Aluminum alloy for a vehicle-mounted liquefied natural gas lightweight cylinder and its liner

Abstract

The present invention discloses a vehicle-mounted liquefied natural gas lightweight cylinder, which relates to the technical field of LNG cylinders, and comprises an outer shell and an inner liner, wherein the outer shell is a stainless steel outer shell, the inner liner is an aluminum alloy inner liner, a vacuum interlayer is arranged between the outer shell and the inner liner, and the outer shell and the inner liner are connected and fixed by a front support and a rear support. The advantage of the present invention is that the patent of the present invention can achieve the use performance specified in the cylinder standard, and can meet the safety and strength performance. It can reduce the weight by about 40%.

Description

Technical Field

[0001] The invention relates to the technical field of LNG gas cylinders, and in particular to a vehicle-mounted liquefied natural gas lightweight gas cylinder and an aluminum alloy for its liner. Background Art

[0002] LNG cylinders for automobiles are special cylinders used to store cryogenic liquefied gas (LNG). They are mainly used in heavy-duty natural gas vehicles to replace traditional fuel vehicles. The storage form of liquefied natural gas (LNG) is special.

[0003] The design is mainly based on the two standards of TSG R0006-2014 "Technical Supervision Regulations for Gas Cylinder Safety", and the welded insulated gas cylinder for liquefied natural gas for vehicles (implementation standard GB / T 34510 "Liquid Natural Gas Cylinder for Vehicles") and the enterprise standards of gas cylinder manufacturers, which have clear provisions on the filling rate of gas cylinders and required type tests. The LNG gas cylinder for vehicles has a double-layer structure, and its interlayer is in a high vacuum state to prevent LNG liquid from convecting and conducting heat with the outside world; there are currently the following problems: 1. The heat transfer supported by the inner liner and the heat radiation of the interlayer will heat the inner liner of the gas cylinder; the LNG liquid in the gas cylinder will be vaporized, thereby increasing the pressure inside the bottle. 2. The inner liner made of stainless steel has good mechanical properties but is too heavy, which seriously affects the energy consumption of the vehicle. 3. Although the use of aluminum alloy inner liner can reduce weight and energy consumption, the following problems still exist: (1) Aluminum alloy has high thermal conductivity, so the vehicle-mounted LNG cylinder needs to have good thermal insulation performance. Therefore, during the design process, this characteristic of aluminum alloy needs to be considered, the cylinder structure needs to be optimized, and heat transfer needs to be reduced as much as possible. (2) Aluminum is easy to react with oxygen in the air at high temperatures to form an aluminum oxide film; this oxide film will improve its corrosion resistance, but the oxide film will affect the welding quality of the aluminum alloy. During the welding process, good protection is required. (3) During welding, the volume shrinkage rate of the aluminum alloy molten pool during solidification is about twice that of steel, so aluminum alloy welds are prone to shrinkage cavities, shrinkage and thermal cracks. Summary of the invention

[0004] In order to reduce the weight of the gas cylinder and overcome the above-mentioned problems, the present invention adopts the following technical scheme: a vehicle-mounted liquefied natural gas lightweight gas cylinder, comprising an outer shell and an inner liner, wherein the outer shell is a stainless steel outer shell, the inner liner is an aluminum alloy inner liner, a vacuum interlayer is arranged between the outer shell and the inner liner, and the outer shell and the inner liner are connected and fixed by a front support assembly and a rear support assembly; the front support assembly comprises an inner sleeve, an outer sleeve, a bushing and a connecting cover, the inner sleeve is inserted into the inner cavity of the sleeve, the bushing is arranged at the front end of the gap between the inner sleeve and the outer sleeve, the connecting cover is arranged at the rear end of the gap between the inner sleeve and the outer sleeve, and the bushing is made of fiberglass; the rear support assembly comprises a first column, a second column, a shaft sleeve and an arc plate, the arc plate is fixedly arranged at the rear part of the inner cavity of the inner liner, and is fixedly connected to the first column, an outer rear head is fixedly arranged at the rear end of the inner cavity of the outer shell, and the second column and the outer rear head are fixedly connected by a shaft sleeve.

[0005] Preferably, the outer sleeve is provided with a through hole.

[0006] Preferably, the front end of the inner sleeve is connected to a distributor.

[0007] Preferably, a front outer head is fixedly provided at the front end of the shell and is fixedly connected to the distributor and the inner sleeve.

