內(nèi)燃機(jī)爆震中共晶硅鋁合金活塞材料損壞機(jī)理
發(fā)布時(shí)間：2019-05-26 22:39
【摘要】：內(nèi)燃機(jī)爆震是限制其燃料經(jīng)濟(jì)性提高的關(guān)鍵結(jié)構(gòu)參數(shù),提高壓縮比是當(dāng)今內(nèi)燃機(jī)節(jié)能減排的重要途徑。因此,闡明缸內(nèi)爆震對活塞等部件破壞的機(jī)理,找出發(fā)生爆震的結(jié)構(gòu)影響因素,避免其對活塞等的破壞,為進(jìn)一步提高發(fā)動(dòng)機(jī)壓縮比以改善內(nèi)燃機(jī)熱效率提供理論支持,本研究工作主要集中在以下幾個(gè)方面。第一,在發(fā)動(dòng)機(jī)上進(jìn)行了燃用純甲醇燃料的爆震燃燒的試驗(yàn)研究。在一臺壓燃式發(fā)動(dòng)機(jī)基礎(chǔ)上搭建試驗(yàn)臺架,運(yùn)行超速超負(fù)荷的強(qiáng)化工況,記錄爆震發(fā)生過程中氣缸壓力。試驗(yàn)中觀察到純甲醇發(fā)動(dòng)機(jī)發(fā)生爆震時(shí),發(fā)動(dòng)機(jī)燃燒室內(nèi)的爆發(fā)壓力迅速升高,而且變化幅度劇烈,形成爆轟壓力波。當(dāng)該壓力波作用在活塞上,其表面及內(nèi)部快速發(fā)生熱氧化腐蝕,直至發(fā)生表面被穿孔,說明了爆震發(fā)生對發(fā)動(dòng)機(jī)部件的強(qiáng)烈損壞作用。第二,對破壞后的活塞進(jìn)行宏觀和微觀結(jié)構(gòu)的金相分析。試驗(yàn)發(fā)現(xiàn)硅鋁合金活塞表面在燃燒室內(nèi)爆震波作用下,宏觀損傷由侵徹穿孔和凹坑構(gòu)成,以侵徹穿孔為主,背面產(chǎn)生了帶裂紋的鼓包及崩落;在壓縮波和反射拉伸波的作用下,表現(xiàn)出分層損傷和崩落破壞。硅鋁合金活塞合金在沖擊波下被擠壓變形,形成高密度的位錯(cuò)以及非晶和微晶。在遠(yuǎn)離侵徹穿孔部位,合金變形減小,缺陷以微裂紋和微孔洞為主。硅鋁合金活塞微觀組織的絕熱剪切帶由沿剪切方向的寬度為15~45nm的拉長組織構(gòu)成,具有較高位錯(cuò)密度,剪切帶中心部位由大量低位錯(cuò)密度的直徑為40~80nm的晶粒組成,具有典型的再結(jié)晶組織特征,再結(jié)晶過程表現(xiàn)為晶粒機(jī)械碎化及晶界遷移、亞晶粗化共同作用的結(jié)果。通過電子顯微鏡掃描進(jìn)一步分析,發(fā)現(xiàn)失效的活塞表面發(fā)生了絕熱剪切熔孔。采用XRD成分確定后,觀察到失效活塞表面的晶型改變;根據(jù)分析結(jié)果,可以說明純甲醇壓燃式發(fā)動(dòng)機(jī)發(fā)生爆震破壞活塞失效的形式是熱力耦合所造成。第三,對發(fā)動(dòng)機(jī)發(fā)生爆震在燃燒室內(nèi)形成超溫和超壓現(xiàn)象進(jìn)行了數(shù)值分析。以二維數(shù)值模擬為基礎(chǔ),研究了錐頂型燃燒室內(nèi)的沖擊波發(fā)展的過程,得到作用于活塞不同位置處的超壓分布。模擬結(jié)果表明:由于燃燒室結(jié)構(gòu)的獨(dú)特性,導(dǎo)致沖擊波能在特定區(qū)域進(jìn)行匯聚,致使該區(qū)域超壓明顯高于其他區(qū)域。將該模擬結(jié)果與實(shí)際破壞失效的活塞進(jìn)行對比,發(fā)現(xiàn)沖擊波匯聚區(qū)域?yàn)榛钊黄茐牡牡胤?數(shù)值模擬結(jié)果和實(shí)際破壞結(jié)果相同,這為設(shè)計(jì)燃燒室形狀以避免沖擊波對活塞造成破壞提供了理論依據(jù)。通過本研究獲得的結(jié)果,可以得出爆震對活塞等材料破壞的機(jī)理是:爆震產(chǎn)生的震蕩燃燒,在一定條件下轉(zhuǎn)化為具有破壞性的爆轟波,爆轟波燃燒室中匯聚并產(chǎn)生作用于部件表面的超溫和超壓的條件,導(dǎo)致爆震壓力波對活塞表面的破壞。本研究的結(jié)果揭示爆震損壞活塞等部件內(nèi)部結(jié)構(gòu)特征,給出了爆震在燃燒室形成超溫和超壓的模型,提出了爆震損壞活塞的基本形式,初步闡明爆震對發(fā)動(dòng)機(jī)活塞等材料的破壞的機(jī)理,為發(fā)動(dòng)機(jī)燃燒系統(tǒng)結(jié)構(gòu)設(shè)計(jì)和運(yùn)轉(zhuǎn)因素控制提出了重要的理論依據(jù)。
[Abstract]:Internal combustion engine knock is a key structural parameter that limits its fuel economy, and it is an important way to improve the energy-saving and emission reduction of the internal combustion engine. therefore, the mechanism of the failure of the in-cylinder knocking on the parts such as the piston and the like is explained, the structural influencing factors of the knocking are found, the damage to the piston and the like is avoided, the theoretical support is provided to further improve the compression ratio of the engine to improve the thermal efficiency of the internal combustion engine, The work of this study is mainly focused on the following aspects. First, a test study on the knock combustion of pure methanol fuel is carried out on the engine. A test-bed frame is built on the basis of a compression-ignition engine, and the intensified working condition of the over-speed overload is operated to record the cylinder pressure during the knocking generation process. In the test, the explosion pressure in the combustion chamber of the engine is rapidly increased when the pure methanol engine is knocking, and the variation amplitude is severe to form the detonation pressure wave. When the pressure wave acts on the piston, the surface and the inside of the piston are rapidly thermally oxidized and corroded until the surface is perforated, and the strong damage effect of the knocking on the engine part is explained. Secondly, the macroscopic and microscopic structure of the damaged piston is analyzed. It is found that under the action of detonation wave in the combustion chamber of the surface of the silicon-aluminum alloy piston, the macroscopic damage is formed by the penetration of the penetrating hole and the pit, and the penetrating hole is the main body, and the back surface produces the drum bag with the crack and the sublevel caving; under the action of the compression wave and the reflected tensile wave, the layer damage and the level caving are shown. The silicon-aluminum alloy piston alloy is extruded and deformed under the shock wave to form high-density dislocations and amorphous and