A distributed measurement method and device for thermodynamic parameters of hydrocarbon fuels

Abstract

The application discloses a kind of distributed measurement methods for hydrocarbon fuel thermodynamic parameters, comprising: target substance is stored in thermostat and maintained at 298K, then pumped into test tube and heated to initial cracking temperature, then heated from initial cracking temperature to the temperature of target substance deep cracking so as to produce coke to block pipeline;According to the parameters monitored in real time, based on calorimetric model, the heat flow density of heat transfer in the test tube along the calorimetric microelement and the target substance in the microelement is measured online;Adjust the pressure, and continue to execute the above steps, obtain the heat flow density of heat transfer in the test tube along the calorimetric microelement and the target substance in the microelement under different pressure conditions;Carry out distributed measurement of target substance thermodynamic parameters, obtain the function of target substance thermodynamic parameters with position, temperature, pressure change.The application also discloses a measuring device using the above method.The method and device realize the distributed measurement of temperature, heat sink, isobaric specific heat and isobaric entropy change, four kinds of thermodynamic parameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal chemistry, thermodynamics and calorimetry of hydrocarbon fuels, and in particular to a distributed measurement method and device for thermodynamic parameters of hydrocarbon fuels. BACKGROUND

[0002] Endothermic hydrocarbon fuel is a new type of fuel developed to meet the future aircraft and missile weapon "miniaturization, high speed and long range", which has excellent volume properties and meets the integrated design requirements of aircraft. Due to the high temperature and high pressure working environment, the fuel has great particularity and complexity in the process of flow heat exchange, cracking and combustion. The fuel is in a supercritical state in the cooling channel of the aircraft at high temperature and high pressure, and it is accompanied by dramatic changes in thermodynamic parameters near the pseudo-critical temperature. As the fuel temperature increases, the fuel cracking reaction deepens and the fuel components change profoundly, often containing hundreds of components such as paraffin, naphthene and aromatic hydrocarbon, further increasing the difficulty of calculating the thermodynamic parameters.

[0003] The distributed calculation method of thermodynamic parameters covers the thermodynamic parameters such as temperature, isobaric specific heat, isobaric enthalpy change, isobaric entropy change and isothermal isobaric Gibbs free energy in the process of flow heat exchange and thermal chemical reaction of hydrocarbon fuel in supercritical state.

[0004] In the traditional thermodynamic parameter measurement method, a thermal property transient measurement method and device are disclosed in the patent with the application number CN201010590586.3, which is used to measure the thermal conductivity, thermal diffusivity, isobaric specific heat and density of the material, and the device meets the law of the change of the thermal properties of the material near room temperature with temperature. However, the application conditions of hydrocarbon fuel in hypersonic aircraft are high temperature, high pressure and high flow rate, which do not meet the actual application scenario of the patent. The patents with the application numbers CN201822011875.8 and CN201510154541.4 respectively disclose the measurement devices of isobaric specific heat of gas and liquid. When the hydrocarbon fuel is used in the active cooling system of the hypersonic aircraft, its phase state will change from liquid to supercritical state like gas and liquid; the above-mentioned patents only measure the isobaric specific heat of single-phase fluid, and the actual application scenario does not match the application scenario of hydrocarbon fuel. The patent with the application number CN201911177444.1 discloses a test method for endothermic hydrocarbon fuel heat sink. The patent uses UI heating model and energy conservation law to measure the fuel heat sink. However, the contact resistance between the heating electrode and the heating pipe in the UI heating model is not clear; secondly, the heat dissipation of the heating electrode plate is not considered separately in the energy balance model.

[0005] Developing the method for measuring the thermodynamic parameters of hydrocarbon fuels and revealing the inherent law of the hydrocarbon fuel flow heat exchange, cracking and combustion process are the research hotspots in the field. Because the hydrocarbon fuel is in the high temperature and high pressure extreme environment in the engine, the fuel components are replaced with time and space, so that the on-line measurement method can be closer to the actual working condition. SUMMARY

[0006] The purpose of the present application is to provide a kind of distributed measurement method and device for the thermodynamic parameters of hydrocarbon fuels, realize the distributed measurement of temperature, heat sink, isobaric specific heat and isobaric entropy change these four thermodynamic parameters.

