Effect of Equivalence Ratio on Propagation Process of Combustible Gas in Venting Tube

2012 ◽  
Vol 442 ◽  
pp. 402-406
Author(s):  
Shao Feng Ren ◽  
Xian Feng Chen ◽  
Yu Jie Wang ◽  
Yin Zhang
Keyword(s):  
Numerical Simulation ◽  
Equivalence Ratio ◽  
Turbulent Model ◽  
Propagation Process ◽  
Pressure Release ◽  
Combustion Models ◽  
Combustible Gas ◽  
Ratio Change ◽  
Simulation Results

To explore the effect of equivalence ratio on the propagation process of combustible gas in the venting tube, in the present study, the κ-ε turbulent model and the combustion models were implemented base on unaltered venting conditions and different equivalence ratio of methane-air. In particular, the numerical simulation results illustrate both speed and pressure were at maximum when equivalence ratio was 1.0. However, methane-air didn't reach the most sufficient combustion when equivalence ratio was 1.0. It was possible that the pressure release caught the equivalence ratio change and failed to generate detonation.

Numerical Investigation of Combustion Instabilities in a Single Element Lean Direct Inject (LDI) Combustor Using Flamelet Based Approaches

2019 ◽  
Author(s):  
Saurabh Patwardhan ◽  
Pravin Nakod ◽  
Stefano Orsino ◽  
Carlo Arguinzoni
Keyword(s):  
Experimental Data ◽  
Equivalence Ratio ◽  
Single Element ◽  
Pressure Amplitude ◽  
Combustion Instabilities ◽  
Time Step ◽  
Impedance Boundary ◽  
Combustion Models ◽  
Flamelet Generated Manifold ◽  
Simulation Results

Abstract In this paper, high-fidelity large eddy simulations (LES) along with flamelet based combustion models are assessed to predict combustion dynamics in low-emissions gas turbine combustor. A model configuration of a single element lean-direct-injection (LDI) combustor from Purdue University [1] is used for the validation of simulation results. Two combustion models based on the flamelet concept, i.e., steady diffusion flamelet (SDF) model and flamelet generated manifold (FGM) model are employed to predict combustion instabilities. Simulations are carried out for two equivalence ratios of φ = 0.6, and 0.4 and the results in the form of mode shapes, peak to peak pressure amplitude and power spectrum density (PSD) are compared with the experimental data of Huang et al. [1]. The effect of variation in the time step size for transient simulations is also studied. The time step sizes corresponding to Acoustic Courant numbers of 4, 8 and 16 are tested. Further, two numerical solver options, i.e., pressure based segregated solver and pressure based coupled solver are used in understanding their effect on the solution convergence regarding the number of time steps required to reach the limit cycle of the pressure oscillations. An additional test for reducing the overall simulation time is explored using a truncated (half) calculation domain and applying an appropriate acoustic impedance boundary condition at the truncated location. The simulation results from this test for the equivalence ratio of φ = 0.6 are compared with the simulation results from the corresponding full domain test. Overall, the simulation results compare well with the experimental data and trends are captured accurately. A clear dominant acoustic mode of 4L is observed for the equivalence ratio of 0.6 that compares well with the experimental data. For the equivalence ratio of 0.4, simulation results show that there is no dominant frequency and the energy is distributed among the first five modes. It is consistent with the observations in the experiments. Both combustion models (SDF and FGM) used in this study capture the combustion instabilities accurately. It builds confidence in flamelet based combustion models for the use in combustion instability modeling which is traditionally done using finite rate chemistry models based on reduced kinetics.

scholarly journals Numerical Simulation Analysis of Cavitation Performance of Tandem Propeller

2018 ◽  
Vol 36 (3) ◽  
pp. 509-515 ◽  
Author(s):  
Xiaoxu Du ◽  
Zhengdong Zhang
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Cavitation Number ◽  
Hydrodynamic Characteristics ◽  
Turbulent Model ◽  
Cavitation Model ◽  
Cavitation Phenomenon ◽  
Cavitation Performance ◽  
Simulation Results ◽  
Good Agreement

