scholarly journals The Eddy Dissipation Concept—Analysis of Different Fine Structure Treatments for Classical Combustion

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1902 ◽  
Author(s):  
Markus Bösenhofer ◽  
Eva-Maria Wartha ◽  
Christian Jordan ◽  
Michael Harasek
Keyword(s):  
Fine Structure ◽  
Turbulent Combustion ◽  
Flow Reactor ◽  
Plug Flow ◽  
Fine Fraction ◽  
Low Oxygen ◽  
Stirred Reactor ◽  
Structure Treatment ◽  
Study Species ◽  
Modeling Study

The Eddy Dissipation Concept (EDC) is common in modeling turbulent combustion. Several model improvements have been proposed in literature; recent modifications aim to extend its validity to Moderate or Intense Low oxygen Dilution (MILD) conditions. In general, the EDC divides a fluid into a reacting and a non-reacting part. The reacting part is modeled as perfectly stirred reactor (PSR) or plug flow reactor (PFR). EDC theory suggests PSR treatment, while PFR treatment provides numerical advantages. Literature lacks a thorough evaluation of the consequences of employing the PFR fine structure treatment. Therefore, these consequences were evaluated by employing tests to isolate the effects of the EDC variations and fine structure treatment and by conducting a Sandia Flame D modeling study. Species concentration as well as EDC species consumption/production rates were evaluated. The isolated tests revealed an influence of the EDC improvements on the EDC rates, which is prominent at low shares of the reacting fluid. In contrast, PSR and PFR differences increase at large fine fraction shares. The modeling study revealed significant differences in the EDC rates of intermediate species. Summarizing, the PFR fine structure treatment might be chosen for schematic investigations, but for detailed investigations a careful evaluation is necessary.

Experimental and kinetic modeling study of ethyl butanoate oxidation in a laminar tubular plug flow reactor

Fuel ◽  
2011 ◽  
Vol 90 (11) ◽  
pp. 3237-3253 ◽  
Author(s):  
H. Bennadji ◽  
P.A. Glaude ◽  
L. Coniglio ◽  
F. Billaud
Keyword(s):  
Kinetic Modeling ◽  
Flow Reactor ◽  
Plug Flow ◽  
Plug Flow Reactor ◽  
Ethyl Butanoate ◽  
Modeling Study

Reactor Design for Simple Reactions

2001 ◽  
Author(s):  
L. K. Doraiswamy
Keyword(s):  
General Class ◽  
Flow Reactor ◽  
Plug Flow ◽  
Reactor Design ◽  
Design Principles ◽  
Plug Flow Reactor ◽  
Organic Reactions ◽  
Variable Volume ◽  
Stirred Reactor

Ideal reactors and their design principles were discussed in Chapter 4. In addition to these ideal reactors, there are certain reactors in which a reasonably welldefined measure of mixing can be introduced. These are the recycle plug-flow reactor and a sequence of fully mixed reactors. Many organic reactions are conducted in a stirred reactor containing a batch of the same or a second reactant, and continuously feeding, or withdrawing, or feeding and withdrawing one or more of the reactants and/or products. These are referred to as semibatch reactors. They belong to a more general class of reactors known as variable volume reactors. The design of all of these types of reactors is briefly considered in this chapter. The principle of the recycle-flow reactor (RFR) is sketched in Figure 10.1.

A Strategy of Reactant Mixing in Methane Direct-Fired sCO2 Combustors

2018 ◽  
Author(s):  
K. R. V. Manikantachari ◽  
Scott Martin ◽  
Ladislav Vesely ◽  
Jose O. Bobren-Diaz ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Power Generation ◽  
Flow Reactor ◽  
Plug Flow ◽  
Kinetic Mechanism ◽  
Operating Conditions ◽  
Lean Burn ◽  
Initial Portion ◽  
Cross Sectional ◽  
Power Cycles ◽  
Stirred Reactor

