Growth of Flame Front Turbulence

1986 ◽  
Vol 108 (4) ◽  
pp. 877-881 ◽  
Author(s):  
T. Tsuruda ◽  
M. Harayama ◽  
T. Hirano
Keyword(s):  
Experimental Study ◽  
Combustion Chamber ◽  
Flame Front ◽  
Pressure Wave ◽  
High Speed ◽  
Wall Turbulence ◽  
Pressure Waves ◽  
Fuel Type ◽  
Fuel Concentration ◽  
Schlieren Photography

An experimental study was performed on the growth of flame front turbulence by stimulating a laminar propagating flame with weak pressure waves, which were generated by sudden breaking of the membrane separating a small chamber from the combustion chamber. The flame front behavior was explored by using high-speed schlieren photography. About one millisecond after the first weak pressure wave passed the flame front, a very fine disturbance appeared at the central part of the flame front, where no effect of the wall turbulence could appear. Then, the area and strength of the disturbance were observed to increase rapidly. The effects of the pressure wave intensity, fuel concentration, and fuel type on the growth of this type of flame front turbulence were examined in detail.

Predicting Flashback Limits of a Gas Turbine Model Combustor Based on Velocity and Fuel Concentration for H2-Air-Mixtures

2016 ◽  
Author(s):  
Matthias Utschick ◽  
Daniel Eiringhaus ◽  
Christian Köhler ◽  
Thomas Sattelmayer
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
High Speed ◽  
Air Flow ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Injector ◽  
Trailing Edge ◽  
Fuel Concentration ◽  
Turbine Model

This study investigates the influence of the fuel injection strategy on safety against flashback in a gas turbine model combustor with premixing of H2-air-mixtures. The flashback propensity is quantified and the flashback mechanism is identified experimentally. The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow-injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). Velocity and mixing fields in mixing zone and combustion chamber in isothermal water flow were measured with High-speed-Particle-Image-Velocimetry (PIV) and Highspeed-Laser-Induced-Fluorescence (LIF). The flashback limit was determined under atmospheric pressure for three air mass flows and 673 K preheat temperature for H2-air-mixtures. Flashback mechanism and trajectory of the flame tip during flashback were identified with two stereoscopically oriented intensified high-speed cameras observing the OH* radiation. We notice flashback in the core flow due to Combustion Induced Vortex Breakdown (CIVB) and Turbulent upstream Flame Propagation (TFP) near the wall dependent on the injector type. The Flashback Resistance (FBR) defined as the ratio between a characteristic flow speed and a characteristic flame speed measures the direction of propagation of a turbulent flame in the flow field. Although CIVB cannot be predicted solely based on the FBR, its distribution gives evidence for CIVB-prone states. The fuel should be injected preferably isokinetic to the air flow along the entire trailing edge in oder to reduce the RMS fluctuation of velocity and fuel concentration. The characteristic velocity in the entire cross section of the combustion chamber inlet should be at least twice the characteristic flame speed. The position of the stagnation point should be tuned to be located in the combustion chamber by adjusting the axial momentum. Those measures lead to safe operation with highly reactive fuels at high equivalence ratios.

Predicting Flashback Limits of a Gas Turbine Model Combustor Based on Velocity and Fuel Concentration for H2–Air Mixtures

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Matthias Utschick ◽  
Daniel Eiringhaus ◽  
Christian Köhler ◽  
Thomas Sattelmayer
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
High Speed ◽  
Air Flow ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Injector ◽  
Trailing Edge ◽  
Fuel Concentration ◽  
Turbine Model

