Method for improving temperature and volume metering accuracy of ethanol gasoline

Abstract

The invention discloses a method for improving the temperature and volume metering accuracy of ethanol gasoline. The method comprises the following steps: calculating through an ethanol gasoline temperature and volume correction coefficient algorithm to obtain an ethanol gasoline blending isothermal temperature and volume correction coefficient; non-isothermal ethanol and component oil blending temperature volume correction is equivalently converted into isothermal ethanol and component oil blending temperature volume correction; according to the ethanol gasoline temperature and volume correction algorithm, the temperature and volume correction value of the blended ethanol gasoline is calculated, and temperature and volume metering errors introduced by blending of ethanol and component oil are effectively reduced; the method has good practical application value for further popularization and use of the ethanol gasoline, and is a good method for ensuring fair and fair trade settlement of the ethanol gasoline produced by pipeline proportion blending.

Description

Technical Field

[0001] The invention relates to the field of ethanol gasoline temperature and volume measurement, and in particular to a method for improving the accuracy of ethanol gasoline temperature and volume measurement. Background Art

[0002] Ethanol gasoline for vehicles (hereinafter referred to as ethanol gasoline) refers to ethanol gasoline used as component oil vehicle fuel after 10% denatured fuel ethanol (hereinafter referred to as ethanol) is added to gasoline component oil (hereinafter referred to as component oil) by volume. Ethanol gasoline is a clean and renewable fuel with great development potential. The addition of ethanol component oil can effectively improve the octane number and oxygen content of the component oil, reduce carbon emissions, particulate matter emissions and other toxic substances in automobile exhaust pollution, and improve air quality. Due to its advantages of optimizing energy structure, improving ecological environment and ensuring energy security, the promotion of ethanol gasoline has become a general trend. At present, ethanol gasoline is mostly produced by oil depots using pipeline proportion blending technology. Due to the limitations of pipeline proportion blending technology, ethanol gasoline cannot be blended evenly in a short time and is in an unstable state. Therefore, at the sales site of ethanol gasoline produced by pipeline proportion blending, it is impossible to accurately measure the volume and temperature parameters of ethanol gasoline.

[0003] The main components of the component oil are long-chain alkanes (C4-C12). After adding ethanol, the force field in the liquid phase changes, causing the hydrogen bonds of some alcohols to break, so the blending process shows an endothermic effect, resulting in a decrease in the temperature of ethanol gasoline. At the same time, hydrogen bond breakage, molecular filling and temperature reduction all affect the volume of ethanol gasoline. Therefore, the blending of ethanol and component oils will cause temperature and volume changes. At present, the technology for reducing the temperature and volume measurement errors introduced by the blending of ethanol and component oils has not been perfected.

[0004] Therefore, a method for improving the accuracy of temperature and volume measurement of ethanol gasoline is needed. Summary of the invention

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for improving the accuracy of ethanol gasoline temperature and volume measurement comprises the following steps:

[0007] (1) Using a high-precision analytical balance and a vibration density meter, ethanol and component oils with an ethanol volume fraction of a% are prepared by mass density method and stored in volumetric flasks A and B, respectively.

[0008] (2) The temperature of ethanol and component oil is controlled by a constant temperature water bath, and two high-precision thermometers are used to monitor the ethanol temperature t1 and the component oil temperature t2 before blending. If the temperatures of ethanol and component oil before blending are different, the thermal equilibrium temperature value t4 of ethanol and component oil is calculated by the thermal balance algorithm. When the temperature of ethanol and component oil is equal to the thermal equilibrium temperature of ethanol and component oil by constant temperature water bath temperature control, the ethanol gasoline blending temperature precision measurement experimental device is used to conduct an isothermal ethanol gasoline blending temperature correction value precision measurement experiment. The thermal equilibrium temperature value calculation formula of ethanol and component oil in the thermal balance algorithm is:

[0009]

[0010] Where, t4 is the thermal equilibrium temperature of ethanol and component oil before blending, °C;

[0011] c1, c2——Specific heat capacity of ethanol and component oil, J·kg -1 ℃ -1 ;

[0012] t1, t2 – temperature of ethanol and component oils before blending, ℃.

[0013] ρ1——Density of ethanol at temperature t1 before blending, g·cm -3 ;

[0014] ρ2——Density of component oil at temperature t2 before blending, g·cm -3 ;

[0015] (3) The temperature of the constant temperature water bath for controlling the temperature of the ethanol gasoline is adjusted by the stepwise approximation method until the difference between the set temperature of the constant temperature water bath and the lowest temperature of the blended ethanol gasoline is less than 0.05° C. At this time, the reading of the high-precision thermometer for monitoring the ethanol gasoline is the temperature t3 of the blended ethanol gasoline;

[0016] (4) Calculate the isothermal ethanol gasoline blending temperature correction value. The temperature correction value calculation formula is:

[0017] Δt=t3-t4 (1)

[0018] Where: Δt——isothermal ethanol gasoline blending temperature correction value, °C;

[0019] t3——Temperature of ethanol gasoline after blending, ℃

[0020] t4——Thermal equilibrium temperature of ethanol and component oil before blending, °C;

[0021] (5) Use the equipment to prepare at least two ethanol gasoline samples with an ethanol volume fraction of a%, and use a high-precision vibration density meter to measure the density of ethanol gasoline in the temperature range of 5°C to 35°C, with a temperature interval of 2°C; record the ethanol gasoline temperatures t5 and t6 respectively, and when t6>t5; calculate the volume expansion coefficient of ethanol gasoline, the calculation formula is:

[0022] β=(ρ5-ρ6) / [ρ6·(t6-t5)] (2)

[0023] Where: β——Volume expansion coefficient of ethanol gasoline at temperature t6, ℃ -1 ;

[0024] t5, t6——ethanol gasoline temperature, °C;

[0025] ρ5, ρ6——density of ethanol gasoline at temperature t5 and temperature t6, g·cm -3 .

