Method for operating two degasifiers fluidly connected in parallel

Abstract

The present invention relates to a method for degasifying a fluid circuit, the fluid circuit having a first vacuum degasifier (10), the first vacuum degasifier (10) having a first inlet valve (12), a first degasifying space (14), a first outlet valve and a first pump (16), wherein the first pump (16) of the first vacuum degasifier (10) is operated continuously, wherein the first vacuum degasifier (10) is operated in two cycle steps, wherein, in a first cycle step, the first inlet valve (12) is open for a first time period (110), wherein, in a second cycle step, the first inlet valve (12) is closed for a second time period (120), the duration of the cycle of the first vacuum degasifier (10) being formed by the sum of the first time period (110) and the second time period (120), characterized in that the fluid circuit has a second vacuum degasifier (20), the second vacuum degasifier (20) having a second inlet valve (22), a second degasifying space (24), a second outlet valve and a second pump (26), wherein the second vacuum degasifier (20) is operated in two cycle steps, wherein, in a first cycle step, the second inlet valve (22) is open for a third time period (130), wherein, in a second cycle step, the second inlet valve (22) is closed for a fourth time period (140), the duration of the cycle of the second vacuum degasifier (20) being formed by the sum of the third time period (130) and the fourth time period (140), wherein, at least in some cycles, the first time period (110) is substituted by a modified first time period (112) or the third time period (130) is substituted by a modified third time period.

Description

[0001] Method for operating two degassers connected in parallel using fluid technology

[0002] The invention relates to a method for operating two vacuum degassers connected in parallel.

[0003] In applications where redundancy is crucial, using two vacuum degassers connected in parallel can be essential. An example of this is the degassing of the cooling water in a fuel cell on board a military submarine. To further reduce the independence of these systems and thus the risk of total failure, it can be beneficial to use slightly different outputs for the two parallel vacuum degassers, for example, by using different pumps. The idea behind this is that a problem causing one pump type to fail might not affect the other, ensuring that at least 50% of the capacity remains available.

[0004] However, if two vacuum degassers are run in parallel, two different extremes emerge. If both run simultaneously in parallel during the cycle, the effect on the fluid circuit, for example the cooling circuit, is maximal; pressure minima and pressure maxima add up. If both vacuum degassers run with half the cycle duration offset, the effect is minimized; the pressure maxima and pressure minima in the overall system are minimized.

[0005] Two vacuum degassers never run perfectly synchronously. Even identical units can have differences, which are naturally more pronounced when different components are used. Different aging processes or deposits can also lead to even slight variations in cycle times. Therefore, it's always possible that both vacuum degassers will run synchronously at a certain point, and the system must be designed to withstand maximum pressure loads, for example, by using a sufficiently large pressure equalization tank. Especially in submarine applications, space and weight are critical, making it desirable to minimize such fluctuations to save space and weight. Additionally, reducing these fluctuations can also minimize noise by reducing pressure pulses, thus reducing the acoustic signature.Analogous considerations apply to all mobile applications, for example in the automotive sector, in aerospace.

[0006] A vacuum degasser is known from the subsequently published DE 10 2020202 024.

[0007] A device for degassing liquid is known from JP 2002 / 239 303 A.

[0008] From DE 10 2011 083 988 A1 a cooling device for a fuel cell system of a submarine is known.

[0009] The object of the invention is to increase redundancy by connecting two vacuum degassers in parallel and to provide a method for operating the two vacuum degassers.

[0010] This problem is solved by the method with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawings.

[0011] The invention serves as a method for degassing a fluid circuit. For example, the fluid circuit is a cooling circuit. The fluid circuit includes a first vacuum degasser, wherein the first vacuum degasser comprises a first inlet valve, a first degassing chamber, a first outlet valve, and a first pump. The vacuum degasser can also have a more complex design, for example, as known from DE 10 2020 202 024. The first pump of the first vacuum degasser is operated continuously. Thus, the first pump continuously pumps fluid from the first degassing chamber back into the fluid circuit. The pump is therefore not temporarily disconnected from the degassing chamber, for example, by closing a valve, but is continuously fluidically connected to the first degassing chamber.The first vacuum degasser operates in two cycles: in the first cycle, the first inlet valve is open for a certain period; in the second cycle, the first inlet valve is closed for a certain period. During the first cycle, fluid flows from the fluid circuit through the first inlet valve into the first degassing chamber and is simultaneously pumped back from the first degassing chamber into the fluid circuit by the first pump. During the second cycle, no fluid can flow in because the first inlet valve is closed. However, the first pump continues to pump fluid from the first degassing chamber, creating a vacuum in the first degassing chamber at the end of the second cycle. This vacuum degasses the fluid that then flows into the vacuum of the first degassing chamber in the next cycle.The duration of the cycle of the first vacuum degasser is formed from the sum of the first time and the second time, since the cycle consists of these two cycle steps.

