压缩空气储能系统膨胀机末级叶片特殊边界处理与失效分析

以压缩空气储能(CAES)系统中膨胀机末级叶片为研究对象,针对末级叶片的离心力工况,提出了一种高效的等效叶冠约束模型,并对比了循环对称约束模型和多叶片模型的仿真结果。同时,还开发了一种能够模拟弹塑性和失效行为的本构程序。结果表明:与其他模型相比,等效叶冠约束模型的仿真结果与全尺寸模型结果最接近,兼具精度和效率优势;所编写的本构子程序可有效模拟17-4ph钢的应力-应变响应曲线;针对所研究的叶片构型,当失效发生在叶片径向约1/4位置处时,失效区域快速扩大。

铁轨重力储能系统效率影响因素研究

储能是建设以新能源为主体的新型电力系统的重要支撑技术,对实现“碳达峰碳中和”目标具有重要意义。铁轨重力储能属于物理储能,具有规模大、成本低、效率高、环境友好以及无自放电等优势,应用前景广阔。本工作基于MATLAB/Simulink搭建了铁轨重力储能系统模型,分析了系统各个部件在储能过程和释能过程中的能量损耗情况,研究了载重车辆质量、车辆速度、斜坡坡度、斜坡高度和滚动摩擦系数等因素对系统效率的影响及其变化规律。研究结果表明,车辆速度、斜坡坡度、斜坡高度和滚动摩擦系数对系统效率的影响十分显著,降低速度和滚动摩擦系数以及适当增加坡度和高度,可有效提高系统效率;在设计工况下,载重车辆160 t、车速20 km/h、斜坡高度200 m、斜坡坡度7°、滚动摩擦系数0.006,对应系统的输出功率为1.04 MW,系统效率达76.20%。

离心式压缩机性能预测方法综述

压缩空气储能被认为是最具发展前景的大规模物理储能技术之一,压缩机作为其关键部件对系统整体性能具有重要影响。离心式压缩机具备大流量、高压比、宽工况的运行特性,在压缩空气储能领域相对其他类型压缩机更具优势。受固定容积储气装置充气特性影响,压缩机常运行于非设计工况,对压缩机性能进行准确预测可提高系统效率,减少研发投入。20世纪50年代起,国内外学者对离心式压缩机性能预测开展了大量研究,建立了多种性能预测方法。本文将性能预测方法分为机理建模类、相似换算类与数据驱动类,在总结各方法基本原理及研究进展的基础上,定性分析了各方法在建模周期、预测精度、可移植性及适用场景等方面的差异,并对性能预测未来发展趋势进行了展望,旨在为离心式压缩机性能预测方法的研究与应用提供指导。

CAES轴流涡轮弯导叶优化设计与流动损失控制机理

应用于压缩空气储能系统(CAES)的轴流涡轮具有运行压力高、导叶展弦比低、端壁二次流影响大的特点。为进一步提高效率,本文引入导叶弯曲造型并进行优化设计,获得了最优导叶弯曲参数及其对流动损失的控制机理。研究结果表明:不同弯高下均存在一个最佳弯角值使等熵效率最大;随弯高增加,最佳弯角值逐渐减小。在不同弯高下,轴流涡轮质量流量均随着弯角先减小后增大,并在弯角为7°左右达到最小值。优化设计结果表明,当弯曲角和相对弯高分别为12.26°和0.31时,轴流涡轮等熵效率提高幅度最大为0.77%,此时质量流量仅增加0.1 kg/s。与应用于其他领域的涡轮不同,最优弯导叶对CAES轴流涡轮流场的改善效果主要集中在动叶通道内部:通过降低动叶轮毂和机匣表面附近进口气流角,消除动叶前缘根部滞止鞍点,限制马蹄涡影响范围;最优弯导叶也使叶顶前缘鞍点位置向下游移动,减低叶顶前缘吸力面附近马蹄涡分支的影响范围,延迟了叶顶间隙泄漏流的产生,减弱叶顶间隙泄漏流与上通道涡作用强度,最终降低流动损失。

