魏 海,謝煥雄,胡志超,顏建春,劉敏基,徐弘博(農(nóng)業(yè)部南京農(nóng)業(yè)機(jī)械化研究所,南京 210014)
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花生莢果氣力輸送設(shè)備參數(shù)優(yōu)化與試驗(yàn)
魏海,謝煥雄※,胡志超,顏建春,劉敏基,徐弘博
(農(nóng)業(yè)部南京農(nóng)業(yè)機(jī)械化研究所,南京 210014)
摘要:針對(duì)現(xiàn)有氣力輸送設(shè)備對(duì)花生莢果輸送損耗大、裂莢、破碎率高等問題,改進(jìn)關(guān)鍵部件結(jié)構(gòu),在分離筒內(nèi)壁安裝硅膠緩沖板,改進(jìn)鎖氣器。通過對(duì)比,改進(jìn)后鎖氣器能更好適應(yīng)莢果輸送。根據(jù)花生莢果在輸送過程中受力破損機(jī)理,選取分離筒內(nèi)壁硅膠緩沖板厚度、風(fēng)機(jī)轉(zhuǎn)速、花生莢果含水率三因素,以白沙花生為原料進(jìn)行氣力輸送正交優(yōu)化試驗(yàn),考察上述三因素對(duì)莢果生產(chǎn)效率、裂莢率、破碎率的影響。結(jié)果表明,硅膠緩沖板厚度對(duì)目標(biāo)因素影響最大,風(fēng)機(jī)轉(zhuǎn)速次之,花生莢果含水率影響最小。當(dāng)硅膠緩沖板厚度為5 mm,風(fēng)機(jī)轉(zhuǎn)速2 700 r/min,花生莢果含水率10%時(shí)輸送效果最佳,裂莢、破碎率降低明顯。該研究可為花生氣力輸送設(shè)備的結(jié)構(gòu)優(yōu)化提供參考。
關(guān)鍵詞:機(jī)械化;優(yōu)化;農(nóng)作物;氣力輸送;花生莢果;低損;試驗(yàn)分析
魏海,謝煥雄,胡志超,顏建春,劉敏基,徐弘博. 花生莢果氣力輸送設(shè)備參數(shù)優(yōu)化與試驗(yàn)[J]. 農(nóng)業(yè)工程學(xué)報(bào),2016,32(2):6-12.doi:10.11975/j.issn.1002-6819.2016.02.002http://www.tcsae.org
Wei Hai, Xie Huanxiong, Hu Zhichao, Yan Jianchun, Liu Minji, Xu Hongbo. Parameter optimization and test of pneumatic conveying equipment for peanut pods[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(2): 6-12. (in Chinese with English abstract)doi:10.11975/j.issn.1002-6819.2016.02.002 http://www.tcsae.org
Email:weihgs@163.com
Email:xhxnq@163.com
花生作為極具國(guó)際競(jìng)爭(zhēng)力的優(yōu)質(zhì)油料作物和經(jīng)濟(jì)作物,其價(jià)值早已引起國(guó)家的高度重視,并作為重要出口創(chuàng)匯、農(nóng)業(yè)結(jié)構(gòu)調(diào)整重點(diǎn)發(fā)展和扶持的農(nóng)產(chǎn)品[1-3]。在花生收獲及加工過程中,輸送設(shè)備的優(yōu)劣是影響花生質(zhì)量和自動(dòng)化程度的主要因素之一[4-7]。
目前,花生主要采用帶式、斗式及螺旋等方式輸送,但由于輸送環(huán)境條件及配套作業(yè)機(jī)具結(jié)構(gòu)復(fù)雜多樣,上述輸送方式不能有效滿足作業(yè)場(chǎng)合需求,而國(guó)外上世紀(jì)80年代從冶金、化工領(lǐng)域發(fā)展起來的氣力輸送技術(shù)[8],因其結(jié)構(gòu)簡(jiǎn)單、配置靈活、易操作,已廣泛應(yīng)用于稻谷、小麥、玉米等主要顆粒散料輸送[9-13]。但由于花生自身物料屬性的原因,氣力輸送設(shè)備作業(yè)原理對(duì)花生莢果損傷較大,不僅對(duì)后期生產(chǎn)造成影響,更會(huì)在儲(chǔ)運(yùn)過程中增加霉變風(fēng)險(xiǎn),極易產(chǎn)生黃曲霉毒素[14-16],因此氣力輸送未能在花生輸送領(lǐng)域得到有效應(yīng)用。在國(guó)內(nèi)外農(nóng)產(chǎn)品輸送領(lǐng)域未見花生莢果氣力輸送的相關(guān)報(bào)道。
本文通過改進(jìn)分離筒內(nèi)壁材料配置、鎖氣器結(jié)構(gòu)并通過正交試驗(yàn),分析影響花生莢果損傷的重要參數(shù),確定使花生莢果裂莢率、破碎率和生產(chǎn)效率加權(quán)最優(yōu)的結(jié)構(gòu)參數(shù)和作業(yè)參數(shù),以期為花生莢果氣力輸送設(shè)備設(shè)計(jì)提供參考。
