CN112649331A - Particle measuring system - Google Patents

Abstract

A system for detecting the size distribution and mass concentration of particles in a particulate gas or liquid by separating the sensing element from the electronic unit and interconnecting using optical fibers, only the sensing element needs to withstand harsh environmental conditions. This reduces design constraints on the electronics, allowing integration of optical components into a sensing probe capable of withstanding high temperature and high pressure environments.

Description

Particle measuring system

Technical Field

The present invention relates to a particle measurement system that includes one or more sensor probes connected by fiber optics or cables to one or more isolated electronic units to detect dust particles or debris within an engine, such as a gas turbine engine. The system is also applicable to air and liquid media.

Background

The present invention addresses the need to characterize particles in harsh environments. Its initial inspiration comes from the need to quantify particulate intake of aircraft gas turbine engines used on aircraft. Such aircraft are increasingly required to operate in harsh environments, particularly those in which a significant amount of dust and sand is present. The ingestion of dust by the gas turbine engine can lead to hardware corrosion, channel plugging, and deterioration of the cooling system. This can lead to reduced engine performance and ultimately to engine failure. Engine manufacturers and customers prefer to implement real-time health monitoring to detect airborne sand/dust and infiltrate it into the core of the engine where the most severe damage is likely to occur. The existing particle measurement systems are not robust enough and cannot be adapted to the harsh environment within a gas turbine engine. The extreme temperature range of such harsh environments is-100 ° F (-73 ℃) to 570 ° F (-300 ℃) or higher, and the pressure range is 0 psia (0 MPa) to 250 psia (1.7 MPa) or higher. For example, a conventional particle measurement system, an optical particle sensor that integrates a laser source and detector electronics, may not survive or function properly under such extreme conditions. Furthermore, as governments impose increasingly stringent regulations on engine exhaust Particulate Matter (PM), monitoring of these emissions becomes critical.

The use of light scattering methods for particle characterization has been repeatedly demonstrated for pollution monitoring in clean facilities, pharmaceutical and food preparation, indoor air quality indication, etc. And monitoring environmental pollution caused by industrial and vehicular emissions, biomass combustion, volcanic activity, and dust excursions caused by wind and vehicles. These methods are suitable for relatively benign environments where temperature and pressure do not differ significantly from atmospheric conditions. Particle measurement systems employing these methods typically integrate the sensing probe assembly and electronic processing and control components into one unit. Thus, more delicate components of a particle measurement system are generally not able to survive in harsh environments. Furthermore, most particle measurement systems use electrical signals that are susceptible to electromagnetic interference (EMI) in the vicinity of harsh environments.

Thus, by separating the passive optical elements from the temperature (and condition) sensitive elements (e.g., lasers and electronics within the electronics), only the sensor probe elements are exposed to the harsh environment. Furthermore, since the optical fiber is used to connect the sensor probe and the electronics unit, the system is also more resistant to electromagnetic interference effects. To survive in harsh environments, sensor probes are typically a sealed device and, therefore, can be used in both gaseous and liquid environments.

Disclosure of Invention

In general, the present invention relates to, but is not limited to, measuring the size, size distribution and mass concentration of particles in harsh environments. In particular, the invention relates to the design and construction of devices for making such measurements using light scattering or light obscuration. The device has a sensing element connected to the electronics by an optical fiber, enabling the electronics to be remotely located and isolated from the harsh environment. The sensing element within the sensor probe, the optical fiber or cable, and the electronics within the electronics unit together constitute the novel particle measurement system outlined in the present invention.

