Design of the rotor blades of a mini hydraulic bulb-turbine

The rotor blades of a mini hydraulic turbine were designed using a quasi-three-dimensional method. The meridional flow is computed by a streamline curvature method and the blade-to-blade flow by a singularity method. The rotor blade sections are the NACA 66 (MOD) with a = 0.8 meanline. The camber and the stagger angle of the blade sections are adjusted to fulfil the prescribed angular momentum distributions, at the rotor inlet and outlet sections, and zero-incidence flow angle, at the blade leading edge.Turbine head and efficiency versus flow rate curves were obtained for different rotor blade stagger angles at constant rotational speed. Radial distributions of time-averaged velocity and pressure, measured at the rotor exit section with a five-hole probe, are also presented.The design and the experimental results are compared with three-dimensional inviscid flow numerical results computed by the FLUENT code. The domain is discretized by unstructured meshes with a maximum of 2.5 × 10⁶ elements. The numerical results show good agreement with the design values and the experimental results, validating the design hypothesis of small radial velocity in the flow through the rotor.     

离心压缩机进口导叶叶型的进一步研究

为提高离心压缩机进口导叶的质量流量调节能力,以原研究成果为基础对导叶叶型做进一步研究。通过数值模拟计算,对不同厚度弯叶型和不同弯度位置导叶的质量流量调节能力进行对比分析。结果表明,虽然减小弯叶型的厚度可扩大其质量流量调节范围,却增加了流动损失,使压缩机效率下降;将弯叶型最大挠度位置向后移,可有效提高导叶的质量流量调节能力,且其产生的损失对压缩机性能影响不大。最终选择出适合于导叶进行质量流量调节的最佳叶型,减少了压缩气体的排空浪费。     

径向导叶与空间导叶的优劣分析与试验

对某一参数的节段式多级泵导叶进行研究。通过数值模拟对比分析传统的径向导叶(正、反导叶)与空间导叶对泵性能的影响并进行试验验证。以通用CFD软件NUMECA为计算平台,分别对叶轮加径向导叶及空间导叶流场进行分析,发现空间导叶在大流量区容易获得较好性能,但在小流量区损失较大,扬程曲线容易出现驼峰。在小流量区径向导叶性能要优于空间导叶。     

Cooling system optimisation of turbine guide vane

This paper discuses the problem of cooling system optimisation within a gas turbine vane. The analysis involves the optimisation of size and location of internal cooling passages within the vane. Cooling is provided with ten circular passages and heat is transported only convectively. The task is approached in 3D configuration. Each passage is fed with cooling air of constant parameters at the inlet. Also a constant pressure drop is assumed along the passage length. The thermal boundary conditions in passages varied with diameter and local vane temperature (passage wall temperature). The analysis is performed by means of the evolutionary approach for the optimisation task and FEM for the heat transfer predictions within the component. The optimisation is realised with genetic algorithm where two ways of individual (cooling system candidate) representations are used and juxtaposed. These are the classical binary representation of the design variables and the floating point form. The results show some potential stored in a vane cooling system. Appropriate passage distribution makes it possible to improve the operation condition for highly loaded thermal components. Also the comparison between binary versus floating point representation of the design variables show some superiority of the latter.     

Leading edge film cooling enhancement for an inlet guide vane with fan-shaped holes

This paper describes the improvement of leading edge film cooling effectiveness for a turbine inlet guide vane by using fan-shaped film cooling holes. The modification details are presented in comparison with the base-line configuration of cylindrical holes. Numerical simulations were carried out for the base-line and modified configurations by using CFX, in which the κ-ε turbulence model and scalable wall function were chosen. Contours of adiabatic film cooling effectiveness on the blade surfaces and span-wise distributions of film cooling effectiveness downstream the rows of cooling holes interested for the different cooling configurations were compared and discussed. It is showed that with the use of fan-shaped cooling holes around the leading edge, the adiabatic film cooling effectiveness can be enhanced considerably. In comparison with the cylindrical film cooling holes, up to 40% coolant mass flow can be saved by using fan-shaped cooling holes to obtain the comparable film cooling effectiveness for the studied inlet guide vane.     

Design method of guide vane for Wells turbine

Guide vanes are installed in the Wells turbine in order to improve its efficiency, self-rotating characteristics and off design performance with stall. This work attempts to explain the role of these guide vanes on the basis of momentum theory. It is shown that the upstream vanes are more effective in enhancing efficiency than the downstream ones. A design method for guide vanes is suggested based on experimental data and potential theory. Experimental studies carried out by the author confirm the theory proposed.     

Design of a solar photovoltaic-powered mini cathodic protection system

A mini cathodic protection (CP) system based on solar photovoltaic power source has been designed and tested in the field. It is concluded that such modular systems are well suited for CP applications especially in remote and hilly terrains.     

