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The usage of a methane-fueled homogeneously charged compression ignition (HCCI) engine process for producing base chemicals like ethylene and synthesis gas together with some work output is investigated. This polygeneration process is studied by numerical modeling, accompanied by rapid compression machine experiments. Studies include the seeding of dimethyl ether (DME) as a reaction enhancer which allows methane conversion already at moderate, technically easily accessible compression ratios and precompression temperatures. The concept is promising for equivalence ratios above 2, predicting product gas mole fractions of up to 25 mol % H2, 20 mol % CO, and 2 mol % C2H4. These simulation results are largely consistent with the outcome of rapid compression machine (RCM) experiments, in which production of up to 20 mol % H2, 16 mol % CO, and 1 mol % C2H4 was detected. In addition to studying the product composition, thermodynamic aspects of the approach were investigated by comparing the exergetic efficiency of fuel-rich and fuel-lean combustion. These calculations also confirmed the advantages of fuel-rich combustion.

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Diethyl ether (DEE) is an interesting species for combustion for at least two reasons: On the one hand, it is used as a kind of "worst case" reference substance for studies concerned with the prevention of accidental ignition events. On the other hand, it is also a candidate bio-fuel. For this reason, in this work, auto-ignition of two different CH 4 /DEE-mixtures (90/10 and 95/5 mol-% CH 4 /DEE) are studied in a rapid compression machine (RCM). In the RCM, the gas mixture is compressed in a piston-cylinder device up to 20 bar and held under isochoric conditions at top dead center. Autoignition occurs after an ignition delay time (IDT). IDTs are measured for compression temperatures ranging between 515 and 925 K, for both, stoichiometric and fuel-rich mixtures (equivalence ratio φ = 2). The experimental data are compared to results of simulations involving detailed chemistry, as well as to other fuels investigated in the same RCM (results from literature).

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