DE10111775B4 - Method and device for determining the gas outlet temperature of the turbine of an exhaust gas turbocharger of a motor vehicle - Google Patents

Abstract

Method for determining the gas outlet temperature of the turbine of an exhaust gas turbocharger of a motor vehicle,
wherein the turbine (2) gas is supplied with a certain gas inlet temperature (T _ASA ) and from the turbine (2) the gas having a certain gas outlet temperature (T _APU ) is output, 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).

Description

The The present invention relates to a method and to a corresponding method Device for determining the gas outlet temperature of the turbine of the Exhaust gas turbocharger of a motor vehicle, d. H. the gas temperature the turbine of the exhaust gas turbocharger.

turbocharger (ATL) are used in car, truck and large engines, such as Ship and locomotive drives, used. The exhaust gas turbocharger consists of two turbomachines, namely one Turbine and a compressor operating on a common shaft, the So-called turbocharger shaft are mounted. The turbine uses the energy contained in the exhaust gas for driving the compressor, the in turn draws in fresh air and pre-compressed air into the cylinder or combustion chambers of the respective internal combustion engine presses. The turbocharger is fluidly with the internal combustion engine only through the air and exhaust gas mass flow coupled. The speed of the turbocharger does not depend on the engine speed but from the power balance between the turbine and the compressor.

With the known engine management systems, it is not possible to Temperature after the turbine, d. H. the gas outlet temperature of Turbine, to determine. The gas outlet temperature of the turbine can but advantageously for the exhaust aftertreatment be evaluated in the motor vehicle. in principle although it is possible Temperature of exhaust gas on a turbine by means of special To detect temperature sensors. But this would be the use of extreme expensive temperature sensors required.

From the DE 195 25 667 A1 a method for monitoring the exhaust gas temperature is known, wherein detected by a temperature sensor, the gas outlet temperature and based on the known gas outlet temperature, the gas inlet temperature is modeled.

In addition, from the post-published DE 199 63 358 A1 a method for determining the gas outlet temperature of the turbine of an exhaust gas turbocharger, wherein the gas outlet temperature is derived from the gas inlet temperature. Also, this document discloses the determination of the rotational speed of the turbine in order to calculate the manipulated variables of the air system can.

Of the The present invention is based on the object, a method and to provide a corresponding device, whereby the Gas outlet temperature of the turbine of the exhaust gas turbocharger of a motor vehicle on as possible simple way can be determined without the use of separate temperature sensors is required.

These The object is achieved by a Method with the features of claim 1 or a Device solved with the features of claim 14. The Define subclaims respectively preferred and advantageous embodiments of the present invention Invention.

According to the invention is for Determination of the gas outlet temperature of the turbine of an exhaust gas turbocharger the evaluation of measured values or information proposed, which are available anyway in a modern engine management system and in particular anyway detected around the turbine of the exhaust gas turbocharger and in the control unit of the respective engine management system are processed. It will in particular, the speed of the turbine or the exhaust gas turbocharger and evaluated the gas inlet temperature of the turbine to make it the gas outlet temperature of the turbine, d. H. the gas temperature after the turbine, divert. With the gas outlet temperature of Turbine is thus an additional information about the gas state before the individual exhaust aftertreatment systems of respective motor vehicle available, so that these additional information about the gas outlet temperature of the turbine for the exhaust aftertreatment advantageous can be used.

In order to determine the gas outlet temperature of the exhaust gas turbocharger turbine, a turbine efficiency map can preferably be used, it being possible to calculate the respectively valid turbine efficiency as a function of the momentary blade position of the turbine and of a special turbine engine speed. The turbine speed 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-normalized) isentropic temperature reduction, in which case the following equation is used in particular: T APU = T ASA - η T · .DELTA.T T, is (1) where T _APU refers to the gas outlet temperature of the turbine or the temperature of an exhaust gas turbine turbine downstream of the exhaust gas turbocharger (APU), T _ASA the turbine inlet temperature or the temperature of an upstream exhaust gas collector (ASA), η _T the turbine efficiency and ΔT _{T, is} the non-normalized isentropic temperature reduction of the turbine, the isentropic temperature decrease 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 respec gen isentropic exponents can be derived.

The Calculation of turbine efficiency is preferably done with the help a polynomial of second degree depending on the respective one Turbine speed. The coefficients of the second degree polynomial become preferably likewise by second degree polynomials depending on represented by the blade path of the turbine.

The The present invention will become more apparent by referring to the attached drawings explained with reference to a preferred embodiment.

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

2 shows a representation to illustrate the calculation of the gas outlet temperature of a in 1 shown turbocharger turbine by a likewise in 1 shown control unit with the aid of a turbine efficiency map, and

3 shows the course of the turbine efficiency as a function of a turbine speed for different blade positions of the turbine.

