激光淬火

激光淬火激光具有许多宝贵的特性：亮度高、单色性和方向性强，在许多方面有广泛应用。以高能量激光为能源，以极快速度加热工件并自冷硬化的淬火工艺，称之为激光淬火。激光淬火具有许多独特之处：加热速度快、质量好、效率高、变形极微小、控制方便，可以应用于许多方面...     

在凸轮轴淬火过程中应力和变形的数值模拟

使用热处理模拟软件DANTE对凸轮轴淬火时的应力和变形过程进行数值模拟,研究凸轮轴在淬火时应力的变化情况及变形大小。结果表明：在淬火过程中凸轮轴应力逐渐增大,最大应力约为450 MPa,经回火处理后,应力数值适当减小;在淬火过程中凸轮轴变形量先减小后略微升高,再减小,最终变形量约为0.25 mm,经回火处理后变形量减小至0.19 mm。模拟结果与试验结果相吻合,表明模拟方案合理有效。     

压力涡流喷油器喷嘴结构因素对喷雾特性的影响

采用MIXTURE双相流数值模拟的方法研究压力涡流喷嘴结构因素对形成中空锥喷雾的影响。喷孔直径由0．5mm增大到1mm时，喷雾贯穿距离减少约60％，空心锥角增大7．5倍；喷孔长度由0．6mm增大到1mm时，喷雾贯穿距离增大约1．4倍，空心锥角减少约40％；有轴针时，空心锥角增加约4倍；改变轴针形状，将轴针头部加工成锥形，空心锥角增加约30％。喷孔内、外有无圆角对喷雾空心锥角大小的影响幅度在30％-40％。研究结果表明：喷孔长径比、喷孔入口处喷孔形状与轴针形状的配合和喷孔出口端形状是影响压力涡流喷嘴空心锥特性的重要因素。     

铝合金活塞淬火变形之初讨

目前国内常用的活塞铝合金为ZL3和ZL8。ZL3一般采用T_1处理,不存在淬火变形。ZL8均采用T6处理,有淬火变形问题,淬火变形主要是由加热和冷却的不均匀造成的内应力所引起的。我厂生产ZL8活塞在空气循环电炉中加热,淬火加热温度515±5℃。淬火冷却介质是水。水温愈低,冷速愈大,淬火效果愈好,但冷淡的增大,将会使铸件产生变形。为防止铸件在冷却过程中产生变形,一般要求在热水中冷却。我们生产ZL8活塞,淬火冷却,采用冷水冷却,表中测试数据是毛坯活塞的口部位进行加工,以止口尺寸为准,选择装料筐的二个位置活塞。一是在认为冷速最大的最低层;二是在中间层,生产试验结果如表1,表2,表3。     

针阀热处理变形规律探寻

本文通过对针阀实施不同的热处理工艺方法，并测定针阀的热处理变形，基本掌握了无锡欧亚柴油喷射有限生产的05WLF019192506（下称F506）针阀淬火变形情况。     

2MW风电机组锁紧盘多同步螺栓紧固设备研究

正2MW风电机组主轴与齿轮箱采用内外锥套结构形式连接,通过螺栓紧固使内外锥套产生径向压力,使内胀套抱紧轴。由于锁紧盘结构型式导致其紧固过程是需要数圈重复紧固,才可以达到内外锥面平齐的最终要求。紧固要求:2MW锁紧盘共有24个六角头螺栓24*M33-12.9,紧固力矩要求2650Nm。如图1齿轮箱锁紧盘示意图。目前,2MW锁紧盘先使用两把1200Nm牧田电动扭矩扳手十字对称紧固,后四人配合手持两把TU-3液压     

