Method and measuring apparatus for determining specific quantities for gas quality

Abstract

A method and a measuring apparatus for determining specific quantities for the gas quality in which the gas or gas mixture flows through an ultrasonic flow sensor as well as through a microthermal sensor, and the former is used for determining the sound and flow velocity and the latter for determining the thermal conductivity and the thermal capacity of the gas or gas mixture. The sound velocity, the thermal conductivity and the thermal capacity are subsequently used for the correlation of the specific quantities for the gas quality.

Claims

1. A method for determining a quantity for a gas quality comprising: moving a gas or gas mixture through an ultrasonic flow measuring device and over a microthermal sensor; determining a temperature of the gas or gas mixture using a temperature sensor; determining a pressure of the gas or gas mixture using a pressure sensor; determining a flow velocity (v.sub.x) or volumetric flow and determining a sound velocity (c.sub.s) of the gas or gas mixture based on information sensed by the ultrasonic flow sensor; determining a density of the gas or gas mixture based on a correlation with the sound velocity (c.sub.s); calculating a mass flow of the gas or gas mixture based on the density and flow velocity (v.sub.x) or the volumetric flow; determining a thermal conductivity of the gas or gas mixture at one or several temperatures; determining a flow factor (?) based on a flow signal of the microthermal sensor; determining a thermal capacity (c.sub.p) or a quantity dependent on the thermal capacity from the flow factor (?) and the mass flow and the thermal conductivity; and determining the quantity for the gas quality using a correlation with the sound velocity and the thermal conductivity and either the thermal capacity or the quantity depending on the thermal capacity.

2. The method according to claim 1, further comprising converting the sound velocity (c.sub.s) to a sound velocity at a standard temperature (T.sub.norm).

3. The method according to claim 1, wherein the thermal conductivity and the sound velocity are used in a preciser correlation to determine the density.

4. The method according to claim 1, wherein the density is a density at a standard condition or at operating conditions.

5. The method according to claim 1, wherein the determining of the quantity of the gas quality includes using the sound velocity, the thermal conductivity information, and the thermal capacity or the quantity depending on thermal capacity in a correlation to determine at least one of a calorific value, a Wobbe index (W), a Z factor and a kinematic viscosity.

6. The method according to claim 5, further comprising calculating a value for energy consumption based on the calorific value and the volumetric flow or the mass flow.

7. A measuring apparatus for determining a quantity for a gas quality or for determining energy consumption comprising: an ultrasonic flow sensor configured to measure at least one of a sound velocity and a flow velocity of the gas, a pressure sensor configured to measure a pressure of the gas, a temperature sensor configured to measure a temperature of the gas, a microthermal sensor configured to measure at least one of a thermal conductivity of the gas and a thermal capacity of the gas or a quantity dependent on the thermal capacity, and an evaluation unit configured to determine the quantity for the gas quality or the energy consumption based on the sound velocity, the thermal conductivity and either the thermal capacity or the quantity dependent on the thermal capacity.

8. The measuring apparatus according to claim 7, wherein the ultrasonic flow sensor and the microthermal sensor are arranged in a gas line.

9. The measuring apparatus according to claim 8, wherein the ultrasonic flow sensor is not invasive to the gas line.

10. The measuring apparatus according to claim 7, wherein the ultrasonic flow sensor is arranged in a main gas line and the microthermal sensor is in a bypass gas line to the main gas line, and an element in the main gas line produces a pressure drop in the main gas line which generates a mass flow in the bypass gas line.

11. The measuring apparatus according to claim 10, wherein a splitting ratio between the mass flow in the bypass gas line and in the main gas line is a known value.

12. The measuring apparatus according to claim 7, wherein the ultrasonic flow sensor and the microthermal sensor are arranged in a bypass gas line to a main gas line, and an element in the main gas line produces a pressure drop in the main gas line which generates a mass flow in the bypass gas line.

13. The measuring apparatus according to claim 7, further comprising a section of a gas line in which at least one of the sensors of the measuring apparatus is arranged.

