Method and apparatus for determining the velocity of a gas flow

A method of measuring velocity of a gas flow, the method comprising the steps of:

• a. exciting a first population of chemical species within the flow with a first laser beam to induce fluorescence and to produce a first population of excited chemical species and producing stable intermediate molecules from the first population of excited chemical species with the first laser beam;
• b. obtaining a location of the first population of excited chemical species by detecting the fluorescence of the first population of excited chemical species at a first time point;
• c. producing a second population of excited chemical species by exciting the stable intermediate molecules with a second laser beam at a second time point;
• d. inducing fluorescence in the second population of excited chemical species with the second laser beam at the second time point;
• e. obtaining a location of the second population of excited chemical species by detecting the fluorescence of the second population of excited chemical species at the second time point,
• f. determining a distance between the location of the first population of excited molecules and the location of the second population of excited molecules and determining an amount of time elapsed between the first and second time points;
• and
• g. calculating the velocity of the gas flow by dividing the distance between the location of the first population of excited molecules and the location of the second population of excited molecules by the amount of time elapsed between the first and second time points.

A method for determining the velocity of an gas flow comprising the steps of:

• a. exciting a first population of oxygen chemical species within the flow with a first laser beam to induce fluorescence and to produce a first population of excited oxygen chemical species;
• b. obtaining a location of the first population of excited oxygen chemical species within the flow by detecting the fluorescence of the first population of excited oxygen chemical species at a first time point;
• c. producing ozone molecules from the first population of excited oxygen chemical species;
• d. producing a second population of excited oxygen chemical species by exciting the ozone molecules with a second laser beam at a second time point;
• e. inducing fluorescence in the second population of excited oxygen chemical species with the second laser beam at the second time point;
• f. obtaining a location of the second population of excited oxygen chemical species within the flow by detecting the fluorescence of the second population of excited oxygen chemical species at the second time point;
• and
• g. calculating the velocity of the gas flow by dividing a distance between the location of the first population of excited oxygen chemical species and the location of the second population of excited oxygen chemical species by an amount of time elapsed between the first and second time points.

Apparatus for measuring velocity of a gas flow, the apparatus comprising:

• a. means for producing a population of stable molecules at a first location within the flow at a first time point;
• b. means for producing a population of excited chemical species in the flow by exciting the stable molecules;
• c. means for inducing fluorescence in the population of excited chemical species at a second location at a second time point;
• d. means for detecting a fluorescence event of the population of excited chemical species at the second location at the second time point.

Apparatus for measuring velocity of a gas flow, the apparatus comprising:

• a. means for producing a first laser beam of a first wavelength at a first location within the flow, the first laser beam exciting a first population of chemical species within the flow, inducing fluorescence in the first population of excited chemical species, and producing stable intermediate molecules from the first population of excited chemical species;
• b. means for producing a second laser beam of a second wavelength at a second location within the flow at a second time point, the second location lying downstream in the flow from the first location, the second laser beam producing a second population of excited chemical species by exciting the stable intermediate molecules at the second time point, inducing fluorescence in the second population of excited chemical species at the second location at the second time point;
• and
• c. means for detecting fluorescence of the first and second populations of excited chemical species at the first and second locations at the first and second time points, the detecting means oriented relative to the flow such that the detecting means observes the intersection of the first laser beam with the flow and intersection of the second laser beam with the flow.

A method of measuring velocity of a gas flow, the method comprising the steps of:

• a. producing a population of stable molecules within the flow at a first location at a first time point;
• b. inducing fluorescence in the population of stable molecules at a second time point;
• c. detecting a fluorescence event of the population of stable molecules at a second location at the second time point;
• and
• d. calculating the velocity of the gas flow by dividing a distance between the first and second locations by an amount of time elapsed between the first and second time points.

A method of measuring velocity of a gas flow, the method comprising the steps of:

• a. producing a population of stable molecules within the flow at a first location at a first time point;
• b. inducing fluorescence in the population of stable molecules at a second time point;
• c. detecting a fluorescence event of the population of stable molecules at a second location at the second time point;
• d. determining a distance between the first location and the second location and determining an amount of time elapsed between the first and second time points;
• and
• e. calculating the velocity of the gas flow by dividing a distance between the first and second locations by an amount of time elapsed between the first and second time points.