Shoshi Shimizu

Instantaneous measurement of two-dimensional temperature and density distributions of flames by a two-band-emission-CT pyrometer

Because temperature is one of the most important factors influencing combustion reactions, a variety of temperature measurement methods have been developed for burnt gas. Infrared radiation pyrometry using water vapor or carbon dioxide, which are present in high density in a burnt gas, has a long history. However, these classical methods can measure only a mean temperature or step-wise temperature distribution of several segments along an optical path. Due to the severe demand for cleaner and more efficient combustion, more detailed temperature information is required. Computed tomography (CT) applied to radiation methods (same as X-Ray CT in medical use) enables measurement of a two-dimensional temperature distribution. The authors have developed several types of infrared CT pyrometers. Because CT methods generally take a long time to obtain projection data, it is thought that they are not applicable for high speed unsteady combustion. In this report, a two-band-emission-CT pyrometer, which was developed by the authors, is further developed to enable time-resolved measurement. An algorithm and optical configuration is introduced for fan-beam scanning. The accuracy is then investigated. The experiment was performed using only one optical unit as a preliminary investigation using a jet flame with good reproducibility.

Simultaneous Measurement of Temperature and Density of Burnt Gases by an Infrared Radiation Computed Tomography

An iterative method which can compensate the influence of absorption of radiation was introduced into an infrared computed tomography for simultaneous measurement of both temperature and density of self-radiating gases. The characteristics of the method are investigated by simulations and experiments. A feasibility to develop this method into the measurement of transient phenomena is suggested.

Measurement of 2-D temperature distribution by a two-band-absorption-CT using statistical model for the spectra of H2O bands

Because temperature is one of the most important factors influencing the mechanisms of combustion processes, a variety of methods have been developed to measure flame temperature. Recently, a strong, need to measure two-dimensional temperature distribution of gases has arisen. The CT method can be one of the answers to meet this demand and many types have been published. The authors have developed two types of infrared CT which employ emission energy from gases. Their accuracies are superior in high temperature regions, but are insensitive in low temperature regions. In this report, CT is adapted to the infrared-two-band-absorption method which uses H 2 O as an absorption medium. The signals are affected by humid air along the optical path outside of the object, but, in compensation, the method has a very wide range of measured temperatures (from room temperature to that of a flame) because it uses absorption signals and employs H 2 O which is very common, not only in a flame region, but also in the vicinity of the flame. The statistical model and Curtis-Godsons method are employed to accurately estimate the absorption spectra of H 2 O bands of a nonhomogeneous optical path, but they cannot be applied directly to CT. An iteration method, which includes compensation of the effect of humidity of the surroundin air, is presented to overcome this difficulty. The dependence of accuracy on the temperature was analyzed theoretically prior to the analysis of CT, and it became clear that the accuracy is higher in the lower temperature region. Reconstructed temperature distributions for the data generated, by both computer simulation and experiment, showed that the iteration method can solve the difficulty of the complicated form of the statistical model and Curtis-Godsons method. The algorithm presented in this paper is applicable for flames of long optical depth, even when surrounded by humid air.

A method to reduce the pressure wave intensity caused by a shock wave radiated from a duct

Modern trains, such as the Shinkansen (Superexpress train in Japan) or TGV (France), pass through long tunnels at such high speed that a pressure or weak shock wave generated by the nose of a train causes a huge booming sound at the exit of the tunnel. The intensity of the noise increases with the speed of train and with the length of the tunnel. This noise is becoming to be one of the bottlenecks to increase the capacity of transportation. This report deals with a method to control a shock wave traveling in a rectangular duct to simulate a tunnel. A density gradient decreasing from the bottom wall of the tunnel toward the top, is created in the gas just before the exit of the duct so that the direction of shock wave propagation will be bent toward the bottom where the density is the highest. The behavior of the pressure wave is investigated by both computer simulation and experiments using a model duct, and a simple method is tried for absorbing the higher pressure wave at the bottom surface of the model duct.