王韋韋,朱存璽,陳黎卿,李兆東,黃 鑫,李金才
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玉米免耕播種機(jī)主動(dòng)式秸稈移位防堵裝置的設(shè)計(jì)與試驗(yàn)
王韋韋,朱存璽,陳黎卿,李兆東,黃 鑫,李金才※
(安徽農(nóng)業(yè)大學(xué)工學(xué)院,合肥 230036)
針對(duì)黃淮海麥玉輪作區(qū)小麥秸稈全量還田下苗床整備前存在多機(jī)具多次下田、生產(chǎn)成本高以及傳統(tǒng)玉米免耕播種機(jī)在小麥秸稈全覆蓋地作業(yè)時(shí)存在開(kāi)溝壅堵、架種、晾種等問(wèn)題,該文設(shè)計(jì)了一種基于“秸稈移位”防堵思路的主動(dòng)式秸稈移位防堵裝置。運(yùn)用EDEM軟件構(gòu)建無(wú)支撐秸稈全覆蓋土壤離散元模型,在秸稈-土壤-主動(dòng)式防堵裝置系統(tǒng)中進(jìn)行秸稈移位虛擬仿真,設(shè)定了主動(dòng)式秸稈移位防堵裝置的刀軸驅(qū)動(dòng)轉(zhuǎn)速為500 r/min、回轉(zhuǎn)半徑為120 mm、刀盤(pán)幅寬為216 mm及刀齒入土深度為10 mm,利用仿真數(shù)據(jù)對(duì)秸稈擾動(dòng)位移、清秸率進(jìn)行分析,檢驗(yàn)主動(dòng)式秸稈移位防堵裝置結(jié)構(gòu)參數(shù)和運(yùn)動(dòng)參數(shù)設(shè)計(jì)的合理性。田間試驗(yàn)結(jié)果表明,安裝主動(dòng)式秸稈移位防堵裝置的玉米免耕播種機(jī)的作業(yè)通過(guò)性穩(wěn)定,改善種床環(huán)境,開(kāi)溝壅堵次數(shù)為0次,秸稈清秸率為90.21%,相比仿真減少8.29個(gè)百分點(diǎn)。該研究可為小麥高留茬、秸稈全覆蓋地的玉米免耕播種機(jī)的設(shè)計(jì)與推廣提供參考。
機(jī)械化;設(shè)計(jì);計(jì)算機(jī)仿真;秸稈移位;離散元法;秸稈全覆蓋地;免耕播種;主動(dòng)式防堵
中國(guó)華北麥玉輪作區(qū)以冬小麥?zhǔn)蘸蟛シN夏玉米為主,傳統(tǒng)耕作模式為小麥秸稈拋灑還田后使用滅茬機(jī)、旋耕機(jī)、播種機(jī)順次作業(yè)下田完成播種。多機(jī)具多次下田導(dǎo)致耕層板結(jié)嚴(yán)重,影響玉米播種質(zhì)量、出苗差、苗質(zhì)弱[1-2]。且小麥秸稈覆蓋地板茬直播玉米依然存在以下主要問(wèn)題:機(jī)具入土部件掛草壅堵,作業(yè)順暢性難以保證;種子易播在秸稈上,造成架種;覆土不可靠,易造成晾種[3-5]。因此,解決開(kāi)溝器鏟柄堵塞問(wèn)題是設(shè)計(jì)免耕播種機(jī)的關(guān)鍵。
秸稈覆蓋還田和免耕播種是機(jī)械化保護(hù)性耕作的核心技術(shù)[6]。目前國(guó)內(nèi)外免耕播種機(jī)上防堵裝置工作方式主要包括分茬和切茬2種類型。其中分茬主要是將粉碎的無(wú)支撐秸稈推離播種區(qū),如凹形圓盤(pán)[7]、拔指輪[8]、伸縮拔桿[9]、分草鏟[10]等。這類防堵裝置在秸稈全量還田時(shí)分茬效果不顯著,防堵性能降低。切茬主要是將播種區(qū)秸稈進(jìn)行二次切斷,以防止秸稈纏繞機(jī)具入土部件。切茬的方法又分為被動(dòng)式和主動(dòng)式2種類型。