Machining method for inner wall of combustion chamber of liquid rocket engine

Abstract

The invention provides a processing method of an inner wall of a combustion chamber of a liquid rocket engine, which adopts a processing method of forging a thin-wall cylinder blank, stamping and necking forming and machining, and comprises the following steps of: stamping and forming the forged thin-wall cylinder blank on a hydraulic machine by using a necking forming die to obtain a small-allowance blank for machining; and machining to obtain a combustion chamber inner wall part meeting the design pattern requirement. Compared with an original combustion chamber inner wall machining method of thick-wall cylinder blank forging and machining, raw materials are saved by more than 70% through thin-wall cylinder blank forging, and the production cost is reduced; after necking forming, the machining allowance is greatly reduced, the machining period is shortened by 60%, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of machining, and particularly relates to a machining method for the inner wall of a combustion chamber of a liquid rocket engine, which is applied to the machining of the inner wall of the combustion chamber made of chromium bronze material of the thrust chamber of a liquid rocket engine. Background Art

[0002] The inner wall of the chromium bronze combustion chamber is an important part of the thrust chamber of a liquid rocket engine. During the engine development stage, the inner wall of the combustion chamber is produced by using a forging thick-walled cylinder blank + machining method, as shown in Figure 1 , and the single-sided allowance of the thick-walled cylinder blank can reach 12 - 55 compared with the finished product. With the increase in engine demand and production volume, the thick-walled cylinder blank + machining method has problems such as low material utilization rate, large process allowance, long production cycle, and high production cost, and is no longer suitable for product production and delivery.

[0003] There is an urgent need to explore a new machining method to reduce costs and increase efficiency and achieve rapid product production. For this reason, the present invention proposes a method of forging a thin-walled cylinder blank + punching and necking forming + machining, which can make up for the deficiencies of the original machining method and achieve low-cost and high-efficiency production of the inner wall products of chromium bronze combustion chambers. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, the inventors of the present invention have conducted intensive research and provided a machining method for the inner wall of a liquid rocket engine combustion chamber. The machining method of "forging a thin-walled cylindrical blank + punching and necking forming + machining" is adopted. A thin-walled cylindrical blank is used, and it is stamped and formed on a hydraulic press with a necking forming die to obtain a small-allowance blank for machining. After machining, an inner wall part of the combustion chamber that meets the requirements of the design drawing is obtained. Compared with the original machining method of "forging a thick-walled cylindrical blank + machining" for the inner wall of the combustion chamber, more than 70% of the raw materials are saved by forging the thin-walled cylinder blank, and the production cost is reduced; after necking forming, the machining allowance is greatly reduced, and the machining cycle is shortened by 60%, improving the production efficiency.

[0005] The technical solution provided by the present invention is as follows:

[0006] In a first aspect, a machining method for the inner wall of a liquid rocket engine combustion chamber includes:

[0007] Obtaining a thin-walled cylinder blank by forging, and the single-sided allowance of the thin-walled cylinder blank is 2.5 - 8 mm;

[0008] Using a pressure device and a necking forming die to perform necking forming on the thin-walled cylinder blank to obtain a necking formed part;

[0009] Performing machining on the necking formed part to obtain an inner wall part of the combustion chamber.

[0010] In a second aspect, an inner wall of a combustion chamber of a liquid rocket engine is obtained by the processing method of the inner wall of the combustion chamber of the liquid rocket engine described in the first aspect.

[0011] A processing method of an inner wall of a combustion chamber of a liquid rocket engine provided by the present invention has the following

[0012] Beneficial effects:

[0013] (1) In the present invention, a thin-walled cylinder blank is obtained by forging. The single-sided allowance of the thin-walled cylinder blank is 2.5 - 8 mm, and a small-allowance machining blank that meets the process requirements can be obtained. Compared with the original forged thick-walled cylinder blank, the weight of the forged thin-walled cylinder blank can be reduced by 70%, greatly reducing the raw material cost.

[0014] (2) The thin-walled necking forming part obtained in the present invention can be directly subjected to finish machining, effectively shortening the machining cycle by 60% and greatly improving the production efficiency.

