Exhaust gas temperature measurement.
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- Measuring the temperature of hot gases is not that easy especially
when the temperature and speed of these gases are continuously changing.
- Due to the properties of heat transfer at and in the thermocouple
the measured temperature at changing condition will always have some
delay to the actual temperature.
- In general the smaller the thermocouple the better it will follow
the actual temperature but at the expense of mechanical stability. In
many stationary industrial application thermocouples with a diameter of
0,5, 1 mm are used with success. Looking to exhaust gas thermometers one
sees in general a diameter of 3 mm.
- The consequence of this 3 mm diameter is a relatively large
- e.g. in air with 2m/s the T0,9 is for 0,5 mm 8 sec.; 1 mm 17 sec and
for 3 mm 64 sec. for the used type of thermocouples.
- The consequence is that the indicated temperature of these very
precise thermocouples is far from precise during temperature change.
- At the moment I do not have delay values for diesel engines at
From the literature safe temperatures are between 250-680
Celsius, 720 Celsius is upper limit.
Engine can be switch off at temperatures below ??? Celsius.
JUMO K with outer 3 mm tube material nr 2.4816 [Inconel 600]
-200..+1200 Celsius, cable silicon -50..+180 Celsius
type 901221/32/1043-3-100-11-2500/000 about 60 euro.
Green + ; White -
Greisinger GTH 2448/1 about 56 euro
Adapter plate with Thermolok seal glands:
Land rover LRJ100000; experimental, should be better then no
gasket; time will show.
The 3 mm and a 1 mm thermocouple are place at the same time
instantly in a hot air stream in a tube.