Thermal expansion compensation mechanism for a piston volumetric tube

Abstract

The application discloses a thermal expansion compensation mechanism for a piston volumetric tube and belongs to the field of liquid flow measurement. The application comprises a mounting seat, a compensation rod, a support inclined block and a slide rail, and further comprises a fixing nut and a heat insulation gasket. The mounting seat is fixedly installed on an equipment base, and the compensation mechanism supports a cylinder body through the support inclined block. The compensation rod is made of the same metal material as the cylinder body, has a hollow structure and is fixed on the mounting seat through the heat insulation gasket and the fixing nut and does not directly contact the mounting seat. The support inclined block is made of a heat insulation material and is fixed at two ends of the compensation rod. The slide rail is fixed on the mounting seat, so that the support inclined block can move along the axial direction of the compensation rod. The application compensates for the axial position change of the cylinder body caused by thermal expansion, ensures that the coaxiality of a piston system and a driving mechanism is within an allowable range during temperature change, maintains the smooth operation of the piston volumetric tube, further expands the temperature range of application of the piston volumetric tube and prolongs the service life of the piston volumetric tube.

Description

Technical Field

[0001] This invention relates to a piston volume tube, and more particularly to a piston volume tube for liquid flow measurement, belonging to the field of liquid flow measurement. Background Technology

[0002] Piston volumetric flowmeters are mainly used for measuring the flow rate of liquids such as petroleum products. They are a volumetric flow rate standard device. They consist of a cylinder, a piston system, and a drive mechanism. During operation, the piston system reciprocates under the drive mechanism.

[0003] Under high temperature conditions, the position of the cylinder axis of the piston volume tube will change due to the thermal expansion of the material, resulting in excessive coaxiality of the piston system and drive mechanism, which will disrupt the smooth operation of the entire system. In severe cases, it may cause severe friction, vibration or even jamming, affecting the performance and life of the piston volume tube.

[0004] Previously, piston volumetric tubes were mainly used for liquid flow metering at room temperature, so there was almost no specific design for addressing the effects of thermal expansion under high-temperature conditions. A few piston volumetric tubes requiring high-temperature operation employed enlarged fit tolerances, leaving a larger clearance between the cylinder and piston system than usual. This prevented direct contact between metal parts within a certain temperature range. However, this method reduced the overall accuracy and sealing of the device, affecting metering performance. Furthermore, it had a limited temperature tolerance range (typically not exceeding 50°C), and problems persisted beyond this range. Summary of the Invention

[0005] To address the problem of misalignment of existing volume tubes after thermal expansion, the present invention discloses a thermal expansion compensation mechanism for piston volume tubes. The technical problem to be solved is to compensate for the change in cylinder axis position caused by thermal expansion, ensure that the coaxiality of the piston system and drive mechanism is within the allowable range during temperature changes, maintain the smooth operation of the piston volume tube, thereby expanding the application temperature range of the piston volume tube and extending its service life.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] This invention discloses a thermal expansion compensation mechanism for a piston volume tube, used to automatically maintain its axial position when thermal expansion caused by temperature changes in the liquid medium within the cylinder leads to a change in the cylinder diameter. The mechanism includes a mounting base, a compensation rod, a support wedge, and a slide rail. It also includes a fixing nut and an insulating gasket. The mounting base is fixedly installed on the equipment base, and the compensation mechanism supports the cylinder via the support wedge.

[0008] Preferably, the compensating rod is made of the same metal material as the cylinder body, has a hollow structure, and is fixed to the mounting base by insulating gaskets and fixing nuts, without direct contact with the mounting base. The support wedges are made of insulating material and fixed to both ends of the compensating rod. The slide rail is fixed to the mounting base, allowing the support wedges to move along the axial direction of the compensating rod.

[0009] Furthermore, to ensure that the movement of the support wedge is compatible with the thermal expansion of the cylinder, the angle between the inclined surface of the support wedge and the horizontal plane is α, and the outer diameter of the cylinder is D. Then, the total length L of the compensating rod...

[0010] L=D / sinα

[0011] The support wedge can only move horizontally, and the angle of its inclined plane remains constant. Therefore, the normal direction of the contact point between the cylinder and the support wedge remains unchanged, always perpendicular to the inclined plane. Thus, when the cylinder diameter D increases by δD, the radius changes by δD / 2. To maintain the axial position, the single-sided support wedge needs to move outward by δL′=δD / 2sinα. Therefore, the total elongation of the compensating rod is δL=δD / sinα. Since the compensating rod and the cylinder are made of the same material and have the same coefficient of thermal expansion, the total length of the compensating rod is L=D / sinα.

