Difference between revisions of "ATM 33.50 (Exhaust Gas Temperature Model)"

Latest revision as of 10:15, 8 January 2012

Refer to the funktionsrahmen for the following diagrams:

atm-main

atm-atm-b1 Exhaust gas temperature model (cylinder bank 1) overview

atm-tmp-stat TMP_STAT engine speed & relative cylinder charge map and corrected for temperature for acceleration, intake air temp., catalyst heating, catalyst warming, ignition angle, lambda and cold engine

atm-dynamik Temperature dynamic for exhaust gas and catalytic converter temperature (in and near the catalytic converter)

atm-tabgm Temperature dynamic: exhaust gas, exhaust pipe wall effect, from the exhaust gas temperature tabgm

atm-tkatm Temperature dynamic for the temperature near the catalytic converter

atm-exotherme Exothermic temperature increase near the catalyst from measurement sites tabgm to tikatm

atm-tikatm Temperature dynamic for the temperature in the catalytic converter

atm-exoikat Exothermic temperature increase in the catalyst from measurement sites tabgm to tikatm

atm-kr-stat Exhaust gas temperature in the exhaust manifold under steady-state conditions

atm-kr-dyn Exhaust gas temperature in the exhaust manifold under dynamic conditions

atm-tmp-start Calculation of the exhaust gas or exhaust pipe wall temperature at engine start

atm-tpe-logik Calculation of the dew point at the pre-cat and post-cat lambda probes

atm-sp-nachl Storage of the dew point conditions at engine switch off

atm-mean Calculation of etazwist average values

atm-tmp-umgm If no ambient temperature sensor is available, calculate a substitute from ambient temperature (tans)

atm-mst If tabst_w is not correct tabstatm = maximum value, request for delay B_nlatm as a function of engine speed and tatu-threshold)

ATM 33.50 (Exhaust Gas Temperature Model) Function Description

The simulated exhaust gas temperatures tabgm and tabgkrm (for SY_TURBO = 1) and catalytic converter temperatures tkatm and tikatm are used for the following purposes:

1. Monitoring the catalyst. If the catalytic converter falls below its starting temperature, then a fault can be detected.

2. For lambda control on the probe after the catalytic converter. This control is only activated after engine start, when the catalyst has exceeded its start-up temperature.

3. For the probe heater control after engine start. If the simulated dew point is exceeded, the probe heater is turned on.

4. Monitoring the heated exhaust gas oxygen (HEGO) sensor (i.e. lambda probe) heating system. If the exhaust gas temperature exceeds 800°C for example, then the lambda probe heater will be switched off, so that the probe is not too hot.

5. For fan motor control.

6. For switching on component protection.

This function provides only a rough approximation of the exhaust gas and catalytic converter temperature profiles, whereas throughout the application especially the four monitoring areas (dew point profiles in the exhaust gas, catalytic converter monitoring, enabling and shutting off lambda probe heating and high temperatures for component protection) should be considered to be critical.

1. Basic function

Steady-state temperature (tatmsta): the same applies for takrstc

With the engine speed/relative cylinder charge map KFTATM the steady-state exhaust gas temperature before the catalyst is set. This temperature is corrected for ambient temperature or simulated ambient temperature from the characteristic ATMTANS:

during boost with the constant TATMSA,

during catalyst heating with the constant TATMKH; catalyst warming with the constant TATMKW

with the ignition-angle efficiency map KFATMZW temperature as a function of ML and ETAZWIST

with the desired lambda map KFATMLA temperature as a function of ML and LAMSBG_W

for a cold engine block (TMOT - TATMTMOT) with TATMTMOT = 90°C.

The catalyst temperature (exothermic) is corrected for:

Temperature increase with the characteristic KATMEXML or KATMIEXML as a function of air mass

Temperature reduction with KLATMZWE or KLATMIZWE as a function of etazwimt (ignition angle influence)

Lambda influence with KLATMLAE or KLATMILAE as a function of lambsbg_w

Temperature set at TKATMOE or TIKATMOE at tabgm <TABGMEX or B_sa = 1

Different temperature increases are applied for the temperature in the catalytic converter tikatm and the temperature after the catalytic converter tkatm due to exothermic reaction and cooling and different ignition angles and lambda-corrections.

