EP2423498A1 - Passive flow control valve - Google Patents

Abstract

The passive flow control valve (1) has valve housing (2) with an inlet (3) and an outlet (4) for a flowable medium. A valve chamber (5) is arranged between the inlet and outlet. An input-side closing element is pre-stressed by a spring (8) against an input-side valve seat (31). A piston (7) is provided on a valve body (6), where outer side of the piston is guided through the wall of the valve chamber in sliding manner. A passage hole (73) is provided in an end face of the piston through which the flowable medium flows. An independent claim is also included for a large diesel engine with flow control valve that is arranged between a high-pressure reservoir for a fuel and a fuel injector nozzle.

Description

The invention relates to a passive flow control valve for a large diesel engine according to the preamble of the independent claim of this category. The invention further relates to a large diesel engine with such a flow control valve.

Large diesel engines that can be designed as two-stroke or four-stroke engines are often used as drive units for ships or in stationary operation, eg. B. used to drive large generators for generating electrical energy.

In modern large diesel engines, the common rail system has become established for fuel supply. In this case, the fuel is conveyed by means of a high pressure pump in a pressure accumulator, which is also referred to as an accumulator or as a rail. In this pressure accumulator is fuel at a pressure of for example 1600 bar or more, z. B. up to 2000 bar. With the fuel under pressure from the accumulator then the fuel injectors of all cylinders are supplied, which inject the fuel into the respective cylinder. It is known to provide between the accumulator and each fuel injector each a passive flow control valve. This has the task to automatically close the flow connection between the accumulator and the respective fuel injector as soon as a predetermined amount of fuel has flowed in the respective working cycle from the pressure accumulator to the fuel injector. This avoids the risk of uncontrolled or undesired escape of fuel in the event of leakage or other damage. In addition, it is possible, for example, for maintenance, to remove the connecting line between the pressure accumulator and a fuel injector when the engine is switched off and the fuel at a relatively low pressure of eg 2 to 20 bar circulated, that is circulated through the storage tank and the pressure accumulator to prevent clogging of the fuel system.

Due to the very high pressure of the fuel from 1600 to 2000 bar, it is necessary that the flow control valve has a very good and reliable sealing function.

A problem known quantity limiting valves in the large diesel engine results from the viscosity fluctuations of the fuel, which are particularly temperature-related. In the large diesel engine heavy fuel is usually used as fuel, which typically has to be heated to temperatures above 100 ° C due to its very high viscosity in order to be sufficiently flowable or even injectable. In addition, however, significantly lower-viscosity marine diesel oil is used, with which usually the engine is started and also switched off. Typically, it is the case that, in particular during ship movements in the port area, the engine is operated with marine diesel oil and then continuously transferred to the heavy oil operation on the open sea. The operation with marine diesel oil is usually done at lower temperatures in the fuel supply system than the operation with heavy oil. Due to these temperature fluctuations, there are also fluctuations in the viscosity of the fuel. However, these changes in viscosity affect the amount of fuel that passes through the flow control valve. If, for example, the quantity limiting valve is set to a certain amount at a first viscosity, it may happen that the quantity limiting valve closes at a different viscosity already after a smaller or only after a larger amount of fuel.

The present invention seeks to remedy this undesirable effect. Accordingly, it is an object of the invention to propose a passive flow control valve for a large diesel engine, in which the amount, after passing the valve closes automatically, is substantially independent of the viscosity of the medium.

The object of the invention solving these objects is characterized by the features of the independent claim of this category.

According to the invention, therefore, a passive flow control valve for a large diesel engine is proposed, with a valve housing having an inlet and an outlet for a flowable medium and a valve chamber arranged therebetween, wherein in the valve chamber, a valve body is provided with an input-side and an output-side closing element, respectively designed for sealing cooperation with an input-side and an output-side Ventisitz, wherein the input-side closing element is biased by a spring against the input-side valve seat, and provided with a valve body piston, the outside of which is slidably guided through the wall of the valve chamber. In the front of the Piston is provided at least one passage bore through which the flowable medium can flow.

The piston divides the valve chamber into a front chamber and a rear chamber, wherein the at least one passage bore in the end face of the piston forms a flow connection between the rear chamber and the front chamber. The fact that the passage bore is provided in the end face of the piston, it can be made very short, so that their flow resistance is substantially independent of the viscosity of the medium. This then results in that the quantity after the flow through the flow control valve closes independently, regardless of the viscosity of the medium.

