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Journal Article

Visualization and Spectroscopic Measurement of Knocking Combustion Accompanied by Cylinder Pressure Oscillations in an HCCI Engine

2013-10-15
2013-32-9166
Combustion experiments were conducted with an optically accessible engine that allowed the entire bore area to be visualized for the purpose of making clear the characteristics that induce extremely rapid HCCI combustion and knocking accompanied by cylinder pressure oscillations. The HCCI combustion regime was investigated in detail by high-speed in-cylinder visualization of autoignition and combustion and emission spectroscopic measurements. The results revealed that increasing the equivalence ratio and advancing the ignition timing caused the maximum pressure rise rate and knocking intensity to increase. In moderate HCCI combustion, the autoignited flame was initially dispersed temporally and spatially in the cylinder and then gradually spread throughout the entire cylinder.
Journal Article

The Influence of Hot Gas Jet on Combustion Enhancement for Lean Mixture in Plasma Jet Ignition

2012-10-23
2012-32-0001
This study clarified the influence of hot gas jet on combustion enhancement effect for lean mixture in the plasma jet ignition. The hot gas jet was generated by the high temperature plasma and was ejected from igniter after plasma jet finished issuing. In combustion tests, propane-air mixture at equivalence ratio of 0.6 was used and the mixture was filled in the combustion chamber at atmosphere pressure and room temperature. For generation of the hot gas jet, the standard air was filled in chamber at same conditions and the hot gas jet was visualized by schlieren method in the absence of combustion. The combustion development processes were also visualized and the combustion pressure was measured. The discharge voltage, discharge current and the plasma luminescence were also measured. The plasma luminescence disappeared within 0.05 ms for any experimental conditions. When cavity depth was deep and orifice diameter was small, the maximum plasma luminescence height was short.
Technical Paper

The Effects of Electric Fields on Flame Propagation of Homogeneous Hydrogen-Air Mixture

2011-11-08
2011-32-0577
The flame propagation behavior of homogeneous hydrogen-air mixture under application of high-voltage uniform or non-uniform electric field was explored by using combustion vessel. When a uniform electric field was applied, two plate electrodes were attached to ceiling and bottom of combustion chamber and, to apply a non-uniform electric field, an electrode in ceiling was needle-shaped and an electrode in bottom was plate-shaped. The positive or negative polarity DC high voltage was applied for an electrode in ceiling. When a positive polarity non-uniform electric field was applied to the mixture at any equivalence ratios and the input voltage was higher than 12 kV, the flame propagation was enhanced in the downward direction. This is because the corona wind was generated from the tip of needle-shaped electrode to grounded electrode by the brush corona.
Technical Paper

The Application of Coconut-oil Methyl Ester for Diesel Engine

2007-10-30
2007-32-0065
The coconut-oil methyl ester is made from coconut oil and methanol, and both cold start performance and ignition characteristics of coconut-oil methyl ester are experimentally investigated by using a diesel engine. In experiments, diesel fuel and coconut-oil methyl ester are used and the blended ratio of coconut-oil methyl ester to diesel fuel is changed. The test is conducted at full load and 3000 rpm. The diesel engine can be run stably with any mixing ratio of coconut-oil methyl ester, however the power is slightly reduced with increasing the mixing ratio of coconut-oil methyl ester. In the cold start condition, when the mixing ratio of coconut-oil methyl ester increases, the combustion chamber wall temperature rises early and the ignition timing is improved. Therefore, the coconut-oil methyl ester has superior compression ignition characteristics and reduces exhaust gas emissions, so that the coconut-oil methyl ester is good alternative fuel for diesel engines.
Technical Paper

Study on Performance of Diesel Engine Applied with Emulsified Diesel Fuel: The Influence of Fuel Injection Timing and Water Contents

