Measuring device and unit having such a measuring device

A measuring device having at least one at least approximately tubular probe device, by means of which an impact pressure, a total pressure or a dynamic pressure of a flow can be determined, and which is designed movable at least between a first operating state and a second operating state, where the probe device can be moved by an actuating unit in a controlled manner between the first operating state and the second operating state and held in said states.

This application claims priority to German Patent Application DE102015109416.9 filed Jun. 12, 2015, the entirety of which is incorporated by reference herein.

This invention relates to a measuring device having at least one at least approximately tubular probe device and a unit, in particular a fluid-flow machine, according to the type defined in more detail in the present disclosure.

In fluid-flow machines or aircraft engines, measuring devices are used, among others, in the bypass flow area between a fan and so-called flow-guiding devices or OGVs (outlet guide vanes) for impact pressure measurement and/or for determining the dynamic pressure. OGVs are stator vanes downstream of the fan in the flow direction and arranged in the bypass flow of the aircraft engine; they are arranged substantially in the radial direction passing through the flow cross-section of the bypass flow area and are connected to an end area with components limiting the bypass flow areas.

Devices known from actual practice for measuring impact pressures in the area of flow cross-sections of jet engines are usually arranged at an outer area of such flow-guiding devices. Measuring devices arranged in these areas of jet engines have however a detrimental effect on the test results of acoustic test routines by means of which an acoustic behaviour of jet engines is determined. This results from the fact that the measuring devices arranged in the outer area of the flow-guiding devices affect the flow in the flow cross-section of a jet engine and hence falsify measurement results during an acoustic test.

To prevent an acoustic test from being affected, for example, the measuring devices are therefore removed before every acoustic test. Several consecutive impact pressure measurements and acoustic tests therefore cause long setup times, which increase the development costs for jet engines to an unwelcome extent.

A device for measuring a static pressure in a combustion chamber is known from EP 2 221 593 B1. A probe device of the measuring device is designed movable substantially translationally or in the axial direction of the measuring device relative to a casing at least partially surrounding the probe device. Furthermore, a spring force of a spring device acting in the direction of a first operating state of the probe device is applied to the probe device, in which operating state the probe device protrudes further out of the casing than is the case in a second operating state moved against the spring device.

Depending on the static pressure prevailing in the combustion chamber in each case, a more or less large setting force opposing the spring force of the spring device and resulting from the static pressure is applied to the probe device. If this pressure-dependent setting force exceeds the spring force of the spring device applied to the probe device, said probe device is moved relative to the casing and against the spring force by the applied static pressure and increasingly received by the casing. The probe device is here moved in the axial direction against the spring until a stop on the casing side prevents any further axial movement of the probe device.

The respective static pressure prevailing in the combustion chamber thus determines the current position of the probe device. Impact pressure measurements can be conducted to the required extent over the entire operating range of an aircraft engine only within limits using the known measuring device, since pressure fluctuations of the impact pressure cause operating state changes in the area of the measuring device and therefore affect the measurement results to an extent that cannot be reconstructed.

The object underlying the invention is on the one hand to provide a measuring device for determining an operating quantity, in particular an impact pressure, by means of which units, in particular fluid-flow machines such as aircraft engines and the like, can be manufactured cost-effectively, and on the other hand to provide a unit in the area of which impact pressure measurements and acoustic tests can be performed to the required extent with short setup times.

It is a particular object of the present invention to provide solution to the above problematics by a measuring device and a unit in accordance with the features of patent Claims1and7, respectively.

The measuring device in accordance with the invention includes at least one at least approximately tubular probe device, by means of which an operating quantity of a flow can be determined, in particular an impact pressure, a total pressure, a dynamic pressure, a temperature and/or dynamic pressure fluctuations, and which is designed movable at least between a first operating state and a second operating state.

In accordance with the invention, the probe device can be moved by an actuating unit in a controlled manner between the first operating state and the second operating state and held in said states.

This advantageously offers the possibility of moving the probe device, regardless of the ambient conditions of the measuring device, at least between two defined positions translationally and/or rotationally about a pivot point in the space or in a plane and to hold it in said positions. The impact pressure measurement can then be conducted in a first position of the probe device. In the at least second position of the probe device, the latter is, with an appropriate arrangement of the measuring device, arranged relative to the flow cross-section guiding the flow such that the flow through the probe device is not affected and the acoustic test supplies unfalsified measurement results.

