DE102007053890A1 - Method for operating internal combustion engine, involves designing of swirl duct valve for increasing swirl amplitude by small valve lifts, particularly in area between two millimeters and four millimeters - Google Patents

Abstract

The method involves designing of a swirl duct valve for increasing the swirl amplitude by small valve lifts, particularly in an area between 2 millimeters and 4 millimeters. A soot number is adjusted by different opening positions of the swirl flap in an operating point. An effective medium pressure of 2 bars and a constant nitrogen oxides untreated emission or a soot number are adjusted in an operating point. An independent claim is included for an internal combustion engine has a compression ignition.

Description

The The present invention relates to a method of operating an internal combustion engine with auto-ignition according to the generic term of the independent claim.

The The invention relates in particular to a generic type Method for operating an internal combustion engine with reduced Soot and nitrogen oxide (NOx) emissions in operation of generic Internal combustion engines are generated. Furthermore, the invention relates a generic internal combustion engine for execution of the procedure.

to Fulfill current and future stringent emission limits for diesel cars is the use of different technologies known that a vote relatively many internal and external motor Include emission reduction measures. Known Motorized measures to reduce raw emissions concern the combustion process (firing design, channel shape, twist the intake flow), adjustment of the lambda value, injection timing and exhaust gas recirculation, injection system (adaptation the course of injection), exhaust gas recirculation, charging, Intercooling, water injection. Engine- Exhaust aftertreatment measures include the use of Particulate filters, oxidation catalysts and NOx catalysts.

Known is also that in diesel engines measures that the soot emissions reduce, tend to increase the knit oxide emissions. While it is still for compliance with Euro4 emission limits was possible at relatively low NOx emissions relative tolerate high levels of soot emissions, as the latter can be tolerated by Exhaust system arranged particulate filters could be collected this is no longer the case with the stricter emission limits according to Euro5 possible because the particle filter already too short time have a high load, which is a frequent regeneration with correspondingly high fuel consumption and increased Carbon dioxide emissions result.

From the DE 3612029 A1 An air-compressing reciprocating internal combustion engine is already known. With an approximately concentric in the piston arc rotationally symmetric combustion bowls, an injection device having a injecting into the combustion bowl injection nozzle having at least four spray holes and with a rotational movement of the entering into the combustion bowl charge air inlet device. The diameter of the combustion bowl amounts to more than 55% of the cylinder diameter. The rotational movement of the charge air generated by the inlet device has a swirl number determined by the impeller method of about 1.5 to 2.5, wherein the injection device for a delivery rate of 5 to 15 mm ³ / degree crank angle and in the pressure chamber of the injector prevailing injection pressures from 500 to 200 bar is designed. The aim of the specified measures is to achieve an increase in the power output, a reduction of the roughness emissions and the emissions of gaseous exhaust gas components, a noise reduction and to relieve the mechanically highly stressed machine parts. However, with these known measures it is not possible to achieve the limit values of the Euro5 emission standard for nitrogen oxides and particulates (PM) for diesel passenger cars.

task The present invention is therefore in an internal combustion engine with auto-ignition a reduction of the raw emissions of nitrogen oxides and soot particles, so that these possible close to the respective limit set by Euro Standard 5 come and in a motor vehicle with a arranged in the exhaust system Particulate filter the said EU5 limit values of end-pipe emissions can be reached or fallen below.

The The object is achieved by a method to operate an internal combustion engine with auto-ignition solved with the features of the independent claim.

The inventive method for operating an internal combustion engine with auto-ignition with an engine block with at least one cylinder and a piston associated therewith, an injection system for direct fuel injection into the cylinder and a
Inlet device for charge air with at least one inlet passage and an associated inlet valve and a
Exhaust device for exhaust gas with at least one outlet channel and an associated exhaust valve and a subsequent exhaust system with particulate filter
wherein the cylinder has a cylinder head and the piston has a piston head and the cylinder head and piston head form inner surfaces of a combustion chamber
and in the surface of the piston head, a piston recess is arranged with a trough edge, wherein in a normalized to a circle trough edge, the ratio of bowl rim diameter to piston diameter is greater than 0.55 or in a 90% filled piston bowl with a normalized to a circle filling surface, the ratio the filling surface to the piston cross-sectional area> 0.30
an inlet channel is formed as a swirl channel with an associated swirl channel valve, wherein the inlet flow into the combustion chamber receives a twist,
the inlet device as a further inlet channel a filling channel with an associated Füllkanalventil wherein the filling channel can be opened and closed by a switchable swirl flap, wherein the swirl flap has at least three open positions
provides that
the swirl duct valve is designed to increase the swirl at small valve strokes, in particular in a range between 2 mm and 4 mm, and
by means of different opening positions of the swirl flap
at an operating point of 1500 1 / min. and an effective mean pressure of 2 bar and a constant NOx raw emission <0.7 g / kWh a soot number FSN <0.2 is set
and or
at an operating point of 2000 1 / min. and 5 bar effective mean pressure and a raw NOx emission <1.2 g / kWh a soot number FSN <0.8 is set
and or
at an operating point at 2000 1 / min. and 8 bar effective mean pressure and a constant NOx raw emission <1.5 g / kWh a soot number FSN <1 is set.

