EP4237803A1

EP4237803A1 - Measuring device for metering fluids, and method for metering by means of a measuring device of this type

Info

Publication number: EP4237803A1
Application number: EP21830586.0A
Authority: EP
Inventors: Wolfgang Sailer
Original assignee: AVL List GmbH
Current assignee: AVL List GmbH
Priority date: 2020-11-11
Filing date: 2021-11-10
Publication date: 2023-09-06
Also published as: WO2022099340A1; US20240003727A1; AT524206B1; AT524206A4; CN116648603A

Abstract

The invention relates to measuring devices for metering fluids, comprising: a container (10) in which the fluid is stored; a fluid inlet (12) that is fluidically connected to the container (10); a fluid outlet (48) that can be fluidically connected to a metering point (11); a metering line (13), via which the fluid inlet (12) is connected to the fluid outlet (48), and in which a delivery pump (20), a density sensor (26) and a flowmeter (38) are situated; and comprising a return line (50) which branches from the metering line (13) downstream of the flowmeter (38) and opens into the container (10). In order both to obtain precise measurement results and to minimise the space requirement at the metering point (11) while requiring simple equipment, according to the invention the flowmeter (38) is situated in a measuring-unit housing (34) which is spaced apart from a pump-unit housing (16) in which at least the delivery pump (20) is situated, wherein the pump-unit housing (16) and the measuring-unit housing (34) are detachably interconnected via a connection portion (33) of the metering line (13).

Description

Measuring device for dosing fluids and method for dosing with such a measuring device

The invention relates to a measuring device for dosing fluids with a container in which the fluid is stored, a fluid inlet which is fluidly connected to the container, a fluid outlet which is fluidly connected to a dosing point, a dosing line via which the fluid inlet is connected to the fluid outlet, and in which a feed pump, a density sensor and a flow meter are arranged, and with a return line, which branches off from the dosing line downstream of the flow meter and opens into the container, and a method for dosing with such a measuring device.

Such measuring devices are used, for example, for oil consumption measurements on test benches for internal combustion engines, with the consumption measurements being able to be carried out both on engines from the automotive sector and on large engines. The challenge with these measuring devices is that it must be possible to measure small amounts of oil of around 10g to be replenished with an accuracy of around 1g and, on the other hand, to be able to fill a complete oil pan with a measurement uncertainty of 1%, as is the case, for example is necessary for a test stand preparation or an oil pan calibration procedure. The required accuracies must also be observed when vibrations occur.

A device for measuring fluid consumption is known from EP 1 729 100 A1. This includes a continuously operating flow sensor, a pressure regulator and a Förderpump pe, which are arranged in a metering line, and a return line for returning the fluid to the container and a conditioning device that at least one heat exchanger, which is used to generate an average temperature of the fluid and to stabilize the energy in the measuring circuit. However, the outlay on equipment is relatively high, so that a large amount of space is required. This is undesirable above all because this device must be arranged in the immediate vicinity of the engine in order to avoid measurement errors due to temperature gradients between the flow sensor and the internal combustion engine, since otherwise metering errors are caused due to the thermal expansion of the fluid in the metering line. These arise above all at different ambient temperatures on the measuring device or on the container, in particular on the oil tank and at the dosing point or at the consumer.

The task is therefore to create a measuring device for dosing fluids and a corresponding method with which both small quantities of fluid that are redosed and large quantities with high throughputs can be measured with a high level of accuracy. The space requirement in the vicinity of the dosing point m should be minimized. Furthermore, it is desirable that the measurement accuracy is maintained even during longer pauses or changes in the ambient temperature. The manufacturing costs should nevertheless be reduced.

This problem is solved by a measuring device for dosing fluids with the features of main claim 1 .

The measuring device has a container in which the fluid, such as oil, is stored. A fluid inlet is connected to the container, while a fluid outlet can be fluidically connected to a dosing point, which can be a consumer, such as an internal combustion engine, but can also be an oil pan. A dosing line is located between the fluid inlet and the fluid outlet, in which a feed pump, a density sensor and a flow meter are arranged are. A return line branches off the metering line downstream of the flow meter and empties into the reservoir so that the fluid can be recirculated between measurements. According to the invention, the flow meter is arranged in a measuring unit housing.

