Metering pump liquid injection amount automatic and accurate control method adapting to different temperature conditions

Abstract

The invention discloses a method for automatically and accurately controlling the liquid injection amount of a metering pump adaptive to different temperature conditions. Under the condition that the cavity volume of the liquid injection pump is determined, the density value of the liquid after the temperature is changed is calculated according to the change condition of the liquid temperature, and then the weight of the liquid pumped out by the liquid injection pump at a single time is calculated according to the density value of the liquid, so that the liquid outlet amount of the liquid injection pump at different temperatures can be accurately controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of energy-saving pump body related equipment, and in particular to an automatic and precise control method for the liquid injection amount of a metering pump that is adaptable to different temperature conditions. Background Art

[0002] The metering injection pump is a special volumetric pump, mainly used for accurate metering and delivery of liquids, especially corrosive liquids. The metering injection pump can meet various strict process requirements, usually requiring its stability accuracy not to exceed ±1%. For situations with higher accuracy requirements, the accuracy level of the metering injection pump will be further divided, and the stability accuracy requirement of some metering injection pumps will not exceed ±0.2%. However, since the density of the liquid will change with the change of temperature, the specific gravity of the liquid will change, which will cause the metering injection pump to output the same volume of liquid but the weight of the liquid to change, resulting in unqualified metering accuracy.

[0003] In some cases, when a metering injection pump with the same metering setting is used to pump liquid in two places with a large temperature difference, there will be deviations in the concentration of the components in the same volume of the same liquid pumped out. This makes the control program of the metering injection pump unable to meet the high-precision usage requirements in different latitudes or different seasonal climate conditions, with large temperature differences between day and night or large changes in ambient temperature.

[0004] In some cases, some liquids, such as lithium-ion battery electrolytes, are generally stored and transported in tank trucks or electrolyte barrels, and inert gas is injected into the storage tank to protect the liquid. During the transportation of the tank truck, the tank generally stores the lithium-ion battery electrolyte at a low temperature. In the process of taking the electrolyte in the tank, the electrolyte will continue to heat up to a temperature range close to the external ambient temperature. Therefore, in this process, the density of the electrolyte will continue to change, causing the weight of the liquid pumped out by the injection pump to change. At the same time, before using the liquid, the liquid needs to be transferred to the transfer tank to discharge the inert gas bubbles in the liquid to avoid interfering with the amount of liquid pumped out. After being transferred to the transfer tank, some inert gas bubbles will inevitably exist in the liquid, and the bubbles are highly sensitive to temperature. When the temperature rises, the volume of the bubbles increases and the density of the liquid decreases; when the temperature drops, the volume of the bubbles decreases and the density of the liquid increases. Because the working principle of the metering injection pump is to measure volume, when the density of the liquid changes due to temperature changes, the weight of the injection metering pump will also deviate.

[0005] Therefore, the prior art has defects and needs to be improved. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for automatically and accurately controlling the liquid injection amount of a metering pump that is adaptable to different temperature conditions.

[0007] The technical solution of the present invention is as follows: a method for automatically and accurately controlling the liquid injection amount of a metering pump adapted to different temperature conditions is provided, comprising the following steps:

[0008] Step 1: Fill a container with a fixed volume V with liquid, and note that the volume V0 of the liquid is the same as the volume V of the container;

[0009] Step 2: Weigh the container and the liquid to obtain the weight W0 of the liquid at the initial temperature T0;

[0010] Step 3: Calculate the initial liquid density ρ0 under the initial temperature T0;

[0011] Step 4: Raise or lower the temperature of the liquid so that the temperature of the liquid after the temperature change is T;

[0012] Step 5: Subtract the initial temperature T0 from the temperature T of the liquid after the temperature change to obtain the temperature change ΔT;

[0013] Step 6: Look up the table to obtain the volume expansion coefficient β of the liquid;

[0014] Step 7: Calculate the liquid density ρ after the temperature change based on the initial liquid density ρ0, the temperature change ΔT and the volume expansion coefficient β T ;

[0015] Step 8: Liquid density ρ after temperature change T Calculate the weight W of the liquid at temperature T T ;

[0016] Step 9: Based on the calculated weight W of the liquid at temperature T T .

