NICE - New Integrated Combustion System for Future Passenger Car Engines
Overview
Background & policy context:
The project clusters of the Fourth and Fifth Framework Programme developed advanced technologies for Otto-cycle engines (in ADIGA and GET-CO 2) and diesel-cycle engines for passenger cars (in ADDI and DULEV). These combustion systems presented opposite problems: the Otto-cycle had a high fuel consumption but low emission levels, while the diesel-cycle showed very low fuel consumption but with substantial problems in meeting low emission levels. In the 2002 annual review of Valencia, a combined combustion system able to join the advantages of both cycles was imagined for the first time and was then being considered by NICE.
Objectives:
The overall objective of the NICE project consisted in the development of different integrated combustion systems (now in plural) for different types of fuel (gasoline, diesel, compressed natural gas, synthetic biomass-based fuels), which could combine the excellent fuel conversion efficiency of a cutting-edge DI diesel engine while complying with very low future emission levels (i.e. EU6).
At the beginning, the vision of the NICE project was one single combustion system, to be realized in the subsequent framework programs 8 and 9, and a convergence towards this single system was expected to occur in the future. During the project, however, this vision changed and the general assumption then became that there would possibly be a convergence of several components and technologies like turbo-charging or direct injection, but that a total fusion within one single concept would not occur. In contrary, future concepts could become even more various. According to this scenario, even the number of different gasoline and diesel engine concepts would increase, depending on local markets incl. local legislation and incentive politics. Furthermore, new fuels would get onto the scene, natural gas being only one of them, and several biogenic fuels would arise.
The concrete objective had to be specified according to type of fuel:
- For a gasoline engine, improving fuel economy while keeping low emission levels was the major goal. This might be achieved by introducing new technology components like direct injection, downsizing by turbo-charging and variable valve train.
- For diesel engines, an important and challenging task consisted in improving the emission levels (towards EU6) without loss in fuel economy when compared to a current EU4 engine, at affordable cost increase.
- CNG (compressed natural gas) engines already exhibit very low CO2 emission levels. Besides further reducing fuel consumption, a major task consisted in making such engines more attractive by modern engine technologies (e.g. turbocharging) in order to enable an increased market share of such engine concepts.
- Biofuels made from renewable biomass are already an efficient means for reducing CO2 emissions. Second generation biofuels, however, offer additional potentials when designing dedicated engines for tailored biofuels. These potentials can be used in order to improve fuel economy as well as to reduce system cost (e.g. after-treatment), especially when applied for fulfilling E
Methodology:
In order to address these topics, the NICE project was divided into four sub-projects:
A1: Enlarged HCCI (Homogeneous charge compression ignition) diesel combustion process under transient operation.
Subproject A1 addressed enlarged HCCI diesel combustion. The purpose was to improve the emission levels of a diesel engine toward EU6 without loss in fuel economy compared to an EU4 current engine. Cost increase should stay reasonable, hence technical solutions were chosen to avoid using costly NOx after treatment. A wide range of work was carried out, ranging from better understanding the combustion with numerical, optical and dedicated testing facilities to the building and calibration of a demonstrator vehicle. Finally, the vehicle was equipped with the selected technologies integrated in a multi-cylinder engine using the HCCI combustion principle on a wide range of operations (at least NEDC cycle) and fully capable of being driven.
A2: Compressed / spark ignited variable engines, including a new diesel-type combustion system for tailored biomass-based fuels.
The main general objectives of sub-project A2 were:
- the development of subsystems of integrated flexed low cost components with the goal of a variable ICE structure;
- the definition of a combustion system able to also run on tailored bio/bio-blend fuels (to this purpose, liquid fuel specs have been investigated and proper recommendations for renewable fuels have been released);
- an increase of the fuel conversion efficiency of about 10% with particular regard to engines running on diesel fuel and gasoline which will have the main impact on the environment in the next 20-30 years.
Sub-project A2 considered different approaches for different combustion processes:
- spark ignited combustion process;
- compression ignited combustion process.
A3: Future CNG internal combustion engines.
Vehicles powered with natural gas have been well known for a long time. However, today's gas engines for passenger cars and commercial vehicles still have the heavy drawback of being developed as multi-fuel engines on the basis of conventional internal combustion engines. Optimised mono-fuel natural gas engines offer additional potential with respect to fuel consumption, emissions and performance. Objective of this subproject was to evaluate this potential and to find out favourable technological concepts.
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