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WO2018185008A1 - Procédé pour déterminer une propriété d'un fluide et dispositif de détection associé - Google Patents

Procédé pour déterminer une propriété d'un fluide et dispositif de détection associé Download PDF

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Publication number
WO2018185008A1
WO2018185008A1 PCT/EP2018/058186 EP2018058186W WO2018185008A1 WO 2018185008 A1 WO2018185008 A1 WO 2018185008A1 EP 2018058186 W EP2018058186 W EP 2018058186W WO 2018185008 A1 WO2018185008 A1 WO 2018185008A1
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WO
WIPO (PCT)
Prior art keywords
fluid
heating element
time
determined
electrical resistance
Prior art date
Application number
PCT/EP2018/058186
Other languages
German (de)
English (en)
Inventor
Rupert SCHREINER
Christoph Langer
Stephan Heinrich
Torsten Reitmeier
Original Assignee
Continental Automotive Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Continental Automotive Gmbh filed Critical Continental Automotive Gmbh
Publication of WO2018185008A1 publication Critical patent/WO2018185008A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/18—Investigating or analyzing materials by the use of thermal means by investigating thermal conductivity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/14—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature
    • G01N27/18—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by changes in the thermal conductivity of a surrounding material to be tested

Definitions

  • the present invention relates to a method for determining at least one property of a fluid, in particular a method for determining the calorific value of the fluid, preferably a gas mixture, such as a natural gas mixture, and a sensor device for determining at least one property of a fluid, in particular the calorific value of the Fluids, preferably a gas mixture, such as a Erd ⁇ gas mixture.
  • a gas mixture such as a natural gas mixture
  • a sensor device for determining at least one property of a fluid, in particular the calorific value of the Fluids, preferably a gas mixture, such as a Erd ⁇ gas mixture.
  • a gas mixture such as a Erd ⁇ gas mixture.
  • Natural gas is herein at ⁇ play around the components methane, ethane, propane, butane, carbon dioxide and nitrogen.
  • the non-combustible gases carbon dioxide and nitrogen play in Ver ⁇ incineration regard knock resistance an important role. Since this selective measurement is very difficult and with a considerable measurement effort is possible, often correlative techniques are applied, with which from individual independent physical quantities, such. As density, speed of sound, thermal conductivity, specific heat capacity or viscosity, the composition or properties of the corresponding mixture is determined.
  • the calorific value is that physical quantity of a gas mixture which is relevant for setting the combustion parameters in an internal combustion engine of a vehicle.
  • Another combustion-relevant variable is the amount of oxygen required for a stoichiometric combustion.
  • thermal conductivity or Thermal conductivity ⁇ ness can be determined relatively easily by temperature sensitive probes, so the specific heat capacity can be achieved only by expensive equipment and conditions in combination with defined set measurement.
  • thermal conductivity also called temperature code
  • the thermal diffusivity is a material property that is used to describe the temporal change in the spatial distribution of the temperature due to heat conduction as a result of a temperature gradient. It is often specific to the material and is made up of the quotient of thermal conductivity and the product of density and specific heat capacity ⁇ fishing. By measuring the individual quantities mentioned in this formula, the temperature conductivity can be calculated from this. Consequently, the two physi ⁇ cal variables thermal conductivity and thermal conductivity are different physical quantities.
  • the thermal diffusivity as a material property is also suitable for the characterization of fluids, in particular gas mixtures, such as natural gas mixtures, and can be used as an input for correlation calculations for determining fluid properties.
  • gas mixtures such as natural gas mixtures
  • the convection and radiation are negligible.
  • an improved Pirani sensor in which the measuring element is arranged in the fluid between a base plate and a heat sink.
  • the measuring element is held by suspensions in the correct position.
  • the suspensions are connected to the base plate and a separate heating element is in turn thermally conductive with the suspensions.
  • the Pirani sensor detects the heat losses through the fluid to the heat sink while balancing the heat losses to the suspensions with the separate heating elements. This compensates for the parasitic heat losses from the Pirani sensor to the suspension.
  • EP 1 409 963 B1 discloses a sensor for generating a signal which has a predetermined physical parameter.
  • the sensor includes a sensor element, to which a drive signal can be applied and dependent on the réelle ⁇ voted physical parameter and the control signal generates an output signal.
