High-pressure viewing cell

Abstract

High-pressure viewing cell (1) for a flowing fluid (1a), comprising a straight cylinder (2) made of a transparent material, through which an observation channel (3) for the fluid (1a) is traversed, an inlet connection (4, 4a) for supplying the fluid (1a) into the observation channel (3), and a return connection (5, 5a) for discharging the fluid (1a) from the observation channel (3), characterized in that a sealing element (6a, 6b) is arranged between the inlet connection (4, 4a) and the observation channel (3), and / or between the return connection (5, 5a) and the observation channel (3), the sealing element being traversed by a sealing channel (7a, 7b) and being supported at the inlet connection (4) or at the return connection (5) such that it is pressed against a base surface (2a, 2b) of the straight cylinder by a fluid pressure in the sealing channel (7a, 7b). (2) is pressed.

Description

[0001] The invention relates to a high-pressure viewing cell for the optical observation of fluids. State of the art

[0002] To monitor technical cleanliness and perform functional tests on equipment, it is often necessary to detect contaminants and other dispersed phases in a continuous fluid flow. One known method involves passing the fluid flow through the beam path of one or more laser beams and inferring the presence of dispersed phases in the fluid flow from the attenuation of the laser beam by the fluid flow. For example, particles in the fluid flow partially obscure the laser beam.

[0003] If the fluid flow is under pressure, a pressure-resistant optical access point is required. Such optical access points are known, for example, from DE 10 2013 003 164 A1.

[0004] High-pressure optical transmission cells, such as those required for SFC-FTIR, are known from DE 38 22 445 A1. These consist of a pressure-resistant housing with two intersecting bores, one forming a liquid channel and the other a light channel. Windows are inserted into the bore forming the light channel. For infrared spectroscopy in supercritical phase chromatography, there is a need for particularly pressure-resistant cells with a simple design.

[0005] Accordingly, in such a measuring cell, the windows are designed as stepped windows, whose central, cylindrical projections engage in the bore used for light transmission, so that the chamber is bounded by the end faces of the projections. O-rings, arranged in triangular-shaped annular spaces, serve as seals. These spaces are bounded by the wall surfaces of the window forming the step and the conical surface of an expanding section of the bore.

[0006] From DE 24 26 494 A1, an infrared cell is known that is suitable for the analysis of materials by infrared spectroscopy, even when the materials are located in the cell at high temperatures and high pressures. The cell can be used for both batch and continuous analyses. It has a special seal that minimizes damage to the infrared-transmitting windows inside. A heating device ensures the necessary temperature conditions for the analysis.

[0007] US Patent 5,054,919 A ​​discloses a measuring cell for spectrophotometric analysis or detection of a substance in a small sample volume. The cell comprises a measuring body with a small sample bore and windows that engage with the measuring body and allow radiation to pass through the sample bore and the windows. Each window is sealed by a gasket that is pre-tensioned in two ways. The inner part of the gasket rests against the window and is pre-tensioned by a first spring-loaded assembly, for example, a disc spring with a piston. The outer part of the gasket is pre-tensioned separately by a ring pressed against the measuring body.

[0008] To examine individual particles or other dispersed events more closely, the fluid flow is guided through the laser beam path with such a small cross-section that the beam path is only ever influenced by such an event at any given time. For fluid flows under high pressures, such as those found in high-pressure diesel injection systems, there is currently no way to guide the fluid flow through a very small cross-section and simultaneously observe it optically. The present invention addresses this need. Disclosure of the invention

[0009] Within the scope of the invention, a high-pressure viewing cell for a flowing fluid was developed. This cell comprises a straight cylinder made of a transparent material, through which an observation channel for the fluid is traversed. Furthermore, an inlet connection for supplying the fluid to the observation channel and a return connection for discharging the fluid from the observation channel are provided.

[0010] According to the invention, a sealing element is arranged between the inlet port and the observation channel, and / or between the return port and the observation channel, and the sealing element is traversed by a sealing channel. The sealing element is supported at the inlet port or the return port in such a way that it is pressed against a base surface of the straight cylinder by a fluid pressure in the sealing channel.