The time-based influence of the exhaust gas temperature before the catalytic converter:

Using a PT1 filter (filter time constant ZATMAML) the dynamics of the exhaust gas temperature are simulated and with a PT1 filter (time constant ZATMRML) the dynamics of the inlet manifold wall temperature are simulated.

The exhaust gas temperature and inlet manifold wall temperature are weighted by the division factor FATMRML.

The catalytic converter temperature tkatm is calculated from the exhaust gas temperature tabgm along with the PT1 filter (filter time constant ZATMKML).

The temperature in the catalyst tikatm is modelled from the exhaust gas temperature tabgm via three filters (time constant ZATMIKML) using the heat transfer principle. Due to a thrust caused by the small air mass flow in the catalytic converter, there is a possible exhaust gas temperature increase due to the greater influence on the matrix temperature by the exhaust gas throughput. This thrust-based temperature increase can be modelled by the positive B_sa side with a temperature, which is composed of the catalyst temperature tikatm and an offset TATMSAE, will be initialised. The time constants of the PT1-filter ZATMIKML are represented by air-mass-dependent characteristic curves.

The initial values ​​for the exhaust and catalyst temperature at engine start can be calculated from the temperatures at switch-off and delay times. The starting values ​​for the exhaust gas and catalyst temperatures should approximate to the manifold wall temperatures at the probe insertion points a few minutes after switch-off. The filter for the exhaust gas temperature is stopped by setting B_stend = 0. The filter for the manifold wall temperature is stopped when B_atmtpa = 1. The filter for the catalyst temperature will be enabled only when B_atmtpk = 1.

2. Dew Point Detection

Initial values ​​for the exhaust gas temperature tabgmst and catalyst temperature tkatmst

When stopping the engine (C_nachl 0 ® 1) the temperatures tabgm and tkatm are stored.

When starting the engine, the initial temperatures tabgmst and tkatmst are calculated from the switch-off temperature (corrected for ambient temperature) and a factor obtained from maps KFATMABKA or KFATMABKK as a function of tabstatm and tatu.

During power fail the switch-off temperature will be determined from the constant TATMSTI.

For test condition (B_faatm = 1), the initial temperatures are given by the constants TASTBFA and TKSTBFA.

Integrated Heat Quantity iwmatm_w

The dew point end time is approximately proportional to the heat quantity after engine start. The heat quantity = Integral (temp. x air mass x C_p) is calculated from the steady-state exhaust gas temperature tatmsta plus TATMWMK multiplied by the air mass. The result of the integration multiplied by the heat capacity at constant pressure C_p (approximately 1 kJ/kgK) gives the heat quantity.

Dew point end for the pre-cat lambda probe B_atmtpa and post-cat lambda probe B_atmtpk

The calculated exhaust gas temperature at engine start tabgmst approximates to the exhaust pipe wall temperature. If the exhaust pipe wall temperature is greater than 60°C for example then no condensation occurs. The values in the map KFWMABG ​​for these temperatures are less than 14 kJ, so the dew point end is detected immediately, or after only a few seconds.

For catalytic converter heating with thermal reaction (B_trkh = 1) the values in maps KFWMABG or KFWMKAT are multiplied by the factor WMKATKH or WMABGKH respectively. Thus, the dew point end-times are very short for this mode of operation.

Repeated starts (extension of the dew point-end-times)

If the engine had not reached the dew point end (B_atmtpa = 0 and B_atmtpf = 0) then when the engine restarts, the counter zwmatmf is increased by 1. After several periods of very short engine running (e.g. 3), the counter zwmatmf value would be set equal to 3. With a constant FWMABGW = 0.25 for example, the values in the map KFWMABG increase by a factor equal to (zwmatmf x KFWMABG + 1) = 1.75. When the engine starts, the dew point end time from the last engine run is detected and the counter zwmatmf is reset.

