Comparison of the effects of multiple injection strategy on the emissions between moderate and heavy EGR rate conditions: part 2-post injections

To draw a comparison of the effect of multiple injection strategy on the engine-out emissions under two different EGR rate conditions, the effect of pilot injection on emissions and combustion was evaluated and discussed in part 1. Thus, in the second research as part 2, the effects of post injection on the engine-out emissions were systemically evaluated for two different EGR rate conditions (30 % and 60 %). Since the behavior of diesel combustion is significantly different as EGR rate is changed, the characteristics of post injection was different between two EGR rate conditions. This research was investigated as varying injection parameters such as the timing and quantity of the post injection. The results show that the close post injection with injection interval as 10 degree has the potential to reduce PM emission, regardless of EGR rate. However, the reason of reduction of PM emission is different for each case. For a moderate EGR rate condition, close post injection with interval 10 degree enhances the fuel at bottom of bowl. Thus, the distribution of fuel can be improved. On the other hand, for a heavy EGR rate condition, close post injection with interval 10 degree has the charge cooling effect to prolong the ignition delay, rather than well-matched injection targeting. Especially, there is an effect to oxidize PM emission under moderate EGR rate condition as post injection is applied. However, post injection for late cycle of combustion under heavy EGR rate condition does not oxidize PM emission due to low oxygen concentration (～ 10%).     

Experimental analysis of emission reduction by the split injection strategy using close post injection with a double-row nozzle in heavy EGR conditions

As EURO-6 regulations will be enforced in 2014, simultaneous reduction of NO_x and PM emissions becomes an important issue in recent diesel engine research. New combustion concepts, such as LTDC and pHCCI, have been introduced to overcome the NO_x and PM trade-off relation. However, these novel combustion concepts are usually implemented with a high EGR rate and by advancing the main injection timing which cause high CO and THC emissions along with poor fuel consumption due to low combustion efficiency. Therefore, the split injection strategy, which was consisted of applying post injection close to the main injection, was carried out in this experiment. Specifically, two different nozzles — a 7-hole conventional nozzle and a 12-hole double-row nozzle — were evaluated to determine the effects of nozzle configurations on engine-out emissions. The result shows that CO emission was reduced by the close post injection strategy regardless of the nozzle configuration. However, THC and PM emissions were reduced only when the 12-hole double-row nozzle was used. Thus, the use of close post injection with the 12-hole double-row nozzle could increase the combustion efficiency in heavy EGR conditions.     

Influence of injection rate shaping on combustion and emissions for a medium duty diesel engine

This paper describes the effects of injection rate shaping on the combustion, fuel consumption and emission of NO_X and soot of a medium duty diesel engine. The focus is on the influence of four different injection rate shapes; square type 1, square type 2, boot and ramp, with a variation of maximum injection pressure and start of injection (SOI). The experiments were carried out on a 1 liter single cylinder research diesel engine equipped with an amplifier-piston common rail injection system, allowing the adjustment of the injection pressure during the injection event and thus injection rate as desired. Two strategies to maintain the injected fuel mass constant were followed. One where rate shaping is applied at constant injection duration with different peak injection pressure and one strategy where rate shaping is applied at a constant peak injection pressure, but with variable injection duration. Injection rate shaping was found to have a large effect on the premixed and diffusion combustion, a significant influence on NO_x emissions and depending on the followed strategy, moderate or no influence on soot emission. Only small effects on indicated fuel consumption were found.     

Investigation of the effects of steam injection on the emissions and performance of a diesel engine using waste chicken oil methyl ester

The use of biodiesel-blended fuels in diesel engines improves the engine performance parameters and the partial recovery of incomplete combustion products, while also increasing the level of NOx emissions. In this study; biodiesel obtained through the transesterification of waste chicken frying oil was mixed with diesel fuel (90% diesel + 10% biodiesel-B10), and was then used as fuel in a direct injection diesel engine. To reduce the increased NOx emissions caused by the use of B10 fuel, the steam injection method (which is one of the NOx reduction methods) was applied. Steam was injected into the intake manifold at different ratios (5%-S5, 10%-S10 and 15%-S15) and at the time of the induction stroke with the aid of an electronically controlled system. Based on the study results, it was observed that steam injection into the engine using B10 fuel improved both the engine performance and the exhaust emission parameters. It was determined that the S15 steam injection ratio resulted in the best engine performance and emissions parameters. In comparison to STD fuel; the highest increase observed at the S15 steam injection ratio in the effective engine power was 2.2%, while the highest decrease in the specific fuel consumption was 3.4%, the highest increase in the effective efficiency was 3.5%, and the highest decrease in NOx emissions was 13.7%.