This study investigates the influence of the fuel injection strategy on safety against flashback in a gas turbine model combustor with premixing of H2–air mixtures. The flashback propensity is quantified and the flashback mechanism is identified experimentally. The A2EV swirler concept exhibits a hollow, thick-walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow injector (JICI)). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector (TEI)). Velocity and mixing fields in mixing zone and combustion chamber in isothermal water flow were measured with high-speed particle image velocimetry (PIV) and high-speed laser-induced fluorescence (LIF). The flashback limit was determined under atmospheric pressure for three air mass flows and 673 K preheat temperature for H2–air mixtures. Flashback mechanism and trajectory of the flame tip during flashback were identified with two stereoscopically oriented intensified high-speed cameras observing the OH* radiation. We notice flashback in the core flow due to combustion-induced vortex breakdown (CIVB) and turbulent flame propagation (TFP) near the wall dependent on the injector type. The flashback resistance (FBR) defined as the ratio between a characteristic flow speed and a characteristic flame speed measures the direction of propagation of a turbulent flame in the flow field. Although CIVB cannot be predicted solely based on the FBR, its distribution gives evidence for CIVB-prone states. The fuel should be injected preferably isokinetic to the air flow along the entire trailing edge in order to reduce the RMS fluctuation of velocity and fuel concentration. The characteristic velocity in the entire cross section of the combustion chamber inlet should be at least twice the characteristic flame speed. The position of the stagnation point should be tuned to be located in the combustion chamber by adjusting the axial momentum. Those measures lead to safe operation with highly reactive fuels at high equivalence ratios.

Validation of ATHLET Code by LOCA-Induced Pressure Wave Propagation Tests

2014 ◽  
Author(s):  
István Trosztel ◽  
Iván Tóth ◽  
György Ézsöl
Keyword(s):  
Wave Propagation ◽  
Flow Rate ◽  
Pressure Wave ◽  
High Speed ◽  
Low Frequency ◽  
Test Facility ◽  
Primary System ◽  
Pressure Waves ◽  
Test Results ◽  
System Pressure

Propagation of pressure waves inside the reactor vessel after a large break LOCA is an issue since it affects pressure drop across core internals and, as a result, induces stresses in different components, like core barrel, core structures and even fuel. For reactor safety analysis pressure wave propagation is traditionally performed by systems codes. However, strong dispersion among the calculated results calls for test results to validate the calculations. The pressure wave propagation following a larger LOCA is being systematically addressed by experiments in the PMK-2 integral-type test facility. In order to capture the high speed propagation of pressure waves special pressure transducers (capable to resolve the pressure variation with a frequency of 4 kHz) have been installed. The first four tests were conducted with rupture disks for opening the break, but a special quick opening valve will be installed for future tests, allowing the adjustment of the opening time between 12 and 50 ms. The paper presents results of validation of the ATHLET code by the test results. The low-frequency oscillation of the measured system pressure was shown to be caused by flow rate coming from the pressuriser that compensates mass lost via the break: the frequency of the oscillation was slightly under-predicted. The propagation of the first rarefaction wave from the top of the downcomer to the upper plenum is very well calculated by ATHLET: in spite of the first order discretisation no numerical diffusion can be observed. The calculated pressure differences between two different locations in the system are of primary interest, since they define the loads on primary system internals. ATHLET somewhat overestimates the amplitude of the pressure difference pulses, while it fairly well describes the frequency of oscillations. First analyses indicate an effect of the calculated break flow rate. ATHLET calculates a slower attenuation of the pressure oscillations as compared to test results. This can be the consequence of rigid walls assumed in the analysis. The tendency of increasing first pressure peak with increasing system pressure is well predicted by the code. In summary, it can be stated that ATHLET calculations produce slightly conservative results based on comparison with measured data.

Pressure wave characteristics of a high-speed train in a tunnel according to the operating conditions

2017 ◽  
Vol 232 (3) ◽  
pp. 928-935 ◽  
Author(s):  
Joon-Hyung Kim ◽  
Joo-Hyun Rho
Keyword(s):  
Numerical Analysis ◽  
Pressure Wave ◽  
High Speed ◽  
High Reliability ◽  
Rate Of Change ◽  
Operating Conditions ◽  
Pressure Waves ◽  
High Speed Train ◽  
Wave Characteristics ◽  
Pressure Characteristics