[0017] Furthermore, the calculation formula of the weight W0 of the liquid at the initial temperature T0 is:

[0018] W0=ρ0·V·g;

[0019] Therefore, the calculation formula for the initial liquid density ρ0 is:

[0020]

[0021] in:

[0022] W0 is the initial weight of the liquid;

[0023] ρ0 is the initial liquid density;

[0024] V is the volume of the container;

[0025] g is the acceleration due to gravity.

[0026] Furthermore, the liquid density after temperature change ρ T The calculation formula is:

[0027] ρ T =ρ0·(1-β·ΔT)

[0028] in:

[0029] ρ T is the density of the liquid at temperature T;

[0030] ρ0 is the liquid density at the initial temperature T0;

[0031] β is the volume expansion coefficient of the liquid;

[0032] ΔT is the change in temperature, which is obtained by subtracting the initial temperature T0 from the temperature T of the liquid after the temperature change, that is, ΔT=T-T0.

[0033] Furthermore, the weight W of the liquid at temperature T T The calculation formula is:

[0034] W T =ρ T ·V·g=ρ0·(1-β·ΔT)·V·g

[0035] in:

[0036] W T is the weight of the liquid at temperature T;

[0037] ρ0 is the liquid density at the initial temperature T0;

[0038] β is the volume expansion coefficient of the liquid;

[0039] ΔT is the change in temperature, which is obtained by subtracting the initial temperature T0 from the temperature T of the liquid after the temperature change, that is, ΔT = T-T0;

[0040] V is the volume of the container;

[0041] g is the acceleration due to gravity.

[0042] By adopting the above scheme, the present invention first calculates the density value of the liquid after the temperature change according to the change of the liquid temperature under the condition of determining the cavity volume of the injection pump, and then calculates the weight of the liquid pumped out by the injection pump in a single time according to the density value of the liquid, thereby meeting the requirements of precise control of the liquid output of the injection pump at different temperatures. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with specific embodiments.

[0044] The present invention provides a method for automatically and accurately controlling the liquid injection amount of a metering pump adapted to different temperature conditions, comprising the following steps:

[0045] Step 1: Fill a container with a fixed volume V with liquid, and note that the volume V0 of the liquid is the same as the volume V of the container.

[0046] Step 2: Weigh the container and the liquid to obtain the weight W0 of the liquid at the initial temperature T0.

[0047] Step 3: Calculate the initial liquid density ρ0 under the initial temperature T0.

[0048] The calculation formula of the weight of the liquid W0 at the initial temperature T0 is:

[0049] W0=ρ0·V·g;

[0050] Therefore, the calculation formula for the initial liquid density ρ0 is:

[0051]

[0052] in:

[0053] W0 is the initial weight of the liquid;

[0054] ρ0 is the initial liquid density;

[0055] V is the volume of the container;

[0056] g is the acceleration due to gravity.

[0057] Step 4: Raise or lower the temperature of the liquid so that the temperature of the liquid after the temperature change is T.

[0058] Step 5: Subtract the initial temperature T0 from the temperature T of the liquid after the temperature change to obtain the temperature change ΔT.

[0059] Step 6: Look up the table to obtain the volume expansion coefficient β of the liquid;

[0060] Step 7: Calculate the liquid density ρ after the temperature change based on the initial liquid density ρ0, the temperature change ΔT and the volume expansion coefficient β T ;

[0061] Step 8: Liquid density ρ after temperature change T Calculate the weight W of the liquid at temperature T T ; The weight of the liquid at temperature T is W T The calculation formula is:

[0062] W T=ρ T ·V·g=ρ0·(1-β·ΔT)·V·g

[0063] in:

[0064] W T is the weight of the liquid at temperature T;

[0065] ρ0 is the liquid density at the initial temperature T0;

[0066] β is the volume expansion coefficient of the liquid;

[0067] ΔT is the change in temperature, which is obtained by subtracting the initial temperature T0 from the temperature T of the liquid after the temperature change, that is, ΔT = T-T0;

[0068] V is the volume of the container;

[0069] g is the acceleration due to gravity.

[0070] Step 9: Based on the calculated weight W of the liquid at temperature T T .