[0012] According to the invention, the fluid circuit includes a second vacuum degasser. This second vacuum degasser has a second inlet valve, a second degassing chamber, a second outlet valve, and a second pump. Like the first vacuum degasser, the second vacuum degasser operates in two cycles. In the first cycle, the second inlet valve is open for a third time, while in the second cycle, the second inlet valve is closed for a fourth time. The basic procedure is the same. However, for example, the second pump can be of a different type than the first pump to make the simultaneous failure of both pumps less likely. The cycle duration of the second vacuum degasser is thus calculated analogously as the sum of the third and fourth times.

[0013] According to the invention, at least in individual cycles, the first time is replaced by a modified first time or the third time by a modified third time. This makes it possible to change the phase position of the first vacuum degasser relative to the second vacuum degasser.

[0014] The aim of this process is to prevent the cycles of the first and second vacuum degassers from running simultaneously, thereby minimizing pressure fluctuations in the fluid circuit. Continuous pumping enables continuous operation, which is beneficial for the pump's service life. Furthermore, it allows for the use of a smaller and therefore quieter pump.

[0015] Another major advantage is that the two vacuum degassers can be switched on at virtually any time interval. After only a few cycles, the inventive method ensures that these two have an optimal phase relationship to each other.

[0016] The first exhaust valve is necessary to remove the gas that has escaped from the fluid in the first degassing chamber from the fluid circuit. Similarly, the second exhaust valve is necessary to remove the gas that has escaped from the fluid in the second degassing chamber from the fluid circuit. Possible operating procedures within the cycle steps can be found, for example, in DE 10 2020 202 024.

[0017] A control unit is particularly preferred for carrying out the method, which controls the first and second inlet valves. In one embodiment, the control unit stores the first, second, third, and fourth times. This control device preferably also includes a clock. The control unit can further be connected, for example, to a first pressure measuring device connected to the first degassing chamber and a second pressure measuring device connected to the second degassing chamber. A modified first time and / or a modified third time can be stored in the control unit. Alternatively, a formula for generating a modified first time and / or a modified third time can be stored in the control unit. In another embodiment, the first and second pumps are also controllable by the control unit.Thus, in this embodiment, the first and second vacuum degassers are not only controllable via the control unit, but can also be switched on and off via the control unit. In an alternative embodiment, the second and fourth time periods are stored in the control unit. Furthermore, a modified first time period and a modified third time period are stored in the control unit. This control device preferably also includes a clock. The control unit is connected to a first pressure measuring device, which is connected to the first degassing chamber, and a second pressure measuring device, which is connected to the second degassing chamber. Furthermore, a first limit value for the pressure that must be exceeded in the respective degassing chamber during the first and third time periods is stored in the control unit.A second pressure limit, which must be undercut in the respective degassing chamber during the second and fourth time periods, can also be stored. Additionally, a temperature sensor can be attached to the degassing chamber, allowing the first or second limit to be stored as a temperature-dependent parameter.

[0018] The control unit opens the first inlet valve at a specific time and the second inlet valve at a specific time, keeping each open until the first pressure limit is exceeded. Simultaneously, the control unit measures the duration of the filling process and stores this time as either the first or third time. After the first pressure limit is exceeded, the control unit closes the first inlet valve for the duration of the second time and the second inlet valve for the duration of the fourth time.

[0019] In this alternative embodiment, the control unit is configured to use a clock to measure the first and third times required by the degassing chambers to reach a specific pressure. Alternatively, the control unit is configured to also determine the second and fourth times, or the total cycle time, of the respective vacuum degassers. From the measured times, the control unit determines the difference in transit times and / or the time offset of the respective switching points. Furthermore, if predefined limits for the difference in transit time and / or the time offset are exceeded, the control unit is configured to replace the first and third times with the modified first time or the modified third time.The modified first time and the modified third time are chosen such that, after the time has elapsed, the specified limits for the transit time difference and / or the time offset are again undershot. This means, in particular, that the first or second inlet valve remains open for a further period of time after the specified pressure has been reached. The modified third time can therefore consist of the third time and an additional time interval, At.

