Numerical investigation on combustion processes of an aircraft piston engine fueled with aviation kerosene and gasoline

Abstract

Replacing gasoline with aviation kerosene for spark-ignition (SI) piston engines applied for aircrafts can get better security and easier logistics, however, this action cannot proceed smoothly by serious knocking combustion. In this study, the in-cylinder combustion for gasoline and aviation kerosene are investigated through computed-fluid-dynamics (CFD) to analyze combustion characteristics, and try to use pre-chamber technology to improve combustion issues.All CFD results demonstrate in-cylinder combustion differences effectively: All injected aviation kerosene cannot be completely evaporated, leading to non-uniformed unburned mixture and slow flame propagation. Some odd test phenomena are caused by unevaporated kerosene. The slower turbulence flame speed, worse equivalence ratio, higher local temperature and lower spontaneous combustion temperature lead to mixture auto-ignition and knocking combustion eventually. After adding a passive pre-chamber, the mixture distribution near spark plugs is more reasonable, higher turbulence kinetic energy (TKE) inside pre-chamber accelerates burning process, the ignition delay period is reduced by about 21.6%. The pre-chamber increases main-chamber's TKE, the whole combustion process is shortened by about 9%, the pre-flame reaction of unburned mixture near cylinder is shortened, contributing to suppress knocking combustion effectively. The passive pre-chamber technology is of great significance to the popularization and application for SI aircraft piston engine fueled with aviation kerosene.