Showing papers on "Tip clearance published in 2020"
TL;DR: In this paper, the tip leakage vortex (TLV) in a mixed flow pump as turbine at pump mode is decomposed and reconstructed by Dynamic Mode Decomposition (DMD) for the first time.
111 citations
TL;DR: In this paper, the authors investigated the effect of tip clearance on the internal flow fields and the hydraulic losses in mixed-flow pump, and the entropy production method with computational fluid dynamics (CFD) was employed to analyze the energy losses in a low specified number mixed-flood pump with guide vane.
105 citations
TL;DR: In this paper, the primary tip leakage vortex (PTLV) trajectory is investigated by numerical simulation validated by experiment measurement with consideration of the tip clearance size δ, the impeller blade number Zi, and impeller rotational speed n. The results show that δ slightly shifts the separation point (SP) of the PTLV but rarely affects the separation angle α.
Abstract:
Tip clearance results in the leakage flow from blade pressure side to suction side, which will further cause the tip leakage vortex (TLV). Moreover, the flow pattern in an impeller is seriously deteriorated due to the TLV and its interaction with the main stream. In this work, the TLV in a mixed flow pump is investigated by numerical simulation validated by experiment measurement. The primary tip leakage vortex (PTLV) trajectory is specially studied with consideration of the tip clearance size δ, the impeller blade number Zi, and the impeller rotational speed n. The results show that δ slightly shifts the separation point (SP) of the PTLV but rarely affects the separation angle α. The increase in Zi and the decrease in n both lead to the shift of the SP toward the blade trailing edge and the decrease in α. Furthermore, a theoretical prediction model is proposed to predict the PTLV trajectory, by which the axial position and radial position of PTLV trajectory versus the rotation angle can be predicted. The proposed model is verified to be accurate to predict the PTLV trajectory, especially for the PTLV trajectory in the main flow passage. The dynamic evolution of TLV under different tip clearance sizes can all be classified into the same three stages: splitting stage, developing stage, and merging stage. Meanwhile, the dynamic evolution frequency fe is the same as the impeller rotational frequency fi.
61 citations
TL;DR: In order to investigate the influence of tip clearance size on the characteristics of mixed-flow pump under stall conditions, the entropy production analysis method is utilized to visualize the high energy loss area of main flow domains in internal flow fields as mentioned in this paper.
47 citations
TL;DR: In this article, the influence of rotating speed on tip leakage vortex in a mixed flow pump as turbine at pump mode is investigated, and a prediction model for separation angle of tip leakage flow and axial momentum also increase.
38 citations
TL;DR: In this article, the energy performance and tip leakage vortex in a mixed flow pump as turbine (PAT) at pump mode is investigated by numerical method validated by experiment measurement with the blade rotation angle α increasing.
33 citations
TL;DR: In this paper, a C groove method is developed to improve the energy performance and suppress the tip leakage vortex and cavitation around a NACA0009 hydrofoil in tidal energy conversion.
32 citations
TL;DR: In this article, the authors examine the accuracy of common numerical models and explain the influence of installing an inducer or increasing the tip clearance gap on the performance of a centrifugal pump.
32 citations
TL;DR: In this paper, the deformation of turbine stage components (turbine rotor, nozzle guide vane, with integral blade shroud) during transient phases is investigated and a one-way coupled transient thermal-structural analysis is performed on a three-dimensional model to capture the actual behaviour of the tip clearance during transient operating conditions.
32 citations
TL;DR: In this paper, a systematic analysis is performed on axial fans with different tip-clearance sizes to gain a clear understanding of the characteristics of tip leakage flow and investigate the generation mechanism of aeroacoustics.
31 citations
TL;DR: In this paper, a large-tip-gap compressor along speed-line experiences three stages: stable state, rotating instability, and rotating stall, and two critical behaviors of tip leakage vortex (TLV) are found to relate to the transition of instability pattern.
01 Jun 2020
TL;DR: In this paper, the effect of impeller tip clearance on internal flow fields and the rotating stall inception was investigated in a mixed-flow pump, where the tip leakage vortex and inlet unsteady flow were investigated.
Abstract: In order to investigate the effect of impeller tip clearance on internal flow fields and the rotating stall inception impacted by tip leakage vortex and inlet unsteady flow in a mixed-flow pump, mi...
TL;DR: In this paper, a new cavitation model combined with LES is utilized to simulate the tip-leakage cavitating flow around a NACA0009 hydrofoil, which considers the effect of non-condensable gas on cavitation.
TL;DR: In this article, the relationship between the swirling strength of TLV and the pressure difference between the pressure side (PS) and the suction side (SS) was analyzed and the velocity distribution in the tip clearance was also investigated in a multiphase pump.
TL;DR: In this article, the effect of the tip-clearance (TC) ratio on both the flow field and the far-field noise was investigated in Diffuser-Augmented Wind Turbines.
TL;DR: In this paper, a novel method of T shape tip is proposed to improve energy performance and suppress tip leakage vortex (TLV) for a NACA0009 hydrofoil.
TL;DR: In this paper, the authors measured the tip clearance of a gas turbine engine in real-time, and showed that it is one of the important parameters affecting the performance, safety and stability of a turbine engine.
Abstract: Blade tip clearance is one of the important parameters affecting the performance, safety and stability of a gas turbine engine. However, it is difficult to measure the tip clearance in real time an...
TL;DR: In this article, the variation laws of exciting force, pressure coefficient and the hydrodynamic coefficients differences have been studied at the different tip clearances and different oblique flow angle, and the time domain data of the pulsating pressure of PJP with cavitation conditions or without cavitation condition was presented, and then which was converted to frequency domain data by fast Fourier transform (FFT).
