Forced oscillating combustion can reduce nitrogen oxides (NOx) as described by the previous research. In this paper, we applied this method to two kinds of radiant tube burner in order to confirm the ...effect of NOx reduction. Fuel is supplied through a solenoid valve which is made open and shat several times a second with various duty ratios. Flow rate of the fuel, temperature of the furnace and air ratio are switched to investigate the effect. About 30% of NOx reduction is observed under acceptable performance of combustion and this method is proved to be applicable to many combustion appliances.
Planar laser-induced fluorescence(PLIF) using OH and NO facilitates noncontact two-dimensional temperature measurements, and is therefore expected to be an effective technique for combustion ...thermometry. However, the accuracy of the measurement has not been clarified. The relaxation in the upper rotational levels of the tracer molecule is not easy to be predicted, and the rotational dependence of the molecular constants, such as absorption and emission coefficient, has not been fully clarified. Furthermore, it is not confirmed whether the rotational distribution of the tracer molecule maintains the quasi-equilibrium states or not. In this study, we investigated the accuracy of thermometry by means of laser-induced fluorescence (LIF) using NO:A-X(0, 0)and OH:A-X(3, 0) excitation for a premixed methaneair laminar flame in atmospheric pressure as a measuring target. These were checked by narrow-band N2 CARS with high spectral resolution, which is believed to be the most reliable temperature standard in flames. NO LIF temperature showed several % lower temperature than N2 CARS one, and OH LIF temperature 30% lower. Both methods were calibrated under exponential dependence assumption of molecular constans, and the calibrated temperature of NO and OH LIF agreed well with N2 CARS one. Furthermore, two-dimensional thermometry in a flame cross section using calibrated NO PLIF was demonstrated.
To develop a high-performance combustor, diagnostics on combustion field is essential. Severalmeasurement methods based on laser techniques have been proposed, such as Laser Doppler Velocimetry (LDV) ...and Laserinduced Fluorescence (LIF). According to the advancement of the laser technology, these diagnostic techniques can be operated without difficulty and we have taken in and developed these techniques.They have been applied for investigation of problems of practical combustors, and for clarification of kinetic calculation of flames. In this paper, several examples of application of laser diagnostics on combustion and flow field in our works were introduced.
There was no method for non-contact thermometry on a solid surface in liquid. IR radiation thermometry cannot be applied because of radiation from liquid surface. A new method for non-contact ...thermometry on the solid surface in liquid was proposed in this paper. Thermo-graphic phosphor method was arranged for this purpose.
Thermographic Phosphor (TP) is optical measurement technique for 2-D temperature distribution on solid surface, using the dependence of a luminescence intensity. This technique requires the ...pre-measurement of the luminescence on a condition of known and uniform temperature. We develop a new technique named "Composite Termographic Phosphor". This method uses composition of a few kinds of phosphors, which have different color and different dependence of intensity on temperature. This article shows the examples of this method. The time resolution is μs-ms order, higher than typical TP measurement.
Two-dimensional mapping of CH, CN and NH intermediates in a turbulent flame cross section, which concerns prompt NO formation, has been obtained by the PLIF technique. These results are achieved ...under low concentration and low quantum yield conditions (that is, a CH4/air flame at atmospheric pressure), by drawing the potential of a high-sensitivity image intensifier capable of photon signal detection by optimizing both the excitation-detection scheme and the light-collecting optics. Thanks to these improvements, semi quantitative CH measurement has been achieved utilizing predissociation. In addition, 2-D imaging of CN (sub ppm) and NH (0.01-0.1 ppm) has been achieved by a single laser pulse in a CH4/air flame, showing that the record of low concentration species detection by PLIF has been improved by an order of 1-2. The authors believe that these visualization techniques will mean a great improvement in the prompt No formation diagnostics in flames.
Forced oscillating combustion can reduce nitrogen oxides (NOχ) emission, as described previous researches. In this paper, in order to estimate the effect on NOχ reduction, the concept is applied to ...two kinds of commercial burners for use in industrial furnaces. Natural gas is supplied through a set of solenoid valves, which are alternately made open and close at several times a second with various duty ratios, whereas preheated air from a recuperator is supplied at a fixed rate. Combustion products are sampled at the exit of recuperator and analyzed using a series of analyzers. It is found that about 30% reduction of NOχ emission is realized by introducing forced oscillation combustion into two kinds of industrial burners, exclusive of an operation of long turbulent jet flame.
Two-dimensional imaging of OH and CH intermediates in a premixed flame using natural gas bunsen burner by means of laser induced fluorescence techinique are described. A tunable laser beam with a ...single laser pulse energy of 1.5mJ is focused by a cylindrical concave lens, which forms laser sheet 5mm high and 0.5mm thick. We have chosen a band near 308nm : OH X2Π(υ=0)→A2Σ(υ=0) excitation and a band near 431nm : CH X2Π(υ=0)→A2Δ(υ=0) excitation. Fluoresence at a right angle is amplified by gated image intensifier and detected by CCD camera. A complete picture of qualitative distribution of OH and CH is obtained by combining several piuctures taken at a series of diffrent distances between the bumer head and laser sheet.
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