JP2006057609A - Reciprocating pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reciprocating pump for preventing a vapor lock, by eliminating pulsation of a delivery fluid, when forcibly feeding liquid of easily generating gas such as liquefied gas. <P>SOLUTION: This vertical reciprocating pump for the liquid has a pressurizing chamber in a cylinder lower part and a piston in an upper part. A suction port is arranged in a pressurizing chamber lower part, and a delivery port is arranged in a piston central part. The horizontal cross-sectional area of a piston rod in a cylinder is set to 1/2 of the horizontal cross-sectional area of the pressurizing chamber. A fluid delivery chamber is arranged in an upper part in the cylinder. The delivery port is conducted to a fluid delivery chamber. Fluid is delivered from a fluid outlet arranged above the piston top dead center of the fluid delivery chamber, and the fluid in the pressurizing chamber desirably intensively passes through the central vicinity of a reciprocating shaft. The reciprocating pump sets a reciprocating speed of the piston constant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reciprocating pump, and more specifically, a liquid reciprocating pump for liquid that quickly discharges gas in a pump chamber and suppresses pulsation when pumping a liquid that easily generates a gas such as liquefied gas. It is about.

  Conventionally, a reciprocating pump has been used to discharge a fluid, particularly a liquid, at a high pressure. This reciprocating pump has a structure in which liquid is sucked into a cylinder, a piston is driven by an external power source in the cylinder, and the liquid inside the cylinder is pressurized by the piston and discharged at a high pressure. There are various types such as vertical pumps, horizontal pumps, multi-stage pumps, etc., all of which generate pulsation due to the alternating suction and discharge strokes as the piston reciprocates. In general, a reciprocating pump for liquid is ideally so-called pulsating with no fluctuation in discharge pressure. Although the number of cylinders can be increased and the pulsation of the discharge pressure can be leveled, there is a drawback that the equipment becomes larger and more complicated and the cost becomes higher. As another pulsation prevention method, an accumulator or the like is provided on the discharge side to control pressure and flow rate. However, this method requires additional equipment and is not preferable.

  Therefore, Patent Document 1 discloses an invention of a reciprocating pump in which pressurization chambers of a cylinder are provided on both the piston tip side and the piston rod side of the piston to stabilize the discharge amount. Patent Document 2 discloses a reciprocating pump provided with three additional pressure chambers. Patent Document 3 discloses a reciprocating pump that is provided with a pre-pressurizing chamber and a main pressurizing chamber and reciprocates the cylinder side. Although these reciprocating pumps can suppress pulsation to some extent, there are difficulties in manufacturing and operation due to complicated pump structure and complicated intake and discharge piping.

JP 2002-202051 A JP 2003-3966 A JP-A-9-158802

  The present invention provides a reciprocating pump capable of stabilizing discharge flow rate and discharge pressure by substantially suppressing pulsation, efficiently discharging gas existing in the pressurizing chamber or generated in the pressurizing chamber to the outside of the cylinder. The purpose is to do.

  The invention for solving the above-mentioned problems is directed to a vertical reciprocating pump for liquid, wherein a suction chamber having a pressurizing chamber at a lower portion of a cylinder, a piston at an upper portion thereof, and a suction valve at a lower portion of the pressurizing chamber is provided at a central portion of the piston head. A suction port with a discharge valve is provided in the pressure chamber, and the suction flow channel and the discharge flow channel in the pressurization chamber are almost on the center line of the piston reciprocating shaft, and the horizontal cross-sectional area of the piston shaft in the cylinder is The space formed by the cylinder in the upper part of the cylinder and the piston rod is defined as a fluid discharge chamber, the discharge port and the fluid discharge chamber are electrically connected, and the pressure chamber is provided in the center of the piston through the discharge port. It is a reciprocating pump which discharges the fluid once discharged from the outer periphery of the piston rod through the flow path to the fluid discharge chamber from a fluid outlet provided above the top dead center of the piston in the fluid discharge chamber. 2. The reciprocating pump according to claim 1, wherein a shape of a piston head surface forming the pressurizing chamber is a funnel shape, and a bottom surface of the pressurizing chamber is a shape in close contact with the piston head surface at a piston bottom dead center. .