  • a driving means is provided in such a manner applies the driving signal having a predetermined waveform to the sensor element, that the output signal of the sensor element reaches a predetermined smoldering ⁇ lenwert.
  • a time measuring circuit of the sensor detects the time duration until which the output signal reaches the aforementioned threshold value from a predetermined starting value of the output signal and generates from the time duration the signal indicating the physical parameter.
  • DE 10 2013 220 908 AI relates to a sensor element with a measuring element and a measuring ⁇ the housing at least partially um ⁇ giving, designed as Kunststoffmoldgeophuse functional ⁇ housing.
  • the measuring element is in this case designed as a hotplate, which is largely thermally decoupled by means of narrow arms mounted on a carrier substrate.
  • a fluid in particular a gas mixture, such as a natural gas mixture
  • This object is achieved by a method according to independent claim 1 and a sensor device according to independent claim 8.
  • Preferred embodiments are specified in the subclaims.
  • the invention is based at least partially on the idea to determine the thermal diffusivity of the fluid by means of a suitable measuring structure and to determine therefrom at least one self- ⁇ shaft of the fluid by means of suitable mathematical calculations correla ⁇ tion. This will be the physical n
  • the temperature-dependent resistance is differently sensitive with suitable control with electrical power to the present fluid, in particular gas mixture, such as natural gas mixture.
  • the thermal conductivity and the thermal conductivity can be determined with the aid of the temperature-dependent resistor, to the fact, as close ⁇ derum as described above on at least one property, such as z.den calorific value of the fluid by means of the correlation calculations.
  • a liquid fuel such as gasoline
  • the operating ⁇ parameters of the internal combustion engine can be optimally adjusted so that the engine can be started with natural gas.
  • a method for determining at least one property of a fluid preferably a gas mixture, such as a natural gas mixture.
  • a Sensorvor ⁇ direction is provided, which can come into contact with the fluid and having a heating capacity can be acted upon with electrical heating element with temperature-dependent resistance.
  • the Invention ⁇ contemporary method comprises exposing the heating element with a predetermined electrical heating power for a predetermined time period, detecting a temporal progression of the electrical resistance of the heating element characterization ⁇ leaders electrical quantity during the predetermined period of time, a determination of the temperature conductivity of the fluid at least based in part on the detected time history of the electrical quantity and determining at least one property of the fluid based at least in part on the determined thermal conductivity of the fluid.
  • the electrical quantity is preferably the voltage drop across the heating element during the predetermined period of time during which the heating element is supplied with an electric current for supplying the predetermined electrical heating power.
  • the electrical size of the current flowing through the heating element ⁇ electric current during the predetermined time period during which is applied the voltage for supplying the predetermined electrical heating power to the heating element.
  • the inventive method further comprises determining a time profile of the electrical resistance of the heating element based at least partially on the detected time profile of the electrical variable and the electrical heating power.
  • the at least one property of the fluid is determined at least partially based on the determined time profile of the electrical resistance of the heating element.
  • the time characteristic of the electrical resistance of the heating element taking into account the predetermined heating power, can be determined via the ohmic law from the time profile of the electrical variable, that is to say via the electrical voltage or the electric current.
  • the determination of the thermal conductivity is also based at least in part on the determined profile of the electrical resistance of the heating element.
  • the sensor device used has a structure similar to a Pirani vacuum gauge.
  • the sensor device compared to a Pirani vacuum gauge only one used as a heat source and heat sink Schu ⁇ element, which is characterized by a temperature-dependent resistance.
  • the method according to the invention further comprises determining the density of the fluid.
  • the determination of the temperature conductivity of the fluid based advantageously at least partly on which it ⁇ mediated density.
  • the density of the fluid is determined by determining a speed of sound in the fluid by emitting and detecting ultrasound waves coupled into the fluid.
  • the determination of the at least one property of the fluid is preferably also based at least in part on the determined sound velocity.
  • the application of the heating element with electrical heating power comprises applying a predetermined electric current pulse to the heating element for the predetermined period of time.
  • the Beauf ⁇ beat of the heating element with electrical heating power can apply a predetermined electrical voltage to the heating element for the predetermined period of time.
  • the inventive method further comprises determining a time constant 0
  • the determination of the thermal conductivity of the fluid and / or the at least one property of the fluid is based at least partially on the determined time constant.