[0026] (6) Using a high-precision vibration density meter to measure the ethanol density, component oil density, and ethanol gasoline density with an ethanol volume fraction of a% in the temperature range of 5°C to 35°C; the isothermal ethanol gasoline blending volume correction coefficient is calculated using the isothermal ethanol gasoline blending volume correction coefficient algorithm; the calculation formula for the isothermal ethanol gasoline blending volume correction coefficient is:

[0027]

[0028] Where: k is the isothermal ethanol gasoline blending volume correction factor, dimensionless;

[0029] ρ4——density of ethanol gasoline at temperature t4, g·cm -3 ;

[0030] ——The average value of the volume expansion coefficient of ethanol gasoline between temperatures t3 and t4.

[0031] (7) Calculating the average oil temperature of ethanol and component oils. The ethanol temperature is calculated by accumulating the product of the instantaneous increase in mass of ethanol during the oiling process and the instantaneous temperature. After the oiling is completed, the accumulated sum is weighted averaged on the actual mass of the oil to obtain the average oil temperature of ethanol. The algorithm principle of the average oil temperature of the component oil is the same as that of the average oil temperature of ethanol.

[0032] (8) Calculate the thermal equilibrium temperature of ethanol and component oils. According to the volume fraction of ethanol, the average temperature of ethanol and component oils, and the specific heat capacity, use formula (5) to calculate the thermal equilibrium temperature value t4 of ethanol and component oils, and convert the non-isothermal ethanol and component oil blending temperature volume correction into the isothermal ethanol and component oil blending temperature volume correction;

[0033] (9) Calculate the isothermal ethanol gasoline blending temperature correction value after blending by using the isothermal ethanol gasoline blending temperature correction value calculation formula, and subtract the isothermal ethanol gasoline blending temperature correction value from the thermal equilibrium temperature of ethanol and component oils to obtain the average oil-generating temperature of ethanol gasoline;

[0034] (10) The isothermal ethanol gasoline blending volume correction coefficient is calculated by the isothermal ethanol gasoline blending volume correction coefficient algorithm. The sum of the volumes of ethanol and component oils multiplied by the isothermal ethanol gasoline blending volume correction coefficient is the ethanol gasoline correction volume.

[0035] Furthermore, the equipment in step (5) includes a high-precision analytical balance, a high-precision vibration density meter, a volumetric flask pipette and a disposable dropper.

[0036] Further, the method for improving the accuracy of ethanol gasoline temperature and volume measurement also includes the following steps:

[0037] (11) The isothermal ethanol and component oil temperature values, ethanol gasoline temperature correction values, and volume correction coefficients are fitted with a quadratic curve to obtain an isothermal ethanol gasoline blending temperature and volume correction data table.

[0038] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0039] 1. The present invention converts the non-isothermal ethanol and component oil blending temperature and volume correction into the isothermal ethanol and component oil blending temperature and volume correction; the isothermal ethanol gasoline blending temperature and volume correction algorithm is used to calculate the temperature and volume correction value of the blended ethanol gasoline, thereby effectively reducing the temperature and volume measurement errors introduced by the blending of ethanol and component oils.

[0040] 2. The present invention effectively improves the temperature and volume measurement accuracy of the automotive ethanol gasoline produced by pipeline proportion blending, has good practical application value for further promoting the use of ethanol gasoline nationwide, and is a good method to ensure the fairness and justice of the trade settlement of ethanol gasoline produced by pipeline proportion blending. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the experimental device for accurately measuring the blending temperature of ethanol gasoline of the present invention.

[0042] Figure 2 This is a temperature variation curve diagram of the isothermal ethanol gasoline blending process of the present invention.

[0043] Figure 3 This is a temperature correction curve diagram of the isothermal ethanol gasoline blending of the present invention. DETAILED DESCRIPTION

[0044] The following embodiments may help those skilled in the art to more fully understand the present invention, but shall not limit the present invention in any way.

[0045] A method for improving the accuracy of ethanol gasoline temperature and volume measurement comprises the following steps:

[0046] (1) Using a high-precision analytical balance and a vibration density meter, ethanol and component oils with an ethanol volume fraction of a% are prepared by mass density method and stored in volumetric flasks A and B, respectively.

[0047] (2) The temperature of ethanol and component oil is controlled by a constant temperature water bath, and two high-precision thermometers are used to monitor the ethanol temperature t1 and the component oil temperature t2 before blending. If the temperatures of ethanol and component oil before blending are different, the thermal equilibrium temperature value t4 of ethanol and component oil is calculated by the thermal balance algorithm. When the temperature of ethanol and component oil is equal to the thermal equilibrium temperature of ethanol and component oil by constant temperature water bath temperature control, the ethanol gasoline blending temperature precision measurement experimental device is activated to conduct isothermal ethanol gasoline blending temperature correction value precision measurement experiment; the ethanol gasoline thermal equilibrium temperature calculation formula in the thermal balance algorithm is:

[0048]

[0049] Where, t4 is the thermal equilibrium temperature of ethanol and component oil before blending, °C;

[0050] c1, c2——Specific heat capacity of ethanol and component oil, J·kg -1 ℃ -1 ;

[0051] t1, t2 – temperature of ethanol and component oils before blending, ℃.

[0052] ρ1——Density of ethanol at temperature t1 before blending, g·cm -3 ;

[0053] ρ2——Density of component oil at temperature t2 before blending, g·cm -3 ;

[0054] (3) The temperature of the constant temperature water bath for controlling the temperature of the ethanol gasoline is adjusted by the stepwise approximation method until the difference between the set temperature of the constant temperature water bath and the lowest temperature of the blended ethanol gasoline is less than 0.05° C. At this time, the reading of the high-precision thermometer for monitoring the ethanol gasoline is the temperature t3 of the blended ethanol gasoline;

[0055] (4) Calculate the isothermal ethanol gasoline blending temperature correction value. The isothermal ethanol gasoline blending temperature correction value calculation formula is:

[0056] Δt=t3-t4 (1)

[0057] Where: Δt——isothermal ethanol gasoline blending temperature correction value, °C;

[0058] t3——Temperature of ethanol gasoline after blending, ℃

[0059] t4——Thermal equilibrium temperature of ethanol and component oil before blending, °C;

[0060] (5) Use the equipment to prepare at least two ethanol gasoline samples with an ethanol volume fraction of a%, and use a high-precision vibration density meter to measure the density of ethanol gasoline in the temperature range of 5°C to 35°C, with a temperature interval of 2°C; record the ethanol gasoline temperatures t5 and t6 respectively, and when t6>t5; calculate the volume expansion coefficient of ethanol gasoline. The calculation formula for the volume expansion coefficient of ethanol gasoline is:

[0061] β=(ρ5-ρ6) / [ρ6·(t6-t5)] (2)

[0062] Where: β——Volume expansion coefficient of ethanol gasoline at temperature t6, ℃ -1 ;

[0063] t5, t6——ethanol gasoline temperature, °C;

[0064] ρ5, ρ6——density of ethanol gasoline at temperature t5 and temperature t6, g·cm -3 .

