帶階梯型諧振腔的Hartmann低頻超聲霧化噴嘴的設(shè)計(jì)及試驗(yàn)
發(fā)布時(shí)間：2019-07-10 14:53
【摘要】：流體動力式超聲霧化噴嘴比一般的二相流噴嘴霧滴質(zhì)量更好,比壓電式超聲霧化噴嘴霧化量大,且可以定向噴霧。而在農(nóng)業(yè)大規(guī)模霧化栽培領(lǐng)域?qū)F滴質(zhì)量及噴嘴噴霧量均有較高的要求,因此研制一種適用于大規(guī)模霧化栽培的流體動力式超聲霧化噴頭是很有必要的。鑒于此,本文根據(jù)哈特曼諧振腔的基本原理,設(shè)計(jì)出了結(jié)構(gòu)參數(shù)可調(diào)節(jié)的帶階梯型諧振腔的Hartmann低頻超聲霧化噴嘴,包括拉瓦爾管、可旋渦流葉輪、階梯腔深度比可調(diào)的階梯型諧振管、錐型整流罩。并通過CFD瞬態(tài)數(shù)值模擬的方法,對錐型整流罩和階梯型諧振管的結(jié)構(gòu)參數(shù)的變化對諧振腔諧振狀態(tài)的影響做了參數(shù)化研究,并據(jù)此確定階梯型諧振腔的關(guān)鍵尺寸。在相同參數(shù)條件下,當(dāng)諧振腔的總深度相等時(shí),階梯型諧振腔的諧振頻率比傳統(tǒng)圓柱型諧振腔的諧振頻率高,當(dāng)階梯型諧振腔深度比超過2時(shí)其諧振頻率即維持在傳統(tǒng)圓柱型諧振腔諧振頻率的1.6至1.7倍;錐型整流罩的加入對腔內(nèi)氣體的入流和出流造成周期性的擾動,從而對諧振腔的諧振狀態(tài)造成影響;階梯孔孔徑比的變化會引起諧振模式的改變。根據(jù)以上結(jié)果,選用較優(yōu)設(shè)計(jì)參數(shù)即孔徑比D1/D2=2進(jìn)行諧振腔的試制,并選用較優(yōu)的拉瓦爾管與諧振腔距離X=5.5mm作為噴霧特性對比測試試驗(yàn)的初始結(jié)構(gòu)參數(shù)值。首先,對不同工況和不同結(jié)構(gòu)型式的噴嘴進(jìn)行了霧滴粒徑測定試驗(yàn),并對噴嘴噴霧系統(tǒng)的流量特性進(jìn)行了測定。試驗(yàn)結(jié)果表明:(1)錐型整流罩使得低壓時(shí)的霧滴粒徑隨供氣壓力變化更加敏感,而在高壓時(shí)其霧滴粒徑與沒有加裝錐型整流罩的帶有階梯腔的噴嘴相比基本一致;對于帶階梯腔的噴嘴,噴嘴與腔體距離為6.5mm附近SMD達(dá)到最小值;霧滴SMD與腔內(nèi)流體壓力、聲壓級以及諧振腔諧振狀態(tài)等因素密切相關(guān)。階梯腔式超聲霧化噴嘴的最小霧滴粒徑為42μm,霧化量約為2L/h。(2)供氣壓力的變化會使液路流體的流量和流體壓力呈現(xiàn)出相反的變化趨勢,而供氣壓力的變大使氣路流量隨著變大。其次,由于聲壓級是影響階梯型諧振腔式超聲霧化噴嘴霧化效果的重要參數(shù)。為了對階梯腔式哈特曼諧振腔的聲場特性做進(jìn)一步了解,對階梯腔式噴嘴的聲場特性進(jìn)行試驗(yàn),對影響階梯型諧振腔聲場特性的因素進(jìn)行了研究。采用均勻設(shè)計(jì)的試驗(yàn)方法,對各因素影響主次順序進(jìn)行分析。試驗(yàn)結(jié)果表明:錐型整流罩能夠有效使噴嘴的聲場能量聚攏在錐型罩的范圍內(nèi),與無圓錐罩相比,其聲壓級最大提升了13dB;供氣壓力是影響聲壓級變化的最主要因素。且試驗(yàn)表明,供氣壓力一定時(shí),聲壓級最大點(diǎn)在階梯腔深度比為0.6至0.8時(shí)出現(xiàn)。將聲場特性試驗(yàn)結(jié)果與霧滴粒徑測試結(jié)果和數(shù)值模擬結(jié)果進(jìn)行對比分析,再次印證聲壓級是影響霧滴粒徑重要參數(shù)的結(jié)論。最后,在不同的結(jié)構(gòu)參數(shù)和工作參數(shù)下對噴霧角及噴霧距離的影響進(jìn)行了試驗(yàn)測定;并設(shè)計(jì)了兩段式霧化栽培器,對帶錐型整流罩和可旋渦流葉輪的階梯腔式超聲霧化噴嘴在霧化栽培中應(yīng)用的可行性進(jìn)行了分析。結(jié)果表明:(1)供氣壓力在0.3MPa以下時(shí),可旋渦流葉輪的旋轉(zhuǎn)使霧滴群在錐型整流罩的輻射范圍內(nèi)分布的更加均勻擴(kuò)散的范圍更大,噴霧距離更長;(2)霧化角最大值出現(xiàn)在供氣壓力處于0.15MPa至0.25MPa范圍時(shí)。這對霧化栽培器內(nèi)噴嘴的布局有一定的指導(dǎo)意義。
[Abstract]:The fluid dynamic type ultrasonic atomizing nozzle has better fog drop quality than the general two-phase flow nozzle, is larger than the atomization amount of the piezoelectric ultrasonic atomizing nozzle, and can be directionally sprayed. However, in the field of large-scale agricultural atomization, it is necessary to develop a hydrodynamic ultrasonic atomizing nozzle suitable for large-scale atomization cultivation. In view of this, the Hartmann low-frequency ultrasonic atomizing nozzle with step-type resonant cavity with adjustable structure parameters is designed according to the basic principle of the Hartmann resonant cavity, which comprises a Laval tube, a vortex flow impeller, a stepped cavity depth ratio adjustable stepped resonance tube and a conical fairing. Through the method of CFD transient numerical simulation, the influence of the structural parameters of the cone-shaped fairing and the stepped-type resonant tube on the resonant state of the resonant cavity is studied, and the critical dimension of the step-shaped resonant cavity is determined accordingly. under the condition of the same parameter, when the total depth of the resonant cavity is equal, the resonance frequency of the step type resonant cavity is higher than that of the conventional cylindrical resonant cavity, and when the depth ratio of the step type resonant cavity is more than 2, the resonance frequency is 1.6 to 1.7 times of the resonance frequency of the conventional cylindrical resonant cavity; The addition of the cone-shaped cowling causes periodic disturbance to the inflow and outflow of the gas in the cavity, so as to influence the resonance state of the resonant cavity, and the change of the aperture ratio of the step hole can cause the change of the resonance mode. According to the above results, the optimal design parameters, i.e., the aperture ratio D1/ D2 = 2, are selected for the production of the resonant cavity, and the optimal Laval tube and the cavity distance X = 5.5mm are selected as the initial structural parameter values of the test for the contrast test of the spray characteristics. First, the droplet size determination test was carried out on the nozzle of different working conditions and different structure types, and the flow characteristics of the nozzle spray system were measured. The experimental results show that: (1) the size of the fog drops at low pressure is more