Numerical and Experimental Investigation of the Fan with Cycloidal Rotor

In this paper, the investigation of the cycloidal rotor fan (CRF) was presented. A CRF with four blades of the NACA0012 profile was used for the analysis. The CFD calculations were carried out by means of Ansys CFX commercial software. The experimental tests were done using velocity field measurement with the LDA technique. Numerical results were compared with experimental measurement in terms of velocity values. The CRF performance characteristic was prepared on the basis of experimental and numerical results.

Flow Velocity Field Measurement of Vertical Upward Oil–Water Two-Phase Immiscible Flow Using the Improved DPIV Algorithm Based on ICP and MLS

Flow velocity field measurement is important for analyzing flow characteristics of oil–water two-phase immiscible flow in vertical well. Digital particle image velocimetry (DPIV) is an effective velocity field measurement method that has overcome single point measurement limitation of traditional instruments. However, multiphase flow velocity fields generated by DPIV are often accompanied by local false vectors caused by image mismatching, which leads to measurement results with low accuracy. In this paper, the reasons for oil–water two-phase immiscible flow image mismatching in inner diameter 125 mm vertical pipe is identified by studying the DPIV calculation process. This is mainly caused by image noise and poor window following performance that results from poor deformation performance of the interrogation window. To improve deformation performance of the interrogation window, and thus improve the accuracy of the algorithm, iterative closest point (ICP) and moving least squares (MLS) are introduced into the window deformation iterative multigrid algorithm in DPIV postprocessing algorithm. The simulation showed that the improved DPIV algorithm had good matching performance, and thus the false vector was reduced. The experimental results showed that, in light of the present investigation, on average, the improved DPIV algorithm is found to yield an accuracy improvement of ~6%; the measurement uncertainty and reproducibility of the improved DPIV algorithm were 0.149 × 10−3 m/s and 1.98%, respectively.

Combustion Characteristics of Natural Gas Fueled, Premixed Turbulent Jet Flame Arrays Confined in a Hexagonal Combustor

In order to extend the operation regime of existing gas turbine combustion systems to lower the minimum loads, the applicability of matrix burners (arrays of jet flames) as an alternative to conventional swirl stabilized burners has been considered. In comparison to well-studied single jet flame systems, the effects of geometry and thermodynamic parameters on characteristics of matrix burner systems have not been studied in detail. Information, which is essential for design processes e.g. scaling of matrix burners, is not yet available in public domain. This work involves a systematic investigation of a matrix burner system operating at highly turbulent flow conditions (Reynolds Number ≈ 20000) prevailing in gas turbine combustion systems. In order to understand the effects of geometrical scaling, three variants of jet diameter have been investigated. A detailed test campaign including lean blow out limits detection, velocity field measurement and hydroxyl radical (OH*) chemiluminescence recording has been conducted. Influence of variation in stoichiometry and exit velocity of fuel-air mixture has been captured. The results show that it is possible to generalize the scaling of the matrix burner using the well-known Peclet criterion.

Three-Dimensional Visualization of Flow Characteristics Using a Magnetic Resonance Imaging (MRI) in a Lattice Cooling Channel

Flow structures in lattice cooling channels are investigated experimentally by measuring three-dimensional velocity components over entire duct. The lattice cooling structure is formed by crossing two sets of parallel inclined ribs. Heat transfer is enhanced when coolant flows through the narrow sub-channels between the ribs. According to the past literature, longitudinal vortex structures are formed inside the sub-channels due to interactions between crossing flows. In this study, three-dimensional velocity field measurement is performed using MRI scanner to clarify the flow mechanism. The rib inclination angle is varied from 30 to 60 degrees. Reynolds number is set at approximately 8,000 based on the whole duct inlet hydraulic diameter and bulk velocity. Working fluid is 0.015mol/L copper sulfate aqueous solution. Measured results show that coolants in the upper and lower sub-channels interact not only at the both ends of the duct, but also at diamond-shaped openings formed by opposite sub-channels. The exchange of momentum between the upper and lower sub-channels occurs at the openings, leading to sustained longitudinal vortex in each sub-channel as mentioned in the literature. When the ribs are arranged with obtuse angle, a large vortex spreads across the contact surface, while the vortex structure independently stays in each sub-channel for acute rib angle. The measured velocity fields are compared with numerically-simulated ones using a RANS solver. Overall flow pattern is captured, but flow interaction between the upper and lower sub-channels is underestimated.