[0065] (6) Using a high-precision vibration density meter to measure the ethanol density, component oil density, and ethanol gasoline density with an ethanol volume fraction of a% in the temperature range of 5°C to 35°C; the isothermal ethanol gasoline blending volume correction coefficient is calculated using the isothermal ethanol gasoline volume correction coefficient algorithm; the calculation formula of the isothermal ethanol gasoline volume correction coefficient algorithm is:

[0066]

[0067] Where: k is the isothermal ethanol gasoline blending volume correction factor, dimensionless;

[0068] ρ4——density of ethanol gasoline at temperature t4, g·cm -3 ;

[0069] ——The average value of the volume expansion coefficient of ethanol gasoline between temperatures t3 and t4.

[0070] (7) Calculating the average oil temperature of ethanol and component oils. The ethanol temperature is calculated by accumulating the product of the instantaneous increase in mass of ethanol during the oiling process and the instantaneous temperature. After the oiling is completed, the accumulated sum is weighted averaged on the actual mass of the oil to obtain the average oil temperature of ethanol. The algorithm principle of the average oil temperature of the component oil is the same as that of the average oil temperature of ethanol.

[0071] (8) Calculate the thermal equilibrium temperature of ethanol and component oils. According to the volume fraction of ethanol, the average temperature of ethanol and component oils, and the specific heat capacity, use formula (5) to calculate the thermal equilibrium temperature value t4 of ethanol and component oils. The non-isothermal ethanol and component oil blending temperature volume correction can be equivalently converted into the isothermal ethanol and component oil blending temperature volume correction;

[0072] (9) Calculate the isothermal ethanol gasoline blending temperature correction value after blending by using the isothermal ethanol gasoline blending temperature correction value calculation formula, and subtract the isothermal ethanol gasoline blending temperature correction value from the thermal equilibrium temperature of ethanol and component oils to obtain the average oil-generating temperature of ethanol gasoline;

[0073] (10) The isothermal ethanol gasoline blending volume correction coefficient is calculated by the isothermal ethanol gasoline blending volume correction coefficient algorithm. The sum of the volumes of ethanol and component oils multiplied by the isothermal ethanol gasoline blending volume correction coefficient is the ethanol gasoline correction volume.

[0074] Furthermore, the equipment in step (5) includes a high-precision analytical balance, a high-precision vibration density meter, a volumetric flask pipette and a disposable dropper.

[0075] Further, the method for improving the accuracy of ethanol gasoline temperature and volume measurement also includes the following steps:

[0076] (11) The isothermal ethanol and component oil temperature values, ethanol gasoline temperature correction values, and volume correction coefficients are fitted with a quadratic curve to obtain an isothermal ethanol gasoline blending temperature and volume correction data table.

[0077] Ethanol gasoline volume calculation model

[0078] The law of conservation of mass means that in any material system isolated from the surroundings (isolated system), no matter what changes or processes occur, its total mass remains unchanged. Therefore, the sum of the masses of ethanol and component oils before blending is equal to the mass of ethanol gasoline after blending. Assuming that the temperatures of ethanol and component oils before blending are t1 and t2 respectively, and the temperature of ethanol gasoline after blending is t3, then

[0079] ρ1·V1+ρ2·V2=ρ3·V3 (1)

[0080] In the formula: ρ1 is the density of ethanol before blending at temperature t1; ρ2 is the density of the component oil before blending at temperature t2; V1 is the volume of ethanol before blending; V2 is the volume of the component oil before blending; ρ3 is the density of ethanol gasoline after blending at temperature t3; V3 is the volume of ethanol gasoline after blending.

[0081] The law of conservation of mass is applicable to any material system that is isolated from the surroundings (isolated system). Therefore, during the ethanol and component oil blending experiment, the volatilization of ethanol, component oil and ethanol gasoline should be reduced as much as possible. When the volatilization of ethanol, component oil and ethanol gasoline can be ignored, the above formula (1) is valid.

[0082] Assuming that the volume fraction of ethanol is a%, the volume fraction of the component oil is 1-a%, and the calculation formula of the volume correction coefficient k introduced by ethanol gasoline blending is shown in formula (2).

[0083]

[0084] The principle of thermal equilibrium refers to the state in which the internal temperature of an object in contact with the outside world is uniform and equal to the outside temperature. Since the temperatures of ethanol and component oils are usually different and not fixed, the concept of thermal equilibrium temperature of non-isothermal ethanol and component oils is introduced for the convenience of research. Under the thermal equilibrium state, the thermal equilibrium temperature of ethanol and component oils before blending is assumed to be t4, and the heat exchange amount of ethanol and component oils is equal. When the ethanol temperature t1 is greater than the component oil temperature t2, then

[0085] c1·ρ1·a%(V1+V2)·(t1-t4)=c2·ρ2·(1-a%)(V1+V2)·(t4-t2) (3)

[0086] Where: c1 and c2 represent the specific heat capacity of ethanol and component oil respectively.

[0087] When the ethanol temperature t1 is greater than the component oil temperature t2,

[0088] c1·ρ1·a%(V1+V2)·(t4-t1)=c2·ρ2·(1-a%)(V1+V2)·(t2-t4) (4)

[0089] The calculation formula obtained from formula (3) and (4) is shown in formula (5).

[0090]

[0091] It can be seen from formula (5) that the thermal equilibrium temperature of ethanol and component oil is determined by the specific heat capacity, density, temperature and volume fraction of ethanol and component oil.

[0092] According to the law of conservation of mass, the mass of ethanol gasoline at temperature t4 is equal to the mass of ethanol gasoline at temperature t3. Since t3<t4, let is the average volume expansion coefficient of ethanol gasoline between temperatures t3 and t4, then

[0093]

[0094] The calculation formula of ρ3 is deduced from formula (6) and is shown in formula (7).