14. The measuring apparatus according to claim 7, wherein the measuring apparatus forms a modular unit including the evaluation unit, or wherein the measuring apparatus forms a modular unit without the evaluation unit, and the evaluation unit is implemented in a separate computing unit.

15. The measuring apparatus according to claim 7, wherein the evaluation unit is further configured to carry out the method comprising: moving a gas or gas mixture through an ultrasonic flow sensor and over a microthermal sensor; determining a temperature and pressure of the gas or gas mixture; determining a flow velocity (v.sub.x) or volumetric flow and determining a sound velocity (c.sub.s) of the gas or gas mixture based on information sensed by the ultrasonic flow sensor; determining a density of the gas or gas mixture based on a correlation with the sound velocity (c.sub.s); calculating a mass flow of the gas or gas mixture based on the density and flow velocity (v.sub.x) or the volumetric flow; determining a thermal conductivity of the gas or gas mixture at one or several temperatures; determining a flow factor (?) based on a flow signal of the microthermal sensor; determining a thermal capacity (c.sub.p) or a quantity dependent on the thermal capacity from the flow factor (?) and the mass flow and the thermal conductivity; and determining the quantity for the gas quality using a correlation with the sound velocity and the thermal conductivity and either the thermal capacity or the quantity depending on the thermal capacity.

16. A method to determine a value of a gas quality comprising: collecting information regarding a flow of a gas or gas mixture using an ultrasonic flow sensor, a microthermal sensor, temperature sensor, and a pressure sensor; based on the collected information, calculating parameters for the flow including at least one of a flow velocity and volumetric flow, a sound velocity, a density, a thermal conductivity, and a flow factor derived from the flow signal of the microthermal sensor; using the parameters, calculating for the flow a mass flow and a thermal capacity or a factor dependent on the thermal capacity of the flow, and determining the value of the gas quality based on the sound velocity, the thermal conductivity and the thermal capacity or the factor dependent on the thermal capacity.

17. The method of claim 16 wherein the value is at least one of a calorific value, a Wobbe index (W) value, a Z factor and a kinematic viscosity value.

Description

SUMMARY OF THE DRAWINGS

(1) The invention is explained below in closer detail by reference to the drawings, wherein:

(2) FIG. 1a shows the schematic configuration of an embodiment of a microthermal anemometer;

(3) FIG. 1b shows a schematic illustration of an ultrasonic flow sensor;

(4) FIG. 2a shows an example of density determination (correlation) on the basis of sound velocity;

(5) FIG. 2b shows an example of improved density determination (correlation) on the basis of the sound velocity and the thermal conductivity;

(6) FIG. 3a shows an example of calorific value determination (correlation) on the basis of the thermal capacity, the thermal conductivity and the sound velocity;

(7) FIG. 3b shows an example for the determination of the Z factor (correlation) on the basis of the thermal capacity, the thermal conductivity and the sound velocity;

(8) FIG. 3c shows an example for the determination of the kinematic viscosity (correlation) on the basis of the thermal capacity, the thermal conductivity and the sound velocity;

(9) FIG. 4 shows an embodiment of the schematic configuration of a measuring apparatus according to the present invention in the main gas line;

(10) FIG. 5 shows a second embodiment of the schematic configuration of a measuring apparatus according to the present invention with a microthermal sensor in a bypass gas line to the main gas line, and

(11) FIG. 6 shows a third embodiment of the schematic configuration of a measuring apparatus according to the present invention in a bypass gas line.

DETAILED DESCRIPTION OF THE INVENTION

(12) FIG. 1a shows an embodiment of a microthermal sensor 7 for use in a measuring apparatus according to the present invention. As shown in FIG. 1a, the microthermal sensor can be an integrated, microthermal CMOS heat-wire anemometer, which in operation is arranged in a section of a bypass gas line and can be supplied with a gas or gas-mixture flow 2a. The microthermal CMOS heat-wire anemometer comprises a substrate 13, which typically contains a membrane 14 with a thickness of a few micrometers. The CMOS heat-wire anemometer further comprises two thermocouples 15.1, 15.2 and a heating element 16 which can be arranged in the direction of flow between the two thermocouples. The temperature can be detected by means of the thermocouples 15.1, 15.2, which temperature is obtained as a result of the heat exchange 15.1a, 15.2a with the gas or gas mixture flow 2a.