1.1氣力輸送設(shè)備構(gòu)造及工作原理
氣力輸送設(shè)備由機(jī)架、高壓風(fēng)機(jī)、變頻調(diào)節(jié)器、風(fēng)量調(diào)節(jié)閥、分離筒(旋風(fēng)式分離器)、重力門(翻板式鎖氣器)、連接管路、輸送管路、卸料器及控制箱等關(guān)鍵部件組成,主要結(jié)構(gòu)及性能參數(shù)見表1,氣力輸送設(shè)備結(jié)構(gòu)圖如圖1所示。
表1 氣力輸送設(shè)備結(jié)構(gòu)及性能參數(shù)表Table 1 Structure and performance parameter for pneumatic conveying
工作原理:打開控制開關(guān),電機(jī)帶動(dòng)風(fēng)機(jī),通過變頻調(diào)速器調(diào)節(jié)電機(jī)轉(zhuǎn)速(調(diào)節(jié)范圍0~3 100 r/min)及輸送管內(nèi)風(fēng)速。負(fù)壓氣流經(jīng)過吸嘴、輸入管路將物料吸入,通過分離筒由過濾篩網(wǎng)筒將空氣與物料分離,物料在分離筒壁旋轉(zhuǎn)下降落入重力門,當(dāng)達(dá)到設(shè)定質(zhì)量時(shí)重力門打開,物料下落至風(fēng)機(jī)出風(fēng)口處,由正壓氣流通過輸出管路壓送到卸料器,卸料器將物料與空氣二次分離后卸出。
圖1 氣力輸送設(shè)備結(jié)構(gòu)圖Fig.1 Structure schematic of pneumatic conveying
1.2莢果損傷的因素及機(jī)理
從力學(xué)角度來看,輸送設(shè)備采用旋風(fēng)式分離器,花生莢果進(jìn)入分離筒后會(huì)受到比較明顯的撞擊與擠壓作用;莢果在管道內(nèi)被輸送時(shí),受到物料與管壁的撞擊與摩擦作用;還有物料與物料之間產(chǎn)生的撞擊與摩擦作用。這些作用構(gòu)成了花生莢果之間的壓力和剪切力,當(dāng)這些壓應(yīng)力和剪切應(yīng)力超過花生莢果的許可應(yīng)力時(shí),莢果就會(huì)產(chǎn)生破損。
1.3影響花生莢果損傷因素
在氣力輸送過程中,由于花生莢果外殼易破損的幾何形態(tài)和生物力學(xué)特性,在攜帶氣流作用下,莢果與機(jī)具內(nèi)壁、莢果之間劇烈碰撞,鎖氣器作業(yè)時(shí)對(duì)莢果的剪切作用,極易產(chǎn)生裂莢和破碎,故影響莢果損傷的主要因素有莢果形狀、輸送氣流速度(風(fēng)量)、莢果與分離筒內(nèi)壁產(chǎn)生的撞擊力、莢果含水率及受壓強(qiáng)度、鎖氣器結(jié)構(gòu)原理。
1.3.1莢果形狀
莢果幾何形狀對(duì)裂莢、破碎率的影響比較明顯,衡量物料形狀的參數(shù)主要是球形度φw為顆粒物料等體積球體表面積/顆粒物料表面積。φw值越大,物料顆粒表面的曲線越復(fù)雜,在輸送過程中更容易破碎。
通過試驗(yàn)對(duì)比白沙和4粒紅2種花生品種,白沙莢果長(zhǎng)度集中在30~35 mm,寬度為10~14 mm,厚度為11.3~14.0 mm,果殼厚度范圍為0.5~1.3 mm,平均為0.94 mm;4粒紅莢果長(zhǎng)度集中在33.3~50.0 mm,寬度為12~14 mm,厚度為12~14 mm,果殼厚度范圍為0.8~1.7 mm,平均為1.28 mm。為得出設(shè)備最優(yōu)工作參數(shù),選用顆粒表面曲線復(fù)雜、果殼較薄的白沙品種作為試驗(yàn)物料。
1.3.2輸送氣流速度
用于輸送物料的氣流速度是影響花生莢果裂莢和破碎率的最重要的參數(shù)。氣流速度越高,被輸送物料的運(yùn)動(dòng)速度就越高。根據(jù)已有的研究資料記載,物料速度和破碎率成冪次關(guān)系[2,4],其關(guān)系式的具體參數(shù)主要是由顆粒的物理性質(zhì)、輸送管道的管徑、管道路徑、輸送方式等參數(shù)決定。從能量角度分析,顆粒物料的速度越快,啟動(dòng)能就越大,在顆粒物料與分離筒發(fā)生碰撞時(shí),顆粒物料的動(dòng)能很容易達(dá)到破碎所需能量,從而發(fā)生破碎。
1.3.3莢果與分離筒內(nèi)壁產(chǎn)生的撞擊力
在輸送過程中,由于負(fù)壓作用,輸送管路風(fēng)速高,莢果通過進(jìn)料管進(jìn)入分離筒時(shí)運(yùn)動(dòng)速度極快,與分離筒壁撞擊接觸時(shí)間短,產(chǎn)生撞擊大,直接導(dǎo)致莢果裂莢、破碎。
為降低莢果與筒壁之間撞擊,在分離筒內(nèi)壁粘貼硅膠緩沖板,既降低莢果進(jìn)入筒內(nèi)時(shí)產(chǎn)生的撞擊力,也減少物料下落過程中與筒壁之間產(chǎn)生的摩擦。在轉(zhuǎn)速2 700 r/min、莢果含水率40%的條件下進(jìn)行試驗(yàn)。與未粘貼硅膠緩沖板相比,粘貼5 mm厚硅膠緩沖板,花生莢果裂莢率由15.33%降低至8.41%,降低了45%;破碎率由10.37%降低至4.83%,降低了53.5%,表明在分離筒內(nèi)壁粘貼硅膠緩沖板可有效降低花生莢果破損,提高輸送機(jī)作業(yè)性能。
