A centrifugal separator for cleaning gas

Abstract

The present invention provides a centrifugal separator (100) for cleaning gas containing contaminants. The centrifugal separator (100) is comprising a stationary casing (210), enclosing a separation space (220) through which a gas flow is permitted; a gas inlet (112) and a gas outlet (114) for guiding the flow of gas through the stationary casing (210) to allow at least some of the contaminants to be separated from the flow of gas; a drainage outlet (215) configured to permit discharge of liquid contaminants that have been separated from the gas; a rotor (230) comprising a plurality of separation members (232) arranged in said separation space (220) and being arranged to rotate around an axis (X) of rotation; and a drive member (234) for rotating the rotor (230). The centrifugal separator (100) is arranged so that a main flow path for gas is formed from the gas inlet (112), through the stationary casing (210) and out through the gas outlet (114) and further comprises a chamber (20) enclosing a volume V that does not form part of the main flow path but is connected in a pressure-equalized manner with the main flow path. The centrifugal separator (100) further comprises a sensor (30) arranged to generate a signal indicative of the gas pressure in said volume V of said chamber (20).

Description

[0001] A CENTRIFUGAL SEPARATOR FOR CLEANING GAS

[0002] Field of the Invention

[0003] The present invention relates to the field of centrifugal separators for cleaning gas. In particular, the present invention relates to a separator for cleaning crankcase gases of a combustion engine from oil particles.

[0004] Background of the Invention

[0005] High-pressure gas in the combustion chambers of an internal combustion engine tends to leak past the piston rings into the engine’s crankcase. If not ventilated from the crankcase, the gas may cause a pressure increase that risks impeding the operation of the engine.

[0006] Typically, the crankcase gas contains contaminants such as unburned fuel, particulate matter, and traces of oil from the reservoir of oil held in the crankcase. Venting the gas directly into the atmosphere contributes to air pollution, which is harmful to the environment and poses a human health hazard.

[0007] To mitigate these issues, a crankcase ventilation system may be employed, comprising a centrifugal separator for separating oil and particulate matter from the crankcase gas before it is released to the environment or redirected back into the engine’s intake for reburning.

[0008] As the cleaning and recycling of the gas from the crankcase often plays a critical role in reducing emissions and maintaining engine health, it is desirable to monitor the operation of the separator and the crankcase ventilation system. This may be performed using e.g. pressure sensors for determining the gas pressure upstream or downstream of the centrifugal separator.

[0009] However, these sensors need to be able to endure the harsh environment and the high temperature of the crankcase gas being cleaned in the separator. Also, the gas may contain oil and particles that may be detrimental for the function of the sensor.

[0010] Thus, there is a need in the art for improved sensor solutions for a crankcase gas separator.Summary of the Invention

[0011] It is an object of the invention to at least partly overcome one or more limitations of the prior art. In particular, it is an object to provide a centrifugal separator having a sensor that may better withstand the operational environment of the separator.

[0012] As a first aspect of the invention, there is provided a centrifugal separator for cleaning gas containing contaminants. The centrifugal separator comprises

[0013] a stationary casing, enclosing a separation space through which a gas flow is permitted;

[0014] a gas inlet and a gas outlet for guiding the flow of gas through the stationary casing to allow at least some of the contaminants to be separated from the flow of gas;

[0015] a drainage outlet configured to permit discharge of liquid contaminants that have been separated from the gas;

[0016] a rotor comprising a plurality of separation members arranged in said separation space and being arranged to rotate around an axis (X) of rotation;

[0017] a drive member for rotating the rotor;

[0018] wherein the centrifugal separator is arranged so that a main flow path for gas is formed from the gas inlet, through the stationary casing and out through the gas outlet, and further comprises a chamber enclosing a volume V that does not form part of the main flow path but is connected in a pressure-equalized manner with the main flow path;

[0019] and wherein the centrifugal separator further comprises a sensor arranged to generate a signal indicative of the gas pressure in said volume V of said chamber.

[0020] The first aspect of the invention is based on the insight that oil and particles present in the main gas flow may interfere with a sensor. Thus, arranging the sensor in a chamber having the same pressure as the gas flow outside of the chamber is beneficial since such risk of contaminants interfering, blocking or destroying the sensor is decreased.

[0021] As used herein, the term “axially” denotes a direction which is parallel to the rotational axis (X). Accordingly, relative terms such as “above”, “upper”, “top”, “below”, “lower”, and “bottom” refer to relative positions along the rotational axis (X). Correspondingly, the term “radially” denotes a direction extending radially from the rotational axis (X). A “radially inner position” thus refers to a position closer to the rotational axis (X) compared to “a radially outer position”. A radial plane is a planehaving its normal parallel to the axis (X) of rotation. An axial plane is a plane having its normal perpendicular to the axis (X) of rotation.

