DE102015201817B4 - Mass flow curve CNG valve - Google Patents

Abstract

System (20) for measuring flow parameters of a valve through which a gas can flow for an internal combustion engine, comprising a measuring chamber (1) with at least one damping sleeve (7), a pressure sensor, a temperature sensor, a pneumatic valve (24) and a position measuring system (21), the is an optical measuring system, characterized in that a transparent body is arranged in the interior of the measuring chamber (2) in the measuring chamber (1) opposite the receiving device for the valve (3) through which gas can flow.

Description

The invention relates to a device for measuring the flow properties of a valve through which a gas can flow, and a corresponding method.

Valves through which gas can flow are used in many technical devices, e.g. B. in engines powered by natural gas. In the development of natural gas engines, also known as CNG engines (compressed natural gas, CNG), optimization of the combustion process using computational fluid dynamics (CFD) plays a major role. Precise knowledge of the injection rate is required as input information for the calculation using CFD. In addition to the amount of gas injected, the course of the injection process over time is also of interest, as this information enables a valve to be precisely assessed. In addition to the simulation, corresponding variables can also be of interest for the evaluation of different injection valves or for checking valves that are already in use. There are several measurement methods for determining the injection rate for liquid media. So e.g. B. a change in a piston stroke can be measured by the displaced volume and the volume flow can be deduced from this. Other methods determine the injection rate using the speed of sound ( DE 10 2005 056 153 A1 , DE 10 2008 040 628 A1 ). Another possibility is based on a closed, liquid-filled chamber into which the liquid is injected. The pressure in the chamber is measured and used to determine the injection rate WO 02/070 996 A2 . Suitable measuring sensors can be arranged in a fluid dosing area ( DE 10 2006 013 512 A1 ). The use of this method is problematic due to the pressure fluctuations that occur, since pressure fluctuations occur in the measuring systems and falsify the measuring signal. Furthermore, continuous measurement of multiple injections is not always possible.

In the pamphlets DE 695 24 725 T2 and U.S. 2013/0 277 039 A1 measuring chamber devices are described which have damping sleeves in the interior space, which divide the interior space in the radial direction into an inner and an outer area. Similar devices are in the references U.S. 2003/0 150 259 A1 and U.S. 2003/0 177 817 A1 described.

There is therefore the task of providing a device with which injections of gaseous media can be measured. There is also the task of providing a corresponding method.

The first object is achieved by a system having the features of claim 1, the second by a method having the features of claim 4. Further refinements and advantageous embodiments of the invention result from the dependent claims, the figures and the exemplary embodiments.

A measuring chamber for measuring parameters of a valve of an internal combustion engine through which a gas can flow has a cylindrical interior, with a receiving device for the valve, a holder device for the valve, at least one bore for receiving a pressure sensor, at least one bore for receiving a temperature sensor, and at least one damping sleeve which is arranged in the interior of the measuring chamber and which divides the interior of the measuring chamber in the radial direction into an inner and an outer area.

The terms "gas-passable valve" and "gas-passable valve" refer to the same device whose parameters are measured in this invention and are used interchangeably. If only the word “valve” is used in this description and the claims instead of a specific designation, this also means a valve through which gas can flow.

A closed space into which gas can be injected is thus formed in the measuring chamber. The injection should take place in the inner area, which is formed by the damping sleeve. The damping sleeve advantageously has a wall with hole-like openings through which the inner area and the outer area of the interior are connected to one another. The damping sleeve is intended to reduce pressure fluctuations towards the outer area formed by the damping sleeve after an injection and thus enable a pressure in the outer area that is equivalent to the averaged chamber pressure in order to obtain more precise measurement results. Furthermore, the measurements disturbing turbulence of the gas in the interior of the measuring chamber are weakened or completely avoided by the damping sleeve. The valve through which gas can flow is, for example, an injection device, and preferably a valve for introducing or injecting natural gas into the combustion chamber of internal combustion engines.

In the measuring chamber there is also access for a path measuring system. The measuring chamber thus advantageously allows, in addition to pressure and temperature measurements, to record the movements of the valve, in particular the height of the valve lift and the duration of the associated movement during injection. On this basis it is possible Partially, in addition to the amount of gas introduced, also track the course of the injection over time and thus determine the injection rate in correlation with the valve lift.

Advantageously, there is also a hole for a pneumatic valve in the measuring chamber. The measuring chamber can be vented between or during the individual injection processes via the pneumatic valve to be arranged in it. This enables continuous measurements over several injection processes.

The damping sleeve consists of a layer having a number of hole-like openings. The hole-like openings bring about a fluid connection between the inner and outer areas of the interior of the measuring chamber formed by the sleeve.

