Analysis and Research on Guiding Cone Angle Parameter of Spray Fan-Pipe

Transcription

1 Internatonal Journal of Flud Mechancs & Thermal Scences 2016; 2(3): do: /.fmts ISSN: (Prnt); ISSN: (Onlne) Analyss and Research on Gudng Cone Angle Parameter of Spray Fan-Ppe Zhang Faun *, Zhang Feng, Yang Xanwe, Yang Jnggn, L Lnz College of Mechancal & Power Engneerng of Chna Three Gorges Unversty, Ychang, Chna Emal address: doctorzyy@126.com (Zhang Faun), @qq.com (Zhang Feng), @qq.com (Yang Xanwe), @qq.com (Yang Jnggn), @qq.com (L Lnz) * Correspondng author To cte ths artcle: Zhang Faun, Zhang Feng, Yang Xanwe, Yang Jnggn, L Lnz. Analyss and Research on Gudng Cone Angle Parameter of Spray Fan-Ppe. Internatonal Journal of Flud Mechancs & Thermal Scences. Vol. 2, No. 3, 2016, pp do: /.fmts Receved: September 28, 2016; Accepted: October 29, 2016; Publshed: November 30, 2016 Abstract: Gudng cone angle s an mportant parameter n the desgn of the spray fan, the dfference of gudng cone angle has a sgnfcant mpact on the spray effect and servce lfe of the fan. Based on ths, the numercal smulate of flud-sold couplng for the pan s carred out by usng the RNG k- model, turbulence equatons and SIMPLEC algorthm, then analyze the fan s changes of the flow feld and structural under the dfferent cone angle. Smulaton results show that wth the ncrease of the cone angle, the pressure and speed of the flow feld, the stress and stran of the blade also ncreased, but when t over a certan angle, the result wll decreases. Further analyss shows when the gudng cone angle of the fan s 20, the performance of the fan s optmal. The results of ths analyss can provde a theoretcal bass for the desgn of the fan. Keywords: Spray Fan, Flud-sold Couplng, Gudng Cone 1. Introducton There are two maor knds of spray fan researchng n chna. The frst s the orchard ar asssted spray fan whch s the axal nlet ar and both sdes outlet ar: Yang Chun [1] et al through numercal smulaton and experment, found the fan wth the current collector and rectfyng cap rased the full pressure and effcency of the fan by 5.2%, after analyss of the two cases of the motor and the hub at dfferent radus and whether a current collector or a rectfer cap was added to the mport. Lv Xaolan [2] et al studed the effects of spray fan s parameters to the droplet deposton; Guo Feng [3] et al made three dmensonal modelng and Smulaton of spray fan whose entrance s cylndrcal by usng numercal smulaton technology. Another knd s the turret ar asssted spray fan: Song Shuran [4] et al optmzed the desgn of the spray tube structure of the ar spray fan by usng numercal methods and orthogonal test, the factors that nfluence the pressure loss and the ar outlet velocty of the spray-duct are obtaned n turn: outlet dameter length of cylnder spray-duct length of concal spray-duct; Lu Qng [5] et al made the spray effect ncreased by 22% to 46% by nstallng a gudng vane n the spray-duct outlet of the 9WZCD-25 ar asssted spray fan. The computer modelng of the spray fan and ts workng envronment parameters are carred out abroad, and the spray process s smulated. The spray effect has great advantages on the effcency and the economy, but most of them are the axal nlet ar and both sdes outlet ar. Delele [6] et al desgned a computatonal flud dynamcs model to study the spray effect of a spray fan n the flow feld generated by the axal flow fan; Endalew [7] et al establshed the three-dmensonal model of the two fan mxed flow orchard ar asssted spray fan by usng CFD technology, the dstrbuton of the spray flow velocty n dfferent canopy densty regons s predcted by Usng ths model, Some foregn scholars also studed the droplets penetraton and performance mprovement of spray fan [8, 9]. Cone angle s one of the most mportant parameters n the desgn of spray fan, the desgns of the cone angle sze are not unform currently and no feasble theory can be used as a bass for desgn. Although ts varaton range s small, the change value has an mportant nfluence on the spray effect, because after atomzaton and separaton by hghly speed rotatng of mpeller blade, the lqud n spray-duct need to be dscharged through the cone, and the sze of the cone angle affect the nternal pressure, especally n the early stage of work, maybe