  • a time constant is determined based on the detected time profile of the electrical quantity. May be selected from the thus determined time constant then ge ⁇ joined directly to the at least one property of the fluid, or additionally or alternatively on the tem- peraturleitdate of the fluid.
  • the method according to the invention further comprises determining a resistance difference between a first electrical resistance of the heating element at the beginning of the predetermined period of time and a second electrical resistance of the heating element at the end of the predetermined period of time.
  • the determination of the at least one property of the fluid based on ⁇ least partly on the determined difference in resistance. It is even more advantageous if further comparison, the inventive drive determining a thermal conductivity of the fluid at least partially based on the determined resistance ⁇ difference has.
  • the time constant which preferably corresponds to the rise time to the predetermined portion of the detected second electrical resistance at the end of the predetermined period, may be proportional to the temperature conductivity.
  • the determined resistance ⁇ difference may be proportional to the thermal conductivity of the present fluid. The two thus determined parameters of temperature and thermal conductivity can then be used as input ⁇ sizes of mathematical correlations for the characterization of the fluid, in particular of the gas mixture, such as the natural gas mixture.
  • characterization of the fluid can then be relevant for setting the combustion parameters of the internal combustion engine for the vehicle operating parameters, such as calorific value, methane number, Wobbe index, oxygen or. Air requirements for the stoichiometric combustion, etc., to be determined.
  • the predetermined heating power which is applied to the heating element for the predetermined period of time, an increasing ⁇ the, falling, sudden, triangular and / or sinusoidal time course.
  • a sensor device for determining at least one property of a fluid, preferably a gas mixture, such as a natural gas mixture.
  • the sensor ⁇ inventive device comprises a carrier substrate, which has at least one recess, and a valve disposed on the carrier substrate sensor ⁇ substrate, which is a sensor portion which at least partially located ⁇ above the recess of the carrier substrate, and at least one deepening The connection of the carrier substrate at least partially surrounding connection area.
  • the sensor is rich by at least two narrow arms so attached to the at least one connection region, that the sensor region of the at least one connection region is substantially thermally decoupled.
  • the sensor device according to the invention also has a heating element arranged on and / or in the sensor region with a temperature-dependent resistance.
  • the heating element is manufactured in MEMS construction. It is even more preferable if the heating element has a meandering shape.
  • the micromechanical structure of the sensor device with the free ⁇ bearing structure of the heating element has the advantage that the parasitic effect of the thermal conductivity of the solid state of the sensor device can be minimized and compensated by introducing correction terms in the temperature value equation or at least partially minimized.
  • the sensor device according to the invention further comprises a control device which is designed to carry out a method according to the invention.
  • the control device is designed to control the heating element according to the method according to the invention and to carry out the evaluations according to the invention.
  • the sensor device according to the invention has a structure which is similar to the structure of a so-called hotplate.
  • a hotplate can provide for a thermal decoupling of the heating element, which is also the sensor element, from the corresponding contact / bonding points on the sensor substrate, which are contacted with a connection circuit.
  • the detected parameters such as thermal conductivity
  • thermal conductivity which can be determined based on the resistance difference
  • density which are determined at least one property of the fluid.
  • the mathematical correlation can be, for example, a polynomial function or an exponential function of the detected parameters.
  • the detected parameters temperature, conductivity, thermal conductivity and density can be per ⁇ wells provided an exponent and multiplied together with to determine a value from which it can at least derive a characteristic of the fluid, such as the calorific value of the fluid.
  • the detected or determined electrical quantities and / or the time constants and / or the differences formed can also be used in the mathematical correlation.
  • FIG. 1 shows a plan view of a sensor ⁇ device according to the invention
  • Fig. 2 shows a sectional view of the sensor device of Fig. 1 along the line II-II shows, in which the
  • FIG. 3 shows the sensor device shown in FIG. 2 at a later production time
  • 4 shows the sensor device shown in FIG. 3 at an even later time of manufacture
  • 5 is a diagram showing the time course of a temperature-dependent resistance of a heating element for two different fluids
  • FIG. 8 is a graph showing the time histories of electric current, voltage, and temperature that result according to the further exemplary method of FIG. 7;
  • Fig. 10 11 represents the temperature-dependent profile of the thermal conductivity of which is shown in Fig. 9 fluids shown, and Fig. The temperature-dependent variation of the temperature conductivity for the in Figs. 9 and 10 Darge ⁇ presented fluids.