Furthermore, it is possible for at least two damping sleeves having different diameters to be arranged in the interior of the measuring chamber. In this case, for example, the damping sleeves are arranged centrally to one another.

A first aspect of the invention relates to a system for measuring flow parameters of a valve of an internal combustion engine through which a gas can flow, comprising a measuring chamber with at least one damping sleeve, a pressure sensor, a temperature sensor, a pneumatic valve and a displacement measurement system, the displacement measurement system being an optical system. The measuring chamber has the features listed above for the measuring chamber.

As mentioned above, the pneumatic valve is used to vent the measuring chamber between individual injection processes. The pneumatic valve is preferably connected to an adjustable throttle with which the discharged volume flow can be varied. The pneumatic valve is preferably also connected to a flow sensor, via which the discharged mass flow can be recorded and used for continuous calibration of the measuring chamber.

The measurement chamber allows the use of non-contact and contact displacement encoders. The path measuring system is a non-contact measuring system and an optical measuring system, for example a laser vibrometer. The displacement measurement system advantageously allows the movement of the valve through which gas can flow, i. H. essentially the valve lift. This detection is advantageous because, due to the principle of conventional measurement methods, no interfering bodies may be introduced into the flow channel where reflections could occur. In the measuring chamber, a transparent body is arranged in the interior of the measuring chamber on the end face of the measuring chamber, opposite the receiving device for the valve through which gas can flow. The transparent body can be introduced into the measurement chamber up to just before the valve through which gas can flow. This advantageously enables optical access to the valve through which gas can flow, which is not disturbed by gas flows. Alternatively, a path measuring system can be arranged in the bottom of the interior of the measuring chamber.

• - Bereitstellen einer Messkammer mit einer den Innenraum der Messkammer in radialer Richtung in einen inneren und einen äußeren Bereich teilenden Dämpfungshülse,
• - Anordnen eines von einem Gas durchströmbaren Ventils, eines Drucksensors, eines Temperatursensors und eines Pneumatikventils in bzw. an der Messkammer,
• - Füllen der Messkammer mit einem Füllgas,
• - Einspritzen eines Messgases durch das von einem Gas durchströmbaren Ventils in den inneren Bereich der Messkammer,
• - Messen von Druck- und Temperaturänderungen im äußeren Bereich der Messkammer,
• - Berechnen der eingespritzten Gasmenge aus den ermittelten Druck- und Temperaturänderungen,

wobei zusätzlich die Bewegung des Gas-durchströmbaren Ventils unter Verwenden eines optischen Wegmesssystems gemessen wird.A second aspect of the invention relates to a method for measuring parameters of a valve through which a gas can flow, using a system according to the invention, comprising the steps

• - providing a measuring chamber with a damping sleeve dividing the interior of the measuring chamber in the radial direction into an inner and an outer area,
• - arranging a valve through which a gas can flow, a pressure sensor, a temperature sensor and a pneumatic valve in or on the measuring chamber,
• - filling the measuring chamber with a filling gas,
• - Injection of a measuring gas through the valve through which a gas can flow into the inner area of the measuring chamber,
• - Measurement of pressure and temperature changes in the outer area of the measuring chamber,
• - Calculation of the injected gas quantity from the determined pressure and temperature changes,

in addition, the movement of the valve through which gas can flow is measured using an optical path measuring system.

The volume of the interior of the measuring chamber remains relatively constant. As a result, when measuring gas is injected into the interior, the pressure in the interior increases. From the change in pressure detected by the pressure sensors, the volume change corresponding to the injected gas quantity can be calculated using the equation of state for ideal or real gases. The detection of the temperature change during an injection by the temperature sensors is included in the equation of state of the gas, which increases the accuracy of the determination of the injected volume.

In addition to the direct measurement of the temperature, the temperature can also be determined using the thermodynamic equations of state Consideration of the measured pressure increase possible.

In the method according to the invention, the same gas is preferably used as the filling gas and as the measurement gas. In other words, the chamber is filled with the same gas that is used for injection.

In the method according to the invention, the movement of the valve through which gas can flow is measured. This can be done with an additional distance measuring system that is arranged in the measuring chamber. An optical path measuring system is used to measure the movement.

Furthermore, it is preferred if a mass flow is discharged from the measuring chamber via the pneumatic valve between individual injection processes. Advantageously, the discharged mass flow is recorded via a flow sensor connected to the pneumatic valve.

• 1 eine seitliche Querschnittsansicht einer Ausführungsform einer Messkammer.
• 2 eine seitliche Querschnittsansicht einer Ausführungsform des erfindungsgemäßen Systems.
• 3 die Messkammer gemäß 1 in seitlicher Perspektive.
• 4 ein Flussdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens.