Of the Internal combustion engine with self-ignition can by means of different opening positions of the Swirl flap operated so that at an operating point of 1500 1 / min. and an effective mean pressure of 2 bar and one constant NOx raw emissions of <than 0.7 g / kWh a soot number FSN of <than 0.2 is set.

Further it is envisaged that at an operating point of 2000 1 / min. and 5 bar effective mean pressure and a raw NOx emission of <1.2 g / kWh Soot number FSN of <than 0.8 is set and / or at an operating point at 2000 1 / min. and 8 bar effective medium pressure and a constant NOx raw emission less than 1.5 g / kWh a soot number FSN of less is set as 1.

The swirl increase is preferably in a range between 2 mm and 4 mm, if necessary. With spin values and flow coefficients as in connection with the 5 and 6 and the associated description has been presented.

The said swirl increase can by means of a processing of the swirl duct valve be achieved, as will be explained in more detail.

The method is executable with an internal combustion engine with self-ignition with an engine block having at least one cylinder and a piston associated therewith, an injection system for fuel injection into the cylinder and a
Inlet device for charge air with at least one inlet passage and an associated inlet valve and a
Exhaust gas outlet device with at least one outlet channel and an outlet valve associated therewith and a downstream exhaust system with particle filter,
wherein the cylinder has a cylinder head and the piston has a piston head and the cylinder head and piston head form inner surfaces of a combustion chamber
and in the surface of the piston head, a piston recess is arranged with a trough edge, wherein in a normalized to a circle trough edge, the ratio of bowl rim diameter to piston diameter is greater than 0.55 or in a 90% filled piston bowl with a normalized to a circle filling surface, the ratio the filling surface to the piston cross-sectional area> 0.30
an intake passage is formed as a swirl passage with an associated swirl passage valve, wherein the intake flow into the combustion chamber receives a swirl.

The internal combustion engine is configured for at least one selected cylinder at single-port opening
the inlet flow at at least one valve lift Vh between 2 mm and Vhh = 0.5 · Vhm has a swirl increase with a valve lift-dependent Tippelmann swirl number D having a value> 0.3, where Vhm denotes the maximum valve lift, in particular with a value Vhm = 8 mm,
the inlet flow in a valve lift range between Vh = 2 mm and Vhh = 0.5 Vhm has a swirl increase with a normalized integral Tippelmann swirl number Di with a value> 0.40 / mm or
the inlet flow in a Ventilhubbereich between Vh = 2 mm and Vhh = 0.5 Vhm has a swirl increase, so that in a measurement of the valve lift-dependent Tippelmann swirl number D at intervals of 0.5 mm, the average Tippelmann swirl number Dm for at least one valve lift interval DeltaV = 1 mm has a value> 0.4.

at Single-channel opening takes place only via the swirl channel a supply of charge air into the combustion chamber.

With It is the internal combustion engine according to the invention possible at operating point 2000 1 / min and an effective Medium pressure of 8 bar a NOx emission of <1.55 g / kWh with a soot emission of <0.08 g / kWh to reach. Preferably, the inventive Internal combustion engine in the above operating point also Emissions of <1.5, 1.43, 1.38 and 1.3 g / kWh at quiescent emissions of <0.075, 0.071, 0.065 or 0.006 g / kWh to reach.

A motor vehicle equipped with the internal combustion engine according to the invention, when operated in the new European driving cycle, has NOx raw emissions of <300 mg / km and raw particle emissions of one value of <35 mg / km. Preferably, such a motor vehicle NOx emissions with a value of <280 mg / km, 235 mg / km, 200 mg / km, 180 mg / km or 160 mg / km and at the same time raw particle emissions, which have a value of 40 mg / km , 45 mg / km, 50 mg / km, 55 mg / km or 60 mg / km.

One Such vehicle reaches or falls below when using a Particulate filter the emission limits of the new European Standard EU5.

In A preferred embodiment provides that the inlet flow at single-channel opening and at maximum valve lift Vhm, in particular with Vhm = 8 mm, a Ventilhubabhängige Tippelmann swirl number D with a value> 0.4 and / or the inlet valve one Ventilhubabhängigen flow coefficient αK> 0.04 has: Thus can be an improved mixture preparation at the same time reach good cylinder filling.

advantageous Further developments of the invention are the dependent claims refer to.

The Invention will hereinafter be independent of the summary Presentation in the claims with reference to in drawings illustrated embodiments described in more detail which results in further advantages and aspects of the invention.

It demonstrate

1 : an internal combustion engine according to the invention with auto-ignition,

2 a piston head with a piston recess,

3a and 3b : Swirl and fill channels of an inlet device with swirl flap,

3c Photos: Valve seats with machining,

4 : a Tippelmann test bench,

5 : a representation of valve lift-dependent swirl and flow in single-channel operation,

6 : a representation of valve lift-dependent swirl and flow in two-channel operation,

7 : Soot emissions depending on open positions of a swirl flap,

8th : Soot emissions depending on open positions of a swirl flap,

9 : Soot emissions depending on open positions of a swirl flap,

10 - 12 : Soot emissions depending on the opening positions of a swirl flap.

In 1 is an inventive passenger car internal combustion engine 101 shown with auto-ignition with which it is possible to achieve both low soot (particle) emissions and NOx raw emissions. The engine according to the invention is preferably after with fuel DIN EN 590 operated.

