FR2859237A1 - Liquid e.g. oil, separation device for thermal engine crankcase, has bypass separator unit, connected in parallel to separator units, with pressure loss relating to maximum pressure difference between crankcase and admission pipe - Google Patents

Abstract

The device has separator units connected in parallel and in downstream to a pressure adjustment valve, and installed in an air evacuation pipe (8) connecting a crankcase to an admission pipe (4). A bypass separator unit (15) is connected in parallel to the units and is connected by a bypass pipe (14) to one of the pipes. The unit (15) presents pressure loss relating to maximum pressure difference between the crankcase and pipe (4).

Description

Field of the invention

  The present invention relates to a device for separating liquid from a gas stream of a crankcase of a heat engine comprising separating elements connected in parallel, connected downstream to a pressure regulating valve and installed in a cone. -duite ventilation from the crankcase being connected to the intake pipe of the engine.

  State of the art DE 102 51 947 discloses a liquid separation device. This device comprises a ventilation duct or air evacuation connecting the crankcase to the intake pipe of the engine; the exhaust air duct has separating elements connected in parallel. Downstream of the separating elements, there is provided a pressure regulating valve acting by throttling to adjust the pressure in the crankcase to a predefined pressure.

  Depending on the operating state of the heat engine, there is a different level of vacuum in the intake pipe, this level decreasing the pressure loss generated by the pressure regulating valve and the separating elements and develops into the intake pipe of the engine. The separating effect of the different separating elements of the device is generally all the better as the flow velocity is high and the pressure loss (pressure drop) is higher in the separating element. The separator elements followed by a pressure control valve can however be provided for a pressure loss of between 5 and 25 millibars because otherwise there could be an unacceptable overpressure or negative pressure in the crankcase for certain operating conditions. In these conditions, the high pressure differences can not serve to increase the separating effect, but they must be attenuated by means of the pressure regulating valve. Thus, with the separating elements the optimum separation effect for high pressure differences between the crankcase and the intake pipe is not achieved.

  DESCRIPTION AND ADVANTAGES OF THE INVENTION The present invention relates to a device of the type defined above, characterized by at least one bypass separator element connected in parallel to the separating elements, this bypass separator element being connected by a bypass line to the exhaust air duct or the intake duct.

  Thus, according to the invention, with simple means, the separation effect is improved for high pressure differences between the crankcase and the intake duct due to the use of high pressure differences between at least one element. bypass separator connected in parallel to the separating elements, this bypass element being connected to the exhaust air duct and to the intake duct via a bypass duct. Under these conditions, for high pressure differences between the crankcase and the intake pipe, a large volume flow will pass through the bypass separator element bypassing the pressure regulating valve; thus the high pressure difference is used almost completely to generate a high flow rate and a high separating effect in the bypass separator element.

  It is particularly advantageous that the bypass separator element has a pressure loss for a gas vein slightly smaller than the minimum gas flow encountered, and that this pressure loss corresponds to the maximum pressure difference produced between the crankcase. crankshaft and the intake pipe because in this way the flow rate is limited to a predefined value so as to avoid any unacceptable depression in the crankcase.

  According to an advantageous embodiment, the separating elements are cyclones, spirals, turns, non-woven layers, yarns and the separating element in derivation is a cyclone, a spiral, a spiral, a nonwoven , or a thread.

  It is also advantageous to drive the gas stream with at least one switching element and depending on the amount of the gas stream to one or more separating elements as these separator elements work in this way in an operating range close to the optimum operating point and ensures a high separation effect.

  It is very advantageous for the bypass line to include a flow restrictor to thereby avoid an unacceptable low in the crankcase.

  It is also advantageous to install a coarse separator upstream of the separator elements to remove large drops of oil contained in the gas and to protect the downstream separator elements operating as fine separators.

  It is furthermore advantageous that the separator elements and the bypass separator element are connected to an oil return receiving the separated liquid in the separating elements and in the bypass separator element in order to return the oil to the separator casing. crankshaft thus avoiding a significant loss of oil.

  Drawings The present invention will be described below in more detail with the aid of an exemplary embodiment of a device for separating the liquid from a gas stream represented in the form of a block diagram in the single attached figure.

Description of the embodiment

  The figure shows a device according to the invention for separating liquid from a gas stream or a gas stream. The device according to the invention serves in particular to separate liquids in particular from the oil of a gas vein; for example, it is generally a question of separating liquid droplets from circulating gas. The device according to the invention is preferably used for ventilation of a crankcase of a heat engine.

