摘 要:航空裝備緩沖氣囊以重量小、成本低等優(yōu)勢(shì)成為航空裝備緩沖系統(tǒng)的研究熱點(diǎn)。為快速解決航空裝備緩沖氣囊的設(shè)計(jì)問(wèn)題,本文運(yùn)用數(shù)值仿真軟件,以航空裝備緩沖氣囊為研究對(duì)象,依據(jù)運(yùn)動(dòng)學(xué)、工程熱力學(xué)及柔性薄殼力學(xué)等理論建立了環(huán)形緩沖氣囊的數(shù)值仿真模型,利用最速下降法對(duì)模型進(jìn)行優(yōu)化設(shè)計(jì);將優(yōu)化參數(shù)的仿真結(jié)果與試驗(yàn)結(jié)果進(jìn)行對(duì)比,驗(yàn)證模型建立的正確性,并分析不同參數(shù)(開(kāi)口面積、開(kāi)口壓力和氣囊高度)對(duì)緩沖氣囊緩沖特性的影響。結(jié)果表明,當(dāng)其他參數(shù)一定時(shí),隨著開(kāi)口面積增加,緩沖過(guò)載減小,著地速度增加;隨著開(kāi)口壓力增加,緩沖過(guò)載增加,著地速度減小;隨著氣囊高度增加,緩沖過(guò)載減小,著地速度變化不大。本文仿真方法可以迅速確定緩沖氣囊的關(guān)鍵設(shè)計(jì)參數(shù)(如開(kāi)口面積、排氣壓力、緩沖高度等)與外形,可以提升緩沖氣囊的設(shè)計(jì)效率,為研究氣囊緩沖特性提供了理論依據(jù)。
關(guān)鍵詞:緩沖氣囊; 數(shù)值模型; 最速下降法; 緩沖特性
中圖分類(lèi)號(hào):V245 文獻(xiàn)標(biāo)識(shí)碼:A DOI:10.19452/j.issn1007-5453.2024.07.013
基金項(xiàng)目: 航空科學(xué)基金(201929010001)
隨著航空航天空投技術(shù)和軟著地技術(shù)的不斷發(fā)展,對(duì)緩沖系統(tǒng)裝置提出了更高更新的要求。緩沖氣囊以成本低和重量小等優(yōu)勢(shì)成為航空裝備緩沖著陸的研究熱點(diǎn)。緩沖氣囊的主要設(shè)計(jì)參數(shù)直接影響航空裝備緩沖系統(tǒng)的緩沖效能,為更深入地探究緩沖氣囊的設(shè)計(jì)與緩沖特性,國(guó)內(nèi)外學(xué)者對(duì)此研究方向進(jìn)行了大量的分析與研究。參考文獻(xiàn)[1]~[6]主要介紹了緩沖氣囊的形式與各自特點(diǎn)及建立的仿真模型。現(xiàn)有的緩沖氣囊理論研究主要有數(shù)值仿真分析與有限元仿真分析。溫金鵬等[7]基于熱力學(xué)方程建立了固定排氣口型緩沖氣囊的解析模型,并采用有限元和試驗(yàn)方法進(jìn)行驗(yàn)證。洪煌杰等[8]對(duì)緩沖特性進(jìn)行解析,并對(duì)參數(shù)進(jìn)行量綱一化,建立量綱一化緩沖氣囊緩沖模型。王一波等[9]主要對(duì)小型電子設(shè)備的緩沖特性進(jìn)行研究,并利用LS-DYNA軟件建立緩沖氣囊有限元模型,討論氣室分布和充氣量對(duì)緩沖性能的影響。韓宇[10]以火星探測(cè)器軟著陸為研究背景,進(jìn)行緩沖氣囊構(gòu)型選擇和建立緩沖氣囊有限元模型,分析不同的影響因素對(duì)緩沖性能的影響規(guī)律。
綜上所述,常見(jiàn)的緩沖氣囊計(jì)算方法主要為有限元分析方法和數(shù)值仿真方法。在解決工程實(shí)際問(wèn)題中,由于有限元分析方法存在計(jì)算周期長(zhǎng)和耗費(fèi)資源等問(wèn)題,因此本文選擇數(shù)值仿真方法進(jìn)行建模與計(jì)算。為快速解決某型緩沖氣囊的設(shè)計(jì)與定型問(wèn)題,本文依據(jù)理想氣體狀態(tài)方程和伯努利方程,采用數(shù)值分析方法建立基于最速下降法優(yōu)化緩沖氣囊模型,并將仿真結(jié)果與試驗(yàn)結(jié)果相對(duì)比,分析緩沖氣囊的緩沖特性,在驗(yàn)證模型正確性的基礎(chǔ)上解決工程實(shí)際問(wèn)題。
1 緩沖氣囊模型建立
氣囊的構(gòu)型有豎直氣囊、水平氣囊和環(huán)形氣囊等,本文選用環(huán)形氣囊構(gòu)型。緩沖氣囊的整個(gè)工作過(guò)程為:緩沖氣囊著陸前充滿(mǎn)氣、被緩沖物著陸緩沖和緩沖結(jié)束。
