Cylinder head cover and method for manufacturing a cylinder head cover

Description

[0001] The present invention relates to a cylinder head cover for an internal combustion engine. Such a cylinder head cover preferably comprises a cover body which, in the assembled state of the cylinder head cover, is arranged on an engine block of the internal combustion engine and covers a cylinder head of the internal combustion engine. Furthermore, such a cylinder head cover preferably comprises a separator device through which a raw gas stream can be passed for cleaning, wherein the separator device is, for example, formed and / or delimited at least partially by the cover body. Alternatively or additionally to such a separator device, a valve device may be provided, which is, in particular, formed and / or delimited at least partially by the cover body.Separation devices, in particular oil separators for internal combustion engines, are known, for example, from WO 2015 / 018691 A1, US 8,915,237 B2, US 2015 / 240732 A1 or US 8,152,884 B1.

[0002] US 8,915,237 B2 discloses in particular a cylinder head cover for an internal combustion engine according to the preamble of claim 1.

[0003] The present invention is based on the objective of providing a cylinder head cover for an internal combustion engine which, in addition to the pure covering function, has further integrated functions.

[0004] This problem is solved by a cylinder head cover for an internal combustion engine according to claim 1.

[0005] Because the cylinder head cover according to the invention comprises a nozzle device which is integrated into the separator device and / or the valve device, the cylinder head cover preferably has at least one further function in addition to its pure covering function. In particular, this allows for a space-saving and cost-effective design of an internal combustion engine.

[0006] According to the invention, the nozzle device comprises a suction jet nozzle by means of which a gas flow can be drawn in and / or discharged.

[0007] According to the invention, it is further provided that the suction jet nozzle comprises a suction section into which, on the one hand, a drive nozzle of the suction jet nozzle and, on the other hand, a gas flow supply open, wherein the suction section is formed in at least two parts, wherein an inner part with respect to a radial direction is formed by an insert element which has an outer cross-section that is essentially constant along a flow direction and / or an inner cross-section that varies along a flow direction, wherein the insert element can be inserted into an outer part of the suction section with respect to a radial direction, wherein the insert element can be inserted into the outer part of the suction section against the flow direction.

[0008] Preferably, the suction jet nozzle comprises a drive nozzle to which a driving medium, in particular charge air, can be supplied to generate a suction effect for drawing in the gas flow.

[0009] In particular, it may be provided that the propellant medium, for example charge air, can be passed through the propellant nozzle in order to create a suction effect to draw in the gas flow.

[0010] The motive medium, in particular the charge air, is preferably the medium which can be supplied to a combustion chamber of the internal combustion engine, especially after passing through a compression device to increase the pressure.

[0011] It can be advantageous if the gas flow is the raw gas flow passed through the separator device.

[0012] The gas flow is preferably crankcase exhaust gas, that is, in particular contaminated gas from a crankcase of the internal combustion engine.

[0013] By drawing in the gas flow using the nozzle device, crankcase ventilation of the internal combustion engine can preferably be achieved. According to the invention, the suction jet nozzle further comprises a suction section into which a drive nozzle of the suction jet nozzle and a gas flow supply open. In particular, the drive nozzle and the gas flow supply are arranged on a common inlet side of the suction section.

[0014] The gas flow to be drawn in and / or discharged by means of the nozzle device can preferably be supplied to the suction section by means of the gas flow supply.

[0015] It may be provided that the suction section, viewed along a flow direction, comprises a tapered section, a cylindrical section and / or a widening section.

[0016] The flow direction is, in particular, the flow direction of the motive medium guided through the drive nozzle and / or flowing out of the drive nozzle. Furthermore, the flow direction is preferably also the flow direction of the motive medium and / or the aspirated gas flow in the suction section.

[0017] The tapered section of the suction section is preferably a section of the suction section following the gas flow supply and / or the drive nozzle, particularly with regard to the flow direction.

[0018] In particular, the combination of the drive nozzle with the tapered section of the suction section preferably results in a suction effect in the vicinity of the drive nozzle when the driving medium flows from the drive nozzle into the tapered section.

[0019] The drive nozzle and the tapered section, in particular the entire suction section, are preferably arranged essentially coaxially to each other.

[0020] Preferably, the drive nozzle and the suction section, in particular the tapered section, the cylinder section and / or the widening section, are essentially rotationally symmetrical.