[0011] It was initially recognized that it is advantageous to combine the observation channel and the optical access to this observation channel in a single component. In this way, significantly smaller channels with a round cross-section under high pressure can be made optically observable than was possible with the previous state of the art. For this purpose, the observation channel can be introduced, for example, by drilling into the straight cylinder.

[0012] A round cross-section is particularly advantageous with regard to the compressive strength of the observation channel. Furthermore, by combining the observation channel and the optical access point into a single component, the fluid encounters only one material as it passes through the channel. This prevents cavitation in the fluid, which can occur when the observation channel is artificially constricted with a transparent or opaque insert.

[0013] The straight cylinder can, for example, be a disc made of transparent material. It advantageously has a height of 2 mm or more, preferably 9 mm or more. This provides sufficient space to guide two or more independent beam paths through the straight cylinder and the observation channel. These beam paths can lie in the same plane or in planes offset from each other. The straight cylinder advantageously has a maximum height of 25 mm. If it is higher, it becomes more difficult to polish the narrow, drilled observation channel to an optically satisfactory standard.

[0014] It was further recognized that the special design of the sealing element allows the transparent material to be mechanically protected even at high fluid pressures. The contact pressure of the sealing element against the straight cylinder is no longer fixed by a preload, but rather follows the fluid pressure in the sealing channel, which leads into the observation channel. In this way, the transparent material is subjected to uniform compressive stress in all spatial directions. Both local increases in compressive stress and local tensile stresses are advantageously avoided. As the diameter of the sealing area increases, the forces that the transparent material must withstand (e.g., in the form of tensile stresses in the circumferential direction) decrease, and the pressure within the sealing element also decreases. The load is distributed outwards.

[0015] Particularly in an advantageous embodiment of the invention, in which the transparent material of the straight cylinder is quartz glass, this enables the operation of the high-pressure viewing cell at significantly higher fluid pressures than according to the prior art. Quartz glass is especially advantageous for in-situ investigations in high-pressure diesel injection systems because its refractive index matches that of the test oil used in such investigations. Furthermore, this material is readily machinable, for example by drilling. Quartz glass has very high compressive strength but is not very tensile. If a local tensile stress causes a small piece of the quartz glass to break off, cracks can propagate from this defect through the entire straight cylinder, ultimately leading to its failure.

[0016] The specific shape of the sealing element depends on the material, since, firstly, each material reacts differently to the fluid pressure in the sealing channel, and secondly, not every material can be machined into every desired shape. For a specific application, a person skilled in the art can design the element accordingly by simulating the forces that occur, for example, using the finite element method. They can then, for instance, design the shape of the sealing element to maximize the uniformity of the pressure forces exerted on the transparent material and minimize local pressure peaks. The most important material properties of the sealing element that play a role here are the modulus of elasticity and Poisson's ratio.

[0017] The high-pressure viewing cell can be designed, in particular, for flow through at a fluid pressure of at least 250 bar, preferably at least 1000 bar, and most preferably at least 2500 bar. These are typical pressures found in high-pressure diesel injection systems.

[0018] The observation channel advantageously has a diameter of 5 mm or less, preferably 3 mm or less. Typical particle concentrations in high-pressure diesel injection systems, particularly with a channel diameter of 2 mm, suggest that a laser beam illuminating the observation channel will only ever be affected by at most one particle at any given time.

[0019] The sealing element is advantageously supported at the inlet and return connections in such a way that it expands in at least one spatial dimension when the sealing channel is subjected to fluid pressure. The contact force is then particularly self-reinforcing under fluid pressure, similar to a roof collar seal.

[0020] In a particularly advantageous embodiment of the invention, the sealing element, with a first cylindrical section, rests directly against a base surface of the straight cylinder, and it has a second cylindrical section with a smaller diameter. The two cylindrical sections of the sealing element can transition into one another, in particular via a chamfer. All transitions can be rounded to meet the requirements regarding the machinability of the material used for the sealing element. The division of the sealing element into two cylindrical sections with different diameters improves, firstly, the deflection of a radial force F exerted in all directions by the fluid pressure. R into a normal force F Non the contact surface between the sealing element and the base of the straight cylinder. Furthermore, this division counteracts the tendency for the sealing element material to retreat under fluid pressure due to its finite compressibility, thereby partially lifting away from the base of the straight cylinder. Such lifting could impair the sealing effect.