锥孔孔深检具设计

在分析了用传统方法测量L480B-2提前器用联接盘1：5锥孔量规尺寸φ15至端面深度尺寸10-0^0.036所存在的弊端的同时，介绍了新设计检具的结构原理和定量测量装置配置。现场使用证明：新检具便捷、高效、可靠，一改过去的定性测量为定量测量，实现了对尺寸参数的精确测量和在生产现场对工件进行100％的检测，保证了产品的质量，满足了生产需要。     

AQ251水溶性淬火介质的工艺试验

通过试块裂纹、变形和试验件的淬火工艺试验,研究了不同浓度的水溶性淬火介质对冷却速度的影响和对试验件裂纹、变形倾向的影响,探讨了适用于汽轮机不同零件所需的最佳浓度范围。     

基于有限元的增压器背盘变形分析

背盘是影响增压器质量的重要因素。利用有限元方法分析某型增压器背盘产生较大变形的原因及其背盘结构改进的方向。首先分析了背盘在正常条件下的变形,然后分析了在不正常手持时的背盘变形,最后分析了不正常装配是否会产生较大变形。通过上述几种分析结果获得了该背盘大变形的原因及解决办法。     

增压器背盘变形有限元分析

背盘是影响增压器质量的重要因素。本文利用有限元方法分析某型增压器背盘产生较大变形的原因及其背盘结构改进的方向。首先分析了背盘在正常条件下的变形;然后分析了在不正常手持时的背盘变形：最后分析了不正常装配是否会产生较大变形。通过上述几种分析结果获得了该背盘大变形的原因及解决办法。     

柴油-甲醇-正丁醇混合燃料对柴油机排放性能的影响

以正丁醇作为助溶剂,形成柴油-甲醇-正丁醇混合燃料,并将混合燃料在单缸四冲程柴油机上进行试验研究,探究混合燃料对柴油机排放特性的影响。试验所用的混合燃料中醇类的体积比为5.09%、9.82%、14.66%和19.35%,其中甲醇在混合燃料中所占体积比为2.51%、5.01%、7.53%和10.08%,正丁醇在混合燃料中所占体积比为2.67%、4.81%、7.13%和9.27%。研究表明:燃用混合燃料柴油机有效燃油消耗率、热效率分别增加0.18%～4.08%和0.28%～3.54%;输出功率、输出转矩分别下降0.75%～11.37%和1.42%～25.03%;CO、NO、NO_x等常规气体排放、PM_(2.5)排放分别下降2.76%～45.15%、3.55%～29.21%和3.55%～20.03%;但柴油中添加醇类燃料会导致甲醛、乙醛及挥发性有机化合物等非常规排放分别上升2.78%～60.53%、5.15%～63.81%和3.75%～45.49%;柴油机燃用混合燃料PM_(2.5)排放降低7.09%～48.94%。综上所述,柴油机燃用柴油与醇类燃料形成的混合燃料可以实现在降低NO_x排放的同时降低PM_(2.5)排放。     

Fractional yield and moisture of corn stover biomass produced in the Northern US Corn Belt

Corn stover is an ideal biomass feedstock but the harvest and storage of this material present many challenges. Information on the fractional yield and moisture of stover grown and collected in the Upper Midwest during the typical grain harvest period was used to estimate the expected yield and moisture when utilizing various harvesting methods. At grain harvest, the ratio of stover to total crop dry mass averaged 48% and approximately 15%, 8%, 21%, and 56% of the total stover dry mass resided in the cob, husk, leaf, and stalk fractions, respectively. Total stover moisture ranged from 66% to 47% when grain moisture was less than 30%. The stalk moisture ranged from 69% to 56%, 63% to 45%, 52% to 32%, and 36% to 27% for the whole, top-three-quarters, top-half, and top-quarter of the stalk, respectively. The total stover:grain moisture ratio averaged 2.15:1. A single-pass stover and grain harvester that would collect the cob and husk plus the top-half, top-three-quarters or the entire stalk (and similar fraction of the leaves) was estimated to harvest 46%, 72%, and 100% of the available stover at a range of moistures from 49% to 33%, 57% to 38%, and 64% to 48%, respectively. Another single-pass stover and grain harvester that would collect the bottom half of the stalks, 50% of the top half of the stalk and 50% of the leaves was estimated to harvest 60% of the available stover at a range of moistures from 69% to 55%.     