  • the at least one property of the fluid which is determined by means of the method according to the invention and the sensor device according to the invention, describes a combustion-relevant size of the fluid, such as the calorific value of the fluid, the amount of oxygen required for stoichiometric combustion of the fluid, etc. It should be emphasized that that does not include at least one self- ⁇ shaft of the fluid, the temperature of the fluid. Fig.
  • the sensor device 100 has a substantially planar micromechanical structure (MEMS).
  • MEMS micromechanical structure
  • the sensor device 100 has a sensor substrate 120 applied to a carrier substrate 110, in and / or on which in turn a heating element 130 in the form of a meander is provided.
  • a carrier substrate 110 which preferably consists of silicon
  • a recess 112 is provided (see also FIG. 4), wherein the sensor substrate 120 extends at least partially over the recess 112.
  • the sensor substrate 120 which preferably consists of silicon nitride, has a sensor region 122 and two connection regions 124, 126.
  • the connection regions 124, 126 are connected to the sensor region 122 via narrow arms 123A, 123B, 123C, 123D such that the sensor region 122 is substantially thermally decoupled from the connection regions 124, 126.
  • the heating element 130 is connected via connecting lines, which run on and / or in the narrow arms 123A, 123B, 123C, 123D, respectively in and / or at the connection areas 124, 126 of FIG Sensor substrate 120 arranged connecting elements 142, 144 electrically connected and can be controlled by a control device (not explicitly shown in the drawings).
  • the connecting elements 142, 144 are preferably made of gold.
  • the heating element 130 has a temperature-dependent electrical resistance.
  • the sensor device 100 of FIG. 1 is a micromechanical structure, i. H. that the sensor device 100 is manufactured in so-called MEMS construction.
  • FIGS. 2 to 4 a manufacturing process of the micromechanical sensor device 100 is described by way of example. 2 to 4 each show a section through the sensor device 100 shown in FIG. 1 along the line II-II of FIG. 1 at different times during the manufacturing process of the MEMS structure.
  • the sensor device 100, the carrier substrate 110, on which the sensor substrate 120 is set ⁇ introduced, in which the heating element 130 and the connection ⁇ elements 142, 144 are at least partially introduced (see FIG. 2).
  • the sensor substrate 120, the heating element 130 and the connecting elements 142, 144 have already been deposited.
  • the sensor substrate 120 is dry-etched in such a way that at least the structure of the heating element 130, in particular in the sensor region 122 of the sensor substrate 120, is released ⁇ (see Fig. 3).
  • the sensor region 122 of the sensor substrate 120, in and / or on which the heating element 130 is arranged is exposed such that the four narrow arms 123A, 123B, 123C, 123D are formed, which are designed to carry the sensor area 122 together with the heating element 130.
  • the recess 112 has a length of about 1 mm to about 2 mm, with the support substrate 110 having dimensions of about 5 mm in length, about 6 mm in width, and about 1 mm in height.
  • the sensor device 100 is preferably arranged in the fuel delivery system of an internal combustion engine (not shown).
  • the natural gas-powered internal combustion engine may for this purpose have a natural gas tank, in which usually the natural gas under a pressure between about 200 and 250 bar is held up.
  • the natural gas tank may be connected to the combustion chambers of the internal combustion engine via a filter, which is also connected to the ambient air for sucking in the ambient air, and a pressure regulator. At a point downstream of the pressure regulator there is a pressure of, for example, a maximum of 20 bar.
  • the sensor device is preferably mounted at a position downstream of the pressure regulator and upstream of the combustion chambers. Consequently, with the sensor device 100 according to the invention, the thermal conductivity of that natural gas mixture can be detected which is immediately before combustion.
  • the internal combustion engine can be operated in an effective and efficient manner with optimized Be ⁇ operating parameters with knowledge of the determined temperature conductivity, calorific value, the methane number, etc.,.
  • the sensor device 100 shown in FIGS. 1 to 4 can be used to detect the thermal diffusivity of the fluid to be measured according to the method shown in FIG. 6 or according to the method shown in FIG. 7, in each case that shown in FIG. 5 shown context is at least partially taken advantage of.
