DE102015203636B3 - A system and method for determining a local temperature of exhaust gas flowing in an exhaust conduit - Google Patents

Abstract

The invention relates to a system (1) for determining a local temperature of an exhaust gas flowing in an exhaust pipe (2), with which the exhaust gas can be supplied to a turbine (3) of an exhaust gas turbocharger (4). In order to enable a more accurate detection of the temperature of a turbine (3) of an exhaust gas turbocharger (4) supplied exhaust gas, the invention proposes that the system (1) at least two on the exhaust pipe (2) can be arranged pressure sensors (5), with respect a flow direction (6) of the exhaust gas flowing in the exhaust pipe (2) arranged at a predetermined distance one behind the other and each for detecting a local static pressure and a total local pressure in the exhaust gas and for generating the respectively detected local static pressure and the respectively detected having at least one signal technically with the pressure sensors (5) connectable electronic unit (7) which is adapted to receive the pressure signals and from the pressure signals and the predetermined distance of the pressure sensors (5) the local temperature of the exhaust gas to investigate.

Description

The invention relates to a system and a method for determining a local temperature of an exhaust gas flowing in an exhaust pipe, with which the exhaust gas can be supplied in particular to a turbine of an exhaust gas turbocharger.

A temperature of a turbine of an exhaust gas turbocharger, with which an internal combustion engine can be charged, via an exhaust gas feedable exhaust gas has a significant influence on the performance of the internal combustion engine. Therefore, the temperature of the exhaust gas is usually monitored and used to control an operation of the internal combustion engine.

For detecting the temperature of the exhaust gas to be fed to a turbine of an exhaust gas turbocharger, it is customary to use temperature encoders. With thin temperature transducers, temperature fluctuations in the exhaust gas can be detected more accurately than with thick temperature transducers. However, thinner temperature transducers are more short-lived than thicker temperature transducers. With such temperature sensors usually only a mean temperature of the exhaust gas can be detected. On the other hand, high-frequency temperature fluctuations which are present in a strongly pulsating exhaust gas flow emanating from an internal combustion engine can not be detected with such inert temperature transducers.

The DE 39 37 784 A1 describes a method for determining the rapidly changing averaged temperature of a flowing medium. For this purpose, a mass flow of the medium flowing through a throttle point is determined. In addition, a pressure is detected on the one hand upstream of the throttle point and on the other hand within the throttle point or downstream of the throttle point, each with a pressure sensor. Due to the mass flow and the pressure, in particular the pressure difference between the pressure upstream of the throttle point and the pressure inside or downstream of the throttle point, the average temperature of the medium is determined.

The DD 265 464 A1 describes a method and an arrangement for measuring temperature in closed piping systems. For this purpose, a static and a dynamic portion of the pressure of a medium in the closed piping system is recorded with a single pressure transducer. The pressure components are converted into electrical signals. From the signals corresponding to the dynamic pressure component, a low-frequency signal component is filtered out, which is generated by internal or external excitations, for example by motors, pumps or the like. This makes possible the use of the closed piping system in the primary circuit of nuclear power plants, heating networks and in the chemical industry. The temperature of the medium is determined by comparing with a characteristic of the temperature of the medium previously determined and stored for the closed-pipe system to be examined by calibration measurements.

The DE 26 59 742 A1 relates to a measuring device for determining high gas temperatures. For this purpose, the measuring device comprises a suction probe with which so much gas is sucked off to determine the local temperature in a hot gas stream that sets the sound velocity of the gas in the smallest passage cross section of a arranged in a head of the suction probe Laval nozzle. The smallest passage cross-section of the Laval nozzle is connected to a pressure measuring instrument, with which a static pressure can be detected. From the Laval nozzle leads a line to a flow meter, to which a suction fan is connected. The flow meter comprises a measuring instrument for measuring the differential pressure between the pressures applied to lines. Between the Laval nozzle and the flow meter, a heat exchanger for cooling the gas flowing in the conduit is arranged. With the suction probe very high temperatures can be measured, as they occur for example in the reaction zone of combustion chambers.

The object of the invention is to enable a more accurate detection of the temperature of an exhaust gas flowing in an exhaust pipe.

This object is solved by the independent claims. Advantageous embodiments are specified in particular in the dependent claims, each of which taken alone or in various combinations with each other can represent an aspect of the invention.

The system according to the invention for determining a local temperature of an exhaust gas flowing in an exhaust gas line, with which the exhaust gas can be supplied to a turbine of an exhaust gas turbocharger, comprises at least two pressure sensors which can be arranged or arranged on the exhaust gas line and which are arranged in a predetermined direction relative to a flow direction of the exhaust gas flowing in the exhaust gas line Disposed one behind the other and each arranged for detecting a local static pressure and a total local pressure in the exhaust gas and for generating the respectively detected local static pressure and the respectively detected local total pressure corresponding pressure signals are arranged, and at least one signal technically connectable to the pressure sensors or connected Electronic unit, which is adapted to receive the pressure signals and to determine the local temperature of the exhaust gas from the pressure signals and the predetermined distance of the pressure sensors.

