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发动机进、排气门的锁夹槽部位,不仅是气门杆部强度最薄弱之处,而且,在发动机工作过程中,气门锁夹槽部位在气门弹簧以及其它相关零件的作用力下,承受着高速的往复冲击负荷和交变载荷。因此,气门锁夹槽槽形加工的精度,即与图纸要求的符合性、一致性,显得由其重要。 相似文献
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在高温、高压、高速以及润滑困难的条件下工作的活塞环,是发动机所有零件中工作寿命最短的,特别是第一道气环,在高温高压和燃烧生成物所产生的化学作用下,油膜很难建立,使其实现完全润滑比较困难,而常常处于临界润滑状态.在各道环的磨损量中,第一道气环磨损量最大,为提高性能,第一道气环通常采用梯形环、桶面环,活塞的环槽镶有耐磨镶圈,采用梯形环槽.环区的温度要求要小于250℃,否则环的弹力降低,油热解、结胶,导致活塞环卡滞,密封失效.第一环槽工作条件苛刻,因此对尺寸精度的要求较高,传统的设计计算方法,效率低、易出错,本文用求解方法得出梯形槽中径的计算公式、梯形环的计算公式,在工程实践中应用方便、准确率高、效率高,对活塞梯形环、环槽的整体设计及配合提供快捷的计算方法. 相似文献
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针对发动机运行过程中气门碰活塞的问题,要进行尺寸链的计算.由于活塞的工作温度变化很大,运动速度又很高,在计算中要考虑活塞膨胀对尺寸链的影响.为分析、计算和改进配气机构提供了指导. 相似文献
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活塞是发动机的重要零件之一.活塞的各部位不仅有较高精度的尺寸公差要求,还有较多的形位公差要求.仅对活塞矩形环槽,笔者就接触过多种形位公差标注方式.通过检测仪器,如何正确无误地得出原设计所要求的形位公差检测结果,是本文阐述的主要问题.1 环槽形位公差标注方式实例我厂自1985年至今已进行了多达几十种活塞新产品试制工作,因为引用的标准不同,活塞环槽的形位公差要求主要有以下几种: 相似文献
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1 锁夹槽的形状种类和加工锁夹槽的形状种类很多 ,目前主要形状有如图1的 a、b、c、d四种。由于形状 ,尺寸精度、形状精度、粗糙度和材质不同其加工方法也不同。加工方法有以下几种 :图 11 一次车成。这种加工方法很难满足产品图纸要求 ,主要是粗糙度达不到图纸要求 ,尤其是 40 Cr这种材质。其次像桑塔钠三条槽和 CA488四条槽难度更大。过去各气门生产厂在加工多条锁夹槽中想了不少办法都不理想 ,如 :用数控车床分别车出三条槽或四条槽 ,尽管编程是正确的 ,但由于车床丝杠、溜板等间隙叠加在一起 ,很难保证槽与槽之间尺寸要求。有的采用… 相似文献
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This experimental study was conducted to investigate the effect of a flame holder on multi-slot film cooling in a ramjet combustor. A prediffuser-type ramjet combustor equipped with a flame holder was utilized in this study. The change in adiabatic film cooling effectiveness on the downstream wall was measured using thermochromic liquid crystals. Experiments were conducted using five different blowing ratios, ranging from 0.5 to 1.5. The effect of the flame holder on heat transfer shows different characteristics between the first and second slots. In the first slot, the accelerated flows by blockage effect suppress the ejected secondary flows resulting in better cooling performance in case with the flame holder. However, the second slot represents the low cooling performance over all the regions by the disturbed flows with the flame holder compared to that without the flame holder. And the difference in cooling performance is enlarged with the increase of blowing ratio. The results reveal that it is essential to consider the effect of a wake behind the flame holder. Therefore, it should be considered in the design of film cooling systems for a practical application in ramjet combustors. 相似文献
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《动力工程学报》2017,(1):1-6