[0020] In a further embodiment of the invention, the first time is replaced by a modified first time if the cycle duration of the first vacuum degasser is shorter than the cycle duration of the second vacuum degasser, or the third time is replaced by a modified third time if the cycle duration of the first vacuum degasser is longer than the cycle duration of the second vacuum degasser. Thus, the faster cycle is modified, and preferably slowed down. For example, if the cycle of the first vacuum degasser were normally about 1 second faster than the cycle of the second vacuum degasser, the first time could be extended by 10 seconds every 10 cycles. This makes it possible to easily compensate for both small and large differences.

[0021] In a further embodiment of the invention, the modified first time is obtained by adding a time interval At to the first time, or the modified third time is obtained by adding a time interval At to the third time. Preferably, the time interval At is selected in the range from (sum of the first time, the second time, the third time, and the fourth time) divided by 40 to (sum of the first time, the second time, the third time, and the fourth time) divided by 8. In other words, the time interval lies in the range from 25% of the average cycle duration to 5% of the average cycle duration. If one were to assume an average cycle duration of 5 minutes, this would result in a range from 10 / 8 minutes = 75 seconds to 10 / 40 minutes = 15 seconds.The first time would be extended by this interval if the first vacuum degasser is faster, or the third time if the second vacuum degasser is faster.

[0022] For example, in this embodiment, the first time, the second time, the third time, and the fourth time, as well as the time interval At, are stored in the control unit. In a further embodiment of the invention, a fixed cycle point is defined that is used jointly for both vacuum degassers. The time difference between the fixed cycle point of the first vacuum degasser and the fixed cycle point of the second vacuum degasser is measured. This makes the phase relationship between the first and second vacuum degassers easily ascertainable. The opening or closing of the inlet valve is particularly suitable as a fixed cycle point. With perfect phase shift, the time difference would ideally correspond to half the average cycle duration. If the deviation from this is, for example, greater than At / 2, the first time or the third time can be modified in the next cycle.It is also possible to calculate the exact difference between the measured time difference and half the average cycle duration and use this value for At, thereby modifying the first or third time in the next cycle. However, due to the significantly simpler control, choosing a constant At is often easier, even though the dynamic method allows for operation closer to the optimum.

[0023] Determining the time difference can be done relatively easily in a control unit. In particular, with a clock integrated into the control unit, it is easy to measure, for example, the time difference between opening the first intake valve and opening the second intake valve, or the time difference between closing the first intake valve and closing the second intake valve.

[0024] In a further embodiment of the invention, the first time is replaced by a modified first time or the third time by a modified third time, provided that the measured time difference deviates from the value (sum of the first time, the second time, the third time and the fourth time) divided by 4 by more than the time interval At.

[0025] In a further embodiment of the invention, a first vacuum degasser with a first flow control device arranged fluidically upstream of the first degassing chamber and / or a second vacuum degasser with a second flow control device arranged fluidically upstream of the second degassing chamber are selected. For example, a flow control device can be inserted only upstream of the faster vacuum degasser. Likewise, it is possible to arrange a flow control device upstream of each vacuum degasser during manufacturing, even if it is not known which will be faster. For the purposes of this invention, a flow control device is any device that can selectively change the quantity of fluid flow. For example, this could be a throttle valve or an orifice plate. However, it could also be a simple two-way valve where the flow rate can be regulated, at least coarsely, by changing the angle.While absolutely precise control of the flow rate is possible, it is not necessarily practical. The ratio between the vacuum degassers can change due to time or temperature fluctuations. To compensate for this, the invention modifies either the first or the third time. The flow rate control device serves only to roughly adjust the first and second vacuum degassers to a similar cycle duration. The first flow rate control device modifies the flow rate through the first vacuum degasser, and thus the first time, and / or the second flow rate control device modifies the flow rate through the second vacuum degasser, and thus the third time, such that the sum of the first and second times is equal to the sum of the third and fourth times with a tolerance of ± 15%.