1.3.4莢果含水率及耐壓強(qiáng)度
含水率是決定輸送過程中莢果受壓能力的重要參數(shù),壓力越低,輸送過程莢果越容易破損。采用深圳三思縱橫WDW-200型微機(jī)控制電子萬(wàn)能試驗(yàn)機(jī),對(duì)烘干前含水率約40%,晾曬過程中含水率約25%和烘干后含水率約10%的花生莢果進(jìn)行受壓試驗(yàn)分析,得出水分含量越高,受壓能力越強(qiáng),當(dāng)莢果受壓力達(dá)到峰值時(shí),莢果破碎。圖2為不同含水率花生莢果受壓能力測(cè)試結(jié)果圖(采用試驗(yàn)機(jī)對(duì)不同含水率花生進(jìn)行受壓能力試驗(yàn),沒有其他因素固定值)。
圖2 不同含水率對(duì)花生莢果受壓能力的影響Fig.2 Influence of different moisture content on peanut pods compressive resistance
1.3.5鎖氣器結(jié)構(gòu)及工作原理
鎖氣器是氣力輸送設(shè)備的關(guān)鍵組成部件,主要是為了在輸送過程中防止氣流回流、定量供料和卸料。鎖氣器的選擇也直接影響氣力輸送花生莢果的整體效果。
現(xiàn)有農(nóng)作物氣力輸送設(shè)備主要采用閉風(fēng)器(旋轉(zhuǎn)式鎖氣器),多用于稻谷、小麥、玉米等外形規(guī)則、表殼堅(jiān)硬的顆粒物料。閉風(fēng)器內(nèi)主要采用葉輪旋轉(zhuǎn)進(jìn)行物料輸送,為防止葉輪與機(jī)殼產(chǎn)生磨損,兩者之間留有間隙,葉輪旋轉(zhuǎn)過程中會(huì)對(duì)物料產(chǎn)生擠壓,旋轉(zhuǎn)到與機(jī)殼相切位置時(shí),還會(huì)對(duì)物料產(chǎn)生較大的剪切作用。這種作業(yè)原理極易導(dǎo)致花生莢果裂莢和破碎,不適用于花生莢果氣力輸送。
根據(jù)力平衡原理,采用翻板式重力回轉(zhuǎn)機(jī)構(gòu),研發(fā)設(shè)計(jì)重力門鎖氣器,作業(yè)時(shí)對(duì)物料無擠壓作用,還有效降低對(duì)物料產(chǎn)生的剪切作用,結(jié)構(gòu)如圖3所示。輸送前調(diào)節(jié)平衡調(diào)節(jié)錘,輸送過程中物料通過輸入管路進(jìn)入分離筒,當(dāng)分離筒內(nèi)莢果質(zhì)量達(dá)到設(shè)定質(zhì)量后,重力門自動(dòng)打開,物料通過重力門下落至輸出管路,再由風(fēng)機(jī)將物料吹出。重力門主要采用重力板開閉進(jìn)行物料輸送,為防止重力門半開閉狀態(tài)及莢果摩擦自鎖造成物料擁堵,在設(shè)計(jì)中將重力門倉(cāng)室和出料口尺寸優(yōu)化,既降低風(fēng)壓壓差,避免重力門出現(xiàn)半開閉狀態(tài);又防止花生莢果之間摩擦造成物料擁堵。輸送過程中,當(dāng)莢果質(zhì)量達(dá)到設(shè)定值時(shí),重力門才會(huì)打開,既減少重力板開閉對(duì)莢果產(chǎn)生的剪切力,又能避免機(jī)械能對(duì)莢果產(chǎn)生擠壓作用。當(dāng)輸送物料量不穩(wěn)定時(shí),重力門可調(diào)節(jié)輸送量,避免輸出過程中氣料混配比減小,加速度增大,在卸料器內(nèi)產(chǎn)生撞擊,造成花生莢果二次破損。重力門結(jié)構(gòu)及性能參數(shù)見表2。
圖3 重力門結(jié)構(gòu)圖Fig.3 Structure schematic of gravity door
表2 重力門結(jié)構(gòu)及性能參數(shù)表Table 2 Structure and performance parameter for gravity door
2.1試驗(yàn)因素
根據(jù)上述分析,風(fēng)機(jī)轉(zhuǎn)速影響輸送氣流速度,決定物料在輸送機(jī)內(nèi)部動(dòng)能大??;硅膠緩沖板厚度影響物料與筒壁之間撞擊緩沖程度;莢果含水率影響花生抗壓能力。因此控制該三因素,從損傷機(jī)理方面可有效降低莢果裂莢率和破碎率。選擇花生品種白沙作為試驗(yàn)材料。選擇分離筒內(nèi)壁粘貼硅膠緩沖板厚度、風(fēng)機(jī)轉(zhuǎn)速和莢果含水率作為試驗(yàn)因素,探討這些因素對(duì)花生莢果破損的影響規(guī)律,并在降低裂莢率和破碎率的基礎(chǔ)上減少對(duì)輸送設(shè)備生產(chǎn)效率的影響。
2.2試驗(yàn)方法
通過對(duì)比試驗(yàn)考察不同鎖氣器對(duì)不同含水率花生莢果裂莢、破碎率的影響。采用正交試驗(yàn)分析硅膠緩沖板厚度、風(fēng)機(jī)轉(zhuǎn)速和莢果含水率對(duì)裂莢、破碎及生產(chǎn)效率加權(quán)最優(yōu)的試驗(yàn)參數(shù)組合。參考目前生產(chǎn)上采用的參數(shù)值,試驗(yàn)因素變化范圍為:粘貼硅膠緩沖板厚度3~7 mm;風(fēng)機(jī)轉(zhuǎn)速3 100~2 700 r/min;含水率10%~40%。
