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WO2018185007A1 - Procédé pour déterminer une propriété d'un fluide - Google Patents

Procédé pour déterminer une propriété d'un fluide Download PDF

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Publication number
WO2018185007A1
WO2018185007A1 PCT/EP2018/058179 EP2018058179W WO2018185007A1 WO 2018185007 A1 WO2018185007 A1 WO 2018185007A1 EP 2018058179 W EP2018058179 W EP 2018058179W WO 2018185007 A1 WO2018185007 A1 WO 2018185007A1
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WO
WIPO (PCT)
Prior art keywords
fluid
heating element
time
predetermined
electrical resistance
Prior art date
Application number
PCT/EP2018/058179
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 WO2018185007A1 publication Critical patent/WO2018185007A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/22—Fuels; Explosives
    • G01N33/225—Gaseous fuels, e.g. natural gas
    • 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.
  • a gas mixture such as a natural gas mixture.
  • Natural gas is this example ⁇ as to the components methane, ethane, propane, butane, carbon dioxide and nitrogen.
  • the non-flammable gases carbon dioxide and nitrogen play an important role in the combustion in terms of knock resistance.
  • 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. She 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 ⁇ fish. 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 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 to determine 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 indicates 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 drive device is provided, which controls the drive signal with a predetermined "
  • 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 of a gas mixture, such as a natural gas mixture
  • This object is achieved by a method according to independent claim 1.
  • Preferred embodiments are specified in the subclaims.
  • the invention is based, at least in part, on the idea of determining the thermal conductivity of the fluid by means of a suitable measurement setup and of determining the at least one property of the fluid by means of suitable mathematical correlation calculations.
  • the physical effect of a temperature-dependent resistor is used. Namely, 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 heat-conducting keit and the thermal diffusivity are determined to turn, as described above, on the at least one property such. As the calorific value of the fluid to be able to conclude by means of the correlation calculations.
  • a method for determining at least one property of a fluid preferably a gas mixture, such as a natural gas mixture.
  • a sensor device (100) is provided, which can come into contact with the fluid and having a heating capacity can be acted upon with electrical heating element with a ⁇ em temperature-dependent electrical resistance.
  • the inventive method comprises applying the heating element with a predetermined first electrical heating power for a predetermined first period of time at a first temperature of the fluid, detecting a first time course of an electrical variable characterizing the electrical resistance of the heating element during the predetermined first period of time Determining a first temperature conductivity of the fluid based at least in part on the detected first time history of the electrical quantity and determining the at least one property of the fluid based at least in part on the determined first temperature conductivity of the fluid.
  • the inventive method further comprises determining a first time profile of the electrical resistance of the heating element at least partially based on the detected first time profile of the electrical variable and the first electrical heating power.
  • the at least one property of the fluid is determined at least partially based on the determined first time profile of the electrical resistance of the heating element.
  • the time profile of the electrical resistance of the heating element are determined in consideration of the predetermined heat output.
  • the determination of the first 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 subjecting the heating element to a predetermined second electrical heating power for a given period of time.
  • a determination of a second time profile of the electrical resistance of the heating element is also provided based at least partially on the detected second time profile of the electrical variable and the second electrical heating power.
  • the at least one property of the fluid is determined based at least partially on the determined second 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 inven tion proper method further comprises determining a second thermal conductivity of the fluid based at least partially on the detected second time course of the electrical quantity and / or at least partially based on the detected second time profile of the electrical resistance of the heating element.
  • the at least one property of the fluid is determined at least partially based on the second determined thermal conductivity.
  • the electrical quantity is preferably the voltage drop across the heating element during the respective predetermined periods of time, during which the heating element is supplied with an electric current for supplying the respective predetermined electrical heating powers.
  • the inventive method further comprises applying the heating element with a predetermined heating power for a predetermined heating period for heating the fluid from the predetermined first temperature to the predetermined second temperature.
  • the heating element can therefore simultaneously assume a heating function in addition to its actual main function as a sensor element.
  • the method according to the invention further comprises determining a first time constant which indicates the time duration that the electrical resistance of the heating element goes from a first electrical resistance at the beginning of the predetermined first time period to a predetermined proportion of a second electrical resistance at the end of the first predetermined first time duration, and determining a second time constant, which indicates the time duration, the electrical resistance of the heating element from a first electrical resistance at the beginning of the predetermined second time period to increase to a predetermined proportion of a second electrical resistance at the end of the predetermined second time period needed.
  • the determination of the composition of the fluid is based at least partially on the determined first time constant and the determined second time constant.
