A Comprehensive Study on the Challenges of Dual Mass Flywheel in Real-World Operating Conditions of the Indian Market 2020-01-1014
Dual mass flywheel (DMF) is widely used to isolate the drivetrain from the high torsional vibrations induced by the engine. While DMF can significantly improve the noise, vibration and harshness (NVH) characteristics of the vehicle, there are multiple challenges experienced in the real-world operating conditions when compared with the single mass flywheel (SMF). This paper explains the challenges of using DMF in a high power-density diesel powertrain for a multi-purpose vehicle (MPV) application in the Indian market. The gradient launch performance of the vehicle is compared for different gradients (6%, 8%, 12%, 18% and 28%) and the results confirmed that the slip time and launch energy of the DMF variant is ~50% higher than the SMF. Moreover, the DMF vehicle could be launched comfortably only upto 12% gradient whereas the SMF variant could negotiate upto 18% gradient easily. Furthermore, the higher launch energy requirement of the DMF is also responsible for a higher temperature of the clutch system by 33% as confirmed by the temperature measurements inside the clutch housing. The increased temperature poses a major threat to the robustness and useful life of the clutch system parts.
Further measurements on the flat-road operating conditions revealed that the DMF vehicle is very sensitive for launch behaviour and requires high clutch modulation. Vibration measurements at driver seat and steering wheel confirm that the SMF vehicle could be launched more comfortably at the engine idle speed of 800 RPM. However, the DMF vehicle needs a "launch assist" of additional 150 RPM to meet the measured vibration levels of the SMF. Subjective evaluations reveal that the DMF vehicle is prone to frequent engine stalling in speed-breaker and pot-hole maneuvers. This is mainly due to the requirement of fuel cut-off strategy which is usually implemented to avoid DMF spring resonance at low engine speeds. However, the requirement of fuel cut-off strategy is not required for the SMF vehicle and hence it could negotiate varying road conditions without any stalling concern. The paper gives an holistic insight on the mentioned challenges with detailed objective and subjective evaluation data.