[0021] The first cylindrical section of the sealing element advantageously has an outer diameter of 15 mm to 50 mm, preferably 20 mm to 30 mm. In a particularly preferred embodiment, the first cylindrical section of the sealing element has an outer diameter of 24 mm. The sealing channel advantageously has a length of 5 mm to 30 mm. The second cylindrical section of the sealing element also advantageously has an outer diameter of 5 mm to 30 mm. The length of the sealing channel is less than or equal to the outer diameter of the second cylindrical section of the sealing element. In a particularly preferred embodiment, the sealing channel is 11 mm long, and the second cylindrical section of the sealing element also has an outer diameter of 11 mm. The sealing channel that opens into the observation channel advantageously has an inner diameter of 1.5 to 3.0 mm. In a particularly preferred embodiment, this sealing channel has an inner diameter of 1.8 mm.

[0022] Advantageously, the contact surface between the sealing element and the base of the straight cylinder is subjected to a maximum load of 2.5 Newtons per square millimeter in the absence of fluid pressure in the sealing channel. The sealing element can rest loosely on the base of the straight cylinder, particularly in the absence of fluid pressure in the sealing channel. The force with which the sealing element is pressed against the base of the straight cylinder then follows the fluid pressure at most. This prevents local pressure surges and tensile stresses that could damage the transparent material.

[0023] In a further particularly advantageous embodiment of the invention, an additional sealing ring is arranged between the inlet connection and the straight cylinder, as well as between the return connection and the straight cylinder. This sealing ring completely encloses the contact surface between the sealing element and the base of the straight cylinder. This sealing ring seals the inlet connection and the return connection, respectively, against the base of the straight cylinder, at least in a low-pressure range where the sealing element pressed against the cylinder by the fluid pressure does not yet ensure a complete seal. Since the contact force between the sealing element and the base of the straight cylinder follows the fluid pressure, this seal requires a certain minimum pressure to be completely leak-proof. In the low-pressure range where this minimum pressure has not yet been reached, the sealing effect can be completed by the additional sealing ring.

[0024] The sealing element can in principle be made of any material that can withstand a radial force F exerted by the fluid pressure from the sealing channel. R into a normal force F acting on the contact surface to the straight cylinder N to deflect the flow. For this purpose, when used in high-pressure applications, it should nevertheless have the highest possible modulus of elasticity and swell as little as possible under the influence of the fluid under investigation. At the same time, the material should ideally be as incompressible as possible so that it does not shrink back and thus does not lift off the contact surface with the straight cylinder. Advantageously, the sealing element consists of a polymer, in particular a polyimide or a polyetheretherketone.

[0025] Advantageously, the inlet and return connections are designed as flanges and connected by bolts. This bolted connection allows for precise control, ensuring that the sealing elements rest loosely on the base of the straight cylinder when there is no fluid pressure in the sealing channel. However, when fluid pressure is present, the bolted connection provides a stable support for the application of the normal force F. N between the sealing elements and the base surfaces of the straight cylinder.

[0026] In a further particularly advantageous embodiment of the invention, the lateral surface of the straight cylinder has at least one light-entry window defined by a mask made of an opaque material. In this way, a beam path that intersects the observation channel can be predefined. To send a laser beam along this beam path through the observation channel, it is then only necessary to direct the laser beam onto the mask. Complex adjustments using apertures are eliminated.

[0027] This is particularly advantageous when two beam paths in two measurement planes, separated by a defined distance, are to intersect the observation channel. If the two beam paths are offset from each other by an angle of 90°, for example, particles or other dispersed events in the fluid flow can be measured in all three spatial dimensions using such a setup. The width of a particle can then be measured in the first plane, and its thickness in the second. The time difference between the signals generated in the two measurement planes, in conjunction with the known distance between the planes, allows the particle's length to be calculated using the flow velocity, analogous to a photoelectric sensor measurement. The precise alignment of the measurement planes relative to each other is essential for the quality of the measurement signal. Defining light entry windows using masks eliminates the need for complex aperture adjustments.