緩沖氣囊在緩7604ba03ca066f3103606c36b374baef236cbfc008c7da071ad075c789cc3198沖過(guò)程中,主要經(jīng)歷絕熱壓縮和排氣緩沖釋能兩個(gè)階段。緩沖氣囊的具體工作原理為:通過(guò)壓縮氣囊內(nèi)部氣體,將被緩沖物的動(dòng)能轉(zhuǎn)變?yōu)闅饽覂?nèi)部氣體的內(nèi)能,氣囊內(nèi)部氣壓增加,緩沖速度減?。划?dāng)氣囊內(nèi)部壓力達(dá)到設(shè)定值時(shí),排氣孔打開(kāi),緩沖氣囊進(jìn)行排氣,從而達(dá)到緩沖的目的,整個(gè)系統(tǒng)下落速度逐步減小直至系統(tǒng)著地。
3.2 開(kāi)口氣壓的影響
除開(kāi)口氣壓變化外,其余模型參數(shù)均相同。取開(kāi)口壓力為p0=151325Pa,1.13p0,0.9p0,0.8p0。圖13~圖16分別為不同開(kāi)口壓力下緩沖氣囊加速度、下落速度、下落高度和氣囊內(nèi)壓的變化曲線(xiàn)。從圖中可以看出,當(dāng)開(kāi)口壓力為1.13p0時(shí),緩沖氣囊的過(guò)載值最大,緩沖過(guò)程中速度變化最大,緩沖過(guò)程中發(fā)生輕微反彈現(xiàn)象,這是由于當(dāng)緩沖氣囊的開(kāi)口壓力較大時(shí),緩沖氣囊內(nèi)氣體密度增加,緩沖氣囊內(nèi)氣體不能有效排出,緩沖速度變化較大且緩沖時(shí)間較長(zhǎng)。當(dāng)開(kāi)口壓力為0.8p0時(shí),緩沖過(guò)載較小,緩沖時(shí)間較短,氣囊內(nèi)氣體被很快排出。綜上所述,在緩沖過(guò)程中,緩沖氣囊加速度變化規(guī)律與氣囊內(nèi)壓變化規(guī)律相同;隨著開(kāi)口氣壓的增加,緩沖過(guò)載與緩沖時(shí)間逐漸增加,著地速度變化越小。
3.3 氣囊高度的影響
除氣囊高度變化外,其余模型參數(shù)均相同。取氣囊高度為h0=0.85m,1.25h0,0.75h0,0.625h0。圖17~圖20分別為不同氣囊高度下緩沖氣囊加速度、下落速度、下落高度和氣囊內(nèi)壓的變化曲線(xiàn)。從圖17~圖20中可以看出,當(dāng)氣囊高度為0.625h0時(shí),緩沖氣囊的過(guò)載值最大,著地速度最大,這是由于當(dāng)氣囊高度較小時(shí),氣囊內(nèi)緩沖氣體的體積較小,緩沖時(shí)間較短,緩沖物很快著地,氣囊不能起到很好的緩沖效果。當(dāng)氣囊高度為1.25h0時(shí),緩沖時(shí)間較長(zhǎng),緩沖過(guò)載與著地速度較小,整個(gè)緩沖過(guò)程中未發(fā)生反彈現(xiàn)象,氣囊起到較好的緩沖效果。綜上所述可知,在緩沖過(guò)程中,隨著氣囊高度的增加,緩沖過(guò)載逐漸減小,著地速度變化不太大,緩沖時(shí)間增加,緩沖加速度的變化規(guī)律與氣囊內(nèi)壓的變化規(guī)律相同。
4 結(jié)論
本文建立了一種依據(jù)工程實(shí)際的緩沖氣囊數(shù)值模型,可以迅速確定航空裝備所需的緩沖氣囊參數(shù),提升了緩沖氣囊的設(shè)計(jì)效率,并研究不同影響因素對(duì)氣囊緩沖性能影響,為緩沖氣囊設(shè)計(jì)提供理論依據(jù),同時(shí)也為工程實(shí)際中不同類(lèi)型緩沖氣囊設(shè)計(jì)提供解決方法。綜上分析可以得出以下結(jié)論:
(1)對(duì)于環(huán)形緩沖氣囊來(lái)說(shuō),氣囊高度與開(kāi)口壓力一定時(shí),開(kāi)口面積越大,緩沖減載過(guò)程中過(guò)載越??;開(kāi)口面積較小時(shí),緩沖氣囊易發(fā)生反彈現(xiàn)象。
(2)氣囊高度與開(kāi)口面積一定時(shí),開(kāi)口壓力越大,緩沖減載過(guò)程中過(guò)載越大,最后著地速度越小。
(3)開(kāi)口壓力與開(kāi)口面積大小一定時(shí),氣囊高度越高,緩沖減載過(guò)程中過(guò)載越小,但是最后著地的速度變化不大。
(4)根據(jù)工程實(shí)際可知,氣囊高度不宜過(guò)高,氣囊高度過(guò)高會(huì)導(dǎo)致被緩沖物在緩沖過(guò)程中易發(fā)生側(cè)翻現(xiàn)象,不利于緩沖。
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Research on the Design and Cushioning Characteristics of Aviatio21f3745545d63c010930f5e0063242cb114b2961ae02a48aefda972963be32c8n Equipment Cushion Airbag