[0021] Preferably, in particular, an inner contour of the suction section is essentially rotationally symmetrical.

[0022] The suction section and the drive nozzle are preferably arranged at least approximately coaxially to each other, with a common central axis preferably being a common axis of rotation.

[0023] It can be advantageous if the gas flow supply enters the suction section in an approximately ring-shaped manner.

[0024] The gas flow supply preferably surrounds the drive nozzle in a substantially ring-shaped manner.

[0025] The gas flow supply preferably allows the drive nozzle to be surrounded by a ring-shaped flow of gas to be drawn in.

[0026] It can be advantageous if the suction section is designed in at least two parts.

[0027] An outer part with respect to a radial direction is preferably formed by a housing component of the separating device and / or by a housing component of the valve device and / or by the hood body.

[0028] A housing component is, for example, a cover element.

[0029] In particular, it may be provided that an outer part of the suction section with respect to a radial direction is formed by a common housing component of both the separating device and the valve device.

[0030] The outer part with respect to the radial direction is preferably a substantially cylindrical tube, for example a connecting piece, of the cylinder head cover.

[0031] According to the invention, the suction section is designed to be at least two-part, wherein an inner part with respect to a radial direction is formed by an insert element which can be inserted into an outer part of the suction section with respect to a radial direction.

[0032] The inner part and the outer part are preferably connectable to each other by means of a snap connection and / or a clip connection, in particular with regard to an insertion direction or insertion direction of the insert element relative to each other.

[0033] According to the invention, the insert element has an outer cross-section that is essentially constant along a flow direction and / or an inner cross-section that varies along a flow direction.

[0034] The insert element is preferably stable and reliably recoilable and / or fixed within a substantially cylindrical element. At the same time, the insert element preferably creates a flow variation zone.

[0035] Preferably, the insert element forms a flow constriction to generate and / or optimize a suction effect of the suction jet nozzle of the nozzle device.

[0036] Preferably, a tapered section, a cylindrical section and / or an expanding section of the suction section is formed by the insert element.

[0037] The insert element is preferably formed in one piece.

[0038] In particular, it may be provided that the insert element is designed as a plastic component, especially as an injection-molded plastic component.

[0039] It can be advantageous if the insert element includes a locking device, in particular one or more locking elements, for securing the insert element to an outer part of the suction section, which has at least two parts.

[0040] The insert element is preferably formed in one piece and preferably comprises, in addition to the tapered section, the cylindrical section and / or the widening section, one or more locking elements.

[0041] In one embodiment of the invention, the hood body, a cover element of the separating device, a cover element of the valve device, a suction section of the nozzle device, and / or a drive nozzle of the nozzle device may be formed by one or more plastic components, in particular injection-molded plastic components. In particular, it may be provided that an outer part of the suction section is formed integrally with the hood body or a cover element as an injection-molded plastic component.

[0042] The valve device preferably includes a pressure regulating valve.

[0043] The pressure regulating valve preferably allows the volume flow of the gas stream to be discharged via the nozzle device to be controlled, in particular depending on a pressure difference between the pressure in an interior space of the combustion engine containing the gas stream to be extracted on the one hand and the ambient pressure of the combustion engine on the other.

[0044] In one embodiment of the invention, the separation device may comprise one or more separation chambers, which are delimited by the hood body and a cover element of the separation device, wherein the hood body and / or the cover element are preferably each formed in one piece and, in addition to the one or more separation chambers, preferably form and / or delimit the following: at least one valve chamber for receiving a valve element of the valve device; and / or a gas flow supply of the nozzle device; and / or a drive nozzle of the nozzle device; and / or a drive medium connection of the nozzle device; and / or an outlet nozzle for discharging the drive medium and / or the gas flow.

[0045] The nozzle device preferably forms an ejector for efficient crankcase exhaust gas discharge.

[0046] The separation device is preferably an oil separator, in particular a fine separator.

[0047] The present disclosure further relates to a method for manufacturing a cylinder head cover.

[0048] The disclosure is based on the objective of providing a method by which a cylinder head cover can be easily manufactured, which, in addition to a purely covering function, has further functions.

