Unintended exothermal reactions monitoring for diesel after-treatment systems
View Patent ↗An algorithm or diagnostic for detecting and alarming unintended exothermic conditions in exhaust after treatment components selectively detects alarming temperature variations in exhaust after treatment components when caused by internal unintended exothermal events, rather than transient conditions that are externally driven. Not only are the output temperature and the delta temperature (T_out−T_in) across the component monitored in each after-treatment device, but also the input temperature is deeply analyzed through its recent history data in order to determine if any input variations caused the output changes.
1. An engine monitoring system to determine an unintended exothermic condition occurring in after-treatment (AT) components including a diesel particulate filter (DPF) of the engine exhaust system, wherein the AT components comprise a first AT component for treating exhaust gas, comprising:
a first temperature sensor upstream of the first AT component and arranged to sense exhaust gas temperature and issue a corresponding first temperature signal;
a second temperature sensor downstream of the first AT component and arranged to sense exhaust gas temperature and issue a corresponding second temperature signal ;
a controller configured with a first function that monitors the first and second temperature signals and calculates a rate of change of temperature of exhaust gas at each sensor, and a second function that compares both the first and second temperature signals and the rate of change of temperature to predetermined thresholds for determining whether an unintended exothermic condition exists within the first AT component, and a third function that issues a fault signal;
a second AT component in series with the first AT component;
the second temperature sensor being between the first and second AT components;
a third temperature sensor downstream of the second AT component and arranged to sense exhaust gas temperature and issue a corresponding third temperature signal;
the first function monitors the third temperature signal and calculates a rate of change of temperature of exhaust gas at the third temperature sensor, and the second function compares the temperature and rate of change of temperature at the second and third temperature sensors to predetermined thresholds for determining whether an unintended exothermic condition exists within the second AT component, and the third function issues a fault signal.
2. The temperature monitoring system according to claim 1 , wherein the third function is disabled during active DPF regeneration.
3. The temperature monitoring system according to claim 1 , wherein the first AT component comprises a DOC unit.
4. The temperature monitoring system according to claim 1 , wherein the first AT component comprises a DPF.
5. The temperature monitoring system according to claim 1 , wherein the first AT component comprises a DOC unit and the second AT component comprises a DPF.
6. The temperature monitoring system according to claim 1 , further comprising a MAF sensor that issues a MAF signal corresponding to a magnitude of mass air flow into the engine; and
wherein the control calculates a gas space velocity based on the MAF signal, and an input gradient and partial and total input variations at a tunable sample time and delay, depending on the gas space velocity.
7. A method of monitoring to determine an unintended exothermic condition occurring in after-treatment (AT) components of the engine exhaust system, wherein the AT components comprise a first AT component for treating exhaust gas, comprising the steps of:
monitoring temperature downstream of the first AT component (T_out) and if the temperature downstream of the first AT component is higher than a threshold at any time establishing a peak fault detection;
monitoring temperature upstream of the first AT component (T_in) and the temperature downstream of the first AT component (T_out) both over time, and if the time derivative of the temperature downstream of the first AT component is higher than a threshold and the time derivative of the temperature upstream of the first AT component is lower than another threshold establishing a dynamic fault detection; and
calculating and monitoring average temperature (T_ave) in the first AT component , wherein
T _ave=( T _in)+( T _out− T _in)×( c _fac)
where:
T_ave=average component temperature
T_in=upstream temperature
T_out=downstream temperature
c_fac=tunable factor
calculating and monitoring gas space velocity (sv_gas) in the first AT component , wherein
sv_gas
=
V
.
gas
Vol
=
[
L
/
s
]
[
L
]
=
[
1
/
s
]
and
V
.
gas
=
MAF_KGH
_PF
*
1000
*
22.4
(
gas_molecular
_weight
)
*
3600
=
[
Kg
/
h
]
*
[
g
/
Kg
]
*
[
L
/
mol
]
[
g
/
mol
]
*
[
s
/
h
]
=
[
L
]
[
s
]
wherein
MAF_KGH_PF is engine intake mass air flow
L=liters
s=seconds
h=hours
g=grams
mol=moles
Kg=kilograms
and Vol=volume, displacement in liters of the first AT component;
monitoring the temperature difference Tout−Tin, and if the temperature downstream of the first AT component is increasing, and if the average temperature in the first AT component is higher than a threshold, and if the temperature difference is higher than a map-based variable threshold that is dependent on average temperature, and if a check of the upstream temperature looking back over time determines that the upstream temperature hasn't been increasing, establishing a static fault detection.