Compressor device and method for operating same

Abstract

The present invention relates to a compressor unit (1) comprising a screw compressor (3) capable of producing a compressed air-oil mixture, a compressor unit outlet (13), an oil separator (11) to which the compressed air-oil mixture can be transferred and to which the compressed air and oil from the compressed air-oil mixture can be separated from each other and the compressed air can be discharged at the compressor unit outlet (13), an oil separation duct (15) connecting the oil separator (11) to the screw compressor (3) and constituting a fan unit (19) of an oil cooler (17), and a control unit (21) capable of adjusting the speed (n) of the fan (19) and thus the cooling of the oil in the oil cooler (17).

Description

[Technical field]

[0001] The present invention relates to a compressor device and a method for operating the same. [Background technology]

[0002] Conventional compressor unit designs usually incorporate means to mitigate the condensation of air humidity taken into the compressor, however, the effect of the cooling intensity on the specific power of the compressor unit at the corresponding operating point is often overlooked or ignored.

[0003] Usually, an expansion element may be installed, where the compression end temperature of the air-oil mixture is preset to a specific value. This set point may be configured to reduce the condensation of intake air humidity in the oil-injected screw compressor, but may be inefficient in terms of cooling strength and associated achievable specific power at the respective operating point.

[0004] The prior art document WO 0246617 describes a method for controlling a compressor system comprising at least one oil-cooled compressor element.

[0005] It is therefore a basic object of the invention to provide a compressor unit and a method for operating the same, which allows the compressor unit to be operated in a particularly energy-efficient manner. Summary of the Invention

[0006] This problem is solved by the features of the independent claims. Further preferred embodiments are disclosed in the dependent claims.

[0007] According to independent claim 1, the following is provided: 1. A compressor unit comprising: a screw compressor capable of generating a compressed air-oil mixture; a compressor unit outlet; an oil separator through which the compressed air-oil mixture can be transferred and from which compressed air and oil can be separated from one another and the compressed air can be discharged at the compressor unit outlet; an oil diversion duct connecting the oil separator to the screw compressor and comprising a fan device in the oil cooler; and a control device by which the speed of the fan and thus the cooling of the oil in the oil cooler can be adjusted, wherein a current operating point of the compressor unit is determinable by the control device and an adjustable value of an oil cooling parameter is determinable as a function of the determined current operating point by means of a particular predefined and / or predetermined relationship stored in the control device, the relationship reflecting relationships between a plurality of operating points of the compressor unit and a plurality of adjustable values ​​of the oil cooling parameter, the determined value of the oil cooling parameter being adjustable by the control device, in particular for operation of a compressor unit having a defined and / or low specific power.

[0008] Furthermore, according to independent claim 4, the following is provided: 1. A method for operating a compressor unit comprising a screw compressor capable of generating a compressed air-oil mixture, a compressor unit outlet, an oil separator through which the compressed air-oil mixture can be transferred and through which compressed air and oil from the compressed air-oil mixture can be separated from one another and through which the compressed air can be discharged from the compressor unit outlet, an oil separation duct connecting the oil separator to the screw compressor and comprising a fan device in the oil cooler, and a control device in which the speed of the fan and thus the cooling of the oil in the oil cooler are adjustable, wherein a current operating point of the compressor unit is determinable by the control device and an adjustable value of an oil cooling parameter is determinable as a function of the determined current operating point by means of a relationship stored in the control device, in particular a predetermined and / or pre-determined relationship, which relationship reflects connections between a plurality of operating points of the compressor unit and a plurality of adjustable values ​​of the oil cooling parameter, and wherein the determined value of the oil cooling parameter is adjusted by the control device, in particular for operation of the compressor unit with a defined and / or low or minimum specific power.

[0009] In this way it is possible to influence the cooling strength of an air-cooled fluid-injected compressor unit ("package") with at least one fan with variable speed for conveying a variable amount of cooling air through the cooler, with the aim to operate the machine within given limits at the respective operating point with an optimum (minimum) specific power. This operating mode helps to reduce the energy consumption of the compressor unit. The compressor unit can be a single-stage or multi-stage compressor unit with at least one screw compressor driven at fixed or variable speed.

[0010] The specific power of the compressor unit is calculated as the quotient of the total power consumption of the compressor unit (dividend) and the discharge volume of the compressor unit (divisor). It should be noted that power is consumed during operation by many components, including the control unit, the drive unit of the fan unit, and the drive unit of the screw compressor. The discharge volume can be defined as the volumetric flow rate of compressed air, preferably generated downstream of the oil separator. The volumetric flow rate can be measured using a suitable measuring device.

[0011] The objective is to modify and adjust the intensity of the cooling process of the compressor unit by influencing the fan speed in such a way as to optimize the specific power of the compressor unit at the corresponding operating point, i.e. to bring it as close as possible to an optimal level (i.e. a minimum value). Due to external constraints, there may be upper and lower limits on the intensity of the cooling process. These include the maximum permissible temperatures of the components or working materials, or the minimum permissible temperatures to avoid condensation of moisture sucked into the compressor unit. The cooling intensity can be modified within these permissible limits, but even with higher or lower cooling intensities outside these limits, a further improvement in the specific power can be achieved.

