Munenobu Tanaka

A Study on the Reformed-Methanol Engine

Selection of the optimum catalyst for the reformation of methanol, and static/dynamic characteristics of a spark ignition engine fueled with both gasoline and methanol reformed gas were studied. Tube test results on reforming characteristics show that a catalyst made of a base metal works best. A methanol reformer with an exhaust gas heat exchanger was used. Results show that the increase of reformed gas ratio increases the stability of combustion and extends the lean limit. It also improves thermal efficiency, owing to the reduced duration of combustion. Moreover, responses of Pmax during sudden opening/closing of the throttle valve were studied. Results indicate that the higher the reformed gas ratio, the quicker the Pmax response and the smoother the combustion process.

A study on corona discharge air mass flowmeter.

A very quick response air mass flowmeter for accurate measurement of intake air of internal combustion engines was developed. This flowmeter consists of a disk-type anode surrounded by two coaxial cylinders which serve as the first and second cathodes. Steady state flow tests show this flowmeter has sufficient accuracy, linearity, and directivity and no hysteresis is observed. The effects of temperature, pressure and humidity of the air are studied. For pulsating air flow, this flowmeter showed excellent dynamic response. Furthermore, this meter succeeded in measuring the intake air flow rate of a single cylinder spark ignition engine under firing conditions. Therefore, this flowmeter is very useful not only for analyzing transient characteristics of internal combustion engines but also for the accurate control of the fuel injection systems of gasoline engines.

A new double-cathode ionic air flowmeter for internal combustion engines

A very quick response air mass flowmeter for accurate measurement of intake air in internal combustion engines was developed. This flowmeter consists of a disk type anode surrounded by two coaxial cylinders which serve as the first and second cathodes, respectively. Steady state flow tests show this flowmeter has sufficient accuracy, linearity, and directivity and no hysteresis was observed. The effects of temperature, pressure, and humidity of the air were studied. For pulsating air flow this flowmeter showed excellent dynamic response. Furthermore, this meter succeeded in measuring the intake air flow rate of a single cylinder spark ignition engine under firing conditions. Therefore, this flowmeter is very useful not only for analyzing the transient characteristics of internal combustion engines, but also for the accurate control of the fuel injection systems of gasoline engines.

The Lean Hunting Phenomenon in Gasoline Engines - part 2

The hunting phenomenon which occurs at the lean air-fuel ratio and under light conditions was studied and it was disclosed that this was not mechanical hunting and the fuel flow delay into the cylinder had a dominant effect on this lean hunting. This paper first describes the experiments which demonstrate that such a fuel flow delay can occur by changing the throttle position sinusoidally in various periods, and that Pmax (the maximum pressure in the cylinder) responds quite differently according to the magnitude of the air-fuel ratio; and then describes the effects of ignition energy and ignition timing on lean hunting.

The lean hunting phenomenon in gasoline engines

A quite interesting self-excited oscillation phenomenon in engine speed, which may not be explained with the classical theory of mechanical hunting, is studied experimentally. The effects of the various engine operating variables on the phenomenon are examined using a four cycle single cylinder gasoline engine with an inertia governor. It was found that the phenomenon occurs when engines are operated at a lean air fuel ratio under light load conditions, and that the hunting phenomenon is ascribable to the temporary shift in air fuel ratio from the steady state value. This shift in air fuel ratio occurs due to the fuel flow delay into the cylinder caused by the fact that the fuel flow into the cylinder cannot follow the movement of the throttle valve.

The dynamic effect of intake pipe length on the air fuel ratio of a carburetor engine.

The air fuel ratio of a carburetor engine having a long intake pipe before the carburetor, changes dynamically with the engine speed. This paper clarified experimentally that this dynamic change in the air fuel ratio mainly comes from fluctuations in fuel flow caused by the pressure wave occurring in the intake pipe. These phenomena were simulated analyticlly by introducing a new parameter, and it was found that such a pulsation effect on fuel flow is predictable theoretically.

Pulsation Effects on the Air Fuel Ratio of Carburetor Engines

A significant wavewise change of air fuel ratio in line with the engine speed having a long intake pipe was studied experimentally and theoretically. The results show the pulsewise change in fuel flow plays the dominant role in the wavewise change in the air fuel ratio. It is found that this pulsewise fluctuation of the fuel flow forms an oscillation wave with both the amplitude and frequency becoming larger according to the engine speed resulted by the phase change of the pulsation wave in the intake pipe according to the engine speed. A modified frequency ratio of gas vibration in the intake pipe to that of engine intake stroke is proposed to explain this pulsation effect on the fuel flow and an effective simulator for this phenomena is established.