EP3508729A1 - Compressor with suction conduit and method for controlling a compressor - Google Patents

Abstract

The disclosure relates to a compressor (100), in particular screw compressor, for generating compressed air and a method for controlling such a compressor (100). The compressor (100) comprises a compressor block (4) with liquid injection for the compression of sucked air, a liquid separator (5) which is connected via a pressure line (52) to the compressor block (4) and a separation vessel (6) and a fine separator ( 7), a return line (53) for the return of separated liquid from the separation vessel (6) in the compressor block (4), a suction line (56) for the extraction of liquid from at least one suction point (33) of the fine separator (7) to a Feed point (34) for supplying the extracted liquid to the compressor block (4), a controllable valve (19) for controlling the flow rate through the suction line (56), a control unit (60) for controlling the valve (19), and a medium change sensor ( 18) for detecting a medium change of a in the suction line (56) flowing medium, in particular of extracted liquid to compressed air, with the Steue purity (60) is connected.

Description

The invention relates to a compressor, in particular a liquid-injected screw compressor, for the production of compressed air according to claim 1 and a method for controlling a compressor according to claim 14.

The liquid injected in liquid-injected screw compressors for lubrication is typically oil or water. In oil-injected screw compressors, the oil injected into the compressor block or the compressor stage must be separated from the generated compressed air in order to keep the oil in the oil circuit and to be able to produce compressed air with as little residual oil content as possible.

For this purpose, the oil is usually deposited in so-called oil separation tanks in two stages. The first separation stage comprises a mechanical pre-separation, wherein the majority of the oil from the compressed air-oil mixture can be separated and accumulates by gravity in the lower part of the oil separation. In the second separation stage, one or more so-called oil separation cartridges are used in a fine separation in order to be able to deposit even the finest oil droplets. These cartridges are equipped with a filter consisting of one or more filter media. The filter side facing the first separation stage usually becomes "wet side" called, the compressed air outlet zugte filter side is usually called "dry side". The oil drops contained in the compressed air / oil mixture settle on both sides of the filter as they pass through the filter. On the wet side of the filter medium, separated oil drops may accumulate on the surface of the filter and return to the oil circuit by draining into the oil separator tank. On the dry side of the filter medium deposited oil drops accumulate, run down the filter due to gravity down and collect depending on the design at the bottom of the filter element or its seat. However, these amounts of oil can not get back into the oil cycle without additional measures, since the compressed air oil Mixture when passing through the filter experiences a pressure drop and a flow against the pressure gradient is not possible.

Usually, these amounts of oil are extracted via a suction line, which returns the oil to a lower pressure level - e.g. the intake area of the compressor block. When the oil accumulated on the dry side has been completely sucked off, compressed air is also conveyed back to the compressor block via the suction line. The suction line is then an undesirable Rührführleitung for compressed air, on the next sucked oil also compressed air can get back into the compressor block. This negatively affects the efficiency and efficiency of the compressor.

In the prior art, various measures are taken to limit the return flow through the suction to a necessary for the extraction of the oil minimum.

In the US 4,070,166 For this example, the cross section of the suction line is dimensioned correspondingly small and / or a nozzle used. However, this alone is not sufficient as a measure, as can be promoted via a line that is just enough in terms of their cross-section to suck the accumulated oil, still unacceptably large compressed air flow rates can be promoted. Also, the cross section can not be reduced arbitrarily, otherwise dirt particles could clog the suction.

Therefore, a reduction of the pressure gradient is known from the prior art as a further measure. Instead of the suction in the intake can a Suction into an area in the compressor block suffice, in which the compression has already begun, the full compression end pressure is not yet reached.

In the US 4,070,166 For example, a suction line is connected to the oil injection line. Depending on the location of the port, an additional check valve may be required to prevent backflow of oil to the dry side of the second separation stage.

However, a suction line optimized in accordance with the above-mentioned measures in cross-section and differential pressure has measurable influence on the efficiency of the compressor. Furthermore, the measures at the expense of the reliability of the exhaust system to go. Narrow cross sections can pollute and clog, low differential pressures favor this behavior. If necessary, check valves may malfunction and thus disable the exhaust system. Other measures known in the prior art only partially solve these problems.

The EP 0 744 550 A2 shows an additional valve in the suction line, which can be opened and closed. However, this arrangement can not prevent the efficiency-reducing backflow of compressed air into the compressor block.

US 2015/0343365 A1 describes an extraction system with oil level monitoring in the area of the second separation stage, which is intended to prevent the efficiency-damaging passage of compressed air into the compressor block. However, the technical realization of this solution is complicated and unreliable. A described float valve is prone to malfunction, eg due to soiling.

The measures known from the prior art solve the problem of backflow of compressed air from a fine separator back to the compressor block only insufficient.

The present invention therefore has for its object to provide a compressor and a method for controlling a compressor for generating compressed air, wherein the return flow of compressed air from a Liquid separator can be reliably prevented in the compressor block. This should in particular improve the efficiency of the compressor.

This object is achieved by a compressor according to claim 1.

• einen Verdichterblock mit Flüssigkeitseinspritzung zur Verdichtung von angesaugter Luft,
• einen Flüssigkeitsabscheider, der über eine Druckleitung mit dem Verdichterblock verbunden ist und einen Abscheidebehälter und einen Feinabscheider aufweist,
• eine Rückführleitung zur Rückführung von abgeschiedener Flüssigkeit aus dem Abscheidebehälter in den Verdichterblock,
• eine Absaugleitung zur Absaugung von Flüssigkeit von mindestens einer Absaugstelle des Feinabscheiders zu einer Zuführstelle, um die abgesaugte Flüssigkeit dem Verdichterblock zuzuführen,
• ein steuerbares Ventil zur Regelung der Durchflussmenge durch die Absaugleitung,
• eine Steuereinheit zur Steuerung des Ventils, und
• einen Medienwechselsensor zur Erfassung eines Medienwechsels eines in der Absaugleitung strömenden Mediums, insbesondere von abgesaugter Flüssigkeit zu Druckluft, der mit der Steuereinheit verbunden ist.

