Large Eddy Simulation of Effects of Primary Rocket jet on Low Frequency Combustion Instability in a RBCC Combustor

2015 ◽  
Author(s):  
Zhiwei Huang ◽  
Guoqiang He ◽  
Fei Qin ◽  
Xianggeng Wei ◽  
Donggang Cao
Keyword(s):  
Large Eddy Simulation ◽  
Combustion Instability ◽  
Low Frequency ◽  
Eddy Simulation ◽  
Large Eddy

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.

Large Eddy Simulation of Laminar and Turbulent Shock/Boundary Layer Interactions in a Transonic Passage

2020 ◽  
Author(s):  
Stephan Priebe ◽  
Daniel Wilkin ◽  
Andy Breeze-Stringfellow ◽  
Giridhar Jothiprasad ◽  
Lawrence C. Cheung
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Low Frequency ◽  
Boundary Layer Separation ◽  
Eddy Simulation ◽  
Turbulent Inflow ◽  
Wide Range ◽  
Large Eddy ◽  
Constant Radius ◽  
Structure Boundary

Abstract Shock/boundary layer interactions (SBLI) are a fundamental fluid mechanics problem relevant in a wide range of applications including transonic rotors in turbomachinery. This paper uses wall-resolved large eddy simulation (LES) to examine the interaction of normal shocks with laminar and turbulent inflow boundary layers in transonic flow. The calculations were performed using GENESIS, a high-order, unstructured LES solver. The geometry created for this study is a transonic passage with a convergent-divergent nozzle that expands the flow to the desired Mach number upstream of the shock and then introduces constant radius curvature to simulate local airfoil camber. The Mach numbers in the divergent section of the transonic passage simulate single stage commercial fan blades. The results predicted with the LES calculations show significant differences between laminar and turbulent SBLI in terms of shock structure, boundary layer separation and transition, and aerodynamic losses. For laminar flow into the shock, significant flow separation and low-frequency unsteadiness occur, while for turbulent flow into the shock, both the boundary layer loss and the low-frequency unsteadiness are reduced.

Analysis of Flow Physics and Jet-Mainstream Interaction in Leading Edge Filmcooling Using Large Eddy Simulation

2006 ◽  
Author(s):  
Ali Rozati ◽  
Danesh K. Tafti
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Low Frequency ◽  
Vortex Pair ◽  
Leading Edge ◽  
Windward Side ◽  
Stagnation Line ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Counter Rotating Vortex Pair

A numerical investigation is conducted to study leading edge film cooling at a compound angle with Large Eddy Simulation (LES). The domain geometry is adopted from an experimental set-up (Ekkad et al. [14]) where turbine blade leading edge is represented by a semi-cylindrical blunt body. The leading edge has two rows of coolant holes located at ±15° of the stagnation line. Coolant jets are injected into the flow field at 30° (spanwise) and 90° (streamwise). Reynolds number of the mainstream is 100,000 and jet to mainstream velocity and density ratios are 0.4 and 1.0, respectively. The results show the existence of an asymmetric counter-rotating vortex pair in the immediate wake of the coolant jet. In addition to these primary structures, vortex tubes on the windward side of the jet are convected downstream over and to the aft- and fore-side of the counter-rotating vortex pair. All these structures play a role in the mixing of mainstream fluid with the coolant. A turbulent boundary layer forms within 2 jet diameters downstream of the jet. A characteristic low frequency interaction between the jet and the mainstream is identified at a non-dimensional frequency between 0.79 and 0.95 based on jet diameter and velocity. The spanwise averaged adiabatic effectiveness agrees well with the experiments when fully-developed turbulence is used to provide time-dependent boundary conditions at the jet inlet, without which the calculated effectiveness is overpredicted.

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.

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