The steady non cavitation hydrodynamic characteristics of CLB4-55-1 tandem propeller and the steady cavitation flows of NACA66 hydrofoil are numerically studied firstly based on the RANS equations of homogeneous multiphase using CFD theory, combined with the SST k-ω turbulent model and Z-G-B cavitation model. Numerical simulation results are in good agreement with the experimental results, which indicates that the numerical method is reliable and accurate. Then, the cavitation performance of the tandem propeller are numerical simulated and analyzed. The results show that the computational model can predict the cavitation performance of tandem propeller accurately. The cavitation performance of tandem propeller is nearly the same as single propeller, however, the cavitation phenomenon of back propeller is greater than the head propeller at certain advance coefficient and cavitation number. The cavitation phenomenon will disappear with the increase of the advance coefficient or the cavitation number.

Numerical Study of the Gas Flow in the Swirl Tube

2012 ◽  
Vol 550-553 ◽  
pp. 3194-3200
Author(s):  
Guang Cai Gao ◽  
Jian Jun Wang ◽  
You Hai Jin
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Reynolds Stress ◽  
Experimental Measurement ◽  
Gas Flow ◽  
Numerical Study ◽  
Separation Performance ◽  
Turbulent Model ◽  
Simulation Results ◽  
Good Agreement

The gas flow field in the swirl tube was studied by experimental measurement and numerical simulation. The results show that the simulation results based on the Reynolds stress turbulent model is in good agreement with the measured results probed by the five orifice Pitot-tube. Meantime, it is analyzed that there is short cut stream at the end of the exit tube, and at the dust discharge jaws, the particles are prone to be re-entrained from the hopper. All results above provide a base for further research on the optimization of the structure and the improvement of the separation performance of the swirl tube.

scholarly journals Numerical Simulation of Temperature Decrease in Greenhouses with Summer Water-Sprinkling Roof

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2435 ◽  
Author(s):  
Jiaming Guo ◽  
Yanhua Liu ◽  
Enli Lü
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Discrete Ordinates ◽  
Multiphase Model ◽  
Temperature Decrease ◽  
Turbulent Model ◽  
Flow Rates ◽  
Symmetrical Model ◽  
Simulation Results

Decreasing the temperature of a greenhouse in summer is very important for the growth of plants. To investigate the effects of a roof sprinkler on the heat environment of a greenhouse, a three-dimensional symmetrical model was built, in which a k-ε (k-epsilon) turbulent model, a DO (Discrete Ordinates) irrational model, a Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm, and a multiphase model were used to simulate the effects of the roof sprinkler, at different flow rates. Based on the simulation results, it was found that the temperature could be further reduced under a proper sprinkle rate, and the temperature distribution in the film on the roof was more uniform. A test was conducted to verify the accuracy of the model, which proved the validity of the numerical results. The simulation results of this study will be helpful for controlling and optimizing the heat environment of a greenhouse.

Numerical Simulation of Agitated Flow Field of Submersible Mixer Based on Computational Fluid Dynamics

2010 ◽  
Vol 34-35 ◽  
pp. 1545-1548
Author(s):  
Wei Xing Xu ◽  
Shou Qi Yuan
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Flow Field ◽  
Constant Velocity ◽  
Simulation Software ◽  
Volume Flow ◽  
The Body ◽  
Design Parameters ◽  
Turbulent Model ◽  
Simulation Results

The flow formulation is founded as console formulation first, and with the body-fitted coordinate system and standard turbulent model, the numerical simulation of the internal 3-D incompressible turbulent flow agitated flow field of submersible mixer is carried out by numerical simulation software Fluent. The results showed that: the mixer impeller produced vortex jet flow, the constant velocity lines advanced as ellipse, the velocity along the centerline are larger than others, and utilized volume flow to transport the liquid. And, by changing some design parameters of mixer impeller, we can compare and analyze the numerical simulation results and present some optimal methods.

