JPS62620A - Subcombustion chamber for diesel engine - Google Patents

Abstract

PURPOSE:To obtain the captioned apparatus which possesses the superior durability and in which generation of crack is prevented at high temperature, by diving or forming a slit onto a subcombustion chamber body made of heat-resisting alloy or ceramics and preventing the concentration of thermal stress by releasing the thermal stress. CONSTITUTION:A subcombustion chamber body 1 made of the heat-resisting material such as heat resisting alloy and ceramics is divided in the longitudinal direction into at least two parts by a cut surface 4 including an injection hole 2. Said two parts are jointed at a regular position by a proper adhesion means, and fastened by an insertion ring 3 which is made of heat-resisting material and forms the flange of the chamber body 1 and an integrally formed body is obtained. In other case, a slit which reaches the outer peripheral surface, including the injection port 2, is formed at one position, and the separated slit surfaces are butt-jointed, and similarly an integrally formed body is obtained. Then, the thermal stress due to the temperature difference at high temperature can be released, and the concentration of thermal stress is avoided, and the generation of crack can be prevented. Thus, the subcombustion chamber which is inexpensive and possesses the superior heat-resisting crackproofness and the superior durability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sub-combustion chamber for a diesel engine, and more specifically, durability is improved by improving the heat cracking resistance of the peripheral edge of the nozzle hole of the sub-combustion chamber. The aim is to

Conventional Technology and Problems In a diesel engine with a sub-combustion chamber, high-temperature, high-pressure air compressed by a piston flows into the vortex chamber 6 to generate a vortex, and most of the fuel injected into this vortex flows into the sub-combustion chamber. The high-temperature gas is injected into the main combustion chamber through the nozzle hole 2, and some unburned fuel due to the ignition delay passes through the nozzle hole 2 and is injected into the main combustion chamber. It has been completely combusted and the combustion condition has been improved.

However, when the nozzle holes 2 are formed in the main body 1 of the auxiliary combustion chamber as shown in FIG. Small acute angles 9 and 10 are formed, and since high temperature gas passes through the nozzle holes, they are exposed to quite high temperatures, so heat accumulates in the acute angles 9 and 10 of the nozzle holes, causing abnormal conditions. When heated, thermal stress concentration occurs due to the difference in thermal expansion coefficient due to temperature difference, and cracks occur due to the thermal stress concentration. Once a crack occurs, the propagation of heat is blocked, and the localized area is heated even more, promoting the crack, and the temperature further increases, causing part of it to burn out and fall off. As described above, there has been a problem in that burnout and cracks occur at the acute angles of the nozzle holes, resulting in poor engine durability.

Furthermore, recently, efforts have been made to improve thermal efficiency in order to reduce engine fuel consumption and improve performance, and the maximum combustion temperature and maximum combustion pressure of the sub-combustion chamber have become higher, and the conditions required for the sub-combustion chamber, which determine the life of the engine, are becoming increasingly strict. These conditions have become increasingly harsh, and the sub-combustion chamber is increasingly required to have heat insulation, heat resistance, heat crack resistance, heat fatigue resistance, etc.

Traditionally, austenitic materials such as S (1, HI3.5UH310, 5UH661, Ni
Heat-resistant steels and heat-resistant alloys such as mocast80, 5UH4 for ferritic type, and 5tJH616゜5UH3 for martensitic type were used, but austenitic type has a large coefficient of thermal expansion and is prone to cracking due to thermal fatigue, while ferritic type has low high temperature strength. Otherwise, it may fall off or become deformed. Martensitic materials have a low coefficient of thermal expansion and high-temperature strength, but are unsatisfactory due to lack of oxidation resistance, resulting in burnout, insufficient thermal fatigue resistance, and thermal shock resistance, and although they have sufficient durability. It's gone.

In addition, Nimocast 80 is made of expensive metal element Co.

Since it contains a large amount of Ni etc., it is very expensive and is not economically satisfactory.

In recent years, ceramics with excellent heat resistance and heat insulation properties have attracted attention, and various applications have been made for chamber materials.In order to improve thermal efficiency, ceramics with particularly excellent heat insulation properties such as zirconia and cordierite are used. However, ceramics with excellent heat resistance, such as silicon nitride and silicon carbide, are particularly suitable for preventing burnout, but this is not satisfactory due to the problem of balancing between improving thermal efficiency and improving durability. do not have.

