Sustainable surface transport

Basic control strategies will be implemented into the ECU for specific CNG functions and multiair managing. After that, calibration of the engine at the test bench will be carried out following an experimental methodology which has to take into account the following engine specificities: multiair system, turbocharging, combustion approach, fuel flexibility.

Dedicated SW strategies have to be studied and developed in order to ensure the engine the capability in adapting automatically the regulation parameters when changing the fuel gas composition (including introduction of limited amount of hydrogen up to 20%-30% by volume) and in order to optimize the aftertreatment efficiency. At the end the engine assessment will take into account different aspects of the engine behaviour, moving from the performance/efficiency ones to pollutant emissions and also the compliancy with temperature and internal pressure limits. The data set obtained will provide also the opportunity to have the first computation for the vehicle consumption/emissions by means of the SIMUWIN code, in order to predict if the main target of the project could be achieved with such a technological approach.

WP A1.3 Combustion process investigations ｨC The aim is to provide a support to the prototype engine development by means of modelling, using the CFD code and experimental activities focused on the comprehension of the combustion process also when using NG/H2 blends. The activities will be carried out with an optical monocylinder engine where also the air/fuel mixing will be studied, and with a 4-cyl. passenger car engine where also EGR potential will be evaluated.

WP A1.4 Aftertreatment system development ｨC The activity will lead to the definition of a dedicated solution for the aftertreatment system, taking into account fuel characteristics and engine specificities (lay out and operating modes). This will be supported in a first step both by the catalyst modelling via the AMESim code and by laboratory tests, which will be followed by screening activities at the engine test bed, able to determine not only the catalyst efficiency under steady state mode but also to evaluate the catalyst performance in terms of light-off delay.

WP A1.5 Global assessment on the validator vehicle ｨC A final assessment of the developed technology will be provided by means of the validator vehicle objective of this work-package; this last step will be preceded by the calibration of the transient conditions (in terms of load, speed and thermal charge) of the engine directly on the vehicle, and also by the light off refinement and catalyst efficiency optimization, activities that will be done in collaboration with IFP on the basis of test bench evaluation activities carried out in WP4. By doing this refinement of calibration, also the modelling of the vehicle behaviour will be completely fitted in order to better foresee the experimental results attended. As final outcome, the complete assessment of the vehicle in terms of performance, fuel economy, emissions and driveability will be presented. Within the WP the fuel storage system developed within SPB1 will be integrate and assessed.

Fig. A1.1 Flowchart of SPA1 work-packages and interactions with other SPsSub-project A2 典urbo DI CNG engine”

A. State of the art of the technology involved in sub-project A2 (SPA2)

Results from combustion system development in IP NICE and IP GREEN show the principal potential of direct injection with charge stratification and in cylinder turbulence generation. CNG shows good stratification capabilities and offers a big potential in fuel consumption. Lower exhaust gas temperature in stratified operation reduces the conversion rate of the catalytic converter, figure A2.1. This limits the usage of such a new highly efficient combustion system.

Fig. A2.1 Stoichiometric vs. stratified operation ｨC Combustion system IP NICE

Typical vaporisation problems as with gasoline DI-injectors are of no relevance for CNG DI injectors due to the gaseous fuel. More challenging is the proper mixing of fuel and air in the cylinder. The 1st generation of a Piezo actuated injector was developed by Siemens CT in the IP NICE. Different fuel qualities, especially in respect of the use of biogas, make a standard approach like in gasoline engines for the ECU structure difficult. Turbo vehicles have further potential via down-sizing and/or down-speeding. This requires increased power density and improved low end torque capability. Especially at low engine speed state of the art MPI CNG engines suffer from insufficient volumetric efficiency. Advanced scavenging strategies are not applicable for state-of-the-art MPI gas engines.

B. Innovative character of SPA2 with respect to the state-of-the-art and its quantitative ambitious objectives

The overall target is to meet the EU6 emission standards with a Turbo DI CNG engine, optimized for mono-fuel CNG operation. Table A2.1 shows the main relevant target values for the validator vehicle regarding performance and fuel consumption respectively CO2 emissions in the NEDC.

