PIV Test Research Articles

PIV test methods and mechanism on liquid turbulence modulation by solid-particles inside a centrifugal pump

As one of high energy consumption pumps, pump used for solid-liquid two-phase mixture transportation, such as slurry pump and mud pump, is extensively used in the hydraulic transportation of solid-liquid mixture through pipes in various fields. The erosion wear in slurry pumps has been identified as a critical issue during transportation of slurry as it affects the equipment performance and reduces its reliability and operation life, leading to the waste of energy. Many studies indicate that the performance and efficiency of solid-liquid two-phase centrifugal pump is controlled by the two-phase flow pattern inside the pump, so understanding flow characteristics and abrasion mechanism has important significance to improve the hydraulic design of the impeller for decreasing the abrasion and increasing the service life of the pump. In the present study, based on solid-liquid two-phase flow as object, an improved experimental facility without agitation was developed can improve the test precision by eliminating the influence of agitation on flow inside pump and improving particle-liquid two-phase flow circulation way. On the base of experimental studies, POD methods were applied to analysis the liquid turbulence modulation by solid-particles and the behavior of large eddy structures will be clearly understood. Thus, the theoretical system of the solid-liquid two-phase flow will be further improved. And a theoretical principle for the solid-liquid two-phase pump optimal design will be presented. The following conclusions are obtained: (ⅰ) a superior PIV two-phase test platform than that in the previous literature is designed and it can be very good to realize a stable solid-liquid two-phase flow measurement of centrifugal pump. Compared with the traditional platform, the results obtained by the novel solid-liquid two-phase centrifugal pump PIV test platform has a very high accuracy and it has a good reference value to understand flow mechanism of a centrifugal slurry pump. The two particle images with and without agitating are shown in Figure 5. As can be seen that a large number of bubbles are brought into the circulation line (Figure 5(a)), which is caused by a higher stirring speed for suspending solid particles, and thus the actual flow images shows a gas-liquid-solid three-phase flow. However, for the present test facility without stirring, there is no such problem, and the original image is very clear without bubbles. (ⅱ) The POD analyses show that the solid-particles injection has an important influence on the large scale turbulence structures which contain a large amount of energy. The modal energy distribution as a function of the POD mode number is displayed in Figure 10. The energy contribution of these large scale structures to the total energy becomes larger due to the injection of solid-particles, whereas the contribution of the small scale structures, which denotes the energy dissipation, becomes smaller. This is why the low solid-phase volume concentration has higher pump head and efficiency. The addition of solid-particle increases the friction loss, but reduces the flow separation loss and inhibits the development of small scale vortex. However, with the increase of solid-particle concentration, the friction loss increases is greater than the flow separation loss reduction, and thus pump head and efficiency decrease. The above phenomena show fully that the solid-particles addition has an important influence on the large scale energetic eddy structures. This is confirmed by the measurement results as shown in Figure 11.

PIV experiment and evaluation of air flow performance of swirl diffuser mounted on the floor

In order to obtain satisfactory effect of air conditioning and ventilation, the floor–supply displacement ventilation has widely applied in many civil buildings. Swirl diffusers mounted on the floor are widely used to provide fresh air into the occupied zone in the floor–supply displacement ventilation system. This paper studied the air distribution performance of swirl diffuser by 2D-PIV (particle image velocimetry). The experiment was implemented in a full-scale room to achieve reliable data of swirl diffusers. Flow visualizations have been carried out to determine the shape of the swirl jet. The whole velocity field was measured by 2D-PIV system, which is very useful to analyze air distribution above the swirl diffuser. With the aid of the flow visualizations and PIV test technology, the macro and micro structure of the air flow above the swirl diffuser is specified in more detail. Moreover, the centerline velocity decay coefficient (K value) and entrainment ratio were obtained. The research work of this paper provides detailed experimental data of air flow above the swirl diffuser, which provide the reference for selection of air terminal devices and a basis for follow-up numerical simulation study.

The study of flow separation control by a nanosecond pulse discharge actuator

The basic dynamic characteristic of a nanosecond (NS) pulse discharge actuator in still air is investigated, which introduces viscid and inviscid effects to the flow, namely, heated air and pressure waves, respectively. The efficacy of a dielectric barrier discharge plasma actuator driven by a nanosecond pulse for active flow separation control is investigated experimentally on a NASA SC(2)-0712 aerofoil at Re=0.5×106 (25m/s). The pressure distribution on the aerofoil surface is measured, and the result indicates that the separation is well controlled at a high angle of attack. The PIV test result shows that the forcing frequency selectively affects the flow over the aerofoil, and a higher forcing frequency has a better influence on the leading edge shear layer. Schlieren imaging experiments at Re=0.1×106 (5m/s) show that the main disturbance factor for the nanosecond pulse plasma actuator is the heating effect, which changes the local temperature and density and induces several vortex structures. The vortex structures entrain the outer high-momentum fluid into the shear layer, thereby strengthening the mixing of the shear layer with the main flow and delaying separation or even reattaching a separated flow. The research reveals the major disturbance factor introduced by NS discharge applied to flow separation control. Furthermore, the spatiotemporal disturbance process induced by the pulse discharge is investigated.