The independence from the viscosity is ensured in particular if, for each passage bore, the ratio of length and diameter of the passage bore is at most 4.

A particularly good sealing function can be achieved. Quantity limiting valve according to one of the preceding claims, when the input-side closing element is designed for line contact with the input-side valve seat.

For the same reason, it is preferable that the output-side closing element is designed for line contact with the output-side valve seat.

The line contact can in particular be rationalized by the fact that the input-side closing element or the output-side closing element have a spherical surface for interacting with the input-side and the output-side valve seat.

In this embodiment, it is a preferred measure that the center of curvature of the spherical surface is eccentric with respect to the longitudinal axis of the valve body. This makes it possible to realize a smaller curvature of the spherical surface, which increases the length of the line contact. As a result, the opening pressure, or more precisely the pressure difference required for opening, can be set to small values.

In a preferred embodiment, the input-side valve seat or the output-side valve seat have a conical surface. This can be achieved particularly good sealing effects.

With regard to a self-centering of the valve body or its two closing elements, it is preferred if the input-side closing element and the output-side closing element are designed the same.

According to a preferred embodiment, the valve body extends inside the spring. This is a structurally particularly simple embodiment.

In practical terms, it is advantageous if each passage bore is arranged outside the spring with respect to the radial direction.

In practice, it has proved to be advantageous if the pressure difference for opening the flow connection between the input-side valve seat and the input-side closing element is 2 bar to 20 bar. This is due to the fact that the flow control valve should remain in the closed state, when circulating the fuel between the reservoir and the pressure accumulator is circulated. Usually amounts the pressure in the accumulator during recirculation between 2 and 20 bar, for example 10 bar. Then, the pressure difference for opening the flow connection between the input-side valve seat and the input-side closing element is set slightly higher, for example to 15 bar, so that no opening results in the circulation operation.

From a constructional point of view, it is preferred if the piston is designed as a separate part and is connected to the valve body.

Furthermore, it is advantageous if the spring is supported on the end face of the piston.

The invention further proposes a large diesel engine with an inventive quantity limiting valve.

The quantity limiting valve is preferably arranged between a high-pressure accumulator for the fuel and a fuel injection nozzle.

Further advantageous measures and preferred embodiments of the invention will become apparent from the dependent claims.

Fig. 1:

einen Längsschnitt durch ein Ausführungsbeispiel eines erfindungsgemässen Mengenbegrenzungsventils,

Fig. 2:

eine schematische Darstellung eines Common Rail Systems eines Grossdieselmotor

Fig. 3:

den Ventilkörper des Ausführungsbeispiels aus Fig. 1, und

Fig. 4:

den Ventilkörper des Ausführungsbeispiels aus Fig. 1 mit aufgesetztem Kolben.

In the following the invention will be explained in more detail by means of embodiments and with reference to the drawing. In the schematic, not to scale drawing show partly in section:

Fig. 1:

a longitudinal section through an embodiment of an inventive Mengenbegrenzungsventils,

Fig. 2:

a schematic representation of a common rail system of a large diesel engine

3:

the valve body of the embodiment Fig. 1 , and

4:

the valve body of the embodiment Fig. 1 with attached piston.

Fig. 1 shows a longitudinal sectional view of an embodiment of an inventive Mengenbegrenzungsventils, which is designated overall by the reference numeral 1. The cut takes place along the longitudinal axis A of the quantity limiting valve 1.

The quantity limiting valve 1 is a passive valve, which means that it is not activated or actuated actively, for example by a control signal, but independently and automatically opens and closes depending on the prevailing pressure differences.

The passive flow control valve 1 has a valve housing 2, which is configured here in two parts, and a lower part 21 and a cover or upper part 22 includes. The upper part 22 and the lower part 21 are connected by means of several screws 23 firmly together. The valve housing 2 has an inlet 3 and an outlet 4 for a flowable medium. Between the inlet 3 and the outlet 4, a valve chamber 5 is provided in the valve housing 2, in which a valve body 6 is arranged, which extends in the direction of the longitudinal axis A.