[0095]

[0096] Substituting formula (8) into formula (2), we get

[0097]

[0098] Assuming k1 = (a%·ρ1+(1-a%)·ρ2) / ρ4, equation (9) can be simplified to equation (10).

[0099]

[0100] In the formula: k1 is the volume correction coefficient of ethanol gasoline (temperature t4) introduced by blending ethanol (temperature t4) and component oil (temperature t4).

[0101] Therefore, the ethanol gasoline blending volume correction coefficient is determined by the temperature correction value, the average value of the volume expansion coefficient in the temperature change range, and the isothermal volume correction coefficient.

[0102] Experimental Study on the Correction Value of Ethanol Gasoline Blending Temperature

[0103] In order to improve the accuracy of temperature measurement, the present invention designs an ethanol gasoline blending temperature precision measurement experimental device to achieve accurate measurement of the temperature correction value after ethanol gasoline blending. Figure 1 shown.

[0104] The ethanol gasoline blending temperature precision measurement experimental device includes a constant temperature water bath A, a constant temperature water bath B, an ethanol gasoline blending device and a high-precision thermometer A, a high-precision thermometer B; the ethanol gasoline blending device includes a double-layer insulation container (with an insulation cover), a stirring motor A, a stirring motor B, a three-layer insulation container (with an insulation cover), and a liquid storage vessel.

[0105] Among them, the outer layer of the double-layer insulation container is connected to the circulating water in the constant temperature water bath A to achieve temperature control and insulation, and the inner layer is used to store ethanol before blending; the outermost insulation layer of the three-layer insulation container is isolated from the influence of ambient temperature by inert gas, and the middle insulation layer is connected to the circulating water in the constant temperature water bath B to achieve temperature control and insulation, and the inner layer is used to store the component oil before blending and the ethanol gasoline after blending. The stirring motor A is used to stir the ethanol before blending, in order to make the temperature of the ethanol uniform. The inner layer of the three-layer insulation container is connected to the inner layer of the double-layer insulation container through a pipeline, and a shut-off valve is provided on the pipeline connecting the inner layer of the three-layer insulation container with the inner layer of the double-layer insulation container; the stirring motor B has two uses, one is to stir the component oil before blending to make the temperature of the component oil uniform; the other is to stir the ethanol gasoline, in order to accelerate the mixing of ethanol and component oil and make the temperature of ethanol gasoline uniform. High-precision thermometers A and B are used to monitor the ethanol temperature t A , component oil temperature t B The three-layer insulation container is also provided with a drain pipe, one end of which is connected to the inner layer of the three-layer insulation container and the other end is connected to the liquid storage container. A shut-off valve is provided on the drain pipe. The liquid storage container is used to store the liquid discharged from the inner layer of the three-layer insulation container. Taking the isothermal ethanol gasoline blending temperature correction value precision measurement experiment as an example, the steps are as follows:

[0106] 1) Configure the volume of ethanol and component oil according to the ethanol volume fraction requirements. Configure the volume values ​​of ethanol and component oil by mass density method, and store the configured ethanol and component oil in sealed volumetric flasks A and B respectively.

[0107] 2) Set the temperature of constant temperature water bath A to t 水浴A , set the temperature of constant temperature water bath B to t 水浴B ; where t 水浴B is the estimated value of the temperature of the blended ethanol gasoline. Put the sealed volumetric flask A and bottle B storing ethanol and component oil into the constant temperature water bath A, connect the constant temperature water bath A to the inner layer of the double-layer insulation container, and connect the constant temperature water bath B to the middle insulation layer of the three-layer insulation container.

[0108] 3) Initially measure the temperature of ethanol gasoline after blending. The ethanol is kept at the expected temperature t 水浴A After that, pour it into a double-layer insulation container, turn on the stirring motor A at a speed of 30r / min; the component oil is kept at the expected temperature t 水浴A After that, put it into a hot water container for heating to t 水浴A +2℃, the main purpose is to ensure that there is enough time for the ethanol and component oil temperatures to reach the expected temperature at the same time 水浴A Pour the component oil into a three-layer insulation container, turn on the stirring motor B at a speed of 60r / min; use high-precision thermometers A and B to monitor the ethanol temperature t A , component oil temperature tB When ethanol and component oil reach the expected temperature t 水浴A When the temperature is low, turn off the constant temperature water bath B, drain the circulating water in the three-layer insulation container, and let the ethanol flow into the three-layer insulation container. Since the blending process of ethanol and component oils shows an endothermic effect, when the blending is uniform, the endothermic effect ends. If the ethanol gasoline does not exchange heat with the outside world, its temperature will reach the lowest point and remain stable. Therefore, take the lowest temperature point t of thermometer B Bmin As the temperature value after blending with ethanol gasoline.

[0109] 4) Accurately measure the temperature value of the ethanol gasoline after blending. Since there is a certain temperature difference between the preset temperature of the constant temperature water bath of the three-layer insulation container and the temperature of the ethanol gasoline after blending, heat exchange occurs between the three-layer insulation container and the ethanol gasoline. Therefore, in order to reduce the impact of heat exchange on the final results of the experiment, the stepwise approximation method is proposed to make the difference between the preset temperature of the constant temperature water bath of the three-layer insulation container and the temperature of the ethanol gasoline after blending as small as possible. According to step 3), roughly measure the temperature value of the ethanol gasoline after blending, and adjust the temperature t of the constant temperature water bath B. 水浴B Repeat step 3) until the set temperature of the constant temperature water bath B reaches t 水浴B The lowest temperature of ethanol gasoline after blending Bmin The temperature difference is less than 0.05℃, and the temperature correction value Δt=t Bmin -t A The temperature correction value of ethanol gasoline was precisely measured by blending ethanol and component oil with an ethanol volume fraction of 10% and a temperature of 25°C. The experimental results are as follows: Figure 2 shown.