[0012] The working method of the thermal expansion compensation mechanism for piston volume tube disclosed in this invention is as follows:

[0013] The same liquid medium as that in the cylinder is introduced into the internal cavity of the compensating rod. When the liquid medium heats up, the cylinder expands thermally, and the radius of the cylinder increases. At the same time, the compensating rod expands thermally, and its length increases. At this time, the support blocks fixed at both ends of the compensating rod separate along the slide rail to both sides, causing the support point of the support blocks on the cylinder to move downward. This change is exactly equivalent to the increase in the axial height caused by the increase in the cylinder radius. This keeps the position of the cylinder axis unchanged and ensures that the coaxiality of the piston system and the drive mechanism is within the allowable range during temperature changes, thus achieving thermal expansion compensation for the piston volume tube.

[0014] In the existing support structure, the support ramp is fixed to the equipment base. When the temperature of the liquid medium inside the cylinder rises, the cylinder temperature rises synchronously, resulting in an increase in the thermal expansion radius. Since the support point remains unchanged, the cylinder axis rises, and the piston system reciprocates within the cylinder, its axis determined by the cylinder axis. However, the drive mechanism does not heat up with the cylinder, causing misalignment between the drive mechanism and the piston system. The drive system generates additional radial force during the reciprocating motion of the piston system, leading to strong friction, noise, and vibration. In severe cases, this can damage seals and the piston, or even cause it to jam and become unusable, affecting the performance and lifespan of the piston volume tube.

[0015] Beneficial effects:

[0016] 1. The present invention discloses a thermal expansion compensation mechanism for a piston volume tube, which can maintain the coaxiality of the piston volume tube cylinder, piston system and drive mechanism during temperature changes, and ensure the stable operation of the equipment.

[0017] 2. The present invention discloses a thermal expansion compensation mechanism for a piston volume tube, which directly uses the liquid medium inside the cylinder, without the need for an additional temperature control device, and is simple and reliable.

[0018] 3. The present invention discloses a thermal expansion compensation mechanism for a piston volume tube, which uses the thermal expansion of one component to compensate for the thermal expansion of another component, thereby ensuring synchronization and accuracy.

[0019] 4. The thermal expansion compensation mechanism for piston volume tube disclosed in this invention can ensure the performance and lifespan of piston volume tube through the above-mentioned improvements. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the thermal expansion compensation mechanism of the present invention;

[0021] Among them: 1—mounting seat, 2—compensation rod, 3—supporting inclined block, 4—slide rail, 5—fixing nut, 6—insulation gasket, 7—cylinder body, 8—equipment base.

[0022] Figure 2 This is a schematic diagram of the compensation process of the present invention;

[0023] Wherein: 9—the portion of the cylinder block's outer diameter increased due to thermal expansion, 10—the position of the support ramp before compensation, and 11—the position of the support ramp after compensation. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, this embodiment discloses a thermal expansion compensation mechanism for a piston volume tube, used to automatically maintain the axial position of the piston volume tube when thermal expansion caused by temperature changes in the liquid medium inside the cylinder 7 leads to a change in the diameter of the cylinder 7. This embodiment of the thermal expansion compensation mechanism for a piston volume tube includes a mounting base 1, a compensation rod 2, a support wedge 3, and a slide rail 4. It also includes a fixing nut 5 and an insulating gasket 6. The mounting base 1 is fixedly installed on the equipment base 8, and the compensation mechanism supports the cylinder 7 through the support wedge 3.

[0026] The cylinder block 7 is made of No. 45 carbon structural steel with an outer diameter of 360mm; the compensating rod 2 is a hollow structure and is also made of No. 45 carbon structural steel; the support inclined block 3 is made of insulating bakelite material, and its inclined surface has an angle of 45° with the horizontal plane; the heat insulation gasket 6 is made of zirconia ceramic material.

[0027] The support block 3 is fixed to both ends of the compensating rod 2 and can move along the axis of the compensating rod 2.

[0028] The equipment uses 4050 aviation lubricating oil as the liquid medium. After the oil is heated, it is simultaneously introduced into the cylinder 7 and the compensating rod 2 to keep their temperatures synchronized.