Engine Torque

State of the art

Target
Max power density @ 4300 ｨC 5500 rpm

~ 45 kW/l

> 70 kW/l
Max torque density @ 1800 ｨC 4300 rpm

~ 85 Nm/l

> 160 Nｷm/l
CO2 emission on NEDC test cycle

~ 170 g/km

< 140 g/km
Table A2.1 Specific targets for the 1.8 liter displacement car belonging to a D segment

(General targets in Tables 1.2 and 1.3)

Combustion System ｨC Late multi injection and stratified engine start open new possibilities for emission reduction in the start phase for a mono-fuel application with direct injection. The stratification capability of CNG is used for split injection for catalyst light-off strategies. These double injection strategy for higher exhaust gas enthalpy and lower HC raw emissions enables reduced emissions at higher catalyst temperature. The innovation in this field is an exactly designed combustion system to meet the requirements. Figure A2.2 shows demonstrative result of using such a strategy on a gasoline DI engine.

Fig. A2.2 Advantage of Split-injection in catalyst heating operation (gasoline DI engine)

Direct injection of CNG enables to vary the exhaust gas components composition depending on the degree of homogenisation. Target is to increase the more reactive CO content at global stoichiometric conditions. This offers some new possibilities to find an optimized coating configuration for faster catalyst light-off, as Input to SPB2
Injection System - The new approach to reduce size and costs is using an optimised injector together with a precise and fast variable injection pressure controller. An injector size similar to that of a state-of-the-art gasoline DI injector is recommended. A new innovative electronically variable pressure controller is part of a carefully designed injection system. The effect of thermal transients (hot soak, Joule Thomson cooling effect) is also part of the investigations to follow the new approach. The gas jet shape is very sensitive to the injector nozzle design. A deep and analytic investigation with advanced methodologies like spray characterisation and 3D-CFD simulation represents an innovative approach to solve the problems in this area.
Engine Control ｨC A cylinder pressure guided ECU could be the innovative approach to cope with different gas qualities and to optimize the combustion. The most direct way is to establish a closed loop control for the combustion timing, which is the key parameter for optimizing efficiency. The system enables cylinder individual combustion control. During the warm-up phase it is able to run the engine close to the cylinder individual misfire limit thereby reducing the light-off time. The variety of CNG gas quality can be high and an online adjustment of combustion relevant parameters represents a major benefit specially when thinking about the use of biogas. The potential of such a cylinder pressure guided approach will be investigated on the steady state test bed.

Vehicle Integration ｨC Advanced scavenging strategies at low engine speed with late injection for enthalpy increase on the turbo charger improve low-end torque for a down-sizing and/or down speeding concept.

C. Concise description of the work-packages (WPs) of SPA2

The subproject SP A2 is structured into 6 work packages (WPs). The chart, figure A2.3, shows the main tasks within each WP and the main interaction between the WPs. Special fuel compositions for testing are delivered by SPB0.1. The main connection can be seen with SPB2 in which an advanced exhaust gas aftertreatment system for gas engines with dedicated methane sensitivity is developed. The development and testing of the system in SPB2 is done at a generation 2 engine delivered by WP A2.3. The validator vehicle equipped with the innovative exhaust gas aftertreatment out of SP B2 represents the demonstrator for a turbocharged direct injection CNG vehicle with an innovative aftertreatment system.

Fig. A2.3 Flowchart of SPA2 work -packages and interactions with other SPs
WP A2.1 - Engine Layout - Target is to define clear project start information for all partners and work packages. In WP A2.1 based on the final results of NICE the new engine configuration and operation strategies for a mono-fuel low emission operation are defined.
WP A2.2 - Injection System Development - In WP A2.2 the specifications of injection system based on the final injector out of the IP NICE are analysed taking into account the new boundaries. The development will be based on the adoption of a centrally mounted position: in fact, tests recently carried out on a multi-cylinder engine showed that a side mounted configuration of the Piezo injector had a clear disadvantage regarding homogenisation (mainly due to the conical jet-shape with an outwardly opening nozzle that allows no asymmetrically jet-shape).