[0022] The contaminants in the gas may comprise liquid contaminants, such as oil, and soot.

[0023] Consequently, the centrifugal separator may be for separating liquid contaminants, such as oil, from gas. The gas may be crankcase gas of an internal combustion engine. However, the centrifugal separator may also be suitable for cleaning gases from other sources, for instance the environment of machine tools which frequently contains large amounts of liquid contaminants in the form of oil droplets or oil mist.

[0024] The stationary casing of the centrifugal separator may comprise a surrounding side wall, and an upper and lower end wall, which enclose the separation space.

[0025] The gas inlet may be in fluid communication and attached to an end wall of the stationary casing, such that gas entering through the gas inlet is directed to the separation space. The gas inlet may be arranged above or below the rotor of the centrifugal separator, i.e. above or below the separation space.

[0026] The gas outlet may in fluid communication with the stationary casing to allow cleaned gas to exit therefrom.

[0027] A main flow path is formed between the gas inlet and gas outlet. The main flow path is thus the path that at least the majority of the gas is guided from inlet through the gas outlet.

[0028] The drainage outlet may be arranged in the lower portion of the separator. The drainage outlet may be connected to the stationary casing or to e.g. a drive module comprising the drive member arranged below the stationary casing. In such examples, separated oil and contaminants may thus be drained from the stationary casing, via a drive module, and the out through the drainage outlet.

[0029] The rotor is arranged for rotation during operation of the separator by means of the drive member. The rotor may comprise a plurality of separation members arranged in the separation space. The separation members of the rotor are examples of surface-enlarging inserts that promote separation of contaminants from the gas. The separation members may be a stack of separation discs. The separation discs of the stack may be frustoconical. A frustoconical disc may have a planar portion extending in a plane that is perpendicular to the axis of rotation, and a frustoconical portion that may extend upwards or downwards. The planar portion may be closer to the rotational axis than the frustoconical portion. Further, the discsof the stack may be radial discs, in which substantially the whole disc extends in a plane having a normal that is perpendicular to the axis of rotation.

[0030] The separation members may also be one or several filter members, such as a coalescing filter elements and / or fibrous filter elements.

[0031] The rotor may comprise a shaft that is journaled within the stationary casing via at least one bearing, such as via an upper and lower bearing arranged axially above and below the plurality of separation members, respectively. The separation members may be arranged around such axial shaft.

[0032] The drive member may for example comprise a turbine wheel, rotated by means of an oil jet from the lubrication oil system of the combustion engine or a free jet wheel comprising a blow-back disk. However, the drive member may also be independent of the combustion engine and comprise an electrical motor, a hydraulic motor or a pneumatic motor.

[0033] The centrifugal separator further comprises a chamber and a sensor that is arranged to generate a signal indicative of the gas pressure in the volume V of said chamber. The volume V of the chamber does not form part of the main flow path but is connected in a pressure-equalized manner with the main flow path. Therefore, the pressure measured in the volume V corresponds to the pressure in the main flow path. Consequently, the chamber is arranged so that there is pressure equalization between the volume in the chamber and the volume outside the chamber, i.e. the volume that forms part of the main flow path.

[0034] In embodiments of the first aspect, the chamber has an inlet opening facing the main flow path, and wherein the chamber is arranged in a direction such that a central line C drawn through the volume V of the chamber from said inlet opening to an opposite end wall of the chamber is not aligned with the flow direction of the main flow path outside the chamber. In this way, the risk of contaminant particles blocking the inlet opening is decreased. The inlet opening is thus the inlet to the volume V of the chamber. The “opposite end wall” is thus a wall that encloses the volume V but is arranged opposite the position of the inlet opening. In embodiments, the sensor is arranged to generate a signal indicative of the gas pressure at the opposite end wall, i.e. the sensing element of the sensor may be positioned at the opposite end wall of the chamber.

[0035] The chamber may be arranged within the stationary casing for measuring a gas pressure within the stationary casing.In embodiments of the first aspect, the chamber is arranged at the gas inlet and / or the gas outlet. Thus, the chamber may be arranged only at the gas inlet, only at the gas outlet or at both the gas inlet and the gas outlet of the separator.

[0036] As an example, the gas inlet may comprise a gas inlet conduit, and the chamber may be arranged in a pressure-equalized manner with the gas inlet conduit via an inlet opening in a wall of the gas inlet conduit. The gas inlet is subjected to a larger amount of oil and particles since it comes into contact with the unseparated gas, which is why it may be more important to shield the sensor, or an opening to a sensor, at the gas inlet.

[0037] The opening in the wall of the gas inlet conduit is thus the inlet opening to the chamber, as discussed above.

