scholarly journals Numerical Investigation of the Plasma-Assisted MILD Combustion of a CH4/H2 Fuel Blend Under Various Working Conditions

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Seyed Mahmood Mousavi ◽  
Reza Kamali ◽  
Freshteh Sotoudeh ◽  
Nader Karimi ◽  
Bok Jik Lee
Keyword(s):  
Reynolds Number ◽  
Working Conditions ◽  
Plasma Flow ◽  
Reacting Flow ◽  
Fuel Blend ◽  
Structural Modifications ◽  
Mild Combustion ◽  
Plasma Injection ◽  
Mass Fractions ◽  
Thermal Nox

Abstract The effects of plasma injection upon MILD combustion of a mixture of methane and hydrogen are investigated numerically. The injected plasma includes the flow of a highly air-diluted methane including C2H2, C2H4, C2H6, CH, CH2, CH3, CO, and CO2. The results show that among all the constitutes of plasma, CH3 is the most effective in improving the characteristics of MILD combustion. Injection of this radical leads to the occurrence of reactions at a closer distance to the burner inlet and thus provides longer time for completion of combustion. Further, mass fractions of OH, CH2O, and HCO are considerably affected by the injections of CH3, indicating structural modifications of the reacting flow. Importantly, as Reynolds number of the plasma flow increases, the volume and width of the flame decrease, while the formations of prompt and thermal NOx are intensified. However, injection of CH3, as plasma, reduces the emission of thermal NOx.

scholarly journals Flow Regimes and Heat Transfer Characteristics in Combustion Chambers

2015 ◽  
Vol 12 (2) ◽  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Swirling Flow ◽  
Local Heat Transfer ◽  
Reacting Flow ◽  
Heat Transfer Characteristics ◽  
Swirl Number ◽  
Number Range ◽  
Transfer Characteristics ◽  
Combustor Liner

This paper presents a numerical computations are performed to investigate the convective heat transfer characteristics of a gas turbine can combustor under non reacting flow conditions in a Reynolds number range 50,000 to 600,000 with a characteristic swirl number of 0.7. A sample of computational predictions of flow behaviors under reacting conditions are also shown for swirling furnace flow of 0.52. The RNG (K-ɛ Model) predictions are compared with the experimental data of local heat transfer distribution on the combustor liner wall. It was observed that the flow field in the combustor is characterized by an expanding swirling flow, which impinges on the liner wall close to the inlet of the combustor. The peak heat transfer augmentation ratio (compared with fully developed pipe flow) reduces from 10.5 to 2.7. Additionally, the peak location does not change with Reynolds number since the flow structure in the combustor is also a function of the swirl number. The size of the corner recirculation zone near the combustor liner remains the same for all Reynolds numbers and hence the location of shear layer impingement and peak augmentation does not change. The heat transfer coefficient distribution on the liner wall predicted from the RNG (K-ɛ Model) is in good agreement with experimental values. The location and the magnitude of the peak heat transfer are predicted in very close agreement with the experiments.

The structure of the convection sustained ion sheath

1976 ◽  
Vol 54 (15) ◽  
pp. 1627-1636
Author(s):  
P. R. Smy
Keyword(s):  
Reynolds Number ◽  
Electric Field ◽  
Electron Temperature ◽  
Electron Density ◽  
Plasma Flow ◽  
Ion Mobility ◽  
Free Space ◽  
Characteristic Length ◽  
Electron Charge ◽  
Detailed Structure

The detailed structure of the convection sustained ion sheath has been examined. With Re = vfL/μikTe/e (the electric Reynolds number) and α = (ε0kTe/nee2)1/2(1/L), where vf = plasma flow velocity, μi = ion mobility, k = Boltzmann's constant, Te = electron temperature, e = electron charge, ε0 = permittivity of free space, ne = electron density, and L = characteristic length, it is found that for [Formula: see text], no 'presheath' or diminution of electron density outside the sheath is evident, whereas for [Formula: see text], a very substantial density gradient exists which is in fact similar to the quasi-neutral region which occurs in stationary plasmas. Calculations are presented which enable ion and electron densities and electric field and potential to be calculated through the presheath and sheath regions.

Reacting flow as an example of a boundary layer under singular external conditions

1969 ◽  
Vol 38 (3) ◽  
pp. 513-535 ◽  
Author(s):  
Raul Conti ◽  
Milton Van Dyke
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Inviscid Flow ◽  
Second Order ◽  
Order Effects ◽  
Reacting Flow ◽  
First Order ◽  
Rate Of Reaction ◽  
External Conditions ◽  
Quantitative Results

An inviscid flow with infinite gradients at the wall poses a problem for the accompanying boundary layer that is fundamentally different from the conventional one of bounded gradients. It turns out that in both cases the external gradients do not affect the first-order boundary layer, but the unbounded gradients generate second-order corrections that are of a lower order in Reynolds number than the conventional ones. The present singularity in stagnation-point reacting flow is of an algebraic type, and the boundary-layer corrections that it generates are proportional to non-integral powers of the Reynolds number, with exponents that vanish with the rate of reaction. The present example clarifies such matters as the matching of boundary layer and singular inviscid flow, the structure and decay of the new corrections, and their ranking in comparison with the conventional second-order effects. Numerical computations illustrate the problem and give quantitative results in a few selected cases.