[0007] The present application provides the following technical solutions:

[0008] A kind of distributed measurement method for the thermodynamic parameters of hydrocarbon fuels, the method comprises:

[0009] (1) the target substance is stored in fuel thermostat and maintained at 298K temperature;

[0010] (2) the target substance is pumped into test tube and heated to the initial cracking temperature to occur cracking reaction, then the target substance is heated from the initial cracking temperature to the target substance deep cracking temperature, and the target substance deep cracking temperature is the temperature that coke plugs the pipeline;

[0011] (3) real-time monitoring target substance import and export temperature change, test pipeline wall temperature development trend along the way, test tube two end system pressure, test tube resistance, test tube two end current and voltage;

[0012] (4) according to the parameters of real-time monitoring of step (3), based on calorimetric model, the energy transferred between test tube calorimetric microelement along the way and target substance in microelement is measured on-line;

[0013] (5) when test tube is cooled to room temperature, adjust the pressure, continue to execute the above steps (1)-(4), obtain the heat transfer heat flux density between test tube calorimetric microelement along the way and target substance in microelement under different pressures;

[0014] (6) industrial computer is based on the heat transfer heat flux density between test tube calorimetric microelement along the way and target substance in microelement under different pressures, carries out the distributed measurement of target substance thermodynamic parameters, obtains the function of target substance thermodynamic parameters with position, temperature change.

[0015] In order to solve the problems that the traditional fluid thermodynamic parameter measurement method cannot obtain the thermodynamic parameters of the hydrocarbon fuel in the test pipe along the way and the hydrocarbon fuel under high temperature and high pressure conditions when the thermal cracking reaction occurs, the present application provides a new thermodynamic parameter measurement method based on a distributed flow calorimetry, which aims to accurately measure the thermodynamic parameters of the hydrocarbon fuel in the test pipe along the way and the related parameters of the hydrocarbon fuel under high temperature and high pressure conditions when the thermal cracking reaction occurs. The thermodynamic parameters measured by the present application include the temperature, heat sink, isobaric specific heat and isobaric entropy change of the hydrocarbon fuel. The accurate measurement of these key thermodynamic parameters is an important basis for studying the fuel flow heat exchange rule and investigating the fuel chemical reaction, so the present application has important significance for the basic research of the hydrocarbon fuel.

[0016] The technical concept of the present application is that the present application measures the heat flow density between the calorimetric microelement along the way of the test pipe and the target substance in the microelement based on a calorimetric model, obtains the temperature, heat sink, isobaric specific heat and isobaric entropy change distribution of the target substance along the way of the test pipe, and studies the changes of the heat sink, isobaric specific heat and isobaric entropy change of the target substance with temperature. By adjusting the back pressure valve to change the pressure of the test system, the temperature, heat sink, isobaric specific heat and isobaric entropy change distribution of the target substance along the way of the test pipe under different pressures are obtained, and the changes of the heat sink, isobaric specific heat and isobaric entropy change of the target substance with temperature under different pressure conditions are studied.

[0017] The measurement method provided by the present application is a distributed flow calorimetry.

[0018] In step (1), the target substance is selected from one or a combination of at least two of alkanes, alkenes, cycloalkanes, cycloalkenes or aromatic hydrocarbons.

[0019] Further, in step (2), the flow rate of the target substance pumped into the test pipe is 0.1-10g / s or 1-1000ml / s, the initial cracking temperature is 773-823K, the deep cracking temperature of the target substance is 1023-1123K, and the heating rate is 5-25K / min.

[0020] For the deep cracking temperature of the target substance, a large amount of coke produced by fuel cracking will block the pipeline, and the upper limit of the temperature during the experiment is generally 1123K.

[0021] Further, in step (2), the cracking reaction of the target substance includes a first-order thermal cracking reaction and a multi-stage thermal cracking reaction; the first-order thermal cracking reaction is the thermal cracking of the target substance itself; and the multi-stage thermal cracking reaction is the multi-step thermal cracking of the first-order thermal cracking product of the target substance.

[0022] Further, in step (4), the calorimetric model is used to calculate the energy required for the temperature rise of the target substance, including the heat flow density (qtotal,x ), the heat flux density of heat transfer from the test tube microelement to the environment (q loss,x ), the heat flux density of heat conduction between test tube microelements (q cond,x ), the heat flux density of heat conduction from the two ends of the test tube to the cold end (q end,x ), the heat flux density of heat transfer from the test tube microelement to the target substance in the microelement (q fluid,x );

[0023] The test tube microelement is an experimental tube with a length of L meters, which is evenly divided into n experimental tube segments with a length of ΔL during calculation. The microelement at the inlet end of the tube is denoted as x = 1, and the microelement at the outlet end of the tube is denoted as x = n. The heat flux density input by the direct current constant voltage power supply to the test tube is obtained by the following method: the function of the resistivity of the test tube changing with temperature is calibrated in advance by four-wire measurement method, and the resistance of the test tube is corrected in real time in combination with the current value and voltage value applied to the two ends of the test tube by the direct current constant voltage power supply. Further, the resistance distribution along the test tube is obtained by the wall surface temperature distribution of the test tube. The heat flux density input by the direct current constant voltage power supply to the test tube microelement is calculated according to the current value, resistance value and surface area of the test tube microelement, i.e. q total,x ;

