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Multi-fuel Range Extender with high efficiency and ultra low emissions

Final Report Summary - FUEREX (Multi-fuel Range Extender with high efficiency and ultra low emissions)

Executive summary:

The FUEREX project takes on the challenge of simultaneously meeting the tough efficiency, emission, noise vibration and harshness (NVH), integration and cost requirements for a range extender. Each of the requirements can be met separately, but the main challenge lies in meeting them all at the same time - and - at a low enough cost to be a competitive solution for the customer demands.

The CONCEPT of the FUEREX project is based upon:

-Compact spark-ignition engines as this type of engines have the largest potential to meet the customer duty requirements in terms of efficiency, NVH, fuel types, exhaust emissions, dimensions, weight and costs. Three types of spark ignition engines will be studied, representing different solutions for low cost Range Extenders and applicable for sub compact passenger cars up to light duty commercial vehicles:
a)An innovative rotary engine concept (AVL) with the largest potential in the long term (2020+),
b)A 3 cylinder piston engine (AVL Schrick) already developed for range extender purpose with potential in the short term (2015+)
c)A 2 cylinder piston engine (CRF) that will be adapted to range extender purpose and CNG (Compressed Natural Gas) with potential application on Light Commercial Vehicles in the short term (2015+).

Project Context and Objectives:

Overall project objectives

The FUEREX project takes on the challenge of simultaneously meeting the tough efficiency, emission, noise vibration and harshness (NVH), integration and cost requirements for a range extender. Each of the requirements can be met separately, but the main challenge lies in meeting them all at the same time - and - at a low enough cost to be a competitive solution for the customer demands.

The CONCEPT of the FUEREX project is based upon:

-Compact spark-ignition engines as this type of engines have the largest potential to meet the customer duty requirements in terms of efficiency, NVH, fuel types, exhaust emissions, dimensions, weight and costs. Three types of spark ignition engines will be studied, representing different solutions for low cost Range Extenders and applicable for sub compact passenger cars up to light duty commercial vehicles :
a)An innovative rotary engine concept (AVL) with the largest potential in the long term (2020+), especially regarding low specific weight, small dimensions, low NVH and low specific mass production costs potential (low number of parts).
This engine concept fits to the demands for high volume production, especially applicable for compact size and medium size vehicles.
b)A 3 cylinder piston engine (AVL Schrick) already developed for range extender purpose with potential in the short term (2015+) especially for compact size and medium size vehicles.
c)A 2 cylinder piston engine (CRF) that will be adapted to range extender purpose and CNG (Compressed Natural Gas) with potential application on Light Commercial Vehicles in the short term (2015+).

-Multifuel capability and flexibility. All engine types will be optimized for at least one type of biofuel (bio ethanol, biomethane), at least one type of regular fuel (petrol, CNG). The possibility to switch between bio and regular fuel will also be assessed for each engine type (multifuel flexibility);

-Vehicle integration of the range extenders in vehicles with state of the art battery packs (e.g. Li-ion, nickel metal hydrids). Complete vehicle integration will be developed with special attention to the difficult NVH issues.

-Demonstration of the integrated technology at a realistic scale (3 type of test vehicles, 2 compact passenger cars and 1 light transport, performance tests).

1.2 Objectives for WP 2 - System definition

1.To define requirements on vehicle level both for performance and for vehicle integration. These will be used in WP 7 for studying the optimal size of the range extender, for defining optimal control and for defining driving cycles suitable for evaluation and optimization.
2.To define requirements and targets for the range extender as well as methods to evaluate the concepts. These requirements will be used in WP 3-7.
3.To define requirements for the vehicle integration of the range extender.

1.3 Objectives for WP 3 - Three cylinder Range Extender engine

This WP is based on WP2 requirements and targets for the range extender and the existing state of the art for 3-cylinder RE engines. It aims at RTD for multi-fuel operation, optimised fuel efficiency, multi-mode operation and ultra-low emissions:

1.Develop and optimise and 3-cylinder reciprocating piston engine for bio methanol and bio-ethanol and petrol as backup fuel with high efficiency.
2.Develop exhaust gas after treatment technologies for the specific demands of range extender operation to achieve less than 50% of EU6 emission levels.
3.Evaluate mechanical and thermal output as basis for the optimisation of the FUEREX CO2 demand at customer duty.
4.Define and verify optimum operating strategies at customer duty. Customer duty specification will be carried over from WP2.

1.4 Objectives for WP 4 - Rotary engine

This WP is based on WP2 requirements and targets for the range extender and the existing state of the art for Rotary Engine RE. It aims at RTD for multi-fuel operation and overall enhanced operating strategies for multi-mode operation.

1.Develop and optimise rotary piston engine layout (thermodynamic concept, e.g injection and ignition timing and port geometry) bio ethanol and petrol as backup fuel.
2.Develop and optimise multimode operation. Three operating modes shall be considered, which can be characterised as follows:
(A) base load to cover electrical power demand and heat demand for pure comfort functions. (e.g. to power the A/C compressor during vehicle standstill, or to provide a heat source for heat-up of the vehicle compartment during standstill);
(B) medium load to provide electrical power demand and heat demand in NVH sensitive driving conditions (e.g. at low vehicle speeds) and
(C)high load to cover the electrical power demand at extra urban travel.
3.Develop exhaust gas after treatment technologies for the specific demands of range extender operation to achieve less than 50% of EU6 emission levels.
4.Evaluate mechanical and thermal output as basis for the optimisation of the FUEREX CO2 demand at customer duty.
5.Define and verify optimum operating strategies at customer duty (i.e OEM). Customer duty specification will be carried over from WP2.

1.5 Objectives for WP 5 - Two cylinder engine for light Commercial vehicle RE

The target of WP5 is the development of an environmental friendly powertrain based on a new CNG (Compressed Natural Gas) combustion engine to be integrated on Range Extender applications for Light Commercial Vehicles.

1.Definition of the subsystems specifications;
2.Development of the dedicated version of the NG two cylinders engine;
3.Development of the electric driveline;
4.Vehicle build up and RE unit integration;
5.Global assessment of the system on the validator vehicle.

