Although the relationship between luminous intensity of radicals and equivalence ratio φ has been investigated, the previous works underestimates an influence of high combustion pressure. The experiment was conducted by applying different initial charge pressure in the constant volume chamber and by changing φ. The result obtained indicates clearly that the luminous intensity for both CH, C₂, and OH radical changes increases exponentially as the combustion pressure increases regardless of φ. Therefore each radical intensity can be approximated as a function of combustion pressure. It shows that luminous intensity of C₂ radical is strongly influenced by the value of φ than that of CH, OH radical, especially in lean mixture state. It is verified that the measurement of φ can be accomplished using the ratio of luminous intensity of CH and C₂ radical, and combustion pressure. The value of φ was estimated and compared with the actual value; the accuracy was about ±5%.

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Achieving the expected future exhaust emission and fuel consumption standards for passenger cars will require fundamental improvements in the combustion process for spark ignition engines. Improvements must be made in the fuel-injection device based on precise studies of the engine-combustion process. Real-time measurements of light emission from inside the cylinder in an actual automotive engine are currently very few. In this paper, a real-time method utilizing an optical combustion sensor that combines fiber optics with a conventional spark plug is presented. The incylinder air-fuel ratio of the flame at an early combustion stroke is measured by means of spectroscopy of the combustion luminosity in not only the steady but the transient state. The fuel-injection device is evaluated in terms of these measured parameters.

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排ガスの瞬時燃料消費量を簡便かつ高速応答で計測する手法を提案する．この手法は超音波方式の排ガス流量計と直挿型O₂センサによる測によって実現した．高い応答速度で，配管内同位置の直接計測を行うことにより時間遅れや応答遅れの影響を受けずに計測を行うことができ，従来計測法との高い相関性を確認できた．

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This paper describes the design and operation of an excess air-ratio sensor, with an electrically heated solid oxide electrolyte, for internal combustion engines. To minimize the exhaust-gas temperature dependence, electrodes are provided only in the heated region with an electrolyte thickness of 1 mm. The heater is controlled to maintain a constant internal resistance of the electrolyte. With this new sensor, the λ range of 0.5 to 1.6 can be covered with sufficient accuracy in the exhaustgas temperature range of 655 K to 850 K.

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In the reciprocating engine with multi-cylinders, estimation of cylinder imbalance characteristics is an important issue for online balancing control in order to obtain high quality torque generation and reduce emission. This paper addresses the individual cylinder A/F estimation with single sensor and control problem. First, a simple model is proposed that provides an estimation of the individual cylinder A/F with multiple sampling data of the single sensor during a cycle. Then, using the model-based estimation, a feedback control approach is shown that is cycle-based PI regulation with the fuel injection as control input. Finally, experimental results carried out on an engine testbench are demonstrated to validate the estimation and the control effectiveness.

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This report explained the local equivalence ratio (air fuel ratio) measurements of engine exhaust gas and direct fuel injection in engine cylinder using laser-induced breakdown spectroscopy (LIBS) and sparkinduced breakdown spectroscopy (SIBS). When we use LIBS/SIBS in combustion system, we can discuss simultaneous laser/spark ignition and equivalence ratio measurement of premixed mixture. The intensity ratio of H/O or H/N showed a good agreement with preset equivalence ratio in engine exhaust gas and premixed mixture in engine cylinder. The influence of spark discharge characteristics on emission spectra was investigated by simultaneous measurement of spark discharge visualization and spectroscopy. The relationship between air-fuel ratio and the emission intensity ratio was obtained in premixed gas combustion in a spark ignition engine. There was a tendency that local air-fuel ratio decreases with advance of the injection timing from the fixed ignition timing. It was observed that spark discharge was affected by the flow due to injection. LIBS/SIBS is very good tool to discuss the combustion characteristics in real engine researches.

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Exhaust emission characteristics in-use of DPF fueled with biodiesel fuel was investigated by continuous measurement of exhaust gas. The DPF used for the tests was a wall-flow type and was made of SiC that the regeneration was completed by batch heating with electric power. From the experimental results, it was found that the spiky peak of CH_3OH was emitted at high engine load. Its level was reduced at a self-regeneration of DPF by biodiesel fuel with lye catalyst

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The object of this research was developing the method of measuring and calculating the internal exhaust gas recirculation (EGR) rate under the internal EGR by means of the intake valve timing control in a direct injection (DI) diesel engine. The obtained results were as follows ; (1) The Internal EGR rate was more exactly calculated by the measuring of the oxygen concentration change during a cycle in the intake port using the oxygen concentration sensor. (2) Considering EGR by the valve overlap under this measuring method, the larger the internal EGR rate becomes, the larger NO_x reduction rate.