TL;DR: In this paper, the effect of the C groove on the energy performance and sources generated by dipoles and quadrupoles around a NACA0009 hydrofoil was investigated.
TL;DR: In this article, a combination of numerical simulation and experiment was carried out and the reliability of numerical method was verified by comparing with the experimental data of the flow field by using high-speed photography.
TL;DR: In this paper, an unsteady numerical simulation was conducted on the three-dimensional full flow field of a pump-jet propeller based on the DES (detached-eddy-simulation) turbulence model and the Z-G-B (Zwart-Gerber-Belamri) cavitation model.
Abstract: When a pump-jet propeller rotates at high speeds, a tip vortex is usually generated in the tip clearance region. This vortex interacts with the main channel fluid flow leading to the main energy loss of the rotor system. Moreover, operating at a high rotational speed can cause cavitation near the blades which may jeopardize the propulsion efficiency and induce noise. In order to effectively improve the propulsion efficiency of the pump-jet propeller, it is mandatory to research more about the energy loss mechanism in the tip clearance area. Due to the complex turbulence characteristics of the blade tip vortex, the widely used Reynolds averaged Navier–Stokes (RANS) method may not be able to accurately predict the multi-scale turbulent flow in the tip clearance. In this paper, an unsteady numerical simulation was conducted on the three-dimensional full flow field of a pump-jet propeller based on the DES (detached-eddy-simulation) turbulence model and the Z-G-B (Zwart–Gerber–Belamri) cavitation model. The simulation yielded the vortex shape and dynamic characteristics of the vortex core and the surrounding flow field in the tip clearance area. After cavitation occurred, the influence of cavitation bubbles on tip vortices was also studied. The results revealed two kinds of vortices in the tip clearance area, namely tip leakage vortex (TLV) and tip separation vortex (TSV). Slight cavitation at J = 1.02 led to low-frequency and high-frequency pulsation in the TLV vortex core. This occurrence of cavitation promotes the expansion and contraction of the tip vortex. Further, when the advance ratio changes into J = 0.73, a third type of vortex located between TLV and TSV appeared at the trailing edge which runs through the entire rotational cycle. This study has presented the dynamic characteristics of tip vortex including the relationship between cavitation bubbles and TLV inside the pump-jet propeller, which may provide a reference for the optimal design of future pump-jet propellers.
TL;DR: In this paper, the authors used the large eddy simulation (LES) method coupled with the Zwart-Gerber-Belamri (ZGB) cavitation model to investigate the cavitation-vortex interaction mechanism.
Abstract: The turbulent cavitating flow around the propelling pump tip clearance is numerically simulated using the large eddy simulation (LES) method coupled with the Zwart-Gerber-Belamri (ZGB) cavitation model to investigate the cavitation-vortex interaction mechanism. The calculated cavitation structures around the blades are in a remarkable agreement with the experimental results. The distributions of the tip clearance vortex under two cavitation conditions are obtained and compared. The results show that the cavitation development enhances the vorticity generation and the flow unsteadiness around the tip clearance of a propelling pump. Vortices are basically located around the cavitation areas, particularly in the tip clearance region, during the cavitation. The relative vorticity transport equation is applied for the cavitating turbulent flows and it is further indicated that the vortex stretching term makes the main contribution in the vortex production, and the baroclinic torque and dilation terms are important source terms for the vorticity generation in the cavitating flow. In addition, the viscous diffusion term and the Coriolis force term are significant in modifying the vorticity field inside the blade tip clearance.
TL;DR: In this article, the design study of an S-CO2 radial inflow turbine based on system optimization is conducted, and the CFD simulation of the turbine under design and offdesign conditions is performed, and tip clearance analysis is conducted to evaluate the turbine performance.
TL;DR: In this paper, the location effect of single grooved casing treatment (CT) on the compressor performance and flow stability is numerically studied at a large tip clearance in a two-stage counter-rotating axial flow compressor.
TL;DR: In this article, the authors focused on the tip clearance gap between the turbine blade tip and the stationary shroud casing and proposed an anti-cavity fin (ACF) to mitigate the tip leakage cavitation.
TL;DR: In this article, the authors investigated the effect of rotor disc vibration on the flow characteristics in the RS cavity and gas ingestion and found that the rotor vibration increased the sealing effectiveness at the rim seal clearance, and the amplitudes of the pressure fluctuation and the radial velocity of the gas ingestion flow at rim sealing clearance.
TL;DR: In this article, the abradable coating is used to protect the tip of axial flow compressor rotor blades from damage to the casing surface, which is not only to allow for closer clearances but also to accept physical events and thermal variation that may be found during its exploitation.
TL;DR: In this paper, a cascade of five rotor blades with the tip clearance of 1.0mm was used to investigate side tip region film cooling of a fan-shaped hole, where the film hole was located at 7/8 height of the total blade.
01 Feb 2020
TL;DR: In this paper, the performance of a ducted axial fan at different tip clearances in the absence and presence of inlet guide vanes is investigated in the presence and absence of inlets.
Abstract: This research aims at the numerical study of the blade tip grooving effect on the performance of a ducted axial fan at different tip clearances in the absence and presence of inlet guide vanes. To ...
TL;DR: In this paper, the performance of the blade element actuator disk (BEAD) method for simulating ducted tidal turbines is investigated and its advantages and disadvantages, in comparison with the actuator line (AL) method, are discussed.