Sadami Yoshiyama

Measurement of hydrocarbon fuel concentration by means of infrared absorption technique with 3.39 μm HeNe laser

Abstract The infrared absorption technique with a 3.39 μm HeNe laser is useful for measuring hydrocarbon concentrations. First, molar absorption coefficients of propane or methane for the 3.39 μm wavelength were investigated in the temperature range of 285–420 K and in the pressure range of 100–800 kPa. It was found that the molar absorption coefficient, ϵ, is independent of temperature, and that pressure has little effect on ϵ in propane, but a strong effect in methane. Second, by applying this technique to a spark ignition engine, the fuel concentration in the vicinity of a spark plug and the hydrocarbon concentration in the exhaust pipe were measured under the c conditions of no residual gas and homogeneous mixture. For the lean mixture, although cycle-to-cycle fluctuation of the fuel concentration was very small, the fluctuation of pressure in the cylinder was large.

Ion current measurement in a homogeneous charge compression ignition engine

Abstract An ion current probe using a spark plug was applied to gasoline-fuelled homogeneous charge compression ignition (HCCI) combustion with hot residual gas in order to verify the possibility of using it as a combustion sensor. The ion current signal for single-cycle HCCI combustion had a simple profile and effectively one maximum value. There is a possibility that a similar ion current signal corresponding to the completed reaction can be obtained, depending on the location of the probe during HCCI combustion. The ionization reaction for HCCI combustion is affected by the chemical ionization reaction with heat release, and there is a possibility that the ion current can be used to detect heat release corresponding to the chemical ionization reaction. A strong correlation between the timing of the integrated ion current and the timing of the mass fraction burned is observed. The timing of the mass fraction burned is assumed from the timing of the integrated ion current, and the mass fraction burned (up to 70 per cent) can be determined, even if the engine driving condition changes within the scope of the test. There is a correlation between the timing of the maximum ion-current and the maximum rate of heat release, and there is a possibility that the maximum value of the rate of heat release can be inferred by detecting the timing of the maximum ion current. There is a correlation between the timing of the maximum ion current and the timing of the maximum pressure at each cycle. Therefore, it may be possible to monitor the variation of the HCCI combustion phasing.

In-situ fuel concentration measurement near spark plug in spark-ignition engines by 3.39 μM infrared laser absorption method

Recently, improving the thermal efficiency and reducing the exhaust emissions of internal combustion engines have become crucial. To this end, it is important to determine the fuel concentration in the vicinity of the spark plug near the spark timing, because initial combustion affects the subsequent main combustion in spark-ignition engines. In this study, a fiber optic system linked to an optical sensor installed in the spark plug, by means of which light can pass through the combustion chamber, was developed to determine the fuel concentration near the spark plug using an IR absorption method. A He−Ne laser with a wavelength of 3.39 μ m that coincides with the absorption line of hydrocarbons was used as a light source. By exchanging an ordinary spark plug for this spark plug with the optical sensor, successive measurement of fuel concentration before the spark timing near the spark plug was performed in a port-injection spark-ignition engine fueled with iso-octane under the firing condition. The effects of pressure and temperature on the molar absorption coefficient of fuel were clarified in advance. The air/fuel ratio averaged for many cycles near the spark plug with this optical system agreed with that measured with a buret, which represented the mean value averaged over a protracted period. Next, this sensor was applied to determine the air/fuel ratio quantitatively in a direct-injection gasoline engine. As a result, it was clarified that the air/fuel ratio and its standard deviation near the spark plug have a strong relationship to stable engine operation.

Combustion diagnostics of a spark ignition engine by using gasket ion sensor

A new technique for combustion diagnostics of a spark ignition engine was developed. In this method the ion sensor with the circular configuration was installed into the cylinder head gasket. This sensor is expected to be applied for production engine. The signal measured by the ion sensor was similar with that of cylinder pressure. The peak timing of Ion current was consistent with the peak timing of pressure. There was a strong correlation between IMEP and the peak timing of ion current. This sensor is available to detect combustion quality in a spark ignition engine.

Measurement of fuel concentration distribution of transient hydrogen jet and its flame using planar laser induced fluorescence method

Abstract It is necessary to know the concentration field of fuel spray or jet because the combustion process strongly depends on it. Recently, the planar laser induced fluorescence (PLIF) measurement has been often used to clarify the two-dimensional concentration field. In this study, diacetyl was used as a fluorescence tracer. At first the basic characteristics of fluorescence were discussed. Next, the PLIF measurement was applied to investigate the concentration distribution of a transient hydrogen jet. Each jet shows a different configuration and concentration distribution, although the averaged jet shows axisymmetric results. The fuel concentration was also measured in the flame jet.

The interdependency between the maximal pressure and ion current in a spark-ignition engine

An experimental investigation on the interdependency between the maximal pressure and ion current in a spark-ignition engine was conducted in this work. Eight ion current sensors were located centrally symmetric in a gasket between the cylinder and its head. The measurements of the ion current and the start timing, peak timing and end timing of the ion current were compared and the optimized interdependency between the maximal pressure and characteristic parameter of ion current was investigated. Experimental results show that the peak timing and the end timing of the ion current depend strongly on the start timing of the ion current for each ion sensor. The interdependency between the maximal pressure and start timing detected from the sensors near the intake port is better than that of the exhaust port. Furthermore, interdependency between the maximal pressure and average start timing from sensors 3 to 7 were found to give the best performance regardless the engine test conditions. The maximum pressure and average start timings were found to vary inversely with increasing intake pressure, ignition timing and excess air fuel ratio.

Analysis on Pattern of Heat Release Rate in Two-Stroke Slow Speed Diesel Engine

In order to estimate the combustion process from the rate of heat release in two-stroke slow-speed diesel engines with side fuel injection type for marine use, it is necessary to grasp characteristics of the rate of heat release data under various engine conditions. Systematic measurements were carried out on assignment of the experiment design method with four parameters using a test engine. As a result, the characteristics of the three important values in the rate of heat release: combustion period, peak height, and period up to the peak could be obtained, depending upon mean effective pressure, engine speed and the four control parameters of engine performance. In particular, it was found that the peak in height does not change with increasing mean effective pressure over a certain level and double peaks can be seen under some fuel injecting conditions.

Turbulent Premixed Flames in a Spark-lgnition Engine. (Study by Analyzing Ion-Current Waves).

In a pentroof type combustion chamber of spark-ignition engine, a tumbling flow is broken down to small scale eddies near the top dead center in compression stroke and promotes the flame propagation. The effects of tumbling flow and its turbulence on combustion were investigated by analyzing combustion pressure and ion-current wave form. The number of peaks of ion current wave N^-p increases with the increase in turbulence intensity. The mean rate of heat release in the early stage of combustion increases linearly with the increase of N^-p. The spacing of flamelet surfaces in burning zone of turbulent flame decreases with the increase in turbulence intensity.

Fractal characteristics of turbulent premixed flames in an engine cylinder

The cross-sectional images of turbulent premixed flames of homogeneous fuel-air mixture in an engine cylinder were obtained by a laser tomography, and the fractal characteristics were investigated. It was observed that in an engine cylinder under high pressure condition, the turbulent flame was a smaller and more complicated structure, comparing with that under the lower pressure condition in a closed combustion chamber. The fractal dimension increases with the increase of the turbulence intensity and mixture density. The fractal dimension is expressed as a function of the increase ratio of mixture density and the ratio of turbulence intensity to laminar burning velocity. The inner cutoff scale of turbulent flames is expressed as a function of Karlovitz number.