[0110] Depend on Figure 2 It can be seen that after ethanol and component oils were blended for about 30 seconds, the temperature of ethanol gasoline reached the lowest point of about 21.9°C and remained stable. The main reason is that when ethanol and component oils are blended, the force field in the liquid phase changes, causing the hydrogen bonds of some alcohols to break, resulting in an endothermic effect and a decrease in temperature. As the number of hydrogen bonds of alcohols breaks increases, the temperature gradually decreases until it stabilizes.

[0111] Experimental analysis of the difference between non-isothermal ethanol gasoline blending and thermal equilibrium isothermal ethanol gasoline blending temperature correction value

[0112] At the ethanol gasoline blending site, there is often a certain difference between the temperature values ​​of ethanol and component oil before blending. Therefore, studying the difference between the non-isothermal ethanol gasoline blending temperature correction value and the isothermal ethanol gasoline blending temperature correction value is the key to realizing the application of temperature correction at the ethanol gasoline blending site. According to the law of thermal equilibrium, when two objects exchange heat in an adiabatic system, there is no heat loss, and the high-temperature object transfers heat to the low-temperature object until the thermal equilibrium state is reached. Since the specific heat capacity is related to the composition of the substance, the specific heat capacity of the component oil varies slightly with the different components. In the range of 5 to 35 ° C, the specific heat capacity of ethanol and component oil changes slightly with the decrease of temperature, but it can be ignored under normal circumstances. Therefore, when calculating the thermal equilibrium temperature, the change in specific heat capacity has a relatively small impact on the result. For the convenience of research, the specific heat capacity (basic) value of ethanol is selected as 2.46 kJ / (kg·℃), and the specific heat capacity (basic) value of component oil is selected as 2.2 kJ / (kg·℃). Substituting the density, temperature, specific heat capacity data of ethanol and component oils and the volume fraction data of ethanol into formula (5), the thermal equilibrium temperature can be calculated. In the range of 5-35°C, three experimental points were selected to conduct precise measurement experiments on the non-isothermal ethanol gasoline blending temperature correction value and the thermal equilibrium isothermal ethanol gasoline blending temperature correction value, with ethanol fractions of 8%, 10%, and 12%, respectively. The obtained data are shown in Table 1.

[0113] Table 1 Comparative experimental temperature data

[0114]

[0115]

[0116] From the data analysis in Table 1, it can be seen that the temperature of the blended ethanol gasoline is significantly lower than the thermal equilibrium temperature. The main reason is that the thermal equilibrium temperature of ethanol and component oil is calculated based on the thermal equilibrium law, without considering the endothermic effect of the blending process of ethanol and component oil. The maximum absolute value of the difference between the non-isothermal ethanol gasoline blending temperature correction value and the thermal equilibrium isothermal ethanol gasoline blending temperature correction value is 0.039°C. Therefore, the non-isothermal ethanol gasoline blending temperature correction value precision measurement experiment can be approximately converted into the thermal equilibrium isothermal ethanol gasoline blending temperature correction value precision measurement experiment. When the ethanol volume fraction is 10%, the ethanol and component oil temperature range is 5 to 35°C. The non-isothermal ethanol and component oil thermal equilibrium temperature table calculated according to formula (5) is shown in Table 2.

[0117] Table 2 Non-isothermal ethanol and component oil heat balance temperature table

[0118]

[0119]

[0120] Precision Test of Volume Expansion Coefficient of Ethanol Gasoline

[0121] The density precision measuring instrument used in the experiment is Anton Paar DMA 5000M high-precision vibration density meter (hereinafter referred to as density meter), with a measuring range of 0-3000kg / cm3, a resolution of 1×10-3kg / cm3, and an expanded uncertainty of U=3×10-2kg / cm3 (k=2). The mass precision measuring instrument is Mettler PL4002-IC precision balance (hereinafter referred to as balance), with a maximum weighing of 4100g, a readability of 10mg, and an accuracy level of Level. Use balance, density meter and volumetric flask to prepare ethanol gasoline samples with ethanol volume fraction of 8%, 10% and 12%, use density meter to measure the density of ethanol gasoline in the temperature range of 5-35℃, and calculate the volume expansion coefficient of ethanol gasoline.

[0122] Experimental Study on the Precision Measurement of Isothermal Volume Correction Coefficient of Ethanol Gasoline Blending

[0123] The density of ethanol and component oil in the temperature range of 5-35°C, as well as the density of ethanol gasoline with ethanol volume fractions of 8%, 10% and 12% were measured using a density meter, and the isothermal volume correction coefficient of ethanol gasoline blending was calculated.

[0124] Data Analysis of Isothermal Ethanol Gasoline Blending Temperature Correction Value

[0125] Two batches of ethanol and component oil samples were collected from the oil depot and labeled L1 and L2 respectively. The ethanol gasoline samples with ethanol volume fractions of 8%, 10% and 12% were labeled P8, P10 and P12 respectively. Through the stepwise approximation method, the temperature values ​​of isothermal ethanol gasoline with ethanol volume fractions of 8%, 10% and 12% were accurately measured using the ethanol gasoline blending temperature precision measurement experimental device, and the isothermal ethanol and component oil blending temperature correction values ​​were obtained (see Table 3). The experimental results were fitted into a curve, such as Figure 3 shown.

[0126] Table 3 Isothermal ethanol gasoline blending temperature correction value

[0127]

[0128]

[0129] From Table 3 and Figure 3It can be seen that when the ethanol volume fraction is constant, the absolute value of the isothermal ethanol gasoline blending temperature correction value increases with the increase of the ethanol gasoline temperature value before blending. The main reason is that as the temperature increases, the number of ethanol hydrogen bonds broken increases, so the temperature drops more. When the ethanol gasoline temperature before blending is constant, the absolute value of the isothermal ethanol gasoline blending temperature correction value increases with the increase of the ethanol volume fraction before blending. The main reason is that as the ethanol volume fraction increases, the number of ethanol hydrogen bonds broken increases, so the temperature drops more. When the ethanol and component oil temperatures before blending are in the range of 5 to 35°C and the ethanol volume fraction is 8% to 12%, the temperature correction value introduced by ethanol gasoline blending is -1.702 to -3.990°C.

[0130] Data Analysis on Volume Expansion Coefficient of Ethanol Gasoline

[0131] By accurately measuring the density of ethanol gasoline at a temperature range of 3 to 35°C and with ethanol volume fractions of 8%, 10% and 12%, the volume expansion coefficient of ethanol gasoline at different temperature points can be obtained through calculation (see Table 4).