其中被動(dòng)式開(kāi)溝防堵裝置多采用破茬圓盤(pán)等結(jié)構(gòu)[11],該類型主要依靠機(jī)具自身質(zhì)量和地面摩擦驅(qū)動(dòng)圓盤(pán)刀刃口滾動(dòng)切斷秸稈、切開(kāi)土壤開(kāi)溝,防堵能力強(qiáng),但當(dāng)?shù)乇斫斩捀采w量過(guò)大時(shí),秸稈不能被切斷而被壓入土壤,導(dǎo)致開(kāi)溝器入土困難,出現(xiàn)晾籽,影響播種質(zhì)量;而主動(dòng)式開(kāi)溝防堵裝置是利用高速旋轉(zhuǎn)的旋耕刀[12]、滅茬刀[13]、破茬圓盤(pán)[14]對(duì)播種條帶進(jìn)行旋耕、滅茬,特點(diǎn)是開(kāi)溝能力強(qiáng),防堵效果好,但存在土壤擾動(dòng)量大,破壞墑情、功耗高,機(jī)具振動(dòng)強(qiáng)烈,作業(yè)環(huán)境惡劣且存在安全隱患等問(wèn)題。
本文研究針對(duì)傳統(tǒng)玉米免耕播種不適應(yīng)高留茬、秸稈覆蓋地作業(yè),存在開(kāi)溝壅堵、架種、晾種等問(wèn)題,設(shè)計(jì)了一種基于“秸稈移位”防堵思路的主動(dòng)式秸稈移位防堵裝置,基于離散元法構(gòu)建土壤-秸稈-防堵裝置系統(tǒng)模型,利用防堵裝置仿真作業(yè)性能試驗(yàn)檢驗(yàn)秸稈移位裝置工作參數(shù)設(shè)計(jì)的合理性;通過(guò)秸稈移位免耕播種機(jī)田間試驗(yàn),驗(yàn)證離散元土壤-秸稈-防堵裝置系統(tǒng)模型的準(zhǔn)確性和可行性,保證玉米免耕播種機(jī)在小麥高留茬、秸稈全量還田時(shí)的通過(guò)性。
2BMY-4型玉米免耕播種機(jī)主要由主機(jī)架、主動(dòng)式秸稈移位防堵裝置、開(kāi)溝施肥裝置、播種單元體、覆土鎮(zhèn)壓裝置組成,如圖1所示。該機(jī)具采用秸稈移位的方式,一次下田作業(yè)可有效完成秸稈全覆蓋板茬地種床整備、側(cè)深施肥、單粒播種、覆土鎮(zhèn)壓等作業(yè)環(huán)節(jié)。
如圖2所示,秸稈移位防堵裝置結(jié)構(gòu)主要包括交叉對(duì)偶立式刀片、旋轉(zhuǎn)刀盤(pán)和旋轉(zhuǎn)軸承。小麥秸稈全覆蓋地“秸稈移位播種”的作業(yè)思路指:待播區(qū)地表上的秸稈在防堵裝置旋轉(zhuǎn)擾動(dòng)作用下,沿著回轉(zhuǎn)刀尖切線方向向種床一側(cè)進(jìn)行移位,實(shí)現(xiàn)待播區(qū)地表平整無(wú)秸稈,隨后開(kāi)溝器完成開(kāi)溝破土、苗床整理、施肥播種。其中,立式刀片與秸稈、土壤間相互作用依次為砍切、擾動(dòng)、平整。且刀片對(duì)稱交叉布置主要為了擾動(dòng)作業(yè)過(guò)程中滿足動(dòng)平衡要求。
1.對(duì)偶立式刀片 2.旋轉(zhuǎn)刀盤(pán) 3.旋轉(zhuǎn)軸承
1.Dual vertical blade 2.Rotating cutter head 3.Rotary bearing
注:v為作業(yè)前進(jìn)速度,m·s-1;為刀盤(pán)工作轉(zhuǎn)速,r·min-1。
Note:vis forward operation velocity, m·s-1;is driving velocity of the cutter shaft, r·min-1.