Storage of the dew point end condition in the delay

For the determination of repeat start dew point end the conditions B_atmtpa in the flag B_atmtpf and B_atmtpk in the flag B_atmtpl are saved at engine switch-off due to a regular switch-off using the ignition or stall (B_stndnl). The function of dew point end for the post-cat lambda probe B_atmtpk is analogous to the function for B_atmtpa.

3. Calculation of a simulated ambient temperature from the intake air temperature (tans) if no ambient temperature sensor is available.

The simulated temperature tatu will be used for calculating the temperature correction via the characteristic ATMTANS and for determining the starting temperatures tabgmst and tkatmst. The intake air temperature (tans) is corrected with the constant DTUMTAT and under certain conditions stored in continuous RAM. If for example at engine start, the temperature tatu > tans, then the temperature value tatu is set on the lower tans value.

With the constant TATMWMK (negative value) the difference in dew point end between catalyst heating and no catalyst heating can be increased.

When catalytic converter heating is active B_khtr = 1 and the bit B_atmtpa can be set equal to 1 immediately after engine start. This is possible only when no problematic condensation is formed during catalyst heating.

With the system constants SY_STERVK = 1 cylinder bank 2 can be applied separately for stereo systems.

For SY_TURBO = 1 the exhaust gas temperature tabgm is essentially identical in addition to the modeled temperature in the manifold tabgkrm.

ATM 33.50 Application Notes

1. Installation locations for temperature sensors in this application, running in the direction of flow:

- In probe installation position before catalytic converter-

1. Exhaust gas temperature (pipe centre) for the high temperatures at high loads for probe heater switch off

2. Manifold wall temperature for the determination of the dew-end times. (Condensation protection)

- Before the catalytic converter

3. Exhaust gas temperature (pipe centre) for the catalyst start-up temperature

- In the catalytic converter

4. Ceramic temperature in and after catalytic converter (in the last third of the catalytic converter or behind the adjoining matrix) to determine the air-mass-dependent time constants.

- After the catalytic converter

5. Pipe wall temperature at probe installation site for the determination of the dew-end times (condensation protection).

Temperature measuring point 3 can be omitted if the distance from probe to catalytic converter is smaller than about 30 cm. The temperature drop from probe installation site to catalytic converter can then be neglected.

For the application of the functional data the modelled temperatures will always be compared with the measured temperatures and the functional data amended until a sufficiently high accuracy is achieved. In so doing, it will be the actual catalyst temperature, the temperature increase due to the exothermic reaction is not considered in the model.

2. Map KFTATM

For the determination of the steady-state temperature for example, before the catalytic converter the temperature corrections should not function. The cooling capacity of the wind on the dynamometer or on the measuring wheel can be simulated only very roughly at the higher engine load range. The map values ​​can be determined on the rolling road dynamometer, but should be corrected on an appropriate test drive.

3. Temperature Corrections

- TATMSA

Boost can cause low exhaust temperatures that fall below the starting temperature of the catalyst. The longer the time period for the thrust condition, the lower the exhaust and catalyst temperatures. For catalyst diagnosis during boost, the exhaust gas temperature model is more likely to calculate a lower value than the measured temperature.

- ATMTANS

At low ambient temperatures, exhaust gas temperature can fall below the catalyst start-up temperature. Therefore, the model temperature is only corrected at the low temperature range.

- TATMKH

As long as the catalyst-heating measures are effective, higher exhaust temperatures will result.

- TATMKW

The catalyst operating temperature will not be not reached during prolonged idling, so the exhaust gas temperature can be raised by the catalyst warming function.

- KFATMZW

The temperature increase as a result of ignition angle retardation can be determined on a rolling road dynamometer. First, on the dynamometer, the characteristic field values ​​KFTATM are applied without ignition angle correction. Ignition angles are then modified so that allowed etazwist values will result in the map. Through the corresponding air mass, the temperature increase will then be displayed in the map KFATMZW.

- KFATMLA

The exhaust temperature is reduced by enrichment. The application is similar to KFATMZW, except that the ignition angle efficiency is changed instead of the enrichment factor.

- TATMTMOT

The map KFTATM is applied with a warm engine. Thus, the model exhaust gas temperature has smaller deviations during cold start. For this operating mode, the temperature is corrected with the difference of the cold engine temperature and the warm engine temperature. TATMTMOT should be about 90 to 100°C.

