The development of heavy-duty (HD) engines is undergoing a rapid evolution. Increased demand for fuel efficiency, emissions and global competition are driving forces. HD engines operate under constraints much more severe than those of passenger cars, such as:
- higher durability (> 600 000 km) of the engine and of the related after-treatment;
- higher mechanical and thermal stress of the engine (heavier load factor);
- higher pressure on reliability (up-time), investment and fuel economy.
The above constraints characterise the HD engines for their more general applications: not only trucks and urban vehicles but also the rail traction and the inland waterway vessels of the directive 2002/765.
New technologies will help in meeting future emission and fuel consumption targets by:
- a new combustion process enabled by variable components;
- new control strategies;
- considering the engine and the exhaust after-treatment as one system;
- considering sustainable fuels.
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 work in GREEN was divided into sub-projects:
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.
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.
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.
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.
The GREEN project ended after 39 month and all partners fulfilled their tasks.
The main results and achievement are summarised and concluded as:
- All technical deliverables and milestones have been fulfilled
- Components at 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 on time or to performe the right action and priorities when there were delays in the project.
In summation, GREEN has given unique low emissions values together with improved fuel consumption, both on heavy duty gas and diesel engine application. These practical results, together with the fundamental knowledge that was gained, will be a basis for a future project. Furthermore the project has a large number of test hours on components, sub-technologies and combustion system providing essential information for the future.
As mentioned above some technologies will be applied in the near future, others require more development on component level. In the end it is the cost benefitsl in each technologies that will the bottom line for application in productions. To establish GREEN's low emissions levels more developments are required on sub-system levels (or component level) to improve the robustness for production. To enable future fuel consumption reduction work on the complete powertrain, as mentioned above, continual modelling development, both on system level but also on fundamental level is required.
Today, it is still possible to improve all the used GREEN components or sub-technologies. However, in the near future more work is required on GREEN technologies in order to improve the robustness on single components if they are to be applied in production.
In the future, the air management system (turbo, valves, etc.) and the cooling system will be crucial sub-systems in order to gain the maximum from the new combustion system based on flexible engine, such as multiple fuel injections and variable valve timing.
For the overall powertrain optimisation and in order to increase energy efficiency, integration between sub-system and close loop functionality is considered to be the key-factor. Furthermore, it 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.