圖2 秸稈移位防堵裝置結(jié)構(gòu)示意圖
Fig.2 Structural diagram of straw-removing anti-blocking device
防堵裝置在旋轉(zhuǎn)工作時(shí)呈現(xiàn)往復(fù)運(yùn)動(dòng),對(duì)偶立式旋刀繞刀盤(pán)中心旋轉(zhuǎn)為相對(duì)運(yùn)動(dòng),作業(yè)機(jī)組勻速前進(jìn)運(yùn)動(dòng)為牽連運(yùn)動(dòng),以防堵裝置旋轉(zhuǎn)中心為原點(diǎn)建立固定坐標(biāo)系,軸正方向與作業(yè)機(jī)組前進(jìn)方向一致,軸為與機(jī)組前進(jìn)方向垂直平面的水平向右方向,如圖3所示。為刀軸回轉(zhuǎn)角速度,v為刀刃端點(diǎn)的切向速度,作業(yè)機(jī)組前進(jìn)速度v,其中防堵裝置回轉(zhuǎn)方向與機(jī)組作業(yè)方向垂直,開(kāi)始時(shí)對(duì)偶立式刀片的端點(diǎn)位于前方水平與軸重合,則防堵裝置端點(diǎn)的運(yùn)動(dòng)軌跡方程為
將式(1)[15-16]中消除時(shí)間參數(shù)數(shù),可得刀齒運(yùn)動(dòng)軌跡方程
式中、為立式對(duì)偶刀端點(diǎn)在任意時(shí)刻的位置坐標(biāo);防堵裝置轉(zhuǎn)角;刀刃端點(diǎn)的切向速度v=R;令為速度比:λ=v/v;為時(shí)間,s。
當(dāng)<1時(shí),由(1)式可得,無(wú)論防堵裝置運(yùn)動(dòng)到什么位置,秸稈的位移方向與機(jī)組作業(yè)方向相同,其運(yùn)動(dòng)軌跡呈短擺線,不能夠達(dá)到清秸防堵的目的;當(dāng)1時(shí),防堵裝置運(yùn)動(dòng)軌跡呈余擺線,對(duì)偶刀片才能滿足向種床側(cè)后方進(jìn)行秸稈移位。
注:O為防堵裝置旋轉(zhuǎn)中心;O1為防堵裝置t時(shí)刻轉(zhuǎn)動(dòng)中心;N為作業(yè)刀刃起始位置;N1為作業(yè)刀刃t時(shí)刻位置;α為刀軸轉(zhuǎn)角,(°);R為防堵裝置旋轉(zhuǎn)中心O到刀刃端點(diǎn)的距離(防堵裝置回轉(zhuǎn)半徑),mm;ω為防堵裝置的角速度,rad·s-1。
四行免耕播種機(jī)防堵裝置布置示意圖如圖4所示。
注:M為第一刀刃t時(shí)刻作業(yè)位置;N為2個(gè)刀刃作業(yè)重合位置;P為第二刀刃t時(shí)刻作業(yè)位置;B為刀盤(pán)幅寬,mm;S為秸稈擾動(dòng)節(jié)距,mm;Δh為凸起高度,mm;H為播種行距,mm。
麥茬田秸稈量大,為了不破壞土壤墑情且保證玉米播種質(zhì)量,必須確保防堵裝置將施肥、播種開(kāi)溝器正前方的秸稈從作業(yè)行移位至苗床行間。為了使四行免耕玉米播種機(jī)(圖4)在麥茬田全面作業(yè),秸稈移位防堵裝置刀盤(pán)位置參數(shù)應(yīng)滿足
同一個(gè)刀盤(pán)上安裝2把立式刀片,則一周內(nèi)兩刀齒相繼對(duì)秸稈的擾動(dòng)間隔時(shí)間為π/,秸稈擾動(dòng)節(jié)距為
其中刀盤(pán)每分鐘的轉(zhuǎn)速n=v/π。
從圖4a可以看出π/2,則π/2,并將式(4) 代入式(6)并變換式(7)得
由方程(2)和方程(7)聯(lián)合可得
令=,取≤2,其中為相鄰刀盤(pán)的重疊量系數(shù),則有
由方程式(11)可知,與成正比例關(guān)系,隨著的減少而減少,從而秸稈擾動(dòng)節(jié)距減小,由于覆蓋秸稈屬于無(wú)支撐多自由度群體,擾動(dòng)節(jié)距越小,開(kāi)溝器正前方作業(yè)行內(nèi)的秸稈量越小。根據(jù)保護(hù)性耕作要求玉米播種時(shí)土壤擾動(dòng)量越小,保墑效果越好,盡量確保主動(dòng)式秸稈移位防堵裝置刀刃不入土或淺入土。播種開(kāi)溝實(shí)際壟形寬度為40~60 mm[17-19],側(cè)位施肥法要求施肥開(kāi)溝器與播種開(kāi)溝器距離30~50 mm,為了同時(shí)保證播種和施肥開(kāi)溝器的空間位置及開(kāi)溝壟行寬度要求,故防堵裝置回轉(zhuǎn)半徑取120 mm。結(jié)合農(nóng)藝要求播種行距為600 mm,播種機(jī)作業(yè)速度取4 km/h。根據(jù)文獻(xiàn)及對(duì)偶立式刀片安裝刀盤(pán)的強(qiáng)度要求,系數(shù)不宜過(guò)小,故取1.5~1.8[20-23],則刀盤(pán)幅寬為216~240 mm,同時(shí)結(jié)合方程(4)、(11)可得速度比為2.9~3.5,則秸稈移位防堵裝置刀軸轉(zhuǎn)速為445~538 r/min。