     

Influence of molding conditions on the shrinkage and roundness of injection molded parts

During the plastic injection molding process, one of the biggest challenges is shrinkage which deteriorates the quality of produced parts. To control and reduce this defect, the essential way is to perfectly determine the variables like molding parameters. In this study, the effects of molding parameters including packing pressure, melt temperature, and cooling time on shrinkage and roundness have been investigated experimentally. Also, the relationship among initial molding parameters, the cavity pressure, and mold temperature was investigated. The results of this experimental study and analysis fulfill various requirements of plastic injection molding and clarify the relationship between molding conditions and the overall quality of produced parts. This study illustrated that packing pressure and melt temperature are dominant factors which determine the quality of parts.     

Some aspects of the mechanism of chemical wear: A correlation between dynamic wear rate and static corrosion rate

A new method for determining the actual contact area of conducting samples by measuring the total electrical resistance of the contacting pair is described. The results of experimental determinations of the actual contact area are given and discussed.     

靶控输注异丙酚与七氟醚吸入对老年患者术后苏醒和认知功能影响比较

目的:比较七氟醚与异丙酚对老年患者术后苏醒和认知功能的影响,为临床麻醉方案的选择提供参考依据。方法:将我院2016年1月至2017年10月96例择期行腹部手术的老年患者随机分为七氟醚组、异丙酚组,各48例。根据组别选择相应麻醉方案,比较两组患者自主呼吸恢复时间、睁眼时间及拔管时间,围术期简易智能状态量表(MMSE)评分变化,以及术后认知功能障碍(POCD)发生率,分析两种麻醉方案对患者苏醒和认知功能的影响。结果:七氟醚组与异丙酚组自主呼吸恢复时间、睁眼时间、拔管时间比较,差异无统计学意义(P> 0.05)。两组患者术后3 h～6 h MMSE评分均较术前1 d下降,七氟醚组术后3 h、术后6 h MMSE评分低于异丙酚组,差异有统计学意义(P <0.05),术后3dMMSE评分低于术前,差异无统计学意义。七氟醚组术后3 h、术后6 h POCD发生率高于异丙酚组,差异有统计学意义(P <0.05)。结论:七氟醚与异丙酚均不会影响老年患者术后苏醒,但均可在一定程度上影响患者认知功能,异丙酚对患者术后早期认知功能的影响略低于七氟醚。     

A new sheet metal forming system based on the incremental punching, part 1: modeling and simulation

In heavy forging, a manipulator is indispensable to assist and help the precision of the forming process. This paper presents a multi-system simulation methodology combining the forging finite element method (FEM) simulation and the kinematics analysis to evaluate the mutual reaction loads between the forging process and the assisting manipulator. The forging is realized by the thermal–mechanical FEM simulation and the kinematics movements are analyzed based on the statics and dynamics modeling of the manipulator. The reaction load generating from the forging process to the manipulator clamps is treated as an input parameter for the kinematics analysis system, which will then calculate the movement of the manipulator. And this movement is regarded as the passive compliant movement constraint and applied on the forging process through the manipulator clamps. Using this coupled system, the study compares the reaction loads with and without the active vertical compliant movement and/or the passive horizontal compliant movement and reveals the effect of these compliant movements on the reaction loads.     

Comparison of the effects of surface texture on the surfaces of steel and UHMWPE

Surface texture has been well studied for metals and ceramics. For the tribo-pair consisted of soft and stiff materials, in order to find out which side is better for texturing, friction tests between steel and UHMWPE were performed to evaluate the effect of dimple patterns at different load–speed conditions.At a light load of 100 N, surface texture on either steel or UHMWPE can reduce friction, but their optimum area densities are different. However, at a heavy load of 700 N, only the pattern textured on UHMWPE can effectively reduce friction. Test results are further analyzed in terms of contact stress.     

