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Technical Paper

Propagation Processes of Newly Developed Plasma Jet Igniter

2000-06-12
2000-05-0014
In plasma jet ignition, combustion enhancement effects occur toward the plasma jet issuing direction. Therefore, when the igniter is attached at the center of cylindrically shaped combustion chamber, plasma jet should issue toward the round combustion chamber wall. The plasma jet igniter that had an annular circular orifice has been developed. The purpose of this study is to elucidate the relationship between the newly developed plasma jet igniter configuration and the combustion enhancement effects. In this newly developed plasma jet igniter, the fine scale turbulence appears on the flame front and flame propagates very rapidly. Plasma jet influences on the flame propagation for long period when the plasma jet igniter has issuing angle 90 [deg.] and large cavity volume. However, in the early stage of combustion, flame front area of issuing angle 45 [deg.] is larger than that of 90 [deg.], because the initial flame kernel is formed by the plasma jet.
Technical Paper

Improvement of Engine Performance With Lean Mixture Ignited By Diesel Fuel Injection and Internal Egr

2000-06-12
2000-05-0076
The uniform lean methanol-air mixture was provided to the diesel engine and was ignited by the direct diesel fuel injection. The internal EGR is added to this ignition method in order to activate the fuel in the mixture and to increase the mixture temperature. The test engine was a 4-stroke, single- cylinder direct-injection diesel engine. The cooling system was forced-air cooling and displacement volume was about 211 (cm3). The compression ratio was about 19.9:1. The experiment was made under constant engine speed of 3000 (r/min). The boost pressure was maintained at 101.3 (kPa). Five values of mass flow rate of diesel fuel injection were selected from 0.060 (g/s) to 0.167 (g/s) and five levels of back pressure: 0), 26.7, 53.3, 80.0 and 106.6 (kPa) were selected for the experiment. The effect of internal EGR is varied by the back pressure level.
Technical Paper

Effects of Uniform and Non-uniform Electric Field on Premixed Combustion

2007-10-30
2007-32-0034
The purpose of this study is to elucidate the flame propagation behavior under the electric field application by using the constant volume vessel. The laser induced breakdown applies the ignition and Nd:YAG laser is used. A homogeneous propane-air mixture is used and three equivalence ratios, 0.7, 1.0 and 1.5 are tested. In the uniform electric field, the premixed flame rapidly propagates toward both upward and downward directions and the flame front becomes a cylindrical shape. The maximum combustion pressure decreases with an increase of input voltage because of an increase of heat loss to the electrode, however the combustion duration is hardly affected by the input voltage. In the non-uniform electric field, the flame propagation velocity of downward direction increases. The combustion enhancement effect is remarkably when the input voltage is larger than 12 kV because the brush corona occurs and intense turbulence is generated on the flame front.
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

54 The Combustion Phenomena Under Corona Discharge Application

2002-10-29
2002-32-1823
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.
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

2002-10-29
2002-32-1776
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

8 A Study of the Influence of Fuel Temperature on Emission Characteristics and Engine Performance of Compression Ignition Engine

2002-10-29
2002-32-1777
In this study, the heated fuels were provided to the diesel engine in order to activate the fuel before the injection. Two test fuels: the normal diesel fuel and cetane, which have different boiling points were used. For both normal diesel fuel and cetane, crank angles at ignition and maximum pressure are delayed and the maximum combustion pressure is decreased as the fuel temperature rises. In cases of large and middle mass flow rate of fuel injection, the brake thermal efficiency and brake mean effective pressure are decreased when the fuel temperature is higher than 570 [K]. However, in the case of small mass flow rate of fuel injection, the brake thermal efficiency is almost independent of fuel temperature. HC and CO concentrations in the exhaust gas emission show constant values regardless of fuel temperature. However, NOx concentration is gradually decreased as the fuel temperature rises.
Technical Paper

Light Emission Behavior of Radicals during Preflame Reactions under Knocking Operation

2002-10-29
2002-32-1775
Knocking is one phenomenon that can be cited as a factor impeding efforts to improve the efficiency of spark-ignition engines. With the aim of understanding knocking better, light emission spectroscopy was applied in this study to examine preflame reactions that can be observed prior to autoignition. Light emission intensity was measured at wavelengths of 306.4 nm (characteristic spectrum of OH), 329.8 nm (HCO), 395.2 nm (HCHO). A four-cycle, air-cooled, single-cylinder gasoline engine with a side valve arrangement was used as the test engine. Light emission behavior was simultaneously observed at two positions (the end zone and the center zone) in the combustion chamber. The test fuel used was n-heptane (0 RON). The test engine was operated at three speed levels (1400, 1800 and 2200 rpm). As a result, preflame reactions were observed. It was also observed that the tendencies seen for the preflame reaction interval varied depending on the engine speed.
Technical Paper

