Blow-By-Filtereinheit

Abstract

Internal combustion engine, including i) an intake manifold with a compression device (7), ii) a piston-cylinder unit, iii) a crankcase, and iv) a blow-by filter unit (1) comprising a blow-by gas inlet (2) and a permeate outlet (3), wherein the blow-by gas inlet (2) is connected to the crankcase and the intake tract has an inlet point (20) for the permeate outlet (3), wherein the inlet point (20) for the permeate outlet (3) is arranged in the flow direction immediately upstream of the compression device (7), characterized by the fact that the filter volume (V opt ) the blow-by filter unit the product K r * N Mot is, where K r an adjustment constant with dimension m 3 / kW is and N Mot The full-load power of the internal combustion engine is in kW, where K r between 0.80*10 -5 and 1.6*10-5 amounts.

Description

[0001] The present invention relates to a blow-by filter unit for an internal combustion engine, comprising an intake tract with a compression device, a piston-cylinder unit, a crankcase, and a blow-by filter unit with a blow-by gas inlet and a permeate outlet, wherein the blow-by gas inlet is connected to the crankcase and the intake tract has an inlet point for the permeate outlet. Furthermore, the invention relates to a method for operating an internal combustion engine.

[0002] Reciprocating piston internal combustion engines produce blow-by gas, which is a leakage flow between the cylinder liner and piston assembly, as well as the bearing lubrication of the compression devices. This total represents approximately 0.5–1% of the total mass flow through the internal combustion engine. This blow-by gas accumulates in the crankcase and must be vented to prevent a pressure increase. Since blow-by gas contains not only unburned fuel but also a portion of oil in the form of a mist, it is redirected back into the intake tract of the internal combustion engine for environmental reasons, where it is fed into the combustion process. This oil mist accounts for approximately 10% of the total oil consumption of the internal combustion engine.

[0003] In modern high-performance engines, it is necessary to remove this oil content in the blow-by gas as completely as possible before it is introduced into the intake tract to prevent contamination-related impairment of the operation of the combustion engine. For this purpose, blow-by oil separators or blow-by filter units are used in various technologies, designs, and applications, according to the state of the art.

[0004] Generic internal combustion engines are disclosed, for example, in US 2004 / 0139734 A1, US 2006 / 0045764 A1, JP 2014-013020 A, JP 2009-074506 A or DE 10 2004 061 938 B3.

[0005] The required separation rate for the oil from the blow-by gas depends, among other things, on the specific full-load power of the combustion engine. This depends on the engine speed and the effective effective pressure (p e ) is the determining factor. Up to a p eof about 16 bar, for example, a separation rate of about 50% of the oil content is sufficient, above p e = 20 bar, however, a separation rate of greater than 99% is required.

[0006] The required separation rate is a determining parameter for the selection of the filter technology, and – along with the criteria of pressure drop and service life – it significantly determines the specific design and dimensions of the blow-by filter. The higher the required separation rate and the lower the maximum permissible pressure drop of the blow-by gas across the filter, the more complex and bulky the filter design becomes.

[0007] The following boundary conditions must be taken into account when designing the blow-by filter to ensure compliance with an upper limit for the pressure drop: • crankcase pressure to be maintained, • Flow resistance in the blow-by line system and • Pressure at the point where the oil-cleaned blow-by gas is introduced into the intake tract of the combustion engine.

[0008] In most applications, a slight negative pressure between -20 and 0 mbar is required for the crankcase pressure to prevent oil leaks in the combustion engine. Excessively high negative pressure can lead to air leaks through the crankshaft seal, which carries the risk of the sealing lips overheating and becoming damaged.

[0009] The pressure at the point where the blow-by gas is introduced into the intake tract depends on a number of boundary conditions: • Engine power, • Air filter resistance and • geometric or fluid-mechanical design of the intake system from the air filter to the point of introduction.

[0010] Typically, design measures and a suitable layout of the air filter system ensure that a negative pressure of approximately -20 to -40 mbar prevails at the inlet point when the internal combustion engine is operating at full load. The pressure loss in the blow-by gas line from the extraction point on the crankcase to the blow-by filter unit and from there to the inlet point on the intake tract is generally assumed to be between 3 and 6 mbar at full engine load. Based on these boundary conditions, the pressure drop at the blow-by filter unit should always be less than approximately 25 mbar in state-of-the-art technology.

