EP1261382A1 - High energy chamber - Google Patents

Abstract

A method of and apparatus for generating a high density of electromagnetic energy within a chamber or conduit having a fluid therein is described. The energy is provided by a laser beam which is reflected by mirrors within a fluid carrying chamber or conduit in a helical path so as to create a high energy flux within the fluid throughout the chamber. Various embodiments of the invention are described.

Description

HIGH ENERGY CHAMBER

The invention relates to a method of distributing by reflection into a chamber at least one high energy electromagnetic radiation beam according to a specific pathway which provides the chamber with a particularly high density of energy.

Conventional decontamination systems are inefficient at killing or filtering a range of harmful pathogens including, for example: certain strains of influenza, tuberculosis, cryptosporidium, aspergillus niger, legionaires and anthrax. Intense light energy sources have been demonstrated to kill these resistant organisms, and benefit is expected from developing laser technology. More specifically, high average and peak power can create reactions and catalytic effects on a molecular level. This energy can be used to destroy pathogens, create combustion effects or catalyze reactions. The energy can alter or otherwise modify the molecular, biochemical, nuclear or atomic structure of a substance. Further, the US EPA now sells "rights to pollute" in open markets. Companies that reduce their emissions are able to sell the permits which they do not use while overpolluters must purchase these rights .

Laser and incoherent light decontamination of surfaces and liquids has been investigated for a range of lasers and light sources but no technology has been developed that is viable economically or has been optimised for delivery of laser or incoherent sources of light, UV or infra-red, RF or Microwave energy. It is convenient to define these wavelength ranges as light. Lasers have historically been too expensive and their deployment too inefficient to develop into a commercially viable decontamination or combustion processes . Laser sources are becoming cheaper and the development of high power solid state lasers will open new opportunities to exploit laser decontamination and combustion applications. Furthermore, there will be development of laser diodes in the blue end of the spectrum, and there will be continued emphasis on developing shorter wavelength sources to maximise the information storage on CD or other optical based storage systems. High power laser diode sources are available from the red to IR part of the spectrum and the future will see development towards the blue and UV end of the spectrum. These devices can be mass-produced cheaply. Development of optics and active optic systems will lead to efficient collimation of incoherent sources that may make them suitable for implementing in systems like the one of the present invention. The future development of optics technology makes these systems even more viable economically. Therefore there is a need for a method and/or apparatus to distribute and effectively amplify electromagnetic radiation energy for the treatment for example decontamination) of air, gas , water and other fluids with the potential to increase the throughput and make such systems viable . Additionally such systems can be used as the basis for efficient laser combustion systems .

According to the present invention there is provided apparatus for providing exposure of a fluid to electromagnetic radiation, said apparatus comprising: - a fluid chamber having an inlet and an. outlet and internal walls; - at least one electromagnetic radiation beam generating means; and - reflection means shaped and positioned on the internal walls of the chamber so as to reflect the electromagnetic radiation beam at least three times within the chamber according to a predetermined pathway which distributes the beam in order to substantially fill the chamber with energy.

Typically, the beam is reflected according to a direction substantially perpendicular to the flow of fluid to be treated.

Preferably, the electromagnetic radiation is a laser. For example, it may be UV, IR or visible light.

The present invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. la is a representation of a first embodiment of the invention which shows a schematic cross-sectioned view of the chamber of the apparatus and the radiation beam reflection pathway;

Fig. lb is a schematic representation of the radiation beam pathway according to the first embodiment of the invention which shows a two-dimensional rendition of two sets of twisted helixes;

Fig. lc is a schematic representation of another embodiment of the invention which shows a cross-sectioned view of the chamber of the apparatus and the radiation beam reflection pathway. For the purpose of illustration, only one reflection from the second strand back to first strand is shown;

Fig. 2 is a schematic representation of a third embodiment of the invention wherein the radiation beam reflection pathway is shown by transparency;

Fig. 3a is a cross-sectioned schematic representation of a fourth embodiment of the invention;

Fig. 3b is three-dimensional cross-section of the fourth embodiment of the invention showing the repetition of the star-shape pattern throughout the chamber of the apparatus;

Fig. 3c is a frontal view of Fig. 3b with the addition of a third and fourth strand being added, and

