Oil-injected multistage compressor device and method for controlling a compressor device

Abstract

Oil-injected multistage compressor device including a low-pressure compressor element (2) with a gas inlet (4a) for gas to be compressed and a gas outlet (5a) for low-pressure compressed gas and a high-pressure stage compressor element (3) with a gas inlet (4b) for low-pressure compressed gas and a gas outlet (5b) for high-pressure compressed gas. The gas outlet (5a) of element (2) is connected to inlet (4b) of element (3) via a conduit (6). The conduit (6) has a regulatable intercooler (9) configured to regulate the temperature at the gas inlet (4b) of the high-pressure stage compressor element (3) so that it is above the dew point. The intercooler (9) includes a regulatable air cooler and/or a regulatable water cooler, and is configured to adjust the temperature of the air or water by using a bypass conduit (16) and/or by screening off part of the intercooler (9).

Claims

1. An oil-injected multistage compressor device comprising: a low-pressure stage compressor (2) with a gas inlet (4a) for gas to be compressed and a gas outlet (5a) for low-pressure compressed gas; and a high-pressure stage compressor (3) with a gas inlet (4b) for low-pressure compressed gas and a gas outlet (5b) for high-pressure compressed gas, wherein the gas outlet (5a) of the low-pressure stage compressor (2) is connected to the gas inlet (4b) of the high-pressure stage compressor (3) via a conduit (6), wherein the oil-injected multistage compressor device further comprises a regulatable intercooler (9) that is connected to the conduit (6) between the low-pressure stage compressor (2) and the high-pressure stage compressor (3) and is configured to regulate a temperature at the gas inlet (4b) of the high-pressure stage compressor (3) to be above a dew point, wherein: the regulatable intercooler (9) comprises a regulatable air cooler or a regulatable water cooler, and the regulatable intercooler (9) is configured in such a way that temperature of air or water is changed by using a bypass conduit (16) or by screening off a part of the regulatable intercooler (9).

2. The oil-injected multistage compressor device according to claim 1, further comprising a controller (11) and at least one sensor, wherein the controller (11) is configured to determine the dew point based on an output of the at least one sensor.

3. The oil-injected multistage compressor device according to claim 1, further comprising a controller (11) and a sensor, wherein the controller (11) is configured to determine the dew point based on an output of the sensor, wherein the sensor is configured to measure humidity at the gas inlet (4b) of the high-pressure stage compressor (3).

4. The oil-injected multistage compressor device according to claim 1, further comprising a controller (11) and a sensor, wherein the controller (11) is configured to determine the dew point based on an output of the sensor, wherein the sensor is configured to measure the temperature at the gas inlet (4b) of the high-pressure stage compressor (3).

5. The oil-injected multistage compressor device according claim 1, wherein the regulatable intercooler (9) comprises the regulatable air cooler, the regulatable air cooler is regulatable by a fan, whereby airflow is regulated by adjusting a speed of the fan.

6. The oil-injected multistage compressor device according to claim 1, wherein the regulatable intercooler (9) comprises the regulatable water cooler, the regulatable water cooler is configured in such a way that it is regulatable by a valve for regulating flow of the water.

7. The oil-injected multistage compressor device according to claim 1, wherein the regulatable intercooler (9) is connected to a heat pump (10).

8. The oil-injected multistage compressor device according to claim 7, wherein the heat pump (10) is regulatable.

9. The oil-injected multistage compressor device according to claim 1, wherein an oil-injection (15) is provided in the conduit (6) downstream from the regulatable intercooler (9).

10. The oil-injected multistage compressor device according to claim 1, further comprising a controller (11) for regulating the regulatable intercooler (9).

11. A method for controlling an oil-injected multistage compressor device (1), comprising the following steps: determining a dew point at a gas inlet (4b) of a high-pressure stage compressor (3) of the oil-injected multistage compressor device (1) based on an output of at least one sensor; regulating an intercooler (9) that is provided upstream of the high-pressure stage compressor, so that a temperature at the gas inlet (4b) of the high-pressure stage compressor (3) is above the dew point, wherein the regulating the intercooler (9) comprises: regulating an air cooler or a water cooler of the intercooler (9), and using a bypass conduit (16) that bypasses the intercooler (9), or screening off a part of the intercooler (9).

12. The method of claim 11, wherein the dew point is determined by measuring of one or more environmental parameters.

13. The method of claim 12, wherein the one or more environmental parameters include at least one from among pressure, temperature, and humidity.

14. The method of claim 11, wherein the dew point is determined by measuring humidity at the gas inlet (4b) of the high-pressure stage compressor (3).

15. The method of claim 11, wherein the dew point is calculated by monitoring a course of the temperature at the gas inlet (4b) of the high-pressure stage compressor (3).