Effect of increasing proportions of lignocellulosic cosubstrate on the single-phase and two-phase digestion of readily biodegradable substrate

The influence of different proportions of lignocellulosic substrate (cow manure with straw, CM) on the single-phase (conventional reactor) and two-phase (acidification/methanation with solids and liquid recirculation) digestion of a readily biodegradable substrate (fruit and vegetable waste, FVW) was investigated in order to determine the optimum cosubstrate ratio and the process best suited for codigestion. Both processes were fed initially with FVW, followed by FVW and CM at 80%:20% and 60%:40% (on volatile solids, VS basis) during an experiment run over eleven months. For the single-phase process, energy yield and VS destruction decreased by 11% and 9% with the 80%:20% FVW and CM ratio and by 16% and 17% with the 60%:40% feed ratio when compared to 100% FVW feed. For the two-phase process, energy yield and VS destruction decreased by 21% and 14% with 80%:20% feed ratio and by 48% and 33% with 60%:40% feed ratio compared to 100% FVW. Substrate solubilization in the acidification reactor was very efficient for all the feed proportions but it resulted in compounds other than volatile fatty acid (non-VFA COD) which were not easily amenable to methane generation. This led to a lower energy yield per kg of VS fed in the two-phase process compared to the single-phase process for the respective waste combination. For single-phase digestion, both 80%:20% and 60%:40% ratios were effective co-substrate combinations due to their higher energy yield. The two-phase process can be used for these ratios if higher VS reduction and a higher loading rate are the objectives.     

Effect of Ash in Coal on the Performance of Coal Fired Thermal Power Plants. Part II: Capacity and Secondary Energy Effects

This article reports the secondary energy effects (wear/erosion/abrasion, slagging, and fouling) of ash in coal on the energy performance of coal fired thermal power plants of capacity range 30–500 MW. It also gives the extent of capacity reduction in equipment due to firing of coals with higher ash contents.

At an ash content of 75% in coal, the effects on the system (without fuel oil support) follow: (a) decrease in Hardgrove index from 80 to 44; (b) 20% of the specific energy consumption (SEC) of induced draft (ID) fans, 10%–12% of that of forced draft (FD) and primary air (PA) fans, 17% of that of drum mills, and 12%–13% of that of ball-race mills and bowl mills, are accounted for by wear/erosion/abrasion effects; (c) decrease of fan efficiencies by 5%–6% points due to wear/erosion/abrasion effects; (d) capacity loss originating from wear/erosion/abrasion effects alone is 8% due to ID fans, 1% due to PA fans, and 6% due to mills; (e) fouling effects are high fouling factor, decrease in boiler efficiency by 3%, and capacity reduction of 2%; and (f) CFs based on overall unit performance are 31% for units below 210 MW, 26% for 210 MW units, and 40% for 500 MW. Considering the capacity restrictions due to individual equipment, CF at an ash content of 57% is 85% due to the boiler fans, 84% due to Raymond bowl mills and drum type ball mills, 71% due to slow speed large ball and race mills, and 88% due to ash slurry pumps. When the coal exceeds 70% and tends toward 76%, the heating value of coal tends toward zero. The effects of slagging (independent of ash content in coal) area 20% decrease in boiler water wall loading, a 3.5% points decrease in boiler efficiency, and capacity reduction of 14%.     