The measuring device in accordance with the invention offers here the particular advantage that an acoustic test can seamlessly follow an impact pressure measurement in the area of an aircraft engine, or an impact pressure measurement can follow an acoustic test, without fitting or removal of a known measuring device, since the probe device must here only be actively moved between the two operating states or positions and held in these states. As a result, successive acoustic tests and impact pressure measurements can be performed cost-effectively to the required extent with short setup times.

In an advantageous embodiment of the measuring device in accordance with the invention, the at least one probe device is designed movable in the axial direction by the actuating unit, and a distance between an end area facing the flow of the at least one probe device and the actuating unit is greater in the first operating state than when the probe device is in the second operating state, so that the probe device can be advantageously arranged with its end area facing the flow in different areas of said flow or can be moved into or moved out of these.

The probe device is designed as a Pitot probe in a simply designed and cost-effective embodiment of the device in accordance with the invention.

If the probe device is a Kiel probe, the measuring precision during determination of the impact pressure of a flow is dependent on the inflow angle of the flow in the area of the probe device to a lesser extent than is the case with other probe devices for determining an impact pressure.

The probe device is, in further advantageous embodiments of the measuring device in accordance with the invention, moved fluidically, mechanically and/or electrically between the first operating state and the second operating state and held in said states. A fluidic actuation is here characterized by a low installation space requirement and at the same time by low maintenance effort, while an electrical actuation of the probe device can be performed with low wear.

If the probe device is connected to a control unit via a connecting means, the control unit can be arranged in a simple design outside a flow cross-section in the area of which the impact pressure measurement is performed.

The unit in accordance with the invention, in particular a fluid-flow machine, has at least one component limiting a flow cross-section and at least one flow-guiding device moving into the flow cross-section substantially in the radial direction.

At least one measuring device designed in accordance with the invention is arranged at least partially in the interior of the flow-guiding device, preventing the measuring device from affecting the flow in simple manner.

In addition, in the first operating state that end of the sensor device facing the flow is, with a corresponding arrangement of the measuring device in the flow-guiding device, arranged projecting into the flow in such a way that an impact pressure measurement can be performed with the measuring device. In the second operating state, that end of the sensor device facing the flow can then be positioned relative to the flow such that the flow through the sensor device and the measuring device is almost unaffected, which is particularly advantageous for acoustic tests during which the measuring device is not needed.

If at least one opening passing through an outer area of the flow-guiding device and corresponding to the probe device is provided, through which opening the probe device can be moved into the first operating state and into the second operating state, the flow inside the flow cross-section is only affected by the measuring device to a minor extent during an impact pressure measurement and almost not affected at all during an acoustic test.

The diameter of the opening is, in an advantageous development of the device in accordance with the invention, equal to or smaller than a defined value at which the fluid flowing around the flow-guiding device is not affected by the opening in the flow-guiding device. This is the case in particular when despite the opening in the flow-guiding device, a corresponding boundary layer forms on the outer circumference of the flow-guiding device and the flow adjacent to it is unaffected by the opening in the area of the flow-guiding device.

The end area of the probe device facing the flow in the flow cross-section protrudes, in an advantageous embodiment of the device in accordance with the invention, in the first operating state of the probe device beyond an outer area of the flow-guiding device by a defined distance value at which an impact pressure measurement can be conducted. In contrast to this, the end area of the probe device facing the flow in the flow cross-section has in the second operating state of the probe device, a position relative to the outer or front area of the flow-guiding device facing the flow in which the flow is not affected by the probe device.

If at least one measuring device is provided with several probe devices, which are arranged running at least approximately parallel to one another and at a distance from one another over the height of the flow-guiding device, a flow field along the flow-guiding device, preferably along a leading edge of said flow-guiding device, can be recorded, and an impact pressure profile can be determined to the required extent over the height of the flow-guiding device or in the radial direction of the flow cross-section.

To determine the individual values measured by the probe devices from a certain area of the flow field upstream of the flow-guiding device, and hence the measurement results obtained in each case in an appropriately comparable and precise manner, the end areas of the probe devices facing the flow in the flow cross-section protrude, in a further advantageous embodiment of the device in accordance with the invention, in the first operating state beyond the outer area of the flow-guiding device by an at least approximately identical distance value.