基于遗传算法的离心压缩机蜗壳参数化及多目标优化

排气蜗壳对离心压缩机的整体性能、工作范围有直接且不可忽视的影响。排气蜗壳由于其完全三维的、湍流的内部流动会引起蜗壳进口周向压力畸变,从而影响上游部件的流动稳定性。本工作针对先进压缩空气储能系统离心压缩机排气蜗壳进行多目标优化设计,提出了一种可变截面形状的参数化设计方法。以总压损失系数和静压恢复系数为优化目标变量,采用多个控制面和控制点的方式对离心压缩机蜗壳截面参数进行全周控制,结合最优拉丁超立方试验设计方法和全三维CFD数值方法生成样本空间,利用二代非支配排序遗传算法对Kriging近似模型进行多目标寻优,建立优化平台和优化方法。研究结果表明:优化后的截面形状能够减小通流截面旋涡中心的剪切应力,使排气蜗壳内部通流速度分布更加均匀;优化方案在设计工况下整级等熵效率提高了0.45%,压比提高了0.36%;与初始模型相比,优化后的排气蜗壳可以有效改善离心压缩机的整体性能。本研究有助于推动数值优化设计方法在离心压缩机排气蜗壳中的应用,为高性能、低总压损失离心压缩机的优化设计提供参考。

新型地下跨季节复合储热系统性能规律

可再生能源受天气、地域、季节限制,具有间歇性和不稳定性属性,从而导致供需不匹配,跨季节储热是解决上述问题的有效方法。然而,传统地下跨季节储热具有储热方式单一、热量损失大等缺点,本文将水箱储热和地埋管储热相结合,组成新型跨季节复合储热系统。建立并通过实验验证了复合储热系统模型,在此基础上,分析了储/释热质量流量、储热体模匹配、地埋管数量和层间距以及土壤热导率等参数对储热体温度、储/释热量、储/释热功率和热量损失等的影响规律。结果表明,随着储/释热质量流量的增加,系统效率也逐渐增加;储热体规模匹配α值增加,系统效率随之上升,但水箱体积占比的提高,会导致热量损失增大,故储热体规模匹配需综合考虑,既要能达到较高的系统效率,获得较大的储/释热功率,又需尽量减少投资成本,同时降低热量损失;提高地埋管数量,有利于增加储/释热量,提升系统效率;地埋管层间距的增大,增加了储热体土壤体积,从而降低了储热温度,不利于释热的进行,导致系统效率降低;土壤热导率的增加,强化了土壤间热量传递,地埋管储热功率增加,储热峰值温度也因此提高,然而热量散失也加快,释热功率显著降低,导致系统效率下降。

新型地下跨季节复合储热系统热量损失机理研究

可再生能源受天气、地域、季节限制,具有间歇性和不稳定性等属性,从而导致供需不匹配。跨季节储热是解决上述问题的有效方法。然而,传统地下跨季节储热具有储热方式单一、热量损失大等缺点。该文将水箱储热(hot water energystorage,HWES)和地埋管储热(boreholethermal energy storage,BTES)方式相结合,建立跨季节复合储热系统,研究该复合储热系统的储释热温度和储释热量变化规律,揭示系统热量损失机理。结果表明:复合储热模式的储热量和释热量均大于水箱储热模式和地埋管储热模式,其储热量随着运行年限的增长而逐渐降低,释热量则随着运行年限的增长而逐渐增加;对比3种不同储热模式的土壤平均温度,得出地埋管储热模式最高,水箱储热模式最低,复合储热模式居于两者中间;此外,研究发现,复合储热模式的热量损失主要来自上边界,系统运行至第五年上边界的热量损失占比高达42.2%,因此需要对复合储热模式上边界进行有效保温,降低热量损失,提高复合储热系统效率。

沸石-液态水吸附储热系统的释热特性

吸附储热是一种有着较高储热密度和较低热损失的储热方式。沸石-液态水吸附储热系统以沸石颗粒作为储热介质,具有系统简单、换热性能好和储热密度大等优点。利用Fluent建立了反应器二维轴对称对流换热模型,分析了进水流速、反应器高径比和颗粒粒径对系统释热过程出口水温的影响。研究表明,在计算条件下,该系统能够获得最大70℃的温升幅度,且进口流速越小,温升幅度越大;高径比越大,温升幅度越大,当高径比≥1.5时,温升不再随高径比的增加而增大;此外,粒径越小,反应速率和温升幅度越大,也越有利于沸石与水的充分反应。本研究有助于完善固-液吸附过程释热特性,为沸石-液态水吸附储热系统的设计和应用提供理论指导。