Effect of guide vane shape on the performance of a Wells turbine

A Wells turbine has inherent disadvantages: lower efficiency and poorer starting characteristics. Providing guide vanes on either side of the rotor could be one of the most effective ways of improving its performance. Several papers have demonstrated the usefulness of 2D guide vanes so far. In order to achieve further improvement in the performance of the Wells turbine, the effect of 3D guide vanes has been investigated experimentally by testing a model under steady flow conditions. Then, the running and starting characteristics under irregular flow conditions have been obtained by a computer simulation using quasi-steady analysis. It is found that the running and starting characteristics of the Wells turbine with 3D guide vanes are superior to those with 2D guide vanes.     

Modeling and experimental validation on pressure drop in a reverse-flow cyclone separator at high inlet solid loading

High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds (CFB). In this work, the effect of high solid loading on pressure drop in a reverse-flow cyclone was experimentally studied. The particles used were sand and γ-Al₂O₃. An extended range of inlet solid loadings (M), up to 30 kg of solids/ kg of air was tested at different inlet air velocities (V _in=16∼24 m/s), well beyond the solid loading range reported before. The experiments showed that, in the tested range of solid loadings, the cyclone pressure drop decreased dramatically with increasing solid loading when M<7.5 kg/kg and then almost remained constant. A new semi-empirical model for predicting cyclone pressure drop was also developed. The calculated and experimental results showed good agreement for particle free flow and particle laden flow.     

Design and experimental validation of looped-tube thermoacoustic engine

The aim of this paper is to present the design and experimental validation process for a thermoacoustic looped-tube engine.The design procedure consists of numerical modelling of the system using DELTA EC tool,Design Environment for Low-amplitude ThermoAcoustic Energy Conversion,in particular the effects of mean pressure and regenerator configuration on the pressure amplitude and acoustic power generated.This is followed by the construction of a practical engine system equipped with a ceramic regenerator-a ...     

Design and experimental validation of looped-tube thermoacoustic engine

The aim of this paper is to present the design and experimental validation process for a thermoacoustic looped-tube engine. The design procedure consists of numerical modelling of the system using DELTA EC tool, Design Environment for Low-amplitude ThermoAcoustic Energy Conversion, in particular the effects of mean pressure and regenerator configuration on the pressure amplitude and acoustic power generated. This is followed by the construction of a practical engine system equipped with a ceramic regenerator — a substrate used in automotive catalytic converters with fine square channels. The preliminary testing results are obtained and compared with the simulations in detail. The measurement results agree very well on the qualitative level and are reasonably close in the quantitative sense.     

Computer modeling and experimental validation of a building-integrated photovoltaic and water heating system

A dynamic simulation model of a building-integrated photovoltaic and water heating system is introduced in this paper. The numerical model was developed based on the finite difference control volume approach. The integrated use of energy balance and fluid flow analysis allows the prediction of the system dynamic behavior under external excitations such as changes in weather, water consumption and make-up conditions. The validity of the modeling approach was demonstrated by comparing its predicted operating temperature changes and system daily efficiencies with the measured data acquired from an experimental rig at the City University of Hong Kong. The predictions from the model show good compliance with the experimental measurements.     

Performance analysis of a centrifugal compressor with variable inlet guide vanes

The flow in a centrifugal compressor stage with variable inlet guide vanes (VIGVs) is investigated by numerical simulation in this paper. Analysis of the performance curves and relative velocity vectograms indicates that performance curves shift toward small flow domain when VIGVs turn positively, and toward large flow domain when VIGVs turn negatively. Stage efficiency drops quickly after work condition enters a small flow domain through the peak efficiency point. Under the circumstance of large setting angles of the guide vanes, there exist obvious flow separations in guide vane passages within wide flow ranges, and back flow regions can be located at the front of splitter suction surfaces under large flow conditions, while under the condition of small flow, flow separations occur on suction surfaces of long blades. __________ Translated from Journal of Power Engineering, 2006, 26(6): 804–807 [译自: 动力工程]     

Effects of a turbine guide vane on hydrogen-air rotating detonation wave propagation characteristics

The rotating detonation engine is a new machine that can generate thrust via continuous rotating detonation waves (RDWs). In this study, experiments were performed on a structure combining a rotating detonation combustor (RDC) and a turbine guide vane to investigate the propagation characteristic of hydrogen-air RDW. The results showed that the velocity of detonation wave initially increased and then decreased with the increase of equivalence ratio, and it got a velocity of 84% Chapman-Jouguet value. The velocity of detonation wave generally rose by 4.31% comparing with the no guide vane tests, while the scope of steady-operation state became narrow. The oscillation pressure was reduced by 64% after passing through the guide vane, and the magnitude of pressure was only 0.4 bar at the guide vane exit. Meanwhile, part of the shock wave was reflected back to combustor resulting in some small pressure disturbances, and the propagation mode of reflected wave was related to the propagation direction of RDW.     