16. The method according to claim 11, wherein the intercooler (9) is regulated by a controller (11) that regulates the intercooler (9) so that the temperature at the gas inlet (4b) of the high-pressure stage compressor (3) is above the dew point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To better demonstrate the features of the invention, the following describes, as a non-exhaustive example, some preferred embodiments of an oil-injected multistage compressor device and method according to the invention, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows the schematic for an oil-injected multistage compressor device according to the invention;

(3) FIGS. 2 and 3 show the schematics for a variant of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(4) The schematically shown oil-injected multistage compressor device 1 in FIG. 1 comprises two steps or ‘stages’ in this case: a low-pressure stage with a low-pressure stage compressor element 2 and a high-pressure stage with a high-pressure stage compressor element 3.

(5) Both compressor elements 2 and 3 in this example are screw compressor elements, but this is not necessary for the invention since other types of compressors can also be used.

(6) Both compressor elements 2 and 3 are also provided with an oil circuit for the injection of oil in the respective compression chambers of the compressor elements 2 and 3. For clarity, these oil circuits are not shown in the Figure.

(7) The low-pressure stage compressor element 2 has a gas inlet 4a for gas to be compressed and an outlet 5a for low-pressure compressed gas.

(8) Gas outlet 5a is connected to gas inlet 4b of the high-pressure stage compressor element 3 via conduit 6.

(9) The high-pressure stage compressor element 3 is also equipped with a gas outlet 5b for high-pressure compressed gas, whereby the outlet 5b is connected to a liquid separator 7.

(10) It is possible for the outlet 8 of this liquid separator 7 to be connected to an aftercooler.

(11) An intercooler 9 is included in the aforementioned conduit 6 between the low-pressure stage compressor element 2 and the high-pressure stage compressor element 3 which, according to the invention, can be regulated.

(12) This intercooler 9 can be designed in various ways.

(13) Intercooler 9 can, for example, include air cooling that can be controlled by a fan 20, for instance, whereby the air flow can be regulated by adjusting the speed of the fan 20.

(14) Alternatively, intercooler 9 can include, for example, a water cooler that can be regulated by a valve 21, for instance, which may control the flow of the water.

(15) It is also possible, for example, to regulate intercooler 9 by changing the temperature of the air or water.

(16) In this case, intercooler 9 is equipped with a heat pump 10, although this is not necessary for the invention.

(17) This heat pump 10 may also be regulatable, but this is not necessarily the case.

(18) With the help of heat pump 10, it will be possible to extract even more heat from the gas.

(19) Compressor device 1 is also equipped with a control unit or regulator 11 for controlling or regulating intercooler 9. If heat pump 10 is regulatable, this control unit or regulator 11 can also control heat pump 10.

(20) In the example in FIG. 1, first measuring means 12 are also provided in the form of a sensor 12a. This sensor 12a is connected to the aforementioned control unit or regulator 11.

(21) This regards, for example, a sensor 12a that can measure one or more environmental parameters at the gas inlet 4a of the low-pressure stage compressor element 2.

(22) This sensor 12a can measure the pressure, temperature, and/or humidity.

(23) It is not excluded that, instead of this sensor 12a or in addition to it, second measuring means 13 are provided, which measure the humidity at gas inlet 4b of high-pressure stage compressor element 3.

(24) These second measuring means 13 could be a sensor 13a, provided at gas inlet 4b of high-pressure stage compressor element 3. The schematic for this is shown with a dotted line in the Figure.

(25) Furthermore, device 1 as shown in the example is equipped with third measuring means 14 in the form of a sensor 14a at gas inlet 4b of high-pressure stage compressor element 3 in order to measure the temperature at this location.

(26) Finally, it is not excluded for device 1 to be equipped with an oil-injection 15 so that oil can be injected into conduit 6 downstream from intercooler 9. The schematic for this is shown with a dotted line.

(27) The operation of the oil-injected multistage compressor device 1 is very simple and as follows.

(28) During operation, the gas to be compressed, e.g. air, will be sucked in via gas inlet 4a of low-pressure stage compressor element 2 and will undergo an first compression stage.

(29) The partially compressed gas will flow via conduit 6 to intercooler 9, where it will be cooled and then to gas inlet 4b of high-pressure stage compressor element 3 for subsequent compression.

(30) Oil will be injected into both low-pressure stage compressor element 2 and in high-pressure stage compressor element 3, which ensures the lubrication and cooling of compressor elements 2, 3.

(31) The compressed gas will leave high-pressure stage compressor element 3 via gas outlet 5b and then be guided to oil separator 7.

(32) The injected oil will be separated and the compressed gas can then possibly be guided to an aftercooler before being sent to consumers.