Fig 4 is a schematic diagram of an apparatus in accordance with a first embodiment of the invention being coupled to a feedback for controlling irradiation of the fluid. According to a first embodiment of the invention which is shown in Fig. la an apparatus 16 is provided which comprises an enclosed conduit 10 throughout which a fluid (not shown) to be treated flows. The conduit 10 is provided with a number of reflectors or mirrored facets 12. Single or multiple lasers or electromagnetic energy sources emit a single or multiple radiation beam 14 that may be either continuous wave or pulsed. In this example, the radiation is light but this need not always be the case. This light beam 14 is fed into the conduit 10 and reflected by mirrors 12 throughout the volume. The light beam 14 bounces inside the system many times in a helical pattern and efficiently fills the conduit 10 with the electromagnetic energy (in this example, light energy) . The multiple reflections from the mirrors 12 have the effect of amplifying the exposure that the contaminants contained in the fluids flowing through the conduit 10 receive. In essence, the apparatus 16 of Fig. la can create an effect of hundreds of light beams with a single unit. This results in an increase in the peak and main power within the conduit 10.

The light beam 14 strikes the first mirror 12a of the helix, within the conduit 10, and the light is reflected to the second mirror 12b that is positioned across the diameter or width of the conduit 10, from where it is reflected to the third mirror 12c of the helix, on the other side of the conduit. The light beam 14 makes many reflections as it travels in a helical pathway down the length of the conduit 10, crossing back and forth.

The total energy density received can be calculated by any person competent in the area of optics and decontamination. Quite clearly the energy density received will be dependent on the type of electromagnetic radiation used (in the case of laser, laser parameters like pulse energy, pulse width, pulse repetition, frequency, beam size) and velocity at which the contaminant is moving through the system. The applied energy density required to achieve the desired process is dependent on the process, the type of electromagnetic radiation beam and the rate of flow of the fluid. The device can be easily optimised for each particular application.

Referring now to Fig lb, as the first double strand helix 20 comes to the end of its journey, it is possible for a second helix to be generated that travels in the opposite direction to the first helix and out of phase therewith. Any number of helixes can be used provided the energy density is sufficient to achieve the required process; this is dependent on the factors described previously. In this way, there will be multiple radiation beams (for example, laser beams) crossing each other many times within the conduit, provided that the pulse length of the laser beam multiplied by the speed of light in the medium is greater than the path length travelled by the beam. In this way, the apparatus according to the invention can be designed so that the contaminant will interact with more than one beam at a time. This results in an additive or amplification effect of the energy. The magnitude of the amplification can be calculated by considering how the beam is attenuated through the system and how many beams intersect at any given point and adding up the resultant spatial energy density profile of the multiple helix system. The beam diameter and the phase between the different helixes can be optimised for any particular application.

To compensate for the loss in energy density as the beam travels down the helix it is possible to make the facets concave, their radius of curvature may be a function of the distance from the first mirror and the number of facets the beam has struck. Additionally this compensates for a diverging electromagnetic radiation beam. If the device creating the beam is a laser then its output mode i.e. its spatial energy distribution has to be considered with the optimisation process for the helix. If the beam has a top-hat distribution then the size of the reflecting facets can be quite close in size to the beam. To reduce diffraction losses and in general optimise the performance of helix the size of the mirrors, their reflectivity profile and radius of curvature can be optimised along its length. These effects can be calculated by any competent person with knowledge of electromagnetic beam propagation and optics.

The electromagnetic radiation projected into the apparatus 10, may come from more than one coherent or incoherent electromagnetic radiation source from any wavelength range. For example, biological and molecular decontamination, require wavelengths of approx 260nm and for thermal effects light at 900 nm - 30 μm is most efficient.

Laser diode arrays operating at 975 nm are useful in that this corresponds to a peak in the absorption spectrum of water. For incoherent sources normal collimating optics are used to ensure propagation of the light through the system. Alternatively a number of sources could be arranged in a helical path down the outside of the conduit with suitable windows on the conduit to allow transmission of the light into the conduit. The windows would be made of material that is appropriate for passing the wavelengths that are most efficient for the process application.

