Assessing the HCCI Characteristics of n-Heptane using a Free Piston Rapid Compression Expansion Machine
Scott Goldsborough, Assistant Professor, Milwaukee, WI 53201
A rapid compression expansion machine (RCEM) has previously been used to investigate the autoignition, or homogeneous charge compression ignition (HCCI) behavior of a wide range of gaseous and liquid hydrocarbon fuels . Reported data were the efficiency and emissions characteristics of these fuels, where the compression ratios required to achieve autoignition ranged from 16:1 to 50:1. The purpose was to assess the potential of HCCI as a driver for a high efficiency, low emissions futuristic powerplant. In  no attempt was made to study the ignition temperatures of the fuel-air mixtures, or the rates and extent of combustion seen under the experimental conditions. These however are important metrics by which kinetic and other combustion models can be validated, and are measures by which the RCEM data can be compared to rapid compression machine (RCM) data. The purpose of this work was to assess the autoignition characteristics of n-heptane in this device where a unique crevice-ring model was employed for the RCEM ringpack. Calculations are presented and compared to recent RCM studies.