Assignment

In the combustion stroke, the flame length in the following combustion should be kept as short as possible through high compression and swirling, thus increasing the economic efficiency and the performance. Through a low exhaust gas recirculation during certain operating conditions, the nitrogen oxide proportion is reduced, even though a high level of efficiency is maintained.

Function

The petrol-air fuel-mixture, in the Otto engine, is compressed to between 8:1 and a maximum of 12,5:1, in the Diesel engine, pure air is compressed to between 18:1 and 24:1 (see picture) if the piston moves from BDC to TDC and the combustion occurs before TDC. Immediately before the combustion, the fuels must be converted into a gas. In addition, a sufficient amount of temperature is necessary.A high compression ratio has a positive influence on the torque, the performance and the fuel consumption because the carbon- and the oxygen atoms are brought closer together, thus providing for short reaction paths. a quicker and stronger combustion, with a low amount of pollutants is the result.The upper limit of the compression ratio is exceeded if the mixture uncontrollably self-ignites (knocking). Thereby, the combustion temperature rises above the load limit which leads to noises, similar to mechanical defects, and the strain on the crank mechanism is substantially higher.

The Diesel engine can have as much compression as, the smooth running, the engine service life, the material complexity or the amount of nitrogen oxide allows. To determine the actual condition of the engine, without dismantling the cylinder head, the compression can be measured. In the petrol engine the spark plugs - in the Diesel engine the nozzles - are removed. The sealings of the valves, the cylinder head gasket and the cylinder sleeves are determined. The measured compression lies somewhat lower than the actual final compression.

Important

Maximum temperature: up to 500°C (petrol engine), up to 900°C (Diesel engine),Pressure: up to 20 bar (petrol engine), up to 50 bar (Diesel engine). 05/10