锅炉燃烧器外文翻译Word下载.docx

1、abstract: A novel spout structure which contains dual-gear rings （DGR） and double conical flaring （DCF） for swirling burner is proposed. Flow field outside the novel burner （DGRDCF burner） is studied in an unconfined environment comparing with a conventional one. The effects of DGR and DCF structure

2、s, secondary air distribution and swirling intensity on reverse flow and turbulence are discussed. Results suggest that the novel burner stabilizes reverse flow and enhances turbulence of the flow field under different air distributions and swirling intensities. The novel burner is further studied i

3、n a wall-fired pilot furnace. Gas temperature distribution, NO x emission and unburned carbon in the fly ash are researched. Higher ignition temperature near the burner spout and a more stable temperature field in the furnace is formed with the novel burner. Reduction of NO x emission and unburned c

4、arbon in the fly ash are achieved. The momentum ratio （M） of inner secondary air to outer primary air is defined to uniform the secondary air distribution. Increase of M raises the temperature level near the burner spout. NO x emission and the unburned carbon in the fly ash both attain their minimum

5、 with M = 4.428 in the experiment range. 2014 Elsevier Inc. All rights reserved.Keywords: Swirling burner、Spout structure、Flow、Combustion、Air distribution1. IntroductionCoal is the fundamental fossil energy source in the world. The pulverized coal burner is considered as an important combustion equi

6、pment which affects the coal combustion efficiency, safe and stable operation of boiler system and pollution emission. Researchers have done a lot of studies on coal combustion and pollution emission control, such as dense-dilute combustion, low-NOx burner, flow field organization , flue gas desulfu

7、ration and denitration. Because of its convenient adjustment, lower cost and important effect on combustion, swirling burner of pulverized coal is always a hot topic for thermal engineering researchers. Smart et al. presented the development of a coal fired precessing jet burner, the program of whic

8、h began in 1994 because of the further incentive for the utility boiler market, and were performed in depth in 1999. They studied the effect of precessing jet momentum ratio and gun position on NOx emission, heat flux and ignition distance in detail. The results showed a positive influence of the us

9、e of precessing jet on combustion characteristic. Costa et al. focused on the gas temperature and species in the burner region of a front wall fired boiler. They obtained temperature level in the burner region and NOx concentration above the boiler nose in 1997. The work provided a considerable effo

10、rt to minimum variations on boiler operating conditions and a reference for 3D mathematical model evaluation and development. Bollettini et al. operated a study on scaling of natural gas burners and integrated substantial experimental data from scaling 400 projects with CFD simulation in 2000. In 20

11、01 Milani and Saponaro introduced the dilute/flameless combustion technology and the high velocity burners, the emphasis of which is on fluid dynamic entrainment and mixing of flue gases. The temperature distribution of flameless combustion was different with conventional flame combustion and the NO

12、x formation was controlled. Nettleton studied the effect of swirling angels of secondary air stream on flame stability and suggested some explanation for the existence of stability limits in 2004. Gu et al. analyzed the relation among the NOx formation, gas flow and pulverized coal moving in a swirl

13、ing burner with numerical simulation. The authors found that the maximum particle penetration depth into the internal recirculation zone （IRZ） Ldav and effective time of IRZ eav lead to the minimum outlet NO emission. Chacn et al. developed a new methodology for the design and ptimization of a low N

14、O x -CO, natural gas burner by numerical simulation to comply with NO x emission limits of European countries . Jing et al. researched the effect rules of outer secondary air vane angels and primary air ratio on flow, combustion characteristic and NOx emission . Li et al. studied the furnace tempera

15、ture, heat flux and char burnout with double swirling flow burner at different loads.To improve both the combustion performance and NOx emission, optimizations of swirling burner structure for pulverized coal are proposed and studied continuously. The Babcock & Wilcox Company in New Orleans, LaRue a

16、nd Wolf proposed an improved burner with a splash plate, deflector and a diffuser to decrease the nozzle pressure drop and NO x formation in 1983. Babcock-Hitachi Kabushiki Kaisha in Tokyo provided a coal combustion apparatus for NOx reduction which comprises coal pipe, multi-air passageways and blu

17、ff body in 1985. Stein Industrie in France provided an axial conduit for feeding fuel in 1987, which is adjustable for varying the preliminary mixing chamber length and supports the ignition and combustion. The Babcock &Wilcox Company also in 1989 proposed a flame stabilizing ring and retractable ga