In particular, the object is achieved by a compressor, in particular screw compressor, for generating compressed air, comprising:

• a compressor block with liquid injection for the compression of sucked air,
• a liquid separator, which is connected via a pressure line to the compressor block and has a separating vessel and a fine separator,
• a return line for returning separated liquid from the separation vessel into the compressor block,
• a suction line for sucking liquid from at least one suction point of the fine separator to a feed point to supply the sucked liquid to the compressor block,
• a controllable valve for controlling the flow rate through the suction line,
• a control unit for controlling the valve, and
• a medium change sensor for detecting a change of media flowing in the suction medium, in particular of extracted liquid to compressed air, which is connected to the control unit.

The pressure line, the liquid separator, and the return line in particular form part of a fluid circuit of the compressor, wherein the injected liquid can serve for lubrication and / or cooling of the compressor block. In particular, the liquid may be oil or water.

The supply point may be provided in the intake area of the compressor block, in the compressor housing, on a bearing cap, in particular at a position after intake and before reaching the compression end pressure, on a liquid injection line, which in particular forms a portion of the return line, or on a mechanical seal of the compressor block. In particular, the feed point is (immediately) upstream or downstream an intake valve of the compressor block is provided. The supply point can be provided in the range of an atmospheric pressure level (eg in the intake area) or in the region of an intermediate pressure level, ie a pressure level above the atmospheric pressure but below the compression end pressure, for example on the compressor housing, on a bearing cap, on a liquid injection line, or on one Mechanical seal of the compressor block. The extraction point is in particular a collection point for separated liquid in the fine separator and preferably arranged in a, opposite to the direction of gravity, the upper region of the liquid separator. The return line is preferably connected to the separating vessel in a lower region of the liquid separator. The compressor block is in particular connected to a drive, in particular a motor, can be connected or coupled to be driven. Alternatively, instead of compressing air, the compressor block could be designed to compress another gas, in particular nitrogen or helium.

In particular, the suction line connects the suction point to a feed point for supplying (feeding) the extracted liquid or the medium flowing in the suction line (back) to the compressor block. A medium flowing in the suction line can be a named liquid or compressed air or a mixture of liquid and compressed air. An aspirated liquid flowing in the suction line can be formed as a two-phase flow of liquid and compressed air, for example a shape of air bubbles mixed with compressed air. The suction line can also (temporarily) only be traversed by compressed air.
As a media change, a transition from a flowing medium, e.g. B. the injected liquid, to another flowing medium, eg. As the generated compressed air or a liquid-compressed air mixture with a relatively high proportion of compressed air to be understood in a line or a specific line section. A change of media can also be reversed, that is, in particular, be carried out by the generated compressed air or a liquid-compressed air mixture to the injected liquid. In particular, a change of media takes place in the suction line when the liquid deposited at the suction point has been (almost) completely sucked off and compressed air flows into the suction line due to a pressure gradient between the suction point and a feed point of the suction line.

A media change sensor is in particular designed to detect a media change on the basis of a detection of a property of the flowing medium. Preferably, the media change sensor detects the volume flow (or the mass flow) of the flowing medium, and is in particular designed to distinguish on the basis of the detected volume flow, the flowing in the suction line media. In particular, a volume flow that changes suddenly or continuously (temporally) can indicate a change of media. For example, a predetermined proportion of compressed air in the volume flow of the medium flowing in the suction line could serve as a criterion for a media change, in particular as a threshold value for the detection of a media change.

The media change sensor is in particular an electronic sensor and can be based on various physical measuring principles, for example a capacitive, calorimetric, optical or acoustic measuring principle and a detection of a pressure of the medium or of vibrations or oscillations. The media change sensor can be a system of several sensors, each of which can be based on different measurement principles. The output of a media change sensor is preferably a digital signal, but may also be an analog signal. The media change sensor can be designed to generate and transmit media change data, which may include, for example, information about the presence of a certain medium (yes / no) or a volume fraction of a particular medium in the suction line as well as physical parameters of the medium flowing in the suction line. The media change sensor may be wired or wireless, in particular via a radio link to be connected to the control unit, wherein an output signal to the control unit of the compressor and / or an external control unit can be transmitted. The media change sensor can in particular be a flow sensor for detecting a changing volume flow of the medium in the suction line.

The control of the valve is preferably carried out based on an output signal of the medium change sensor received by the control unit. The control unit comprises in particular a computing unit, for example a CPU or a microprocessor, and can output control commands for an electronically controllable valve or electrical control signals for an electrically controllable valve.

In particular, the flow rate of a medium through the suction line can be regulated via the valve. The suction can be fully opened or released by the valve and completely closed or blocked, preferably at least substantially air or liquid-tight. In particular, the valve between a release position and a blocking position back and forth switchable, whereby intermediate positions of the valve may be provided, which may in particular be infinitely adjustable to control the flow through the suction line. In contrast to the prior art, the valve according to the invention is in particular not a check valve.

A compressor according to the invention has the advantage that the suction line is only released as needed as long as it is possible to actually aspirate liquid. As soon as the media change sensor detects a media change from liquid to compressed air, the suction line can be blocked by the valve. In this way, the efficiency-reducing return flow of compressed air is reliably prevented in the compressor block or at least largely avoided. The deposited at the suction liquid is sucked as needed. In addition, the suction line can thereby be dimensioned with a larger cross section and a larger pressure gradient, whereby the operating reliability is increased. A known from the prior art check valve in the suction can be omitted because the suction in the operating conditions of the compressor, in which the pressure gradient could reverse over the suction, for example, when switching from load to standstill, or emergency stop, by the Valve can be safely blocked. By eliminating the check valve, the reliability continues to increase. Overall, the reliability is increased and improved efficiency by a compressor according to the invention with a media change sensor and a controllable valve.

In an advantageous development of the invention, the media change sensor is arranged at least partially in the suction line and / or designed to detect a change in a physical parameter of the flowing medium in the suction without contact. The medium change sensor can be arranged partially or completely in the suction line in order to be in contact with the medium flowing in the suction line for the purpose of detecting a physical parameter or by a physical parameter of the type described in US Pat Suction line flowing medium to detect contactless. The media change sensor can alternatively be arranged outside the suction line, preferably on or on the suction line, in order to detect a physical parameter of the medium flowing in the suction line without contact. The medium change sensor can be arranged, for example, as a calorimetric sensor, optical sensor, in particular a reflection or turbidity sensor, or as a vibration or vibration sensor in the suction line, ie in contact with the medium. Alternatively or additionally, a media change sensor as a capacitive sensor or an acoustic sensor, in particular an ultrasonic sensor or as a microphone, be designed to measure without contact, ie without direct contact with the medium.