This is arranged at a distance, which can be several meters, from a pump unit housing, in which at least the feed pump is arranged. The pump unit housing is detachably connected to the measuring unit housing via a connecting section of the metering line, so that the fluid can flow from the pump unit housing into the measuring unit housing via this connecting section. This makes it possible to minimize the space required at the dosing point and still ensure that the measured mass flow corresponds to the mass flow actually supplied to the dosing point, since the same temperatures and thus the same densities of the fluid can be assumed due to the close arrangement. The container, which can take up a lot of space depending on the measurement to be made, and the pump unit housing can be arranged accordingly in another room or at any position at a distance from the measuring unit housing. Coriolis meters can be used as flow meters, but because of their small cross-sections they produce a greater pressure loss and are therefore usually replaced by volumetric displacement meters in the case of highly viscous fluids, where the temperature and density must be measured to convert them into a mass flow.

The object is also achieved by a method in which, before dosing, the fluid is circulated via the return line, with the fluid being removed in the lower area of the container and returned in the upper area of the container. This flushing process equalizes the temperature over the entire circuit. This means that changes in temperature of the fluid over time are significantly reduced during the measurement, which also means that the Density changes otherwise resulting from this are eliminated and/or at least slowed down and minimized, which could lead to measurement errors. Temperature changes during the following measurements only occur very sluggishly.

The density sensor is preferably arranged in the pump unit housing downstream of the feed pump in the metering line. This serves in particular to convert a volume flow into a mass flow. When the density meter is arranged in the pump unit housing, the base density measured by the density meter is converted into the actual medium density at the flow meter using a known thermal expansion coefficient that is dependent on the fluid, for which the temperature prevailing there must be known.

Furthermore, it is advantageous if a filter is arranged in the feed pump housing upstream of the feed pump in the metering line, which filter serves to filter out dirt from the fluid and which prevents damage to the density sensor, the flow meter or the feed pump.

In a preferred embodiment, a non-return valve is arranged in the measuring unit housing upstream of the flow meter in the dosing line, which prevents the fluid from flowing back through the flow meter, which can lead to measurement errors.

Furthermore, a temperature sensor is arranged in the measuring unit housing directly downstream of the flow meter in the dosing line. The temperature sensor is used to calculate the correct density of the fluid when converting a volume flow into a mass flow. A choke is also placed downstream of the flow meter and protects it from damage or malfunction due to excessive flow applied pressure differences, which are limited to permissible values by the throttle.

A shut-off valve is also arranged in front of the fluid outlet, and the line between the fluid outlet and the shut-off valve should be as short as possible. The shut-off valve is closed when there is flow through the return line and between measurements in order to be able to separate the measuring unit from the dosing point.

Furthermore, a fluid return valve should be arranged in the return line in order to be able to shut off the return line during the measurements.

A differential pressure sensor, which measures a differential pressure across the flow meter, is preferably arranged on the dosing line in the measuring unit housing. The differential pressure sensor ensures that the pressure loss in the flow meter does not become too great. Depending on the data from the differential pressure sensor, the throttle can be readjusted accordingly if the pressure differential is too high. Furthermore, the differential pressure sensor can be used to also record the respective differential pressures on the flow meter, which depend on the viscosity of the measurement medium, when calibrating the flow meter with different flow rates. If this calibration is repeated with several media of different viscosity, then (particularly when using a volumetric displacement meter) the measurement accuracy can subsequently be improved during a measurement process by including this calibration data in the event of any changes in the viscosity of the measurement medium.

The density sensor in the pump unit housing can advantageously be bypassed via a shut-off device. Thus, a density sensor occurring undesirably high pressure loss, which can occur especially when measuring highly viscous fluids, can be eliminated from the measuring circuit.

It can also be advantageous if the delivery pump can be bypassed via a proportional valve, since in this way the delivery flow in the metering line can be adjusted by changing the flow resistance in this bypass line. This is necessary above all in order to reduce the volume flow before the end of a batch dosing and thus to be able to set an exact dosing quantity.

It is also useful if the delivery pump can be bypassed via a safety valve. This serves to protect the downstream components and hose lines from excessive pressure.

