Jonathan Hall

A Study of Fuel Converter Requirements for an Extended-Range Electric Vehicle

Current focus on techniques to reduce the tailpipe carbon dioxide (CO 2 ) emissions of road vehicles is increasing the interest in hybrid and electric vehicle technologies. Pure electric vehicles require bulky, heavy, and expensive battery packs to enable an acceptable driveable range to be achieved. Extended-range electric vehicles (E-REVs) partly overcome the limitations of current battery technology by having an onboard fuel converter that converts a liquid fuel, such as gasoline, into electrical energy whilst the vehicle is driving. Thus enabling the traction battery storage capacity to be reduced, whilst still maintaining an acceptable vehicle range. This paper presents results from a drive style analysis toolset that enable US and EU fleet vehicle drive data to be categorised and compared. Key metrics, such as idle frequency, idle duration, vehicle speed, and vehicle acceleration are analysed. Vehicle usage patterns in the US and EU have been compared against each other and to relevant legislative drive cycles. Based on results from examination of the fleet data, a drive-cycle is selected and used as the basis for analysis of the fuel converter requirements for a hypothetical E-REV based on a typical European C-class vehicle. The influence of drive-cycle and battery pack size on the fuel converter requirement is discussed. Finally, the influence of the fuel converter efficiency upon the new European Drive Cycle (NEDC) fuel consumption of the E-REV is assessed.

Design of a Dedicated Range Extender Engine

Current focus on techniques to reduce the tailpipe CO2 emissions of road vehicles is increasing the interest in hybrid and electric vehicle technologies. Pure electric vehicles require bulky, heavy, and expensive battery packs to enable an acceptable drive-able range to be achieved. Extended-range electric vehicles (E-REV) partly overcome the limitations of current battery technology by having a ‘range extender’ unit, which consists of an onboard fuel converter that converts a liquid fuel, such as gasoline, into electrical energy whilst the vehicle is driving. This enables the traction battery storage capacity to be reduced, whilst still maintaining an acceptable vehicle driving range. In a previous paper the power requirement of a range extender for a typical C segment passenger car was investigated using drive-cycle modelling over real world cycles. This paper presents the detailed design of the range extender engine. Key attributes for the engine have been identified, these being minimum package volume, low weight, low cost, and good NVH. The selection of the appropriate engine technology to enable the final design to fulfil these attributes is described. The resulting design is highlights are presented and the final design is presented.

Heavily downsized gasoline demonstrator

Gasoline engine downsizing is already established as a proven technology to reduce automotive fleet CO2 emissions by as much as 25 %. Further benefits are possible through more aggressive downsizing, however, the trade-off between the CO2 reduction achieved and vehicle drive-ability limits the level of engine downsizing currently adopted.

Analysis of Real World Data from a Range Extended Electric Vehicle Demonstrator

MAHLE Powertrain has built a range-extended electric vehicle demonstrator, with a series hybrid configuration. The vehicle is intended to operate predominantly purely electrically. Once the battery state of charge is depleted a gasoline engine (range extender) is activated to provide the energy required to propel the vehicle. As part of the continuing development of this vehicle, MAHLE Powertrain has recorded data during real world driving, with the aim of further investigating the actual usage a range-extended electric vehicle under nonlaboratory test conditions. The vehicle is instrumented with a data acquisition system which records physical parameters, for example coolant temperatures, as well as CAN-based data from the engine and vehicle management systems. This recorded data has been analysed, using tools developed in-house, to establish the effect of environmental factors such as ambient temperature, human behavioral characteristics and variation in usage patterns on the efficiency and operational behaviour of the range-extended electric vehicle system as a whole. Of particular interest are factors such as the frequency, and duration, of operation of the range extender engine under normal daily usage. The resulting data will guide the design direction and specification, at both component and system level, in future range-extended electric vehicle design and development programmes. This paper presents an overview of the recorded data and analysis of the key trends identified. The hardware and software systems are briefly discussed and the control strategy is described within the context of the results presented. This paper also demonstrates that both the range extender unit and the traction circuit components have been sized correctly and that a reduction in traction battery pack size, relative to a pure electric vehicle, is both feasible and appropriate.

