本文選題：氣吸振動 + 精密排種裝置�。� 參考：《江蘇大學(xué)》2013年博士論文

【摘要】：精密排種裝置是實現(xiàn)精密播種作業(yè)的關(guān)鍵設(shè)備,其性能優(yōu)劣直接關(guān)系到作物生產(chǎn)的產(chǎn)量和品質(zhì)。目前,超級稻穴盤育苗精密排種裝置還處于探索研究階段,現(xiàn)有的水稻排種裝置大都屬機械式,傷種較嚴(yán)重,且每穴播種達3-5粒,難以滿足超級稻種植對播種技術(shù)的農(nóng)藝要求(2±1粒／穴,低傷種率),因此,急需開展超級稻穴盤育苗精密排種裝置的理論與試驗研究。本文以設(shè)計的新型氣吸振動盤式精密排種裝置為研究對象,通過振動理論、計算流體動力學(xué)、離散元法、機構(gòu)學(xué)、實驗優(yōu)化等理論,并結(jié)合先進的計算機仿真技術(shù)深入研究播種過程中排種裝置機構(gòu)運動、振動激勵和氣力對超級稻種子的作用機理及種群的運動規(guī)律、連續(xù)播種過程最佳吸種效果的參數(shù)組合,提出了精密播種理論,主要研究工作包括： (1)采用專業(yè)測量儀器對三個品種超級稻芽種基礎(chǔ)物理特性參數(shù)進行測試和分析,得到芽種的三軸幾何尺寸分布概率、千粒重、密度、摩擦系數(shù)、休止角、恢復(fù)系數(shù)和力-位移變化關(guān)系,為離散元仿真和排種裝置吸種部件設(shè)計提供依據(jù)。 (2)運用FLUENT對排種裝置氣流場進行研究：①分析吸種盤氣流場分布規(guī)律,得出影響氣流場的主要因素為吸孔孔徑、真空負(fù)壓值,得到均勻穩(wěn)定流場的最佳結(jié)構(gòu)及工作參數(shù)；②分析氣流場中種子顆粒受力影響因素,得出其主次順序為種子與吸孔的距離、種子姿態(tài)、真空負(fù)壓值、吸孔孔徑；建立種子受力數(shù)學(xué)模型,分析得出：真空負(fù)壓值與孔徑應(yīng)合理匹配,小孔徑需較大的真空負(fù)壓值,高度方向的種子最容易被吸附；真空負(fù)壓值為3～5kpa范圍內(nèi),吸孔孔徑為1.5mm～2.0mm時,吸孔吸附距離范圍為0.34mm～1.90mm;③對吸種盤正壓氣流場進行模擬,得出流量對吸種盤正壓氣流場影響大,隨著流量增加,吸孔口氣流流速急劇增大,種子受到氣流吹力增大,內(nèi)板厚度對正壓氣流場分布和流量幾乎無影響；④進行氣流場流量測定及種子顆粒吸附試驗,試驗結(jié)果與FLUENT模擬值基本吻合,表明數(shù)值模擬結(jié)果的正確性。 (3)進行排種裝置的機構(gòu)運動分析：①采用ADAMS對振動種盤機構(gòu)運動進行分析,得到機構(gòu)動力源的變化規(guī)律：隨著頻率和振幅的增大,最大驅(qū)動扭矩逐漸增大；②基于機構(gòu)學(xué)理論,研究符合水平調(diào)節(jié)要求的并聯(lián)機構(gòu),對一平移兩轉(zhuǎn)動并聯(lián)機構(gòu)進行型綜合,設(shè)計水平調(diào)節(jié)機構(gòu),獲得機構(gòu)位置關(guān)系和精度模型；③建立攜種過程種子顆粒受力數(shù)學(xué)模型,推導(dǎo)帶動吸種盤運動的機械手動力學(xué)特性要求。隨著負(fù)壓值的增大,機械手臨界加速度增加。長度方向吸附的種子最容易發(fā)生掉落,機械手設(shè)計時應(yīng)滿足長度方向不發(fā)生掉落的條件；④建立種子顆粒與吸種盤的碰撞運動數(shù)學(xué)模型,得出種子顆粒不被碰離吸種盤面板的彈回臨界速度與負(fù)壓值的關(guān)系。隨著負(fù)壓值增大,種子顆粒彈回臨界速度增加。長度方向碰撞的種子最容易發(fā)生彈回掉落,當(dāng)碰撞彈回速度大于臨界彈回速度時,種子將脫離氣流場約束并彈離吸孔。 (4)基于離散元理論,研究振動種盤內(nèi)種群運動,得出：①單顆粒種子運動具有波動性,受種群顆粒間約束力的相互作用,種群的運動呈規(guī)律性變化；②隨著振動種盤振動頻率和振幅的增加,種群豎直方向平均位移、平均速度和顆粒受力逐漸增大,種群拋擲運動的激烈程度增加,相對空間分布密度逐漸變小,增大頻率和振幅能有效增大種群拋擲高度。單層種群拋擲高度、顆粒平均法向力和平均切向力大于其他種層厚度種群,其他種層厚度種群的豎直方向平均位移和平均速度、顆粒間平均受力及種群空間離散程度受種層厚度的影響較小。種子顆粒受到的作用力最大值小于0.03N,得出振動種盤的運動對種子損傷極��；③分析連續(xù)播種過程振動種盤內(nèi)種子逐漸減少的變質(zhì)量系統(tǒng)種層厚度與振動種盤振動參數(shù)的關(guān)系,建立排種裝置工作參數(shù)與吸種距離(吸種盤面板與種層表面之間距離)之間的數(shù)學(xué)模型。得出影響種群拋擲高度的因素主次順序為：振動頻率、振幅、種層厚度,振動頻率與振幅應(yīng)合理匹配；仿真模擬傾斜狀態(tài)振動種盤內(nèi)種群運動,振動種盤傾角越大時種群運動均勻性越差,傾角越小對振動種群空間分布均勻性越有利；④基于CFD-DEM耦合理論,應(yīng)用FLUENT-EDEM耦合方法仿真模擬了排種裝置吸種過程,得出了參數(shù)變化規(guī)律。 (5)研制一種新型氣吸振動盤式精密排種裝置試驗臺,并開展臺架試驗。①進行單因素試驗和正交試驗,著重分析真空負(fù)壓值、吸孔孔徑、振動種盤振動頻率、振幅、吸種距離等因素對播種性能指標(biāo)的影響,得出影響合格率的因素主次順序為：吸種距離、振動頻率、振幅、真空負(fù)壓值、吸孔孔徑；影響重播率的因素主次順序為：真空負(fù)壓值、吸孔孔徑、吸種距離、振動頻率、振幅；影響空穴率的因素主次順序為：吸種距離、真空負(fù)壓值、吸孔孔徑、振動頻率、振幅；吸種距離和頻率對播種合格率有顯著影響,真空負(fù)壓值和吸孔孔徑對重播率有顯著的影響,吸種距離和負(fù)壓真空值對空穴率有顯著影響。②建立排種裝置工作參數(shù)與播種性能指標(biāo)之間的數(shù)學(xué)模型,進行遺傳算法的多目標(biāo)優(yōu)化,得到最優(yōu)解：真空負(fù)壓值3.68kPa,吸孔孔徑1.84mm,振動頻率10.90Hz,振幅4.09mm,吸種距離3.92mm,并進行試驗驗證。③對不同品種超級稻進行播種試驗,證明排種裝置對不同品種超級稻芽種具有較好適應(yīng)性。采用排種裝置對芽種進行播種育苗試驗,證明排種裝置不損芽。通過對播種后的穴盤進行育苗后發(fā)現(xiàn),該排種裝置能滿足超級稻種植的育苗要求。試驗結(jié)果與理論分析相一致,為精密排種裝置的設(shè)計提供理論依據(jù)。
