Analysis and discussion of diesel engine powertrain torsional resonance during start-up

A phenomenon exists in diesel or compression ignition engine powertrains with torsionally flexible couplings where the powertrain sometimes cannot accelerate through a torsional resonance such as during engine start-up. This phenomenon is sometimes referred to as resonance stall, resonance hang-up, or a jackhammer start. The current theory is that the hysteretic damping of an elastomeric coupling is dissipating input energy from the engine, thereby prohibiting the system from accelerating through the resonance. This theory comes about because the elastomeric coupling, with its hysteretic damping, heats up during resonance and is obviously dissipating energy. By conducting a theoretical study of the energy balances of vibration for a powertrain model and by carefully considering field observations, this paper will show that energy dissipated by the torsionally flexible coupling does not come at the expense of the mean or working torque that was input by the engine. Therefore, this energy dissipation is not the root cause of resonance stall. Further, by considering the overall powertrain response to resonance, this paper presents a new theory for the cause of resonance stall.