[0024] The heat flux density of heat transfer from the test tube microelement to the environment is obtained by the following method: the functions of the heat flux density of heat convection and heat radiation of the test tube microelement wall surface changing with the wall surface temperature of the experimental tube are calibrated in advance, i.e. q loss,x ;

[0025] The heat flux density of heat conduction between test tube microelements is obtained by the following method: the function of the thermal conductivity of the test tube changing with temperature is calibrated in advance, the thermal conductivity distribution along the test tube and the first derivative function of the wall surface temperature along the test tube are obtained in combination with the wall surface temperature distribution of the test tube, and further, the heat flux density of heat conduction between test tube microelements is obtained, i.e. q cond,x ;

[0026] The heat flux density of heat conduction from the two ends of the test tube to the cold end is obtained by the following method: the cold end temperature at the inlet of the tube is set to 298K in advance, and the cold end temperature at the outlet of the tube is set to the outlet temperature of the fluid. In combination with the wall surface temperature distribution of the test tube, the thermal conductivity and the first derivative value of the wall surface temperature of the test tube for heat conduction from the two ends to the cold end are obtained, and further, the heat flux density of heat conduction from the two ends to the cold end is obtained, i.e. q end,x ;

[0027] The heat flux density of heat transfer from the test tube microelement to the target substance in the microelement is obtained by the following method: the energy conservation equation is established, i.e. (q total,x -q loss,x )·A out =(Δq cond,x +q end,x / n)·S+q fluid,x ·Ain ; wherein A out is the outer surface area of the test tube element; A in is the cross section of the test tube element; n is the number of test tube elements; x is the serial number of the test tube element; q fluid,x is the heat flux of the test tube element to the target substance in the test tube element.

[0028] Further, in step (6), the thermodynamic parameters include the temperature, heat sink, isobaric specific heat and isobaric entropy change distribution of the target substance along the test tube.

[0029] Further, in step (6), the functions of the thermodynamic parameters of the target substance with respect to position, temperature and pressure include the temperature, heat sink, isobaric specific heat and isobaric entropy change distribution of the target substance along the test tube at different pressures, respectively, T x , H x , C p,x , S x ; the functions of the heat sink, isobaric specific heat and isobaric entropy change of the target substance with respect to temperature at different pressures, respectively, H(T), C p (T), S(T).

[0030] Further, in step (6), the functions of the thermodynamic parameters of the target substance with respect to position, temperature and pressure are as follows: since the serial number x of the test tube element and the temperature of the target substance in the test tube element are in one-to-one correspondence,

[0031] the heat sink distribution along the test tube is H x = q fluid,x ·A in / m;

[0032] the function of the heat sink with respect to temperature is H(T) = -H inlet +∑q fluid,x ·A in / m; wherein H inlet is the heat sink of the target substance at 298K;

[0033] the temperature distribution along the test tube is T x = H -1 (T) = H -1 [-H inlet +∑q fluid,x ·A in / m];

[0034] the isobaric specific heat distribution along the test tube is C p,x = q fluid,x ·A in / (m·ΔT f,x );

[0035] The function of the isobaric specific heat changing with temperature is: C p (T) = q fluid,x ·A in / (m·ΔT f,x );

[0036] The isobaric entropy change distribution along the test tube is: S x =∫m C p (T)·(M0T) -1 ·dT; where C p (T) is the function of isobaric specific heat as a function of temperature;

[0037] The function of the isobaric entropy change with temperature is: S(T)=-S inlet +∫m C p (T)·(M0T) -1 dT; where S inlet is the entropy of the target substance at 298K;

[0038] Where m is the mass of the target substance in the microelement, ΔT f,x is the temperature difference between the two ends of the test tube microelement, and M0 is the relative molecular weight of the target substance.

[0039] The present invention also provides a distributed measurement device for thermodynamic parameters of the above method, the measurement device comprising:

[0040] A high-pressure constant-flow pump is used to stably pump the target substance into the test tube;

[0041] Liquid gear flowmeter is used to monitor fluid mass flow in real time;

[0042] The DC regulated power supply is used to input stable energy to the test tube and monitor the voltage and current at both ends of the test tube in real time;

[0043] The test tube is used for energy balance;

[0044] Thermocouples are used to monitor the fluid outlet temperature in real time;

[0045] Infrared thermal imager is used to monitor the temperature of the test tube wall in real time;

[0046] The pressure sensor is used to monitor the system pressure in real time;

[0047] The back pressure valve is used to provide a stable system pressure;

[0048] The gas-liquid separation tank is used to separate the cracking gas and cracking liquid of the target substance;

[0049] The waste gas and waste liquid recovery device is used to recover the cracking gas and cracking liquid of the target substance;

[0050] The industrial computer is used for executing steps (4) and (6).

