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Viewing 1 to 30 of 57
2010-09-28
Journal Article
2010-32-0064
Yasuo Moriyoshi, Minoru Iida
In a motorcycle gasoline engine, the port fuel injection system is rapidly spread. Compared to an automotive engine, the injected fuel does not impinge on the intake valve due to space restriction to install the injector. In addition, as the air flow inside the intake pipe may become very fast and has large cycle-to-cycle variation, it is not well found how the injector should be installed in the intake pipe to prepare “good” fuel-air mixture inside the intake pipe. In this study, the formation process of the fuel-air mixture is measured by using ILIDS system that is a 2-D droplets' size and velocity measurement system with high spatial resolution. Experiments with changing conditions such as flow speed and injection direction are carried out.
2010-04-12
Journal Article
2010-01-0845
Tatsuya Kuboyama, Yasuo Moriyoshi, Koichi Hatamura, Masatoshi Suzuki, Junichi Takanashi, Toshio Yamada, Shunsuke Gotoh
In order to extend the HCCI high load operational limit, the effects of the distributions of temperature and fuel concentration on pressure rise rate (dP/dθ) were investigated through theoretical and experimental methods. The Blow-Down Super Charge (BDSC) and the EGR guide parts are employed simultaneously to enhance thermal stratification inside the cylinder. And also, to control the distribution of fuel concentration, direct fuel injection system was used. As a first step, the effect of spatial temperature distribution on maximum pressure rise rate (dP/dθmax) was investigated. The influence of the EGR guide parts on the temperature distribution was investigated using 3-D numerical simulation. Simulation results showed that the temperature difference between high temperature zone and low temperature zone increased by using EGR guide parts together with the BDSC system.
2013-10-15
Journal Article
2013-32-9172
Shunsuke Gotoh, Tatsuya Kuboyama, Yasuo Moriyoshi, Koichi Hatamura, Toshio Yamada, Junichi Takanashi, Yasuhiro Urata
HCCI combustion can realize low NOx and particulate emissions and high thermal efficiency. Therefore, HCCI combustion has a possibility of many kinds of applications, such as an automotive powertrain, general-purpose engine, motorcycle engine and electric generator. However, the operational range using HCCI combustion in terms of speed and load is restricted because the onset of ignition and the heat release rate cannot be controlled directly. For the extension of the operational range using either an external supercharger or a turbocharger is promising. The objective of this research is to investigate the effect of the intake pressure on the HCCI high load limit and HCCI combustion characteristics with blowdown supercharging (BDSC) system. The intake pressure (Pin) and temperature (Tin) were varied as experimental parameters. The intake pressure was swept from 100 kPa (naturally aspirated) to 200 kPa using an external mechanical supercharger.
2011-04-12
Journal Article
2011-01-0896
Tatsuya Kuboyama, Yasuo Moriyoshi, Koichi Hatamura, Junichi Takanashi, Yasuhiro Urata, Toshio Yamada PhD
The objective of this study is to develop a practical technique to achieve HCCI operation with wide operation range. To attain this objective, the authors previously proposed the blowdown supercharge (BDSC) system and demonstrated the potential of the BDSC system to extend the high load HCCI operational limit. In this study, experimental works were conducted with focusing on improvement of combustion stability at low load operation and the reduction in cylinder to cylinder variation in ignition timing of multi-cylinder HCCI operation using the BDSC system. The experiments were conducted using a slightly modified production four-cylinder gasoline engine with compression ratio of about 12 at constant engine speed of 1500 rpm. The test fuel used was commercial gasoline which has RON of 91. To improve combustion stability at low load operation, the valve actuation strategy for the BDSC system was newly proposed and experimentally examined.
2011-08-30
Technical Paper
2011-01-1874
Koji Morikawa, Akio Yoshimatsu, Yasuo Moriyoshi, Tatsuya Kuboyama, Kenta Matsuura
To avoid knocking phenomena, a special crank mechanism for gasoline engine that allowed the piston to move rapidly near TDC (Top Dead Center) was developed and experimentally demonstrated in the previous study. As a result, knocking was successfully mitigated and indicated thermal efficiency was improved [1],[2],[3],[4]. However, performance of the proposed system was evaluated at only limited operating conditions. In the present study, to investigate the effect of piston movement near TDC on combustion characteristics and indicated thermal efficiency and to clarify the knock mitigation mechanism of the proposed method, experimental studies were carried out using a single cylinder engine with a compression ratio of 13.7 at various engine speeds and loads. The special crank mechanism, which allows piston to move rapidly near TDC developed in the previous study, was applied to the test engine with some modification of tooling accuracy.
