CN111322169A

CN111322169A - Steel top piston for large-cylinder-diameter gas engine

Info

Publication number: CN111322169A
Application number: CN202010242968.0A
Authority: CN
Inventors: 曾志龙; 赖柱波; 唐克远; 莫员; 王家祥
Original assignee: Guangxi Yuchai Machinery Co Ltd
Current assignee: Guangxi Yuchai Marine and Genset Power Co Ltd
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2020-06-23

Abstract

The invention discloses a steel top piston for a large-cylinder-diameter gas engine, relates to the technical field of gas engine pistons, and solves the technical problem of an all-aluminum or all-steel piston in the using process. The piston adopts a structure of a steel top iron skirt, an internal cooling oil cavity in the piston is communicated with an oil return cavity through a plurality of channels, the top end of the piston skirt is provided with an oil return hole for communicating the oil return cavity and an inner cavity of the piston skirt, and the height of an orifice of the oil return hole is higher than the bottom surface of the oil return cavity and the bottom surface of the channel; the top end of the piston head is provided with a sunken combustion chamber, and a bulge is arranged in the combustion chamber; the piston head is connected with the piston skirt through a connecting assembly. The invention has high reliability and lower cost than that of an all-steel piston, not only ensures good heat exchange performance in the piston and improves the reliability of the piston and the combustion efficiency of fuel gas, but also improves the extrusion speed of mixed gas, accelerates the combustion speed, shortens the stagnation period and ensures more perfect combustion.

Description

Steel top piston for large-cylinder-diameter gas engine

Technical Field

The invention relates to a piston of a gas engine, in particular to a steel top piston for a large-cylinder-diameter gas engine.

Background

The adaptability, high reliability, high power density and thermal efficiency of the air supply are the main concerns of the user for gas engines. When the gas engine is applied to high-heating-value gas, measures such as a high-pressure-ratio technology, an inter-cooling technology, a Miller cycle technology and a high-energy ignition technology are often adopted, and higher reliability, high power density and thermal efficiency are ensured by improving the explosion pressure in the cylinder. In such a case, it has been difficult for the conventional aluminum piston to satisfy the requirements of high burst pressure, high temperature resistance, and high reliability. The main body of the device is as follows:

(1) along with the continuous promotion of detonation pressure in the combustion chamber, especially when selecting higher compression ratio, the traditional aluminum piston is difficult to bear detonation pressure impact, easily leads to cracking failure;

(2) with the temperature rise in the combustion chamber, the traditional aluminum piston is easy to have the fault of piston melting, so that the engine is damaged and the requirement is difficult to meet.

This series of problems for aluminum pistons can only be solved by the material of the lifting piston. The current solution for small cylinder diameter gas engine is to adopt all-steel piston, while for large cylinder diameter gas engine (cylinder diameter ≧

200mm), the adoption of all-steel pistons often faces a series of problems of high die cost, difficult welding process of the inner cavity of the oil duct at the head part of the piston, large overall weight of the piston and the like.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art, provides a steel top piston for a large-cylinder-diameter gas engine, and solves the technical problem of an all-aluminum or all-steel piston in the using process.

The technical scheme of the invention is as follows: a steel top piston for a large-cylinder-diameter gas engine comprises a steel piston head and a piston skirt part made of ductile iron, wherein the piston skirt part is inserted into the piston head and is connected through a connecting assembly; the joint of the piston head and the piston skirt and the position close to the edge form an inner cooling oil cavity, the middle part of the joint of the piston head and the piston skirt forms an oil return cavity, and the oil return cavity is communicated with the inner cooling oil cavity through a plurality of channels; the top end of the piston skirt is provided with an oil return hole for communicating the oil return cavity with the inner cavity of the piston skirt, and the height of an orifice of the oil return hole is higher than the bottom surface of the oil return cavity and the bottom surface of the channel; the top end of the piston head is provided with a sunken combustion chamber, and a bulge is arranged in the combustion chamber.

In a further improvement, the height of the orifice of the oil return hole is higher than the bottom surface of the oil return cavity and the bottom surface of the channel, and the top surface of the channel is higher than the orifice of the oil return hole.

Furthermore, the bottom surface of the inner cooling oil cavity is positioned below the bottom surface of the oil return cavity.

Furthermore, the ratio of the cross-sectional area of the internal cooling oil cavity to the cross-sectional perimeter thereof is between 0.1 and 0.2.

Furthermore, the bottom surface of the oil return cavity is positioned below the bottom surface of the channel.

Further, the channel is rectangular.

Furthermore, the square ratio of the throat diameter of the combustion chamber to the square of the cylinder diameter of the engine cylinder is between 0.6 and 0.7.