2 Internatonal Journal of Flud Mechancs & Thermal Scences 2016; 2(3): causng severe overshoot phenomenon and then damage the blade and the whole structure of the fan. Therefore, the study of the parameters of the nozzle cone angle has mportant engneerng sgnfcance for the desgn of the cone angle. In ths paper, the model s numercally analyzed by usng the constant couplng method whch s based on the vehcle mounted sprayer. In order to get a better angle of gudng cone angle and provde the theory reference for the desgn of the vehcle mounted sprayer, analyss on pressure of spray fan, velocty, stress and stran of model under dfferent gude cone angle are carred out. 2. Mathematcal Smulaton 2.1. Geometrc Model and Mesh Dvson The three-dmensonal model of the fan s establshed by usng SoldWorks. Usng ADINA analyze the model of spray fan. The motor rated power s 5.5KW, the rated speed s 1430rpm. The dameter of the rotary shaft s 0.08 meters. The related parameters of the blade model of the fan: the outer dameter of the fan s 0.4 meters; the dameter of shaft that the blades connected s 0.08 meters; the shaft length of the rotary shaft s 0.08 meters; the blade length, wdth and thckness of the study model are 0.16 meters, 0.06meters and 0.01 meters; the number of blades s 3, and the blade s 120 degrees equangular dstrbuton; the blade surface s a quas streamlne surface, and nstallaton angle s 35 degrees. Usng FCBI-C unt, the degree of freedom of the element s defned at the center of the unt whch conform to the flud-sold couplng problem. Because of the soluton of the spray fan flud-sold couplng analyss s manly concentrated n the two ntersectng nterface, the calculaton of the couplng part needs the mesh qualty to be very hgh. In order to obtan hgh qualty mesh, we must adopt the method of dvdng the grd nto the block whch can reduce the number of the grd the fullest extent, and does not affect the accuracy of the soluton. For blade sectons, because of ther regular geometrcal shape and the small gradent change of flow feld of varous physcal quanttes, the mappng grd adopt (rule based) 8 node hexahedron grd dvson. For the rotary shaft, because of the complexty of the geometrc structure, dvdng mappng mesh exsts certan dffcultes, n addton, the changes of some physcal quantty n the flow feld are relatvely bg, so the free mesh adopts (free-form) 8 node hexahedron grd dvson, and encrypt the area where the stress concentrate n the blade root. Fg. 1 and Fg. 2 respectvely are the grd partton of the blade and the flow feld. Fg. 2. Axal fan flow feld grd. In order to accurately reflect the nfluence of the overshoot phenomena on the spray-duct flow feld and the blades, the frst 20 steps couplng calculaton step tme s taken as 0.005s, and total s 0.1 s; the afterwards 200 steps couplng calculaton step tme s taken as 0.01 s, and total s 2 s. Ths selecton of step tme can characterze some moton characterstcs of the fan n the runnng process, and guarantee the accuracy of the results Mathematcal Model The flow feld n the spray fan s smulated, and consderng the strong rotatng flow feld has a strong ansotropy, the Reynolds stress model started from turbulence ansotropy s used to smulate the gas phase flow feld, and control equatons are as follows: Contnuty equaton: Momentum equaton: v p v x = 0 ρ v = + µ + ( ρvv ) v v x x x x x + ρg x The Reynolds stress whch stands for turbulent pulsatng effect s solved by usng Reynolds stress transport equaton: ρv v v x k = P + φ + x k ( vv ) µ 2 t µ + ρδ σ x 3 k k k (1) (2) (3) Where, stress generatng tem: Fg. 1. Axal fan structured grd.

3 18 Zhang Faun et al.: Analyss and Research on Gudng Cone Angle Parameter of Spray Fan-Ppe ( / ) ( / ) (4) P = ρ vv v x + v v v x Stress-stran terms: k k k k 2 ( / ) ( ) 1 2/3, (5) ( 1/3) P δ φ = C ρ k vv kδ [ ] C P kk The turbulent dsspaton rates solved by solvng transport equatons: µ t ( ρv ) = µ + σ x x x 1 ( C p C ρ ) + k where, C1=1.8, C2=0.6, C =1.44, C 1 =1.92, σ 2 k =1, σ =1.3. PRESTO method s used to deal wth the pressure gradent, and the convectve terms of each equatons are dscretzed by QUICK dfference scheme. The couplng of pressure and velocty s calculated by SIMPLE-C method. 3. Results and Analyss 3.1. Flow Feld Pressure and Velocty Analyss 1) The nfluence of cone angle on flow feld pressure (a) The pressure of secton X under 0 (6) (c) The pressure of secton X under 20 (d) The pressure of secton X under 30 Fg. 3. The pressure of flow feld under dfferent cone angle. Fgure 3 s the pressure dstrbuton chart of spray fan on x=0 longtudnal secton whch take the maxmum node as a basc pont under dfferent gudng cone angle. From Fgure 5 (a) and (b), t can be clearly seen that the flow feld has an axal symmetry and dstnct separaton happened on whch the cone angle changes, and the upper surface pressure of blade s larger at ths pont. When the fan gude cone angle s 20 degrees to 30 degrees, the pressure range have ncreasng trend. Table 1 shows the pressure change to have more detaled observaton of the changng trend. From table 1, when the gude cone angle ncreases, the maxmum flow feld pressure n the spray-duct ncreases at the same tme, and the absolute value of the mnmum pressure ncreases. However, when the cone angle s 20 degrees, the spray-duct pressure ncreases to a certan value, for the meantme the negatve pressure also reduced to a certan value. The greater pressure can ensure the energy requred for transportng fog partcles, and the smaller dfferental pressure wll ensure the ampltude value of alternatng load decreases n the operaton, and servce lfe of the spray fan can be extended. Table 1. The pressure of X secton and Z secton under dfferent cone angle. cone angle Pressure of X secton (Pa) Pressure of Z secton (Pa) MAX MIN MAX MIN (b) The pressure of secton X under 10 2) The nfluence of cone angle on flow feld velocty In order to ensure the effectve transmsson of fog partcles, n addton to the flow feld pressure, velocty dstrbuton of

