EP3063408A1

EP3063408A1 - Method for controlling knocking in a piston compressor

Info

Publication number: EP3063408A1
Application number: EP14783541.7A
Authority: EP
Inventors: Robert Adler; Sascha Dorner; Martin Pfandl; Christoph Nagl
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2013-10-29
Filing date: 2014-10-02
Publication date: 2016-09-07
Also published as: JP2016535834A; US20160305420A1; RU2016120861A; WO2015062698A1; DE102013017944A1

Abstract

The invention relates to a method for controlling knocking in a piston compressor (1) and to a piston compressor (1) that is designed to carry out the method according to the invention. The method according to the invention is characterized in that, if a knocking noise (100) made by a piston (10) of the piston compressor (1) hitting a cylinder head (12) is detected by means of a structure-borne noise sensor (2) provided on the piston compressor (1), the piston stroke (16) of the piston compressor (1) is decreased or, if no knocking noise (100) is detected over a predefinable period of time, the piston stroke (16) is increased.

Description

description

Method for knock control in a reciprocating compressor

The invention relates to a method for knock control in a reciprocating compressor according to claim 1 and claim 9 and a reciprocating compressor according to claim 10.

From the prior art, a variety of methods for the compression and delivery of fluids are known, including reciprocating compressors, with the aid of a fluid can be compressed and re-issued in the compressed state. In such a reciprocating compressor, a piston in a cylinder oscillates between a first and a second reversal point along the cylinder axis, wherein the distance between the first and the second reversal point represents the piston stroke. Furthermore, a cylinder head is arranged at one end of the cylinder, wherein the first reversal point is closer to the cylinder head than the second reversal point. The reversal points of the piston are also called dead centers.

The cylinder head usually has a pressure valve and a suction valve. One cycle or period of the reciprocating compressor begins when the piston is at the first reversal point. Now moves the piston in the cylinder in the direction of the second reversal point, on the one hand, the pressure valve is closed and by the

Suction valve sucked the fluid to be compressed in the compression space, which is given by the volume between the cylinder head and piston. Then the piston moves from the second turning point back towards the first

Turning point closes the suction valve and the previously sucked into the compression space fluid is compressed in the compression chamber, wherein at a

presettable pressure in the compression chamber opens the pressure valve and the compressed fluid flows out of the compression space through the pressure valve, in particular until the piston has reached the first reversal point and the cycle starts again from the beginning.

When designing a reciprocating compressor, the dimensions and tolerances should, if possible, be chosen such that the piston abuts the cylinder head is avoided. This is done primarily by design measures, which are usually associated with a reduced flow rate.

Due to the temperature differences occurring in compressors it is

For example, in piston compressors structurally necessary to provide length tolerances that go hand in hand with an increase in the dead space. The dead volume is here the volume enclosed by the cylinder head and the piston when it is at the first turning point. The caused by the dead space increased gas re-expansion means a reduced flow rate.

For those compressors that have a variable stroke and thus no fixed

Turning points have further problems. By disregarding a length tolerance between the reversal point and the cylinder head, the piston, due to a late change in the direction of movement, on

Knock on the cylinder head.

The technical challenge of compressors is therefore in particular to choose the geometry and the materials used so that the permissible

Surface pressure is not exceeded in case of striking the piston on the cylinder head. Often, exceeding the permissible surface pressure, for example, due to minimal oblique placement of the piston on

Cylinder head, can not be avoided. In this case, there is a plastic deformation of the components. Frequently, this deformation is accompanied by a continuous flaring of the abutting or impacted parts. In the event of an emergency, this leads to the defect of one or more relevant components and often ends with a failure of the machine.

A constant impact of the components also leads to a considerable

Noise pollution. This noise pollution is particularly problematic for plants whose installation is planned close to residential areas. Here there are special requirements, which can sometimes be achieved only by a separate sound insulation.