2011-08-30
Journal Article
2011-01-1766
Tatsuya Kuboyama, Yasuo Moriyoshi, Koichi Hatamura, Junichi Takanashi, Yasuhiro Urata, Toshio Yamada
To extend the operating range of a gasoline HCCI engine, the blowdown supercharging (BDSC) system and the EGR guide were developed and experimentally examined. The concepts of these techniques are to obtain a large amount of dilution gas and to generate a strong in-cylinder thermal stratification without an external supercharger for extending the upper load limit of HCCI operation whilst keeping dP/dθmax and NOx emissions low. Also, to attain stable HCCI operation using the BDSC system with wide operating conditions, the valve actuation strategy in which the amount of dilution gas is smaller at lower load and larger at higher load was proposed. Additionally to achieve multi-cylinder HCCI operation with wide operating range, the secondary air injection system was developed to reduce cylinder-to-cylinder variation in ignition timing. As a result, the acceptable HCCI operation could be achieved with wide operating range, from IMEP of 135 kPa to 580 kPa.
1999-09-28
Technical Paper
1999-01-3330
Yasuo Moriyoshi, Kazuhiro Mori, Koji Morikawa
To survive the severe regulations for both the exhaust gas emissions and fuel economy, research on small two-stroke gasoline engines from both the experimental and theoretical viewpoints is quite necessary. In the present study, firstly, performance tests of a direct injection small two-stroke gasoline model engine were carried out. Based on these experimental results, three-dimensional flow calculations from scavenging pipe to exhaust pipe during the gas-exchange and piston compression processes were made with the same experimental conditions. As a result, the gas exchange process was investigated and some problems were clarified. Secondly, parametric calculations with changing just exhaust port timings were performed to solve the problems found in the above calculations.
1999-09-28
Technical Paper
1999-01-3322
Takumi Muroki, Yasuo Moriyoshi, Susumu Sekizuka
The authors have experimentally produced a new type of Rotary Valve (ca11ed R.V.) which has a unique gas sealing mechanism. In this study, first, the mechanical loss in the valve train was measured comparing to that of the poppet valve drive train, and it was found that the mechanical loss of rotary valve train is much lower level. Secondary, three dimensional numerical calculation of the flow field from the intake-port to in-cylinder during the intake stroke was carried out. As a result, it was found that the flow field is very complicated due to the interaction between the moving piston and valve and that the profiles of “valve notch” and intake port affect the flow field and then, the modification of profile with a round edge form of the “notch” enables higher mass flow rate.
2004-09-27
Technical Paper
2004-32-0080
Masatoshi Suzuki, Satoshi Iijima, Yasuo Moriyoshi, Masaki Sano
In reciprocating internal combustion engines, the piston stops in a moment at top dead center (TDC), so there exists a necessary time to proceed combustion. However more slowing piston motion around TDC, does it have a possibility to produce the following effects? The slowed piston motion may expedite combustion proceed and increase cylinder pressure. This may lead to an increase of degree of constant volume. As a result, thermal efficiency may be improved. In order to verify this idea, two types of engines were tested. The first engine attained high cylinder pressure as expected. The P-V diagram formed an almost ideal Otto cycle. However, this did not contribute to the improvement in the thermal efficiency. Then the second engine with further slower piston motion by active piston control was tested in order to examine the above reason.
2005-04-11
Technical Paper
2005-01-0240
Koji Morikawa, Makoto Kaneko, Yasuo Moriyoshi, Masaki Sano
A new combustion method of high compression ratio SI engine was studied and proposed in order to achieve higher thermal efficiency of SI engine comparable to that of CI engine. Compression ratio of SI engine is generally restricted by the knocking phenomena. A combustion chamber profile and a cranking mechanism are studied to avoid knocking with high compression ratio. Since reducing the end-gas temperature will suppress knocking, a combustion chamber was considered to have a wide surface at the end-gas region. However, wide surface will lead to high heat loss, which may cancel the gain of higher compression ratio operation. Thereby, a special cranking mechanism was adopted which allowed the piston to move rapidly near TDC. Numerical simulations were performed to optimize the cranking mechanism for achieving higher thermal efficiency. An elliptic gear system and a leaf-shape gear system were employed in the simulations.
