基于频域法的超超临界锅炉水冷壁动态特性模型验证及计算分析

为了研究超超临界锅炉水冷壁出口参数的动态特性,采用频域法建立了超临界压力下的水冷壁系统动态特性计算模型。通过试验验证,计算值与试验测量数据符合较好。对某电厂超超临界锅炉下炉膛水冷壁进行了计算,得到75%热耗率验收工况(THA)负荷下的动态响应特性,研究了热负荷、入口焓、入口质量流量、出口压力阶跃时的动态特性,同时分析了不同压力、入口焓、入口质量流量、热负荷和管段长度对各参数阶跃时出口工质参数动态响应的影响。结果表明：入口焓、入口质量流量和热负荷增大时,扰动造成的响应时间减小,入口压力、管段长度增大时,扰动造成的响应时间增加。     

低品位热能超临界有机朗肯循环发电特性分析

利用超临界有机朗肯循环(ORC)发电系统回收温度低于150℃的低品位热能,对超临界工况的3个关键问题:工质选择、加热过程和系统性能进行了分析.结果表明:对于适合超临界ORC发电系统的工质,临界温度相对较高的工质的系统循环热效率较高,膨胀机入口压力和冷凝压力较低,临界温度相对较低的工质的循环热效率较低,但能量利用率较高,膨胀机入口压力和冷凝压力较高;超临界加热器中较高的换热压力和较低的膨胀机入口温度能使热源与工质有更好的热匹配;在热源进口温度和最小换热温差的限制下,存在最佳膨胀机入口温度和膨胀机入口压力,使得系统循环热效率最高.     

一种SCWR概念设计方案的系统水动力特性

对一种典型的超临界水堆(SCWR)设计方案中的反应堆冷却剂系统(RCS)和非能动余热排出系统(PRHRS)回路进行了简化,建立了两系统在超临界压力下的统一水动力模型。利用模型对SCWR主系统和非能动余热排出系统的水动力特性及输热、排热能力进行了计算,并在此基础上分析了堆芯进口温度、泵特性、回路高度、系统阻力等因素对系统运行的影响。     

超临界二氧化碳再压缩再热火力发电系统关键参数的研究

针对含分流再压缩和一次再热的超临界二氧化碳布雷顿循环火力发电系统,建立了其数学模型,并用Fortran语言编制了计算程序.通过详细计算,深入分析了分流系数、主压缩机出口压力、主压缩机入口压力、透平入口温度等关键参数对循环效率的影响.结果表明:随着一次工质温度或二次工质温度的升高,循环效率线性升高;但由于超临界二氧化碳物性的特点以及高、低温回热器最小换热温差的约束,主压缩机出、入口压力和分流系数等参数对循环效率的影响均非单调变化,这与传统的蒸汽朗肯动力循环完全不同;超临界二氧化碳动力循环系统存在最优的压缩机出、入口压力和分流系数的耦合关系,使得该系统的循环效率最高.     

500MW超临界压力直流锅炉机组实时仿真数学模型

在分析５００ＭＷ超临界压力直流锅炉机组结构和特性的基础上,以质量,能量,动量守恒定律为依据,建立了炉内传热算法和各锅内过程算法。并采用模块化的建模技术,建立了苏制５００ＭＷ超临界压力直流锅炉的实时仿真数学模型。该模型能够准确地模拟实际机组的动态特性和静态特性。     

中间再热抽汽式汽轮机DEH控制系统的响应特性研究

对采用DEH控制系统的中间再热抽汽式汽轮机热电负荷的自整性进行了分析,对不同控制模式下系统的负荷适应性进行了研究。结果表明,由于DEH控制系统中PID调节器积分控制作用的存在,能够消除热电荷之间的相互静态干扰。新汽压力扰动时,调节级压力控制回路具有较好的瞬态响应特性;而负荷扰动时,功率控制回路具有较好的动态响应特性。因此,应根据机组的扰动情况选择控制回路。     

2953t/h超临界锅炉垂直水冷壁水动力特性研究

建立超临界锅炉垂直水冷壁水动力特性计算模型,首先按出口工质温度相等的原则计算节流补偿压降,再以给定热的负荷以及节流方式进行了流量分配和压降特性校核计算,并研究了2953t/h超临界锅炉垂直水冷壁水动力特性。研究结果表明:以50%锅炉最大连续出力工况为基准来设计水冷壁入口节流压降是合理的,该方法可以使各负荷下的回路特性均趋于理想回路特性,能够获得较均匀的出口工质温度分布,热力偏差小并能够维持合适的水冷壁金属温度。水冷壁总压降的变化趋势与锅炉负荷变化相符。对于弱受热回路,重位压降所占总压降比例大于摩擦压降,因而弱受热具有自然循环特性;对于强受热回路,重位压降所占总压降比例小于摩擦压降,因而强受热回路具有直流特性。100%BMCR工况下,最高金属壁温为497℃,低于管材规定的580℃,因此锅炉机组的运行安全性可以得到保证。     