Means for Solving the Problems The present invention has focused on the peculiarities of the auxiliary combustion chamber described above, and has researched materials for the auxiliary combustion chamber main body that are inexpensive and have excellent heat cracking resistance. Materials that can withstand these conditions have become increasingly high-quality and expensive, and their workability has also deteriorated, reaching the limits of performance and economics as a single, sufficiently durable material.

The inventors believe that rather than changing the conventional way of thinking and considering how to withstand the concentration of thermal stress that causes cracks, we can release the thermal stress that causes cracks and eliminate the concentration of thermal stress. We came up with the idea that it might be possible to prevent the occurrence of cracks, and as a result of continued research, we arrived at the present invention.

A sub-combustion chamber main body 1 made of a heat-resistant material such as a heat-resistant alloy or ceramics is cut at a cut surface 4 including the nozzle holes 2.
A heat-resistant material that is vertically divided into two or more blocks, and the two or more divided blocks are joined together at a proper position using an appropriate adhesive means to form the flange 3a of the sub-combustion chamber main body 1. Tighten with insert ring 3 to make it into one piece. Alternatively, one slit 5 including the nozzle hole 2 and extending vertically to the outer circumferential surface is provided in the chamber body 1 of the sub-combustion chamber,
The cut surfaces of the separated slits are butted together using an appropriate bonding means to form a regular perfect circle, and then tightened with the insert ring 3 that forms the flange 3a of the auxiliary combustion chamber main body 1 to form an integrated structure. By dissipating the thermal stress caused by the difference in thermal expansion coefficient due to temperature difference, it eliminates the concentration of thermal stress and prevents the occurrence of cracks.It is an inexpensive, durable secondary combustion chamber with excellent heat crack resistance. This is what we provide.

It is of course possible to combine heat-resistant materials as appropriate, such as by making the chamber body 1 from ceramics and the insert ring 3 from a heat-resistant alloy to form an integrated structure.

EXAMPLES Hereinafter, examples of the present invention will be specifically explained based on the drawings.

1 to 4 show an embodiment in which the auxiliary combustion chamber chamber body 1 is divided.

As shown in Figures 1 and 2, a sub-combustion chamber main body 1 made of heat-resistant alloy 5UH310 is vertically divided into two along a cut plane 4 on a center line parallel to the nozzle holes 2. After combining the two divided blocks at the proper abutting positions with appropriate adhesive means, the flange 3a of the auxiliary combustion chamber chamber body 1 is made of heat-resistant alloy 5UH310. Naru insert ring 3
It was baked in and made into an integrated piece.

FIG. 3 shows an embodiment in which the chamber main body 1 of the auxiliary combustion chamber is vertically divided into two pieces along a cut surface 4a perpendicular to the nozzle hole 2. As shown in FIG.

FIG. 4 shows an embodiment in which the chamber main body 1 of the auxiliary combustion chamber is vertically divided into three parts including the nozzle holes 2 by cutting surfaces 4b at one place in a parallel direction and at two places having a certain inclination.

In addition, the position and number of divisions of the main body of the auxiliary combustion chamber are appropriately selected in consideration of the occurrence of thermal stress and the occurrence of cracks.

FIGS. 5 and 6 show an embodiment in which a slit 5 is provided in the chamber main body 1 of the auxiliary combustion chamber.

Figure 5 shows that a slit 5 containing the nozzle hole 2 and extending vertically to the outer circumferential surface of the sub-combustion chamber main body 1 made of heat-resistant alloy 5UH310 is cut out by inserting a slit 5 parallel to the nozzle hole 2 on the center line of the inclination direction. After the cut surfaces of the slits 5 are butted together and temporarily fixed in a regular perfect circle state using an appropriate adhesive means, the auxiliary combustion chamber chamber body 1 is assembled as shown in FIG.
It was shrink-fitted into an insert ring 3 made of heat-resistant alloy 5UH310 that forms the flange 3a of the flange 3a.

FIG. 6 shows an example in which a slit 5a is provided at one location on the center line of the nozzle hole 2 on the opposite side to the direction of inclination.

In addition, the position where the slit is made in the main body of the auxiliary combustion chamber is appropriately selected in consideration of the occurrence of thermal stress and the state of occurrence of cracks.

When a slit is formed, the outer circumferential surface of the sub-combustion chamber is processed into an elliptical shape, including the cutting margin of the slit 1-, so that when the slit is made and the slit surfaces are butted together, the outer circumferential surface becomes a perfect circle.