There are devices and methods are known which are suitable for knock detection in internal combustion engines, such as "method for knock detection at Internal combustion engine ", EP 1184651 B1, as well as EP 1208364 B1. Whereby" knocking "in an internal combustion engine is commonly referred to as the knocking noise resulting, for example, from premature or incomplete combustion of the fuel in the engine cylinder. A knocking sound, which is caused by the striking of the piston on the cylinder head, is not to be equated with these caused by ignition and combustion processes in internal combustion engines noises.

On this basis, the object of the present invention is therefore to provide a piston compressor and a control method which are improved with regard to the aforementioned problem.

This problem is solved by a knock control method in a reciprocating compressor according to claim 1 and claim 11. Advantageous embodiments of the invention are i.a. specified in the dependent claims.

According to claim 1, it is provided that the piston stroke is reduced when a knocking sound is detected by striking the piston on the cylinder head by means of a structure-borne sound sensor arranged on the piston compressor, or that the piston stroke is increased if no over a predefinable period

Tapping sound is detected.

Recognizing the impact of the piston on the cylinder head, especially in the start-up phase of the reciprocating compressor in which large temperature changes occur within short time intervals, and a subsequent control advantageously allows the reduction of the probability of failure of the compressor, which increases the service life - while lower service cost , For

Positionless operated compressor, as is to be thought of, for example, synchronous linear motor driven reciprocating compressor, such knock detection and control is an additional safety device.

Furthermore, the lower noise emission due to the avoidance of knocking noises makes it possible to install, in particular, hydrogen refueling stations in the vicinity of residential areas. Furthermore, in the absence of knocking noises further untypical operating noise can be better detected and closed on possible system errors. By stopping the constant beating of the Namely compressor components can the acoustic fault finding due to the

Remaining noise coverage significantly improved.

A reduction of the piston stroke is usually achieved by moving the first and the second reversal point toward one another, wherein the reversal points can be shifted towards one another, in particular by the same length amount. Correspondingly, an increase in the piston stroke is achieved, for example, by the first and the second reversal point being displaced away from one another (in particular likewise by the same length amount). In this form of regulation so only the deflection of the piston in both

Oscillation directions reduced / enlarged.

However, it is also conceivable that an "asymmetrical" reduction / reduction of the piston stroke is achieved by shifting only the first reversal point in the direction of the second reversal point In this case, the deflection is only changed along one direction, namely in the direction of the cylinder head, and the two reversal points can be shifted toward or away from each other by different amounts.

For example, the piston stroke is controlled so that the distance of the first

Turning point of the cylinder head is a fraction of the piston stroke, in particular, this fraction is less than one-thousandth or less than a two-thousandth.

In a preferred variant of the invention it is provided that the piston stroke is reduced at least once by a first amount of length, if the

Knocking sound is detected, in particular, the piston stroke is reduced so often by the first amount of length until the knocking sound is no longer detected.

In this case, the first length amount is, for example, 0.5 mm.

A further embodiment of the invention is characterized in that the piston stroke is increased by a second amount of length when the piston stroke has been reduced at least once by the first amount of length, wherein the second amount of length is in particular smaller than the first amount of length and the piston stroke is in particular so often increased by said second amount of length until again a knocking sound is detected.

In a further preferred variant, the piston stroke is increased, in particular by the second length amount, if a knocking sound is not detected over the predefinable time period, wherein the second length amount is in particular smaller than the first length amount, and wherein the piston stroke is increased or increased so often is increased by said second amount of length, in turn, a knocking sound is detected.

The predefinable period is for example 30-300 s and is in particular of the piston frequency and the expected temperature changes of the

Piston compressor dependent. The lower the piston frequency, the longer can be the predefinable time. The second length amount is for example 20% of the first length amount, ie in particular 0.1 mm.

In an advantageous variant of the invention, the piston stroke is further reduced at least once by a third amount of length after the knocking sound has been re-detected, in particular the piston stroke so often by a third

Length is reduced until the knocking sound is no longer detected.