Modeling study of the surface tension and gravitational effects on flow injection in center-gated disks

Flow injection in center-gated disks was experimentally studied in this paper for possible applications in the manufacturing of composite materials in space. The experimental set-up used in this study was designed to provide flow visualization of the mold filling process. To record the progression of the fluid flow front in the mold, the experiment was filmed using a CCD. The effects of gravitation and surface tension on the development of flow front progression and front shape were examined for a wide range of the governing parameters (namely, the capillary and Stokes numbers). It has been found that surface tension tends to hold the flow front in symmetric shape while gravitation tends to distort it. The balance of these two forces has significant effects on the progression of the flow and the front shape. Results obtained from this experimental model not only validate the finite element method (FEM) model thus developed but also provide useful information in the design of the resin transfer molding process in space.     

重型构件夹持机构驱动力与夹持力关联模型研究

建立了含摩擦转动副大型夹持机构的夹紧力模型,并在此基础上对典型重型夹持机构力的传递进行分析,建立了含摩擦转动副重型夹持机构液压缸输出力(驱动力)与钳口夹持力之间的关联模型,并通过实例计算验证了此模型的准确性,为重型构件夹持系统设计提供了理论依据.     

中强度静磁场对白血病细胞增殖、荷瘤鼠生存期和血管生成的影响

磁场作为一种非侵入性方法,近几十年来受到了广泛的关注。关于磁场对肿瘤的影响,已经进行了很多的研究。本次实验研究了中强度静磁场（强度0．2T-0．4T）对白血病细胞L1210增殖和荷L1210白血病小鼠生存期的影响。此外,采用胛r方法研究了中强度静磁场（强度0．2T-0．4T）对内皮细胞HUVEC增殖的影响,并采用鸡胚绒毛尿囊膜和基质胶小室两种体内模型研究了中强度静磁场对血管生成的影响。实验结果表明中强度静磁场可以抑制白血病细胞和血管内皮细胞的增殖,延长荷L1210小鼠的生存期,阻止鸡胚绒毛尿囊膜和基质胶小室两种体内模型中新血管的形成。实验结果提示中强度静磁场对人类白血病以及血管生成相关疾病的治疗可能有应用价值。     

Comparison of slam-freezing and high-pressure freezing effects on the DNA cholesteric liquid crystalline structure

Using in parallel electron microscopy of ultrathin frozen-hydrated sections and freeze-fracture replicas, we compare the ultrastructural consequences of two freezing techniques: slam-freezing at liquid helium temperature and high-pressure freezing, on a model system, the DNA cholesteric liquid crystalline phase. Both freezing techniques are able to vitrify DNA liquid crystalline solutions containing up to 85% water, but induce structural rearrangements of the molecular organization. The cholesteric structure is preserved by the slam-freezing method despite the formation of periodic distortions induced by the mechanical compressive stress. In contrast, high-pressure freezing does not preserve the structure of the liquid crystal: the long-range cholesteric stratification disappears, and the local continuous twist between molecules is modified. These results show that vitrification, though necessary, may not be a sufficient token of preservation of the native state of hydrated materials. We discuss the possible origins of the molecular rearrangements that have time to occur in the specimens as a result of the low freezing rate permitted by the high-pressure freezing process.     

The effects of injector nozzle geometry and operating pressure conditions on the transient fuel spray behavior

Effects of injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure, and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details inside model nozzle and real nozzle were also investigated both experimentally and numerically. For the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.     

Review of principles and methods applied to the optimum calculation and design of externally-pressurized bearings: Part 1: Low/moderate speed bearings

A review is presented of the main calculations, design principles and methods for optimization of externally-pressurized bearings (EPBs). Several EPB optimizing aspects are presented followed by a brief presentation of various author's approaches to this problem. To permit more systematic use of the available information an overall classification of the possible solutions to the problem is given. Starting from the speed criterion, the differences in calculation and optimization between low-speed and high-speed bearings respectively are presented by means of the concept of the hybrid bearing. This paper treats only the problem of low/moderate-speed bearings, using classical methods. The recommended values are given comparatively as optimum for the main geometric and functional parameters.     