If the unit is an aircraft engine and the flow-guiding device is arranged in a bypass flow of the aircraft engine, impact pressure measurements and acoustic tests of the aircraft engine can be conducted to the required extent with little effort and cost-effectively.

Both the features stated in the patent Claims and the features stated in the following exemplary embodiments of the subject matter in accordance with the invention are each suitable, singly or in any combination with one another, to develop the subject matter of the invention.

Further advantages and advantageous embodiments of the subject matter in accordance with the invention become apparent from the patent Claims and the exemplary embodiment described in principle in the following with reference to the accompanying drawings.

FIG. 1andFIG. 2each show areas of a unit13representing an aircraft engine designed with components14,15limiting a flow cross-section. A bypass flow of the aircraft engine13is routed here inside the flow cross-section of said aircraft engine13. The component15here corresponds to an outer engine casing, while the component14separates the bypass flow area from an inner engine area.

Several flow-guiding devices5extend between the outer component15and the inner component14in a manner known per se, withFIG. 1andFIG. 2each showing one device. The flow-guiding device5corresponds to a stator vane or a so-called OGV (outlet guide vane) which is arranged inside the aircraft engine1, in the bypass flow area of said aircraft engine1, downstream of a fan (not shown in detail) in the flow direction, to transform the flow in the bypass flow area downstream of the fan into a preferably laminar flow with the lowest possible losses.

In order that upstream of the flow-guiding devices5an operating quantity such as an impact pressure, a total pressure and/or a dynamic pressure can be determined, one or more measuring devices1in this case with several probe devices2are arranged at least in the interior of one of the flow-guiding devices5. In the exemplary embodiment of the measuring device1shown inFIG. 1andFIG. 2, said measuring device1includes six probe devices2that are at a distance from one another over the height of the flow cross-section of the bypass flow area of the aircraft engine13and are arranged at least approximately parallel to one another inside the flow-guiding device5.

The probe devices2are each designed at least approximately identical and tubular and are fastened to a probe device carrier10. The probe devices2are designed movable, using the probe device carrier10, between a first operating state and a second operating state and can be held in said states. The probe devices2are here designed translationally or axially movable in the flow direction of the flow S in the flow cross-section of the bypass flow area of the aircraft engine1.

An actuating unit3is provided for moving the probe devices2between the first operating state shown inFIG. 1and the second operating state shown inFIG. 2. The actuating unit3is connected via a connecting means4to a control unit16positioned externally to the aircraft engine13and is controlled by said control unit16. Using the actuating unit3, the probe devices2are moved to the respectively required operating state and held in the defined positions once the required positions of the actuating unit3and of the probe devices2have been reached.

In this connection, the term “held” subsumes not only axial guidance of the probe devices2but also locking of the probe devices2in the respectively required positions of the first and second operating states.

The probe devices2are here, in the embodiment of the unit13shown inFIG. 1andFIG. 2, moved mechanically, by gear wheels11and by racks12meshing with them, between the axial position corresponding to the first operating state and the axial position corresponding to the second operating state of the probe devices2and respectively held or locked in said positions. There is a possibility here to drive the gear wheels11rotationally by one or more electric motors and to transform the rotational drive via the rack into a translational actuation movement of the probe devices2. The racks12are here connected to the probe device carrier10for that purpose.

Alternatively, it is also possible here to axially adjust the probe devices2using other electric drives, for example using an electromagnet, or fluidic actuators such as pneumatic or hydraulic piston-cylinder units.

A measuring device1has several probe devices2. In the example shown inFIG. 1andFIG. 2, six probe devices2are arranged in a row approximately parallel to the leading edge of the flow-guiding device5. The measuring device1is arranged in the interior of the flow-guiding device5.

The probe devices2are designed tubular and are fastened to a probe device carrier10. The probe devices2are designed jointly movable with the probe device carrier10and are here each designed as a Pitot probe, to permit determination of the impact pressure of the flow S to the required extent.

