DE10111775A1 - Method and device for determining the gas outlet temperature of the turbine of an exhaust gas turbocharger of a motor vehicle - Google Patents

Abstract

A method and a corresponding device are proposed for determining the gas outlet temperature (T¶APU¶) of the turbine (2) of an exhaust gas turbocharger of a motor vehicle in the simplest possible manner. The information obtained in this way can advantageously be used for exhaust gas aftertreatment in the motor vehicle. According to the invention, it is proposed in particular to derive the gas outlet temperature (T¶APU¶) from the speed (n¶ATL¶) of the turbine (2) and the gas inlet temperature (T¶ASA¶) of the turbine (2), in particular using a turbine efficiency map comes.

Description

The present invention relates to a method and a corresponding device for Determination of the gas outlet temperature of the turbine of the exhaust gas turbocharger Motor vehicle, d. H. the gas temperature after the turbine of the exhaust gas turbocharger.

Exhaust gas turbochargers (ATL) are used in passenger car, truck and large engines, such as marine and locomotive drives. The exhaust gas turbocharger consists of two Turbomachines, namely a turbine and a compressor, on a common shaft, the so-called turbocharger shaft, are attached. The turbine uses the energy contained in the exhaust gas to drive the compressor, which in turn is fresh air draws in and pre-compressed air into the cylinders or combustion chambers of each Combustion engine presses. The exhaust gas turbocharger is only through the air and Mass flow of exhaust gas is fluidly coupled to the internal combustion engine. The The speed of the exhaust gas turbocharger does not depend on the engine speed, but on that Performance balance between the turbine and the compressor.

With the known engine management systems, it is not possible to adjust the temperature the turbine, d. H. to determine the gas outlet temperature of the turbine. The The gas outlet temperature of the turbine can, however, advantageously be used for the Exhaust gas aftertreatment in the motor vehicle can be evaluated. Basically there is although the possibility of adjusting the temperature of the exhaust gas after the turbine with the help of special Detect temperature sensors. However, this would involve the use of extremely expensive ones Temperature sensors required.

The present invention is therefore based on the object of a method and a provide appropriate device, with which the gas outlet temperature of the turbine of the exhaust gas turbocharger of a motor vehicle is determined in the simplest possible manner can be achieved without the need for separate temperature sensors.

This object is achieved by a method with the features of Claim 1 and a device with the features of claim 14 solved. The  Sub-claims each define preferred and advantageous embodiments of the present invention.

According to the invention, one is used to determine the gas outlet temperature of the turbine Exhaust gas turbocharger proposed the evaluation of measured values or information that are available in a modern engine management system anyway in particular recorded in any case around the turbine of the exhaust gas turbocharger and in the control unit of the respective engine management system are processed. In particular, the Speed of the turbine or the exhaust gas turbocharger and the gas inlet temperature of the turbine evaluated to determine the gas outlet temperature of the turbine, d. H. the gas temperature after the turbine. With the gas outlet temperature of the turbine there is therefore one additional information about the gas condition before the individual Exhaust gas aftertreatment systems of the respective motor vehicle are available, so that this additional information about the gas outlet temperature of the turbine for the Exhaust gas aftertreatment can be used advantageously.

A turbine efficiency map can preferably be used to determine the gas outlet temperature of the exhaust gas turbocharger turbine, it being possible to calculate the respectively valid turbine efficiency as a function of the current blade position of the turbine and a special turbine run number. The turbine run number is preferably derived from the normalized turbine speed. The gas outlet temperature of the turbine can then be calculated on the basis of the gas inlet temperature of the turbine, the turbine efficiency and a (non-standardized) isentropic temperature drop, the following equation being used in particular:

T _APU = T _ASA - η _T .ΔT _{T, is} (1)

T _APU denotes the gas outlet temperature of the turbine or the temperature of an exhaust gas system (APU) downstream of the turbine of the exhaust gas turbocharger, T _ASA the gas inlet temperature of the turbine or the temperature of an exhaust gas collector (ASA) upstream of the turbine, η _T the turbine efficiency and ΔT _{T, iS} the non-standardized isentropic temperature reduction of the turbine, the isentropic temperature reduction can be derived in particular from the gas inlet temperature of the turbine and the gas pressure ratio between the gas pressures before and after the turbine, taking into account the respective isentropic exponent.

The turbine efficiency is preferably calculated using a polynomial second degree depending on the respective turbine run number. The coefficients of the Second degree polynomials are also preferably represented by second degree polynomials in Dependence on the blade path of the turbine is shown.

