Federal-Mogul Powertrain has launched its new electrification strategy for medium- and heavy-duty vehicles at this year's IAA Commercial Vehicles show in Hanover, Germany (19 – 27 September, Hall 13, Stand C30).
Developed by its Controlled Power Technologies product group, the company is displaying a cost-effective, fully scalable, modular approach that can be optimised for the unique demands of each commercial vehicle segment and application. The technology portfolio can be individually customised and integrated to meet the specific needs of engine manufacturers to economically meet their emission and efficiency targets.
"One of the key questions that motivates us at Federal-Mogul is how we can improve fuel economy and CO2 emissions in commercial vehicles by harvesting waste energy, including both vehicle kinetic energy that is lost during braking and exhaust gas energy. Our solution must include how to then store it efficiently and return it to do useful work," said Gian Maria Olivetti, Chief Technology Officer, Federal-Mogul Powertrain. "Electrification can provide an attractive answer, but for medium- and heavy-duty commercial vehicles the most efficient way to achieve this is very different to that for passenger cars, so attempting to adapt traction-focused technologies can lead to solutions that are far from ideal," said Nick Pascoe, managing director of Federal-Mogul Controlled Power Ltd.
Diesel engines are highly efficient in a steady state but are substantially less efficient during transients (changes in torque request). Instead of trying to replace or supplement the internal combustion engine (ICE) with an electric traction motor, Federal-Mogul Powertrain engineers are using electrification to further enhance the efficiency of the ICE, both during steady-state operation and particularly to improve the fuel-economy and emissions impact of challenging transient conditions.
In the new approach, the engineering team around Nick Pascoe is supplementing kinetic energy recovered through an engine or driveline-mounted generator by electricity generated from a carefully-controlled exhaust-driven generator. Energy is then returned either through an electric motor supporting the engine/driveline or by electric supercharging.
Independently-conducted tests have shown that a highly-responsive Federal-Mogul motor-generator as small as 12 kW applied to the engine or driveline can enable fuel savings of up to 8 percent on a full-size bus by recuperating energy as the vehicle decelerates and boosting the engine's torque as it accelerates. The machine's compact size, fully integrated electronics and efficient thermal management, combined with increasingly standardized control protocols and a wide range of design and simulation tools, makes integration of the motor-generator fast and efficient, even on existing powertrain designs.
Federal-Mogul's engineers are seeing further opportunities for waste energy recovery by electrification of the air-loop system. While turbocharging recovers some of the 20-30 percent of the fuel's energy that leaves the engine in the exhaust gas, there is still more to be captured and returned. "Simple, cost-effective exhaust gas energy recovery requires a control system that avoids harvesting events that are harmful to the performance of the base engine or damaging to the generator itself or to the aftertreatment system," said Pascoe.
Helping existing systems deliver more
The on-board electrical energy, ideally recovered from the vehicle's kinetic energy or exhaust gas, can be used to improve the dynamic response of the airflow by electric supercharging. This can enable engine-downsizing, improve emissions and additionally yield up to five percent fuel economy improvement by reducing pumping losses combined with improved fueling and re-optimized gear shift strategies.
"The first few tenths of a second during a transient event, when the combustion system is most heavily challenged, are the worst with regards to the production of toxic emissions, including NOx and particulates," said Pascoe. "The latest fuel systems can respond far more quickly than the airstream, so our strategy allows more benefit to be derived from existing investments in these highly-capable vehicle technologies. By speeding up the supply of air to match the response of the fuel system, we can improve both fuel economy and emissions performance by maintaining better control of the air-to-fuel ratio."
Rigorous, high-speed control of air-to-fuel ratio is also vital for avoiding detrimental effects to the base engine performance and for managing the temperature and chemical composition of the exhaust gas.
The key elements in the air-loop electrification approach are TIGERS (Turbo-generator Integrated Gas Energy Recovery System) and COBRA (Controlled Boosting for Rapid Response Application). TIGERS combines an exhaust-driven turbine and liquid-cooled Switched Reluctance (SR) generator to produce a proven, technically mature system that seamlessly converts exhaust gas energy into electrical energy. COBRA liquid-cooled electric superchargers provide the engine with an 'on-demand' air supply, able to match the most demanding drive and operating cycles thanks to their low rotor inertia and excellent thermal management. When combined with the company's CPT SpeedTorq highly-responsive electric assist motor/generator technology, the portfolio offers a modular approach that allows the optimum solution to be specified for each vehicle weight and application.
Pascoe says that the need to capture large amounts of energy quickly, then return it to the driveline quickly without the long-term storage needed for traction applications means that smaller, more affordable energy storage solutions, including light-weight ultra-capacitors, are well-suited to the Federal-Mogul Powertrain strategy. CPT SpeedTorq, TIGERS and COBRA can each be specified for 12 volts, 24 volts or 48 volts, allowing an electrical system that is substantially smaller, lighter and more affordable than high-voltage battery hybridization. He also emphasizes the modular nature of the new approach, which provides the flexibility needed to optimize the solution.
Exceeding CV durability targets
"While uncertainty remains over the future rate of progress of electrification, many vehicle manufacturers, especially in the medium and heavy-duty sector, are seeking ways to extend the life of existing engine designs to meet next generation market and regulatory demands," said Pascoe.
"Together with our customers our technologies can be readily integrated into existing powertrains by our engineering teams to give a new level of fuel efficiency and emissions reduction and, because they are modular and scalable, can be cost-effectively tailored for vehicles of different sizes and end uses."