(33) In order to ensure that condensate is not formed when the gas is cooled by intercooler 9, this intercooler 9 must be properly regulated to accommodate changes in the environmental parameters and/or drive parameters of compressor elements 2, 3.

(34) For this, the control unit or regulator 11 will regulate intercooler 9 so that the temperature of inlet 4b of high-pressure stage compressor element 3 is above the dew point. As previously mentioned, this results in no condensate forming after intercooler 9 at gas inlet 4b of high-pressure stage compressor element 3.

(35) In a first step, the dew point, or accordingly the presence of condensate, at gas inlet 4b of high-pressure stage compressor element 3 is determined or calculated. The dew point depends on various parameters and is therefore a variable and not a fixed value.

(36) There are different options or ways to determine the dew point.

(37) In the case of the embodiment shown in FIG. 1, the dew point is determined by measuring the environmental parameters using a sensor 12a.

(38) For this, the measured values of sensor 12a are transmitted to the control unit or regulator 11, which calculates the dew point on this basis.

(39) If the oil-injected multistage compressor device 1 is equipped with a humidity sensor 13b at gas inlet 4b of high-pressure stage compressor element 3, it is also possible to directly determine the dew point, or accordingly the presence of condensate, based on measuring the humidity at gas inlet 4b. Humidity sensor 13b will also transmit the measured value to control unit 11 at this point.

(40) Another alternative is to determine the dew point by following the course of the temperature at gas inlet 4b of high-pressure stage compressor element 3, e.g. by using temperature sensor 14b at inlet 4b of high-pressure stage compressor element 3 or another sensor specially provided for this purpose.

(41) In this case, temperature sensor 14b will transmit the measured values of the temperature at gas inlet 4b to the control unit or regulator 11, which monitors and evaluates the course of the measured temperatures to use as a basis for determining the dew point.

(42) Once the dew point has been determined, the control unit or regulator 11 will regulate intercooler 9 as necessary so that the temperature at gas inlet 4b of high-pressure stage compressor element 3 is above the dew point.

(43) For this purpose, the control unit or regulator 11 will request the temperature at gas inlet 4b using temperature sensor 14b and compare it with the determined dew point.

(44) Control unit 11 will allow intercooler 9 to cool more when this temperature at inlet 4b is higher than the dew point, since the temperature of the gas can fall even more without the formation of condensate.

(45) If the temperature is still higher than the dew point when intercooler 9 is already cooling at maximum output, control unit 11 will start heat pump 10.

(46) Of course, it is also possible that heat pump 10 is continuously in operation and that the regulation is carried out only using intercooler 9.

(47) It is also possible for heat pump 10 to be regulated, so that when the dew point falls and there is then an increase in the required cooling capacity, control unit 11 allows an increase in cooling capacity first in intercooler 9 and then heat pump 10 or vice versa or both simultaneously or alternately.

(48) If the temperature at gas inlet 4b of high-pressure stage compressor element 3 is lower or equal to the dew point, control unit 11 will have intercooler 9 cool less, so that the temperature of the gas will rise to prevent the formation of condensate.

(49) If heat pump 10 is also regulatable, control unit 11 can first lower the cooling capacity of heat pump 10 or alternatively lower the cooling capacity of intercooler 9 and of heat pump 10.

(50) If the dew point drops, the control unit or regulator 11 can have intercooler 9 once again cool more, so that the temperature of the gas will fall again.

(51) In this way, maximum cooling is always possible without the formation of condensate.

(52) Always being able to cool optimally means that the performance of high-pressure stage compressor element 3 can be maximized.

(53) If device 1 is equipped with oil-injection 15, this can be used to achieve additional cooling of the gas. In addition, the injected oil will provide additional lubrication for high-pressure stage compressor element 3.

(54) An alternative embodiment is shown in FIG. 2, in which in this case a bypass conduit 16 is provided over intercooler 9, which bypass conduit 16 is configured to divert part of the gas so that it can flow directly from low-pressure stage compressor element 2 to high-pressure stage compressor element 3 without passing through intercooler 9. For this purpose, bypass conduit 16 can be equipped with a valve 17 to regulate the amount of gas flowing through bypass conduit 16. In this case, valve 17 is connected to the control unit or regulator 11 for its control.

(55) FIG. 3 shows yet another design embodiment of intercooler 9, whereby a part of intercooler 9 can be screened off, e.g. with a plate 18 or similar, so that not the entire intercooler 9 is used. In other words, the gas to be cooled is not exposed to the entire intercooler 9.

(56) The present invention is by no means limited to the embodiments described as examples and shown in the figures, but an oil-injected multistage compressor device according to the invention and a method for controlling a compressor device can be achieved following different variants without going beyond the scope of the invention.