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.