There may be economic benefit from using 355 ran, in that the efficiency and lifetime of the optics are greater than at 260 nm. The light may be generated from Nd:YAG lasers or KrFl excimer lasers, or laser diodes or laser diode arrays, light emitting diodes or any other light source. The beam may be delivered to the system of mirrors within the system using fibre optics, mirrors, and/or diffractive optics operating in reflection or transmission or using scanning optics.

There will be economy of scale at which point it is no longer sensible to have further reflective optics when the benefit gained from additional mirrors does not yield any further benefit to the process, be it decontamination or changing the molecular properties of a material, for example Volatile Organic Compounds (VOCs). Furthermore, because of the natural reduction in the energy of the beam as it travels through the system, it will not be necessary to have optics beyond the position at which the energy density is below that required to achieve the process i.e. in the case of decontamination it will be below the threshold energy density to give the required level of sterility assurance for a particular contaminant or the required exposure to reduce the level of VOCs to an acceptable limit. However, the shape of the conduit may be altered to adjust the rate of flow of the medium through it such that it has a longer contact time in the beam where the energy density of the beam has been reduced.

The last mirror of the system could be partially transmissive, and a detector could be placed behind it to measure the energy transfer through the system and determine whether the system is functioning properly. Other sensor systems can include a detector or series of detectors to measure the scattered light, or conventional particle counters for monitoring the particles. A system could be implemented before, during and/or after the helix. Data collected by the sensors would be used as feed-back to determine, control and optimise the efficiency of the system. For example, error control signals would be generated to control the electromagnetic energy sources for optimum use. If the substrate is relatively clean then a lower power can be used, if the substrate is highly contaminated then a higher power will be needed. The sensor system increases the overall efficiency of the system.

If the absorption through the fluids is known and the energy loss through the system is measured by one of the monitoring/sensing systems then the quality of the optics can be ascertained and appropriate action taken. The sensor system allows for quality control measures to ensure that complete destruction or reaction has been achieved.

The flow of the contaminated fluid through the system has to be optimised. Aerofoils placed strategically through any of the systems will help the flow stability and uniformity. For some turbid fluids there may be an advantage in deliberately introducing turbulence into

system will be dominated by the losses associated with the mirrors . If the initial energy density is many times higher than the killing threshold then the beam can make many reflections before the energy density is below the threshold to give the desired level of decontamination or sterility.

As with the multiple helix design with the electromagnetic radiation bouncing up and down the conduit, it is possible to have multiple helixes originating from the same end of the conduit with or without the return helixes incorporated into the system. Here there may be multiple sources hitting the first mirror of each helix or a single source and mirror system designed to strike each first mirror of several helixes in turn or in any desired combination. It is possible to have the source or sources at one or either end of the conduit, or to use mirrors to input the radiation to each helix from either end of the system. The helix itself may rotate and one or multiple sources be used. In these cases the firing of the electromagnetic radiation source and alignment of the mirrors can be done by using optical sensors or otherwise to detect when the optics are in the correct position and triggering the electromagnetic radiation sources as appropriate.

The conduit could contain two or more distinct sets of helixes that are used to distribute two or more different wavelengths. For example one helix may be utilised to produce a photochemical effect associated with a UV laser while simultaneously a second laser energy is reflected off a secondary grouping of helixes which produce a photothermal effect associated with IR lasers. Fig 2 is an example of a tapered helix for a conical-based conduit. At the narrow part of the tube the medium will be travelling faster and will spend less time in the beam than at the wider part of the tube. Hence the energy density at the thinner end will have to be greater and this will be the position where the electromagnetic radiation is injected into the helix. At the wider part of the conduit, the flow will be slower and the energy density will be lower, so this is suitable for the beam after it has experienced some attenuation. Alternatively, if the radiation is injected into the wider end first, then a higher energy density will be given to the material as it flows through the system.

An alternative to the double strand of reflectors that has been described hereinabove in the first, second other embodiments is to reflect the electromagnetic radiation beam according to a plane perpendicular to the flow of fluid. This is achieved with the embodiment of the invention which is shown in Fig. 3a where the beam is reflected in a plane according to a star shape pattern.