[0015] (3) In the necking forming die adopted in the present invention, the ejector plate and the lower die jointly enclose the forming space of the inner wall of the combustion chamber in the lower die. The ejector plate plays a positioning role in the forming of the necking forming part; at the same time, the upper surface of the ejector plate is a conical structure and is in surface contact with the necking end of the necking forming part. Compared with the line contact mode of the ejector plate with a flat structure, the structural stability of the necking forming part is improved. Description of the Drawings

[0016] Figure 1 For the process flow of the traditional forged thick-walled cylinder blank + machining method.

[0017] Figure 2 For the process flow of the forged thin-walled cylinder blank + impact necking forming + machining method of the present invention.

[0018] Figure 3 For the structural schematic diagram of the necking forming die of the present invention. Detailed Embodiments

[0019] The present invention will be described in detail below, and the features and advantages of the present invention will become clearer and more definite with these descriptions.

[0020] The special term "exemplary" here means "serving as an example, embodiment or illustration". Any embodiment described as "exemplary" here does not have to be construed as superior to or better than other embodiments.

[0021] The present invention provides a processing method of an inner wall of a combustion chamber of a liquid rocket engine, as Figure 2 shown, including the following steps:

[0022] Step (1): Obtain a thin-walled cylinder blank by forging. The single-sided allowance of the thin-walled cylinder blank is 2.5 - 8 mm. Forging a thinner-walled cylinder blank of a smaller size can reduce the weight of the cylinder blank by 70%. The axial length of the thin-walled cylinder blank is 18 - 30 mm longer than that of the finished part, and about 10 mm (8 - 20 mm) longer than the axial length allowance of the thick-walled cylinder blank, which is beneficial to the subsequent assembly of the necking die and the feasibility of necking forming.

[0023] Step (2): Use a hydraulic press and a necking die to perform necking forming on the thin-walled cylinder blank to obtain a necking formed part.

[0024] As Figure 3 shown, the necking die includes an upper template, an upper die, a lower die, a lower template, a knockout plate, and a ejector rod; an upper die is fixed below the upper template, driving the upper die to move up or down; the upper die is a double-layer frustum structure, the lower frustum extends into the thin-walled cylinder blank to form a taper on the port of the thin-walled cylinder blank; the upper frustum abuts against the end face of the thin-walled cylinder blank to apply pressure to the thin-walled cylinder blank;

[0025] a lower die is fixed above the lower template. The lower die serves as a female die, which is a hollow die with an inner surface identical to the outer surface of the necking formed part; the knockout plate is placed inside the lower die, and its upper surface is a conical structure, located at the outlet of the inner surface of the lower die. The knockout plate and the lower die jointly enclose the forming space of the inner wall of the combustion chamber inside the lower die; the ejector rod passes through the lower template and abuts against the knockout plate. After the necking formed part is formed, it drives the knockout plate to move up to eject the die.

[0026] The specific implementation method of this step is: Place the thin-walled cylinder blank into the necking die, and control the upper die to slowly move down on the hydraulic press, causing the cylinder blank to move towards the lower die. Plastic deformation occurs at the lower part of the cylinder blank. When the lower end face of the cylinder blank contacts the conical surface of the knockout plate, the forming is completed.

[0027] Step (3): Machine the necking formed part to obtain a combustion chamber inner wall part.

[0028] The machined blank after necking forming does not need to be rough-machined and can be directly subjected to finish machining of the inner and outer surfaces. The machining cycle is shortened by 60% compared to the original machining method.

[0029] Embodiment

[0030] As Figure 2 shown, a thin-walled cylinder blank is obtained by forging. The outer diameter of the blank is φ400 mm, the height is 460 mm, and the wall thickness is 18 mm. The single-sided allowance compared to the finished product is 2.5 - 8 mm. The mass of the thin-walled cylinder blank is 89 kg, and the mass of the original thick-walled cylinder blank is 322 kg. The mass of the thin-walled cylinder blank is reduced by 72.4% compared to the thick-walled cylinder blank of the original machining method.