2015-09-01
Journal Article
2015-01-1865
Yasuo Moriyoshi, Tatsuya Kuboyama, Koji Morikawa, Toshio Yamada, Yasuo Imai, Koichi Hatamura, Masatoshi Suzuki
The authors investigated the reasons of how a preignition occurs in a highly boosted gasoline engine. Based on the authors' experimental results, theoretical investigations on the processes of how a particle of oil or solid comes out into the cylinder and how a preignition occurs from the particle. As a result, many factors, such as the in-cylinder temperature, the pressure, the equivalence ratio and the component of additives in the lubricating oil were found to affect the processes. Especially, CaCO3 included in an oil as an additive may be changed to CaO by heating during the expansion and exhaust strokes. Thereafter, CaO will be converted into CaCO3 again by absorbing CO2 during the intake and compression strokes. As this change is an exothermic reaction, the temperature of CaCO3 particle increases over 1000K of the chemical equilibrium temperature determined by the CO2 partial pressure.
2015-09-01
Journal Article
2015-01-1895
Taisuke Shiraishi, Atsushi Teraji, Yasuo Moriyoshi
In order to realize the high compression ratio and high dilution combustion toward improvement in thermal efficiency, the improvement in stability of ignition and initial phase of combustion under the high gas flow field is the major challenge. In terms of the shift on the higher power side of the operating point by downsizing and improvement of real world fuel consumption, the improvement of ignitability is increasingly expected in the wide operating range also including high load and high engine speed region. In this study, the effects of the gas pressure, gas flow velocity near the spark gap at ignition timing, and discharge current characteristics on spark channel formation were analyzed, focusing on restrike event and spark channel stretching in the spark channel formation process. And the relationship between the average discharge current until 1 ms and the EGR combustion limit was considered.
2015-09-01
Technical Paper
2015-01-1870
Koji Morikawa, Yasuo Moriyoshi, Tatsuya Kuboyama, Toshio Yamada, Masatoshi Suzuki
The effect of properties of lubricating oil on low speed pre-ignition (LSPI) was investigated. Three different factors of oil properties such as cetane number, distillation characteristics and Calcium (Ca) additive (with and without) are prepared and examined. Then actual engine test of LSPI was carried out to evaluate the effect and to clarify the mechanism and role of lubricating oil. Finally it is clarified that the oil cetane number and/or Ca additive strongly affect LSPI phenomena.
2015-09-01
Technical Paper
2015-01-1814
Tatsuya Kuboyama, Shunsuke Goto, Yasuo Moriyoshi, Keiichi Koseki, Yoichi Akiyama
In this study, the effect of the low octane number fuel on HCCI engine performance was experimentally investigated using a slightly modified commercial four-cylinder gasoline engine. To operate the engine in HCCI strategy with wide operational range, the blowdwon supercharging (BDSC) system proposed by the authors was applied in the test engine. Research octane number (RON) of test fuels was varied from 90 to 78.5 as an experimental parameter. Experimental results showed that in the range of the present study, HCCI operational range, brake thermal efficiency and exhaust emissions during HCCI operation were little affected by the RON of the test fuels. In contrast, during SI operation, thermal efficiency was deteriorated with lower RON fuel because of knocking.
2015-11-17
Technical Paper
2015-32-0767
Yasuo Moriyoshi, Tatsuya Kuboyama, Hisashi Goto, Minoru Iida
PFI (Port Fuel Injection) gasoline engines for motorcycles have some problems such as slow transient response because of wall wet of fuel caused by the injector's layout. Hence, it is important to understand the characteristics of fuel sprays such as droplet size and distribution of fuel concentration. Considering the spray formation in a port, there are three kinds of the essential elements: breakup, evaporation and wall impingement. However, it is difficult to observe three of them at the same time. Therefore, the authors have made research step by step. In the authors' previous study, the authors focused on the wall collision, droplet sizes, droplet speeds and the space distribution of the droplets. In this study, the authors focused on evaporation. A direct sampling method using FID (Flame Ionization Detector) for evaporating fuel was established and the concentration distribution of evaporating fuel in the port was measured and analyzed.
