Large Eddy Simulation of Combustion Instability of Low-Swirl Flames in a Multi-Nozzle Combustor

2017 ◽  
Author(s):  
Weijie Liu ◽  
Bing Ge ◽  
Shusheng Zang ◽  
Mingjia Li ◽  
Wenyan Xu
Keyword(s):  
Large Eddy Simulation ◽  
Heat Release ◽  
Pressure Fluctuation ◽  
Combustion Instability ◽  
Eddy Simulation ◽  
Numerical Result ◽  
Large Eddy ◽  
Reversal Flow ◽  
Flame Flashback ◽  
Flow Vortex

Large eddy simulation of self-induced combustion instability of low-swirl flames in a multi-nozzle combustor is carried out. The unsteady behaviors in the multi-nozzle burner including pressure fluctuation, velocity oscillation, PVC and triggering mechanism are studied in detail. Numerical result is compared with experimental measurement in terms of frequency and amplitude of pressure fluctuation. Results show LES successfully predicts the longitudinal instability mode in the multi-nozzle combustor with a reasonable agreement with experimental data. Flow parameters in the burner, such as pressure, axial velocity and CH4 mass fraction oscillate with the same frequency but different phases. Combustion instability leads to flame flashback into the burner due to the reversal flow. Vortex generation and shedding off in the outer shear layer result in unsteady heat release at the tail edge of the outer flame near combustor wall. Meanwhile, the unsteady heat release feedback to the pressure and flowfield, which is the main reason for inducing combustion instability.

scholarly journals Large Eddy Simulation of Periodic Transient Pressure Fluctuation in a Centrifugal Pump Impeller at Low Flow Rate

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 311
Author(s):  
Renfei Kuang ◽  
Xiaoping Chen ◽  
Zhiming Zhang ◽  
Zuchao Zhu ◽  
Yu Li
Keyword(s):  
Large Eddy Simulation ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Low Frequency ◽  
Pump Impeller ◽  
Eddy Simulation ◽  
Inlet Flow Rate ◽  
Large Eddy ◽  
Centrifugal Pump Impeller

This paper presents a large eddy simulation of a centrifugal pump impeller during a transient condition. The flow rate is sinusoidal and oscillates between 0.25Qd (Qd indicates design load) and 0.75Qd when the rotating speed is maintained. Research shows that in one period, the inlet flow rate will twice reach 0.5Qd, and among the impeller of one moment is a stall state, but the other is a non-stall state. In the process of flow development, the evolution of low-frequency pressure fluctuation shows an obviously sinusoidal form, whose frequency is insensitive to the monitoring position and equals to that of the flow rate. However, inside the impeller, the phase and amplitude in the stall passages lag behind more and are stronger than that in the non-stall passages. Meanwhile, the strongest region of the high-frequency pressure fluctuation appears in the stall passages at the transient rising stage. The second dominant frequency in stall passages is 2.5 times to that in non-stall passages. In addition, similar to the pressure fluctuation, the evolution of the low-frequency head shows a sinusoidal form, whose phase is lagging behind that by one-third of a period in the inlet flow rate.

Prediction of Pressure Fluctuation on a Vehicle by Large Eddy Simulation

2015 ◽  
Author(s):  
Yoshinobu Yamade ◽  
Chisachi Kato ◽  
Akiyoshi Iida ◽  
Shinobu Yoshimura ◽  
Keiichiro Iida
Keyword(s):  
Structural Analysis ◽  
Large Eddy Simulation ◽  
Unsteady Flow ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Sound Fields ◽  
Eddy Simulation ◽  
Acoustical Analysis ◽  
Wide Range ◽  
Large Eddy

The objective of this study is to predict accurately interior aeroacoustics noise of a car for a wide range of frequency between 100 Hz and 4 kHz. One-way coupled simulations of computational fluid dynamics (CFD), structural analysis and acoustical analysis were performed to predict interior aeroacoustics noise. We predicted pressure fluctuations on the outer surfaces of a test car by computing unsteady flow around the car as the first step. Secondary, the predicted pressure fluctuations were fed to the subsequent structural analysis to predict vibration accelerations on the inner surfaces of the test car. Finally, acoustical analysis was performed to predict sound fields in the test car by giving vibration accelerations computed by the structural analysis as the boundary conditions. In this paper, we focus on the unsteady flow computations, which is the first step of the coupled simulations. Large Eddy Simulation (LES) was performed to predict the pressure fluctuations on the outer surfaces of the test car. We used the computational mesh composed of approximately 5 billion hexahedral grids with a spatial resolution of 1.5 mm in the streamwise and spanwise directions to resolve the dynamics of the small vortices in the turbulence boundary layer. Predicted and measured pressure fluctuation at several sampling points on the surface of the test car were compared and they matched well in a wide range of frequency up to 2 kHz.

Large Eddy Simulation for a Deep Surge Cycle in a High-Speed Centrifugal Compressor With Vaned Diffuser

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Ibrahim Shahin ◽  
Mohamed Gadala ◽  
Mohamed Alqaradawi ◽  
Osama Badr
Keyword(s):  
High Pressure ◽  
Large Eddy Simulation ◽  
Centrifugal Compressor ◽  
Pressure Fluctuation ◽  
High Speed ◽  
Computational Study ◽  
Mean Flow ◽  
Vaned Diffuser ◽  
Eddy Simulation ◽  
Large Eddy

This paper presents a computational study for a high-speed centrifugal compressor stage with a design pressure ratio equal to 4, the stage consisting of a splittered unshrouded impeller and a wedged vaned diffuser. The aim of this paper is to investigate numerically the modifications of the flow structure during a surge cycle. The investigations are based on the results of unsteady three-dimensional, compressible flow simulations, using large eddy simulation (LES) model. Instantaneous and mean flow field analyses are presented in the impeller inducer and in the vaned diffuser region through one surge cycle time intervals. The computational data compare favorably with the measured data, from the literature, for the same compressor and operational point. The surge event phases are well detected inside the impeller and diffuser. The time-averaged loading on the impeller main blade is maximum near the trialing edge and near the tip. The amplitude of the unsteady pressure fluctuation is maximum for the flow reversal condition and reaches values up to 70% of the dynamic pressure. The diffuser vane exhibits high-pressure fluctuation from the vane leading edge to 50% of the chord length. High-pressure fluctuation is detected during the forward flow recovery condition as a result of the shock wave that moves toward the diffuser outlet.

Sign in / Sign up

Export Citation Format

Share Document