sensitive with the change of the air supply pressure, and the particle size of the fog drops at high pressure is basically the same as that of the nozzle with the step cavity without the conical fairing; for the nozzle with the step cavity, The distance between the nozzle and the cavity is 6.5 mm, and the SMD reaches the minimum value; the droplet SMD is closely related to the pressure of the fluid in the cavity, the sound pressure level and the resonance state of the resonant cavity. The minimum droplet size of the step-cavity ultrasonic atomizing nozzle is 42. m u.m, and the atomization amount is about 2 L/ h. (2) The change of air supply pressure will make the flow and fluid pressure of the fluid flow in the reverse direction, and the gas path flow of the change of the air supply pressure will increase with the increase. Secondly, the sound pressure level is an important parameter that affects the atomization effect of the step-type resonant cavity type ultrasonic atomizing nozzle. In order to further understand the sound field characteristics of the stepped cavity type Hartmann resonator, the sound field characteristics of the stepped cavity type nozzle are tested, and the factors that influence the sound field characteristics of the stepped cavity are studied. By means of the method of uniform design, the primary and secondary order of each factor is analyzed. The experimental results show that the cone-shaped fairing can effectively gather the sound field energy of the nozzle in the range of the cone-shaped cover, and the sound pressure level of the cone-shaped cowling is up to 13 dB as compared with the non-conical cover, and the air supply pressure is the most important factor affecting the change of the sound pressure level. And the test results show that when the air supply pressure is constant, the maximum point of the sound pressure level appears when the depth ratio of the step cavity is 0.6 to 0.8. The result of sound field characteristic test is compared with the result of the particle size test and the numerical simulation result, and the conclusion that the sound pressure level is the important parameter to influence the particle size of the fog drop is confirmed again. finally, the influence of the spray angle and the spraying distance is tested under different structural parameters and working parameters, and a two-section type atomization culture device is designed, The feasibility of the application of the step-cavity ultrasonic atomizing nozzle with a cone-shaped fairing and a vortex-flow impeller in the atomization cultivation is analyzed. The results show that (1) when the air supply pressure is less than 0.3 MPa, the rotation of the vortex flow impeller causes the droplets to be distributed more uniformly in the radiation range of the cone-shaped fairing, and the spraying distance is longer; and (2) the maximum of the atomization angle occurs when the gas supply pressure is in the range of 0.15 MPa to 0.25 MPa. It is of great significance to the layout of the nozzle in the atomizer.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S237
本文編號：2512670
[Abstract]:The fluid dynamic type ultrasonic atomizing nozzle has better fog drop quality than the general two-phase flow nozzle, is larger than the atomization amount of the piezoelectric ultrasonic atomizing nozzle, and can be directionally sprayed. However, in the field of large-scale agricultural atomization, it is necessary to develop a hydrodynamic ultrasonic atomizing nozzle suitable for large-scale atomization cultivation. In view of this, the Hartmann low-frequency ultrasonic atomizing nozzle with step-type resonant cavity with adjustable structure parameters is designed according to the basic principle of the Hartmann resonant cavity, which comprises a Laval tube, a vortex flow impeller, a stepped cavity depth ratio adjustable stepped resonance tube and a conical fairing. Through the method of CFD transient numerical simulation, the influence of the structural parameters of the cone-shaped fairing and the stepped-type resonant tube on the resonant state of the resonant cavity is studied, and the critical dimension of the step-shaped resonant cavity is determined accordingly. under the condition of the same parameter, when the total depth of the resonant cavity is equal, the resonance frequency of the step type