Assessing idling effects on a compression ignition engine fueled with Jatropha and Palm biodiesel blends

In this study, performance of a diesel engine operated with Jatropha and Palm biodiesel blends at high idling conditions has been evaluated. The result obtained from experiment elucidate that, at all idling modes HC and CO emissions of both blends decreases, however, NO_x emissions increases compared to pure diesel fuel. Jatropha biodiesel has higher viscosity compared to Palm biodiesel, which might have degraded the spray characteristics and caused slightly improper mixing which might have led to slightly incomplete combustion, thus at both idling conditions, Jatropha blends emitted higher CO and HC compared to Palm biodiesels. Compared to diesel fuel, CO emissions were 5.9–9.7%, 17.6–22.6%, 23.5–29%, 2.9–6.4%, 5.9–14.5% and 11.8–17.74% less, HC emissions were 10.3–11.5%, 24.13–30.76%, 34.5–39%, 6.9–7.7%, 26–27% and 31–35% less and NO_x emissions were 8.3–9.5%, 14–15%, 22–25%, 5–7.14%, 10–11.3% and 17–18% more respectively for 5, 10 and 20% blends of Palm and Jatropha biodiesel. Compared to diesel fuel, at high idling conditions brake specific fuel consumption all Palm and Jatropha biodiesel–diesel blends increased. Compared to diesel fuel, BSFC were 1.14–1.35%, 2.28–2.96%, 7.1–8.35%, 2.28–2.69%, 3.98–5.39% and 8.83–9.29% more respectively for 5, 10 and 20% blends of Palm and Jatropha biodiesel.     

柴油机燃用100%生物柴油的性能与排放

在4100QB-2柴油机上进行100%生物柴油与纯柴油的性能与排放对比试验研究.试验结果表明:使用100%生物柴油的动力性下降5%～9%;有效燃油消耗率上升7%～11%;烟度排放下降50%～70%,大负荷时改善更为明显;十三工况总排放量得到大幅度改善,NO、CO、THC和PM排放量分别下降了19.4%、65.5%、56.8%和63.0%,表明燃用100%生物柴油后具有良好的环境友好效能.     

Experimental study of engine performance and emissions for hydrogen diesel dual fuel engine with exhaust gas recirculation

With an alarming enlargement in vehicular density, there is a threat to the environment due to toxic emissions and depleting fossil fuel reserves across the globe. This has led to the perpetual exploration of clean energy resources to establish sustainable transportation. Researchers are continuously looking for the fuels with clean emission without compromising much on vehicular performance characteristics which has already been set by efficient diesel engines. Hydrogen seems to be a promising alternative fuel for its clean combustion, recyclability and enhanced engine performance. However, problems like high NOx emissions is seen as an exclusive threat to hydrogen fuelled engines. Exhaust gas recirculation (EGR), on the other hand, is known to overcome the aforementioned problem. Therefore, this study is conducted to study the combined effect of hydrogen addition and EGR on the dual fuelled compression ignition engine on a single cylinder diesel engine modified to incorporate manifold hydrogen injection and controlled EGR. The experiments are conducted for 25%, 50%, 75% and 100% loads with the hydrogen energy share (HES) of 0%, 10% and 30%. The EGR rate is controlled between 0%, 5% and 10%. With no substantial decrement in engine's brake thermal efficiency, high gains in terms of emissions are observed due to synergy between hydrogen addition and EGR. The cumulative reduction of 38.4%, 27.4%, 33.4%, 32.3% and 20% with 30% HES and 10% EGR is observed for NOx, CO2, CO, THC and PM, respectively. Hence, the combination of hydrogen addition and EGR is observed to be advantageous for overall emission reduction.     