[0028] The mask can, for example, be a metallization applied to the lateral surface of the straight cylinder. Aluminum, which has a very low optical penetration depth, is particularly suitable as a material for the metallization. The metal can be applied, for example, using a vacuum process such as sputtering or another vapor deposition method. A light entry window can be exposed from such a metallization, for example, by local irradiation with an ultrashort pulse laser. The size of the light entry window depends on the diameter of the observation channel. With an observation channel diameter of 2 mm, the light entry window advantageously has a size between 1 mm x 0.01 mm and 5 mm x 1 mm; a size of 2 mm x 0.1 mm is preferred. If two beam paths intersect the observation channel, their offset along the axis of the observation channel depends on the specific application.It is advantageously between 0.01 mm and 5 mm, and particularly preferably 0.1 mm.

[0029] The outer diameter of the straight cylinder should be greater than or equal to the diameter of the sealing element bearing against its base. Advantageously, it is at least 25 mm; in a preferred embodiment for a fluid pressure of 2500 bar, it is 50 mm.

[0030] The high-pressure visualization cell is generally suitable for characterizing and quantifying dispersed components in multiphase flows. If the continuous phase is a gas, the dispersed phase can, for example, contain solid particles or a liquid. If the continuous phase is a liquid, the dispersed phase can, for example, contain solid particles, gas inclusions, or another liquid. Since narrower observation channels can be used compared to the prior art, lower volume flows and dispersed components with smaller dimensions of the individual dispersed events can be studied.

[0031] The high-pressure viewing cell can be used, for example, in the manufacturing of high-pressure diesel injection pumps to monitor the number of particles contained within them. The existing microscope selection test, in which randomly selected pumps were flushed and the particles removed during flushing were examined under a microscope, can be expanded to provide 100% assurance of product quality.

[0032] Other potential applications include hydraulic test benches and the online monitoring of machines and the fluids they contain. For example, fluids can be checked for wear particles from machine parts (such as gears) or water ingress. This allows, for instance, wind turbine gearboxes, hydraulic circuits, and cooling compressors to be monitored for wear.

[0033] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments of the invention, with reference to figures. Examples of implementation

[0034] It shows: Fig. 1 Perspective partially cutaway view of a high-pressure viewing cell according to an embodiment of the invention. Fig. 2 Sectional drawing of the in Fig. 1 shown embodiment along the in Fig. 1. Drawing of the section plane. Fig. 3. Design of the inlet connection and the return connection as corresponding flanges. Fig. 4 Definition of two beam paths crossing the observation channel through light entry windows.

[0035] Fig. Figure 1 shows an embodiment of the high-pressure viewing cell 1 in a perspective, partially cutaway view. The fluid 1a flows through the high-pressure viewing cell 1 from top to bottom. The central element of the high-pressure viewing cell 1 is a straight cylinder 2 made of quartz glass, which is designed as a disk and through which an observation channel 3 for the fluid 1a is traversed. The fluid 1a is fed into the observation channel 3 via an inlet connection 4 with a fitting 4a. After passing through the observation channel 3, the fluid 1a is discharged through a return connection 5 with a fitting 5a. A first sealing element 6a, through which a sealing channel 7a is traversed, is arranged between the inlet connection 4 and the observation channel 3. The fluid 1a passes from the inlet connection 4 through the sealing channel 7a into the observation channel 3. A second sealing element 6b is arranged between the observation channel 3 and the return connection 5, which is traversed by a further sealing channel 7b.After passing through the observation channel 3, the fluid 1a flows through the sealing channel 7b into the return port 5. The sealing elements 6a and 6b are supported at the inlet port 4 and the return port 5, respectively, such that, in the absence of fluid pressure in the sealing channels 7a and 7b, they rest loosely on the base surfaces 2a and 2b of the straight cylinder 2. However, if fluid pressure is present in the sealing channels 7a and 7b, the sealing elements 6a and 6b are pressed against the base surfaces 2a and 2b of the straight cylinder 2, respectively, thus creating a seal with a force that corresponds to the pressure of the fluid 1a. In this process, the straight cylinder 2 is subjected to compressive stress on all sides, particularly at the location of the observation channel 3 and in its immediate vicinity, but not to tensile stress.