Avalanche Features in Silicon Schottky-FETs in Accordance with Numerical Simulation Results

2006 ◽  
Vol 65 (16) ◽  
pp. 1533-1546
Author(s):  
Yu. Ye. Gordienko ◽  
S. A. Zuev ◽  
V. V. Starostenko ◽  
V. Yu. Tereshchenko ◽  
A. A. Shadrin
Keyword(s):  
Numerical Simulation ◽  
Simulation Results

Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish

2020 ◽  
pp. 095440622096768
Author(s):  
Jialei Song ◽  
Yong Zhong ◽  
Ruxu Du ◽  
Ling Yin ◽  
Yang Ding
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Efficiency ◽  
The Body ◽  
Caudal Fin ◽  
Fish Model ◽  
Swimming Efficiency ◽  
Simulation Results ◽  
Propulsive Mechanism ◽  
High Depth

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

scholarly journals Experiment and simulation about the effect of wear-ring abrasion on the performance of a marine centrifugal pump

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402199811
Author(s):  
Wu Xianfang ◽  
Du Xinlai ◽  
Tan Minggao ◽  
Liu Houlin
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Vibration Velocity ◽  
Test Results ◽  
Obvious Effect ◽  
Performance Change ◽  
Pump Test ◽  
Simulation Results ◽  
Axis Passing

The wear-ring abrasion can cause performance degradation of the marine centrifugal pump. In order to study the effect of front and back wear-ring clearance on a pump, test and numerical simulation were used to investigate the performance change of a pump. The test results show that the head and efficiency of pump decrease by 3.56% and 9.62% respectively at 1.0 Qd due to the wear-ring abrasion. Under 1.0 Qd, with the increase of the front wear-ring the vibration velocity at pump foot increases from 0.4 mm/s to 1.0 mm/s. The axis passing frequency (APF) at the measuring points increases significantly and there appears new characteristic frequency of 3APF and 4APF. The numerical simulation results show that the front wear-ring abrasion affects the flow at the inlet of the front chamber of the pump and impeller passage. And the back wear-ring abrasion has obvious effect on the flow in the back chamber of the pump and impeller passage, while the multi-malfunction of the front wear-ring abrasion and back wear-ring abrasion has the most obvious effect on the flow velocity and flow stability inside pump. The pressure pulsation at Blade Passing Frequency (BPF) of the three schemes all decrease with the increase of the clearance.

scholarly journals Development of Depth-Limited Wave Boundary Layers over a Smooth Bottom

2020 ◽  
Vol 9 (1) ◽  
pp. 27
Author(s):  
Hitoshi Tanaka ◽  
Nguyen Xuan Tinh ◽  
Xiping Yu ◽  
Guangwei Liu
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Boundary Layers ◽  
Wave Motion ◽  
Numerical Study ◽  
Experiment Data ◽  
Tidal Motion ◽  
Long Period ◽  
Simulation Results ◽  
Wave Boundary

A theoretical and numerical study is carried out to investigate the transformation of the wave boundary layer from non-depth-limited (wave-like boundary layer) to depth-limited one (current-like boundary layer) over a smooth bottom. A long period of wave motion is not sufficient to induce depth-limited properties, although it has simply been assumed in various situations under long waves, such as tsunami and tidal currents. Four criteria are obtained theoretically for recognizing the inception of the depth-limited condition under waves. To validate the theoretical criteria, numerical simulation results using a turbulence model as well as laboratory experiment data are employed. In addition, typical field situations induced by tidal motion and tsunami are discussed to show the usefulness of the proposed criteria.

Design of Impeller of Centrifugal Compressor for Water-Air Engine

2014 ◽  
Vol 496-500 ◽  
pp. 642-645
Author(s):  
Yun Wang ◽  
Wei Zhang
Keyword(s):  
Numerical Simulation ◽  
Power System ◽  
Centrifugal Compressor ◽  
Centrifugal Impeller ◽  
3D Design ◽  
Pump Impeller ◽  
Aero Engine ◽  
Simulation Results

In view of power system in water-air UAV requirements, combine with the centrifugal impeller for aero-engine and the pump impeller. The design of a impeller of centrifugal compressor can work on the air and in the water for the new concept of air-water engine. With 3D design and a 3D CFD solver on it and analysis the results of numerical simulation. Results show that the designed impeller successfully reached the goal on the air and in the water. The experiences accumulated in this procedure are useful for similar impeller aerodynamic designs.

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