  • time constants are respectively determined based on the detected time profiles of the electrical quantity. From the time constants determined in this way, it is then possible to deduce directly the at least one property of the fluid, or additionally or alternatively the temperature conductivities of the fluid.
  • the method fer ⁇ ner comprises determining a first electrical resistance difference between a first electric resistance of the heating element at the beginning of said predetermined first period and a second electrical resistance of the heating element at the end ofcuit ⁇ approved first time period and determining a second electrical resistance difference between a first electrical resistance of the heating element at the beginning of the predetermined second time period and a second electrical resistance of the heating element at the end of the predetermined second time period.
  • the determination of the at least one property of the fluid is based at least in part on the determined first electrical resistance difference and the determined second electrical resistance difference.
  • the method further comprises thereby to determining a first thermal conductivity of the fluid at least partially ba ⁇ sierend on the detected first electrical resistance difference and determining a second thermal conductivity of the fluid at least partially based on the detected second electrical resistance difference (AR). It is based on that Determining the composition of the fluid at least partially on the determined first thermal conductivity and the determined second thermal conductivity.
  • the application of a predetermined electrical current pulse to the heating element with the respective electrical heating power in each case for the predetermined periods of time It may be preferred if the predetermined current pulses have a rising, falling, sudden, triangular and / or sinusoidal time course.
  • 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 time constants which preferably corresponds to the respective rise time to the predetermined proportion of the determined second electrical resistance at the end of the respective predetermined time period, can be proportional to the respective thermal conductivity.
  • the resistance difference determined can be proportional to the thermal conductivity ⁇ ability of the present fluid.
  • the respective plurality of such parameters determined thermal diffusivity and thermal conductivity can be as input variables of mathematical correlations for the characterization of the fluid, in particular of the gas mixture, such as natural gas mixture zoom are drawn ⁇ . From the 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 at least one property of the fluid are determined.
  • the mathematical correlation can be, for example, a polynomial function or an exponential function of the detected parameters.
  • the detected parameters thermal diffusivity, thermal conductivity and density can each be 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.
  • 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 an exemplary Sensorvor ⁇ direction
  • FIG. 2 shows a sectional view of the sensor device of FIG. 1 along the line II - II, in which the sensor device is at a first production step
  • FIG. 1 shows a plan view of an exemplary Sensorvor ⁇ direction
  • FIG. 2 shows a sectional view of the sensor device of FIG. 1 along the line II - II, in which the sensor device is at a first production step
  • FIG. 3 shows the sensor device shown in FIG. 2 at a later production time
  • FIG. 4 shows the sensor device shown in FIG. 3 at an even later time of manufacture
  • FIG. 5 is a diagram showing the time course of a temperature-dependent resistance of a heating element for two different fluids
  • FIG. 6 is a flowchart of an example method
  • FIG. 8 is a graph showing the time courses of the electric current, the electric voltage and the temperature, which result according to the method according to the invention of FIG. 7, FIG.
  • FIG. 10 shows the temperature-dependent course of the thermal conductivity for the fluids shown in FIG. 9, and
  • FIG Fig. 11 shows the temperature-dependent profile of the thermal 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. 1 shows a plan view of an exemplary sensor ⁇ device 100 is adapted to determine the composition and a property of a fluid mixture fluid, especially a gas mixture, such as a natural gas mixture.
  • the sensor device 100 has an essentially planar micromechanical structure (MEMS).
  • MEMS micromechanical structure
  • the sensor device 100 includes an applied on a support substrate 110.
  • Sensor substrate 120 in and / or on which in turn a heating element is seen 130 in the form of a meander in front ⁇ .
  • the 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 electrically connected via connecting lines which run on and / or in the narrow arms 123A, 123B, 123C, 123D, to connecting elements 142, 144 respectively arranged in and / or on the connecting regions 124, 126 of the sensor substrate 120, and can be of a control device (not explicitly shown in the drawings) are driven.
  • 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. the sensor device 100 is produced in a 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 from ⁇ are already separated.
  • 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 area 122 of the sensor substrate 120, is placed freely ⁇ (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 four arms 123A, 123B, 123C, 123D are as narrow and thin as possible in order to ensure that the thermal conductivity of the solids (ie the heating element 130, the sensor region 122 of the sensor substrate 120 and the four arms 123A, 123B, 123C, 123D) are as small as possible and consequently only the thermal diffusivity of the fluid to be measured is detected.
  • the parasitic influence of the aforementioned interference temperature conductivities can thus be minimized.