為了驗(yàn)證秸稈移位防堵裝置結(jié)構(gòu)參數(shù)和運(yùn)動(dòng)參數(shù)設(shè)計(jì)的合理性,運(yùn)用離散元法進(jìn)行主動(dòng)式秸稈移位防堵裝置作用下秸稈移位虛擬仿真試驗(yàn)。本文采用EDEM 2.6軟件建立秸稈全覆蓋土壤模型,為了能夠準(zhǔn)確地反映防堵裝置移位秸稈的作業(yè)效果,首先需要確定離散元仿真參數(shù)。
接觸模型是離散元法的重要基礎(chǔ),其實(shí)質(zhì)是準(zhǔn)靜態(tài)下顆粒固體的接觸力學(xué)彈塑性分析結(jié)果[24]。接觸模型的分析計(jì)算直接決定了顆粒所受的力、力矩和位移的大小,對(duì)不同的仿真對(duì)象,須建立不同的接觸模型,確保仿真結(jié)果的準(zhǔn)確性。在離散元單元法中,顆粒在運(yùn)動(dòng)過(guò)程中主要受2種力作用,即自身重力mg,土壤-秸稈顆粒間或者秸稈顆粒與防堵裝置法向碰撞接觸力F、法向阻力F、切向碰撞接觸力F、切向阻力F。根據(jù)牛頓第二運(yùn)動(dòng)定律,容易得到顆粒運(yùn)動(dòng)方程如式(12)所示。
其中
式中I為顆粒的轉(zhuǎn)動(dòng)慣量,kg·m2;n為與顆粒的碰撞接觸總數(shù),Hz;v為顆粒的移動(dòng)速度,m/s;T為顆粒受切向力形成的力矩,N·m;T為顆粒受到滾動(dòng)力矩,N·m;F為顆粒法向結(jié)合力,N;A為顆粒接觸面積,m2;k為黏附能量密度,kg/m3。
F根據(jù)秸稈顆粒是否有粘聚力進(jìn)行設(shè)定。試驗(yàn)區(qū)土壤為砂姜黑土,具有散粒體物料特性,顆粒表面黏附力較小,且具有一定的壓縮性,因此本研究設(shè)定土壤顆粒塑性變形的Hysteretic Spring接觸模型和添加一個(gè)法向黏聚力的Linear Cohesion接觸模型。土壤本征參數(shù)經(jīng)測(cè)量及多數(shù)研究者在離散元土壤模型相關(guān)文獻(xiàn)[25-26]可得如表1。
表1 土壤參數(shù)和接觸參數(shù)
通過(guò)掃描電子顯微鏡及傅里葉紅外光譜測(cè)定小麥秸稈是一種典型的多相、篩狀、不連續(xù)、不均勻、各向異性的復(fù)合材料,故仿真小麥秸稈難度較大。至今未見(jiàn)有運(yùn)用商業(yè)離散元軟件建立全方位柔性體秸稈模型的相關(guān)研究[27-28],本文采用EDEM中軟球模型建立秸稈顆粒模型,其中軟球顆粒的法向力簡(jiǎn)化為彈簧k和阻尼器C,切向力簡(jiǎn)化為彈簧k、阻尼器c和滑動(dòng)摩擦器。選用10個(gè)半徑為6 mm、球心間隔為14 mm組成的長(zhǎng)為140 mm的長(zhǎng)線性模型作為秸稈顆粒,如圖5所示,每1節(jié)是具有剛度和阻尼的空心圓柱體連接2個(gè)圓球顆粒形成的。仿真過(guò)程中所使用的防堵裝置參數(shù)及秸稈顆粒之間的恢復(fù)系數(shù)、靜摩擦因素、滾動(dòng)摩擦因素參照文獻(xiàn)[29-32],如表2所示。
注:kn為秸稈顆粒模型的剛度,N·m-1;cn為秸稈顆粒模型的阻尼系數(shù);μ為秸稈相鄰顆粒模型的摩擦系數(shù)。
表2 秸稈參數(shù)和接觸參數(shù)
通過(guò)對(duì)土壤-秸稈-防堵裝置系統(tǒng)相互接觸模型及仿真參數(shù)的測(cè)定,建立2 400 mm(長(zhǎng))×800 mm(寬)× 200 mm(高)離散元秸稈全覆蓋土壤模型,為了減少土壤表層仿真秸稈與實(shí)際對(duì)應(yīng)的覆蓋秸稈密度的誤差,虛擬秸稈覆蓋土槽0~150 mm深度的耕作層土壤顆粒為隨機(jī)排列;150~200 mm深度的秸稈顆粒采用隨機(jī)(孔隙率12.5%)排列;仿真共生成250 000個(gè)土壤顆粒和4 000個(gè)秸稈顆粒。防堵裝置采用65 Mn鋼加工,選用“L”型立式刀片,為了減少覆蓋秸稈下耕作層的土壤擾動(dòng)量,達(dá)到保墑的目的,主動(dòng)式秸稈移位防堵裝置刀齒入土深度設(shè)為10 mm。結(jié)合上述秸稈移位防堵裝置參數(shù)分析,應(yīng)用UG/NX軟件創(chuàng)建不同參數(shù)的防堵裝置幾何仿真模型,并將幾何仿真模型導(dǎo)入EDEM中。仿真開(kāi)始前,防堵裝置位于系統(tǒng)模型的一端,圖6所示為土壤-秸稈-防堵裝置系統(tǒng)模型。
圖6 土壤-秸稈-防堵裝置系統(tǒng)模型
利用建立的秸稈全覆蓋土壤離散元模型對(duì)主動(dòng)式秸稈移位防堵裝置進(jìn)行仿真試驗(yàn)。根據(jù)2.2節(jié)運(yùn)動(dòng)方程求解及后期整機(jī)設(shè)計(jì)中換向器傳動(dòng)比選型要求,仿真設(shè)置中對(duì)刀軸轉(zhuǎn)速進(jìn)行取整為500 r/min、回轉(zhuǎn)半徑為120 mm、刀盤(pán)幅寬216 mm、刀齒入土深度為10 mm、前進(jìn)速度為4 km/h。通過(guò)導(dǎo)出防堵裝置刀刃切向力、秸稈位移量、秸稈作用力及移位效果等指標(biāo),驗(yàn)證秸稈移位防堵裝置結(jié)構(gòu)參數(shù)和運(yùn)動(dòng)參數(shù)設(shè)計(jì)的合理性。在保證秸稈移位仿真過(guò)程中秸稈顆粒運(yùn)動(dòng)的連續(xù)性的前提下,設(shè)定仿真時(shí)間步長(zhǎng)為3.5×10-3s,仿真總時(shí)間為6.5 s。