[0012] According to a specific example embodiment, the compressor unit may comprise an air-cooled, single-stage, oil-injected screw compressor with a variable speed fan for conveying a variable amount of cooling air through a fan unit in the oil circuit, with the screw compressor having a variable drive speed.

[0013] In this embodiment, the operating point can be characterized by the pressure at the outlet of the compressor unit or the internal pressure of the compressor unit (oil separator wet side), the speed of the screw compressor, the temperature and density of the available cooling air at the inlet to the screw compressor, the flow resistance of the cooling air at the inlet or outlet resulting from the installation conditions of the compressor, the current properties of the oil (e.g. viscosity class and viscosity index), the fouling state of the oil separator cartridge, and the fouling state of the cooler. This operating point results from external boundary conditions, the current aging state of components or working materials in the compressor, the pressure or volume flow control method (discharge control method) implemented in the compressor control system, and / or control commands from a higher-level control system to the compressor control system. The operating point can be considered to be time-variable and predetermined at any point in time.

[0014] Increasing the fan speed not only increases the power consumption of the fan drive unit, but also increases the amount of cooling air, resulting in more intensive cooling of the compressor (in a specific embodiment, the oil in the fan unit). More intensive cooling also leads to a decrease in the temperature at which the oil is injected into the screw compressor and the temperature at which the mixture of air and oil leaves the screw compressor (compression end temperature, VET). A lower oil temperature increases the working viscosity of the oil, which leads to higher viscosity losses when transporting the oil in the screw compressor, thus increasing the required shaft power. A higher working viscosity improves the sealing effect of the oil in the screw compressor, which reduces the internal leakage losses during the compression process, which in turn affects the discharge volume and required shaft power of the screw compressor.

[0015] The strength and sign of the effect of increasing the fan speed or increasing cooling on the screw compressor discharge and shaft power requirement depends on the current operating point and the current fan speed. For example, an increase in fan speed always results in an increase in the power consumption of the fan drive, but an increase in fan speed can increase or decrease the screw compressor discharge or shaft power requirement depending on the current operating point and the current fan speed.

[0016] Reducing the fan speed has a similar effect, though with a different manifestation.

[0017] Varying the fan speed has the following effects at each operating point: - Change in power consumption of fan drive - Change in required shaft power of screw compressor - Change in power consumption of fan drive

[0018] These variables are included in the specific power of the compressor unit (the quotient of the total power consumption and the discharge). When the above mentioned effects are superimposed, there exists a fan speed at each operating point for which the specific power of the compressor unit is optimal, i.e. at a minimum. This can be called the optimal fan speed and includes the optimal cooling intensity, in particular the optimal VET or the optimal oil injection temperature.

[0019] The objective is to essentially adjust the optimum fan speed or optimum cooling intensity, in particular the associated optimum VET, during operation of the compressor unit, to track the operating point over time, provided that the cooling intensity is maintained within the permissible limits, or to approach this optimum as closely as possible, provided that this is possible while respecting the permissible limits of the cooling intensity.

[0020] These tolerance limits can be fixed or variable. An example of a fixed limit on cooling intensity is the VET upper limit to counteract the deterioration of oil over time.

[0021] In a preferred embodiment, the compressor device has an oil temperature sensor between the fan device and the screw compressor. The compressor device may have at least one air temperature sensor for the air sucked by the screw compressor and / or for the ambient air. The compressor device may further comprise a temperature sensor for the temperature of the air-oil mixture, in particular at the outlet of the screw compressor. Furthermore, the compressor device may comprise a pressure sensor for the pressure of the generated air-oil mixture, in particular in or at the oil separator. The compressor device may also comprise a pressure sensor for the pressure of the generated compressed air, in particular downstream of the oil separator or at the compressor device outlet. The control device may be connected to at least one of these sensors and configured to read them.

[0022] The control device can adjust, in particular manually or automatically, a number of defined pressures for the compressed air generated by the compressor device. For variable operation, a number of defined and / or variable speeds of the screw compressor can be adjusted by the control device. In this case, the control device can approach different speeds, for example, depending on the pressure resulting from the compressed air demand of the user. In a preferred method, in order to determine the current operating point, a number of, in particular two, operating points of the compressor device can be determined using a relationship that reflects the relationship between the operating parameter and the oil cooling parameter. By taking into account the two operating parameters that characterize the operating point in the above relationship, the operation can be optimized in a particularly simple and effective way.

[0023] To determine the current operating point, it is particularly preferred to determine the speed of the screw compressor as an operating parameter and the pressure of the air-oil mixture, in particular generated in or at the oil separator, as an operating parameter. The oil cooling parameter is therefore determined via a relationship as a function of these two operating parameters. Determining the pressure of the air-oil mixture is advantageous here, since an increase in the pressure loss in the oil separator, in particular in the oil separator cartridge of the oil separator, does not affect the pressure of the air-oil mixture or the pressure on the wet side of the oil separator.