micro-crystals. The deformation of the alloy is reduced and the defects are mainly micro-cracks and micro-holes at the location away from the penetration hole. the adiabatic shear band of the micro-structure of the silicon-aluminum alloy piston is composed of an elongated tissue with a width of 15-45 nm in the shearing direction, has higher dislocation density, The recrystallization process is the result of grain mechanical crushing and grain boundary migration and grain-grain coarsening. A further analysis of the surface of the failed piston was found by a further analysis of the electron microscope. The change of the crystal form of the surface of the failed piston is observed after the determination of the XRD composition, and the form of failure of the piston of the pure methanol compression-ignition engine can be explained according to the analysis result, which is caused by the thermal coupling. In the third part, a numerical analysis of the occurrence of super-mild over-pressure in the combustion chamber is carried out for the occurrence of knocking of the engine. Based on the two-dimensional numerical simulation, the process of the development of the shock wave in the cone-type combustion chamber is studied, and the overpressure distribution at different positions of the piston is obtained. The simulation results show that, due to the uniqueness of the combustion chamber structure, the shock wave can be collected in a specific area, so that the overpressure in the region is obviously higher than that of other regions. The simulation result is compared with the actual failure of the piston, and it is found that the shock wave convergent region is the place where the piston is damaged, the numerical simulation result and the actual damage result are the same, which provides a theoretical basis for designing the shape of the combustion chamber to avoid the damage of the shock wave to the piston. As a result of this study, it can be concluded that the mechanism of the destruction of the material such as the knock to the piston is that the shock generated by the knocking is converted into a condition with a destructive detonation wave, a detonation wave combustion chamber and a super-moderate overpressure which acts on the surface of the component under certain conditions, Resulting in a failure of the detonation pressure wave to the piston surface. The results of this study revealed that the internal structure of the parts such as knocking damaged the piston and so on. The model for forming the super-mild overpressure in the combustion chamber was given. The basic form of the knock-damaged piston was put forward, and the mechanism of the destruction of the material such as the engine piston and the like was clarified. The important theoretical basis for the structure design and operation factor control of the engine combustion system is put forward.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG146.21;TK401
本文編號：2485689
[Abstract]:Internal combustion engine knock is a key structural parameter that limits its fuel economy, and it is an important way to improve the energy-saving and emission reduction of the internal combustion engine. therefore, the mechanism of the failure of the in-cylinder knocking on the parts such as the piston and the like is explained, the structural influencing factors of the knocking are found, the damage to the piston and the like is avoided, the theoretical support is provided to further improve the compression ratio of the engine to improve the thermal efficiency of the internal combustion engine, The work of this study is mainly focused on the following aspects. First, a test study on the knock combustion of pure methanol fuel is carried out on the engine. A test-bed frame is built on the basis of a compression-ignition engine, and the intensified working condition of the over-speed overload is operated to record the cylinder pressure during the knocking generation process. In the test, the explosion pressure in the combustion chamber of the engine is rapidly increased when the pure methanol engine is