[0051] The present application has the following advantages:

[0052] The distributed measurement method provided by the present application focuses on the change of the thermodynamic parameters of the carbon-hydrogen fuel under the working conditions of high temperature, high pressure, multiple components and variable composition: the carbon-hydrogen fuel is pumped into the test pipeline under constant working conditions, and is heated under certain heat flux density conditions, and then a thermal chemical reaction occurs; after a stable temperature field is formed among the fuel, the test pipeline and the environment, the temperature change of the fuel inlet and outlet and the development trend of the wall surface temperature along the test pipeline are measured online by using the temperature measuring component; and the industrial computer carries out distributed calculation of the thermodynamic parameters based on the calorimetric model and the thermodynamic law. The measured thermodynamic parameters include the temperature, the heat sink, the isobaric specific heat and the isobaric entropy change of the fuel.

[0053] The present application is based on the distributed flow calorimetry method and the axial differential idea, and creatively proposes a distributed measurement method for the thermodynamic parameters of the carbon-hydrogen fuel, which takes the fuel and the test pipeline element as the research object, deeply considers the phenomenon that the components are replaced constantly with the change of space and time in the thermal chemical process of the fuel, constructs the mapping relationship among the position, pressure, temperature and thermodynamic parameters, realizes the monitoring of the change trend of the thermodynamic parameters in the thermal chemical process of the fuel, and provides data support for clarifying the fuel flow heat transfer mechanism and the chemical thermodynamic mechanism, and provides a test and evaluation method for developing a new type of fuel. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The flow chart of the measurement steps of the thermodynamic parameters of the carbon-hydrogen fuel;

[0055] Figure 2 The structural schematic diagram of the measurement device of the thermodynamic parameters of the carbon-hydrogen fuel;

[0056] Figure 3 The schematic diagram of the heat transfer among the environment, the test pipeline element and the fuel;

[0057] Figure 4 The change trend of the heat flux density of the heat transfer from the test pipeline element to the environment with the temperature of the test pipeline;

[0058] Figure 5 The distribution of the heat flux density input by the direct current stabilized power supply to the test pipeline element along the pipeline (toluene, 5MPa, 1g / s);

[0059] Figure 6 The distribution of the heat flux density of the heat transfer from the test pipeline element to the environment along the pipeline (toluene, 5MPa, 1g / s);

[0060] Figure 7 The distribution of the heat flux density of the heat conduction among the test pipeline elements along the pipeline (toluene, 5MPa, 1g / s);

[0061] Figure 8 Distribution of heat flux density along the test tube for the micro-element of the fuel (toluene, 5 MPa, 1 g / s);

[0062] Figure 9 Distribution of heat sink along the test tube for toluene (5 MPa, 1 g / s);

[0063] Figure 10 Growth trend of heat sink of toluene along the test tube (5 MPa, 1 g / s);

[0064] Figure 11 Variation trend of heat sink of toluene with temperature (5 MPa, 1 g / s);

[0065] Figure 12 Growth trend of temperature of toluene along the test tube (5 MPa, 1 g / s);

[0066] Figure 13 Distribution of isobaric specific heat of toluene along the test tube (5 MPa, 1 g / s);

[0067] Figure 14 Variation trend of isobaric specific heat of toluene with temperature (5 MPa, 1 g / s);

[0068] Figure 15 Distribution of isobaric entropy change of toluene along the test tube (5 MPa, 1 g / s);

[0069] Figure 16 Variation trend of isobaric entropy change of toluene with temperature (5 MPa, 1 g / s);

[0070] Figure 17 Growth trend of heat sink of n-decane along the test tube (1 g / s);

[0071] Figure 18 Growth trend of temperature of n-decane along the test tube (1 g / s);

[0072] Figure 19 Growth trend of isobaric specific heat of n-decane along the test tube (1 g / s);

[0073] Figure 20 Variation trend of isobaric entropy change of n-decane with temperature (1 g / s)。 DETAILED DESCRIPTION

[0074] The following examples can make the professional personnel more fully understand the present application, but do not limit the present application in any way.

[0075] The flow of the distributed measurement method of thermodynamic parameters of hydrocarbon fuel provided by the present application is as shown in Figure 1 The structural schematic diagram of the measuring device is as shown inFigure 2 The principle of distributed measurement of thermodynamic parameters is shown in Fig. 1. Figure 3 The principle of distributed measurement of thermodynamic parameters is shown in Fig. 1.

