Tribological Properties of Ti-DLC Coatings on Piston-pin Surfaces

A magnetically filtered cathode vacuum arc deposition system was used to deposit Ti-doped diamond-like carbon coatings(Ti-DLC)on pin surfaces to improve the wear resistance of high-power density diesel engine piston pins.The coating structure,composition,and morphology were characterised using field emission scanning electron microscopy(FE-SEM),X-ray photoelectron spectroscopy(XPS),Raman spectroscopy,and other techniques.Friction tests were carried out using a universal tribometer to study the tribological properties of pins with or without coatings under dry friction and oil lubrication.The surface morphology and cross-sectional morphology of the Ti-DLC coating show that the coating has a uniform crosssection and good surface properties.The XPS spectrum shows that the coating contains Ti-C,Ti-C*,sp2-C,sp3-C,and C-O/C=O.Raman spectroscopy shows that there is an amorphous carbon phase in the Ti-DLC coating.The friction test shows that the friction temperature increase of the pin with the Ti-DLC coating is lower than that without the coating,especially under dry-friction conditions.At the end of the test,the difierence in temperature increase is 16.7%.The friction coefficient when using high-viscosity lubricating oil with a coating is relatively lower than that without a coating,especially under low-speed and heavy-duty conditions.In the dryfriction state,the coated surface has better wear resistance than the uncoated surface,which primarily manifests as abrasive wear,and the surface without a coating mainly experiences adhesive wear.

着火位置与车窗破裂耦合作用下的车厢火灾机理研究

为了研究着火位置和车窗破裂对车厢火灾蔓延的影响机理,本文通过火灾动力学软件(FDS)对火车车厢火灾开展了一系列的数值模拟。研究考虑了四个着火位置,车窗玻璃破裂的触发温度被设定为400℃。火灾模型监测了温度、热释放速率(HRR)、破窗时间和火焰传播等参数。研究发现,火源位置和窗户破裂通过改变车厢的通风来影响火灾的发展。当火灾发生在车厢中部时,热释放速率和燃烧强度都比火源位于车厢两端时大。火灾释放的高温会导致窗户破损,增加通风口面积,进而加剧车厢内可燃物的燃烧。通风是车厢火灾演变的一个关键因素,引入通风系数变化率来描述热释放率和窗户破裂之间的关系。因此,应尽可能避免车厢与外界的空气流通,并加强车厢内的火灾探测和报警,以提高灭火和应急救援能力。

Mechanistic investigation on Hg^(0) capture over MnO_(x) adsorbents:effects of the synthesis methods

This study demonstrated the impacts of the synthesis methods on the textural structures,chemical properties,and Hg^(0)capture capability of the MnO_(x)system.Compared with the samples synthesized using the precipitation(PR)and hydrothermal(HT)methods,the adsorbent prepared via the sol-gel(SG)technique gave the best performance.At 150℃,ca.90%Hg^(0)removal efficiency was reached after 7.5 h for MnO_(x)prepared by the SG method,ca.40%higher than that of the other two methods.The specific surface area of the adsorbent synthesized via the SG technique(23 m^(2)/g)was almost double that of the adsorbent prepared by the HT method(12 m^(2)/g)and three times that of the one prepared by the PR method(7 m^(2)/g).The presence of plentiful acid sites from the SG method facilitated the physisorption of Hg^(0),making more Hg^(0)available to be oxidized to HgO by the redox sites and thus giving the adsorbent prepared by the SG method the highest Hg^(0)removal efficiency.The strong oxidative ability accelerated the oxidation of the physically adsorbed Hg^(0)to HgO,which explained the higher Hg^(0)removal efficiency of the sample prepared using the HT method than that of the one synthesized by the PR technique.During the whole Hg^(0)removal cycles,chemisorption dominated,with the initial adsorption stage and the external mass-transfer process playing important roles.

Review of elemental mercury(Hg^(0))removal by CuO-based materials

Mercury emission has become a great environmental concern because of its high toxicity,bioaccumulation,and persistence.Adsorption is an effective method to remove Hg^(0)from coal-fired flue gas,with adsorbents playing a dominant role.Extensive investigations have been conducted on the use of CuO-based materials for Hg^(0)removal,and some fruitful results have been obtained.In this review,we summarize advances in the application of CuO-based materials for Hg^(0)capture.Firstly,the fundamentals of CuO,including its crystal information and synthesis methods,are introduced.Then,the Hg^(0)removal capability of some typical CuO-based adsorbents is discussed.Considering that coal-fired flue gas also contains a certain amount of NO,SO_(2),H_(2)O,NH_(3),and HCl,the impacts of these species on adsorbent Hg^(0)removal efficiency are summarized next.By generalizing the mechanisms dominating the Hg^(0)removal process,the rate-determining step and the key intermediates can be discovered.Apart from Hg^(0),some other air pollutants,such as CO,NOx,and volatile organic compounds(VOCs),account for a certain portion of flue gas.In view of their similar abatement mechanisms,simultaneous removal of Hg^(0)and other air pollutants has become a hot topic in the environmental field.Considering the Hg^(0)re-emission phenomena in wet flue gas desulfurization(WFGD),mercury capture performance under different conditions in this device is discussed.Finally,we conclude that new adsorbents suitable for long-term operation in coal-fired flue gas should be developed to realize the effective reduction of mercury emissions.

A numerical study on smoke behaviors in inclined tunnel fires under natural ventilation

To investigate the effect of tunnel slope on hot gas movement and smoke distribution in a slopping tunnel fire,a series of tunnel fire models are built by fire dynamics simulator(FDS),with a slope varies from 0 to 10%.Parameters such as ceiling temperature and airflow velocity are measured.The results indicate that the relationship between smoke back-layering length and tunnel slope can be described as an exponential function.The smoke temperature at the downstream exit first increased and then decreased with a higher slope.The airflow velocity at downstream outlet increased nonlinearity when tunnel slope was less than 8%.In the slope tunnel,the fire smoke spread process can be divided into three stages.Fire smoke spreads upstream to the peak distance,subsequently,the upstream smoke layer decreases gradually,the tunnel fire reaches a quasi-steady state.The backflow characteristics of smoke in sloped tunnels are coupled with the downstream length and outlet smoke temperature.In the initial stage of a slope tunnel fire,smoke spreads upstream for a long distance,endangering human health.