For a better understanding shows Fig. 3 another illustration of the valve body 6. Its two axial ends are formed by two closing elements 63, 64, namely the input side Closing element 63 and the output-side closing element 64. These closing elements 63, 64 are designed for sealing cooperation with an input-side valve seat 31 and an output-side valve seat 41. Both valve seats 31, 41 are provided in the valve housing 2, namely at the input end of the valve chamber 5 and at the output end of the valve chamber 5. The valve seats 31, 41 can be incorporated directly into the valve housing 2, or they are made as separate parts, the then inserted into corresponding recesses in the valve housing 2 and fixed there, for example by shrinking. Depending on the application, it may be more advantageous to make the valve seats 31, 41 as separate parts, because this results in a higher flexibility with respect to the material. Because the valve seats 31, 41 can then be made of a different material than the valve housing. 2

In the present embodiment, both the input-side valve seat 31 and the output-side valve seat 41 each have a conical surface 32 and 42, which cooperate with the input-side closing element 63 and with the output-side closing element 64.

On the valve body 6, a piston 7 is provided, which is dimensioned with respect to its outer diameter so that the outer side is slidably guided through the wall of the valve chamber 5. Between the outside of the piston 7 and the wall of the valve chamber 5, a slight clearance is provided. For a better understanding shows Fig. 4 a representation of the valve body 6 with the piston 7. The piston 7 is designed substantially cylindrical and arranged so that its cylinder axis coincides with the longitudinal axis A. The piston 7 has on its side facing the inlet 3 an end face 71, the other axial end of the piston 7 is open.

The valve body 6 and the piston 7 may be configured in one piece. Manufacturing technology, however, it is usually cheaper to make the valve body 6 and the piston 7 as two separate components and then connect them. The piston 7 can also be made of more than one part, for example of different materials, to optimally adapt its properties to the particular application or to simplify the production.

In the embodiment described here, the end face 71 of the piston 7 is provided with a central recess 72 which serves to receive the valve body 6. The valve body 6 has a flange-like projection 65, which serves as a stop for the end face 71. The valve body 6 is pushed from the inside through the central recess 72 in the end face 71 until the flange-like projection 65 bears against the end face 71 from the inside. The dimensions are coordinated so that the input-side closing element 63 of the valve body 6 extends completely beyond the end face 71 of the piston 7 (see Fig. 4 ). In the embodiment described here, the piston 7 is shrunk onto the valve body 6.

According to the invention, at least one passage bore 73 is provided in the end face 71 of the piston, which extends in the axial direction parallel to the longitudinal axis A through the end face 71. In the embodiment described here, a plurality of passage bores 73 are provided.

Each passage bore 73 has a diameter d and a length L, wherein the diameter d is the diameter which is decisive for the flow resistance, that is to say generally the smallest diameter of the passage bore 73.

In the lateral surface of the piston 7, a plurality of bores 74 are also provided, which each extend in the radial direction through the wall of the piston 7. With the radial direction is meant the direction perpendicular to the axial direction, wherein the axial direction is determined by the longitudinal axis A. Through the holes 74, the flowable medium can escape and reach the wall of the valve chamber 5, to provide here, for example, for a lubrication of the piston 7.

As this particular Fig. 1 shows, the valve body 6 is biased together with the piston 7 by means of a spring 8 against the input-side valve seat 31, so that the input-side closing element 63 is pressed against the input-side valve seat 31. The spring 8 extends in the axial direction and coaxial with the valve body 6, so that the valve body 6 extends in the interior of the spring 8. The spring 8 is supported on the one hand on the valve housing 2, namely around the output-side valve seat 41 around, and on the other hand inside on the end face of the piston. 7

Before further details are explained, the operation of the quantity limiting valve 1 will first be explained. The quantity limiting valve 1 is suitable for the common rail system of a large diesel engine. In modern large diesel engines, there are usually several common rail systems, for example for fuel injection, gas exchange or auxiliary systems. In the following, reference will be made to the application of fuel injection. Large diesel engines are usually operated with heavy fuel oil, which means that the flowable medium is heavy oil in this case. As a further fuel often marine diesel oil is used, which is used in particular for engine operation in the port, that is, before the ship leaves the port or when it enters the harbor area, the large diesel engine is typically operated with marine diesel. The operating temperature of the fuel is when operating with diesel fuel usually much lower than in heavy oil operation. This also results in fluctuations in the viscosity of the fuel.

