动叶间隙对压气机气动性能的影响

为研究动叶间隙大小对压气机性能及流动的影响,以一台高亚声速一级半压气机级为研究对象,在设计间隙、0. 5倍、1. 5倍及2倍设计间隙下进行定常三维数值模拟。计算结果表明,随着间隙增大,压气机效率及总压比下降。大间隙下泄漏流增强,导致动叶叶尖及其下游区域损失增加,压气机转子效率随间隙增大而线性下降;同时,泄漏流的增强也恶化了动静叶匹配,导致静叶上端壁产生额外损失,压气机级效率下降幅度大于转子效率。     

叶顶间隙对跨音速离心压气机气动性能影响分析

基于控制变量法对某跨音速离心压气机进行数值模拟,研究了叶轮尾缘叶间隙改变对其气动性能的影响。仅改变该离心叶轮的尾缘叶顶间隙,在设计转速下进行全三维黏性数值模拟,对相关气动参数进行分析。计算结果表明,相较于小流量工况,尾缘叶顶间隙的改变对离心压气机大流量工况的气动性能影响更大;在设计流量下,离心叶轮的压比、效率与叶轮尾缘出口间隙大小之间具有一定的线性关系,随着叶尖间隙增大,叶轮叶尖泄漏流的强度明显增强,导致叶轮的增压能力下降。     

端壁相对运动对压气机叶栅间隙流场影响的数值模拟

压气机端壁与叶片间的相对运动是影响叶顶间隙气流流动的重要因素.采用数值模拟的方法考察了端壁运动对不同叶顶间隙压气机叶栅内三维流场的影响.结果表明:端壁相对运动改变了叶栅间隙流场结构,叶栅通道内出现向相邻叶片压力面运动的刮削泄漏涡,上通道涡及叶顶分离涡受到抑制,叶尖负荷增大,间隙泄漏流量增加,叶栅总损失由于叶顶区掺混损失减少而减少.     

高海拔条件下压气机结构优化及其对柴油机性能的影响

基于二级可调增压柴油机高海拔性能试验,采用计算流体力学(CFD)和柴油机工作过程计算方法,开展高海拔条件下压气机叶轮结构优化及其对柴油机性能影响的研究.研究结果表明:海拔5 500 m,压气机叶轮主叶片及分流叶片前缘前掠6.27°、分流叶片向主叶片压力面偏折12.09°,压气机叶轮流道内流动损失明显降低,出口处流动稳定性提高,压比、效率及流量范围分别提高4.16%、2.63%及6.58%;压气机叶轮优化后,二级可调增压柴油机中低转速燃烧过程得到明显改善,滞燃期和燃烧持续期缩短;柴油机1 200 r/min全负荷工况最高燃烧压力升高9.53%,累计放热量提高8.78%,转矩提高5.82%,燃油消耗率降低4.42%.     

自由活塞发动机电动压气机优化及熵产分析

为了使设计工况下匹配的增压器性能更优从而提高系统能量利用率,针对自由活塞发动机匹配的电动压气机,采用遗传算法对原压气机进行了优化,研究了优化前、后压气机内部流场特性,以熵产分析的方法量化了3种不可逆因素导致的流动损失,并将优化前、后压气机熵产和涡度分布对比分析,进一步明确了压气机的优化策略．结果表明：叶轮和扩压器中湍流耗散、传热耗散和黏性耗散的比例近乎为6∶3∶1．不可逆损失主要集中在叶顶间隙和叶片压力面,损失来源为间隙泄漏流与部分主流掺混形成的反向涡团．压壳中湍流耗散占比超过85%,具体表现为局部损失和沿程损失．优化后压气机等熵效率提高了6%,流道内涡团的范围、幅值大幅减小,不可逆流动损失降低．上述工作揭示了压气机流场中不同耗散机制的不可逆因素对能量损失的影响机理,为压气机气动优化设计提供指导．     

叶顶间隙对离心式压气机效率的影响研究

针对涡轮增压器压气机的叶顶间隙进行数值模拟计算,探究其对压气机效率损失的影响。研究结果表明:在均匀叶顶间隙下,随着叶顶间隙的增大,压气机的效率随之降低;在恒定转速下,随着压气机稳定流量的增加,叶顶间隙变化引起的效率衰减量逐渐增加;在恒定流量下,随着压气机转速的增加,叶顶间隙的变化引起的效率损失逐渐减小;在变叶顶间隙下,叶轮出口叶顶间隙的减小可以使压气机效率得到明显的改善。     