[0038] As an example, the gas inlet conduit may extend in a direction D1, and the chamber may have an inlet opening facing the main flow path. The chamber may then be arranged in a direction such that a central line C drawn through the volume V of the chamber from said inlet opening to an opposite end wall of the chamber forms an angle of at least 45° such as at least 75°, such as being perpendicular, with D1.

[0039] The gas inlet conduit may be configured for connection to a hose or conduit for transporting gas to be cleaned to the separator. The gas inlet conduit may be a straight, curved or comprise both a straight portion and a curved portion, such as an upstream straight portion and a downstream curved portion. The curved portion may at least be partially curved around the axis X of rotation, such as spiralling axially downwards around the axis X of rotation.

[0040] In embodiments, the gas inlet is arranged for guiding the gas so that particles in the gas are pressed against an inner side wall of the gas inlet, and wherein the chamber has an inlet opening at a position in the gas inlet that is not positioned at the inner side wall onto which particles in the gas are pressed. Thereby, the sensor may be shielded from at least a major portion of contaminant particles in the gas to be cleaned.

[0041] As an example, the gas inlet may comprise a gas inlet conduit having a spiralling shape so that particles guided through the gas inlet conduit are pressed against an inner side wall that forms the outer lap of the spiralling shape, and wherein the chamber has an inlet opening at a position in gas inlet conduit that is not part of the outer lap of the spiralling shape.When gas is being guided through a conduit of spiralling shape, centrifugal forces may press contaminant particles in the gas against the “outer lap”, so that inner walls of the gas inlet conduit forming part of the “inner lap” come into contact with fewer particles in the gas. Thus, it may be an advantage to arrange the inlet opening to the chamber with the sensor at an inner wall that is not forming part of the outer lap. The outer lap of the inner wall may be the inner wall that is radially outside of the central line of the spiralling shape of the gas inlet conduit, as seen from the rotational axis around which the gas inlet conduit spirals.

[0042] The gas inlet conduit having a spiralling shape may spiral around the axis of rotation.

[0043] As an example, the chamber may have an inlet opening that is positioned centrally in the spiralling shape. In embodiments of the first aspect, the inlet opening has a cross-sectional area that is smaller than the cross-sectional area of the gas inlet conduit.

[0044] As an example, the inlet opening may have a cross-sectional area that is less than 50%, such as less than 25 % of the cross-sectional area of the gas inlet conduit.

[0045] According to embodiments, said gas inlet comprises a gas inlet conduit having a downstream end portion that opens up in a gas inlet chamber. Such gas inlet chamber is arranged around the axis of rotation (X), and the chamber is arranged in a pressure-equalized manner with said gas inlet chamber via an inlet opening in a wall of the gas inlet chamber, such as in an upper wall of the gas inlet chamber.

[0046] The gas inlet chamber has a larger cross-sectional area than the gas inlet conduit, as seen in the axial plane. The cross-sectional area is the area having a normal along the direction of the gas flow.

[0047] The gas inlet chamber may be arranged axially above the stationary casing and be arranged to communicate with the separation space.

[0048] In embodiments, the gas inlet conduit has a curved shape that forms an upper inner wall of the gas inlet conduit, whereas the lower wall of the gas inlet conduit opens up in the gas inlet chamber. Thus, the gas inlet chamber may have an upper end wall that has a curved shape, thus aiding in rotating the gas to be cleaned.

[0049] Arranging the chamber in which the pressure is measured in contact with a gas inlet chamber may allow for a more compact structure of the whole separator, since the sensor and any connections may be arranged centrally of the separator.According to embodiments, the gas outlet comprises a gas outlet conduit, and said chamber may be arranged in a pressure-equalized manner with said gas outlet conduit via an inlet opening in a wall of the gas outlet conduit.

[0050] Further, the gas outlet conduit may extend in a direction D2, and the chamber may have an inlet opening facing the main flow path. The chamber may then be arranged in a direction such that a central line C drawn through the volume V of the chamber from said inlet opening to an opposite end wall of the chamber forms an angle of at least 45° such as at least 75°, such as being perpendicular, with D2.

[0051] Further, the inlet opening may have a cross-sectional area that is smaller than the cross-sectional area of the gas outlet conduit.

[0052] As an example, the inlet opening may have a cross-sectional area that is less than 50%, such as less than 25 % of the cross-sectional area of the gas outlet conduit.

[0053] In embodiments, the gas outlet comprises a gas outlet chamber in which a valve element is arranged, and wherein said chamber is arranged in a pressure-equalized manner with said gas outlet chamber via an inlet opening in a wall the gas outlet chamber.

[0054] The gas outlet chamber has a larger cross-sectional area than the gas outlet conduit, as seen in the axial plane. The cross-sectional area is the area having a normal along the direction of the gas flow.