基于变工质模化方法的超临界CO_(2)储能透平膨胀机相似特性分析

变工质下透平膨胀机的相似模化特性研究是特殊工质透平膨胀机研发的关键技术手段和必要方法,也是提升研发效率和节约成本的有效途径。本文提出了一种基于转速、进口总温、绝热指数和气体常数的适用于透平膨胀机变工质的新型模化方法,并利用某透平膨胀机对超临界CO_(2)与空气的相似模化进行了数值验证。结果显示,在总体性能参数的模化上具有较高的精确度;在内部流场预测(马赫数、速度分布)等方面也具有良好的模化效果。该方法适用于利用空气模化高温度、高压力下的超临界CO_(2)储能做功过程。

大型空气压缩机变工况性能试验研究

压缩空气储能系统压缩机受系统自身特性影响,长期处于变工况运行状态。对某多级压缩空气储能系统大型空气压缩机变工况条件下级间性能开展试验研究,即利用压缩机管网特性试验平台,开展排气压力6.5~9.5MPa范围试验测试,对压缩机各级吸气和排气压力、吸气和排气温度、压缩机排气量、电机电流、电压等参数进行实时采集。通过对压缩机实时变工况下各项参数分析,具体研究压缩机的容积效率、循环指示功率、等温效率、各级压比分配和各级压损随出口负荷变化而变化的规律。研究结果表明:压缩机的容积效率基本不随工况的变化而变化,平均为0.96;循环指示功率随出口负荷的增加而增加;压缩机的多变效率从74.02%上升到78.14%,多变效率随着排气压力的增加而增加;低压级压比增大速度较快,易达到额定状态,高压级压比达到额定状态较缓;一~四级的相对压力损失基本保持不变,五级出口排气到集气汇管的相对压力损失随着出口负荷的增大而减小。

跨声速轴流压缩机动静叶弯参数耦合关系

发展压缩空气储能技术是解决可再生能源大规模接入电网的有效途径,也是实现“碳达峰,碳中和”目标的重要技术手段之一。轴流压缩机是压缩空气储能(CAES)系统的重要部件之一,需要有宽工况、大流量、高压比等特点。采用数值模拟方法,以NASA Stage35为原型,通过正交试验法研究不同动静叶弯高、弯角之间的耦合关系,并对其进行优化。选取L49(7^(4))正交表,以失速裕度、峰值效率、压比为优化目标,选取动静叶的弯高、弯角4个试验参数,进行4因素7水平的正交设计。优化设计后失速裕度提升了60.56%,效率和压比降低幅度在可接受范围内。通过极差分析发现弯叶片可以普遍提高失速裕度,但是峰值效率和压比普遍降低,动叶弯角对压缩机的气动性能影响最大。叶根附近,采用弯叶片使吸力面角区分离更加严重;在叶展中部,采用弯叶片可以弱化激波强度,减少低能流体的堆积,削弱附面层与激波的相互作用;在叶尖处,采用弯叶片可以延迟叶尖泄漏流与主流的交界面到达叶尖前缘,扩大失速裕度。

基于析湿系数法活塞压缩机级间变工况析水特性

压缩空气储能系统膨胀吸热过程使压缩空气中水蒸气结冰,不仅会对膨胀机叶片造成机械损坏,而且影响膨胀机性能。开展储能子系统中多级活塞压缩机级间析水特性研究,为压缩系统设计以及膨胀机入口前压缩空气预处理提供参考。首先综合考虑压缩因子和增强因子,采用析湿系数法对析水过程进行理论推导,得出各级析水量的表达式,然后建立压缩机管网特性试验平台,对压缩机各级吸、排气压力,吸、排气温度、排气量、分离器液位等参数进行采样,开展在变工况条件下压缩机各级析水特性研究。结果表明压缩机排气压力从1.5 MPa增大到9.0 MPa时,湿空气经过第一级压缩机时,液态水未析出;经过其他四级压缩后,二级析水量最大,其余各级依次递减;各级析水量理论与试验研究的结果误差在0~10%左右波动。

基于大容量内存单片机的涡街流量变送器研制

涡街流量计存在易受管道振动干扰和难以测量小雷诺数流量的难题,需要开发更为复杂的数字信号处理算法予以解决。现有的涡街流量变送器的内存容量不足以实时实现这类算法,若在现有的系统上外扩内存,则无法满足低功耗的要求。为此,采用TI公司最新推出的66 KB大容量内存的超低功耗单片机MSP430F6459为核心,研制低功耗实时处理的涡街流量变送器系统。研制系统的功耗为2.693 mA,反应时间小于300 ms,满足低功耗和实时性的要求。测量涡街频率和电流输出电路的最大相对误差分别为0.4022%和0.0025%,HART通信模块可准确的调制和解调FSK信号,实现了大内存、低功耗、实时处理的高精度涡街流量变送器系统。