The sCO2 power cycle concept is identified as a potentially efficient, economical, and pollutant free power generation technique for future power generation. Recent work in the literature provides some strategies and best operating conditions for direct-fired sCO2 combustors based on zero-dimensional reactor modeling analysis, however there is a need for a detailed investigation using accurate combustion chemical kinetics and thermophysical models. Here, the sCO2 combustor is modelled by coupling perfectly stirred reactor (PSR) and plug flow reactor (PFR) models. The real gas effects are incorporated using the Soave-Redlich-Kwong (SRK) equation of state. Also, the detailed Aramco 2.0 kinetic mechanism is used for the combustion kinetic rates. It is found that the primary zone must be diluted either with thirty or forty-five percent of the total CO2 in the cycle to have a feasible combustor design. However, the forty-five percent dilution level at 950 K and 1000 K yielded a better consumption of CO, O2 and CH4. Also, the cross-sectional area of the sCO2 combustor can be scaled-down to 10 to 20 times smaller than a traditional combustor with the same power output. Further, from this investigation, it is also recommended to have a gradually increasing secondary dilution in the dilution zone, by using progressively larger diameter holes. This design would help retain relatively high temperature in the initial portion of the dilution zone and would help consume fuel species such as, CO and CH4. It appears that, for sCO2 combustors “lean burn” is the better strategy over stoichiometric burning to eliminate CO build up at the combustor exit. The lean burn condition at equivalence ratio (ϕ) equal to 0.9 is recommended for sCO2 combustor operation. Also, the length of the dilution zone can be scaled-down to 50% by lean burn operation of the combustor. It is also observed that the lean burn increases the net turbine power. Current work provides crucial design considerations for the development of advanced sCO2 combustors to be used with direct-fired power cycles.

Effects of Hydrogen Fueling on NOx Emissions: A Reactor Model Approach for an Industrial Gas Turbine Combustor

2017 ◽  
Author(s):  
D. Kroniger ◽  
M. Lipperheide ◽  
M. Wirsum
Keyword(s):  
Gas Turbine ◽  
Flow Reactor ◽  
Plug Flow ◽  
Nox Emissions ◽  
Flame Zone ◽  
Gas Turbine Combustor ◽  
Reactor Model ◽  
Stirred Reactor ◽  
Set Up ◽  
Reactor Network

Addition of hydrogen (H2) to gas turbine fuel has recently become a topic of interest facing the global challenges of CO2 free combustion. As a drawback, Nitrogen oxide (NOx) emissions are likely to increase in hydrogen-rich fuel combustion which in return limits the use of the technology. In the course of this development, a model-based quantification of NOx emission increase by fuel flexibility may identify possible operation ranges of this technology. This paper evaluates the effect of an increased hydrogen fraction in the fuel on the NOx emissions of a non-premixed 10 MWth gas turbine combustor. A simple reactor network model has been set up using a perfectly stirred reactor (PSR) to simulate the flame zone and a plug flow reactor (PFR) to simulate the post flame zone. The change of residence time in the flame zone is accounted for by an empirical expression. The model is validated against data from high-pressure test rig experiments of an industrial non-premixed gas turbine combustor. The model results are in good agreement with the experimental data. Based on the model results, a fundamental correlation of the effect of hydrogen on the NOx emissions is formulated.

Soot particle size distributions in a well-stirred reactor/plug flow reactor

2007 ◽  
Vol 31 (1) ◽  
pp. 675-683 ◽  
Author(s):  
Samuel L. Manzello ◽  
David B. Lenhert ◽  
Ahmet Yozgatligil ◽  
Michael T. Donovan ◽  
George W. Mulholland ◽  
...  
Keyword(s):  
Particle Size ◽  
Soot Particle ◽  
Flow Reactor ◽  
Plug Flow ◽  
Plug Flow Reactor ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Stirred Reactor

A Strategy of Mixture Preparation for Methane Direct-Fired sCO2 Combustors

2018 ◽  
Author(s):  
K. R. V. Manikantachari ◽  
Scott Martin ◽  
Ladislav Vesely ◽  
Jose O. Bobren-Diaz ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Residence Time ◽  
Flow Reactor ◽  
Plug Flow ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Time Requirement ◽  
Stirred Reactor ◽  
Primary Zone ◽  
Real Gas Effects ◽  
Time Required