超临界压力下航空煤油在竖直管内的传热研究

对竖直上升管内超临界压力下航空煤油的传热特性进行了实验研究。分析了不同质量流量、热流密度、压力和进口温度对超临界压力下航空煤油传热特性的影响。实验结果表明,提高质量流量或进口温度均使煤油传热效果变好。而热流密度对流体传热的影响主要在于改变了流体和壁面温度,热流密度越大,传热系数越高。压力对煤油传热影响不大,一般情况下,提高压力会恶化传热。超临界状态下,煤油物性变化很大,因此对煤油的传输和热力学性质的准确计算是研究超临界压力下传热现象的关键。利用拓展的对比态法来计算煤油的密度和传输特性,如黏度、热导率等。给出了煤油在超临界压力下的传热关联式,其计算值和实验值吻合良好。     

水流温度不均匀对超临界压力蒸发管水动力特性的影响

对超临界压力锅炉蒸发管的水动力特性进行了理论分析，通过对不同配置方式管组的水动力特性进行计算，指出在超临界压力下的大比热区（i＝1700－2500kJ／kg）必须考虑水流的温度不均匀性对超临界压力锅炉水动力特性的影响。     

超临界锅炉风烟系统的流体网络动态数学模型

介绍了2种流体网络建模方法--节点压力法和网络法,并通过实例比较了2种方法的静态计算结果和动态响应过程,结果表明:网络法模型计算精度高,收敛速度快,可以快速响应压力的变化.在详细分析超临界锅炉风烟系统的基础上,建立了系统流动阻力的数学模型,采用模块化的建模思想编制了风烟系统的仿真算法,并在仿真平台Simpanel上对其静态和动态特性进行了仿真研究.通过分析表明:所建立的风烟系统仿真模型具有良好的静态精度和动态响应特性,能够满足仿真实时性的要求.     

中压进汽腔的流场数值模拟比较

通过数值模拟计算,对中压对称进汽和切向进汽两种结构的流场进行了分析比较,结果表明,单一切向进汽腔的总压损失更小,出口汽流角的周向分布均匀度更好。更进一步,为整体评估中压进汽腔的流场以及对叶片级的流动影响,对中压进汽腔及第1级叶片的整体流体域流场情况进行了分析比较,结果表明,采用大几何角静叶的切向进汽腔气动性能最优;当采取切向进汽腔时,需合理选择第1级静叶几何角并耦合计算,才能实现进汽腔的气动优化。     

Effect of inlet guide vanes on the performance of small axial flow fan

Effects of the inlet guide vanes on the static characteristics, aerodynamic noise and internal flow characteristics of a small axial flow fan are studied in this work. The inlet guide vanes with different outlet angle are designed,which are mounted on the casing and located at the upstream of the impeller of the prototype fan. Both steady and unsteady flow simulations are performed. The steady flow is simulated by the calculations of Navier-Stokes equations coupled with RNG k-epsilon turbulence model, while the unsteady flow is computed with large eddy simulation. According to the theoretical analysis, the inlet guide vanes with outlet angle of 60° are regarded as the optimal inlet guide vanes. The static characteristic experiment is carried out in a standard test rig and the aerodynamic noise is tested in a semi-anechoic room. Then, performances of the fan with optimal inlet guide vanes are compared with those of the prototype fan. The results show that there is reasonable agreement between the simulation results and the experimental data. It is found that the static characteristics of small axial flow fan is improved obviously after installing the optimal inlet guide vanes. Meanwhile, the optimal inlet guide vanes have effect on reducing noise at the near field, but have little effect on the noise at the far field.     

跨音速离心压气机级间静压测量研究

为获得车用涡轮增压器离心压气机各元件进出口及周向静压分布,开展了跨音速离心压气机级间静压测试研究。研究结果表明:蜗舌结构未造成导风轮进口静压分布周向不均匀(导风轮进口周向压力波动在2.5 kPa之内);蜗舌结构导致短叶片轮缘静压分布的周向不均匀性;同一转速下,跨音速流动最高效率工况周向静压分布不均匀;叶轮跨音速时,蜗壳沿着流动方向进行减速扩压;同一转速下,扩压器静压提升变化很小(约在3 kPa之内),而叶轮静压提升变化很大(约13～50 kPa),叶轮静压提升的改变决定压比流量特性线的陡峭程度。     

汽封力作用下的转子-轴承系统稳定性研究

通过分析汽封力对轴承静态平衡点的影响,表明汽封力能够改变轴承的静、动特性。计算了滑动轴承油膜力和汽封力共同作用下的系统一阶临界转速和一阶对数衰减率,并用实验进行了验证。研究表明,汽封力对系统稳定性的影响是复杂的,其影响因素包括进出口压力、进口预选速度、密封参数等。     

涡旋式膨胀机的非线性数学模型及动态仿真

为了设计涡旋式膨胀机控制系统,根据涡旋式膨胀机机理分析,以膨胀机的进气管道、进气腔、膨胀腔和排气腔等组建的静态数学关系为基础,建立了阀门开度与膨胀机进气管道压力以及膨胀机内部功率与转子转速两组非线性微分方程,通过膨胀机进气管道压力与膨胀机内部功率之间的关系,得到了阀门开度与转子转速的动态模型．仿真结果表明：所建立的动态模型符合涡旋式膨胀机的特性,在一定程度上证明了模型的正确性和有效性．     