Further, the protrusion height of the protrusion is between 1/10-1/15 of the combustion chamber depth.

Further, the combustion chamber is of a straight barrel type.

Further, the connecting assembly comprises a plurality of connecting bolts and a positioning pin, wherein the connecting bolts penetrate through the skirt portion of the piston and are mounted on the head portion of the piston; a check washer is arranged between the bolt head and the piston skirt of the connecting bolt; one end of the positioning pin is arranged on the head of the piston, and the other end of the positioning pin is arranged on the skirt of the piston.

Advantageous effects

The invention has the advantages that:

1. the piston skirt is inserted in the piston head and connected through the connecting assembly, so that the size of the inner cooling oil cavity is effectively guaranteed, the volume and the cooling capacity of the inner cooling oil cavity are improved, the contact area of cooling oil and the inner cooling oil cavity is larger, good heat exchange is ensured, and the reliability of the piston and the combustion efficiency of fuel gas are improved.

2. The height of the orifice of the oil return hole is higher than the bottom surface of the oil return cavity and the bottom surface of the channel, so that partial cooling oil can be effectively ensured to be always in the channel in the piston, and the piston is favorably cooled; and when the piston acts, the cooling oil in the channel vibrates, the cooling oil vibration effect is utilized to enhance cooling, and the heat exchange between the piston and the cooling oil is better ensured.

3. The combustion chamber positioned at the top end of the piston head is internally provided with a bulge, so that the structure is favorable for improving the turbulent flow speed of the mixed gas in the cylinder body, accelerating the combustion of fuel and shortening the stagnation period; meanwhile, the combustion eddy loss can be reduced, and the combustion process is closer to the flame propagation rule, so that the flame propagation is faster and the combustion is more perfect.

4. The design of the inner cooling oil cavity is controlled according to the S/L of 0.1-0.2, so that the volume of the inner cooling oil cavity and the contact area of cooling oil and the piston can be well ensured, and better heat exchange between the piston and the cooling oil is ensured.

Drawings

FIG. 1 is a schematic cross-sectional view of a piston according to the present invention;

FIG. 2 is a schematic cross-sectional view of the piston head of the present invention;

FIG. 3 is a schematic cross-sectional view of the skirt portion of the piston of the present invention;

FIG. 4 is a schematic top view of the skirt portion of the piston of the present invention;

fig. 5 is a schematic view of the structure of the connecting bolt of the present invention.

Wherein: 1-piston head, 2-piston skirt, 3-inner cooling oil chamber, 4-oil return chamber, 5-oil return hole, 6-combustion chamber, 7-bulge, 8-connecting bolt, 9-positioning pin, 10-anti-loose gasket, 11-channel, 81-bolt head, 82-threaded end, 83-cylinder and 84-chamfer structure.

Detailed Description

The invention is further described below with reference to examples, but not to be construed as being limited thereto, and any number of modifications which can be made by anyone within the scope of the claims are also within the scope of the claims.

Referring to fig. 1 to 4, the steel crown piston for the large-bore gas engine of the invention comprises a steel piston head 1 and a piston skirt 2 made of ductile iron. The strength of the steel piston head 1 is effectively guaranteed, and the problem that an aluminum piston is easy to crack and melt is avoided. The iron piston skirt 2 solves the problems of high cost, difficult welding process and large overall weight caused by all-steel pistons. The piston of the steel top iron skirt effectively improves the reliability of the piston.

The piston skirt 2 is inserted into the piston head 1 and connected by a connecting assembly. Namely, the piston head 1 is in clearance fit connection with the piston skirt 2. Compared with the traditional friction welding technology, the piston head part 1 and the piston skirt part 2 which are connected in a clearance fit mode have the advantages that the process is simpler, the cost is lower, the size of the inner cooling oil cavity 3 is well guaranteed, the capacity of the inner cooling oil cavity 3 is guaranteed, the contact area of cooling oil and the inner cooling oil cavity 3 is larger, good heat exchange is guaranteed, the reliability of the piston is improved, and combustion of fuel gas is facilitated.

The joint of the piston head 1 and the piston skirt 2 and the position close to the edge form an inner cooling oil cavity 3, and the inner cooling oil cavity 3 is an annular cavity. Specifically, the ratio of the sectional area of the internal cooling oil chamber 3 to the sectional perimeter thereof is 0.1 to 0.2. In this embodiment, the sectional area of the internal cooling oil chamber 3 is denoted by S, and the sectional perimeter thereof is denoted by L, that is, the design of the internal cooling oil chamber 3 is controlled to S/L of 0.1 to 0.2. Due to the design, the volume of the inner cooling oil cavity 3 and the contact area between the cooling oil in the inner cooling oil cavity and the piston can be well guaranteed, better heat exchange between the piston and the cooling oil is guaranteed, and the combustion efficiency of fuel gas is favorably improved.