[0055] The valve element at the gas outlet may be arranged to restrict, or vary, the outflow of clean gas from the stationary casing. By such valve element, it is possible to limit negative pressures within the separator and thus the crankcase.

[0056] In embodiments of the first aspect, the sensor is a pressure sensor.

[0057] As an example, the pressure sensor may comprise a sensing element and a processing unit. The sensing element may then be arranged in the volume V of said chamber, and wherein the processing unit may be arranged outside of said volume V of said chamber.

[0058] The sensing element is thus responsive for the gas pressure, and the processing unit may be configured for converting the sensed pressure to an electrical variable, such as an electric signal that may be measured and processed. The processing unit may further comprise electronics that amplifies or changes the form of the electric signal.The sensing element may be a diaphragm sensing element, forming a differential pressure sensor measuring the difference between the pressure in the chamber a reference pressure, such as the ambient atmosphere. Other types of sensors are however possible.

[0059] As a second aspect of the invention, there is provided a method for cleaning gas containing contaminants, the method comprising

[0060] guiding gas containing contaminants to a centrifugal separator according to the first aspect above during rotation of the rotor,

[0061] discharging cleaned gas from the gas outlet, and

[0062] discharging contaminants from the drainage outlet.

[0063] The contaminants in the gas may comprise liquid contaminants, such as oil, and soot.

[0064] This aspect may generally present the same or corresponding advantages as the former aspects. Effects and features of the second aspect are largely analogous to those described above in connection with the first aspect.

[0065] Brief description of the Drawings

[0066] The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description, with reference to the appended drawings. In the drawings like reference numerals will be used for like elements unless stated otherwise.

[0067] Figure 1 is a schematic representation of an engine and a crankcase ventilation system according to some examples.

[0068] Figure 2 shows a cross section of a centrifugal separator according to some examples.

[0069] Figure 3 shows a cross-section of an embodiment of a gas inlet tube and a gas inlet chamber.

[0070] Figure 4 shows a cross-section of an embodiment of the gas outlet.

[0071] Figures 5a - 5c show an embodiment of a curved gas inlet having a pressure sensor.

[0072] Detailed Description

[0073] The centrifugal separator according to the present disclosure will be further illustrated by the following description with reference to the accompanying drawings.Figure 1 is a schematic illustration of an internal combustion engine (ICE) 10, which typically operates by combusting a fuel-air mixture within a cylinder to generate a high-pressure gas that causes a piston to move in a reciprocating movement. The reciprocating movement is converted by a crankshaft 14 into a rotation motion that can be used to propel a vehicle or drive a generator, for example.

[0074] During the combustion process, some of the high-pressure gases and a small amount of the fuel-air mixture may leak past the piston rings into the crankcase 12. This crankcase gas, also referred to as ‘blow-by’ gas, needs to be ventilated from the crankcase 12 to not impede the operation of the engine 10. As the crankcase gas typically contains unburnt fuel, oil vapour, and combustion byproducts, it is desirable to subject the vented gas to a cleaning process.

[0075] Figure 1 shows an example of a centrifugal separator 100 in which the crankcase gas is guided from the crankcase 12 via an exhaust conduit 131. The separator 100 comprises a gas inlet 112 for receiving the flow of gas from the exhaust conduit 131 and a gas outlet 114 through which the cleaned flow of gas may be exhausted from the separator 100. The gas inlet 112 and the gas outlet 114 may thus be arranged to guide the flow of gas through the separator 100 to allow the separator 100 to remove contaminants such as oil and particulate matter from the crankcase gas. The cleaned crankcase gas may then be transported away from the separator 100 by a conduit 130 which, according to some examples, feeds the gas back into the engine’s 10 intake for re-burning. In the present example, this may be achieved by feeding the gas to a turbocharger 135. The separated oil may preferably be returned to the crankcase 12 via a return conduit 132.

[0076] The pressure at the gas inlet 112 and / or the gas outlet 114 may be measured by means of one or several pressure sensors. The information of these pressures may be used to e.g. control the operation of the centrifugal separator 100 and / or to detect if the separator 100 has been disconnected from the crankcase ventilation system. The inventor has realized that the contaminants in the gas may interfere with the function of such a sensor, and that a position of the sensor away from the main gas flow may decrease such negative effect, as will be described below.

[0077] Figure 2 shows an example of a centrifugal separator 100 configured to separate a liquid phase from a gaseous phase by means of a rotational movement of a rotor 230. The separator 100 may be configured similarly to the one discussed in connection with figure 1. The separation takes place in a stationary casing, i.e. thestationary casing 210, defining at least a part of separation space 220, in which a plurality of separation members 232 are rotatably arranged. The separation members 232 forms part of rotor 230 extending through the separation space 220 in an axial direction X, around which the rotor 230 and the separation members 232 are arranged to rotate during operation. The rotor 230 may be brought to rotate by a driving member 234, which, for example, may be a turbine wheel driven by a stream of oil, such as engine lubricating oil. Other driving means are also possible, such as an electric motor.

