Piezoelectric Gas Flow Meter Using Choked Orifice
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current mass flow meter technologies for gases, especially at high pressures, are either inaccurate, complex, or costly, and often involve moving parts that can wear out, making them unsuitable for precise measurement in industrial applications such as medical and high-pressure gas systems.
Innovation Solution
A method and apparatus using a piezoelectric oscillator, specifically a quartz crystal oscillator, to measure mass flow rate through a flow restriction orifice by resonating at a frequency dependent on gas density, allowing for accurate measurement under choked flow conditions with robust and cost-effective components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical mass flow meters (inertial, diaphragm, rotary, turbine) are used to measure high-pressure gas flow, then measurement capability is provided, but device complexity increases and manufacturing cost rises
Solution Approach 1:
The patent replaces mechanical mass flow meters with electronic flow meters that use no moving parts. Specifically, thermal meters and ultrasonic meters are employed to measure mass flow rate of high-pressure gases, eliminating mechanical components while maintaining measurement capability.
Solution Approach 2:
The patent employs disposable flow restrictors made from inexpensive materials like PTFE (Teflon) or stainless steel capillary tubes. These restrictors are replaced periodically rather than maintained, reducing long-term costs associated with mechanical component maintenance.
2Measurement precision
If mechanical mass flow meters are used, then mass flow measurement is achieved, but manufacturing cost increases due to complex systems
Solution Approach 1:
The patent replaces expensive mechanical mass flow meters with more cost-effective electronic flow meters. Thermal meters and ultrasonic meters are used, which have fewer components and lower manufacturing costs while providing adequate measurement precision for high-pressure gas applications.
Solution Approach 2:
The patent uses inexpensive disposable flow restrictors made from materials like PTFE or stainless steel capillary tubes. These restrictors are designed to be replaced rather than maintained, significantly reducing manufacturing and maintenance costs compared to mechanical flow meters.
3Measurement precision
If electronic flow meters (thermal, ultrasonic) are used to measure high-pressure gas flow, then measurement capability is provided, but device complexity and cost remain high
Solution Approach 1:
The patent employs flow meters that can handle multiple gas types and pressure ranges with minimal configuration changes. The electronic flow meters are designed to be universally applicable to different high-pressure gas applications, reducing the need for multiple specialized devices.
Solution Approach 2:
The patent extracts and addresses the signal processing complexity as a separate consideration, focusing on the core measurement function. The flow meters are selected or designed to minimize signal processing requirements while maintaining measurement accuracy for high-pressure gas applications.
4Measurement precision
If conventional flow meters are used in high-pressure systems, then flow measurement is achieved, but reliability decreases due to wear and environmental sensitivity
Solution Approach 1:
The patent replaces mechanical flow meters with electronic flow meters that have no moving parts, eliminating wear-related reliability issues. Thermal and ultrasonic flow meters are used, which are inherently more reliable in high-pressure environments as they have no mechanical components subject to wear or environmental sensitivity.
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
Enables precise and reliable measurement of mass flow rate of gases at high pressures with minimal environmental disturbance and low maintenance, suitable for industrial applications requiring high accuracy and durability.
Implementation Method 1
a piezoelectric oscillator in contact with the gas upstream of the orifice
Implementation Method 2
driving the piezoelectric crystal oscillator such that the piezoelectric crystal oscillator resonates at a resonant frequency; measuring the resonant frequency of the piezoelectric oscillator
Implementation Method 3
measuring the mass flow rate of a gas through an orifice through which choked flow occurs
Data Source
AI summary
There is provided a meter (200; 350) for measuring the mass flow rate of a gas. The meter comprises a conduit (206) through which the gas flows in use. The conduit has a flow restriction orifice (212) through which choked flow occurs in use. The flow restriction orifice divides the conduit into an upstream portion (214) upstream of said orifice and a downstream portion (216) downstream of said orifice. The meter further comprises a sensor assembly (204), the sensor assembly including a piezoelectric crystal oscillator (218) in said upstream portion such that said piezoelectric oscillator is in contact with said gas when the meter in use. The sensor assembly is arranged: to drive the piezoelectric crystal oscillator such that the piezoelectric crystal oscillator resonates at a resonant frequency; to measure said resonant frequency of said piezoelectric crystal oscillator; and to determine, from the resonant frequency, the mass flow rate through the orifice.