[0076] The method for distributed measurement of thermodynamic parameters of hydrocarbon fuel by using the measuring device provided by the present application comprises the following steps:

[0077] (1) storing the target substance in the fuel thermostat and maintaining the temperature at 298 K;

[0078] (2) pumping the target substance into the test tube and heating to the initial cracking temperature to cause cracking reaction, and then heating the target substance from the initial cracking temperature to the temperature at which the target substance is deeply cracked to produce coke to block the pipeline;

[0079] (3) real-time monitoring of the temperature change of the target substance at the inlet and outlet, the temperature development trend of the wall surface along the test pipeline, the system pressure at both ends of the test tube, the resistance of the test tube, the current and voltage at both ends of the test tube;

[0080] (4) based on the parameters monitored in real time in step (2), measuring the heat flux density between the calorimetric microelement along the test tube and the target substance in the microelement based on the calorimetric model;

[0081] (5) when the test tube is cooled to room temperature, adjusting the pressure, and continuing to perform the above steps (1)-(3) to obtain the heat flux density between the calorimetric microelement along the test tube and the target substance in the microelement under different pressure conditions;

[0082] (6) the industrial computer carries out distributed measurement of thermodynamic parameters of the target substance based on the energy transferred between the calorimetric microelement along the test tube and the target substance in the microelement under different pressures, and obtains the function of the thermodynamic parameters of the target substance changing with position, temperature and pressure.

[0083] Example 1

[0084] In this embodiment, the heat flux density of the test tube microelement to the environment needs to be calibrated in advance; the test tube without fluid is heated to establish the energy conservation equation,

[0085] q loss, x = [h x (T surface,x )·A x ·(T surface,x - T amb )+ε rad ·σ·(T surface,x 4 -T amb 4 )]·A x -1 (1-1)

[0086] wherein q loss,x is the heat flux density of the heat loss of the surface of the pipe element; h x (T) is a function of the change of the convective heat transfer coefficient of the surface of the pipe element with the temperature of the pipe; A x is the surface area of the pipe element; T surface,x is the temperature of the surface of the pipe element; T amb is the temperature of the natural environment; ε rad is the emissivity of the surface of the pipe element; and σ is the Stefan-Boltzmann constant.

[0087] Taking the environmental temperature as 288 K, the empirical formula fitted from the experimental data is:

[0088] q x,loss = [-12064.52 + 63.35 x T - 0.11 x T 2 + 8.82 x 10 -5 x T 3 - 3.39 x 10 -8 x T 4 ] / n (1-2)

[0089] wherein T is the temperature of the wall of the test pipe, and n is the number of the pipe elements of the test pipe.

[0090] The embodiment establishes the heat flux density of the heat transfer of the pipe elements of the test pipe to the environment when the environmental temperature is 288 K to 308 K, as shown in FIG. 1. Figure 4

[0091] Further, in the embodiment, taking toluene as an example, the toluene is transported to the test pipe by the high-pressure constant-flow pump under the condition of 5 MPa and 1 g / s; the direct-current stabilized power supply applies the heat flux density to the test pipe, and the toluene is gradually heated from 298 K to 1073 K in the test pipe; the thermocouple monitors the temperature change of the inlet and outlet of the test pipe in real time; the infrared thermal imager monitors the temperature change of the wall surface of the test pipe in real time, and the pressure sensor monitors the system pressure in real time; after the industrial computer stores the fluid mass flow, the input heat flux density data, the wall temperature data of the test pipe, the inlet and outlet temperatures of the fluid, and the system pressure, the thermodynamic parameter measurement is carried out according to the calorimetric model.

[0092] The direct-current stabilized power supply applies different sizes of energy to the test pipe, and the industrial computer obtains the change of the input heat flux density with the wall surface temperature based on the calorimetric model:

[0093] q heater, x (x) = I 2 ·ρ(T)·S x -2 ·dx (1-3)

[0094] wherein q heater,x ​is the heat flux density of heat transfer between pipe elements, I is the current applied to the pipe element by the DC motor, p(T) is the function of resistivity changing with pipe temperature, dx is the actual length of the pipe element, S is the cross-sectional area of the pipe element x is the cross-sectional area of the pipe element.

[0095] As shown in Figure 5 is the heat flux density distribution along the path of the DC voltage stabilizer input to the test pipe element when the toluene outlet temperature is 473-773 K.

[0096] Further, according to Figure 4 the heat flux density of heat transfer from the test pipe element to the environment changes with the ambient temperature and the test pipe wall temperature, the heat flux density distribution along the path of the test pipe element to the environment when the toluene outlet temperature is 473-773 K is obtained, as shown in Figure 6 .

