NL8603136A - GAS CARBURETOR. - Google Patents

Description

NO 34194 *

Gas carburettor.

The invention relates to a gas / air mixing device of the carburettor type with venturi and at least one space surrounding the venturi, gaseous or other gaseous medium, the feed means for the gas being in a plane perpendicular to the center line. the venturi is provided with at least one outflow opening on the circumference of the narrowest section of the venturi, and wherein at least one streamlined body is placed in the passage of the ventricle with respect to the flow direction of the air.

A gas / air mixing device of the above-mentioned type is known from Dutch patent application 8401537. The mixing device shown and discussed in Fig. 4 of the said publication is intended for use in gas engines, in particular spark-ignited gas engines, which very strict requirements must be met with regard to the composition of their exhaust gases under all operating conditions. The intended engine operation takes place either with a relatively lean air / fuel mixture in the lower and medium power range or with a stoichiometric amount in the high power range.

In both operating situations, all requirements can be met, provided that all cylinders of a multi-cylinder engine are always accurately supplied with the same aspirated mixture.

In practice, however, situations nevertheless appear to occur with less pure exhaust gas composition than is theoretically possible.

Moreover, successive burns in one and the same cylinder and from cylinder to cylinder do not appear to be the same, so that no impermissible and relatively high-frequency irregularities occur in the engine. In the case of generator drive, this can easily lead to mains pollution with higher harmonics. Research has shown that the cylinders are not supplied with a sufficiently homogeneous and uniform mixture from suction stroke to suction stroke. The problem was found to be completely solved by installing a high-quality, commercially available, static mixer 35 between the carburettor with its downstream throttle and the suction line along the engine's cylinders. Since such a static mixer is relatively large and often cannot be easily mounted on a motor and would greatly affect the entire layout of all auxiliary equipment on the motor, and is moreover expensive, the eye-mark of the invention consists of this, the known to improve the mixing device in such a way that it can deliver a more homogeneous mixture to all cylinders under all operating conditions. A complication here is the fact that the mixing device must not only be able to mix air with gas, but also air with gas and recycled exhaust gas.

The problem is caused by the fact that in the known mixing device the sucked-in gas and also the possibly drawn-in EGR through the annular feed gaps along the circumferential wall of the throat of the venturi are carried along as a virtually laminar layer by the air flowing past and hardly to mix. except on the boundary layer between the air and the supplied gas or the supplied EGR. The actual mixing device therefore produces if not pure air at the core of the flow, yet a mixture too lean on the components to be mixed, and a mixture too rich along the periphery.

Finally, the improvement of the mixer should increase its flow resistance as little as possible, despite the desired improvement in the homogeneity of the delivered mixture, because any resistance increase reduces the power and efficiency of the motor. For that reason, too, the use of a static mixer is undesirable.

In order to achieve the desired object, the gas / air mixing device described in the preamble is characterized in that - the streamlined body is cylindrical and with its centerline substantially located in the plane of the narrowest throat section, - that it is internally is hollow and is connected with its ends to the gas-carrying space of the mixing device, - that in the same plane of the narrowest throat section a number of spaced apart gas outflow openings are arranged in the side walls of the hollow body, - which are arranged in the The periphery of the venturi section is provided with a number of evenly distributed outflow openings, each of which has a passage substantially equal to that of the openings in the body.

The sole purpose of the streamlined body used according to the known mixing device was to obtain, at a given volume flow through the throat of the carburettor, a sufficiently long circumference, so that through the narrow supply slots sufficient gas and / or EGR (recycled exhaust gas) is obtained. - Exhaust Gas Recirculation) could be supplied.

According to the invention, this body is now transformed in a streamlined manner such that it is perpendicular to the direction of flow of the air through the throat of the venturi at the location of its narrowest section. This body is made hollow and is connected at both ends to the gas-carrying space of the mixing device. Both the side walls of the hollow streamlined body and the narrowest throat section of the venturi are provided with evenly distributed openings, the total passage of which volumetrically corresponds to the annular supply gap of the known carburettor. This not only achieves that the substantially laminar gas layer along the inner circumference of the venturi section is divided into alternately a gas stream and an air stream, but moreover, in the core of the air flow 10, the gas stream also alternately creates an air stream and an air stream. In order to satisfy the physical properties of such a carburettor type already used in the known carburettor, namely that it gives a constant mixture strength under all operating conditions, according to the invention all openings are both in the circumference of the venturi and in the side walls of the hollow body, substantially the same size. Although at the core of the flow through the venturi the airflow velocity will be higher than along the walls, this does not pose a problem with the consistency of the mixture strength, because this higher core flow velocity will also cause more gas (or E6R) to pass through the openings. suction. After all, these openings have the same dimensions.