GPS Based Energy Management Control for Plug-in Hybrid Vehicles

In 2012 MAHLE Powertrain developed a range-extended electric vehicle (REEV) demonstrator, based on a series hybrid configuration, and uses a battery to store electrical energy from the grid. Once the battery state of charge (SOC) is depleted a gasoline engine (range extender) is activated to provide the energy required to propel the vehicle. As part of the continuing development of this vehicle, MAHLE Powertrain has developed control software which can intelligently manage the use of the battery energy through the combined use of GPS and road topographical data. Advanced knowledge of the route prior to the start of a journey enables the software to calculate the SOC throughout the journey and pre-determine the optimum operating strategy for the range extender to enable best charging efficiency and minimize NVH. The software can also operate without a pre-determined route being selected. In this case, the software will interrogate a database of previous drive data and select the most likely route being driven. Based on the predicted route the software will then select a suitable charging strategy for best efficiency. The system considers an array of factors to determine the optimum charging strategy such as the driving style of the driver. It is capable of improving upon its own predictions of vehicle energy usage over a series of journeys and aims to produce the most efficient charging strategy. The software has the potential to allow the vehicle to operate 100% electrically in Congestion Charging zones, by pre-emptively charging the battery prior to entering such zones. This paper presents and overview of the software and strategy developed and shows the energy consumption benefits which this software can provide, based on example drive data for the MAHLE REEV demonstrator, thus further improving the overall fuel consumption of the vehicle and reducing the vehicle emissions.

30 % Höhere Effizienz bei 50 % Weniger Hubraum

Wie lassen sich die Potenziale des Downsizings von Verbrennungsmotoren ausloten? Mahle stellte sich der Thematik mit einem Technologie-Demonstrator, einem 1,2-l-Ottomotor mit drei Zylindern, den das Unternehmen vor drei Jahren der Offentlichkeit prasentierte. Allerdings konnte der damals noch junge Demonstrator die ambitionierten Zielwerte noch nicht unter Beweis stellen. Doch jetzt. In diesem Artikel beschreibt Mahle, wie der Dreizylindermotor bessere Volllastkennwerte als ein Vergleichsmotor mit 2,4 l Hubraum erreicht. Damit wird im „Neuen Europaischen Fahrzyklus“ unter Beibehaltung der Leistungscharakteristik eine Reduzierung von Kraftstoffverbrauch und CO2-Emission von mehr als 30 % erreicht.

Compressed-natural-gas optimised downsized demonstrator engine:

The complexity of modern powertrain development is demonstrated by the combination of requirements to meet future emission regulations and test procedures such as the real driving emissions, the reductions in the fuel consumption and the carbon dioxide emissions as well as the expectations of customers that there must be a good driving performance. Gasoline engine downsizing is already established as a proved technology to reduce the carbon dioxide emissions of automotive fleets. Additionally, alternative fuels such as natural gas offer the potential to reduce significantly both the tailpipe carbon dioxide emissions and the other regulated exhaust gas emissions without compromising the driving performance and the driving range. This paper presents results showing how the positive fuel properties of natural gas can be fully utilised in a heavily downsized engine. The engine was modified to cope with the significantly higher mechanical and thermal loads when operating at high specific outputs on compressed natural gas. In this study, peak cylinder pressures of up to 180 bar and specific power output levels of 110 kW/l were realised. It is also shown that having cylinder components specific to natural gas can yield significant reductions in the fuel consumption and, in conjunction with a variable-geometry turbine, a port-fuelled compressed-natural-gas engine can achieve a impressive low-speed torque (a brake mean effective power of 2700 kPa at 1500 r/min) and good transient response characteristics. The results achieved from the test engine while operating on compressed natural gas are compared with measurements from the baseline gasoline-fuelled direct-injection engine. In addition, a comparison between port fuel injection and direct injection of compressed natural gas is presented. This also includes an investigation into the specific performance challenges presented by port-fuel-injected compressed natural gas. The potential carbon dioxide savings offered by this heavily downsized compressed-natural-gas engine, of up to 50% at peak power and 20–40% for the driving-cycle region (including real-driving-emissions testing), are presented and discussed.

