Low-speed two-stroke engine piston

Abstract

The invention relates to a low-speed two-stroke engine piston. The low-speed two-stroke engine piston comprises a piston rod, a piston skirt, a piston head, an end flange, a flange cover, a central cooling spray pipe, a bolt, an external cooling spray pipe, an oil return pipe, an annular oil inlet channel, a cross-shaped oil inlet hole, a piston skirt oil cavity, an external cooling oil cavity, a central cooling oil cavity, a through hole, a kidney-shaped through hole, a cross-shaped oil return hole, a flange cover oil cavity and an oil return channel. Jet cooling is introduced, the action form of cooling oil and a piston head cooling cavity is improved, the cooling oil is jetted to the surface of a piston cooling oil cavity at a high speed, piston heat transfer is enhanced through a multiple heat transfer mechanism, the coupling effect of jet cooling and oscillation cooling is achieved, and the defect that oscillation cooling is insufficient in heat exchange in the interval near a bottom dead center is overcome. The piston cooling mode provided by the invention can be suitable for higher heat load, so that the phenomena of strength damage and preignition caused by overhigh heat load of the low-speed two-stroke engine piston can be avoided, and the requirements of continuous optimization and continuous power density improvement in the thermodynamic cycle process of the engine are met.

Description

technical field [0001] The invention relates to the technical field of engines, in particular to a low-speed two-stroke engine piston. Background technique [0002] The piston is in direct contact with the high-temperature gas during the working process. It not only has to bear the high-temperature thermal load of the instantaneous gas conversion, but also bears the gas pressure and the mechanical load imposed during the reciprocating process. With the continuous optimization of the engine thermodynamic cycle process and the continuous increase of power density, the maximum cycle temperature also increases, which makes the temperature of the piston continue to increase. Once the cooling is insufficient and the design temperature is exceeded, it may lead to: a sharp drop in the mechanical properties of the material, cracks or severe deformation, threatening the reliability of the piston; coking of the piston ring and engine oil, causing the piston ring to be stuck and the cyl...

AI Technical Summary

Problems solved by technology

Once the cooling is insufficient and the design temperature is exceeded, it may lead to: a sharp drop in the mechanical properties of the material, cracks or severe deformation, threatening the reliability of the piston; coking of the piston ring and engine oil, causing the piston ring to be stuck and the cylinder to be pulled; the formation of carbon deposits on the top surface of the engine oil causes Local temperature increases. For dual-fuel diesel engines, pre-mixed natural gas may ignite in advance at high temperature points and induce early combustion, which will lead to a series of problems such as insufficient engine power and increased emissions of harmful substances.

[0003] For low-speed two-stroke engines, the increasing heat load on the piston cannot be met by oscillation cooling alone

The cooling oil in the piston cooling chamber oscillates continuously with the up and down reciprocating motion of the piston assembly to take away the heat of the piston, but when the piston runs to the area near the bottom dead center (about 140-220°crankshaft angle), the cooling oil is subjected to downward inertia The force gathers at the bottom of the oil chamber, which separates the top and high-temperature areas of the fire bank from the cooling oil, and enters the "blocking period" where heat exchange cannot be performed in time

Due to the high speed and fast reciprocating frequency of medium and high-speed diesel engines, and the small structural size of the piston cooling oil chamber, the duration of the "blocking period" is extremely short. The vibration cooling can achieve good cooling, while the speed of low-speed two-stroke engines is less than 300r / min, and the cooling The structure size of the oil chamber is large. When the thermal load of the piston increases, it is difficult to obtain sufficient cooling only by the oscillation of the cooling oil

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