Method of, and apparatus for, regulating the mass flow rate of a gas
AssigneeAir Products and Chemicals, Inc.
InventorNeil Alexander Downie
Life of this patent
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Abstract
There is provided a method of automatically controlling the mass flow rate of a gas through an orifice through which, in use, choked flow is arranged to occur. The method uses an electronic valve located downstream of a gas source, a piezoelectric oscillator in contact with the gas upstream of the orifice and downstream of the electronic valve and a temperature sensor. The method comprises: a) driving the piezoelectric crystal oscillator at a resonant frequency b) measuring the resonant frequency of the piezoelectric oscillator c) measuring the temperature of the gas; and d) controlling the electronic valve in response to the resonant frequency of the piezoelectric oscillator and the temperature of the gas in order to regulate the mass flow rate of gas through said orifice.
Claims17
A method of automatically controlling the mass flow rate of a gas through an orifice through which, in use, choked flow is arranged to occur, the method using an electronic valve located downstream of a gas source, a piezoelectric oscillator in contact with the gas upstream of the orifice and downstream of the electronic valve and a temperature sensor, wherein the piezoelectric oscillator has a resonant frequency which is proportional to the density of the gas upstream of the orifice, and wherein the density of gas upstream of the orifice is, under choked flow conditions, proportional to the mass flow rate through the orifice, the method comprising:
- a) driving the piezoelectric oscillator at the resonant frequency;
- b) measuring the resonant frequency of the piezoelectric oscillator;
- c) measuring a temperature of the gas;
- and
- d) controlling the electronic valve by means of an electronic feedback loop in response to the resonant frequency of the piezoelectric oscillator and the temperature of the gas in order to regulate the mass flow rate of the gas through said orifice.
A method according to claim1, the method further using a further piezoelectric oscillator in contact with the gas downstream of the orifice;
- and wherein step a) further comprises driving the further piezoelectric oscillator at a resonant frequency;
- step b) further comprises measuring the resonant frequency of the further piezoelectric oscillator;
- and step c) further comprises controlling the electronic valve in response to the resonant frequency of the piezoelectric oscillator, the resonant frequency of the further piezoelectric oscillator and the temperature of the gas in order to regulate the mass flow rate of gas through said orifice.
A controller for regulating the mass flow rate of a gas, the controller being operable to control automatically the mass flow rate of a gas through an orifice through which, in use, choked flow is arranged to occur, the controller comprising an electronic valve located downstream of a gas source, a piezoelectric oscillator in contact with the gas upstream of the orifice and downstream of the electronic valve and a temperature sensor, wherein the piezoelectric oscillator has a resonant frequency which is proportional to the density of the gas upstream of the orifice, and wherein the density of gas upstream of the orifice is, under choked flow conditions, proportional to the mass flow rate through the orifice, the controller being operable to:
- drive the piezoelectric oscillator at a resonant frequency;
- measure the resonant frequency of the piezoelectric oscillator;
- measuring a temperature of the gas;
- and control the electronic valve by means of an electronic feedback loop in response to the resonant frequency of the piezoelectric oscillator and a temperature of the gas in order to regulate the mass flow rate of the gas through said orifice.
Dependencies are inferred from the claim text.