scholarly journals Air-side heat transfer enhancement by self-agitators

2019 ◽  
Author(s):  
◽  
Kuojiang Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Working Conditions ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Flow Mixing

Airfoil-based self-agitators (AFAs), bio-inspired rectangular-shaped self-agitators (RSAs), and caudal-fin inspired hourglass-shaped self-agitators (CHSAs) were installed inside plate-fin heat exchanger. The heat transfer enhancement and pressure drop characteristics of these AFAs, RSAs, CHSAs design were experimentally investigated and compared with the clean channel case. We found that the self-agitators vibrate periodically and generate vortices, which enhance flow mixing and thus heat transfer performance. For the chosen heat sink and assigned working conditions, the best heat transfer performance was obtained with four rows AFAs, which caused an 80% increase in overall Nusselt Number over the clean channel at same Reynolds Number, and a 50% rejected heat increase at the same pumping power due to the strong longitudinal vortices generated by the presence of the AFAs. Experiments were conducted at a wide range of Reynolds numbers from 400 to 10000, which covered laminar-transitional-turbulent regime with CHSAs. Experimental correlations of the pressure drop as a function of dimension parameter and friction factor and Nusselt number as functions of dimensionless ones have been proposed. Mutual coupling motions and effects of multiple-row flapping CHSAs in parallel and tandem configurations were studied by using a high-speed camera. A stereo Particle Image Velocimetry (PIV) system was used to conduct detailed flow field measurements to quantify the flow mixing level. For the chosen plate-fin heat exchanger and assigned working conditions, the best heat transfer performance was obtained with six-row CHSAs with a pitch of 25mm, which caused a 200% increase in the Nusselt number over the clean channel at the same Reynolds number. However, the best overall performance was obtained with twelve-row CHSAs with a pitch of 12.5mm, which caused a 68% enhancement in thermal-hydraulic characteristic compared to the clean channel at the same Reynolds number.

Numerical Study of Turbulent Flow in a Tangentially Injected Swirl Generator

2007 ◽  
Author(s):  
Sandeep Mogili ◽  
Jie Cui
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Momentum Flux ◽  
Numerical Study ◽  
Fixed Ratio ◽  
Flux Ratio ◽  
Reacting Flow ◽  
Momentum Flux Ratio ◽  
Swirl Generator ◽  
Swirl Intensity

The swirl effects in inert and reacting flow systems have been studied for many years. Some processes have appreciated the presence of swirl while some have entitled to curtail the swirl. The swirl intensity is an important parameter in characterizing flows with swirl. In this study, the turbulent flow in a tangentially injected swirl generator was analyzed using commercial CFD software Fluent. The Reynolds numbers considered were 12,500, 15,300, and 30,600 for a fixed ratio of tangential to total momentum flux of 7.84. At Reynolds number 12,500, several cases with various injector configuration and momentum flux ratio were also studied. The numerical results were validated with available experimental data. The results showed that the flow in the generator can be classified into two regions, core and annulus. Reversed flow region was observed in all these cases. The swirl intensity was found to decay exponentially along the axial lengths. The simulations also showed that the swirl intensity was significantly affected by the momentum flux ratio and the Reynolds number.

Improvement of One-Dimensional Analytical Model of Rotating Long Orifice with Chamfered or Radiused Inlet

2013 ◽  
Vol 444-445 ◽  
pp. 320-331
Author(s):  
Hong Wu ◽  
Peng Li ◽  
Dong Dong Liu ◽  
Zhi Tao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Analytical Model ◽  
Working Conditions ◽  
Low Reynolds Number ◽  
Pressure Ratio ◽  
Acceptable Error ◽  
One Dimensional ◽  
Low Reynolds

In this paper, computational fluid dynamics calculations were conducted under various kinds of complex working conditions for rotating long orifice. As one of the most important structures of throttling and pressure limiting, orifice plays a significant role in flow control of the whole system. The existing empirical correlation was improved by correction on characteristics of low Reynolds number and compressibility. Then, improved one-dimensional analytical model of rotating long orifice with chamfered or radiused inlet was developed by programming. The model was verified against the results of commercial computational fluid dynamics codes. It turns out that the model has high precision, excellent convergence, and can predict the flow parameters under working conditions of low Reynolds number, supersonic and high pressure ratio with an acceptable error. And only geometric features, rotational speed and boundary conditions are required for one-dimensional modeling. Thus, it can be applied in the one-dimensional calculation and design of secondary air system widely.

Frictional Flow Properties of Coal-Oil Slurries at Low Reynolds Number

1986 ◽  
Vol 108 (3) ◽  
pp. 211-213
Author(s):  
E. W. Beans ◽  
K. C. Masiulaniec
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Particle Distribution ◽  
Reynolds Numbers ◽  
Loss Coefficient ◽  
Flow Properties ◽  
Pressure Loss Coefficient ◽  
Mass Fractions ◽  
Established Relationship

The pipe friction factor (f) and the pressure loss coefficient for a 90-deg EL (K90) were measured for coal-oil slurries at Reynolds numbers less than 100. A range of mass fractions (0 to 0.4) was examined for a single particle distribution. The pipe friction factor correlated well with the established relationship for laminar flow (f = 64/ReD) where Reynolds number is based on slurry properties. The loss coefficient for the elbow has a similar correlation.

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