Entwicklung kostengünstiger und wasserhaltiger Dieselkraftstoffe zur nachhaltigen Schadstoffreduktion (English shop)

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In times of climate change, water-containing fuels can make an effective contribution to reducing exhaust emissions from in-cylinder combustion and thus also to compliance with legal requirements. In this context, breaking the barely controllable soot–NOx trade-off is of decisive importance. The use of water makes it possible to dispense with complex and expensive exhaust gas aftertreatment technology. Within the scope of this work, fuel microemulsions with diesel and GtL were characterised, optimised and simplified. These were further developed into efficient, surfactant-lean and water-rich nanoemulsions that meet engine-related and ecological requirements. Nanoemulsions offer the advantage of structures comparably small to those of microemulsions and thus of very finely dispersed water, while requiring only small amounts of surfactant. These nanoemulsions were investigated with regard to their structure and stability by means of dynamic light scattering. In addition, the formation and decay kinetics were analysed using stopped-flow measurements. In this way it could be ensured that the rate of formation is sufficiently high for formation within the engine itself. Such fuel emulsions were generated in a BMW test vehicle with dynamic on-board water admixture. The emission behaviour was investigated on the basis of the WLTP cycle with respect to CO, CO2, HC and NOx, fuel consumption and soot. Furthermore, the soot was characterised with regard to its particle size distribution. In these investigations, considerable improvements in emissions could be detected. The use of water in some cases even led to fuel savings and increased engine efficiency. Breaking the soot–NOx trade-off could be confirmed for all systems investigated. Significant reductions in nitrogen oxide emissions were achieved as well as considerable soot reductions of up to 66%. Finally, the exhaust gas investigations revealed that for every operating point of the engine there exists a specific water content that achieves optimal results in terms of emission reduction. Through the use of optimised nanoemulsions, this can be set in a targeted manner.