[0024] Alternatively, it is also possible to determine the current operating point by determining the speed of the screw compressor as an operating parameter and the pressure of the compressed air generated downstream of the oil separator, in particular at the compressor unit outlet, as an operating parameter. The oil cooling parameter is thus determined via a relationship as a function of these two operating parameters.

[0025] In principle, the oil cooling parameters can be formed by the speed of the fan assigned to the fan device, which is controlled in a defined manner by the control device to adjust the speed derived from the relationship, thereby adjusting the speed.

[0026] However, preferably, the oil cooling parameter is formed in particular by the temperature of the air-oil mixture generated at the outlet of the screw compressor, the temperature of the air-oil mixture derived from the relationship being adjusted and / or regulated by the control device and the fan device.

[0027] In particular, a simple design consists of modifying the control method of the VET, which is usually present in compressor units and uses the fan speed as a control variable, by determining and using a setpoint value of the VET for each operating point, and by adjusting this setpoint, the optimum fan speed or the optimum cooling power, which belongs to the optimum or minimum specific power, is adjusted.

[0028] Alternatively, the oil cooling parameters can also be formed by the oil temperature downstream of the oil cooler, in particular at the oil inlet of the screw compressor, the oil temperature resulting from the relationship being adjusted and / or regulated by the control device and the fan device.

[0029] The relationship can be designed as a formula, in particular derived from a performance map and / or a mathematical formula. Preferably, the mathematical formula is a performance map approximation of a performance map determined in tests. Alternatively, the relationship can be designed as a performance map and stored in the control device.

[0030] For example, the VET at which the specific power output is optimal can be determined in a series of tests for a number of operating points to determine the optimal VET setpoint for each operating point. A performance map can be created from the series of tests from which the optimal VET setpoint for each operating point can be obtained or calculated, and by adjusting the fan speed, a good approximation of the optimal specific power output of the screw compressor can be obtained. This performance map can be used to determine the optimal VET setpoint at the current operating point.

[0031] When deriving the performance map, individual variables characterizing the operating point that have a relatively small influence on the optimal cooling intensity can be omitted: if, for example, the operating point is characterized only by the pressure at the outlet of the compressor unit and the speed of the screw compressor, and fixed reference values ​​are used for all other variables characterizing the operating point, then one obtains a method that works reliably in practice and achieves the optimal specific power to a good approximation.

[0032] An example of a fixed reference value that can be used as a basis for creating a performance map can be the temperature of the available cooling air (the performance map created is based on a cooling air temperature of, for example, 20° C.) and the particular oil for the new conditions (viscosity class and viscosity index).

[0033] In a preferred method, the temperature of the air taken in by the compressor device and / or the ambient air can be determined by the control device, and the oil cooling parameter determined by the relationship is corrected according to a predetermined correction model, particularly in the form of a mathematical formula, which takes into account the determined air temperature, whereby the oil cooling parameter, preferably corrected by the correction model, is adjusted by the control device. In this way, the current air temperature can be taken into account in a simple and effective way.

[0034] A drawback of the embodiment based only on the performance map is that the method does not receive feedback on whether or what quality the specification of the set values ​​based on the performance map values ​​actually leads to an adjustment of the optimal cooling intensity or the optimal specific power. If the relevant variables characterizing the operating point are not taken into account in the performance map, relevant differences may occur between the actual optimal cooling intensity at the respective operating point and the cooling intensity set based on the performance map values, and the actual specific power may not reach the optimum. For example, if the temperature of the available cooling air is not taken into account when creating the performance map and the series of tests used to create the performance map was only carried out at a reference temperature, then different temperatures of the available cooling air will affect the cooling intensity set by the process when the process is actually carried out. The series of tests shows that when the temperature of the available cooling air is high and there is no change in the variables characterizing the operating point, the optimal specific power is adjusted to a higher VET, which includes the optimal fan speed or the optimal cooling intensity.

[0035] For example, if the current temperature of the available cooling air is taken into account, the target VET determined from the performance map can be mathematically corrected at the operating point. As a first approximation, the deviation from the reference temperature when calculating the target VET can be written as follows:

[0036] VET Soll,korr =VET Soll +[(ta-tr)×n / n max ] where ta is the temperature of the available cooling air, tr is the reference temperature when the performance map was developed, and n is the screw compressor speed.

[0037] In a further preferred method, a search, in particular an iterative search, for a second value, in particular an optimum value, of the oil cooling parameter at which the compressor unit is operated with a lower specific power than at the first value of the oil cooling parameter derived from the relationship, in particular corrected, can be performed by the control device at the current operating point, in this way an operating mode of the compressor unit with a particularly low specific power can be achieved.

[0038] Preferably, if a second value is found during the search, the second value is adjusted by the controller at the current operating point.