2008-04-14
Technical Paper
2008-01-0468
Kimitoshi Tanoue, Eiki Hotta, Yasuo Moriyoshi
A newly developed small-sized IES (inductive energy storage) circuit with static induction thyristor at turn-off action was successfully applied to an ignition system. This IEC circuit can generate repetitive nanosecond pulse discharges. In this paper, the ignition system using repetitive nanosecond pulse discharges was investigated as an alternative to conventional spark ignition systems. The experiments were conducted using spherically expanding flame configuration for CH4 and C3H8-air mixtures under various conditions. In conclusions, the ignition system using repetitive nanosecond pulse discharges was found to extend lean flammability limits compared with conventional spark ignition systems. In addition, the ignition system using repetitive nanosecond pulse discharges could shorten ignition delay time.
2007-10-30
Technical Paper
2007-32-0098
Takafumi YAMADA, Yasuo MORIYOSHI
For a disaster relief and automatic inspections, an unmanned helicopter is strongly expected. To develop this, a very high power density source is required. A Wankel-type rotary engine can be the best candidate for the power source. In this study, the development of a very small rotary engine with a displacement of 30 cc is targeted. In order to improve the combustion efficiency, gas exchange and stable ignition, a multi dimensional simulation inside the combustion chamber was carried out. At first, the effect of volumetric efficiency on the maximum power is mentioned. Secondly, the effect of scavenging efficiency is discussed. Thirdly, a blow off through a plug hole is described. The position of plug hole was found important to reduce the blow off amount. Finally, the effect of combustion speed on the engine performance is predicted. As a result, the proposed design will be tested using a proto-type engine.
2010-04-12
Technical Paper
2010-01-0173
Kimitoshi Tanoue, Tatsuya Kuboyama, Yasuo Moriyoshi, Eiki Hotta, Naohiro Shimizu, Yuichiro Imanishi, Katsuji Iida
A newly developed small-sized IES (inductive energy storage) circuit with a semiconductor switch at turn-off action was successfully applied to an ignition system. This IES circuit can generate repetitive nanosecond pulse discharges. An ignition system using repetitive nanosecond pulse discharges was investigated as an alternative to conventional spark ignition systems in the previous papers. Experiments were conducted using constant volume chamber for CH₄ and C₃H₈-air mixtures. The ignition system using repetitive nanosecond pulse discharges was found to improve the inflammability of lean combustible mixtures, such as extended flammability limits, shorted ignition delay time, with increasing the number of pulses for CH₄ and C₃H₈-air mixtures under various conditions. The mechanisms for improving the inflammability were discussed and the effectiveness of IES circuit under EGR condition was also verified.
2009-11-03
Journal Article
2009-32-0119
Tatsuya Kuboyama, Yasuo Moriyoshi, Kimitoshi Tanoue, Eiki Hotta, Yuichiro Imanishi, Naohiro Shimizu, Katsuji Iida
A newly developed small-sized IES (inductive energy storage) circuit with semiconductor switch at turn-off action is successfully applied to an ignition system of a small gasoline internal combustion engine. This IES circuit can generate repetitive nanosecond pulse discharges. An ignition system using repetitive nanosecond pulse discharges is investigated as an alternative to a conventional spark ignition system. The present study focuses on the extension of the operational limits for lean and diluted combustion using the repetitive nanosecond pulse discharges. First, in order to investigate the flame kernel formation process when the repetitive nanosecond pulse discharges are used, the initial flame kernel is observed using Schlieren photography with a high speed camera. As a result, the flame kernel generated by repetitive pulse discharges is larger than by a conventional ignition system.
2009-04-20
Technical Paper
2009-01-0496
Tatsuya Kuboyama, Yasuo Moriyoshi, Koichi Hatamura, Toshio Yamada, Junichi Takanashi
The objective of this study is to extend the high load operation limit of a gasoline HCCI engine. A new system extending the high load HCCI operation limit was proposed, and the performance of the system was experimentally demonstrated. The proposed system consists of two new techniques. The first one is the “Blow-down super charging (BDSC) system”, in which, EGR gas can be super charged into a cylinder during the early stage of compression stroke by using the exhaust blow-down pressure wave from another cylinder phased 360 degrees later/earlier in the firing order. The other one is “EGR guide” for generating a large thermal stratification inside the cylinder to reduce the rate of in-cylinder pressure rise (dP/dθ) at high load HCCI operation. The EGR guides consist of a half-circular part attached on the edge of the exhaust ports and the piston head which has a protuberant surface to control the mixing between hot EGR gas and intake air-fuel mixture.
