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This article investigates the effects of various primary reference fuel (PRF) blends, compression ratios, and intake temperatures on the thermodynamics and performance of homogeneous charge compression ignition (HCCI) combustion in a Cooperative Fuels Research (CFR) engine. Combustion phasing was kept constant at a CA50 phasing of 5° after top dead center (aTDC) and the equivalence ratio was kept constant at 0.3. Meanwhile, the compression ratio varied from 8:1 to 15:1 as the PRF blends ranged from pure n-heptane to nearly pure isooctane. The intake temperature was used to match CA50 phasing. In addition to the experimental results, a GT-Power model was constructed to simulate the experimental engine and the model was validated against the experimental data. The GT-Power model and simulation results were used to help analyze the energy flows and thermodynamic conditions tested in the experiment.

A CFD investigation has been conducted to study the efficiency and emissions characteristics of Thermally Stratified Compression Ignition (TSCI) combustion with direct water injection. The motivation for using this new low temperature combustion mode is its ability to control the heat release process by introducing a forced and controlled thermal stratification beyond what would occur naturally. In this case, TSCI is enabled using direct water injection. The added degree of control over the combustion process allows for a significantly broader operable load range compared to HCCI. The effects of injection parameters including the pressure, start of injection (SOI) timing, and spray pattern have been shown previously to affect the heat release of TSCI and its induced thermal stratification. In the present work, the efficiency and emissions considerations were investigated in detail, and the effects of injected mass are presented.