The return line preferably branches off geodetically upwards from the metering line downstream of the flow meter. Air bubbles that are between the flow meter and the branch of the return line at the start of dosing are thus discharged upwards in the direction of the return line due to the lower density instead of being conveyed in the direction of the dosing point, where they would lead to large measurement errors. During the following flushing processes, these air bubbles are reliably discharged to the container.

In a further preferred embodiment, the dosing line extends behind the flow meter in a descending direction, so that air bubbles are also discharged from this area of the dosing line into the return line and erroneous measurements are avoided.

It is particularly preferred if the dosing line extends upwards from the fluid outlet, in which case it extends upwards Section of the metering line, the shut-off valve and the throttle are arranged. In this way, air bubbles can be reliably discharged from the entire area between the junction of the return line and the fluid outlet.

In a further embodiment of the invention, the dosing line extends steadily increasing from the fluid outlet into the return line to the fluid return valve. This constant training ensures that any air bubbles that are present actually get into the return line and can thus be removed from the system during the flushing process.

Preferably, the continuously rising section of the dosing line is made of a material with a thermal conductivity coefficient of more than 30W/mK and is thermally insulated. Due to this good heat conduction on the dosing line and the simultaneous insulation to the outside, the heat of the fluid in the system during a flushing process is also transferred to the area that is not flushed through, in which the throttle and the shut-off valve are arranged. In this way, temperature differences between this section of the dosing line and the rest of the dosing line, which could lead to measurement errors, can be eliminated or at least significantly reduced.

In a preferred embodiment, the flow meter is a Coriolis flow meter or a volumetric displacement meter. With the Coriolis flow meter, a mass flow can be determined directly and without additional calculation steps. However, this causes increased pressure losses due to narrow line cross-sections, especially with high viscosities of the measuring fluid. In these cases, a rotary displacement meter is used, the measured volume flow of which can also be converted into a mass flow via the density and also provides precise measured values. The throttle is advantageously designed as a sleeve introduced into the metering line to narrow the cross section. On the one hand, this has the advantage of a very cost-effective solution and, on the other hand, the sleeve has the throttling function to reduce the pressure difference across the flow meter and to reduce the flow cross section, which means that the temperature in the area of the throttle is quickly adjusted to the temperature of the flushed line section of the metering line he follows.

In a preferred embodiment of the method according to the invention, the fluid return valve is opened before metering and the shut-off valve in the metering line in the measuring unit housing is closed. The fluid is then conveyed in a circuit by the feed pump until the temperature of the fluid at the temperature sensor is approximately constant. This means that the entire system adapts to an average temperature of the fluid due to the circulating fluid. The feed pump is then switched off and the fluid return valve is closed. In the following, the shut-off valve is opened for dosing and measuring the mass flow, so that the feed pump delivers the fluid to the dosing point, while the mass flow is measured via the flow meter.

A measuring device for dosing fluids and a method for dosing fluids with such a measuring device are thus created, with which errors caused by temperature differences in the system are significantly reduced by temperature compensation in the system. Nevertheless, it is possible to place the measuring unit close to the dosing point with little space requirement, while the container with the fluid and the pump unit can be set up at a greater distance. In this way, the space requirement on the test stand is minimized and measurement errors due to temperature differences between the measuring point and the dosing point avoided. Measurement errors caused by dosing lines leading to a dosing point with fluid in them are excluded. In this way, very precise measured values can be achieved with a simple and inexpensive structure.

An exemplary embodiment of a measuring device according to the invention for dosing fluids is shown in the figure and is described below with the associated method according to the invention.

The figure shows a flow diagram of a measuring device according to the invention.

The measuring device according to the invention has a container 10 in which the fluid to be metered is stored. This can be, for example, an oil pan that provides oil to a dosing point 11, such as a large internal combustion engine on a test stand, with the oil consumption being measured.

In the lower area of the container 10 there is an opening which forms a fluid inlet 12 into a metering line 13 . This section of the metering line 13 is designed as a hose line and is connected via a hose coupling 14 to a pump unit housing 16 in which the metering line 13 continues.