3.4.1 秸稈微觀運(yùn)動(dòng)
全覆蓋無(wú)支撐秸稈顆粒隨機(jī)排列在土壤顆粒表層,每一時(shí)刻秸稈所受刀齒的切向力的EDEM仿真結(jié)果可以用來(lái)研究擾動(dòng)過(guò)程中秸稈的運(yùn)動(dòng)軌跡。首先分析余擺運(yùn)動(dòng)的刀齒在50 mm深的秸稈顆粒中擾動(dòng)作業(yè)時(shí)所受切向力如圖7所示,刀刃所受切向力隨時(shí)間變化呈出不規(guī)律的上下浮動(dòng),其切向力平均值為5.8 N。
圖7 50 mm深處刀刃所受切向力的時(shí)域曲線
為了更好地分析秸稈的運(yùn)動(dòng)軌跡,隨機(jī)選取的3根秸稈顆粒(1號(hào)、2號(hào)、3號(hào))在主動(dòng)式秸稈移位防堵裝置的擾動(dòng)下運(yùn)動(dòng),設(shè)定所有秸稈顆粒的初始位置為坐標(biāo)原點(diǎn),從圖8a受力-時(shí)間曲線可以看出旋轉(zhuǎn)刀刃的瞬間滑切擾動(dòng)作用產(chǎn)生一個(gè)波峰力,隨后秸稈顆粒移位脫離刀刃接觸,作用力開(kāi)始衰減至0左右,其中單根秸稈顆粒受力平均值為55.2×10-3N。從圖8b位移-時(shí)間曲線圖中可以看出秸稈位移在作用力0.2 s以后位移量瞬間突增,后來(lái)的飛濺運(yùn)動(dòng)靠自身的慣性,作用力消失后1.2 s左右,秸稈位移矢量值穩(wěn)定在400~580 mm范圍內(nèi),秸稈顆粒從作業(yè)行移位至苗床行間,符合農(nóng)藝行要求。
圖8 防堵裝置作業(yè)秸稈顆粒的運(yùn)動(dòng)分析
3.4.2 秸稈移位效果
仿真過(guò)程中秸稈受防堵裝置刀齒作用力發(fā)生運(yùn)動(dòng),不考慮秸稈被切斷的情況。由于仿真時(shí)間0~3.65 s內(nèi),沒(méi)有前進(jìn)運(yùn)動(dòng),裝置處于下降調(diào)整入土深度運(yùn)動(dòng)。3.65 s后防堵裝置開(kāi)始作前進(jìn)和回轉(zhuǎn)耦合運(yùn)動(dòng),秸稈顆粒開(kāi)始發(fā)生位置變化,對(duì)回轉(zhuǎn)區(qū)域內(nèi)的約1 200根秸稈顆粒進(jìn)行位移追蹤,同時(shí)對(duì)作業(yè)區(qū)初始位置秸稈顆粒數(shù)和仿真結(jié)束后該位置秸稈顆粒數(shù)進(jìn)行統(tǒng)計(jì),設(shè)定作業(yè)區(qū)內(nèi)初始位置秸稈顆粒數(shù)與被移至的秸稈顆粒數(shù)比值百分?jǐn)?shù)為秸稈清秸率,則仿真試驗(yàn)統(tǒng)計(jì)在回轉(zhuǎn)區(qū)域內(nèi)秸稈清秸率達(dá)98.5%,同時(shí)對(duì)無(wú)秸區(qū)行寬進(jìn)行隨機(jī)采樣測(cè)量取平均值為245.5 mm,符合無(wú)秸區(qū)開(kāi)溝施肥、播種要求,故秸稈移位防堵裝置的機(jī)構(gòu)參數(shù)和運(yùn)動(dòng)參數(shù)設(shè)計(jì)可行。如圖9所示不同時(shí)刻秸稈移位追蹤效果圖,隨著防堵裝置擾動(dòng)前進(jìn)出現(xiàn)一片無(wú)秸稈區(qū)域。
圖9 不同仿真時(shí)刻秸稈移位效果圖
田間試驗(yàn)選定安徽省宿州市現(xiàn)代農(nóng)業(yè)示范園安徽農(nóng)業(yè)大學(xué)皖北試驗(yàn)站進(jìn)行試驗(yàn)。主要考核麥秸稈粉碎全量還田,秸稈留茬高度40 mm、秸稈覆蓋量均值為1.24 kg/m2下玉米免耕播種防堵技術(shù)試驗(yàn)。將主動(dòng)式秸稈移位防堵裝置安裝在2BMY-4型玉米免耕播種機(jī)機(jī)架上,整機(jī)作業(yè)幅寬2 400mm,作業(yè)效率為0.56 hm2/h。使用功率55 kW拖拉機(jī)進(jìn)行田間試驗(yàn),其中拖拉機(jī)后輸出最高轉(zhuǎn)速為720 r/min,其中換向器傳動(dòng)比為0.9,實(shí)際田間試驗(yàn)時(shí)實(shí)測(cè)作業(yè)轉(zhuǎn)速可達(dá)到秸稈移位防堵需要刀軸轉(zhuǎn)速為500 r/min的條件,開(kāi)溝器深度為150 mm,機(jī)具的前進(jìn)速度4 km/h。
1)通過(guò)性
根據(jù)農(nóng)業(yè)行業(yè)標(biāo)準(zhǔn)《免耕播種機(jī)質(zhì)量評(píng)價(jià)技術(shù)規(guī)范》[33](NY/T1768-2009)及農(nóng)業(yè)部農(nóng)機(jī)鑒定總站免耕播種機(jī)性能檢測(cè)要求,按照正常的作業(yè)速度前進(jìn),觀察機(jī)具在作業(yè)過(guò)程中能否正常作業(yè),記錄機(jī)具停下來(lái)清茬的次數(shù),本試驗(yàn)采用往返作業(yè)300 m為一組,共記錄5組。并與傳統(tǒng)玉米免耕直播機(jī)進(jìn)行對(duì)比。