It is understood that in others, in the 1 not shown embodiments, certain components that are shown in Figure, missing or other components may be added without departing from the scope of the invention.

Of the 1 shown self-igniting internal combustion engine 101 has an engine block 102 , four cylinders (not provided with reference numerals), an inlet direction 103 for charge air, designed as a common rail injection system 104 for fuel injection into the cylinders as well as an outlet device 105 for exhaust on. To the outlet 105 is an exhaust system 106 with a diesel particulate filter 107 connected. Upstream of the diesel particulate filter 107 is an oxidation catalyst 107a arranged, which may be missing in other embodiments of the invention.

The diesel particulate filter 107 keeps back the soot particles produced during combustion of the diesel fuel. The particle filter preferably works 107 without the addition of additives; However, it is also the use of particulate filters that require additives conceivable. The particle filter consists of a porous ceramic component with a precious metal-containing coating. To ensure the continuity of the filter in the long term, the particles deposited in the filter must be removed by passive and / or active regeneration. With wall-flow filters today high deposition rates of 95% and more of the total particle mass can be achieved with a small increase in fuel consumption. Similarly high values are achieved with flow filters in which a more than 90% reduction in the number of particles can be achieved.

The exhaust system is equipped with an exhaust gas recirculation (EGR) system with an EGR valve 109 and EGR cooling 110 connected, the exhaust gas recirculation cooling 110 provided with a low temperature oil circuit. With the exhaust system is also a turbocharger 115 connected. Downstream of the compressor of the exhaust gas turbocharger 115 is arranged a charge air cooler.

It is understood that to meet strict emission standards, the various in 1 shown components must be coordinated sen.

in the The following are important components of an inventive Internal combustion engine shown in more detail. Preferably, this is for fast running passenger cars or light commercial vehicles designed.

In 2 is a piston head 201 of an internal combustion engine according to the invention with auto-ignition shown schematically, wherein in the surface 202 of the piston head 201 a piston recess formed by a recess 206 is arranged. The hollow 206 is formed by a trough contour forming the wall area 207 defined, located in the piston surface 202 starting from the piston edge 208 extends. As a trough edge 208 becomes the outermost part of the piston recess 206 understood as the bowl edge diameter of the cross-sectional diameter of the trough 206 at the point where the trough contour 207 a slope 1 has been designated. At this point is the trough contour 207 parallel to the piston axis 209 ,

The in 2 illustrated piston head 201 is arranged in the operation of the internal combustion engine in a cylinder, not shown in the figure, in which the piston reciprocates and is connected to a crankshaft, not shown, that the piston performs a movement with a reversal at an upper and lower dead center. The cylinder has a cylinder head, which forms with the piston head inner surfaces of a combustion chamber, is injected into the fuel. The injected into the cylinder fuel forms with compressed gas, a fuel-gas mixture that is ignited by generated during operation of the internal combustion engine heat of compression.

typically, The internal combustion engine has four to six cylinders.

The piston recess 206 indicates an area of the contour 207 with less depth and a peripheral area of the contour 207 with a greater depth, in each case with respect to the piston surface, wherein the invention comprises embodiments with larger and smaller differences in depth.

The piston recess 206 can also have a non-circular piston edge 208 exhibit. In this case, the bowl rim diameter becomes 203 defined at a bowl edge nominated for a circle.

The Ratio of bowl rim diameter to piston rim diameter is> 0.55, preferably> 0.58, 0.60, 0.62, 0.65, 0.70 or 0.80, resulting in a larger free Injection length and improved mixture preparation leads.

In a further embodiment of the invention is in a 90% filled piston recess 206 in the case of a filling surface nominated for a circle, the ratio of the filling surface to the piston cross-sectional area> 0.30. Also in this embodiment of the invention is a relatively large piston recess with the corresponding advantages presented above.

In the 2 shown piston recess 206 has in its peripheral wall region on an undercut, that is, the maximum piston inner diameter is greater than the piston rim diameter 203 , In other embodiments of the invention, the piston recess 206 no undercut.

The maximum bowl internal diameter is preferably at most 15%, 10%, 8%, 6%, 4%, 3% or 1% larger than the bowl rim diameter 203 , Thus, a larger free jet length of the injected fuel can be achieved and the order of liquid fuel can be reduced to the peripheral wall area.

Of the or the cylinders have a bore of less than 110 mm. Preferably, the bore also ≤ than 100 mm, 95 mm or 90 mm. The single cylinder volume is less than 0.8 l, preferably <than 0.7 l or 0.6 l.

Further is the cylinder with an injection system for direct fuel injection connected to the cylinder. The injection system is in common rail technology trained with the fuel with up to 1800 bar in the cylinder is injected. It is understood that the invention also with other injection systems and / or higher injection pressures is working.

The Injection system includes to ensure a high Homogeneity of the mixture and low soot formation during of the diesel combustion process an injector with a nozzle seat and a nozzle element with more than 7 holes. Preferably the injector has a number of holes of> = 8, 9, 10, 12 or 14. The injector is preferably arranged centrally to the piston recess.

at an injector with 8 hole nozzle is a hole diameter of 0.123 mm preferred. The larger number of holes allows a more even distribution of the fuel in the combustion chamber and thus a emission reduction if possible low fuel consumption.