In the pump unit housing 16, a filter 18 is arranged in the metering line 13, through which solids are separated from the fluid flow. This metering line leads further to a Förderpum pe 20, through which the fluid is conveyed from the container 10 and through the metering line 13. In the present exemplary embodiment, the feed pump 20 can be bypassed either via a proportional valve 22 or a safety valve 24 . The safety valve 24 protects the lines, components and couplings of the measuring device from closing high pressures by the safety valve 24 opens when the pressure is too high, causing the pump pressure of the Förderpum pe 20 falls. The proportional valve 22, which is alternatively or additionally arranged in another bypass line 25 that bypasses the delivery pump 20, is used to regulate the flow cross section and thus the flow resistance in this bypass line 25, whereby the flow rate in the metering line 13 can be changed, for example to set an exact metering stop time by slowly reducing the dosed mass flow before the end of dosing.

A density sensor 26 is also arranged in the metering line 13 in the pump unit housing 16 and is used to measure the density of the fluid in order to convert a volume flow into a mass flow. This density depends on the temperature, so that the density measured by the density sensor 26 must be converted to an actual density in the area of a volume flow measurement, depending on the temperature present there. In the event that the flow resistance of the density sensor 26 is too high so that the desired flow rate in the metering line 13 cannot be achieved, a bypass line 30 bypassing the density sensor 26 is provided, in which a shut-off device 28 is arranged so that the Bypass line 30 can be opened or closed, with opening of the bypass line 30, the flow in the metering line 13 and the metering point 1 1 is increased.

Thus, the feed pump 20 with the filter 18 and the density sensor 26 and the valves 22, 24, 28 and bypass lines 25, 30 described form a pump unit 32 in the present embodiment, which is arranged in the pump unit housing 16. Downstream of the density sensor 26 m, the dosing line 13 first ends at a further hose coupling 14 provided on the pump unit housing 16. A connecting section 33 of the dosing line 13 is attached to this according to the invention, with any other coupling also being possible within the meaning of the invention. This connecting section leads to a further hose coupling 14, which is fixed to a measuring unit housing 34, so that the pump unit housing 16 and the measuring unit housing 34 can be arranged at any desired distance from one another.

The dosing line 13 continues accordingly in the measuring unit housing. In the dosing line 13 in the measuring unit housing 34, a non-return valve 36 is arranged upstream of a flow meter 38, which prevents fluid from flowing in the reverse direction through the flow meter 38. Depending on the viscosity, this can be designed as a Coriolis flow meter or a volumetric displacement meter such as a gear, oval wheel or screw spindle meter.

A differential pressure sensor 40 can be arranged in a pressure line 41 surrounding the flow meter 38, via which the pressure drop across the flow meter 38 can be determined accordingly defined value must not be exceeded. In this case, an adjustable throttle 44 is arranged downstream of the flow meter 38 in the measuring unit housing 34 in the dosing line 13, via which the pressure drop across the flow meter 38 can be adjusted depending on the measured values of the differential pressure sensor 40.

Furthermore, in the immediate vicinity of the flow meter 38 is a

Temperature sensor 42 is arranged via which the fluid temperature is measured which is used both to assess whether there is an approximately uniform temperature distribution in the entire measuring device and to be able to correct the density to calculate a mass flow.

A shut-off valve 46 is also arranged in the metering line 13 downstream of the throttle 44 in front of a fluid outlet 48 via which the connection to the metering point is established. The shut-off valve 46 serves to be able to separate the measuring device from the dosing point 11 fluidically.

A return line 50 branches off from the dosing line 13 between the flow meter 38 and the throttle 44, in which a fluid return valve 52 is arranged, which is designed as a switching valve so that the return line 50 can be released or closed. The return line 50 leads via a connecting section 54 between the measuring unit housing 34 and the pump unit housing 16 into the pump unit housing and ends downstream of the pump unit housing in an upper region of the container 10. The connection of the individual line sections inside and outside of the pump unit housing 16 and the measuring unit housing 34 takes place again via hose couplings 14, with any other connections of the power sections being conceivable here as well.