4. Maps ZATMAML, ZATMRML, FATMRML, ZATMKML, ZATMKKML, ZATMIKML und ZATMIKKML

The air-mass-dependent time constants ZATMAML, ZATMRML (temperature measuring points 1 or 3), and ZATMKML, ZATMKKML, ZATMIKML, ZATMIKKML (temperature measuring point 4), can help to more accurately determine “spikes in the air mass” during sudden load variations. Thereby "air mass jumps" at full load and in particular during boost can be avoided. For example, for an air mass jump from 30 kg/hr to 80 kg/hr, the measured time constant is applied to the air mass flow of 80 kg/hr. For large air mass jumps during idle, the time constants ZATMKKML and ZATMIKKML can be input instead of ZATMKML or ZATMIKML if required.

5. Block EXOTHERME:

- KATMEXML

The exothermic temperature is a function of air mass flow (warming by realizing emissions, reducing warming via a larger air mass). First KATMEXML applies, then KLATMZWE, KLATMLAE.

- KLATMZWE

When ignition angle retardation increases the temperature before the catalyst, the catalyst temperature drops.

- KLATMLAE

For lambda < 1 (richer), the air mass is lacking to improve emissions so the catalyst temperature decreases.

- TABGMEX

If the temperature before the catalyst tabgm < TABGMEX (catalyst switch-off temperature) then the temperature correction = TKATMOE.

- TKATMOE

Temperature correction during boost or through tabgm> TABGMEX

- TATMSAE

Temperature increase in the boost in the catalyst in terms of tkatm

Block EXOIKAT:

- KATMIEXML, KLATMIZWE, KLATMILAE, TIKATMOE

Application depends on the application for Block EXOTHERME

- TATMSAE

Temperature increase in the thrust in the catalyst in terms of tikatm

6. Dew point end times for exhaust gas temperatures vary greatly between the centre of the exhaust pipe and the pipe wall. Dew point end times for the tube wall temperatures before the catalyst (temperature measuring points 2) or after the catalyst (temperature measuring points 5) should be used. These times are usually due to delaying control readiness for too long, in which case the temperature gradients at the probe mounting location must be examined more closely. To avoid probe damage by “water hammer”, the sensor heater must be fully turned on until the dew point temperature is exceeded or the dew point end time is detected thus condensation will no longer occur.

When the switch-off time in the ECU delay is calculated, then the switch-off time tabst_w after ECU delay will be incorrect. At engine start after ECU delay, the switch-off time tabstatm therefore, will be set to the maximum value of 65,535 (i.e. 2¹⁶-1). The ECU delay requirement for the time TNLATM when engine speed > TNLATMTM & tumg (tatu) > TNLATMTU.

8. For blocks KR_STAT and KR_DYN as appropriate, the descriptions in points 3 and 4 shall apply.

Typical Values:

KFTATM: x: engine speed/RPM, y: relative cylinder charge/%, z: temperature/°C

KFATMZW: x: temperature/°C, y: ml_w/kg/hr, z: etazwimt

KFATMLA: x: temperature/°C, y: ml_w/kg/hr, z: lamsbg_w

KFWMABG: x: energy/kJ, y: tabgmst/°C, z: tmst/°C

KFWMKAT values ​​correspond to KFWMABG x 5

In the heat quantity maps KFWMABG and KFWMKAT a value of 0.0 is never required! It should always have at least the value to be entered; the 2 sec corresponds to idle after cold start. Only then does the repeat-start counter operate after several starts where the dew point was not reached.

