Cummins has achieved a Euro6 technology achievement by reaching over 1,500 hybrid-adapted engine installations in buses operating across the UK. Cummins ‘H’ versions of the B4.5 and B6.7 are specially configured engine-generators integrated with a hybrid driveline that provide a stop/start function for vehicles to save fuel and reduce roadside NO2 emissions.
Stop/start technology reduces fuel consumption by automatically switching the engine off when boarding, alighting, or when stationary. The Cummins-developed technology can reduce fuel consumption of a Euro6 London double-decker by up to 8%, operating on average 16 stops per hour. Taking 0.5sec, the engine position sensor ensures a near instant soft restart following electric-only launches.
Buses fitted with stop/start could save between 4 and 6tonnes of CO2 annually and significantly reduce kerbside NO2, taking some Cummins-powered buses to below Euro6 emission levels.
Evaluation work is also underway to look at introducing the F2.8 engine as a hybrid-adapted version for midi-size bus and shuttle applications. The Cummins hybrid engine configuration removes the need for drive steering pumps, fan drives, air compressors and air-conditioning as these requirements can be run directly from the electrical supply from the battery. For midi-size and shuttle applications, the traditional starter motor can also be removed from the power unit. Removing these engine-driven accessories creates space while retaining as much as 80hp (60kW) compared to a conventional bus engine.
Downsizing offers the opportunity to release useful installation space and reduce weight, while maintaining performance through faster torque response. The B6.7-H offers up to 300hp (224kW) with a peak torque of 1200Nm, while the B4.5-H is available up to 210hp (157kW) with a peak torque of 850Nm. The B4.5-H and B6.7-H can also be installed in ether series or parallel hybrid configurations, with engine parameters adjusted for lower or higher average speed duty cycles.
Ashley Watton, Cummins director — on-highway business Europe, said: “Cummins engine hybridisation expertise has played a key role in helping many bus manufacturers on the road to electrification. This technology is helping achieve remarkable results in terms of fuel savings, emissions reduction and vehicle sociability, particularly since the move to the strict Euro6 standard.
“Our hybrid engine installation work continues with some exciting projects underway, including a double-articulated tram bus, regional coach and even a UK railcar technology demonstrator intended for where electric lines are unavailable. The efficiency of the hybrid technology will continue to improve and provide operators with the energy choice they need alongside conventional clean diesel, natural gas and full electric solutions.”
Each new hybrid bus installation is custom-calibrated by Cummins to deliver power and torque at specific points on the duty-cycle, aligned to load-demands or the battery state-of-charge. Smart engine logic interfaces with the hybrid drive to determine an effective use of energy and maintains exhaust aftertreatment at an optimum thermal condition. The Cummins application engineering team at the Darlington facility has created a series of feature sets enabling ‘H’ adapted engines to be fully optimized for leading hybrid drive suppliers such as BAE Systems, Siemens, Eaton and others.