A media change sensor may be a sensor based on different measurement principles. The media change sensor may be a capacitive sensor. A calorimetric sensor may be adapted to detect a media change. A reflection sensor comprises, in particular, a sensor head with a plastic hemisphere and an infrared sensor and receiver. When wetting the hemisphere with the medium, the refractive index or the reflection behavior for the reflection sensor can change detectable. With a turbidity sensor, a change in the absorption behavior of the flowing medium can be detected. An ultrasound sensor in particular emits an ultrasound signal and evaluates the ultrasound echo. A change in the echo due to a changed transit time or a changed reflection or damping behavior can indicate a change of media. A similar sensor could be based on the TDR (Time Domain Reflectometry) method, especially in the microwave spectrum. A microphone as a media change sensor could detect a change in the flow noise in the suction line caused by a media change. In the case of a vibration or vibration sensor could be a, z. Fork-shaped, vibratory element, e.g. be excited by a piezoelectric crystal to vibrate, with a change in the medium flowing through the element, could indicate a change in media by changing the resonant frequency. In addition, a media change sensor may include one or more pressure sensors.

In an advantageous embodiment of the invention, the media change sensor is adapted to a proportion of compressed air in the volume flow of the medium in the To detect suction and detects a media change, especially at a detected compressed air content of more than 10%, preferably more than 20%, more preferably more than 30%, more preferably more than 40%, more preferably more than 50%. When a predetermined compressed air component exceeds the volume flow of the medium, a media change sensor can generate an output signal which represents or indicates a medium change and, in particular, transmits it to the control unit.

In an advantageous development of the invention, the medium change sensor is designed as a first pressure sensor for detecting a pressure in the suction line, wherein a nozzle is provided upstream of the pressure sensor in the suction line, the compressor (100) in particular at least one second pressure sensor (42, 43). , preferably upstream of the nozzle (21). The second pressure sensor is, for example, a sensor for detecting an operating pressure, e.g. within the separator tank. The first and second pressure sensors are in particular connected to the control unit. The control unit may be configured to determine a change in the pressure difference between the pressures detected by the first and second pressure sensors. A (temporal), in particular abrupt, change in the pressure difference due to a change in the pressure drop across the nozzle can indicate a change of media in the suction line. A media change sensor with pressure sensors and a nozzle has the advantage that the implementation is easy and low maintenance, especially if a second pressure sensor in a compressor or a compressor system is already present.

In an advantageous development of the invention, the valve releases the suction line in a release position for the medium and blocks it in a blocking position for the medium, wherein the valve is designed in particular as an electrically controllable 2/2-way valve, preferably as a solenoid valve. The valve can also be designed as a proportional valve or as a 3/2-way valve.

In an advantageous embodiment of the invention, the valve is designed as a, preferably continuously, controllable proportional valve, wherein in particular in an idling operation of the compressor intermediate positions of the proportional valve between a release position and a blocking position are adjustable by the control unit. When using a proportional valve the suction line is preferably connected to a supply point upstream of an inlet valve of the compressor. A proportional valve is advantageous for an idle control of the compressor, in which an idle pressure level by a proportional valve, preferably continuously, is adjustable. With a proportional valve also an idle control of the compressor can be implemented, in which the idling pressure or the liquid injection volume flow is reduced, in particular until a rise in the compression end temperature is detected by a temperature sensor.

In an advantageous development of the invention, the control unit is designed to switch the valve from the blocking position to the release position after a predetermined blocking time interval, wherein the blocking time interval is preferably determined based on the generated compressed air volume flow of the compressor. A generated compressed air volume flow (delivery quantity) could be determined based on a rotational speed of the compressor or the intake volume flow. For a fixed-speed compressor, an aspirated volume flow could be determined from the run-time under load. The compressor may include a speed sensor for detecting the speed of the compressor and / or a flow sensor for detecting the intake volume flow. A blocking time interval may be a stored (stored) fixed or variably determined, for the control unit to be calculated, in particular by the control unit to be calculated value for a period of time. By a suitably selected blocking time interval ensures that after an obstruction of the suction due to a detected media change the now accumulated at the suction point liquid can be sucked.

In an advantageous embodiment of the invention, the compressor has at least one pressure sensor for detecting an operating pressure and / or a flow sensor for detecting the liquid volume flow in the suction line, wherein the control unit is designed in particular, at least on the basis of a detected operating pressure and / or a detected liquid volume flow Locking period and / or a Absaugzeitintervall to determine. A determination or calculation of a blocking time interval can be based on detected system parameters of the compressor, for example on the operating pressure, the volume flow of the suction line, a delivery quantity of the compressor, a nominal value for a drainage value (so-called "inner drainage"). and / or in the maximum volume in the fine separator, in particular on the "dry side" of the fine separator. The term "internal drainage" can be understood as meaning a liquid volume flow per compressed air volume flow (amount of liquid per delivery quantity) which accumulates in the fine separator, in particular on the "dry side" of the fine separator. As a parameter, a value stored in the control unit, a function, a map or a measured value can be understood. For variable speed compressors, the lock time interval may be adjusted based on a given or generated compressed air flow rate (ie, a generated delivery rate profile). In this way, the oil accumulated at the suction point within this blocking time interval can be reliably sucked off, in particular so as not to exceed a permissible maximum volume of the separated liquid accumulated at the suction point. As soon as the media change sensor detects a media change, the suction line can be blocked again.

In an advantageous embodiment of the invention, the control unit is adapted to detect a release time interval for the suction, preferably from a switching time of the valve from the blocking position to the release position, and in particular to compare with a predetermined Absaugzeitintervall to preferably a warning or interference signal generate if the release time interval falls below or exceeds the extraction time interval. In this case, a predetermined buffer time interval can be taken into account in addition to the Absaugzeitintervall. The control unit in particular comprises a time detection unit for detecting the release time interval, which can be understood as the actual release duration of the suction line. A suction time interval may be understood as a period of time that would be required for trouble-free operation of the suction line to draw a cumulative amount of liquid. The Absaugzeitintervall can be determined or calculated from previously mentioned operating parameters of the compressor. A warning signal can be generated optically (warning lamp or LED) or acoustically (warning tone) or an error message issued by the control unit or a maintenance message. A warning or interference signal is generated in particular in the case of a blockage of the suction line or in case of malfunction of the media change sensor. As a result, the reliable operation of the compressor can be monitored or restored.