1.6 Objectives for WP 6 - System integration

Main objective of this work package is to define, design and develop the necessary software/hardware interfaces and functionalities to be able to integrate the subcomponents into the Range-Extender-Concept and furthermore, to integrate the Range-Extender into the surrounding of a (demonstrator) vehicle. Key performance indicators of the concepts can be quantitatively assessed only, if complete vehicle dynamics is taken into consideration. This includes the specification of the battery system, possible strategies of customer usage, derating, diagnosis features and limp-home functionalities.

1.7 Objectives for WP 7 - Vehicle level studies

The main objective of WP7 is to use the actual performance of the Range extenders to determine how they should be controlled and how they will perform in different type of use.

The main parts of this work package are:
1.Creating improved driving cycles which take into account how electric vehicles with range extenders are used, including charging patterns and cold starts of Range extender. This include proposal for what type of driving cycles are suitable for future standards for fuel consumption and emission certification of range extender battery electric vehicles and discuss why these should differ from today's standard driving cycles.
2.Define optimized control strategies of how and when to use the range extender taking into account cold start, charging patterns and thermal management. Also the optimum size of the range extender will be analysed at the same time.
3.Comparing the three range extender concepts and describe the vehicle performance, emission levels and fuel consumption when they are used in the specified driving cycles.

1.8 Objectives for WP 8 - Dissemination and exploitation

Objectives for the whole duration of the project:
1.To maximise the dissemination of results and to express them in terms that are readily understandable to stakeholders (e.g. governments, industry and suppliers) in order to accelerate the implementation of the research findings.
2.To promote the dissemination of the project findings through presentations at the project workshops, scientific publications and preparing information for the project website.
3.To facilitate technology transfer and accelerate dissemination of on-going research activities.
4.To achieve an optimum knowledge management including appropriate handling of IPR's; implementation and exploitation of the obtained results;

Project Results:

This chapter describes the main Science and Technological results and foreground generated for each work package.

2.1 WP 2 - System definition
In 'Task 2.1 - Define requirements on vehicle level' a method to describe the performance requirements for an electric power train has been defined. The method is based on describing the normalized net force which the power train shall be able to produce. By normalizing the force, by dividing it with the effective vehicle mass, values be compared between vehicles despite differences in size of the vehicle and yet show the performance experienced by the driver.

2.1.1 Main results

The main results from the WP are listed below:

-A method to define performance requirements of an electric drive line in a way which allows simple comparison for vehicle performance from driver perspective.
-Performance requirements for the three target vehicles for the range extenders.
-Vehicle integration requirements documented in the specifications for the range extenders of the demonstration vehicles.
-Defined method to analyse and evaluate the range extenders.

2.2 WP3 3-Cylinder Range Extender concept

The objective of FUEREX WP3 was to develop and evaluate a 3 cylinder piston engine for range extender purpose with potential in the short term (2015+) especially for compact size and medium size all-purpose vehicles. AVL Schrick designed, provided hardware and assembled samples of the 3-cylinder combustion engine. The combustion system for multi fuels with optimized fuel consumption and a new cold start strategy was developed on an engine test bench. The engine is combined with generator, inverter and control system developed in WP6 by Bosch by an all new belt drive system.

2.2.2 Range extender package concept in the vehicle as basis for the 3-cylinder combustion engine design and development

Due to the additional systems which are present in a Range Extender Vehicle there are special requirements on the package of the car. In the former front engine bay the electrical drive motor is installed with drive shafts to both front wheels. Furthermore the inverter of the electrical AC motor and parts of the complex thermal management system like radiators and heaters are installed there.

2.2.3 3-cylinder combustion engine design

The chosen engine for the prototype is a three cylinder engine. It has been designed as a variant of an existing state-of-the art inline four cylinder engine for standard powertrains, which have a direct connection to the wheels through a gearbox.

2.2.4 Combustion system for multi fuels with optimized fuel consumption

The engine size and combustion system concept selection shows that the use of a relative large (compared to other demonstrated concepts) 1,35L engine based on a state-of-the art TGDI engine has significant benefits:

-The intake and exhaust ports and combustion chamber of all state-of-the-art TGDI engines like the reference engine are designed in such way that high Tumble air charge motion is established creating a stable combustion process. As a results knock sensitivity is low and high compression ratio can be tolerated resulting in good efficiency
-A 3 cylinder with 1.35L capacity is enabling 35kW power already at very moderate engine speed.
-All gasoline engines achieve the lowest fuel consumption in the speed range of 2000 - 3000 rpm. The speed range is selected in a way that it covers the range of the best fuel consumption with just little deterioration at low or peak power.
-In the standard approach for naturally aspirated engines in standard powertrains the air charge system and cam timing are designed for highest possible volumetric efficiency, but knock limitation sets limits to the compression ratio and thus the thermodynamic efficiency.
-Due to high torque and power the reference baseline 2.0L TGDI engine is built in a much more robust way than required for the REX causing much higher friction than a dedicated all-new engine.

2.2.5 Emission reduction concept - new cold start strategy

During that combustion development it has already been considered that high Tumble air charge motion which creates a stable combustion process with reduced knock sensitivity also improves the cold start emission capability. With both alternative combustion systems, the Miller Cycle (early intake valve closing before BDC) and the Atkinson cycle (late Intake valve closing after BDC) the demanding fuel consumption targets are met, so both shall also be investigated concerning their emission capability.

2.2.6 Test bench results of complete Range Extender - Efficiency

Before the cold start development could be started the combustion engine must be integrated with the generator. As described above a belt drive system is used for package and efficiency reasons. An all new system layout, design of the main components and the development of an assembly procedure with suitable measurement tools has been created by AVL Schrick Afterwards the complete FUEREX system is installed on a test bench. The overall efficiency of the FUEREX and the efficiency of all sub-systems are investigated. The analysis of the rotational oscillations shows if the belt drive has weak points and if it is generally suitable to handle the drive power.

In order to match the optimum speed range of the combustion engine with the optimum efficiency area in the generator map of the Bosch SMG 180x120 a transmission is required. A belt drive with a gear ratio of 1 : 1.95 shifts all operation points of the combustion engine full load curve into the sweet spot with 94% generator efficiency. Without the transmission the generator efficiency at low speed would be around 86%.