[0026] Theoretically, instead of the modified first and third times, one could leave the first and third times unmodified and use a modified second and fourth time analogously. However, in this alternative, fluid would be pumped out of the degassing chamber for a longer period, which in extreme cases could lead to gas entering the pump, which would again be disadvantageous. Therefore, it would be possible to provide a level sensor for each degassing chamber in this variant to detect a minimum fill level. However, this is somewhat more complex. Therefore, this alternative is not preferred. In a further embodiment of the invention, a first pressure is measured in the first degassing chamber and a second pressure is measured in the second degassing chamber.Here, the time difference between the pressure maximum in the first degassing chamber and the pressure maximum in the second degassing chamber is measured. The time interval between the pressure maxima is compared with (sum of the first time, the second time, the third time and the fourth time) divided by 4. If the deviation is, for example, greater than At / 2, then the first time or the third time can be modified in the next cycle.

[0027] In a further aspect, the invention relates to the use of the inventive method in a submarine with a fluid circuit, wherein the inventive method is carried out to degas a fluid circuit. The submarine is particularly preferably a military submarine with a fuel cell device, where reliability is therefore a high priority.

[0028] The process can be adapted to three, four or more vacuum degassers connected in parallel, whereby the time difference between the individual vacuum degassers is then set to cycle time divided by the number of degassers.

[0029] The method according to the invention is explained in more detail below with reference to an embodiment shown in the drawings.

[0030] Fig. 1 Fluid circuit with two vacuum degassers Fig. 2 Time axis without modification Fig. 3 Time axis with modification

[0031] Figure 1 shows a fluid circuit with two vacuum degassers 10 and 20. In the example shown, the fluid circuit serves as a coolant circuit for a fuel cell device 40, in which a coolant pump 50 transports the coolant via a heat exchanger 70. A pressure equalization tank 30 is connected to the circuit to compensate for, for example, volume changes caused by temperature changes of the coolant. The arrows shown serve to illustrate the

[0032] The coolant flow and the coolant flow direction are described. The coolant flow splits before the fuel cell device 40; for example, and preferably, 80% to 95% of the coolant flows through the fuel cell device 40. Only 5% to 20% of the coolant flows through the first vacuum degasser 10 or the second vacuum degasser 20. Theoretically, the coolant circuit can also be operated, at least briefly, without the two vacuum degassers 10, 20, for example, to temporarily reduce the acoustic signature by switching them off.

[0033] Fluid-technically, the first vacuum degasser 10 and the second vacuum degasser 20 are connected in parallel to the fuel cell device 40. The first vacuum degasser 10 has a first inlet valve 12, a first degassing chamber 14, and a first pump 16. The second vacuum degasser 20 has a second inlet valve 22, a second degassing chamber 24, and a second pump 26. The first inlet valve 12 and the second inlet valve 22 are controlled by a control unit 60 according to the method according to the invention. This is shown with reference to the time sequences in Figures 2 and 3.

[0034] Fig. 2 shows the time series for the first time interval (110), the second time interval (120), the third time interval (130), and the fourth time interval (140). The upper graph represents the state of the first intake valve 12. A high graph indicates that the first intake valve 12 is open; a low graph indicates that the first intake valve 12 is closed. The lower graph represents the state of the second intake valve 22. A high graph indicates that the second intake valve 22 is open; a low graph indicates that the second intake valve 22 is closed.

[0035] In the example shown, the first time is 110 35 s, the second time 120 35 s, the third time 40 s, and the fourth time 40 s. For simplicity, the first time (110 s) and the second time (120 s), as well as the third time (130 s) and the fourth time (40 s), are all chosen to be the same length; this serves only to simplify and improve clarity. In reality, all four times will differ from one another.

[0036] At the start of the cycle, the first vacuum degasser 10 and the second vacuum degasser 20 (shown on the far left) operate in perfectly opposite directions, resulting in minimal pressure fluctuations in the fluid circuit. Due to the difference in cycle duration (here 10 s), the cycles shift relative to each other, so that after a certain time they would run in parallel, thus maximizing the pressure fluctuations. To prevent this, in some cycles of the example shown, the initial time 110 is modified to a modified initial time 112, since the cycle duration of the first vacuum degasser 10 is shorter than that of the second vacuum degasser 20. This is shown in Fig. 3. For this purpose, a time interval At of 20 s is added, resulting in a modified initial time 120 of 55 s.

