Investigation on Combustion Characteristics in Channel with Obstacles for Internal Combustion Wave Rotor

This paper establishes a simplified test system for internal combustion wave rotor with a single channel and designs different intensifying combustion obstacles and arrangements. Moreover, this paper analyzes the intensifying effect of obstacles on combustion process of the internal combustion wave rotor from the stable operation range, pressure gain and flame progression process perspective. The results show that the range of inlet velocity under stable operation of the internal combustion wave rotor narrows after the addition of obstacles, and the corresponding velocity values substantially reduce while the flame propagation speed can be improved by 2 - 4 times. At the rotation rate of 1500 rpm, the pressure gain increases significantly during the combustion process. These results provide technical supports for further research and application of the internal combustion wave rotor.

Experimental and Numerical Research on Strengthening the Performance of Wave Rotor Equipment with Curved Passages

The wave rotor technology is an energy exchanging approach that achieves efficient energy transfer between gases without using mechanical components.The wave rotor technology has been successfully utilized in gas turbine cycle systems,gas expansion refrigeration and a variety of other industrial domains,yielding numerous researches and application outcomes.The structure of wave rotor passages inside which the energy exchange between gases is realized has an important impact on the equipment performance.In this study,based on gas wave ejection technology,the first application trials of an expansion wave rotor with curved passages were conducted.Additionally,the performance enhancing effect and mechanism of curved passages on the energy exchanging process were studied precisely by the combination of experimental and three-dimensional numerical simulation methods.The experimental results demonstrate that the curved passage rotor(CIR rotor)employed in this research has a maximum isentropic efficiency of 61.6%,and the CIR rotor achieves higher efficiency than the straight passage rotor(STR rotor)on all working conditions in this study.Compared with the STR rotor,the maximum efficiency improving ratio of CIR rotor can exceed 14.2%at each experimental expansion ratio,and the maximum relative increments of ejection rate are more than 5%.In addition,the CIR rotor can also effectively increase the proportion of static pressure in total pressure of the medium-pressure gas,and reduce the device power consumption.The three-dimensional numerical investigations revealed the principle of gas ejection in the wave rotors and explained why the CIR rotor performed better.According to the numerical findings,the curved passages of the CIR rotor may effectively minimize various energy losses created in the processes of high-pressure gas incidence,exhausting flow in nozzle,and high-speed gas flow in the passages.

Study on wave rotor refrigerators

As a novel generation of a rotational gas wave machine,the wave rotor refrigerator(WRR)is an unsteadyflow device used for refrigeration,in whose passages pressured streams directly contact and exchange energy due to the movement of pressure waves.In this paper,the working mechanism and refrigeration principle are inves-tigated based on the one-dimensional unsteadyflow theory.A basic limitation on main structural parameters and operating parameters is deduced and the wave diagram of WRR to guide designing is sketched.The main influential factors are studied through an experiment.In the DUT Gas Wave Refrigeration Studying and Development Center(GWRSDC)lab,the isentropic efficiency can now reach about 65%.The results show that the WRR is a feasible and promising technology in pressured gas refrigeration cases.

Design point analysis of two-shaft gas turbine engines topped by four-port wave rotors for power generation systems

Wave rotors are rotating equipment designed to exchange energy between high and low enthalpy fluids by means of unsteady pressure waves.In ground power plants,they can be used as topping devices to existing gas turbines aiming to improve their performance characteristics.A four-port wave rotor is an attractive configuration to be integrated into the gas generator of a two-shaft gas turbine,typical for power generation and propulsion systems,by slightly modifying the architecture of existing engines.In particular,in the present article the wave rotor-topped engine utilizes the same compressor,combustion chamber and turbine inlet temperature of the baseline engine.Cycle analysis for two-shaft gas turbine engines topped with four-port wave rotors is studied and their performance at design point is compared to the performance of the baseline engines accordingly.It is concluded that important benefits are obtained with respect to the ones of the baseline engines in terms of specific work and specific fuel consumption.Furthermore calculations by varying the pressure ratio within the wave rotor and the pressure losses in the ducts connecting the wave rotor to the engine’s components indicate the effect on performance,for engines with different compressor pressure ratios and turbine inlet temperatures.