[0039] In a preferred specific embodiment, for the particular iterative search for the second value, multiple values ​​of the oil cooling parameter are adjusted by the control device and the specific power of the compressor unit is determined and / or estimated by the control device for each adjusted value.

[0040] If the oil cooling parameter considered in the relationship is fan speed, some values ​​for the fan speed can be adjusted when searching for the second value. If the oil cooling parameter considered in the relationship is VET, some values ​​for VET or fan speed can be adjusted when searching for the second value. If the oil cooling parameter considered in the relationship is oil injection temperature, some values ​​for the oil injection temperature or fan speed can be adjusted when searching for the second value.

[0041] The iterative search can be performed, for example, as follows. Starting point (e.g., |VET Soll -VET IstStarting from |<0.5K), iterative incremental changes to the cooling intensity can be performed. The effect of the change steps on the specific power is then evaluated and, based on this, a next change step that is likely to improve the specific power can be determined. If the previous change step, for example increasing the fan speed by one speed increment, improved (i.e. reduced) the specific power, then in the next change step the fan speed can be increased again by one speed increment. Otherwise, the fan speed can be decreased by one speed increment. The size of the speed increment for changing the fan speed can be, for example, 20 rpm at the start of the iteration. The amount of the speed increment can advantageously be adapted to the change in specific power observed in the previous change step relative to the previous speed increment (step width control). Thereby, it is advantageous to make small incremental changes when the cooling intensity is close to the optimum and large incremental changes when the current cooling intensity is far from the optimum.

[0042] To evaluate the change in the specific power output in the incremental iteration process, there are several options. For example, the total power consumption and the discharge of the screw compressor can be measured by suitable sensors and the measurements can be made available to the process. From this, the specific power output can be calculated in the process as the quotient of the total power consumption and the discharge of the screw compressor. The evaluation of the modification consists of a comparison of the specific power output calculated on the basis of the measurements before and after the modification step. Alternatively, all or part of these measurements can be replaced by so-called "virtual sensors" or "virtual sensor values". These are values ​​calculated or simulated on the basis of suitable models and represent a good approximation of the real values ​​of the physical variables, even if measurements from real sensors are not available or used for these physical variables. For example, conventional frequency inverters provide an approximation of the power consumption of the frequency inverter via an interface that is based at least in part on such "virtual sensors".

[0043] The compressor arrangement may advantageously be characterised by the features and advantages already mentioned in the context of the method, and vice versa. [Brief description of the drawings]

[0044] The invention will now be described in more detail with reference to the drawings in which: [Figure 1] 1 is a schematic diagram showing a first embodiment of a compressor device according to the present invention. [Diagram 2] FIG. 4 is a diagram illustrating the operation of the compressor device. [Diagram 3] FIG. 2 shows a schematic diagram of a performance map for the operation of the compressor unit; [Figure 4] 11 is a table illustrating a method for determining a performance map. [Diagram 5] FIG. 3 is a diagram showing a second embodiment of the compressor device according to the present invention shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] 1 shows diagrammatically a compressor unit 1. The compressor unit 1 comprises an oil-injected screw compressor 3 for generating compressed air. The compressor 3 is driven by a drive motor 5, here designed as an electric motor.

[0046] During operation of the compressor 3, air 8 is sucked in through the air inlet 6, compressed in the compression chamber of the compressor 3 and mixed with oil. The air-oil mixture 9 leaving the compressor 3 is fed to an oil separator vessel as an oil separator 11 for separating the oil from the generated compressed air. Starting from the oil separator 11, the compressed air 12 from which the oil has been removed is led to the compressor unit outlet 13 of the compressor unit 1. A compressed air cooler (not shown) can also be arranged between the oil separator 11 and the compressor unit outlet 13 to cool the generated compressed air. The separated oil 15 is returned to the compressor 3 via an oil separation duct 16 with a fan unit 17 and injected into its compression chamber.

[0047] The fan arrangement 17 is fitted with a fan 19 for delivering cooling air to the fan arrangement 17. The fan or ventilation arrangement 19 is driven here by a speed-controlled drive motor 20. The speed of the fan 19 can be variably adjusted via a control device 21 of the compressor arrangement 1 at defined speed values. In this way, the cooling air supplied by the fan 19 to the fan arrangement 17 and thus also the cooling of the oil 15 is regulated.

[0048] The speed of the screw compressor 3 can also be variably adjusted at defined speed values ​​by the control device 21. Furthermore, measured values ​​from several sensors 25, 29, 31, 35, 36 are sent to the control device 21.

