CN-115087847-B - Method for measuring the liquid flow rate at the outlet of a pump

Abstract

The methods for measuring the flow rate of a liquid (5) at the outlet of a pump (11) are notable in that a known volume of a gas accumulator (13) is provided at the outlet of the pump, the gas or liquid pressure of the gas inside the accumulator (13) is measured, from which the volume of the gas inside the accumulator (13) is derived, then the volume of the liquid inside the accumulator (13), then the flow rate of the liquid at the outlet of the accumulator (13).

Inventors

• G. Magan

Assignees

• 纬湃科技有限责任公司

Dates

Publication Date

20260505

Application Date

20210209

Priority Date

20200217

Claims (8)

1. 1. Method for measuring the flow rate of a liquid (5) at the outlet of a pump (11), characterized in that a gas reservoir (13) of known volume is provided at the outlet of the pump, in the bottom (19) thereof for positioning down in service, with the inlet of said liquid leaving the pump, the gas or liquid pressure inside the reservoir (13) is measured, from which the volume (V0, V1, V2) of the gas inside the reservoir (13) is derived, then the volume of said liquid inside the reservoir (13) is derived from the volume (V0, V1, V2) of the gas, and then the flow rate of said liquid at the outlet of the reservoir (13) is derived from the volume of said liquid, said outlet of said liquid (5) being placed in the upper part of the reservoir and for positioning up in service, Wherein the liquid (5) entering the accumulator (13) through the inlet in the bottom (19) of the accumulator (13) is in direct communication with the gas inside the accumulator (13).
2. 2. A method according to claim 1, characterized in that the speed of the pump (11) is controlled as a function of the measured flow rate.
3. 3. A method according to any one of claims 1 or 2 applied to measure the flow rate of urea to reduce NOx emissions in the exhaust gas of a diesel engine.
4. 4. The method of any one of claims 1 or 2 applied to measuring the flow of water used to cool a gasoline engine.
5. 5. A gas accumulator (13) for implementing the method according to any one of claims 1 to 4, characterized in that it comprises, in its bottom (19) for positioning downwards in service, an inlet for the liquid, and in its upper part for positioning upwards in service, an outlet for the liquid (5), which is provided with a dip tube (17), the end (23) of which extends from the upper part of the gas accumulator (13) to above the inlet for the liquid and the distance (d) of the end (23) of which is calibrated with respect to the bottom (19).
6. 6. A gas accumulator (13) according to claim 5, characterized in that it has a shape with a cross section decreasing towards its bottom.
7. 7. A gas accumulator (13) according to any of claims 5 or 6, characterized in that it comprises a constriction (25) in its middle portion.
8. 8. Device for measuring the flow of liquid at the outlet of a pump, characterized in that it comprises an accumulator (13) according to any one of claims 5 to 7, and a control means programmed to implement the method according to any one of claims 1 to 4.

Description

Method for measuring the liquid flow rate at the outlet of a pump Technical Field The present invention relates to a method for measuring the liquid flow rate at the outlet of a pump and finds its application in particular in the automotive field. Background Various methods and devices for measuring the liquid flow rate at the outlet of a pump are known from the prior art, which typically use a flow meter or a volumetric pump. Technical problem to be solved The cost of these flow meters and these volumetric pumps is relatively high and their reliability is questionable. The object of the present invention is therefore in particular to provide a device for measuring the flow rate of a liquid at the outlet of a pump which makes it possible to reduce costs and remain reliable over time. Disclosure of Invention This object, as well as other objects that will appear when reading the following description, are achieved by a method for measuring the flow rate of a liquid at the outlet of a pump, which is notable in that a gas reservoir of known volume is provided at the outlet of the pump, in the bottom thereof for positioning downwards in service, with the inlet of said liquid exiting from the pump, the gas or liquid pressure inside the reservoir is measured, from which the volume of gas inside the reservoir is derived, followed by the volume of said liquid inside the reservoir, followed by the flow rate of the liquid at the outlet of the reservoir, said outlet of said liquid being placed in the upper part of the reservoir and for positioning upwards in service. Thanks to this method, accurate information about the flow rate leaving the gas accumulator can be obtained by simply measuring the gas pressure above the liquid, which is then used to derive therefrom the volume of this gas inside the accumulator using the ideal gas equation. From the difference, the volume of liquid inside the accumulator is derived, from which the volume of liquid leaving the accumulator per unit time (i.e. the liquid flow rate at the outlet of the accumulator) can then be derived by calculating the integral over time. In this way, a very accurate measurement of the liquid flow rate at the outlet of the gas accumulator is obtained without the use of a flow meter. It should also be noted that the use of a gas accumulator (i.e. in fact a simple reservoir comprising a liquid phase overridden by a gas phase) eliminates any mechanism of the spring and/or separation membrane type between the two phases, making it possible to eliminate all the risks of seizing or failure (hysteresis, etc.) inherent in these mechanisms and to minimize manufacturing costs, in particular because the pressure sensor and the processing of the information provided by this sensor already form part of the host system, ensuring pressure regulation. According to other optional features of the method according to the invention, which may be taken alone or in combination: The speed of the pump is controlled as a function of the measured flow rate, the adjustment mechanism being controllable by the electronic controller of the vehicle making it possible to adjust the speed of the pump to the desired liquid flow rate; this particular application of the method is indicated in particular for this type of engine, in which it is important to be able to perform a regulation of the precise regulation of the urea flow rate; it is indeed important that the intended urea volume is delivered to meet the criteria applicable to the treatment of exhaust gases from diesel engines; This particular application of the method may be suitable for future pollution prevention requirements where fuel usage is likely to be prohibited to reduce the internal temperature of the engine. The invention also relates to a gas accumulator for implementing the method according to the above, notably comprising an inlet for said liquid in its bottom for positioning downwards in service and an outlet for said liquid in its upper portion for positioning upwards in service, provided with a dip tube whose end is calibrated with respect to the distance of said bottom. Such a gas accumulator makes it possible to know precisely the volume of gas corresponding to the case where the level of the liquid just reaches the end of the tube, since the distance of the end of the separator tube from the bottom of the accumulator is known precisely. According to other optional features of the gas accumulator that may be taken alone or in combination: the gas accumulator has a shape with a cross-section decreasing towards its bottom, this particular shape of the accumulator making it possible to reduce the variation of the volume of liquid and therefore of gas when the inclination of the accumulator is modified (i.e. when the vehicle is travelling on a sloping land); the gas accumulator comprises a constriction in its middle part, which particular shape of the accumulator makes it possible to reduce gas losses if the free sur