[0011] Blow-by filter units, which ensure an oil separation rate of greater than 99% and must maintain a pressure drop of less than 25 mbar within the typically required filter service life of several thousand full-load operating hours, are designed with a large volume according to the state of the art and require a relatively large amount of unit space. However, the size of the blow-by filter unit determines the integration options in the combustion engine unit and significantly influences the cost of the blow-by filter unit, as well as the expenditure for the mounting brackets, the piping, and the thermal insulation.

[0012] The present invention proposal is based on the task of significantly reducing the effort and costs for the blow-by filter unit of modern high-performance internal combustion engines, which have an oil separation rate of greater than 99%, compared to the state of the art and of significantly improving the integration options into the design of the internal combustion engine unit.

[0013] This task is solved by an internal combustion engine, comprising (i) an intake tract with a compression device, (ii) a piston-cylinder unit, (iii) a crankcase, and (iv) a blow-by filter unit, with a blow-by gas inlet and a permeate outlet, wherein the blow-by gas inlet is connected to the crankcase and the intake tract has an inlet point for the permeate outlet, wherein the inlet point for the permeate outlet is arranged in the flow direction immediately upstream of the compression device, characterized in that the filter volume (V opt ) of the blow-by filter unit the product K r * N Mot where K r an adjustment constant with dimension m 3 / kW and N Mot is the full load power of the combustion engine in kW, where K r between 0.80* 10 -5 and 1.6*10 -5 amounts.

[0014] Immediately before the compression device means in the sense of the present invention that no functional unit (such as an air inlet, an air filter or a fuel inlet) is provided between the inlet point for the permeate outlet and the compression device, but only lines, connecting flanges or the like.

[0015] It is therefore intended that the air inlet in the intake tract is arranged in the flow direction upstream of the inlet point for the permeate outlet.

[0016] The piston-cylinder unit is a conventional piston-cylinder unit of reciprocating piston engines, wherein at least one such piston-cylinder unit is provided, but preferably several, particularly preferably at least four piston-cylinder units.

[0017] In one embodiment, it is provided that the compression device has an impeller with a diameter (d) and is connected to the intake tract by means of a connecting flange, wherein the distance from the inlet point for the permeate outlet to the connecting flange is a maximum of 1.5 times the diameter (d) of the impeller.

[0018] In one design variant, the combustion air flow velocity at this inlet point for the permeate outlet is between 85 and 110 m / s, averaged across the cross-section, at full engine load. The flow cross-section at this point must be designed accordingly.

[0019] Essentially, the above-mentioned measures ensure that the volume of the blow-by filter, relative to the engine power, can be reduced to less than half of the current state of the art.

[0020] In a preferred embodiment, it is a so-called mixture-charged internal combustion engine, i.e. an internal combustion engine in which the fuel inlet (in the direction of flow) is arranged in front of the compression device, so that not only air but an air-fuel mixture is compressed in the compression device.

[0021] The compression device is preferably an exhaust gas turbocharger.

[0022] Further advantageous embodiments can be found below and in the dependent patent claims.

[0023] The blow-by filter unit is preferably designed such that the separation rate for oil in the blow-by gas is at least 99% (v / v).

[0024] The blow-by filter unit is preferably designed such that the pressure drop of the blow-by gas does not change by more than 50% (or by a factor of 1.5) relative to the new condition of the blow-by filter unit over the intended service life of the blow-by filter unit until replacement.

[0025] The proposed solution includes a number of additional optional design features and details, each of which contributes to the optimal fulfillment of the purpose and which, in combination, result in an extremely economical overall concept compared to the state of the art.

[0026] In one embodiment variant, the blow-by filter unit is designed such that the pressure drop between the blow-by gas inlet and a permeate outlet at full load of the combustion engine in the new state of the blow-by filter unit is at least 25 mbar.

[0027] In one embodiment, it is provided that the internal combustion engine has an oil pan and that the blow-by filter unit has a housing, wherein the housing base of the blow-by filter unit is at a vertical distance (H opt ), wherein the vertical distance (H opt ) the sum of the constant H r and the product 4π*j*Δp, where Δp is the pressure drop between the blow-by gas inlet and the permeate outlet of the blow-by gas across the blow-by filter unit at full load of the combustion engine in the new condition of the blow-by filter unit, j is a dimensional converter with the value 1 mm / mbar and H r between 150 and 250 mm.

