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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.

An experimental study was conducted on a Ricardo Hydra single-cylinder light-duty diesel research engine. Start of Injection (SOI) timing sweeps from -350 deg aTDC to -210 deg aTDC were performed on a total number of five pistons including two baseline metal pistons and three coated pistons to investigate the effects of thick thermal barrier coatings (TBCs) on the efficiency and emissions of low-temperature combustion (LTC). A fuel with a high latent heat of vaporization, wet ethanol, was chosen to eliminate the undesired effects of thick TBCs on volumetric efficiency. Additionally, the higher surface temperatures of the TBCs can be used to help vaporize the high heat of vaporization fuel and avoid excessive wall wetting. A specialized injector with a 60° included angle was used to target the fuel spray at the surface of the coated piston.

Homogeneous Charge Compression Ignition (HCCI) is a combustion concept with the potential for future clean and efficient automotive powertrains. In HCCI, the thermal stratification has been proven to play an important role in dictating the combustion process, mainly caused by heat transfer to the wall during compression. In this study, a multi-zone, control-mass model with thermal stratification and chemical kinetics was developed to simulate HCCI combustion. In this kind of model, the initial conditions and the zonal heat transfer fraction distribution are critical for the modeling accuracy and usually require case-by-case tuning. Instead, in this study, the Thermal Stratification Analysis (TSA) methodology is used to generate the zonal heat transfer fraction distribution from experimental HCCI data collected on a fired, metal engine.