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To get accurate indicator diagrams without the use of pressure transducers, the strain and the displacement of the various parts of engine structures that would have some relationship with the pressure variation in the cylinder were measured and analyzed mathematically. By measuring the strain of the cylinder head bolts, the horizontal displacement of the crank shaft end, and the vertical displacement of the intake valve stem, we realized that the indicator diagrams could be obtained easily without a passage from the interior to the outside of the combustion chamber. Accurate indicator diagrams were estimated by applying the pressure-strain diagram obtained from the static pressure test in the cylinder to the strain variation in the cylinder head bolts. On this occasion, the accuracy of the estimated indicator diagrams could be improved by providing the cylinder head system with a one degree freedom vibration system.

A critical factor in improving performance of crankcase-scavenged two-stroke gasoline engines is to reduce the short-circuiting of the fresh charge to the exhaust in the scavenging process. To achieve this, the authors developed a reciprocating exhaust control valve mechanism and direct air-fuel injection system. This paper investigates the effects of exhaust control valve and direct air-fuel injection in the all aspect of engine performance and exhaust emissions over a wide range of loads and engine speeds. The experimental results indicate that the exhaust control valve and direct air-fuel injection system can improve specific fuel consumption, and that HC emissions can be significantly reduced by the reduction in fresh charge losses. The pressure variation also decreased by the improved combustion process. CRANKCASE SCAVENGED two-stroke gasoline engines suffer from fresh charge losses leading to poor fuel economy and it is a reason for large increases of HC in the exhaust.

This paper presents results of experiments to reduce smoke emitted from direct Injection diesel engines by strong turbulence generated during the combustion process. The turbulence was created by jets of burned gas from an auxiliary chamber installed in the cylinder head. Strong turbulence, which was induced late in the combustion period, enhanced the mixing of air with unburned fuel and soot, resulting in a remarkable reduction of smoke and particulate; NOx did not show any increase with this system, and thermal efficiency was improved at high loads. The paper also shows that the combination of EGR and water injection with this system effectively reduces the both smoke and NOx.

This paper presents a theoretical and experimental study on the possibility of combustion similarity in differently sized diesel engines. Combustion similarity means that the flow pattern and flame distribution develop similarly in differently sized engines. The study contributes to an understanding and correlating of data which are presently limited to specific engine designs. The theoretical consideration shows the possibility of combustion similarity, and the similarity conditions were identified. To verify the theory, a comparison of experimental data from real engines was performed; and a comparison of results of a three dimensional computer simulation for different engine sizes was also attempted. The results showed good agreement with the theoretical predictions. THE PURPOSE of this research is to determine the possibility of the existence of combustion similarity in differently sized diesel engines, and to propose conditions for realizing model experiments.

Experiments on a large number of soluble fuel additives were systematically conducted for diesel soot reduction. It was found that Ca and Ba were the most effective soot suppressors. The main determinants of soot reduction were: the metal mol-content of the fuel, the excess air factor, and the gas turbulence in the combustion chamber. The soot reduction ratio was expressed by an exponential function of the metal mol-content in the fuel, depending on the metal but independent of the metal compound. A rise in excess air factor or gas turbulence increased the value of a coefficient in the function, resulting in larger reductions in soot with the fuel additives. High-speed soot sampling from the cylinder showed that with the metal additive, the soot concentration in the combustion chamber was substantially reduced during the whole period of combustion. It is thought that the additive acts as a catalyst not only to improve soot oxidation but also to suppress soot formation.

This paper uses NO Reaction Kinetic to determine NO formation characteristics in diesel engines. The NO formation was calculated by Extended Zel'dovich Reaction Kinetics in a diffusion process. The results show that the NO formation rate is independent of the mixing of the combustion gas, and that internal EGR (combustion gas mixing in a cylinder) has no effect on NO reduction. The paper also shows the potential of two stage combustion, and its effect strongly depends on the time-scale of mixing. Additionally the paper investigates the mechanism of increased NOx emissions in high pressure fuel injection.

This paper presents experimental results of the reduction of both particulate and NOx emitted from direct injection diesel engines by a two stage combustion process. The primary combustion is made very rich to reduce NOx and then the particulate is oxidized by strong turbulence generated during the secondary combustion. The rich mixture is formed by low pressure fuel injection and a small cavity combustion chamber configuration. The strong turbulence is generated by a jet of burned gas from an auxiliary chamber installed at the cylinder head. The results showed that NOx was reduced significantly while maintaining fuel consumption and particulate emissions. An investigation was also carried out on the particulate reduction process in the combustion chamber with the turbulence by gas sampling and in-cylinder observation with an optical fiber scope and a high speed camera.

Lean-burn engines now being developed employ in-cylinder injection which requires high pressures and so necessitates expensive injection equipment. The injection system proposed here is an air assisted in-cylinder injection system which is injecting a mixture of air and fuel in the cylinder during the intake stroke and allowing atomization at lower injection pressures than those necessary in compressing fuel with a usual solid injection. This time, the experiments used a testing engine of a 4 stroke gasoline OHV type replacing the Side Valve type. Performance with a small depression in the main combustion chamber was investigated with a spark plug and reed valve installed in the depression. The engine was operated then following the same method as last year (SAE 982698). As a result, the lean burn method employed here was possible over a wide range of engine speeds and loads. Moreover, it was also shown that this operation was possible with a fully opened throttle valve.

In the present work, an attempt was made to predict engine noise from the shape of the burning rate curve. Thus, the influence of the shape of the burning rate curve on engine noise, especially on combustion noise was studied in detail and clarification of the relationship was successfully made. At first, an approximation of burning rate curve using a function was attempted. And in second, the transfer rate from cylinder pressure to combustion noise was obtained. Then, the relation between the deciding parameters of burning rate curve and noise and performance of engine were studied.