[0028] In simpler terms, this relationship can be represented as follows: Hopt(mm)=Hr+4π*j*Δp with Δp pressure drop in (mbar) across the oil separator at full engine load and when the filter medium is new j Dimension converter with 1 mm / mbar H r Adjustment constant, unit [mm], where H r can take a value between 150 and 250 mm

[0029] The blow-by filter unit is provided with a vacuum limiting device with which the vacuum at the permeate outlet of the blow-by filter unit can be adjusted. The vacuum limiting device is preferably arranged between the permeate outlet and the intake tract. In the simplest case, the vacuum limiting device can be an adjustable throttle resistance, e.g., a throttle valve.

[0030] The vacuum limiting device can also comprise a vacuum control or regulating device. Preferably, such a vacuum control or regulating device is provided so that the suction pressure at the outlet from the actual filter can be regulated or adjusted according to specific specifications.

[0031] Furthermore, it can be provided that a vacuum limiting valve is arranged—particularly on the inlet side, i.e., at the blow-by gas inlet of the blow-by filter unit. This valve, starting at a predeterminable vacuum at the blow-by gas inlet, releases a flow cross-section to the ambient air through which ambient air can be drawn in, thereby limiting the vacuum in the inlet chamber of the blow-by filter unit in a defined manner. This allows the maximum vacuum in the crankcase of the combustion engine to be limited to a defined level.

[0032] In one embodiment, it is provided that the distance (D opt ) between the permeate outlet of the blow-by filter unit and the compression device, the sum of a constant D r in mm and the product 0.0225 * i * N Mot where i is a dimensional converter with the value 1 mm / kW and N Mot is the full load power of the combustion engine in kW, where Dr a value between 100 and 160 mm. In practice, this means that the permeate outlet is located very close to the compression device, with the optimum distance (D opt ) between the blow-by filter and the compression device, a narrowly limited range of values ​​is proposed, which depends in a linear function on the engine power, according to the formula: Dopt(mm)=Dr+0.0225*i*NMot. with D r Adjustment constant (mm) i Dimension converter = mm / kW N Mot Full load power of the engine (kW), where D r can take a value between 100 and 160 mm.

[0033] Furthermore, it has proven advantageous if the filter volume (V opt ) of the blow-by filter unit the product K r * N Mot where K r an adjustment constant with dimension m 3 / kW and N Motis the full load power of the combustion engine in kW, where K r between 0.80*10 -5 and 1.6*10 -5 amounts: Vopt(m3)=Kr*NMot with K r Adjustment constant - Dimension: m 3 / kW N Mot Full load power of the engine

[0034] Regarding the introduction of the purified blow-by gas into the intake tract, it is state of the art to locate the introduction point at a location where a flow velocity of between 20 and 50 m / s prevails when the combustion engine is operating at full load. This is because the resulting static negative pressure, combined with the pressure drop across the air filter, produces a negative pressure of approximately 15 - 30 mbar, which is generally sufficient for an economical design of the blow-by filter unit.

[0035] In addition, this relatively low negative pressure ensures that there is no excessive suction effect on the blow-by filter unit, which would lead to increased oil entry into the blow-by filter unit and thus to the risk of oil flooding the blow-by filter unit and subsequently the intake tract.

[0036] In contrast, in the present case, an inlet point is selected at which, at full load of the combustion engine, a flow velocity averaged over the cross-section of between 85 and 110 m / s occurs, and where this point is at most 1.5 times the impeller diameter of the compression device away from the compressor connection flange.

[0037] The reason for this proposal is that at this flow velocity, ideal kinetic turbulence energy exists, leading to complete mixing of the blow-by gas with the combustion air within a path length that approximately corresponds to the diameter of the flow cross-section. This ensures a uniform inflow to the compressor across the entire cross-section of the compressor intake port, and the risk of vibration excitation of the compressor blades is no longer present. This velocity range between 85 and 110 m / s is somewhat higher than the flow-dynamically optimal design velocity at the outer edge of the compressor inlet funnel (also called the compressor intake port) at full load of the internal combustion engine, as generally desired in engine technology. This compressor intake port will be the location of the connection flange in the following.