Due to the large distance between engine and generator (there is the oilsump in between) also relative large pulleys can be used, which reduce the belt force. The idler and the tensioner are positioned close together to achieve a large deflection angle of the belt around the pulleys, which increases the transmittable force of the belt. Under these conditions an 8 PK belt (Poly-V-belt with 8 rips) will cover all operation conditions between cold start at -30°C with 150 Nm motoring torque and the above mentioned full load with a calculated lifetime close to 3000 hours.

2.2.7 Cold start emission calibration and cycle fuel consumption

For the cold start calibration and emission development the FUEREX with ICE, generator, belt drive and all vehicle-like intake and exhaust system parts was installed in the same type of sub-frame which is also used in the Volvo C30 prototype vehicle. The whole Range Extender unit is installed in a hybrid test cell at Chalmers University. A battery simulator enables the full flexibility of electrical input and output without the limitation of the battery which was used before.

An electric vehicle with range extender enables further operation freedom when using pure electric respectively battery mode or combined with the range extender if necessary. The main advantage of this concept is to operate the vehicle only with electric energy with the possibility to use the combustion engine as range extender if required. Furthermore, if the combustion engine is required for range extending, it could be operated at best efficiency due to the freedom of operation point definition.

In order to achieve comparable results test to a passenger car with standard powertrain, the required work of the vehicle which is necessary to run the NEDC electrically has to be generated by the range extender during the test. That means the SOC of the battery at the end of the test like at start.

For NEDC test on engine test bed the required drive work for NEDC of the range extender is defined by vehicle measurements of the Volvo C30 electric passenger car.

The operation strategy of the FUEREX is defined to operate the range extender at different power stages depending on vehicle speed. With increasing vehicle speed the interior noise increases. Due to NVH reasons the high power stages are defined at higher vehicle speed to reduce the noticeability of the range extender operation for the vehicle driver and passenger.

Two power stages with 20 kW and 26 kW have been defined. The range extender starts first time when 60 km/h are exceeded. The second power stage is activated when 80 km/h are exceeded.

2.3 WP4 - Rotary engine

The focus of the FUEREX project was on emission, fuel consumption, noise vibration and harshness and durability development of the rotary engine. The development was done as planned in the DOW by simulation and verification at the engine test bed, at the chassis dynamometer and on the road with the vehicle:
-Design updates were defined, simulated and implemented. Component and material selection made sure, that bio fuels can be used without restrictions.
a)Since the rotary engine has to exceed EURO6 emission standards, it was mandatory to minimize oil consumption in the combustion process.
b)Counter measures were defined, calculated and developed mainly to improve cooling and rigidity of the RE unit.
c)A reduction of rotary piston surface temperature by more than 100° in critical areas was achieved, which leaded to essentially reduced deformation and improved combustion process.

Piston Surface temperatures (old and updated design)

d)To avoid deposits especially in the spark plug area, the cooling system of the trochoid housing was re-evaluated in simulation for improved heat transfer.
e)Due to further optimization of the water jacket flow combined with analysis of mechanical stress caused by the assembly process, a reduction of planar distortion of liner and reduced deformation of housing due to bolt load is expected.

-Performance and emission development on the rotary engine which leaded to the best fuel consumption while keeping the EU6 emission regulations for passenger cars:
a)Detailed investigations were carried out on ignition process and piston bowl design.
b)This investigation did lead to the implementation of a modified design for the orifice of the first spark plug in rotating direction which improved the combustion process.
c)Hardware investigation were made for different injector types and spray patterns, different high fuel injection pressures, different catalyst locations and catalyst inlet cones as well as heated catalytic converter. Also injector position, air intake and exhaust system variant were optimized.
d)Performance development was performed for both test fuels, gasoline and ethanol (E85).
e)A dedicated algorithm was developed to calculate the adjustment of injection volume and timing. A range of selected injectors made sure that the requested injector valve flow rates due to lower calorific value of ethanol can be met.
f)The injection timing and volume are controlled continuously until the 1 level is reached and stabilized again.
g)Test results proved that HC and particle emissions are reduced compared to standard fuel without loss of engine power for typical range extender operating areas.

-The development of aftertreatment system was performed for petrol and bio ethanol. The real world fuel consumption is influenced by the thermal management requirements for the aftertreatment system. The development work was structured in hardware optimization and operating strategy to fulfill under real world range extender conditions EU6 emission level with reasonable engineering margins.
a)Dedicated fast light-off strategies were implemented, taking into account the specific characteristics of the rotary engine and of the vehicle inertia. This was also managed by the system layout, in order to ensure the highest temperatures after the engine crank up avoiding us much as possible increase of fuel consumption.
b)Individual tests were performed for injector types, injector targeting, injector positioning, intake and outlet geometry and other design features as well as for impact of operating strategies.

-Cold start development fulfilling the special requirements of range extender application
a)Beside injection and air path, the focus was on catalyst setup. In a specific approach to initiate conversion as soon as possible, an optimized catalyst intake has been designed and tested.
b)Catalyst heating @ 4500 rpm did allow fast warm-up due to increased heat input to Catalytic converter.
c)The installation of a relatively small starter catalyst did lead to a reduction of HC Peak in start phase due to fast conversion start because of the reduced diameter
d)With the final test setup it was possible to demonstrate, that the EURO6 targets for HC and particles can be met with a rotary engine with a reasonable development margin.