  The reciprocating pump of the present invention is always in a fluid discharge state except when the piston is at top dead center and bottom dead center, and pulsation is suppressed. The reciprocating pump of the present invention is a saddle type pump, and the discharge port is arranged at the top of the pressurizing chamber, so that the gas present in the pressurizing chamber is easily discharged out of the pressurizing chamber. Thereby, the gas lock of a pump and the discharge amount fall can be suppressed. Furthermore, the heat generated by adiabatic compression of the gas present in the pressurized chamber is prevented, and as a pump for liquids such as liquefied gas that easily vaporizes due to temperature rise, excellent effects such as improved pump efficiency and improved operating performance are demonstrated. To do. Furthermore, as an indirect effect, it is possible to reduce or omit the accumulator as a countermeasure against pulsation.

  The reciprocating pump of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view for explaining an example of a reciprocating pump according to the present invention. FIG. 1A shows a state in which the piston is being lowered and just before bottom dead center. FIG. b shows a state where the piston is rising and just before top dead center. The reciprocating pump of the present invention has a structure in which a pressurizing chamber 3 is provided at the lower part of a cylinder 1 and the piston 2 is reciprocated by a piston rod 7 connected from the upper part, as in the case of a vertical reciprocating pump normally found. . In the reciprocating pump of the present invention, the fluid suction port 5 is provided in the lower part of the pressurizing chamber 3 and is usually provided in the center of the pressurizing chamber bottom surface 11. This is because the fluid sucked into the pressurizing chamber 3 from the suction port 5 at the time of inhaling the fluid can quickly and evenly flow into the entire pressurizing chamber. In particular, in order to reduce the gap in the pressurizing chamber 3 at the bottom dead center of the piston, when the shapes of the piston head surface 10 and the pressurizing chamber bottom surface 11 are aligned and the closeness is improved, the fluid begins to rise when the piston 2 starts to rise. It is important to have a structure that easily flows into the center and a structure that prevents a pressure drop from occurring in a part of the pressurizing chamber to prevent the gas from being generated near the cylinder wall.

  A fluid discharge port 6 is provided at the center of the piston 2. The discharge port 6 is provided at the center of the piston 2 because the piston 2 is at the top of the pressurizing chamber, and the gas present in the pressurizing chamber 3 after gas-liquid separation for some reason is lighter than the liquid. This is because it moves to the upper part of the pressure chamber and is discharged preferentially from the pressurizing chamber 3 through the discharge port 6 in the pressurizing process of the pump. In particular, if the discharge port 6 is in the center of the piston and the piston head surface 10 has a concave funnel shape, the gas in the pressurizing chamber 3 tends to gather near the discharge port 6 and the gas near the cylinder wall. The above effects are best exhibited. In a liquid pump, gas remaining in the pressurized chamber and repeating compression and expansion not only deteriorates the efficiency of the pump, but also causes an emptying state due to insufficient compression called gas lock, or generates adiabatic compression heat. However, the pump may be destroyed. Even if the pump is not broken, the liquid, which is a fluid, is liable to vaporize due to the temperature rise of the pump, and further gas is generated and may cause gas lock.

  In the reciprocating pump of the present invention, check valves 14 and 15 are provided in the fluid suction port 5 and the discharge port 6 of the pressurizing chamber 3 as in the case of a normal pump. The structure is such that discharge is performed. In FIG. 1, since it is assumed that the piston is rising, the check valve 14 is in an open state and the check valve 15 is in a closed state. That is, the suction chamber is a state in which liquid flows into the pressurizing chamber 3. In the figure, the check valves 14 and 15 are a top-like valve and a ball valve using gravity. The check valve may be any type of check valve commonly used. For example, a plate-like valve may be used, or a valve using the force of an elastic body such as a spring regardless of gravity.

