Time-frequency analysis application to the evaluation of instantaneous combustion noise

A novel approach to combustion noise has been proposed in the present paper with the time-frequency analysis technique. By evaluating the energy content of the combustion pressure signal, which has been measured as a function of time on Euro 5 and Euro 6 diesel engines, different combustion phases have been identified and the combustion noise due to the difference between in-cylinder pressure and motored trace has been evaluated for each phase. The algorithm for the calculus of this instantaneous combustion noise contribution versus time has been realized through a home-made tool and has been applied to single and double injection schedules. The time-frequency analysis allows more detailed information to be obtained on the contribution of the different combustion phases to the combustion noise and the cause-and-effect relationships between injection schedule and combustion noise to be better highlighted. The research investigation provides a hint for onboard diagnostics and real-time control of combustion noise, but the developed tool also can be provided as a practical validation tool for the refinement of combustion models.