  • 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 is kept under a pressure between about 200 and 250 bar.
  • 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, the thermal conductivity of that natural gas mixture which is immediately before combustion can be detected.
  • the internal combustion engine can be optimized operating parameters with knowledge of the thermal diffusivity determined, the fuel ⁇ value, the methane number, etc., are operated in an effective and efficient manner.
  • 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 profiles of the temperature-dependent resistance R of the heating element 130, which vary with different Fluids Fl, F2 has come into contact and was applied with a predetermined heating power for a predetermined period of time At.
  • the heating element 130 for the certain period of time before ⁇ At with a predetermined current pulse was alsschlagt loading.
  • 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 is supplied with the predetermined current pulse for the predetermined period of time ⁇ t, 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 for determining the at least one characteristic of the fluid Fl, F2 are attracted ⁇ forth. This is particularly advantageous in applying a con- stant current pulse, since this results in a proportional to the elec trical resistance profile ⁇ electrical voltage curve.
  • 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 resistance R for the heating element 130, which is in contact with a first fluid Fl
  • the dashed line in FIG. 1 shows the time profile of the resistance R of the heating element 130th represents, in which 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 approximately 70% methane and approximately 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.
  • 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.
  • the fluid temperature can be detected by means of a further current pulse following the 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 RFH on.
  • 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 F2 is higher in temperature and the electric resistance R of the heating element 130 has a second electrically ⁇ en resistor R F 22.
  • FIG. 6 shows a flowchart of an exemplary method for determining the composition of the fluid F1 (see FIG. 5).
  • reference is made to the time profile of the electrical resistance R of the heating element 130 of FIG. 5 reference.
  • the process of FIG. 6 starts at a step 200 and then goes to step 201 where 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. As shown in Fig. 5, thereby resulting in different fluids Fl, F2 different temporal profiles of the elec tric ⁇ resistance. This is particularly important for the attributable to different thermal conductivities and thermal diffusivities of the different fluids.
  • the time profile of the electrical resistance R of the heating element 130 can be determined, for example, by detecting the electrical voltage resulting from the application of the current pulse and the conversion of the current pulse together with the electrical voltage by means of the ohmic law. As already mentioned, alternatively, the time profile of the electrical voltage drop across the heating element 130 can be evaluated directly with regard to 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 temporal profile of the electrical resistance R of the heating elements ⁇ 130th
  • 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 one 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, the predetermined proportion is approximately 63.2%. The value of about 63, 2% results from 1 / e.
  • the time constant ii 63 is a characteristic quantity.
  • the determination of the time constant ii 63 is carried out with knowledge of the first and second electrical resistance R F H, R F I2 and with the predetermined proportion, from which the electrical resistance value R F I 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 specifically, 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 time constant ii 63, the thermal diffusivity a (ie the quotient given above) is determined directly or at least partially can be estimated.
  • the composition of the fluid F1 can be determined by means of a suitable mathematical correlation.
  • 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 speed of sound determined at step 205 is taken into account (adiabatic) compression modulus determines the density p of the fluid Fl.
  • 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 parameters recorded thermal 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, as in ⁇ example, 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. As 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 even more precise determination of the composition of the fluid F1 in addition to the sensor device 100 is an additional ultrasonic sensor for detecting the speed of sound in the fluid Fl required. borrowed.
  • the viscosity can be ⁇ it averages, which in turn can be considered in the mathematical correlation by means of a viscosity sensor.
  • FIG. 7 a method according to the invention for operating the sensor device 100 of FIGS. 1 to 4 for determining the composition of a fluid F1 is shown.
  • the following description of the method according to the invention of FIG. 7 is given in conjunction 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.
  • FIG shows.
  • the inventive method of FIG. 7 makes use of the knowledgeable ⁇ It utilizes the fact that the thermal conductivity ⁇ , the Tempe ⁇ raturleit impart 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 temperature conductivities and the thermal conductivities determined at different temperatures serve as input variables for the mathematical correlations already mentioned above.
  • determining the temperature conductivities and the thermal conductivities at different temperatures eliminates the determination of the density of the fluid by means of ultra-sound waves, whereby an additional ultrasonic sensor is no longer needed, which can lead to a reduction in the cost of the sensor.
  • the mechanical structure of the sensor device is simplified and requires less space.
  • the method of FIG. 7 begins at step 300 and then moves to step 301, at which the heating element is applied with a predetermined first electrical heating power for a predetermined first time period Atl in a réelle ⁇ voted first temperature T Pi 130th
  • the first time period Atl extends between a first time ti and a second time t 2 .
