排气歧管总成热应力分析及温度场试验验证

采用了流固耦合的方法分析排气歧管总成的温度场和热应力。首先计算排气歧管总成的稳态内流场,得到了耦合面的温度分布,以此为边界条件计算了排气歧管总成的温度场,同时采用试验验证了排气歧管总成温度场计算结果的准确性。再以计算出的温度场为依据进一步算出了排气歧管总成的热应力,结果表明热应力的集中处位于排气歧管入口位置,排气歧管总成结合处在实际工作中不会因为较大的热应力而造成开裂,这为发动机的开发提供了参考。     

某柴油机排气歧管CFD分析

为了在排气歧管的研发过程中准确预测其热负荷,需要进行热应力分析,该分析需要CFD计算提供边界。将CFD软件与结构软件耦合进行两轮瞬态计算生成温度和换热系数边界,并且进行稳态计算,得到压力分布和速度分布。     

3D打印燃气轮机天然气喷嘴的流场仿真分析

开展3D打印天然气喷嘴流场仿真研究,为小型化燃气轮机控制技术的提升奠定基础.利用Solidworks、ANSYS ICEM CFD软件进行3D打印天然气喷嘴模型建模和网格划分,基于FLUENT仿真完成不同压力工况下稳态天然气喷射流场的数值模拟计算.在天然气喷嘴外流场中形成的几何回流区会随着供气压强的增大而消失,中心回流...     

A numerical study on the characteristics of transient flow in a pressure regulator resulting from closure of the pressure control valve

This study investigates characteristics of transient flow and the possibility of freezing in a pressure regulator and the rear connecting pipe of the pressure regulator during the closing process of the pressure control valve (PCV), which is an essential element in the operation of a natural gas pipeline network. For this purpose, the study develops a numerical model for the PCV and its rear connecting pipe by applying computational fluid dynamics method. The analysis is conducted in each of two cases: (1) a steady-state analysis in the case of normal operation and (2) an unsteady-state analysis in the case of emergency closure in problematic situations. First, we closely examine characteristics of internal flow in the pressure regulator and the rear connecting pipe when the PCV operates regularly with a 50% opening ratio in a steady state. Afterwards, unsteady-state analysis examines characteristics of transient flow, such as lowered pressure and temperature, velocity change, etc., of rear flow in the pressure regulator when the PCV is closed because of trouble in the pressure control system.     

直接空冷机组排汽管道内加装导流片的流场的数值模拟

研究直接空冷机组排汽管道的重点是均衡各蒸汽分配管内的流量和降低压降。利用计算流体力学软件FLU-ENT,在典型工况下对某600MW直接空冷汽轮发电机组排汽管道内的蒸汽流场进行了数值模拟,然后在管道内增加和调整导流片进行模拟来得出最佳的导流片布置方式。结果表明:在最佳导流片布置的情况下,蒸汽在蒸汽分配管道内流量均衡,流动阻力减少。     

Measuring of accoustic wave influences generated at various configurations of racing engine inlet and exhaust system on brake mean effective pressure

In this paper there are presented the results from measurement of a high-powerful racing combustion engine. These results are obtained by means of the system EwaC, which is operating as the data-recording process. That is such measuring equipment, which is sensing and recording information during the engine current operation under the real conditions and real operational loading. A modular approach to the individual measuring consists in a sequential assembly of the individual components belonging to the engine inlet and exhaust system. An investigation of the individual configuration influences of the both systems is performed by means of the sequential experimental measuring. The measurement of the exhaust pipe was based on the application of tuned racing exhaust system. In order to perform experiments oriented to the inlet system it was developed a new system of the thrust-ejector suction, which enables to solve problems connected with an insufficient feeding of cylinder with a fresh mixture. The pressure of air, which is sucked into the engine, is changed from the atmospheric value to the overpressure level. This phenomenon causes an increasing of the engine power output and torque. According to the gained results was investigated a relation between the newly developed inlet pipe and increasing of the engine torque. Furthermore, the experimentally obtained results are well corresponding with the analytical relations described in the relevant literature. These results can be presented for a wide spectrum of the high-powerful engines because the air inlet system is independent on the engine design and arrangement. The analysed system was successful in the motorbike applications. Thus, taking into consideration the positive results there was registered in the last year as well as the patent application concerning this new design arrangement.     