Alternatively, it is also possible to design the probe devices as a Kiel probe, also termed “Kiel head probe” or “Kiel tube”. A Kiel probe substantially includes a Venturi nozzle, in which a Pitot probe is arranged in addition. The Venturi nozzle of a Kiel probe of this type deflects the flow S in the axial direction during the impact pressure measurement and thus ensures a constant flow onto the Pitot probe. The deflection of the flow S in the axial direction makes the measured impact pressure values to a certain degree independent of the pitch angle of the probe devices2relative to the flow S.

FIG. 3shows a further embodiment of the measuring device1, in which a probe device2is firmly connected to a piston unit9. The piston unit9is arranged movable longitudinally or in the axial direction in a cylinder unit8designed as a hollow cylinder.

If a first pressure p_1is applied in the area of a first line L1, the piston unit9is moved relative to the cylinder unit8such that the probe device2increasingly protrudes from the interior of the cylinder unit8. In addition, a second pressure p_2can be applied to the piston unit9that counteracts the first pressure p_1in the area of a second line L2. By selective application of the two pressures p_1and p_2, the probe device2can be axially adjusted to any required extent and for example held in the first operating state of the probe device2and in the second operating state of the probe device2and in the axial positions corresponding to said states.

With further reference to the representations according toFIG. 1andFIG. 2, the probe devices2are adjustable relative to the flow-guiding device5, regardless of the design of the actuating unit3, in the manner described in more detail in the following.

In the first operating state shown inFIG. 1, the probe devices2are at a distance x_2from the actuating unit3opposite the flow-guiding device5with their end areas2A facing the flow S, from a front area5A of the flow-guiding device5likewise facing the flow S, and at a distance x_1from the actuating unit3, and the probe devices2each protrude with a defined length into the flow cross-section or bypass flow area of the aircraft engine13. In this first operating state of the probe devices2, an impact pressure measurement can be conducted in the area of said probe devices2.

In contrast to this, the probe devices2each have in the positions shown inFIG. 2their second operating state, in which the end areas2A of the probe devices2close substantially flush with the front area5A of the flow-guiding device5. As a result, the distance x_1between the end area2A of one of the probe devices2facing the flow S and the actuating unit3, and the distance x_2between the end area2A of one of the probe devices2facing the flow S and the front area5A of the flow-guiding device5, are by definition larger in the first operating state of the probe device2than in the second operating state of said probe device2.

The flush arrangement between the front area5A of the flow-guiding device5and the end areas2A of the probe devices2has the effect that in the second operating state of the probe devices2the flow S is not affected by the measuring device1and in the so-called retracted operating state of said probe devices2an acoustic test of the jet engine13can be performed to the required extent without prior removal of the measuring device1.

The distance value x_2in the first operating state of the probe devices2is selected such that the end areas2A of the probe devices2are not only at a distance from the outer area5A of the flow-guiding device5, but additionally also protrude beyond a boundary layer7of the flow S forming on the outer circumference of the flow-guiding device5. The end areas2A of the probe devices2facing the flow S in the flow cross-section are thus outside the boundary layer7in the first operating state of said probe devices2. This ensures that the results of the impact pressure measurement reproduce the pressure conditions actually prevailing in the bypass flow area.

The probe devices2of the measuring device1can be passed, through openings6of the flow-guiding device5provided in the front area5A, out of the interior of the flow-guiding device5into the bypass flow area of the aircraft engine13and protrude through these openings6out of the flow-guiding device5in the correspondingly adjusted operating state.

To prevent the flow S from being affected by the openings6, said openings6have a defined diameter d. Above defined diameter values for the openings6, the flow S is impaired both in the second operating state of the probe devices2and in later operation of the aircraft engine13with the measuring device1removed, which however is unwelcome.

Depending on the respective application, it is also possible that some of the end areas2A of the probe devices2in the second operating state of the probe devices2, unlike in the flush arrangement, protrude to a minor extent beyond the front area5A of the flow-guiding device5and project at least partially into the boundary layer7. Furthermore, it can also be provided that some of the end areas2A of the probe devices2facing the flow S are arranged in the interior of the flow-guiding device5at a distance from the front area5A of the flow-guiding device5.

Regardless of the respective positions of the end areas2A of the probe devices2in the second operating state of said probe devices2, it must in any event be ensured that the probe devices2in their second operating states do not impair or affect the flow S around the flow-guiding device5, to permit an acoustic test to be conducted to the required extent.

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