[Abstract]:Precision seed metering device is the key equipment to realize precision seeding operation. Its performance is directly related to the yield and quality of crop production. At present, the precision seed metering device for super rice seedling raising is still in the stage of exploration and research. The existing plant seed metering devices are mostly mechanical, and the injury species is more serious, and 3-5 seeds per hole can not be satisfied. Therefore, it is urgent to carry out the theoretical and Experimental Research on the precision seed metering device for super rice seedling raising and seedling raising. In this paper, a new type of pneumatic vibrating disc type precision seed metering device is designed as the research object. Through the vibration theory, the fluid dynamics, the discrete element method, the mechanism and the reality are calculated. According to the theory of optimization and so on, combined with the advanced computer simulation technology, the mechanism of the arrangement of plant mechanism, the mechanism of the action of vibration and gas on the seed of super rice and the movement rule of the population, the combination of the optimum seed sucking effect in the continuous sowing process are studied. The theory of precision seeding is put forward, and the main research work includes:
(1) to test and analyze the physical parameters of three varieties of super rice sprouts based on professional measuring instruments, the probability of geometric size distribution of three axes, 1000 grain weight, density, friction coefficient, repose angle, recovery coefficient and force displacement change are obtained, which provide the basis for the design of the discrete Yuan Fangzhen and seed metering device.
(2) using FLUENT to study the airflow field of the seed metering device: (1) analysis of the distribution law of the flow field of the suction disc, the main factors affecting the airflow field are the aperture of the suction hole and the vacuum negative pressure value, and the best structure and working parameters of the uniform stable flow field are obtained. Secondly, the influence factors of the force of the seed particles in the airflow field are analyzed, and the order of its primary and secondary is the seed. The distance between the seed and the hole, the attitude of the seed, the vacuum negative pressure and the aperture of the hole, the mathematical model of the force of the seed is established. It is concluded that the vacuum pressure value should match the pore size reasonably, the small aperture needs the larger vacuum negative pressure, the high direction of the seed is most easily adsorbed; the vacuum vacuum pressure is within the range of 3 ~ 5kpa, and the aperture of the suction hole is 1.5mm to 2.0mm, The range of absorption distance of the suction hole is 0.34mm ~ 1.90mm; thirdly, the positive air flow field of the sucking disc is simulated. It is found that the flow rate has great influence on the positive air flow field of the seed suction disc. With the increase of the flow rate, the flow velocity of the suction hole is increased sharply, the seed is increased by the air blowing force, and the thickness of the inner plate has little effect on the distribution and flow of the positive pressure flow field. The results of field flow measurement and seed particle adsorption test agree well with the FLUENT simulation values, indicating the correctness of the numerical simulation results.