In an advantageous development of the invention, the control unit is designed to determine a drainage value, in particular based on the detected release time interval for the suction line and a detected liquid volume flow in the suction line, and to compare with a predetermined drainage threshold, preferably a warning or interference signal when the drainage value is less than or greater than the predetermined drainage threshold. Other operating parameters of the compressor may be taken into account when determining the drainage value and / or drainage threshold. A drainage value (also referred to as "inner drainage") can be understood as meaning a liquid volume flow per compressed air volume flow which accumulates in the fine separator, in particular on the "dry side" of the fine separator. in particular the proportion of the liquid to be separated from the compressed air volume. By such a warning or interference signal, the reliable operation of the compressor can be monitored or restored.

In an advantageous development of the invention, the fine separator is arranged in the separation vessel of the liquid separator, wherein the fine separator preferably has at least one filter for fine separation of liquid from the compressed air generated, wherein the suction point is provided in particular downstream of the filter. Alternatively, however, the fine separator can also be arranged outside the separating container of the liquid separator, for example as an outer separator cartridge. Preferably, the liquid separator is constructed in two stages, wherein in a first stage, a pre-separation, preferably by gravity, and in the second stage, a fine deposition, preferably by filtering, takes place. In particular, liquid deposited in the fine separator upstream of the filter can flow back into the separation vessel, in particular drain off.

In an advantageous development of the invention, the suction line is connected to a feed point upstream of an inlet valve of the compressor, in particular of an inlet valve disk. In this way, the suction line can be used additionally or alternatively to the suction function for an idle control and / or a bleed control of the compressor.

In an advantageous development of the invention, the suction line is connected to a feed point of a liquid-lubricated sealing system, preferably a mechanical seal, of the compressor block, wherein preferably a branching from the return line to the suction seal supply line is provided, wherein the seal supply line is connected in particular to the valve, preferably is designed as a 3/2-way valve, wherein the suction line and / or the seal supply line in particular each have at least one nozzle. As an alternative to separate, a common nozzle for the suction and the seal supply line may be provided. A nozzle may also be provided in the form of a nozzle bore, in particular integrated into a component of the compressor, wherein the nozzle bore is, in particular, determining the cross-section. The media change sensor may be located downstream or upstream of the valve. The mechanical seal is provided in particular on the drive side of the compressor block, preferably in a passage opening for the drive or rotor shaft of a compressor element, in particular screw rotor, in the housing of the compressor block. By providing a seal supply line as a separate line with a corresponding connection on the compressor block for supplying lubricating fluid, preferably oil, to the mechanical seal, supply bores in the housing can be dispensed with. This allows a very accurate metering and adjustment of the amount of lubrication fluid supplied to the mechanical seal possible. In addition, the amount of liquid supplied can be reduced, which can have a positive effect on the efficiency of the compressor.

The stated object is also achieved by a method according to claim 14.

• Absaugen von Flüssigkeit von mindestens einer Absaugstelle des Feinabscheiders in den Verdichterblock durch eine von einem steuerbaren Ventil freigegebene Absaugleitung;
• Erfassen eines Medienwechsels des in einer Absaugleitung strömenden Mediums, insbesondere von abgesaugter Flüssigkeit zu Druckluft, durch einen Medienwechselsensor;
• Versperren einer Absaugleitung durch Ansteuern eines steuerbaren Ventils durch eine Steuereinheit aufgrund des erfassten Medienwechsels.

In particular, the object is achieved by a method for controlling a compressor, in particular a screw compressor, in particular according to a compressor according to the invention, with a compressor block with liquid injection, connected via a pressure line to the compressor block liquid separator with a separating vessel and a fine separator, and a return line for the return of separated liquid from the separation vessel into the compressor block, comprising the following steps:

• Aspirating liquid from at least one suction point of the fine separator into the compressor block by means of a suction line released by a controllable valve;
• Detecting a media change of the medium flowing in a suction line, in particular of extracted liquid to compressed air, by a medium change sensor;
• Blocking a suction by controlling a controllable valve by a control unit due to the detected media change.

In particular, the method comprises a step of releasing the suction line by actuating the valve by the control unit after a predetermined blocking time interval has elapsed. The blocking time interval can be calculated and stored by a computing unit of the control unit based on detected and / or stored operating parameters of the compressor. Alternatively, a fixed predetermined value can be read out for a blocking time interval. By releasing the suction line, the liquid accumulated within the blocking time interval in the fine separator is sucked off according to the first-mentioned step of the method according to the invention. During operation of the compressor, the process is repeated cyclically, wherein the control unit may provide that for a particular operating condition of the compressor deviated from the method or the method is suspended, in particular in which outputs the control unit independent of the output signal of the media change sensor control commands to the valve in particular during an idle control or a bleed control. The inventive method has similar advantages, as have already been described in connection with the compressor according to the invention. The method can be carried out by the compressor according to the invention. The method may further implement some or all of the process features described in the context of the compressor. The method allows a compressor to operate more reliably and efficiently.

A further embodiment of the method according to the invention for controlling a compressor, in particular screw compressor, in particular a compressor according to the invention, with a compressor block with liquid injection, one via a pressure line to the compressor block connected liquid separator with a separating vessel and a fine separator, and a return line for returning separated liquid from the separation vessel in the compressor block, comprises an idle control of the compressor, wherein the following step is provided: releasing a suction line between a suction of the Feinabscheiders and a feed point of the compressor block by controlling a controllable valve arranged in the suction line, in particular if the compressor has reached a predetermined operating state, in particular a predetermined temperature, preferably at least a predetermined proportion of a predetermined liquid injection temperature or a predetermined final compression temperature.

