Air expenditure
The air consumption is a measure of the fresh gaseous charge supplied to an internal combustion engine . In addition to the degree of delivery, the air consumption is an important parameter for describing the gas exchange quality, whereby the air consumption rather allows a statement to be made about the quality of the intake system and process.
calculation
The air consumption is the ratio of the mass of fresh mixture actually supplied to a reciprocating piston engine (or its cylinder) during a work cycle to the theoretically possible mass , which results from the geometric displacement and the theoretical charge density in the ambient condition. This applies to engines with free suction. With supercharged engines , the state of the fresh charge downstream of the compressor or charge air cooler is taken into account.
The fresh charge supplied (for a cylinder) or (for the entire engine) and thus the air consumption depend on various factors, v. a. Valve timing and opening cross-section of the valves as well as the speed and the geometrical relationships of the intake tract and combustion chamber, so that the air consumption usually remains below 1 (it could only be greater than 1 through resonance effects).
- or for a cylinder
In a gasoline engine with external mixture formation (outside the cylinder), the entire fresh charge supplied to the engine consists of:
and for diesel engines and gasoline engines with direct injection :
literature
- Richard van Basshuysen , Fred Schäfer : Handbook Internal Combustion Engine Basics, Components, Systems, Perspectives. 3. Edition. Friedrich Vieweg & Sohn Verlag / GWV Fachverlage, Wiesbaden 2005, ISBN 3-528-23933-6 .
- Franz Pischinger : Combustion Engines, Volume I and Volume II; Lecture reprint. Chair of Applied Thermodynamics, RWTH Aachen , self-published, 1987.