2009-04-20
Journal Article
2009-01-0505
Kimitoshi Tanoue, Tatsuya Kuboyama, Yasuo Moriyoshi, Eiki Hotta, Yuichiro Imanishi, Naohiro Shimizu, Katsuji Iida
A newly developed small-sized IES (inductive energy storage) circuit with semiconductor switch at turn-off action was successfully applied to an ignition system. This IES circuit can generate repetitive nanosecond pulse discharges. An ignition system using repetitive nanosecond pulse discharges was investigated as an alternative to conventional spark ignition systems. Experiments were conducted using spherically expanding flame configuration for CH4 and C3H8-air mixtures under various conditions. The ignition system using repetitive nanosecond pulse discharges was found to improve inflammability of lean combustible mixtures, such as extended flammability limits, shorted ignition delay time, with increasing the number of pulses. The authors seek for the mechanisms for improving the inflammability in more detail to optimize ignition system, and verify the effectiveness of IES circuit in EGR condition, for real engine use.
2009-04-20
Technical Paper
2009-01-1502
Yasuo Moriyoshi, Ryo Uchida, Masahide Takagi, Masato Kubota
The analysis of spray characteristics is important to examine the combustion characteristics of DI (Direct Injection) gasoline engines because the fuel-air mixture formation is controlled by spray characteristics and in-cylinder gas motion. However, the mixture formation process has not been well clarified yet. In this study, the characteristics of a fan-shaped spray caused from a slit-type injector, such as the droplet size, its velocity and the droplet distribution were simultaneously measured on a 2D plane by using improved ILIDS (Interferometric Laser Imaging for Droplet Sizing) method. ILIDS method is an optical measurement technique using interference fringes by illuminating a transparent spherical particles with a coherent laser light. In the measurement of the wall-impinging spray, effects of the distance to the wall and the wall temperature on the spray characteristics were investigated.
2006-11-13
Technical Paper
2006-32-0098
Masatoshi Suzuki, Satoshi Iijima, Hayato Maehara, Yasuo Moriyoshi
In reciprocating internal combustion engines, the Otto cycle indicates the best thermal efficiency under a given compression ratio. To achieve an ideal Otto cycle, combustion must take place instantaneously at top dead center, but in fact, this is impossible. Meanwhile, if we allow slower piston motion around top dead center, combustion will be promoted at that period; then both the in-cylinder pressure and degree of constant volume will increase, leading to higher thermal efficiency. In order to verify this hypothesis, an engine with slower piston motion around top dead center, using an ideal constant volume combustion engine, was built and tested. As anticipated, the degree of constant volume increased. However, thermal efficiency was not improved, due to increased heat loss.
2007-07-23
Technical Paper
2007-01-1898
Yasuo Moriyoshi, Masahide Takagi, Change-seong Ryu
In this study, the characteristics of diesel spray droplets, such as the velocity and the diameter were simultaneously measured by using an improved ILIDS (Interferometric Laser Imaging for Droplet Sizing) method on a 2D plane to evaluate the droplet breakup modeling. In numerical analysis, DDM (Discrete Droplet Model) was employed with sub-models such as droplet breakup, droplet drag force and turbulence. Experiments have been performed with an accumulator type unit-injector system and a constant-volume high-pressure vessel under the condition of quiescent ambient gas. The injection pressure and ambient gas pressure were set up to 100 MPa and 0.1 / 1 MPa, respectively. The nozzle orifice diameter was 0.244 mm with a single hole. The measurement region was chosen at 40 ∼ 60 mm from the nozzle-tip. Numerical analysis of diesel sprays was conducted and the results were compared to the measured results.
2005-10-12
Technical Paper
2005-32-0067
Yasuo MORIYOSHI, Masaki SANO, Seung-hwan CHOI, Masatoshi SUZUKI, Satoshi IIJIMA
In order to improve thermal efficiency of spark ignition engines, the authors have studied means to improve degree of constant volume. The ideal Otto cycle realizes the maximal degree of constant volume with an instantaneous combustion at TDC. However, it is actually impossible to achieve instantaneous combustion as the combustion speed is limited. Thereby, the authors thought of an idea to increase degree of constant volume. That is to make the piston speed slow during combustion period by active piston-movement control, allowing more time for combustion. As a result, degree of constant volume was improved, but indicated thermal efficiency, estimated by integrating P-V diagram, was deteriorated. A longer expansion stroke was found to keep a longer period of high temperature and then, heat loss increased, leading to a decrease in indicated work.