As can be seen in Fig 3a, the apparatus is provided with a chamber or conduit 110 throughout which a fluid to be purified or catalyzed is passed. The apparatus is provided with means to introduce a electromagnetic radiation beam 114 into it which is directed to a first reflector or mirror 112a which directs it to a second reflector 112b and then to a third reflector 112c and so on in order to accomplish a revolution.

A star shaped pattern is formed whereby the electromagnetic radiation (eg. light) would first bounce within a plane several or many times before being reflected down the conduit to a primary point on a secondary star shape, this process continues down the length of the conduit.

In this way, any contaminant that crosses the irradiated planes will effectively encounter a superpositioning of many radiation beams. The amplification can be calculated in a similar way as before by any competent person knowledgeable in the field. The electromagnetic radiation beam can be made to pass through the plane in any number of configurations. As an example, the first beam can pass through the centre of the conduit, strike the first mirror on the far wall of the conduit, from where it is reflected to a second mirror positioned close to the entry point of the first beam, it is then reflected through the middle of the conduit, such that it passes through the position where the first beam went, it strikes the third mirror positioned close to the first mirror, from where it is reflected towards a mirror positioned close to the second mirror. The beam reflected from this mirror passes through the centre of the conduit and strikes a mirror positioned close to the third mirror. In this way, the beam is passed many times through the centre of conduit forming a multiple star pattern, a substance passing through this plane experiences an amplified effect of the radiation beam. The last optic in the plane reflects the radiation towards the first mirror of the next star pattern further down the conduit slightly out of phase with the first star pattern. The radiation bounces around this star pattern and is finally reflected to the next set of mirrors on the third plane, again out of phase with the second star. The first mirror of each plane may form a helix shape through the length of the conduit, so that the radiation completely fills the conduit. Spinning optics and/or multiple sources can be used to fire the electromagnetic radiation beam into different planes. The planes may be separate or overlap so as to completely fill the conduit.

This system could be incorporated with the helix or multiple helixes described above, where many electromagnetic radiation beams interact with each other. These systems could be designed so that interference and diffraction patterns are deliberately generated increasing the maximum intensity available from the systems. The interference patterns could be stepped through the conduit in a helical pattern giving a good fill geometry to the system.

Referring now to Fig 3b, after completion of the first perpendicular star shape, the last reflector 120 on the first star would be aimed at the first point 122 on a secondary star slightly further down the length of the conduit and slightly out of phase with the original star. These would be arranged in a helical pattern whereby each star would be slightly out of alignment with the previous star shaped pattern whereby the stars would descend down the length of the conduit in a helical shape.

If one more than one wavelength source is used then multi-photon ionization processes may occur that result in transformation of harmful pathogens or high levels thereof into safe or safer ones or more efficient combustion processes.

Systems could be attached to smokestacks and other pollution producing or gas expulsion or bi-product diffusion systems to reduce the negative environmental impact of the off gases . Similarly, polluted water or other liquid agents could be treated to reduce the environmental impact.

A secondary catalytic effect could be created whereby the initial stage of decontamination may use a coherent light source or other electromagnetic energy source then followed by the use of an incoherent light source, such as a xenon flashlamp or other electromagnetic energy source or vice versa. During one or both of these processes a gas stream could be introduced to further facilitate a beneficial catalytic effect.

In some cases the photochemical effect will produce ozone which could further aid in a catalytic effect whereby a molecular "scrubbing" would occur.

In some cases a secondary gas or liquid could be introduced into the helix chamber. This could produce several desirable effects including osmosis, reaction or bonding. For example one could introduce a hydrocarbon based fuel into a chamber and simultaneously introduce pure oxygen. The effect of for example, an IR laser, would be to create a more complete combustion of the material.

One could also create compounds whereby two elements or compounds would be introduced into the chamber and either a photochemical or photothermal or other electromagnetic energy effect would occur to create a different molecule or compound. Additionally, other reactions could be created by the same principal including atomic and or nuclear reastions.

The helix could be used as a preheater of materials to be burned or otherwise heated.

Economic benefits would include a reduction in the volume of waste being generated. This would equate to a direct economic benefit in that fines can be imposed to companies that over pollute.

Formulas will be created to weigh the overall cost per unit of energy, the specific application, throughput, reaction to peak vs mean power, molecular effects, coupling and economic factors.