[0049] This problem is solved by a method for manufacturing a cylinder head cover, the method comprising: providing a cover body which, in the assembled state of the cylinder head cover, is arranged on an engine block of the internal combustion engine and covers a cylinder head of the internal combustion engine; Providing and arranging a cover element on the hood body to form at least one separation chamber of a separation device and / or at least one valve chamber of a valve device, wherein the hood body and / or the cover element comprise or form at least one section of a nozzle device.

[0050] The method preferably has one or more of the features and / or advantages described in connection with the cylinder head cover according to the invention.

[0051] Preferably, the cylinder head cover according to the invention can be manufactured by carrying out the method.

[0052] Furthermore, the cylinder head cover according to the invention and / or the method may have one or more of the features and / or advantages described below: The nozzle device preferably serves for vacuum-assisted crankcase ventilation and / or for efficient oil separation.

[0053] The nozzle device can preferably be provided as an alternative or supplement to an external pump or an external ejector.

[0054] Preferably, the nozzle device of the cylinder head cover according to the invention has no moving parts during operation and / or no electronic components and / or no control system.

[0055] By integrating the nozzle device into the cylinder head cover, a particularly compact design for the entire crankcase ventilation system can preferably be achieved.

[0056] The nozzle device is preferably integrated into the valve device.

[0057] In particular, it may be provided that a suction section of the nozzle device is arranged and / or designed in an outlet nozzle of the pressure regulating valve.

[0058] The suction section is or preferably comprises a mixing tube in which the gas flow to be drawn in and / or discharged is mixed with the motive medium.

[0059] The mixing tube can, for example, be an insert element (insert part) for insertion into the outlet nozzle of the pressure regulating valve.

[0060] Furthermore, the mixing tube can be formed by appropriately shaping the outlet nozzle.

[0061] The drive nozzle is preferably formed by suitable shaping of the pressure regulating valve and / or a cover element.

[0062] It can be advantageous if a cover element of the separating device forms both a section of the separating device and of the valve device and / or the nozzle device.

[0063] Preferably, a propellant medium connection, an outlet nozzle and a cover element, which delimits one or more separation chambers and / or one or more valve chambers, are formed in one piece, for example as an injection-molded plastic component.

[0064] The nozzle device is preferably arranged at least sectionally between the separating device and the valve device.

[0065] Further preferred features and / or advantages of the invention are the subject of the following description and the graphic representation of an exemplary embodiment.

[0066] The drawings show: Fig. 1 a schematic perspective view of a cylinder head cover; Fig. 2 a schematic perspective section through a suction section and a drive nozzle of a nozzle assembly of the cylinder head cover. Fig. 1 ; Fig. 3 shows a further schematic perspective section through the nozzle device of the cylinder head cover. Fig. 1 Fig. 4 shows a schematic top view of the upper side of the cylinder head cover. Fig. 1 ; Fig. 5 a schematic section along line 5-5 in Fig. 4 ; Fig. 6 an enlarged view of area VI in Fig. 5 ; Fig. 7 a schematic section along line 7-7 in Fig. 4 ; Fig. 8 a schematic section along line 8-8 in Fig. 4 ; Fig. 9 a schematic section along line 9-9 in Fig. 4 ; Fig. 10 a schematic section along line 10-10 in Fig. 4 ; and Fig. 11 a schematic section along line 11-11 in Fig. 4 .

[0067] Identical or functionally equivalent elements are provided with the same reference symbols in all figures.

[0068] One in the Fig. 1 bis 11 The illustrated embodiment of a cylinder head cover designated as a whole by 100 is used in particular on an internal combustion engine 102, for example a vehicle engine.

[0069] The cylinder head cover 100 is specifically arranged on a cylinder head 104 of the internal combustion engine 102 in order to cover the cylinder head 104.

[0070] In conventional known embodiments, the cylinder head cover 100 can serve exclusively to cover the cylinder head 104.

[0071] Preferably, however, the cylinder head cover 100 has further functions in order to provide, in particular, a particularly compact internal combustion engine 102.

[0072] The cylinder head cover 100 according to the one in the Fig. 1 bis 11 The illustrated embodiment includes in particular a hood body 106, which fulfills the function of a conventional cylinder head hood 100 and covers the cylinder head 104.

[0073] The hood body 106, for example, is a plastic component, such as an injection-molded plastic component.

[0074] Additionally, the cylinder head cover 100 preferably includes a separator device 108 and / or a valve device 110.

