U.S. patent application number 12/877164 was filed with the patent office on 2011-03-31 for system for acquiring, measuring and checking the operating parameters of a reciprocating fluid machine.
Invention is credited to Massimo Altamore, Filippo Gerbi, Francesco Grifoni, Marco Lazzeri.
Application Number | 20110072964 12/877164 |
Document ID | / |
Family ID | 41600764 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110072964 |
Kind Code |
A1 |
Gerbi; Filippo ; et
al. |
March 31, 2011 |
SYSTEM FOR ACQUIRING, MEASURING AND CHECKING THE OPERATING
PARAMETERS OF A RECIPROCATING FLUID MACHINE
Abstract
The invention describes a validation system for a reciprocating
fluid machine. The system comprises a base plate or foundation on
which at least one frame of the reciprocating fluid machine is
removably applied; a first shaft, rotatably coupled with the base
plate, to activate the components of the frame; at least one system
for generating loads, placed in operative connection with such
components and put in rotation by a transmission system through at
least one second shaft. The system for generating loads is able to
simulate the loads generated by the working fluid on a cylinder of
the reciprocating fluid machine.
Inventors: |
Gerbi; Filippo; (Sesto
Fiorentino, IT) ; Altamore; Massimo; (Florence,
IT) ; Lazzeri; Marco; (Empoli, IT) ; Grifoni;
Francesco; (Vicchio, IT) |
Family ID: |
41600764 |
Appl. No.: |
12/877164 |
Filed: |
September 8, 2010 |
Current U.S.
Class: |
92/5R |
Current CPC
Class: |
F04B 51/00 20130101 |
Class at
Publication: |
92/5.R |
International
Class: |
F01B 31/12 20060101
F01B031/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2009 |
IT |
MI20009A001666 |
Claims
1. A validation system for a reciprocating fluid machine, the
system comprising: a base plate on which at least one frame of said
reciprocating fluid machine is removably applied; a first shaft
rotatably coupled with said base plate, to activate the components
of said frame; and at least one system for generating loads, placed
in operative connection with said components of said frame and put
in rotation by an actuation system, said system for generating
loads being configured to simulate the loads generated by the
working fluid on a cylinder of said reciprocating fluid
machine.
2. A system according to claim 1, wherein said reciprocating fluid
machine is of the high performance type.
3. A system according to claim 1, wherein said system for
generating loads is of the mechanical, pneumatic, hydraulic or
electric type.
4. A system according to claim 1, wherein said system for
generating loads further comprises at least one first elastic
element placed in operative connection with said components of said
frame and put in rotation by at least one eccentric, wherein said
eccentric is put in rotation by at least one second shaft of said
actuation system.
5. A system according to claim 4, further comprising one or more
preloading devices acting on said first elastic element, so as to
adjust its preloading.
6. A system according to claim 4, further comprising a yielding
element interposed between said eccentric and said first elastic
element to decrease the friction and promote the contact between
said eccentric and said first elastic element.
7. A system according to claim 6, further comprising a second
elastic element associated with said eccentric and with said
yielding element, so as to ensure the contact between said
eccentric and said yielding element in any operative condition and
to uncouple the rigidity of said first elastic element from that
necessary to maintain the contact between said yielding element and
said eccentric.
8. A system according to claim 7, further comprising an adjustment
element configured to adjust the preloading of said second elastic
element, so as to further improve the contact between said
eccentric and said yielding element.
9. A system according to claim 4, wherein said first elastic
element and said at least one eccentric are configured to be
removed from said system to be replaced with elastic elements
and/or with eccentrics of a different kind, in the case in which
measurements and/or validations must be made on different
reciprocating fluid machines or for different requirements.
10. A system according to claim 1, wherein said actuation system is
a mechanical system, comprising at least one actuation motor, and
configured to at least partially return the energy absorbed in the
outward stroke during the return stroke, decreasing the power that
said actuation motor must deliver.
11. A system according to claim 10, wherein said actuation system
comprises a system of rigid connecting rods and of cranks actuated
by said actuation motor.
12. A system according to claim 4, further comprising one or more
sensors configured to acquire and measure the operating parameters
relative to said frame and to the assembly consisting of said first
elastic element and said eccentric.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention refers to a system for validating or
checking a reciprocating fluid machine, in particular but not
exclusively a reciprocating compressor of the type with
single-acting cylinders connected to a cross-head.