In this idle control, the suction line is preferably connected to a feed point upstream of an inlet valve of the compressor, in particular of an inlet valve disk. In particular, the method further provides for detecting an operating state, in particular an operating temperature, of the compressor by means of a temperature sensor, and preferably a comparison with a setpoint temperature. An operating temperature may be, for example, a compression end temperature of the compressed liquid-compressed air mixture or a liquid temperature (oil temperature) of the liquid to be injected (oil), or a percentage, for. B. 70%, 80% or 90%, to reach a target temperature. The idle control has the advantage that a further, in particular lower, idle pressure level for idle operation of the compressor can be achieved. By releasing the suction line during idling operation, a cross-sectional enlargement for promoting the idle flow rate is achieved. As a result, the idling pressure of the compressor decreases. In particular, in a compressor that (still) not running to operating temperature (high viscosity of the liquid, higher differential pressure in the liquid circuit), with the suction line obstructed, a higher idle pressure level in the compressor, while in a compressor running at operating temperature (low viscosity the liquid, lower differential pressure in the liquid circuit), by releasing or opening the suction line can set a lower idle pressure level. This can lead to a reduced idle power consumption (power loss) of the compressor. Such idle control may also be combined with a bleed control.

In an advantageous development of this method according to the invention, an idle control of the compressor is further provided with the following step: blocking the suction line by controlling the valve, in particular if the compressor has not reached a predetermined operating state.

In an advantageous embodiment of the method according to the invention further driving the designed as a proportional valve valve is provided to set an idling pressure level between the first and the second idle pressure level, preferably continuously. The flow rate through the suction line can be adjusted by a proportional valve (infinitely variable) according to the operating conditions. Thereby, the efficiency can be further improved for a certain idle operating state of the compressor.

Under an idle operation of the compressor, an operating condition can be understood, during which the drive (drive motor) continues to drive the compressor block, but no compressed air is fed into the network. In order to consume as little energy as possible during idling operation, the inlet valve can be closed except for a small minimum opening in order to keep the amount of air to be compressed as low as possible. Further, a vent valve may be opened between the liquid separator, preferably its dry side, and the atmosphere to reduce the pressure level to a pressure level which ensures safe operation of the compressor, which may be referred to as the idle pressure level. For example, an idle pressure level is between 1.0 to 1.8 bar (gauge pressure).

• Freigeben der Absaugleitung durch Ansteuern des Ventils;
• Erfassen eines Betriebsdrucks des Kompressors durch einen Drucksensor;
• Versperren der Absaugleitung durch Ansteuern des Ventils, falls der erfasste Betriebsdruck unterhalb eines vorbestimmten Restbetriebsdrucks liegt.

A further embodiment of the inventive method for controlling a compressor (100), in particular screw compressor, in particular a compressor according to the invention, with a compressor block (4) with liquid injection, a via a pressure line (52) connected to the compressor block (4) liquid separator (5) a separation tank (6) and a fine separator (7), and a recirculation line (53) for returning separated liquid from the separation tank (6) into the compressor block (4), comprises a bleed control of the compressor (100), the following steps being provided are:

• Releasing the suction line by activating the valve;
• Detecting an operating pressure of the compressor by a pressure sensor;
• Blocking the suction line by driving the valve, if the detected operating pressure is below a predetermined residual operating pressure.

In such a vent control, the suction line is preferably connected to a supply point upstream of an inlet valve of the compressor, in particular of an inlet valve disk. By such a method, a venting of the compressor with two different ventilation speeds can be achieved. When the suction line is released, a higher ventilation speed is set for rapid venting. If the suction line is blocked, a lower ventilation speed is set for a slower venting. In this way, in oil as a liquid, foaming of the oil by relaxing the air bubbles located in the oil can be prevented or reduced. As a result, wetting of the dry side of the fine separator by the foaming of the oil is at least partially prevented. A residual operating pressure may, for example, be between 0.5 bar and 10 bar, preferably between 1 bar and 5 bar, more preferably between 1 bar and 3 bar, particularly preferably approximately 2.0 bar, relative to the ambient pressure.

In an advantageous embodiment of the invention, the release of the suction line by driving the valve for suction of the liquid in the load run is only performed when the compressor is running at full load or runs in a speed range above a predetermined minimum speed. A minimum speed is for example between 70% and 100%, preferably between 80% and 100%, more preferably between 90% and 100% of a maximum speed of the compressor. When the suction line is connected to a feed point upstream of an inlet valve of the compressor, in particular in the suction area of the compressor block, the liquid sucked out of the fine separator can be swirled and atomized in the suction area. As a result, the intake area and / or the air filter can be wetted. Sucking the liquid only under full load or, in a variable speed compressor, in a sufficiently high speed range, ensures that the intake air entrains the extracted liquid or a liquid mist in the compressor block so as to prevent wetting of the suction region ,

• Erfassen von mindestens zwei Betriebsdrücken des Kompressors durch einen Drucksensor während sich der Kompressor im Lastlauf befindet, insbesondere unter Teillast läuft;
• Vergleichen der erfassten Betriebsdrücke mit einem vorbestimmten Solldruck;
• Freigeben der Absaugleitung durch Ansteuern des Ventils, zum Absaugen der Flüssigkeit, falls die erfassten Betriebsdrücke innerhalb eines vorbestimmten Druckbereichs unterhalb eines vorbestimmten Sollbetriebsdrucks liegen und der später erfasste Betriebsdruck höher ist als der früher erfasste Betriebsdruck.

In a preferred embodiment of the method according to the invention, the following steps are further provided:

• Detecting at least two operating pressures of the compressor by a pressure sensor while the compressor is under load, in particular under partial load;
• Comparing the detected operating pressures with a predetermined target pressure;
• Releasing the exhaust duct by driving the valve to exhaust the liquid if the detected operating pressures are within a predetermined pressure range below a predetermined target operating pressure and the later detected operating pressure is higher than the previously detected operating pressure.

In this way, it is ensured that an extraction takes place as soon as possible before a change of the compressor to idle or standstill, so that when changing as little liquid as possible is present at the suction point of the fine separator. A change of the compressor to idle or standstill can be predicted by an evaluation of the current operating pressure and the pressure gradient. If the current operating pressure in the load run is only slightly below the setpoint operating pressure and continues to rise, it is to be expected that the compressor will shortly change from load run to idle or standstill.

