柴油机湿式缸套的穴蚀分析

穴蚀是影响缸套寿命的重要因素,穴蚀群往往集中在连杆摆动平面两侧。由于活塞侧推力的作用,使缸套高频振动,引起冷却液产生气泡,气泡破裂,产生高压冲击波,使缸套穴蚀。采用减轻缸套振动,改进冷却系统,增强缸套抗蚀能力等方法,可以减轻和防止缸套穴蚀的产生。     

柴油机湿式缸套的穴蚀分析

穴蚀是影响缸套寿命的重要因素,穴蚀群往往集中在连杆摆动平面两侧。由于活塞侧推力的作用,使缸套高频振动,引起冷却液产生气泡,气泡破裂,产生高压冲击波,使缸套穴蚀。采用减轻缸套振动,改进冷却系统,增强缸套抗蚀能力等方法,可以减轻和防止缸套穴蚀的产生。     

缸套熔着磨损的产生及预防

缸套熔着磨损的产生及预防江苏省南通市农机学校苏成玲１缸套熔着磨损的产生当缸套、活塞环间的油膜被破坏或中断时，两种金属的接触表面在高温、高压下相互滑动，产生摩擦热，如不及时排除，就会使局部金属表面的温度急剧上升，当温度增至金属熔点时，就会引起金属表面局...     

在油－气两相流状态下柴油机喷油系统中压力波传播速度的研究

本文通过在喷油泵试验台上测定高压油路实际压力波传播速度，论述了在油一气两相状态下，柴油机喷油系统中高压油管和喷油嘴油道内音速的变化规律，并指出造成高压油路各段音速不同的原因是高压油路内气泡分布的不均匀性。特别值得注意的是，喷油嘴油道内平均音速明显低于高压油管中的音速，这说明喷油嘴盛油槽内的气泡要多于高压油管中的气泡。     

怎样判断缸套产生了裂纹

湿式缸套产生裂纹,这是个可能发生的实际问题。裂纹的产生,就缸套本身而言,涉及铸造质量、尺寸精度以及安装使用等方面,在此不作阐述。本文仅以水冷式柴油机为例,讨论、总结缸套裂纹产生后的判断方法。柴油机缸套产生裂纹的部位和形态具有规律性。裂纹在缸套的内壁位置,处于活塞上止点时第一道气环稍上,对应的外壁位置     

在油—气两相流状态下柴油机喷油系统中压力波传播速度的研究

本文通过在喷油泵试验台上测定高压油路实际压力波传播速度，论述了在油－气两相状态下，柴油机喷没系统中高压油管和喷油嘴油道内音速的变化规律，并指出造成高压油路各段音速不同的原因是高压油路内气泡分布的不均匀性，特别值得注意的是，喷油嘴油内平均音速明显低于高压油管中的音速，这说明喷油嘴盛油槽内的气泡要多于高压油管中的气泡。     

自制直读式外径检具

在气缸套的检验过程中,大多数缸套生产厂都采用千分尺测量缸套外径。由于气缸套的产量不断增加,测量时千分尺的使用频率也不断增加,平均日达几千次之多,故易使千分尺产生磨损,出现凹心现象,非专业检修人员很难发现,且长期使用千分尺,易使操作者产生疲劳,且操作不方便,从而导致测量失准。 针对上述事实,我们设计了一种符合缸套外圆测量要求的直读式外圆尺寸专用测量器。 1检具的组成     

汽缸套“端磨”的探讨

柴油机缸套的拉缸和穴蚀显著改善以后,缸套的端磨问题日趋突出。本文针对柴油机缸套端磨情况,进行了广泛调查研究,分析产生端磨的原因,从国外机车柴油机缸套借鉴,提出国产柴油机缸套改善端磨的理由、原因和办法。 本文在研究解决端磨问题的同时,从理论上进行分析校核,以证明解决端磨的途径,从 而提高缸套的使用寿命。     

不同载荷对柴油机缸套变形的影响研究

建立了缸体、缸盖、缸套等部件的四缸柴油机装配耦合模型,在加载热负荷的基础上分析了热应力、螺栓预紧力、缸内最高燃烧压力及活塞侧击力对缸套变形的影响。研究结果表明:在各加载方案中,缸套膨胀和压缩变形均表现为1#缸、4#缸缸套变形较大,2#缸、3#缸缸套变形较小;不同加载方案的缸套变形规律相似,缸套热应力产生的热变形占主导地位;在加载热负荷的基础上,螺栓预紧力、缸内最高燃烧压力对缸套综合变形最大值影响较大,而活塞侧击力对缸套综合变形最大值影响较小;活塞侧击力对缸套径向变形最大值的分布区域影响较大,但对机体与缸套主应力及变形值影响较小。     

湿式气缸套周向应变的动态测试与分析

针对内燃机气缸套在工作时的动态变形问题,提出一套对湿式缸套工作时的变形进行测试与分析的方法,得出应变-时间波形,根据所测数据,给出应变频谱,并用曲线拟合的方法近似绘出缸套圆周在工作时受冲击产生的变形。比较缸套各部位不同工况下变形的特点,结果表明,缸套变形及其振动能量所分布的频带和转速的关系十分密切,并且缸套主推力面中部变形和振动最为剧烈。     