腺性膀胱炎与膀胱癌关系及腺性膀胱炎癌变率调查

目的 :探讨腺性膀胱炎(Cystitis glandularis,CG)与膀胱癌(Bladder cancer,BC)的关系,并调查CG的癌变率。方法 :追踪分析2006年1月至2016年12月首诊确诊为CG患者中复诊资料完整病例,分析其CG癌变率,并将单纯CG患者纳入未癌变组,将转化至BC者纳入癌变组,比较两组患者年龄、性别、病程、病理分型、毒物接触史、合并症等临床资料的差异,将存在统计学差异的因素纳入Logistic多因素回归分析,总结影响CG进展至BC的危险因素。结果 :173例入组患者,共21例确诊BC,CG癌变率为12.14%。多因素分析结果,病程≥1年、毒物接触史≥1年、病理分型肠上皮型、合并膀胱结石是影响CG癌变的独立危险因素,且上述因素的危险度(OR)均超过10(P<0.05)。结论 :CG癌变率较高,可能是正常膀胱粘膜发展至BC的中间节段,且病程、毒物接触史较长及肠上皮型、合并膀胱结石者具有更高的BC发生风险,应予以积极治疗、密切随访,早期发现癌变。     

中外标准对焊材储存及再烘干规定的对比和思考

通过AWS和RCC-M,BS EN,ISO,JIS系列标准对比,发现焊材储存方面,中外标准区别很明显,美国AWS系列标准都清晰地规定焊材储存条件,而欧洲系标准基本上都有焊材储存条件一律遵守焊材制造厂家的相关规定;并发现国外典型的焊材厂家会有很细致和专业的规定,而国内焊材厂家基本不提出比JB/T 3223更细致严格的规定。现场焊条储存温度失控导致焊条受潮以及再烘干堆叠层数失控均有发生。建议JB/T 3223或类似标准更新时,不可把焊材管理责任推给焊材制造商,并且应改进温度/相对湿度参数及再烘干堆叠层数等标准细节。     

Synergy between tribo-oxidation and strain rate response on governing the dry sliding wear behavior of titanium

The present work provides an insight into the dry sliding wear behavior of titanium based on synergy between tribo-oxidation and strain rate response. Pin-on-disc tribometer was used to characterize the friction and wear behavior of titanium pin in sliding contact with polycrystalline alumina disk under ambient and vacuum condition. The sliding speed was varied from 0.01 to 1.4 ms^?1, normal load was varied from 15.3 to 76 N and with a sliding distance of 1500 m. It was seen that dry sliding wear behavior of titanium was governed by combination of tribo-oxidation and strain rate response in near surface region of titanium. Strain rate response of titanium was recorded by conducting uni-axial compression tests at constant true strain rate of 100 s^?1 in the temperature range from 298 to 873 K. Coefficient of friction and wear rate were reduced with increased sliding speed from 0.01 to 1.0 ms^?1. This is attributed to the formation of in situ self lubricating oxide film (TiO) and reduction in the intensity of adiabatic shear band cracking in the near surface region. This trend was confirmed by performing series of dry sliding tests under vacuum condition of 2 × 10^?4 Torr. Characterization tools such as optical microscopy, scanning electron microscopy, and X-ray diffractometer provided evidence of such processes. These experimental findings can be applied to enhance the dry sliding wear behavior of titanium with proper choice of operating conditions such as sliding speed, normal load, and environment.     

Compliant layer bearings in artificial joints. Part 1: the effects of different manufacturing techniques on the interface strength between an elastomeric layer and a rigid substrate

The premise that elastomeric materials could be used as one or more of the articulating components in both hip and knee prostheses was postulated first by Unsworth and co-workers. It was thought that such materials might have the capacity to mimic natural joint behaviour more closely than the more rigid bearing surfaces commonly in use. A more natural joint function in artificial joints should promote better tribology, with full fluid-film lubrication being the goal. Early tests showed that this objective could potentially be achieved with a judicious choice of materials and carefully controlled manufacturing techniques. This paper (Part 1 of a two-part series) describes and explains the techniques used to verify the material selection as well as to determine the most appropriate manufacturing procedure to obtain a strong and robust interface between the support and bearing material of the prosthesis. Two polycarbonate urethane (PU) materials with different hardness values (Corethane 80A and Corethane 75D) gave sufficient interfacial strength when moulded under optimum conditions. Corethane 80A was used as the soft bearing material while Corethane 75D provided the rigid backing component. Peel tests revealed strong interface bonds, varying with processing conditions between 350 and 862 N. Fourier transform infrared spectroscopy and micro-thermal analysis showed that a fusion bond over 30 microm thick formed at the interface. The results of the range of tests and analyses, which have been used in this study, have provided sufficient evidence to validate the process used to manufacture these components.