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A fiber optic infrared spectroscopic sensor was developed to measure the crank angle resolved residual fraction of burned gas retained in the cylinder of a four-stroke SI engine. The sensor detected the attenuation of infrared radiation in the 4.3 μm infrared vibrational-rotational absorption band of CO2. The residual fraction remaining in the cylinder is proportional to the CO2 concentration. The sensor was tested in a single-cylinder CFR spark ignition engine fired on propane at a speed of 700 rpm. The sensor was located in one of two spark plug holes of the CFR engine. A pressure-transducer-type spark plug was used to record the cylinder pressure and initiate the spark. The temporal resolution of the measurements was 540 μs (equivalent to 2.3 crank angle degrees) and the spatial resolution was 6 mm. Measurements were made during the intake and compression stroke for several intake manifold pressures. The compression ratio of the engine was varied from 6.3 to 9.5.

A piezoelectric sensor to measure the mass of fuel that impacts the piston top during injection in a direct injection spark ignition (DISI) engine was developed. The sensor used a 3.18 cm (1.25-inch) long, 0.318 cm (0.125-inch) wide piezo bending motor. The principle of operation is based on the change in natural vibration frequency that occurs to the cantilever piezo beam due to a change in its mass caused by the presence of liquid fuel on its surface. An electrical impulse is used to set the piezo element in vibration after which the natural vibrational frequency is measured using a FFT analyzer. The concept was evaluated outside the engine and calibrated for the frequency shift as a function of the weight of liquid on the bending element. The change in the frequency was found to be approximately proportional to the liquid mass on the sensor. The piston top of the engine was modified to accommodate the sensor on its surface.

A fiber optic infrared spectroscopic sensor has been developed to measure the time-resolved concentration of exhaust gas recirculated (EGR) into the intake manifold of an internal combustion engine. The sensor detects the attenuation of infrared radiation in the 4.3 μm infrared vibrational-rotational absorption band of CO2. The EGR mass fraction in the intake manifold is proportional to the CO2 concentration. The sensor was tested in a single-cylinder spark ignition engine fired on propane at a speed of 700 rpm. The sensor was located 10 cm upstream of the intake valve. The temporal resolution of the measurements was 700 μs (equivalent to 2.5 crank angle degrees) allowing the local EGR concentration throughout the cycle to be measured. Measurements were made with both real and simulated EGR. The EGR flows were introduced at various locations upstream of the probe.