Refine Your Search

Search Results

Journal Article

Analysis of Interaction between Autoignition and Strong Pressure Wave Formation during Knock in a Supercharged SI Engine Based on High Speed Photography of the End Gas

2017-11-15
2017-32-0119
Engine knock is the one of the main issues to be addressed in developing high-efficiency spark-ignition (SI) engines. In order to improve the thermal efficiency of SI engines, it is necessary to develop effective means of suppressing knock. For that purpose, it is necessary to clarify the mechanism generating pressure waves in the end-gas region. This study examined the mechanism producing pressure waves in the end-gas autoignition process during SI engine knock by using an optically accessible engine. Occurrence of local autoignition and its development process to the generation of pressures waves were analyzed under several levels of knock intensity. The results made the following points clear. It was observed that end-gas autoignition seemingly progressed in a manner resembling propagation due to the temperature distribution that naturally formed in the combustion chamber. Stronger knock tended to occur as the apparent propagation speed of autoignition increased.
Technical Paper

A Study of Autoignition Behavior and Knock Intensity in a SI Engine under Different Engine Speed by Using In-Cylinder Visualization

2017-11-05
2017-32-0050
Internal combustion engines have been required to achieve even higher efficiency in recent years in order to address environmental concerns. However, knock induced by abnormal combustion in spark-ignition engines has impeded efforts to attain higher efficiency. Knock characteristics during abnormal combustion were investigated in this study by in-cylinder visualization and spectroscopic measurements using a four-stroke air-cooled single-cylinder engine. The results revealed that knock intensity and the manner in which the autoignited flame propagated in the end gas differed depending on the engine speed.
Technical Paper

The Possibility for Realization of Dual Combustion Cycle for Spark Ignition Engine

2017-11-05
2017-32-0091
The purpose of this study is to operate the spark ignition engine by the dual combustion cycle. The dual combustion cycle has two combustion processes, these are the constant volume combustion and the constant pressure combustion. The lean combustion and the direct fuel injection were applied to realize the dual combustion cycle for spark ignition engines. The combustion of lean mixture was corresponding to the constant volume combustion. The fuel was directly injected to combustion chamber and was burned with the remained oxygen after the lean combustion, so that this was corresponding to the constant pressure diffusion combustion. The combustion experiments were conducted by using the constant volume vessel. The lean propane-air mixture of which equivalence ratios were 0.6, 0.7, 0.8 and 0.9 were used and liquid n-heptane was injected by using the high-voltage electrical discharge.
Technical Paper

An Effect of Bio Diesel Fuel for Low Compression Ratio Diesel Engine

2017-11-05
2017-32-0088
The purpose of this study is to explore an effect of the coconut oil methyl ester (CME) and vegetable oil methyl ester (VME) on a low compression ratio diesel engine performance. CME and VME were produced from coconut oil and vegetable oil with methanol, respectively. Vegetable oil was assumed to contain 60 wt.% of soybean oil and 40 wt.% rapeseed oil. The engine performance was measured in the steady operating condition at 3600 rpm of engine speed. The ignition timings of CME and VME were advanced and the maximum cylinder pressures of CME and VME were higher as compared with the diesel fuel at low compression ratio, because CME and VME consisted of medium chain fatty acid methyl esters. The ignitability of CME was superior to VME, because CME consisted of saturated fatty acid. The brake thermal efficiency of diesel fuel was slightly higher than CME and VME at any compression ratios.
Technical Paper

Analysis of Supercharged HCCI Combustion Using Low-Carbon Alternative Fuels

2017-11-05
2017-32-0085
This study investigated the effects of recirculated exhaust gas (EGR) and its principal components of N2, CO2 and H2O on moderating Homogeneous Charge Compression Ignition (HCCI) combustion. Experiments were conducted using two types of gaseous fuel blends of DME/propane and DME/methane as the test fuels. The addition rates of EGR, N2, CO2 and H2O were varied and the effects of each condition on HCCI combustion of propane and methane were investigated. The results revealed that the addition of CO2 and H2O had the effect of substantially delaying and moderating rapid combustion. The addition of N2 showed only a slight delaying and moderating effect. The addition of EGR had the effect of optimally delaying the combustion timing, while either maintaining or increasing the indicated mean effective pressure and indicated thermal efficiency ηi.
Technical Paper

A Study of Ignition and Combustion in an SI Engine Using Multistage Pulse Discharge Ignition

2017-11-05
2017-32-0069
Lean-burn technology is regarded as one effective way to increase the efficiency of internal combustion engines. However, stable ignition is difficult to ensure with a lean mixture. It is expected that this issue can be resolved by improving ignition performance as a result of increasing the amount of energy discharged into the gaseous mixture at the time of ignition. There are limits, however, to how high ignition energy can be increased from the standpoints of spark plug durability, energy consumption and other considerations. Therefore, the authors have focused on a multistage pulse discharge (MSPD) ignition system that performs low-energy ignition multiple times. In this study, a comparison was made of ignition performance between MSPD ignition and conventional spark ignition (SI). A high-speed camera was used to obtain visualized images of ignition in the cylinder and a pressure sensor was used to measure pressure histories in the combustion chamber.
Technical Paper