Heavily Downsized Demonstrator Engine Optimised for CNG Operation

The complexity of modern powertrain development is demonstrated by the combination of requirements to meet future emission regulations and test procedures such as Real Driving Emissions (RDE), reduction of fuel consumption and CO2 emissions as well as customer expectations for good driving performance. Gasoline engine downsizing is already established as a proven technology to reduce automotive fleet CO2 emissions. Additionally, alternative fuels such as natural gas, offer the potential to significantly reduce both tailpipe CO2 and other regulated exhaust gas emissions without compromising driving performance and driving range.

Through-the-Road Parallel Hybrid with In-Wheel Motors

Present automobile development is keenly focused on measures to reduce the CO2 output of vehicles. Plug-in hybrid electric vehicles (PHEVs) enable grid electricity, which is clean in tail-pipe emissions terms, to be utilised whilst the on-board electrical storage has sufficient charge. MAHLE Powertrain and Protean have jointly developed a plug-in hybrid demonstrator vehicle based on a C-segment passenger car. The vehicle features Protean’s compact direct drive in-wheel motors with integrated inverters on the rear axle and retains the standard gasoline engine, and manual transmission, on the front axle. To support this one-off prototype, a flexible vehicle control unit has been developed, which is easily re-configurable and adaptable to any hybrid vehicle architecture. The unit operates using software developed by MAHLE Powertrain to achieve a fully configurable vehicle control unit (VCU), intended to provide a rapid and cost effective platform for the development of demonstrator and niche volume vehicle fleets. This paper describes some of the challenges, and solutions, associated with the vehicle conversion, including key vehicle integration topics, such as the CAN interface, vehicle control strategy, and the cooling system.

Energy Efficiency of Autonomous Car Powertrain

This paper investigates the energy efficiency and emissions benefits possible with connected and autonomous vehicles (CAVs). Such benefits could be instrumental in decarbonising the transport sector. The impact of CAV technology on operation, usage and specification of vehicles for optimised energy efficiency is considered. Energy consumption reductions of 55% - 66% are identified for a fully autonomous road transport system versus the present. 46% is possible for a CAV on todays roads. Smoothing effects and reduced stoppage in the drive cycle achieve a 31% reduction in travel time if speed limits are not reduced. CAV powertrain optimised for different scenarios requires just 10 kW - 40 kW maximum power whilst the vehicle mass is reduced by up to 40% relative to current cars. Urban-optimised powertrain, with only 10 kW - 15 kW maximum power, allows energy consumption reductions of over 71%. UK energy consumption by cars could be 30% - 45% of current levels with a fully autonomous road transport system, depending on an energy efficiency versus travel time trade off. This could be reduced to just 26% if ride-sharing in urban areas achieves a doubling in average occupancy and travel times remain at todays levels. A comparison of IC engine and battery-electric powertrains optimised for a fully autonomous road transport system indicates the benefits of electric powertrain, with a primary energy requirement per unit distance of the equivalent IC engine CAV. Greenhouse gas emissions per unit distance for the battery-electric CAV are 55% of an IC engine CAV with current UK electricity emissions intensity, reducing to 13% at 2030 emissions target levels. Reduced drive cycle energy requirements (44% of current levels) allow greater range and improved economics of electric vehicles whilst reduced power variance allows smaller batteries for hybrids, similarly helping their case.