Dimethyl carbonate (DMC) and Methyl Formate (MeFo): Emission characteristics of novel, clean and potentially CO2-neutral fuels including PMP and sub-23 nm nanoparticle-emission characteristics on a spark-ignition DI-engine. (15th November 2019)

• Record Type: Journal Article
• Authors: Maier, Thomas; Härtl, Martin; Jacob, Eberhard; Wachtmeister, Georg
• Is Part Of: Fuel. Volume 256(2019)
• Publication Date: 2019-11-15
• Subjects: AFR air fuel ratio -- C1- molecules with no C–C bonds -- CA crank angle -- CS catalytic stripper -- CPC condensation particle counter (of particle size distribution) -- D50 CPC cut-off-size (50% counting efficiency) -- DMC dimethyl carbonate (C3H6O3) -- DI direct injection -- ET evaporation tube -- FID flame ionization detector -- FTIR fourier transform infrared exhaust analyzer -- GHG greenhouse gases -- GMD geometric mean diameter -- ICE internal combustion engine -- IMEP indicated mean effectivepressure -- MeOH methanol (CH3OH) -- MeFo methyl formate (C2H4O2) -- MEXA HORIBA multicomponent motor exhaust analyzer -- mfb mass fraction burned -- OME oxy methylene ether (CH3-O-[CH2-O]n-CH3) poly oxy methylene dimethyl ether -- PMP particle measurement programme -- PN particle number -- PNCS particle number countingsystem (PMP system) -- PND particle number diluter -- PNmin LVK PNCS prototype -- ROHR rate of heat release -- RON research octane number -- RWGS reverse water gasshift -- SMPS scanning mobility particle sizer -- SOI start of injection -- SPCS solid particle counting system (HORIBA PNCS) -- Sub- PN measurements with instrument efficiency -- 23nm more sensitive to particles below 23nm than conventional PMP-setups -- TDC top dead center (aTDC: after TDC) -- TWC three way catalyst (aTWC: after TWC) -- VPR volatile particle remover -- VOC volatile organic ccompounds; DMC -- MeFo -- E-fuel -- PtL -- Alternative fuel -- Synthetic fuel -- Combustion -- Gasoline -- DISI direct-injection (DI) spark-ignition (SI) -- Emission -- Nanoparticles -- Solid particle number (PN) -- PMP -- Sub-23 nm -- Particle size distribution; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2019.115925
• Languages: English
• ISSNs: 0016-2361

Abstract

Abstract: Dimethyl carbonate (DMC) and methyl formate (MeFo) are oxygenate fuels characterized by a very high octane number and boiling points in the range of commercial gasoline (DMC: 90 ° C / 363, 2 K, MeFo: 31.5 ° C / 304, 7 K ). Due to their molecular structure without C–C bonds (C1-fuel) and their high oxygen content of 53.3 %, DMC and MeFo are expected to avoid the formation of soot precursors in combustion and thus to distinctly reduce particulate number (PN) emissions. Beyond todays solid particle number (PN) limits, which are based on the definition of the particle measurement program (PMP) using a 23 nm cut-off of the counter, sub-23 nm particles are currently discussed to be a health concern. The measurement of smaller solid particles is not standardized yet and is potentially impeded by the presence of volatile nucleation mode particles below 23 nm . Moreover, standard techniques for additionally determining particle size distributions usually are below their sensitivity limit due to the low particle concentrations produced by oxygenate fuels. At the Technical University of Munich, DMC and MeFo were tested as pure substances in their emission and performance behavior compared to conventional gasoline fuel, using a single-cylinder, direct injection SI-engine. Primary (limited: CO, HC, NO x ) and secondary (non-limited: CH 2 O, CH 3 OH, NH 3 ) gaseous emissions pre- and after a TWC as well as particle number (PN) emissions were investigated. Regarding the challenges of particle number measurements, this work presents our method to also assess the properties of such ultra-low concentration aerosols from engine exhaust considering trends in particle size and potential artifacts caused by volatile, sub-23 nm particles. The method described uses two differently constructed PMP PN counting systems, operating in parallel, using largely different dilution schemes and rates. Both systems are equipped with two condensation particle counters (CPC) each, which are set to cut-off ratios of 23 nm and 10 nm, allowing to gain further insights using the ratios of the different systems (indication of potential artifacts) as well as ratios of the two CPC (indicating size trends) respectively. The test outcomes of steady-state operating points during lambda-sweeps show positive effects of the fuels on raw gaseous emissions while still maintaining high conversion rates over the TWC. PN emissions drop significantly and are even below ambient concentrations both for DMC and MeFo in DI-mode. However, a higher relative share of sub-23 nm particles is observed among the low number of remaining particles, and the data of both particle systems is used for further analysis of size trends and volatility. While displaying ultra-low pollutant emissions, DMC and MeFo are also potentially CO 2 neutral substances, and their potential sustainable production using green electricity and waste CO 2 will be also summarized.