The injector flow rate is adjusted to the number of holes. Preferably, for a number of holes> 7, the flow rate DDF at the fuel through the injector is determined within 30 seconds at an injection pressure of 100 bar by DDF = (-230 + 70 · L) · (1 + - 0.20), wherein the number of holes is denoted by L.

at the measurement of the flow rate of the injector is only the nozzle seat measured without nozzle element.

With the cylinder is an inlet device for charge air with at least one inlet channel with an associated inlet valve and an exhaust gas outlet device having at least one Exhaust valve and associated with this outlet valve, as will be shown in more detail below. As a charge air is the called charge of fresh air to the engine - too in the case of an engine without turbocharging or the like.

at The engine according to the invention has the inlet device at least one inlet channel, which as swirl channel with an associated Swirl channel valve is formed, wherein the inlet flow in the combustion chamber receives a swirl - a turbulence the charge air with a substantially parallel to the cylinder axis oriented axis of rotation. As inlet flow, the during the intake phase in the cylinder inflowing charge air called.

Of the Swirl of intake flow into the combustion chamber supported the mixture preparation and can the kinetic energy in the cylinder increase what contribute to accelerated combustion can. Since the twist the ignition delay at the Increase combustion, it reduces the order of fuel on the cylinder walls and thus the formation of hydrocarbons and Russ. On the other hand, a low twist leads to less Heat loss, better efficiency before ignition and lower NOx emissions. Therefore, more or less Spin favorable for the particle and NOx emissions be. The invention aims at optimizing the inlet flow dell to reduce soot formation with low NOx formation.

Of the Swirl of the inlet flow is determined by the geometry of the Intake channel and the inlet valve determines; with more than one Inlet through the geometry of the inlet channels and the inlet valves each flows through the charge air become. To achieve a given twist, the geometry intake passage and associated intake valve by itself set known optimization method.

In a preferred embodiment, the inventive Internal combustion engine an inlet device with a swirl duct and a filling channel, wherein the filling channel for Charge air operating point dependent opened or closed can be.

In 3a . 3b are a spin channel 301 and a filling channel 302 an inlet device for charge air of the internal combustion engine according to the invention shown.

swirl channel 301 and filling channel 302 each have a swirl channel valve 307 or filling channel valve 308 on. The filling channel 302 can by a switchable swirl flap 303 be opened and closed. Preferably, the swirl flap 303 at least two open positions, preferably three and more open positions. The open position is understood to mean the closed position. Furthermore, the swirl flap can also be adjusted continuously.

In 3a is the swirl flap 303 closed, in 3b is the swirl flap 303 open against it. When the swirl flap is closed, charge air can only pass through the swirl channel 301 be supplied to the combustion chamber.

In the in the 3a . 3b shown swirl channel 301 it is a tangential channel with direct inflow. However, the invention also includes swirl channels of other geometries, such as a baffle tangential channel or spiral or flat helical ramp spiral channels.

The filling channel 302 is traversed as straight as possible, to a higher cylinder filling than through the swirl duct 301 to allow in which the air flow obstructs the flow. By means of the swirl channel 302 Therefore, depending on demand, the air flow can be increased. However, the filling channel can also be designed as a spiral channel.

The swirl passage valve is designed according to the invention to increase the swirl at low valve strokes, as exemplified in 3c is illustrated.

to Raising the twist at low valve lift, the valve seat a, preferably asymmetric with respect to a vertical valve axis, machining on; for example, in the manner of masking or shielding, whereby the air mass flow at the beginning of the valve in a defined direction is steered.

In the case of a valve with shielding, the defined flow direction is predetermined by a shielding plate on the valve; compare left side of 3c , At a small valve lift is in an area of the periphery of the valve seat 315 between 30 ° and 210 ° a gap 317 educated.

The right side of 3c shows a valve seat, wherein in the cylinder head a bevel is incorporated, which is referred to as Sitzdrallfase (SDF). At a small valve lift is in one Area of the periphery of the valve seat 315 between 30 ° and 210 ° a gap 318 educated.

In both cases, the air mass flow at small valve strokes (in a range of 2 mm to 4 mm or 50% of the maximum valve lift Vhm) through the gap 317 respectively. 318 stream. Preferably, the air mass flow is deflected at small valve strokes of the cylinder wall and thus causes a rotation of the cylinder charge.

In the context of the invention, the swirl of the inlet flow is characterized by the valve-dependent Tippelmann swirl number, which can be measured on a Tippelmann test bench; see. JB Heywood Internal Combustion Engine Fundamentals, 1998 ,

• • M_z – Drehmoment an der Wabe
• • R_Zyl – Zylinderradius
• • V – Volumenstrom durch den Zylinder
• • p_L – Dichte der Luft im Zylinder

In 4 is the schematic structure of a Tippelmann test bench 401 for measuring the valve lift-dependent Tippelmann swirl number D shown, wherein through an inlet channel 404 with an inlet valve 405 incoming charge air to the interior of the cylinder 402 is supplied. A swirling flow 406 is in the cylinder 402 over a honeycomb 403 in the direction of the cylinder axis 407 diverted. That from the angular momentum of the swirling flow 406 resulting torque M _z is applied to the honeycomb 403 depending on the valve lift of the intake valve 405 measured. From the torque M _z , the valve lift-dependent Tippelmann swirl number D can be calculated using the following equation.