[0132] Table 4 Volume expansion coefficient of ethanol gasoline

[0133]

[0134]

[0135] It can be seen from Table 4 that under normal pressure, when the ethanol volume fraction is 8% to 12%, the volume expansion coefficient of ethanol gasoline increases with the increase of temperature. At the same temperature point, the volume expansion coefficient of ethanol gasoline increases with the increase of ethanol volume fraction. By fitting the temperature value and volume expansion coefficient of ethanol gasoline with a quadratic curve, the volume expansion coefficient table of ethanol gasoline can be obtained.

[0136] Data Analysis of Isothermal Volume Correction Factor of Ethanol Gasoline Blending

[0137] Under normal pressure, the density of ethanol and component oil before blending was precisely measured by a density meter, and the density of isothermal ethanol gasoline with ethanol volume fractions of 8%, 10% and 12% was precisely measured. The preparation of different ethanol volume fractions is controlled by a balance and a density meter, but affected by factors such as instrument measurement accuracy and personnel operation, the actual volume fraction of ethanol should be calculated based on the actual mass and density data of ethanol and component oil, and the weighted average density of ethanol gasoline should also be calculated based on the actual volume fraction of ethanol. After calculation, the isothermal volume correction coefficient data of ethanol gasoline was obtained (see Table 5).

[0138] Table 5 Isothermal volume correction factor for ethanol gasoline blending

[0139]

[0140]

[0141] It can be seen from Table 5 that under normal pressure, the isothermal volume correction coefficient of ethanol gasoline blending is greater than 1, that is, the volume of the isothermal ethanol gasoline after blending becomes larger. The main reason is that ethanol has strong intermolecular hydrogen bonds, and the molecules are arranged more tightly in the liquid state. After mixing with the component oil, the hydrocarbon molecules break some hydrogen bonds in ethanol, making it impossible for the ethanol molecules to maintain a tight arrangement. This effect on the volume is greater than the effect caused by the molecular filling effect during mixing. When the ethanol volume fraction remains unchanged, the isothermal volume correction coefficient increases with the increase of the temperature of ethanol and component oil. When the temperature of ethanol and component oil remains unchanged, the isothermal volume correction coefficient increases with the increase of the ethanol volume fraction.

[0142] Data Analysis of the Temperature Volume Correction Coefficient of Isothermal Ethanol Gasoline Blending

[0143] The isothermal ethanol gasoline blending temperature volume correction coefficient is calculated from the isothermal ethanol gasoline blending temperature correction value, the average value of the volume expansion coefficient in the temperature change range, and the isothermal volume correction coefficient (see Table 6).

[0144] Table 6 Isothermal ethanol gasoline blending temperature volume correction factor

[0145]

[0146] It can be seen from Table 6 that the temperature range of ethanol and component oil before blending is 5-35°C, and when the volume fraction of ethanol is 8%-12%, the temperature error introduced by ethanol gasoline blending is 1.702-3.990°C, and the ethanol volume correction coefficient is 0.99716-0.99890. Therefore, the temperature correction value can reduce the temperature error of ethanol gasoline by 1.702-3.990°C, and the volume correction coefficient can reduce the volume error of ethanol gasoline by 0.110%-0.285%. The isothermal ethanol and component oil temperature values, ethanol gasoline temperature correction values ​​and volume correction coefficients are fitted with a quadratic curve to obtain the isothermal ethanol gasoline blending temperature and volume correction data table.

[0147] Field Validation Experimental Design

[0148] The temperature and volume correction data table of ethanol gasoline is only the experimental results of ethanol and component oil sampling. The effect of applying it to the production of ethanol gasoline by pipeline proportion blending needs to be verified on site. The ethanol gasoline dispensing site of a Sinopec Guangxi oil depot is used as a pilot, and the field verification experiment design is as follows.

[0149] 1) Measure the temperature and volume of ethanol and component oil before blending. Install 0.2-grade graphite scraper flowmeter and high-precision thermometer on the ethanol and component oil delivery pipelines respectively. The indication error of the flowmeter is calibrated on-site with a second-class standard metal measuring instrument, and the correction value is based on the on-site calibration data. The correction value of the thermometer is based on the data in the calibration certificate. The temperature of ethanol and component oil before blending is calculated by correcting the weighted average of the thermometer indications, and the volume of ethanol and component oil before blending is calculated by summing the flowmeter indications after correction.

[0150] 2) Actual measurement of the temperature and volume of the blended ethanol gasoline. The volume of ethanol gasoline was measured using an online calibration device for an ethanol gasoline flow meter with a stirring function for a tank depot vehicle, and the temperature of ethanol gasoline was sampled three times using a high-precision thermometer and the average was taken.

[0151] 3) Analysis of the effect of on-site blending. Query the non-isothermal ethanol and component oil heat balance temperature table to determine the isothermal point, and query the ethanol gasoline blending temperature and volume correction data table to determine the temperature correction value and volume correction coefficient. After correcting the actual measured values ​​of the temperature and volume of the ethanol and component oil before blending, compare them with the actual measured values ​​of the ethanol gasoline flow meter online calibration device and the thermometer standard to analyze the on-site application effect.

[0152] Field validation data analysis

[0153] 1) At the ethanol gasoline delivery site of a Sinopec Guangxi oil depot, the delivery volumes of ethanol and component oil were set to 3000L respectively, and the flow meter indication was the cumulative flow value displayed by flow meters A and B. The actual volume was 3000L. The second-class standard metal reading data was converted to the volume value at the temperature of flow meters A and B. The high-precision flow meters A and B installed on the ethanol and component oil delivery pipelines were calibrated respectively, and the calibration data are shown in Table 7.

[0154] Table 7 Flow meter calibration data

[0155]

[0156] It can be seen from Table 7 that the maximum indication error of the high-precision flowmeter measured on site is 0.042%, and the maximum repeatability is 0.017%. Therefore, after the flowmeter indication is corrected, the high accuracy of the ethanol and component oil metering before blending can be ensured.