Together with engine investigations and input from the combustion system development an optimized injector concept and nozzle layout is developed. 3D-CFD Simulation represents the key method to develop a new nozzle group. Main focus is put on packaging, system costs and an optimized gas-jet formation with clear focus on a series production solution. Analysis and improvement of the over all injection system including also the pressure regulator, piping and injectors is done in this WP.

WP A2.3 - Hardware Procurement ｨC In WP A2.3 the engines for testing and validation are build up. All engine related components are procured and tested for integration. The interfaces between the components and the ECU are defined. One cylinder head for the transparent engine, one Multi Cylinder Engine generation 1 (MCE #1) and two multi cylinder engines generation 2 (MCE #2) are built up. One of the generation 2 engines is delivered to SPB2. Two ECU generations will be developed and procured.
WP A2.4 - Combustion system development ｨC Target of this WP is to find the best compromise between mono-fuel starting capability, catalyst heating strategies, part load fuel consumption and full load capabilities. The combustion development is assisted by transparent engine investigations and 3D-CFD simulations to analyse the mixture formation and combustion. ECU function development supports the combustion investigation and development process with new functionalities including also controlling aspects. The combustion system is also developed in boosted full load operation conditions to enable the low-end torque demand for a down-sizing concept. Tests are carried out to define the boundary conditions for the aftertreatment development in SPB2 (Input to SPB2).
WP A2.5 - Transient engine testing - In WP A2.5 the potential of a direct combustion control is assessed and ECU functionalities for combustion control are analysed. Main focus is on transient capability and emission control. The deep analysis of the interaction between combustion system, boosting system and calibration in transient conditions represents a new approach to optimize low-end torque performance of a natural gas engine. In this phase also chassis dyno tests will be done on a preliminary test vehicle.
WP A2.6 ｨC Vehicle validator ｨC In this WP the test vehicle is set-up for the combustion and function development. A Gen 2 engine is delivered to SPB2 for transient engine testing of the new exhaust gas aftertreatment system. Vehicle calibration work is done in this WP. NEDC simulation on the fully dynamic testbed is done for transient engine development, emission calibration and fuel consumption optimization. The EURO 6 emission capability shall be demonstrated on transient engine testbed. The test vehicle represents the functional demonstrator.
Sub-project A3 釘oosted lean burn gas engine”

A. State of the art of the technology involved in the sub-project A3 (SPA3)

Compared to the state-of-the-art CNG-technology full load operation as well as operation in the NEDC-relevant map area show significant improvement potential. All measures will be targeted in last consequence on increased efficiency respective to the corresponding decrease of the currently intensively discussed CO2-emission (downsizing) in connection with a proper aftertreatment device for NOx and CH4. The advanced layout of the lean combustion system offers sufficient margins towards driveability-limits and exhaust gas temperature-limits in the high load operation. Increased mechanical strength of the engine especially would result in a torque-increase. In consideration of the wide spread speed range of an Otto-cycle engine, the appropriate layout of the boosting system offers high potential. With raised rated speeds, primarily the power output can be affected positively. Using an advanced 1 or 2-stage charging system furthermore the low end operation as well as the transient behaviour will be improved. In combination with an advanced charging device high EGR rates can be realized. This gives the opportunity to reduce throttle losses.

B. Innovative character of SPA3 with respect to the state-of-the-art and its quantitative ambitious objectives

In the lower load areas the engine performance is preferentially determined by the emission relevant setup. As explained in the state-of-the-art, the strong trade-off between the engine out NOx-emission and the engine efficiency ｨC especially under low NOx-conditions ｨC can be dealt by using an external NOx aftertreatment system. In an exemplary part load operation point (BMEP = 5.15 bar @ 1813 rpm; Üハ= 1.6) the achievable efficiency gain depending on the NOx-emission is as follows: The change from very low NOx (0.31 g/kWh / 27 ppm) to medium values (1.8 g/kWh / 258 ppm) is linked with an efficiency improvement of more than 10%. According to this, the required NOx-conversion rate is in the range of 85%. In combination with the corresponding aftertreatment-system the targeted objectives are achievable. As opposite to the technology ways of Sub-Projects A1 and A2, the technology way A3 predominantly focus on engine operation with high air excess to enable high specific power and moderate levels of NOx-emissions together with EGR. Minimized NOx-engine out emissions ensure a sufficient conversion in an external NOx-reduction system. The development of a sophisticated control strategy results in an improved driveability.