resonant cavity is higher than that of the conventional cylindrical resonant cavity, and when the depth ratio of the step type resonant cavity is more than 2, the resonance frequency is 1.6 to 1.7 times of the resonance frequency of the conventional cylindrical resonant cavity; The addition of the cone-shaped cowling causes periodic disturbance to the inflow and outflow of the gas in the cavity, so as to influence the resonance state of the resonant cavity, and the change of the aperture ratio of the step hole can cause the change of the resonance mode. According to the above results, the optimal design parameters, i.e., the aperture ratio D1/ D2 = 2, are selected for the production of the resonant cavity, and the optimal Laval tube and the cavity distance X = 5.5mm are selected as the initial structural parameter values of the test for the contrast test of the spray characteristics. First, the droplet size determination test was carried out on the nozzle of different working conditions and different structure types, and the flow characteristics of the nozzle spray system were measured. The experimental results show that: (1) the size of the fog drops at low pressure is more sensitive with the change of the air supply pressure, and the particle size of the fog drops at high pressure is basically the same as that of the nozzle with the step cavity without the conical fairing; for the nozzle with the step cavity, The distance between the nozzle and the cavity is 6.5 mm, and the SMD reaches the minimum value; the droplet SMD is closely related to the pressure of the fluid in the cavity, the sound pressure level and the resonance state of the resonant cavity. The minimum droplet size of the step-cavity ultrasonic atomizing nozzle is 42. m u.m, and the atomization amount is about 2 L/ h. (2) The change of air supply pressure will make the flow and fluid pressure of the fluid flow in the reverse direction, and the gas path flow of the change of the air supply pressure will increase with the increase. Secondly, the sound pressure level is an important parameter that affects the atomization effect of the step-type resonant cavity type ultrasonic atomizing nozzle. In order to further understand the sound field characteristics of the stepped cavity type Hartmann resonator, the sound field characteristics of the stepped cavity type nozzle are tested, and the factors that influence the sound field characteristics of the stepped cavity are studied. By means of the method of uniform design, the primary and secondary order of each factor is analyzed. The experimental results show that the cone-shaped fairing can effectively gather the sound field energy of the nozzle in the range of the cone-shaped cover, and the sound pressure level of the cone-shaped cowling is up to 13 dB as compared with the non-conical cover, and the air supply pressure is the most important factor affecting the change of the sound pressure level. And the test results show that when the air supply pressure is constant, the maximum point of the sound pressure level appears when the depth ratio of the step cavity is 0.6 to 0.8. The result of sound field characteristic test is compared with the result of the particle size test and the numerical simulation result, and the conclusion that the sound pressure level is the important parameter to influence the particle size of the fog drop is confirmed again. finally, the influence of the spray angle and the spraying distance is tested under different structural parameters and working parameters, and a two-section type atomization culture device is designed, The feasibility of the application of the step-cavity ultrasonic atomizing nozzle with a cone-shaped fairing and a vortex-flow impeller in the atomization cultivation is analyzed. The results show that (1) when the air supply pressure is less than 0.3 MPa, the rotation of the vortex flow impeller causes the droplets to be distributed more uniformly in the radiation range of the cone-shaped fairing, and the spraying distance is longer; and (2) the maximum of the atomization angle occurs when the gas supply pressure is in the range of 0.15 MPa to 0.25 MPa. It is of great significance to the layout of the nozzle in the atomizer.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S237
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