Engine Performance of Lean Methanol-Air Mixture Ignited by Diesel Fuel Injection Applied with Internal EGR

2000-06-19
2000-01-2012
The uniform lean methanol-air mixture was provided to the diesel engine and was ignited by direct diesel fuel injection. In this study, the internal EGR is added to this ignition method in order to activate the fuel in the mixture and to increase the temperature of the mixture before the ignition. It is confirmed that the lean methanol-air mixture of air-fuel ratio between 130 and 18 could be ignited and burned when the back pressure of 80 [kPa] is added. The ignition and combustion characteristics can be improved by the internal EGR, however the engine performance and NOx emission deteriorated.
Technical Paper

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

2006-11-13
2006-32-0043
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.
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

The Fuel Injection System Using the High-Voltage Electrical Discharge

2005-10-12
2005-32-0075
The new fuel injection method which is using the high-voltage electrical discharge has been proposed. The plasma jet ignition technology is applied to this injection system, and the component parts of fuel injector are similar to the plasma jet igniter. The purpose of this study is to elucidate the spray characteristics and the fuel injection development processes of this injection method. To obtain the influence of injector configuration and supplied electrical discharge energy on the fuel spray, the fuel is ejected into the open atmosphere and fuel injection development process is visualized by the schlieren method. The penetration depth, maximum width and projected area of fuel spay increase with increasing in the electrical discharge energy and an orifice diameter. In the case at which the large electrical discharge energy is provided, the fuel injection is finished within a short duration and the mean fuel spray velocity becomes fast.
Technical Paper

The Influence of High Voltage Electrical Field on the Flame Propagation

2005-10-12
2005-32-0074
The purpose of this study is to elucidate the development process of hot kernel generated by the laser induced breakdown and to clarify the relationship between corona discharge application and flame propagation. The mixture can be ignited by the laser induced breakdown. Nd:YAG laser is used for the ignition and laser light is optically focused on the central part of combustion chamber by a plano convex lens. The hot kernel is observed in the absence of combustion and is rapidly developed into the laser incidence side. The homogeneous propane-air mixture is used and six equivalence ratios between 0.7 and 1.5 are tested. For generating the positive corona discharge in the combustion chamber, a non-uniform electric field is applied by the needle to plane gap. In a lean mixture, the whole flame front shifts to downward from the breakdown point and, in the rich mixture region, the combustion is strongly enhanced.
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

2005-10-24
2005-01-3732
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

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

Effect of EGR-Induced Hot Residual Gas on Combustion when Operating a Two-Stroke Engine on Alcohol Fuels

2000-10-16
2000-01-2972
In this research, the effect of high-temperature residual gas, resulting from the application of a certain level of EGR, on combustion was investigated using a two-stroke engine and alcohol fuels (ethanol and methanol) and gasoline as the test fuels. Measurements were made of the light emission intensity of the OH radical on the intake and exhaust port sides of the combustion chamber and of the combustion chamber wall temperature (spark plug washer temperature) and the exhaust gas temperature. Data were measured and analyzed in a progression from normal combustion to autoignited combustion to preignition and to knocking operation.
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

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

A Study on Influence of Forced Over Cooling on Diesel Engine Performance

2011-11-08
2011-32-0605
The ignitability and engine performance of FAMEs at the cold condition were experimentally investigated by using two FAMEs, i.e. coconut oil methyl ester (CME) and soybean oil methyl ester (SME). The cold start test and forced over cooling test were conducted. In the forced over cooling test, engine was forced cooled by the injecting water mist to engine cooling fin. In the cold start test, the cylinder pressure of CME rose earliest because CME has a superior ignitability. The crank angle at ignitions of diesel fuel and CME were not so affected by the forced over cooling, however ignition timing of SME was remarkably delayed. In cases of forced over cooling, COV of maximum combustion pressure of CME was lower than that of normal air cooling condition. The forced over cooling has a potential to reduce NOx emission, however HC, CO and smoke concentrations were increased in a high load due to incomplete combustion.
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.
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