韓永超 李明
摘要: 研究了考慮船體垂蕩運(yùn)動(dòng)時(shí)船用轉(zhuǎn)子-軸承系統(tǒng)的動(dòng)力學(xué)特性。首先,在非慣性參考系基于短軸承理論建立了船體垂蕩作用下轉(zhuǎn)子-軸承系統(tǒng)的動(dòng)力學(xué)模型,結(jié)果顯示垂蕩作用下船用轉(zhuǎn)子-軸承系統(tǒng)具有幾何非線性特性;其次,采用數(shù)值方法,分析了系統(tǒng)的分岔圖、最大Lyapunov指數(shù)、穩(wěn)態(tài)響應(yīng)、軸心軌跡、Poincaré映射等,并與船體不發(fā)生垂蕩時(shí)的轉(zhuǎn)子系統(tǒng)動(dòng)力學(xué)特性進(jìn)行比較;最后,研究了垂蕩激勵(lì)幅值對(duì)轉(zhuǎn)子-軸承系統(tǒng)非線性動(dòng)力學(xué)特性的影響。結(jié)果表明:垂蕩運(yùn)動(dòng)會(huì)顯著地影響轉(zhuǎn)子的動(dòng)力學(xué)行為。在轉(zhuǎn)速較低時(shí),系統(tǒng)呈現(xiàn)周期1運(yùn)動(dòng),垂蕩對(duì)轉(zhuǎn)子的運(yùn)動(dòng)特性影響此時(shí)占主導(dǎo)作用;隨著轉(zhuǎn)速的增加,系統(tǒng)出現(xiàn)準(zhǔn)周期、周期2和雙Hopf現(xiàn)象,具有周期1、準(zhǔn)周期、周期2和混沌運(yùn)動(dòng)等復(fù)雜動(dòng)力學(xué)特性。
關(guān)鍵詞: 非線性動(dòng)力學(xué); 船用轉(zhuǎn)子-軸承系統(tǒng); 垂蕩; 短軸承模型
中圖分類號(hào): O322; O347.6 文獻(xiàn)標(biāo)志碼: A 文章編號(hào): 1004-4523(2019)03-0501-08
DOI:10.16385/j.cnki.issn.1004-4523.2019.03.015
引 言
艦船在航行時(shí)會(huì)產(chǎn)生橫蕩、縱蕩、垂蕩、橫搖、縱搖和艏搖等運(yùn)動(dòng)。這些運(yùn)動(dòng)形式都是典型的牽連運(yùn)動(dòng),會(huì)對(duì)船用轉(zhuǎn)子-軸承系統(tǒng)產(chǎn)生嚴(yán)重的影響,如艦船航行的安全性、可靠性、舒適性以及隱蔽性和作戰(zhàn)能力[1]。牽連運(yùn)動(dòng)對(duì)轉(zhuǎn)子-軸承系統(tǒng)動(dòng)力學(xué)特性的影響,主要集中在機(jī)載情況下轉(zhuǎn)子系統(tǒng)的動(dòng)力學(xué)問題。例如,文獻(xiàn)[2]建立了飛機(jī)飛行條件下雙盤懸臂轉(zhuǎn)子系統(tǒng)的動(dòng)力學(xué)模型,并對(duì)轉(zhuǎn)子系統(tǒng)的振動(dòng)特性進(jìn)行了討論;文獻(xiàn)[3]研究了飛行器在機(jī)動(dòng)飛行狀態(tài)下,機(jī)載轉(zhuǎn)子系統(tǒng)動(dòng)力學(xué)響應(yīng)的變化規(guī)律,結(jié)果表明飛行器垂直加速度分量過大或水平加速度過小的兩個(gè)極限狀態(tài)都會(huì)使原來穩(wěn)定的SFD-轉(zhuǎn)子系統(tǒng)變得不穩(wěn)定。文獻(xiàn)[4]對(duì)任意機(jī)動(dòng)飛行條件下的飛機(jī)建立了柔性轉(zhuǎn)子系統(tǒng)的線性動(dòng)力學(xué)模型,并針對(duì)幾種典型條件分析了系統(tǒng)的動(dòng)力學(xué)特性。文獻(xiàn)[5]建立了有不同類型支承條件及含有不同故障的轉(zhuǎn)子系統(tǒng)模型,并對(duì)在Herbs機(jī)動(dòng)飛行、水平盤旋、垂直面內(nèi)正弦機(jī)動(dòng)以及爬升-俯沖等機(jī)動(dòng)飛行環(huán)境下轉(zhuǎn)子系統(tǒng)的非線性動(dòng)力學(xué)行為及振動(dòng)機(jī)理進(jìn)行了研究。
對(duì)于船體在航行中遇到風(fēng)浪產(chǎn)生的牽連運(yùn)動(dòng)研究也取得一定的進(jìn)展。文獻(xiàn)[6]用Hamilton原理以歐拉角為參量描述船舶的搖擺運(yùn)動(dòng),建立了船舶參數(shù)下縱橫搖耦合運(yùn)動(dòng)的數(shù)學(xué)模型,研究了船舶的動(dòng)力學(xué)響應(yīng)。文獻(xiàn)[7]在低雷諾數(shù)的水隧道中,通過測(cè)量力、力矩和對(duì)液體流量可視化研究,優(yōu)化了經(jīng)歷橫搖和垂蕩運(yùn)動(dòng)的SD8020箔片水翼的推力產(chǎn)生性能和效率。文獻(xiàn)[8]研究了經(jīng)歷橫搖和垂蕩運(yùn)動(dòng)的剛性箔推進(jìn)性能的縮放規(guī)律,并通過水隧道實(shí)驗(yàn)驗(yàn)證了此規(guī)律。結(jié)果顯示:推力、功率和效率的縮放數(shù)據(jù)等都與系統(tǒng)所減少的頻率間存在依賴關(guān)系。文獻(xiàn)[9]研究了船舶在共振和最大激振條件下的波浪響應(yīng),發(fā)現(xiàn)當(dāng)滿足共振和最大激振條件時(shí),船舶響應(yīng)強(qiáng)烈。
