Viewing 1 to 30 of 54
Technical Paper
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.
Journal Article
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.
Technical Paper
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.
Journal Article
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.
Journal Article
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.
Journal Article
Tatsuya Kuboyama, Yasuo Moriyoshi, Koji Morikawa
Abstract In this study, in order to clarify the mechanism of preignition occurrence in highly boosted SI engine at low speed and high load operating conditions, directphotography of preignition events and light induced fluorescence imaging of lubricant oil droplets during preignition cycles were applied. An endoscope was attached to the cylinder head of the modified production engine. Preigntion events were captured using high-speed video camera through the endoscope. As a result, several types of preignition sources could be found. Preignition caused by glowing particles and deposit fragments could be observed by directphotography. Luminous flame was observed around the piston crevice area during the exhaust stroke of preignition cycles.
Technical Paper
Yasuo Moriyoshi, Toshio Yamada, Daisuke Tsunoda, Mingzhao Xie, Tatsuya Kuboyama, Koji Morikawa
Abstract 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.
Technical Paper
Koji Morikawa, Yasuo Moriyoshi, Tatsuya Kuboyama, Yasuo Imai, Toshio Yamada, Koichi Hatamura
Abstract LSPI is an important issue to enable and enhance the effect of downsizing in SI engines. Experimental work was carried out by using 4 cylinder turbocharged gasoline engine, attaching the extra supercharger to get a higher boost pressure. Many parameters of driving condition, engine specification and lubricants were studied and some of them were extracted as the major items which affect the possibility of LSPI. Coolant temperature and Calcium (Ca) additive to lubricant had strong effect on the frequency of LSPI. Combustion strategy of strong miller cycle and LPEGR were also studied and compared in very high BMEP condition. Finally IMEPg of 3MPa at 1500rpm was achieved by using a single cylinder test engine equipped with 2-stage mechanically supercharged intake system.
Journal Article
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.
Technical Paper
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.
Journal Article
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.
Journal Article
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.
Technical Paper
Tatsuya Kuboyama, Yasuo Moriyoshi, Koichi Hatamura, Toshio Yamada, Junichi Takanashi, Yasuhiro Urata
To find an ignition and combustion control strategy in a gasoline-fueled HCCI engine equipped with the BlowDown SuperCharging (BDSC) system which is previously proposed by the authors, a one-dimensional HCCI engine cycle simulator capable of predicting the ignition and heat release of HCCI combustion was developed. The ignition and the combustion models based on Livengood-Wu integral and Wiebe function were implemented in the simulator. The predictive accuracy of the developed simulator in the combustion timing, combustion duration and heat release rate was validated by comparing to experimental results. Using the developed simulator, the control strategy for the engine operating mode switching between HCCI and SI combustion was explored with focus attention on transient behaviors of air-fuel ratio, A/F, and gas-fuel ratio, G/F.
Technical Paper
Yasuo Moriyoshi, Hitoshi Nomura, Youhei Saisyu
A direct injection gasoline engine system which employs a unique combustion system with enhanced gas motion is evaluated. Enhanced gas motion is produced by employing both a moderately strong swirl flow and a cavity in the piston. Advantages of this system are that the injection timing or spark timing need not be controlled severely and that since the injection timing can be set at near the intake BDC, time for evaporation can be gained to reduce soot emissions. Problems to be improved are that the Nox emissions level is worse than other lean burn systems and full load operation is not evaluated. According to the numerical calculations, the problems may be solved by enhancing the in-cylinder gas motion with axial stratification of swirl intensity at intake BDC; strong swirl near the cylinder head and weak swirl near the piston surface.
Technical Paper
Yasuo Moriyoshi, Hideaki Morikawa, Takeyuki Kamimoto, Tomokazu Hayashi
Local inhomogeneity of mixture concentration affects combustion characteristics in the lean burn system and also in the stratified charge combustion system. To investigate such combustion systems, the effects of inhomogeneous mixtures were examined using a carefully controlled experimental system. In this study, a constant-volume chamber, which can simulate an idealized stratified charge by using a removable partition inside the chamber, was developed. Flow and combustion characteristics were examined by indicated pressure analysis, Schlieren photography, ion probe measurements and local equivalence ratios measurements while varying the combination of initial equivalence ratios on each side of the partition. As a result, combustion characteristics of charge stratified, very lean propane-air mixture were clarified.
