DE102007040910A1 - Device for inserting gaseous fuel, particularly hydrogen into combustion chamber of internal-combustion engine, has fuel tank side inlet, combustion chamber side outlet, and flow channel extending axially between inlet and outlet - Google Patents

Abstract

The device has a fuel tank side inlet (102), a combustion chamber side outlet, a flow channel (103) extending axially between the inlet and the outlet. A closure element is assigned to the flow channel. An outlet side unit (100) is provided for fanning out the fuel at an accumulation element (106). The fanning out unit is suitable for flow deflection and has a radially arranged discharge. An independent claim is included for a method for inserting a gaseous fuel, particularly hydrogen into a combustion chamber of an internal-combustion engine.

Description

The The invention relates to a device for introducing a gaseous Fuel, in particular hydrogen, in a combustion chamber of a Internal combustion engine comprising a fuel tank side inlet, at least one combustion chamber outlet, one between Inlet and at least one outlet substantially axially extending Flow channel and an associated with the flow channel Closing member and a method for introducing a gaseous fuel, in particular hydrogen, in one Combustion chamber of an internal combustion engine by means of the same device.

When alternative fuels for internal combustion engines are gases, especially hydrogen, increasingly the subject of development activities. there offers above all the internal mixture formation due to minimal combustion anomalies and high power density special advantages. A high pressure injection also offers many degrees of freedom to the burning process to optimize its efficiency. A key role especially the fuel injection and thus the nozzle design of the injector too.

Are known multi-hole nozzle tips, such a nozzle is for example in the DE 10 2004 048 603 A1 shown and described. If, in early fuel injection, the injection directly into the combustion chamber of the internal combustion engine begins immediately after the closing of the intake valves, a substantially homogeneous distribution of fuel is achieved. With regard to the efficiency at partial and full load and thus also in terms of power density, however, a late injection of the gaseous fuel is especially desirable, since this is thermodynamically advantageous. This late mixture formation is characterized by the small amount of time between injection and start of combustion, which generally causes a stratified distribution of the fuel.

at gaseous fuels causes the high speed during the injection a rapid penetration into the combustion chamber. by virtue of The gas dynamics of the supercritical injection arise for gaseous fuels versus liquid Fuels, such as diesel or gasoline, despite a comparatively low inflation pressure very high speeds in the post-expansion zone after exiting the nozzle holes. At the nozzle hole even speeds of around 1000 m / s may be present. Consequently results despite comparatively low density of the gaseous Fuel a correspondingly high pulse.

The usual Configuration of the multi-hole nozzle has two essential Disadvantages of late injection: First, a single hole causes a selective alignment of the jet pulse in the combustion chamber, so that the penetration speed is reduced only slowly (classic Free jet). This makes it difficult to fuel as desired to place centrally in the combustion chamber, it comes to a rather fast-moving and compact fuel cloud, which only insufficient with the available in the combustion chamber Air mixed, deflected at the opposite combustion chamber wall and subsequently to strong near-wall fuel concentration leads. Secondly, adjacent individual beams influence each other due to the suction effect of each free jet each other, which lead to a large single beam until fusion can (Coanda effect). This does not cause the fuel more in the desired respective directions of the single holes can spread, but only in the flow direction of the Total beam. Thus, especially at later insufflation in large parts of the combustion chamber, the intake air is not fueled mixed. To a certain extent, this stratification is desirable, however can cause too much inhomogeneity even at globally lean Air ratio lead to local oxygen deficiency. This lack of oxygen in turn causes a locally incomplete Burning when passing through the flame front, so later Mixing operations with the air in the combustion chamber to a delayed and thus low-efficiency Energy release in the thermodynamic system lead.

task The invention is therefore to provide an aforementioned device, with the rate of penetration of gaseous fuel reduced and achieved an improved mixing of the fuel can be. In addition, a method of operation provided the device according to the invention become.

The Solution of the task is done with a device with the Features of claim 1, by an outlet side device provided for fanning the fuel to a baffle element is. This will increase the rate of penetration of the gaseous Fuel reduces and there are rich mixture zones of the combustion chamber wall largely kept away. In addition, an improved mixing of the fuel centrally in the combustion chamber and overfat Zones are avoided. Furthermore, the task with a method solved with the features of claim 8, by the flow first deflected in the subsonic area and subsequently to supersonic speed is accelerated. As a result, the Einblaseimpuls is received and at the - usually supercritical - blowing lies the critical cross-section only after the deflection.

Especially preferred embodiments and developments of the invention are the subject of the dependent claims.

Preferably is the device for fanning the flow deflection suitable and has at least one substantially radially directed Exit to. As a result, in the operation of a deflection of the axially extending flow channel of the fuel introduction device flowing fuel into a substantially radial Direction and flow rate is reduced.