上述的研究主要集中在飛行條件下轉(zhuǎn)子-軸承系統(tǒng)的非線性動(dòng)力學(xué)特性和波浪載荷作用下的船體運(yùn)動(dòng)響應(yīng)。對(duì)于牽連運(yùn)動(dòng)下的船用轉(zhuǎn)子-軸承系統(tǒng)動(dòng)力學(xué)特性研究,文獻(xiàn)[10]分析了艦船在水平和垂直擺動(dòng)情況下船用軸承的油膜力特性;文獻(xiàn)[11]考慮了艦船在橫搖、縱搖運(yùn)動(dòng)下,發(fā)動(dòng)機(jī)轉(zhuǎn)子-軸承系統(tǒng)的非線性動(dòng)力學(xué)響應(yīng);文獻(xiàn)[12]建立了氣囊-浮筏耦合船用轉(zhuǎn)子-軸承系統(tǒng)的動(dòng)力學(xué)模型,并且詳細(xì)分析了其動(dòng)力學(xué)特性。本文討論在垂蕩運(yùn)動(dòng)時(shí)船用轉(zhuǎn)子-軸承系統(tǒng)的動(dòng)力學(xué)響應(yīng),重點(diǎn)分析了在非線性油膜力作用下系統(tǒng)的動(dòng)力學(xué)行為,從而為船用轉(zhuǎn)子-軸承系統(tǒng)的振動(dòng)控制提供理論依據(jù)。
3 結(jié) 論
考慮在垂蕩運(yùn)動(dòng)情況下,基于短軸承理論建立了非慣性參考系下的轉(zhuǎn)子-軸承系統(tǒng)動(dòng)力學(xué)模型,分析了垂蕩幅值對(duì)轉(zhuǎn)子-軸承系統(tǒng)非線性動(dòng)力學(xué)特性的影響。結(jié)果表明:垂蕩運(yùn)動(dòng)對(duì)系統(tǒng)的非線性動(dòng)力學(xué)特性的影響較大,其中垂蕩運(yùn)動(dòng)在轉(zhuǎn)子轉(zhuǎn)速較低時(shí)對(duì)其動(dòng)力學(xué)特性影響起主導(dǎo)作用,此時(shí)系統(tǒng)表現(xiàn)為同步運(yùn)動(dòng)為主的周期1特性;隨著轉(zhuǎn)速的增加,系統(tǒng)會(huì)出現(xiàn)準(zhǔn)周期分岔,垂蕩還會(huì)引起非線性油膜力的變化,出現(xiàn)了明顯的油膜渦動(dòng)現(xiàn)象。隨著轉(zhuǎn)速的進(jìn)一步升高,轉(zhuǎn)子系統(tǒng)出現(xiàn)雙Hopf分岔現(xiàn)象,而后再次進(jìn)入準(zhǔn)周期分岔直至混沌,并且垂蕩運(yùn)動(dòng)會(huì)使轉(zhuǎn)子系統(tǒng)提前進(jìn)入混沌運(yùn)動(dòng)狀態(tài)。另外,垂蕩幅值的變化也會(huì)影響系統(tǒng)的動(dòng)力學(xué)特性,此時(shí)產(chǎn)生一條新的混沌路徑:周期2→準(zhǔn)周期→混沌。上述結(jié)果為艦船垂蕩作用下轉(zhuǎn)子-軸承系統(tǒng)的動(dòng)力學(xué)設(shè)計(jì)、狀態(tài)監(jiān)測(cè)及振動(dòng)控制提供理論依據(jù)。
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Abstract: With the ship heaving motion considered, the dynamic behaviors of the marine rotor-bearing system is studied in this paper. First, the dynamic model of the rotor-bearing system under the heaving motion is established based on the short bearing theory in the non-inertial reference system, in which the geometric nonlinearity is found to take place in the marine rotor-bearing system when with the action of heaving motion is taken into account. In addition, the dynamic characteristics, such as the bifurcation diagram, the maximum Lyapunov exponents, the steady state response, the rotor orbit and its Poincaré map are analyzed through numerical method, and the results are compared with those of the rotor-bearing system without heaving motion. Finally, the influence of the amplitude of the heaving excitation on the nonlinear dynamic characteristics of the rotor-bearing system is studied. The results show that the system exhibits a single cycle motion at low rotating speed and the heaving motion effect for this situation is obvious. With the increase of the speed, the phenomena of quasi-periodic, period two and double Hopf bifurcations occur in the system, and its dynamic characteristics present a single cyclic motion, quasi-periodic, period two and chaos etc..
Key words: nonlinear dynamics; marine rotor-bearing system; heaving; short bearing model
作者簡(jiǎn)介: 韓永超(1993-),男, 碩士研究生。電話: 18291875802; E-mail: 526702348@qq.com
李 明(1963-),男, 教授,博士生導(dǎo)師。電話: 13572980962; E-mail: limingnuaa@hotmail.com