[0071] In the embodiment provided by the invention, corresponding inference verification is carried out. At room temperature (25°C), an injection pump with a pump chamber of 1ml is used to inject the lithium-ion battery electrolyte. The electrolyte pumped out once is weighed, and the weighing value is 1.2g. Substituting it into the formula, it is calculated that the density of the electrolyte at room temperature is 1.2g / ml.

[0072] The lithium ion electrolyte is heated to 35°C (i.e. 308K). At this time, the volume of the pump cavity remains unchanged. The heated battery electrolyte is injected through the injection pump, and the electrolyte pumped out once is weighed.

[0073] At the same time, the estimated value of the volume expansion coefficient of the electrolyte of the lithium-ion battery is known to be β = -0.000833 (1 / K). Substituting the known conditions into the formula, the weight W of the electrolyte at 35°C is calculated. T = 1.49 g, and the calculated weight W T The accuracy is verified by calculating the weight of the electrolyte after the temperature rises. The accuracy of the control method provided by the present invention can be verified by experiments, and can be applied to actual work. The weight of the electrolyte pumped out once under the current temperature conditions can be quickly obtained without weighing the electrolyte after the temperature rises for a second time, and the output of the injection pump can be controlled based on this, so as to meet the demand for precise control of the amount of lithium ion electrolyte during the processing.

[0074] To summarize, the present invention, under the condition of determining the cavity volume of the injection pump, first calculates the density value of the liquid after the temperature change according to the change in liquid temperature, and then calculates the weight of the liquid pumped out by the injection pump in a single time according to the density value of the liquid, thereby meeting the requirements of precise control of the liquid output of the injection pump at different temperatures.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for automatically and accurately controlling the liquid injection amount of a metering pump adapted to different temperature conditions, characterized in that: The steps include: Step 1: Fill a container with a fixed volume V with liquid, and note that the volume V0 of the liquid is the same as the volume V of the container; Step 2: Weigh the container and the liquid to obtain the weight W0 of the liquid at the initial temperature T0; Step 3: Calculate the initial liquid density ρ0 under the initial temperature T0; Step 4: Raise or lower the temperature of the liquid so that the temperature of the liquid after the temperature change is T; Step 5: Subtract the initial temperature T0 from the temperature T of the liquid after the temperature change to obtain the temperature change ΔT; Step 6: Look up the table to obtain the volume expansion coefficient β of the liquid; Step 7: Calculate the liquid density ρ after the temperature change based on the initial liquid density ρ0, the temperature change ΔT and the volume expansion coefficient β T ; Step 8: Liquid density ρ after temperature change T Calculate the weight W of the liquid at temperature T T ; Step 9: Based on the calculated weight W of the liquid at temperature T T .

2. The automatic and precise control method for liquid injection volume of a metering pump adapted to different temperature conditions according to claim 1 is characterized in that: The calculation formula of the weight of the liquid W0 at the initial temperature T0 is: W0=ρ0·V·g; Therefore, the calculation formula for the initial liquid density ρ0 is: in: W0 is the initial weight of the liquid; ρ0 is the initial liquid density; V is the volume of the container; g is the acceleration due to gravity.

3. The automatic and precise control method for liquid injection volume of a metering pump adapted to different temperature conditions according to claim 1 is characterized in that: Liquid density after temperature change ρ T The calculation formula is: r T =ρ0·(1-β·ΔT) in: ρ T is the density of the liquid at temperature T; ρ0 is the liquid density at the initial temperature T0; β is the volume expansion coefficient of the liquid; ΔT is the change in temperature, which is obtained by subtracting the initial temperature T0 from the temperature T of the liquid after the temperature change, that is, ΔT=T-T0.

4. The automatic and precise control method for liquid injection volume of a metering pump adapted to different temperature conditions according to claim 1 is characterized in that: The weight W of the liquid at temperature T T The calculation formula is: W T =ρ T ·V·g=ρ0·(1-β·ΔT)·V·g in: W T is the weight of the liquid at temperature T; ρ0 is the liquid density at the initial temperature T0; β is the volume expansion coefficient of the liquid; ΔT is the change in temperature, which is obtained by subtracting the initial temperature T0 from the temperature T of the liquid after the temperature change, that is, ΔT = T-T0; V is the volume of the container; g is the acceleration due to gravity.

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