It should be noted that this variant of the invention can also be carried out in particular, if previously the piston stroke was increased by the second length amount, even if no knocking sound was detected, because a control intervention was carried out, for example, by the expiration of the predefinable period.

It should be noted that the third length amount is preferably both smaller than the second length amount and smaller than the first length amount. Preferably, the third length amount is 20% of the first length amount, ie in particular 0.1 mm.

In a preferred embodiment of the invention it is provided that the

Piston stroke is increased by a fourth amount of length, when the piston stroke has been reduced at least once by the third amount of length, the fourth amount of length is in particular smaller than the third amount of length, and wherein the Piston stroke is particularly often increased by the said fourth amount of length, in turn, a knocking sound is detected.

In a further preferred embodiment of the invention, it is provided that the piston stroke is reduced once after the detection of the said knocking sound by the fourth length amount. The fourth length amount is, for example, 50% of the third length amount, ie in particular 0.05 mm.

In an advantageous embodiment of the invention, the reduction and / or enlargement of the piston stroke lasts shorter than the period of the oscillating piston lasts.

Furthermore, the problem of the invention by a method with the

Characteristics of claim 9 solved.

In particular, the application of the method according to the invention in an existing reciprocating compressor is in the foreground.

Thus, the method according to the invention or the inventive

Device a more accurate modeling of the dead space between the piston and

Cylinder head. Thereby, e.g. in an existing reciprocating compressor under operating conditions, the distance between the piston and the cylinder head to be further reduced until a knocking sound is perceived by the dead space is manually reduced (ie in particular not by changing the piston stroke). This happens, for example, by the inclusion of thrust washers. The knock indicates that the stroke is too small, so the thrust washer must be replaced with a slightly thinner one. This process is repeated until a knock-free compression sets. Taking into account all operating points, there is no need for the knock detection after the adjustment according to the invention by the thrust washers.

Furthermore, the problem according to the invention is solved by a reciprocating compressor having the features of claim 10, wherein the reciprocating compressor is designed in particular for carrying out the method according to the invention. Thereafter, a structure arranged on the piston compressor structure-borne sound sensor is provided, which is adapted to detect structure-borne noise or knocking noises by

Striking the piston of the reciprocating compressor to the cylinder head of

Piston compressor were generated, wherein the structure-borne sound sensor is adapted to generate upon detection of such knocking an output signal, wherein a control unit is provided which is adapted to control the piston stroke in response to the output signal, in particular the control unit is adapted to the piston stroke to reduce to the output signal, and wherein in particular the control unit is adapted to increase the piston stroke, if over a predefinable period of time no knocking sound is detected.

The piston compressor or its control unit is preferably designed to carry out the individual process steps according to the invention. Preferably, the structure-borne sound sensor used is particularly sensitive to

Sound frequencies, frequency patterns and / or frequency profiles / sequences, which preferably occur when the piston is hit the cylinder head.

Furthermore, to determine a sequence of the predefined period of time explained above, a time-measuring means may be provided that communicates with the control unit

interacts. The control unit can be designed to be of the

Timing means to receive corresponding signals or the time measuring means

read, start, stop and / or reset. In a further preferred variant of the invention, the piston compressor has a drive for driving the piston, wherein the drive is designed in particular as a linear motor, wherein the drive drives the piston in such a way that the piston in the cylinder between the first and the second reversal point hin- and is moved here.

Furthermore, a position sensor may be provided (eg, the drive may have a position sensor), which indicates the instantaneous position of the piston or of a drive element connected to the piston, in particular the reversal points. The control unit can then make an adjustment of the piston stroke with the aid of these position data, ie reduce or increase it. In a preferred variant of the invention, the structure-borne noise sensor is arranged on the cylinder head and in particular represents an integral part of the cylinder head.

