Yoshishige Ohyama

Mixture formation of fuel injection systems in gasoline engines

Mixture formation technology for gasoline engine multipoint fuel injection systems has been investigated. The fuel injectors spray, the volatility of droplets floating in the air flow, the movement of droplets around the intake valves upper surface, the volatility of droplets on heated surfaces, and the process of atomizing droplets in the intake valve air flow was analyzed. Droplet diameters and spray patterns for good mixture formation without liquid film in cylinders have been clarified

ENGINE CONTROL USING COMBUSTION MODEL

The combination of physical models of an advanced engine control system was proposed to obtain sophisticated combustion control in ultra-lean combustion, including homogeneous compression-ignition and activated radical combustion with a light load and in stoichiometric mixture combustion with a full load. Physical models of intake, combustion and engine thermodynamics were incorporated, in which the effects of residual gas from prior cycles on intake air mass and combustion were taken into consideration. The combined control of compression ignition at a light load and spark ignition at full load for a high compession ratio engine was investigated using simulations. The control strategies of the variable valve timing and the intake pressure were clarified to keep auto-ignition at a light load and prevent knock at a full load.

A study on the oxygen-biased wide range air-fuel ratio sensor for rich and lean air-fuel ratios

Abstract Using computer simulations and experiments, we have studied a method of meausring automobile air-fuel ratios over a wide range from rich to lean. The method utilizes the oxygen pumping action of solid oxide electroyte in an air-fuel ratio sensor. The air-fuel ratios were experimentally confirmed as being measurable from 0.8

High Performance Engine Control System

The basic structure of a new engine control system for highly accurate air-fuel ratio control is introduced. Improved engine power and decreased fuel consumption are required for todays engines. Better air-fuel ratio control must be attained to set the air-fuel ratio to that of the maximum power and minimum fuel consumption. In order to enhance the accuracy of the air-fuel ratio control, the air flow meter, air-fuel ratio sensor, and fuel supply device are improved in the new system. Accuracy is lost in conventional system owing to the sensors deterioration over long-term use. So prevention of air flow meter deterioration and compensation of air-fuel ratio sensor deterioration are taken into consideration. Fuel atomization of the fuel supply device is improved in order to reduce the air-fuel ratio fluctuation in the transient operating state. High power and decreased fuel consumption over long-term use are made possible with the new system.

ANTI-DIRT PROPERTY OF HOT-WIRE AIR FLOW METER

Hitachi has recently developed a hot-wire air flow meter which uses a temperature-sensitive resistor of an extremely thin platinum wire wound around a ceramic bobbin and coated with glass. This temperature-sensitive resistor, or a hot wire, is located in a bypass of the intake air passage of an engine and responds exactly for the effective control of engine operation. The flow meter of this construction is sturdy enough to withstand impacts of backfires and vibration and reduces variation in engine output characteristic likely to be caused by dust and dirt present in the intake air. Furthermore, this device requires no cleaning or other maintenance.

Engine control using intake and combustion models

The combination of physical models to produce an advanced engine control system is proposed as a means of obtaining sophisticated combustion control in ultra-lean-burn internal combustion engines, including homogeneous compression ignition and active radical combustion.

Measurement of In-Cylinder Air-Fuel Ratio at Early Combustion Stroke Using an Optical Combustion Sensor.

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.

Pulsating Flow Characteristics of Hot-Wire Air Flow Meter for Gasoline Fuel-Injection System

Pulsating flow characteristics of hot-wire air flow meters for gasoline fuelinjection systems were investigated to analyze simple methods of measuring data processing. It was clarified that backward flow components due to pulsation are detected as forward flow by the probe in the conventional meters, increasing errors. The errors due to pulsation can be reduced by using a meter with a hot-wire probe located in a bypass passage, compensating aerodynamically forward and backward flow components.

The atomization characteristics of a vibration type atomizer when fuel is supplied intermittently.

The atomization characteristhcs of an atomizer of the ultrasonic vibration type are investigated when fuel is supplied intermittently to the vibration member. The interval time of the liquid supply is 100ms and the supply period is varied from 5ms to 20ms. The mean diameter, velocity, and flow rate of the spray are measured by a phase doppler-type analyzer. The velocity is 0.2-1.0m/s and the mean diameter is 70-90μm. When the fuel is supplied intermittently to the vibratory member, the large size droplet is generated initially. The droplet size is reduced by improving the vibratory member shape and controlling vibration.

An analysis of hollow cone spray patterns.

A study was conducted on hollow cone spray which was injected from a pintle-type and swirl-type injector. The effects of the surrounding pressure and liquid temperature on the spray patterns are discussed experimentally and analytically. The calculated results which are based on the hollow cone spray model including the effects of surface tension, centrifugal force and liquid density almost coincide with the experimental results.