Within the Cluster of Excellence "Tailor-Made Fuels from Biomass", a new reaction sequence to transform biomass into 2-methylfuran has been developed. In the present study, the influence of this potential biofuel on in-cylinder spray formation and evaporation as well as engine performance is studied experimentally using a direct-injection spark-ignition single-cylinder research engine. The results obtained for 2-methylfuran are benchmarked against investigation on the same engine using conventional research octane number (RON) 95 fuel and ethanol. The in-cylinder spray formation and evaporation process is characterized by high-speed Mie scattering visualizations, indicating quicker evaporation of 2-methylfuran compared to ethanol. Engine experiments support the findings of the optical measurements by revealing excellent combustion stability, especially in cold conditions, combined with a hydrocarbon emission reduction of at least 61 % in the relevant spark timing range compared to conventional fuel. The enleanment capability was also found to be higher by 0.16 units of relative air/fuel ratio. A noticeable drawback resulting from the combustion of 2-methylfuran is higher emissions of nitrogen oxides. The knock resistance of 2-methylfuran at full load is significantly better compared to RON 95, however, worse than ethanol. It allows for a compression ratio increase of more than 3.5 units compared to RON 95. The measured efficiency benefits with a compression ratio increase of 3.5 units range up to 9.9 % at full load.

Increasing carbon dioxide accumulation in earth's atmosphere and the depletion of fossil resources pose huge challenges for our society and, in particular, for all stakeholders in the transportation sector. The Cluster of Excellence 'Tailor-Made Fuels from Biomass' at RWTH Aachen University establishes innovative and sustainable processes for the conversion of whole plants into molecularly well-defined fuels exhibiting tailored properties for low-temperature combustion engine processes, enabling high efficiency and low pollutant emissions. The concept of fuel design, that is, considering fuel's molecular structure to be a design degree of freedom, aims for the simultaneous optimisation of fuel production and combustion systems. In the present contribution, three examples of tailor-made biofuels are presented. For spark ignition engines, both 2-methylfuran and 2-butanone show increased knock resistance compared to RON95 gasoline, thus enabling a higher compression ratio and an efficiency gain of up to 20% at full-load operation. Moreover, both fuels comprise a good mixture formation superior to the one of ethanol, especially under difficult boundary conditions. For compression ignition engines, 1-octanol enables a remarkable reduction in engine-out soot emissions compared to standard diesel fuel due to the high oxygen content and lower reactivity. This advantage is achieved without sacrificing the high indicated efficiency and low NO X emissions.

No abstract

Further significant CO 2 emission reduction beyond 2020 is mandatory in the United States and might also become mandatory in Europe, depending on the passenger car CO 2 legislation, which is to be enacted. Hybrid and plug-in hybrid vehicles might account for a big portion of these CO 2 reductions as a consequence of the favourable current legislative treatment which does not associate CO 2 emissions from electric power generation with vehicle CO 2 emissions. Nevertheless, these powertrains benefit from a highly efficient combustion engine. Exhaust heat recovery poses new synergetic possibilities for technologies to mitigate knock like cooled external exhaust gas recirculation and condensed water injection. The condensed water injection concept, which is proposed in this article, demonstrates a potential for efficiency increase of 3.3%-3.8% in the region of the minimum specific fuel consumption on a stoichiometric combustion concept with Miller cycle and cooled external exhaust gas recirculation. Further improvement of the efficiency of up to 16% is possible at full-load operation. If water injection is used in addition to homogeneous lean combustion, an efficiency gain of 4.5% in the region of the minimum specific fuel consumption is achieved.

No abstract