[0078] The separation members 232 provide a separation aid in the form of a stack of frustoconical separation discs. Interspaces are provided between the separation discs 232, through which the crankcase gas can travel from an inner periphery towards an outer periphery while being separated into the liquid phase and the gaseous phase as the separation members 232 rotate in the separation space 220.

[0079] The axial thickness of each interspace between the discs in the stack 232 may e.g. be in the order of 0.5 -2 mm, such as 1-2 mm. The separation discs of the stack 232 may be made of plastic or metal.

[0080] In Figure 2, only some of the separation discs 232 are indicated. It will be appreciated that while the frustoconical separation discs 232 in the present example are stacked with their wide ends facing downwards, other configurations are also possible. In an example, the separation discs 232 may be stacked with their wide ends facing upwards. In further examples, other types of separation aids may be utilised, including, e.g., axially extending vanes projecting radially outwards from the rotor 230. The separation members 232 may also comprise one or several filter members, such as a coalescing filter elements and / or fibrous filter elements.

[0081] During operation, the flow of crankcase gas is guided into the separator 120 through the gas inlet 112, which in the present example is arranged in an upper, centre portion of the stationary casing 210. The gas enters the stack of separation members 232 from a central portion thereof. As the separation members 232 rotate, heavy constituents such as oil particles are separated from the gas and propelled as droplets against a circumferential inner wall surface 214 of the stationary casing 210. The separated liquid phase may be transported by gravity along the inner wall 214 and through a lower bearing 236, or via through-holes next to the lower bearing 236, to a lower end portion 212 of the separator 100 - in this example a drive housing - and further through a drainage outlet 215 for liquid contaminants.The separator 100 also includes a valve device 120, which is connected to the gas outlet 114. The valve device 120 may be connected in series with the gas outlet 114 and the gas outlet conduit 130, such that the flow of gas exiting the separator 100 passes through the valve device 120 on its way from an opening 120 in the stationary casing 210 to the gas outlet conduit 130. The valve device 120 provides a variable constriction of the flow path, which may be used to protect the separator 100 and the crankcase 12 from excessive negative pressures, such as negative pressures generated by a downstream turbocharger 135.

[0082] The variable constriction may be formed by a valve element 122, such as a diaphragm or a membrane, which may be actuated by the pressure differential between the interior and the exterior of the valve device 120. The valve element 122 may interact with a valve seat 125 to form the variable constriction of the flow path. In some examples, an elastic element 127, such as a spring, may be arranged to push the valve element 122 away from the seat 125 to allow the valve device 110 to be in a normally open state.

[0083] The main flow of the crankcase gas and the cleaned gas through the separator 100 are indicated by arrows A in Fig. 2. Hence, the centrifugal separator 100 is arranged so that a main flow path for gas is formed from the gas inlet 112, through the stationary casing 210 and out through the gas outlet 114.

[0084] In this example, the separator 100 further comprises a chamber 20 at the gas inlet 112. The walls of the chamber 20 encloses a volume V. Due to a gas inlet opening 22 in the wall of the gas inlet conduit 50, the volume V is connected in a pressure-equalized manner with the main flow path but does not itself form part of the main flow path for the gas through the separator. The inlet opening 22 to the chamber 20 has a cross-sectional area that is smaller than the cross-sectional area of the gas inlet conduit 50, such as having cross-sectional area that is less than half, such as less than 25 % of the cross-sectional area of the gas inlet conduit 50.

[0085] In addition, the separator 100 comprises a sensor 30 that is arranged to generate a signal indicative of the gas pressure of the volume V of the chamber 20.

[0086] By measuring the pressure in the chamber 20, i.e. by arranging the sensor 30 so that the gas pressure is measured in the chamber 20, the risk of oil and soot particles clogging the sensor 30 or interfering with the sensor 30 decreases, since the volume V of the chamber 20 does not form part of the main flow path.

[0087] The pressure sensor 30 comprises a sensing element 31 and a processing unit 33. In this example, the sensing element 31 is arranged in the volume V of thechamber so that it forms at least part of an opposite end wall 23 of the chamber 20, i.e. a wall opposite the inlet opening 22 of the chamber 20. The processing unit 33, on the other hand, is arranged outside of the volume V of the 20. This may thus wired facilitate connections to the sensor 30. The processing unit 33 is configured for converting the sensed pressure to an electrical variable, such as an electric signal that may be measured and processed. The processing unit 33 may further comprise electronics that amplifies or changes the form of the electric signal. The centrifugal separator 100 may further comprise a control unit (not shown) that is configured to receive input from the processing unit 33 and send operational requests to e.g. an electric drive motor 234 used for rotating the rotor 230 or to other parts of the internal combustion system. Thus, the control unit may not form part of the centrifugal separator but may form part of e.g. an On-Board Diagnostics (OBD) system in a vehicle, such as a truck.

