Inspection and Maintenance - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 192

Fig. 13.5 Distribution of particle diameters

The rough running of the crankshaft is basically monitored to recognize com-
bustion misfires, similar to the spark ignition engine technology [ 15 ].
A usual reason for increased fuel consumption is a change in the injection
time caused by wearing and aging. For the exact recognition and corresponding
compensation of the deterioration, a small quantity of the fuel is injected into
the cylinder. A revolution sensor recognizes the resulting change in the number
of revolutions which is coupled with the amount of fuel injected. The process is
repeated in all cylinders at different operation points. The fuel consumption can be
corrected through an adjustment of the access time of the injectors [ 16 ].
The pressure of the turbocharger can also be controlled in certain time intervals.
Changes in the position of the turbine wheel and the bypass valve of the exhaust
gate cause a decrease of the charging air pressure which is monitored by pressure
sensors [ 17 ].
Self ignition engines with a Common Rail system do not produce big particles
which can be monitored by measuring the opacity of the exhaust gases. Modern
self ignition engines, with a high pressure level of injection of fuel and intake air,
produce small particles (see Fig. 13.5 )[ 18 ].
The emission of particles can be checked in the ''free acceleration'' process at
the test bench. However, an idling self ignition engine produces fewer particles
or none at all compared to real driving on the road. Therefore, the measurement of
the opacity correlates only in an indirect way with the real mass and number of
particles [ 19 ].
Micro particle sensors are still in development. The requirements are extremely
high. On-board sensors must work under the hardest operating conditions.
Components must bear dirt, wetness, blows and temperature changes during daily
operation. Despite their small size, micro sensors are very complex in construction
and operation. For safety reasons a redundant system, consisting of two intelligent
sensors for each important function, could be necessary [ 20 ].