A Study of HCCI Operating Range Expansion by Applying Reaction Characteristics of Low-Carbon Alternative Fuels

2016-11-08
2016-32-0011
Issues that must be addressed to make Homogeneous Charge Compression Ignition (HCCI) engines a practical reality include the difficulty of controlling the ignition timing and suppression of rapid combustion under high load conditions. Overcoming these issues to make HCCI engines viable for practical application is indispensable to the further advancement of internal combustion engines. Previous studies have reported that the operating region of HCCI combustion can be expanded by using DME and Methane blended fuels.(1), (2), (3), (4), (5) The reason is that the reaction characteristics of these two low-carbon fuels, which have different ignition properties, have the effect of inducing heat release in two stages during main combustion, thus avoiding excessively rapid combustion. However, further moderation of rapid combustion in high-load region is needed to expand the operation region. This study focused on supercharging and use of blended fuels.
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.
Journal Article

Influence of Ca-, Mg- and Na-Based Engine Oil Additives on Abnormal Combustion in a Spark-Ignition Engine

2015-11-17
2015-32-0771
One issue of downsized and supercharged engines is low-speed pre-ignition (LSPI) that occurs in the low-speed and high-load operating region. One proposed cause of LSPI is the influence of the engine oil and its additives. However, the effect of engine oil additives on pre-ignition and the mechanism involved are still not fully understood. This study investigated the influence of engine oil additives on abnormal combustion in a spark-ignition engine. A four-stroke air-cooled single-cylinder engine with a side valve arrangement was used in conducting combustion experiments. The research methods used were in-cylinder pressure analysis, in-cylinder visualization and absorption spectroscopic analysis. Engine oil additives were mixed individually at a fixed concentration into a primary reference fuel with an octane number of 50 and their effect on knocking was investigated.
Technical Paper

A Study on the Practical Application of Cellulosic Liquefaction Fuel for Diesel Engine

2015-11-17
2015-32-0801
In recent years, it has been expected the conversion of wasted biomass to industry available energy. In this study, 80 wt.% of wood and 20 wt.% of polypropylene were liquefied by the mineral oil used as solvent. The liquefied material was distilled, and distillation fraction of temperature from 493 to 573 K was recognized as light oil fraction CLF (Cellulose Liquefaction Fuel) and that from 378 to 493 K was recognized as naphtha fraction CLF. CLFs were blended with light oil and, in engine performance test, mixing ratio of light oil fraction CLF was 5 wt.%, and in vehicle running test, weight mixing ratios were 5 or 10 wt.%. In engine performance test, indicator diagrams and rate of heat releases of light oil fraction CLF 5 wt.% mixed light oil were almost equivalent to those of light oil in all load conditions, and engine performance and exhaust gas emissions were also almost equivalent to light oil.
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

An Analysis of Conditions Producing Two-Stage Main Combustion Heat Release in a Supercharged HCCI Engine using a Gaseous Fuel Blend

2015-09-01
2015-01-1785
In this study, a detailed analysis was made of supercharged HCCI combustion using a two-component fuel blend of dimethyl ether (DME), which has attracted interest as a potential alternative fuel, and methane. The quantity of fuel injected and boost pressure were varied to investigate the equivalence ratio and operating region conducive to optimal HCCI combustion. The results revealed that varying the boost pressure according to the engine load and applying a suitable equivalence ratio induced two-stage main combustion over a wide load range, making it possible to avoid excessively rapid combustion.
Technical Paper

Laser Breakdown-Assisted Long-Distance Discharge Ignition

2015-09-01
2015-01-1897
We developed a novel ignition method called laser breakdown-assisted long-distance discharge ignition (LBALDI) that combines laser breakdown with a discharge to realize lean combustion. The creation of laser breakdown plasma between electrodes for discharge enables discharges over longer distances than those of conventional sparkplug as inferred from laser-triggered lightning or laser-triggered gas switches. This method should help realize volumetric ignition through the creation of a long-distance discharge. Experiments on the fundamental discharge and ignition of methane/air mixtures were conducted. The optimum incident time of the laser prior to the application of a high voltage was found to reduce the sparkover voltage and markedly reduce the voltage required by LBALDI under pressurized air conditions. In the ignition experiment, LBALDI showed the fastest heat release rate at the lean flammable limit.
Journal Article

Analysis of Combustion Characteristics and Efficiency Improvement of a Supercharged HCCI Engine Achieved by Using the Different Ignition Characteristics of Gaseous Fuels