多级轴流超临界二氧化碳压气机气动性能研究

二氧化碳作为动力循环工质可获得更高的循环效率和部件紧凑性,应用前景广阔。基于给定参数设计了1台4级轴流式超临界二氧化碳(SCO_2)压气机,通过划分六面体网格,采用有限体积法及SSTk-ω湍流模型对其气动性能进行了详细分析,并对叶顶间隙的影响规律进行了研究。研究表明,由于流动加速和引射作用,叶顶间隙泄漏流造成了叶尖吸力侧流体温度和压力的下降,因此该区域可能会发生冷凝现象,并且叶顶间隙的增大进一步降低了该区域的参数,将会导致级效率和压比的降低。研究成果可为SCO_2压气机设计提供参考。     

汽轮机动叶顶部间隙泄漏流动特性的数值模拟

以一个小展弦比轴流透平级为研究对象,采用数值方法对不同动叶顶部间隙情况下的间隙泄漏流动进行了分析,研究了间隙流和间隙涡的形成、发展及其对透平级性能的影响.以三维流线和极限流线为手段,分析了6种间隙尺寸下动叶顶部的泄漏流和泄漏涡造成的损失及其与主流掺混的过程.结果表明:动叶顶部间隙两侧压力面和吸力面之间的压力差使汽流从压力面被吸入间隙,跨过叶顶,进入相邻叶栅通道的吸力面,导致泄漏流动;与无间隙的情况相比,叶顶间隙的存在使上端壁处的流场发生明显变化,引起损失迅速增长;随着间隙的增大,泄漏涡的产生位置提前,强度增大,从而导致更大的流动损失.     

抑制叶顶间隙泄漏的叶轮机械叶片的流场模拟

根据叶顶间隙流对叶轮机械的性能有重要影响这一特性,设计了一种叶片.该叶片顶部带有"燕尾冠",在叶顶的压力侧和吸力侧都形成"倒钩".通过对带有"燕尾冠"的叶片和一般的叶片的流场进行数值模拟,在同等条件下比较两者之间压气机的总体性能、流场特性以及叶顶间隙的泄漏量的区别,得到优化设计后的"燕尾冠"叶片能较好的保持住叶片表面的压力,削弱了叶顶间隙泄漏涡的产生和减少了通过叶顶间隙的泄漏量.数据结论为改进和提高叶轮机械的运转性能提供参考依据.     

高原工况压气机叶轮振动失效特征分析

针对高原工况下离心压气机叶轮振动失效问题,以某增压发动机压气机叶轮为研究对象建立仿真模型,使用非定常计算流体动力学方法分析高原共振工况下叶轮受到的气流激励时域与频域特征,并基于单向流固耦合,使用瞬态动力学与谐响应方法研究气流激励作用下叶轮共振响应特征,得出高原工况叶轮振动失效原因。结果表明,高原工况叶轮在4阶气流激励作用下发生共振,激励主要来源于叶片与蜗舌间的动静干涉作用,叶顶间隙泄漏流增大了吸力面20%弦长位置的压力波动。气流激励下叶轮共振导致叶片前缘振动应力升高,振动应力幅值达101.5 MPa,与实际叶片振动失效情况一致。     

Unerroric of control of mutual compliance of the efficiency of hydrogen engines of unmanned vehicles in the conditions of mass production

The issues related to the reliability of hydrogen engines of unmanned vehicles and increasing the efficiency of using hydrogen as fuel when using the method of its production during the decomposition of hydrogen-containing molecules of liquid-phase organic compounds in a plasma discharge under the action of intense ultrasonic exposure are considered. Experiments have shown that as a result of decomposition in the acoustoplasma discharge of liquid hydrocarbons, solid-phase carbon-containing products are formed, chemical transformations occur in the liquid phase and hydrogen-containing combustible gas is formed. Hydrogen-containing gas can be used as fuel immediately after synthesis, i.e. it does not require separation, since in addition to hydrogen it contains only impurities of CO₂ and water vapor. The purpose of the study is to formalize the basic conditions for tightening the control of mutual compliance with the efficiency of hydrogen engines of the same series in the conditions of their mass production. Methods of mathematical statistics and hardware-software modeling were used in the study. The term “unerroric of quality mutual compliance control” is introduced to describe a set of hardware and software tools for such control. The principle of in-depth testing of the technical condition of such engines of one series is described in a multidimensional formulation of the quality control problem for three of their operating parameters at once. The conditions for increasing the mutual correspondence of the measured values of such parameters in the conditions of serial production of hydrogen engines are formalized.     