An Evaluation of Several Metals and Ceramics in Lubricated Sliding

A numerical scheme that has been successfully used to solve a wide variety of compressible flow problems, including flows with large and small discontinuities, entitled the space-time conservation element and solution element (CE/SE) method, is extended to compute compressible viscous flows in pressurized thin fluid films. This method is applied to calculate the pressure distribution in a hybrid gas journal bearing. The formulation of the problem is presented, including the modeling of the feeding system. The numerical results obtained are compared with experimental data. Good agreement between the computed results and the test data were obtained, and thus, validate the CE/SE method to solve such problems.     

Simulation and experimental study of phase segregation in helical pipes: A new method for flow conditioning

The aim of the present study is to contribute some knowledge of phase separation phenomena of gas–liquid turbulent flow in curved pipe and provide a basis for the development of an in-line gas–liquid separator and flow pattern conditioning device. A systematic study of gas–liquid three-phase flow in 3D helical pipes was numerically performed. Gas phase distribution in the flow through the helical pipe was analyzed for various flow parameters conditions and different pipe geometries. Experimental qualitative results show that a helical pipe can, successfully, be used to condition a bubble flow into a stratified (stratified wavy flow). The main idea is to put it just upstream of sensors that are flow regime dependent; ensuring that the sensor, once calibrated to work in this flow pattern, suffers no reduction in its performance and, consequently, avoid additional sources of error.     

Analysis of transient flow in a pump-turbine during the load rejection process

The transient flow in pump-turbines during the load rejection process is very complex. However, few studies have been conducted on three-dimensional (3-D) numerical simulation. Hence, we simulated 3-D transient turbulent flow in a pump-turbine during the load rejection process using the calculation method of coupling the flow with the rotor motion of rigid body. To simulate the unsteady boundary conditions, the dynamic closing process of the guide vanes was simulated with the dynamic mesh technology. The boundary conditions at the spiral-casing inlet and the draft tube outlet were determined using the user defined functions (UDF) according to the experimental data. The numerical results of the rotational speeds show a good agreement with the experimental data. Then, the complex transient flow in the pump-turbine during the load rejection process was analyzed based on the numerical results. The results show that there are severe unsteady vortex flows in the vaneless space near the conditions under which the hydraulic torque on the runner equals to zero. When the pump-turbine operates into the maximum reverse discharge condition in the reverse pump operating process, the unsteady vortex flows in the vaneless space are instantaneously impacted into the region between the guide vanes and the stay vanes by the sudden reverse flows. The formation and development mechanism of the unsteady vortex flow in the vaneless space is associated with the distribution characteristic of the velocity field.     

Passive prandtl-meyer expansion flow with homogeneous condensation

Prandtl-Meyer expansion flow with homogeneous condensation is investigated experimentally and by numerical computations. The steady and unsteady periodic behaviors of the diabatic shock wave due to the latent heat released by condensation are considered with a view of technical application to the condensing flow through steam turbine blade passages. A passive control method using a porous wall and cavity underneath is applied to control the diabatic shock wave. Two-dimensional, compressible Navier-Stokes with the nucleation rate equation are numerically solved using a third-order TVD (Total Variation Diminishing) finite difference scheme. The computational results reproduce the measured static pressure distributions in passive and no passive Prandtl-Meyer expansion flows with condensation. From both the experimental and computational results, it is found that the magnitude of steady diabatic shock wave can be considerably reduced by the present passive control method. For no passive control, it is found that the diabatic shock wave due to the heat released by condensation oscillates periodically with a frequency of 2.40 kHz. This unsteady periodic motion of the diabatic shock wave can be completely suppressed using the present passive control method.     

Experimental and numerical study of the flow characteristics of a novel olive-shaped flowmeter (OSF)

A novel differential pressure flowmeter with an olive-shaped flowmeter (OSF) is proposed and investigated both experimentally and numerically. The streamline, pressure and velocity are obtained and numerically analysed. The results indicate that the proposed OSF exhibits less permanent pressure loss than the orifice plate flowmeter (OPF). The pressure also tends to be more stable in the OSF, which ensures high measurement accuracy and repeatability. The OSF is superior to the OPF in terms of relative pressure loss, streamline distribution, pressure distribution and velocity distribution. In the experiment, an oil pump transported diesel oil into the measurement pipe, through the check valve, filter, pressure-regulating container, and flow-regulating valve, before it was finally returned to the fuel tank. The experimental results showed that the pressure loss of the OSF was only about 14.94% of that of the OPF under the same conditions. The pressure loss curve of the OPF increased rapidly by up to 2,700 Pa with each 1 m³/h increase in the flow rate, whereas that of the OSF increased only slightly.     