4 Internatonal Journal of Flud Mechancs & Thermal Scences 2016; 2(3): flow feld whch s parallel to the spray-duct axs drecton (that s Z axs drecton) must also be consdered. So ths artcle dd a comparatve analyss on the speed of the spray-duct flow feld n the drecton of Z axs. the spray-duct. The velocty change n axs Z drecton s shown n table 2. From the table, when the cone angle s 0 degree the speed n the drecton of axs Z s maxmum, but the pressure angle s too small to ensure the effectve transmsson of fog partcles. However, when the cone angle s 20 degrees, the speed n axs Z has reached the maxmum whch s proptous to the effectve transmsson of fog partcles. Table 2. The speed n drecton Z under dfferent cone angle. cone angle Speed of X secton n drecton Z(m/s) MAX MIN (a) The speed of secton X under The analyss of Stress and Stran of the Fan The nternal flow feld characterstc parameter of the fan s closely related to the cone angle, and the lqud atomzng manly s happened n the fan blade segment and gudng cone secton. The change of gudng cone angle naturally leads to the changes n ts nternal flow feld, and nfluences the effectve range and floatng effect of spray lqud after sprayed. 1) The nfluence of cone angle on stress of blades (b) The speed of secton X under 10 (a) The stress nephogram under 0 (c) The speed of secton X under 20 (b) The stress nephogram under 10 (d) The speed of secton X under 30 Fg. 4. The speed n drecton Z of flow feld under dfferent cone angle. From Fgure 4, we can see that the velocty dstrbuton n (c) The stress nephogram under 20

5 20 Zhang Faun et al.: Analyss and Research on Gudng Cone Angle Parameter of Spray Fan-Ppe (d) The stress nephogram under 30. (c) The stran nephogram under 20 Fg. 5. The stress nephogram under dfferent cone angle. From Fg. 5, t can be seen that the fan blade roots bear alternate load, and the maxmum and mnmum pressure dstrbuton n the blade roots. In order to observe the stress dstrbuton of the fan blade under dfferent gudng cone angle, the maxmum external pressure and the maxmum nternal pressure are shown n Table 3. Table 3. The max stress of structure feld under dfferent cone angle. cone angle stress(mpa) Exteror stress Interor stress From table 3, when the cone angle ncreases, the fan blade stress ncreases, but a tny drop when the cone angle s 20 degrees. It means that the load that fan blade bearng has a tny drop at ths tme, whch can guarantee the servce lfe of the fan. 2) The nfluence of cone angle on stran of blades From Fgure 6, t can be seen that the deformaton of the blades s manly concentrated n the root of the blades. In order to observe the change of the stran of blades n detal, the maxmum and the mnmum stran value of the blades are shown n Table 4. (d) The stran nephogram under 30 Fg. 6. The stran nephogram under dfferent cone angle. Table 4. The stran of the fan under dfferent cone angle. cone Exteror stran(x10-4m) Interor stress(x10-4m) angle MAX MIN MAX MIN From table 4, t can be seen that when the mnmum deformaton of blades s 0 degrees and 20 degrees. The flow feld n the 0 degree pressure angle and the velocty of the Z drecton are smaller, but the pressure angle of the 20 degree angle s approprate. Therefore when the degree angle s 20 degree, the varaton of the stran s the mnmum, the alternate load of the blades s the mnmum, the number of alternatng load on the fan wll ncrease, whch can ensure the fatgue strength of the blades. 4. Concluson (a) The stran nephogram under 0. (b) The stran nephogram under 10 In the case of the gudng cone angle changes, smulated the nfluence of the spray flow feld on the fan blade, and dd the numercal analyzaton. The conclusons are as follow: (1) Wth the ncrease of the cone angle of the vehcle mounted sprayer, the pressure and velocty n the drecton of the axs Z of the flow feld also ncreased. The ncreasng pressure and speed can ensure the effectve transmsson of the fog partcles, but also easly lead to the stress concentraton n the root of the blade. (2) Changng cone angle can effectvely mprove the performance of the spray fan, especally when the angle s 20 degrees, the nternal pressure and the speed n Z drecton of the spray fan can reach a relatvely large value. but stress and stran of the blades reached the relatvely small. (3) In ths paper, the contrastve analyss of smulaton

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