The middle part of the joint of the piston head 1 and the piston skirt 2 forms an oil return cavity 4, and the oil return cavity 4 is communicated with the inner cooling oil cavity 3 through a plurality of channels 11 so as to realize the flow of cooling oil in the two cavities. The top end of the piston skirt part 2 is provided with an oil return hole 5 for communicating an oil return cavity 4 with the inner cavity of the piston skirt part 2 so as to realize the flow of cooling oil in the piston and cool the whole piston. Specifically, the internal cooling oil cavity 3 is communicated with the oil return cavity 4 through four channels 11, so that the flowing of cooling oil is effectively ensured, and the problem of cooling oil stagnation is avoided.

The opening of the oil return hole 5 of the present embodiment is higher than the bottom surface of the oil return cavity 4 and the bottom surface of the channel 11, but the top surface of the channel 11 is higher than the opening of the oil return hole 5. On one hand, the structure ensures that cooling oil always exists in the oil return cavity 4 and the channel 11, and is more beneficial to cooling the piston; on the other hand, the cooling oil in the channel 11 is not completely filled in the channel 11, and the cooling effect of the cooling oil is utilized to enhance the cooling of the piston. When the piston moves, vibration is caused, so that the cooling oil in the channel 11 follows the vibration, and the vibrating cooling oil forms a plurality of fine cooling oil drops, thereby better absorbing high temperature in the piston.

Preferably, the bottom surface of the internal cooling oil cavity 3 is located below the bottom surface of the oil return cavity 4, so that cooling oil is always stored in the internal cooling oil cavity 3, heat exchange can be carried out with the piston in time, and the reliability of heat dissipation of the piston is effectively improved.

Preferably, the bottom surface of the oil return cavity 4 is located below the bottom surface of the channel 11, so that more cooling oil can be stored in the oil return cavity 4 for better cooling the piston.

Preferably, the bottom surface of the internal cooling oil cavity 3 is 10mm-20mm lower than the bottom surface of the channel 11; the height 2/3 of the channel 11 is below the oil return hole 5 and the height 1/3 of the channel 11 is above the oil return hole 5. Thus, the amount of cooling oil in the inner cooling oil cavity 3 and the channel 11 is well ensured, and the heat dissipation performance of the piston is ensured.

Preferably, the channel 11 is rectangular in shape. Compared with the circular channel 11, the rectangular channel 11 has larger surface area in the same radial direction, so that the contact area of cooling oil and the piston is increased, and heat dissipation is facilitated. And the rectangular channel 11 is more beneficial to the oscillation of cooling oil, so that more cooling oil drops are formed in the channel 11, and the high temperature in the piston is better absorbed.

The top end of the piston head 1 is provided with a concave combustion chamber 6, and a bulge 7 is arranged in the combustion chamber 6. When the gas is impacted into the combustion chamber 6 at a high speed, the bulge 7 at the bottom of the combustion chamber plays a role in forming turbulent flow on the gas, so that the gas forms small vortex, turbulent flow is formed, and the gas and air are more fully mixed. The height of the bulge 7 is 1/10-1/15 of the depth of the combustion chamber 6, and the bulge 7 is an arc bulge, so that the structure is favorable for improving the turbulent flow speed of the mixed gas in the cylinder body, effectively quickens the combustion of fuel and shortens the stagnation period.

Preferably, the ratio of the square of the throat diameter of the combustion chamber 6 to the square of the engine cylinder bore diameter is between 0.6 and 0.7. In this example, the throat diameter of the combustion chamber 6 is denoted by D, and the cylinder diameter is denoted by D, i.e., the throat diameter is designed as D²/D²The control is 0.6-0.7, the caliber of the combustion chamber at the piston head 1 is well ensured, and the extrusion flow of mixed gas is facilitated. Moreover, the combustion chamber 6 of the embodiment is in a straight barrel shape, so that the loss of combustion vortex is effectively reduced, the mixed gas is closer to the flame propagation rule in the combustion process, the flame propagation is faster, and the combustion is more perfect.

The connecting assembly of this embodiment includes four connecting bolts 8 and positioning pins 9. The connecting bolt 8 is mounted on the piston head 1 through the piston skirt 2. The four connecting bolts 8 are symmetrically arranged in pairs in the piston, so that the stress of the connected part is uniform. The anti-loosening gasket 10 is arranged between the bolt head 81 of the connecting bolt 8 and the piston skirt 2, so that the problem that the connecting bolt 8 is loosened due to mechanical vibration is avoided, and the reliability of the connected part is greatly improved. One end of the dowel pin 9 is mounted on the piston head 1 and the other end is mounted on the piston skirt 2. During installation, the piston head 1 is firstly positioned on the piston skirt 2 through the positioning effect of the positioning pin 9, and then the connecting bolt 8 is installed, so that the installation accuracy and speed can be effectively improved.