The inventive flow control valve 1 is heavy oil suitable and can therefore be used in the common rail system of the fuel injection of a large diesel engine. Fig. 2 shows a schematic representation of such a common rail system of a large diesel engine. The system comprises a high pressure pump 50, with which the fuel, namely the heavy oil, is conveyed into a pressure accumulator 51, which is also referred to as an accumulator or as a rail. This pressure accumulator 51 is usually designed as a tube-like component which extends approximately at the level of the cylinder heads along the engine. From the pressure accumulator branch off lines 52 which lead to the fuel injection nozzles 53 in order to supply them with heavy oil. In Fig. 2 only one such conduit 52 and only one fuel injector 53 is shown because it is sufficient for understanding. In the accumulator, the heavy oil is under a pressure which substantially corresponds to the injection pressure. This pressure is 1600 bar, for example, but may even be higher, for example up to 2000 bar. Between the pressure accumulator 51 and the line 52, the flow limiting valve 1 is provided, which is for example mounted directly on or on the pressure accumulator 51. The quantity limiting valve 1 is arranged so that its inlet 3 is in fluid communication with the pressure accumulator 51 and its outlet 4 with the line 52nd

As long as the fuel injector 53 still injects no fuel into the cylinder, the quantity limiting valve 1 is in the in Fig. 1 illustrated closing position in which the input-side closing element 63 sealingly cooperates with the input-side valve seat 31 so that no heavy oil can flow through the flow control valve 1. In this condition prevails at the outlet 4 and on Inlet 3, substantially the same fluid pressure through the heavy oil. The spring 8 presses the input-side closing element 63 sealingly into the input-side valve seat 31.

As soon as the fuel injection nozzle 53 begins to inject the heavy oil into the combustion chamber of the cylinder, the pressure in the conduit 52 drops. This has the consequence that the valve body 6 with the piston 7 Darstellungsgemäss ( Fig. 1 ) is moved upward, whereby the input-side closing element 63 is lifted out of the input-side valve seat 31, so that the heavy oil from the pressure accumulator 51 pass through the passage holes 73, the quantity limiting valve 1 and can flow into the conduit 52. The pressure difference required to open the flow connection at the input side valve seat 31 can be adjusted by various measures, which will be explained later. Advantageously, this pressure difference is set to a value of 2 bar to 20 bar. The pressure difference is set to a value which is greater than the pressure in the pressure accumulator 51 during the circulation operation.

If the flow connection is open at the inlet-side valve seat 31, then the stroke of the piston 7 is dependent and at least approximately proportional to the amount of the injected amount of heavy oil. Once the injection process is completed, ie the fuel injector 53 is closed, the pressure in the line 52 builds up again. As a result, and by the tension of the spring 8, the piston 7 moves as shown ( Fig. 1 ) down, wherein the heavy oil can flow through the passage holes 73. This movement ends when the input-side closing element 63 is again pressed sealingly into the eigangsseitigen valve seat 31.

The piston 7 reaches its maximum stroke when the maximum amount of heavy oil has flowed through the flow restrictor valve 1. Usually, the quantity limiting valve 1 is dimensioned or designed so that in a regular or normal injection process, the maximum stroke of the piston 7 is not sufficient to press the output-side closing element 64 sealingly in the output-side valve seat 41.

Occurs, for example, downstream of the flow control valve 1 leakage or malfunction of the fuel injector 53, so more heavy oil flows through the flow control valve 1 as in a normal injection process. As a result, the piston has its representation ( Fig. 1 ) Upward movement continues until the output-side closing body 64 is sealingly pressed into the output-side valve seat 41. Once this happens, no more heavy oil can flow through the flow control valve 1 in the line 52 more.

It may be desirable, for example during maintenance, to disassemble the conduit 52 or the fuel injector 53. For this purpose, the large diesel engine is switched off. So that the fuel does not cool and becomes so heavy or almost solid that it clogs the fuel supply system, it is customary in a circulation operation, the fuel from the reservoir through the pressure accumulator 51 and by an in Fig. 2 not shown return flow line to circulate back into the reservoir. This circulation operation usually takes place only with backing pumps, not shown, that is, the high-pressure pump 50 is not active in this circulation operation. Typically, the pressure in the pressure accumulator 51 in the circulation operation is 2 bar to 20 bar, for example 10 bar.