Technical Paper
Yasuo Moriyoshi, Takeyuki Kamimoto, Miki Yagita
A prediction model of the cycle-to-cycle variation of the in-cylinder flow in IC engines which employs the time averaged k-ε turbulence model is proposed. The concept is based on an assumption that the power spectrum of the cycle-to-cycle variation can be deduced from the power spectra of both the mean velocity and turbulence intensity. To validate this model, in-cylinder velocity measurement in a transparent cylinder engine with a 2-valve cylinder-head is made using an LDV system. Comparisons of in-cylinder flow fields between the calculation and measurement show a good agreement in the cycle-to-cycle variation as well as the turbulence intensity. Finally, this model is applied to three kinds of flow fields to examine how the cycle-to-cycle variation may be effected. As a result, it is found that the swirl flow is effective to reduce the cycle-to-cycle variation, while the tumbling flow enhances the turbulence generation around the compression TDC.
Technical Paper
Yasuo Moriyoshi, Takumi Muroki, Wenbin Xu
A model combustion chamber of Wankel type rotary engine was employed to study the DISC RE system. A two-stroke Diesel engine's cylinder head was replaced with this combustion chamber to simulate temporal change of air flow and pressure fields inside the chamber as an actual engine. The base engine was motorized to operate as a continuous rapid compression and expansion machine. Pilot fuel spray was injected onto a glow plug to form a pilot flame and it ignites the main fuel spray. The ignitability of pilot fuel, mixture formation process, ignition process of main fuel by pilot flame and the effect of pilot and main injection timings on combustion characteristics were examined.
Technical Paper
Yasuo Moriyoshi, Takumi Muroki
A new idea for controlling the in-cylinder mixture formation in SI engines is proposed. This concept was developed by applying the results of numerical calculations. Fuel that is directly injected into the cylinder is transferred toward the cylinder head to form a mixture stratification by using the in-cylinder gas motion that is generated by the interaction between the swirl and squish flows inside a combustion chamber. At first, the flow characteristics were measured in the whole in-cylinder space using an LDV system. Also, numerical calculations of the in-cylinder flow were made using measured data as the initial conditions. Secondly, the local equivalence ratio at several points inside the combustion chamber was measured by using a fast gas sampling device.
Technical Paper
Yuanwei Song, Yasuo Moriyoshi, Tukumi Muroki
In order to enhance the reliability of a pilot flame ignition system, three kinds of subchambers in which a pilot injector and a glow plug were set up were tested with a model combustion chamber of DISC rotary engine. A two-stroke Diesel engine's cylinder head was replaced with this model combustion chamber to simulate temporal changes of air flow and pressure fields inside the chamber as an actual engine. The behavior of the pilot flame generated in the subchamber, ignition process of main fuel spray by the pilot flame, the most suitable mixture distribution between the main chamber and the subchamber, and the effect of nozzle diameter of main injector on combustion characteristics were studied by using a high-speed video camera and ion probes.
Technical Paper
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.
Technical Paper
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.
Technical Paper
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.
Technical Paper
Yasuo Imai, Yasuo Moriyoshi, Kazuki Toyoda
In order to measure the spatial distribution of fuel jet concentration quantitatively, a technique combining methods of fluorescence with absorption was developed. LIF method can obtain the spatial fuel distribution qualitatively, but quantitative measurement is difficult. Meanwhile, laser-beam absorption method can quantitatively obtain the integrated jet concentration on the light-path. In addition, scanning the laser-beam allows for a quasi 2-D quantitative measurement of the jet concentration. Firstly, in this study, this measurement system was tested in a homogeneously charged field while varying the dopant NO2 concentration, the laser-beam scanning speed, and the ambient pressure. As a result, some data-correction techniques were developed to produce a quantitative measurement. Secondly, this system was applied to gaseous jet fields in a constant volume bomb.
Technical Paper
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.
Technical Paper
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.
Technical Paper
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.
Technical Paper
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.
Technical Paper
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.
Technical Paper
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.
Technical Paper
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.
Viewing 1 to 30 of 54


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