Qiao Fang, Feng Zhijie, Zhou Hao, Bao Jianping, An Aokun AVIC Aerospace Life-Support Industries,Ltd.,Xiangyang 441100,China
Abstract: Aviation equipment cushioning airbag has become a research hotspot in aviation equipment cushioning systems due to their advantages such as small weight and low cost. To quickly solve the design problem of a certain type of buffer airbag, this paper uses numerical simulation software and takes the buffer airbag of a certain type of aviation equipment as the research object, a numerical simulation model of the annular buffer airbag was established based on the kinematics, engineering thermodynamics and flexible thin shell mechanics theories, and the steepest descent method was used to optimize the design of the model. By comparing the simulation results of the optimized parameters with the experimental results to verify the correctness of the model establishment, and analyze the impact of different parameters (opening area, opening pressure, and airbag height) on the buffering characteristics of the buffer airbag, the results show that when other parameters are constant, as the opening area increases, the buffering overload decreases and the landing speed increases with the increase of the opening area; the buffering overload increases and the landing speed decreases with the increase of the opening pressure; the buffering overload decreases, and the changes of landing speed are not significant with the increase of the airbag height. This simulation method can quickly determine the key design parameters (such as opening area, exhaust pressure, buffer height, etc.) and shape of the buffer airbag, which can improve the design efficiency of the cushion airbag, and provide a theoretical basis for studying the cushion characteristics of the airbag.
Key Words: cushion airbag; numerical model; steepest descent method; buffering characteristics