Performance Analysis of Constant-Pressure Pumped Hydro Combined with Compressed Air Energy Storage System Considering Off-Design Model of Compressor

With the wide application of renewable energy, energy storage technology has become a research hotspot. In order to overcome the shortcomings of energy loss caused by compression heating in compressed air energy storage technology, a novel constant-pressure pumped hydro combined with compressed air energy storage system was proposed. To deepen the understanding of the system and make the analysis closer to reality, this paper adopted an off-design model of the compressor to calculate and analyze the effect of key parameters on system thermodynamics performance. In addition, the results of this paper were compared with previous research results, and it was found that the current efficiency considering the off-design model of compressor was generally 2% - 5% higher than the previous efficiency. With increased preset pressure or with decreased terminal pressure, both the previous efficiency and current efficiency of the system increased. The exergy destruction coefficient of the throttle valve reached 4%. System efficiency was more sensitive to changes in water pump efficiency and hydroturbine efficiency.

Off-Design Modelling of a Turbo Jet Engine with Operative Afterburner

Gas turbines are considered as one of the leading internal combustion engines in modern air transportation due to its favourable power to weight ratio and its continuous combustion process. Recent research focus has been concerned with performance improvements aimed at reduced fuel consumption and hence reduced impact on the environment. This study is aimed at using theoretical and computational methods to model the operation and performance a turbojet gas turbine engine. The commercial software GasTurb13 was used for the theoretical simulation while Microsoft Excel was used for the analytical study. GasTurb13 solved the model using pseudo-perfect gas models i.e. component maps since the specific gas ratio could not be inputted into the solver. The effect of changes in the Mach number and altitude on the engine performance was studied. Also the effect of changes in the compressor pressure ratio, the turbine inlet temperature and the afterburner exit temperature were also studied. Results obtained showed the optimum pressure ratio at maximum thrust constraint to be 16.78 for the turbojet engine operating at Mach number (Ma) = 0.8 and altitude = 10,000 m, Turbine inlet temperature (TIT) = 1200 K and Afterburner exit temperature = 1800 K.

Numerical Simulation and Experimental Research on Wake Field of Ships Under off-Design Conditions

Different operating conditions(e.g. design and off-design) may lead to a significant difference in the hydrodynamics performance of a ship, especially in the total resistance and wake field of ships. This work investigated the hydrodynamic performance of the well-known KRISO 3600 TEU Container Ship(KCS) under three different operating conditions by means of Particle Image Velocimetry(PIV) and Computational Fluid Dynamics(CFD). The comparison results show that the use of PIV to measure a ship's nominal wake field is an important method which has the advantages of being contactless and highly accurate. Acceptable agreements between the results obtained by the two different methods are achieved. Results indicate that the total resistances of the KCS model under two off-design conditions are 23.88% and 13.92% larger than that under the designed condition, respectively.

Experimental Study on Hydrodynamics of L-type Podded Propulsor in Straight-ahead Motion and Off-Design Conditions

试验性的测试被进行评估 L 类型 podded propulsor 的水动力学性能在直向前，用一台开水的测量仪器的运动和离开设计条件为 podded propulsors 由作者发展了，拖引坦克的一个轮船模型，并且在水粒子图象 velocimetry (PIV ) 下面测量系统。在条件的三种类型下面， L 类型 podded propulsor 的主要参数被测量，包括推进器戳和转矩，以及整个豆荚单位的戳，方面力量，和时刻。另外，在推进器和神气之间的节上的流动领域被分析。试验性的结果证明动态 azimuthing 率和方向和转弯的方向在推进器和整个豆荚单位上影响力量。因为推进器旋转的效果，力量不均匀地在左、正确的 azimuthing 方向之间被散布。这研究的调查结果为关于 L 类型 podded propulsors 的进一步的研究提供一个基础。

Off-design Characteristics of IGCC System Based on Two-stage Coal-slurry Gasification Technology

整体煤气化联合循环（integrated gasification combinedcycle,IGCC）机组在一定情况下处于非设计工况运行。为了研究IGCC系统变工况特性,采用ThermoFlex软件建立基于两段式水煤浆气化技术的200 MW级整体煤气化联合循环系统模型,主要考查燃气轮机负荷、整体空分系数Xas、大气温度、大气压力对系统性能的影响。研究结果表明,降低燃气轮机负荷或者提高大气温度系统效率均呈先升高而后降低的趋势。整体空分系数Xas增加,机组发电效率降低。大气压力对系统效率影响较小。上述条件下采用两段水煤浆气化技术,系统性能可以得到有效改善。研究结果可为采用两段式水煤浆气化技术的IGCC系统的设计、运行提供参考。