According to the invention, no temperature encoders are used to determine the local temperature of the exhaust gas flowing in the exhaust gas line. Instead, pressure sensors are used with which the local static pressure and the local total pressure, and in particular also high-frequency pressure fluctuations, can be detected very accurately in the exhaust gas. Since the local temperature of the exhaust gas is derived from these very accurate pressure measurements, a much more accurate determination of the local temperature of the exhaust gas can thus take place via these pressure sockets. With conventional temperature sensors such an accurate determination of the local temperature of the exhaust gas is not possible.

To determine the local temperature of the exhaust gas from the pressure signals and the predetermined distance of the pressure sensors known fluid dynamic equations or known physical relationships can be used. For the local temperature T of the exhaust gas, the following equation can be derived:

Here, x _1, the location of a pressure sensor, x ₂ of the location of the other pressure sensor, x ₂ -x _1, the predetermined distance between the pressure sensors, the isentropic exponent, R γ the specific gas constant, P _tot of the local total pressure and p _stat of the local steady- Print.

The electronics unit may comprise at least one microprocessor capable of executing at least one algorithm containing the above equation. The respectively generated pressure signals and the predetermined distance of the pressure sensors are the input variables for such an algorithm.

The electronics unit may be configured to determine the local temperature of the exhaust gas in a time-resolved manner, thereby enabling accurate monitoring of the local temperature of the exhaust gas and accurate prediction of anticipated thermal loading of the turbine of the exhaust gas turbocharger with heat contained in the exhaust gas. As a function of this prediction, a control and / or regulation of an operation of an internal combustion engine charged with the exhaust-gas turbocharger can take place, as a result of which the operation of the internal combustion engine can be optimized, in particular with regard to the power of the internal combustion engine. The data obtained by monitoring the local temperature of the exhaust gas can be used to design an internal combustion engine and / or exhaust gas turbocharger or to design the operation of the internal combustion engine. Furthermore, the data can be used to evaluate existing theoretical models.

According to an advantageous embodiment, the electronic unit is set up to determine a local Mach number in the exhaust gas from a ratio of the respective detected local total pressure and the respective detected local static pressure, from the pressure signals and the predetermined distance of the pressure sensors a speed of a pressure wave in the Determine exhaust gas to determine from the respectively determined local Mach number and the respectively determined speed of the pressure wave, a local speed of sound in the exhaust gas, and from the respectively determined local Mach number, the respectively determined speed of the pressure wave and the respectively determined local sound velocity to determine the local temperature of the exhaust gas. The velocity of the pressure wave in the exhaust gas is a function of the local Mach number in the exhaust gas and the local velocity of sound in the exhaust gas, where the local velocity of sound is again a function of the local temperature of the exhaust gas. To determine the speed of the pressure wave in the exhaust gas from the pressure signals and the predetermined distance of the pressure sensors, the times can be detected by means of the electronic unit, at which a pressure wave passes the upstream pressure sensor and the same pressure wave passes the pressure sensor downstream of this pressure sensor. From this, the electronic unit can determine the time required for the pressure wave to pass from the upstream pressure sensor to the downstream pressure sensor. Subsequently, the predetermined distance between the pressure sensors can be divided by the determined time, resulting in the speed of the pressure wave.

According to the method according to the invention for determining a local temperature of an exhaust gas flowing in an exhaust pipe, with which the exhaust gas of a turbine of an exhaust gas turbocharger can be fed to at least two with respect to a flow direction of the exhaust gas flowing in the exhaust pipe at a predetermined distance successively arranged measuring points a local static Detects pressure and a local total pressure in the exhaust gas and generates the respectively detected local static pressure and the respectively detected local total pressure corresponding pressure signals, wherein from the pressure signals and the predetermined distance of the pressure sensors, the local temperature of the exhaust gas is determined.

With the method, the advantages mentioned above with respect to the system are connected accordingly. In particular, the system can be set up to carry out the method.

According to an advantageous embodiment, a local Mach number in the exhaust gas is determined from a ratio of the respective detected local total pressure and the respectively detected local static pressure, a velocity of a pressure wave in the exhaust gas is determined from the pressure signals and the predetermined distance of the measurement points From the respectively determined local Mach number and the respective determined speed of the pressure wave, a local speed of sound in the exhaust gas is determined, and is determined from the respectively determined local Mach number, the respectively determined speed of the pressure wave and the respectively determined local speed of sound, the local temperature of Exhaust gas determined. With this embodiment, the advantages mentioned above with respect to the corresponding embodiment of the system are connected accordingly.