The sensor probe of the particle measurement system contains the optical elements required to manipulate the emitted and received light into and out of the detection zone. Light transmitted from the interconnecting optical fiber to the sensor probe is directed to the detection zone by suitable optical components known to those skilled in the art. Scattered light from the detection zone is received by the same or a separate optical element and transmitted from the sensor probe by the same or a separate optical fiber. Thus, only optical elements are required within the sensor probe, enabling the sensor probe to withstand the extreme conditions of a harsh environment. All components of the sensor probe can be selected by suitable materials and designed to withstand low or high temperatures, low or high pressures, and electromagnetic interference. Many housing materials and optical materials known to those skilled in the art are capable of withstanding various pressure and temperature extremes. For example, a sensor probe with a stainless steel housing, silicon fiber and optical elements made of silicon or sapphire can withstand temperatures as low as 1000 ° F (538 ℃). Since the signals within the sensor probe are optical, the sensor probe itself has the ability to resist electromagnetic interference. The various components of the sensing probe may be secured together by various methods known to those skilled in the art, including fusion, adhesives (epoxies, cements, etc.), and mechanical attachments (clamps, set screws, etc.). The method used to secure the components together may impose additional limitations on the allowable pressure and temperature ranges. For example, using an epoxy with an upper limit of 250 ° F (121 ℃) to secure the components together imposes this temperature limit on the sensing probe itself.

An interconnecting optical fiber or cable transmits light between the sensor probe and the one or more electronics units. These fibers may include connectors at both ends of the fibers or at both ends. When multiple optical fibers are incorporated into one cable, the cable end may similarly include multiple or a single connector at either or both ends of the cable. When the connector is not included on the fiber or cable end, individual fibers are secured within the sensor probe or electronics, respectively, to properly direct the light.

The electronics unit contains a light source, an optical detector and additional optical and electronic components to provide light to the sensor probe and receive light collected from the same probe. Each light source (e.g., laser) is coupled into an optical fiber using methods known to those skilled in the art. The optical fiber is then connected to the outside of the electronics unit or directly to the sensor probe. Furthermore, an optical fiber containing a light source may be connected to the fiber coupler to allow bi-directional transmission of light to and from the sensor probe. Each optical detector may also be coupled into an optical fiber using methods known to those skilled in the art. The optical fiber may then be connected to the outside of the electronic device or directly to the sensor probe. Furthermore, an optical fiber coupled to the detector may be connected to the fiber coupler to allow bi-directional transmission of light to and from the sensor probe. The electronics are used to drive the light source, adjust the output of the detector, and may incorporate additional signal processing capability into the electronics unit.

Multiple light sources of different wavelengths may also be used to achieve a wavelength dependent response. When multiple light sources with different wavelengths are used, light from a single fiber with a return signal can be transmitted through a wavelength dispersive or wavelength selective element using methods known to those skilled in the art. This is useful where a wavelength dependent scattering response can be expected.

Using light source illumination, the particles scatter light in all directions through the sensing location. An optical detector aimed at the sensing location from any direction responds to the passing particles by generating a pulse signal, the amplitude of which may depend on particle diameter, particle shape and particle composition. The amplitude of the pulse signal may be monotonically related to the particle diameter for a particular detector orientation and arrangement. For such an orientation, pulses are received over time, and a histogram of particle diameters can be generated to provide particle size distribution and other particle statistics including average particle size. Calculating the total number of particles passed over a finite time period can provide a particle loading rate (also referred to as a total concentration and the like). Given the distribution of particles over a finite measurement time, in combination with a known mass density of the particles, the mass concentration can be determined. Thus, with signal processing, the passage of multiple particles can produce a number of particle statistics, including particle size distribution, particle loading rate, and mass concentration. This type of signal processing, known to those skilled in the art, may be performed in hardware or software.

Drawings

Fig. 1 shows the concept of a particle measurement system with a sensor probe, an electronics unit comprising a light source and a detector, and interconnecting optical fibers.

FIG. 2 illustrates an example implementation of an engine-based particle measurement system having a laser light source and two optical detectors.

Fig. 3 illustrates a complete sensor system including a sensor probe and sensor electronics interconnected with optical fibers, a signal processing unit, and local or remote display and control.

Detailed Description

The above and other objects and advantages of the present invention will be readily apparent to those skilled in the art from a reading of the following description of the embodiments of the invention. The description and drawings illustrate exemplary embodiments of the invention and enable one skilled in the art to make or use the invention, and are not intended to limit the scope of the invention in any way. The steps are exemplary in nature and, thus, the order of the steps is not necessary or critical to the methods disclosed and described.

As used herein, the terms "first," "second," "third," and "fourth" may be used interchangeably to distinguish one component from another component and are not intended to denote the position or importance of a single component.