[0037] Reference numerals: 10 first vacuum degasser, 12 first inlet valve, 14 first degassing chamber, 16 first pump, 20 second vacuum degasser

[0038] 22 second inlet valve

[0039] 24 second degassing room

[0040] 26 second pump

[0041] 30 pressure equalization tanks

[0042] 40 Fuel cell device 50 Coolant pump

[0043] 60 Control unit

[0044] 70 heat exchangers

[0045] 110 first period

[0046] 112 modified first time

[0047] 120 second time

[0048] 130 third time 140 fourth time

Claims

Patent claims 1. A method for degassing a fluid circuit, wherein the fluid circuit comprises a first vacuum degasser (10), the first vacuum degasser (10) comprising a first inlet valve (12), a first degassing chamber (14), a first outlet valve, and a first pump (16), wherein the first pump (16) of the first vacuum degasser (10) is operated continuously such that the first pump continuously pumps fluid from the first degassing chamber back into the fluid circuit, the first vacuum degasser (10) being operated in two cycle steps, wherein in a first cycle step the first inlet valve (12) is open for a first time (110), and wherein in a second cycle step the first inlet valve (12) is closed for a second time (120), the duration of the cycle of the first vacuum degasser (10) being the sum of the first time (110) and the second time (120), characterized in that the fluid circuit comprises a second vacuum degasser (20)wherein the second vacuum degasser (20) comprises a second inlet valve (22), a second degassing chamber (24), a second outlet valve, and a second pump (26), wherein the second vacuum degasser (20) is operated in two cycle steps, wherein in a first cycle step the second inlet valve (22) is open for a third time (130), wherein in a second cycle step the second inlet valve (22) is closed for a fourth time (140), wherein the duration of the cycle of the second vacuum degasser (20) is formed from the sum of the third time (130) and the fourth time (140), wherein at least in individual cycles the first time (110) is replaced by a modified first time (112) or the third time (130) is replaced by a modified third time, such that simultaneous parallel operation of the cycles of the first vacuum degasser (10) and the second vacuum degasser (20) is avoided, and thus Pressure fluctuations in the fluid circuit are minimized.

2. Method according to claim 1, characterized in that the first time (110) is replaced by a modified first time (112) if the duration of the cycle of the first vacuum degasser (10) is less than the duration of the cycle of the second vacuum degasser (20), or the third time (130) is replaced by a modified third time is replaced if the duration of the cycle of the first vacuum degasser (10) is greater than the duration of the cycle of the second vacuum degasser (20).

3. Method according to one of the preceding claims, characterized in that the modified first time (112) is obtained by adding a time interval At to the first time (110) or the modified third time (130) is obtained by adding a time interval At to the third time.

4. Method according to claim 3, characterized in that the time interval At is selected in the range from (sum of the first time (110), the second time (120), the third time (130) and the fourth time (140)) divided by 40 to (sum of the first time (110), the second time (120), the third time (130) and the fourth time (140)) divided by 8.

5. Method according to one of the preceding claims, characterized in that a fixed cycle point is defined, wherein the time difference is measured which lies between the fixed cycle point of the first vacuum degasser (10) and the fixed cycle point of the second vacuum degasser (20).

6. Method according to a combination of claim 4 and claim 5, characterized in that the first time (110) is replaced by a modified first time (112) or the third time (130) is replaced by a modified third time, provided that the measured time difference deviates from the value sum of the first time (110), the second time (120), the third time (130) and the fourth time (140)) divided by 4 by more than the time interval At.

7. Method according to one of the preceding claims, characterized in that a first vacuum degasser (10) is arranged with a first flow rate control device arranged fluidically upstream of the first degassing chamber (14) and / or a second vacuum degasser (20) is arranged with a second flow rate control device arranged fluidically upstream of the second degassing chamber (24). A flow control device is selected, whereby the first time (110) is changed by means of the first flow control device and / or the third time (130) is changed by means of the second flow control device. is modified such that the sum of the first time (110) and the second time (120) is equal to the sum of the third time (130) and the fourth time (140) with a tolerance of ± 15%.

8. Use in a submarine with a fluid circuit, wherein the method for degassing a fluid circuit is carried out according to one of the preceding claims.

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