The pressure waves of a high-speed train in a tunnel exhibit complicated variations in their characteristics because the waves propagate and reflect with superposition. Studies have been consistently carried out on the pressure waves of a single train since changes in the area of pressure is a key element that influences ride comfort. Recently, the frequency of the operation of coupled trains has increased in order to improve the efficiency of running a train. The cross-sectional area of a train entering a tunnel has a rate of change that greatly influences the pressure characteristics; therefore, a coupled train can have different pressure characteristics when compared to a single train. However, adequate research works have not been done to assess these characteristics. To this end, the pressure characteristics of a train according to the operating conditions are investigated in this study. A high-speed train operating in practice and a tunnel located in a service section were chosen for this study, and the pressure characteristics of a single train were assessed via numerical analysis and an experiment. The numerical analysis was carried out with high reliability by comparing and verifying each result. After the pressure wave characteristics caused by running a coupled train had been assessed by the established numerical analysis, an obvious pressure variation was confirmed to occur at the connecting point. In addition, the maximum pressure applied to a tunnel and a passenger car increased. Thus, the aerodynamic effect of a coupled train should be considered as an important parameter in the early design state of a new high-speed train.

The Effect from Hole Area on Pressure Waves Produced by a High-Speed Train through Tunnel with Perforated Wall

2011 ◽  
Vol 94-96 ◽  
pp. 1733-1736
Author(s):  
Yuan Gui Mei ◽  
Yong Xing Jia
Keyword(s):  
Numerical Method ◽  
Pressure Wave ◽  
High Speed ◽  
Method Of Characteristics ◽  
Pressure Waves ◽  
High Speed Train ◽  
One Dimensional ◽  
Isentropic Flow ◽  
Perforated Wall ◽  
Hole Area

The perforated wall has great effect on pressure waves produced by high-speed train through a tunnel. In this paper the effect is investigated numerically by the method of characteristics based on one-dimensional unsteady compressible non-isentropic flow theory. The numerical method is validated by experimental results of Netherlands NLR. The effect from hole area in perforated wall is investigated principally and the results shows that the pressure wave is alleviated remarkably in tunnel with perforated wall.

Iterative learning control of air pressure variation inside a high-speed train under the excitation of the tunnel pressure wave with a fixed-morphologic form

2021 ◽  
pp. 095440972110327
Author(s):  
Zhiying He ◽  
Chunjun Chen ◽  
Dongwei Wang ◽  
Chao Deng ◽  
Jia Hu ◽  
...  
Keyword(s):  
Iterative Learning Control ◽  
Pressure Wave ◽  
High Speed ◽  
Learning Control ◽  
Pressure Variation ◽  
Iterative Learning ◽  
Air Pressure ◽  
High Speed Train ◽  
Comfort Index ◽  
Simulation Signal

Based on the characteristics that the tunnel pressure wave has a fixed-morphologic form when the same train passes through the same tunnel, an applicational approach based on the iterative learning control (ILC) is developed, aiming at overcoming the drawbacks of the traditional strategy for controlling the air pressure variation inside a high-speed train carriage. To achieve the goal, the control system is mathematically modelled. Then, the problem is formulated. The task of suppressing the influence of the tunnel pressure wave on the air pressure inside the carriages is shifted as an ILC problem of tracking the comfort index with varying trial length. The algorithm of refreshing the control signal from trial to trial is determined and the process of ILC control is designed. Next, the convergence of the newly-developed applicational ILC algorithm is discussed and the algorithm is simulated by the simulation signal and field-test signal. Results show that the applicational ILC algorithm be more adaptable in handling the control of the air pressure inside carriage under the excitation of varying-amplitude, varying-scale and varying-initial-states tunnel pressure wave. Meanwhile, the matching with tunnel pressure wave makes the applicational ILC algorithm will take both the riding comfort and fresh air into consideration, which upgrades the performances when the high-speed train passing through long tunnels.

Experimental study on laminated glass responses of high-speed trains subject to windblown sand particles loading

2021 ◽  
Vol 300 ◽  
pp. 124332
Author(s):  
Gongxun Deng ◽  
Wen Ma ◽  
Yong Peng ◽  
Shiming Wang ◽  
Song Yao ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Laminated Glass ◽  
Windblown Sand ◽  
High Speed Trains ◽  
Sand Particles
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