[0097] Further, the heat flux density of heat transfer between the test pipe elements due to temperature difference is shown in Figure 7 , the internal heat conduction of the pipe element under the conditions of fluid temperature of 473, 573, 673 and 773 K is calculated. The calculation formula is:

[0098]

[0099] where q cond,x is the heat flux density of heat transfer between pipe elements, unit is J·s -1 ·m -2 ; λ tube (T) is the thermal conductivity of the pipe element W·m -1 ·k -1 ; is the temperature derivative of the pipe element between the pipe elements.

[0100] Further, the heat flux density of heat transfer from the test pipe element to the toluene in the element is obtained by the following energy conservation equation:

[0101] (q total, x - q loss, x )·A out = (Δq cond, x + q end, x / n)·S + q fluid, x ·A in (1-5) The energy conservation equation of heat transfer from the pipe element to toluene is

[0102] P heat sink,x = q fluid, x ·A in = (q total, x -q loss, x )·A out - (Δq cond, x +q end, x / n)·S x (1-6)

[0103] Among them A out A is the surface area of ​​the microelement of the test tube; in is the surface area of ​​the test tube microelement; S is the cross section of the test tube microelement;

[0104] The heat flux density distribution along the test tube transferred to the fuel is obtained as follows: Figure 8 shown.

[0105] Furthermore, a constraint condition is set at the fuel inlet end. The constraint condition is that when the fuel temperature is 25℃, the fuel heat sink is 0MJ·kg -1 Based on the laws of thermodynamics, P heat sink,x Converted into heat sink along the toluene, the heat sink of toluene at xm in the test tube is obtained by the following energy equation:

[0106]

[0107] The heat sink distribution of toluene along the test tube is as follows Figure 9 and 10 shown.

[0108] Furthermore, based on the above steps, the toluene temperature-heat sink function relationship is calibrated, taking the working condition of 5MPa and 1g / s as an example, as shown in FIG. Figure 11 As shown; the functional relationship established is:

[0109] 298.15 K≤T<685 K, H(T) = -172.16-0.24×T +0.0028×T 2 (1-8)

[0110] 685 K≤T<870 K, H(T) = -20081.31+62.26×T-0.046×T 2 (1-9)

[0111] 870 K≤T≤1023.15 K, H(T) = -1014.76+3.11×T -1.65×T 2(1-10)

[0112] where T is the toluene temperature;

[0113] According to the NIST standard database, the measurement error of toluene heat sink is less than 2%.

[0114] The average temperature of toluene at any position along the test tube is solved by H(T) function inversion, as shown in the following formula: Figure 12

[0115] Further, the P heat sink,x The fuel energy change Q fuel,x at the outlet and inlet cross section of the pipeline microelement is defined as the temperature difference ΔT fuel,x of the microelement outlet and inlet temperature obtained by the toluene temperature distribution along the pipeline; and the isobaric heat calculation formula is as follows:

[0116] C p, fuel, x = Q fuel, x ·ΔT fuel, x -1 (1-11)

[0117] The isobaric heat of toluene along the pipeline is solved by the calculation formula, as shown in the following formula: Figure 13

[0118] Further, the isobaric heat of toluene along the pipeline is related to the toluene temperature distribution along the pipeline, and the change trend of the isobaric heat of toluene with temperature is obtained, as shown in the following formula: Figure 14

[0119] According to the NIST standard database, the measurement error of toluene isobaric heat is less than 3%.

[0120] Further, the isobaric entropy change of toluene along the pipeline is obtained according to the isobaric heat of toluene along the pipeline and the toluene temperature distribution along the pipeline; and the isobaric entropy change calculation formula is as follows:

[0121] dS p, fuel, x = n C p, fuel ,x ·T -1 ·dT (1-5)

[0122] The isobaric entropy change of toluene along the pipeline is solved by the calculation formula, as shown in the following formula: Figure 15

[0123] ​​​​Further, the toluene temperature distribution along the pipeline is associated with the toluene isobaric entropy change distribution along the pipeline, and the toluene isobaric entropy change trend with temperature is obtained, as shown in Figure 16 Combining with the NIST standard database, it can be known that the toluene isobaric entropy change measurement error is less than 2%.

[0124] Further, in the embodiment, n-decane is taken as an example, and the experimental conditions are as follows: the system pressure is maintained at 2 MPa and 4 MPa respectively, the mass flow rate is 1 g / s, and the outlet temperature is 373-1023 K. The distributed thermodynamic parameters of n-decane under high-temperature and high-pressure and thermal chemical reaction conditions are measured.

[0125] According to the above steps, the heat sink change and temperature change of n-decane along the pipeline are obtained, as shown in Figure 17 and 18 .

[0126] The isobaric specific heat change of n-decane along the pipeline is obtained by the isobaric specific heat calculation formula, as shown in Figure 19 .