Very it is expedient if the at least one radial Outlet referred to the axial flow channel an extended Has cross section, so that despite the diversion of the fuel flow whose momentum is essentially preserved. The cross-sectional extension causes similar to the diffuser of a Laval nozzle one Flow acceleration, in this case at supersonic speed.

According to one Particularly preferred embodiment of the invention is the at least one radial outlet formed slit-like. The gaseous fuel is thereby fan-shaped introduced into the combustion chamber.

When Advantageously, it is considered that a single substantially radially directed outlet is provided, which has an angular range from 90-180 °, in particular from about 120-150 °, covered. at an eccentric with respect to the combustion chamber axis arrangement the fuel introduction device is the exit in the direction directed to the combustion chamber axis and / or an ignition source.

at an internal combustion engine with a crankcase and a with this cylinder head connected along a joint plane It has proved to be advantageous, the radial outlet in installation position at least approximately parallel to the connection plane.

following becomes a particularly preferable embodiment the invention with reference to figures explained in more detail, thereby show schematically and by way of example

1 a device for fanning fuel on a storage element,

2 a fuel introduction device with horizontal, fan-shaped beam configuration and

3 two results of a 3D CFD simulation (computational fluid dynamics) for a late mixture of hydrogen.

1 shows a device 100 for fanning fuel on a baffle element 106 , The device is part of a fuel injection device ( 2 . 200. ) for fuel injection directly into the combustion chamber of a gaseous fuel, in particular hydrogen, operable internal combustion engine of a motor vehicle.

An axially extending flow channel 103 with an inlet 102 is against the baffle element 106 directed. With the baffle element 106 At the injector nozzle tip, a stagnation point is formed, at which the gaseous fuel to be injected - in the figure indicated by arrows - is fanned out. The resulting cross-sectional enlargement 104 in the radial direction can basically be made arbitrarily large, since this no flow separations occur. In the case of gaseous fuels, it has proved to be advantageous if the diversion at the stagnation point with respect to the preservation of the Einblaseimpulses still occurs in the subsonic area, so that the injection, which usually takes place at a supercritical pressure ratio, only the entry into the slot-shaped cross-sectional widening 104 represents the critical cross section. The radial cross-sectional widening 104 in the slot itself causes similar to the diffuser of a Laval nozzle acceleration to supersonic speed.

When The result of this nozzle geometry is the gas in the form of a Fächerers introduced into the combustion chamber. Compared with one Free jet out of a hole will penetrate the penetration rate the continuous cross-sectional enlargement of the beam is greatly reduced. The impulse is not cultivated, but only occurs a distribution or diversification. A conscious, annihilation ' the pulse in the nozzle tip to reduce the penetration rate is to be avoided as this is for a good mixing with the air in the combustion chamber is required.

A fuel introduction device 200. with horizontal, fan-shaped beam configuration 202 is in 2 shown. By means of the fuel introduction device 200. gaseous hydrogen is introduced directly into the combustion chamber. The combustion chamber is formed in a crankcase of the internal combustion engine and is upwardly from a cylinder head connected to the crankcase along a connection plane 204 completed. A cylinder liner is with 208 designated. The cylinder head 204 also includes inlet and exhaust valves and an ignition source 206 for the spark ignition of a combustion chamber located in the fuel-air mixture.

The fuel injection device 200. is relative to the cylinder axis off-center and relative to the cylinder axis significantly inclined, in this case 60 ° -80 °, in particular about 70 ° -75 °, arranged.

The fuel injection device 200. comprises a fuel tank side inlet, a combustion chamber side outlet, a flow channel axially extending between inlet and outlet and a closing member associated with the flow channel, by means of a control device based on input parameters and stored in the control parameter between an open and a closed position, optionally also intermediate positions , is controllable. The fuel, in the present case hydrogen, is stored cryogenic in the fuel tank in the liquid state and is heated with respect to the storage temperature in a gaseous manner into the combustion chamber. Downstream of the metering device of the fuel introduction device 200. is the referring to 1 ( 100 ) described device 201 arranged for fanning fuel. The device 201 is so to the longitudinal axis of the fuel introduction device 200. Angled arranged that the fan-shaped beam 202 directed at least approximately parallel to the connecting plane crankcase / cylinder head.

Given the flat shape of the combustion chamber with a piston position near the top dead center, the horizontal, fan-shaped beam configuration ensures 202 especially with late injection a much improved distribution of fuel in the combustion chamber. The variant shown uses only one sector of the 1 schematically shown arrangement. In principle, any fan angles can be realized, but in particular in the arrangement shown, the fuel introduction device is preferred 200. an angular range of 90-180 °, in particular of about 120-150 °.