储能实验中心建设管理对储能技术发展的影响——以毕节国家能源大规模物理储能技术研发中心为例

储能技术具有调节可再生能源发电和削峰填谷的作用,对实现“双碳”目标具有重要意义。储能实验中心对储能技术的发展至关重要。通过研究储能实验中心的建设管理制度发现,多样化的储能实验室、特色人才队伍的建设、结合现代化信息技术的管理模式,能够保证储能实验中心的稳定健康发展。研究结果可为建设高水平的储能实验中心提供依据,也为其他储能实验中心的建设管理提供参考。

Comparative Analysis of Diagonal and Centrifugal Compressors with Synergy Theory in Compressed Air Energy Storage System

Energy storage technology is an essential part of the efficient energy system.Compressed air energy storage(CAES)is considered to be one of the most promising large-scale physical energy storage technologies.It is favored because of its low-cost,long-life,environmentally friendly and low-carbon characteristics.The compressor is the core component of CAES,and the performance is critical to the overall system efficiency.That importance is not only reflected in the design point,but also in the continuous efficient operation under variable working conditions.The diagonal compressor is currently the focus of the developing large-scale CAES because of its stronger flow capacity compared with traditional centrifugal compressors.And the diagonal compressor has the higher single stage pressure ratio compared with axial compressors.In this paper,the full three dimensional numerical simulation technologies with synergy theory are used to compare and analyze the internal flow characteristics.The performance of the centrifugal and diagonal impellers that are optimized under the same requirements for large-scale CAES has been analyzed.The relationship between the internal flow characteristics and performance of the centrifugal and diagonal impellers with the change of mass flow rates and total inlet temperature is given qualitatively and quantitatively.Where the cosine value of the synergy angle is high,the local flow loss is large.The smaller proportion of the positive area is the pursuit of design.Through comparative analysis,it is concluded that the internal flow and performance changes of centrifugal and diagonal impellers are different.The results confirm the superiority and feasibility of the off-design performance of the diagonal compressor applied to the developing large-scale CAES.

Design Strategy of Diagonal Compressors in Compressed Air Energy Storage System

As a kind of large-scale physical energy storage,compressed air energy storage(CAES)plays an important role in the construction of more efficient energy system based on renewable energy in the future.Compared with traditional industrial compressors,the compressor of CAES has higher off-design performance requirements.From the perspective of design,it needs to pay attention not only to the performance of the design point,but also to the performance of all the stable working range.However,from the previous literature,no diagonal compressor was used in CAES which can meet the requirements,which also reflects the design program can be further improved.Therefore,this paper studies the design strategy of high efficient diagonal compressor for large-scale CAES,and gives the complete strategy algorithms used for different program modules.The pressure ratio,isentropic efficiency and stable working range are comprehensively considered.In the design process,the criteria for the key parameters of the diagonal flow angle of the diagonal compressor are given for the first time.The results show that the isentropic efficiency at the design point is 92.7%,the total pressure ratio is1.97,and the stable working range exceeds 20%,which meets the design requirements of the compressor for CAES and exceeds the overall performance of the previous compressors in the entire working range.

A Surrogate Model for a CAES Radial Inflow Turbine with Test Data-Based MLP Neural Network Algorithm

It is usually to conduct a full-scale three-dimensional flow analysis for a radial turbine to find a way to increase the efficiency of a Compressed Air Energy Storage(CAES)system.However,long solving time and huge consumption of computing resources become a major obstacle to the analysis.Therefore,in present study,a surrogate model with test data-based multi-layer perceptron(MLP)Neural Network is proposed to overcome the difficulty.Instead of complex flow field solving process,it provides reliable turbine aerodynamic performance and flow field distribution characteristics in a short solution time by“learning the measurement results”.The validation results illustrated that the predicted maximum relative errors of isentropic efficiency,corrected mass flow rate and corrected power are only 0.03%,0.22%and 0.26%respectively.The predicted flow distribution parameters in chamber,shroud cavity and outlet region of rotor are also basically consistent with the experimental results.In the chamber,it can be found that a pressure stagnation point is observed at circumferential angle of 270°when total pressure ratio is decreased.In the shroud cavity,obvious pressure variation is found near outlet of shroud cavity which although labyrinth seals exist.At outlet of rotor,obvious variations of velocity and pressure are found in the 0.0–0.4 and 0.6–0.8 of blade height.At the same time,obvious variations of velocity and pressure are found in the 0.0–0.4 and 0.6–0.8 of blade height and this is because the influence of upper passage vortex,lower passage vortex and end wall secondary flow.The present study can provide further reference for the dynamic performance evaluation of CAES radial inflow turbine.