The present invention uses an in-situ approach in which the light source, detector and electronics are separated from the harsh measurement area in the sensor probe using fiber optic cable interconnections. Several interconnected optical fibers transmit the light source to the detection zone and may also transmit the measured scattered light back to the detector simultaneously through a cable connector or connectors. The fiber configuration may be from a plurality of single core fibers to a multi-core fiber to a single core fiber with multiple data to any combination thereof. The single optical fiber may be a multimode fiber, a single mode fiber, or a polarization maintaining fiber, depending on the requirements of the sensor system, and the system may include any combination of these fibers. The sensor probe can be mounted flush to the process wall and have a single joint, if desired. The sensor probe contains beam shaping optics, collection optics, an optical aperture and an optical fiber, all of which can be designed for use in high temperature environments because the sensing probe does not contain electronics. For engine dust intake and other applications, multiple sensors may also be placed at multiple sensing locations to better understand the spatial variation of particle characteristics.

The fiber-based design is flexible, allowing for the implementation of single or multiple light sources and single or multiple optical detectors. FIG. 1 illustrates in schematic form a sensor system 10 for carrying out the present invention. More specifically, an electronics unit 19 is connected to the sensor probe 35 via the fiber optic connector 25 to measure the particles in the particle stream 40. The entire sensor system may also include one or more electronics units 19, one or more fiber optic couplers 25, one or more sensor probes 35, and may interrogate one or more particle-containing streams 40. Electronics 19 may include a detector 11 or multiple detectors 12 and a light source 15 or multiple light sources 16, as well as any additional optics needed to control the light transmitted from the light sources and to control the light entering the detectors. The sensor probe 35 may include a sensor head 36 and any other optical components for controlling the light transmitted to the particle-containing stream 40. An opto-coupler 25 connecting the sensor probe 35 and the electronics 19 connects the optical fiber from the electronics 22 to the optical fiber from the sensor probe 28. The fiber coupler 25 may include a single or multiple paths for transmitting light 20 and receiving light 30. The interconnection with the optical fiber provides the advantage of flexible sensor mounting and placement while exposing the sensor probe to only harsh environments with moderate or high temperatures and pressures, such as gas turbine engines. Furthermore, this design allows the use of 1-x (or even m) couplers if more detectors, more locations, or more light sources are detected. In addition to design requirements such as dust size and range, flow rate or particle velocity, and the above concentration limits, sensor calibration of dust size quantities is often required.

Figure 2 shows an embodiment of the invention with one light source and two detectors. More specifically, the sensor probe 70 is connected to the electronics unit 50 using a fiber optic bundle 61. The light source 51 transmits light to the fiber coupler 57 through the optical fiber 56. Which transmits the light through an optical fiber 58 to a first fiber optic connector 59 located outside the electronics unit 50. The fiber optic connector 59 and all other fiber optic connectors in the system may be comprised of a single or multiple fiber cores, or may be comprised of multiple connectors. The second fiber connector 60 is connected to the fiber connector 59 and transmits the light source through the fiber core in the fiber bundle 61 to the third fiber connector 62. A fourth fiber connector 71 outside the sensor probe 70 is connected to the fiber connector 62 and transmits the light source to the sensor probe 70 through an optical fiber 72. It should be noted that any pair of fiber optic connectors may be replaced with a continuous length of optical fiber, thereby eliminating the ability to split the optical path at that location. The light exiting the optical fiber 72 may be transmitted directly or may be shaped using an optical component 75 (e.g., a lens). The transmitted light then passes through window 76 to a sensing location 80 in particle stream 81. The space beam shaping performed at 75 is to achieve the specified performance at 80 and is known to those skilled in the art. In this figure, the sensor probe 70 is flush mounted on a wall 77 that confines the particle flow 81. Whether the sensor probe is flush mounted depends on the application and will be apparent to those skilled in the art. All of the components of the sensor probe 70 are contained within a housing 78 with the fiber optic connector 71 and the opening of the window 76. The body of the housing 78 may also have a predetermined shape, such as a threaded end 79, configured to secure the probe in an existing position in a measurement application.

