A Comprehensive Study on the Challenges of Dual Mass Flywheel in Real-World Operating Conditions of the Indian Market 2020-01-1014

The present work is focussed on the real-world challenges of a dual mass flywheel (DMF) equipped vehicle in the Indian market. DMFs are widely used to isolate the drivetrain from the high torsional vibrations induced by the engine. While DMFs can significantly improve noise, vibration and harshness (NVH) characteristics of a vehicle, there are multiple challenges experienced in real-world operating conditions when compared with the single mass flywheel (SMF). The present work explains the challenges of using a DMF in a high power-density diesel powertrain for a multi-purpose vehicle (MPV) application in the Indian market. Measurements on the flat-road operating conditions revealed that the DMF vehicle is very sensitive for launch behaviour and requires a higher clutch modulation. Vibration measurements at the driver’s seat confirm that the SMF vehicle could be launched more comfortably at the engine idle speed of 850 RPM. However, the DMF vehicle needs a "launch assist" of an additional 100 RPM to meet the acceptable vibration levels in line with that of the SMF. Further, 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 up to 12% gradient whereas the SMF variant could negotiate up to 18% gradient easily.

Furthermore, the higher launch energy requirement of the DMF is also responsible for the higher temperature of the clutch system by 33% as confirmed by the temperature measurements inside the clutch housing. The increased temperatures pose a major threat to the robustness and useful life of the clutch system parts. Subjective evaluations reveal that the DMF vehicle is prone to frequent engine stalling in speed-breaker and pot-hole manoeuvres. This is mainly due to the requirement of a 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 present work gives a holistic insight into the mentioned challenges with the detailed objective and subjective evaluation data.