The same basic idea of the invention can also be applied when the carburettor is intended to supply not only gas as fuel, but also other gases, such as, for example, recycled exhaust gas (EGR). In the mixing device described in the preamble, in which the venturi has an elongated cylindrical throat, with - viewed in air flow direction - a first cross section with feed means for a first medium, such as EGR and downstream a second cross section with gas supply means, a preferred embodiment according to the invention characterized in that - the streamlined hollow body extends in the direction of the center line of the venturi along both the first section and the second section, - that the internal cavity is divided by a partition into a first and a second space. wherein these spaces are connected to the EGR or the gas-carrying spaces of the mixing device, - that in the plane of the first and the second cross-section, each space contains a number of outflow openings for EGR and gas, respectively, - that the supply means are circumferential of the venturi for the EGR in 8603136 * 4 4 the first cross section e, respectively, for gas in the second cross-section, consists of a number of outflow openings uniformly distributed over the circumference, the passage of each of which is substantially equal to that of the corresponding openings in the body.

The same inventive idea is also applied here, namely supplying as many small gas and / or EGR flows as possible into the drawn-in air, so that from the very first supply a considerably more uniform and homogeneous mixture flow leaves the actual mixing device.

Further refinements of the initial distribution are possible and are described in the subclaims and the figure description. Without causing a significant increase in flow resistance, the downstream end of the streamlined hollow body can be sharply broken to cause macro vortices in the core flow, which promote homogeneous mixing. These macro vortices are opposed to the micro vortices that occur with each outflow of the gas or EGR in the accelerating airflow.

As described below as an example, the invention can also be applied to mixers of which the venturi has a rectangular cross section.

It should also be noted that it is known per se to provide separate openings instead of an annular gas supply slit in the throat of a venturi. Introducing gas or EGR into the nuclear flow through the venturi, however, from one or more openings is new, as is essentially splitting the nuclear flow into two or more sub-nuclear flows, thus directly from the actual point of introduction of the with medium to be mixed, a more or less finely distributed subdivision of the flow paths already occurs.

These will be explained in more detail below with reference to the appended drawings of preferred embodiments of the invention.

Fig. 1 and 2 show a longitudinal section and a section across the venturi section of a simple gas / air mixing device according to the invention, respectively.

Fig. 3 schematically shows a longitudinal section of a mixing device 35 according to the invention, suitable for admixing two different gases to the air flow, namely EGR and fuel gas.

Fig. 4a and 4b show cross sections similar to that of Fig. 3 of alternative embodiments of the hollow streamlined body.

Fig. 5 is a cross-sectional view, similar to that of FIG. 2, of the venturi throat of a star-shaped alternative embodiment of the 8603136 5 * streamlined hollow body disposed in the throat of a venturi.

Fig. 6 and 7 respectively show a top view and a longitudinal section of a mixing device according to the invention with rectangular section of the venturi, suitable for admixing both EGR and gas.

Before discussing the various figures separately, it is to be explained in general that, where applicable, the improvements according to the invention have been applied to a gas / air mixing device as described in Fig. 4 of Dutch patent application 8401537.

As far as possible, the same reference numerals have been used for corresponding parts.

Figures 1 and 2 schematically show, in longitudinal section and in section across the venturi section, the parts of a gas / air mixing device according to the invention which are the most important for the invention. The central part of the mixer is indicated by 4, the passage through the throat of the venturi with 6, the inflow side of the venturi with 7, the throat with 9 and the outflow side with 8. The arrows L schematically indicate the air flow weather and flow direction. Around the outside of the venturi there is a closed, preferably annular space 14, 20 to which gas G is supplied via a pipe connection. In the plane of the narrowest throat section of the venturi, a number of outflow openings 23 are arranged distributed over the circumference, through which gas can be entrained by the air flow and in which diagrammatic arrows L indicate how limited gas flows from each outflow opening. 23 are taken along the inner wall of the venturi by the airflow. These are alternately alternated by webs of air along the circumference of the widening vent wall 8.

According to the invention, a cylindrical streamlined body is arranged in the throat of the venturi such that it extends perpendicularly to the direction of flow of the air right through the throat of the venturi. With its centerline C-C it lies substantially in the plane of the narrowest throat section 9. This body 10 is rounded on the inflow side 11 and can be truncated at its downstream end 12. The cylindrical flow-shaped body is hollow and connected at its ends to the gas-carrying space 14. Since the cavity of the streamlined body 10 is also gas-carrying, the cavity is designated 140. In the same plane in which the outflow openings 23 are located in the wall of the venturi section, a number of regularly distributed outflow openings 40, 230, each of which have substantially the same passage as the openings 23 in the hollow body 10, are also arranged in the side walls of the hollow body 10. outer wall of the venturi throat. Thanks to the provision of the gas outflow openings 230 in the core of the air flow through the venturi, as many gas flow paths are introduced into the air flow paths, so that the distribution of the gas in the air downstream is considerably more homogeneous than in the known mixing device.