-Development of Noise Vibration and Harshness (NVH) for engine and for the complete RE in the vehicle:
a)Acoustic layout of mounts for housing and internal components
b)Acoustic refinement of acoustic damping performance (noise radiation surfaces)
c)Acoustic layout of air filter box and low frequent resonators and subsequent fine tuning
d)Acoustic layout of muffler, low frequency resonators and high frequency resonator and subsequent fine tuning
e)improvement of airborne noise damping to vehicle interior
f)Due to the fact that the engine operates in well-defined speed load areas the system was optimized in a very specific manner using narrow band / high damping features.
g)A key element to reduce the sound pressure to acceptable levels was the encapsulation of the range extender module. The core generator-engine unit up to the exhaust manifold was installed inside a module housing which was using sound absorbing materials to reduce airborne sound radiation.
h)Sound deadening material was also applied to the ventilation air duct, which was Exhaust - Silencer System Design Optimization
i)The intake system, exhaust system and the damping elements of the module mounts have been optimized by detailed acoustic simulation to accomplish an averaged outside 1m-sound pressured of 65dbA at the back of the vehicle and an interior level of 58dBA at the drivers right ear.
j)Combined counter measures lead to sound levels for real-life vehicle operation, which enable the use of RE at dedicated operating points with no noticeable negative impact on sound pattern of EV.
k)With a strict continuation of the high load point operation below speeds of 60 km/h the RE becomes the dominant issue for acoustic convenience. The subjective noise perception can be improved by some degree of tracking the vehicle speed by definition of different RE load points according to vehicle speed and energy requirements. For high-speed driving the general vehicle noise level allows a dedicated high-power load point by increasing engine speed and mean effective pressure to avoid HV-battery depletion also at highway driving speeds.

-Vehicle integration and test of the rotary engine RE system in a demonstrator vehicle based on chassis dyno tests and real world driving. For real-life testing, an improved RE system with 15kW electric power at 4500rpm was integrated into a demonstrator vehicle which has been built on the BMW Mini basis. This electric vehicle is specified and designed for use as a City car and has been equipped with a 12kWh Li-Ion HV-battery, which allows an all electric range of 50km city driving. The described 15kW RE module and a fuel-tank of about 12l guarantee independency for an additional range of at least 200km. Propelled by a permanent magnet synchronous motor with 75kW peak power, the vehicle accelerates from 0-100km/h in about 12 seconds (0-60km/h in 5.4 seconds) and accomplishes a continuous maximum speed of 100km/h with a peak vehicle speed exceeding 130km/h.

The RE integration was performed under main aspects:
a)No restriction to passenger compartment and trunk
b)Utilization of stiff chassis areas to support a low acoustic chassis excitation by the RE system
c)Reduction of auxiliary components like mounts, high voltage cables, connectors, cooling lines, …
d)Low impact on vehicle chassis design to avoid expensive additional tooling
e)Integration of system assembly process with assembly of drivetrain alternatives
f)Vehicle crash requirements
g)Vehicle system safety and electro-magnetic-radiation (EMR) requirements
h)Axle-load distribution requirements

-Comparison of the range extender vehicle to a state of the art combustion engine setup including start-stop strategy and brake energy recuperation.
a)A real world driving route was utilised as major bases for fuel consumption optimisation. It shows a representative combination of city, extra urban and highway profile. A very important fact is that there are typical gradients which are influencing the driving strategies of EVs significantly.
b)For the direct comparison with conventional drivetrain concepts an identical BMW Mini with 1.4l NA engine with fully variable valve train, start-stop strategy and intelligent battery management to recuperate brake energy were defined. To compare the CO2 emissions of both concepts the electric energy of the plug-in charging was considered according to the German power-plant mix with 625grCO2/kWh.
c)For cold start at ambient temperatures of 0°C and city driving conditions the FUEREX car shows even with battery electric cabin heating significant CO2-emissions advantages.

-System assessment and optimisation. Based on the test bed and real life operation of the FUEREX vehicle additional fuel consumption improvement potentials were identified be vehicle simulation in summer and winter operation
a)Advantage of the REEV is its ability for recuperating the brake energy. For city driving, 20 - 25% can be achieved.
b)A CO2 reduction potential up to 35 % for the vehicle resulted in the NEDC cycle by vehicle and drive train optimisation such as reduction of air resistance, weight, power of electric drive or additional transmission. The same methodology has been applied to the AVL test cycle, which is much more representative for real world driving conditions than NEDC.
c)Although total energy consumption is higher than in ideal NEDC cycle, the potential savings in the range of 30% confirm the severe impact of combined counter measures for realistic driving conditions and the according CO2 reduction potential.
d)The results of the reduction potential evaluation performed for NEDC and a real world cycle give a clear indication for future steps in the development towards lower CO2 emissions.

2.4 WP 5 - 2-cylinder NG RE based powertrain

The activities performed in two year of the project mainly focused on:
-Definition of the subsystems specifications;
-Development of the electric driveline;
-Development of internal combustion engine (engine calibration, engine control system adaptation)
-Evaluation of the potential in using hydrogen/natural gas blends
-Development of power electronic and RE management system
-On vehicle engine calibration
-Emission optimisation
-Validator vehicle final assessment

2.4.1 Definition of the subsystems specifications

The specifications have been derived starting from both the vehicle targets and the RE-Unit architecture definition. The subsystems have been identified and described in term of electrical, mechanical and fluidic interfaces. A first packaging analysis of the RE-Unit has been performed in order to identify the main mechanical constraints to be considered during the next design phase.

The main results of the activities performed in the specification phase, are about the definition of:
-the Internal combustion engine configuration and its target working points
-the electric machine required performances
-the electric machine mechanical interface requirements
-the inverter unit required performances
-the electric and electronic architecture of the RE-Unit
-the cooling requirements for the power electronic
-the complete I/O interface definition of the RE-Unit

2.4.2 Development of the dedicated version of the NG two cylinders engine

The ICE configuration optimization activities consisted mainly in Fluidynamic optimization performed at engine test bench supported by engineering (design, simulation and laboratory) activities. This development activity had the aim to optimize the engine specific fuel consumption with a particular attention to the area of the two main working points chosen: 20kW and 40kW.
In order to increase efficiency in these two working points some development of combustion has been done.

2.4.3 Development of the electric driveline

The development of the electric driveline covered both the mechanical expect and Electric generator functionality.

The Electric generator is supported by an interface bolted to the internal combustion engine crankcase. This interface is made of two parts: an aluminum alloy support derived from a gearbox housing, and a plate that also provides the attachments for the Range Extender suspension mounts. This interface will prevent dust to enter in the area where there are the flywheel (modified from base the engine) and the torsional connection to the electric Generator.

To be sure that E-gen support is properly designed the complete Range Extender global modes has been calculated.

The torsional connection between ICE and E-gen has been designed in order to fulfil the requirements of transmit the torque and recover little misalignments between flywheel and electric motor axis. The final configuration of the transmission is based on a dual mass flywheel.