[0029] The length of the compensation rod 2 is obtained by the following method:

[0030] The amount of thermal expansion deformation of a material can be obtained by the following formula:

[0031] δL=α·L·δT 1)

[0032] in:

[0033] δL thermal expansion deformation

[0034] The coefficient of thermal expansion of α-materials

[0035] Length of material L before temperature change

[0036] δT temperature change

[0037] The diameter of the cylinder block (7) is D, and the coefficient of linear expansion of the cylinder block material is α1. When the temperature changes by δT, the change in diameter is:

[0038] δD=α1·D·δT 2)

[0039] At this time, the change in cylinder radius is:

[0040] δR=δD / 2 3) To keep the axis position unchanged, the distance that the single-sided support inclined block 3 needs to move outward is:

[0041] The total elongation of the compensating rod (2) is: δL′=δD / 2sinα4)

[0042] δL=δD / sinα5)

[0043] The coefficient of linear expansion of the compensating rod (2) is α2. When the temperature change of the compensating rod 2 is also δT, the total length of the compensating rod (2) should be:

[0044] L=δL / (α2·δT)=α1·D / (α2·sinα)6)

[0045] When the coefficient of linear expansion of the compensating rod (2) and the cylinder (7) is the same, equation (5) simplifies to:

[0046] L = D / sinα 7) The length L of the compensating rod 2 is calculated using the aforementioned formula 7), where D = 360mm and α = 45°. The specific calculation is as follows:

[0047] L = D / sinα = 509 mm.

[0048] The working method of a thermal expansion compensation mechanism for a piston volume tube disclosed in this embodiment is as follows:

[0049] During assembly, first fix the mounting base 1 on the equipment base 8; then pass the compensating rod 2 through the mounting hole in the middle of the mounting base 1, and install the heat insulation gaskets 6 and fixing nuts 5 at both ends; next, fix the support inclined blocks 3 at both ends of the compensating rod 2, and install the slide rail 4 on the mounting base 1; finally, place the cylinder body 7 on the support inclined blocks 3 and adjust its position.

[0050] During the test, the oil temperature inside cylinder 7 increased from 25℃ to 95℃. During this process, the position change of the cylinder shaft was less than 0.1mm, which well ensured the concentricity of the piston system and the drive mechanism, maintained the smooth operation of the piston volume tube, and thus expanded the temperature range of the piston volume tube and extended its service life.

[0051] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermal expansion compensation mechanism for a piston volume tube, characterized in that: For piston volume tube, used to automatically maintain its axial position when the diameter of cylinder (7) changes due to thermal expansion caused by temperature change of liquid medium in cylinder (7); the piston volume tube thermal expansion compensation mechanism includes mounting base (1), compensation rod (2), support inclined block (3) and slide rail (4); it also includes fixing nut (5) and heat insulation gasket (6); mounting base (1) is fixedly installed on equipment base (8), and the compensation mechanism supports cylinder (7) through support inclined block (3); The compensating rod (2) is made of the same metal material as the cylinder body (7), has a hollow structure, and is fixed to the mounting base (1) by the heat insulation gasket (6) and the fixing nut (5), without directly contacting the mounting base (1); the supporting inclined block (3) is made of heat insulation material and is fixed to both ends of the compensating rod (2); the slide rail (4) is fixed to the mounting base (1), so that the supporting inclined block (3) can move along the axial direction of the compensating rod (2); The angle between the inclined plane of the supporting wedge (3) and the horizontal plane is α, and the outer diameter of the cylinder (7) is D. Then the total length L of the compensating rod (2) is: L=D / sinα The support block (3) can only move horizontally. The angle of the inclined plane of the support block (3) remains unchanged. Therefore, the normal direction of the contact point between the cylinder (7) and the support block (3) remains unchanged and is always perpendicular to the inclined plane. Therefore, when the diameter D of the cylinder (7) increases by δD, the radius changes by δD / 2. In order to keep the axis position unchanged, the single-sided support block (3) needs to move outward by δL′=δD / 2sinα. Then the total elongation of the compensating rod (2) is δL=δD / sinα. Since the compensating rod (2) and the cylinder (7) are made of the same material and have the same coefficient of thermal expansion, the total length of the compensating rod (2) is L=D / sinα.

2. The thermal expansion compensation mechanism for a piston volume tube as described in claim 1, characterized in that: The same liquid medium as that in the cylinder (7) is introduced into the internal cavity of the compensating rod (2). When the liquid medium heats up, the cylinder (7) undergoes thermal expansion and its radius increases. At the same time, the compensating rod (2) undergoes thermal expansion and its length increases. At this time, the support blocks (3) fixed at both ends of the compensating rod (2) separate to both sides along the slide rail (4), so that the support point of the support blocks (3) on the cylinder (7) moves down. This change is exactly equivalent to the increase in the axis caused by the increase in the radius of the cylinder (7), keeping the axis position of the cylinder (7) unchanged, and ensuring that the coaxiality of the piston system and the drive mechanism is within the allowable range during the temperature change process, thereby realizing thermal expansion compensation for the piston volume tube.

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