2011-11-08
2011-32-0606
The application of emulsified fuel for diesel engines is expected to reduce NOx and soot simultaneously. The purpose of this study is to clarify the influence of water content in emulsified fuel and fuel injection timing on diesel engine performance. The engine performance of emulsified fuel was compared with the water injection method. In the water injection test, water was injected to intake manifold and diesel fuel was directly injected into combustion chamber. Two emulsified fuels of which mixing ratio of water and emulsifier to diesel fuel were 15 and 30 vol.% were tested. Engine performance and exhaust gas emission of water injection method were almost similar to those of diesel fuel, so that water presented in combustion chamber had almost no influence on engine performance. Therefore, it can be considered that the micro explosion of fuel droplet enhanced the fuel atomization and mixing of fuel and air.
Technical Paper

Study on Knocking Characteristics for High-Efficiency Operation of a Super-Lean Spark Ignition Engine

2018-10-30
2018-32-0002
This study investigated the influence of EGR and spark advance on knocking under high compression ratio, ultra-lean mixture and supercharged condition using premium gasoline as a test fuel. A high-compression ratio, supercharged single cylinder engine was used in this experiment. As a result, the period from ignition to autoignition was prolonged. In addition, knock intensity was drastically reduced. In other words, it is inferred that by combining an appropriate amount of EGR and spark advance, high efficiency operation avoiding knocking can be realized.
Technical Paper

Study on Flame Behavior Control by the Electric Field

2015-11-17
2015-32-0738
The purpose of this study is to elucidate flame propagation behavior of homogeneous propane-air mixture under application of non-uniform electric field. A needle-shaped electrode was attached to the ceiling and a plate electrode was set at bottom of combustion chamber, so that the electric field was applied in the direction of the chamber's vertical axis. A homogeneous propane-air mixture was supplied at equivalence ratio of 1.0 and was ignited by leaser induced breakdown under atmospheric pressure and room temperature. It was found that the flame front and plate electrode were repelled each other and a thin air layer was formed between the flame and plate electrode when a relatively low positive DC non-uniform electric field was applied to the needle-shaped electrode. It might be thought that the induced current was generated in the flame front, so that the flame front and plate electrode repelled each other.
Technical Paper

Study of Supercharged Gasoline HCCI Combustion by Using Spectroscopic Measurements and FT-IR Exhaust Gas Analysis

2014-11-11
2014-32-0004
One issue of Homogeneous Charge Compression Ignition (HCCI) engines that should be addressed is to suppress rapid combustion in the high-load region. Supercharging the intake air so as to form a leaner mixture is one way of moderating HCCI combustion. However, the specific effect of supercharging on moderating HCCI combustion and the mechanism involved are not fully understood yet. Therefore, experiments were conducted in this study that were designed to moderate rapid combustion in a test HCCI engine by supercharging the air inducted into the cylinder. The engine was operated under high-load levels in a supercharged state in order to make clear the effect of supercharging on expanding the stable operating region in the high-load range. HCCI combustion was investigated under these conditions by making in-cylinder spectroscopic measurements and by analyzing the exhaust gas using Fourier transform infrared (FT-IR) spectroscopy.
Technical Paper

Study of Diffusion Combustion by Using the High-Voltage Electrical Discharge

2007-10-30
2007-32-0035
A new combustion method which is using the characteristic of plasma jet ignition is proposed. This new combustion method has features of diffusive combustion, however the fuel is injected and ignited by the electrical discharge. In the procedure of plasma jet ignition, a high-voltage electrical discharge is generated from the electrode to the orifice and then the gas in the cavity is transformed to a plasma state. When the cavity is filled with liquid fuel, the fuel plasma jet spreads into combustion chamber and is mixed with air in combustion chamber, and then the diffusive combustion occurs. Tests are carried out with four kinds of fuel by using a constant volume vessel. All kinds of fuel are surely injected by the electrical discharge and are certainly ignited and burned by this combustion method. The diffusion flame development process is influenced by fuel properties and is affected by the orifice diameter size.
Technical Paper

Spectroscopic Study of Two-Stage High Temperature Heat Release Behavior in a Supercharged HCCI Engine using Blended Fuels