2.3試驗(yàn)測(cè)試內(nèi)容
試驗(yàn)前對(duì)花生進(jìn)行清選,去除裂莢和破碎莢果后稱質(zhì)量,每批次試驗(yàn)用量100 kg;采用烘箱法測(cè)試花生莢果含水率;使用西門子6SE6420變頻調(diào)速器和優(yōu)利德UT371轉(zhuǎn)速計(jì)調(diào)節(jié)測(cè)試風(fēng)機(jī)轉(zhuǎn)速。在試驗(yàn)過程中需要測(cè)定的參數(shù)有風(fēng)機(jī)轉(zhuǎn)速、氣流速度和花生莢果輸送生產(chǎn)率等?;ㄉv果氣力輸送參數(shù)表如表3所示。
試驗(yàn)測(cè)試過程:接通電源,將變頻調(diào)速器調(diào)節(jié)至最小,緩慢調(diào)節(jié)頻率,使電機(jī)轉(zhuǎn)速逐漸加大,到達(dá)設(shè)定轉(zhuǎn)速后讓風(fēng)機(jī)工作平穩(wěn);測(cè)定進(jìn)、出料口風(fēng)速;通過吸嘴將花生莢果吸入輸送設(shè)備,同時(shí)用計(jì)時(shí)器計(jì)時(shí),測(cè)定輸送時(shí)間,完成試驗(yàn)后計(jì)算生產(chǎn)率(設(shè)備生產(chǎn)率2.5~3 t/h)。
表3 花生莢果氣力輸送參數(shù)表Table 3 Parameter for peanut pods pneumatic conveying
由表3可知,輸送氣速由風(fēng)機(jī)轉(zhuǎn)速控制,轉(zhuǎn)速越高,氣速越快。在設(shè)定的4個(gè)轉(zhuǎn)速下,只有轉(zhuǎn)速≥2 700 r/min時(shí),實(shí)際生產(chǎn)率符合設(shè)備生產(chǎn)率2.5~3 t/h要求,滿足正常生產(chǎn)需要。
2.4性能評(píng)價(jià)指標(biāo)
為評(píng)價(jià)輸送效果,以生產(chǎn)效率、裂莢率、破碎率作為評(píng)價(jià)指標(biāo),各指標(biāo)參數(shù)具體定義如下。
1)生產(chǎn)效率
2)莢果裂莢率
3)莢果破碎率
2.5氣力輸送設(shè)備關(guān)鍵參數(shù)正交優(yōu)化試驗(yàn)
根據(jù)上文選定的試驗(yàn)因素,確定如表4所示的因素和水平表,每組試驗(yàn)隨機(jī)取5個(gè)試樣,重復(fù)3次取平均值,選用L9(34)正交表進(jìn)行試驗(yàn)。
表4 花生莢果氣力輸送試驗(yàn)因素水平表Table 4 Experimental scheme of peanut pods pneumatic conveying
3.1不同鎖氣器輸送試驗(yàn)結(jié)果對(duì)比分析
不同鎖氣器對(duì)不同含水率花生莢果輸送試驗(yàn)結(jié)果評(píng)價(jià)指標(biāo)值如表5所示。
表5 不同鎖氣器對(duì)不同含水率花生莢果裂莢率和破碎率的影響Table 5 Comparison of different air locks effect on dehiscence and broken rate of peanut pods with different moisture contents
由表5可知,與閉風(fēng)器式鎖氣器相比,采用重力門式鎖氣器花生莢果裂莢率降低了4.86%~9.25%,破碎率降低了2.57%~7.42%,表明采用重力門進(jìn)行花生莢果氣力輸送試驗(yàn)具有較好的適應(yīng)性。
3.2花生莢果氣力輸送正交優(yōu)化試驗(yàn)結(jié)果與分析
由于該試驗(yàn)屬于多指標(biāo)正交試驗(yàn),為便于數(shù)據(jù)分析,選用綜合加權(quán)評(píng)分法將多個(gè)性能指標(biāo)的試驗(yàn)結(jié)果轉(zhuǎn)化為一個(gè)單指標(biāo)的試驗(yàn)結(jié)果,然后利用單指標(biāo)試驗(yàn)結(jié)果的分析方法進(jìn)行分析。
3.2.1確定各項(xiàng)試驗(yàn)指標(biāo)的權(quán)值
根據(jù)各項(xiàng)指標(biāo)的重要性,設(shè)定莢果輸送生產(chǎn)效率、裂莢率、破碎率的權(quán)重W1、W2、W3分別為0.1、0.4、0.5。
3.2.2統(tǒng)一各項(xiàng)指標(biāo)值的變化趨勢(shì)
為保證綜合加權(quán)平均值越大越好,應(yīng)將變化趨勢(shì)越小越好的指標(biāo)值轉(zhuǎn)化為越大越好,為此在其值前加以負(fù)號(hào),如式(1)所示。對(duì)于花生莢果裂莢率和破碎率其值越小越好。
式中y2 j為花生莢果裂莢率指標(biāo)第j號(hào)試驗(yàn)的評(píng)分值;y3 j為花生莢果破碎率指標(biāo)第j號(hào)試驗(yàn)的評(píng)分值。