Now, if the pressure in the pressure accumulator 51 has dropped to this value, the line 52 is depressurized and can then be dismantled. As a result, the pressure drops at the outlet 4 of the flow control valve 1. But since the pressure difference for opening the flow connection between the input-side valve seat 31 and the input-side closing element 63 is set so that it is greater than the pressure in the circulation operation - in this example, this pressure difference is set to about 15 bar - the piston does not move, but even with pressure-free line 52, the piston remains in the in Fig. 1 illustrated closed position.

Just to make such a disassembly of the line 52 as simple as possible, it is advantageous if the pressure difference for opening the flow connection between the input-side valve seat 31 and the input-side closing element 63 is set to a value of 2 bar to 20 bar, namely to a value , which is greater than the pressure in the pressure accumulator 51 during the circulation operation. As a result, the heavy oil can be recirculated in a simple manner. A pressure difference of 2 bar to 20 bar means that the input-side closing element 63 opens only when the pressure at the representation according to ( Fig. 1 ) Underside of the end face 71 is smaller by this value between 2 and 20 bar than the pressure at the inlet 3 of the quantity limiting valve 1.

An essential aspect of the inventive quantity limiting valve 1 is that the at least one passage bore 73 is provided in the end face 71 of the piston 7. By this measure, each passage bore 73 through which the fuel flows (or is pushed back) can be kept very short, whereby the hydrodynamic flow resistance of the passage bore 73 is independent of the viscosity of the fuel. This ensures that even with viscosity fluctuations of the fuel, the amount of fuel to which the flow control valve is set remains constant. Is that so Set quantity limiting valve 1 to a certain maximum amount, the amount of fuel at which this maximum is reached, remains constant even when the viscosity of the fuel changes or when the viscosity fluctuates. This independence of viscosity means that a very accurate and consistent limitation of the fuel quantity can be realized to a certain value, this value being subject to no changes even in the case of viscosity fluctuations.

Thus, the hydrodynamic flow resistance of the passage bore is independent of the viscosity of the medium flowing through, it has proved to be particularly advantageous if the ratio of the length L of the passage bore 73 to the diameter d of the passage bore 73 is at most 4. By diameter d is meant the diameter d which is decisive for the flow resistance, which in the case of a diameter varying over the length L is generally the minimum or the smallest diameter.

Since the operating pressure in the accumulator 51 is very large, for example, 1600 bar or up to 2000 bar, it is of course very important that a very good sealing effect between the input-side valve seat 31 and the input-side closing element 63 and between the output-side valve seat 41 and the output side closing element 64 is achieved. For this purpose, it has proved to be particularly advantageous if the input-side closing element 63 or the output-side closing element 64 and in particular both closing elements 63, 64 are designed for line contact with the input-side valve seat 31 and the output-side valve seat 41. Such a line contact between the involved partners is very efficient and in particular leak-free. Furthermore, the line contact is very tolerant of tilting of the piston 7, ie even with slight tilting or misalignment of the piston 7, the high sealing effect is ensured. In the exemplary embodiment described here, the line contact is realized both at the input-side valve seat 31 and at the output-side valve seat 41, that the input-side closing element 63 and the output-side closing element 64 each have a spherical surface 631 and 641 for cooperation with the respective conical surface 32 and 42 of the input-side and the output-side valve seat 31, 41 have.

The position of the line contact with respect to the axial direction influences the pressure difference necessary for opening the respective flow connection. For example, in the case of the input-side valve seat 31, the length of the line contact, which is measured over the entire circumference, is the higher the higher-with respect to the illustration in FIG Fig. 1 - The line contact with respect to the axial direction is .. The greater the length of the line contact, the lower the pressure difference, which is required to open the flow connection. Thus, the pressure difference can be set via the position of the line contact of the spherical surface 631 or 641, in which the respective flow connection is opened.

Since the preferred pressure difference with 2 to 20 bar is relatively small, it is advantageous if the length of the line contact is large. This can be ensured, in particular, by virtue of the fact that the center of curvature M of the spherical surface 631 or, respectively, 641 is eccentric with respect to the longitudinal axis A of the valve body 6. This means that the center of curvature M, here as the center of the sphere on whose surface the spherical surface 631 or 641 is located, lies on a straight line K that lies parallel to the longitudinal axis A and has a distance e from the longitudinal axis A. By this measure, a significantly lower curvature can be realized than when the center of curvature lies on the longitudinal axis A.

