Nobuyuki Kawahara

The development of a light-collecting probe with high spatial resolution applicable to randomly fluctuating combustion fields

A high-luminosity-light-collection system for highly spatial detection of chemiluminescence of radical species in flames has been developed. The system, multi-colour integrated Cassegrain receiving optics (MICRO) is based upon a Cassegrain-type configuration, which implies that it employs only reflective components (in combination with an optical fibre for light collection). It provides therefore spherical- and chromatic-aberration-free detection, which is of importance for high-spatial-resolution measurements and for the simultaneous monitoring of signals in different wavelength regions from a given spatial volume. The effective light-collection volume has been estimated to be only 1.6 mm × 0.2 mm × 0.2 mm by ray-tracing techniques, which is more than three orders of magnitude smaller than that provided by a corresponding simple single-lens system and comparable to that of laser-based techniques, e.g. Doppler anemometry. The system is also easily aligned since the active probe volume can be visualized by sending in visible light through the system in the reverse direction. In order to demonstrate the performance of the system, OH-radical chemiluminescence in a Bunsen flame was monitored using MICRO and compared with the ion-current signal from a Langmuir probe with a minute sensor tip. A good correlation between the fluctuations in the two signals could be obtained, proving the high spatial and temporal resolution of the MICRO system.

Flux measurements of O2, CO2 and NO in an oil furnace

The flow velocity measurements and flux measurements of the gas species O2, CO2 and NO in an oil furnace were carried out. The velocity profiles in combustion and non-combustion were measured by the developed laser Doppler velocimeter, and the results show that the reversing flow regions for both cases were located at the same place and their volumes were almost equal. The comparisons of measured concentration and flux obtained using velocity and temperature were performed in spray combustion. The results show that there is little difference in the flame region but a large discrepancy outside the flame region. The generated gas species in the flame and their convection outside the flame were discretized, and the application of flux in spray combustion research was found to be very useful and effective.

In situ CO2 Concentration Measurement inside a Combustion Chamber Using Infrared Laser Absorption Technique

This paper describes the development and application of an optical fiber sensor using an infrared absorption technique to quantify the instantaneous CO2 concentration inside a combustion chamber. An in situ laser infrared absorption method was developed using an optical fiber sensor and a 4.301-Pm quantum cascade laser (QCL) as the light source. We discuss the feasibility of obtaining in situ CO2 concentration measurements inside the engine combustion chamber. Lambert–Beer’s law can be applied for the case of a single absorption line of CO2, and the dependence of the CO2 molar absorption coefficient on the ambient pressure and temperature of was determined using a constant volume vessel. This coefficient decreased with increasing pressure, saturating at pressures over 1.0 MPa. The newly developed CO2 concentration measurement system using QCL and optical fiber sensor allowed us to measure the CO2 concentration inside the combustion chamber.