Application of electrical resistance tomography to two-phase pipe flow parameters measurement

This paper introduces the TERT-IV prototype developed by Tianjin University. The application of the TERT-IV system to measurement parameters of two-phase flow has been studied. The methods of analyzing measured data of ERT system are presented and applied to identify flow regimes and estimate void fraction. For the several typical flow regimes, the methods of principal component analysis and artificial neural network to identify the two-phase flow regimes is presented, and that is proved to have higher recognition rate by experimental test. For the different phase distribution on a pipe cross-section, the methods of relative changes summation and polynomial regression are used to estimate void fraction, and are proved to be possible by comparing the results of simulation calculation to the analytic results of experimental measured data.The research results show that the method is feasible using feature extraction and analysis data to measure the parameters of two-phase flow under the different flow conditions, and prove that it is possible to monitor on-line the transportation process of air/water two-phase flow using ERT system.     

An improved particle image velocimetry method for efficient flow analyses

This study proposes a spatiotemporally Adaptive Search Area (SA) size selecting algorithm for Particle image velocimetry (PIV), ASAPiv. The presented method releases the constraint of conventionally used static SAs, offering a significant computational performance increase through optimizing the dimensions of the SA according to the local flow conditions in a transient manner. The algorithm is implemented as a part of a new PIV framework, developed within the MATLAB environment. The most relevant steps of PIV and the related methods are reviewed, starting from image pre-processing up to the post-processing of raw PIV results. The performance of the proposed algorithm and the PIV tool in general is demonstrated through three examples of different nature, including a synthetic image sequence, a conventional, laser illuminated PIV case and a large-scale, field application. The dynamic alteration of the SAs is found to be consistent with the prevailing flow conditions, while the accuracy of PIV in general is maintained. Total calculation times with static and dynamic SAs are compared. The benchmark cases highlight the relevance of adaptive SAs in cases of spatiotemporally varied flow conditions, where significant (up to 900%) computational performance increase is achieved. In case of unidirectional, steady flow conditions the method offers moderate speed-up compared to the employment of static SA sizes.     

Numerical simulation of fully developed flow and heat transfer characteristics in a curved tube with pulsating pressure gradient

Characteristics of fluid flow and convective heat transfer of a pulsating flow in a curved tube have been investigated numerically. The tube wall is assumed to be maintained at a uniform temperature peripherally in a fully developed pulsating flow region. The temperature and flow distributions over a cross-section of a curved tube with the associated velocity field need to be studied in detail. This problem is of particular interest in the design of Stirling engine heat exchangers and in understanding the blood flow in the aorta. The time-dependent, elliptic governing equations are solved, employing finite volume technique. The periodic steady state results are obtained for various governing dimensionless parameters, such as Womersley number, pulsation amplitude ration, curvature ratio and Reynolds number. The numerical results indicate that the phase difference between the pressure gradient and averaged axial velocity increases gradually up to π/2 as Womersley number increases. However, this phase difference is almost independent of the amplitude ratio of pulsation. It is also found that the secondary flow patterns are strongly affected by the curvature ratio and Reynolds number. These, in turn, give a strong influence on the convective heat transfer from the pipe wall to the pulsating flow. The results obtained lead to a better understanding of the underlying physical process and also provide input that may be used to design the relevant system. The numerical approach is discussed in detail, and the aspects that must be included for an accurate simulation are discussed.     

Simulation of flow meter calibration factors for various installation effects

The determination of flow meter calibration factors has been made using a computer simulation approach. The proposed technique is based on computational fluid dynamics (CFD). The CFD tools were used to determine the flow field in a flow meter as developed by three different pipe configurations. These flow fields were used to determine the calibration factor for an ultrasonic flow meter. The results have been compared with calibration factors obtained by CFD using detailed LDV input boundary data, analytical calculations and experimental data. Tests were made for reference conditions of 10013 straight-pipe and for single- and double-elbow pipe configurations using Reynolds numbers from 100 to 100,000. For reference conditions good agreement is shown. For disturbed flow conditions the simulations well resembled the experimental data. However we find differences for transitional and swirl flows.     

The fractal flow conditioner for orifice plate flow meters

The sensitivity of orifice plate flow meters to the quality of the approaching flow continues to be a cause for concern in flow metering. The distortions caused by pipe fittings such as valves, bends, compressors and other devices located upstream of the orifice plate can lead to non-standard velocity profiles and give errors in measurement. The design of orifice plate meters that are independent of the initial flow conditions of the upstream is a major goal in flow metering. Either using a long straight pipe, or a flow conditioner upstream of an orifice plate, usually achieves this goal.The effect of a fractal flow conditioner for both standard and non-standard flow conditions was obtained in experimental work and also using simulations. The measurement of mass flow rate under different conditions and different Reynolds numbers was used to establish a change in discharge coefficient relative to a standard one. The experimental results using the fractal flow conditioner show that the combination of an orifice plate and a fractal flow conditioner is broadly insensitive to upstream disturbances.The simulation results also show that the device can be used as a part of a flow metering package that will considerably reduce installation lengths. Previous work with orifice plates has shown that a combination of flow conditioner and orifice plate was promising. The results of using a combination of the fractal flow conditioner and orifice plate for non-standard flow conditions including swirling flow and asymmetric flow show that this package can preserve the accuracy of metering up to the level required in the Standards.     