Investigation of pressure wave behaviors in the rotational speed effects on a pressure-exchange wave rotor

A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves.The experimental and CFD results showed some slopes in the circumferential pressure distributions,and the slopes indicated the traces of specific unsteady pressure waves.Such traces varied regularly if the rotational speed varied within a range from-11%to+11%off the baseline value,but they were seriously disturbed if the rotational speed varied by-45%from the baseline value.It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent,and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent.Because of the pressure wave behaviors,the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.

Shock Wave Observation in Narrow Tubes for a Parametric Study on Micro Wave Rotor Design

波浪转子被期望急速地改进微煤气的汽轮机的表演。在波浪转子设计，转子速度被试管长度主要决定。因此，当它可以产出更厚的墙界面层时，一个更长的试管更好让使小型化的波浪转子在轴承和润滑油系统避免困难，冲击波驱散等等。在现在的学习，一台试验性的仪器被造设想波浪转子在由 schlieren 的一个狭窄的试管的内部流动动力学方法和激光 Doppler 风力测定。另外，试管的不同长度被采用并且与相比调查墙磨擦的效果。最后， 2D 数字模拟被执行，结果与实验的那些相比。

Effects of Rotor Solidity on the Performance of Impulse Turbine for OWC Wave Energy Converter

Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.

倾斜偏心对同步发电机转子力学特性的影响

气隙偏心是一种常见的发电机机械故障。已有研究主要关注正常和轴向气隙均匀偏心对转子受载和振动特性的影响,较少关注轴向气隙非均匀偏心,即转子倾斜偏心。作为补充,全面分析转子倾斜偏心状态下故障程度差异对同步发电机转子力学特性的影响。其中,转子力学特性包括转子不平衡磁拉力激励特性和振动特性。以一台5kVA的两极故障模拟发电机为研究对象,分别进行理论分析、有限元仿真计算和实验验证。结果表明:正常情况下转子不平衡磁拉力为零,转子振动频率以常规基频和定子传递的各偶次谐波为主。在转子发生倾斜偏心故障后,转子不平衡磁拉力/振动以二次谐波为主。随着偏心程度增加,转子不平衡磁拉力/振动的二次谐波幅值将增大。此外,转子不平衡磁拉力沿轴向非均匀分布,在气隙越小的位置不平衡磁拉力越大。

齿调制作用下转子开槽对永磁电机电磁振动影响

为了研究齿调制作用下转子表面开槽对永磁同步电机电磁振动的影响,以小功率分数槽集中绕组(FSCW)内置永磁同步电机(IPMSM)为研究对象,通过麦克斯韦应力张量法推导径向电磁力波的频率及空间阶数特征。分析齿调制作用在FSCW-IPMSM中将空间高阶电磁力波调制为低阶电磁力波的过程,并给出转子表面开槽在齿调制作用影响下与电磁振动间的联系。研究表明,转子表面开槽结构的改变会使各次谐波磁场发生变化,进而改变以极数阶电磁力波为代表的高阶电磁力波的幅值。在齿调制作用下,这些高阶电磁力波会被调制为幅值较高的低阶电磁力波,并引起不同幅度的低阶振动。然后建立C型、V型两种不同转子表面开槽结构的10极12槽FSCW-IPMSM电磁及结构有限元分析模型并进行仿真分析。结果表明,极数阶即10阶电磁力波会被调制为2阶并引起2阶振动,且两种不同开槽结构间的电磁振动存在着高达22.1%的差异。最后,在一台10极12槽样机上进行振动实验,验证理论与仿真分析结果。