However, it is also possible that the structure-borne sound sensor is arranged on the cylinder or at another point on the piston compressor, wherein particular care should be taken that the structure-borne sound sensor is arranged as close as possible to the origin of the (knocking) noise generation and in particular a good

Structure-borne sound transmission from the reciprocating compressor to the structure-borne sound sensor

is guaranteed, e.g. by attaching the structure-borne sound sensor to smooth

Surfaces of the reciprocating compressor.

In a preferred embodiment of the invention it is provided that the

Structure-borne sound sensor is a piezo-electric sensor that converts pressure change on the sensor surface, based on the piezoelectric effect, into electrical signals. Of course, other sound sensors can be used.

The invention advantageously enables an optimization of

Compression performance in terms of usable piston travel, as determined by the

Reduction of the dead space, the capacity is increased. The reduced

Mechanical stress also allows the use of materials with a lower permissible surface pressure. This reduces the acquisition and production costs of the individual components. By using the reciprocating compressor according to the invention or the method according to the invention, furthermore, an operational reference travel of a compressor with a variable piston stroke can be dispensed with. Such a reference travel is used, for example, the zero point finding of the piston, or the change in length compensation due to differential thermal expansion in non-stationary operating states.

Further details and advantages of the invention will be explained by the following description of exemplary embodiments with reference to the figures. Fig. 1 sectional view of a piston compressor according to the invention Fig. 2 flowchart of the method according to the invention.

FIG. 1 shows a piston compressor 1 according to the invention, which is driven by a drive, which is preferably a servo-tube linear motor with a frequency of 10 Hz, ie twenty piston strokes or ten suction and pressure cycles per pressure stage per second. The piston stroke 16 is 120 mm but is variably adjustable. The reciprocating compressor 1 has a structure-borne sound sensor 2, which is connected to a

Cylinder head 12 of the reciprocating compressor 1 is arranged. It is the

Structure-borne sound sensor 2 as full as possible, i. without air gaps, connected to the cylinder head 12 so that the best possible structure-borne sound transmission from

Cylinder head is guaranteed to the sensor 2.

In the reciprocating compressor 1, a piston 10 oscillates in a cylinder 11 of the

Piston compressor 1 between a first or upper reversal point OT and a second or lower reversal point UT (in particular with a maximum stroke of 120mm). As a result of the movement of the piston 10 from the first reversal point OT to the second reversal point UT, the pressure in a compression chamber 13 formed between the piston 10 and the cylinder head 12 decreases. As soon as the opening pressure of a suction valve 14 provided on the cylinder head 12 is fallen below, this suction valve 14 becomes opened and to be compressed fluid is sucked into the compression chamber 13. Upon reaching the second reversal point UT, the piston 10 changes its direction of movement in the direction of the first reversal point OT, whereby the pressure in the compression chamber 13 increases. The suction valve 14 closes as soon as the pressure in the compression chamber 13 is greater than the suction pressure. If the pressure in the compression chamber 13 then exceeds the opening pressure of a pressure valve 15 provided on the cylinder head 14, the pressure valve 15 opens and the compressed fluid flows out of the compression chamber 13 and leaves the piston compressor 1. Upon reaching the first reversal point OT, the piston 10 again changes its direction of movement Direction to the second turning point UT. The period is given by such a complete compression cycle. If the piston 10 now bounces on the cylinder head 12 in the compression phase, this collision is due to an associated knocking sound from the

Structure-borne sound sensor 2 detected. So that this structure-borne noise can be detected as close as possible to its origin, the structure-borne noise sensor 2 is fixed here at the center of a cylinder head surface facing away from the piston. The contact surfaces of the structure-borne sound sensor 2 and the cylinder head 12 are preferably designed as smooth as possible.

As soon as a frequency range, frequency patterns and / or volumes typical for the knocking noise are picked up, a control intervention is carried out by a corresponding control unit.