2)秸稈清秸率
秸稈清秸率的測(cè)定,利用五點(diǎn)取樣法進(jìn)行隨機(jī)取樣,選取秸稈移位裝置作業(yè)區(qū)域測(cè)量作業(yè)前后每平方米地表覆蓋的秸稈量,并稱質(zhì)量11、22。按照式(14)計(jì)算作業(yè)前后開(kāi)溝器正前方測(cè)定區(qū)內(nèi)秸稈清秸率[11]。
式中為秸稈清秸率,%;11為作業(yè)前單位面積秸稈總質(zhì)量,kg/m2;22為作業(yè)后單位面積秸稈總質(zhì)量,kg/m2。
4.3.1 通過(guò)性
相同試驗(yàn)條件下,使用安裝主動(dòng)式秸稈移位防堵裝置的玉米免耕播種機(jī)進(jìn)行田間作業(yè),試驗(yàn)過(guò)程中未發(fā)現(xiàn)開(kāi)溝器壅堵現(xiàn)象;對(duì)照組使用傳統(tǒng)免耕播種機(jī)作業(yè),在試驗(yàn)過(guò)程中開(kāi)溝器一共出現(xiàn)8次壅堵并進(jìn)行清茬工作。其中秸稈移位玉米免耕播種機(jī)田間作業(yè)前后效果如圖10所示,通過(guò)田間試驗(yàn)驗(yàn)證秸稈移位防堵裝置功能的可行性。
圖10 主動(dòng)式秸稈移位防堵裝置作業(yè)前后秸稈覆蓋效果
4.3.2 秸稈清秸率
為了減少覆蓋秸稈下耕作層的動(dòng)土量,達(dá)到保墑的目的,主動(dòng)式秸稈移位防堵裝置刀齒入土深度為10 mm。表4測(cè)定結(jié)果表明:采用加裝秸稈移位裝置的免耕播種機(jī),秸稈清秸率平均值為90.21%,相比仿真減小8.29個(gè)百分點(diǎn)。
表4 秸稈清秸率測(cè)定結(jié)果
本文基于“秸稈移位播種”作業(yè)思路,設(shè)計(jì)了麥茬秸稈全覆蓋地玉米免耕播種開(kāi)溝防堵裝置,有效解決了傳統(tǒng)玉米免耕播種在秸稈全覆蓋地作業(yè)過(guò)程中出現(xiàn)開(kāi)溝器壅堵、架種和晾種等問(wèn)題。
1)運(yùn)用EDEM軟件建立了土壤-秸稈-防堵裝置系統(tǒng)模型,設(shè)定刀軸轉(zhuǎn)速為500 r/min,回轉(zhuǎn)半徑為120 mm,刀盤(pán)幅寬為216 mm,秸稈移位玉米免耕播種機(jī)防堵裝置刀齒入土深度為10 mm,通過(guò)分析秸稈微觀運(yùn)動(dòng)和秸稈移位效果,檢驗(yàn)了刀軸工作轉(zhuǎn)速、回轉(zhuǎn)半徑和刀盤(pán)幅寬等參數(shù)設(shè)計(jì)的合理性。
2)田間試驗(yàn)表明,留茬高度40 cm、覆蓋量1.24 kg/m2的小麥秸稈全覆蓋田,使用主動(dòng)式秸稈移位防堵裝置的2BMY-4型玉米免耕播種機(jī)作業(yè),未發(fā)生堵塞現(xiàn)象,通過(guò)性良好,秸稈平均清秸率90.21%,較仿真結(jié)果低8.29個(gè)百分點(diǎn)。
本研究可解決麥玉輪作區(qū)麥茬秸稈全量還田下玉米免耕播種通過(guò)性提供可行性方案,影響秸稈移位免耕播種通過(guò)性能的因素較多,如刀軸轉(zhuǎn)速、回轉(zhuǎn)半徑及驅(qū)動(dòng)裝置類型等,本研究建立的仿真模型是在小麥秸稈全覆蓋地某一特定的刀軸轉(zhuǎn)速、驅(qū)動(dòng)裝置類型和回轉(zhuǎn)半徑條件下構(gòu)建的,需進(jìn)一步探究最佳組合參數(shù)。不同作物秸稈全覆蓋地免耕防堵要求不一,需要根據(jù)農(nóng)業(yè)生產(chǎn)實(shí)際進(jìn)行調(diào)節(jié)。
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Design and experiment of active straw-removing anti-blocking device for maize no-tillage planter
Wang Weiwei, Zhu Cunxi, Chen Liqing, Li Zhaodong, Huang Xin, Li Jincai※
(230036,)