The Electric machine has been delivered by Bosch on the base on the given specification. The machine has been preliminary tested at the electric traction laboratories of CRF.

2.4.4 Engine performance at test bench

Main scope of this activity is the characterization of the engine in terms of performance, emission and fuel consumptions.

This purpose is pursued through the regulation of the engine parameters: ignition advance, fuel injection, Multiair valves command, turbocharger regulation system. In the same time a specific after-treatment management for natural gas engine is tested to improve the pollutant emissions conversion.

2.4.5 Evaluation of the potential in using hydrogen/natural gas blends

The potential in using hydrogen and natural gas bland has been evaluated considering the potential benefit on fuel consumption/emission and the impact on the systems. Blending H2 in NG is a technically viable solution to introduce a growing fraction of renewables lowering fuel carbon content.

A 30% H2 by volume blend is an appealing compromise between emission/combustion benefit and vehicle range reduction due to the lower energy density in the blend. Under the same engine efficiency the correspondent CO2 reduction is 11% compared to pure NG, while the resulting vehicle range is 20% shorter.

The use of NG/H2 blends asks for 2 action lines:
1) Adapting engine control parameter
2) Adapting materials of the storage and feeding system to prevent embrittlement phenomena due to hydrogen.

Calibration data set must be adapted mainly in order to:
- Set the corresponding stoichiometric A/F ratio;
- Set new gas injector model (to transform fuel mass into injection pulse width);
- Set spark ignition timing (check of knocking under full load conditions);
- Adapt the control parameters on the lambda probe to optimize catalyst conversion efficiency.

2.4.6 Development of the power electronic and RE management system

During the second year of the project, two inverter samples were delivered and some preliminary test on the functionality has been done at CRF test laboratories. The main parts that compose the Range Extender are the Internal Combustion Engine (ICE), the Electric Generator, the Inverter, the Electronic Control Units and the fuel supply.

The inverter was realized according to the specification requested in the present document. In particular the inverter:
-will be electrically connected to a three phases AC e-generator (electric machine);
-will be electrically connected to a DC storage system (traction battery);
-will control the e-generator by a PWM technique at the appropriate frequency (up to 20kHz available);

-will be liquid-cooled and a dedicated cooling circuit has to be adopted at vehicle side (same circuit of the traction motor and inverter);
-will be mechanically fixed with an appropriate flange to the vehicle chassis in the engine compartment;

On the other end, the e-generator is electrically coupled to the inverter and will be used as an electric machine that acts:

a. as a generator when the thermal engine is on;
b. as a motor in order to crank the thermal engine.

The housing of the inverter has been designed in order to provide:
-electrical power dissipation through cooling fluid circuit heat-sink
-water proof case for engine compartment installation
-ruggedness against mechanical vibrations
-assembly and interconnections solutions for the electronic components and PCBs

Concerning the electronic assembly, the layout of the whole electronic assembly is provided. The IGBT modules, the DC link capacitor and the connectors are mounted onto the mechanical box and interconnected through different bus bars. The current sensors are already mounted onto the control pcb board. The IGBT driver board and the control board are then stacked each other.

The RE-Unit has two electronic units: the Engine Control Unit (ECU) to control the thermal engine and the inverter to control the electric machine and to manage the system.

2.4.7 Demonstrator Vehicle Integration

RE (APU, Alternator and inverter) and storage system were defined and developed with the partners. Using an existing electric platform that complies above performance requirements electric storage system energy, CNG storage system and APU performance were defined. To reach 20 kWh ESS EOL available energy, storage system was reduced from 3 to 2 Z5 batteries that comply with the requirements both in terms of energy and power. To reach 30 kWh R.E. capability at DC link level, a 8 kg, 56 l CNG storage system is the lower limit.

2.4.7.1 Demonstrator build up

Buildup of demonstrator vehicle was performed as well as startup, tuning and preliminary testing of the complete vehicle

On track testing with data logging was performed in order to verify and asses drive-ability and performance according to vehicle requirements, as defined in year one.

2.4.8 On vehicle engine calibration

As described in the procedures, the calibration of the engine on vehicle requires carrying out tests in a repeatable manner in many conditions of operation both on roller bench and at the proving ground. Since it was not available in CRF a bench adequate for this test on the vehicle we proceeded to the design and realization of a 'bench' to perform these tests. The main requirements that the test bench must have are: safety requirements, functionality and reliability of testing. This test bench has been described in details in Deliverable D5.3

Scope of the vehicle test bench was the tuning of the power generation function, including coordinated control of both electric generator and thermal engine.

The vehicle has been kept at standstill, due to safety and practical reasons. This gave also the possibility to use external instrumentation.

At zero vehicle speed, generated power directly feeds the on-board batteries, which can be charged only for a limited amount of time. In order to tune the control, activity that requires to test the power generation even for long time, the generated electrical power shall be removed from the vehicle and routed to an external electrical devices able to absorb it continuously without damage.

The first tests on the APU control strategies were performed with the vehicle not moving and the high voltage battery pack connected in parallel to the external regenerative bidirectional DC power supply (AC/DC converter), just described.

The first steps consisted in the calibration of the electrical machine speed control in order to be able to set the thermal engine to different speed and torque conditions. The thermal engine control was then improved, starting from idle and low power generation and then increasing the generated power which was absorbed by the AC/DC converter. An evaluation of the thermal engine consumption was then performed with the aim of refining the speed and torque working points (for several requested power levels) to maximize the APU efficiency.

The second step was the calibration of the electric machine speed control (See D5.3 for details).

Due to the mission of this kind of system, it is not necessary to have too high performance in dynamic response (the requirement for the motor generator dynamic response was about 5kW/sec; this means a maximum derivative of about 500 rpm/sec). This allowed calibrating the speed control to a value that did not require too much power during thermal engine cranking and during speed set point transitions in general.

A speed and torque set point curve depending on the requested power level was initially determined on the efficiency map of the motor-generator. Since the efficiency of the electric motor is almost constant in the range taken into account for power generation, the curve was set following the highest efficiency path on the thermal engine efficiency map.