[0038] However, since turbulence-related flow losses already occur at this speed, which are no longer negligible, it is advisable to keep the pipe sections where these velocities occur as short as possible. Likewise, it is advantageous from a flow dynamics perspective not to provide unnecessary cross-sectional expansions between the blow-by supply point and the suction port of the compressor to avoid turbulence that leads to shock losses.

[0039] In order to complete the mixing up to the suction mouth, but to keep the flow losses as low as possible, an introduction point that is located exactly between 1 and 1.5 times the compressor impeller diameter from the compressor connection flange to which the compressor suction mouth is connected proves to be ideal.

[0040] At the proposed location for introducing the blow-by gas into the intake tract of the combustion engine, a very high negative pressure occurs, which, although it offers great advantages for the design and construction of the blow-by filter unit, also entails considerable problems and risks for the operational reliability of the entire system.

[0041] In particular, there is a risk that engine oil will be sucked into the intake tract via the oil drain line, with the consequences described above, and that excessive negative pressure in the crankcase will cause the blow-by volume flow and thus the oil load to the blow-by filter unit to increase significantly.

[0042] These problems and dangers can be counteracted, for example, by providing a pressure control device between the blow-by filter unit and the discharge point, as mentioned above, which limits or regulates the maximum suction pressure at the actual filter.

[0043] It is also very advantageous to provide an adjustable vacuum relief valve at the blow-by gas inlet or in the inlet chamber of the blow-by filter unit, which can be used to limit the maximum vacuum in the crankcase to a desired level. A vacuum relief valve has proven particularly advantageous in this regard. It opens a cross-section for the inflow of ambient air when a certain vacuum level is reached, so that the incoming air reduces the vacuum at the blow-by gas inlet into the filter.

[0044] As noted above, in order to avoid the problems and hazards mentioned, it is advantageous to use blow-by filter technologies in which, despite very high separation rates of > 99% achieved, the pressure drop of the blow-by gas across the actual filter over the entire intended service life of the filter medium does not increase by more than 1.5 times the new condition of the filter medium based on full engine load.

[0045] The analyses conducted have shown that, when using a blow-by filter unit with these properties, it is very advantageous to design the filter medium so that the pressure drop in the new filter medium (relative to full engine load) is greater than 25 mbar. While this contradicts the established design principles, according to which the pressure drop of blow-by filter units in the new filter medium should be less than 15 mbar, the objective of the task—namely, the realization of an extremely cost-effective blow-by filter unit—can be achieved precisely under the aforementioned conditions and in conjunction with the aforementioned measures.

[0046] The theoretical considerations, confirmed by tests, have shown that, under the aforementioned conditions, a narrow range of values ​​can be specified for the ideal vertical distance between the lower edge of the filter housing and the oil level in the crankcase. This range proves to be extremely favorable both in terms of ensuring sufficient protection against oil backflow via the oil drain line into the blow-by filter unit and in terms of minimizing the length of this oil drain line. In the equation given above, the ideal vertical distance is linearly dependent on the design pressure drop of the blow-by gas across the filter medium, with an additive constant within a narrow range of values ​​serving for fine-tuning.

[0047] All of these measures listed lead to improvements as individual measures, but in combination to complete freedom from problems and operational reliability of the entire system, despite a very high intake pressure level at the point where the blow-by gas is introduced into the intake tract of the combustion engine.

[0048] The suggestions and measures described above make it possible to specifically design the blow-by filter unit with a very small volume. This opens up further optimization options that significantly improve the functionality of the blow-by filter unit. In particular, it makes it possible to position the blow-by filter unit(s) very close to the point where the purified blow-by gas is introduced into the intake tract, and thus to one of the compression units.