The Life Assessment of API 5L Grade B Geothermal Pipeline in Correlation with Corrosion under Insulation

The corrosion under insulation dominates metal loss in the case of API （American Petroleum Institute） 5L Grade B geothermal pipeline, whereas, the other possible corrosion causes, such as stress corrosion and thermal cracking, did not serve a role as critical factors regarding to pipeline degradation during 26-years working operation. Actually, the header pipe diameter 32 inches and 40 inches require priority for inspection due to higher corrosion rate compared to smaller pipe diameters. By simulation method on similar heavy duty service condition in which the working pressure of 15 bars and temperature of 183 ℃, it was proved that corrosion rate will severely occur at corrosion rate more than 10 mpy in the pipe diameters of 20 inches, 32 inches and 40 inches. Further,condensation factor may contribute more significant in the case of corrosion under insulation. Practically, the metal loss at a half initial thickness requires priority for inspection, intensive maintenance or possible partial replacement.     

Hydrogen generation from MgNdNiMg15 composites by hydrolysis reaction

The effects of the Mg content on the microstructure and hydrogen generation kinetics of MgNdNiMg₁₅ composites by hydrolysis reaction in seawater (3.5 wt% NaCl) was investigated. The presence of NdNiMg₁₅ in Mg matrix promotes galvanic corrosion. Thus, a galvanic coupling was observed between the NdNiMg₁₅ phase (cathode) and the Mg phase (anode). An acceleration of the corrosion rate of Mg phase was observed due to this galvanic coupling. Electrochemical tests confirm that pure Mg has a corrosion rate in salt water up to 750 times lower than that of the Mg phase in the MgNdNiMg₁₅ 90% composite. The best hydrolysis performance (100% of the theoretical hydrogen generation yield in slightly more than 15 min) observed for MgNdNiMg₁₅ 90% composite, was explained by a combined effect of galvanic corrosion, intergranular corrosion and pitting corrosion.     

Corrosion resistance of functionally graded TiN/Ti coatings for proton exchange membrane fuel cells

Bipolar Plates (BPP) are important components of proton exchange membrane fuel cell (PEMFC) stacks. In the development of innovative fuel cell designs, it is advantageous to use aluminum for these applications, however, this material lacks the necessary corrosion resistance. Since the performance of PEMFC stacks depends on BPP properties, in particular, corrosion resistance, depositing titanium nitride (TiN) thin films onto aluminum substrates may improve their efficiency and durability. The present work focuses on improving corrosion resistance and hydrophobicity of TiN/Ti by using N graded films deposited onto aluminum substrates (AA-1100) by grid-assisted magnetron sputtering (GAMS). Electrochemical impedance spectroscopy (EIS) and potentiodynamic and potentiostatic polarization are used to investigate the performance of the substrate/film system at room temperature and 70 °C, thus simulating a prototypic PEMFC electrolyte environment. Electrochemical test results showed that graded TiN films improved corrosion resistance when compared with both the homogeneous films and the AA1100 uncoated substrate. Furthermore, contact angle results reveal improved hydrophobicity for both homogeneous and graded TiN coatings when compared with the AA1100 substrate.     

Applicability of Waterside Corrosion Models in Range of IFPE Database

Fuel rod cladding waterside corrosion is one of the phenomena that limit the life time of nuclear fuel. Corrosion performance depends on the cladding material properties as well as operating conditions during the irradiation of the fuel. As a function of temperature, power history, water chemistry, time, etc., waterside corrosion is of great concern in fuel performance evaluation, especially for high burnup fuels. This paper is dedicated to the study of the waterside corrosion phenomenon using the IFPE database by COPERNIC, which is developed for the analysis of fuel rod behaviors in normal operation and transient conditions. Different models, MATPRO, FRAMATOME and EPRI models, for example, are adopted in the simulations. The results derived from the models are compared and the unconformities are analyzed. Based on the comparative analysis, reasonable models are chosen to simulate certain irradiated fuel rods. Our analyses indicate that potential affecting factors which are not considered in COPERNIC code, such as water chemistry and alloy composition, should be responsible for discrepancies of certain rod predictions.     

Corrosion inhibition of mild steel in acidic media using newly synthesized heterocyclic organic molecules

Hydrogen evolution reaction (HER) (cathodic reaction) of mild steel immersed in H₂SO₄ acid was investigated. Electrochemical corrosion behavior and hydrogen evolution reaction of mild steel has been investigated using different electrochemical techniques. Steel was polarized vs. saturated calomel electrode (SCE) in naturally aerated 1.0 M H₂SO₄ aqueous solution containing four organic inhibitors (newly synthesized heterocyclic compounds) of different concentrations. The observed different influence of corrosion inhibitors on the hydrogen evolution reaction was associated with the different chemical composition and structure. Polarization results showed that corrosion current density, i_corr, and hydrogen evolution decreases with increasing concentration of inhibitors in 1.0 M H₂SO₄, indicating a decrease in the corrosion rate. Electrochemical impedance spectroscopy (EIS) measurements confirmed this behavior. An increase of temperature leads to increase in the corrosion or hydrogen evolution rate and a decrease of the total resistance value, R_T. The obtained results were confirmed by surface examination.     

