Chemical kinetic modeling of hydrocarbon combustion

Optimization and analysis of large chemical kinetic mechanisms using the solution mapping method—combustion of methane

The Homogeneous Charge Compression Ignition (HCCI) is the third alternative for combustion in the reciprocating engine. Here a homogeneous charge is used as in a spark-ignited engine, but the charge is compressed to autoignition as in a diesel. The main difference compared with the Spark Ignition (SI) engine is the lack of flame propagation and hence the independence from turbulence. Compared with the diesel engine, HCCI has a homogeneous charge and hence no problems associated with soot and NOdx formation. Earlier research on HCCI showed high efficiency and very low amounts of NOdx, but HC and CO were higher than in SI mode. It was not possible to achieve high IMEP values with HCCI, the limit being 5 bar. Supercharging is one way to dramatically increase IMEP. The influence of supercharging on HCCI was therefore experimentally investigated. Three different fuels were used during the experiments: iso-octane, ethanol and natural gas. Two different compression ratios were used, 17:1 and 19:1. The inlet pressure conditions were set to give 0, 1, or 2 bar of boost pressure. The highest attainable IMEP was 14 bar using natural gas as fuel at the lower compression ratio. The limit in achieving even higher IMEP was set by the high rate of combustion and a high peak pressure. Numerical calculations of the HCCI process have been performed for natural gas as fuel. The calculated ignition timings agreed well with the experimental findings. The numerical solution is, however, very sensitive to the composition of the natural gas. (Less)

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Supercharged Homogeneous Charge Compression Ignition

—Extensive experimental results were obtained on the oxidation of many aliphatic hydrocarbons in a high temperature, turbulent flow reactor developed for kinetic studies. These results indicated the viability of presenting this complex kinetic situation in the format of a simplified, overall kinetic scheme which could accurately predict the major species formed and the temperature-time history (rate of heat release) of the system. The proposed overall mechanism follows the general form:

G.B. Skinner

Papers

Shock-tube investigation of ignition in methane--oxygen--argon mixtures. [Temperature from 1500 to 2150/sup 0/K and pressures of 2 to 10 atm]

Shock tube investigation of ignition in propane--oxygen--argon mixtures. [At temperatures of 1250 to 1600/sup 0/K and pressures from 2 to 10 atm]