[0049] The temperature T of the air 8 sucked in by the screw compressor 3 is measured by the temperature sensor 25. Instead of the temperature of the sucked in air, the temperature of the surrounding air can also be measured. The temperature sensor 29 is used to measure the temperature T of the air-oil mixture 9 at the outlet 37 of the compressor 3 (compression end temperature, VET). The pressure sensor 31 is used to measure the internal pressure p of the air-oil mixture 9 in the oil separator 11, upstream of the oil separation element 39 or on the wet side of the oil separator 11, viewed in the flow direction. The pressure sensor 35 arranged downstream of the oil separator 11 is used to measure the pressure p of the compressed air generated at the compressor unit outlet 13 (final system pressure). Furthermore, the temperature sensor 36 measures the temperature T of the oil 15 downstream of the fan unit 17 at the oil inlet 18 of the compressor 3 (oil injection temperature).

[0050] The relationship in the form of a mathematical formula is also stored in the control device 21. This formula is used to map or approximate a performance map 41 (FIG. 3) determined in a series of tests. This formula is used by the control device 21 to determine the compression end temperature (VET) as an oil cooling parameter when the compressor unit 1 is operated at its current operating point with a particularly low specific power and, correspondingly, a particularly high energy efficiency. This VET can be adjusted by the control device 21 via the adjustable speed of the fan 19 and the temperature sensor 29.

[0051] 3, the internal pressure p of the air-oil mixture 9 in the oil separator 11 and the current speed n of the compressor 3 are entered into a performance map 41 as operating parameters characterizing the current operating point of the compressor installation 1. In principle, further or other operating parameters can also be taken into account in the performance map 41.

[0052] In the case of a speed-controlled screw compressor, the current speed n of the screw compressor is already available in the control device and this value can be calculated in the frequency converter of the drive motor. It is also possible to measure the current speed n of the compressor 3 during operation.

[0053] The VET is also entered into the performance map 41. In the schematic representation of the performance map 41 in Fig. 3, three temperature ranges 43, 45, 47 of the VET are filled in by way of example with different hatchings. The temperature ranges 43, 45, 47 are shown on a temperature scale 49.

[0054] The performance map 41 reflects the relationship between the operating parameters and the VET. Depending on the values ​​of the operating parameters, the control device 21 can derive an assigned value of the VET from the performance map 41. The assigned value is the VET at which the compressor device 1 is operated with a particularly low specific power at the current operating point. Depending on the pressure p and the speed n, the VET at which the compressor device 1 is operated with a particularly low specific power is different.

[0055] It can also be seen from the performance map 41 that at a certain internal pressure p at a higher speed n, a higher VET is derived from the performance map 41 than at a lower speed n. Thus, at a higher speed n, the control device 21 adjusts or sets a higher VET than at a lower speed n in order to operate the compressor device 1 at a particularly low specific power.

[0056] It can also be seen from the performance map 41 that at a particular speed n at a higher internal pressure p, a lower VET is derived from the performance map 41 than the VET at a lower internal pressure p.

[0057] A mathematical formula stored in the controller 21 for mapping or approximating the performance map 41 may be, for example, as follows:

[0058] y(x;z)=P0+P1×c+P2×x 2 +P3×x 3 +P4×1 / x +P5×z+P6×z 2 +P7×z 3 +P8×x×z where y is the VET, x is the speed n of the screw compressor 3, and z is the internal pressure p. As an alternative to a mathematical formula, the performance map 41 can also be stored in the controller 21 as a relationship.

[0059] Instead of the compression end temperature (VET), the oil injection temperature or the fan 19 speed can be considered as an oil cooling parameter in the performance map 41 or formula.

[0060] Instead of the internal pressure p of the oil separator 11, the final system pressure p can be taken into account as an operating parameter in the relationship.

[0061] An exemplary operation of the compressor unit 1 will now be described with reference to FIG.

[0062] First, the control device 21 determines the VET SollDepending on the determined current internal pressure p of the screw compressor 3 and the determined current speed n, the VET at which the compressor device 1 is operated with a particularly low specific power is determined using a relationship in the form of the formula: VET Soll Also called VET. Soll is determined continuously during operation of the compressor unit 1.

[0063] Next, in step 53, the control device 21 calculates the determined VET Soll A check is made as to whether an additional mathematical correction of should be performed. One criterion for whether a mathematical correction is performed or not can be the deviation of the current temperature Ta of the intake air from a defined reference temperature Tr, for example |Ta-Tr|>1 K (Kelvin).

[0064] In a particular operating situation, the mathematical correction is calculated based on the VET target can be used to determine a VET having a higher energy efficiency than ΔVET. If no mathematical correction is required, the value ΔVET m is set to 0 K (Kelvin). If mathematical correction is performed, the value ΔVET m is the defined reference temperature Tr, the current temperature Ta of the intake air, the current speed n of the compressor 3, and the defined maximum speed n of the compressor 3. max As a function of, in step 55, the following equation, stored in the control device 21, can be used as the correction model:

[0065] ΔVET m = [(Ta-Tr) × n / n max ]

[0066] The defined reference temperature Tr is the temperature of the cooling air delivered by the fan 19, selected in a series of tests to determine the performance map 41. Also, the current intake air temperature Ta of the compressor, measured by the temperature sensor 25, is assumed to correspond to the current cooling air temperature of the compressor.