Off-Design Performance Analysis of Axial Flow Fan in Helicopter

A theoretical calculation method of off-design performance is developed for an axial flow fan of oil cooling system in helicopter,including calculation of aerodynamic parameters and performance parameters.When calculating inlet shock loss,the shock loss coefficient is obtained by comparing results of theoretical calculation,experimental and numerical calculation.The theoretical results and numerical results show that all air velocity components increase from hub to shroud in main flow area at rated condition.Tip leakage vortex moves downstream as flow rate increases.When flow rate decreases,Re decreases,and boundary layer thickness from hub to shroud area all increases gradually.Tip leakage vortex moves upstream,and secondary loss increases.Low speed area in the passage is widened along with high speed area moving to hub area,influenced by boundary layer separation.Consequently wake area and jet area at fan outlet are both larger than rated condition.Therefore optimization design for off-design performance of the fan is required on aerodynamic parameters influencing fan loss.A reliable method is supplied for estimating altitude performance of lubricating system in helicopter.

Supercritical CO_(2) Cycles for Nuclear-Powered Marine Propulsion:Preliminary Conceptual Design and Off-Design Performance Assessment

Using the efficient,space-saving,and flexible supercritical carbon dioxide(sCO_(2)) Brayton cycle is a promising approach for improving the performance of nuclear-powered ships.The purpose of this paper is to design and compare sCO_(2) cycle power systems suitable for nuclear-powered ships.Considering the characteristics of nuclear-powered ships,this paper uses different indicators to comprehensively evaluate the efficiency,cost,volume,and partial load performance of several nuclear-powered sCO_(2) cycles.Four load-following strategies are also designed and compared.The results show that the partial cooling cycle is most suitable for nuclear-powered ships because it offers both high thermal efficiency and low volume and cost,and can maintain relatively high thermal efficiency at partial loads.Additionally,the new load-following strategy that adjusts the turbine speed can keep the compressor away from the surge line,making the cycle more flexible and efficient compared to traditional inventory and turbine bypass strategies.

Design Optimization of Ocean Thermal Energy Conversion(OTEC)Considering the Off-Design Condition

The comprehensive optimization of thermodynamic and economic performances is significant for the engineering application of ocean thermal energy conversion(OTEC).Motivated by this,this paper develops a thermo-economic OTEC model and conducts a sensitivity analysis of the OTEC system concerning its thermodynamic and economic performances.Specifically,the impact of warm-seawater temperature and cold-seawater pumping depth on the net thermal efficiency and the total investment cost are investigated.The results indicate that,an increase in warm-seawater temperature and cold-seawater pumping depth can improve the net thermal efficiency and a higher installed capacity is beneficial to the system economics.Building on these,a design optimization method with considering the on-design and off-design conditions is proposed in this paper,and the dynamic variation of warm-seawater temperature are considered in this method.In multi-objective optimization procedure,with the objective functions being the average net thermal efficiency and unit power cost within the operational cycle,the non-dominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ) is employed to maximize the net thermal efficiency and minimize the unit power investment cost,resulting in the Pareto front.The net thermal efficiencies of OTEC systems using ammonia and R245fa as working fluids are 4.13% and 3.8%,respectively.This represents an improvement of 19.4% and 57.0%,respectively,compared to traditional optimization methods that do not account for off-design conditions.

有机工质向心透平数值模拟及变工况内流特性研究

基于国内外研究现状,分别对设计工况下和非设计工况下有机朗肯循环向心透平的工作状态进行了三维数值模拟。以透平功率、效率、反动度、静叶损失系数、动叶损失系数作为评价指标,分析了透平在非设计工况下的性能;同时开展了透平在非设计工况下流动状况的描述。结果表明:设计工况下透平输出功率为122.3 kW,透平等熵效率为83.54%;在非设计工况下,透平功率和效率在转速比为0.8~1.0时的增幅较大,透平反动度和静叶损失系数均与转速呈线性关系,而动叶损失系数在转速比为0.8~1.2时存在最小值;当转速低于设计转速时,在动叶前缘吸力面存在涡流,当转速高于设计转速时,涡流存在于动叶压力面的前缘,造成此现象的主要原因是动叶转速与静叶出口流速的周向分量之间存在差值。

高速S-CO_(2)向心透平几何参数优化及变工况特性分析

透平是热力循环中实现热功转换的核心设备,优化透平几何参数以改善气动性能,是提升系统热效率的关键。该文以面向某船舶主机烟气余热利用的超临界二氧化碳布雷顿循环透平设计参数为基础,给出向心透平主要几何参数,采用耦合CO_(2)真实物性参数的CFX仿真方法,分析几何参数动、静叶包角以及叶轮出口几何角对透平性能的影响规律并进行参数优化,进一步研究非设计工况下的透平运行特性。结果表明:增大静叶包角会使动叶前缘出现扰动涡流并减少余速损失,增大叶轮出口几何角,动叶包角对透平效率的影响规律不变,但效率峰值点会沿动叶包角减小的方向移动;动、静叶包角和叶轮出口几何角分别为49°、21.5°、25°时透平设计点总-静等熵效率高达87.99%,相比优化前,提高0.54个百分点;透平偏离设计点±20%工况下等熵效率大于80%。结果可为超临界二氧化碳高速向心透平设计提供一定参考。