Referring to fig. 5, the connecting bolt 8 of the present embodiment is a dedicated bolt, and is characterized in that: one end of the connecting bolt 8 opposite to the bolt head 81 is a threaded end 82, the bolt head 81 is connected with the threaded end 82 through a cylinder 83, and the surface height of the cylinder 83 is consistent with the height of the bottom of a thread groove of the threaded end 82; the junction of the cylinder 83 with the bolt head 81 and the threaded end 82 is a chamfered formation 84.

Since the piston head 1 is made of steel and the piston skirt 2 is made of a ball, screwing the threaded end 82 of the connecting bolt 8 to the steel piston head 1 inevitably obtains a larger locking force and is more reliable. Therefore, in the present embodiment, the connecting bolt 8 is divided into a bolt head 81, a cylinder 83 and a threaded end, the bolt head 81 abuts against the piston skirt 2, the cylinder 83 is inserted into the piston skirt 2, and the threaded end 82 is screwed to the piston head 1, so that the piston head 1 and the piston skirt 2 are reliably connected. And only through holes for inserting the connecting bolts 8 are formed in the piston skirt part 2, so that the processing technology is simplified. The height of the surface of the cylindrical body 83 is the same as the height of the bottom of the thread groove of the thread end 82, which not only ensures the strength of the connecting bolt 8, but also reduces the overall weight of the connecting bolt 8. And the joints on the connecting bolts 8 are all chamfer structures 84, so that the joints are effectively strengthened, and the reliability of the connecting bolts 8 is ensured.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various changes and modifications without departing from the structure of the invention, which will not affect the effect of the invention and the practicability of the patent.

Claims

1. A steel top piston for a large-cylinder-diameter gas engine is characterized by comprising a steel piston head (1) and a piston skirt part (2) made of ductile iron; the piston skirt (2) is inserted into the piston head (1) and connected through a connecting component; the joint of the piston head (1) and the piston skirt (2) and the position close to the edge form an inner cooling oil cavity (3), the middle part of the joint of the piston head (1) and the piston skirt (2) forms an oil return cavity (4), and the oil return cavity (4) is communicated with the inner cooling oil cavity (3) through a plurality of channels (11); the top end of the piston skirt part (2) is provided with an oil return hole (5) for communicating the oil return cavity (4) with the inner cavity of the piston skirt part (2); the top end of the piston head (1) is provided with a sunken combustion chamber (6), and a bulge (7) is arranged in the combustion chamber (6).

2. The steel crown piston for the large-cylinder-diameter gas engine according to claim 1, characterized in that the height of the orifice of the oil return hole (5) is higher than the bottom surface of the oil return cavity (4) and the bottom surface of the channel (11), and the top surface of the channel (11) is higher than the orifice of the oil return hole (5).

3. The steel crown piston for a large-bore gas engine according to claim 1, characterized in that the bottom surface of the internal cooling oil chamber (3) is located below the bottom surface of the oil return chamber (4).

4. A steel crown piston for a large-bore gas engine according to claim 1 or 3, characterized in that the ratio of the cross-sectional area of said internal cooling gallery (3) to the cross-sectional perimeter thereof is between 0.1 and 0.2.

5. A steel-topped piston for a large cylinder diameter gas engine according to claim 1, wherein the bottom surface of the oil return chamber (4) is located below the bottom surface of the gallery (11).

6. A steel headed piston for large bore gas engines according to claim 1 or 2 or 5 wherein the channel (11) is rectangular in shape.

7. A steel-topped piston for a large bore gas engine according to claim 1, wherein the ratio of the square of the throat diameter of the combustion chamber (6) to the square of the engine cylinder bore diameter is between 0.6 and 0.7.

8. A steel-topped piston for a large bore gas engine according to claim 1, wherein the height of the projection (7) is between 1/10-1/15 of the depth of the combustion chamber (6).

9. A steel crown piston for large-bore gas engines, according to claim 1, 7 or 8, characterized in that said combustion chamber (6) is of the straight-barrel type.

10. A steel-topped piston for a large cylinder diameter gas engine according to claim 1, wherein the connecting assembly comprises a plurality of connecting bolts (8) and locating pins (9), the connecting bolts (8) are mounted on the piston head (1) through the piston skirt (2); a check washer (10) is arranged between the bolt head (81) of the connecting bolt (8) and the piston skirt (2); one end of the positioning pin (9) is arranged on the piston head (1), and the other end of the positioning pin is arranged on the piston skirt (2).