The reactor residence time required for a sCO2 combustor is comparatively higher than an equal power, airdiluted conventional combustor. Therefore, the strategies to reduce the reactor residence time are very important in the design of sCO2 combustors. The current work recommends a method to reduce the residence time requirement in the sCO2 combustion chamber. Here, the combustor is modelled by coupling the perfectly-stirred-reactor (PSR) and plug-flow-reactor (PFR) models along with the detailed Aramco 2.0 combustion chemical kinetic mechanism. The real gas effects are considered by using the Soave-Redlich-Kwong (SRK) equation of state incorporated in CHMEKIN-RG. Though, the CO emission level at the exit of the primary zone of the sCO2 combustor is lower or in some cases equal to the conventional combustor, the further decline of CO in the dilution zone is identified as very poor. Therefore, very high CO levels can be expected at the exit of the sCO2 combustor compared to conventional combustors. CO from the sCO2 combustor exhaust can be eliminated by lean operation of the combustor and the excess O2 retained in the re-cycled CO2 stream due to lean operation can be mixed with primary methane before entering the primary combustion zone. This strategy is shown to reduce the primary zone residence time requirement of sCO2 combustion. However, the minimum level of O2 in the re-cycled CO2 stream is approximately 5000 ppm and the minimum required residence time in this pre-mixing chamber is around 4 ms. Also, it is observed that the primary zone residence time requirement decreases linearly with respect to the O2 level in the re-cycled CO2 stream.

Modeling of enzymatic reaction in an airlift reactor using an axial dispersion model

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Ivan Sikula ◽  
Jozef Markoš
Keyword(s):  
Flow Reactor ◽  
Dispersion Model ◽  
Enzymatic Reaction ◽  
Plug Flow ◽  
Axial Dispersion ◽  
Airlift Reactor ◽  
Enzymatic Oxidation ◽  
Biochemical Processes ◽  
Stirred Reactor ◽  
Axial Dispersion Model

AbstractThis work was focused on modeling of biochemical processes in a 40-L internal-loop airlift reactor. Due to different mixing in the specific zones of the reactor four main sections, bottom, riser, separator and downcomer, were recognized. Each zone was modeled by an adequate mixing model: bottom and separator sections by the model of ideally-stirred reactor; riser and downcomer sections by the model of plug-flow reactor with axial dispersion. In the model, the effects of mass transfer, hydrodynamics, and reaction kinetics were taken into account. The model of the reactor was experimentally verified by the aerobic enzymatic oxidation of glucose to gluconic acid. Simulations are in good agreement with experimental data.

Allene oxidation in jet-stirred reactor : a kinetic modeling study

1990 ◽  
Vol 87 ◽  
pp. 1159-1172 ◽  
Author(s):  
P Dagaut ◽  
M Cathonnet ◽  
B Aboussi ◽  
JC Boettner
Keyword(s):  
Kinetic Modeling ◽  
Stirred Reactor ◽  
Allene Oxidation ◽  
Modeling Study

A stochastic model for two-station hydraulics exhibiting transient impact

1997 ◽  
Vol 36 (5) ◽  
pp. 19-26 ◽  
Author(s):  
J. L. Jacobsen ◽  
H. Madsen ◽  
P. Harremoès
Keyword(s):  
Parameter Estimation ◽  
Flow Reactor ◽  
Deterministic Model ◽  
Plug Flow ◽  
Stochastic Methods ◽  
Sewer System ◽  
Statistical Tool ◽  
Water Level Variation ◽  
Deterministic Description ◽  
Linear Reservoir

The objective of the paper is to interpret data on water level variation in a river affected by overflow from a sewer system during rain. The simplest possible, hydraulic description is combined with stochastic methods for data analysis and model parameter estimation. This combination of deterministic and stochastic interpretation is called grey box modelling. As a deterministic description the linear reservoir approximation is used. A series of linear reservoirs in sufficient number will approximate a plug flow reactor. The choice of number is an empirical expression of the longitudinal dispersion in the river. This approximation is expected to be a sufficiently good approximation as a tool for the ultimate aim: the description of pollutant transport in the river. The grey box modelling involves a statistical tool for estimation of the parameters in the deterministic model. The advantage is that the parameters have physical meaning, as opposed to many other statistically estimated, empirical parameters. The identifiability of each parameter, the uncertainty of the parameter estimation and the overall uncertainty of the simulation are determined.

Sign in / Sign up

Export Citation Format

Share Document