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Green Heavy Duty Engine

Final Report Summary - GREEN (Green Heavy Duty Engine)

The main objective of the integrated project GREEN was to perform research leading to subsystems for a heavy-duty powertrain based on the intelligent integration of a new engine concept, characterised by:
- flexible components
- an improved combustion process
- models for a model based closed loop emission control
- high power density
- integrated exhaust after-treatment system with good reliability at low load in wide range of operating conditions
- on a competitive cost base
- with the highest fuel conversion efficiency of the Diesel cycle
- near-zero real world pollutant emissions and significant reduction of CO2.

The objectives broken down to a subproject level gives the following scientific objectives to the project:

Subproject A1:
Perform a gas engine with maximum thermal efficiency potential with:
- Electro-hydraulic variable valves motion management (EVMG)
- Very near to valves multipoint port-gas injection and experimental study of DI injection
- Cooled EGR
- Gas quality assessment.
The work carried out within SPA1 allowed to reach outstanding results respect to the state-of-the- art in terms of performance, consumption and emissions. The technologies integrated onto the final multi-cylinder CNG engine validator could be available on the market within a short-medium period (two-three years from the completion of the Project). In order to facilitate their industrial introduction some efforts should be dedicated to the development of a more advanced engine control system (integrated single ECU) for managing all the new functionalities and including the capability to adapt the regulation parameters to the gas fuel composition also taking into account the opportunity to use methane + hydrogen blends. The use of this kind of blend represents an additional step in the reduction of both pollutant emissions and CO2 formation. Apart from the 'natural' extra reduction of the CO2 emissions due to the increase of the H/C ratio of the fuel, hydrogen represents a flame propagation booster which could provide an additional gain to the thermodynamic efficiency. Moreover, a reduction in THC emissions is also expected taking into account the reduction of the flame quenching phenomena.

Subproject A2:
Evaluate the potential of different variability in combination with tailored exhaust after-treatment systems based on novel fuel injection and variable valve actuation (VVA) system combined with:
- Functional particulate filter and catalyst
- New control strategies for filter regeneration and injection
- Assessment of different concepts.
The flexible engine approach to reach the GREEN targets resulted in that the emission targets was fully reached and the fuel consumption targets was reached partly.

The F1 fuel injection is very interesting for the future as it gives the opportunity to combine very injection pressures with flexible rate shaping potential and excellent multiple injection capacity. There is also shown, on a prototype level, a good functionality in engine testing. The variable valve system has an excellent functionality, but the capacity was difficult to use fully as it was often a problem with fuel consumption penalty when using the functionality. However a better boosting system (than available in this project) in combination with variable valve system is an interesting opportunity for the future. It is also depending in which engine out emission level that is required. The LNA system worked very well, but the NOx conversion efficiency was lower than for a state-of-the art SCR system. It is possible to reach as high conversion efficiencies with LNA system as with SCR systems, but as the noble metal content is high in such LNA systems it is probably not cost efficient to use them for heavy duty applications.

Subproject A3:
Develop the concept of a new combustion process and the first step to a model based closed loop powertrain control characterised by:
- High pressure engine with optimised combustion chamber
- Totally new amplified common rail (CR) system with variable nozzle
- Raw emission, thermodynamic and exhaust system models
- Assessment of the developed models in the context of a model based closed loop emission control.

A high potential of improvement has been demonstrated with the variable injection system, however, it becomes obvious that this cannot be simply transferred to multi cylinder applications. On the one hand, sophisticated hardware such as the KVD nozzle will not be available for multi cylinder applications in the foreseeable future. On the other hand, the project gave an idea of the system complexity and the required efforts to apply it to multi cylinder engines and to utilise all its benefits.
The engine models derived in combination with the new methodology permit investigating:
- future offline front-loading powertrain concepts involving system configuration and operation strategies
- future innovative integrated powertrain control systems.

To complete the tool chain, simplified aftertreatment models need to be derived and coupled with the engine model. Based on this virtual powertrain system, the best control concept can be derived and afterwards realised and evaluated in real-life. Finally, it is emphasised that both - any improvements in the combustion concept and any improvements in control - can be combined with other improvements which refer to the engine cycle, exhaust aftertreatment, downsizing etc.

Subproject A4:
Investigate the potential of a high BMEP engine with development of:
- One- and two-stage turbochargers
- New engine design
- Variable compression ratio system
- An exhaust gas energy recovery system.

It was possible to further improve engine efficiency even at more stringent emission limits and higher BMEP. The costs of the related technologies were highlighted. A variable compression ratio system (VCR) is feasible also for heavy duty HBMEP engines and could be a way to increase the power of existing engines with standard structure with no impact on the engine outer dimensions. An improved single stage turbocharger (axi / radial compressor) was realised and tested. It fulfilled the requirements for this engine. From studies of exhaust heat recuperation systems, further potential for BSFC- reduction was revealed by simulations. Experience was gained with different EGR- systems and related problems of condensation, corrosion and engine. Tribological and friction behaviour of a high PFP engine were evaluated. The technologies for high BMEP engines will be used step by step for future applications. The improved single stage turbo-charging can fulfil the requirements for the next performance steps with not too demanding space requirements for actual vehicles. The high pressure common rail injection, EGR and the SCRT- after-treatment will probably become standard for on-road applications in Europe. Improved materials for castings and steel pistons will be applied in some cases to build more compact and lighter engines at the required power output. Improved structure design will fulfil short term requirements.

The GREEN project has been ended after 39 month and all partners have fulfilled their tasks. The main results and achievement are summarised and concluded as:
- All technical deliverables and milestones have been fulfilled
- Component on sub-system level have been developed and tested. Their performance and potential have been stated and recommendations for future work are given.
- The GREEN emission targets have been fulfilled, both in gas and diesel engine application.
- The fuel consumption has been improved in all applications.
Different single or combinations of components and sub-technologies have enabled these promising results. But also the very good collaboration between the partners have been a determining factor in order to deliverer in time or to do the right action and priorities when delays were present in the project.

Today, it is still possible to improve all the used GREEN components or sub-technologies. However, in the near future more work are required on GREEN technologies in order to improve the robustness on single components if they should be applied in production.

In the future, the air management system (turbo, valves, etc.) and the cooling system are crucial sub-systems in order to gain the maximum from the new combustion system based on flexible engine, as multiple fuel injections and variable valve timing.

For the overall powertrain optimisation and in order to increase the energy efficiency, integration between sub-system and close loop functionality is considered to be the key-factor. Further on, is improved in-cylinder pressure and heat recovery system approaches that will improve the fuel consumption, but the effect will be different on various applications.