• • M _z - torque on the honeycomb
• • R _Cyl cylinder radius
• • V - flow through the cylinder
• • p _L - density of air in the cylinder

In contrast to the swirl moment M _z , the swirl number D is directly comparable for different cylinder heads of similar engines and is therefore used to characterize the swirl according to the invention.

The relatively large piston recess has the advantage of a better Fill with charge air and a lower thermal load of the piston, however, due to a decrease in the twist a relatively smaller piston recess. This decrease of the twist will counteracted according to the invention.

According to the invention, the internal combustion engine has an inlet flow with swirl lift at low valve lifts, wherein it is provided that
the inlet flow at at least one valve lift Vh between 2 mm and Vhh = 0.5 · Vhm a swirl increase with a valve lift-dependent Tippelmann swirl number D with a value>0.3;0.4;0.5;0.6; 0.7, wherein Vhm denotes the maximum valve lift, in particular with a value Vhm = 8 mm,
the inlet flow in a valve lift range between Vh = 2 mm and Vhh = 0.5 · Vhm has a swirl lift with a normalized integral Tippelmann swirl Di having a value> 0.40 / mm, 0.50 / mm or 0.60 / mm or
the inlet flow in a Ventilhubbereich between Vh = 2 mm and Vhh = 0.5 Vhm has a swirl increase, so that in a measurement of the valve lift-dependent Tippelmann swirl number D at intervals of 0.5 mm, the average Tippelmann swirl number Dm for at least one valve lift interval DeltaV = 1 mm a value ≥ 0.4; 0.5; 0.6; 0.7.

inlet flows of internal combustion engines with compression ignition comparable with relatively large piston recess in the prior art have for small valve strokes (range from 2 mm to 5 mm or range of 2 mm to 50% of Vhm) a valve lift-dependent Tippelmann swirl number D with a value around 0.2.

Advantageous has in the internal combustion engine according to the invention the inlet flow into a range of small valve strokes a swirl increase, so that in this Ventilhubbereich a definite maintain high swirl orientation of the inlet flow that is in a piston with a relatively large piston recess with a ratio of bowl rim diameter to piston rim diameter> 0.55 it allows both achieve low emissions of particulate matter as well as NOx.

The 5 shows measurements of the swirl number in an inlet device with a swirl channel and a filling channel, wherein the filling channel is closed by a swirl flap (single-channel operation), and thus an increased swirl of the inlet flow is effected. The swirl increase at small valve strokes is preferably achieved by machining the valve seat of the swirl passage valve. Particularly preferred is the mentioned Sitzdrallfase SDF.

In 5 is with the curves 501 respectively. 503 the valve lift-dependent Tippelmann swirl number D is plotted against the valve lift, wherein 501 the swirl number according to the invention with a Sitzdrallfase and the curve 503 describes the swirl number with otherwise the same swirl passage and swirl passage valve without swirl increase by a Sitzdrallfase.

Of the maximum valve lift has a value of 8 mm, but it goes without saying also have a different value.

It can be seen that the inlet flow according to curve 501 at low valve strokes of 2 mm, 3 mm or 4 mm, each have high values D of 0.7, 0.4 and 0.3.

Prefers are within the scope of the invention also values of the swirl number> 2; 3; 4 in the valve lift 2 mm to 5 mm.

Further can inlet flow in a valve lift between Vh = 2 mm and Vhh = 0.5 · Vhm a swirl lift with a normalized integral Tippelmann swirl Di having a value> 0.40 / mm. As a normalized integral Tippelmann spin number, the integral of over a valve lift interval divided by the interval length designated.

Further The intake flow may be in a valve lift range between Vh = 2 mm and Vhh = 0.5 Vhm have a swirl lift, so that during a measurement of the valve lift-dependent Tippelmann swirl number D at intervals of 0.5 mm the central Tippelmann swirl number Dm for at least one valve lift interval DeltaV = 1 mm has a value ≥ 0.4.

In 5 It can be seen that the swirl number plotted against the valve lift between a value at Vh = 2 mm and a value at 8 mm at about 4 mm valve lift has a minimum. The swirl number decreases from its value at 2 mm valve lift, reaches a minimum within a range of 0.5 Vhm and then increases again. With this "bathtub shape" it is possible to achieve high swirl numbers with low and high valve lift.

The inlet flow according to curve 503 on the other hand has smaller swirl numbers D in the range between 0.15 and 2 for small valve strokes in the range between 2 and 4 mm.

According to the invention Furthermore, a high twist D of more than 0.4, even at maximum valve lift provided in order to further improve the mixture preparation. The high swirl at maximum valve lift is preferably by design reached the swirl channel.

Next the swirl number is the flow through the inlet valve (s) an important parameter for the characterization of Inlet flow.

The valve-lift-dependent flow coefficient αk characterizes the inflow into the cylinder through the intake valve (s), that is, the permeability of the valve, wherein an actual mass air flow is related to a theoretically possible air mass flow, as for example in the publication C. Kopp, variable valve control for passenger car diesel engines with direct injection, Magdeburg 2006 is shown. A high value of α _k has a positive effect on the cylinder filling.