[0067] In step 56, the control device 21 Soll and ΔVET m The sum of and the value VET Soll,korr1 It was decided.

[0068] VET Soll,korr1 =VET Soll +ΔVET m

[0069] Finally, in step 57, the control device 21 Soll,korr1 It is checked whether an additional iterative search for a VET with a specific power (second VET value) lower than the specific power (first VET value) should be performed at the current operating point. The iterative search can be performed, for example, if the compressor unit 1 has the option to evaluate, for example using a suitable sensor system, the influence of different VET values ​​set during the iterative search on the specific power of the compressor unit 1. If an additional iterative search is not performed, the value ΔVET i is set to 0K. If an iterative search is performed, first the following condition is checked in step 59:

[0070] |VET Soll,korr1 -VET Ist |<0.5K (Kelvin)

[0071] VET Ist is the current temperature of the VET measured by the temperature sensor 29. The value 0.5 K represents an exemplary value of the defined temperature difference. If the condition is met, an iterative search (iteration loop) is performed in step 61. If the condition is not met, the iterative search is not performed, which may be the case, for example, if the speed is changed in the load operation, resulting in a new VET Soll In this case, ΔVET i The value of is set to 0K.

[0072] In an iterative search, the specific power of the compressor arrangement 1 is determined, respectively, for different adjusted VETs. For this purpose, the power consumptions of the control device 21, the drive 5 of the compressor 3 and the drive 20 of the fan 19, as well as the discharge rate of the compressor arrangement 1 can be measured by a suitable sensor system during operation of the compressor arrangement 1.

[0073] For example, the iterative search starts with VET Soll,korr1 The specific power at VET can then be determined. The VET is then increased or decreased by a defined value and the specific power is determined at each set VET. Alternatively, the speed of the fan 19 can also be increased or decreased by a defined value and the specific power is determined at each set speed.

[0074] Finally, a VET is determined at which the specific power of the compressor unit 1 is relatively low and therefore most energy efficient.

[0075] Correction value ΔVET i is derived from the results of the iterative search in step 63.

[0076] In step 64, the control device 21 Soll,korr1 and ΔVET i The sum of and the value VET Soll,korr2 Determine.

[0077] VET Soll,korr2 =VET Soll,korr1 +ΔVET i

[0078] Furthermore, the control device 21 determines the determined VET Soll,korr2 Check whether it is within the following acceptable range.

[0079] VET min ≦VET Soll,korr2 ≦VET max

[0080] VET Soll,korr2 is the defined VETmin VET should not be less than 0.05 V, which prevents the formation of condensation in the compressor unit 1. min is determined by the control device 21 depending on the temperature of the intake air and the relative humidity of the surrounding air. Furthermore, to counteract deterioration of the oil 15, the VET Soll,korr2 is the defined VET max VET max is a constant here. Soll,korr2 If is not within the tolerance range, VET min or VET max Either of the following is VET Soll,korr2 The value is defined as VET min If it is below VET min VET Soll,korr2 And VET max If it exceeds VET max VET Soll Let us assume that.

[0081] In step 65, the determined VET Soll,korr2 is transmitted to a VET adjustment device (VET control device) of the control device 21. The speed of the fan 19 to be adjusted is determined therethrough in step 67. This speed is adjusted in step 69 via the drive motor 20 of the fan 19.

[0082] A similar operating mode to the compressor installation 1 according to FIG. 2 can be realised if instead of the VET the oil injection temperature is taken into account as the oil cooling parameter in the equation as a relation.

[0083] FIG. 4 shows an example of how a performance map 41 is determined in a series of tests.

[0084] A series of tests is carried out at defined reference values, that is, a defined temperature of the cooling air delivered by the fan 19 to the fan arrangement 17 and the type of oil 15 delivered by the compressor arrangement 1 and under defined conditions, in this example new conditions.

[0085] According to Fig. 4, in order to determine the specific power P of the compressor arrangement 1, several measurements are carried out in a test series, in this example 18 measurements. Each determination of the specific power P is carried out at a different operating point of the compressor arrangement 1. The operating points set in the test series are also called characteristic map points. The specific power P is the quotient of the power consumption and the discharge rate of the compressor arrangement 1. To determine the specific power P, the power consumption and the discharge rate of the compressor arrangement 1 are measured.

[0086] As an example, three series of measurements 71 are performed with six measurements each at pressures p1, p2, p3 defined as the internal pressure p of the oil separator 11. In each series of measurements 71, two exemplary series of measurements 73 are performed, each series of measurements 73 with three measurements at speeds n1, n2 defined as the speed n of the compressor 3. Furthermore, the defined temperatures T1, T2, T3 are adjusted as the compression end temperature T(VET) for each series of measurements 73. Each measurement is therefore at a different operating point of the compressor device 1.

[0087] After carrying out the measurements, it is determined at which operating point of the compressor installation 1 the specific power P of the compressor installation 1 is relatively low and therefore the most energy efficient. It is therefore determined at which VET has to be adjusted at a given pressure p and a given speed n in order to achieve a particularly energy efficient operation of the compressor installation 1. From these values ​​a performance map 41 is created.