2004-09-27
Technical Paper
2004-32-0065
Yasuo Moriyoshi, Masaki Sano, Masatoshi Suzuki, Satoshi Iijima
In order to improve thermal efficiency of spark ignition engines, a novel method to increase degree of constant volume was considered. Because the combustion speed is not infinity as assumed in Otto cycle but limited, it is necessary to decrease the piston-movement around TDC so as to increase degree of constant volume. At first, experimental study was made to confirm this. A test engine which has longer expansion stroke than compression stroke and enables a slow piston-movement during combustion period was built. The experimental data indicated an increase in degree of constant volume, but did not show an increase in thermal efficiency. In order to clarify this reason, numerical simulations are conducted in this paper. As a result, the gain due to the increase in degree of constant volume caused by piston-motion during combustion was found not exceeding the loss by increased heat loss.
2004-09-27
Technical Paper
2004-32-0040
Yasuo Moriyoshi, Masayuki Arai, Junpei Katsuta, Koji Morikawa
Conventional two-stroke engines have defects such as unstable combustion, high fuel consumption rate and high HC emissions. In order to overcome the defects, a direct fuel injection system and a novel scavenging system were adopted. The authors tested a newly developed reverse uniflow-type two-stroke direct injection gasoline engine that was designed by numerical simulations. In comparison with the base engine at low engine speed, HC emission was decreased by up to 80%, and BSFC was reduced by around 40%. Power and BSFC were superior to those of a latest port-injection four-stroke engine. Furthermore, it was found that engine performance of exhaust gas emissions, fuel economy or output power can be selectively optimized by switching homogeneous and stratified combustion.
2006-04-03
Technical Paper
2006-01-1344
Yasuo Moriyoshi, Seung-Hwan Choi, Shigemi Kobayashi, Takafumi Tsunekawa
The phenomenon of autoignition is an important aspect of HCCI and knock, hence reliable information on local gas temperature in a combustion chamber must be obtained. Recently, several studies have been conducted by using laser techniques such as CARS. It has a high spatial resolution, but has proven difficult to apply in the vicinity of combustion chamber wall and requires special measurement skills. Meanwhile, a thermocouple is useful to measure local gas temperature even in the vicinity of wall. However, a traditional one-wire thermocouple is not adaptable to measure the in-cylinder gas temperature due to slow response. The issue of response can be overcome by adopting a two-wire thermocouple. The two-wire thermocouple is consisted of two fine wire thermocouples with different diameter hence it is possible to determine the time constant using the raw data from each thermocouple.
1991-02-01
Technical Paper
910261
Yasuo Moriyoshi, Takeyuki Kamimoto, Hideo Ohtani, Miki Yagita
Control of turbulence during the compression stroke is suggested by both theoretical calculations and experimental results obtained with an LDV measurement in a motored engine. The authors have found experimentally that when an axial distribution of swirl intensity exists, a large-scale annular vortex is formed inside the cylinder during the compression stroke and this vortex generates and transports turbulence energy. A numerical calculation is adopted to elucidate this phenomenon. Then, an axial stratification of swirl intensity is found to generate a large-scale annular vortex during the compression stroke by an interaction between the piston motion and the axial pressure gradient. The initial swirl profile is parametrically varied to assess its effect on the turbulence parameters. Among calculated results, turbulence energy is enhanced strongest when the swirl intensity is highest at the piston top surface and lowest at the bottom surface of the cylinder head.
1994-10-01
Technical Paper
941927
Wenbin Xu, Yasuo Moriyoshi, Takumi Muroki
A new DISC combustion system with a pilot flame for ignition was analyzed by using a model combustion chamber of a Wankel type rotary engine. A two-stroke diesel engine's cylinder head was replaced with this combustion chamber to simulate temporal changes of air flow and pressure fields inside the chamber as in actual engines. Two types of fuel injection systems were tested to obtain combustion characteristics such as the heat release rate. Direct photographs of spray and combustion were analyzed to understand the mixture-formation process of the main spray and to see the flame temperature distribution and flame moving velocity vectors. In order to understand the mixture-formation process, numerical calculations were made using a gaseous fuel. Finally, the effect of the fuel characteristics on combustion was examined using diesel fuel and n- hexane.
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