  In the reciprocating pump of the present invention, the discharge port 6 provided in the piston 2 is electrically connected to the fluid discharge chamber 4 provided in the upper part of the cylinder, that is, on the piston rod side. The fluid discharged from the discharge port 6 is once guided to the fluid discharge chamber 4 and flows out from the fluid outlet 8 provided in the upper portion of the fluid discharge chamber 4. The fluid outlet 8 is provided above the piston top dead center so that the fluid discharge chamber 4 is electrically connected to the fluid outflow portion 13 to the outside of the pump even at the top dead center of the piston 2.

In the suction process of the pressurizing chamber 3 as shown in FIG. b, the piston 2 is raised, the discharge port 6 is closed, and the fluid in the fluid discharge chamber 4 only flows out from the fluid outlet 8. When the horizontal cross-sectional area inside the cylinder, that is, the pressurizing chamber 3 is A, the horizontal cross-sectional area of the piston rod 7 is set to A / 2. Since the horizontal sectional area of the fluid discharge chamber 4 is obtained by subtracting the horizontal sectional area of the piston rod 7 from the horizontal sectional area inside the cylinder, the horizontal sectional area of the fluid discharging chamber 4 is also A / 2. Here, when the rising speed of the piston is R, the outflow speed of the fluid from the fluid outlet 8 is expressed as (A × R) / 2. At the same time, the fluid flows into the pressurizing chamber 3 at an inflow rate of A × R. Each horizontal sectional area is an area of a cross section perpendicular to the reciprocating axis of the piston 2. In order to set the horizontal sectional area of the piston rod 7 to ½ of the horizontal sectional area inside the cylinder, for example, when the diameter of the piston rod 7 is d, d = D / 2 ^{1 /} with respect to the inner diameter D of the cylinder 1. ² may be used.

  As shown in FIG. a, when the pressurizing chamber 3 is in the compression process, the piston 2 descends from the top to the bottom, and fluid flows from the pressurizing chamber 3 through the discharge port 6 into the fluid discharge chamber 4. come. The inflow speed is expressed as A × R, where A is the horizontal sectional area of the pressurizing chamber 3 and R is the descending speed of the piston. On the other hand, in the compression process of the pressurizing chamber 3, the volume of the fluid discharge chamber 4 above the cylinder increases as the piston 2 descends. The volume increase rate of the fluid discharge chamber 4 is represented by (A × R) / 2. When the fluid is a liquid, there is almost no change in volume due to pressure, so the outflow speed of the fluid that does not stay in the fluid discharge chamber 4 and flows out from the fluid outlet 8 depends on the fluid inflow speed from the pressurizing chamber 3. 4 is the remainder after subtracting the volume increase rate, and is expressed as (A × R) − (A × R) / 2 = (A × R) / 2. That is, the reciprocating pump of the present invention has a speed (A × R) / 2 that is proportional to the reciprocating speed of the piston in both the ascending and descending directions except for the moment when the piston stops at the top dead center and the bottom dead center. Can supply pressurized fluid.

  If the piston is controlled so that the ascending speed and descending speed are constant, the reciprocating pump of the present invention can maintain both the ascending and descending pistons except for the moment when the piston stops at the top dead center and the bottom dead center. A fluid can be supplied at a flow rate (A × R) / 2, and the reciprocating pump supplies a constant flow rate with almost no pulsation. Any power device may be used for making the reciprocating speed of the piston constant. For example, a hydraulic cylinder or a pneumatic cylinder having a constant working fluid supply amount may be used to shorten the reversing time.

  Next, the improvement of the gas discharge mechanism of the pressurizing chamber 3 will be described. By providing the discharge port 6 in the center of the piston 2 at the upper part of the pressurizing chamber, the gas present in the pressurizing chamber 3 is discharged at the beginning of the fluid discharge process as described above, but a part of the gas is piston. There is a case where it adheres to the periphery of the head surface 10 and is not discharged. In order to prevent this, it is effective to make the shape of the piston head surface 10 into a funnel shape. In the funnel shape, the piston head surface 10 is recessed from the outer peripheral portion toward the center portion, and if the piston 2 is turned upside down, the piston head surface 10 can function as a funnel and poured into the piston head surface 10. In this structure, the collected liquid can be collected in the vicinity of the discharge port 6. In the funnel shape, the piston head surface 10 only needs to rise from the outer peripheral portion toward the center portion as described above, and the rising slope does not need to be linear. For example, a hemispherical shape or a dome shape may be used. Further, it does not have to be horizontal in the circumferential direction. Any structure may be used as long as the gas is present in the outer peripheral portion of the piston head surface so as to be gathered in the vicinity of the discharge port 6 in the central portion of the piston head surface 11 by the rising force due to the difference in specific gravity. Since the pump according to the present invention has a structure in which gas is always discharged first, the pump starts up well and accidents such as trips are unlikely to occur.