[0003] 2. Description of the Prior Art
[0004] As known, a compressor is a machine capable of raising the
pressure of a compressible fluid (gas) through the use of
mechanical energy. In reciprocating compressors the compression of
the fluid is carried out by one or more pistons, moving with
reciprocating motion inside a respective cylinder. The fluid to be
compressed is taken into the cylinder through one or more intake
ducts, whereas the compressed fluid is expelled from the cylinder
towards one or more delivery ducts. Commonly, the piston or the
pistons of a reciprocating compressor are actuated by electric
motors or else by internal combustion engines, through a crankshaft
for transmitting the motion and a conventional crank and connecting
rod mechanism.
[0005] For example, in double-acting reciprocating compressors each
piston does not carry out any "loadless" strokes, since it
compresses the gas in both of its directions of motion. Precisely
for this reason, the piston itself cannot be directly connected to
the connecting rod of the crank and connecting rod mechanism,
because the closed-type cylinder would not allow the connecting rod
to oscillate. Thus a mechanism known as "cross-head" is placed
between the piston and the connecting rod. The piston is connected
to a rod, mobile exclusively with rectilinear motion, and the rod
is connected to the cross-head. The stem does not therefore
oscillate whereas the connecting rod, connected to the other side
of the cross-head, can on the other hand oscillate freely.
[0006] The cross-head, through the sliding blocks with which it is
provided, is able to slide inside suitable fixed guides, called
"runners", which allow its movement in the same direction of stroke
of the piston. Given that the outer surfaces of the sliding blocks
of the cross-head move with respect to the inner surfaces of the
relative guides, it is necessary to introduce lubricant oil that
prevents them from making contact with each other. The lubrication
system is of the forced type and, by providing the cross-head with
support mainly of the hydrostatic type, it prevents the wearing of
the moving parts involved.
[0007] During the reciprocating movement of the cross-head there
can be particular operating conditions, for example when the piston
moves at low speed, in which the cross-head is unable to feed a
sufficient amount of lubricant oil. In such a situation the layer
of lubricating oil becomes extremely thin and there can be losses
by friction, with consequent production of heat and increase in the
temperature of the lubricant oil itself that reduce its viscosity,
further decreasing the lubricating capabilities. In the worst
situations, the surfaces can even come into contact with each
other, with consequent possible damage to the fluid machine.
[0008] Both the size and the set-up of a reciprocating compressor,
whether it is single or double-acting, must therefore be carried
out in a particularly precise manner, so as to avoid the occurrence
of criticalities in the compressor itself when it operates in limit
operating conditions. Consequently, the step of determining the
operating parameters of a reciprocating compressor is extremely
important, said parameters including the loads that weigh down upon
the shaft of the piston and on the cross-head, the temperature, the
pressure and the flow rate of the oil to lubricate the cross-head,
the rotation speed of the crankshaft, the clearances between the
sliding blocks and the runners and others.
[0009] Document WO 2005/108744 A1 illustrates an apparatus and
method for checking the operation of a reciprocating compressor.
The apparatus comprises a mobile element operatively connected to
one of the moving components of the compressor, like for example
the cross-head. The mobile element is provided with a sensor
capable of detecting the parameter or parameters of interest, which
will then be sent to an external data processing unit for the
necessary evaluations. The reciprocating compressor must be
complete in every part thereof in order to be able to correctly
provide the required parameters.
[0010] Document WO 2008/157496 A1 describes a method for
calculating the operating parameters of a reciprocating compressor.
The method foresees the use of a program for a processor capable of
simulating the operating conditions of the compressor. However,
also in this case the basic parameters must be directly obtained
from a real operating reciprocating compressor.
[0011] The known apparatuses and methods thus foresee the need to
be able to have a reciprocating compressor, complete in every part
thereof and operating, in order to be able to evaluate its
characteristic parameters. This means that, in the case of
parameters that are incorrect or not corresponding to those
foreseen, modifications, even substantial ones, must be made to the
machine, like for example the replacement of some of its
fundamental components, with a consequent increase in costs and
set-up time.
[0012] Moreover, the presence of the cylinder and of the relative
systems for gas circulation, for cooling and for lubrication,
although necessary when the compressor operates in normal mode,
requires that the measurement of the parameters be carried out in a
very complex testing environment, with consequent high energy
absorption by the compressor itself, equal to what occurs in normal
operating conditions of the machine, with consequent need for a
motor of suitable power.