The effect of secondary flows on the starting pressure for a second-throat supersonic ejector

The effect of the secondary flow on the starting pressure of a second-throat supersonic ejector has been investigated by adapting the height of the secondary flow inlet. The obtained results show that an optimum value of the secondary inlet height exists, and the starting pressure of the ejector becomes a minimum at that condition. Based on the results of the pressure measurements, a qualitative analysis has been made to clarify the flow behavior and the physical meaning of the performance diagram. It appears that the choking phenomenon of the secondary flow plays an important role in the starting process of the ejector. When the secondary inlet height is relatively small, the choked secondary flow and the supersonic primary flow could be employed to protect the static pressure in the suction chamber from being disturbed by the back pressure effect at a certain primary stagnation pressure, which is lower than the starting pressure for the case of the zero-secondary flow. However, as the secondary inlet height increases and exceeds a critical value, the static pressure in the suction chamber rapidly increases, and the starting pressure of the ejector increases accordingly.     

电站锅炉过热器、再热器集箱静压分布的数值研究

利用数值模拟的方法，研究了径向引入引出型分配、汇流集箱系统的静压分布规律。为了消除计算中伪扩散的影响，选用了QUICK格式。数值计算结果表明：在三通附近，气流的变化非常强烈，在远离三通的区域．气流逐渐平稳。在分配集箱进口三通的两侧存在2个涡流区，正对三通中心线的支管处静压最高，远离三通的区域，静压分布与轴向引入引出方式规律基本一致。利用该方法计算了某电厂锅炉末级再热器的流量分配和热偏差情况，与实测结果相吻合。图6表1参2     

Automatic efficiency optimization of an axial compressor with adjustable inlet guide vanes

The inlet attack angle of rotor blade reasonably can be adjusted with the change of the stagger angle of inlet guide vane (IGV); so the efficiency of each condition will be affected. For the purpose to improve the efficiency, the DSP (Digital Signal Processor) controller is designed to adjust the stagger angle of IGV automatically in order to optimize the efficiency at any operating condition. The A/D signal collection includes inlet static pressure, outlet static pressure, outlet total pressure, rotor speed and torque signal, the efficiency can be calculated in the DSP, and the angle signal for the stepping motor which control the IGV will be sent out from the D/A. Experimental investigations are performed in a three-stage, low-speed axial compressor with variable inlet guide vanes. It is demonstrated that the DSP designed can well adjust the stagger angle of IGV online, the efficiency under different conditions can be optimized. This establishment of DSP online adjustment scheme may provide a practical solution for improving performance of multi-stage axial flow compressor when its operating condition is varied.     

The change of the inlet geometry of a centrifugal compressor stage and its influence on the compressor performance

The impact on the compressor performance is important for designing the inlet pipe of the centrifugal compressor of a vehicle turbocharger with different inlet pipes. First, an experiment was performed to determine the compressor performance from three cases: a straight inlet pipe, a long bent inlet pipe and a short bent inlet pipe. Next, dynamic sensors were installed in key positions to collect the sign of the unsteady pressure of the centrifugal compressor. Combined with the results of numerical simulations, the total pressure distortion in the pipes, the pressure distributions on the blades and the pressure variability in the diffuser are studied in detail. The results can be summarized as follows: a bent pipe results in an inlet distortion to the compressor, which leads to performance degradation, and the effect is more apparent as the mass flow rate increases. The distortion induced by the bent inlet is not only influenced by the distance between the outlet of the bent section and the leading edge of the impeller but also by the impeller rotation. The flow fields in the centrifugal impeller and the diffuser are influenced by a coupling effect produced by the upstream inlet distortion and the downstream blocking effect from the volute tongue. If the inlet geometry is changed, the distributions and the fluctuation intensities of the static pressure on the main blade surface of the centrifugal impeller and in the diffuser are changed accordingly.     

Turboexpander wheel design for helium liquefaction plant

A turboexpander wheel, that is, turbine, is one of the critical components for a helium liquefaction plant. It helps to provide the cooling effect required for the liquefaction. The percentage of liquefaction depends upon the effective design of the turbine. The present work includes the design of a radial turbine for the intended power output of approximately 1.5 kW, with input conditions of 40‐g/s mass flow rate at inlet, inlet total pressure of 14 bar, inlet temperature of 40 K, and outlet static pressure of 6 bar. The pressure values are taken to be absolute. Inlet conditions are selected on the basis of required refrigeration effect of approximately 1 kW. The outlet static pressure of 6 bar is maintained to avoid the turbulence, which may occur due to expansion for high pressure ratios. The present work involves the design and optimization of a turbine on the basis of the mean line analysis, initiating with the assumption of values for total‐to‐static efficiency. As per mean line design concept, a one‐dimensional flow is considered for this analysis and the mean values of different parameters are considered at different sections. Losses are considered as the main constraint in design and it is desirable to get optimum net power. Besides, it is also desirable to achieve values for other design parameters in a specified range.