In many cases, the curvature is relatively small in terms of practical feasibility, but it should advantageously be so large as to ensure line contact between the surfaces 631 and 641 and the conical surfaces 32 and 42, respectively. The length of the respective line contact - and thus the pressure difference required for opening can be adjusted for a given curvature over the size of the distance e.

Another measure with which the pressure difference for opening the respective flow connection can be influenced or adjusted is the choice of the elastic properties, especially the choice of the spring constants, of the spring 8.

Another advantageous measure is when the input-side closing element 63 and the output-side closing element 64, at least with respect to the surface, which cooperates with the respective valve seat 31, 41, are designed the same. By this symmetry, a self-centering effect of the valve body 6 can be realized. Due to the slight play between the lateral surface of the piston 7 and the wall of the valve chamber 5, a simple centering of the valve body 6 is achieved.

A line contact between the input-side closing element 63 and the input-side valve seat 31 or between the output-side closing element 64 and the output-side valve seat 41 can also be realized by other geometric configurations of the respective interacting surfaces. For example, both cooperating surfaces may each be configured as spherical surfaces, or both interacting surfaces are each configured as conical surfaces, in particular with different cone angles.

As already mentioned, all the passage bores 73 are preferably outside the spring 8 with respect to the axial direction, that is to say the distance between the center axis of the passage bore 73 and the longitudinal axis A is greater than half the outside diameter of the spring 8 plus the radius of the respective bore 73 for each passage bore on the outer surface of the end face 71 of the piston.

Claims (15)

Passive flow control valve for a large diesel engine with a valve housing (2) having an inlet (3) and an outlet (4) for a flowable medium and a valve chamber (5) arranged therebetween, wherein in the valve chamber (5) a valve body (6) is provided with an input-side and an output-side closing element (63; 64) which are each designed for sealing cooperation with an input-side and an output-side Ventisitz (31; 41), wherein the input-side closing element (63) by a spring (8) against the Input side valve seat (31) is biased, as well as with a on the valve body (6) provided piston (7) whose outer side is slidably guided through the wall of the valve chamber (5), characterized in that in the end face (71) of the piston (7 ) is provided at least one passage bore (73) through which the flowable medium can flow. A quantity limiting valve according to claim 1, wherein for each passage bore (73) the ratio of length (L) and diameter (d) of the passage bore (73) is at most 4. Quantity limiting valve according to one of the preceding claims, wherein the input-side closing element (63) for line contact with the input-side valve seat (31) is configured. A quantity limiting valve according to any one of the preceding claims, wherein the output side closing member (64) is adapted for line contact with the output side valve seat (41). A quantity limiting valve according to one of the preceding claims, in which the inlet side closing element (63) or the outlet side closing element (64) have a spherical surface (631; 641) for cooperation with the inlet-side and outlet-side valve seats (31; 41). A quantity limiting valve according to claim 6, wherein the center of curvature (M) of the spherical surface (631; 641) is eccentric with respect to the longitudinal axis (A) of the valve body (6). A quantity limiting valve according to one of the preceding claims, in which the inlet-side valve seat (31) or the outlet-side valve seat (41) have a conical surface (32; 42). Quantity limiting valve according to one of the preceding claims, wherein the input-side closing element (63) and the output-side closing element (64) are designed the same. A quantity limiting valve according to any one of the preceding claims, wherein the valve body (6) extends inside the spring (8). A quantity limiting valve according to any one of the preceding claims, wherein each passage bore (73) is located outside the spring (8) with respect to the radial direction. Quantity limiting valve according to one of the preceding claims, wherein the pressure difference for opening the flow connection between the input-side valve seat (31) and the input-side closing element (63) is 2 bar to 20 bar. Quantity limiting valve, in which the piston (7) is designed as a separate part and is connected to the valve body (6). Quantity limiting valve according to one of the preceding claims, in which the spring (8) on the end face (71) of the piston (7) is supported. Large diesel engine with a flow control valve according to one of the preceding claims. A large diesel engine according to claim 14, wherein the mass limiting valve is disposed between a high pressure accumulator (51) for the fuel and a fuel injector (53).

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