If the gas / air mixing device were to be used for a large engine with a relatively wide throat section of the venturi, then, as shown in Figs. 6 and 7, it would be possible to convert the one flow-line body of Fig. 1 and 2 to be replaced by two parallel adjacent hollow streamlined cylindrical bodies, each again provided on both sides with evenly distributed outflow openings 230. As a result, even more gas-carrying flow paths are introduced into the air flow through the throat of the venturi. 15, which further increases homogeneity.

It is also possible to arrange a star-shaped streamlined body in top view into the throat of the venturi, as shown schematically in fig. 5. Depending on the dimensions, the calorific value of the fuel gas and other variables, the star may , four contain 20 or even more spokes. It will be clear that each spoke is in open communication with the gas-carrying space 14 and that each spoke in itself forms a hollow cylindrical streamlined body according to the invention. The downstream end 12 of the hollow streamline body will be explained in more detail below when discussing Figures 4a and 4b.

In Fig. 2, for clarification only on the right-hand side, it is schematically indicated how flow paths of air and gas alternate to promote the homogeneity of the outflowing gas / air mixture.

FIG. 3 shows a corresponding mixing device as shown in FIGS. 1, 2 and 5, again provided with a hollow cylindrical streamlined body, but intended for admixture in the air flow of two gaseous media, such as recycled exhaust gas (EGR) and fuel gas ( g). For this purpose, the throat of the venturi 9 has been extended in a known manner by a cylindrical part, as has the streamlined body 10 placed in the extended throat. For a detailed description of such a mixing device, reference is again made to Dutch patent application 8401537. The surrounding around the bottom part of the throat of the venturi gas space provided is again indicated by 14 -40, while the upstream annular gas space 860 3 1 3 6 7 έ · 19 is intended for supplying the EGR. The two spaces 14 and 19 are separated from each other by a wall. Each space 14 and 19 respectively has a number of circumferentially distributed outflow openings 23 and 24. Similarly, the cavity of the streamlined body is divided by a partition into a gas-carrying (lower) cavity 140 and an upper EGR-carrying cavity 190. In the side walls, outflow openings 230 for the gas G and 240 for the EGR are arranged in a similar manner as in the embodiment according to FIGS. 1 and 2. It can be noted that the outflow openings 23, 230; 24, 10 240 are rectangular, which is preferable especially when for structural reasons the venturi is divided into a number of elements, the dividing line being situated in the plane through the top edge or the bottom edge of said outflow openings. It will be clear that the round outflow openings according to Fig. 1 can also be used with Fig. 3, but that the rectangular ones according to Fig. 3 can also be used with the other figures.

Although this is not clearly shown in Fig. 3, the homogeneous distribution of the EGR and the gas flow paths in the air paths can be promoted by arranging the outflow openings 23 and 230 staggered in the circumferential direction of the throat of the venturi. the outflow openings 24, 240. The same applies to the star-shaped body according to Fig. 5, if the venturi according to Fig. 5 is also intended for a mixing device of eg EGR and gas with air, so that two gaseous medium-carrying spaces in flow direction are created. see behind each other and are present separately from each other. In order to indicate this schematically in Fig. 5, the reference signs for EGR and for gas are both indicated.

In Figs. 4a and 4b, alternative embodiments are schematically depicted of the cut hollow cylindrical streamlined body 10 adapted to supply both EGR and gas G. At the partition wall between the EGR-carrying cavity 190 and the gas-carrying cavity 140 the side wall of the streamlined body may be constricted at 12b to cause vortices which promote mixing of the effluent EGR with the air. The downstream end 12a may be sharply cut to generate vortices there due to return flows, while the upstream end 11a of the lower cavity 140 is more streamlined.

An even further elaborated elaboration of this inventive idea 40 is shown in Fig. 4b, where the two cavities 190 and 140 are entirely separated from each other by 8603136 8 by an interspace S. At 12d, a chopped downstream end of the EGR carrying streamlined body 10, so that the strongest possible vertebrae are generated by means of backflow. The upstream end 11b of the subsequent part of the streamlined body 10 is streamlined so as not to generate an unnecessary increase in flow resistance. The mutual distance S is chosen such that the generated vortices can be smoothly discharged by the air flow L. It is generally known that the generation of the described work yields only an insignificant increase in the flow resistance, but nevertheless a considerable positive influence acts on the homogenization of the mixture.

