Cleaning apparatus and method, and monitoring thereof

1. An apparatus comprising:

a hollow body having a rear wall at a rear of the hollow body and a conical element extending forward from the rear wall to an outlet at a front end of the hollow body, the hollow body defining a cavity configured to contain a liquid, the conical element having a conical wall having a circular cross-sectional shape, wherein the conical wall, as seen from inside the conical element, has a concavely curved segment having a first diameter and a convexly curved segment having a second diameter that is smaller than the first diameter and being located between the concavely curved segment and the front end, with a nozzle comprising a nozzle body located at the outlet at the front end of the conical element and configured to receive the liquid from the conical element, and a nozzle outlet configured to discharge a stream of the liquid toward a surface;

an inlet conduit configured to supply an inlet stream of the liquid;

a manifold located at the rear of the hollow body and connected to the inlet conduit to receive the inlet stream, the manifold having a plurality of secondary conduits defining a plurality of inlet flow passages, such that the manifold is configured to divide the inlet stream into the plurality of inlet flow passages, wherein the plurality of secondary conduits are connected to a plurality of inlets positioned at different locations at the rear of the hollow body, each of the inlets being in fluid communication with the hollow body, such that the manifold is configured to introduce the liquid into the cavity defined by the hollow body through the plurality of inlet flow passages and the plurality of inlets;

a common housing containing the rear wall and the conical element of the hollow body and the manifold, such that the rear wall, the conical element, and the manifold are connected together within the common housing, and the nozzle outlet is configured to discharge the stream of the liquid out of the common housing;

an acoustic transducer positioned at the rear wall, the acoustic transducer configured to generate acoustic energy and to introduce the acoustic energy into the liquid contained in the conical element;

a controller configured for controlling the acoustic transducer to generate the acoustic energy by generating pulses of the acoustic energy; and

a gas bubble generator configured to generate gas bubbles within the stream,

wherein the plurality of inlets are located such that the plurality of inlets are configured for introducing the inlet stream into the cavity adjacent to an inner surface of the rear wall and in front of the acoustic transducer.

2. The apparatus of claim 1 , further comprising:

a second controller configured for controlling the gas bubble generator to generate pulses of the gas bubbles into the liquid.

3. The apparatus of claim 1 , wherein the controller is configured for switching the acoustic transducer on and off intermittently to generate the pulses of the acoustic energy.

4. The apparatus of claim 1 , wherein the apparatus includes a modulator configured for modulating an output of the acoustic transducer to generate the pulses of the acoustic energy.

5. The apparatus of claim 1 , further comprising:

a surfactant injector configured to inject surfactant into the stream, thereby controlling a surfactant concentration in the stream,

wherein the surfactant concentration is optimized to prevent coalescence of the bubbles, achieve a desired gas bubble diameter, and achieve a desired gas bubble activity level at the surface.

6. The apparatus of claim 5 , wherein an activity level of the gas bubbles at the surface is configured to be at a high activity level when the surfactant concentration is between 0.003 and 0.015% by volume.

7. The apparatus according to claim 5 , wherein the surfactant injector injects surfactant in an amount configured to result in gas bubbles of a diameter from 15 to 190 μm at the surface.

8. The apparatus of claim 1 , wherein the shape of the conical element assists transmission of the acoustic energy from the conical element to the stream flowing into and through the nozzle and avoids an impedance mismatch between the acoustic energy in the stream flowing through the conical element and the acoustic energy of the stream exiting the nozzle outlet.

9. The apparatus of claim 1 , wherein the conical element is composed of a material that can function as a pressure release interface when fluid is directed thereagainst.

10. The apparatus of claim 1 , wherein the acoustic transducer is configured to generate the acoustic energy as amplitude or frequency modulated acoustic energy based on a configuration of a modulator.

11. The apparatus of claim 1 , further comprising a device for monitoring cleaning of the surface, the device comprising first and second electrodes, forming an electrochemical cell, adapted to be respectively located at a portion of the surface and interconnected by a resistance measuring apparatus.

12. The apparatus of claim 1 , wherein the acoustic transducer has a face adjacent to the rear wall, and the rear wall is circular.

13. The apparatus of claim 12 , wherein the manifold is configured such that the plurality of inlets are distributed around a circumference of the rear wall and in front of the face of the acoustic transducer.

14. A method comprising:

providing an apparatus comprising:

a hollow body having a rear wall at a rear of the hollow body and a conical element extending forward from the rear wall to an outlet at a front end of the hollow body, the hollow body defining a cavity configured to contain a liquid, the conical element having a conical wall having a circular cross-sectional shape, wherein the conical wall, as seen from inside the conical element, has a concavely curved segment having a first diameter and a convexly curved segment having a second diameter that is smaller than the first diameter and being located between the concavely curved segment and the front end, with a nozzle comprising a nozzle body located at the outlet at the front end of the conical element and configured to receive the liquid from the conical element, and a nozzle outlet;

an inlet conduit configured to supply an inlet stream of the liquid;

a manifold located at the rear of the hollow body and connected to the inlet conduit to receive the inlet stream, the manifold having a plurality of secondary conduits defining a plurality of inlet flow passages, such that the manifold is configured to divide the inlet stream into the plurality of inlet flow passages, wherein the plurality of secondary conduits are connected to a plurality of inlets positioned at different locations at the rear of the hollow body, each of the inlets being in fluid communication with the hollow body;

a common housing containing the rear wall and the conical element of the hollow body and the manifold, such that the rear wall, the conical element, and the manifold are connected together within the common housing, and the nozzle outlet is configured to discharge a stream of the liquid out of the common housing;

an acoustic transducer positioned at the rear wall; and

a gas bubble generator configured to generate gas bubbles within the stream;

introducing the liquid from the inlet conduit into the cavity defined by the hollow body through the plurality of inlet flow passages and the plurality of inlets, to discharge the stream of the liquid through the nozzle outlet and toward a surface, wherein the plurality of inlets are located such that the liquid is introduced through the plurality of inlets into the cavity adjacent to an inner surface of the rear wall and in front of the acoustic transducer;

operating the acoustic transducer to generate pulses of acoustic energy and to introduce the acoustic energy into the liquid contained in the conical element, such that the acoustic energy travels down the stream toward the surface; and

operating the gas bubble generator to generate the gas bubbles within the stream.

15. The method of claim 14 , wherein operating the acoustic transducer to generate pulses of the acoustic energy comprises switching the acoustic transducer on and off intermittently to generate the pulses of acoustic energy.

16. The method of claim 14 , wherein operating the acoustic transducer to generate pulses of the acoustic energy comprises modulating an output of the acoustic transducer generate the pulses of acoustic energy, using a modulator.

17. The method of claim 14 , wherein the shape of the conical element assists transmission of the acoustic energy from the conical element to the stream flowing into and through the nozzle and avoids an impedance mismatch between the acoustic energy in the stream flowing through the conical element and the acoustic energy of the stream exiting the nozzle outlet.

18. The method of claim 14 , wherein the conical element is composed of a material that can function as a pressure release interface when fluid is directed thereagainst.

19. The method of claim 14 , wherein the acoustic transducer generates the acoustic energy as amplitude or frequency modulated acoustic energy based on a configuration of a modulator.

20. The method of claim 14 , wherein the apparatus further comprises a controller, and wherein operating the acoustic transducer comprises controlling the acoustic transducer using the controller.

21. The method of claim 14 , wherein the acoustic transducer has a face adjacent to the rear wall, and the rear wall is circular.