  During the operation of a heat engine 1, the small leaks between the piston, the piston rings and the surface of the cylinder allow a gas to escape from the combustion chamber which arrives in the crankcase 2 of the heat engine 1. This gas is called blowing gas. These very small gas leaks from the combustion chamber of the engine unacceptably increase the pressure in the crankcase 2 so that it is necessary to compensate the pressure by a crankcase ventilation 3 Since the gas has a very high concentration of hydrocarbon, it can not be released into the atmosphere but it must be conducted in the intake con-ducite 4 of the engine 1 to fuel the combustion. The gas entering at high flow velocity and the moving particles in the crankcase 2 there generate an oil mist consisting of a large number of small and large oil droplets. These oil droplets must be separated in the ventilation of the crankcase 3 by means of the device according to the invention in order to avoid a significant loss of oil and not to influence combustion in a negative manner.

  In the intake duct 4 of the engine,. Inique 1, there is a pressure depending on the operating state of the heat engine 1 decreased by the loss of pressure that develops into the device according to the invention.

  The crankcase 2 is connected to the intake duct 4 via an air or ventilation duct 8. The ventilation duct 8 comprises several, for example three separator elements 7 connected in parallel, installed each time in a parallel segment 8.1, 8.2, 8.3 of the ventilation duct 8.

  The separating elements 7 are preferably cyclones; but it may also be other separating elements such as for example spirals, turns, nonwoven webs, son or similar means. The separation of the small oil droplets is done in known manner in the separator elements 7.

  The parallel segments 8.1, 8.2, 8.3 meet downstream of the separating elements 7.

  A pressure regulating valve 10 is installed in the exhaust air duct 8 downstream of the separating elements 7 and the parallel segments 8.1, 8.2, 8.3. The pressure regulating valve 10 is for example a diaphragm valve. The opening section of the pressure regulating valve 10 is important when the pressure difference between the crankcase 2 and the intake pipe 4 is small; this section decreases when the pressure difference increases.

  Upstream of the parallel segments 8.1, 8.2, 8.3, the ventilation duct 8 may be equipped with a coarse separator 6, for example a stabilization chamber, a turn or at least one jet-breaker wall. The coarse separator 6 thus serves to filter the large drops of oil.

  With an exception, for example, each separator element 7 is associated with a switching valve 9 upstream in the direction of passage of the fluid. The switching valves 9 are made for example in the form of flat-seat valves, but other forms of switching valves can also be envisaged. The separator elements 7, preceded by a switching valve 9, can be separately connected or cut according to the gas flow so that the number of separator elements 7 traversed by the gas is variable. Preferably a separator element 7 is not preceded by a switching valve 9 so that when the pressure regulating valve is open, this separator element 7 always remains through the fluid.

  Instead of associating a switching valve 9 with each separating element 7, it is also possible to use a single switching valve for all the separating elements 7 connected in parallel.

  Each switching valve 9 is prestressed in the closing direction, for example at. by means of a valve spring and opens, due to the different prestressing of the valve springs, to a different opening pressure. Thus the separating elements 7 are connected or cut in a stepped manner depending on the size of the gas stream. If the pressure increases in the crankcase 2 and thus in the ventilation duct 8 upstream of the switching valves 9 due to the increase in the amount of gas, one or more switching valves 9 will open for associate one or more separator elements 7. If the pressure drops in the crankcase 2 and thus in the ventilation pipe 8 upstream of the switching valves 9, one or more separating elements 7 will be cut off by closing a or several switching valves 9. The number of separator elements 7 traversed by the fluid thus adapts to the variation of the gas stream as a function of time. The control of the number of separator elements 7 traversed by the fluid allows the separating elements 7 to work in the vicinity of their optimum operating point and thus there will be only a small pressure difference between the crankcase 2 and the driving line. suction 4 ensuring a good effect of separation.

  It is possible to have a pressure difference of up to 120 millibars between the crankcase 2 and the intake pipe 4 for a diesel engine; the usable pressure difference can reach up to 800 millibars in the case of a gasoline engine. Since the pressure regulating valve 10 is provided downstream of the separator elements 7 connected in parallel, separating elements 7 can be designed solely for a pressure loss (pressure drop) of between 5 and 25 millibars, since otherwise could cause overpressure or excessive depression in the crankcase 2 for certain operating conditions. Thus a high pressure difference between the crankcase 2 and the intake pipe 4 will not result in an increase in the flow velocity and therefore the separation effect of the separator elements 7 but will be reduced to a great extent by the pressure regulating valve 10. The potential of the separation effect of the device according to the state of the art will not be exhausted completely under these conditions.