[0036] The inlet port 4 and the return port 5 are designed as corresponding flanges, which are bolted together by screws 13. Two windows 50 and 51 are incorporated into the return port 5, through which a first beam path can be guided through the straight cylinder 2 and the observation channel 3. Furthermore, two additional windows 52 and 53 are incorporated into the return port 5, through which a second beam path, perpendicular to the first beam path, can be guided through the straight cylinder 2 and the observation channel 3.

[0037] A further sealing ring 12a is arranged between the inlet port 4 and the base 2a of the straight cylinder 2. A further sealing ring 12b is arranged between the return port 5 and the base 2b of the straight cylinder 2. The sealing rings 12a and 12b ensure the sealing of the inlet port 4 and the return port 5, respectively, against the straight cylinder 2 in a low-pressure range, in which the sealing elements 6a and 6b are not yet pressed against the bases 2a and 2b of the straight cylinder 2 with a force sufficient for a complete seal.

[0038] Fig. 2 shows that in Fig. Figure 1 shows an embodiment in a sectional drawing. The sealing elements 6a and 6b each have a first cylindrical section 8 that rests directly against the base surface 2a and 2b, respectively, of the straight cylinder. They each also have a second cylindrical section 9 with a smaller diameter. The first cylindrical section 8 and the second cylindrical section 9 transition into each other via a chamfer 10, the edges of which are additionally rounded due to the boundary conditions for the machining of the material of the sealing elements 6a and 6b.

[0039] The additional sealing rings 12a and 12b enclose the contact surface 11 between the sealing elements 6a and 6b and the base surfaces 2a and 2b of the straight cylinder 2 on all sides.

[0040] In Fig. In addition, areas 4f of the inlet connection 4 and 5f of the return connection 5 are shown, which are held in a force-fit connection by the screw connection 13. This screw connection 13 does not exert any preload force on the contact surface 11 between the sealing elements 6a and 6b and the base surfaces 2a and 2b of the straight cylinder 2. The normal force F acting on this contact surface 11 N follows solely the pressure of fluid 1a.

[0041] In the enlarged section in Fig. 2 is the deflection of the radial force F exerted by the pressure of the fluid 1a R into a normal force F N sketched between the sealing element 6a and the base 2a of the straight cylinder 2.

[0042] Fig. Figure 3 illustrates the design of the inlet connection 4 and the return connection 5 as corresponding flanges in a perspective, partially cutaway view. The inlet connection 4 contains a channel section 4b, which is fed with fluid 1a from the fitting 4a. Section 4c is designed to accommodate the sealing element 6a. Channel section 4b then opens into the first sealing channel 7a. The structures labeled 4d enclose the straight cylinder 2 and prevent it from slipping. Similarly, the straight cylinder 2 is enclosed on the other side by the structures labeled 5d of the return connection 5. Section 5c is designed to accommodate the second sealing element 6b. Its sealing channel 7b directs the fluid 1a, after it has passed through the inspection channel 3, through channel section 5b into the fitting 5a.The force transmission between the corresponding flanges 4 and 5 is mediated by the area 4e resting on the area 5e and by the area 4f resting on the area 5f.

[0043] Fig. Figure 4 illustrates the guidance of two beam paths (measuring planes) 54 and 55 through the straight cylinder 2 and the observation channel 3. The first beam path 54 is defined by a light entry window 58 in a metallized area 59 on the lateral surface 2c of the straight cylinder 2. The second beam path 55, which is perpendicular to the first beam path 54, is defined by a second light entry window 56 in a second metallized area 57 on the lateral surface 2c of the straight cylinder 2.

[0044] To transmit light along beam paths 54 and 55 through the straight cylinder 2 and the observation channel 3, only the metallized areas 59 and 57, respectively, need to be targeted. More precise adjustment is not required. As can be seen from the previous figures, the straight cylinder 2 is located deep inside the high-pressure viewing cell 1. The inlet port 4 and the return port 5 each have a significantly larger outer diameter than the straight cylinder 2; the lateral surface 2c of the straight cylinder 2 is difficult to see through the windows 50 and 52 in the return port 5. The fact that precise adjustment of the laser beams to the lateral surface 2c of the straight cylinder 2 is unnecessary due to the light entry windows 58 and 56 is therefore a significant simplification of the procedure.