Conventional farming methods with multiple operations by multiple types of machinery may lead to serious shallow soil hardening and cost increases for wheat-maize rotation cropping areas in Huang-Huai-Hai Plain of China. In addition, there are several technical problems for the traditional maize no-tillage planter when seeding in the fields covered by heavy wheat straw, 1) soil-buried parts of the no-tillage planter are easy to be blocked by the wheat straw, which cannot guarantee the smooth operation; 2) the seeds may be improperly planted on the top of wheat straw since the soil is totally covered by the wheat straw; 3) the germinated seeds cannot grow up normally as no soil covered, which result in production declines. In the current study, an active anti-blocking device was designed for the maize no-till planter for removing wheat straw that covered on the soil surface. During seeding in the field, the wheat straw that covered on the surface was disrupted and thrown into the air by the device and was transferred backward before it landed. Then, the planter would ditch, fertilize and seed in the cleaned field produced by the device. At the last, the smashed straw was evenly covered on the fields after planting. The structural parameters and motion parameters of the anti-blocking device were determined based on a simulation model built by the discrete element method (DEM). The model was composed of soil, full-coverage straw, and device, which can be used to simulate the process of removing the unsupported straw from the soil surface. The model and interaction system was established in EDEM 2.6 simulation environment, and their physical properties were calibrated with the real properties of lime concretion black soil and wheat straw. According to theoretical design to set simulation parameters, the radius of the cutter head was set to 120 mm, the driving speed of the cutter shaft was set to 500 r/min, and the depth of the cutting edge was set to 10 mm, the operating velocity of the active anti-blocking device was set to 4 km/h.The simulation experiment was used to analyze the displacement and the clearance rate of straw for selecting suitable structural parameters and motion parameters for design. The simulation results indicated that the tangential force of the cutting edge was irregularly fluctuating with time, and the average tangential force was 5.8 N; the straw clearance rate was 98.5% in the disrupted zone, the average width of the area without straw was 245.5 mm according to the random sampling, which was in accordance