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Journal Article

A Study of HCCI Combustion using Spectroscopic Techniques and Chemical Kinetic Simulations

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.
Technical Paper

A Study of HCCI Combustion Using a Two-Stroke Gasoline Engine with a High Compression Ratio

In this study, it was shown that Homogeneous Charge Compression Ignition (HCCI) combustion in a 4-stroke engine, operating under the conditions of a high compression ratio, wide open throttle (WOT) and a lean mixture, could be simulated by raising the compression ratio of a 2-stroke engine. On that basis, a comparison was then made with the characteristics of Active Thermo-Atmosphere Combustion (ATAC), the HCCI process that is usually accomplished in 2-stroke engines under the conditions of a low compression ratio, partial throttle and a large quantity of residual gas. One major difference observed between HCCI combustion and ATAC was their different degrees of susceptibility to the occurrence of cool flames, which was attributed to differences in the residual gas state. It was revealed that the ignition characteristics of these two combustion processes differed greatly in relation to the fuel octane number.
Journal Article

A Study of HCCI Combustion Using Spectroscopic Measurements and Chemical Kinetic Simulations: Effects of Fuel Composition, Engine Speed and Cylinder Pressure on Low-temperature Oxidation Reactions and Autoignition

The Homogenous Charge Compression Ignition (HCCI) engine is positioned as a next-generation internal combustion engine and has been the focus of extensive research in recent years to develop a practical system. One reason is that this new combustion system achieves lower fuel consumption and simultaneous reductions of nitrogen oxide (NOx) and particulate matter (PM) emissions, which are major issues of internal combustion engines today. However, the characteristics of HCCI combustion can prevent suitable engine operation owing to the rapid combustion process that occurs accompanied by a steep pressure rise when the amount of fuel injected is increased to obtain higher power output. A major issue of HCCI is to control this rapid combustion so that the quantity of fuel injected can be increased for greater power. Controlling the ignition timing is also an issue because it is substantially influenced by the chemical reactions of the fuel.
Technical Paper

A Study of HCCI Combustion Characteristics Using Spectroscopic Techniques

The principal issues of Homogeneous Charge Compression Ignition (HCCI) combustion that must be addressed include ignition timing control and expansion of the stable operation region. Detailed analyses of ignition and combustion mechanisms must be undertaken to resolve these issues. In this study, spectroscopic techniques were used to investigate the effects of the fuel octane number and residual gas state on ignition and combustion characteristics. Spectroscopic measurements were made of light emission intensity and of absorbance at a wavelength corresponding to HCHO (formaldehyde) which plays an important role in the low-temperature reaction (i.e. cool flame). The results revealed that varying the fuel octane number and the residual gas state changed the cool flame magnitude and the duration of the low-temperature reaction period, which substantially altered the ignition characteristics of HCCI combustion.
Technical Paper

A Study of HCCI Combustion Assisted by a Streamer Discharge Based on Visualization of the Entire Bore Area

This study investigated the effect of streamer discharge on autoignition and combustion in a Homogeneous Charge Compression Ignition (HCCI) engine. A continuous streamer discharge was generated in the center of the combustion chamber of a 2-stroke optically accessible engine that allowed visualization of the entire bore area. The experimental results showed that the flame was initiated and grew from the vicinity of the electrode under the application of a streamer discharge. Subsequently, rapid autoignition (HCCI combustion) occurred in the unburned mixture in the end zone, thus indicating that HCCI combustion was accomplished assisted by the streamer discharge. In other word, ignition timing of HCCI combustion was advanced after the streamer discharging process, and the initiation behavior of the combustion flame was made clear under that condition.
Technical Paper

A Study of Combustion in an HCCI Engine Using Non-Equilibrium Plasma Discharge Assist

This study focused on a non-equilibrium plasma discharge as a means of assisting HCCI combustion.Experiments were conducted with a four-stroke single-cylinder engine fitted with a spark electrode in the top of the combustion chamber for continuously generating non-equilibrium plasma from the intake stroke to the exhaust stroke. The results showed that applying non-equilibrium plasma to the HCCI test engine advanced the main combustion period that otherwise tended to be delayed as the engine speed was increased. In addition, it was found that the combined use of exhaust gas recirculation and non-equilibrium plasma prevented a transition to partial combustion while suppressing cylinder pressure oscillations at high loads.
Technical Paper

A Spectroscopic Study of the Effects of Multicomponent Fuel Blends on Supercharged HCCI Combustion