3.2.3統(tǒng)一各指標(biāo)數(shù)量級(jí)和量綱
為了消除各指標(biāo)數(shù)量級(jí)和量綱對(duì)其加權(quán)評(píng)分值的影響,使各指標(biāo)的加權(quán)評(píng)分值具有可比性,需統(tǒng)一各指標(biāo)的數(shù)量級(jí)和量綱。由式(2)可得到各指標(biāo)的數(shù)量級(jí)、無量綱的評(píng)分值。
3.3試驗(yàn)結(jié)果分析
各項(xiàng)指標(biāo)的綜合加權(quán)評(píng)分結(jié)果如表6所示。將綜合加權(quán)評(píng)分結(jié)果作為各次試驗(yàn)的結(jié)果進(jìn)行方差分析,方差分析結(jié)果如表7所示:3個(gè)因素對(duì)氣力輸送花生莢果生產(chǎn)效率、裂莢率和破碎率影響程度順序依次是A>B>C,即是否在分離筒內(nèi)壁粘貼硅膠緩沖板對(duì)花生莢果輸送效果的影響最大,風(fēng)機(jī)轉(zhuǎn)速次之,花生莢果含水率影響最??;由表6極差分析可知?dú)饬斔突ㄉv果效果最佳的組合方案是A2B3C3,即硅膠緩沖板為5 mm,風(fēng)機(jī)轉(zhuǎn)速2 700 r/min,花生莢果含水率10%時(shí)輸送效果最佳。
3.4驗(yàn)證試驗(yàn)與分析
根據(jù)正交試驗(yàn)結(jié)果,硅膠緩沖板為5 mm,風(fēng)機(jī)轉(zhuǎn)速2 700 r/min,花生莢果含水率10%時(shí)進(jìn)行驗(yàn)證試驗(yàn),每組試驗(yàn)隨機(jī)取5個(gè)試樣,重復(fù)3次取平均值,試驗(yàn)測(cè)得生產(chǎn)效率為89.42%、裂莢率為0.738%、破碎率為0.185%,通過綜合加權(quán)評(píng)分得值為91.135%,試驗(yàn)結(jié)果明顯優(yōu)于正交試驗(yàn)結(jié)果90.115%,因此A2B3C3為最優(yōu)組合。
表6 花生莢果氣力輸送正交試驗(yàn)結(jié)果Table 6 Results of orthogonal experiment of peanut pod pneumatic conveying
表7 花生莢果氣力輸送方差分析結(jié)果Table 7 Results of analysis of variance of peanut pods pneumatic conveying
1)與閉風(fēng)器式鎖氣器相比,采用重力門式鎖氣器花生莢果裂莢率降低了4.86%~9.25%,破碎率降低了2.57%~7.42%,表明重力門式鎖氣器能有效適應(yīng)花生莢果氣力輸送。
2)對(duì)影響輸送效果的關(guān)鍵結(jié)構(gòu)參數(shù)和運(yùn)動(dòng)參數(shù)進(jìn)行正交優(yōu)化試驗(yàn),輸送結(jié)果表明:3個(gè)因素對(duì)花生莢果低損氣力輸送效果影響程度由大到小的順序?yàn)楣枘z緩沖板厚度、風(fēng)機(jī)轉(zhuǎn)速、莢果含水率;在硅膠緩沖板厚度為5 mm,風(fēng)機(jī)轉(zhuǎn)速為2 700 r/min,花生莢果含水率10%時(shí),花生莢果氣力輸送損失最小。
3)與采用閉風(fēng)器式鎖氣器、風(fēng)機(jī)轉(zhuǎn)速2 700 r/min、不粘貼硅膠緩沖板時(shí),含水率10%的花生莢果輸送效果相比,采用最優(yōu)組合A2B3C3方案時(shí),裂莢率從15.326%降低至0.738%,破碎率從10.375%降低至0.185%。
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Parameter optimization and test of pneumatic conveying equipment for peanut pods
Wei Hai, Xie Huanxiong※, Hu Zhichao, Yan Jianchun, Liu Minji, Xu Hongbo
(Nɑnjing Reseɑrch Institute of Agriculturɑl Mechɑnizɑtion, Ministry of ɑgriculture, Nɑnjing 210014, Chinɑ)