2.4.9 On vehicle calibration refinement at proving ground

Two types of tests were performed in order to assess and improve the behavior of the system in real driving conditions:
-Tests on the road. These were useful to improve the intervention of the voltage limit control and, in general, to assess the response of the whole system in real dynamic conditions. The behavior of the APU with changing power requests and the interaction with the traction motor were tested and improved.
-Tests on track with a specific urban-like mission. The mission required a maximum speed of about 40 km/h and a vehicle stop each 400 meters, with an average speed of 20-25 km/h. These were the final tests where the APU intervention strategy was refined while checking the overall behavior of the vehicle.

The following temperature measurements have been taken into account to determine the maximum available torque:

-Temperature of the electrical machine (wirings)
-Temperature of the inverter

The final calibration values were determined during tests on the road and on track, studying the available temperature measurements: these values allowed keeping the electric motor temperature below a maximum value of about 130°C in long duration tests on track.

2.4.10 Emissions optimization

The engine used is equipped with a 3-way catalyst and lambda control and works in quasi-stationary condition (Range Extender). In this behavior the emission are very low because the maximum efficiency window of the cat is easy to achieve.

For this reason the activity to reduce the emission is focused during the first minutes after the start of the engine when the thermal transient of the catalyst ('light-off phase') don't allow to have a good efficiency of pollutants conversion.

In NEDC cycle for a traditional ICE vehicle motored only with a CNG engine most of the pollutant emissions are produced in the acceleration maneuvres during the Light-off catalyst phase (first 100 sec of the cycle).

2.4.11 Control SW definition and tuning

According to system requirements and specifications a specific control sw was defined and implemented:
-Main input are: actual SOC, vehicle speed, e-drive power (ESS Voltage), e-mode requested and target SOC;
-Output are: APU requested status, OFF or ON and APU requested power;
-APU management strategy was defined according the following main drivers:
a)Smoothed load follower strategy to reduce ESS energy throughput
b)Engine stopped when vehicle is running below a fixed minimum speed
c)Engine stopped (E - mode) if SOC = defined value 1
-APU requested power according optimized design point, from 5 kW to 30 kW;
-E-mode on request and if SOC = defined value 2;
-Load follower strategy adjustment in order to reach / maintain a defined target SOC.

2.4.12 Tests results

Range extender system with load follower APU has shown the following advantages:

-Allows all electric vehicle benefits
-Avoids range anxiety
-Increases EV flexibility and range
-Reduces investments costs
-Allows more than 60% EV mode overall a year
-Reduces EV TCO on the same yearly mission
-Is suitable to use renewable electric energy and fuel
-Increases energy efficiency

2.5 WP 6 - System integration

2.5.1 Introduction

The role of the Robert Bosch GmbH (Germany) and the Robert Bosch AG (Austria) was defined in WP6, to perform major activities as
1)Design and delivery of an electrical machine for optimized use as Range Extender.
Uses: to start the combustion engine and generate electrical energy by the rotational torque of the combustion engine.
2)Design and delivery of power electronic unit.
Uses: to control the E-Machine for combustion engine start up and providing a DC current for charging the battery.
3)Specification of functional control of the combustion engine by the Bosch Electronic Control Unit (ECU) ME17 and development of a common control strategy for an encapsulated Range Extender system with respect to the different needs of operation, safety and charging the battery.
4)Support of an Operation Strategy for an easy functional implementation of this Range Extender system into the vehicle.

2.5.2 Overview Bosch Range Extender System

All the interfaces to the BEV (Battery Electric Vehicle) for a functional Range Extender system must be developed with respect to the design of the system and their components. Therefore during design of the electrical machine (marked in this report as generator) all the requirements for direct coupling (ALTRA use) and indirect coupling via belt drive (Volvo use) to the combustion engine and cooling demands must be met. The power electronic unit must fulfil all the demands of the High Voltage supply system required by the HV-battery and guarantee excellent efficiency with the electrical machine for charging the battery while meeting cooling demands. Additionally the ECU must gather data from all the needed sensors and actors to control the combustion engine for a safe and efficient operation in alignment with the generator and the power electronic unit.

2.5.3 Design and specification of the electrical machine

The requirements for the concept of the electrical machine and power electronics must fulfil the demands for rectifying the alternating current, charging the battery and starting the combustion engine. It is important to make the correct choice of the appropriate system concept, electrical and mechanical layouts, mechanical linkage and electrical connection as well as thermal cooling. The generator is designed as a 3-phase synchronous electrical machine with permanent magnets, shielded alloy housing and integrated water jacket cooling. The coupling to the combustion engine is designed in one version for a direct mounting to body parts of the combustion engine (ALTRA) and in another version by coupling via a newly designed belt drive (Volvo). The belt drive allows a ratio with best efficiency of the generator in combination with the speed range of the Volvo combustion engine.

The electrical machine is connected to the power electronic unit by three different electrical connectors:
-3 phase High Voltage cable to the power electronic unit.
-Temperature sensor for thermal control of the stator (measured with the help of a NTC sensor) and HV Interlock signals (to avoid electric shock caused by direct and indirect touching) in a common connector to the power electronic unit.
-Speed and position measurement of the rotor in the generator (Resolver for rotor position) for direct and efficient control of the machine by the power electronic unit.

2.5.4 Design and specification power electronic

The design of the power electronic unit must fulfil the requirements for rectifying the alternating current, charging the battery and to start the combustion engine. For this the electrical and mechanical layout takes care of the requirements for the mechanical link, electrical connection, cooling demands and the needs of the high voltage net (including battery and other components which are connected to HV).

So in the design of the power electronic unit various requirements for HW characteristics must be met in order for the design parameters, thermal limits and robustness to be optimized for all mechanical and electrical design.

The power electronic housing is made of shielded metal for mounting directly to body parts of the vehicle. The power electronic will be connected to the electrical system by three different electrical connectors. The design of the connectors for the cooling liquid of power electronic and generator is the same.