[0008] Preferably, an inner front cover is fixedly provided at the front end of the inner liner and is fixedly connected to the outer sleeve.

[0009] Preferably, an inner rear head is fixedly provided at the rear end of the inner tank and is fixedly connected to the first column.

[0010] An aluminum alloy for a lightweight liner of a vehicle-mounted liquefied natural gas cylinder comprises components of Al, Mg, Zn, Mn, Ti, Cu, and at least one of a light rare earth element and Zr.

[0011] Furthermore, the components are calculated by weight as follows: Mg 4.95-5.05%, Zn 0.15-0.2%, Zr 0.08-0.1%, Mn 0.3-0.35%, Ti 0.1-0.12%, Cu 0.12-0.15%, and the balance is Al.

[0012] Preferably, the components are calculated by weight as follows: Mg 4.95-5.05%, Zn 0.15-0.2%, Mn 0.3-0.35%, Ti 0.1-0.12%, Cu 0.12-0.15%, light rare earth elements 0.15-0.2%, and the balance is Al.

[0013] The advantage of the present invention is that the patent of the present invention can achieve the performance specified in the gas cylinder standard, and can meet the safety and strength performance, and can reduce the weight by about 40%. Taking the gas cylinder model CDPW850-1000-1.37MPa as an example, the weight of the gas cylinder can be reduced by about 130Kg. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the present invention;

[0015] Figure 2 is a schematic diagram of the front support assembly;

[0016] Figure 3 Schematic diagram of the rear support assembly. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] like Figure 1 As shown, a vehicle-mounted liquefied natural gas lightweight cylinder includes an outer shell 1 and an inner shell 2. The outer shell 1 is made of stainless steel, and the inner shell 2 is made of aluminum alloy. A vacuum interlayer is arranged between the outer shell 1 and the inner shell 2. The outer shell 1 and the inner shell 2 are connected and fixed by a front support assembly 4 and a rear support assembly 5. A front outer head 7 made of stainless steel is fixedly arranged at the front end of the outer shell 1, and is fixedly connected to the distributor 3 and the inner sleeve 41. An inner front head 8 is fixedly arranged at the front end of the inner shell 2, and is fixedly connected to the outer sleeve 42. An inner rear head 10 is fixedly arranged at the rear end of the inner shell 2, and is fixedly connected to the first column 51.

[0019] like Figure 2 As shown, the front support assembly 4 includes an inner sleeve 41 made of stainless steel, an outer sleeve 42 made of aluminum alloy, a bushing 43 made of fiberglass and a connection cover 44. The inner sleeve 41 is inserted into the inner cavity of the sleeve 42, the bushing 43 is arranged at the front end of the gap between the inner sleeve 41 and the outer sleeve 42, and the connection cover 44 is arranged at the rear end of the gap between the inner sleeve 41 and the outer sleeve 42. The outer sleeve 42 is provided with a through hole 45. The front end of the inner sleeve 41 is connected to the distributor 3.

[0020] like Figure 3 As shown, the rear support assembly 5 includes a first column 51 made of aluminum alloy, a second column 52 made of stainless steel, a sleeve 53 made of stainless steel and an arc plate 21 made of aluminum alloy. The arc plate 21 is fixedly arranged at the rear part of the inner cavity of the liner 2 and is fixedly connected to the first column 51. The rear end of the inner cavity of the outer shell 2 is fixedly arranged with an outer rear head 9 made of stainless steel. The second column 52 and the outer rear head 9 are fixedly connected by a sleeve 53.

[0021] The inner liner is welded by a special machine using a variable polarity melting electrode welding method, and the outer shell uses the traditional stainless steel welding method. Because the connector between the inner liner and the outer liner of the present invention adopts a transition method, the combination of the inner and outer liner is the same as that of the traditional stainless steel bottle, ensuring the convenience and uniformity of production.

[0022] Currently, most of the common aluminum alloy low-temperature pressure vessels on the market use 5083 aluminum alloy. Although it has good welding performance and mechanical properties, there are still a certain amount of welding defects in actual production. The welds are prone to shrinkage cavities, shrinkage and thermal cracks, and the scrap rate is still high.

[0023] Therefore, in order to find the best liner material, the following examples are made for comparison.