Certain processes and effects are dependant on high peak power but are not cessarily reliant on high mean power. This can aid in reducing the costs by looking at the specific effects created by these factors and matching them to their application.

In some cases the catalytic effect could be used to produce a more complete disintegration of the material being treated. This could include liquid gas and gas compounds. This effect could be utilised to, for example, create the complete combustion of a hydrocarbon based fuel whereby the fuel would be exposed to large amounts of electromagnetic energy. Such applications could include for example a laser combustion engine, a laser turbo booster, or laser jet engine. In this case an IR laser may be more effective. One could ignite, for example, hydrogen using apparatus in accordance with the present invention.

The shape of the helix could be advantageous from a aero/fluid dynamic standpoint in that the helix could be abutted by a fin in order to keep debris away from the reflective facets. This would also keep the gas or liquid moving in a desirable direction from a control standpoint. The fins would act to create venturi, vortexes or screw shapes and could be modified and adapted to create desirable effects .

On the last mirror could be a sensor to monitor the level of electromagnetic energy being produced. This would allow for quality control measures to ensure that complete destruction was being achieved.

Reference is now made to Fig. 4 of the drawings which depicts a schematic diagram of apparatus according to a first embodiment of the invention in which a cylindrical conduit 10 has an inlet 10a and an outlet 10b through which fluid to be treated flows. The conduit has a plurality of mirrors 12 disposed on the internal surface. When a laser source 13 emits a laser beam 14 into the conduit via window 15 it is reflected by the mirrors respective forward and reverse helical paths 17, 19 to create a high level of electromagnetic energy throughout the conduit 10. The conduit 10 has a partially optically transmissive window 21 through which some laser light passes and impinges on a photo-detector 23 disposed at the window. The photo-detector generates a signal which is amplified by amplifier 25 and which is then fed back to be compared with an input 27 signal, in a summation block 29, as is well known in the art, so that the output of the summation block is the input signal 31 to the laser light source 13 is modified to control the power of the laser beam 14 and hence the energy in the chamber applied to the fluid thus optimising the system.

Modifications and improvements may be made to the foregoing without departing from the scope of the invention. For example, the embodiments hereinbefore described may be used for fume scrubbing or combustion where a high energy density is required. References

1. Ward, G., Watson, I. A., Stewart-Tull , D., Wardlaw, A., Chatwin, C.R. ' Inactivation of bacterial and yeasts on agar surfaces with high power Nd : YAG laser light', Letters in Applied Bacteriology, 23, 136- 140. ISSN 0266 8254. 2. Photonics Spectra, Lasers aid in bacteria destruction, February 1998, 32(2), 45. Laurin Publishing Company, Inc., Berkshire Common, PO Box 2037, Pittsfield MA, 01202-2037, USA. 3. Ward, G., Watson, I. A., Stewart-Tull, D., Wardlaw, A. 'Inactivation of E.coli. in liquid suspension with Nd:YAG laser light', Seventh International Congress on Engineering and Food, Brighton April, 1997. 4. Wang, R. K., Ward, G., Watson, I. ., Stewart-Tull, D., Wardlaw, A. 'Temperature distribution of Escherichia . coli. liquid suspensions during irradiation by a high power Nd:YAG laser irradiation for sterilization applications', Journal of Biomedical Optics, 2/3, 295-303, May 1997. ISSN 1083-3668/97. 5. Watson, I., A., Ward, G., Wang, R., Sharp, J., Budgett, D., Stewart-Tull, D., Wardlaw, A., Chatwin, C. (1996) Comparative bactericidal activities of lasers operating at seven different wavelengths. Journal of Biomedical Optics, 1(4), pp 1-7. ISSN 0140-018/97.

Claims

1. Apparatus for providing exposure of a fluid to electromagnetic radiation, said apparatus comprising:

- a fluid chamber having an inlet and an outlet and internal walls;

- at least one electromagnetic radiation beam generating means; and

- reflection means shaped and positioned on the internal walls of the chamber so as to reflect the electromagnetic radiation beam at least three times within the chamber according to a predetermined pathway which distributes the beam in order to substantially fill the chamber with energy.