Abstract:As the internationally competitive oil crop and cash crop, peanuts have attracted great attention in China, and become an important export commodity and the key to the agricultural structure adjustment. Transportation equipment has directly affected the peanut quality after harvest and the degree of automation. Nowadays, people are increasingly concerned about food safety, and the quality risk of peanut pods during the process of conveying, such as dehiscence and break, has drawn more attention. Due to various factors, the peanut pods are easy to break in the process of conveying, which not only affects the later production, but also increases the risk of aflatoxin in the process of transportation and storage. Pneumatic conveying has great advantages for granular materials because of its simple structure, flexible operation and stable production efficiency and so on, which is widely used in the areas of agricultural product processing. Aiming at the problems of power loss, peanut pod’s dehiscence and break, crushing rate and unstable production efficiency, the structure and parameters of the existing pneumatic conveying equipment were improved and optimized. Besides, the experiments were conducted in main production areas of peanut. Through analyzing, the pod’s damage elements, including pod physical characteristics, fan speed,pod moisture content and air lock structure, were determined respectively. In the process of conveying, the impact of various forces on peanut pods would cause damage easily. To avoid these damages, the silicone buffer plate was installed on the wall of separate cylinder, which reduced the force between the material and the separate cylinder effectively. In order to adjust airflow velocity, the frequency conversion governor was installed on the conveyor equipment to control the fan speed, which could reduce the impact force to achieve the best conveying effect without the decrease of production efficiency and the break of peanut pods, when materials entered the equipment. By using WDW-200 type computer-controlled electronic universal testing machine, the compression capabilities of different peanut varieties were contrasted, and we selected white sand peanuts as the test materials, whose shells are coarse and thin. Then, we measured the moisture content of this kind of peanut in different drying periods. Afterwards, the rotate plank type air lock was designed to replace the original rotation type air lock,which would remain to be closed