• • m_tats – tatsächlicher Luftmassenstrom [kg/s]
• • m_theor – theoretischer Luftmassenstrom [kg/s]
• • A_zyl – Querschnittsfläche des Messzylinders [m²]
• • c_s – Strömungsgeschwindigkeit bei isentroper Durchströmung [m/s]
• • p_s – Luftdichte im Zylinder bei isentroper Durchströmung [kg/m³]

wobei

• • R_L – spezielle Gaskonstante für Luft [J/(kg·K)]
• • T – Temperatur [K]
• • κ – Isentropenexponent [-]
• • p_nach – Druck nach Ventil [Pa]
• • p_vor – Druck vor Ventil [Pa]

α _k for a cylinder can be determined according to the following formula.

• • _actual - actual air mass flow [kg / s]
• • m _theor - theoretical mass air flow [kg / s]
• • A _zyl - cross-sectional area of the measuring cylinder [m ² ]
• • c _s - flow velocity with isentropic flow [m / s]
• • p _s - air density in the cylinder with isentropic flow [kg / m ³ ]

in which

• • R _L - special gas constant for air [J / (kg · K)]
• • T - temperature [K]
• • κ - isentropic exponent [-]
• • p _after - pressure after valve [Pa]
• • p _before - pressure before valve [Pa]

The pressure before the valve p _before corresponds to the ambient pressure in the above equations. After the valve the pressure prevailing in the measuring cylinder pressure p is given _by by the compressor of the test stand. During the measurement, a constant pressure difference of 50 hPa is set.

at the design of the inlet ducts and inlet valves is preferably a target conflict between high spin for a good mixture preparation and a high permeability the valve for a good cylinder filling bill be worn. This is achieved by the fact that at low valve lifts a swirl increase and at maximum valve lift a high flow is provided.

In 5 turns curve 503 the course of the valve lift-dependent flow coefficient αk in a range of the valve lift between 2 mm and 8 mm.

Preferably is in the engine according to the invention at 8 mm valve lift the flow coefficient> 0.04. In further embodiments of the invention, the flow coefficient αk> 0.045 or 0.005 at 8 mm valve lift. Thus, in the invention, a high twist at small valve lifts with a high flow coefficient combined with large or maximum valve lift.

The 6 shows measurements of the swirl number in an inlet device with a swirl channel and a fully open filling channel (two-channel operation), wherein the filling channel is not closed by a swirl cap and thus a higher throughput of charge air can be achieved. For a valve lift in a range between 2 and 4 mm, the valve lift-dependent Tippelmann swirl number has a value> 0.035. With a 2 mm valve lift, the swirl number is> 0.45. With a valve lift of 8 mm, the swirl number is> 0.35.

In 6 is analogous to 5 recognizable that the swirl number plotted against the valve lift between a value at Vh = 2 mm and a value at 8 mm approximately at 4 mm valve lift has a minimum. The swirl number decreases from its value at 2 mm valve lift, reaches its minimum within a range of 0.5 Vhm (8 mm) and then increases again. With this "bathtub shape" it is possible to achieve high swirl numbers with low and high valve lift.

In In another embodiment, the swirl number contributes 8 mm valve lift has a maximum value of 0.6.

The curve 602 represents the course of the valve lift-dependent flow coefficient αk and points opposite to the curve 502 of the 5 an increase in the valve lift-dependent flow coefficient αk.

The Invention allows operating point dependent at constant NOx raw emissions, the soot raw emissions depending on an open position of a Adjust swirl flap.

In 7 are exemplary for a supercharged 4-cylinder diesel engine with 1,968 cm ³ capacity and a bore of 81 mm 95.5 mm stroke, a depression diameter of 53 mm, a bowl rim diameter of 51.88 mm, a maximum power of 103 kW at a Speed of 4200 rpm, a maximum torque of 320 Nm at a speed of 1750 to 2500 1 / min, a compression of 16.5 to 1 soot raw emissions in units of filter smoke number (FSN) at a constant NOx raw emission of 0.5 g / kWh. The operating point is at a speed of 1500 1 / min. and an effective mean pressure of 2 bar. It is understood that the invention is not limited to this specific engine, but includes similar engines, if necessary, even without charging.

The Here employed inlet means in this case has a swirl duct and a filling channel, wherein the filling channel with a swirl flap is provided. The swirl flap can, preferably continuously switched to different opening positions being at a position of 90 °, the swirl flap closed and fully open at an open position of 0 ° is. Intermediate positions of 60 ° and 40 ° are preferred.

The curve 701 indicates the course of the soot emissions in an inventive engine with swirl lift. For comparison, the curve shows 702 the course of the soot emission as a function of the opening position of the swirl flap in a same engine without swirl increase. It can be seen that the soot emissions according to curve 701 for the engine according to the invention at all opening positions by at least 0.1 FSN below the values of the comparison curve 702 lie. It can also be seen that the soot emissions with a closed swirl flap, ie a single-channel operation via the swirl duct, are the lowest and increase with increasing opening of the swirl flap.