[0024] Embodiment 1: The components of the aluminum alloy inner liner are calculated by weight as follows: Mg 5%, Zn 0.15%, Zr 0.1%, Mn 0.35%, Ti 0.1%, Cu 0.15%, and the balance is Al.

[0025] Embodiment 2: The components of the aluminum alloy inner liner are calculated by weight as follows: Mg 5%, Zn 0.15%, Zr 0.1%, Mn 0.35%, Ti 0.1%, Cu 0.15%, light rare earth elements 0.15-0.2%, and the balance is Al.

[0026] Embodiment 3: The components of the aluminum alloy inner liner are calculated by weight as follows: Mg 5%, Zn 0.15%, Mn 0.35%, Ti 0.1%, Cu 0.15%, and the balance is Al.

[0027] The experimental data are as follows:

[0028] 5083 Aluminum Alloy Embodiment 1 Embodiment 2 Embodiment 3 Weldability (full score 5 points) 4 points 4 points 5 points 3.5 points Room temperature tensile strength 315MPa 359Mpa 415Mpa 295Mpa Room temperature yield strength 230Mpa 270Mpa 320Mpa 213Mpa

[0029] It can be seen from the above test data that the welding performance and mechanical properties of Examples 1 and 2 are greatly improved compared with the 5083 aluminum alloy commonly used in the market, but the indicators of Example 3 are lower than those of 5083 aluminum alloy, which shows the outstanding role of Zr and light rare earth elements, especially the addition of trace light rare earth elements can greatly improve the welding performance and mechanical properties.

[0030] The production process of the aluminum alloy substrate in the above-mentioned embodiments refers to the production process of 5083 aluminum alloy.

[0031] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Some technical contents well known to ordinary technicians in the field will not be repeated here. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present invention, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the present invention.

Claims

1. A vehicle-mounted lightweight liquefied natural gas cylinder, comprising an outer shell (1) and an inner shell (2), characterized in that: The outer shell (1) is a stainless steel outer shell, the inner shell (2) is an aluminum alloy inner shell, a vacuum interlayer is provided between the outer shell (1) and the inner shell (2), and the outer shell (1) and the inner shell (2) are connected and fixed by a front support assembly (4) and a rear support assembly (5); the front support assembly (4) comprises an inner sleeve (41), an outer sleeve (42), a bushing (43) and a connecting cover (44); the inner sleeve (41) is inserted into the inner cavity of the outer sleeve (42), the bushing (43) is provided at the front end of the gap between the inner sleeve (41) and the outer sleeve (42), and the connecting cover (44) is provided between the inner sleeve (41) and the outer sleeve (42), the bushing (43) is made of glass fiber reinforced plastic; the rear support assembly (5) comprises a first column (51), a second column (52), a sleeve (53) and an arc plate (21); the arc plate (21) is fixedly arranged at the rear of the inner cavity of the inner liner (2) and is fixedly connected to the first column (51); an outer rear head (9) is fixedly arranged at the rear end of the inner cavity of the outer shell (1); the second column (52) and the outer rear head (9) are fixedly connected by the sleeve (53); the inner liner is welded by a special machine using a variable polarity melting electrode welding method, and the components of the aluminum alloy inner liner are calculated by weight as follows: Mg 5%, Zn 0.15%, Zr 0.1%, Mn 0.35%, Ti 0.1%, Cu 0.15%, light rare earth elements 0.15-0.2%, and the balance is Al.

2. The vehicle-mounted liquefied natural gas lightweight cylinder according to claim 1, characterized in that: The outer sleeve (42) is provided with a through hole (45).

3. The vehicle-mounted liquefied natural gas lightweight cylinder according to claim 1, characterized in that: The front end of the inner sleeve (41) is connected to the distributor (3).

4. The vehicle-mounted liquefied natural gas lightweight cylinder according to claim 3, characterized in that: A front outer cover (7) is fixedly provided at the front end of the outer shell (1) and is fixedly connected to the distributor (3) and the inner sleeve (41).

5. The vehicle-mounted liquefied natural gas lightweight cylinder according to claim 1, characterized in that: An inner front sealing head (8) is fixedly provided at the front end of the inner liner (2) and is fixedly connected to the outer sleeve (42).

6. The vehicle-mounted liquefied natural gas lightweight cylinder according to claim 1, characterized in that: An inner rear end cover (10) is fixedly disposed at the rear end of the inner container (2) and is fixedly connected to the first column (51).

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