An experimental setup for simulation of two-phase hydrocarbon mixture flow in porous stratums

A procedure for simulating the two-phase flow of three-component hydrocarbon gas mixtures (for example, of the methane-propane-butane mixture gas condensate) in a porous stratum with the use of strain-gauge pressure sensors is proposed. Results are presented of experimental studies of two-phase hydrocarbon methane-propane-butane mixture filtration through a porous medium on the PLAST setup of the Joint Institute for High Temperatures under conditions close to reality. It is shown that the coordinate of the gas condensate plug formation region in the experimental section of a pipe can be determined with an accuracy up to 10% of its length.     

Identification of gas/liquid two-phase flow regime through ERT-based measurement and feature extraction

Gas/liquid two-phase flow is of great importance in various industrial processes. As the most important characteristic of a two-phase flow, the flow regime not only characterizes the flow condition in an explicit way, but also determines the measurement model in each measuring method. Based on the application of Electrical Resistance Tomography (ERT) to a gas/liquid two-phase flow on a vertical pipe, features reflecting the characteristics of gas/liquid two-phase flow are extracted directly from the measured data without reconstruction of the cross-sectional images. The statistical features are derived through time series statistical analysis. Meanwhile features in the wavelet-scale domain are derived through both one-dimensional and two-dimensional wavelet transform. All extracted features are considered as the input of a Support Vector Machine (SVM) algorithm to recognize the flow regime. The preliminary results show that the feature extraction methods of multi-feature fusion and high-dimensional wavelet transform are suitable for the identification of gas/liquid two-phase flow regimes.     

Reproduction of air velocity in the entrance region of the test pipe in a wind tunnel

The airflow development in the pipe, in the entrance region of the wind tunnel located in the Lithuanian Energy Institute, the laboratory of Heat Equipment Research and Testing is investigated to analyze the conditions for the reproduction of air velocity values. The analysis is performed to reveal undeveloped flow conditions where the calibration of the devices is usually made, the entrance region of the pipes, or free stream from the nozzles. In this study, different flow regimes have been investigated using different air velocity measurement methods. Experimental and numerical results clearly show the features of the developing flow. They both demonstrate the stable core of the velocity profile up to 5 D in the pipe and ≤1 D from the entrance into the free stream in the testing chamber. Ultrasonic anemometer (UA) installed in the aerodynamic test facility shows reliable and highly comparable results with another non-intrusive device – laser Doppler velocimeter (LDA) in a range of velocities from 0.05 m/s up to 30 m/s. UA integrated into the wind tunnel is not found to be used for metrological issues for air velocity. Due to the fast response, they both enabled to analyze fluctuations in the flow. Local vortices identified in the flow have influenced the low-frequency fluctuations and the scatter of measurement results. Moreover, high-frequency fluctuations found in the flow originated from the flow turbulence and might be due to the electronic or acoustic noise. The stabilization of the entrance region in the pipe influences the mean value of air velocity, the transversal distribution of velocity and the development of axial velocity in different test sections of the pipe in a wind tunnel. Along with the recirculation zones in cavities of ultrasonic transducers, these factors are essential that make an impact on the reproduction of air velocity value.     

Fluid flow characteristics in the aquaculture tank for a breeding fish

The aquaculture tank is used for breeding fish in sea water which was pumped up to land. The flow characteristics in the aquaculture were investigated with varying the tank geometry and flow rate. The numerical analysis has been employed for calculating the velocity and temperature distributions in a water tank of rectangular type. The finite volume method and SIMPLE algorithm with 3-dimensional standard k-ε turbulence model were used for the numerical analysis. For comparison with experimental results, the PIV system was applied to visualize the flow patterns quantitatively. The numerical results showed good agreements with the experimental results. The mean velocity and temperature versus aquarium depth were represented for various circulating flow rates. Especially, the aquaculture environment is recommended that the aquarium depth has to be d=0.5 m, and this case is the condition of higher velocity and temperature in winter season.