Figur 1

eine schematische Darstellung einer Ausführungsform eines erfindungsgemäßen Kompressors mit einer Absaugung zu einer Zuführstelle stromaufwärts des Einlassventils in einem Blockschaltbild;

Figur 2

eine schematische Darstellung einer Ausführungsform eines erfindungsgemäßen Kompressors wie in Figur 1, wobei der Medienwechselsensor als ein Drucksensor ausgebildet ist;

Figur 3

eine schematische Darstellung einer Ausführungsform eines erfindungsgemäßen Kompressors mit einer Absaugung zu einer Zuführstelle stromabwärts des Einlassventils in einem Blockschaltbild;

Figur 4

eine schematische Darstellung einer Ausführungsform eines erfindungsgemäßen Kompressors mit einer Absaugung zu einer Zuführstelle an einer Gleitringdichtung des Verdichterblocks in einem Blockschaltbild.

Embodiments of the invention are explained below with reference to the drawings. Hereby show:

FIG. 1

a schematic representation of an embodiment of a compressor according to the invention with a suction to a feed point upstream of the intake valve in a block diagram;

FIG. 2

a schematic representation of an embodiment of a compressor according to the invention as in FIG. 1 wherein the medium change sensor is formed as a pressure sensor;

FIG. 3

a schematic representation of an embodiment of a compressor according to the invention with a suction to a Supply point downstream of the inlet valve in a block diagram;

FIG. 4

a schematic representation of an embodiment of a compressor according to the invention with a suction to a feed point to a mechanical seal of the compressor block in a block diagram.

In the following description of the invention, the same reference numerals are used for the same and like elements.

FIG. 1 shows a first embodiment of a compressor 100, which is designed here as an oil-injected screw compressor, the following description is also applicable to water-injected screw compressor. A drive motor 3 drives z. B. via a drive shaft, a belt drive or a gearbox mounted in a housing of the compressor block 4 screw rotors (not shown). The compressor block 4 sucks in ambient air through the inlet valve 2 from an air inlet 31 via the air filter 1 and the suction line 51. The hot air is compressed by injection of oil for lubrication and cooling in the compressor block 4. The intake valve includes a check valve, a 2/2-way valve and a throttle connected in parallel. The compressed in the compressor block 4 liquid-compressed air mixture is conveyed via the pressure line 52 into the liquid separator 5 (oil separator). Here, the majority of the oil is separated by gravity, and possibly by centrifugal forces due to a rotating liquid-compressed air mixture, from the air stream in a first separation stage and collects in the lower part of the separation tank 6. From there, the oil through the Pressure in the separation vessel 6 through the return line 53 via a liquid cooler 10 (oil cooler) or a bypass line 55 via a temperature control valve 8 for controlling the Flüssigkeitseinspritztemperatur or - inlet temperature (oil injection temperature), a liquid filter 9 (oil filter) and a liquid injection line 54, as a Section of the return line 53 can be considered, led back to the compressor block 4 and injected there.

The compressed air purified in the liquid separator 5 passes via an outlet line 58, a minimum pressure check valve 11 and an air cooler 12 to a compressed air outlet 32, where the compressed air generated is a compressed air network or a consumer is made available. The network pressure is detected via a pressure sensor 43. The pressure in the separation tank 6 is detected by the pressure sensor 42. In addition, a temperature sensor 41 for detecting the compression end temperature (compressor discharge temperature) is provided on the pressure line 52. From the outlet conduit 58, a control line 59a and a vent line 59b branch off to a combined control / vent valve. In the vent line 59 b, a silencer 16 is arranged.

The liquid separator 5 is formed in two stages. In the separation vessel 6 of the liquid separator 5, a fine separator 7 is arranged, which has one or more filters, for example in the form of at least one Ölabscheidepatrone. The liquid (oil) separated in the fine separator 7 collects at a suction point 33 of the fine separator 7. Between the suction point and a feed point 34 runs a suction line 56, which could also be referred to as a drainage line, in order to feed liquid separated in the fine separator back to the compressor block 4. In the suction line 56, a medium change sensor 18, a controllable valve 19 and a muffler 20 are arranged. The suction line 56 opens into the suction line 51 upstream of the inlet valve 2, in particular upstream of an inlet valve disk, at a feed point 34. Preferably, the medium change sensor 18 is arranged upstream of the valve 19. The valve 19 is designed as a 2/2-way valve, here as an electrically controllable solenoid valve that regulates the flow rate in the suction line 56 insofar as it in a release position, the suction line 56 (completely) releases or opens and in a blocking position, the suction line 56 (completely) locks or closes. In FIG. 1 the valve 19 is shown in the blocking position, in which the 2/2-way valve is energized. The valve 19 is controllable or switchable via the control unit 60. The media change sensor 18 may be based on various physical measurement principles and be designed both as a non-contact measuring sensor or be arranged in the suction line 56 in contact with the flowing medium.

In one embodiment according to FIG. 2 the medium change sensor 18 is designed as a pressure sensor. Upstream of the pressure sensor 18, a nozzle 21 is provided. By means of a second pressure sensor upstream of the nozzle 21, for example pressure sensor 42 for detecting the operating pressure, the control unit 60 can a pressure difference which changes during a change of media is detected via the nozzle 21, which indicates a change of media. In FIG. 2 the valve 19 is shown in the release position, so that liquid can be sucked through the suction line 56. An operating pressure of the compressor 100 is for example between 3 and 15 bar (overpressure relative to the environment), but may also be higher.

Hereinafter, an embodiment of a method for controlling the compressor 100 according to FIG. 1 described. In a release position of the valve 19, liquid (oil), which accumulates at the suction point 33 in the fine filter 7, the suction line 56 are sucked to the feed point 34. When the liquid is sucked off (almost) completely, compressed air, or a liquid-compressed air mixture, can flow into the suction line 56 due to the pressure gradient between the separating tank 6 and the feed point 34. In the case of a return flow of compressed air to the compressor block 4, the efficiency of the compressor 100 would be adversely affected. If the media change sensor 18 detects a change of the medium flowing in the suction line 56 of liquid (oil) to compressed air or a liquid-compressed air mixture with a relatively high compressed air content, the medium change sensor 18 generates a corresponding output signal via a connecting line 61 to the control unit 60 is transmitted. The control unit 60 can control the valve 19 via a connecting line 61 based on this output signal in order to switch it from a release position to a blocking position. As a result, the suction medium 56 for the flowing medium is blocked and flow to the compressor block 4 is reliably prevented. After a predetermined blocking time interval, the valve 19 is switched from a blocking position back into a release position to allow a suction. The lock time interval may be a fixed predetermined period of time or a period variably calculated based on one or more detected or stored parameters in the controller 60. When a release time interval detected by the control unit 60 exceeds a predetermined suction time interval, for example, in the case of clogging of the suction pipe 56 or malfunction of the medium change sensor 18, the control unit 60 may output a warning or noise signal. A Absaugzeitintervall corresponds to a theoretically required period of time for a suction of the accumulated at the suction point 33 liquid with properly functioning suction line 56th