  The pressurizing chamber bottom surface 11 has a shape that is in close contact with the piston head surface 10 at the bottom dead center of the piston, so that the dead space at the bottom dead center of the piston can be minimized and the efficiency as a pump is improved. . In addition, it is desirable from the viewpoint of minimizing the dead space that the volume of the suction port 5 is made small as long as the check valve function can be exhibited and the fluid suction amount can be secured. The check valve 14 of the suction port 5 preferably has a structure in which a flow path is provided in the center of the valve and fluid flows into the center of the bottom of the pressurizing chamber 3. Thereby, it is possible to prevent gas from adhering to the suction port 5 and the wall of the pressurizing chamber 3.

  FIG. 1 is a schematic diagram of a cross-sectional view of a liquid hydrogen pump. Liquid hydrogen is supplied from a fluid inlet 12 to a fluid supply chamber 9 made of a heat insulating container. A reciprocating pump according to the present invention is installed in the fluid supply chamber 9, and a suction port 5 is provided at the lowermost part of the pump. The suction port 5 is provided with a check valve 14 using gravity and hydraulic pressure having a generally top-like shape and a flow path in the center. The suction port 5 is opened in the pump suction process as shown in FIG. In the pressurization process as shown in FIG. The bottom surface 11 of the pressurizing chamber 3 has a conical shape that is convex upward, and the piston head surface 10 has a conical shape that is concave upward, so that both surfaces are in close contact at the bottom dead center of the piston. ing. A fluid discharge port 6 is provided at the center of the piston 2, and the discharge port 6 is electrically connected to a fluid discharge chamber 4 provided on the upper side of the piston head 2 in the cylinder 1. The horizontal sectional area of the piston rod 7 is adjusted so that the horizontal sectional area of the fluid discharge chamber 4 is ½ of the horizontal sectional area of the pressurizing chamber 3. A check valve 15 is provided at the discharge port 6, and the discharge port 6 is opened in the pressurization process and closed in the suction process. In addition, the conduction | electrical_connection part with the fluid discharge chamber 4 of the discharge outlet 6 is provided in the position connected with the fluid discharge chamber 4 also in a piston top dead center. A fluid outlet 8 is installed at the uppermost part of the fluid discharge chamber 4, and pressurized liquid hydrogen is supplied from a fluid outlet 13 connected thereto.

  The operating status of this pump will be described. Liquid hydrogen is a liquid that is very easy to vaporize and requires sufficient cooling and heat insulation. For this reason, the pump is installed in a relatively large fluid supply chamber 9 so as not to vaporize in the process of boosting the fluid in the pump. Thus, a small amount of heat generated in the pump is absorbed by hydrogen in the fluid supply chamber 9. Liquid hydrogen is sucked into the pressurizing chamber 3 from the suction port 5 at the bottom of the pump in the piston ascending process as shown in FIG. In this case, the check valve 14 is open and the check valve 15 is closed. At this time, the volume of the fluid discharge chamber 4 decreases in proportion to the rising speed of the piston. Liquid hydrogen corresponding to the reduced volume is discharged from the fluid outlet 8. If the horizontal cross-sectional area of the inside of the cylinder, that is, the pressurizing chamber 3 is A, the horizontal cross-sectional area of the fluid discharge chamber 14 is A / 2, and if the piston rising speed is R, the liquid hydrogen discharge speed is (A × R) / 2.