[0075] The separating device 108 is in particular an oil separator 112, for example a fine separator 114, for separating oil, in particular oil droplets, from a gas stream.

[0076] In particular, the separating device 108 serves to separate oil from a raw gas stream, which originates, for example, from the cylinder head 104 and / or a crankcase of the internal combustion engine 102.

[0077] The separation device 108 preferably comprises one or more separation chambers 116, which are provided, for example, with separation elements, in particular impact separators, filter elements, etc.

[0078] The one or more separation chambers 116 are, in particular, delimited on one side by the hood body 106. On the other hand, a cover element 118 is provided which delimits the one or more separation chambers 116.

[0079] Preferably, the one or more separation chambers 116 are formed entirely by means of the hood body 106 and the cover element 118.

[0080] The lid element 118, for example, is a plastic component, in particular an injection-molded plastic component.

[0081] Preferably the cover element 118 is arranged on an inside or outside of the hood body 106, for example welded in place.

[0082] During the Fig. 1 bis 11 In the illustrated embodiment of the cylinder head cover 100, the cover element 118 is arranged on an outer side of the cover body 106.

[0083] The separating device 108 comprises an inlet section through which raw gas to be cleaned can flow into the separating device 108, in particular can be drawn in.

[0084] Furthermore, the separating device 108 includes an outlet through which purified gas can be discharged.

[0085] The outlet of the separating device 108 is preferably formed by the valve device 110.

[0086] By means of the valve device 110, it is therefore possible to... Fig. 1 bis 11 In the illustrated embodiment of the cylinder head cover 100, a gas flow passing through the separator device 108 is regulated.

[0087] The valve device 110 is preferably formed section by section by the cover element 118 of the separating device 108.

[0088] In particular, a valve chamber 120 of the valve device 110 is limited by the cover element 118.

[0089] The valve chamber 120 is in particular a space in which a valve element 122, in particular a diaphragm 124, of the valve device 110 is received or can be received.

[0090] The valve device 110 preferably further comprises a support plate 126, on which a spring element 128 of the valve device 110 acts.

[0091] By means of the spring element 128, the support plate 126, which is further connected to the diaphragm 124, can be arranged in an open position under given pressure conditions.

[0092] In this open position, a gas flow can in particular flow out of the separating device 108 and be fed into a gas flow supply 130.

[0093] The valve device 110 is in particular designed as a pressure regulating valve 132, in which an opening or a closing of the valve device 110 results automatically from varying pressure conditions on the two sides of the valve element 122.

[0094] One side of the valve element 122 is connected to the environment of the cylinder head cover 100 via a reference pressure hole 134 in a pressure regulating valve cover 136 of the valve device 110, so that the ambient air pressure is always present on this side of the valve element 122.

[0095] The other side of the valve element 122 is connected, on the one hand, to the separating device 108 and, on the other hand, to a nozzle device 138 which is yet to be described, in a fluid-effective and / or pressure-effective manner.

[0096] The valve element 122 is in particular movable and can be brought into an open or closed position in such a way that a fluid connection between the separating device 108 and the nozzle device 138 can be established or separated.

[0097] As especially from Fig. 6 As can be seen, the valve device 110 is essentially arranged on an outer side of the cover element 118 facing away from the hood body 106.

[0098] The pressure regulating valve cover 136 is secured to the cover element 118 in particular by means of a clip connection and / or snap connection and / or weld connection.

[0099] The nozzle device 138 includes in particular a suction jet nozzle 140.

[0100] The suction jet nozzle 140 includes in particular a drive nozzle 142 through which a driving medium, for example charge air, can be passed.

[0101] By means of the drive nozzle 142 and the drive medium passed through the drive nozzle 142, a suction effect can preferably be generated in a suction section 144 of the suction jet nozzle 140.

[0102] This suction effect can be used in particular to draw gas from the separator device 108.

[0103] The gas flow supply 130 preferably leads into the suction section 144.

[0104] The gas flow supply 130 is preferably essentially ring-shaped and surrounds the drive nozzle 142.

[0105] By means of the gas flow supply 130 and the drive nozzle 142, the driving medium and the gas discharged from the separator device 108 can thus be supplied essentially coaxially to the suction section 144.

[0106] The suction section 144 is essentially tubular in shape.