[0088] Pressure measurements by the pressure sensors 30 arranged at the gas inlet 112 and / or the gas outlet may be used in methods or analysis for determining a malfunction state, in which the separator has been bypassed, disconnected, or otherwise tampered with.

[0089] As visualized in Fig. 1 , the chamber 20 at the gas inlet is oriented in a direction to further decrease the risk of any soot or oil (or other contaminants) from the main gas flow entering the chamber 20. In this example, the chamber 20 is arranged in a direction such that the central line C drawn through the volume V of the chamber 20 from the inlet opening to the opposite end wall 23 of the chamber 20 - in this case to the sensing element 31 - is not aligned with the flow direction of the main flow path outside the chamber 20. Rather, the central line C is oriented more or less perpendicularly to the main flow path in the gas inlet conduit 50 outside the chamber 20 (indicated by arrow A) .

[0090] In certain configurations of the centrifugal separator 100, the gas inlet conduit extends with an angle to the axis X of rotation. Such an example is illustrated in Fig.

[0091] 3, in which the gas inlet 112 comprises a gas inlet conduit 50 having a downstream end portion 52 that ends in a gas inlet chamber 60 that is arranged around the axis X of rotation. The gas inlet conduit 50 itself is arranged around the perpendicularly to the axis X of rotation and has an upstream straight portion 51 configured for being connected to a hose for receiving the gas to be cleaned. In other embodiments, the gas inlet conduit 50 is curved, such as curved around the axis X of rotation, and has its downstream end portion 52 exiting in the gas inlet chamber 60. The whole gasinlet 112, with a conduit 50 and gas inlet chamber 60, may be formed as a single unit that is attached to the upper end wall of the stationary casing 210.

[0092] Consequently, the gas inlet conduit 50 may be integrated to, or forms part of, a wall that defines the volume of the gas inlet chamber 60, which in this example means that the walls of the gas inlet conduit also form and defines at least a portion of the volume of the gas inlet chamber 60.

[0093] The gas inlet chamber 60 is in fluid communication with the separation space 220, so that gas entering the gas inlet chamber 60 is transported through a central volume formed within the disc stack 232 and then through the interspaces that are formed between the separation discs.

[0094] The main gas flow A is thus formed from the gas inlet conduit 50, via the gas inlet chamber, and then to the separation space 220.

[0095] The chamber 20 in which the pressure is measured is arranged in a pressure-equalized manner with the inlet chamber 60 via an inlet opening 22 in a wall of the gas inlet chamber 60. In this example, the chamber 20 is arranged in an upper portion of the gas inlet chamber 60. Furthermore, the chamber 20 is arranged in a direction such that the central line C drawn through the volume V of the chamber 20 from the inlet opening to the opposite end wall 23 of the chamber 20 - in this case to the sensing element 31 of the sensor 30 - is not aligned with the flow direction of the main flow path outside the chamber 20.

[0096] The chamber 20 in which the gas pressure is measured may be arranged at the gas outlet 120 instead, or in some examples at both the gas inlet 112 and the gas outlet 120. Fig. 4 shows a side view of the separator 100 from Fig. 2, and thus a cross-section of the gas outlet 112. For clarity reasons, the valve member 122 and spring 127 have been omitted from Fig. 4. The gas outlet comprises a gas outlet conduit 130 that is connected to a gas outlet chamber 70, so that gas exiting the opening 80 in the stationary casing 210 is led to the gas outlet chamber 70 - via valve seat 125 - and further out through the gas outlet conduit 130. As in the previous figures, the main flow path is illustrated by arrows A in Fig. 4.

[0097] In this example, the chamber 20 in which the pressure is measured is arranged in a pressure-equalized manner with the gas outlet chamber 70 - i.e. the chamber in which the valve element 120 is arranged - via an inlet opening 22 in a wall the gas outlet chamber 70. The chamber 20 having a volume V and the pressure sensor 30 may be arranged as discussed in relation to Fig. 2 and 3 above. As an example,the chamber 20 at the gas outlet 112 may be oriented in a direction to further decrease the risk of any soot or oil (or other contaminants) from the main gas flow entering the chamber 20. As seen in Fig. 4, the chamber 20 is arranged in a direction such that the central line C drawn through the volume V of the chamber 20 from the inlet opening 22 to the opposite end wall 23 of the chamber 20 - in this case to the sensing element 31 - is not aligned with the flow direction of the main flow path outside the chamber 20. Rather, the central line C is oriented with an angle to the main flow path (indicated by arrow A) in the gas outlet chamber 60 outside of the chamber 20.

