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Effect of the Supply of the Mixture During Injection Into the Intake Manifold
Sector:
Language:
German
Abstract
Thermodynamic considerations provide a good overview of orders
of magnitude in mixture preparation. A rough calculation at 20°C
ambient temperature and with thorough mixing with air reveals that
approximately 70% of the gasoline evaporates. Through polytropic
compression up to the point of ignition it is possible for a
further 10% of the gasoline to evaporate. The remainder of the
gasoline must be evaporated by the hot intake manifold and the hot
combustion chamber. The problem is alleviated by the property of
the hydrocarbons since the specific heat of vaporization converges
toward zero with increasing pressure and temperature.
Mechanical atomization both with the K-Jetronic nozzle and the
L-Jetronic valve provides most of the mixture preparation;
additional air shrouding produces slight advantages in idle
consumption and greater advantages in smoothness of running in the
range close to idle.
Shifting the point of injection upstream and away from the inlet
valve is impractical due to the necessity of acceleration
enrichment.
Advancing the moment of injection to before the intake stroke in
the case of sequential injection likewise improves mixture
preparation with the L-Jetronic. There are further advantages to
sequential injection.
Stratification in the open combustion chamber is still an
unsolved problem.