Microthermal Sensor Gas Properties Taylor-Couette Flow
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Solution Overview
Problem
Existing gas flow measurement techniques struggle to accurately determine physical gas properties such as density, thermal conductivity, and heat capacity, especially when gas quality changes, which is crucial for combustion control and engine efficiency, as they often rely on gas-dependent measurement principles and lack precision in correlating these properties with combustion-relevant variables like the Wobbe index and air requirement.
Innovation Solution
A microthermal sensor using a CMOS hot-wire anemometer measures gas properties independently of flow rate through Taylor-Couette flow dynamics, allowing for the determination of heat capacity and thermal conductivity, enabling the calculation of combustion-relevant parameters like calorific value and Wobbe index by measuring the ratio of these properties and mass or volume flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional thermal flow meters are used to measure gas flow, then the measurement principle is simple, but the measurement precision of physical gas properties deteriorates because the measurement inherently depends on gas properties themselves
Solution Approach 1:
The patent introduces a Taylor-Couette flow system with rotating cylinders as an intermediary mechanism. This system creates a controlled flow field where the flow rate can be precisely determined by rotational speed measurements, independent of gas properties. The intermediary flow dynamics system decouples the flow rate determination from direct gas property measurement, enabling accurate determination of physical gas properties like thermal conductivity and heat capacity.
Solution Approach 2:
The patent replaces conventional thermal measurement methods with a microthermal CMOS hot-wire anemometer that uses electrical resistance changes to detect temperature variations. This substitution allows for precise measurement of thermal conductivity and heat capacity by monitoring the electrical properties of the hot wire in the gas flow, rather than relying on mechanical or conventional thermal sensors that are sensitive to gas property variations.
2Device complexity
If gas flow measurement techniques that depend on gas properties are used, then the device complexity is low, but the reliability for determining combustion parameters deteriorates when gas quality changes
Solution Approach 1:
The patent creates a multi-functional measurement system that simultaneously determines multiple physical gas properties (flow rate, thermal conductivity, heat capacity, density) using a single integrated setup. The Taylor-Couette flow system combined with the microthermal anemometer can measure various parameters that are all relevant to combustion processes, making the system universally applicable for different combustion control applications regardless of gas quality variations.
Solution Approach 2:
The patent utilizes changes in thermal and electrical parameters of the hot-wire anemometer to detect and measure different physical gas properties. By monitoring how the wire's temperature and electrical resistance change in response to gas flow and composition, the system can reliably determine combustion-relevant parameters even when gas quality changes, transforming physical changes into measurable electrical signals.
3Adaptability or versatility
If thermal conductivity measurement is performed with flowing gas, then the measurement is integrated with flow measurement, but the manufacturing precision of separate measurements deteriorates
Solution Approach 1:
The patent segments the measurement functions into distinct computational steps while using a single physical system. The Taylor-Couette flow provides the flow rate measurement, while the microthermal anemometer separately measures thermal conductivity. The control unit then computationally combines these measurements to determine heat capacity and other derived parameters. This segmentation allows each measurement component to be optimized independently while maintaining overall integration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the upgrading of gas flow measurement techniques into high-accuracy gas quality sensors, simplifying the determination of combustion-relevant variables, enhancing the precision and cost-effectiveness in various applications, including gas firing control and natural gas engine management.
Implementation Method 1
the microthermal measurement of the complementary variable in the product of equation (2), depending on which one Individual size or combination of sizes is the best starting point for determining the sizes relevant to combustion. According to an advantageous embodiment of the invention, a mass flow meter is upgraded to a gas quality sensor with the microthermal sensor, in that the ratio between heat capacity and thermal conductivity c p /λ is measured as a complementary quantity to the mass flow
Implementation Method 2
the specification of the flow rate is achieved by utilizing gas-independent flow dynamics, for example by means of a Taylor-Couette flow in rotating cylinders
Implementation Method 3
a sensor block with an integrated, microthermal CMOS hot-wire anemometer, through which the gas mixture flows, by measuring two temperatures upstream and downstream of the heating wire
Data Source
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AI summary
The method involves measuring physical gas mixture property using a sensor. The complementary value of the thermal capacity is measured based on ratio between the flow rate and heat conductivity separately measured by gas quality sensor and microthermal sensor. The value of the thermal capacity is correlated with caloric value of the gas mixtures. An independent claim is included for microthermal sensor for determining physical gas properties.