Search Results

This study was conducted to investigate the influence of low-temperature reactions on the Homogeneous Charge Compression Ignition (HCCI) combustion process. Specifically, an investigation was made of the effect of the residual gas condition on low-temperature reactions, autoignition and the subsequent state of combustion following ignition. Light emission and absorption spectroscopic measurements were made in the combustion chamber in order to investigate low-temperature reactions in detail. In addition, chemical kinetic simulations were performed to validate the experimental results and to analyze the elemental reaction process. The results made clear the formation behavior of the chemical species produced during low-temperature HCCI reactions.

In this study, light emission and absorption spectroscopic measurement techniques were used to investigate the Homogeneous Charge Compression Ignition (HCCI) combustion process in detail, about which there have been many unclear points heretofore. The results made clear the formation behavior and wavelength bands of the chemical species produced during low-temperature reactions. Specifically, with a low level of residual gas, a light emission band was observed from a cool flame in a wavelength range of 370–470 nm. That is attributed to the light emission of formaldehyde (HCHO) produced in the cool-flame reactions. Additionally, it was found that these light emission spectra were no longer observable when residual gas was applied. The light emission spectra of the combustion flame thus indicated that residual gas has the effect of moderating cool-flame reactions.

This study examined Homogeneous Charge Compression Ignition (HCCI) combustion characteristics in detail on the basis of in-cylinder combustion visualization, spectroscopic measurements of light emission and absorption and chemical kinetic simulations. Special attention was focused on investigating and comparing the effects of the fuel octane number and residual gas on combustion characteristics. The results made clear the relationship between the production/consumption of formaldehyde (HCHO) in the HCCI autoignition process and flame development behavior in the cylinder. Additionally, it was found that both the fuel octane number and residual gas have the effect of moderating low-temperature oxidation reactions. Furthermore, it was observed that residual gas has the effect of shifting the temperature for the occurrence of the hot flame to a higher temperature range.

Suppression or reduction of soot emissions is an important goal in the development of automotive engines for environmental and human health purposes. A better understanding at the molecular level of the formation process of soot particles resulting from collision and aggregation of smaller particles made of Polycyclic Aromatic Hydrocarbon (PAH) is needed. In addition to experiments, computational methods are efficient and valuable tools for this purpose. As a first step in our detailed computational chemistry study, we applied Ultra-Accelerated Molecular Dynamics (UAQCMD) and Canonical Monte-Carlo (CMC) methods to investigate the nucleation process. The UA-QCMD can calculate chemical reaction dynamics 107 times faster than conventional first principle molecular dynamics methods, while CMC can calculate equilibrium properties at various temperatures, pressures, and chemical compositions.