SUMMARY OF THE INVENTION
[0013] The general purpose of the present invention is therefore to
make a system for acquiring and monitoring the operating
parameters, applied in particular but not exclusively to a
reciprocating compressor of the aforementioned type, which is able
to solve the drawbacks quoted above of the prior art in an
extremely simple, cost-effective and particularly functional
manner, irrespective of the technical characteristics of the
respective cylinders, thus being highly versatile.
[0014] Another purpose of the invention is to make a system for
acquiring, measuring and checking the operating parameters of a
reciprocating fluid machine that does not require the preparation
of complete prototypes in order to work out its operating
characteristics, being able to replace at least some of the
component or systems normally present on each machine to be
analysed, like for example the cylinders, the pistons, the valves
and the gas circuits, cooling circuits and lubrication circuits,
with simpler and interchangeable components.
[0015] A further purpose of the invention is to make a validation
system that is easy to manufacture and that does not require
complex and expensive actuations systems in order to be put into
operation, since the energy required for its operation is much less
than that necessary to make a complete reciprocating machine
work.
[0016] These purposes according to the present invention are
accomplished by making a validation system for a reciprocating
fluid machine, in particular but not exclusively a reciprocating
compressor, as outlined in claim 1.
[0017] Further characteristics of the invention are highlighted by
the dependent claims, which are an integral part of the present
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The characteristics and advantages of a system for
validating, measuring and checking the operating parameters of a
reciprocating fluid machine according to the present invention will
become clearer from the following description, given as an example
and not for limiting purposes, referring to the attached schematic
drawings, in which:
[0019] FIG. 1 is a schematic section view that shows the main
components of a reciprocating compressor;
[0020] FIG. 2 is a schematic view that shows the operating
principle of a reciprocating compressor;
[0021] FIG. 3 schematically shows a reciprocating compressor, in a
configuration with many cylinders;
[0022] FIG. 4 is a perspective view (flywheel side) that
illustrates a non-limiting example embodiment of a system for
validating the operating parameters of a reciprocating fluid
machine according to the present invention;
[0023] FIG. 5 is another perspective view (cam side) of the system
of FIG. 4;
[0024] FIG. 6 is a side elevational view (flywheel side) of the
system of FIG. 4;
[0025] FIG. 7 is a plan view from above of the system of FIG.
4;
[0026] FIG. 8 is an enlarged side elevational view (cam side), of
the system of FIG. 4; and
[0027] FIGS. 9 to 11 show the operating principles of a system
according to the present invention.
[0028] It should be noted that, in each figure, the same reference
numerals correspond to the same systems or components of the
previous and/or subsequent figures.
DETAILED DESCRIPTION OF THE INVENTION
[0029] With reference in particular to FIG. 1, the essential
elements present inside a reciprocating fluid machine, in this case
represented by a reciprocating compressor of the double-acting
type, are shown schematically.
[0030] The compressor comprises a shaft 10 with at least one crank,
connected to a connecting rod 12 that transfers the rotary motion
of the shaft 10, actuated by a generic motor 36, electric or
thermal, through the interposition of a flywheel 38 (FIG. 3), to a
cross-head 14 through a pin 16. The cross-head 14 has the task of
converting rotary motion into reciprocating motion, being forced to
move inside suitable opposite guides or runners 18 and 20 that
allow it to move in the same direction as the stroke of the piston
22. A shaft 24, provided with a sealing system 44 consisting of a
stuffing box, connects the cross-head 14 to the piston 22. The
piston 22, moving inside the cylinder 26, is therefore able to
compress the gas.
[0031] The gas to be compressed, at a certain intake pressure, is
introduced inside the cylinder 26 through one or more intake valves
28 and 28' and is then compressed by the piston 22 so that it
reaches a desired final pressure value. Once the gas has reached
such a final pressure value, it is expelled from the cylinder 26
through one or more discharge valves 30 and 30'. In a double-acting
cylinder 26, like the one schematised in FIG. 1, the compression
takes place inside two distinct chambers, in other words the
chamber 32 facing towards the head of the cylinder 26 and the
chamber 34 facing towards the cross-head 14.
[0032] The compressor can be of the single-cylinder type or else it
can have many cylinders 26, for example horizontal and opposite as
shown in FIG. 3. A lubrication system 40 and a water-operated
cooling system 42 complete the compressor and make it possible for
it to work at the different rotation speeds.
[0033] The assembly of mechanical components of the compressor, in
other words the shaft 10, the connecting rod 12, the shaft 24 and
the cross-head 14, with the elements associated with it that ensure
its reciprocating movement, can be identified as the frame 46 of
the compressor itself. The frame 46 can thus be distinct from the
cylinder 26 as a whole, i.e. provided with all of the hydraulic
channels 28, 28', 30, 30', 40 and 42 associated with it, since
there is no circuit for the circulation of the gas in it.