In the piston compressor 1 according to the invention, the cylinder head 12 and the piston 10 are preferably made of Austentischem stainless steel, wherein the

Speed of sound is in the range 5100m / s. The structure-borne sound sensor 2 is here preferably a piezoelectric element which, for example, has a measuring range of +/- 60 g and a frequency range of 0.13-11000 Hz. The sensitivity of the structure-borne sound sensor 2 is preferably approximately 100 mV / g. FIG. 2 shows a flow chart of the method according to the invention. In this case, in response to the detection of a knocking noise 100 caused by a striking of the piston 10 on the cylinder head 12 in a first step 101, the piston stroke 16 is reduced by L1 in the subsequent period, and in particular so often until the knocking sound 100 stops. A preferred value for L1 here is 0.5 mm

In a subsequent second step 102, the piston stroke 16

in particular in several steps (incrementally) increased by a respective length amount L2 until a knocking sound 112 is detected by striking the piston on the cylinder head again. Here, step by step means that such a step 102 is executed per period. This process serves to minimize the dead space. A preferred value for L2 is 0.1 mm per stroke (period).

In a subsequent third step 103, the piston stroke 16 is a

Length reduced L3, which is preferably smaller by a factor of 5 than L1 (L3 = 0.1 mm). In a fourth step 104, the piston stroke is increased by a fourth length L4, wherein L4 is preferably 0.05 mm here. This increase of the piston stroke 16 by L4 is repeated (stepwise) until a knocking sound 14 is detected again. As soon as a knocking sound 114 is detected again, the piston stroke 16 is reduced again by L4, ie 0.05 mm.

Will be later, e.g. detected by a thermal shortening of the cylinder 11, again a knocking sound 100, the control is again, starting with the first step 101. Causes of a repeated knocking sound 100 can

Length changes due to different temperature expansions of the individual compressor components. By knock detection these changes in length are compensated. In order to compensate for the dead space (volume present between the piston 10 and the cylinder head 12 when the piston is at the first turning point OT) due to thermal expansion, after a predefinable period of time, the method according to the invention begins with the second step 102 (increasing the Hubs around L2 = 0.1mm) started 116. Typical values for the said period are here 30-300s.

The factors and dimensions used are mainly of the

Positioning accuracy of the entire system depends. The expected value for the time interval between the individual knocking noises corresponds to the frequency of the compression process (stroke frequency). In the application example this is

For example, at 10 Hz. The control system, with which the structure-borne sound sensor interacts, therefore preferably has a correspondingly high

Processing speed in order to account for the control operations preferably already at the next piston stroke 13 (in the next period) can. A striking of the piston 10 to the cylinder head 12 can be very high

Accelerations are accompanied, according to the preferred design of the structure-borne sound sensor 2 for these high accelerations.

By precisely adjusting the allowable length tolerance, as compared with a prior art system, an increased delivery rate arises due to the reduced dead space. The structure-borne noise measurement on the cylinder head also offers the possibility of more accurately detecting the behavior of the suction and pressure valves in the compressor. The placement of the valve in the end positions causes a Structure-borne sound wave in the cylinder head, which can be detected. In order to influence the behavior of the valve when opening, closing or in the open state, there are numerous possibilities available. So valve springs, valve lift valve and cylinder head shape can be varied. The aim of the adjustments is a quick release of the available Saugventilringspalts, followed by a gentle touchdown in the upper end position. A gentle touchdown of the valve reduces the valve recoil after touchdown, which would reduce the annular gap. Similarly, the closing of the pressure valve must be done as quickly as possible to minimize backflow of the already compressed medium.

Claims

Patent claims

Method for knock control in a piston compressor (1), wherein a piston (10) in a cylinder (1 1) oscillates between a first reversal point (OT) and a second reversal point (UT) along the cylinder axis (17), the distance between the the first reversal point (OT) and the second reversal point (UT) define a piston stroke (16), and wherein a cylinder head (12) is arranged at one end of the cylinder (11), and wherein the first reversal point (OT) is closer to the cylinder head (12 ) is the second reversal point (UT), characterized in that the piston stroke (16) is reduced when a knocking noise (100) is caused by the piston (10) striking the cylinder head (12) by means of a piston compressor (1). Structure-borne noise sensor (2) is detected, or that the piston stroke (16) is increased if no knocking noise (100) is detected over a predefinable period of time.