In the present exemplary embodiment, the flow meter 38 with its pressure line 41, the check valve 36, the throttle 44, the shut-off valve 46, the fluid return valve 52 and the temperature sensor 42 form a measuring unit 56 which is arranged in the common measuring unit housing 34 and which requires little installation space and can be arranged in the immediate vicinity of the dosing point 11. A downstream section 49 of the dosing line 13 extends continuously upwards from the fluid outlet 48 via the shut-off valve 46 and via the throttle 44 to the return line 50 in the measuring unit housing 34 . This section 49 should also be placed as close to the flow meter 38 as possible. This serves to ensure that gas bubbles rise between the flow meter 38 and the fluid outlet 48 in the return line 50 and thus do not reach the dosing point 11, as this would lead to a falsification of the measurement results, since these gas bubbles are measured as a filled line section on the flow meter 38 would if the gas bubbles were not discharged.

According to the invention, a rinsing process is carried out before each metering. For this purpose, the shut-off valve 46 is closed and the fluid return valve 52 is opened. By energizing the feed pump 20, the fluid is then circulated out of the container via the metering line 13 and the return line 50 and fed back into the container 10 via the pump unit 32 and the measuring unit 56, whereby the gas bubbles are initially removed from the section of the return line 50 upstream of the fluid return valve 52 into the container 10 and can thus no longer falsify measurements. Furthermore, this promotion has the consequence that a temperature equalization takes place between the various sections of the metering line 13, the container 10 and the return line 50, since the supply in the upper area of the container 10 and the discharge from the lower area of the container 10 and the uniform flow through all line sections sets an average temperature which is independent of the distance from the container 10 to the pump unit 32 and the pump unit 32 to the measuring unit 56 and which can be measured by the temperature sensor 42, so that dosing, if desired, only begins when the temperature differences move within a specified interval over a defined period of time. As soon as this is the case, the feed pump PE 20 is first issued, and the fluid return valve 52 is closed. To start the dosing process, the delivery pump 20 is switched on again and the shut-off valve 46 is opened, so that the fluid is now delivered from the container 10 via the delivery pump 20 and the flow meter 38 to the fluid outlet and thus to the metering point. This also ensures that the entire mass flow takes place exclusively via the metering line 13 . During operation, the flow meter 38 measures the mass flow or volume flow that is conducted via it and thus supplied to the dosing point 11, which can be converted into a mass flow using the determined density.

The temperature of the fluid remains largely constant, so that very precise measurement results can be achieved. Errors caused by a distance and any associated temperature difference between the flow meter 38 and the dosing point 11 are also avoided, since the measuring unit 56 can be arranged in the immediate vicinity of the dosing point 11 without requiring more space than the pump unit 32 and the container 10 can be arranged at a distance of several meters from the measuring unit 56, since the measuring device is divided into different units which are only connected to one another by detachable lines. With such a measuring device, both large and small dosing quantities can be determined very precisely. The measuring accuracy is maintained even with longer pause times or changed ambient temperatures. Nevertheless, this structure is very inexpensive, since few components are required. For example, heat exchangers for establishing temperature equilibrium can be dispensed with.

In addition, measurement errors caused by gas bubbles in the dosing line are reliably avoided.

It should be clear that the scope of protection of the present

Main claims not limited to the described embodiment is. All components shown in dashed lines are only optionally available. The density sensor can also be arranged at any position or in an additional bypass line. The return line can also be routed outside the pump unit housing, so that the container can be connected directly to the measuring unit. Instead of the adjustable throttle, a narrowing of the cross-section can be used by inserting a sleeve to reduce the pressure difference at the flow meter. A throttle can also be dispensed with if necessary, particularly in the case of volumetric displacement meters.