  • FIG. 5 shows time courses of the temperature-dependent resistance R of the heating element 130 which has come into contact with different fluids F1, F2 and has been applied with a predetermined heating power for a predetermined period of time ⁇ t.
  • the heating element 130 for the certain period of time before ⁇ At was charged with a predetermined current pulse.
  • the predetermined period of time At is about 60 ms, for example.
  • the greater the pressure of the fluid the greater the predetermined time period ⁇ t. That is, the heating element 130 for the predetermined period of time At with the predetermined current pulse is applied, for example, a constant current pulse of about 2 mA to about 4 mA.
  • the electrical resistance R of the heating element 130 is detected. For example, 130 detected with the particular front ⁇ current pulse which berthing at the heating element 130 by means of the voltage and see Ohm 'law of ent ⁇ speaking electric resistance R during the application of the heating element are determined.
  • electric voltage can be detected and are contemplated for determining the at least one characteristic of the fluid Fl, F2 zoom ⁇ .
  • this is advantageous when applying a constant current pulse, since in this case a proportional to the elec ⁇ cal resistance curve electrical
  • FIG. 5 essentially shows two characteristic curves for two different fluids F1 and F2.
  • the solid line shows the time profile of the temperature-dependent resistor R for the heating element 130, which is in contact with a first fluid Fl, wherein the dashed line in Fig. 1 represents the time course of the resistance R of the heating element 130, wherein the heating element 130 is in contact with a second fluid F2, which is different from the first fluid Fl.
  • the first fluid Fl is a gas mixture consisting of 100% methane.
  • the second fluid F2 is a gas ⁇ mixture consisting of about 70% methane and about 30% nitrogen. It can thus be seen from FIG. 5 that the time profile of the electrical resistance of the heating element 130 during the predetermined period of time ⁇ t may depend on the composition of the gas mixture. , 0
  • the heating element 130 is acted upon at a first time ti with the predetermined current pulse, which is switched off again at a later second time t 2 .
  • the predetermined current pulse is preferably a constant current pulse.
  • the predetermined current pulse may have a rising shape, a falling shape, a sine shape, or any other known current pulse shape.
  • the time interval between ti and t 2 describes the predetermined time t.
  • the temperature of the two fluids Fl and F2 are at the same level at the beginning of the application of the heating element 130 with the predetermined heating power, for example at ambient temperature.
  • the fluid temperature is a relevant parameter, since the time course of the electrical resistance of the fluid temperature depends significantly. Consequently, the detection of the temperature of the fluid is advantageous, for example by means of a separate temperature sensor. Al ternatively ⁇ the fluid temperature can be detected by means of a further, adjoining the power pulse current pulse.
  • the first fluid Fl has the predetermined temperature and the electrical resistance R of the heating element 130 has a first electrical resistance Rpn.
  • the first fluid Fl a higher temperature and the electric resisting ⁇ stand the heating element 130 has a second electrical resistance R F i2.
  • the second fluid F2 has the predetermined temperature and the electrical resistance R of the heating element 130 has a first electrical resistance R F 2i.
  • the second fluid F 2 has a higher temperature and the electrical Resistor R of the heating element 130 has a second electrical ⁇ en resistor R F 22.
  • FIG. 6 shows a flow chart of an exemplary method according to the invention for determining the composition of the fluid F1 (see FIG. 5).
  • a predetermined heating power is applied to the heating element 130 in the form of a predetermined constant current pulse for the predetermined period of time ⁇ t.
  • the predetermined heating power may also be provided in the form of a predetermined constant voltage applied to the heating element 130.
  • step 202 which also begins predominantly simultaneously with step 201, the time profile of the electrical resistance R of the heating element 130 is recorded or determined during the predetermined period of time ⁇ t.
  • a subsequent step 202 which also begins predominantly simultaneously with step 201, the time profile of the electrical resistance R of the heating element 130 is recorded or determined during the predetermined period of time ⁇ t.
  • Fig. 5 thereby resulting in different fluids Fl, F2 different temporal profiles of the elec tric ⁇ resistance. This is due, in particular, to the differing thermal conductivities and thermal conductivities of the different fluids.
