Abstract
Determining when the combustion event occurs in a Homogeneous Charge Compression Ignition (HCCI) engine call prove challenging given that the combustion event is governed by temperature Sensitive chemical-kinetics which results ill auto-ignition of the fuel/air mixture. Auto-ignition variability call affect emissions and efficiency. Thus, measuring and controlling the combustion event is of the utmost importance. Ion sensors can be used reasonably to detect the combustion event for various fuels used in HCCI engines over a wide range of operating conditions. Experiments have been conducted to measure ion signals produced from the combustion of gasoline, ethanol, and n-heptane in a 4-cylinder HCCI engine with different equivalence ratios and intake pressures. It was found that the ion signal is reduced under several situations: with an increase in intake pressure, reducing equivalence ratio (Under]can conditions), and decreasing the bias voltage Source. Results from a Well-Mixed-Reactor (WMR) model Suggest that gasoline and ethanol produces more ions than n-heptane during combustion Under the same operating conditions; these predictions are supported by experiments. (c) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.