until the weight of peanut pods reached the set value. This kind of air lock could not only reduce the shear force to the pods when the gravity plate was opening and closing, but also avoid the squeezing action to the peanuts. At the same time, when the conveyed material quantity was unstable, the gravity door of the air lock could adjust the conveying quantity, which avoided the reduction of gas material mix proportion and the increase of peanut pod’s acceleration,and thus avoided the second break by relieving the strike of peanut pods in the unloader. According to the contrast test, the rotate plank type air lock caused a minor injury compared with the rotation type air lock. On this basis, pneumatic conveying orthogonal optimization test was conducted with the improved equipment. The influences of silicone buffer plate thickness, fan speed and peanut pod moisture content on productivity, dehiscence rate and broken rate were considered respectively. According to the comprehensively weighted evaluation and variance analysis, the results showed that the silicone buffer plate thickness had the most obvious influence, followed by the fan speed and peanut pod moisture content. When the thickness of silicone buffer plate was 5 mm, the fan speed was 2 700 r/min and the moisture content of peanut was 10%, the dehiscence and broken rate of peanut pods reached the minimum, which achieved the best conveying effect. This study can provide reliable evidence for structure optimization of pneumatic conveying equipment of peanuts.
Keywords:mechanization; optimization; crops; pneumatic conveying; peanut pods; reduce breakage; test analysis
通信作者:※謝煥雄,男,廣西浦北人,研究員,主要從事農(nóng)產(chǎn)品加工技術(shù)與裝備研究。南京農(nóng)業(yè)部南京農(nóng)業(yè)機(jī)械化研究所,210014。
作者簡(jiǎn)介:魏海,男,甘肅蘭州人,助理研究員,主要從事農(nóng)產(chǎn)品加工技術(shù)與裝備研究。南京農(nóng)業(yè)部南京農(nóng)業(yè)機(jī)械化研究所,210014。
基金項(xiàng)目:國(guó)家花生產(chǎn)業(yè)技術(shù)體系專項(xiàng)基金(CARS-13-產(chǎn)后加工機(jī)械);中國(guó)農(nóng)業(yè)科學(xué)院科技創(chuàng)新工程(農(nóng)產(chǎn)品分級(jí)與貯藏裝備創(chuàng)新團(tuán)隊(duì));公益性行業(yè)(農(nóng)業(yè))科研專項(xiàng)(201203037)
收稿日期:2015-07-22
修訂日期:2015-12-09
中圖分類號(hào):S229+.2
文獻(xiàn)標(biāo)志碼:A
文章編號(hào):1002-6819(2016)-02-0006-07
doi:10.11975/j.issn.1002-6819.2016.02.002