Corrosion of platinum catalyst in alkaline solutions

The corrosion behavior, as affected by time and potential, of platinum black in alkaline solution at 20 and 70 °C has been studied. It is shown that over the potential range 0.85 – 1.37 V platinum undergoes dissolution, the maximum corrosion rate being observed at E = 0.93 – 0.95 V. With time, the corrosion current decreases to 10^?6–10^?7 A/m². When platinum passes into solution the complex ion [Pt(OH)₆]^2? is formed. The influence of platinum pretreatment, leading to removal of surface oxygen compounds, on the rate of corrosion has been investigated. It has been found that Ba²⁺ ions slow down the dissolution process, while Cl^? ions increase its rate. The relationship between the platinum corrosion process and the shift of the oxygen electrode potential from the equilibrium value is discussed. Some conclusions are drawn about the mechanism of platinum corrosion.     

Inhibition effect of natural polysaccharide composite on hydrogen evolution and P110 steel corrosion in 3.5 wt% NaCl solution saturated with CO2: Combination of experimental and surface analysis

For the analysis of corrosion and hydrogen production inhibition, we have synthesized Guar gum and methylmethacrylate (GG-MMA) composite. The synthesized composite was used as an eco-friendly corrosion inhibitor for P110 steel in 3.5% NaCl solution saturated with carbon dioxide at 50 °C. The primary corrosion techniques like weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) was used to analyze the corrosion inhibition process. EIS study reveals the kinetically controlled corrosion inhibition process. The results of PDP proposed that GG-MMA composite is the cathodic type of inhibitor. The corrosion inhibition performance of GG-MMA alone is 90% at 400 mg/L, and that of formulation with KI (5 mM) + GG-MMA (300 mg/L) is 96.8%. The adsorption of GG-MMA over P110 steel is spontaneous and mixed type i.e., both physical and chemical. The conformation of GG-MMA molecule adsorption was done using a scanning electron microscope (SEM), Contact angle measurement, Atomic force microscopy (AFM), Scanning Electrochemical Microscopy (SECM) and X-ray photoelectron spectroscopy studies.     

Electrochemical carbon corrosion in high temperature proton exchange membrane fuel cells

Electrochemical carbon corrosion occurring in a high temperature proton exchange membrane fuel cell (HT-PEMFC) operating under non-humidification conditions was investigated by measuring CO₂ generation using on-line mass spectrometry and comparing the results with a low-temperature proton exchange membrane fuel cell (LT-PEMFC) operated under fully humidified conditions. The experimental results showed that more CO₂ was measured for the HT-PEMFC, indicating that more electrochemical carbon corrosion occurs in HT-PEMFCs. This observation is attributed to the enhanced kinetics of electrochemical carbon corrosion due to the elevated operating temperature in HT-PEMFCs. Additionally, electrochemical carbon corrosion in HT-PEMFCs showed a strong dependence on water content. Therefore, it is critical to remove the water content in the supply gases to reduce electrochemical carbon corrosion.     

Effects of polystyrene sulfonate/graphene and Mn3O4/graphene on property of aluminum(zinc)-air batteries

A polystyrene sulfonate/graphene-based NaOH electrolyte and a Mn₃O₄/graphene catalyst were prepared for fabricating and testing metal-air batteries with pure Al and Zn anodes. Electrochemical performances, corrosion rates and surface morphologies were investigated. The operating voltage, anodic utilization rate and energy density of the assembled aluminum-air battery are 1.167 V, 88% and 2546 Wh·Kg⁻¹, respectively. This overall performance is better than Al-air battery with 4 M NaOH solution and MnO₂ catalyst. Apparently, polystyrene sodium sulfonate/graphene improves the conductivity of the solution and reduces the corrosion rate of aluminum anode, and Mn₃O₄/graphene reduces cathode polarization of air cathode.     

Corrosion behavior of polyphenylene sulfide–carbon black–graphite composites for bipolar plates of polymer electrolyte membrane fuel cells

The aim of this work was to study the corrosion behavior of polyphenylene sulfide (PPS) – carbon black – graphite composites regarding their application as bipolar plates of polymer electrolyte membrane (PEM) fuel cells. Electrochemical impedance spectroscopy (EIS), potentiostatic and potentiodynamic polarization tests were used to characterize the electrochemical response of the composites in a simulated PEM fuel cell environment. Cross-sectional views of fractured specimens were observed by scanning electron microscopy (SEM). The results showed that the corrosion behavior depends on the carbon black content incorporated into the composite formulation. There was a trend of decreasing the corrosion resistance for higher carbon black contents. This behavior could be explained based on the porosity and electrical conductivity of the composites.