Additionally or alternatively to the function of the suction, the suction line 56 can be used in the idle of the compressor 100 as an additional line for the promotion (circulation) of compressed air, wherein the line cross-section increases overall and the idle pressure level is thereby lowered. For this purpose, the control unit 60 can switch the valve 19 in the idling mode to a release position, in particular independently of the output signal of the medium change sensor 18. A return flow of compressed air through the suction line 56 is desirable when idling. In an embodiment in which the valve 19 is designed as a proportional valve, the flow rate through the suction line 56 can be controlled steplessly by corresponding intermediate positions of the valve, so that an idling pressure level matched to the operating state of the compressor 100 is adjustable. Such an idle pressure level is between a low idle pressure level established with the exhaust passage 56 released and a higher idle pressure level established with a trapped exhaust passage 56. In particular, when the compressor 100 runs at the intended target operating temperature, an improvement of the efficiency in the form of a reduced idle power loss can be achieved by a corresponding idling control.

Alternatively or in addition to the function of the suction and the idle control, the suction line 56 can be used for venting of the compressor 100, with a release of the suction line 56 through the valve 19, a faster venting is achieved. Once a certain residual operating pressure of e.g. 2.0 bar is reached, the suction line 56 can be blocked to reduce the ventilation speed and prevent foaming of the oil.

In a compressor having a supply point 34 upstream of the intake valve, it is advantageous if exhaust is permitted only at full load or high speed of the compressor 100 to prevent wetting of the air filter 1 and / or the suction area of the compressor block by the extracted liquid.

FIG. 3 shows an embodiment of a compressor 100 according to the invention, in which the suction line 56 at a feed point 34 downstream of the Inlet valve 2 opens into the compressor block 4. Except for in connection with the embodiment according to FIG. 1 described idle control and vent control, the operation of the compressor 100 is the same. There is no silencer provided in the suction line. In particular, the problem of wetting the air filter or the suction area of the compressor block 4 in this embodiment can not occur by design.

FIG. 4 shows an embodiment of a compressor 100 according to the invention, in which the suction line 56 is connected to a feed point 34 of a mechanical seal of the compressor block 4. The return line 53 or the section of the liquid injection line 54 leads the majority of the liquid returned from the liquid separator 5 back into the compressor block 4 for injection, similar to FIGS FIGS. 1 . 2 and 3 , From the return line 53, a seal supply line 57 branches off to the suction line 56, wherein the liquid volume flow in the seal supply line 57, (in particular) by a suitable choice of the line cross-sections or a nozzle, (less) than the liquid volume flow in the liquid injection line 54. The seal supply line 57 is connected to the controllable valve 19, which is designed as a 3/2-way valve. The suction line 56 comprises a suction section 56a and a supply section 56b for supplying liquid to a mechanical seal of the compressor block 4. The liquid (oil) to be supplied with mechanical seal (not shown) is preferably on the drive side of the compressor block in a through hole for the drive or Rotor shaft of a screw rotor provided in the housing of the compressor block. In the suction section 56a and the seal supply line 57, a nozzle 21 for adjusting the pressure levels and the volume flows in the lines is provided in each case. In a basic switching position of the valve 19, ie in the non-switched state, liquid is passed from the seal supply line 57 via the nozzle 21 to the mechanical seal. In the switched state of the valve 19, liquid is passed from the fine separator 7 via the strainer 17 and a nozzle 21 to the mechanical seal until the medium change sensor 18 detects a change of media in the suction line 56. By a separate seal supply line 57, in particular instead of provided in the housing of the compressor block 4 supply holes, a very accurate dosing and adjustment of the supplied liquid flow to supply the Mechanical seal possible. In addition, the amount of the supplied liquid can be reduced. The efficiency of the compressor 100 can be further improved.

It should be noted at this point that all aspects of the invention described above taken alone and in any combination, in particular the details shown in the drawings, as essential for the invention claimed. Variations thereof are familiar to the person skilled in the art.

LIST OF REFERENCE NUMBERS

1

air filter

2

intake valve

3

drive motor

4

airend

5

Liquid separator, in particular oil separator

6

separating vessel

7

Fine separator, in particular Ölabscheidepatrone

8th

Temperature control valve

9

Liquid filter, in particular oil filter

10

Liquid coolers, in particular oil coolers

11

Minimum pressure check valve

12

air cooler

13

combined control / vent valve

14

control valve

15

vent valve

16

silencer

17

strainer

18

Media change sensor

19

Valve (controllable)

20

silencer

21

jet

31

air intake

32

compressed air outlet

33

extraction point

34

induct

41

temperature sensor

42

Pressure sensor for recording the operating pressure

43

Pressure sensor for detecting the network pressure

51

suction

52

pressure line

53

Return line

54

Liquid injection line

55

bypass line

56

suction

56a

suction section

56b

feeding

57

Seal supply line

58

outlet pipe

59a

control line

59b

vent line

60

control unit

61

connecting line

100

compressor

Claims (18)