(13) For further details concerning the functionality of the integrated microthermal CMOS heat-wire anemometer, reference is made to D. Matter, B. Kramer, T. Kleiner, B. Sabbattini, T. Suter, Mikroelektronischer Haushaltsgaszahler mit neuer Technologie [Microelectronic domestic gas meter with new technology], Technisches Messen 71, 3 (2004), p. 137-146.

(14) FIG. 1b shows an embodiment of an ultrasonic flow sensor 4 for use in a measuring apparatus according to the present invention. For example, two units 17 and 18 which both generate and receive sound (e.g., piezo actuators or receptors) are arranged on obliquely opposite positions on the measuring line. A sound pulse emitted by the actuator 17 reaches the receptor 18 more rapidly than a sound impulse emitted simultaneously by the actuator 18 reaches the receptor 17. Both the sound velocity c.sub.s and also the flow velocity v.sub.x can be calculated from the runtimes t.sub.12 and t.sub.21, together with geometry factors of the arrangement.

(15) For further details concerning the functionality of the ultrasonic sensor, reference is hereby made to L. C. Lynnwortha, Yi Liub, Ultrasonic flowmeters: Half-century progress report, 1955-2005 in Ultrasonics, 44, Supplement (2006), p. e1371-e1378.

(16) FIG. 4 shows an embodiment of the schematic configuration of a measuring apparatus according to the present invention. In the embodiment, the measuring apparatus 11 comprises an evaluation unit 10 which is set up for carrying out a method according to the present invention, an ultrasonic flow sensor 4, a microthermal sensor 7, as well as a pressure sensor 8 and a temperature sensor 9, wherein the sensors can be arranged in a gas line 1. Some of these components or all of these components can be combined into a modular unit, wherein the evaluation unit 10 can be a component of the said modular unit (variant 11a), or the evaluation unit can be attached separately (variant 11b), e.g. in a higher-level computing unit.

(17) The configuration of the embodiment shown in FIG. 4 is especially suitable for the determination of specific quantities for the gas quality in small and minute gas flows, as occur in the field of gas analyses for example, and where primarily the information concerning the gas quality is relevant.

(18) The measuring apparatus in the embodiment shown in FIG. 4 can be used for example as an analytical unit or as a separate analytical device, wherein the analytical unit or the analytical device advantageously contains a gas line 1 in which the sensors 4, 7, 8, 9 of the measuring apparatus are arranged. Gas samples can be taken and analysed with the analytic unit or the analytic device. The connections and valves necessary for this purpose are not shown in FIG. 4.

(19) An embodiment of the method for determining specific quantities for the gas quality of a gas and gas mixture according to the present invention will be described below with reference to FIG. 4. In this method, the gas or gas mixture flows in the gas line 1 through an ultrasonic flow sensor 4 and over a microthermal sensor 7. Pressure and temperature of the gas or gas mixture, i.e. the operating conditions, are determined with a pressure sensor 8 and a temperature sensor 9 additionally arranged in the gas line. The ultrasonic sensor further measures the sound velocity and the flow velocity or volumetric flow. Correlation of the density occurs subsequently on the basis of the sound velocity, wherein the density determined by means of correlation is appropriately converted to the density at the given temperature and the given pressure (operating conditions).

(20) Furthermore, the thermal conductivity of the gas at one or several temperatures is measured with the microthermal sensor 7, in that the heating power of the heating wire is varied. If necessary, the result of this measurement can also be included in the correlation of the density. The mass flow is subsequently calculated from the value of the density and the volumetric flow. The ratio between thermal capacity and thermal conductivity of the gas is calculated from the flow factor, which is also measured with the microthermal sensor and, together with the already known thermal conductivity, the value of the thermal capacity is calculated. The sound velocity, thermal conductivity and thermal capacity are subsequently used for the correlation of the specific quantities for the gas quality, e.g. the calorific value or Wobbe index (W) or Z factor or kinematic viscosity. If necessary, the energy consumption can be determined by multiplying the mass flow with the calorific value.