NACA翼型叶顶对低展弦比向心涡轮影响特性

针对压缩空气储能向心涡轮叶片展弦比低、叶顶间隙泄漏损失大的问题,将NACA0004翼型引入叶片顶部厚度分布以改善气动性能。采用ANSYSCFX软件对向心涡轮三维流场进行数值求解,分析0.5%~8%叶顶间隙范围内NACA0004翼型叶顶对间隙泄漏流结构和损失特征的影响。结果表明,NACA0004翼型叶顶对向心涡轮等熵效率的影响随叶顶间隙而变化。当叶顶间隙为0.5%时,NACA0004翼型叶顶使向心涡轮等熵效率降低0.3%;当叶顶间隙由1%增加至8%时,NACA0004翼型叶顶对等熵效率提升值由0.4%增加到1.9%。不同叶顶间隙下NACA0004翼型叶顶对间隙泄漏流损失特影响机理存在差异,当叶顶间隙为0.5%时,NACA0004翼型叶顶使泄漏流集中在叶片吸力面附近,并在叶轮出口区域产生更多泄漏流,增加叶片吸力面附近流动损失;当叶顶间隙为1%~8%时,NACA0004翼型叶顶能够降低叶片前缘和尾缘附近叶片压力面和吸力面压差,减小叶顶间隙泄漏流速度,降低与主流掺混强度,抑制流动损失。与此同时,叶轮强度也满足要求。研究成果可为同类向心涡轮叶顶间隙泄漏损失的控制提供参考。

Design of a Centrifugal Compressor with Low Solidity Vaned Diffuser(LSVD) for Large-Scale Compressed Air Energy Storage(CAES)

Compressed Air Energy Storage(CAES) has tremendous promotional value in the intermittent renewable energy supply systems. CAES has special requirements for compressor(e.g. heavy load, high pressure ratio, wide range). With advantages of higher efficiency and wider operation range, IGC(Integrally Geared Compressors) is selected to fulfill the special requirements of the large-scale CAES. To get a better aerodynamic performance, in this paper, based on the analysis of internal flow of centrifugal compressor, a multi-objective one-dimensional optimization design program was put forward combined with modified Two-Zone model and a low solidity vaned diffuser(LSVD) design method. Then, a centrifugal compressor aerodynamic component optimization design system was established with the three-dimensional blade optimization design method based on neural network and genetic optimization algorithm. Then a validation was done by redesigning the Krain-Impeller to get better performance. Finally, the aerodynamic design of the first stage of IGC was completed. The CFD calculation results indicated that the total-to-total pressure ratio of the first stage was 2.51 and the polytropic efficiency was 91.0% at the design point. What’s more, an operation margin and surge margin of the compressor was about 26.5% and 16.4% respectively.

Synergy Methodology for Internal Flow of Turbomachinery

The complex curvature of turbomachinery rotor blade channels combined with strong rotational effect and clearance leakage brings on intricate internal flow phenomenon.It is necessary to study the internal flow and energy loss mechanism to reveal the influence law of the key parameters and to achieve its optimal design.Considering features of flow and temperature fields in rotor passage,the concept of synergy analysis derived from equation of energy conservation was put forward.Typical NASA low-speed centrifugal compressor(LSCC)rotor was chosen for analysis using CFD.Numerical results showed remarkable agreement with experiment datum in both the tendency of the performance characteristics and quantitative pressure values.Under different flow rates and inlet total temperatures conditions,thermal-fluid interaction effect and losses were studied by synergy analysis.Results showed that peak synergy positive value zones located around blade leading edge,across the shroud wall and hub wall,and at the position where tip-leakage flow was mixing with the bulk flow and high entropy zones existed.Increasing flow rate from design condition,positive and negative synergy areas both changed tiny around leading edge and trailing edge.Reducing flow rate,positive synergy areas tended to increase and negative areas decreased at same positions.The relationship between flow separation,heat transfer and losses in turbomachinery rotor can be revealed based on synergy analyses.