knocking, and the variation amplitude is severe to form the detonation pressure wave. When the pressure wave acts on the piston, the surface and the inside of the piston are rapidly thermally oxidized and corroded until the surface is perforated, and the strong damage effect of the knocking on the engine part is explained. Secondly, the macroscopic and microscopic structure of the damaged piston is analyzed. It is found that under the action of detonation wave in the combustion chamber of the surface of the silicon-aluminum alloy piston, the macroscopic damage is formed by the penetration of the penetrating hole and the pit, and the penetrating hole is the main body, and the back surface produces the drum bag with the crack and the sublevel caving; under the action of the compression wave and the reflected tensile wave, the layer damage and the level caving are shown. The silicon-aluminum alloy piston alloy is extruded and deformed under the shock wave to form high-density dislocations and amorphous and micro-crystals. The deformation of the alloy is reduced and the defects are mainly micro-cracks and micro-holes at the location away from the penetration hole. the adiabatic shear band of the micro-structure of the silicon-aluminum alloy piston is composed of an elongated tissue with a width of 15-45 nm in the shearing direction, has higher dislocation density, The recrystallization process is the result of grain mechanical crushing and grain boundary migration and grain-grain coarsening. A further analysis of the surface of the failed piston was found by a further analysis of the electron microscope. The change of the crystal form of the surface of the failed piston is observed after the determination of the XRD composition, and the form of failure of the piston of the pure methanol compression-ignition engine can be explained according to the analysis result, which is caused by the thermal coupling. In the third part, a numerical analysis of the occurrence of super-mild over-pressure in the combustion chamber is carried out for the occurrence of knocking of the engine. Based on the two-dimensional numerical simulation, the process of the development of the shock wave in the cone-type combustion chamber is studied, and the overpressure distribution at different positions of the piston is obtained. The simulation results show that, due to the uniqueness of the combustion chamber structure, the shock wave can be collected in a specific area, so that the overpressure in the region is obviously higher than that of other regions. The simulation result is compared with the actual failure of the piston, and it is found that the shock wave convergent region is the place where the piston is damaged, the numerical simulation result and the actual damage result are the same, which provides a theoretical basis for designing the shape of the combustion chamber to avoid the damage of the shock wave to the piston. As a result of this study, it can be concluded that the mechanism of the destruction of the material such as the knock to the piston is that the shock generated by the knocking is converted into a condition with a destructive detonation wave, a detonation wave combustion chamber and a super-moderate overpressure which acts on the surface of the component under certain conditions, Resulting in a failure of the detonation pressure wave to the piston surface. The results of this study revealed that the internal structure of the parts such as knocking damaged the piston and so on. The model for forming the super-mild overpressure in the combustion chamber was given. The basic form of the knock-damaged piston was put forward, and the mechanism of the destruction of the material such as the engine piston and the like was clarified. The important theoretical basis for the structure design and operation factor control of the engine combustion system is put forward.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG146.21;TK401
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，本文編號：2485689
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