(21) FIG. 5 shows a second embodiment of the schematic configuration of a measuring apparatus 11 according to the present invention with a microthermal sensor 7 in a bypass gas line 6 to the main gas line 1. An element 5 which produces a pressure drop is provided in this case in the main gas line, so that a pressure drop is formed in operation via the bypass gas line, which leads to a gas flow 2 in the bypass gas line, wherein a characteristic flow splitting ratio 3 is obtained between the main gas line and the bypass gas line.

(22) In the illustrated embodiment, the measuring apparatus comprises, in addition to the microthermal sensor 7, an evaluation unit 10 which is set up for carrying out a method according to the present invention, as well as an ultrasonic flow sensor 4, a pressure sensor 8 and a temperature sensor 9, which are typically arranged in the main gas line 1. Some of these components or all these components can be combined into a modular unit, wherein the evaluation unit 10 can be a component of the said modular unit (variant 11a), or the evaluation unit can be attached separately (variant 11b), e.g. in a higher-level computing unit.

(23) The configuration in the embodiment shown in FIG. 5 is suitable both for the determination of specific quantities for the gas quality and also, in the case of the calorific value as the gas quality, for the energy consumption measurement for medium to large gas flows, which occur for example in the domestic field, in industry or in custody transfer.

(24) The ultrasonic flow sensor 4 need not necessarily be installed in the gas line or main gas line 1, but can also be attached from the outside to the gas line or main gas line as a so-called clamp-on device. The microthermal sensor 7 on the other hand requires only minute flow quantities and is therefore preferably arranged in a bypass gas line 6.

(25) A second embodiment of the method for determining specific quantities for the gas quality of a gas and gas mixture according to the present invention is described below by reference to FIG. 5. In the method, the gas or gas mixture flows in a main gas line 1 over or through an element 5 producing a pressure drop. A bypass gas line 6 branches off before the element 5 producing a pressure drop and joins the main gas line again after said element. A portion of the gas or gas mixture 2 is forced by the element 5 producing the pressure drop to flow through the bypass gas line 6 and over a microthermal sensor 7 which is arranged therein. The main gas flow is supplied to the ultrasonic flow sensor 4.

(26) The pressure and temperature of the gas or gas mixture, i.e. the operating conditions, are determined with a pressure sensor 8 and a temperature sensor 9 additionally arranged in the main gas line. The sound velocity and the flow velocity or volumetric flow are further measured with the ultrasonic sensor. This is followed by the correlation of the density on the basis of the sound velocity, wherein the density determined by means of correlation is appropriately converted to the density at the given temperature and the given pressure (operating conditions).

(27) Furthermore, the thermal conductivity of the gas at one or several temperatures is measured with the microthermal sensor 7, in that the heating power of the heating wire is varied. If necessary, the result of this measurement can also be included in the correlation of the density. The mass flow through the main gas line 1 is subsequently calculated with the value of the density and the volumetric flow. The splitting ratio of the mass flow between the main gas line and bypass gas line is subsequently appropriately used to calculate the mass flow in the bypass gas line. The splitting ratio can be determined in advance for example in a calibration measurement with known gases.

(28) The ratio between thermal capacity and the thermal conductivity of the gas or gas mixture is calculated from the flow factor which was also measured with the microthermal sensor and, with the already known thermal conductivity, the value of the thermal capacity is calculated. Sound velocity, thermal conductivity and thermal capacity are subsequently used for the correlation of the specific quantities for the gas quality. In the case of the calorific value as the gas quality, the multiplication of the mass flow in the main gas line with the calorific value additionally supplies the energy consumption.