Method according to claim 1, characterized in that the piston stroke (16) is reduced (101) at least once by a first length amount (L1) when the knocking noise (100) is detected, in particular the piston stroke (16) being so often by the first Length amount (L1) is reduced (101) until the knocking noise (100) is no longer detected.

Method according to claim 2, characterized in that the piston stroke (16) is increased (102) by a second length amount (L2) when the piston stroke (16) has been reduced (101) at least once by the first length amount (L1), the second length amount (L2) is in particular smaller than the first length amount (L1), and the piston stroke (16) is in particular increased by said second length amount (L2) until a knocking noise (112) is detected again.

4. Method according to one of the preceding claims, characterized

characterized in that the piston stroke (16) is increased (102), in particular by the second length amount (L2) if the knocking noise (100) is not detected over the predefinable period of time, the second length amount (L2) being in particular smaller than the first length amount (L1), and the piston stroke (16) in particular being so often is increased, in particular by the said second length amount (L2), until a knocking noise (112) is detected.

5. The method according to claim 3 or 4, characterized in that after detecting the knocking noise (112), the piston stroke (16) is reduced at least once by a third amount of length (L3), in particular the piston stroke (16) being reduced so often by a third amount of length (L3) is reduced until the knocking noise (1 12) is no longer detected.

6. The method according to claim 5, characterized in that the piston stroke (16) is increased by a fourth length amount (L4) when the piston stroke (16) has been reduced at least once by the third length amount (L3), the fourth length amount (L4 ) is in particular smaller than the third length amount (L3), and the piston stroke (16) is increased in particular by the said fourth length amount (L4) until again

Knocking noise is detected (114).

7. The method according to claim 6, characterized in that after detecting the knocking noise (114), the piston stroke (16) increases once by the fourth

Length amount (L4) is reduced.

8. Method according to one of the preceding claims, characterized

characterized in that reducing and/or increasing the

Piston stroke (16) lasts shorter than the period of the oscillating piston (10).

9. Method for adjusting a dead space between a piston (10) and a cylinder head (12) in a piston compressor (1), thereby

characterized in that in order to adapt a dead space between a piston (10) and a cylinder head (12) in a piston compressor (1), the dead space between the piston (0) and the cylinder head (12) in particular as often

Adding a suitable body, especially in the form of a Thrust washer, is reduced until a knocking noise is detected, whereby when a knocking noise is detected, the distance between the piston (10) and

Cylinder head (12) so often in particular by replacing an added thrust washer or body with a thinner one

Thrust washer or a thinner body is enlarged until no

Knocking noise is no longer detected.

10. Piston compressor designed to compress a fluid and in

to output the compressed state

- a cylinder (11),

- A piston (10) arranged in the cylinder (11), which is designed to oscillate in the cylinder (1 1) between a first reversal point (OT) and a second reversal point (UT) along the cylinder axis (17), the distance defines a piston stroke (16) between the first reversal point (OT) and the second reversal point (UT), and

- a cylinder head (12), which is arranged at one end of the cylinder (11), and wherein the first reversal point (OT) is closer to the cylinder head (12) than the second reversal point (UT), characterized in that a piston compressor ( 1) arranged structure-borne sound sensor (2) is provided, which is designed to detect knocking noises that were generated by striking the piston (10) of the piston compressor (1) on the cylinder head (12) of the piston compressor (1), the structure-borne sound sensor ( 2) is designed to generate a first output signal when such a knocking noise is detected, a control unit being provided which is designed to control the piston stroke (16) depending on the first

to regulate the output signal.

11. Piston compressor according to claim 10, characterized in that the structure-borne sound sensor (2) is arranged on the cylinder head (12) and in particular is an integral part of the cylinder head (12).