ZATMAML

ml_w/kg/hr, Time constant/sec 10, 30 ; 20, 20 ; 40, 13 ; 80, 5 ; 180, 4 ; 400, 3 ; 600, 2 ;

ZATMKML

ml_w/kg/hr, Time constant/sec 10, 150 ; 20, 60 ; 40, 35 ; 80, 20 ; 180, 10 ; 400, 7 ; 600, 4 ;

ZATMIKML

value represents approximately ZATMKML x 0.3

ZATMKKML

for neutral input, the data must correlate to ZATMKML

ZATMIKKML

for neutral input, the data must correlate to ZATMIKML

ZATMRML

ml_w/kg/hr, Time constant/sec 10, 300 ; 20, 80 ; 40, 55 ; 80, 30 ; 180, 20 ; 400, 10 ; 600, 7 ;

FATMRML

ml_w/kg/hr, Time constant/sec 10, 0.5 ; 20, 0.6 ; 40, 0.7 ; 80, 0.8 ; 180, 0.95 ; 400,0.95 ; 600, 0.96;

KATMEXML

ml_w/kg/hr, Time constant/sec 10, 0 ; 20, 0 ; 40, 0 ; 80, 0 ; 180, 0 ; 400, 0 ;

KLATMZWE

etazwimt, Factor 1, 0 ; 0.95, 0 ; 0.9, 0 ; 0.8, 0 ; 0.7, 0 ; 0.6, 0 ;

KLATMLAE

lamsbg_w, Factor 1.15, 0 ; 1 , 0 ;0.95, 0 ; 0.9, 0 ; 0.8, 0 ; 0.7, 0 ;

TATMTP: 52°C

TKATMOE: 0°C

TATMSAE: 0°C

KATMIEXML

ml_w/kg/hr, Time constant/sec 10, 0 ; 20, 0 ; 40, 0 ; 80, 0 ; 180, 0 ; 400, 0 ;

KLATMIZWE

etazwimt, Factor 1, 0 ; 0.95, 0 ; 0.9, 0; 0.8, 0 ; 0.7, 0 ; 0.6, 0 ;

KLATMILAE

lamsbg_w, Factor 1.15, 0 ; 1 , 0 ;0.95, 0 ; 0.9, 0 ; 0.8, 0 ; 0.7, 0 ;

TIKATMOE: 0°C

KFATMABKA: x: tatu/°C, y: tabstatm_w/seconds, z: no units

KFATMABKK: x: tatu/°C, y: tabstatm_w [s], z: no units

ATMTANS tatu/°C, Temp./°C -40, 60 ; -10, 20 ; 20, 0 ;

TATMSA: 100°C

TATMKH: 80°C

TATMTRKH: 200°C

TATMKW: 100°C

TATMTMOT: 90°C

TATMSTI: 20°C

TASTBFA: 40°C

TKSTBFA: 40°C

TATMWMK: -80°C

WMABGKH: Factor of 1.0

WMKATKH: Factor of 1.0

FWMABGW: Factor of 0.25

FWMKATW: Factor of 0.25

DTUMTAT: 20°C

VTUMTAT: 40 km/h

NTUMTAT: 1800 rpm

IMTUMTAT: 1 kg

TUMTAIT: 20°C

TNLATMTM: 80°C

TNLATMTU: 5°C

TNLATM: 660 seconds

Only when SY_TURBO = 1:

For neutral input (tabgkrm_w = tabgm_w)

KFATMKR = KFTATM

KFATZWK = KFATMZW

KFATLAK = KFATMLA

TATMKRSA = TATMSA

ZATRKRML = ZATMRML

ZATAKRML = ZATMAML

FATRKRML = FATMRML

ATMTANS tans/°C, Temp./°C -40, 40 ; -20, 25 ; 0, 12 ; 20, 0 ; 60, -30

The functional data for cylinder bank 2 correspond to the functional data from cylinder bank 1 Note:

In order that ATM 22:20 for the application is backward compatible the default values should be entered thus: ​​KATMEXML, KLATMZWE, KLATMLAE, TKATMOE = 0 and TABGMEX = 1220°C.

In order that ATM 33.10 remains application-neutral with ATM 22.50, TATMTRKH must be set equal to TATMKH and WMKATKH should be set equal to 1. Tikatm is not used in a function because the input can be used in the path in the exhaust gas temperature model without impact on safety, however, the default values for ​​KATMIEXML, KLATMIZWE, KLATMILAE and TIKATMOE should be set equal to 0 and TABGMEX = 1220°C.

In DKATSP areas TMINKATS and TMAXKATS, a high accuracy is required for tikatm!

Abbreviations