The invention is explained in more detail with reference to the figures. Show it:

• 1 12 is a cross-sectional side view of an embodiment of a measurement chamber.
• 2 a side cross-sectional view of an embodiment of the system according to the invention.
• 3 the measuring chamber according to 1 in side perspective.
• 4 a flowchart of an embodiment of the method according to the invention.

The in the representation of 1 The measuring chamber 1 shown for measuring parameters of a valve through which a gas can flow has a cylindrical interior space 2 . The interior space 2 is spatially connected to a receiving device for a valve 3 through which gas can flow. The valve through which gas can flow (not shown) is an injection device, and in particular a CNG valve for introducing compressed natural gas into the combustion chamber of an internal combustion engine. Furthermore, a holding device for the valve 4 through which gas can flow is arranged on the measuring chamber, which is used to lock the valve through which gas can flow during a measuring process. A bore 5 serves to accommodate a pressure sensor which is designed to measure pressure fluctuations triggered by an injection. A bore 6 is used to accommodate a temperature sensor that detects and measures temperature changes during an injection. An essential part of the measuring chamber 1 is a damping sleeve 7, which is arranged inside the measuring chamber 1 and which divides the interior of the measuring chamber 2 in the radial direction into an inner and an outer area. The interior 2 is preferably designed in the form of a right circular cylinder; but it can also have another appropriate form. The measuring chamber 1 also has access for a displacement measuring system 8, which can also be a bore, for example. Furthermore, the measuring chamber 1 has a bore for the connection of a pneumatic valve 9 (shown in Fig 2 ).

An overall impression of the measuring chamber 1 results from the perspective view of FIG 3 . The dimensions of the measuring chamber are determined by their stability; she must e.g. B. a valve and various measuring devices such as pressure gauges and temperature gauges and remain stable. The measuring chamber is conveniently made of one or more metals or a metal alloy, but can also be made of another material that meets the requirements for stability.

The wall of the damping sleeve 7 has a plurality of hole-like openings 10 z. B. be formed by drilling. The inner area and the outer area of the interior 2 are connected to one another through these holes 10, ie a gas or also a liquid can flow from one area into the other. The wall of the damping sleeve can preferably consist of one layer, but also of several layers. As in 2 shown, a second, optional, damping sleeve 28 can be arranged in the measuring chamber 1, which has a different diameter than the first damping sleeve 7 and is arranged centrally to this. The measuring chamber 1 can also have additional damping sleeves. If there is more than one damping sleeve, the space or spaces between the damping sleeves can optionally be filled with an additional damping material 29 .

Together with the valve through which gas can flow and the measuring devices, the measuring chamber 1 forms as shown in FIG 2 a system 20. The system 20 consists of the measuring chamber 1, a pressure gauge (not shown), a temperature gauge (not shown), and an optical displacement measuring system 21 for measuring the valve lift, or in other words the movement of the valve head. The optical path measuring system is a laser vibrometer 21. Access for the laser vibrometer 21 is provided opposite the valve. The beam path 22 leads from the laser vibrometer 21 through the optical passage 23 to the valve disk of the valve (not shown), which is arranged in the receiving device 3 . Via access 8, for an optical passage 23 that is not disturbed by gas flows, up to the valve, a transparent body can be inserted into the interior until just before the valve Space of the measuring chamber 2 are introduced. Alternatively, other measuring systems, including touching ones, can also be introduced into the measuring chamber 1 via the access 8 in order to measure the valve movement.

At the hole 9 is in the representation of 2 a pneumatic valve 24 connected. The measuring chamber 1 can be vented between the individual injection processes via the pneumatic valve 24 . This enables continuous measurements over several injection processes. An adjustable throttle 26 is arranged to vary the discharged mass flow of gas. The discharged mass flow can be recorded with conventional flow sensors 27 and used for the continuous calibration of the measuring chamber 1 . A compensating volume 25 is arranged behind the pneumatic valve 24 in order to reduce the gradient of the mass flow across the flow sensor 27 .

