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Particle emissions of Diesel busses with RME/Diesel blends

Mayer A., Czerwiński J., Wyser M., Heitzer A.

Prace Naukowe Instytutu Nafty i Gazu

2010

nr 172

37-60

Vegetable oils blended to Diesel fuel are becoming popular. Economic, ecological and even political reasons are cited to decrease dependence on mineral oil and improve CO2 balance. The chemical composition of these bio fuels is different from mineral fuel, having less carbon and much more oxygen. Hence, internal combustion of Diesel + RME (Rapeseed Methyl Ester) blends was tested with particular focus on nanoparticle emissions, particle filtration characteristics and PAH-emissions. Fuel economy and emissions of bus engines were investigated in traffic, on a test-rig during standardized cycles, and on the chassis dynamometer. Fuel compositions were varied from standard EN 590 Diesel with < 50 ppm sulfur to RME blends of 15, 30, and 50%. Also 100% RME was tested on the test-rig. Emissions were compared with and without CRT traps. The PAH profiles of PM were determined. Particles were counted and analyzed for size, surface, and composition, using SMPS, PAS, DC and Coulometry. Results show little difference for legislated emissions HC, NOx and PM. Size distribution and chemical composition of the particles however vary with increase of RME in the blend. Particles from RME-combustion tend to be smaller and PM contains much less EC but more HC. Little effect of RME-blends on PAH, 100% RME however shows increased PAH-content of PM at high engine loads. Lower calorific value reflects in fuel consumption. DPF efficiency remains high, 99.8% independent of RME content. CRT regeneration is sustained, possibly due to the combination of a highly Pt-coated DOC and DPF, i.e. the DOC "dries" the particles and the DPF only partially receives the high HC content of engine-out particles. NO \to NO2 conversion is high with CRT, as usual, independent of RME-blend ratio. Overall assessment: the impact of RME on emissions is minor. And despite lower EC particle emission, the particle trap remains indispensable.

Influences of Alternative Fuels GTL, RME and ROR on Combustion and Emissions of a Modern HD-Diesel Engine

Czerwinski J., Zimmerli Y., Neubert T., Heitzer A., Kasper M.

Silniki Spalinowe

2007

R. 46, nr SC3

180-200

Due to the limited energy resources as well as due to increasing CD2-emissions the importance of alterative- and biogene fuels is continuously increasing. Investigations of the engine operation were performed on a latest technology Liebherr engine for construction machines. It was operated using crude rapseed oil (RDR)'), rapeseed oil methyl ester (RME), synthetic Gas-To-Liquid fuel (GTL) and diesel (as reference fuel). The combustion diagnostics, the performance of the injection system as well as the pollutant emissions, including unlimited nanoparticles were assessed. The most important findings ean be summarized as joilows : Fuel injection - Both, RME and RDR shortened the injection delay which was due to a quicker increase of injection pressure and a faster needle lift, - the highest maximum injection pressure was observed with RDR (1610 bar), followed by RME (1580 bar), Diesel (1450 bar) and GTL (1410 bar), - As compared to diesel, GTL exhibited no significant differences of hydraulic behavior. Combustion - Usually, GTL caused a shorter ignition delay, but it burned slower, so that 50% of heat release took place at the same CA-position, as for Diesel. in addition, GTL provoked a lower rate of pressure raise and reduced the maximum combustion pressure. These effects were particularly pronounces at lower and medium loads. - At higher engine load RDR and RME started to bum earlier and at a higher rate, than Diesel and GTL. Therefore, 50% of the heat release followed with ROR and RME 1-2 CA earlier which had consequences for the NOx emissions. Limited emissions and energy consumption GTL lowered generally ail emission components - as compared to standard Diesel fuel. In addition, the energy consumption with GTL was equal or slightly lower. RME lowered CO and HC emissions and increased NOx emissions at ail operating points. It lowered PM at higher engine loads and increased PM at lower engine loads. RME had no effect on specific energy consumption. ROR lowered CO, HC and PM at ail operating points by at least 50% or more. In the high-load-operation RDR reduced the specific energy consumption (approx. 2%) and increased NOx (up to approx.5%). At low-load-operating points (1500 rpm/10%) ROR did not affect CO and NOx, but increased PM emissions and energy consumption. Nanoparticle emissions - GTL and diesel nanoparticle emissions were identical, - Both RME and RDR moved the PSD spectra to smaller sizes and increased the nuclei mode due to spontaneous condensate formation, - Both RME and RDR caused lower particle emissions at high load and higher emissions at low load, The use of ROR resulted in a particularly high portion of condensates (SDF) at low load and idling.