针对某电厂采用缝隙式燃烧器的W火焰锅炉高负荷下存在的飞灰含碳量高、屏式过热器超温严重、侧墙结渣严重、排烟温度过高及炉膛前后墙出现偏烧等问题,对锅炉的配风方式和炉膛出口氧体积分数等进行燃烧调整,并提出了相应的优化运行方式.结果表明:优化后的运行方式为中间二次风开度控制在85%,两侧二次风开度控制为90%,三次风开度减小到40%,内二次风保持原工况不变,外二次风开度增大至50%,炉膛出口氧体积分数控制在3%~3.5%,乏气缩孔开度关小至30%;优化后过热器超温问题得到解决,飞灰含碳质量分数降低了7.5%左右,排烟温度降低了8K左右,锅炉效率达到设计值,燃烧经济性显著提高,有效缓解了侧墙结渣和前后墙偏烧的程度. 相似文献
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Perumal Selvaraj Kumaresan Natesan Karuppanna Velusamy Thirumalachari Sundararajan 《传热工程》2019,40(1-2):193-201
To study the effect of irradiation on materials, sample coupons are irradiated in cyclotron facilities. During the irradiation process, these samples produce significant heat. This heat needs to be continuously removed from the samples in order to avoid melting of the samples as well as to keep the samples at a particular temperature during irradiation. The area available for heat transfer is limited due to small size of the samples. To increase the heat transfer rate, jet cooling is used as it provides large heat transfer co-efficient. To understand the heat transfer characteristics of jet cooling under these conditions, experiments have been carried out. Two inclined jets hitting on both sides of the target plate give maximum cooling and uniform temperature distribution. This paper gives the details of the numerical and experimental studies carried out and the discussions about the results obtained. 相似文献
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为研究燃气轮机叶片表面曲率对气膜冷却性能的影响,对二维斜缝曲面模型(凹面、凸面和平板)进行了数值模拟,选取冷却流体射流入射角35°、主射流密度比1.5,采用RNGk-ε湍流模型计算得到不同吹风比(0.5、1.2和2.0)下斜缝气膜冷却曲面模型壁面的传热系数.结果表明:低吹风比(M=0.5)时,壁面压力梯度越大,传热系数越小;中吹风比(M=1.2)时,射流对主流扰动加剧,传热加强,凹面总体传热系数比凸面小;高吹风比(M=2.0)时,曲率对传热系数的影响减弱,传热系数差异不大. 相似文献
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当压气机叶片负荷很大时,吸力面会发生严重的分离,在此基础上若正攻角继续增加,则叶片整个吸力面都可能发生分离,吸力面分离起始点不断向叶片前缘移动,可能出现类似外流中大攻角三角翼的非对称结构.利用数值模拟方法,采用边界层吹气技术,研究了具有68°折转角的矩形缝隙叶栅在不同攻角条件下的流动特点和气动性能.计算结果表明,叶片采用压力面到吸力面的吹气槽,在正攻角较大时能有效控制扩压叶栅中的附面层分离,消除原型叶栅中非对称的旋涡结构,降低气动损失,其中在+4°攻角下可将能量损失系数降低约12.5%,同时可使流通能力大大改善,扩大稳定工作范围. 相似文献
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This paper summarizes the results of an experimental and analytical investigation of the slot ripples in the damper windings of a salient-pole synchronous machine under steady state operation. A new method of measuring damper winding currents and voltages directly has been established and used to examine the ripples due to the stator slot openings, which appear in the damper bar currents and voltages, air gap flux density distributions and terminal voltages. By examining the physical relationship between air gap fluxes and damper winding currents and voltages both at no load and on load, slot ripples phenomena have been made clearer than before 相似文献
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潘丽 《电网与水力发电进展》2009,25(5):74-76
某电站下闸蓄水后,工作闸门一、二期混凝土之间发生较大渗漏,选用背水面顶水化学灌浆方案,科学制定灌浆次序,改进灌浆工艺,漏水被成功封堵。该电站的化学灌浆取得了良好效果。 相似文献