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Journal Article

Extension of Operating Range of a Multi-Cylinder Gasoline HCCI Engine using the Blowdown Supercharging System

2011-04-12
2011-01-0896
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

Development of Continuously Variable Phase and Lift/Duration Mechanism for Widely Available Automobile Engines

2013-04-08
2013-01-0591
The variable valve lift and duration (in the following: VVLD) devices, some have been mass-produced already in the world, are necessary to be assembled with the variable cam phaser (in the following: VCP) to optimize open and close valve timing. On the other hand, with the variable valve phase and lift (in the following: VVPL) mechanism, the valve event is advanced with decreasing the valve lift and duration. Hence, no additional VCP is required when using the VVPL for throttle-less operation. A new VVPL has been developed as a mechanical, swing-cam actuation mechanism. The mechanisms of the conventional production VVLD devices are investigated and the functional analysis of the possible mechanisms is carried out to identify and design a simple mechanism for the new VVPL. The designed VVPL system is capable of continuously varying the valve lift from 0 mm to 10 mm, with the higher valve lift for any of the given duration.
Technical Paper

Extension of Lean and Diluted Combustion Stability Limits by Using Repetitive Pulse Discharges

2010-04-12
2010-01-0173
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

Very Lean and Diluted SI Combustion Using a Novel Ignition System with Repetitive Pulse Discharges

2009-11-03
2009-32-0119
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

Effect of Fuel and Thermal Stratifications on the Operational Range of an HCCI Gasoline Engine Using the Blow-Down Super Charge System

2010-04-12
2010-01-0845
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

A Study of High Compression Ratio SI Engine Equipped with a Variable Piston Crank Mechanism for Knocking Mitigation

2011-08-30
2011-01-1874
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

A Study of Newly Developed HCCI Engine With Wide Operating Range Equipped With Blowdown Supercharging System

2011-08-30
2011-01-1766
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

A Study of Control Strategy for Combution Mode Switching Between HCCI and SI With the Blowdown Supercharging System

2012-04-16
2012-01-1122
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.
Journal Article

Visualization and Analysis of LSPI Mechanism Caused by Oil Droplet, Particle and Deposit in Highly Boosted SI Combustion in Low Speed Range

2015-04-14
2015-01-0761
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

Numerical Simulation to Understand the Cause and Sequence of LSPI Phenomena and Suggestion of CaO Mechanism in Highly Boosted SI Combustion in Low Speed Range

2015-04-14
2015-01-0755
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.
Journal Article

Development of a Novel Ignition System Using Repetitive Pulse Discharges: Application to a SI Engine

2009-04-20
2009-01-0505
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.
Technical Paper

An Experimental Study of a Gasoline HCCI Engine Using the Blow-Down Super Charge System

2009-04-20
2009-01-0496
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.
Technical Paper

Improvement in Thermal Efficiency of Lean Burn Pre-Chamber Natural Gas Engine by Optimization of Combustion System

2017-03-28
2017-01-0782
To understand the mechanism of the combustion by torch flame jet in a gas engine with pre-chamber and also to obtain the strategy of improving thermal efficiency by optimizing the structure of pre-chamber including the diameter and number of orifices, the combustion process was investigated by three dimensional numerical simulations and experiments of a single cylinder natural gas engine. As a result, the configuration of orifices was found to affect the combustion performance strongly. With the same orifice diameter of 1.5mm, thermal efficiency with 7 orifices in pre-chamber was higher than that with 4 orifices in pre-chamber, mainly due to the reduction of heat loss by decreasing the impingement of torch flame on the cylinder linear. Better thermal efficiency was achieved in this case because the flame propagated area increases rapidly while the flame jets do not impinge on the cylinder wall intensively.
Technical Paper

1-D Simulation Model Developed for a General Purpose Engine

2016-11-08
2016-32-0030
In recent years, improvements in the fuel economy and exhaust emission performance of internal combustion engines have been increasingly required by regulatory agencies. One of the salient concerns regarding general purpose engines is the larger amount of CO emissions with which they are associated, compared with CO emissions from automobile engines. To reduce CO and other exhaust emissions while maintaining high fuel efficiency, the optimization of total engine system, including various design parameters, is essential. In the engine system optimization process, cycle simulation using 0-D and 1-D engine models are highly useful. To define an optimum design, the model used for the cycle simulation must be capable of predicting the effects of various parameters on the engine performance. In this study, a model for predicting the performance of a general purpose SI (Spark Ignited) engine is developed based on the commercially available engine simulation software, GT-POWER.
Journal Article