[0127] The n-decane temperature distribution along the pipeline is associated with the n-decane isobaric specific heat distribution along the pipeline, and the n-decane isobaric specific heat trend with temperature is obtained, as shown in Figure 20 .

[0128] In summary, the present application solves the difficult problem of the traditional fluid thermodynamic parameter measurement method in the pipeline along the pipeline carbon hydrocarbon fuel thermodynamic parameter distribution and the high-temperature and high-pressure state of the carbon hydrocarbon fuel thermodynamic parameter measurement method under the condition of the carbon hydrocarbon fuel thermal cracking reaction, and a new thermodynamic parameter measurement method based on the distributed flow heat method is proposed, and the thermodynamic parameters of the carbon hydrocarbon fuel along the pipeline and the related parameters of the carbon hydrocarbon fuel under the condition of the high-temperature and high-pressure thermal cracking reaction are measured.

Claims

1. A method for distributed measurement of thermodynamic parameters of a hydrocarbon fuel, characterized in that, The method comprises: (1) storing the target substance in a fuel thermostat and maintaining the temperature at 298 K; (2) pumping the target substance into the test tube and heating to the initial cracking temperature to occur cracking reaction, and then heating the target substance from the initial cracking temperature to the target substance deep cracking temperature, which is the temperature at which coke blocks the pipeline; (3) real-time monitoring of the temperature change of the target substance at the inlet and outlet, the temperature development trend of the test tube along the pipeline, the system pressure at both ends of the test tube, the test tube resistance, the current and voltage at both ends of the test tube; (4) based on the parameters monitored in real time in step (3), the heat transfer heat flux between the test tube along the pipeline and the target substance in the microelement is measured online based on the calorimetric model; (5) when the test tube is cooled to room temperature, adjust the pressure, and continue to perform the above steps (1)-(4) to obtain the heat transfer heat flux between the test tube along the pipeline and the target substance in the microelement under different pressure conditions; (6) the industrial computer carries out distributed measurement of the thermodynamic parameters of the target substance based on the energy transferred between the test tube along the pipeline and the target substance in the microelement under different pressures, and obtains the function of the thermodynamic parameters of the target substance with position, temperature and pressure; The heat flow density of the test tube microelement to the environment in step (4) is used to calculate the energy required for the target substance to heat up, including the heat flow density of the direct current constant voltage power supply input test tube q total,x , the heat flow density of the test tube microelement to the environment q loss,x , the heat flow density of heat conduction between test tube microelements q cond,x , the heat flow density of heat conduction from both ends of the test tube to the cold end q end,x , the heat flow density of the test tube microelement to the microelement target substance heat transfer q fluid,x ; The test tube micro-element is a test tube with a length of L meters, which is divided into n test tube segments with a length of Δ L in calculation, and the test tube inlet end micro-element is x =1, the test tube outlet end micro-element is x = n ; The heat flux of the direct current constant voltage power supply input test tube is obtained by the following way: the function of the test tube resistivity changing with temperature is calibrated in advance by four-wire measurement method, and the test tube resistance is corrected in real time in combination with the current value and voltage value of the direct current constant voltage power supply applied to the test tube; further, the test tube resistance distribution along the path is obtained by the test tube wall temperature distribution along the path; and the heat flux of the direct current constant voltage power supply input test tube microelement is calculated according to the test tube microelement current value, resistance value and microelement surface area, that is q total,x ; The heat flux density of the test tube micro-element to the environment is obtained by pre-calibrating the functions of the heat flux density of the test tube micro-element wall heat convection and heat radiation with respect to the test tube wall temperature; and combining the test tube wall temperature distribution to obtain the heat flux density of the test tube micro-element to the environment, i.e. q loss,x ; The heat flux density of the heat conduction between the micro elements of the test tube is obtained by the following way: a function of the heat conductivity of the test tube changing with temperature is calibrated in advance, the heat conductivity distribution along the test tube and the first derivative function of the wall surface temperature along the test tube are obtained according to the wall surface temperature distribution along the test tube, and further, the heat flux density of the heat conduction between the micro elements of the test tube is obtained, that is q cond,x ; The heat flux of the heat conduction from both ends of the test tube to the cold end is obtained by the following method: the cold end temperature at the inlet of the pipe is set to 298 K in advance, the cold end temperature at the outlet of the pipe is the outlet temperature of the fluid, the heat conductivity and the first derivative value of the wall surface temperature of the test tube are obtained according to the wall surface temperature distribution of the test tube along the pipeline, and further, the heat flux of the heat conduction from both ends of the test tube to the cold end is obtained, that is q end,x ; The heat flux density of the test tube micro-element to the target substance in the micro-element is obtained by establishing an energy conservation equation, i.e. q total,x - q loss,x )· A out = (Δ q cond,x + q end,x / n )· S + q fluid,x · A in ; Wherein A out is the outer surface area of the test tube micro-element; A in is the inner surface area of the test tube micro-element; S is the cross section of the test tube micro-element; n is the number of test tube micro-elements; x is the serial number of the test tube micro-element; q fluid,x is the heat flux density of the test tube micro-element to the target substance in the micro-element.