[0049] This results in significant advantages: • Minimal space requirement and optimal integration into the engine concept as well as short connecting lines between the filter medium and the inlet point, thus avoiding vibration problems. • Use of the radiant heat from the compression device to heat the housing surface of the blow-by filter unit. The associated heating of the engine oil separated in the filter fabric, particularly in the area close to the housing, with the resulting effect of a significant reduction in oil viscosity, leads to improved oil flow from the filter medium and the blow-by filter unit as a whole. This reduces the filter's hold-up and the pressure drop of the blow-by gas in the filter medium. • To fully utilize these advantages, it is therefore recommended that the blow-by filter unit be as small as the measures listed allow. Calculations have shown that, under the above conditions, a simple quantitative relationship can be specified for the optimal value range for the volume of the blow-by filter unit, with this optimum being linearly dependent on the engine's full-load power. The corresponding formula is given above.

[0050] Furthermore, it was found that for the optimal distance of the filter (D opt) from the compressor of the compression unit (or for the space between the filter and the compressor), upstream of which the purified blow-by gas is introduced, a narrow range of values ​​can be specified. Like the volume, this range depends linearly on the full-load performance of the combustion engine. If this range of values ​​is maintained for the distance between the blow-by filter unit and the compressor, a very favorable situation arises for the heat balance of the blow-by filter unit, with the aforementioned advantage of reducing oil viscosity. The corresponding formula was given above.

[0051] In the following, the invention proposal is described in its entirety and explained in more detail by means of schematic figures, sketches and diagrams, and the difference from the prior art is highlighted by way of example. Fig. 1 shows a schematic flow diagram of the intake tract and the blow-by filter unit. Fig. 2 shows the arrangement of the blow-by filter unit and compression device. Fig. 3 shows a detail of the blow-by filter unit of Fig. 2 Fig. Figure 4 shows the mean flow velocity at the point of blow-by gas introduction as a function of the pressure drop of the blow-by gas in the blow-by filter unit at full load of the combustion engine and in new condition of the filter medium. Fig. 5 shows the vertical distance H opt the lower edge of the filter housing from the oil level in the oil pan of the combustion engine as a function of the pressure drop of the blow-by gas in the blow-by filter unit at full load of the combustion engine and with the filter medium in a new condition. Fig. 6 shows the distance D optof the Permat outlet of the blow-by filter unit from the housing of the compression device, before which the filtered blow-by gas is introduced as a function of the full load power of the combustion engine in kW. Fig. Figure 7 shows the oil separation rate of the blow-by filter unit as a function of the specific filter volume.

[0052] In Fig. Figure 1 shows the schematic flow diagram with the symbolically sketched components relevant for use in a gas engine as an internal combustion engine. The blow-by filter unit 1 has a blow-by gas inlet 2 for the unfiltered blow-by gas arriving from the crankcase, as well as a permeate outlet 3 for the filtered blow-by gas and an oil outlet 4 for the separated oil. The filtered blow-by gas is introduced into the intake tract of the internal combustion engine via an intermediate element 5 directly upstream of the compressor 6 of the compression device 7 in the form of an exhaust gas turbocharger. The intake tract also includes the air filter 8 and a fuel supply device 9.The combustion air is sucked in at the inlet of the air filter 8 from the environment or from the engine room, flows through the fuel supply 9 and through the intermediate member 5, in which the filtered blow-by gas is introduced, together with the fuel and the blow-by gas to the compressor 6 of the compression device 7 in the form of an exhaust gas turbocharger 7.

[0053] In Fig. 2 shows a more detailed illustration of the arrangement of the relevant components. The combustion air flows with the previously added fuel to the intermediate member 5, where the filtered blow-by gas is introduced, and then to the suction port 11 on the flange of the compressor 6. The sectional view of the compressor 6 shows the compressor impeller 10, which is connected to the turbine impeller 12 via a shaft. The compressor impeller 10 and turbine impeller 12, together with the shaft connecting them, form the rotor of the compression device 7 in the form of an exhaust gas turbocharger. A vacuum relief valve 13 is shown schematically at the inlet for the blow-by gas on the blow-by filter unit 1. When a defined vacuum, e.g. determined by a spring adjustment, occurs in the blow-by inflow line, an air supply valve is actuated, which relieves the pressure by admixing outside air.On the outlet side of the blow-by filter unit 1, another throttle element 14 in the form of a vacuum regulating or vacuum control valve 14 is also shown schematically. This valve 14 and its control ensure that excessive suction vacuum prevailing at the inlet point is reduced to a suitable or desired level. For the distance 15 between the housing of the compressor 6 and the housing of the blow-by filter unit 1, a relatively narrow value range is advantageous depending on the engine power. The vertical distance 16 of the lower edge of the housing of the blow-by filter unit 1 from the oil level 17 in the oil pan 18 of the internal combustion engine is also specified. For this, a very narrow value range was also proposed depending on the pressure drop of the blow-by gas across the filter.