[0107] Preferably, the suction section 144 comprises a section 148 tapering along a flow direction 146, a cylinder section 150 and a section 152 widening in the flow direction 146.

[0108] The tapered section 148, the cylindrical section 150 and the widening section 152 are preferably arranged successively in this order along the flow direction 146.

[0109] The flow direction 146 is in particular the flow direction 146 of the motive medium, which is supplied to the suction section 144 through the motive nozzle 142, and / or of the gas, which is drawn into the suction section 144 via the gas flow supply 130.

[0110] The tapered section 148 has an internal cross-section that tapers along the flow direction 146. In particular, the tapered section 148 preferably surrounds a frustoconical cavity.

[0111] The cylinder section 150 preferably has an internal cross-section that is essentially constant along the flow direction 146, for example circular. In particular, the cylinder section 150 preferably surrounds a cylindrical, for example circular cylindrical, cavity.

[0112] The expanding section 152 preferably has an internal cross-section that widens in the flow direction 146. Preferably, the expanding section 152 surrounds a frustoconical cavity.

[0113] By means of the tapered section 148, the cylinder section 150 and the widening section 152, a flow narrowing is formed in the suction section 144, which allows a suction effect of the suction jet nozzle 140 to be generated and / or optimized.

[0114] The suction section 144 is preferably integrated into an outlet nozzle 154.

[0115] The outlet nozzle 154 is in particular a connection nozzle for connecting a gas-carrying hose in order to ultimately supply charge air together with the exhausted gas from the oil separator 112 to the combustion chambers of the internal combustion engine 102.

[0116] According to the invention, the suction section 144 is designed in two parts or in more parts.

[0117] For example, it may be provided that a radially inner part of the suction section 144 with respect to the flow direction 146, which is hereinafter referred to as radially inner part 156, is designed as a plastic component, in particular an injection-molded plastic component.

[0118] The radially inner part 156 is, for example, an insert element 158, which can be inserted, for example, into a substantially hollow-circular radially outer part 160 of the suction section 144. The radially outer part 160 of the suction section 144 is preferably a component of the hood body 106 and / or the cover element 118.

[0119] During the Fig. 1 bis 11 In the illustrated embodiment of the cylinder head cover 100, the radially outer part 160 of the suction section 144 is the outlet nozzle 154, which is part of the cover element 118.

[0120] A locking device 162 is preferably provided for connecting the radially inner part 156 and the radially outer part 160.

[0121] The locking device 162 preferably comprises one or more locking elements 164, by means of which the radially inner part 156 and the radially outer part 160 of the suction section 144 can be locked together.

[0122] For example, several locking elements 164 are formed on the insert element 158 ​​and can be locked with the radially outer part 160.

[0123] According to the invention, the insert element 158 ​​can be inserted into the outer part 160 of the suction section 144 against the direction of flow 146.

[0124] For example, from Fig. 1 As can be seen, the drive nozzle 142 and the suction section 144 are integrated into the separating device 108 and the valve device 110 in such a way that a drive medium connection 166 as well as the outlet nozzle 154 are directly adjacent to the separating device 108 and / or the valve device 110, for example at least sectionally between the separating device 108 on the one hand and the valve device 110 on the other hand and / or are arranged.

[0125] The propellant medium connection 166 is in particular a charge air supply nozzle 168, which, like the outlet nozzle 154, is preferably formed in one piece with the cover element 118.

[0126] For example, the Fig. 2 , 3 , 10 and 11 As can be seen, the insert element 158 ​​does not extend solidly outwards to the radially outer part 160 of the suction section 144.

[0127] Rather, several webs 170 are preferably provided for attaching the insert element 158 ​​to the radially outer part 160 of the suction section 144.

[0128] The locking elements 164 are preferably extensions of these webs 170.

[0129] The in the Fig. 1 bis 11The illustrated cylinder head cover 100 is preferably easy to manufacture and preferably enables the provision of an internal combustion engine 102 with small external dimensions by comprising, in addition to the cover body 106 with its conventional covering function, further components with additional functions. These are, in particular, the separator device 108, the valve device 110, and the nozzle device 138.

[0130] Because, for example, the cover element 118 forms parts of both the separating device 108 and the valve device 110 and the nozzle device 138, a large number of functions can be realized in the cylinder head cover 100 with low manufacturing and production costs.