[0098] In other embodiments, the chamber 20 in which the pressure is measured is arranged in a pressure-equalized manner with the gas outlet conduit 130 via an inlet opening (not shown) in a wall of the gas outlet conduit 130. The gas outlet conduit 130 is arranged downstream of the gas outlet chamber 60, thus meaning that the chamber 20 may be arranged downstream of the gas outlet chamber 60. Also, such an opening in the wall of the gas outlet conduit may have a cross-sectional area that is substantially smaller than the cross-sectional area of the gas outlet conduit 130.

[0099] Figs. 5a and 5b show an embodiment of a centrifugal separator 1 having a curved inlet 112. Fig. 5a shows a top view of the separator 1 , and thus the top of the stationary casing 210 onto which the gas inlet 112 is attached. The gas inlet 112 comprises a gas inlet conduit 50, having a straight upstream portion 51 - thus configured to be connected to a hose or the like and for receiving the gas to be cleaned - and a curved downstream end portion 52 that opens up in a gas inlet chamber 60. The pressure sensor 30 is arranged to measure a pressure in a chamber 20 that is in fluid communication with this gas inlet chamber 60. This is further illustrated in Fig. 5b, which shows the section of the inlet 112 along line Y in Fig. 5a.

[0100] The gas inlet chamber 60 is in fluid communication with the separation space 220 via channels 61 that are arranged radially outside an upper bearing 62 used to journal the rotor 230 within the stationary casing 210. The gas to be cleaned thus flows through the straight portion 51, via the curved portion 52 down to the gas inlet chamber 60. The chamber 20 in which the pressure is measured opens up to the gas inlet chamber 60 only, and not to the curved portion 52 or straight portion 51. The curved portion 52 opens up in the gas inlet chamber 60 at a position that is off-center relative the axis X of rotation, i.e. at a position that is radially displaced relative the axis X of rotation in the gas inlet chamber 60. In this way, the volume Vof the chamber 20 does not form part of the main flow path for the gas. As discussed in relation to Figs. 2-4 above, the sensor 30 comprises a sensing element 31 forming an end wall in the chamber 20, and the processing unit 33 is arranged outside the chamber 20, namely on the outer surface of the gas inlet 112, for easy access with wired connections.

[0101] As seen in Figs. 5a and 5b, the curved gas inlet conduit 50 has with its curved portion 52 a spiralling shape. Thereby, contaminant particles in the gas are pressed against an inner side wall 57 of the gas inlet conduit 50 as the gas is guided therein. The chamber 20 has an inlet opening 22 at a position in the gas inlet conduit 50 that is not positioned at such an inner side wall 57 onto which particles in the gas are pressed. Thereby, the sensor may be shielded from at least a major portion of contaminant particles in the gas to be cleaned. This is further illustrated in Fig. 5c, which shows the cross-section of the curved portion 52 of the gas inlet conduit 50 at line Z in Fig. 5a. Since the curved shape of the gas inlet conduit spirals around the axis of rotation X, contaminant in the gas being guided through the gas inlet conduit 50 will be pressed against the “outer lap” 57 of the inner wall of the conduit 50. Thus, the inner wall forming part of the “inner lap” 58 is being subjected to fewer amount of contaminants, meaning that it will be an advantage to position an inlet 22 to the chamber 20 at a position on the inner wall that is not part of the outer lap 57, such anywhere on the inner lap 58. The outer lap 57 of the inner wall of conduit 50 is in this case the part of the inner wall that is radially outside (as seen in relation to rotational axis X) the central line C2 of the spiralling gas inlet conduit 50.

[0102] As seen in the example of Fig. 5b, the chamber 20 has an inlet opening 22 that is positioned centrally in the spiralling shape, in an inner wall that is not part of an inner wall 57 forming an “outer lap” of the spiralling shape of the gas inlet conduit 50.

[0103] The invention is not limited to the embodiment disclosed but may be varied and modified within the scope of the claims set out below. The invention is not limited to the orientation of the axis (X) of rotation disclosed in the figures. The term “centrifugal separator” also comprises centrifugal separators with a substantially horizontally oriented axis of rotation. In the above the inventive concept has mainly been described with reference to a limited number of examples. However, as is readily appreciated by a person skilled in the art, other examples than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.

