Plasma-based electro-optical sensing and methods
This disclosure relates to systems and methods detecting a change in pressure, wall shear flow, or both. The method includes generating DC plasma having an electrical field based on an input DC voltage and a DC current, detecting changes to the electrical field, and identifying a change in wall shear flow, pressure, or both based on the change in the electrical field when the DC plasma is disposed in a flow field.
1. A plasma sensor for a propulsion system, the plasma sensor comprising:
a first electrode coupled to the propulsion system and configured to generate DC plasma with an electrical field as a virtual sensor of the propulsion system based on an input DC voltage and a DC current; and
a probe coupled to the propulsion system and positioned relative to the first electrode to detect a change in the electrical field,
wherein the first electrode and the probe are encapsulated in a cap, the cap configured to confine the DC plasma.
2. The plasma sensor of claim 1 , wherein the cap includes at least one screen, at least one hole, at least one slit, or combinations thereof.
3. The plasma sensor of claim 1 , wherein the cap defines a cylindrical cavity, the cylindrical cavity having a proximal end and a distal end, the proximal end configured to receive the first electrode and the probe.
4. The plasma sensor of claim 3 , wherein the proximal end includes a chamfered interior portion.
5. The plasma sensor of claim 3 , wherein the proximal end includes an interior portion having an elliptically shaped-fill.
6. The plasma sensor of claim 1 , wherein the probe includes at least one Langmuir probe, at least one second electrode, or combinations thereof.
7. A plasma-based sensing system, comprising:
a plasma sensor including:
a first electrode configured to generate DC plasma having an electrical field based on an input DC voltage and a DC current, the first electrode configured to position the DC plasma in a flow field; and
a probe configured to detect a change in the electrical field when the DC plasma is positioned in the flow field;
a power control unit configured to supply the input DC voltage and the DC current to the first electrode;
a current limiting resistor electrically coupled in series with the power control unit; and
a processor in electrical communication with the probe and configured to identify a change in at least one of wall shear flow or pressure based on the change in the electrical field, and to determine a fluid dynamic based on the input DC voltage and the DC current.
8. The system of claim 7 , further including a user interface configured to enable user control of DC plasma properties.
9. The system of claim 7 , further including a display to display the identified change in pressure.
10. The system of claim 7 , wherein the processor is further configured to:
determine a plasma property including sheath potential (φpl(0), electron number density (ne), floating potential (φf(t)), or combinations thereof.
11. The system of claim 7 , wherein the processor is further configured to determine pressure based on the input DC voltage and the DC current of the first electrode.
12. The system of claim 7 , wherein the first electrode and the probe are encapsulated in a cap, the cap configured to confine the DC plasma.
13. The system of claim 7 , wherein the plasma sensor further includes a conductive, porous cap disposed over the first electrode and the probe, the cap configured to confine the DC plasma.
14. The system of claim 13 , wherein the cap includes ceramic.
15. The system of claim 9 , wherein the probe includes a Langmuir probe.
16. The system of claim 9 , wherein the probe includes a second electrode.
17. A method for detecting a change in pressure and wall shear flow, the method comprising:
generating DC plasma having an electrical field based on an input DC voltage and a DC current;
positioning the DC plasma in a flow field;
detecting a change in the electrical field of the DC plasma;
identifying a change in at least one of wall shear flow or pressure based on the change in the electrical field; and
determining a plasma property including sheath potential (φpl(t)), electron number density (ne), floating potential (φf(t)), or combinations thereof.
18. The method of claim 17 , the method further including:
determining a change in a local pressure dynamic field.
19. The system of claim 7 , wherein the plasma sensor is coupled to a propulsion system.
20. The system of claim 7 , wherein the processor determines a change in a local pressure dynamic field based on the plasma property.