[0157] The volumes of ethanol and component oil are set to 300L and 2700L respectively according to the ethanol volume fraction of 10%. The temperatures of ethanol and component oil before blending are calculated by weighted average of the indications of thermometers A and B, and the volumes of ethanol and component oil before blending are calculated by summing the indications of flowmeters A and B after correction. The actual temperature value of ethanol gasoline is averaged by sampling three times by high-precision thermometer C, and the actual volume value is the volume value converted from the volume value read by the online calibration device (with stirring function) of the ethanol gasoline flowmeter for oil depot vehicles to the actual temperature. The temperature and volume indication errors introduced by the on-site measurement of ethanol gasoline blending are listed in Table 8.

[0158] Table 8 Temperature and volume indication error introduced by blending

[0159]

[0160]

[0161] It can be seen from Table 8 that when the weighted average temperature of ethanol gasoline before blending is in the range of 31.73-31.81°C, the temperature indication error introduced by blending is 3.528-3.710°C, and the volume relative indication error is 0.22%-0.25%.

[0162] 3) According to the ethanol volume fraction and the thermal equilibrium temperature values ​​of ethanol and component oils before blending, the temperature correction value and volume correction coefficient are obtained by querying the ethanol gasoline blending temperature and volume correction data table, and the corrected indication error is obtained by calculation as listed in Table 9.

[0163] Table 9 Corrected indication error table

[0164]

[0165] It can be seen from Tables 8 and 9 that the thermal equilibrium temperature of ethanol and component oil is 31.7-31.8°C. The research results can reduce the temperature error by 3.457-3.609°C and the volume error by 0.18%-0.24%. The field use effect is good and has good field applicability.

[0166] The ethanol and component oils with a thermal equilibrium temperature of 5 to 35°C are blended in pipeline proportion to produce ethanol gasoline. The project research results are used to automatically correct the temperature and volume in the oil depot oil distribution system, which can reduce the temperature error of ethanol gasoline by 1.702 to 3.990°C and the volume error by 0.110% to 0.285%. The method has been verified on site to have a good application effect and has good practical application value for further promoting the use of ethanol gasoline nationwide. It is a good method to ensure the fairness and justice of the trade settlement of ethanol gasoline produced by pipeline proportion blending.

[0167] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A method for improving the accuracy of temperature and volume measurement of ethanol gasoline, characterized in that: The steps include: (1) Using a high-precision analytical balance and a vibration density meter, ethanol and component oil with an ethanol volume fraction of a% are prepared by mass density method, and stored in volumetric flasks A and B respectively; (2) The temperature of ethanol and component oil is controlled by a constant temperature water bath, and two high-precision thermometers are used to monitor the ethanol temperature t1 and the component oil temperature t2 before blending. If the temperatures of ethanol and component oil before blending are different, the thermal equilibrium temperature value t4 of ethanol and component oil is calculated by a thermal equilibrium algorithm. When the temperatures of ethanol and component oil are equal to the thermal equilibrium temperature of ethanol and component oil, the ethanol gasoline blending temperature precision measurement experimental device is used to conduct an isothermal ethanol gasoline blending temperature correction value precision measurement experiment. (3) adjusting the temperature of the constant temperature water bath for controlling the temperature of the ethanol gasoline until the difference between the set temperature of the constant temperature water bath and the lowest temperature of the blended ethanol gasoline is less than 0.05° C.; at this time, the reading of the high-precision thermometer for monitoring the ethanol gasoline is the temperature t3 of the blended ethanol gasoline; (4) Calculate the isothermal ethanol gasoline blending temperature correction value; (5) Use the equipment to prepare at least two ethanol gasoline samples with an ethanol volume fraction of a%, and use a high-precision vibration density meter to measure the density of the ethanol gasoline in the temperature range of 5°C to 35°C, with a temperature interval of 2°C; record the ethanol gasoline temperatures t5 and t6 respectively, and when t6>t5; calculate the volume expansion coefficient of the ethanol gasoline; (6) using a high-precision vibration density meter to measure the ethanol density, the component oil density, and the ethanol gasoline density with an ethanol volume fraction of a% in the temperature range of 5°C to 35°C; and calculating the isothermal ethanol gasoline blending volume correction factor using an isothermal ethanol gasoline blending volume correction factor algorithm; (7) Calculating the average oil temperature of ethanol and component oils. The ethanol temperature is calculated by accumulating the product of the instantaneous increase in mass of ethanol during the oiling process and the instantaneous temperature. After the oiling is completed, the accumulated sum is weighted averaged on the actual mass of the oil to obtain the average oil temperature of ethanol. The algorithm principle of the average oil temperature of the component oil is the same as that of the average oil temperature of ethanol. (8) Calculating the thermal equilibrium temperature of ethanol and component oils, using the thermal equilibrium temperature value calculation formula of ethanol and component oils to calculate the thermal equilibrium temperature value t4 of ethanol and component oils, and converting the non-isothermal ethanol and component oil blending temperature volume correction into the isothermal ethanol and component oil blending temperature volume correction; (9) Calculate the isothermal ethanol gasoline blending temperature correction value after blending by using the isothermal ethanol gasoline blending temperature correction value calculation formula, and subtract the isothermal ethanol gasoline blending temperature correction value from the thermal equilibrium temperature of ethanol and component oils to obtain the average oil-generating temperature of ethanol gasoline; (10) The isothermal ethanol gasoline blending volume correction coefficient is calculated by the isothermal ethanol gasoline blending volume correction coefficient algorithm. The sum of the volumes of ethanol and component oils multiplied by the isothermal ethanol gasoline blending volume correction coefficient is the ethanol gasoline correction volume.

2. The method for improving the temperature and volume measurement accuracy of ethanol gasoline according to claim 1, characterized in that: In step (2), the calculation formula for the thermal equilibrium temperature values ​​of ethanol and component oil in the thermal equilibrium algorithm is: Where, t4 is the thermal equilibrium temperature of ethanol and component oil before blending, °C; c1, c2——Specific heat capacity of ethanol and component oil, J·kg -1 ℃ -1 ; t1, t2 – temperature of ethanol and component oils before blending, ℃. ρ1——Density of ethanol at temperature t1 before blending, g·cm -3 ; ρ2——Density of component oil at temperature t2 before blending, g·cm -3 .