In 8th are for the same motor in an operating point with a speed of 3000 1 / min. and an effective mean pressure of 8 bar the soot emission at a constant NOx pipe mission of 1.3 g / kWh for different opening positions of the swirl flap shown. The curve 801 indicates the course of the soot emission as a function of the open position of the swirl flap according to the invention, while the curve 802 Comparative data without swirl increase according to the invention shows. It can be seen that the soot emission in the case according to the invention is at least 0.1 FSN lower than in the case of conventional technology. In contrast to the situation according to 7 At this operating point, the two-channel operation with fully open swirl flap is more favorable than the single-channel operation.

In 9 are for the same engine at an operating point at a speed of 2000 1 / min and an effective mean pressure of 5 bar, the soot raw emissions at a constant NOx raw emissions of 1 g / kwh different opening positions of the swirl flap shown. The curve 901 indicates the course of the soot emission dependency from the opening position of the swirl flap according to the invention, while the curve 902 Comparative data without swirl increase according to the invention shows. A minimum value of the soot emission is here at an intermediate position of the swirl flap with an open position of about 60 °.

The 10 - 12 show the 7 - 9 corresponding representations, whereby the soot emissions are plotted not in units FSN but in units g / kWh.

The internal combustion engine with self-ignition can therefore, if the swirl passage valve has a processing for swirl increase at small valve lifts by means of different opening positions the swirl flap are operated so that at an operating point of 1500 1 / min. and an effective mean pressure of 2 bar and a constant NOx raw emissions of <than 0.7 g / kWh a Rußzahl of <0.2 FSN (this corresponds to soot emissions of <than 0.2 g / kWh) is set. The swirl increase is preferably in a range between 2 mm and 4 mm, if necessary. With spin values and flow coefficients as in connection with the 5 and 6 and the associated description has been presented.

Further it is envisaged that at an operating point of 2000 1 / min. and 5 bar effective mean pressure and a raw NOx emission of <1.2 g / kWh Soot number is a soot number FSN of <0.8 (corresponding to soot emissions of <0.1 g / kWh) is and / or at an operating point at 2000 1 / min. and 8 bar effective Medium pressure and a constant NOx raw emissions of less than 1.5 g / kWh is a carbon number <1 FSN (corresponding to soot emissions of less than 0.2 g / kWh) is set.

101

internal combustion engine

102

block

103

intake means

104

injection

105

outlet

106

exhaust system

107

particulate Filter

107a

catalyst

108

Exhaust gas recirculation system

109

Exhaust gas recirculation valve

110

Exhaust gas recirculation cooling

111

Cooling circuit

115

turbocharger

116

Intercooler

201

piston head

202

surface of the piston head

203

Bowl rim diameter

204

Piston diameter

205

cooling channel

206

piston bowl

207

depression contour

208

bowl edge

209

piston axis

301

swirl channel

302

filling channel

303

swirl flap

304

Airflow swirl channel

305

airflow filling channel

306

cylinder

307

Valve

308

Valve

310

intake means

315

valve seat

316

valve seat

317

gap

401

Tippelmann Measuring Stand

402

cylinder

403

honeycomb

404

inlet channel

405

Valve

406

swirl flow

407

cylinder axis

501

Curve

502

Curve

601

Curve

602

Curve

701

Curve

702

Curve

801

Curve

802

Curve

901

Curve

902

Curve

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3612029 A1 [0005]

Cited non-patent literature

• - DIN EN 590 [0034]
• - JB Heywood Internal Combustion Engine Fundamentals, 1998 [0071]
• - C. Kopp, Variable Valve Control for Car Diesel Engines with Direct Injection, Magdeburg 2006 [0089]

Claims (22)