In 1 is an internal combustion engine 1 shown with four combustion chambers or cylinders. The internal combustion engine 1 is coupled to an exhaust gas turbocharger (ATL), which is a turbine 2 and a compressor 7 includes, the turbine 2 and the compressor 7 on a common shaft, the so-called turbocharger shaft 14 , are appropriate. The turbine 2 uses the exhaust gas of the internal combustion engine 1 contained energy to drive the compressor 7 , which has an air filter 6 Fresh air sucks and pre-compressed air into the individual cylinders of the internal combustion engine 1 suppressed. The one by the turbine 2 , the compressor 7 and the turbocharger shaft 14 formed exhaust gas turbocharger is fluidly with the internal combustion engine only by the air and exhaust gas mass flow 1 coupled.

The of the compressor 7 over an air filter 6 sucked in and pre-compressed air is supplied via a charge air cooler (LLK) 8th , which is the thermal load of the internal combustion engine 1 , which reduces exhaust gas temperature and thus the NO _x emission as well as the fuel consumption, a so-called replacement volume (ERS) 9 fed. The individual combustion chambers of the internal combustion engine 1 is an intake collector (EIS) 10 upstream. That in the combustion chambers of the internal combustion engine 1 generated exhaust gas is from an exhaust collector (ASA) 11 collected and the turbine 2 fed. The turbine 2 is in the exhaust gas flow direction the exhaust system (APU) 12 downstream of the motor vehicle, which the pollutant components during operation of the internal combustion engine 1 degrades resulting exhaust gases and derived the remaining exhaust gases as quietly as possible. Part of the in the combustion chambers of the internal combustion engine 1 generated exhaust gas is from the exhaust manifold 11 via an exhaust gas recirculation (EGR) to the intake manifold 10 recycled. With the reference number 13 are respectively arranged in corresponding air or gas paths arranged valves.

Furthermore, in 1 a control unit 4 which is a component of a corresponding engine management system of the motor vehicle. From the controller 4 various sizes or parameters of the system shown are monitored, which are detected by means of corresponding sensors and via an interface 3 the control unit 4 be supplied. These may be, for example, those via the air filter 6 with the help of the compressor 7 sucked amount of fresh air that in the replacement volume 9 existing air temperature or the corresponding air pressure or even in the exhaust manifold 11 existing exhaust gas temperature, which is the gas inlet temperature of the turbine 2 corresponds, and the turbine or turbocharger shaft speed act. The way this is from the controller 4 acquired measured variables are evaluated in order to generate different control signals for the engine management system dependent thereon. As in 1 can be shown over the interface 3 from the controller 4 output control signals, for example, the duty cycle of the arranged in the exhaust gas recirculation valve 13 , the vane adjustment 15 the turbine 2 or also the injection time and the injection quantity of the into the individual combustion chambers of the internal combustion engine 1 via an injection system 5 controlling injected air-fuel mixture.

As will be explained in more detail below, is the controller 4 capable of evaluating certain measured variables, which are already available in known engine management systems, the gas outlet temperature of the turbine 2 ie the temperature after the turbine 2 to determine which can be used advantageously for the exhaust aftertreatment.

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

As a basis for the normalization serves a certain reference temperature, as Refe temperature, in particular a measurement temperature of the turbine 2 , in this case 873K. In equation (2), n * / T denotes the normalized turbine speed, n _ATL the speed of the exhaust gas turbocharger or of 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 ,

From the normalized turbine speed, a reduced (normalized) peripheral speed of the turbine can be calculated as follows: u * T = π 30 · n * T · r T = ω * T · r T (3)

In this case, u * / T or ω * / T denotes the reduced circumferential or circular velocity of the turbine 2 and r _{T is} the radius of the turbine 2 , In general, the reduced peripheral speed u * / T can be achieved by multiplying the product n * T · r T with a constant k (in the present case k = π 30 ) be won.

If the so-called isentropic reduced temperature reduction ΔT * / is used as the intermediate variable, the ideal gas velocity can be derived therefrom. The isentropic reduced temperature reduction is defined as follows:

Where T _{0 is} the ambient temperature and Π _{T is} the pressure ratio between the pressure upstream of the turbine 2 and the pressure after the turbine 2 , ie the pressure ratio Π _T is defined as follows:

With p _ASA , the gas pressure in the exhaust collector 11 ie the gas pressure in front of the turbine 2 , while with p _APU the gas pressure in the exhaust system 12 ie the gas pressure after the turbine 2 , referred to as.

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

From the above isentropic reduced temperature reduction, the ideal gas velocity c * / s can be calculated as follows:

C _p denotes the specific heat capacity of the turbine 2 ,

From the calculated according to equation (3) reduced peripheral speed of the turbine 2 and the ideal gas velocity calculated according to equation (6), a turbine speed r * / UC can be derived as follows:

This turbine speed r * / UC is provided by the controller 4 is used to determine the instantaneous turbine efficiency η _T , which is a function of the turbine speed r * / UC and the blade position s of the turbine 2 is. Ie. it applies: η T = f (s, r * UC ). (8th)

Using the non-normalized isentropic temperature drop of the turbine 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 , be determined as follows: T APU = T ASA - η T · .DELTA.T T, is (9)

Here, the non-normalized isentropic temperature reduction based on the gas inlet temperature T _{ASA of} the turbine 2 defined as follows:

The previously described function of the control unit 4 for determining the gas outlet temperature T _APU is simplified in 2 , wherein the input variables are shown, which are converted into the output variable T _APU 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 speed r * / UC. It should be noted in particular that the gas outlet temperature T _APU or the temperature change of the turbine 2 from the gas inlet temperature T _{ASA of} the turbine 2 and the turbine or exhaust gas turbocharger speed n _{ATL is} derived. According to the invention thus the gas outlet temperature of the turbine 2 derived from measured values, which anyway in the field of turbocharger turbine 2 detected and by the control unit 4 are processed.