R32热泵系统稳定性与变工况特性实验研究

实验研究了变热源进口温度工况和变热水进口温度工况下膨胀阀开度对R32热泵系统稳定性和系统性能的影响规律。结果表明:不同工况下系统存在不同的过热度振荡区间,且热源进口温度对起始振荡过热度的影响较显著,而热水进口温度对其影响则不明显;变热源进口温度(15~25℃)工况下,制热量随着过热度的变化呈现不同的变化规律,而其COP则呈现相同的变化规律,且系统均在过热度振荡区间内获得最大COP;变热水进口温度(30~40℃)工况下,制热量和COP均随着过热度的变化呈现相同的变化趋势,且两者均在过热度振荡区间内取得最大值;热源进口温度的升高和热水进口温度的降低均可使系统获得的最大制热量和最大COP增大,且两者在热源进口温度为25℃时分别为9.287 kW和4.646,而在热水进口温度为30℃时则分别为9.148 kW和5.665。

基于PLC可控电源保护装置的优化设计

针对以电气设备为主的技能实训操作平台由于有时忘记关闭电源而引发的安全问题,设计一种集操作与保护为一体的电源保护装置。文章介绍该保护装置的结构设计,并从硬件及软件两个方面介绍了控制系统的设计。通过调试运行结果显示,该装置不仅能安全控制设备电源的通断,而且对长时间处于带电状态而无人操作的实训设备实现断电保护功能,在一定程度上消除了实训室的用电安全隐患,降低实训室的管理难度。

垂直起降无人机气动布局设计研究进展

垂直起降无人机是当前航空领域的研究热点。文章介绍了倾转旋翼、倾转涵道和双系统式三类垂直起降无人机的工作原理和典型机型,分析和讨论了其气动布局特征及其设计研究进展,提出了垂直起降无人机气动布局设计和优化、飞行控制、侧风效应和结构轻量化设计方面的研究建议。

Exploration of combined adjustment laws about IGV,stator and rotational speed in off-design conditions in an axial compressor

Experimental investigations are performed in a three-stage low-speed axial compressor with variable inlet guide vanes(IGV) and adjustable stators.The characteristics of the compressor,especially the efficiency and stall margin,are analyzed in design and off-design operation conditions by adjusting stagger angles of IGV and stators as well as changing the rotational speed.The experimental results show that the off-design performance of the multistage axial compressor is improved by restaggering of IGV and stators related to rotational speed.Considering the background of engineering applications,digital signal processing(DSP) technique is used to realize online adjustment of stagger angles according to the corresponding relations between incidence angles of rotor and rotational speed.

Prediction of the precessing vortex core in the Francis-99 draft tube under off-design conditions by using Liutex/Rortex method

The turbulent flow in the draft tube of a Francis turbine is very complicated while working under off-design conditions. Although the off-design conditions were widely studied, the vortex core line in the draft tube of a Francis turbine with splitter blades is not well understood, especially the vortex rope property. This letter presents a prediction of the behavior of the vortex rope in the draft tube of the Francis-99 turbine obtained by the computational fluid dynamics (CFD), where the Liutex/Rortex method, as the most recent vortex definition, is applied to analyze the periodical precession of the vortex rope in the draft tube cone. The advantage of this Liutex/Rortex method is shown by its enhanced ability to represent the vortex rope structurewith the vortex-core lines. Furthermore, since it seems to be very hard to define a sharp boundary surface for the whole vortex structure, it is advantageousfocusing only on the vortex core line,by which different vortex structures can be clearly differentiated. The evolution of the vortex core and the process of the vortex breakdown in the draft tube are revealed, which might help to comprehend the development of the turbulent flow in the draft tube.