The present invention is described below with reference to the accompanying drawings Explained with reference to a preferred embodiment.

Fig. 1 showed a simplified representation of a real-time simulator for simulating the flow of gas in a motor vehicle according to the present invention,

Fig. 2 is a diagram for illustrating the calculation shows the gas outlet temperature of a turbocharger turbine shown in FIG. 1 by a likewise in Fig. 1 shown control unit with the aid of a turbine efficiency map, and

Fig. 3 shows the profile of the turbine efficiency as a function of a turbine speed for different paddle settings of the turbine.

In Fig. 1, an engine 1 having four cylinders or combustion chambers is illustrated. The internal combustion engine 1 is coupled to an exhaust gas turbocharger (ATL), which comprises a turbine 2 and a compressor 7 , the turbine 2 and the compressor 7 being mounted on a common shaft, the so-called turbocharger shaft 14 . The turbine 2 uses the energy contained in the exhaust gas of the internal combustion engine 1 to drive the compressor 7 , which draws in fresh air via an air filter 6 and presses pre-compressed air into the individual cylinders of the internal combustion engine 1 . The exhaust gas turbocharger formed by the turbine 2 , the compressor 7 and the turbocharger shaft 14 is fluidly coupled to the internal combustion engine 1 only by the air and exhaust gas mass flow.

The air, which is sucked in and precompressed by the compressor 7 via an air filter 6 , is passed through a charge air cooler (LLK) 8 , which reduces the thermal load on the internal combustion engine 1 , the exhaust gas temperature and thus the NO _x emissions and fuel consumption, a so-called replacement volume (ERS). 9 fed. An inlet manifold (ELS) 10 is connected upstream of the individual combustion chambers of the internal combustion engine 1 . The exhaust gas generated in the combustion chambers of the internal combustion engine 1 is collected by an exhaust gas collector (ASA) 11 and fed to the turbine 2 . The turbine 2 is followed by the exhaust system (APU) 12 of the motor vehicle in the exhaust gas flow direction, which breaks down the pollutant components of the exhaust gases generated during operation of the internal combustion engine 1 and discharges the remaining exhaust gases as quietly as possible. A part of the exhaust gas generated in the combustion chambers of the internal combustion engine 1 is returned from the exhaust manifold 11 to the intake manifold 10 via an exhaust gas recirculation (EGR). The reference number 13 denotes valves arranged in corresponding air or gas paths.

Furthermore, a control device 4 is shown in FIG. 1, which is a component of a corresponding engine management system of the motor vehicle. The control unit 4 monitors various sizes or parameters of the system shown, which are detected with the aid of appropriate sensors and are fed to the control unit 4 via an interface 3 . This can be, for example, the fresh air quantity sucked in via the air filter 6 with the aid of the compressor 7 , the air temperature or the corresponding air pressure present in the replacement volume 9 or also the exhaust gas temperature present in the exhaust manifold 11 which corresponds to the gas inlet temperature of the turbine 2 , and act on the turbine or turbocharger shaft speed. The measured variables detected in this way by the control device 4 are evaluated in order to generate various actuating signals for the engine management system as a function thereof. As shown in FIG. 1, the control signals output by the control unit 4 via the interface 3 can, for example, the duty cycle of the valve 13 arranged in the exhaust gas recirculation, the guide vane adjustment 15 of the turbine 2 or the injection timing and the injection quantity of the individual combustion chambers of the Control internal combustion engine 1 via an injection system 5 injected air-fuel mixture.

As will be explained in more detail below, the control device 4 is able to determine the gas outlet temperature of the turbine 2 , ie the temperature after the turbine 2 , which is advantageous for the exhaust gas aftertreatment, by evaluating certain measured variables which are available in known engine management systems anyway can be used.

For this purpose, the turbine speed or the speed of the exhaust gas turbocharger or the turbocharger shaft 14 is first standardized as follows:

A certain reference temperature serves as the basis for the standardization, a measurement temperature of the turbine 2 , in this case 873 K, in particular being used as the reference temperature. In equation (2), n * | T denotes the normalized turbine speed, n _ATL the speed of the exhaust gas turbocharger or the turbocharger shaft 14 or the turbine 2 and T _ASA the exhaust gas temperature in the exhaust manifold 11 , ie the gas inlet temperature of the turbine 2 .

A reduced (normalized) peripheral speed of the turbine can be calculated from the normalized turbine speed as follows:

Here u * | T or ω * | T denotes the reduced peripheral or circular speed of the turbine 2 and r _T the radius of the turbine 2 . In general, the reduced peripheral speed u * | T can be obtained by multiplying the product n * | Tr _T by a constant k (in the present case k = π / 30).

