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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.

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.

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.

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.

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.

In this paper, visualization by means of the Schlieren method was accomplished in a two dimensional flow channel model of a CNG engine mixer. From the visualization results:(1)Mixing in the region of the venturi tube and throttle valve was influenced by the throttle opening and by the distance of the nozzle and valve, and in addition in this region natural gas behavior shows many different flow patterns.(2)The mixing (diffusion) characteristics clarified the relationship between the throttle opening and two natural gas flows; high velocity flow near the channel wall and swirl flow under the throttle valve.(3)The concept of gas and air mixing being affected by the dimensions of the main elements (main nozzle, venturi tube, throttle valve, their relative relationships and auxiliary air) of the CNG mixer were clearly shown. Premixing of natural gas and air in a CNG engine vehicle is said to be inadequate because it adversely influences the engine combustion and emission characteristics.

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.

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.

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.

There are several all-aluminum cylinder blocks. A typical example is a mono-block cylinder of alusil alloy produced by low pressure die casting. This material's resistance to abrasion and seizure, however, is not satisfactory for motorcycle; in addition, long processing time is another disadvantage. To cope with these problems, the authors developed a light and highly productive all-aluminum cylinder block with a cast-in liner through die casting. The liner is made from powder metallurgy composite (PMC) with 3 to 5 % alumina and 0.5 to 3 % of graphite additives. The PMC reconciles abrasion resistance and machinability. The hardness deterioration of the composite due to the heat at die casting is avoided by using heat-resistant rapidly-solidified powders, made from an aluminum-silecon-iron alloy, for the matrix.

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.

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.

In order to study air flow distribution to individual cylinders of an SI engine at transient conditions, a new small-sized high-response air flow meter was investigated and developed to measure instantaneous air flow rates. The experiments were performed with changes in initial throttle opening, throttle movement angle and period, and crank-angle at the opening of the throttle valve and related engine speeds. Air flow rates for individual cylinders of a four cylinder engine were measured during acceleration. The relative rising rate was used for estimation of air distribution values, namely, the ratio of the initial amount of increased air flow rate of to the air flow rate for each cylinder. Air flow begins to increase from the second induction stroke from throttle opening. The variations of crank-angle at throttle opening influences the rate of increase. The effect of transient conditions on air flow rate distribution was researched.

The objective of this experimental study is to clarify the air flow rate characteristics of an MPI gasoline engine intake-manifold at transient conditions. A new high-response air flow meter was investigated and developed for the study which can simultaneously measure the air flow rate of all four cylinders. The influence of transient conditions to air flow rate distribution to each cylinder were researched and verified with regard to the geometry of the ram pipe length and location, and intake air pipe location for the air distributor. The transient conditions were examined by varying the following: initial throttle opening, throttle operating opening, throttle operating period, and engine speed and crank angle at starting to open the throttle valve. A comparison was also made with a “Siamese” type manifold.

This paper has two purposes: the first is to study the air flow behavior in the MPI type engine manifold by means of flow visualization; the second purpose is the verification of the air flow characteristics described in SAE paper No.950066 (1)using the results of that paper. The tuft grid method was adopted for air visualization. The MPI type engine manifold used in this study (common chamber) has dimensions of 332 × 79 × 74mm. The amount of the tuft is 630 points. Two directions(yz and xz planes, respectively) of the tuft were instantaneously photographed at every 20 degrees of crank angle and the composed direction was calculated. The experimental conditions are 1) steady air flow, 2) transient flow, 3) the inlet pipe position and 4) ram pipe locations.

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.

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.

In recent years, efforts have “been undertaken to increase the stress load on spring materials and to decrease wire diameter in order to reduce weight. However, progress has “been slow due to the resulting increase in spring sag. This report describes the characteristics of steel wire subjected to a new strain method. After quenching and tempering, while the wire is still warm, strain is imposed on the wire to improve its sag resistance. Results show that sagging in springs made of this wire is approximately one half that of springs made of conventionally quenched and tempered wire of the same strength. Moreover, strain-imposed wire can be quenched and tempered to a lower strength than, yet have the same sag resistance as, extremely high-strength conventional wire. As a result, problems encountered when high strength material is used to improve sag resistance - such as damaged cutting tools and decreased shot peening effect can be avoided.

A swirl-type injector is commonly used for the gasoline direct injection IC engines. To control and optimize the engine combustion, analyses of mixture formation process inside the cylinder are quite important. In this study, an evaluation of a DDM (Discrete Droplet Model) including breakup and evaporation sub-models has been made by making comparisons between the calculation and measurement. In the calculation, two kinds of initial conditions were tested; one was from empirical expressions and the other was from calculated results using a VOF (Volume Of Fluid) model that had a feature to examine the free fluid surface of a liquid fuel spray. As a result, the authors have found that a DDM can basically explain the spray formation process. However, much further modification of the breakup model and initial conditions would be required to have a quantitatively good agreement between the calculation and measurement

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.