  According to the invention there is provided in parallel with the separating elements 7, a bypass separator element 15 in a bypass line 14. The bypass line 14 of the ventilation duct 8 is connected upstream of the segments in parallel 8.1, 8.2, 8.3, either to the ventilation duct 8 downstream of the pressure regulating valve 10 or directly to the inlet duct 4. The bypass separator element 15 is designed so that for a gas vein slightly already less than the minimum gas stream leaving the crankcase 2, there is a loss of pressure (pressure drop) corresponding to the maximum possible pressure difference between the crankcase 2 and the intake pipe 4. Thus, the gas stream passing through the separating element 15 bypass, is limited to a predefined volume flow which protects the crankcase 2 against depressions of too high intensity. If the gas stream in the crankcase 2 is greater than the predefined volume flow for the bypass separator element 15, a portion of the predefined volume flow passes through the bypass separator element 15 and the remaining portion passes through one or more several separator elements 7. The bypass separator element 15 is preferably a cyclone; but it can also be another separating element such as a spiral, a coil, a nonwoven web, a wire or the like.

  According to the invention, the gas stream divides downstream of the coarse separator 6 between a first volume flow rate passing through one or more parallel segments 8.1, 8.2, 8.3 equipped with separator elements 7 or by means of the control valve. pressure 10 at least partially open and a second volume flow through the bypass line 14 equipped with the bypass separator element 15.

  For a high pressure difference between the crankcase 2 and the intake pipe 4, a substantial portion of the gas stream will bypass the pressure control valve 10 through the bypass line 14, to use the difference in pressure. high pressure ranging for example up to 120 millibars in the case of a diesel engine and up to 800 millibars in the case of a gasoline engine, to have a high flow rate in the bypass separator element 15 and in this way achieve a large separating effect in the bypass separator element 15 stronger than that which is possible in the separating elements 7 because of the downstream pressure control valve 10.

  For a small pressure difference between the crankcase 2 and the intake pipe 4, the main part of the gas stream passes through the separating elements 7 and the downstream pressure regulating valve 10, while the shunt separator element 15 is crossed only by a reduced vein. The separation effect of the separator elements 7 and the bypass separator element 15 is substantially the same for this operating mode.

  Since the separation effect of the device according to the invention is significantly greater for a high pressure difference than in the state of the art, but also in the entire operating range of the device, the average of the separating effect is better than in the state of the art.

  A flow restrictor 16 may equip the bypass line 14, for example a diaphragm or a throttling element, in order to further limit the volume flow passing through the bypass line 14.

  The coarse separator 6, the separator elements 7 and the bypass separator element 15 are connected to an oil return 17 which returns the liquid deposited in the coarse separator 6, in the separator elements 7 and in the separator element. bypass 15 in the crankcase 2.

Claims (8)

  1) Device for separating liquid from a gas stream of a crankcase of a heat engine comprising separator elements connected in parallel, connected downstream to a pressure regulating valve and installed in a starting ventilation duct the crankcase being connected to the intake duct of the engine, characterized by at least one bypass separator element (15) connected in parallel to the separating elements (7), this bypass separator element being connected by a pipe bypass (14) to the exhaust air duct (8) or to the intake duct (4).   2) Device according to claim 1, characterized in that the bypass separator element (15), for a vein of gas slightly less than the minimum of the gas stream generated in the crankcase (2), a loss of pressure corresponding to the maximum pressure difference produced between the crankcase (2) and the intake pipe (4).   3) Device according to claim 1, characterized in that the separating elements (7) are cyclones, spirals, turns, nonwoven webs or son.   4) Device according to claim 1, characterized in that the bypass separator element (15) is a cyclone, a spiral, a coil, a nonwoven web or a wire.   5) Device according to claim 1, characterized in that the gas stream is conducted via a switching valve (9) depending on the amount of gas to one or more separating elements (7).   6) Device according to claim 1, characterized in that the branch line (14) comprises a flow limiter (16).   7) Device according to claim 1, characterized by a coarse separator (6) installed upstream of the separator elements (7).   8) Device according to claim 1, characterized in that the separating elements (7) and the bypass separator element (15) are connected to an oil return (17) which returns the separated liquid in the separator elements (7) in the crankcase (2).