基于车用永磁同步电机转子结构的电磁噪声优化仿真分析

针对目标电机低速加速段中存在明显类似“口哨”的高频噪声的问题及电机量产降本原则,将48槽8极峰值功率62 kW的乘用车前驱动电机作为案例进行电磁方案设计。基于设计指标及存在问题设计了定子结构相同内置式转子拓扑结构不同的优化方案,推导计算了两电机方案气隙磁场幅值波形时空分布方程及电磁力表达式,建立了两电机方案有限元模型及电磁-结构声场耦合模型,仿真分析比较两电机气隙磁密及径向电磁力谐波含量。基于仿真结果得到优化方案,在不牺牲电磁性能的前提下削弱了低速段加速过程的0阶6f1径向电磁力,并使磁钢用量从1.474 kg降低到了1.371 kg,实现了降本目的。最后分别制作样机进行实验验证,结果表明优化方案明显削弱了低速段径向振动,降低了24倍频电磁噪声,与仿真结果相吻合。

基于声表面波传感器的转子叶片应变无线测量研究

声表面波传感器可以实现无线无源工作,该特性使其在高速旋转部件测试中有重要的应用前景。利用硅酸镓镧压电晶体设计并制备了谐振型SAW传感器,研究了其应变敏感特性,并成功应用于转子叶片应变的无线测试试验。结果表明,所制备的SAW传感器的谐振频率为217.794 MHz,品质因子达到5807,应变灵敏度为-317 Hz/με。在3000~15000 r/min转速下,无线测试了转子叶片应变,测试结果与电阻应变计测量结果及有限元仿真计算结果基本一致。研究结果可以为SAW传感器在高速旋转设备的无线测试工程应用提供参考。

纵摇运动下船用转子-轴承-浮筏气囊耦合系统非线性动力学特性

以纵摇运动作用下转子-轴承-浮筏气囊耦合系统的非线性动力学特性作为研究对象。首先,考虑转子不平衡力、轴承油膜力、浮筏气囊弹性回复力以及船体纵摇运动惯性力等因素,根据Lagrange方程建立转子轴承-浮筏气囊耦合系统的动力学模型。基于数值方法,结合瀑布图、轴心轨迹图及相图、时域和频谱图等对转子-轴承-气囊浮筏耦合系统非线性动力学特性进行分析。结果表明:随着转子转速的增加,纵摇运动下的转子轴承-浮筏气囊耦合系统运动状态从拟周期运动到混沌运动;与不考虑纵摇运动时相比,纵摇运动下转子的振动响应幅值明显增大,同时响应中存在纵摇频率及工频的组合倍频。最后讨论纵摇幅值的变化对于转子轴承-浮筏气囊耦合系统动力学特性的影响。

基于增益控制的永磁同步电机低速转子位置估算方法

当永磁同步电机工作在零低速域内时,受系统延迟时间的影响,采用高频脉振方波电压注入的传统差分解调法会出现系统失稳和动态性能下降的问题。提出了误差系数标幺下的增益控制策略。分析了不同延迟时间下传统差分解调法的开环增益变化趋势,得出了延迟时间会影响增益幅值和符号的结论;通过求解延迟时间变化时的实际开环增益表达式,并用实际增益值对误差函数进行标幺,提升了系统的稳定性和收敛性。实验结果表明,该方法不仅提升了位置估算系统的稳定性,而且收敛速度快。

基于励磁电压方波调制的三级式同步起动/发电机转子初始位置估算方法

现有基于高频注入的三级式同步起动/发电机转子初始位置估算方法由于高频衰减,面临失效风险。该文基于主电机定转子互感,提出一种“基于励磁电压方波调制的三级式同步起动/发电机转子初始位置估算方法”,将励磁电压作为载波,用低频方波对其进行调制后,提取主电机定子侧低频响应电流用于转子初始位置估算。定子逆变器三相下管导通状态下,该方法分为2步:首先对励磁电压进行低频方波调制,采集主电机定子低频感应电流用于转子初始位置预估算;其次,由预估算初始位置,判断励磁电压断电前后相关电流特征,得到包含磁极信息的最终初始位置。所提方法通过虚拟角度变换和方差对采集低频电流进行处理。实验表明所提方法具有较高估算精度。