[0054] For the throttle element 14, arranged at a point between the outlet of the blow-by gas from the filter medium and the introduction point 20 into the intake tract, a special device is proposed with which a defined flow resistance is generated in the blow-by gas line as a function of the negative pressure (compared to atmosphere) at the introduction point 20. It has proven particularly advantageous to select the dependence of the flow resistance on the negative pressure at the introduction point 20 in such a way that this resistance only becomes effective above a certain engine power and increases with increasing negative pressure in a defined manner, which can be tailored to the specific requirements by setting parameters via an adjustment device. One simple way to implement this is to have a throttle element 14 at the outlet area orto install a spring-loaded control valve in the connecting line from blow-by filter unit 1 to inlet point 20, as shown in . Fig. 3 shown schematically: Fig. Figure 3 shows the pressure relief valve for the blow-by gas at the outlet of the blow-by filter unit 1. For this purpose, a functional component is mounted on the housing of the blow-by filter unit 1. This component includes a cylindrical control slide 24 preloaded by the spring 21, a spacer 22, and an adjustment device 23 for the position of the spacer, which determines the spring force. If the negative pressure in the outlet line 19 is sufficiently high, the external pressure pushes the control slide 24 inward against the spring force, thus reducing the outlet cross-section of the outlet line 19.

[0055] In the following, several diagrams are used to illustrate the difference between the invention (E) and the prior art (S): The diagram in Fig. Figure 4 shows the range of values ​​for the average flow velocity of the intake air at the point of introduction of the blow-by gas into the intake tract as a function of the pressure drop across the filter (relative to full engine load and new condition of the filter medium) according to the known and practiced prior art S, as well as according to the invention proposal E. This shows that the proposed range of values ​​differs very significantly from the prior art S. As explained above, this is only possible without problems by combining the proposed measures. Fig. Figure 5 shows a diagram showing the difference between the prior art S and the invention proposal E for the vertical distance of the lower edge of the filter housing from the oil level 17 in the oil pan 18 of the internal combustion engine, also as a function of the pressure drop across the filter medium. Here, too, as in Fig. 4, the difference from the prior art S becomes very clear. The proposed value range according to invention proposal E is limited to a very narrow band, slightly increasing with the pressure drop, which is relatively far removed from the value range corresponding to the known and practiced prior art S. Fig. Figure 6 compares the value ranges for the distance of the blow-by filter unit 1 from the compressor 6, before which the blow-by gas is introduced into the intake tract. Here, too, the value range provided by the invention differs significantly from the prior art.

[0056] Fig.7 finally shows the obvious difference between the proposed value ranges for the specific filter size and the state of the art S. Due to the significantly smaller filter volume, significantly more cost-effective and compact filters can be used, which can subsequently also be better integrated into the aggregate structure. List of reference symbols: E Invention proposal S State of the art 1 blow-by filter unit 2 Blow-by gas inlet 3 Permeate outlet 4 Oil outlet 5 intermediate link 6 compressors 7 Compaction device 8 air filters 9 Fuel supply 10 Compressor impeller 11 Suction mouth 12 Turbine runner 13 Vacuum relief valve 14 Throttle element 15 Distance measure 16 vertical distance 17 Oil level 18 Oil pan 19 Outlet line 20 Discharge point 21 spring 22 spacers 23 Adjustment device 24 control slides

