CS200906B1 - Combustion area of the engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a combustion chamber of an engine with an insert. SUMMARY OF THE INVENTION The object of the invention is to improve the combustion process of the fuel, to reduce the ignition delay and to reduce the heat transfer to the engine piston.

The diesel engine piston is one of the most thermally and mechanically stressed engine components. The thermal stress of the piston is related to the high velocities of movement of the hot combustion products in the combustion chamber and above the face of the piston. Cooling of the piston is well feasible for larger engines, eg by spraying oil, through the oil cooling line in the piston housing. The edge of the combustion chamber where the temperatures exceed 300 ° C is most stressed. Therefore, for example, the surface of the piston is anodized to reduce the heat transfer coefficient, the piston edge is made of another material, eg copper or its alloys. welded to the piston body, the combustion chamber is removably connected to the piston as an oil-cooled non-ferrous alloy liner, etc. The shape and design of the combustion chamber decisively affects the preparation and combustion of the mixture. The good combustion of the mixture is conditioned by the high flow velocities which are achieved, in particular, by the geometric modifications of the combustion chamber. However, not all air is used in the reaction. In order to improve combustion, it is therefore proposed to give the charge in the combustion chamber an additional movement, for example in a tangential direction, or in the piston, to make cavities to act as reservoirs of clean air for the end of combustion. protection of the piston and improved combustion of the mixture.

200 906

200 000

Economic aspects and stricter hygiene regulations require a comprehensive solution to the problems of mixture combustion and piston thermal protection. Measures that improve the breakdown process while limiting peak combustion pressures and the resulting exhaust gas composition, particularly the Ν0 _{χ level} , include design interventions in the combustion chamber geometry to reduce the degree of compression in the cylinder. However, a reduction in the degree of compression is associated with a prolonged ignition delay, poor startability, fire instability at lower loads and idling. It has been proven that the ignition delay can be reduced in particular by increasing the intensity of the rotary motion of the air mass in the combustion chamber and by increasing the temperature of the combustion chamber wall when the fuel is injected into the combustion chamber. Higher flow rates are achieved by reducing the size of the inlet throat of the combustion chamber and reducing the distance between the felt head at the top dead center of the piston. However, the wall temperature, which would result in a substantial shortening of the ignition flow, is close to 600 ° C, which is too high for the piston material.

The enclosed drawing shows a combustion chamber with an insert which simultaneously solves the question of thermal protection of the combustion chamber wall at higher temperatures of the wall to which the fuel is injected and at higher flow rates achievable due to the thermal protection of the piston. The progress achieved by the invention consists in improving the process of forming and burning the mixture, shortening the ignition delay and improving the thermal protection by having a liner 1 in the combustion chamber in the piston 2, which is separated from the piston 2 by a gap 6. The piston insert 5 contacts only a few points or surfaces. The fuel is injected through the nozzle 3 onto the inner side of the liner by means of spokes 6. It is not necessary for the nozzle 3 to be coaxial with the combustion chamber or cylinder.

In the combustion chamber, the air mass moves in the vortex ring b. A relatively stationary conical air mass c is maintained above the bottom of the bottom, which does not participate in the rotation in the viral ring b, and which is not affected by beams and fuel injections. The air from the conical formation 6 enters the gap 6 near point A at the bottom, passes through the gap 6 and exits at point B near the mouth of the combustion chamber. The air stream dissipates the heat of the piston 2 and the liner X, protects the orifice of the combustion chamber from the direct effect of the flame, and enters the combustion process in the swirl ring b, where it supplies the necessary oxygen for combustion, thereby improving its progress. The movement of the air in the gap s is caused by a pressure difference of 4 p between point a and point B. The velocity of movement of the air w ejected from the volume above the face of the piston 2 into the combustion space is highest at any time above the orifice.

R - r (1 + V ZK ^and / Jt

).

It is instantaneous £ remoteness face of the piston 2 from the engine head, V is the volume of a combustion free from ^interference »£ p J® instantaneous velocity of the piston. R is the radius of the inlet throat and R is the radius of the cylinder of the engine

At the bottom in the middle of the combustion chamber near point A, the flow rate is negligible. The outlet reservoirs designated by point B are in the vicinity of the orifice of the combustion chamber, so that the velocity of the air w _{2 is} rising. z of gap s is close to the instantaneous velocity w over the orifice of the combustion chamber. In the gap mezi between point a and point B a pressure drop Δp occurs when pro

200> 0 «imaginary current filament in the gap mezi between point A ^and point B the approximate relation ww applies, where W je is the instantaneous speed value at point A and w. ₂ J · instantaneous value of velocity in ba> B and ψ is instantaneous value of specific gravity of air mass in the engine cylinder.

While the engine is running, the flow near the combustion chamber orifice does not cease, so that point B is a relatively low pressure point and the air collected in the region of the conical formation c flows therefrom. , the orifice of the combustion chamber, before the direct effect of the flame. Therefore, the mouth of the combustion chamber may extend to a sharp edge so that, when it flows around both sides from the space above the face of the piston 2 and the vortex formation b, there is no deterioration in the vortex formation b as required by the vortex intensity. Selection of the size of the inlet throat £. then the thermal stress aspects are not limited and it is only possible to maintain or increase the flow velocity w with respect to the throttling losses w by changing the size of the inlet throat r i while increasing the volume V of the combustion chamber. The higher temperature of the liner 1 shortens the ignition delay, which is particularly advantageous for engines with a cylinder compression ratio of less than 13 and improves engine start-up. Operation at partial loads and idling is positively affected. Lowering the temperature of the piston 2. means lower demands on the cooling efficiency, higher reliability of the piston group and the possibility of using cheaper oils while extending their replacement time. The preparation and combustion of the mixture is favorably influenced by the higher flow velocity and better utilization of the air mass. Improved combustion with liner 1 will result in improved quality of gaseous emissions, noise shrinkage and reduced fuel consumption.

Claims (2)

SUBJECT OF THE INVENTION *, · An engine combustion chamber formed in a piston housing and provided with an insert for thermal protection of the piston and improving combustion of fuel, characterized in that a gap (s) is formed between the insert (1) and the piston housing (2). Combustion chamber according to claim 1, characterized in that the liner (1) is provided with at least one bottom opening opening into a gap (s) between the liner (1) and the piston (2), the at least one opening opening near the piston face. (2).