  • the time course of the electrical resistance R of the heating elements 130 can be determined ⁇ see, for example, by detecting the resulting by applying the electric current pulse voltage and converting the current pulse together with the electric voltage by the Ohm 'law.
  • the time profile of the electrical voltage dropping across the heating element 130 can be directly indicated. visually evaluated the at least one property of the fluid.
  • a first electrical resistance R F n at the time ti and a second electrical resistance R F i2 at the time t 2 are determined from the determined time profile of the electrical resistance R of the heating element 130.
  • a resistance difference AR which is proportional to the thermal conductivity ⁇ of the fluid F1 is also formed at step 203.
  • the thermal conductivity ⁇ of the fluid F1 can be determined or at least partially estimated.
  • the time constant ⁇ ii 63 is determined at step 203 from the time variation of the electric resistance R of the heating element 130 with which the composition of the first fluid Fl is detected.
  • the time constant ii 63 is thus a rise time, which indicates that length of time that the elekt ⁇ generic resistance R of the heating element 130, starting from the first electrical resistance R F n to rise to a Budapest ⁇ agreed proportion of the second electrical resistance R F i2 be ⁇ compels ,
  • the predetermined proportion is preferably in a range between about 30% and about 90%, more preferably in a range between about 55% to about 70%. In the most preferred embodiment of the method according to the invention, the predetermined proportion is approximately 63.2%. The value of approximately 63.2% results from 1 / e.
  • the time constant ii 63 is a charac teristic ⁇ size.
  • the determination of the time constant ii 63 is carried out with knowledge of the first and second electrical resistance R F n, R F i2 and with the predetermined proportion, from which the electrical resistance value RFI 63 is determined.
  • the electric resistance value R i F 63 via the time course associated value is the time constant Ti ⁇ ⁇ 63
  • the time constant 63 determined ii is proportional to the Tem ⁇ peraturleitrange a (or the thermal diffusivity) of the fluid Fl. This means that with a measuring cycle, namely the single application of the heating element 130 with temperature-dependent resistance with a predetermined heating power, the thermal diffusivity a of the present fluid Fl by determining the time constant ii 63 and the thermal conductivity ⁇ of the ⁇ lying fluid Fl by determining the resistance difference AR can be determined.
  • the temperature conductivity a of the fluid Fl can be determined. More precisely, in order to determine the thermal diffusivity a, the specific heat capacity c P and / or the density p of the fluid Fl need not be determined, since by determining the thermal diffusivity a Time constant ii 63 the thermal diffusivity a (ie the above quotient) can be determined directly or at least partially estimated. Determined from the determined via the time constant ii 63 Temperaturleit ⁇ a capability and the resistance difference AR thermal conductivity ⁇ can by means of suitable mathematical correlation, the composition of the fluid Fl be determined.
  • the density p of the fluid F1 can be determined in accordance with the method of FIG. 6 in addition to the thermal conductivity a and the thermal conductivity ⁇ .
  • the pitch coupled with ⁇ means of an ultrasonic transmitter and ultrasonic ⁇ lempfsseners, ultrasonic waves in the fluid Fl, and the reflections thereof detected.
  • a reflector within the fluid is provided, to which the out ⁇ emitted ultrasounds can reflect.
  • the reflector has to the ultrasonic transmitter / receiver on a predetermined distance. By recording the transit time of the ultrasound over the predetermined distance (way and return), the sound velocity ⁇ speed can be determined in the fluid Fl.
  • the density p of the fluid F1 is determined from the sound velocity determined at step 205 taking into account the (adiabatic) compression modulus.
  • the density p of the fluid Fl can then, together with the previously determined sizes, thermal diffusivity a and heat conductivity ⁇ ⁇ operates comparable means of a mathematical correlation (see step 207).
  • the mathematical correlation can be, for example, a polynomial function or an exponential function of the detected parameters.
  • the detected Temperature conductivity, thermal conductivity and density are each provided with an exponent and multiplied together to determine a value from which one can derive the at least one property of the fluid, such as the calorific value of the fluid.
  • a mathematical correlation might look like this:
  • H ⁇ 2 ⁇ eP 'a
  • H indicates the calorific value of the fluid.