(29) FIG. 6 shows a third embodiment of the schematic configuration of a measuring apparatus 11 according to the present invention in a bypass gas line 6 to the main gas line 1. An element 5 which produces a pressure drop is provided in this case in the main gas line, so that a pressure drop via the bypass gas line is formed in operation, leading to a gas flow 2 in the bypass gas line, wherein a characteristic flow splitting ratio 3 is formed between the main gas line and the bypass gas line.

(30) In the illustrated embodiment, the measuring apparatus comprises an evaluation unit 10 which is set up to carry out a method according to the present invention, as well as an ultrasonic flow sensor 4 and a microthermal sensor 7 which are arranged in the bypass gas line 6. The measuring apparatus further comprises a pressure sensor 8 and a temperature sensor 9, which are mostly also arranged in the bypass gas line 1. Some of these components or all of these components can be combined into a modular unit, wherein the evaluation unit 10 can be a component of the said modular unit (variant 11a), or the evaluation unit can be attached separately (variant 11b), e.g. in a higher-level computing unit.

(31) The configuration in the embodiment shown in FIG. 6 is preferably obtained when the ultrasonic sensor 4 is formed in microtechnology, and said sensor, as also the microthermal sensor 7, require only minute flow quantities. Both sensors are then advantageously arranged in a bypass gas line 6.

(32) A third embodiment of the method for determining specific quantities for the gas quality of a gas and gas mixture according to the present invention will be described below by reference to FIG. 6. The method is both suitable for the continuous and also for the intermittent determination of specific quantities for the gas quality or energy consumption. Optionally required connections and valves are not shown in FIG. 6.

(33) In the third embodiment of the method, the gas or gas mixture flows in a main gas line 1 over or through an element 5 which produces a pressure drop. A bypass gas line 6 branches before the element 5 producing a pressure drop and joins the main gas line again after said element. A portion of the gas or gas mixture 2 is forced by the element 5 producing the pressure drop to flow through the bypass gas line 6 and through an ultrasonic flow sensor 4 and over a microthermal sensor 7 which are arranged in said bypass gas line. The ultrasonic flow sensor 4 and the microthermal sensor 7 are supplied with the same gas flow.

(34) The pressure and the temperature of the gas or gas mixture, i.e. the operating conditions, are determined by a pressure sensor 8 and a temperature sensor 9 which are additionally arranged in the bypass gas line. The sound velocity and the flow velocity or the volumetric flow are further measured with the ultrasonic sensor. Correlation of the density occurs subsequently on the basis of the sound velocity, wherein the density determined by means of correlation is appropriately converted to the density at the given temperature and the given pressure (operating conditions).

(35) Furthermore, the thermal conductivity of the gas at one or several temperatures is measured with the microthermal sensor 7, in that the heating power of the heating wire is varied. If necessary, the result of said measurement can also be included in the correlation of the density. The mass flow through the bypass gas line 6 is subsequently calculated with the value of the density and the volumetric flow.

(36) The ratio between the thermal capacity and the thermal conductivity of the gas and, together with the already known thermal conductivity, the value of the thermal capacity is calculated from the flow factor which is also measured with the microthermal sensor. The sound velocity, thermal conductivity and thermal capacity are subsequently used for the correlation of the specific quantities for the gas quality.

(37) Since the aforementioned measurements and calculations relate to the bypass gas line, the splitting ratio of the mass flow between the main gas line and bypass gas line is used in order to calculate the mass flow in the main gas line. The splitting ratio can be determined in advance for example in a calibration measurement with known gases. If the calorific value was determined as the specific quantity for the gas quality, the multiplication of the mass flow in the main gas line with the calorific value additionally supplies the energy consumption.

(38) The method and the measuring apparatus according to the present invention and the aforementioned embodiments and variants for determining specific quantities for the gas quality or the energy consumption can be used in high-pressure and low-pressure gas networks, and provide a comparatively high level of precision in the determination of the aforementioned quantities due to the correlation from the three independent variables of sound velocity, thermal conductivity and thermal capacity.

(39) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.