2012-10-23
2012-32-0075
This study focused on the use of a two-component fuel blend and supercharging as possible means of overcoming these issues of HCCI combustion. Low-carbon gaseous fuels with clean emissions were used as the test fuels. The specific fuels used were dimethyl ether (DME, cetane number of 55 or higher) that autoignites easily And exhibits pronounced low-temperature oxidation reactions, methane (cetane number of 0) that does not autoignite readily and is the main component of natural gas which is regarded as petroleum substitute, and propane (cetane number of 5) that is a principal component of liquefied petroleum gas. The results of previous investigations have shown that the use of a blended fuel of DME and methane produces a two-stage main combustion process under certain operating conditions, with the result that combustion is moderated.
Journal Article

Analysis of Supercharged HCCI Combustion Using a Blended Fuel

2011-11-08
2011-32-0521
Homogeneous Charge Compression Ignition (HCCI) combustion has attracted much interest as a combustion system that can achieve both low emissions and high efficiency. But the operating region of HCCI combustion is narrow, and it is difficult to control the auto-ignition timing. This study focused on the use of a two-component fuel blend and supercharging. The blended fuel consisted of dimethyl ether (DME), which has attracted interest as alternative fuel for compression-ignition engines, and methane, the main component of natural gas. A spectroscopic technique was used to measure the light emission of the combustion flame in the combustion chamber in order to ascertain the combustion characteristics. HCCI combustion characteristics were analyzed in detail in the present study by measuring this light emission spectrum.
Technical Paper

Analysis of Knocking in an SI Engine based on In-cylinder: Spectroscopic Measurements and Visualization

2010-09-28
2010-32-0092
There are strong demands today to further improve the thermal efficiency of internal combustion engines against a backdrop of various environmental issues, including rising carbon dioxide (CO2) emissions and global warming. One factor that impedes efforts to improve the thermal efficiency of spark ignition engines is the occurrence of knocking. The aim of this study was to elucidate the details of knocking based on spectroscopic measurements and visualization of phenomena in the combustion chamber of a test engine that was operated on three primary reference fuels with different octane ratings (0 RON, 30 RON, and 50 RON). The ignition timing was retarded in the experiments to delay the progress of flame propagation, making it easier to capture the behavior of low-temperature oxidation reactions at the time knocking occurred.
Technical Paper

A Study of IDI 2-Stroke Cycle Compression Ignition Engine with DME

2009-11-03
2009-32-0063
DME is alternate fuel for diesel engines, however DME has defects such as small lower calorific value, inferior lubricity and weak fuel penetration. To compensate disadvantages, In-direct injection 2-stroke diesel engine with low pressure fuel injection system was proposed. The fuel injection timing near TDC gave good performance because the heat loss of low temperature oxidation reaction reduced. The brake torque and brake thermal efficiency of 2-stroke IDI diesel engine were lower than those of 4-stroke engine. However, the exhaust gas emissions were very low level because the intake air leaked through the exhaust port and the exhaust gas was diluted.
Technical Paper

Influences of Compression Ratio and Methane Additive on Combustion Characteristics in a DME-HCCI Engine

2005-10-24
2005-01-3745
In this study, a spectroscopic method was used to measure the combustion characteristics of a test diesel engine when operated on dimethyl ether (DME) under a homogenous charge compression ignition (HCCI) combustion process. A numerical analysis was made of the elementary reactions using Chemkin 4.0 to perform the calculations. The results of the analysis showed that compression ratio changes and the methane additive influenced the autoignition timing in the DME-HCCI combustion process. In the experiments, reducing the compression ratio delayed the time of the peak cylinder pressure until after top dead center, thereby increasing the crankshaft output and thermal efficiency. The addition of methane enabled the DME-HCCI engine to provide crankshaft output equivalent to that seen for diesel engine operation at a low equivalence ratio. This paper discusses these effects in reference to the experimental and calculated results.
Technical Paper

The Effects of the Compression Ratio, Equivalence Ratio, and Intake Air Temperature on Ignition Timing in an HCCI Engine Using DME Fuel

2005-10-12
2005-32-0002
Attention has recently been focused on homogeneous charge compression ignition combustion (HCCI) as an effective combustion process for resolving the essential nature of combustion. Meanwhile, dimethylether (DME) has attracted interest as a potential alternative fuel for compression ignition engines. Authors measured the combustion process of DME HCCI by using a spectroscopic method. A diesel engine was used as the test engine. The results of these analyses showed that changes in the compression ratio, intake air temperature and equivalence ratio influenced the ignition timing in the HCCI combustion process. This paper discusses these effects in reference to the experimental and calculated results.
Technical Paper

Analysis of the Characteristics of HCCI Combustion and ATAC Combustion Using the Same Test Engine

2004-09-27
2004-32-0097
Homogeneous Charge Compression Ignition (HCCI) combustion has attracted considerable interest in recent years as a new combustion concept for internal combustion engines. On the other hand, two combustion concepts proposed for two-cycle spark-ignition (SI) engines are Active Thermo-Atmosphere Combustion (ATAC) and Activated Radical (AR) combustion. The authors undertook this study to examine the similarities and differences between HCCI combustion and ATAC (AR) combustion. Differences in the low-temperature oxidation reaction behavior between these two combustion processes were made clear using one test engine.
X