The CAN communication between the ECU ME 17 and the power electronic unit INV.2.2 implemented as a private CAN-Bus, ensures the proper and safe control between both components. The ECU receives the desired electrical power and 'on/off' requests via vehicle CAN and forwards this demand on one side to the combustion engine for mechanical power (torque) and on the other side to the power electronic unit in the Range Extender system (rotational speed). To do this the power electronic unit receives the actual values for operation mode and electrical power and provides the needed electrical current via high voltage connection due to the desired limits of the battery. The feedback of the internal signals from the power electronic unit to the ECU via internal CAN is basis of an efficient closed loop control.

The SW structure of the power electronic unit will be able to operate in different operating modes:

- Torque control:a specified set point torque is set (internal torque model controlled).
- Speed control: internal power electronic unit controls a setpoint speed.
- Standby:defined as a safe state in a case of an error or shut down.
- Pre charge:pre charge status from first HV activation command till the HV battery contactors is closed.
- Discharge mode:active and passive discharge of internal capacitors in case of an error or shut down.

2.5.5 Specification Range Extender Control Strategy

The ECU ME17 is responsible to control the combustion engine and the power electronic unit. It is able to fulfil following requirements in the FUEREX project:
-The 3 cylinder Port Fuel Injection (PFI) engine shall be supported with external ignition according to the specification of the FUEREX partner Volvo.
-The combustion engine is supposed to have a simple set up (PFI, no turbo charging, no camshaft phasing and no air flow sensor). Use of Gasoline fuel or Ethanol shall be supported.
-The HW setup supports two CAN buses, one for the connection to the range extender power electronic unit and the second one to the Vehicle Control Unit (VCU).
-The design of the HW supports a normal average lifetime of a car.
-The HW shall be capable to support future EU6 functionalities.
-The cost of the range extender package shall be limited, so the ECU can handle low prices for a potential future series production.

2.5.6 Vehicle Operation Strategy of the Range Extender system

Together with Volvo the following functionalities could be demonstrated as a main result by implementation of the Bosch Range Extender system in the Volvo C30 BEV demonstrator.

-Communication with the Vehicle Control Unit (VCU) and the Battery Management System (BMS)
-Battery high voltage start up (connected additionally with the range extender unit)
-Engine cranking and switching to generator mode
-Cranking with start of injections at high engine speeds
-Cat heating
-Power control mode with automatically selected operation points
(including control improvements)
-Speed control mode by VCU preselected operating points
-Dynamic transitions: fast response for negative power drop, ramped transition for power increase
-Combustion Engine shut down

2.5.7 Conclusion for Bosch Range Extender System within FUEREX

The Bosch system architecture supports an integration of the shown range extender unit into an existing electric vehicle. The Range Extender can be easily activated or deactivated via control of the vehicle as demanded and the desired electrical power is delivered as demanded to the vehicle.

2.6 WP 7 - Analysis of performance, control strategy and sizing for different driving cycles

To be able to optimize the size of the range extender and the battery as well as defining an optimal control strategy it is vital to define how the vehicle will be used. Different usage will of course lead to different optimal design. However, it is important that the selected sizing is suitable for a wide spectrum of use. Therefore, several driving cycles for different types of driving is being defined to provide a robust design of the system and to be able to analyse the performance for a spectrum of typical usage profiles. I.e. it is not sufficient to describe an average driving for a vehicle type, as different vehicles of that type will experience very different types of driving. It is for instance very important to model the variation in daily driving distances accurately as that will significantly influence the required size of the battery and the real life fuel consumption significantly. Also the charging patterns must be modelled as well as cold starts of the engine. All in all this means that a large set of driving cycles are required to describe all these aspects.

2.6.1 Main results

The main results from WP7 are:

-A method of how to create driving cycles, reflecting not only an average drive of an electric vehicle but which is capable of modelling the main categories of different driving which a vehicle will be used in. The driving cycles reflect the variation in, for instance, daily driving distances and variation in road type and traffic conditions. The driving cycles are also defined such that they can reflect how frequent different type of driving are for different vehicle types. Reported in D7.1
-Developed the convex optimization model such that the Range extender vehicle can be modelled in a mathematically convex form, and such that the optimal control of the range extender power will be found through optimization for the developed driving cycles.
-Shown how the sizing of range extender is influenced by the driving profile of the vehicle, and how the size can be reduced if smart control is used to save energy in the battery for some extreme driving situations.
-Shown that battery electric vehicles without a range extender has a very small market niche, if the drivers are not prepared to change the driving habits, while a similar vehicle with a range extender can meet all the required driving situations for all the investigated drivers and normally also lead to a lower cost.
-Summary of the results for the three range extenders on a vehicle level.

Potential Impact:

3 Impact

3.1 Potential impact
The targeted final result of FUEREX is to prove within 2 years from its start the feasibility/viability of the RE technology for the markets for sub-compact passenger cars up to light duty commercial vehicles by delivering:
1.Three REs with multi-fuel capability demonstrating state of the art performance and integration;
2.Bench test demonstrating emissions, efficiency and performance for the total RE;
3.Vehicle test demonstrating integration/NVH and vehicle performance;
4.A study on volume production optimization (low cost solutions);
5.Design guidelines of how a RE should be optimized for a given vehicle and how the RE itself is optimized.

Environmental impact of FUEREX

In Europe, the European Union is committed under the Kyoto Protocol to reduce GHG emissions by 8 per cent by 2008-2012 compared to the 1990 level. In addition, the EU has committed to a 20% cut in its greenhouse gas emissions by 2020. The EU has also adopted a target improving energy efficiency in the European Union by 20% by 2020.

These targets were legally implemented with the adoption of the 'climate and energy package' in December 2008: this package contains laws on the emissions trading scheme, 'effort sharing', carbon capture and storage, renewable energy, transport fuel quality and car emissions.

The FUEREX concepts meet these targets and even more important the project will address all the main obstacles for developing successful REs for battery vehicles paving the way for a broad introduction of RE-BEV's and thus play a major role in the greening of the transport sector in Europe.

Strategic and economic impact of FUEREX

With the global requirement to reduce CO2 emissions driving a move to the increased electrification of the vehicle, the realities of economics provide a serious challenge for electrical cars. Whereas stationary energy consumers do not require a significant energy storage capability, vehicles do and current battery technology is both heavy and expensive.