Method for operating an internal combustion engine with auto-ignition with an engine block having at least one cylinder and a piston associated therewith, an injection system for direct fuel injection into the cylinder and an intake device for charge air with at least one inlet passage and an associated intake valve and an outlet device for exhaust gas with at least one exhaust passage and an associated exhaust valve and a subsequent exhaust system with particulate filter wherein the cylinder has a cylinder head and the piston has a piston head and cylinder head and piston head inner surfaces of a combustion chamber and in the surface of the piston head a piston recess is arranged with a trough edge, wherein at one on a circle normalized bowl rim, the ratio of bowl rim diameter to piston diameter is greater than 0.55 or, in the case of a piston bowl filled to 90% with a filling surface normalized to a circle, the Ver is the ratio of the filling surface to the piston cross-sectional area> 0.30 an inlet channel is formed as a swirl duct with an associated swirl duct valve, wherein the inlet flow into the combustion chamber receives a twist, the inlet device as a further inlet channel having a filling channel with an associated Füllkanalventil, wherein the filling channel by a switchable Swirl flap can be opened and closed, wherein the swirl flap has at least three open positions, characterized in that the swirl passage valve for swirl increase at small valve strokes, especially in a range between 2 mm and 4 mm, designed and by means of different opening positions of the swirl flap at an operating point of 1500 1 / min. and an effective mean pressure of 2 bar and a constant NOx raw emission <0.7 g / kWh a soot number, preferably FSN <0.2 is set and / or at an operating point of 2000 1 / min. and 5 bar effective mean pressure and a raw NOx emission <1.2 g / kWh a soot number, preferably FSN <0.8 is set and / or at an operating point at 2000 1 / min. and 8 bar effective mean pressure and a constant NOx raw emission <1.5 g / kWh a soot number, preferably FSN <1 is set. Internal combustion engine with auto-ignition an engine block with at least one cylinder and one associated with it Piston, an injection system for direct fuel injection in the cylinder as well as one Inlet device for Charge air with at least one inlet passage and an inlet valve associated therewith and one Discharge device for exhaust gas with at least an outlet channel and an outlet valve associated therewith and a subsequent exhaust system with particle filter in which the cylinder has a cylinder head and the piston has a piston head Has and cylinder head and piston head inner surfaces of a Form combustion chamber and in the surface of the piston head a piston recess is arranged with a trough edge, wherein at a normalized to a circle trough edge the ratio from bowl rim diameter to piston diameter larger 0.55 or in the case of a 90% filled piston bowl a normalized to a circle filling the Ratio of the filling surface to the piston cross-sectional area> 0.30 one Inlet duct as a swirl duct with an associated swirl duct valve is formed, wherein the inlet flow into the combustion chamber gets a spin, characterized in that for at least one selected cylinder the inlet flow at least one valve lift Vh between 2 mm and Vhh = 0.5 · Vhm a swirl increase with a valve lift-dependent Tippelmann swirl number D with a value> 0.3 where Vhm is the maximum valve lift or, in particular, value Vhm = 8 mm, the inlet flow in one Valve lift range between Vh = 2 mm and Vhh = 0.5 · Vhm one Swirl lift with a normalized integral Tippelmann swirl number Di with a value> 0.40 / mm or the inlet flow in a valve lift area between Vh = 2 mm and Vhh = 0.5 Vhm has a swirl lift, such that during a measurement of Ventilhubabhängigen Tippelmann twist number D at intervals of 0.5 mm the middle one Tippelmann swirl number Dm for at least one valve lift interval DeltaV = 1 mm has a value ≥ 0.4. Internal combustion engine according to claim 2, characterized that the inlet flow at maximum valve lift Vhm, in particular with Vhm = 8 mm, a valve lift-dependent Tippelmann swirl number D with a value> 0.4 and / or the inlet valve has a valve lift-dependent flow coefficient αK> 0.04. Internal combustion engine according to claim 2 or 3, characterized characterized in that the inlet device as a further inlet channel a filling channel with an associated Füllkanalventil having. Internal combustion engine according to claim 4, characterized that the filling channel is opened by a switchable swirl flap and can be closed, wherein the swirl flap is preferably at least has two open positions. Internal combustion engine according to claim 4 or 5, characterized characterized in that the inlet flow at full open filling channel at least one valve lift Vh between 2 mm and Vhh = 0.5 · Vhm a valve lift dependent Tippelmann twist number D with a value> 0.3. Internal combustion engine according to claim 6, characterized that at maximum valve lift Vhm and fully open Filling channel The valve lift-dependent Tippelmann swirl number D is a value> 0.6 and / or the valve lift-dependent passage coefficient αK of swirl channel valve and filling channel valve has a value> 0.06. Internal combustion engine according to one of the preceding claims 1 to 6, characterized in that up to an effective mean pressure pme of less than 4 bar operating only with over the swirl duct supplied charge air is possible. Internal combustion engine according to one of the preceding claims 1 to 8, characterized in that after a range between 3 and 7 bar operation with a partially open Fill channel is possible. Internal combustion engine according to one of the preceding Claims 1 to 9, characterized in that for an effective mean pressure pme> 5 bar operation with fully open filling channel is possible. Internal combustion engine according to one of the preceding Claims 1 to 10, characterized in that the swirl flap is pivotable about an axis and at least two open positions from the group of opening positions of 90 °, 60 °, 40 ° or 0 ° can take. Internal combustion engine according to claim 11, characterized in that that the throttle valve at a speed of 1500 1 / min. and one effective mean pressure of 2 bar with a constant NOx emission soot emissions which has a value of at least 0.1 units below the Value of soot emissions without swirl increase at the same speed, same effective mean pressure and the same NOx emission are. Internal combustion engine according to claim 11 or 12, characterized characterized in that at an operating point at a speed of 2000 1 / min. and an effective mean pressure of 8 bar soot emissions a value of at least 0.1 units below the value without swirl increase lie in the same operating point. Internal combustion engine according to one of the preceding Claims 1 to 13, characterized in that an exhaust gas recirculation system is provided. Internal combustion engine according to one of the preceding Claims 1 to 14, characterized in that an exhaust gas turbocharger is provided. Internal combustion engine according to one of the preceding Claims 1 to 15, characterized in that the injection system is designed as a common rail system. Internal combustion engine according to one of the preceding Claims 1 to 16, characterized in that the piston recess a middle area of lesser depth and a peripheral area Area with a greater depth, each related has on the flat area of the piston surface. Internal combustion engine according to one of the preceding claims 1 to 17, characterized in that the piston recess in their peripheral wall portion has an undercut. Internal combustion engine according to one of the preceding Claims 1 to 18, characterized in that the selected Cylinder a hole <= 100 mm. Internal combustion engine according to one of the preceding Claims 1 to 19, characterized in that the single cylinder volume is <= 0.8 L. Internal combustion engine according to one of the preceding Claims 1 to 20, characterized in that the rated speed> than 3100 1 / min. is. Internal combustion engine according to one of the preceding Claims 1 to 21, characterized in that the specific Performance> than 30 kW is.