  • the charging of the heating element with the first electric heating power is effected by applying the heating element 130 with a predetermined first current pulse I P i (see FIG. 8).
  • 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.
  • ⁇ beat of the heating element 130 with the predetermined first current pulse I which pi-applying to the heating element 130 detects voltage U and see using the Ohm 'law the time characteristic of the resistance R after Beauf be determined as follows:
  • the first electrical current pulse I pi is a constant electric current pulse.
  • the first electric current pulse I P i a rising ⁇ to form a sloping shape, a sinusoidal shape or jeg- Liehe comprise other known current pulse shape.
  • a first one is determined clamping ⁇ voltage difference 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 Upi determined at the end of the predetermined first time Atl needed.
  • the predetermined first time period Atl extends from a first time t1 to a second time t2.
  • a first thermal conductivity ⁇ of the first voltage difference AU P i and a first thermal conductivity can al be determined from the first time constant ⁇ ⁇ ⁇ 63 at the first temperature T Pi .
  • these two physical quantities as already described with reference to the example shown in FIG.
  • 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 ⁇ duration At He i z , which extends between the second time t2 and a third time t3.
  • the heating element ⁇ 130 is subjected to 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, and any increase in temperature can be implemented.
  • the first current pulse I P i can be approximately 2 mA, for example.
  • 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. ⁇ 0
  • a second heating power preferably a second current pulse I P 2
  • 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. This means that even during the second time period At2, the heating current I H is present, so that the fluid Fl continues to be heated.
  • the subsequent steps 307-309 are essentially the same be ⁇ registered already in relation to the first current pulse I P i steps 302 to 304, wherein a second thermal conductivity of a second Temperaturleit ⁇ ability is determined a2 at the second temperature T2 at step 309, X2 and ,
  • 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.
  • AR P2 electrical resistance R (relative to the starting resistance at time t3) at the heating element 130 during the second electric current pulse I P2 ,
  • ⁇ a first thermal conductivity of the first fluid temperature Tl and a first thermal conductivity and at a2 of the second fluid temperature T2, a second thermal conductivity X2 and a second temperature conductivity a2 ,
  • 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. With reference to FIGS. 9 to 11, the temperature-dependent curves of the specific heat capacity (see FIG. 9), the thermal conductivity ⁇ (see FIG.
  • the temperature conductivity a (see FIG. 11) are for predetermined fluids, in particular natural gases , namely, for methane, ethane, propane, n-butanes, nitrogen dioxide and nitrogen.
  • natural gases namely, for methane, ethane, propane, n-butanes, nitrogen dioxide and nitrogen.
  • the solid lines describe the progressions for methane, the dashed-dotted lines the progressions for ethane, the dash-dotted lines the progressions for propane, the long-dashed short-dashed lines the progressions for N Butane, the dotted lines the gradients for nitrogen and the dotted lines the gradients for carbon dioxide.
  • the natural gas, methane, ethane, propane, and N-butanes are combustible hydrocarbons such, whereas the nitrogen and carbon dioxide, inert gases ⁇ and thus are not combustible.
  • the present fluid can be specified.
  • the composition of the fluid and thus the calorific value (or other properties of the fluid) so that the operating parameters of an internal combustion engine operated exclusively with natural gas can be set such that the internal combustion engine can also 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. Selon l'invention, un dispositif de détection (100) peut entrer en contact avec le fluide (F1, F2) et ledit dispositif comporte 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 première puissance de chauffe électrique prédéfinie pendant une première durée prédéfinie (Δt1) à une première température (T1) du fluide (F1, F2), à acquérir une première variation dans le temps de la résistance électrique (R) de l'élément chauffant (130) pendant la première durée prédéfinie (Δt1), à déterminer une première diffusivité thermique (a1) du fluide (F1, F2) au moins en partie sur la base de la première 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 première diffusivité thermique (a1) déterminée.
PCT/EP2018/058179 2017-04-07 2018-03-29 Procédé pour déterminer une propriété d'un fluide WO2018185007A1 (fr)

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DE102021125294A1 (de) 2021-09-29 2023-03-30 Infineon Technologies Ag Verfahren zur Bestimmung einer Gaskonzentration und Gaskonzentrationssensor

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DE102021125294A1 (de) 2021-09-29 2023-03-30 Infineon Technologies Ag Verfahren zur Bestimmung einer Gaskonzentration und Gaskonzentrationssensor

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