生物質(zhì)論文基于ANSYS的秸稈活塞式成型特性及摩擦熱分析

1、生物質(zhì)論文：基于ANSYS的秸稈活塞式成型特性及摩擦熱分析【中文摘要】秸稈固化成型技術(shù)能使松散的秸稈致密化,提高秸稈能量密度和燃燒特性,使其可作為清潔能源直接替代煤用于生產(chǎn)生活各個領(lǐng)域,同時也能解決秸稈儲存、運輸困難問題,是實現(xiàn)秸稈綜合化、規(guī)模化利用的重要技術(shù)手段。但是目前該技術(shù)尚需在成型過程特性及成型摩擦熱方面加深理論研究,揭示秸稈成型粘結(jié)機(jī)理,為成型制品品質(zhì)預(yù)測和控制、設(shè)備優(yōu)化提供理論依據(jù)。本文通過對秸稈化學(xué)組成、物理特性及常溫成型機(jī)理的分析,得出影響秸稈常溫固化成型品質(zhì)的關(guān)鍵因素是壓縮力和成型過程中的摩擦熱?；谠摻Y(jié)論,根據(jù)活塞式成型技術(shù)間歇式生產(chǎn)的特點,對活塞一次沖壓成型中成型力變化和

2、物料移動進(jìn)行實驗研究,提出適合活塞式成型技術(shù)的“半閉式”成型模型,即成型過程未達(dá)到推移階段前,物料相當(dāng)于在由模具和靠摩擦力作用下保持靜止的已成型制品組成的閉式環(huán)境中進(jìn)行壓縮。運用彈塑性力學(xué)、接觸力學(xué)、粘彈性和有限元理論對秸稈固化成型主壓縮階段進(jìn)行限元分析,研究主壓縮階段物料形變規(guī)律、應(yīng)力分布及接觸應(yīng)力情況,為模具設(shè)計和成型工藝改進(jìn)提供方法指導(dǎo)和依據(jù)。基于摩擦學(xué)、傳熱學(xué)原理,結(jié)合秸稈活塞式常溫成型技術(shù)的特點,對成型過程中的摩擦熱問題進(jìn)行研究,通過引入平均壓力、當(dāng)量速度等物理量推導(dǎo)成型過程中摩擦熱產(chǎn)生方程,將成型過程摩擦熱問題轉(zhuǎn)化為第二、三類邊界條件的無內(nèi)熱源的非穩(wěn)態(tài)傳熱問題；建立成型摩擦熱有限元

3、分析模型,對摩擦熱引起的溫度場分布進(jìn)行研究,并通過實驗驗證有限元模擬的正確性,得出摩擦熱引起的溫度場變化規(guī)律；通過對實驗樣機(jī)在不同生產(chǎn)率條件下的摩擦熱模擬分析,研究表明模具在摩擦熱作用下,溫度隨著時間升高并穩(wěn)定在一定溫度,其增長速度和穩(wěn)態(tài)溫度隨著生產(chǎn)率的提高而提高。在摩擦熱引起的溫度場規(guī)律研究基礎(chǔ)上,針對目前秸稈類生物質(zhì)材料的熱物性參數(shù)欠缺的現(xiàn)狀,進(jìn)行了秸稈物性參數(shù)的實驗研究,得出秸稈導(dǎo)熱系數(shù)、比熱隨含水率、溫度和密度的變化規(guī)律,為本文研究摩擦熱引起的溫度場在成型制品的傳導(dǎo)提供數(shù)據(jù)支持的同時,也能為秸稈類材料熱相關(guān)的技術(shù)研究提供依據(jù)；建立秸稈成型過程中摩擦熱傳導(dǎo)模型,分析不同條件下摩擦熱在制品