In the following, the invention will be explained by way of example with reference to the attached figure with reference to a preferred embodiment, wherein the features shown below may represent an aspect of the invention both taken alone and in various combinations with each other. It shows:

1 a schematic representation of an embodiment of a system according to the invention.

1 shows a schematic representation of an embodiment of a system according to the invention 1 for determining a local temperature of an exhaust pipe 2 flowing exhaust gas, with which the exhaust gas of a turbine 3 an exhaust gas turbocharger 4 can be fed.

The system 1 includes two on the exhaust pipe 2 arranged pressure sensors 5 , with respect to a flow direction 6 in the exhaust pipe 2 flowing exhaust gas at a predetermined distance x ₂ -x ₁ arranged _one behind the other and each for detecting a local static pressure p _stat , a positive local total pressure p _{pos, tot} and a negative local total pressure p _{neg, dead} in the exhaust gas and for generating the respectively detected local static pressure p _stat , the respectively detected positive local total pressure p _{pos, tot} and the respectively detected negative local total pressure p _{neg, dead} corresponding pressure signals are set up.

The system 1 furthermore comprises a signal line with the pressure sensors via signal lines S 5 connected or connectable electronics unit 7 which is arranged to receive the pressure signals and from the pressure signals and the predetermined distance x ₂ -x _{1 of} the pressure sensors 5 to determine the local temperature of the exhaust gas.

The electronics unit 7 can be configured to determine from a ratio of the respectively detected local total pressure p _{pos, tot} or p _{neg, dead} and the respectively detected local static pressure p _stat a local Mach number in the exhaust gas, from the pressure signals and the predetermined distance x ₂ -x _{1 of} the pressure sensors 5 To determine a speed of a pressure wave in the exhaust gas to determine from the respectively determined local Mach number and the respectively determined speed of the pressure wave, a local speed of sound in the exhaust gas, and from the respectively determined local Mach number, the respectively determined speed of the pressure wave and the respectively determined local sound velocity to determine the local temperature of the exhaust gas.

LIST OF REFERENCE NUMBERS

1

 system

2

 exhaust pipe

3

 turbine

4

 turbocharger

5

 pressure sensor

6

 flow direction

7

 electronics unit

S

 signal line

Claims (4)

System ( 1 ) for determining a local temperature of an in an exhaust pipe ( 2 ) flowing exhaust gas, with which the exhaust gas of a turbine ( 3 ) of an exhaust gas turbocharger ( 4 ) can be supplied, characterized by at least two on the exhaust pipe ( 2 ) can be arranged or arranged pressure sensors ( 5 ), which with respect to a flow direction ( 6 ) of the exhaust pipe ( 2 ) arranged exhaust gas at a predetermined distance one behind the other and which are respectively adapted to detect a local static pressure and a local total pressure in the exhaust gas and to generate the respectively detected local static pressure and the respectively detected local total pressure corresponding pressure signals, and at least one signal technically with the pressure sensors ( 5 ) connectable or connected electronic unit ( 7 ), which is adapted to receive the pressure signals and from the pressure signals and the predetermined distance of the pressure sensors ( 5 ) to determine the local temperature of the exhaust gas. System ( 1 ) according to claim 1, characterized in that the electronic unit ( 7 ) is set up to determine a local Mach number in the exhaust gas from a ratio of the respectively detected local total pressure and the respective detected local static pressure, from the pressure signals and the predetermined distance of the pressure sensors ( 5 ) to determine a speed of a pressure wave in the exhaust gas to determine from the respectively determined local Mach number and the respectively determined speed of the pressure wave, a local speed of sound in the exhaust gas, and from the respectively determined local Mach number, the respectively determined speed Pressure wave and the respectively determined local sound velocity to determine the local temperature of the exhaust gas. Method for determining a local temperature of an in an exhaust pipe ( 2 ) flowing exhaust gas, with which the exhaust gas of a turbine ( 3 ) of an exhaust gas turbocharger ( 4 ) can be fed, characterized in that at least two with respect to a flow direction ( 6 ) of the exhaust pipe ( 2 A local static pressure and a total local pressure in the exhaust gas are detected at a predetermined distance and a respective local pressure and the respectively detected local total pressure corresponding pressure signals are generated from the pressure signals and the predetermined distance of the measuring points the local temperature of the exhaust gas is determined. A method according to claim 3, characterized in that from a ratio of the respectively detected local total pressure and the respectively detected local static pressure, a local Mach number is determined in the exhaust gas, from the pressure signals and the predetermined distance of the measuring points, a speed of a pressure wave in the Exhaust gas is determined from the respectively determined local Mach number and the respectively determined speed of the pressure wave, a local speed of sound is determined in the exhaust gas, and from the respectively determined local Mach number, the respective determined speed of the pressure wave and the respectively determined local sound velocity the local temperature of the exhaust gas is determined.

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