[0034] Now with reference to FIGS. 4 to 10, a preferred embodiment
of a system for validating, acquiring, measuring and checking the
operating parameters of a reciprocating fluid machine according to
the present invention is shown, wholly indicated with reference
numeral 50.
[0035] The system 50 preferably comprises a base plate or a
foundation 52 on which the components necessary for the operation
of the system 50 itself are installed. Thus the base plate 52 has
at least one frame 46 of a reciprocating fluid machine, in
particular a reciprocating compressor, removably applied to it,
where by frame 46 we mean the assembly of all of the components of
the machine that do not comprise the circuits for the gas (see
previous description). More specifically, the frame 46 comprises at
least one connecting rod 12 and a cross-head 14, mobile with
reciprocating motion and fixedly connected, at least one of its two
ends, to a shaft 24 that in turn is mobile with reciprocating
motion.
[0036] The components 12, 14 and 24 of the frame 46 are moved with
reciprocating motion by means of a first crankshaft 54, rotatably
coupled with the base plate 52. In turn, the shaft 54 is set in
rotation, based on a predefined angular velocity but in any case
variable, by an actuation motor 56, preferably electric, through
the interposition of an actuation system 58 supported by the base
plate 52.
[0037] In the illustrated example embodiment, the actuation system
58 consists of a system of rigid connecting rods 58' and of
respective crankshafts 58'', actuated by the motor 56 through a
belt 60 and a flywheel-pulley 62. The flywheel 62 is connected to
the first crankshaft 54 through the central crankshaft 58''.
[0038] According to the invention, on the base plate 52 of the
system 50 at least one system for generating loads 80 is mounted
that is suitable for replicating the loads of the gas acting on the
frame 46, as occurs in the real fluid machine.
[0039] In a particularly advantageous embodiment of the invention,
the system for generating loads 80 is of the mechanical type.
Clearly it should not be ruled out that such a system for
generating loads 80 can be of any other type, like for example
hydraulic, electric, pneumatic or other.
[0040] In the preferred embodiment, the system for generating loads
80 comprises an elastic or yielding element 64 placed in operative
connection with at least one eccentric or cam 66.
[0041] More specifically, each elastic element 64 is interposed
between each shaft 24 and each eccentric 66 (see diagrams of FIGS.
10 and 11) and is compressed and released in sequence based on the
reciprocating motion of the shaft 24 of the frame 46 and the rotary
motion of the eccentric 66, which occur simultaneously. The
assembly consisting of the elastic element 64 and the eccentric or
cam 66 is thus able, once actuated by the motor 56 and after having
been suitably calibrated, as will be specified more clearly
hereafter, to simulate the load of the cylinder 26 of a generic
reciprocating fluid machine, like for example the reciprocating
compressor described earlier. In practice, each elastic element 64,
made in the form of a coil spring operating by compression in the
illustrated example embodiment, is able to reproduce the same
forces that act on the components of the reciprocating compressor
(in particular on the cross-head 14 and on the relative pin 16), in
the operating conditions of interest.
[0042] A yielding element 74 is advantageously and preferably
interposed between the eccentric 66 and the spring 64 to decrease
the friction and promote the contact between the cam and the
spring.
[0043] In an advantageous embodiment, a further elastic element 82
(FIGS. 5 and 8) is associated with the shaft 68 of the cam and with
the shaft of the yielding element 74, so as to ensure the contact
between yielding element 64 and cam 66 in every operation
condition. This elastic element 82 can be adjusted through an
adjustment element 78 that, in the case shown in the Figures, is
made with a screw 78 acting on a plate 76.
[0044] In this way it is possible to uncouple the rigidity of the
main spring 64 (designed so as to obtain the desired load on the
cross-head 14) from that necessary to maintain the contact between
yielding element 64 and cam 66 for any rotation speed.
[0045] The system 50 is advantageously provided with one or more
sensors 84 capable of acquiring and measuring the operating
parameters relative both to the frame 46 and to the assembly
consisting of the spring 64 and the cam 66, which reproduces the
cylinder 26. Such parameters comprise:
[0046] clearances (in thousandths of a millimetre) between sliding
blocks of the cross-head 14 and relative runners 18 and 20;
[0047] crank angle (.theta.);
[0048] forces (F.theta.) acting upon the cross-head 14 and upon the
shaft 24;
[0049] rotation speed (.omega.) of the shaft 10 and linear speed
(V.theta.) of the cross-head 14;
[0050] temperature, pressure and flow rate of the lubricant oil
present in the gap between sliding blocks of the cross-head 14 and
relative runners 18 and 20.