Numerical simulation of the effect of LPG blending on the characteristics of a diesel engine

The present work aims to investigate numerically the effect of LPG blending on the characteristics of diesel engines subjected to variable compression ratio, injection timing, and engine speed. Three blends of LPG are used, which are 10% LPG + 90% diesel, 20% LPG + 80% diesel, and 30% LPG + 70% diesel. The numerical investigation is carried out using the simulation software Diesel-RK. Increasing the percentage of LPG in diesel starts combustion early where the lowest delay period is recorded for a blend of 30% LPG + 70% diesel 6.36 deg. The combustion pressure and heat release are decreased due to the difference in the heating values of blended fuels. Although the peak energy release for diesel is 0.05458 (1/deg.) at 375 deg. BTDC, it was 0.0542, 0.05424, and 0.0537 (1/deg.) at 375 deg. BTDC for 10%, 20%, 30% LPG, respectively. Diesel with 30% LPG has a higher spray penetration followed by 20% LPG then 10% LPG and diesel come last. The diesel with 10% LPG gives a 5.35% reduction in NOx, while diesel with 20% and 30% LPG emit less NOx emission by 9.05% and 16.5%, respectively. Increasing the percentage of LPG in diesel yields to reduce soot concentration because LPG has lower carbon to hydrogen ratio. The lowest ability to emit smoke is detected for fuel with 30% LPG where a 7.4% reduction is obtained. It is worth noting that blending LPG with diesel can fight the trade-off relation between Soot-NOx as a reduction in both of them is obtained. Based on the results obtained, the blending ratio is 30% LPG. The obtained results are validated with the results of other researchers.     

End-use energy utilization efficiency of Nigerian residential sector

In this paper, the end-use efficiencies of the different energy carriers and the overall energy efficiency in the Nigerian residential sector (NRS) were estimated using energy and exergy analysis. The energy and exergy flows were considered from 2006 to 2011. The overall energy efficiency ranges from 19.15% in 2006 to 20.19% in 2011 with a mean of (19.96±0.23)% while the overall exergy efficiency ranges from 4.34% in 2006 to 4.40% in 2011 with a mean of (4.31±0.059)%. The energy and exergy efficiency margin was 15.58% with a marginal improvement of 0.07% and 0.02%, respectively when compared with previous results. The contribution of the energy carriers to the total energy and exergy inputs were 1.45% and 1.43% for electricity, 1.95% and 3% for fossil fuel and 96.6% and 95.57% for bio-fuel. The result shows that approximately 65% of the residence use wood and biomass for domestic cooking and heating, and only a fraction of the residence have access to electricity. LPG was found to be the most efficient while kerosene, charcoal, wood and other biomass the least in this order. Electricity utilization exergy efficiency is affected by vapor-compression air conditioning application apart from low potential energy applications. In addition, this paper has suggested alternatives in the end-use application and has demonstrated the relevance of exergy analysis in enhancing sustainable energy policies and management and improved integration techniques.     

Investigation of hydrogen addition to methanol-gasoline blends in an SI engine

In this study, effects of hydrogen-addition on the performance and emission characteristics of Methanol-Gasoline blends in a spark ignition (SI) engine were investigated. Experiments were conducted with a four-cylinder and four stroke spark ignition engine. Performance tests were performed via measuring brake thermal efficiency, brake specific fuel consumption, cylinder pressure and exhaust emissions (CO, CO₂, HC, NOx). These performance metrics were analyzed under three engine load conditions (no load, 50% and 100%) with a constant speed of 2000 rpm. Methanol was added to the gasoline up to 15% by volume (5%, 10% and 15%). Besides, hydrogen was added to methanol-gasoline mixtures up to 15% by volume (3%, 6%, 9% and 15%). Results of this study showed that methanol addition increases BSFC by 26% and decreases thermal efficiency by 10.5% compared to the gasoline. By adding hydrogen to the methanol - gasoline mixtures, the BSFC decreased by 4% and the thermal efficiency increased by 2% compared to the gasoline. Hydrogen addition to methanol – gasoline mixtures reduces exhaust emissions by about 16%, 75% and 15% of the mean average values of HC, CO and CO2 emissions, respectively. Lastly, ?t was concluded that hydrogen addition improves combustion process; CO and HC emissions reduce as a result of the leaning effect caused by the methanol addition; and CO2 and NOx emission increases because of the improved combustion.