Claims

CLAIMS1. A centrifugal separator (100) for cleaning gas containing contaminants, said centrifugal separator (100) comprisinga stationary casing (210), enclosing a separation space (220) through which a gas flow is permitted;a gas inlet (112) and a gas outlet (114) for guiding the flow of gas through the stationary casing (210) to allow at least some of the contaminants to be separated from the flow of gas;a drainage outlet (215) configured to permit discharge of liquid contaminants that have been separated from the gas;a rotor (230) comprising a plurality of separation members (232) arranged in said separation space (220) and being arranged to rotate around an axis (X) of rotation;a drive member (234) for rotating the rotor (230);wherein the centrifugal separator (100) is arranged so that a main flow path for gas is formed from the gas inlet (112), through the stationary casing (210) and out through the gas outlet (114), and further comprises a chamber (20) enclosing a volume V that does not form part of the main flow path but is connected in a pressure-equalized manner with the main flow path;and wherein the centrifugal separator (100) further comprises a sensor (30) arranged to generate a signal indicative of the gas pressure in said volume V of said chamber (20).

2. A centrifugal separator (100) according to claim 1, wherein said chamber (20) has an inlet opening (22) facing the main flow path, and wherein the chamber (20) is arranged in a direction such that a central line C drawn through the volume V of the chamber (20) from said inlet opening (22) to an opposite end wall (23) of the chamber (20) is not aligned with the flow direction of the main flow path outside said chamber (20).

3. A centrifugal separator (100) according to claim 1 or 2, wherein said chamber (20) is arranged at the gas inlet (112) and / or the gas outlet (114).

4. A centrifugal separator (100) according to claim 3, wherein said gas inlet (112) comprises a gas inlet conduit (50), and wherein said chamber (20) is arranged in a pressure-equalized manner with said gas inlet conduit (50) via an inlet opening (22) in a wall of the gas inlet conduit (50).

5. A centrifugal separator (100) according to claim 4, wherein the gas inlet conduit (50) extends in a direction D1, and wherein the chamber (20) has an inlet opening (22) facing the main flow path and is arranged in a direction such that a central line C drawn through the volume V of the chamber (20) from said inlet opening (22) to an opposite end wall (23) of the chamber (20) forms an angle of at least 45° with D1.

6. A centrifugal separator (100) according to claim 4 or 5, wherein said inlet opening (22) has a cross-sectional area that is smaller than the cross-sectional area of the gas inlet conduit (50).

7. A centrifugal separator (100) according to claim 3, wherein said gas inlet (112) comprises a gas inlet conduit (50) having a downstream end portion (52) that opens up in a gas inlet chamber (60), said gas inlet chamber (60) being arranged around the axis of rotation (X), and wherein said chamber (20) is arranged in a pressure-equalized manner with said gas inlet chamber (60) via an inlet opening (22) in a wall of the gas inlet chamber (60).

8. A centrifugal separator (100) according to any one of claims 3-7, wherein the gas inlet (112) is arranged for guiding the gas so that particles in the gas are pressed against an inner side wall (57) of the gas inlet (112), and wherein the chamber (20) has an inlet opening (22) at a position in the gas inlet (112) that is not positioned at said inner side wall (57) onto which particles in the gas are pressed.

9. A centrifugal separator (100) according to claim 8, wherein the gas inlet (112) comprises a gas inlet conduit (50) having a spiralling shape so that particles guided through the gas inlet conduit (50) are pressed against an inner side wall (57) that forms the outer lap of the spiralling shape, and wherein the chamber (20) has an inlet opening (22) at a position in gas inlet conduit (50) that is not part of the outer lap of the spiralling shape.1810. A centrifugal separator (100) according to claim 8 or 9, wherein the chamber (20) has an inlet opening (22) that is positioned centrally in the spiralling shape.

11. A centrifugal separator (100) according to claim 3, wherein said gas outlet (114) comprises a gas outlet conduit (130), and wherein said chamber (20) is arranged in a pressure-equalized manner with said gas outlet conduit (130) via an inlet opening (22) in a wall of the gas outlet conduit (130).

12. A centrifugal separator (100) according to claim 11, wherein said inlet opening (22) has a cross-sectional area that is smaller than the cross-sectional area of the gas outlet conduit (130).

13. A centrifugal separator (100) according to claim 3, wherein said gas outlet (114) comprises a gas outlet chamber (70) in which a valve element (122) is arranged, and wherein said chamber (20) is arranged in a pressure-equalized manner with said gas outlet chamber (70) via an inlet opening (22) in a wall the gas outlet chamber (70).

14. A centrifugal separator (100) according to any previous claim, wherein said sensor (30) is a pressure sensor.

15. A centrifugal separator (100) according to claim 14, wherein said pressure sensor (30) comprises a sensing element (31) and a processing unit (33), wherein said sensing element (31) is arranged in said volume V of said chamber (20), and wherein said processing unit (33) is arranged outside of said volume V of said chamber (20).

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