Claims

[1] Internal combustion engine, comprising i) an intake tract with a compression device (7), ii) a piston-cylinder unit, iii) a crankcase, and iv) a blow-by filter unit (1) having a blow-by gas inlet (2) and a permeate outlet (3), wherein the blow-by gas inlet (2) is connected to the crankcase and the intake tract has an inlet point (20) for the permeate outlet (3), wherein the inlet point (20) for the permeate outlet (3) is arranged in the flow direction immediately upstream of the compression device (7), characterized by that the filter volume (V opt ) of the blow-by filter unit the product K r * N Mot where K r an adjustment constant with dimension m 3 / kW and N Mot is the full load power of the combustion engine in kW, where K r between 0.80*10 -5 and 1.6*10 -5amounts. [2] Internal combustion engine according to claim 1, characterized by that the compression device (7) is connected to the intake tract by a connecting flange and has an impeller (10) with a diameter (d), wherein the distance (31) from the inlet point (20) for the permeate outlet (3) to the connecting flange (30) is a maximum of 1.5 times the diameter (d) of the impeller (10). [3] Internal combustion engine according to claim 1 or claim 2, characterized by that a fuel inlet (9) is provided which is arranged in the flow direction upstream of the compression device (7). [4] Internal combustion engine according to one of claims 1 to 3, characterized by that at the inlet point (20) for the permeate outlet, at full load of the combustion engine, there is a flow velocity of the combustion air averaged over the cross section of between 85 and 110 m / s. [5] Internal combustion engine according to one of claims 1 to 4, characterized bythat the blow-by filter unit (1) is designed such that the pressure drop between the blow-by gas inlet (2) and the permeate outlet (3) at full load of the internal combustion engine in the new state of the filter medium of the blow-by filter unit (1) is at least 25 mbar. [6] Internal combustion engine according to one of claims 1 to 5, characterized by that the internal combustion engine has an oil pan (18) and that the blow-by filter unit (1) has a housing, wherein the housing bottom of the blow-by filter unit (1) is at a vertical distance (H opt ), wherein the vertical distance (H opt ) the sum of the constant H rand the product 4π*j*Δp, where Δp is the pressure drop between the blow-by gas inlet (2) and the permeate outlet (3) of the blow-by gas across the blow-by filter unit (1) at full load of the combustion engine in the new state of the filter medium of the blow-by filter unit (1), j is a dimensional converter with the value 1 mm / mbar and H r between 150 and 250 mm. [7] Internal combustion engine according to one of claims 1 to 6, characterized by that the blow-by filter unit (1) has a negative pressure limiting device (14) with which the negative pressure at the permeate outlet (3) of the blow-by filter unit (1) can be adjusted. [8] Internal combustion engine according to claim 7, characterized by that the vacuum limiting device (14) has a vacuum control device. [9] Internal combustion engine according to claim 7, characterized bythat the vacuum control device (14) comprises a spring-loaded control slide which, due to the pressure difference between the pressure in the connecting line between the blow-by gas inlet (2) and the introduction point (20) and the ambient pressure, experiences a change in position against the spring force, whereby the free flow cross-section can be changed. [10] Internal combustion engine according to one of claims 1 to 9, characterized by that the blow-by filter unit (1) is assigned a vacuum limiting valve (13) which, from a predeterminable vacuum at the blow-by gas inlet, releases a flow cross-section to the ambient air through which ambient air can be sucked in. [11] Internal combustion engine according to one of claims 1 to 10, characterized by that the distance (D opt ) between the housing of the blow-by filter unit (1) and the compression device (7) the sum of a constant D r in mm and the product 0.0225 * i * N Motwhere i is a dimensional converter with the value 1 mm / kW and N Mot is the full load power of the combustion engine in kW, where D r takes a value between 100 and 160 mm. [12] Blow-by filter unit, characterized by a vacuum limiting device (13, 14) with which the vacuum at the permeate outlet or at the blow-by gas inlet can be adjusted, wherein a vacuum limiting valve is provided which, from a predeterminable vacuum at the blow-by gas inlet, releases a flow cross-section to the ambient air through which ambient air can be sucked in. [13] Blow-by filter unit according to claim 12, characterized by that the vacuum limiting device has a vacuum control device. [14] Blow-by filter unit according to claim 13, characterized bythat the vacuum control device comprises a spring-loaded control slide which, due to the pressure difference between the pressure in the connecting line between the blow-by gas inlet and the introduction point and the ambient pressure, experiences a change in position against the spring force, whereby the free flow cross-section can be changed. [15] Method for operating an internal combustion engine according to one of claims 1 to 11, with an intake tract, a compression device, a piston-cylinder unit, a crankcase, and a blow-by filter unit, wherein blow-by gas is passed from the crankcase via the blow-by filter unit and introduced into the intake tract immediately upstream of the compressor unit.

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