The Knock Test And Analysis Of Aviation Gasoline Engine

Knock has an important impact on the safety of the gasoline engine, piston aviationgasoline does not allow the occurrence of knock, and requires a certain safety margin. Thesignal in the knock frequency band was analyzed based on high-frequency pressure signalin engine cylinder.First, we designed the intake heater hot days to mimic the ambient temperature.Three-dimensional simulation in Fluent shows that heater outlet temperature fielddistribution. Fuzzy PID temperature controller used to control the intake air temperaturewell.Second, by measuring the cylinder pressure, we have a spectrum and filter analysison cylinder pressure data. Theoretical calculations show that the engine knock occurswhen the pressure shocks in the frequency range between3.5kHz~10.3kHz. Weevaluated the filtered knock signal by the German Bosch company’s knock threshold.Based on labview, we developed gasoline engine knock analysis system, through the serialport and network communications to integrate with the existed test equipment. Thecylinder pressure analysis of each work cycle between the state point of poor and rich oilindicates that, the signal energy is weak in the3kHz~12kHz frequency band, and themaximum of knock signal is1.2bar, less than the detonation threshold. It shows thisengine did not knock under all conditions from rich oil to poor state. From the maximumsignal and the knock threshold we can see that the engine is far away from the edge ofknock.Finally, the combustion analysis of the engine has been done by using the single-zonecombustion model based on the cylinder indicator diagram. Analysis shows that the actualcompression ratio of this engine is too low, due to excessive intake of later closure angle,the unit to the maximum power decreased for the intake heater. In addition, the wall heattransfer coefficient has a greater impact on engine combustion analysis.