The growing severity of global environmental issues in recent years, including air pollution and the depletion of fossil fuels, has made it necessary for internal combustion engines to achieve higher efficiency and lower exhaust emission levels. Calls for reducing atmospheric emissions of carbon dioxide (CO₂) necessitate thoroughgoing measures to lower the levels of CO₂ originating in the combustion process of internal combustion engines and to facilitate operation on diverse energy sources. Homogeneous Charge Compression Ignition (HCCI) combustion has attracted widespread interest because it achieves high efficiency and can reduce particulate matter (PM) and nitrogen oxide (NOx) emissions simultaneously. These characteristics are obtainable because HCCI combustion can take place at ultra-lean conditions exceeding the limits of flame propagation.
Technical Paper

A Spectroscopic Analysis of a Homogeneous Charge Compression Ignition Engine

Homogeneous Charge Compression Ignition (HCCI) combustion offers the advantages of high efficiency and low emissions of pollutants. However, ignition timing control and expansion of the stable operation region are issues remaining to be addressed in this combustion process. Detailed analyses of ignition and combustion characteristics are needed to resolve these issues. HCCI combustion of a low octane number fuel is characterized by two-stage heat release attributed to a cool flame and a hot flame, respectively. In this study, spectroscopic techniques were used to investigate the effect of exhaust gas recirculation (EGR) on ignition and combustion characteristics using a low octane number fuel, which is apt to give rise to a cool flame. The reaction mechanism of a cool flame produces formaldehyde (HCHO). Measurements were made of spontaneous light emission and absorption at wavelengths corresponding to the light emitted at the time HCHO was produced.
Technical Paper


A new concept of combustion which is using the characteristic of plasma jet ignition, that is the plasma jet diffusive combustion is proposed. The constant volume vessel is used for the experiment, and methanol is charged in the cavity of plasma jet injector and the air at room temperature and atmospheric pressure is charged in the combustion chamber. The combustion characteristic is analyzed by measuring the combustion pressure and visualization of the combustion process. The plasma jet injector configuration and the ratio of methanol volume to cavity volume influence not only the plasma jet diffusive combustion process but also the maximum combustion pressure. In cases of small orifice diameter, the plasma jet diffusive combustion is not recognized, and the maximum combustion pressure increases as the orifice area becomes large.
Technical Paper

A Comparative Study of HCCI and ATAC Combustion Characteristics Based on Experimentation and Simulations Influence of the Fuel Octane Number and Internal EGR on Combustion

Controlled Autoignition (CAI) combustion processes can be broadly divided between a CAI process that is applied to four-stroke engines and a CAI process that is applied to two-stroke engines. The former process is generally referred to as Homogeneous Charge Compression Ignition (HCCI) combustion and the later process as Active Thermo-Atmosphere Combustion (ATAC). The region of stable engine operation differs greatly between these two processes, and it is thought that the elucidation of their differences and similarities could provide useful information for expanding the operation region of HCCI combustion. In this research, the same two-stroke engine was operated under both the ATAC and HCCI combustion processes to compare their respective combustion characteristics. The results indicated that the ignition timing was less likely to change in the ATAC process in relation to changes in the fuel octane number than it was in the HCCI combustion process.
Technical Paper

7 Experimental Research Concerning the Effect of the Scavenging Passage Length on the Combustion State and Exhaust Gas Composition of a Small Two-stroke Engine

This paper presents the results of experiments conducted with a two-stroke engine that was the world's first such engine to comply with the emissions regulations applied to small off-road engines by the U.S. state of California in 2000. This engine is fitted with a scavenging passage that runs around the crankcase before the scavenging port. The aim of this research was to investigate how changes in the quantity of heat transferred to the fresh air as a result of varying the length of the scavenging passage would affect the state of combustion and exhaust gas composition. An ion probe was fitted to the end zone of the combustion chamber in order to detect the state of combustion. A voltage of 60 V was applied to the ion probe and measurements were made of the voltage drop that occurred due to the presence of high concentrations of ions (H3O+, C3H3+, CHO+, etc.) at the flame front.
Technical Paper

54 The Combustion Phenomena Under Corona Discharge Application

In this study, the effect of corona discharge on the combustion phenomenon has been made clear. A homogeneous propane-air mixture was used and six equivalence ratios were tested. For generating the positive and negative corona discharge, a non-uniform electric field was applied to the combustion chamber by the needle to plane gap. One or five needle-shaped electrodes were used to change the corona discharge state. When the positive corona discharge was applied, the luminescence from corona with five electrodes was weak as compared with that of one needle-shaped electrode. When the negative corona discharge was applied, the luminescence from corona and combustion were not affected by the number of electrode. When the positive corona discharge was applied by low voltage, the combustion was improved in the case of one needle-shaped electrode, but the index of combustion with one needle-shaped electrode was almost equal to that of five electrodes when the high voltage was applied.