For the detection of parameters of a valve through which gas can flow, in one embodiment according to the presentation of the method according to the invention in 4 In a first step S1, a measuring chamber 1 is provided with a damping sleeve that divides the interior of the measuring chamber 2 in the radial direction into an inner and an outer area. In a second step S2, a valve through which a gas can flow, a pressure sensor, a temperature sensor and a pneumatic valve 24 are arranged in the measuring chamber 1 . In step S3, the measuring chamber 1 is filled with a filling gas. In this case, the filling gas is preferably the same gas as that used for injection. In step S4 a measurement gas is injected through the valve through which a gas can flow into the inner area of the measurement chamber 1 formed by the damping sleeve 7 . Since the measuring chamber 1 is closed, the volume of the interior of the measuring chamber 2 does not change, but rather the pressure of the gas in the interior 2 by increasing. Pressure peaks in the interior 2 are damped by the damping sleeve 7 so that a pressure is set in the outer area formed by the damping sleeve 7 which corresponds to the mean chamber pressure and can be detected by the pressure sensors also arranged in the outer area. The temperature in the interior 2 increases on the one hand by converting the kinetic energy of the injected gas into heat and on the other hand by a temperature increase in the interior 2 due to the pressure increase. In step S5, the pressure change in the outer area of the measuring chamber is recorded with a constant volume of the interior space 2 . Due to the short injection duration, the temperature change during the injection process can only be measured with difficulty. The temperature change during the injection process is therefore advantageously modeled from the measured pressure signal via the polytropic relationship and compared with the measured temperature before and after the injection process. The polytropic exponent n is determined from the continuously performed mass flow measurement and the temperature measurement. In step S6, the gas mass present in the chamber at any point in time during the injection is determined from the measured pressure profile and the modeled or measured temperature profile using the description equations for an ideal or real gas. The change in the gas mass enclosed in the measuring chamber over time allows the determination of the mass flow and thus the injection rate.

If gas is taken from the measuring chamber via connection 9 during a measurement or injection, for example, this must and can be taken into account in the mass flow calculation.

The valve lift is measured with a laser vibrometer 21 as a path measuring system. In addition to this non-contact, optical distance measuring system, other, also touching, distance measuring systems can be used to measure the valve lift, e.g. B. can be arranged in the bottom of the measuring chamber. The laser vibrometer 21 generates a laser beam, which is guided through the optical passage 23 opposite the valve into the measuring chamber 1 and reaches the valve disk of the valve. From the height of the valve lift and the duration of the associated movement during injection, in addition to the quantity and progression of the gas introduced, an additional time progression of the valve lift is recorded, which represents a comparison variable for the injection rate. By removing a mass flow from the interior of the measuring chamber 2 via the pneumatic valve 24, continuous measurements over several injection processes are possible.

Reference List

1

measuring chamber

2

Interior of the measuring chamber

3

Receiving device for a valve through which gas can flow

4

Holder device for a valve through which gas can flow

5

Hole for a pressure sensor

6

Hole for a temperature sensor

7

damping sleeve

8th

possible access for position measuring system

9

Connection for a pneumatic valve

10

hole-like perforations

20

system

21

laser vibrometer

22

laser beam path

23

optical passage

24

pneumatic valve

25

balancing volume

26

adjustable throttle

27

flow sensor

28

optional damping sleeve

29

optional cushioning material

Claims (7)

System (20) for measuring flow parameters of a valve through which a gas can flow for an internal combustion engine, comprising a measuring chamber (1) with at least one damping sleeve (7), a pressure sensor, a temperature sensor, a pneumatic valve (24) and a position measuring system (21), the is an optical measuring system, characterized in that in the measuring chamber (1) opposite the receiving device for the valve (3) through which gas can flow, a transparent body is arranged in the interior of the measuring chamber (2). system (20) after claim 1 , in which the pneumatic valve (24) is connected to an adjustable throttle (26). system (20) after claim 1 or 2 , in which the pneumatic valve (24) is connected to a flow sensor (27). Method for measuring parameters of a valve through which a gas can flow with a system (20) according to one of Claims 1 - 3 , comprising the steps of - providing a measuring chamber (1) with a damping sleeve (7) dividing the interior of the measuring chamber (2) in the radial direction into an inner and an outer area, - arranging a valve (3) through which a gas can flow, a pressure sensor , a temperature sensor and a pneumatic valve (24) in the measuring chamber (1), - filling the measuring chamber with a filling gas, - injecting a measuring gas through the valve (3), through which a gas can flow, into the inner area of the measuring chamber (1), - measuring of pressure and temperature changes in the outer area of the measuring chamber (1), - calculating the injected gas quantity from the determined pressure and temperature changes, characterized in that the movement of the gas-throughflow valve (3) using an optical distance measuring system (21) is measured. procedure after claim 4 , whereby the same gas is used as filling gas and as measuring gas. procedure after claim 4 or 5 , with a mass flow being discharged from the measuring chamber (1) via the pneumatic valve (24) between individual injection processes. procedure after claim 6 the discharged mass flow being recorded via a flow sensor (27) connected to the pneumatic valve (24).

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