A Study of Low Speed Preignition Mechanism in Highly Boosted SI Gasoline Engines

2015-09-01
2015-01-1865
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

Analyses of Cycle-to-Cycle Variation of Combustion and In-Cylinder Flow in a Port Injection Gasoline Engine Using PIV and PLIF Techniques

2017-10-08
2017-01-2213
Reduction in the cycle-to-cycle variation (CCV) of combustion in internal combustion engines is required to reduce fuel consumption, exhaust emissions, and improve drivability. CCV increases at low load operations and lean/dilute burn conditions. Specifically, the factors that cause CCV of combustion are the cyclic variations of in-cylinder flow, in-cylinder distributions of fuel concentration, temperature and residual gas, and ignition energy. However, it is difficult to measure and analyze these factors in a production engine. This study used an optically accessible single-cylinder engine in which combustion and optical measurements were performed for 45 consecutive cycles. CCVs of the combustion and in-cylinder phenomena were investigated for the same cycle. Using this optically accessible engine, the volume inside the combustion chamber, including the pent-roof region can be observed through a quartz cylinder.
Technical Paper

Heat Transfer Analysis in a Diesel Engine Based on a Heat Flux Measurement Using a Rapid Compression and Expansion Machine

2017-11-05
2017-32-0115
To investigate the heat transfer phenomena inside the combustion chamber of a diesel engine, a correlation for the heat transfer coefficient in a combustion chamber of a diesel engine was investigated based on heat flux measured by the authors in the previous study(8) using the rapid compression and expansion machine. In the correlation defined in the present study, thermodynamically estimated two-zone temperatures in the burned zone and the unburned zone are applied. The characteristic velocity given in the correlation is related to the speed of spray flame impinging on the wall during the fuel injection period. After the fuel injection period, the velocity term of the Woschni’s equation is applied. It was shown that the proposed correlation well expresses heat transfer phenomena in diesel engines.
Technical Paper

Effect of Coolant Water and Intake Air Temperatures on Thermal Efficiency of Gasoline Engines

2017-11-05
2017-32-0116
An optimization of thermal management system in a gasoline engine is considered to improve thermal efficiency by minimizing the cost increase without largely changing the configuration of engine system. In this study, the influence of water temperature and intake air temperature on thermal efficiency were investigated using an inline four-cylinder 1.2L gasoline engine. In addition, one-dimensional engine simulations were conducted by using a software of GT-SUITE. Brake thermal efficiency for different engine speeds and loads could be quantitatively predicted with changing the cooling water temperature in the cylinder head. Then, in order to predict the improvement of the fuel consumption in actual use, vehicle mode running simulation and general-purpose engine transient mode simulation were carried out by GT-SUITE. As a result, it was found that by controlling the temperatures of the cooling water and intake gas, thermal efficiency can be improved by several percent.
Technical Paper

The Effect of In-Cylinder Flow and Mixture Distributions on Combustion Characteristics in a HCCI Engine

2017-11-05
2017-32-0061
It has been widely known that thermal and fuel stratifications of in-cylinder mixture are effective to reduce in-cylinder pressure rise rate during high load HCCI operations. In order to optimize a combustion chamber design and combustion control strategy for HCCI engines with wide operational range, it is important to know quantitatively the influence of the temperature and fuel concentration distributions on ignition and heat release characteristics. At the same time, it is important to know the influence of in-cylinder flow and turbulence on the temperature and fuel concentration distributions. In this study, a numerical simulation of HCCI combustion were conducted to investigate the effects of the in-cylinder flow and turbulence, and the distributions of temperature on ignition and combustion characteristics in HCCI combustion.
Technical Paper

Effects of Coolant Temperature and Fuel Properties on Soot Emission from a Spark-ignited Direct Injection Gasoline Engine

2019-12-19
2019-01-2352
Effects of measurement method, coolant temperature and fuel composition on soot emissions were examined by engine experiments. By reducing the pressure fluctuation in the sampling line, the measured soot emissions with better stability and reproducibility could be obtained. With lower coolant temperatures, larger soot emissions were yielded at much advanced fuel injection timings. Compared to gasoline, soot emissions with a blend fuel of normal heptane, isooctane and toluene were significantly decreased, suggesting the amounts of aromatic components (toluene or others) should be increased to obtain a representative fuel for the predictive model of particulate matter in SIDI engines.
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