Owing to its high efficiency, direct injection has established itself as the standard technology in gasoline engines. Compared to external carburetion, however, health-damaging particles are produced. The aim of this project was to analyse the mechanisms for particle formation and in a second step to reduce particle number emissions. To this end, the project partners analysed the carburetion and combustion processes using optical measurement technology. With the use of electron microscopic investigations they gained knowledge about the morphology and the composition of particles. The findings revealed that the essential parameter on particle formation is carburation, which is mainly influenced by the injection system, the charge movement and the injection strategy. The oxygen concentration and the gas temperature profile in the primary zone of the combustion chamber significantly influence particle oxidation. These results form the basis for the further development of emission reduction technologies.
» The investigations provide us with a thorough understanding of the key influencing factors of particle formation in direct injection gasoline engines. We now know which parameters we need to look at to reduce particle number emissions. «
Engines with gasoline direct injection prepare the air-fuel mix directly in the combustion chamber. All that flows through the open intake valve in the intake duct is fresh air. High-pressure injection valves inject the fuel directly into the combustion chamber. This cools the combustion chamber, making basic compression higher and reducing propensity to knock.
Particle composition of the exhaust gas (Source: Schmid, P., Investigation of the gravimetric measurement technology with regard to future emission limits (Thesis), Technical University, Darmstadt, 1998).
The shape of the spray that forms in the combustion chamber plays a crucial role in the search for improved performances. The chart contrasts the spray targeting of the three multi-hole injectors used.
Direct injection – the direct injection of fuel in the combustion chamber – together with turbocharging has become a key technology in gasoline (GDI) engines. One disadvantage compared with external formation of the air-fuel mix is, however, an increase in particle emissions in exhaust gas. Owing to their tiny size, these particles can enter the lungs and in this manner are hazardous to health. A thorough understanding of the engine internal sources for particle formation is a prerequisite for avoiding PN emissions.
Using optical measurement methods, the carburetion and combustion processes were analysed, the particle concentration and size distribution in exhaust gas were measured, and emitted soot was examined for its morphology and chemical composition using an electron microscopy. A single-stroke engine and one-cylinder aggregate with direct injection and central injector storage served as the test vehicle. At the beginning, the focus of the investigations was on reviewing the influence of different compositions. Then through a restriction of the injector diversity, the influence of different parameters on PN emissions could be established.
The carburetion as a sum of direct injection system, charge movement and injection strategy has the largest influence on particle formation. The particle oxidation is mainly determined by the oxygen concentration and the gas temperature profile in the primary zone of the combustion chamber. The investigation also showed that both spray targeting – the optimal spatial distribution of fuel mixture in the combustion chamber – and wear on components can influence the oil concentration in the exhaust gas and thus also the lubricant oil content of particles. Further investigations offer the possibility of performing the PN measurement directly in the exhaust gas system and of further developing the engine internal data / measured value acquisition.
Particles at Otto-DI I | Investigations to reduce particulate-emissions from Otto-DI-engines | Project No. 1046
Particles at Otto-DI II | Investigations into reducing particle number emissions from GDI engines | Project No. 1144
Particles at Otto-DI III | Investigations into reducing particle number emissions from GDI engines | Project No. 1193
Public & FVV Funding
2010-08-01 to 2013-07-31 Part I
2013-07-01 to 2014-06-30 Part II
2015-06-01 to 2017-03-31 Part III
Dr.-techn. Herwig Richter | I
Dr.-Ing. h. c. F. Porsche AG
Dr.-Ing. Daniel Sabathil
Opel Automobile GmbH | II+III
Institute of Internal Combustion Engines (IFKM) | Karlsruhe Institute of Technology (KIT)
Head of research:
Prof. Dr.-Ing. Ulrich Spicher | I
Prof. Dr. sc. techn. Thomas Koch | I-III
Dipl.-Ing. Markus Bertsch | II+III
Dipl.-Ing. Helge Dageförde | I
Denis Notheis, MSc | III
Research & Technology Performers
Research Association for Combustion Engines eV
Lyoner Strasse 18
60528 Frankfurt am Main
T +49 69 6603 1345