Yoshisuke Hamamoto

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.

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.

Temperature measurement of end gas under knocking condition in a spark-igniyion engine by laser interferometry

Abstract Knocking is one of the most significant problems that limits the efficiency of an internal combustion engine. It is caused by autoignition of the unburned gas ahead of the flame. In order to understand the knock phenomenon, it is important to measure the temperature of the unburned gas. In this study, with polarization preserving fibers, the laser interference measurement of the unburned gas temperature was performed in a constant-volume and a specially designed engine which could be ignited only once. The engine was fueled with n- butane , oxygen and argon, and was operated under knocking conditions. When the density of the gas changes, the change of the optical path length of the test beam corresponds to the change of the refractive index. The temperature history of the unburned gas was determined by measuring the pressure and the change of interference signal. The optical fiber interference system had the advantage of resisting mechanical vibration because the test and reference beams were transmitted in the same optical fiber and were separated only in the test section.

Measurement of the temperature history of unburned gas before knocking in a spark-ignition engine using laser interferometry

It is very important to know the temperature history in a spark-ignition engine when the phenomenon of knocking is being studied. However, measurement of the gas temperature is not easy and some work has been done using laser diagnostics etc. In this study, the temperature history until the time of occurrence of knocking in a spark-ignition engine was measured by a form of laser interferometry designed especially for use in the combustion chamber. Not only the change in temperature but also the absolute value of the temperature could be determined with this interferometer, by utilizing the change of the gas density on the reference side. This is a non-intrusive measurement and high resolution is expected. The temperature resolution is about 5 K near the occurrence of knocking.

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.

Three-dimensional analysis for explosions of a propane-air mixture in cylindrical vessels

A mathematically simple spatial difference method has been applied for analysing three-dimensionally, and for illustrating graphically, the process of the development of a flame after the propane-air stoichiometric mixture is ignited. The calculated results show that the mathematical simulation can well express the process of mixture explosion in cylindrical vessels, and can evaluate the effects of laminar swirl flow on the flame development. It is concluded that the swirl motion deforms the flame front and accelerates the flame enlargement. Described also is a comparison of swirl flame calculation, with and without the centripetal effect caused by the difference in densities between burnt and unburnt gases.

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.

Temperature Measurement of End Gas under Knocking Condition in a S. I. Engine by Laser Interferometry

Knock is one of the most significant problems that limit the efficiency of an internal combustion engine. It is caused by autoignition of the unburned gas ahead of the flame. In order to understand the knock phenomenon, it is important to measure the temperature of unberned gas. In this study, with polarization maintaining optical fibers, the laser interference measurement of unburned gas temprature was performed in a constant volume vessel and a specially designed engine which could be ingited only once. The engine fueled with n-butane, oxygen and argon, was operated under knocking conditions. When the density of the gas changes, the change of the optical path length of test beam corresponds to the change of refractive index. The temperature history of the unburned gas was determined by measuring the pressure and the change of interference signal. The optical fiber interference system had the advantage of resisting mechanical vibration because test and reference beams were transmitted in the same optical fiber and were seperated only in the test section.

Ambient gas entrainment into a transient gas jet (visualization of surrounding air motion and an estimation of entrainment amount by path line method)

For the study of the combustion in a transient gas jet used in gas diesel engines, it is very important to investigate the entrainment process of the surroundings of the jet. In this study, a path line method utilizing a CCD camera with various shutter times was applied. Large (40μm), light weight micro-balloon particles are used for scattering the path lines of the surroundings and fine particles (0.75μm) are used for visualizing the approximate shape of the jet. The transient gas velocity was also measured with a two-component laser Doppler velocimeter. Consequently, (1) the jet shape and the entrainment process could be visualized simultaneously, and (2) this path line method was found to be very useful fot estimating the amount of entrainment air because of the good agreement with the value obtained using LDV data.