor has a profile section 7, 9 with a profile
exhibiting screw-shaped ribs and grooves, wherein the ribs and
grooves of the two profile sections 7, 9 mesh with one another. On
both sides of the profile sections 7, 9 are shaft pins 7a, 7b, 9a,
9b, the surfaces of which cooperate with seal rings 11 to seal the
rotor in the rotor housing 1. The shaft pins 7a, 7b, 9a, 9b are
also rotatably held in the rotor housing 1 by bearings 13, 15.
[0011] The upper rotor 3 in FIG. 1 is the main rotor, at the left
end of which in FIG. 1 is an extension 7c of its shaft pin provided
to hold a drive gear (not shown) that meshes with a corresponding
gear in a drive transmission (not shown) in order to turn the rotor
3. At the right end in FIG. 1, the two rotors 3, 5 have two gears
17, 19 that mesh with one another, thus forming a synchronizing
transmission that conveys the rotation of the upper rotor 3 to the
lower rotor 5, which is the secondary rotor, at the desired RPM
ratio. This ensures that the profile sections 7, 9 of the rotors 3,
5 mesh with one another without touching.
[0012] The screw compressor described is preferred to be a
"dry-running" compressor, i.e. in which no lubricating, cooling or
sealing oil is fed to the compression chamber. Despite this fact,
the rotor profiles mesh with one another without touching and form
a seal nevertheless. This is an advantage for all applications in
which the compressed gas must be completely free of oil. Oil is
only fed external to the compression chamber, i.e. outside the zone
sealed off by the seals 11. The oil is used to lubricate the drive
gear (not shown), the bearings 13, 15 and the synchronizing
transmission 17, 19.
[0013] In FIG. 2, the two rotors 3, 5 of the screw compressor of
FIG. 1 are shown separately in a perspective view. It can be seen
from FIG. 2 that rotor 3, which is the main rotor, has a profile
section 7 whose profile is made up of six screw-shaped ribs 7'. The
lower rotor 5, which is the secondary rotor, has a profile section
9 with a profile that is made up of eight screw-shaped ribs 9'. The
total number of screw-shaped ribs 7', 9' of the two rotors, that is
the total number of "teeth", is thus 14.
[0014] Furthermore, FIG. 2 shows areas 7a, 7b, 9a, 9b of the shaft
pins next to the profile sections 7 and 9 of each rotor 3, 5 on
both sides, said areas having diameters (D, D') that are more than
half the outer diameter of their respective profile sections.
[0015] FIG. 3 shows the profile sections 7, 9 of the two rotors in
a section perpendicular to the axes. Profile 7 of the main rotor
has six screw-shaped ribs 7' that are separated from one another by
grooves 7''. The tips of the ribs 7' define the outer circular
envelope Ka of the profile with diameter Da. The bottom surfaces of
the grooves 7'' define the inner circle Ki at diameter Di. The
radial distance between circles Ka and Ki is called the rib height
or the tooth height H.
[0016] This is not larger, and is preferably smaller than 0.15
times the diameter Da of the outer circle Ka. The same applies to
the eight ribs 9' and the grooves 9'' separating them for the lower
rotor (secondary rotor) 9, i.e. the tooth height H is also not
larger than 0.15 times the outer profile diameter Da in this
case.
[0017] As the screw compressor shown in FIG. 1 is operated, the gas
to be compressed (in particular air) is fed to its intake chamber
10, which is located adjacent to the left end of the profile
sections 7, 9 in the rotor housing 1 in FIG. 1. This air is
preferred to have been pre-compressed by one or more upstream
compressor stages (not shown) to an intermediate pressure, for
example a pressure in the range of 10 to 15 bar, preferably 12 bar.
This pre-compressed gas is conveyed to the right to an outlet (not
shown) in FIG. 1 by the profile sections 7, 9 of the two rotors 3,
5 and in the process compressed to a final pressure preferred to be
in the range of 30 to 50 bar, in particular about 40 bar. The
rotors of the screw compressor are designed such that they are
insensitive to the lateral forces produced by the compressed gas at
these high pressures.
* * * * *