[0051] All of the parameters acquired and measured by the sensors
84 can be sent, through a suitable wireless communication line 70
or via cable, to a central processing unit (not shown), capable of
recording and graphically representing, in real time, such
parameters according to each single revolution of the shaft 54.
[0052] The system 50 according to the invention is therefore
capable of carrying out validation tests of reciprocating fluid
machines such as compressors, for example in the operating
conditions known as full load or partial load, without the need to
also make and actuate the cylinder or the cylinders 26 of the
machine with the relative gas delivery and expulsion circuits,
which use up a substantial amount of energy. One of the advantages
of the system 50 is indeed the fact that the actuation motor 56 can
deliver a substantially lower power with respect to what is
required of a normal motor 36 able to be used for normal operation
of a complete reciprocating compressor. This is essentially due to
the fact that during the operation of the system 50, when the
spring 64 is released during the return stroke of the cross-head
14, the spring 64 itself returns the energy absorbed in the outward
stroke (see diagrams of FIG. 11), decreasing the power requirement
that the actuation motor 56 must deliver.
[0053] In the case in which measurements and/or validations have to
be carried out on different machines or for different requirements,
in addition to the possibility of removing the frame 46 from the
system 50 (as mentioned earlier and as shown, for example, in FIG.
5), it is also possible to remove the springs 64 and/or the cams 66
from the system 50, replacing them with other springs and/or cams
of a different type. For example, it is possible to use springs 64
with different dimensions and elastic coefficient, or else
differently designed cams 66.
[0054] Alternatively or in addition, again in order to vary the
test conditions of the reciprocating machine, the system 50 can be
provided with one or more preloading devices 72 acting upon each
spring 64. In detail, based upon the illustrated example
embodiment, the preloading device 72 (FIG. 8) consists of a rotary
ring nut system, operating according to the screw-nut principle,
interposed between the shaft 24 of the frame 46 and the relative
spring 64. The preloading device 72 is thus able to increase or
decrease the compression on the spring 64, respectively, by
bringing the shaft 24 closer to or farther from the spring 64
itself.
[0055] The system 50 according to the invention can be made based
on different embodiments from the one described and illustrated up
to here, whilst still maintaining the basic operating principles
shown in the diagrams of FIGS. 9-11. For example, the transmission
of motion from the actuation motor 56 to the shafts 54 and 68 could
take place through a series of linkages 58 different from the rigid
connecting rods 58' and from the respective cranks 58''. The
linkages 58 could indeed consist, according to the technical
requirements, of a system of belts, chains and/or gears interposed
between the actuation motor 56 and the shafts 54 and 68, or else
other equivalent systems. Similarly, a different number of motors
can be foreseen. However, it should be specified that the system
consisting of the rigid connecting rods 58' and the respective
crankshafts 58'' is considered to be preferable to ensure the
perfect phased rotary movement of the shafts 54 and 68 that
respectively control the reciprocating movement of the frame 46 and
the rotary movement of the cams 66.
[0056] It should also be noted that it is possible to make a frame
46 that reproduces to scale a frame of a real compressor. In this
way the system 50 is able to carry out validation tests on a scale
prototype of the real compressor, substantially decreasing its
manufacturing and installation costs and at the same time
increasing its versatility.
[0057] The system according to the present invention is
particularly useful for the acquisition, measurement and checking
of the operating parameters of a reciprocating fluid machine for
high performance in industrial systems or plants where making the
circuit for the gas is particularly complex and expensive, like for
example in industrial plants for producing low density polyethylene
that work at pressures of up to about 3500 bars or more.
[0058] Clearly it should not be ruled out that such a system can be
used on reciprocating machines or industrial plants of a different
type.
[0059] The system for acquiring, measuring and checking the
operating parameters of a reciprocating fluid machine of the
present invention thus conceived can in any case undergo numerous
modifications and variants, all of which are covered by the same
inventive concept; moreover, all of the details can be replaced
with technically equivalent elements. In practice, the materials
used, as well as the shapes and sizes, can be whatever according to
the technical requirements.
[0060] The scope of protection of the invention is therefore
defined by the attached claims.
* * * * *