2011-08-30
2011-01-1788
This study examined the effects of fuel composition and intake pressure on two-stage high temperature heat release characteristics of a Homogeneous Charge Compression Ignition (HCCI) engine. Light emission and absorption spectroscopic measurement techniques were used to investigate the combustion behavior in detail. Chemical kinetic simulations were also conducted to analyze the reaction mechanisms in detail. Blended fuels of dimethyl ether (DME) and methane were used in the experiments. It was found that the use of such fuel blends together with a suitable intake air flow rate corresponding to the total injected heat value gave rise to two-stage heat release behavior of the hot flame, which had the effect of moderating combustion. The results of the spectroscopic measurements and the chemical kinetic simulations revealed that the main reaction of the first stage of the hot flame heat release was one that produced CO from HCHO.
Technical Paper

Performance of Air Motor with Regenerating System Designed for Propulsion of Bicycle

2011-11-08
2011-32-0615
An air motor with regenerating system for propulsion of a bicycle was newly developed. An air motor was driven by the compressed air and the bicycle was propelled. When the bicycle was decelerating, the air motor was acted as a compressor and the kinetic energy of bicycle was regenerated as compressed air. The purpose of this study is to elucidate the performance of air motor and driving characteristic of bicycle. The air motor in this study was the reciprocating piston type like an internal combustion engine, and cylinder arrangement was in-line two-cylinder. The output power increased with an increase of supply air pressure although the maximum cylinder pressure was less than the supply air pressure. The output power decreased as the revolution increased due to friction loss. The maximum cylinder pressure reduced as the rotational frequency increased because the inlet valve opening duration was decreased.
Journal Article

Optical Measurement of Autoignition and Combustion Behavior in an HCCI Engine

2010-09-28
2010-32-0089
In this study, optical measurements were made of the combustion chamber gas during operation of a Homogeneous Charge Compression Ignition (HCCI) engine in order to obtain a better understanding of the ignition and combustion characteristics. The principal issues of HCCI engines are to control the ignition timing and to optimize the combustion state following ignition. Autoignition in HCCI engines is strongly influenced by the complex low-temperature oxidation reaction process, alternatively referred to as the cool flame reaction or negative temperature coefficient (NTC) region. Accordingly, a good understanding of this low-temperature oxidation reaction process is indispensable to ignition timing control. In the experiments, spectroscopic measurement methods were applied to investigate the reaction behavior in the process leading to autoignition.
Technical Paper

Light Emission and Absorption Spectroscopic Study of HCCI Combustion

2009-06-15
2009-01-1846
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.
Technical Paper

Influence of Various Biodiesel Fuels on Diesel Engine Performance

2009-11-03
2009-32-0100
The composition ratio of saturated and unsaturated fatty acid methyl esters (FAME) is depended on feedstock. Three FAMEs: soybean (SME), palm (PME) and coconut oil (CME) methyl esters were mixed to make fuels which have different composition ratio. The ignitability of fuel which mainly consisted of unsaturated FAME was inferior. Power was slightly reduced with increasing of mixing ratio of CME; however exhaust gas emissions were improved because CME contained a lot of oxygen atoms. Fuel which was equal mixture SME and CME indicated almost the same ignition characteristic as that of PME because they have same composition ratio.
Technical Paper

Influence of Supercharging and EGR on Multi-stage Heat Release in an HCCI Engine

2016-11-08
2016-32-0009
Homogeneous Charge Compression Ignition (HCCI) combustion has attracted widespread interest as a combustion system that offers the advantages of high efficiency and low exhaust emissions. However, it is difficult to control the ignition timing in an HCCI combustion system owing to the lack of a physical means of initiating ignition like the spark plug in a gasoline engine or fuel injection in a diesel engine. Moreover, because the mixture ignites simultaneously at multiple locations in the cylinder, it produces an enormous amount of heat in a short period of time, which causes greater engine noise, abnormal combustion and other problems in the high load region. The purpose of this study was to expand the region of stable HCCI engine operation by finding a solution to these issues of HCCI combustion.
Technical Paper