基于发电机转子接地保护的可靠性分析与建议

上海某燃机电厂的发电机转子接地保护配置了两套注入式保护,分别为工频电压注入式及1~3 Hz低频方波注入式。由于两套转子接地保护之间在原理上相互影响,因此在运行中只投运一套(以1~3 Hz低频方波注入式转子接地保护为主),另一套保护备用。近期该厂#4发电机1~3 Hz低频方波注入式转子接地保护出现过两次保护回路故障报警,均由发电机转子接地碳刷接触不良引起。通过对该保护原理及保护回路逻辑的介绍,找出了转子接地保护回路故障的原因,并对发电机转子接地保护的可靠性进行分析,提出了相应的建议与措施。

转子激励对永磁同步电机电磁振动影响分析

对于电动汽车用永磁同步电机,气隙内的电磁激励会产生高频振动和噪音。通常将气隙电磁激振力施加到定子齿部,并通过理论计算或仿真得到定子或壳体外表面的振动噪音响应,而由转子激励引起的振动噪音被忽略。为研究转子激励对整体电磁振动噪音的贡献度,首先依据麦克斯韦应力张量法对气隙电磁力谐波进行理论分析,同时建立单电机的电磁振动仿真模型。然后以一台8极定子48槽内置式永磁同步电机为样机,通过试验模态分析和仿真分别对定子和转子的材料参数进行修正。再分别进行转子动力学和电磁激励下的整机动力学仿真,结果表明由转子偏心引起的不平衡电磁激励能够引起转子系统共振,并且在单位电磁力波的激励下,转子激励引起的响应与定子激励引起的响应在低频段具有同等的重要性。最后通过样机振动试验对上述结论进行了验证。

轴承副接触对立式转子系统动力学行为的影响研究

考虑轴尖-宝石轴承副的接触力,建立立式转子系统非线性动力学模型,分析轴承副接触参数对转子系统固有特性的影响,讨论横向连接刚度、滑动摩擦系数对转子系统动力学行为的影响。结果表明,引入轴承力模型将导致在轴尖模态频率附近出现共振峰值,轴承副接触区变化将触发低频进动;随着连接刚度增大,轴尖磨损状态将发生从圆环接触逐渐向偏磨接触最终向大范围圆环接触的转变;当处于边界润滑时,滑动摩擦系数不会对转子系统产生影响,处于干摩擦状态时,滑动摩擦系数增加将加速系统产生偏磨;研究结果对立式转子系统动力学优化设计具有重要意义。

Initial Rotor Position Detection of 12/10 Flux-switching Permanent Magnet Motors

电机转子初始位置检测的精度直接决定其启动运行时的性能。针对12/10极永磁磁通切换型电机,在验证其凸极性的基础上,采用注入脉振高频信号实现转子初始位置估计。通过对传统高频脉振正弦电压信号注入的分析,研究了基于高频方波或三角波的注入方法,再利用电流差值调制或直接信号调制方法得到位置误差信号,同时根据磁路的饱和效应,通过对d轴电流过零点时间差值的累加,实现了磁极方向辨识。分析了位置误差信号的系数与初始位置检测收敛性的关系。通过实验验证了所提方法的正确性和可行性。

斜流式气波制冷机制冷性能数值模拟研究

提出一种波转子为锥形结构的斜流式气波制冷机,能够提供一定的离心效果.建立了从0°(轴流式)至90°(径流式)不同锥角的波转子数值模型,通过Ansys Fluent模拟其增压和制冷性能.在同样的工况和结构参数下,斜流式气波制冷机具有比轴流式更高的循环压差,比径流式更低的轴功消耗,其制冷效果高于二者且随锥角增大先增大后减小,在锥角为12°时达到最优,制冷温降和等熵效率相较轴流式分别高9.59℃和13.8%,相较径流式分别高20.48℃和30.9%.然后固定锥角12°,探究一定范围内转速和压比对性能的影响.结果表明,增压效果随转速增大而提升,制冷效果在转速2500 r/min时最优;压比增大会使循环压差降低,但制冷温降和等熵效率均有所提升.