with the requirement of ditching, fertilizing, and seeding. The field experiment was carried out by a straw-removing maize no-tillage planter with the designed anti-blocking device mounted, for ditching, fertilizing and seeding, within a field covered by 1.24 kg/m2wheat straw with stubble height of 40 mm. The planter was hauled by a high-power tractor of over 55 kW with an operating velocity of 4 km/h and a working width of 2 400 mm, resulting in a pure productivity of more than 0.56 hm2/h. The field experiment and measurement results showed that the straw-removing no-tillage planter with an active anti-blocking device had a stable operation that can significantly improve the seeding environment. The number of clear straw was 0, the straw clearance rate was 90.21%, and reduced by 8.29 percentage points compared with the simulated value. This study illustrated that the maize no-tillage planter with active anti-blocking device was suitable for removing the covering straw, cleaning the seedbed, fertilizing, and covering the seedbed with wheat straw. Meanwhile, the research provides a reference for the design and extending of the no-tillage planter for the fields with full coverage of straw.
mechanization; design; computer simulation; straw-removing; discrete element method; straw-cover field; no-tillage seeding; active anti-blocking
10.11975/j.issn.1002-6819.2017.24.002
S224.29
A
1002-6819(2017)-24-0010-08
2017-07-11
2017-11-01
公益性行業(yè)(農(nóng)業(yè))科研專項(xiàng)(201503136);“十三五”國(guó)家重點(diǎn)研發(fā)計(jì)劃課題(2017YFD0300408、2017YFD0301307);研究生創(chuàng)新基金項(xiàng)目(2017yjs-42)
王韋韋,博士生,主要研究方向?yàn)楸Wo(hù)性耕作技術(shù)與機(jī)具。Email:wangww0618@163.com
李金才,教授,博士生導(dǎo)師,主要從事作物栽培及秸稈還田理論與技術(shù)研究。Email:ljc5122423@126.com
王韋韋,朱存璽,陳黎卿,李兆東,黃 鑫,李金才. 玉米免耕播種機(jī)主動(dòng)式秸稈移位防堵裝置的設(shè)計(jì)與試驗(yàn)[J]. 農(nóng)業(yè)工程學(xué)報(bào),2017,33(24):10-17. doi:10.11975/j.issn.1002-6819.2017.24.002 http://www.tcsae.org
Wang Weiwei, Zhu Cunxi, Chen Liqing, Li Zhaodong, Huang Xin, Li Jincai. Design and experiment of active straw-removing anti-blocking device for maize no-tillage planter[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(24): 10-17. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2017.24.002 http://www.tcsae.org