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The object of this research was clarifying the engine performance, exhaust gas emissions and combustion characteristics, and developing the method of measuring the rate of internal exhaust gas recirculation (EGR) under the internal EGR in a direct injection (DI) diesel engine. The obtained results were as follows; (1) The rate of internal EGR was exactly measured by the oxygen concentration sensor, and the variation of internal EGR rate in each cylinder was clarified. (2) The internal EGR has the large effect of NOx emissions reduction because the combustion temperature is reduced by means of the increase of heat capacity in a cylinder gas.

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Methanol has emerged as a near-term alternative to hydro-carbon fuel. On the one hand, in Japan, LPG fuel has been utilized for the Taxi as an alternate to gasoline in respect of economy. This paper reports a comparison of methanol and propane as LPG fuel to base gasoline on S. I. engine performance. The results obtained are as follows: (1) the compression ratio is as high as 12:1; the maximum methanol and propane engine output is higher by approximately 20% and 8% respectively than the base gasoline engine. (2) brake thermal efficiency of the methanol and propane engine is better than the base gasoline engine, but the difference becomes smaller as the engine output becomes lower. (3) engine out emission level of methanol fuel are lower than gasoline, especially for NO_x and THC; but the NO_x level of propane fuel is higher than that for gasoline.

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The high thermal efficiency is established by increasing the compression ratio while the engine is operated in SI engine. In order to suppress knocking, the octane number of the fuel is raised by partially cracking the hydrocarbon molecules. Concept that onboard fuel reforming system utilizing waste heat produced from engine is practically effective on the high thermal efficiency. In this study, the fuel reformer was tentatively constructed and the fuel component was measured with GC-MS. The primary reference fuel 90(PRF90) was used as the test fuel. It was found that the fuel was partially cracked into small size hydrocarbons such as ethylene and propene. This fuel was supplied to the test engine, which was a 4-cylinder, 2-litter, turbo gasoline engine and the compression ratio was modified to be 12. The thermal efficiency increased by approximately 4〜6%.

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This paper describes the results of on-board measurement of engine performance and emissions in D.I. diesel vehicle operated with waste-cooking oil bio-fuel. Here, two waste-cooking oils were investigated. One fuel is the waste-cooking oil methyl esters. This fuel is actually applied to the garbage collection vehicle with D.I. diesel engine (B100) and the city bus (B20; B100 is mixed 20 vol.% in gas oil) as an alternative fuel of gas oil in Kyoto City. Another one is the raw waste-cooking oils removed impurities. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixing fuel (i-BDF) is applied into several tracks and buses in Wakayama City. It is confirmed that PM emission of biodiesel fuel is remarkably lower than that of gas oil. And PM emission in summer increases comparing with that in autumn. On the contrary, NOx emission in summer is lower than that in autumn.

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An experimental study was made on a natural gas fueled spark ignition engine to improve its thermal efficiency and exhaust emissions by the lean burn operation. A multi-cylinder engine was tested for purposes of practical application. Investigated were the effects of the piston design and the gas motion induced by a shrouded inlet valve on the combustion process, the thermal efficiency, exhaust emissions and the lean limit of stable operation. It was found that a bowl-in-piston resulted in higher thermal efficiency and extended lean limit as compared with a flat piston. A shrouded inlet valve generally resulted in shorter duration of combustion, lower NO_x emissions and lower thermal efficiency than a conventional valve. When a shrouded inlet valve was set so as to direct the mixture flow toward the prechamber throat, the lean limit was extended with low exhaust emissions and relatively high thermal efficiency.

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Smoke emission from single-cylinder DI and IDI diesel engines was found to strongly depend on oxygen content in the fuel regardless of the oxygenate molecular structure. Thus, various kinds of oxygenate were assessed based on blending properties with commercial diesel fuel and potential cost. The combined use of cetane improver with glycol ether oxygenate reduced the amount of particulate, HC, and CO emission, but not that of NO_x. The oxygenate seldom affected deterioration of fuel system rubber of the vehicle and storage stability.

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