(3) the mechanism motion analysis of the seed metering device: (1) the motion of the vibratory disc mechanism is analyzed by ADAMS, and the change rule of the mechanism power source is obtained: with the increase of frequency and amplitude, the maximum driving torque is gradually increased; secondly, based on the mechanism theory, the parallel mechanism which meets the requirements of the horizontal adjustment is studied and the two rotation of a horizontal shift is carried out. The joint structure is integrated, the horizontal adjustment mechanism is designed, the position relationship and the precision model of the mechanism are obtained. Thirdly, the mathematical model of the force of the seed particles in the carrying process is set up, and the mechanical mechanical properties of the mechanical hand are derived. With the increase of the negative pressure, the critical acceleration of the manipulator increases. The seeds with the length direction are the easiest to adsorb. When the manipulator is dropped, the manipulator should meet the condition that the length direction does not fall when the manipulator is designed. (4) establish the mathematical model of the collision motion between the seed particles and the seed suction disc, and get the relationship between the critical velocity and the negative pressure of the seed particles not being touched from the suction plate panel. With the increase of the negative pressure, the critical velocity of the seed particles increases. When the impact velocity is greater than the critical rebound velocity, the seed will be released from the gas flow field and will be released from the suction hole.
(4) based on the discrete element theory, the movement of the population in the vibrating seed disc is studied. The results are as follows: (1) the motion of single grain seeds is fluctuant, and the movement of the population is regularly changed by the binding interaction between the particles. Secondly, the average displacement of the vertical direction of the population, the average velocity and the force of the particle with the increase of the vibration frequency and amplitude of the vibrating seed disc Gradually increasing, the intensity of the population throwing movement increases, the relative spatial distribution density gradually becomes smaller and the increase of frequency and amplitude can effectively increase the height of the population throwing. The single single population throws the height, the average normal force and the mean tangential force of the particle are larger than those of the other layer thickness, and the average displacement of the vertical direction of the species with the thickness of his seed layer is peaceful. The average force between particles and the degree of spatial dispersion of the population are less affected by the thickness of the seed layer. The maximum force of the seed particles is less than 0.03N, and the motion of the vibratory disc is very little to the seeds. Thirdly, the thickness of the seed layer of the variable mass system and the vibration type disc vibration of the continuous sowing in the continuous sowing process are analyzed. The relationship between the dynamic parameters and the mathematical model between the working parameters of the seed metering device and the distance of the seed suction (the distance between the seed plate and the surface of the seed). The order of the factors that affect the height of the throwing height of the population is the vibration frequency, amplitude, the thickness of the seed layer, the vibration frequency and the amplitude, and the simulation and Simulation of the incline vibration species in the disc. The worse the population movement is, the worse the population movement uniformity is, the less the inclination is, the more favorable to the uniformity of the spatial distribution of the vibrating population. (4) based on the CFD-DEM coupling theory, the FLUENT-EDEM coupling method is used to simulate the seed sucking process of the seed metering device, and the variation of the parameters is obtained.
(5) develop a new type of air suction vibrating disc type precision seed metering device test bed and carry out a bench test. (1) single factor test and orthogonal test are carried out to analyze the influence of vacuum negative pressure value, hole suction aperture, vibration frequency, amplitude and distance of seed suction on the performance index of sowing, and the order of factors affecting the qualified rate is obtained. The main and secondary factors affecting the replay rate are vacuum negative pressure, aperture, distance, vibration frequency and amplitude; the main and secondary order of the factors affecting the hole rate are suction distance, vacuum pressure value, aperture, vibration frequency, amplitude, distance and frequency of sucking. The rate has a significant influence on the qualified rate of sowing, the vacuum negative pressure value and the aperture of the suction hole have a significant influence on the replay rate, the suction distance and the vacuum value have a significant influence on the hole rate. Secondly, the mathematical model between the working parameters of the seed metering device and the performance index of the seeding is established, and the optimal solution of the vacuum negative pressure is obtained by the multi-objective optimization of the genetic algorithm. Value 3.68kPa, hole aperture 1.84mm, vibration frequency 10.90Hz, amplitude 4.09mm, seed distance 3.92mm, and test verification. 3. Sowing experiments on different varieties of super rice proved that seed metering device has better adaptability to different varieties of super rice bud. Seed planting experiment with seed metering device is used to prove that seed planting device does not damage bud. After seedling raising after seeding, it is found that the plant can meet the requirements of the cultivation of super rice. The result of the experiment is consistent with the theoretical analysis, and provides a theoretical basis for the design of precision seed metering device.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：S223.25;TH112

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