[0088] Next, an operation mode of another compressor device 75 will be described with reference to FIG.

[0089] In the case of the compressor arrangement 75, a mathematical formula is stored in the control device as a relationship reflecting the relationship between the internal pressure of the oil separator 11 as an operating parameter, the speed of the compressor 3 as an operating parameter, and the speed n of the fan 19 as an oil cooling parameter. Depending on the values ​​of the operating parameters, the control device 21 can derive an assigned value of the speed n of the fan 19 from the formula. The assigned value of the speed n is the speed n of the fan 19 at which the compressor arrangement 75 is operated with a particularly low specific power at the current operating point. This speed n of the fan 19 is n Soll It is also called.

[0090] In the following, only the essential differences between the operating mode of the compressor device 75 and the operating mode of the compressor device 1 will be described.

[0091] In step 51, the fan speed n Soll This determines the speed value n available after step 64. L,Soll,korr2 is determined in a speed determination unit 81 highlighted by a dashed line in the same manner as in the compressor device 1. L,Soll,korr2 The allowable range of values ​​is the defined maximum speed n L,max,max The minimum speed n defined from L,min It is in the range of up to.

[0092] The following conditions are also checked for compressor unit 75 in step 59:

[0093] |ΔVET Ist / Δt|≦0.01K / s (Kelvin / second)

[0094] ΔVET Ist is the measured VET Ist is the difference value changed over a defined time interval Δt. The value 0.01 K / s represents an example value for a defined temperature change over time.

[0095] If the condition of step 59 is satisfied, in step 61, n Soll,Korr1An iterative search is performed at a rate n that is more energy efficient than in Soll,korr1 The specific power at can first be determined. The speed is then increased or decreased by a defined amount and the specific power at each set speed is determined.

[0096] If the condition is not met, the iterative search is not performed, which means that, for example, a new n Soll is obtained, so that VET is currently adjusted.

[0097] n in the speed determination unit 81 L、Soll、korr2 In parallel or simultaneously with the continuous determination of VET, the control device determines in step 77 the measured current VET Ist Continuously check whether satisfies the following condition:

[0098] VET Ist ≦VET max

[0099] If this condition is not met, the system proceeds to step 85. If this condition is met, the controller determines in step 79 the measured current VET Ist Check whether the following conditions are also satisfied:

[0100] VET Ist ≧VET min

[0101] If this condition is not met, proceed to step 87. VET min and VET max is the same value as in the case of the compressor unit 1. In steps 77 and 79, the measured current VET Ist But VET min and VET max If it is determined that the measured VET is not within the tolerance between 0 and 1, then step 85 or step 87 is performed by the control system depending on the measured VET.

[0102] In step 85, VET max However, VET should be adjusted Soll In step 87, the VET min VET should be adjusted Soll The VET to be set in steps 85 and 87 is specified as Soll After designating, in step 89, the VET adjustment device (VET regulator) of the control device 21 is operated. In the following step 91, the speed n of the fan 19 to be adjusted is determined. VETRegler is provided by the VET regulator.

[0103] Finally, in step 93, the speed to which the fan 19 should be adjusted is determined. VETRegler is the speed n determined in parallel from the speed determination unit 81. Soll,korr2 takes precedence over

[0104] Therefore, the VET adjustment device of the control device is inactive (this is the VET Ist is within the tolerance range), n determined in step 65 Soll,korr2 is set as the speed of the fan 19 to be adjusted. The VET adjustment device of the control device is activated (VET Ist is not within the tolerance range), in step 91, VETRegler is set as the speed of the fan 19 to be adjusted. The speed thus determined is adjusted in step 69 via the drive motor 20 of the fan 19.

[0105] Instead of using a VET regulator, max If this is exceeded, the fan 19 will operate at its maximum speed n max You can simply increase the speed of the fan 19 until it reaches VET min If the speed is less than the minimum speed n of the fan 19 min The speed of the fan 19 is reduced until it reaches

Claims

1. 1. A compressor apparatus comprising: a screw compressor (3) capable of producing a compressed air-oil mixture; A compressor unit outlet (13); an oil separator (11) through which the compressed air-oil mixture can be conveyed, compressed air and oil can be separated from each other from the air-oil mixture, and the compressed air can be discharged to the compressor unit outlet (13); an oil separation duct (15) connecting the oil separator (11) to the screw compressor (3) and including a fan device (19) provided in an oil cooler (17); a control device (21) capable of adjusting the speed (n) of the fan device (19) and thus the cooling of the oil in the fan device (17), a current operating point of the compressor device (1) is determinable by the control device (21); a predetermined and / or predefined relationship (41) stored in the control device (21) allows the adjustable value of the oil cooling parameter to be determined as a function of the determined current operating point, said relationship (41) reflecting a relationship between a plurality of operating points of the compressor device (1) and a plurality of adjustable values ​​of the oil cooling parameter, The determined value of the oil cooling parameter is adjustable by the control device (21), in particular for operation of the compressor device (1) with a defined and / or low specific power.