Particles in sensing location 80 send scattered light back to sensor probe 70. The first scattered light enters the optical fiber 72 directly or through the optical element 75. Likewise, the second scattered light enters the optical fiber 73 directly or through an optical component 74. Spatial beam shaping at 75 and 74 also achieves the specified performance of the collected light at 72 and 73 and is known to those skilled in the art. Light entering the optical fiber 72 returns through the fiber bundle 61 and enters the optical fiber 58 using the same path as the emitted light. In the fiber coupler 57, the received scattered light is separated from the emitted light, and is sent to the optical fiber 55 and then to the detector 52. Any method known to those skilled in the art may be used to separate the emitted light from the received light, such as polarization rotation. The light entering the fiber 73 is directed in turn to the fourth fiber connector 71, the third fiber connector 62, the fiber bundle 61, the second fiber connector 60, the first fiber connector 59, into the fiber 54 where it is transmitted to the detector 53. The components of the electronic unit 50 are controlled by a controller 49, which controller 49 provides voltage control, current control and signal control to a light source 51, a detector 52 and a detector 53. The controller 49 may also include separate control elements or signal processing elements on each component.

It should be apparent to those skilled in the art that many variations on FIG. 2 are possible. Other light sources, detectors, optical fibers and connectors may be included in the sensor probe 70, electronics unit 50 and fiber optic bundle 61. In addition, the sensor probe 70, the electronics unit 50 and the fiber bundle 61 may also be included in a complete particle measurement system, especially when measurements are made at a plurality of distributed locations. The position of one fiber relative to another fiber in the sensor probe can also be flexible. For example, the optical fiber 72 and the optical fiber assembly 75 may be adjacent to the optical fiber 73 and the optical fiber assembly 74 to construct a compact probe. Alternatively, the prescribed distance may separate the fiber and the assembly to examine different aspects of particle light scattering. In addition, various elements may be combined together to optimize part count and aid assembly. For example, some of the optical elements in 75 may be combined with 72 optical fibers to form a fiber focuser or a fiber collimator. Further, window 76 may be combined with other optical elements in 75 or 74 to convert the window into a focusing lens or beam distributor. A single sensor probe 70 may also have multiple sensing locations 80, which may require additional optical fibers 72 or 73 and additional beam shaping optics 74 or 75. The optical fiber interconnects (e.g., 62 and 71) may also be replaced with continuous optical fibers, thereby eliminating connections, but improving signal transmission or possible connection contamination.

Figure 3 shows the sensor system connected to additional signal processing resources. The sensor probe 80, the optical fibre 81 and the electronics unit 82 have been described previously. The electronics unit 82 may then be connected to additional signal processing hardware 84 via wires and cables 83. The processing hardware 84 may then be connected to a local or remote display or control system 86 via a communication line 85. The system 86 may be used to display results or further processing information from the processing hardware 84 and may also be used to control the operation of the processing hardware 84.

One example of processing hardware 84 is a signal classifier. A signal classifier is an electronic device, such as an FPGA or DSP based multi-channel signal analyzer, that classifies particles according to their pulse height of the scattered signal and is known to those skilled in the art. The diameter of the particles can be classified according to the pulse amplitude of the detector signal generated by the particles. The classified diameters are then processed into particle characteristics such as particle size distribution, particle loading rate (also referred to as total concentration and the like), and particle mass concentration. For engine applications, the particulate measurement system may be connected to an engine control unit to provide early warning during engine health management and excessive dust intake.

Claims (1)

1. A system for optically detecting particles and measuring the size distribution and mass concentration of particles in a gas or liquid, the system comprising: one or more sensing probes, each probe consisting of at least one or more light source paths directing multiple light beams through optional beam shaping optics to one or more detection zones and at least one or more sensing paths having a plurality of optics collecting scattered light from particles within the detection zones and passing said light signals to said electronics unit; one or more electronic devices housing a plurality of light sources, a plurality of detectors to convert light scattering signals generated by particles passing through a detection zone into pulsed electrical signals whose amplitude depends on particle size, particle shape, and particle composition, corresponding light source and detector control electronics, a signal classifier providing a plurality of size channels into which the measured pulse signals are classified, and signal processing hardware to convert the classified pulse signals into particle statistics including particle distribution, total particle volume, average particle size, average particle surface area, and particle mass concentration; and a plurality of fiber optic connections between the sensing probe and the electronics unit.

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