3.1.1 AVL City EV with range extender, IVECO electric Daily with CRF 2-cylinder range extender and Volvo family car with AVL-Schrick 3 cylinder range extender

The final user as a customer is requesting 'green', reliable technology at affordable costs. EV technology is on a good way with promising results, but it is expected that it will need some years to overcome mainly the cost and lifetime topics. Therefore RE technology can provide an adequate offer to the end consumer for the next years. Besides the cost factor, the range anxiety is a major concern that can be overcome with RE EV. Another benefit is the (almost) 'free of charge' heating, when taken from a combustion engine, which would be very expensive and associated with a significant range reduction, when taken out of battery energy of the pure BEV. For the automotive customer - typically the OEM community - a well-integrated design solution, which is respecting all constraints (e.g. energy + thermal management, package, lifetime, business case etc.) from design sources and system suppliers is a major advantage in the development and implementation of this kind of technology.

3.1.2 Chalmers Analysis of performance, comparison method

The results from the analysis of the sizing and control of the range extender vehicles has contributed to a better understanding of the influence of different car usage profiles. It is clear that the range extender vehicle should not be optimized for an average user. This knowledge will make it easier to develop more attractive range extender solutions for different types of users. Allowing a better adaptation to different users will most likely make the range extender vehicles attractive for a larger number of users and increase the market niche for the range extender vehicles.

3.2 Dissemination activities

To accelerate the acceptance and implementation of Range Extended Electric vehicles, which is one of the main objectives of the FUEREX project, the Dissemination activities were initiated since the beginning of the project. For this, several tools were setup and used and at the end of the project also a half day session at the eMobility conference was organised to show the final project results to a wide audience.

3.2.1 Website - http://www.fuerex.eu

The FUEREX website is divided in two parts; a public site and restricted area only for partners.

The public website has been designed to act as a contact point for third parties who might be interested in the progress and/or outcomes of FUEREX project. It provides a brief summary and information on the project. The partners involved in FUEREX are also presented in the website, and all their logos are linked to their web sites.

3.2.2 Flyer and Newsletters

A dissemination database has been generated based on contact databases from the partners. The database includes person names, organisations and their contact details. It includes over 200 contacts clustered in the following categories: Car manufacturers, Suppliers, Research Groups, Academia and Others. This grouping allows for dedicated mailings to the various groups. The database is used for the distribution of the flyer, the newsletter and invitations for the public workshop.

Also via the public website: http://www.fuerex.eu it is possible to register for the FUEREX Newsletters and Flyer. For this there is a link on the home page to register to the newsletter:

3.2.2.1 General Flyer

A general Flyer is created in the first month of the project and distributed to all relevant stakeholders, using the dissemination database. The flyer is also published on the website as news item and under downloads, FUEREX Public Flyer.pdf.

3.2.2.2 Newsletters

In the project, in total four newsletter are created and published with a frequency of approxamity 6 months. All four newsletter are send to the contacts and downloadable in the public website:
-01.FUEREX-Newsletter.pdf
-02.FUEREX-Newsletter.pdf
-03.FUEREX-Newsletter.pdf

3.2.3 Final conference

The final workshop for the FUEREX project was organised as special session to the eMobility conference in Graz, 30 and 31 of January 2013.

Session: Range Extender Concepts for Electric Vehicles: results of the EC funded project FUEREX. In total one overview presentation was given (Dr Sams, AVL) and five technical presentations by the Work package leaders.

The presentations are available on the FUEREX project website.

3.2.4 Publications

Peer-reviewed articles
[1]N. Murgovski, L. Johannesson, J. Sjoberg, B. Egardt, 'Component sizing of a plug-in hybrid electric powertrain via convex optimization', Journal of Mechatronics, vol. 22, no. 1, pp. 106-120, 2012.
In this article we present a general framework that will allow a computationally efficient design optimization of electrified vehicles. The key contribution is convex modeling steps for solving the problem of simultaneous powertrain sizing and control of electrified vehicles which have access to predictive information.
[2]N. Murgovski, L. Johannesson, J. Sjoberg, 'Engine on/off control for dimensioning hybrid electric powertrains via convex optimization', accepted at IEEE Transactions on Vehicular Technology.

Peer-reviewed conference contributions
[3]N. Murgovski, L. Johannesson, J. Sjoberg, 'Convex modeling of energy buffers in power control applications', IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling (E-CoSM), Rueil-Malmaison, Paris, France, 2012.
[4]N. Murgovski, L. Johannesson, A. Grauers, J. Sjoberg, 'Dimensioning and control of a thermally constrained double buffer plug-in HEV powertrain', 51st IEEE Conference on Decision and Control, Maui, Hawaii, 2012.

3.3 Exploitation of results

3.3.1 AVL City EV with Rotary range extender, IVECO electric Daily with CRF 2-cylinder range extender and Volvo family car with AVL-Schrick 3 cylinder range extender

Before the battery electric vehicle (BEV) will become a mass product - mainly due to the battery performances and related costs - range extended electric vehicles (REEV) will be an important bridge technology.

Besides the business case topic for the OEM, the automotive application potential will play an important role for all those concepts. On the one hand OEMs will use and adapt their existing high volume engines (e.g. GM VOLT / Opel Ampera) or share their engine families; on the other hand suppliers with strong capabilities in technology, production and financial background will get additional market shares with very innovative, future-oriented solutions.

3.3.2 BOSCH integration / electric components

The Bosch system architecture supports an integration of the shown range extender unit into an existing electric vehicle. The Range Extender can be easily activated or deactivated via control of the vehicle as demanded and the desired electrical power is delivered as demanded to the vehicle.

3.3.3 Chalmers analysis methods

The convex optimization tool, which partly has been developed within FUEREX, is a general tool and it has already found its use in several different research projects as well as design analysis studies together with vehicle OEM's. For example it has played a role in a project analysing plug-in hybrid buses with Volvo, where both the sizing of the battery in the bus but also the optimal charging infrastructure has been studied.

The method to create compact driving cycles for robust design has been one of the base components when the Swedish Hybrid Vehicle centre has started an industry-university collaboration project on tools to analyse driving and generate driving cycles for different usage like concept analysis (like in FUEREX), control design, diagnostic system development or control with preview.

List of Websites:

http://www.fuerex.eu

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