2. 2. The compressor arrangement according to claim 1, further comprising an oil temperature sensor (36) between the fan arrangement (17) and the screw compressor (3), and / or at least one air temperature sensor (25) for the air taken in by the screw compressor (3) and / or for the ambient air, and / or a temperature sensor (29) for the temperature of the air-oil mixture, in particular at the outlet (18) of the screw compressor (3), and / or a pressure sensor (31) for the pressure of the air-oil mixture, in particular in or at the oil separator (11), and / or a pressure sensor (35) for the pressure of the generated compressed air, in particular downstream of the oil separator (11) and / or at the compressor arrangement outlet (13), and wherein the control device (21) is connected to at least one of these sensors and is configured to read these sensors.

3. 3. Compressor arrangement according to claim 1 or 2, characterized in that several defined and / or variable speeds of the screw compressor (3) are adjustable by the control device (21) and / or several defined pressures of the compressed air produced by the compressor arrangement (1) are adjustable by the control device (21).

4. The compressor device (1), in particular said screw compressor (3) producing said air-oil mixture; the compressor unit outlet (13); an oil separator (11) into which the air-oil mixture is transferred, in which the compressed air and the oil are separated from each other from the air-oil mixture, and in which the compressed air is discharged from the compressor unit outlet (13); the oil separator (11) is connected to the screw compressor (3), and the oil separation duct (15) is provided with the fan device (19) in the oil cooler (17); a control device (21) for adjusting the speed of the fan device (19) and thus the cooling of the oil in the fan device (17), The control device (21) determines a current operating point of the compressor device (1); an adjustable value for the oil cooling parameter is determined as a function of the determined current operating point by a particular predetermined and / or predefined relationship (41) stored in the control device (21), said relationship (41) reflecting a relationship between a plurality of operating points of the compressor device (1) and a plurality of adjustable values ​​of the oil cooling parameter, 4. The method according to claim 1, wherein the determined value of the oil cooling parameter is adjusted by the control device (21) in particular for operation of the compressor unit (1) with a defined and / or low specific power.

5. 5. The method according to claim 4, wherein to determine the current operating point, a plurality of, in particular two, operating parameters (p, n) of the compressor unit (1) are determined, and the relationship (41) reflects a relationship between the operating parameters (p, n) and the oil cooling parameter.

6. 6. The method according to claim 4 or 5, wherein the speed (n) of the screw compressor (3) and in particular the pressure (p) of the air-oil mixture generated upstream of or in the oil separator (11) are determined as operating parameters for determining the current operating point.

7. 6. The method according to claim 4 or 5, wherein, in order to determine the current operating point, as operating parameters the speed (n) of the screw compressor (3) and in particular the pressure of the compressed air generated downstream of the oil separator and / or at the compressor unit outlet are determined.

8. 8. The method according to claim 4, wherein the oil cooling parameter is formed by the speed of the fan device (19) relative to the fan device (17), the fan device (19) being controlled by the control device to set a speed derived from the relationship.

9. The method according to any one of claims 4 to 7, wherein the oil cooling parameter is formed in particular by the temperature of the air-oil mixture produced at the outlet (37) of the screw compressor (3), the temperature derived from the relationship (41) being adjusted and / or regulated by the control device (21) and the fan device (19).

10. 8. The method according to claim 4, wherein the oil cooling parameter is formed by the oil temperature downstream of the oil cooler (17), in particular at the oil inlet (18) of the screw compressor (3), and the oil temperature derived from the relationship is adjusted and / or regulated by the control device (21) and the fan device (19).

11. The method according to any one of claims 4 to 10, wherein the relationship (41) is designed in particular as a performance map and / or a formula derived from a mathematical formula or as a performance map.

12. 12. The method according to claim 4, wherein the temperature of the air taken in by the compressor unit and / or the ambient air is determined by the control device (21), the oil cooling parameter determined by the relationship is corrected according to a predetermined correction model, in particular in the form of a mathematical formula, which takes into account the determined air temperature, and the oil cooling parameter corrected by the correction model is preferably adjusted by the control device (21).

13. 13. The method according to claim 4, wherein the control device (21) performs a search, in particular an iterative search, for a second value, in particular an optimal value, of the oil cooling parameter at which the compressor unit (1) is operated at a lower specific power at the current operating point than at a first value of the oil cooling parameter derived from the relationship, in particular corrected by the correction model.

14. 14. The method according to claim 13, wherein if the second value is found during the search, this second value is adjusted by the control device (21) at the current operating point.

15. 15. The method according to claim 13 or 14, wherein for the search for the second value, in particular iteratively, a number of different values ​​of the oil cooling parameter are adjusted by the control device (21), and at each adjusted value the specific power of the compressor device (1) is determined by the control device (21).

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