[0031] On an 800-ton hydraulic press, a chromium bronze thin-walled cylinder blank is plastically formed using a necking forming die. The upper die is controlled to move slowly in jog mode, prompting the cylinder blank to move towards the female die. Plastic deformation occurs at the lower part of the cylinder blank. When the lower end face of the cylinder blank contacts the conical surface of the ejector plate, the forming is completed. The ejector rod rises, and the ejector plate ejects the part, and the part is taken out. The forming process is completed in one step. The necking forming force is 350 tons, and the lower end face is closely attached to the ejector plate of the die. After forming, the surface state of the part is good. The outer diameter of the upper port of the cylinder blank is φ400 - φ401 mm, the thickness of the upper port is 18 mm, the outer diameter of the lower port is φ295 - φ296 mm, the axial height is 457 - 458 mm, and the thickness of the lower port is 20 mm. The outer surface is inspected with a cutting surface template. The gap of the straight cylinder section is 0.6 - 0.8 mm, and the gap of the lower curved surface section is 0.4 - 0.5 mm.

[0032] The necking formed part undergoes subsequent mechanical finishing to obtain a qualified part that meets the design requirements. Under the original processing method, the part needs to go through rough machining and finishing, and the processing time is 19 hours. In this embodiment, after the necking forming of the thin-walled cylinder blank, finishing can be directly carried out, and the processing time is 7 hours, which is 63.2% shorter than the original processing method.

[0033] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements can be made to the technical solutions of the present invention and their implementation manners, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0034] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A method for processing the inner wall of a liquid rocket engine combustion chamber, characterized in that: include: A thin-walled tube blank is obtained by forging, wherein the single-side margin of the thin-walled tube blank is 2.5 to 8 mm; Using pressure equipment and a shrinking forming die, the thin-walled tube blank is shrink-formed to obtain a shrink-formed part; The necking formed part is machined to obtain the combustion chamber inner wall part.

2. The method for processing the inner wall of a liquid rocket engine combustion chamber according to claim 1, characterized in that: The shrinking forming die comprises an upper die plate, an upper die plate, a lower die plate, a stripper plate and a push rod; an upper die plate is fixed below the upper die plate to drive the upper die plate to move upward or downward; the upper die is a double-layer truncated cone structure, the lower truncated cone extends into the thin-walled tube blank to shape the end of the thin-walled tube blank; the upper truncated cone presses against the end surface of the thin-walled tube blank to apply pressure to the thin-walled tube blank; A lower die is fixed above the lower die plate. The lower die is a female die and is a hollow die with the same inner profile as the outer profile of the necking part. The stripper plate is placed in the lower die, and its upper profile is a conical structure, located at the outlet of the inner profile of the lower die. The stripper plate and the lower die together form a forming space for the inner wall of the combustion chamber in the lower die. The ejector pin passes through the lower die plate and abuts against the stripper plate. After the necking part is formed, the stripper plate is driven to move up and out of the die. The diameter of the straight section of the inner profile of the lower die is equal to the outer diameter of the thin-walled blank.

3. The method for processing the inner wall of a liquid rocket engine combustion chamber according to claim 1, characterized in that: The axial length of the thin-walled tube blank is 18-30 mm longer than that of the finished part, and is greater than the axial length margin of the thick-walled tube blank.

4. The method for processing the inner wall of a liquid rocket engine combustion chamber according to claim 1, characterized in that: The steps of obtaining the necked formed part are specifically implemented as follows: a thin-walled tube blank is loaded into a necked forming die, and the upper die is controlled to slowly descend on a hydraulic press to cause the tube blank to move toward the lower die, causing plastic deformation to occur at the lower part of the tube blank, and when the lower end face of the tube blank contacts the conical surface of the stripping plate, the forming is completed.

5. The method for processing the inner wall of a liquid rocket engine combustion chamber according to claim 4, characterized in that: The diameter of the straight tube section of the inner surface of the lower die is equal to the outer diameter of the thin-walled tube blank.

6. The method for processing the inner wall of a liquid rocket engine combustion chamber according to claim 1, characterized in that: When machining the necking formed part, the inner and outer surfaces of the necking formed part are directly finished without rough machining.

7. A liquid rocket engine combustion chamber inner wall, characterized in that: The liquid rocket engine combustion chamber is processed by the processing method of any one of claims 1 to 6.

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