When the method described in Fig. 4b is used in the embodiment according to Fig. 5, in the embodiment for both admixture of EGR and gas, two separate star-shaped bodies are displaced one behind the other in flow direction. These can therefore also be arranged in a circumferential direction with respect to each other, so that the flow resistance will increase somewhat more, but also the homogenization will be strongly promoted.

Finally, Figures 6 and 7 show the inventive idea applied to an occasionally used venturi mixer with a rectangular cross-section of the venturi. Fig. 6 is a plan view, while FIG. 7 is a longitudinal section of an embodiment for admixing both EGR and gas. Fig. 7 is thus comparable to Fig. 3, but provided with two juxtaposed cylindrical hollow streamlined bodies 10. Thanks to the reused corresponding reference numerals, the figures speak for themselves.

As can already be seen from Figures 1 and 3, the outflow openings for gas and / or EGR can be round or also rectangular. Triangular outflow openings can also be used, preferably with the base as the outflow edge. Although some are preferred for flow or production reasons, essentially any shape is possible. The vortices generated on the outflow of the gas or EGR from their outflow openings 23, 230; 24, 240 in air could be termed micro turbulent, while those generated by the cut-off discharge side 12, 12d of the cylindrical streamlined body could rather be termed macro turbulent. Other embodiments of the outflow edge of the outflow openings can therefore effectively influence the homogeneity.

Good mixing and a low flow loss per se contradict each other, but with the aid of the invention an important improvement of the homogeneous mixing can be achieved with constant flow losses.

8603136

Claims (8)

1. Carburettor-type gas / air mixing device with venturi and at least one gaseous or other gaseous medium surrounding the venturi, with as feed means for the gas in a plane perpendicular to the axis through the venturi - the circumference of the narrowest section of the venturi is arranged, and in which at least one streamlined body is placed in the passage of the venturi throat, characterized in that - the streamlined body is cylindrical and is centered substantially in the plane of the narrowest throat section, - that it is internally hollow and connected with its ends to the gas-carrying space of the mixer, - that in the same plane of the narrowest throat section, a number of spaced apart gas outflow openings are provided in the side walls of the hollow body, - a number of which are located in the circumference of the venturi 20 evenly distributed outflow openings are provided, the passage of each of which is substantially equal to that of the openings in the body. Gas / air mixing device according to claim 1, wherein the venturi has an elongated cylindrical throat, with - viewed in air flow direction - a first section with supply means for a first medium, such as EGR and downstream a second section with supply means for gas, with characterized in that the streamlined hollow body extends in the direction of the centerline of the venturi along both the first cross section and the second cross section, 30. that the internal cavity is divided by a partition into a first and a second space, wherein these spaces are connected to the EGR or the gas-carrying spaces of the mixing device, - that in the plane of the first and the second cross-section, each space contains a number of outflow openings for EGR or gas, respectively, - that the feed means are in the periphery of the venturi for the EGR in the first section and for gas in the second section, from a number of data There are evenly distributed outflow openings distributed around the circumference, the passage of each of which is substantially equal to that of 40 the corresponding openings in the body. 8603136 11 3. Device according to claim 2, characterized in that the elongated streamlined hollow body is externally constricted at the location of the internal partition. Device as claimed in claim 3, characterized in that the elongated streamlined hollow body is constricted in such a way that it consists essentially of two separate bodies, the second of which (viewed in flow direction) has a streamlined inflow side. Device as claimed in claim 4, characterized in that the two separate streamlined bodies are spaced apart, in particular at a distance such that the flow through the vent - as a function of the Reynolds number occurring - in the interspace comes to significant (some) turbulence. 6. Device as claimed in claims 4 or 5, provided with a venturi of circular cross section, characterized in that the first and the second streamlined hollow body are placed radially rotated relative to each other. 7. Device as claimed in claims 1-5, provided with a venturi of circular cross section, characterized in that the streamlined hollow body is star-shaped, the spokes of the star being in the first 20 and / or second cross section and the center of the star is located on the center line of the venturi, and all spokes are hollow and provided with outflow openings for EGR and gas, respectively, and that, if two stars are placed one behind the other in the direction of flow, they are mounted radially with respect to each other. can be. The device according to claims 1 to 5, wherein the cross section of the venturi is rectangular, characterized in that there are at least two parallel streamlined hollow bodies which are evenly distributed over the narrowest throat cross section. 8603136