Compressor (100), in particular screw compressor, for generating compressed air, comprising: - A compressor block (4) with liquid injection for the compression of sucked air, a liquid separator (5) which is connected to the compressor block (4) via a pressure line (52) and has a separating vessel (6) and a fine separator (7), - A return line (53) for returning separated liquid from the separation vessel (6) in the compressor block (4), - A suction line (56) for the extraction of liquid from at least one suction point (33) of the Feinabscheiders (7) to a feed point (34) to supply the extracted liquid to the compressor block (4), a controllable valve (19) for regulating the flow rate through the suction line (56), - A control unit (60) for controlling the valve (19), and - A media change sensor (18) for detecting a media change of a in the suction line (56) flowing medium, in particular of extracted liquid to compressed air, which is connected to the control unit (60). A compressor (100) according to claim 1,
characterized in that
the medium change sensor (18) is at least partially disposed in the suction line (56) and / or is adapted to contactlessly detect a change in a physical parameter of the medium flowing in the suction line (56). A compressor (100) according to claim 1 or 2,
characterized in that
the media change sensor (18) is adapted to detect a proportion of compressed air in the volume flow of the medium in the suction line (56) and in particular at a detected compressed air content of more than 10%, preferably more than 20%, more preferably more than 30%, more preferably more than 40%, more preferably more than 50%, recorded a change of media. Compressor (100) according to one of the preceding claims,
characterized in that
the medium change sensor (18) as a first pressure sensor for detecting a pressure in the suction line (56) is formed, wherein upstream of the pressure sensor (18) in the suction line (56) is provided a nozzle (21), wherein the compressor (100) in particular at least one second pressure sensor (42, 43), preferably upstream of the nozzle (21). Compressor (100) according to one of the preceding claims,
characterized in that
the valve (19) releases the suction line (56) in a release position for the medium and blocks it in a blocking position for the medium, wherein the valve (19) is designed in particular as an electrically controllable 2/2-way valve, preferably as a solenoid valve , Compressor (100) according to one of the preceding claims,
characterized in that
the valve (19) is designed as a, preferably infinitely, controllable proportional valve, in particular in an idling operation of the compressor (100) intermediate positions of the proportional valve (19) between a release position and a blocking position by the control unit (60) are adjustable, preferably by a Set idling pressure level. Compressor (100) according to one of the preceding claims,
characterized in that
the control unit (60) is designed to switch the valve (19) from the blocking position to the release position after a predetermined blocking time interval, wherein the blocking time interval is preferably determined based on the generated compressed air volume flow of the compressor (100). Compressor (100) according to one of the preceding claims,
characterized in that
the compressor (100) has at least one pressure sensor (42, 43) for detecting an operating pressure and / or a flow sensor for detecting the liquid volume flow in the suction line (56), wherein the control unit (60) is designed, in particular, at least on the basis of a detected operating pressure and / or a detected liquid volume flow to determine a blocking time interval and / or a Absaugzeitintervall. Compressor (100) according to one of the preceding claims,
characterized in that
the control unit (60) is designed to detect a release time interval for the suction line (56), preferably from a switching time point of the valve (19) from the blocking position into the release position, and in particular to compare it with a predetermined suction time interval, preferably to alert or generate noise signal if the release time interval is less than or greater than the suction time interval. Compressor (100) according to one of the preceding claims,
characterized in that
the control unit (60) is adapted to determine a drainage value, in particular at least based on the detected release time interval for the suction line (56) and a detected Liquid volume flow in the suction line (56), and to compare with a predetermined drainage threshold, preferably to generate a warning or interference signal when the drainage value is less than or exceeds the predetermined drainage threshold. Compressor (100) according to one of the preceding claims,
characterized in that
the fine separator (7) is arranged in the separation tank (6) of the liquid separator (5), wherein the fine separator (7) preferably has at least one filter for the fine separation of liquid from the generated compressed air, wherein the suction point (33) is provided in particular downstream of the filter , Compressor (100) according to one of the preceding claims, in particular according to claim 6,
characterized in that
the suction line (56) is connected to a feed point (34) upstream of an inlet valve (2) of the compressor (100), in particular an inlet valve disk. Compressor (100) according to one of claims 1 to 11,
characterized in that
the suction line (56, 56a, 56b) is connected to a supply point (34) of a liquid-lubricated sealing system of the compressor block (4), preferably a mechanical seal, preferably a seal supply line branching from the return line (53) to the suction line (56, 56a, 56b) (57) is provided, wherein the seal supply line (57) in particular to the valve (19) is connected, which is preferably designed as a 3/2-way valve, wherein the suction line (56, 56 a, 56 b) and / or the seal supply line (57 ) in particular each have at least one nozzle. Method for controlling a compressor (100), in particular screw compressor, in particular according to one of Claims 1 to 13, with a liquid injection compressor block (4), a liquid separator (5) connected to the compressor block (4) via a pressure line (52) having a Separation container (6) and a Fine separator (7), and a return line (53) for returning separated liquid from the separation vessel (6) in the compressor block (4),
comprising the following steps: - Extraction of liquid from at least one suction point (33) of the fine separator (7) in the compressor block (4) by a by a controllable valve (19) released suction line (56); - Detecting a change of media in a suction line (56) flowing medium, in particular of extracted liquid to compressed air, by a medium change sensor (18); - Blocking a suction line (56) by controlling a controllable valve (19) by a control unit (60) due to the detected media change. Method for controlling a compressor (100), in particular screw compressor, in particular a compressor (100) according to one of claims 1 to 13, preferably according to claim 12,
with a liquid injection compressor block (4), a liquid separator (5) connected to the compressor block (4) via a pressure line (52), a separator tank (6) and a fine separator (7), and a recirculation return line (53) Liquid from the separation tank (6) in the compressor block (4),
in particular the method according to claim 14, with an idling control of the compressor (100),
marked by
Releasing a suction line (56) between a suction point (33) of the fine separator (7) and a feed point (34) of the compressor block (4) by activating a controllable valve (19) arranged in the suction line (56), in particular if the compressor (100 ) has reached a predetermined operating state, in particular a predetermined temperature, preferably at least a predetermined proportion of a predetermined liquid injection temperature or a predetermined compression end temperature. A method of controlling a compressor (100) according to claim 15,
marked by
Blocking the suction line (56) by controlling the valve (19), in particular if the compressor (100) has not reached a predetermined operating state. Method for controlling a compressor (100), in particular screw compressor, in particular a compressor (100) according to one of claims 1 to 13, preferably according to claim 12,
with a liquid injection compressor block (4), a liquid separator (5) connected to the compressor block (4) via a pressure line (52), a separator tank (6) and a fine separator (7), and a recirculation return line (53) Liquid from the separation tank (6) in the compressor block (4),
in particular, method according to one of claims 14 to 16, with a ventilation control of the compressor (100),
characterized by the following steps: - releasing the suction line (56) by driving the valve (19); - detecting an operating pressure of the compressor (100) by a pressure sensor (42, 43); - Blocking the suction line (56) by controlling the valve (19) if the detected operating pressure is below a predetermined residual operating pressure. Method for controlling a compressor (100) according to one of claims 15 to 17,
characterized in that
the release of the suction line (56) is carried out by activating the valve (19) for suction of the liquid in the load run only when the compressor is running at full load or running in a speed range above a predetermined minimum speed.

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