4、內(nèi)的分布及對木質(zhì)素粘結(jié)作用進(jìn)行分析,研究表明制品內(nèi)溫度場分布是由模具溫度和制品在模具內(nèi)滯留時間共同決定的；對于本文實驗樣機(jī),雖然當(dāng)生產(chǎn)率為60kg/h時,摩擦熱引起的溫度場能達(dá)到220230,生產(chǎn)率為50kg/h時溫度場為180190,但是由于制品在模具內(nèi)滯留時間的影響,生產(chǎn)率為50kg/h,制品中心木質(zhì)素也能達(dá)到軟化溫度,成型品質(zhì)較高；該研究能為成型生產(chǎn)工藝改進(jìn)、提高成型品質(zhì)和設(shè)備設(shè)計提供理論依據(jù)。【英文摘要】Straw curing briquetting technology can densify unconsolidated straws, increase the energy d

5、ensity, improve the combustion properties, replace coals as clean energy used in every field of production and living, and solve storage and transportation problems. It is an important technical method of integrated and large-scale use of straws. However, it still needs to be deepened on the theoret

6、ical research of briquetting process properties and briquetting frictional heat, so as to reveal briquetting adhesive mechanism of straws, and provide theory support for predicting and controlling quality of briquetting products and optimizing equipments.Through the analysis of chemical compositions

7、, physical properties and normal temperature briquetting mechanism of straws, it can be concluded that the key factor of impacting curing briquetting qualities under normal temperature is compression force and frictional heat in the briquetting process. Based on this conclusion, changes of riquettin

8、g forces and transportation of materials in the piston one-time stamping molding process are studied according to properties of piston-type briquetting technologies. Semi-closed briquetting model that suits to the piston-type briquetting technologies is built:materials are compressed in the closed e

9、nvironment equivalent to be made up of mould and briquetted products which remains stationary by the action of friction. The finite element analysis method is established in the primary compression stage of straw curing briquetting using the plastoelasticity, contact mechanics, viscoelastic and fini

10、te element theory. With this method, material deformation law, stress distribution and contact stress situation in the primary compression stage are studied, which provides method guideline to mold design and briquetting process improvement.Research on frictional heat in the briquetting process is c

11、arried out combing with piston-type nomal tempreture briquetting technologies based on tribology and heat transfer theroy. By introducing physical quantity such as average pressure and equivalent velocity, the equation of the frictional heat generation in the briquetting process is derived, which co

12、nverts the frictional heat problem in the briquetting process into transient heat transfer problems without inner heat source under the second and third boundary condition. The finite element analysis model of briquetting frictional heat is built, and then the temperature field distribution caused b

13、y frictional heat is researched. The rule of temperature field variation caused by frictional heat is drawn through validating the correctness of finite element simulation by experiments. Based on the frictional heat simulation and analysis of prototype under different productivities conditions, it

14、is shown that the tempreture of the mould is increasing and remain stable at a certain tempreture over time under the action of frictional heat, and the growth rate and steady temperature go up with the increasing productivities.On the basis of research on the rule of temperature field distribution

15、caused by frictional heat, the experimental study of straw thermophysical parameters is carried out according to lack of thermophysical parameters of biomass materials currently. The change rule of thermal conductivity and specific heat with the changes of moisture content, tempreture and density is

16、 obtained. It can not only provide data support for the research on conduction of temperature field caused by frictional heat in briquetting products, but also provide basis for research on technologies related to heat of straws. The model of friction heat transfer in the straw briquetting process i

17、s built. And the distribution of frictional heat in briquetting products under different conditions is analyzed; aslo the cohesive action of lignin is studied. It is revealed that temperature field distribution in briquetting products is determined by both mold temperature and residence time that th

18、e briquetting products stay in the mold. With regard to the prototype in this paper, when the productivity is 60kg/h, the temperature field caused by frictional heat can reach 220-230, and when the productivity is 50kg/h, the temperature field is 180190. However, because of the impact of residence time that the briquetting products stay in the mold, when the productivity is 50kg/h, the lignin in the center of briquetting products