Claims

[1] High-pressure viewing cell (1) for a flowing fluid (1a), comprising a straight cylinder (2) made of a transparent material, through which an observation channel (3) for the fluid (1a) is traversed, an inlet connection (4, 4a) for supplying the fluid (1a) into the observation channel (3) and a return connection (5, 5a) for discharging the fluid (1a) from the observation channel (3), characterized by , that between the inlet port (4, 4a) and the observation channel (3), and / or between the return port (5, 5a) and the observation channel (3), a sealing element (6a, 6b) is arranged, which is traversed by a sealing channel (7a, 7b) and is supported at the inlet port (4) or at the return port (5) in such a way that it is pressed against a base surface (2a, 2b) of the straight cylinder (2) by a fluid pressure in the sealing channel (7a, 7b). [2] High-pressure viewing cell (1) according to claim 1, characterized bythat it is designed for flow through with a fluid pressure of at least 250 bar, preferably at least 1000 bar and most preferably at least 2500 bar. [3] High-pressure viewing cell (1) according to one of claims 1 to 2, characterized by , that the observation channel (3) has a diameter of 5 mm or less, preferably 3 mm or less. [4] High-pressure viewing cell (1) according to any one of claims 1 to 3, characterized by , that the transparent material of the straight cylinder (2) is quartz glass. [5] High-pressure viewing cell (1) according to any one of claims 1 to 4, characterized by , that the sealing element (6a, 6b) is supported at the inlet connection (4) or at the return connection (5) in such a way that it is expanded in at least one spatial dimension when the sealing channel (7a, 7b) is subjected to a fluid pressure. [6] High-pressure viewing cell (1) according to any one of claims 1 to 5, characterized by, that the sealing element (6a, 6b) with a first cylindrical area (8) directly abuts a base surface (2a, 2b) of the straight cylinder (2) and that it has a second cylindrical area (9) with a smaller diameter. [7] High-pressure viewing cell (1) according to claim 6, characterized by , that the two cylindrical areas (8, 9) of the sealing element (6a, 6b) merge into each other via a chamfer (10). [8] High-pressure viewing cell (1) according to one of claims 6 to 7, characterized by , that the first cylindrical area (8) of the sealing element (6a, 6b) has an outer diameter of 15 mm to 50 mm, preferably of 20 mm to 30 mm. [9] High-pressure viewing cell (1) according to any one of claims 6 to 8, characterized by, that the sealing channel (7a, 7b) has a length of 5 mm to 30 mm and that the second cylindrical region (9) of the sealing element (6a, 6b) has an outer diameter of 5 mm to 30 mm, wherein the length of the sealing channel (7a, 7b) is less than or equal to the outer diameter of the second cylindrical region (9) of the sealing element (6a, 6b). [10] High-pressure viewing cell (1) according to any one of claims 1 to 9, characterized by , that the contact surface (11) between the sealing element (6a, 6b) and the base surface (2a, 2b) of the straight cylinder (2) in the absence of fluid pressure in the sealing channel (7a, 7b) with a maximum of 2.5 N / mm 2 is contaminated. [11] High-pressure viewing cell (1) according to any one of claims 1 to 10, characterized by, that between the inlet port (4) and the straight cylinder (2), as well as between the return port (5) and the straight cylinder (2), a further sealing ring (12a, 12b) is arranged, which completely surrounds the contact surface (11) between the sealing element (6a, 6b) and the base surface (2a, 2b) of the straight cylinder (2) and seals the inlet port (4) or the return port (5) at least in a low-pressure area in which the sealing element (6a, 6b) does not yet ensure a complete seal, against the base surface (2a, 2b) of the straight cylinder (2). [12] High-pressure viewing cell (1) according to any one of claims 1 to 11, characterized by , that the sealing element (6a, 6b) consists of a polymer, in particular of a polyimide or a polyetheretherketone. [13] High-pressure viewing cell (1) according to any one of claims 1 to 12, characterized by, that the inlet connection (4, 4a) and the return connection (5, 5a) are designed as flanges and are connected by screws (13). [14] High-pressure viewing cell according to any one of claims 1 to 13, characterized by , that the lateral surface (2c) of the straight cylinder (2) has at least one light entry window (56, 58) defined by a mask (57, 59) made of an opaque material.

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