3. The method for improving the temperature and volume measurement accuracy of ethanol gasoline according to claim 1, characterized in that: In step (4), the isothermal ethanol gasoline blending temperature correction value calculation formula is: Δt=t3-t4 (1) Where: Δt——isothermal ethanol gasoline blending temperature correction value, °C; t3——Temperature of ethanol gasoline after blending, ℃ t4——Thermal equilibrium temperature of ethanol and component oils before blending, ℃.

4. The method for improving the temperature and volume measurement accuracy of ethanol gasoline according to claim 1, characterized in that: In step (5), the calculation formula of the volume expansion coefficient of ethanol gasoline is: β=(ρ5-ρ6) / [ρ6·(t6-t5)] (2) Where: β——Volume expansion coefficient of ethanol gasoline at temperature t6, ℃ -1 ; t5, t6——ethanol gasoline temperature, °C; ρ5, ρ6——density of ethanol gasoline at temperature t5 and temperature t6, g·cm -3 .

5. The method for improving the temperature and volume measurement accuracy of ethanol gasoline according to claim 1, characterized in that: In step (6), the calculation formula of the isothermal ethanol gasoline volume correction coefficient algorithm is: Where: k is the isothermal ethanol gasoline blending volume correction factor, dimensionless; ρ4——density of ethanol gasoline at temperature t4, g·cm -3 ; ——The average value of the volume expansion coefficient of ethanol gasoline between temperatures t3 and t4.

6. The method for improving the temperature and volume measurement accuracy of ethanol gasoline according to claim 1, characterized in that: In step (2), the ethanol gasoline blending temperature precision measurement experimental device comprises a constant temperature water bath A, a constant temperature water bath B, an ethanol gasoline blending device and a high-precision thermometer A, a high-precision thermometer B; the ethanol gasoline blending device comprises a double-layer insulation container, a stirring motor A, a stirring motor B, a three-layer insulation container, and a liquid storage vessel; The outer layer of the double-layer insulation container is connected to the circulating water in the constant temperature water bath A to achieve temperature control and insulation, and the inner layer is used to store ethanol before blending; the outermost insulation layer of the three-layer insulation container is isolated from the influence of ambient temperature by inert gas, and the middle insulation layer is connected to the circulating water in the constant temperature water bath B to achieve temperature control and insulation, and the inner layer is used to store the component oil before blending and the ethanol gasoline after blending; the inner layer of the three-layer insulation container is connected to the inner layer of the double-layer insulation container through a pipeline, and a shut-off valve is arranged on the pipeline connecting the inner layer of the three-layer insulation container with the inner layer of the double-layer insulation container; the stirring motor A is used to stir the ethanol before blending; the stirring motor B is used to stir the component oil before blending and for stirring the ethanol gasoline; the high-precision thermometers A and B are used to monitor the temperature t of the ethanol respectively. A , component oil temperature t B The three-layer thermal insulation container is also provided with a drain pipe, one end of which is connected to the inner layer of the three-layer thermal insulation container and the other end is connected to the liquid storage container; a shut-off valve is provided on the drain pipe.

7. The method for improving the temperature and volume measurement accuracy of ethanol gasoline according to claim 6, characterized in that: The experiment of accurately measuring the correction value of the blending temperature of the medium-temperature ethanol gasoline in step (2) comprises the following steps: 1) Configure the capacity of ethanol and component oil according to the ethanol volume fraction requirements; configure the capacity values ​​of ethanol and component oil by mass density method, and store the configured ethanol and component oil in sealed volumetric flasks A and B respectively; 2) Set the temperature of constant temperature water bath A to t 水浴A , set the temperature of constant temperature water bath B to t 水浴B ; where t 水浴B is the estimated value of the temperature of the blended ethanol gasoline; put the sealed volumetric flask A and bottle B storing ethanol and component oil into the constant temperature water bath A, connect the constant temperature water bath A to the inner layer of the double-layer insulation container, and connect the constant temperature water bath B to the middle insulation layer of the three-layer insulation container; 3) Initially measure the temperature of ethanol gasoline after blending; ethanol is kept at the expected temperature t 水浴A After that, pour it into a double-layer insulation container, turn on the stirring motor A at a speed of 30r / min; the component oil is kept at the expected temperature t 水浴A After that, put it into a hot water container for heating to t 水浴A +2℃, the main purpose is to ensure that there is enough time for the ethanol and component oil temperatures to reach the expected temperature at the same time 水浴A ; Pour the component oil into a three-layer insulation container, turn on the stirring motor B at a speed of 60r / min; use high-precision thermometers A and B to monitor the ethanol temperature t A , component oil temperature t B ; When ethanol and component oil reach the expected temperature t at the same time 水浴A , turn off the constant temperature water bath B, drain the circulating water in the three-layer insulation container, and let ethanol flow into the three-layer insulation container; since the blending process of ethanol and component oils exhibits an endothermic effect, when the blending is uniform, the endothermic effect ends; if ethanol gasoline does not exchange heat with the outside world, its temperature will reach the lowest point and remain stable; take the lowest temperature t of thermometer B Bmin As the temperature value after blending ethanol gasoline; 4) Accurately measure the temperature of the ethanol gasoline after blending; make the difference between the preset temperature of the constant temperature water bath of the three-layer insulation container and the temperature of the ethanol gasoline after blending as small as possible; according to step 3), roughly measure the temperature of the ethanol gasoline after blending, and adjust the temperature t of the constant temperature water bath B. 水浴B Repeat step 3) until the set temperature of the constant temperature water bath B reaches t 水浴B The lowest temperature of ethanol gasoline after blending Bmin The temperature difference is less than 0.05℃, and the temperature correction value Δt=t Bmin -t A ; The temperature correction value of ethanol gasoline was precisely measured by blending ethanol and component oils with an ethanol volume fraction of 10% and a temperature of 25°C.

8. The method for improving the temperature and volume measurement accuracy of ethanol gasoline according to claim 1, characterized in that: The method for improving the accuracy of ethanol gasoline temperature and volume measurement also includes the following steps: (11) The isothermal ethanol and component oil temperature values, ethanol gasoline temperature correction values, and volume correction coefficients are fitted with a quadratic curve to obtain an isothermal ethanol gasoline blending temperature and volume correction data table.

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