Water pumping analysis and experimental validation of beach well infiltration intake system in a seawater source heat pump system

Based on energy conservation equation and Darcy’s law, a model of beach well infiltration intake system applied in a seawater source heat pump system was established. The model consists of the seawater seepage and the heat transfer process. A porous medium model in a software named FLUENT was applied to simulate the seepage and the heat transfer process. This model was also validated by field experiment conducted on the seashore in Tianjin, China. The maximum relative error between simulation results and experimental results was 2.1% (less than 5%), which was acceptable in engineering application. The porosity and coefficient of thermal conductivity of the aquifer soil were determined to be 0.49 W/(m·K) and 1.46 W/(m·K), respectively in the simulation. In addition, the influencing factors of pumping water of beach well were also analyzed. The pumping water was found to increase when the distance between the beach well and the impervious boundary becomes longer, when the distance between the beach well and the supplying water source shortens, when the diameter of the beach well enlarges, and the drawdown enlarges.     

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.     

Numerical and Experimental Studies of 3D Hypersonic Inlet

The results of numerical and experimental studies of a new configuration of 3D hypersonic inlet with the minimum throat area, which was called a convergent inlet, are presented in this paper. It is shown that the use of this inlet configuration allows one to reduce the drag and thermal protection of surfaces of a hypersonic engine within the entire range of flight velocities. The calculations were performed within the framework of inviscid gas model by the method of finite volumes. The flow and inlet characteristics, taking account of viscosity, were also calculated using the boundary layer equations. The experimental studies were performed within the Mach number range from 2 to 10.7 and Reynolds number based on the model inlet height of Re=1-5×106. The results included the flow parameters on the external compression surface and in the inlet duct, the Mach number in the throat, the air flow rate, the total pressure recovery coefficient, the inlet drag, and the boundary layer characteristics on compressi     

Influence of strength differential effect on material effort of a turbine guide vane based on thermoelastoplastic analysis

The strength differential (SD) effect has been observed in many iron-based metals such as 4310, 4330, maraging steel, and HY80 steels as well as titanium, aluminium 2024-T351, magnesium, and nickel-based super alloys such as aged Inconel 718. Moreover, the SD effect increases with temperature. The Huber–Mises–Hencky (HMH) J₂ yield condition is insu?cient to simulate the response of metals that exhibit the SD effect. Our work demonstrates the importance of taking into account the SD effect during strength analysis of turbine components. Two yield conditions are considered: the HMH condition and the SD-dependent Burzynski condition. The equivalent stresses produced by these conditions in the elastic state are compared. Plastic zone areas and effective strain values predicted by the two conditions are compared. Our investigation was performed based on thermal-fluid-structure interaction (FSI) analysis of a turbine guide vane made of a nickel-based super alloy that exhibits the SD effect. Conjugate heat transfer analysis was performed, and then elastoplastic stress analysis was performed with boundary conditions obtained from the computational fluid dynamics (CFD) analysis. The paraboloid Burzynski yield condition was implemented in an FE code. Implementation was based on the Euler backward method with consistency tangent moduli evaluated in the explicit form.     

Design of the measurements validation procedure and the expert system architecture for a cogeneration internal combustion engine

A research activity has been initiated to study the development of a diagnostic methodology, for the optimization of energy efficiency and the maximization of the operational time in those conditions, based on artificial intelligence (AI) techniques such as artificial neural network (ANN) and fuzzy logic.The diagnostic procedure, developed specifically for the cogeneration plant located at the Engineering Department of the University of Perugia, must be characterized by a modular architecture to obtain a flexible architecture applicable to different systems. The first part of the study deals with the identifying the principal modules and the corresponding variables necessary to evaluate the module “health state”.Also the consequent upgrade of the monitoring system is described in this paper. Moreover it describes the structure proposed for the diagnostic procedure, consisting of a procedure for measurement validation and a fuzzy logic-based inference system. The first reveals the presence of abnormal conditions and localizes their source distinguishing between system failure and instrumentation malfunctions. The second provides an evaluation of module health state and the classification of the failures which have possibly occurred. The procedure was implemented in C++.     

分流导叶垂直轴风力机气动性能研究

为提高垂直轴风力机气动性能,提出一种随相位角变化而改变相对夹角的分流导叶结构。以NACA0021为基础翼型,采用计算流体力学方法对分流导叶作用下垂直轴风力机风能利用系数、单叶片瞬时转矩、压力系数及速度场进行数值分析。结果表明：静态和动态分流导叶均可提高垂直轴风力机气动性能,且动态分流导叶提升效果更为显著;相较于静态分流导叶,动态分流导叶垂直轴风力机在尖速比为2.33时风能利用系数最高可提升23%,在尖速比为2.03时静态分流导叶垂直轴风力机较原始垂直轴风力机风能利用系数提高37%;分流导叶也可使最佳尖速比前移,稳定叶片转矩波动,提升垂直轴风力机的运行稳定性。