To calculate the turbine efficiency η _T , a second degree polynomial is used as a function of the turbine speed 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 in 3 shown for different blade positions s. 3 shows that the blade position s has a decisive influence here. The turbine speed already enters 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 polynomials of the second degree as a function of the blade position or the blade travel s, as follows: a i = b 0i + b 1i · S + b 2i · s 2 , (12)

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 the turbine

p _ASA

gas pressure in front of the turbine

_APU

gas pressure after the turbine

s

vane position the turbine

n _ATL

rotation speed the turbocharger shaft or the turbine

T _ASA

Gas inlet temperature the turbine

T _APU

Gas outlet temperature the turbine

η _T

Turbine efficiency

r * / UC

Turbine speed

Claims (15)

Method 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 from the turbine ( 2 ) the gas is discharged at a certain gas outlet temperature (T _APU ), and wherein the gas outlet temperature (T _APU ) of the turbine from the turbine speed (n _ATL ) and the turbine inlet temperature (T _ASA ) ( 2 ) is derived. A method according to claim 1, characterized in that from the turbine speed (n _ATL ) and an isentropic reduced temperature reduction of the turbine ( 2 ) the turbine efficiency (η _T ) is derived, and that from the turbine efficiency (η _T ) and the gas inlet temperature (T _ASA ) of the turbine ( 2 ) the gas outlet temperature (T _APU ) of the turbine ( 2 ) is derived. A method according to claim 2, characterized in that the turbine efficiency (η _T ) as a function of the blade position (s) of the turbine ( 2 ) as well as a turbine speed with the aid of a turbine efficiency map. A method according to claim 3, characterized in that the turbine _{speed is} derived from the turbine speed (n _ATL ). A method according to claim 3 or 4, characterized in that the turbine efficiency (η _T ) is obtained by means of a second degree polynomial function of the turbine speed. Method according to Claim 5, characterized in that the coefficients of the second-degree polynomial are in turn expressed by second-order polynomials as a function of the blade position (s) of the turbine ( 2 ) are formed. Method according to one of claims 3-6, characterized in that the turbine speed (r * / UC) is determined as follows:

where u * / T is one of the speed of the turbine ( 2 ) derived peripheral speed of the turbine ( 2 ) and c * / s a gas velocity of the turbine derived from the isentropically reduced temperature reduction ( 2 ) designated. Method according to one of the preceding claims, characterized in that for determining 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. Method according to claims 7 and 8, characterized in that the peripheral speed u * / T of the turbine ( 2 ) as follows from the normalized speed of the turbine ( 2 ) is derived: u * T = k · n * T · r T . where n * / T is the normalized speed of the turbine ( 2 ), r _{T is} the radius of the turbine ( 2 ) and k denotes a constant. Method according to one of claims 2-9, characterized in that the isentropic decrease in temperature from the ambient temperature of Turbine ( 2 ), a pressure ratio between the gas pressure upstream of the turbine ( 2 ) and the gas pressure after the turbine ( 2 ) as well as an isentropic exponent. Process 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 is} the gas pressure upstream of the turbine ( 2 ) and p _APU the gas pressure after the turbine ( 2 ) and wherein the gas velocity c * / s in the turbine ( 2 ) is derived as follows from the isentropic temperature reduction:

where c _{p is} the specific heat capacity of the turbine ( 2 ) designated. Method according to one of claims 2-11, characterized in that the gas outlet temperature T _{APU of} the turbine ( 2 ) as follows from the gas inlet temperature T _{ASA of} the turbine ( 2 ) and the efficiency η _{T of} the turbine ( 2 ) is derived: T APU = T ASA - η T · .DELTA.T T, is . where ΔT _{T, is} a non-normalized isentropic temperature drop of the turbine ( 2 ) designated. A method according to claim 12, characterized in that the non-normalized isentropic temperature drop ΔT _{T, is} as follows from the gas inlet temperature T _{ASA of} the turbine ( 2 ) and an isentropic exponent κ is derived:

where Π _{T is} the pressure ratio between the gas pressure (p _ASA ) in front of the turbine ( 2 ) and the gas pressure (p _APU ) after the turbine ( 2 ) designated. 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 at a certain gas outlet temperature (T _APU ), and wherein a control device ( 4 ) 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 ) is used. Apparatus according to claim 14, characterized in that the control device ( 4 ) for determining the gas outlet temperature (T _APU ) of the turbine ( 2 ) according to the method of any one of claims 1-13 is configured.