  • the composition of the fluid F1 is finally determined from the mathematical correlation of the variables density p, thermal conductivity ⁇ and thermal conductivity a before the method of FIG. 6 ends at a step 209. From the determined composition of the fluid Fl then further relevant for the operating parameters of an exclusively natural gas-powered internal combustion engine such. B. the calorific value of the fluid Fl, the methane number of the fluid and the oxygen demand for a stoichiometric combustion of the fluid Fl, are determined.
  • an additional ultrasonic sensor for detecting the speed of sound in the fluid Fl is erforder ⁇ Lich for more accurate determination of the composition of the fluid Fl in addition to the sensor apparatus 100.
  • the viscosity can be ⁇ it averages, which in turn can be considered in the mathematical correlation by means of a viscosity sensor.
  • FIG. 7 another exemplary method of operating the sensor device 100 of FIGS. 1-4 to determine the composition of a fluid F1 is illustrated.
  • the following description of the method of FIG. 7 is given in FIG Together with the diagram of FIG. 8, which shows the time profiles of the electrical current I applied to the heating element 130, the electrical voltage U applied to the heating element 130 and the temperature T of the fluid F.
  • the further exemplary method of FIG. 7 makes use of the knowledge that the thermal conductivity ⁇ , the Tem ⁇ peraturleitrichlor A and the specific heat capacity c p of fluids is temperature-dependent (see in particular Figs. 9 to 11). This means that the thermal diffusivity a and the
  • Thermal conductivity ⁇ can be determined at different temperatures of the fluid to be measured, in which case the Temperaturleitzuen determined at different temperatures and the planteleitzuen serve as input to the already mentioned above mathematical correlations.
  • the further exemplary method of FIG. 7 starts at step 300 and then arrives at step 301, where the heating element 130 is acted upon at a predetermined first temperature T Pi with a predetermined first electrical heating power for a predetermined first time Atl.
  • the first time period Atl ⁇ extends 2 ⁇
  • the heating element 130 can be subjected to the predetermined first electrical heating power by applying a predetermined first voltage U to the heating element 130.
  • step 302 which starts simultaneously with step 301, the time profile of the resistance R of the heating element 130 is detected. For example, after the Beauf ⁇ beat of the heating element 130 to the predetermined first current pulse I P i which berthing at the heating element 130 detects voltage U and see using the Ohm 'law the time course of the resistor R are determined as follows: With :
  • FIG. 8 An exemplary time profile of the electrical voltage U applied to the heating element 130 upon application of the heating element 130 with the predetermined first electrical current pulse I P i for the first predetermined time period Atl at the first temperature T 1 is shown in FIG. 8. It is also apparent from FIG. 8 that the first electrical current pulse I P i is a constant electric current pulse. Alternatively, the first electric current pulse I P i, a rising ⁇ to form a sloping shape, a sinusoidal shape or any other known current pulse shape comprise. In a subsequent step 303, from the detected time profile of the electrical voltage U, in a manner similar to that already described with respect to the method according to FIG.
  • a first one is determined Spann ⁇ ungsdifferenz AUpi and a first time constant ⁇ ⁇ ⁇ 63, indicating the that time period that the voltage at the heating element 130 from a first voltage Uo at the beginning of the predetermined first time period Atl to rise to a predetermined portion of a second electrical voltage U P i at the end of the predetermined first time period Atl needed determined.
  • the predetermined first time period Atl extends from a first time t1 to a second time t2.
  • a first thermal conductivity can ⁇ from the first voltage ⁇ difference AUpi and a first temperature conductivity al from the first time constant ⁇ ⁇ ⁇ 63 are determined at the first temperature T Pi .
  • a first thermal conductivity .lambda..sub.i and the first temperature .alpha are determined at the first temperature T Pi .
  • Conductivity al via the electrical voltage U it is alternatively possible for these two physical variables, as already described in detail in relation to the method illustrated in FIG Determining the course of the electrical resistance R, namely via a first resistance difference and a first time constant determined from a first resistance at the beginning of the first time period Atl and a second resistance at the end of the first time length Atl. It is also possible, the first thermal conductivity ⁇ over the To determine the time course of the voltage dropping at the electrical resistance.
  • the fluid Fl has the first temperature Tl.
  • the heating element 130 is subjected to a predetermined heating power for heating the fluid near the sensor to a predetermined second temperature T2.