The principle of the pitot tube is not necessarily bound to a lateral mounting position, but proves in the examined engine configuration, the concept-related route from the nozzle outlet to the center of the combustion chamber as low, to a well mixed and only relatively slowly moving fuel cloud near the spark plug 206 to reach.

In 3 By way of example, two results of a 3D CFD simulation (computational fluid dynamics) for a late mixture formation of hydrogen are compared with one another. Both representations compare mixtures of the same Einblaseverlaufs immediately after closing the Einblaseeinheit, the representation is due to the prevailing symmetry in this case, only for half the combustion chamber. As shown in the upper picture for the used multi-hole nozzle according to the prior art, the fuel jet resulting from the contracted single rays penetrates 302 Too quickly into the combustion chamber. The momentum directed by the injector (shown at the bottom right in the combustion chamber) on the opposite side of the combustion chamber is so strong that the fuel cloud is deflected there at the combustion chamber wall and thus flows back along the bushing in the direction of the injection unit. The result is a near-wall stratification of the fuel in conjunction with high speeds in the combustion chamber, which significantly increase the loss of wall heat in the high pressure phase.

The lower picture shows the corresponding mixture formation when using the fuel introduction device according to the invention 200. , Despite the also short time for the mixture formation here are large parts of the central combustion chamber with fuel / air mixture 312 filled, whereby a rapid and complete implementation of the fuel during the flame front run can be ensured. In addition, it is obvious that the penetrating fuel has not reached the opposite side of the combustion chamber due to the fanning of the pulse, but has already largely reduced its speed when reaching the combustion chamber center. This reduction in the internal engine flow velocities and the largely centrally placed mixture cloud are responsible for a significant minimization of the wall heat losses.

at later injection of gaseous fuels can when using the pitot tube at low as well as at high loads due to the reduced wall heat the efficiency be optimized. At high loads additionally affects the good homogenization within a short time positive to a thermodynamically optimal, rapid and, above all, complete Implementation of the introduced fuel from.

Special Advantages arise in terms of significantly improved utilization of the high thermodynamic potential of late direct-insufflations gaseous fuels in the high pressure phase of an engine process, due to good homogenization in the shortest possible time, to super-rich mixed zones to avoid by lowering the wall heat losses due Lower speeds in the combustion chamber and avoiding near-wall fat Mixture zones, by in the efficiency-relevant range of low Partial load fuel-free squish and a correspondingly Reduced wall heat transfer can be realized. In addition, the resulting lower heat input in help prevent the wall from glowing.

A stable mixture formation is under Relatively low velocities in the central combustion chamber assure a highly flammable mixture near the spark plug within a large time window.

at All loads result in advantages in the efficiency by the theoretical thermodynamic advantage of late injection in mixture formation with the pitot tube over the entire load range significantly better than conventional ones Multi-hole geometries is the case.

After all an increased medium pressure potential is achieved because at otherwise the same conditions, the comparatively lower losses especially by wall heat as well as imperfect and incomplete Combustion to increased medium pressure and thus performance potential to lead.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102004048603 A1 [0003]

Claims (8)

Facility ( 200. ) for introducing a gaseous fuel, in particular hydrogen, into a combustion chamber of an internal combustion engine, comprising a fuel tank-side inlet, at least one combustion chamber-side outlet, a flow channel extending substantially axially between the inlet and at least one outlet, and a closure member associated with the flow channel, characterized by an outlet-side Facility ( 100 ) for fanning the fuel to a baffle element ( 106 ). Facility ( 200. ) according to claim 1, characterized in that the device ( 100 ) is suitable for fanning out the flow deflection and at least one substantially radially directed outlet ( 104 ) having. Facility ( 200. ) according to one of the preceding claims, characterized in that the at least one radial outlet ( 104 ) relative to the axial flow channel ( 103 ) has an expanded cross-section. Facility ( 200. ) according to one of the preceding claims, characterized in that the at least one radial outlet ( 104 ) is formed slit-like. Facility ( 200. ) according to one of the preceding claims, characterized in that a single substantially radially directed outlet ( 104 ) is provided. Facility ( 200. ) according to one of the preceding claims, characterized in that the radial outlet ( 104 ) an angle range of 90-180 °, in particular of about 120-150 °, covered. Facility ( 200. ) according to one of the preceding claims, wherein the internal combustion engine comprises a crankcase and a cylinder head connected thereto along a connecting plane, characterized in that the radial outlet ( 104 ) is directed in the installed position at least approximately parallel to the connection plane. Method for introducing a gaseous fuel, in particular hydrogen, into a combustion chamber of an internal combustion engine by means of a device ( 200. ) according to one of the preceding claims, characterized in that the flow is first deflected in the subsonic area and subsequently accelerated to supersonic speed.