  When the piston reaches top dead center, the pressurizing chamber 3 has a maximum volume, and the fluid discharge chamber 4 has a minimum volume. Also in this case, the fluid outlet 8 is above the top dead center of the piston, and the fluid in the fluid discharge chamber 14 can be discharged until just before the top dead center.

  Next, the piston 2 enters the descending process, and the pressurizing process of the pump pressurizing chamber 3 is performed. When the piston 2 is lowered, the check valve 14 is closed by the function so that the liquid hydrogen in the pressurizing chamber 3 does not flow out to the fluid supply chamber 9 side, and the pressure in the pressurizing chamber 3 is equal to or higher than the pressure in the fluid discharge chamber 4. When this happens, the check valve 15 opens and the liquid hydrogen in the pressurizing chamber 3 is discharged to the fluid discharge chamber 4 side. The discharge speed is represented by the product (A × R) of the pressure chamber cross-sectional area A and the piston lowering speed R. On the other hand, the volume of the fluid discharge chamber 4 is increasing at the same time, and the increasing speed is (A × R) / 2. As a result, the outflow speed of the liquid hydrogen discharged from the fluid outlet 8 is (A × R) − (A × R) / 2 = (A × R) / 2. That is, this pump can discharge liquid hydrogen at a discharge speed of (A × R) / 2 in both the suction process and the pressurization process.

  Although not shown in FIG. 1, if the driving device of the pump is a piston with a constant ascending and descending speed of the piston, for example, a hydraulic cylinder with a constant working fluid supply amount, the pump is dead at the top dead center. Liquid hydrogen can be supplied at a constant flow rate except for a moment.

  Furthermore, since the piston head surface 10 of this pump has a concave conical shape, the gas generated in the liquid hydrogen always gathers near the discharge port 6 at the center of the piston head surface 10 due to the difference in specific gravity, In the discharge process, it is discharged preferentially and does not stay in the pressurizing chamber. As a result, troubles such as a decrease in pump efficiency and gas lock due to the gas staying in the pressurizing chamber can be prevented. The pumps shown in the examples are thus excellent in pump efficiency and operability.

  The reciprocating pump of the present invention is a liquid reciprocating pump with little pulsation, no gas lock, and good rise at start-up, and can be used as various liquid pumps. In particular, it exhibits an excellent effect as a liquid pump that is liable to vaporize due to changes in temperature and pressure, such as liquefied hydrogen, liquid air, liquid nitrogen, LNG, and liquefied petroleum gas. Furthermore, the reciprocating pump of the present invention has a simple structure, is easy to manufacture, repair and operate, and is highly usable from various economical viewpoints as various liquid pumps.

These are explanatory drawings of the reciprocating pump of the present invention. These are the schematic views of the reciprocating pump of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Pressurization chamber 4 Fluid discharge chamber 5 Intake port 6 Discharge port 7 Piston rod 8 Fluid outlet 9 Fluid supply chamber 10 Piston head surface 11 Pressurization chamber bottom surface 12 Fluid intake port 13 Fluid outflow part 14 Check valve 15 Check valve

Claims (2)

  In a vertical reciprocating pump for liquid, a pressure chamber is provided at the bottom of the cylinder, a piston at the top, a suction port with a suction valve at the bottom of the pressure chamber, and a discharge port with a discharge valve at the center of the piston head The suction flow path and the discharge flow path in the pressurizing chamber are substantially on the center line of the piston reciprocating shaft, and the horizontal cross-sectional area of the piston rod in the cylinder is ½ of the horizontal cross-sectional area of the pressurizing chamber. The space formed by the upper cylinder and the piston shaft is used as a fluid discharge chamber. The discharge port and the fluid discharge chamber are connected to each other, and from the outer periphery of the piston rod through the flow path provided in the center of the piston through the discharge port from the pressurization chamber. A reciprocating pump that discharges fluid discharged to the fluid discharge chamber from a fluid outlet provided above the top dead center of the piston in the fluid discharge chamber. The reciprocating pump according to claim 1, wherein the piston head surface forming the pressurizing chamber has a funnel shape, and the pressurizing chamber bottom surface is in close contact with the piston head surface at the bottom dead center of the piston.

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