Influence of Internal EGR on Knocking in an HCCI Engine

2015-11-17
2015-32-0807
Homogeneous Charge Compression Ignition (HCCI) engines have attracted much attention and are being widely researched as engines characterized by low emissions and high efficiency. However, one issue of HCCI engines is their limited operating range because of the occurrence of rapid combustion at high loads and misfiring at low loads. It is known that knocking accompanied by in-cylinder pressure oscillations also occurs in HCCI engines at high loads, similar to knocking seen in spark-ignition engines. In this study, HCCI combustion accompanied by in-cylinder pressure oscillations was visualized by taking high-speed photographs of the entire bore area. In addition, the influence of internal exhaust gas circulation (EGR) on HCCI knocking was also investigated. The visualized combustion images revealed that rapid autoignition occurred in the end-gas region during the latter half of the HCCI combustion process when accompanied by in-cylinder pressure oscillations.
Technical Paper

Influence of Engine Speed on Autoignition and Combustion Characteristics in a Supercharged HCCI Engine

2017-11-05
2017-32-0090
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. However, because HCCI engines lack a physical means of initiating ignition, it is difficult to control the ignition timing. Another issue of HCCI engines is that the combustion process causes the cylinder pressure to rise rapidly. The time scale is also important in HCCI combustion because ignition depends on the chemical reactions of the mixture. Therefore, we investigated the influence of the engine speed on autoignition and combustion characteristics in an HCCI engine. A four-stroke single-cylinder engine equipped with a mechanically driven supercharger was used in this study to examine HCCI combustion characteristics under different engine speeds and boost pressures.
Technical Paper

Influence of EGR on Knocking in an HCCI Engine Using an Optically Accessible Engine

2016-11-08
2016-32-0012
This study was conducted to investigate the influence of cooled recirculated exhaust gas (EGR) on abnormal combustion in a Homogenous Charge Compression Ignition (HCCI) engine. The condition of abnormal HCCI combustion accompanied by cylinder pressure oscillations was photographed with a high-speed camera using a 2-stroke optically accessible engine that enabled visualization of the entire bore area. Exhaust gas was cooled with a water-cooled intercooler for introducing cooled EGR. Experiments were conducted in which the quantity of cooled EGR introduced was varied and a comparison was made of the autoignition behavior obtained under each condition in order to investigate the influence of cooled EGR on abnormal HCCI combustion. The results revealed that cylinder pressure oscillations were reduced when cooled EGR was introduced. That reduction was found to be mainly ascribable to the effect of cooled EGR on changing the ignition timing.
Technical Paper

Influence of Combustion Chamber Wall Temperature on Combustion in an HCCI Engine Using an Alternative Fuel

2015-11-17
2015-32-0790
Internal combustion engines today are required to achieve even higher efficiency and cleaner exhaust emissions. Currently, research interest is focused on premixed compression ignition (Homogeneous Charge Compression Ignition, HCCI) combustion. However, HCCI engines have no physical means of initiating ignition such as a spark plug or the fuel injection timing and quantity. Therefore, it is difficult to control the ignition timing. In addition, combustion occurs simultaneously at multiple sites in the combustion chamber. As a result, combustion takes place extremely rapidly especially in the high load region. That makes it difficult for the engine to operate stably at high loads. This study focused on the fuel composition as a possible means to solve these problems. The effect of using fuel blends on the HCCI operating region and combustion characteristics was investigated using a single-cylinder test engine.
Technical Paper

Influence of Calcium-Based Additives with Different Properties on Abnormal Combustion in an SI Engine

2016-11-08
2016-32-0007
Technologies for further improving vehicle fuel economy have attracted widespread attention in recent years. However, one problem with some approaches is the occurrence of abnormal combustion such as low-speed pre-ignition (LSPI) that occurs under low-speed, high-load operating conditions. One proposed cause of LSPI is that oil droplets diluted by the fuel enter the combustion chamber and become a source of ignition. Another proposed cause is that deposits peel off and become a source of ignition. A four-stroke air-cooled single-cylinder engine was used in this study to investigate the influence of Ca-based additives having different properties on abnormal combustion by means of in-cylinder visualization and absorption spectroscopic measurements. The results obtained for neutral and basic Ca-based additives revealed that the former had an effect on advancing the time of autoignition.
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