2. Apparatus as claimed in claim 1 wherein the beam is reflected according to a direction substantially perpendicular to the flow of fluid to be treated.

3. Apparatus as claimed in claim 1 or 2 wherein the electromagnetic radiation is a laser.

4. Apparatus for irradiating a fluid with electromagnetic radiation, said apparatus comprising:

a chamber for receiving a fluid, said chamber having a fluid inlet and a fluid outlet and an internal surface;

at least one electromagnetic radiation source for generating at least one beam of electromagnetic radiation within said chamber; a plurality of beam reflectors coupled to said internal surface for reflecting said beam of electromagnetic radiation in a substantially helical path within said chamber to substantially fill said chamber with electromagnetic energy.

5. Apparatus as claimed in claim 4 wherein said chamber is a conduit of substantially uniform cross-section throughout the length of said conduit.

6. Apparatus as claimed in claim 4 wherein the said chamber is a conduit having a cross-section which changes throughout the length of said conduit .

7. Apparatus as claimed in any preceding claim wherein the substantially helical path is provided by mirrors helically arranged around the internal surface in a helix or by mirrors arranged in spaced parallel planes and which reflect the beam a plurality of times within a plane then into an adjacent plane.

8. Apparatus as claimed in any one of claims 4 to 7 wherein said at least one electromagnetic radiation source is a laser.

9. Apparatus as claimed in claim 8 wherein two laser sources are used to provide two separate laser beams .

10. Apparatus as claimed in claim 8 or claim 9 wherein said laser beams are reflected by said beam reflectors to transcribe helical laser beam paths within said chamber.

11. Apparatus as claimed in claims 8 or 9 wherein said beam reflectors are coupled to said internal surface to cause said laser beam to be reflected in a plane substantially orthogonal to a main fluid flow direction within said chamber before said beam is reflected to a parallel plane.

12. Apparatus as claimed in any one of claims 10 to 11 wherein said laser beams are of different wavelengths .

13. Apparatus as claimed in any preceding claim wherein said beam reflectors are coupled to said internal surface in a helical pattern.

14. Apparatus as claimed in any preceding claim wherein said beam reflectors are coupled to said internal source in a plane substantially orthogonal to the direction of flow of said fluid.

15. Apparatus as claimed in any preceding claim wherein said beam reflectors are mirrors having a concave reflecting surface disposed towards said electromagnetic beams.

16. Apparatus as claimed in any preceding claim wherein said chamber defines a plurality of windows for permitting said electromagnetic beams to pass therethrough and enter said chamber.

17. Apparatus as claimed in any preceding claim wherein said plurality of windows are helically arranged around said chamber, and a plurality of electromagnetic beam sources are disposed at said windows for transmitting said beams into said chamber.

18. Apparatus as claimed in any preceding claim wherein at least one of said beam reflectors is partially optically transmissive for transmitting at least some beam radiation from said chamber, said apparatus including an electromagnetic beam detector coupled to said partially optically transmissive window for detecting radiation passing therethrough.

19. Apparatus as claimed in any preceding claim including a feedback loop coupled between said detector and said electromagnetic beam source for generating error signals for controlling the amount of electromagnetic radiation generated by said source.

20. A method of irradiating a fluid with electromagnetic radiation comprising the steps of

passing said fluid through a chamber, irradiating said chamber with a first beam of electromagnetic radiation, and

reflecting said beam within said chamber in a substantially helical path to fill said chamber with electromagnetic energy.

21. A method as claimed in claim 20 including the step of reflecting said beam from mirrors arranged in a helical path.

22. A method as claimed in claim 20 wherein including the step of sequentially reflecting said beam in successive parallel planes within said chamber such that said beam effectively transcribes said helical path.

23. A method as claimed in claim 19 or claim 20 including the step of irradiating said fluid with at least two electromagnetic beams of different wavelengths .

24. A method as claimed in any one of claims 20 to 23 wherein said method includes the steps of,

detecting the level of electromagnetic energy within said chamber,

generating a signal corresponding to said detected level, comparing the detected signal with an incident signal level being used to energise said chamber, and adjusting the level of the incident signal to control the level of electromagnetic energy within said chamber to a predetermined value.