  • the heating of the fluid near the sensor takes place during a heating period At He iz, which extends between the second time t2 and a third time t3.
  • the heating element 130 is beauf ⁇ beat with a predetermined heating current I H, which for example is constant and about 15 mA is (see Fig. 8).
  • the electrical voltage at the heating element 130 rises from the second electrical voltage U P i to an electrical heating voltage U H.
  • the temperature increase from T1 to T2, for example, is about 25 ° C.
  • the first current pulse I P i can carry, for example, about 2 mA be ⁇ .
  • the heating current I H is z. For example, about 15 mA.
  • the second current pulse I P2 is approximately 17 mA, wherein therein the heating current I H is taken into account and thus the absolute value of the second current pulse I P2 relative to the heating current is equal to the absolute value of the first current pulse I P i.
  • the second current pulse I P2 is preferably selected such that it represents a sum of the first current pulse I P i and the heating current I H.
  • the subsequent steps 307 to 309 essentially correspond to the steps 302 to 304 already described in relation to the first current pulse I P i, wherein a second thermal conductivity X 2 and a second temperature conductivity a 2 at the second temperature T 2 are determined at step 309.
  • the heating element 130 is acted upon by the second electrical current pulse I P2 for a second time period At2, which extends between the third time point t3 and a fourth time point t4.
  • the first time period Atl and the second time duration At2 are the same length.
  • the first electric current pulse IPI is equal to the second electric current pulse IP2.
  • the steps can be repeated 305 to 309 after the step 309 again, so that further heat conductivities ⁇ ⁇ ⁇ and further temperature conductivities a n of the fluid at another different temperatures T n can be determined. It can be said that the accuracy of the determined composition of the gas temperature increases with the increase of the determined thermal conductivities and thermal conductivities.
  • the composition of the fluid can be determined with reference to FIGS. 9 to 11 from the plurality of detected thermal conductivities ⁇ and the plurality of detected thermal conductivities a using a mathematical correlation.
  • the solid lines describe the curves for methane, the dash-dot lines, the profiles for ethane, the chain double ⁇ dot lines the curves for propane, the long dashed short dashed lines the curves for N Butane, the dashed The curves for nitrogen and the dotted lines the curves for carbon dioxide.
  • the natural gas, methane, ethane, propane and butanes are N-combustible coal ⁇ hydrogens, whereas the nitrogen and carbon dioxide, inert gases and, consequently, are non-flammable.
  • the present fluid can be specified. This may indicate the composition of the
  • Fluids and thus on the calorific value (or other properties of the fluid) are closed, so that the operating parameters of an exclusively natural gas-powered internal combustion engine can be adjusted so that the internal combustion engine can be started with natural gas and operated optimally.
  • the project leading to the present application received funding from the European Union's Horizon 2020 research and development program under grant agreement number 652816.

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Abstract

L'invention concerne un procédé pour déterminer la composition d'un fluide (F1, F2), de préférence d'un mélange gazeux, tel que par exemple un mélange de gaz naturel, ainsi qu'un dispositif de détection (100) qui peut entrer en contact avec le fluide (F1, F2) et qui comprend un élément chauffant (130) pouvant être soumis à une puissance de chauffe électrique et présentant une résistance électrique (R) dépendant de la température. Le procédé comprend les étapes consistant à soumettre l'élément chauffant (130) à une puissance de chauffe électrique prédéfinie pendant une durée prédéfinie (Δt), à acquérir la variation dans le temps de la résistance électrique (R) de l'élément chauffant (130) pendant la durée prédéfinie (Δt), à déterminer une diffusivité thermique (a) du fluide (F1, F2) au moins en partie sur la base de la variation dans le temps de la résistance électrique (R) de l'élément chauffant (130) acquise et à déterminer la composition du fluide (F1, F2) au moins en partie sur la base de la diffusivité thermique (a) déterminée.
PCT/EP2018/058186 2017-04-07 2018-03-29 Procédé pour déterminer une propriété d'un fluide et dispositif de détection associé WO2018185008A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11543377B2 (en) * 2017-06-16 2023-01-03 Oxford University Innovation Limited Sensing apparatus and sensing method
CN111077180A (zh) * 2018-10-19 2020-04-28 代傲表计有限公司 热式气体传感器、测量气体的热扩散率和热导率的方法

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