Mixture formation will be investigated both, as a port fuel injection (PFI) as well as a low pressure DI injection. Next to exclusive NG operation, the influence of NG/H2-mixtures on the combustion process will be investigated.

Table A3.1 Specific targets of subproject A3 for 1.9 liter displacement LD vehicle with inertia mass of 1490 kg (General targets in Tables 1.2 and 1.3)

State of the arta)

TargetMax power density ~ 47 kW/l> 60 kW/lMax torque density~ 90 Nm/l> 160 Nm/lCO2 emission on NEDC~ 140 g/km< 110 g/kma) Today LD vehicles using the stoichiometric approach
C. Concise description of the work-packages (WPs) of Sub-Project A3
WP A3.1 Concept Phase and Design Specifications ｨC A first step in this work package is the definition of the base engine for further development work. Especial it will be checked to use the light duty vehicle 纏afira(curb weight approx. 1600 kg) with the 1.9 l diesel engine as base engine. On the base of best precondition to achieve the performance targets regarding power output, emission behaviour and fuel consumption the base engine will be determined. According to the SP A3 strategy, high demands are made on the boosting- and aftertreatment-devices. Catalytic removal of methane and NOx in lean gas are different from stoichiometric gas catalysts and therefore require special catalyst types. Definition of aftertreatment requirements with ensuing identification of configuration of optimal catalyst types will be made. Identification of boundary conditions and exhaust gas composition will be made. Fuel penalty considerations will be critical for selection of NOx removal technology- SCR versus lean NOx traps. As sulphur is critical for catalyst performance, requirements to the sulphur content in fuel and lubrication oil will be identified. In the first step modelling on these topics are done. After modelling and preliminary calculations the respective specifications will be defined. Decision regarding boosting, if single-stage is sufficient or advanced two-stage has to be applied. Vehicle related design specifications concerning engine and fuel system packaging as well as the first layout of the control strategy will be done in-between this work package.
WP A3.2 Components, Engine Design and Procurement ｨC Included in this work package is the modelling, design and procurement of the components needed. Boosting devise and aftertreatment system will be designed by using the results from WP A3.1 and the modelling carried out in this WP. The key characteristics for the design work are future legal requirements, environmental friendly concerns as well as weight and cost efficiency. The data will be treated, for example an in-house developed computational simulation tool will be used, and validated with measured engine data. The conclusions will, in addition to previous experience, subsequently give ideas of potential prototype materials. These prototypes are then to be tested in experimental set-up and in WP A3.3.

In the case of regular combustion of methane, three way catalysts (TWC) are used. For such aftertreatment systems, the optimization parameters are Precious Group Metal (PGM) loading and wash-coat technology in addition to and/or trade-off against high temperature durability. For oxygen rich combustion other chemical compositions are needed. For example is the nitrogen oxide (NOx) reduction under lean conditions a very delicate problem. To address this issue, at least two different (for other applications well known such as NOx storage and ammonia SCR) methods will be investigated from a CNG applicability perspective. However, newer academic state-of-the-are technologies may be considered, e.g. hydrocarbon SCR. The catalytic control of slip methane (methane conversion) may also be a problematic topic as it is known from experience that this process is very sensitive to temperature, oxygen content and trace level of sulphur compounds. Even with the latest catalyst developments, accurate exhaust temperature control to the catalysts for fulfilling regulatory driving cycle limits is required in parallel with a low level of sulphur from fuel and lubrication oil in the exhaust gas is secured. To ensure the success of the aftertreatment project, the interaction between the similar tasks in the other sub-projects A1, A2 and B2, is essential as the final vehicle may need to utilize all three combustion stoichiometries in different parts of the speed-load range. Potential suppliers are contacted.

