RU2041377C1 - Method of preparing fuel-air mixture for internal combustion engine - Google Patents

Abstract

FIELD: engine engineering. SUBSTANCE: fuel-air mixture is prepared by passing liquid fuel through a porous member and evaporation of the fuel in air sucked by the engine. Upstream of evaporation the fuel is separated into separate micro-jets using disconnected pores in the member by which fuel is separated from air. The area of the surface of contact between the porous member and fuel or between the fuel and air can be changed. EFFECT: improved accuracy of controlling mixture composition. 2 cl, 3 dwg

Description

 The invention relates to methods for preparing a fuel-air mixture using a carburetor and can be used mainly in internal combustion engines (ICE) and spark ignition.

 Closest to the proposed is a method of preparing a fuel-air mixture for ICE by passing liquid fuel through a porous element and evaporating the fuel into the air sucked by the engine.

 In the known method, the contact area of the porous element with air is changed.

 The main disadvantage is the low productivity of mixing.

 The aim of the invention is to increase the productivity of preparing a homogeneous vapor-air mixture when using multicomponent fuel such as gasoline, as well as improving the accuracy of regulation of the composition of the mixture.

 To this end, in the known method of preparing an air-fuel mixture for an internal combustion engine by passing liquid fuel through a porous element and evaporating the fuel into the air sucked by the engine, the fuel is separated into separate micro-jets before evaporation by means of non-communicating pores in the porous element by which the fuel is delimited and the contact surface area of the porous element is changed with fuel.

 A porous element pierced by many capillaries constantly filled with fuel is similar in its evaporative properties to the free surface of the fuel. At the maximum density of capillaries (when the thickness of the walls separating them is minimal), the total cross-sectional area of the capillaries is close to the area of the corresponding fuel surface. But the area of the convex or concave surface of the liquid in the capillary (with which evaporation occurs) significantly exceeds the cross-sectional area of the capillary. In addition, with intense evaporation, the liquid level in the capillary decreases and the walls of the capillary exposed thereby additionally increase the evaporation surface. Thus, the evaporation surface of the porous septum (even if it is flat) can be significantly larger than the corresponding surface of the free liquid.

 As is known, the evaporation rate increases with increasing air velocity. Since the porous surface protects the fuel surface from direct exposure to air, the speed of the latter can be increased to the required value without the risk of capturing large droplets, i.e., without reducing the quality of the mixture. The active effect of air on the porous septum leads to the fact that in addition to steam, droplets of liquid will be pulled out of the capillaries. The sizes of these drops are very small, since they are limited by the size of the cross section of the capillaries, so the drops will have time to completely evaporate. In fact, at the appropriate speed and direction of air, fuel will atomize from a variety of micro-atomizers, such as capillaries. Thanks to this phenomenon, it will become possible to introduce into the air a mixture of fuel fractions that differ from each other by boiling point and density, i.e. ordinary gasoline, almost uniformly.

 In the proposed method, the contact surface area of the porous septum is changed with air or fuel, or both at the same time. Operational change of the evaporation surface and / or the wetting surface with fuel allows to vary widely the degree of enrichment of the mixture depending on the engine operating mode.

 To regulate the fuel supply to the evaporation surface in the method, the pressure difference on both sides of the porous septum is changed. An increase in air velocity reduces pressure above the evaporation surface and improves evaporation and, due to the resulting pressure drop, intensifies the flow of fuel through the capillaries to the evaporation surface. The same effect is obtained by increasing the pressure of liquid fuel at a constant pressure from the moving air.

 To maintain optimal evaporation rate, the porous septum is heated, for example, periodically, maintaining its temperature within predetermined limits. Evaporation requires heat, so the partition is cooled. This reduces the evaporation rate and the rate of fuel flow through the partition. With increasing air velocity, cooling will become so significant that the partition will freeze due to atmospheric or dissolved moisture. Therefore, the porous septum is heated, so that, regardless of air flow, its temperature is most suitable for the evaporation of fuel of this fractional composition.

 In FIG. 1 shows a design variant with a flat porous septum element for implementing the method; in FIG. 2 conventional carburetor with a falling flow and an annular porous partition, the evaporation surface of which is controlled by changing the contact area of the partition with the fuel; in FIG. 3 is the same, but the evaporation surface is regulated by a movable screen separating the partition from the air.

 The air sucked by the engine from the atmosphere during the inlet is fed into the evaporation chamber of the carburetor and passed over the surface of the porous septum, which separates the fuel and air. Acting on fuel in the capillaries of the septum, moving air enhances evaporation by removing fuel vapor and reducing pressure above it and forms a vapor-air mixture of the required composition. To adjust the composition of the mixture change the surface area of the contact of the porous septum with air or fuel, or simultaneously. In addition, change the pressure difference on both sides of the partition. The latter is heated, maintaining its temperature in predetermined limits, in accordance with the fuel used.

 A device that implements this method consists of a closed housing 1, divided into fuel and evaporation chambers communicating with each other with gasoline 2, the level of which is supported by a float 3 with a valve 4 blocking the output of the gasoline supply pipe 5. The fuel chamber communicates with the atmosphere through opening 6. A porous element (porous baffle) 7 in contact with liquid fuel (gasoline) is installed in the evaporation chamber. The pipe 8 space 9 above the element 7 is communicated with the atmosphere, and the suction pipe 10 with the throttle valve 11 with the engine cylinders. In a more compact design with the annular element shown in FIG. 2, the regulation of the evaporation surface is carried out by changing the level of gasoline in the evaporation chamber. In a similar construction to FIG. 3 regulate the contact area of the surface of the element 7 with air, for which a tubular screen 12 is introduced coaxially, with a small gap, held by a thread 13 thrown through a block 14 mounted on an axis connected to the throttle.

 The device is used mainly like a conventional carburetor. The air flow rate is regulated by a throttle valve, and the speed near the porous element 7 is increased by known methods, providing the necessary evaporation rate. In accordance with the change in air flow, its speed relative to the element changes, automatically changing the number of vapors given off by the element. To adjust the ratio of fuel and air in accordance with the operating modes of the engine, the contact area of fuel with element 7 is controlled by known methods, changing the pressure drop on both sides of the latter, and its area blown by air. In this case, with an increase in the air flow through the carburetor when the throttle valve is opened, for example, the screen 12 lowers and the corresponding evaporation surface decreases for the necessary depletion of the mixture at medium engine operating modes.

Element 7 has a porous structure formed by a plurality of capillaries. The thickness of the element 7 should be minimized while ensuring sufficient rigidity and strength. The capillaries are located mainly perpendicular to the surface of the element 7, i.e., form non-communicating pores. The capillary cross section should be as possible as possible, provided that the largest droplets formed by it are completely evaporated. The material of the element 7 must withstand temperatures up to 100-150 ^about With and be electrically conductive. The latter will maintain the necessary temperature of the element 7 by passing an electric current.

 The invention improves the productivity and quality of the preparation of the vapor-air mixture of the required composition when using multicomponent fuel and can be implemented with a simpler and more compact carburetor.

Claims (2)

 1. METHOD FOR PREPARING A FUEL-AIR MIXTURE FOR THE INTERNAL COMBUSTION ENGINE by passing liquid fuel through a porous element and evaporating the fuel into the air sucked by the engine, characterized in that, in order to increase productivity, the fuel is separated into individual micro-particles before it is evaporated by which distinguish between fuel and air.  2. The method according to claim 1, characterized in that, in order to improve the accuracy of regulation of the composition of the mixture, change the surface area of the contact of the porous element with fuel or with fuel and air.

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