If the so-called isentropic reduced temperature drop ΔT * | is is used as an intermediate variable, the ideal gas velocity can be derived from this. The isentropic reduced temperature drop is defined as follows:

T ₀ denotes the ambient temperature and Π _T the pressure ratio between the pressure before turbine 2 and the pressure after turbine 2 , ie the pressure ratio Π _T is defined as follows:

P _ASA denotes the gas pressure in the exhaust manifold 11 , ie the gas pressure upstream of the turbine 2 , while p _APU denotes the gas pressure in the exhaust system 12 , ie the gas pressure downstream of the turbine 2 .

κ denotes the isentropic exponent, which has the value 1.37 for air.  

The ideal gas velocity c * | s can be calculated from the isentropic reduced temperature reduction given above as follows:

Here, c _p denotes the specific heat capacity of the turbine 2 .

A turbine run number r * | UC can be derived as follows from the reduced peripheral speed of turbine 2 calculated according to equation (3) and from the ideal gas speed calculated according to equation (6):

This turbine run number r * | UC is used by the control unit 4 to determine the instantaneous turbine efficiency η ^T , which is a function of the turbine run number r * | UC and the blade position s of the turbine 2 . That is, the following applies:

η _T = f (s, r * | UC) (8)

Using the non-standardized isentropic temperature drop ΔT _is the turbine 2 , which is defined as follows:

T _APU = T _ASA - η _T .T _{T, is} , (9)

can be determined from the gas inlet temperature of the turbine 2 , ie the gas temperature T _ASA in the exhaust manifold 11 , and the turbine efficiency η _T, the gas outlet temperature of the turbine 2 , ie the gas temperature in the exhaust system 12 , as follows:

T _APU = T _ASA - η _T .ΔT _{T, is} (9)

The non-standardized isentropic temperature reduction based on the gas inlet temperature T _{ASA of} the turbine 2 is defined as follows:

The previously described function of the control device 4 for determining the gas outlet temperature T _APU is shown in simplified form in FIG. 2, the input variables being shown using the turbine efficiency η _T , which is in the form of a turbine efficiency map as a function of the blade position s and the turbine run number r * | UC is present, can be converted into the output variable T _APU . It should be noted in particular that the gas outlet temperature T _APU or the temperature change of the turbine 2 is derived from the gas inlet temperature T _{ASA of} the turbine 2 and the turbine or exhaust gas turbocharger speed n _ATL . According to the invention, the gas outlet temperature of the turbine 2 is thus derived from measured values, which are detected anyway in the region of the exhaust gas turbocharger turbine 2 and processed by the control unit 4 .

To calculate the turbine efficiency η _T , a second degree polynomial is used depending on the turbine run number r * | UC:

η _T = a ₀ + a ₁ .r * | UC + a ₂ .r * | UC ² with s = const. (11)

The result of this calculation is shown in FIG. 3 for different blade positions s. Fig. 3 shows that the vane position here s has a decisive influence. The turbine speed is already included in the previously described model formation via the reduced peripheral speed u * | T. It is therefore not necessary to describe the coefficients of the polynomial according to equation (11) as a function of the turbine speed. Therefore, the coefficients of the polynomial according to equation (11) can also be formed by second-degree polynomials depending on the blade position or the blade path s as follows:

a _i = b _0i , + b _1i .s + b _2i .s ² . (12)

Reference Draw List

1

internal combustion engine

2

turbine

3

interface

4

control unit

5

injection

6

air filter

7

compressor

8th

Intercooler

9

spare volume

10

intake manifold

11

collector

12

exhaust system

13

Valve

14

turbocharger shaft

15

Guide vane adjustment of the turbine
p _ASA

Gas pressure in front of the turbine
p _APU

Gas pressure after the turbine
s Turbine blade position
n _ATL

Speed of the turbocharger shaft or turbine
T _ASA

Gas inlet temperature of the turbine
T _APU

Gas outlet temperature of the turbine
η _T

Turbine efficiency
r

       * | UC     

Turbine speed

Claims (15)