MgO膨胀剂细度对MgO水化和水泥浆体膨胀的影响

基于《水工混凝土掺用氧化镁技术规范》中的Ⅰ型氧化镁（MgO）,研究了该型MgO膨胀剂（MEA）细度对掺粉煤灰水泥浆体膨胀性能的影响。即采用X射线衍射分析(XRD)及同步热分析（TG DSC）分析了掺MEA水泥浆体中MgO的水化性。结果表明,养护温度相同时,MEA的细度对水泥浆体内MEA中MgO的水化和水泥浆体的膨胀无显著影响,产生的膨胀均能补偿水泥浆体的收缩;MEA的细度可从试验设计采用的45 μm筛筛余15%左右增加到30%左右,这将有利于MEA生产企业的节能降耗。     

小型锅炉烟尘测试时锅炉出力的计算

锅炉烟尘测试时,必须对锅炉出力进行测试。但监测中,许多小型锅炉往往不具备相关的计量装置和仪表,为解决这一问题,文章提出了用烟气量和空气过剩系数来计算锅炉的出力的公式,在实际使用中,该方法简单易行,其结果和实测值具有很好的一致怀。     

Heat of vaporization of mixtures

General expressions for the heat of vaporization of mixtures at constant pressure; at constant temperature; and at constant pressure, temperature, and composition are proposed. The last one is related to the liquid-vapor interface where steady vaporization or condensation is taking place. Numerical examples by the proposed expressions are shown for binary mixtures of HCFC22(R22) and (HCFC123(R123) © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(1): 12–24, 1996     

生物质催化热裂解技术的研究进展

生物质催化裂解是生物质热化学转化的一种重要途径。综述了生物质催化热裂解技术使用的反应器、催化剂类型,以及催化热裂解过程中热裂解温度、吹扫气、升温速率、生物质原料等条件的影响,展望了生物质催化热裂解技术的发展趋势。     

燃烧流化床气泡能量分布模型

应用瞬态谱分析方法对燃烧流化床声波信号进行了频谱分析,发现气泡能量分布呈Ｇａｍｍａ分布形式,在Ａｒｇｙｒｉｏｕｓ和Ｙｏｓｈｉｄａ等人提出的模型的基础上,发展了燃烧流化床气泡能量分布模型,并通过优化迭代对模型参数进行求解,在实验和理论的基础上得出了更加切合实际的燃烧流化床气泡能量分布模型     

促进城镇生活污水处理装置产业化

城镇生活污水处理装置是由农村户用沼气地发展演变而来，是一种小型、分散化处理污水的装置 ，是环境建设的需要。文章着重从我国环保政策及目标、生活污水造成的污染状况、急需整治的公共设施、生活污水净化装置的演变以及社会经济效益和环境效益等方面，阐述了其产业化的重要性。     

中国煤炭地下气化技术的发展

本文综述了煤炭地下汽化技术的国内外发展现状,对我国“长通道、大断面”煤炭地下气化新工艺给予了技术经济评述,并提出了发展煤炭地下汽化技术的政策建议。     

Investigation of effect of variation of cycle parameters on thermodynamic performance of gas-steam combined cycle

The paper deals with second law thermodynamic analysis of a basic gas turbine based gas-steam combined cycle. The article investigates the effect of variation of cycle parameters on rational efficiency and component-wise non-dimensionalised exergy destruction of the plant. Component-wise inefficiencies of the combined cycle have been quantified with the objective to pin-point the major sources of exergy destruction. The parameter that affects cycle performance most is the TIT (turbine inlet temperature). TIT should be kept on the higher side, because at lower values, the exergy destruction is higher. The summation of total exergy destruction of all components in percentage terms is lower (44.88%) at TIT of 1800 K & r_p,c = 23, as compared to that at TIT = 1700 K. The sum total of rational efficiency of gas turbine and steam turbine is found to be higher (54.91%) at TIT = 1800 K & r_p,c = 23, as compared to that at TIT = 1700 K. Compressor pressure ratio also affects the exergy performance. The sum total of exergy destruction of all components of the combined cycle plant is lower (44.17%) at higher value of compressor pressure ratio (23)& TIT = 1700 K, as compared to that at compressor pressure ratio (16). Also exergy destruction is minimized with the adoption of multi-pressure-reheat steam generator configuration.     

Review of theory of distortion and disintegration of liquid streams

Linear and nonlinear analyses of the instabilities and distortion of liquid streams injected into a gaseous media are discussed. The various fundamental mechanisms and the predictive capabilities for the distortions are emphasized. Round jets, planar sheets, annular sheets, and conical sheets are discussed in detail. The balance between capillary and inertial forces is primarily examined. The method for simplifying the analyses in the case of thin liquid sheets is discussed. The capabilities for representing the droplet size distribution that follows the stream disintegration are outlined.