WP A3.3 Component, Engine and Powertrain Testing ｨC Decoupled from engine testing, this work package covers the characterisation of components and sub-systems on specific test rigs. In detail the boosting system as well as the aftertreatment system will be investigated and improved by:

Setup of a Single Cylinder Engine (SCE) and experimental analysis will be carried out to validate the system potential and to assess the technologies integration issues.

Combustion system optimisation (compression ratio, gas exchange, mixture formation regarding port fuel injection as well as direct injection of NG, mixture charge motion respective in-cylinder turbulence, EGR, knocking behaviour and lean burn capability).

Single cylinder investigations will be focussed on stationary operation.

Carry over of the combustion system layout of the SCE to the Multi Cylinder Engine (MCE)

Built up of a prototype engine.

Testing under stationary and transient conditions.

Fine-tuning of the prototype engine setup to optimise sub-systems (combustion, boosting, aftertreatment) under real engine conditions.

Adoption of the engine control strategy.

Investigation of the influence of NG/H2 mixtures on the combustion process.

WP A3.4 Vehicle Procurement, Vehicle Testing and Potential Evaluation ｨC The systems developed in the previously described work packages will be integrated into a validator vehicle. This work package covers the vehicle and the related materials. It also covers:

In-vehicle calibration and testing with regard to driveability, efficiency and emissions.

Integration of CNG fuel system, prototype engine and prototype emission control in the validator vehicle.

In-vehicle calibration and testing under real world driving conditions.

Emission and fuel economy calibration and testing under certification conditions on chassis dyno with extra focus on methane and NOx emissions.

Assessment of validator test results versus best in class vehicles available in the market and evaluation of further potentials of the new technology.

Fig. A3.1 Flowchart of SPA3 work -packages and interactions with other SPsSub-project B0 擢uels for advanced CNG engines”

A. State of the art of the technology involved in the sub-project B0 (SPB0)

The natural gas quality differs greatly all over Europe according to regional and local conditions: different supply sources, process-inherent variation of the concentration of trace components like oil/particulates at the fuelling station, admixture of biogas and, in future, hydrogen (H2). Fig. B0.1 shows the expected development up 2020 of natural gas supplies in Europe, while Table B0.1 shows an excerpt from a German standard which is now in preparation for natural gas as a fuel and which will presumably form the basis of a European standard in the near future; the figures in this standard refer to the requirements which have basically been defined for present vehicle concepts and the demands of fuel components for suction pipe injection systems. The quality of natural gas is affected by trace components linked to the technology of the fuelling station. On one side, particles or the amount of higher hydrocarbons, sulphur and water will be reduced through filtering-, drying- and separating systems. On the other side, if not efficiently filtered compressor oil and particles can be carried into the gas during the compression process. Special issues associated with trace components are:

too much compressor oil can impair the function of components in the feeding system;

sulphur compounds and particles can increase the wear and tear of components (sulphur is necessary for odorisation when S-free odorants are not used).

Fig. B0.1 Development of natural gas supplies in Europe [source E.ON Ruhrgas]B. Innovative character of SPB0 with respect to the state-of-the-art and its quantitative ambitious objectives

The development of advanced gas vehicles has to be supported by a survey of the gas composition (including trace components) in the relevant EU countries. The investigation of the reaction of advanced CNG engines to changing gas compositions through bench tests and simulation will create the basis for reliable control strategies ensuring an optimal engine operation for the specified range of gas compositions and avoiding power loss, engine damage, emission increase and driveability loss by gas quality fluctuation. Starting from known property identification concepts for bi-fuel and partly optimised mono-fuel engines, innovative strategies for a gas property detection for advanced CNG engines will be based on the evaluation of operational engine management data and on additional sensors dedicated to fuel property measurement. The results will be incorporated in gas standardisation guidelines considering engine requirements as well as gas supply and fuelling station requirements. The use of upgraded biogas (biomethane) and NG/biogas mixtures as a fuel will be also investigated, in particular some questions concerning the composition of upgraded biogas as well the addition of LPG to adjust upgraded biogas to H-Gas quality. Finally the properties of natural gas and hydrogen mixtures will be investigated.