18、s element to create a low oxygen/fuel rich flame resulting in reduced NOx formation . Tenova also started in 2002 a research program, which led to a new family of low NOx burners named FlexyTechTSX based on the flameless technology which allows to reach a low NOx emission . Orfanoudakis et al. have

19、studied the effect of swirl number on flow and particle characteristic especially near internal recirculation zone （IRZ） in the near-burner region of a multi-fuel laboratory burner in 2005. Li et al. in 2008 made a comparison between an enhanced ignition-dual register （EI-DR） burner and centrally fu

20、el rich （CFR） swirling burner experimentally on combustion characteristic, and found that CFR burners have higher combustion efficiency, less NOx emission and more stable flame at low load in a 300 MW（e） wall-fired utility boiler. To burn low rank coal centrally-fuel rich swirling coal combustion bu

21、rner was proposed and studied both experimentally and numerically by Chen et al. They focused on the gas-particle flow analysis to control the gas temperature level and NOx formation. With development of measurement technology and numerical calculation, the investigations on swirling burners become

22、more comprehensive. Allouis et al. proposed a new diagnostic tool based on fast infrared imaging to test the combustion stability for burners and help adjusting flame. Khanafer et al. used computational fluid dynamics simulation coupled with chemical equilibrium calculation to analyze NOx formation

23、in swirling burners. All the studies on the swirling burner mentioned above have mainly focused on the effects of air distribution, swirling intensity and retrofit structures on combustion and NOx emission.However, little study of novel flame ring and flaring effect on the swirling burner, which hav

24、e significant impact on flow and combustion, has been reported. In this paper, a novel burner spout with dual-gear rings （DGR） and double conical flaring （DCF） is proposed as shown in Figs. 1 and 2. Cold air test and combustion experiment are carried out under different secondary air distributions,

25、swirling intensities and coal types. The flow characteristic, combustion performance and NOx emission are discussed. Comparing with a conventional one, the novel burner is proved to be helpful to obtain stable, efficient and clean combustion for pulverized coal.2. Novel burner modelThe proposed nove

26、l structures were installed on a radial dual register burner, which is geometric similarity with the ratio of 1:6 to the prototype, the dual register swirling burner of WGZ1246/18.-1 boiler made by Wuhan Boiler Group Co., Ltd. In China. DGR was set in the inner primary air pipe outlet in order to en

27、hance the turbulence and mixing of primary air and pulverized coal in the fuel-rich and oxygen-lean zone in Fig. 1. DCF was set on the outer primary air pipe, so as to induce outer primary air towards center recirculation zone and delay the mixing of secondary air and primary air as Fig. 2 shows. Th

28、e novel burner spout is expected to reduce the ignition heat and form a fuel-rich field near the spout in the ignition zone.Fig. 1. Design concept of DGR in inner primary air pipe （a） traditional inner primary air spout （up）; （b） DGR in the inner primary air spout （down）.Fig. 2. Design concept of DC

29、F on the outer primary air pipe （a） traditional spout（up）; （b） DCF spout （down）.3. Cold air test study3.1. Cold air test procedure and methodsDue to the limitation of flow field measurement under a practical combustion state, the isothermal modeling experiment is usually operated to study the flow c

30、haracteristic . According to the modeling principle , the air flow with more than 1.0105 of the critical Renolds number to second self-modeling zone was selected.A dimensionless coordinate is built with R and X in two directions for describing flow field position. R = r/d 3 , and X = x/d 3 , where r

31、 represents the radial distance off the central axis of the burner, x stands for the axial distance off the end of the burners jet, while d3 is the diameter of ISA duct.Two sets of measuring point arrays were introduced. A 631 array was set next to the burner spout in which the radial distance betwe

32、en two closed measuring points was D R = 0.1, while the axial distance was D X = 0.3. Meanwhile, a 529 array was set after in which D R = 0.2 and D X = 1.0. A 1050A type dual-channel hot wire anemometer with the range of 030 m/s and resolution of 0.01 m/s was used to measure velocity and turbulence instantaneously, while the direction of velocity was obtained by ribbon tracer method. The measurement error is 5% of indication or 0.025 m/s under the temperature range from 18 to 93.