| The aerodynamic field in furnaces is an important factor determining the safe and economical operation. But all along, there's no a nonintrusive, real-time and online technique on measurement of the aerodynamic field in large-scale furnaces. For the present, generally the cold aerodynamic fields are measured in power or industrial boilers. In the measurements, the ribbons are mainly adopted together with the anemometer or hot-line anemometer. Since the traditional methods are intrusive and pointwise, there needs quite much expense, nevertheless with long time and low accuracy. However, the acoustic method is nonintrusive and full-field to measure the aerodynamic field in furnaces. Based on the reseach of the predecessors, the paper amplified and developed the theory on acoustic velocity field measurement. The primitive acoustic measurement system and method have been developed creatively for cold measurement. And with the system, the velocity field measurements are performed. The related reports haven't been found in the world, with only relavant theoretic research.Before the discussion on acoustic measuring the aerodynamic field in furnaces, an experiment on the traditional methods testing is carried out. The measured objection is a horizontal jet flow field of a newtype burner. By the practice of five-hole probe, PIV and simulation with CFD software, the faults of trandional techniques as well as the advantages are acquainted. Among the preceding methods, five-hole probe approach is immediate and relatively easy. But because of insufficient sensitivity, it can hardly measure the weak flow area. PIV method has perfect accuracy and sensitivity, however, it needs a great deal of work, and is particular at the measuring conditions. And for flow fields with difined conditions, CFD simulation can give detaild description. But it's hard to trace the real-time variation of flow fields for CFD. So, for the aerodynamic field measurement in real furnaces, it's requisite to find a new monitoring method that is more fit and advantageous.Sound wave is a kind of mechanical wave. Its propagation is effected by the attributes of the medium and the movement as well. This is the physical base of the acoustic measuring the aerodynamic fields in furnaces. Firstly, the measurement of a singular path in an air flow field by acoustic method is performed. This experiment can give an essential and direct argument of acoustic method used for measuring the air velocity field. By the practical situation, a relatively reasonable air flow field is designed. It is a proper linear interval taken in an open air jet flow from a horizontal circular tube. Acoustic and five-hole probe methods are used respectively to measure the flow field. The comparison between the results proved the feasibility of acoustic method for the measurement of the gas flow field.For the acoustic measurement of 2-D aerodynamic field in furnace, a right number of sound sensors are configured on the boundary of the measured field, and reticular sound projections are formed. By measuring the transit times of the sound waves in the reciprocal directions on the paths, the continuous velocity distribution can be reconstructed with a vector tomography algorithm. Regarding the simulation research, we firstly build up a simplified tangential flow field model. By calculation of the direct problem and reconstruction of the inverse problem, and also error analysis of different levels with the results, the performance and availability of the acoustic method in measuring the 2-D velocity fields is validated. Concerning the real tangential flow field, a reconstruction program of 2-D velocity field is developed. The program is examined with different degrees of phantom based on the preceding simplified tangential model. The result showed that the program is accurate and reliable to some extent, so it's promising to be used to reconstruct the real tangential aerodynamic field in furnace.Based on the simulating study, the cold model experiment is performed on the 2-D flow field measurement with acoustic method. For that, a bench-scale furnace model of 1.0m×1.0m×2.45m is designed and built. In the experiment, the flow fields under the symmetrical and unsymmetrical air-supply conditions are measured respectively by acoustic method. Both have relatively satisfactory results. As comparison, the first case is also measued with a hot-wire anemometer, and simulated by CFD as well. For the second case, only the CFD simulation is used. With the measurement simulation results, qulitive and quantitative analyses are given. It is proved that, under relatively stable air conditions, the acoustic measuring results accord well with those by the other two methods. The experiment shows the feasibility of acoustic measuring flow fields in furnace, and also the obvious superiority. It's prosperous to become an advanced and effective technique of aerodynamic field measurement, which is online and realtime. For the present, the measuring scheme of the acoustic system is each transducer emitting sound wave by turns, with about 5s for an integral measurement.As a prosperous monitoring technique of furnace aerodynamic field, the paper also discusses the impact factors and corresponding reforms with it for the measurement in hot furnace. What's more, due to its great characteristics, its use on the gas speed and the temperature distributions in the horizontal flue is also mentioned.
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