1. Method for determining the gas outlet temperature of the turbine of an exhaust gas turbocharger of a motor vehicle,
wherein gas is supplied to the turbine ( 2 ) with a specific gas inlet temperature (T _ASA ) and the gas ( 2 ) is discharged with a specific gas outlet temperature (T _APU ), and
wherein the gas outlet temperature (T _APU ) of the turbine is derived from the speed (n _ATL ) of the turbine and the gas inlet temperature (T _ASA ) of the turbine ( 2 ). 2. The method according to claim 1, characterized in that
that the turbine efficiency (η _T ) is derived from the turbine speed (n _ATL ) and an isentropic reduced temperature drop in the turbine ( 2 ), and
that the gas outlet temperature (T _APU ) of the turbine ( 2 ) is derived from the turbine efficiency (η _T ) and the gas inlet temperature (T _ASA ) of the turbine ( 2 ). 3. The method according to claim 2, characterized in that the turbine efficiency (η _T ) is determined as a function of the blade position (s) of the turbine ( 2 ) and a turbine run number with the aid of a turbine efficiency map. 4. The method according to claim 3, characterized in that the turbine run number is derived from the turbine speed (n _ATL ). 5. The method according to claim 3 or 4, characterized in that the turbine efficiency (η _T ) is obtained with the aid of a second degree polynomial depending on the turbine running number. 6. The method according to claim 5, characterized in that the coefficients of the second degree polynomial are in turn formed by second degree polynomials depending on the blade position (s) of the turbine ( 2 ). 7. The method according to any one of claims 3-6, characterized in that the turbine running number (r * | UC) is determined as follows:
* where u | T * a group derived from the rotational speed of the turbine (2) peripheral speed of the turbine (2) and c | s denotes a group derived from the isentropic reduced temperature reduction gas velocity of the turbine (2). 8. The method according to any one of the preceding claims, characterized in that to determine the gas outlet temperature (T _APU ) of the turbine ( 2 ), the speed (n _ATL ) of the turbine ( 2 ) as a function of the gas inlet temperature (T _ASA ) of the turbine ( 2 ) and normalized based on a specific reference temperature. 9. The method according to claims 7 and 8, characterized in that the peripheral speed u * | T of the turbine ( 2 ) is derived as follows from the normalized speed of the turbine ( 2 ):
u * | T = kn * | Tr _T ,
where n * | T is the normalized speed of the turbine ( 2 ), r _{T is} the radius of the turbine ( 2 ) and k is a constant. 10. The method according to any one of claims 2-9, characterized in that the isentropic temperature reduction from the ambient temperature of the turbine ( 2 ), a pressure ratio between the gas pressure before the turbine ( 2 ) and the gas pressure after the turbine ( 2 ) and an isentropic Exponent is derived. 11. The method according to claims 7 and 10, characterized in that the isentropic reduced temperature decrease ΔT * | is as follows from the ambient temperature T _{0 of} the turbine ( 2 ), the isentropic exponent κ and the pressure ratio Π _T = p _ASA / p _APU is derived:
where p _ASA denotes the gas pressure before the turbine ( 2 ) and p _APU denotes the gas pressure after the turbine ( 2 ), and
the gas velocity c * | s in the turbine ( 2 ) being derived from the isotropic temperature drop as follows:
where c _p denotes the specific heat capacity of the turbine ( 2 ). 12. The method according to any one of claims 2-11, characterized in
that the gas outlet temperature T _{APU of} the turbine ( 2 ) is derived as follows from the gas inlet temperature T _{ASA of} the turbine ( 2 ) and the efficiency η _{T of} the turbine ( 2 ):
T _APU = T _ASA - η _T .ΔT _{T, is} ,
where ΔT _{T, is} a non-standardized isentropic temperature reduction of the turbine ( 2 ). 13. The method according to claim 12, characterized in that
that the non-standardized isentropic temperature drop ΔT _{T, is is derived} as follows from the gas inlet temperature T _{ASA of} the turbine ( 2 ) and an isentropic exponent κ:
where Π _T denotes the pressure ratio between the gas pressure (p _ASA ) before the turbine ( 2 ) and the gas pressure (p _APU ) after the turbine ( 2 ). 14. Device for determining the gas outlet temperature of the turbine of an exhaust gas turbocharger of a motor vehicle,
wherein the turbine ( 2 ) gas with a certain gas inlet temperature (T _ASA ) is supplied and the turbine ( 2 ) outputs the gas with a certain gas outlet temperature (T _APU ), and
A control device ( 4 ) is provided for determining the gas outlet temperature (T _APU ) of the turbine ( 2 ) from the speed (n _ATL ) of the turbine ( 2 ) and the gas inlet temperature (T _ASA ) of the turbine ( 2 ). 15. The apparatus according to claim 14, characterized in that the control device ( 4 ) for determining the gas outlet temperature (T _APU ) of the turbine ( 2 ) is designed according to the method according to any one of claims 1-13.