风电-火电-压缩空气储能综合能源系统运行特性研究

为提升电网消纳风电的能力,改善火电机组运行灵活性,本文基于压缩空气储能系统容量大、多能流耦合的特点提出了一种包含两台600 MW燃煤机组的风电-火电-压缩空气储能综合能源系统。首先通过构建系统热力学变工况模型,分析了关键参数对压缩空气储能系统性能的影响,然后以降低弃风率为目标,探究了综合能源系统在典型特征日的能流匹配和运行特性。结果表明,电能分配比由57.3%增加至76.0%时,储能系统输出热电比由0.84下降至0.30,对储能系统输出影响最为显著;典型特征日的仿真场景下,综合能源系统负荷调节能力强,能流匹配良好,弃风率仅为2.28%。通过上述分析,验证了所提出的系统具备可观的风电消纳潜力和运行灵活性。

基于Seidel像差理论的离轴四反初始结构自动化设计方法研究

离轴反射系统设计的关键环节是确定适用初始结构并进行优化,一般从同轴结构或者专利库中寻找相似的结构开始优化,这往往需要耗费大量的时间。以Seidel像差理论为依据,研究了一种获取离轴四反系统初始结构的设计方法。在设计之初引入视场偏置,通过追迹近轴光线给出五种单色像差的初级Seidel像差表示。以Seidel像差绝对值最小化作为目标函数,同时加入对光学和系统结构上的限制条件构建含有约束条件的单目标非线性优化模型,并通过粒子群优化算法进行求解。在此基础上,通过MATLAB调用CODE V API接口,判断此视场偏置情况下是否满足无遮拦的条件,并从中挑选出满足条件的初始结构。设计了一款焦距为1200 mm,视场1.2°×20°,F数为6的离轴四反光学系统,系统结构布局紧凑,成像质量良好,各项指标均满足设计要求。

Off-Design Performance of 9F Gas Turbine Based on gPROMs and BP Neural Network Model

Gas turbines are increasingly and widely used,whose research and production reflect a country’s industrial capacity and level.Due to the changeable working environment,gas turbines usually work under the condition of simultaneous changes of ambient temperature,load and fuel.However,the current researches mainly focus on the change in single condition,and do not fully consider the simultaneous change in different conditions.On the basis of single condition,this paper further studies the dual off-design performance of gas turbines under three conditions:temperature-load,fuel-load and fuel-temperature.Firstly,the whole machine model of a gas turbine is established,in which the compressor model has the greatest impact on the performance of gas turbines.Therefore,this paper obtains a more accurate compressor model by combining the engineering modeling advantages of gPROMs and the powerful mathematical calculation ability of MATLAB neural network.Then,according to the established gas turbine model,the dual off-design performance is studied,which is mainly based on the parameter of output and efficiency.The result shows that the efficiency and power output of gas turbines will decrease with the increase of ambient temperature.With the decrease of fuel calorific value,power output and efficiency will increase.As the load decreases,the efficiency of the gas turbines will decrease,and these changes are consistent with the single off-design performance.However,when the fuel and temperature change simultaneously,only adjusting the IGV angle cannot avoid the surge when the temperature is above 30°C.At this time,it is necessary to adjust the extraction rate in order to ensure the safe and stable operation of gas turbines.Therefore,the research on dual off-design performance of gas turbines has an important significance for the peak shaving operation of gas turbines.

空冷机组汽轮机主轴直接驱动给水泵的变工况运行仿真试验

汽轮机主轴直接驱动给水泵技术是一种全新的给水泵驱动方式,目前国内尚无成熟的运行经验。针对采用该技术的某350 MW直接空冷机组进行了系列变工况运行仿真试验。结果表明:对于配置1台100%容量主机泵和1台50%容量备用泵的机组,该技术完全能够满足在机组背压快速变化、负荷变化及给水泵故障等工况下给水流量的需求。

Comparison and Error Analysis of Off-design and Design Models of Energy Hubs

The accuracy of the simulation model has a pro-found impact on the optimal operation of the energy hubs(EHs).However,in many articles,the constant model of the efficiency of equipment is adopted to formulate the operation system,which would probably lead to a simplification of the simulation models.But,EHs are typically operated under off-design condition due to the fluctuations in cooling,heating,electricity requirement.More-over,even though the off-design characteristics are considered,few studies have suggested comparing the differences between those two models by considering the operation cost.In order to assess the effect of the off-design characteristics of EH on the optimal operation accuracy in this paper,two test cases are performed on the fixed and variable load conditions,respectively.In addition,the individual effect of off-design characteristics of each equipment on the optimal operation cost of the EH is also investigated through four optimization runs.It is worth mentioning that the optimal operation problem of the EH considering the off-design characteristics and on-off status of the equipment is a mixed integer non-linear programming problem(MINLP).By testing the design and off-design models on the two cases,the results of simulation demonstrate that the optimal operation cost for the off-design model is larger than that for the design model.Nonetheless,in the aspect of the authenticity of the system operation strategy,the off-design model performs better than the design model.Furthermore,a larger relative error of the system operation cost between the two models can be observed when the EH is operated under a relatively lower load condition,revealing that the influence of off-design characteristic on the optimal operation of EHs is too significant to be neglected.