2. The method for distributed measurement of thermodynamic parameters of a hydrocarbon fuel according to claim 1, characterized in that, In step (1), the target substance is selected from one or a combination of at least two of alkanes, alkenes, cycloalkanes, cycloalkenes or aromatic hydrocarbons.

3. The method for distributed measurement of thermodynamic parameters of a hydrocarbon fuel according to claim 1, characterized in that, In step (2), the flow rate of the target substance pumped into the test tube is 0.1-10 g / s or 1-1000 ml / s, the initial cracking temperature is 773-823 K, the target substance deep cracking temperature is 1023-1123 K, and the heating rate is 5-25 K / min; in step (5), the pressure is set to 0.1-12 MPa, and the increase step is 0.05-1 MPa.

4. The method for distributed measurement of thermodynamic parameters of a hydrocarbon fuel according to claim 1, characterized in that, In step (2), the cracking reaction of the target substance includes a first-order thermal cracking reaction and a multi-stage thermal cracking reaction; the first-order thermal cracking reaction is the thermal cracking of the target substance itself; the multi-stage thermal cracking reaction is the multi-step thermal cracking of the first-order thermal cracking product of the target substance.

5. The method for distributed measurement of thermodynamic parameters of a hydrocarbon fuel according to claim 1, characterized in that, In step (6), the distributed measurement of thermodynamic parameters includes the distribution of target substance temperature, heat sink, isobaric specific heat and isobaric entropy change along the test tube.

6. The method for distributed measurement of thermodynamic parameters of a hydrocarbon fuel according to claim 1, characterized in that, In step (6), the function of the target substance thermodynamic parameters with position, temperature, pressure change contains the temperature, heat sink, isobaric specific heat and isobaric entropy change distribution of the test tube along the way under different pressures, respectively T x 、 H x 、 C p,x 、 S x ; the function relationship of heat sink, isobaric specific heat and isobaric entropy change with temperature change of the target substance under different pressures, respectively H ( T )、 C p ( T )、 S ( T ).

7. The method for distributed measurement of thermodynamic parameters of a hydrocarbon fuel according to claim 6, characterized in that, The function of the target substance thermodynamic parameter with position, temperature, and pressure is: x and the temperature of the target substance in the test tube microelement corresponds to each other. The test tubes are distributed along the heat sink: H x = q fluid,x · A in / m ; The function of the heat sink as a function of temperature is: H T - H inlet q fluid,x ·A in m ; wherein H inlet is the heat sink of the target substance at 298 K;​​​​ The temperature profile along the test tube is: T x = H -1 ( T ) = H -1 [- H inlet + ∑ q fluid,x ·A in / m ]; The test tube isobaric specific heat is distributed along the path as: C p,x = q fluid,x ·A in / ( m· Δ T f,x ); The function of the isobaric specific heat as a function of temperature is: C p ( T ) = q fluid,x ·A in / ( m· Δ T f,x ); The isobaric entropy change distribution along the test tube is: S x = ∫ mC p ( T )·( M 0 T ) -1 ·d T ;in C p ( T ) is the isobaric specific heat as a function of temperature; The function of the isobaric entropy change as a function of temperature is: S T S inlet mC p T M T -1 T ; wherein S inlet is the entropy of the target substance at 298 K;​​​​​​​​ wherein, m M is the mass of the target substance in the microelement, Δ T f,x is the temperature difference between the two ends of the test tube microelement, M 0 is the relative molecular mass of the target substance.

8. A distributed measurement apparatus of thermodynamic parameters using the method according to any one of claims 1 to 7, characterized in that, The measuring device comprises: a high-pressure constant-flow pump for stably pumping the target substance into the test tube; a liquid gear flow meter for real-time monitoring of fluid mass flow; a direct-current stabilized power supply for inputting stable energy to the test tube and real-time monitoring of the voltage and current at both ends of the test tube; a test tube for energy balance; a thermocouple for real-time monitoring of the outlet temperature of the fluid; an infrared thermal imager for real-time monitoring of the test tube wall temperature; a pressure sensor for real-time monitoring of the system pressure; a back pressure valve for providing stable system pressure; a gas-liquid separation storage tank for separating the cracking gas and cracking liquid of the target substance; a waste gas and waste liquid recovery device for recovering the cracking gas and cracking liquid of the target substance; The industrial computer is used to perform steps (4) and (6).

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