[0131] Because the suction section 144 of the nozzle device 138 is designed in two parts, the radially outer part 160 can be designed as a conventional outlet nozzle 154, while the suction-effect-optimizing flow constriction is created by means of the insert element 158.

Claims

1. Cylinder head cover (100) for an internal combustion engine (102), comprising: - a cover body (106) which, in the assembled state of the cylinder head cover (100), is arranged on an engine block of the internal combustion engine (102) and covers a cylinder head (104) of the internal combustion engine (102); - a separation device (108) through which a crude gas stream can be fed for the purification thereof, wherein the separation device (108) is formed and / or bounded at least in sections by the cover body (106); and / or - a valve device (110) which is formed and / or bounded at least in sections by the cover body (106), wherein the cylinder head cover (100) comprises a nozzle device (138) which is integrated into the separation device (108) and / or into the valve device (110), wherein the nozzle device (138) comprises a suction jet nozzle (140) by means of which a gas stream can be drawn in and / or removed, wherein the suction jet nozzle (140) comprises a suction section (144) into which, on the one hand, a drive nozzle (142) of the suction jet nozzle (140) and, on the other hand, a gas stream supply (130) open, wherein the suction section (144) has at least two parts, wherein an inner part (156) with respect to a radial direction is formed by an insertion element (158) which has a substantially constant outer cross-section along a flow direction (146) and / or a varying inner cross-section along a flow direction (146), wherein the insertion element (158) can be inserted into an outer part (160) of the suction section (144) with respect to a radial direction, characterized in that the insertion element (158) can be introduced into the outer part (160) of the suction section (144) counter to the flow direction (146).

2. Cylinder head cover (100) in accordance with claim 1, characterized in that the suction jet nozzle (140) comprises a drive nozzle (142) to which a drive medium, in particular charge air, can be supplied in order to generate a suction effect for drawing up the gas stream.

3. Cylinder head cover (100) in accordance with any one of claims 1 or 2, characterized in that the gas stream is the crude gas stream fed through the separation device (108).

4. Cylinder head cover (100) in accordance with any one of claims 1 to 3, characterized in that the suction section (144), seen along a flow direction (146), comprises a tapering section (148), a cylinder section (150) and an enlarging section (152).

5. Cylinder head cover (100) in accordance with any one of claims 1 to 4, characterized in that the suction section (144) and the drive nozzle (142) are arranged at least approximately coaxially to each other.

6. Cylinder head cover (100) in accordance with any one of claims 1 to 5, characterized in that the gas stream supply (130) opens at least approximately annularly into the suction section (144).

7. Cylinder head cover (100) in accordance with any one of claims 1 to 6, characterized in that the outer part (160) of the suction section (144) with respect to a radial direction is formed by a housing component (118) of the separation device (108) and / or by a housing component (118) of the valve device (110) and / or by the cover body (106).

8. Cylinder head cover (100) in accordance with any one of claims 1 to 7, characterized in that the insertion element (158) comprises a detent device (162), in particular one or more detent elements (164), for fixing it on the outer part (160) of the at least two-part suction section (144).

9. Cylinder head cover (100) in accordance with any one of claims 1 to 8, characterized in that the cover body (106), a cover element (118) of the separation device (108), a cover element (118) of the valve device (110), the suction section (144) of the nozzle device (138) and / or a drive nozzle (142) of the nozzle device (138) are formed by one or more plastic components, in particular injection-molded plastic components.

10. Cylinder head cover (100) in accordance with any one of claims 1 to 9, characterized in that the valve device (110) comprises a pressure-regulating valve (132) by means of which a volumetric flow of the gas stream to be removed via the nozzle device (138) can be regulated.

11. Cylinder head cover (100) in accordance with any one of claims 1 to 10, characterized in that the separation device (108) comprises one or more separation chambers (116) which are bounded by the cover body (106) and a cover element (118) of the separation device (108), wherein the cover body (106) and / or the cover element (118) are each formed in one piece and form and / or bound the following in addition to the one or more separation chambers (116): - at least one valve chamber (120) for receiving a valve element (122) of the valve device (110); and / or - a gas stream supply (130) of the nozzle device (138); and / or - a drive nozzle (142) of the nozzle device (138); and / or - a drive medium connection (166) of the nozzle device (138); and / or - an outlet connecting piece (154) for removing the drive medium and / or the gas stream.