Mitsuru Inada

Industrial applications of temperature and species concentration monitoring using laser diagnostics

Industrial applications of laser diagnostics have been demonstrated for the purpose of clarifying combustor chemical reaction mechanisms, as well as temperature and harmful substance monitoring in large-scale burners and commercial plant exhaust ducts, and the combustion control of commercial plants. Laser induced fluorescence (LIF), laser induced breakdown spectroscopy (LIBS), and tunable diode laser absorption spectroscopy (TDLAS) have accordingly been applied in various industrial fields. In this study, temperature and species concentration were measured inside gas turbine combustors, a diesel engine, and a large-scale industrial burner using LIF. This technique introduces a new tool with respect to practical combustors for the analysis of NO formation characteristics, turbulent flame front structure, and differences between standard and improved combustors. On-line monitoring of trace elements to the ppb level was also successfully demonstrated using LIBS. The automated LIBS unit was found to be capable of monitoring trace element concentration fluctuations at ppb levels with a 1 min detection time under actual plant conditions. In addition, real-time measurement of O2 and CO concentrations in a commercial incinerator furnace was performed using TDLAS to improve the combustion control. By using the multiple-point laser measurement results to control secondary air allocation, higher secondary combustion efficiency was achieved, and CO concentration (considered to be a substitute indicator for dioxins) was reduced from 11.9 to 8.0 ppm.

Spray combustion characteristics in a highly pressurized swirl-stabilized combustor

Flame structure and droplet behavior in a swirl-stabilized gas turbine combustor at elevated pressure were investigated. The combustion chamber was specially designed and optimized for laser diagnostics, such as phase Doppler anemometry and laser-sheet visualization. Direct observation and CH* chemiluminescence measurements were used to investigate the flame structure and its dependence on ambient pressure. The setup parameters of phase Doppler anemometer were optimized for high-pressure flow field measurements and this considered the thickness of the optical windows and the refractive index of the ambient air in the combustor were taken into account, respectively. The parameter to be discussed in the study is the pressure dependence of droplet velocity, slip velocity, size distribution, and mass flux. This study concentrated on a spray pilot flame burner in order to have stable flame holding but reduce soot and NOx at elevated pressure, then we focused on flame shape, spray droplet size, and velocity, which were measured directly using a high-speed camera and phase Doppler anemometer (PDA). The pressure dependencies of these characteristics are discussed. Image analysis of flame shape indicated that the spray angle narrowed and the flame lengthened as ambient pressure increased. The same tendency was observed with the PDA measurements. The axial velocity difference was not very large, although the fuel flow rate was increased in the high-pressure condition. These results are due to centrifugal force and the variation in the size of the recirculation region within the hollow cone.

LIF Applications for Practical Combustors

This study demonstrates the applicability of LIF in several practical combustors. Temperature and species concentration were measured inside industrial model burners, gas turbine combustors, diesel engines, and large scale industrial burners. This visualization technique introduces a new tool for use with practical combustors for the analysis of NO formation characteristics, turbulent flame front structure, and differences between normal and improved combustors.

Investigation of Combustion Structure Inside Low NOx Combustors for a 1500°C-Class Gas Turbine

This paper describes the cold flow tests and low pressure combustion tests which were conducted for the development of a 1500°C-class low NOx combustion system. In the cold flow tests, the effect of vane angle and the momentum ratio of fuel to air flow on mixing characteristics inside the premixing nozzles was investigated. The stabilization of the flow field inside the combustor was confirmed by measurement of the axial velocity distribution and observations by using a tuft of soft thread.Combustion characteristics in terms of emissions and stability were investigated initially by low pressure combustion tests, and the gas temperature distribution inside the combustor was measured. NOx emissions for a 1500°C-class gas turbine as low as 50ppm at 15% oxygen at design pressure were demonstrated.Copyright

Development of Gas Turbine Combustors for Low BTU Gas

Large-capacity combined cycles with high-temperature gas turbines burning petroleum fuel or LNG have already been operated in large numbers in both domestic and foreign countries and have achieved good results. On the other hand, as the power generation technology utilizing coal burning the coal gasification combined plants are also under research. Since coal-gasified gas is lower in BTU and harder to burn than conventional fuel, development of this combustor is one of the important problems to be solved. To develop the combustor burning low BTU gas in our company, we have proceeded the study for blast furnace gas, i.e. by-product gas in the ironworks and have succeeded in practical use of the multi-can type combustor burning low BTU gas in the combined plant supplied to Chiba Works, Kawasaki Steel Corporation.

OH and NO Visualization Inside a Gas Turbine Combustor Using Laser-Induced Fluorescence.

This study demonstrates the applicability of 2D species visualization inside a gas turbine combustor using larer-induced fluorescence (LIF). Time-averaged and single-shot OH and NO distributions were analyzed to clarify the characteristics of the NO formation inside the combustor. The turbulent flame front was clearly seen using single-shot OH measurement to elucidate the burning pattern in the combustor. It became clear that NO was mainly produced near the pilot burner and that it tended to exist at the center of the combustor.