Analysis of Flow Field in the KYF Flotation Cell by CFD

The characteristics of flow field in the KYF-0.2 flotation cell are studied by CFD, and PIV test is also carried out to verify CFD simulation results. CFD simulation results show that there is a vortex near the slurry-ward surface of impeller blades in the direction against the rotation direction, there appears the maximum velocity which is higher than the speed at blade tips. Both PIV measuring results and CFD simulation results indicate that high velocity region appears near the exterior of stator blades,where the velocity value is about 1.5 m/s. Comparison between CFD and PIV show that there are good consistency in velocity change trend and velocity value.

Experimental Study on Combined-cascade

In this paper, experimental study had been carried out to demonstrate aerodynamic performance of combined-cascade by NACA0012 and NACA63012. Based on results obtained from performance experiments and PIV tests, it is found that the novel combined-cascade has competitive advantages in comparison with a single row of cascade composed by some symmetrical or bi-symmetrical airfoils. The results also reveal that, when two combination parameters, such as overlap ratio and pitch ratio, are set properly, not only is the lift-drag ratio increased, but also the stable working range is improved. Moreover, when overlap ratio is adopted as much as 0.3 and pitch ratio is between 0.4 and 0.5, the combined-cascade is achieved to the optimal performance due to positive interactions between two rows of cascade.

Research Analysis and Experiment Study on Flow Field of Hydrodynamic Coupling

CFD simulation and PIV test technology provide effective solution for revealing the complex flow of hydrodynamic coupling’s internal flow field. Some articles reported that the combination of CFD simulation and PIV test can be used for analyzing the internal flow field of coupling, and such analysis focuses on one-phase flow. However, most internal flow field of coupling are gas-fluid two-phase flow under the real operation conditions. In order to reflect the gas-fluid two-phase flow of coupling objectively, CFD three-dimensional numerical simulation is conducted under two typical operation conditions. In addition, modern two-dimensional PIV technology is used to test the two-phase flow. This method of combining experiments and simulation presents the characteristics of the flow field when charging ratios are different.

Particle Transport Analysis of Sand Ingestion in Gas Turbine Engines

Significant interest exists in the military and commercial aerospace industry to better predict and improve the durability of gas turbine jet engines that are operating in hostile desert environments, specifically, jet engines that see significant inlet sand or ash ingestion. This paper describes the development of a mixed CFD-empirical software tool that allows a detailed analysis of the kinematic and impact behavior of sand and other particulates in the near-field of turbomachinery blades and impellers. The tool employs a commercially available CFD solver to calculate the machine’s transient flow field and then uses the output to determine a set of nondimensional coefficients in a set of empirical functions to predict the statistical probability of particles impacting on rotating or stationary surfaces. Based on this tool’s output information, improved inlet air filtering techniques, optimized engine maintenance practices, and component designs can be realized. To determine the empirical coefficient and to validate the method, PIV testing was performed on an airfoil in a wind tunnel; then particle injection into a simple rotating impeller was tested on SwRI’s high-speed compressor test rig. Results from these tests allowed optimizing of the model to reflect rotating machinery particle impact behavior more accurately.

PIV 계측과 CFD 해석을 통한 오일펜스 만곡부 단면에서의 유동장 특성

PIV measurements of the velocity field, pressure field, vorticity, and turbulent intensity in the rear of curved section of an oil fence with current speed showed that the flow directions in the rear of flow boundary area were similar to those in the front of it. As the current speed increased, the patterns of pressure distribution were changed, and the turbulent flow became more irregular. CFD simulations under the same conditions as the PIV tests showed that the flow patterns of the wake were similar to those by PIV tests in speed of 0.3 m/s and less, but were distinctively deviated from those in 0.4 m/s due to the flexibility of the oil fence, which was not properly taken care of in CFD modeling.

중형 엔진 터보차져의 원심압축기에 관한 공력학적 3차원 형상 및 구동용 연소기 설계

An aerodynamic design for centrifugal compressor which was applied to medium speed diesel engine has been done. First of all, exact compressor specifications must be defined by accurate engine system matching. This matching program has been developed. Using the meanline prediction method, geometric design and performance curves for compressor were established and verified by comparing three dimensional viscous CFD results. The deviation at the design point was about 2.3%.<br/> Combustor has been designed and manufactured for the performance test of medium speed diesel engine turbocharger. Fuel nozzle of combustor was designed and its characteristics was analyzed by PIV and PDPA test equipment. Through these results, spray characteristics were studied and flow coefficient equation was deduced.

Three-dimensional particle image velocimetry: experimental error analysis of a digital angular stereoscopic system

Experimental error analysis of a digital angular stereoscopic PIV system is presented. The paper firstly describes an experimental rig which includes the design of a novel PIV test block for in situ calibration. This allowed the user to set up a static seeded flow volume which was translated in and out of plane to record PIV images using two megapixel CCD cameras positioned for angular stereoscopic viewing. PIV data were collected for a range of camera angles up to and for a range of flow displacements and processed by cross correlation into a set of two-dimensional calibration and flow displacement vectors. These 2D data were then processed into three-dimensional data by the use of geometric and bicubic spline interpolation algorithms and an error analysis performed on the predicted displacements. Results from this analysis have shown optimum system performance will be obtained by using camera angles of between 20 and and f numbers of f16 and higher. The results have also shown a theoretical prediction of system performance derived in previous work, which considers the ratio of out of plane to in plane errors, matches to within 8 and 18% of the experimental system performance.