Overhead-valve combustion chamber of two-stroke gasoline direction injection engine

Abstract

The invention discloses an overhead-valve combustion chamber of a two-stroke gasoline direction injection engine. The overhead-valve combustion chamber is a cavity encircled by a cylinder cover, an intake valve, an exhaust valve, a piston, a cylinder sleeve, a gasoline injector and a spark plug. The inclined surface of a ceiling at the intake side of the cylinder cover is composed of two connected inclined surfaces having different included angles with the axis of the piston, and a spherical gasoline avoiding pit is sunken in the inclined surface; the position of an intake door seat is higher than the ceiling at the intake side in a vertical direction, and the intake door seat and the ceiling form a step; the gasoline injector is a piezoelectric crystal outwards-opening gasoline injector and arranged at the centre of the cylinder with the spark plug; and the centre of the piston is bulged, the top surface of the bulge is inclined, and a spherical pit is sunken in the top surface. According to the overhead-valve combustion chamber disclosed by the invention, reverse tumble scavenging is realized through the step on the ceiling, and intake short-circuit is reduced; wall wetting due to fuel oil is reduced through the gasoline avoiding pit, the top surface of the bulge of the piston and the pit of the piston; and a layered mixed gas is organized through the outwards-opening gasoline injector arranged at the centre. The overhead-valve combustion chamber disclosed by the invention is capable of realizing efficient scavenging for the two-stroke gasoline engine, optimizing the layering of the fuel oil and reducing the wall wetting due to the fuel oil, and beneficial to realizing the miniaturization of the gasoline engine.

Description

technical field [0001] The invention belongs to the technical field of engines, in particular to a combustion chamber of an overhead valve two-stroke in-cylinder direct-injection gasoline engine. Background technique [0002] Gasoline engine miniaturization can reduce gasoline engine fuel consumption by reducing gasoline engine displacement or reducing engine speed, so that the gasoline engine can run in a more economical working condition and reduce friction loss at the same time. The ignition cycle of a two-stroke gasoline engine is half of that of a four-stroke gasoline engine. It has the advantages of high torque output, high energy density, and stable operation. [0003] However, the traditional two-stroke engine is limited by its structure and scavenging process, and if it is directly used to achieve small strengthening, it will not bring economic improvement. First of all, the traditional two-stroke gasoline engine uses the piston movement to control the air port to ...

AI Technical Summary

Problems solved by technology

[0006] However, the practical application of the overhead valve two-stroke direct injection gasoline engine still faces technical problems in terms of the composition of the mixture in the cylinder and the control of combustion stability.

First of all, under heavy load conditions, the gas density in the cylinder is high, and the fuel injection timing is relatively late under the limitation of the large valve overlap angle, which is not conducive to the atomization and fragmentation, evaporation and diffusion of fuel, and the formation of stratified mixture necessary for flame propagation. , especially when using a vertical air inlet combined with roof stepped structure to improve charging and scavenging, the internal structure of the cylinder head poses a difficult problem for the more advanced spray-guided direct injection system and the arrangement of spark plugs

At the same time, no matter whether the high residual exhaust gas rate is adopted under small and medium loads or the strong gas flow in the cylinder is used under large loads, it is not conducive to the formation and development of the initial fire core in the early stage of flame propagation, resulting in low early combustion stability, ignition and Difficult to control combustion phase

In addition, there are hidden dangers of knocking and high pressure rise rate under heavy load conditions, which will cause engine damage

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