When the auxiliary combustion chamber main body 1 is shrink-fitted to the insert ring 3, the shrink-fitting margin is appropriately selected so that tightening force is applied even at high temperatures and no loosening occurs. In addition, consideration has been given to preventing loosening by interposing a heat-resistant cushioning material between the auxiliary combustion chamber and the insert ring, which contracts when compressed and restores itself appropriately when relaxed.

A heat crack resistance test was conducted on each of the following sub-combustion chambers formed by the above method.

(IA) Divided into two pieces according to Figure 2.

(IB) Divided into two pieces according to Figure 3.

(IC) Divided into three parts according to Figure 4.

(nA) With slits as shown in Figure 5.

(nB) With slits as shown in Figure 6.

As a comparative material, a sub-combustion chamber having the chemical components shown in Table 1 was used.

(m) RI K-MB (IV) of martensitic structure
Aus-rf I-Organization SUH310 (V) Nimo
cast80 This test was conducted using the first
The auxiliary combustion chamber main body 1 of the test piece is fixed to the holder 13 shown in Figure 0, heated from the bottom to about 950°C with the gas burner 14, and then the test bag @ 12 is rotated and the auxiliary combustion chamber main body 1 is sprayed with the spray 15. Move it above the room, spray water on it, cool it to about 4°C, and then air cool it. After repeating the heating and cooling cycle shown in FIG. 11 300 times, a crack 1 appeared on the bottom periphery of the nozzle hole 2 as shown in FIG.
The lengths of 1 were measured, and the heat crack resistance was determined based on the total length.

The test results for heat cracking resistance are (■) RIK with low oxidation resistance.
-MB had severe scale caused by oxidation, and as the scale grew and peeled off repeatedly, the sharp corners of the nozzle holes became thin and fell off, causing burnout. (IV)S
The total length of the UH31'O crack is 14.1ame (V)
The total crack length of Nimocast 80 was 10.5 mm, whereas the crack length of the present invention was 10.5 mm.
B), (I C) and the slit (■A
) and (JIB), no cracks were observed and it was recognized that the heat cracking resistance was significantly improved.

Effects As an auxiliary combustion chamber for diesel engines, the main body of the auxiliary combustion chamber, which is conventionally made of heat-resistant alloys or ceramics, is divided or slitted in advance to release thermal stress and eliminate concentration of thermal stress. It is possible to provide a sub-combustion chamber for diesel engines at a low cost that has excellent durability and can withstand the harsh conditions that will be required to improve the performance of future engines by preventing the occurrence of cracks even when exposed to The practical effect is remarkable.

[Brief explanation of the drawing]

Fig. 1 A sectional view showing an example of the auxiliary combustion chamber according to the present invention Fig. 2 A plan view divided into two parallel to the nozzle hole Fig. 3 A plan view divided into two at right angles to the nozzle hole Fig. 4 Parallel to the nozzle hole Figure 5: A plan view divided into three parts by a plane with a certain angle of inclination. Figure 6: A plan view where a slit is cut in the direction of inclination of the nozzle hole. Figure 7: A plan view where a slit is cut in the direction opposite to the direction of inclination of the nozzle hole. Fig. 8 is a plan view showing the occurrence of cracks; Fig. 9 is a cross-sectional view of a conventional auxiliary combustion chamber; Fig. 10 is a schematic diagram of the thermal fatigue testing device; Figure 11 Graph showing the heating and cooling cycle of thermal fatigue test 1: Sub-combustion chamber chamber body 2: Nozzle hole 3: Insert ring 3a: Flange 4: Divided surface 4a
: Divided surface 4b: Divided surface 5 nislit 5a nislit 6: Swirl chamber 9: Acute angle part 10: Acute angle part 11
: Crack 12: Thermal fatigue test device 13: Holder 1
4: Burner 15 Nispray

Claims (1)

[Claims] A sub-combustion chamber main body 1 for a diesel engine made of a heat-resistant material is vertically divided into two or more blocks at a dividing surface 4 including nozzle holes 2, and each block divided into two or more blocks is bonded with an appropriate bonding means. Either they are temporarily fixed in their proper abutting positions, or one slit 5 is formed in the main body 1 of the auxiliary combustion chamber for a diesel engine made of a heat-resistant material, which includes the nozzle hole 2 and extends vertically to the outer circumferential surface. Then, the cut surfaces of the separated slits are butted together using an appropriate adhesive means, and temporarily fixed in a regular perfect circle state. An auxiliary combustion chamber for a diesel engine, characterized in that it is integrally shrink-fitted into an insert ring 3 forming an insert ring 3a.