Claims

Claims Measuring device for dosing fluids with a container (10) in which the fluid is stored, a fluid inlet (12) which is fluidly connected to the container (10), a fluid outlet (48) which is fluidly connected to a dosing point (1 1) can be connected, a dosing line (13), via which the fluid inlet (12) is connected to the fluid outlet (48), and in which a delivery pump (20), a density sensor (26), and a flow meter (38 ) are arranged, and with a return line (50) which branches off from the dosing line (13) downstream of the flow meter (38) and opens into the container (10), characterized in that the flow meter (38) is in a measuring unit housing (34 ) is arranged, which is arranged at a distance from a pump unit housing (16), in which at least the feed pump (20) is arranged, the pump unit housing (16) having the measuring unit housing (34) via a connecting section (33) of the dosing oil line (13) are detachably connected to each other. Measuring device for dosing fluids according to Claim 1, characterized in that the density sensor (26) is arranged in the pump unit housing (16) downstream of the feed pump (20) in the dosing line (13). Measuring device for dosing fluids according to one of the preceding claims, characterized in that a filter (18) is arranged in the pump unit housing (16) upstream of the delivery pump (20) in the metering line (13). Measuring device for dosing fluids according to one of the preceding claims, characterized in that a check valve (36) is arranged in the measuring unit housing (34) upstream of the flow meter (38) in the dosing line (13). Measuring device for dosing fluids according to one of the preceding claims, characterized in that a temperature sensor (42) is arranged in the measuring unit housing (34) immediately downstream of the flow meter (38) in the dosing line (13). Measuring device for dosing fluids according to one of the preceding claims, characterized in that a throttle (44) is arranged in the measuring unit housing (34) downstream of the flow meter (38) in the dosing line (13). Measuring device for dosing fluids according to one of the preceding claims, characterized in that a shut-off valve (46) is arranged in the measuring unit housing (34) downstream of the flow meter (38) in the dosing line (13) directly upstream of the fluid outlet (48). Measuring device for dosing fluids according to one of the preceding claims, characterized in that a fluid return valve (52) is arranged in the return line (50). Measuring device for metering fluids according to one of the preceding claims, characterized in that a differential pressure sensor (40) is arranged on the metering line (13) in the measuring unit housing (34), which measures a differential pressure across the flow meter (38). Measuring device for dosing fluids according to one of the preceding claims, characterized in that the density sensor (26) can be bypassed via a shut-off element (28). Measuring device for dosing fluids according to one of the preceding claims, characterized in that the feed pump (20) can be bypassed via a proportional valve (22). Measuring device for dosing fluids according to one of the preceding claims, characterized in that the feed pump (20) can be bypassed via a safety valve (24). Measuring device for dosing fluids according to one of the preceding claims, characterized in that the return line (50) branches off geodetically upwards from the dosing line (13) downstream of the flow meter (38). Measuring device for dosing fluids according to one of the preceding claims, characterized in that the dosing line (13) extends downstream of the flow meter (38) in a descending direction. Measuring device for dosing fluids according to one of the preceding claims, characterized in that the dosing line (13) extends upwards from the fluid outlet (48), the shut-off valve (46) and the throttle (44) are arranged. Measuring device for dosing fluids according to one of the preceding claims, characterized in that the dosing line (13) rises steadily from the fluid outlet (48) into the return line (50) to the fluid return valve (52). Measuring device for dosing fluids according to any one of the preceding claims, characterized in that the steadily rising section (49) of the dosing pipe (13) is made of a material with a thermal conductivity coefficient greater than 30W/mK and is thermally insulated. Measuring device for dosing fluids according to one of the preceding claims, characterized in that the flow meter (38) is a Coriolis flow meter or a volumetric displacement meter. Measuring device for metering fluids according to one of Claims 5 to 18, characterized in that the throttle (44) is designed as a sleeve introduced into the metering line (13) to narrow the cross section. Measuring device for dosing fluids according to one of the preceding claims, characterized in that the pump unit housing (16) is detachably connected to the measuring unit housing (34) via a connecting section (54) of the return line (50). Method for dosing with a measuring device according to one of the preceding claims, characterized in that prior to dosing the fluid is circulated via the dosing line and the return line (50), the fluid being removed from the lower region of the container (10). and is returned in the upper region of the container (10). Method for dosing according to Claim 21 with a measuring device according to Claims 7 and 8, characterized in that before dosing the fluid return valve (52) is opened, the shut-off valve (46) in the dosing line (13) in the measuring unit housing (34) is closed and the fluid is circulated by the feed pump (20) until the temperature of the fluid at the temperature sensor (42) is constant and then the feed pump (20) is switched off and the fluid return valve (52) is closed and then to measure the mass flow the check valve (46) is opened and the fluid via the Förderpum pe (20) to Metering point (1 1) is funded while the flow meter (38) is measured, the mass flow.