APPLICATION OF A PARTIALLY STIRRED REACTOR MODEL FOR TAKING INTO ACCOUNT THE TURBULENCE-COMBUSTION INTERACTION ON THE BASIS OF REYNOLDS EQUATIONS

2018 ◽  
Vol 49 (8) ◽  
pp. 825-840 ◽  
Author(s):  
Anna Alexandrovna Shiryaeva
Keyword(s):  
Reactor Model ◽  
Reynolds Equations ◽  
Stirred Reactor ◽  
Partially Stirred Reactor

Modeling of Chemical Processes in a Diesel Engine With Alcohol Fuels

2007 ◽  
Vol 129 (4) ◽  
pp. 355-359 ◽  
Author(s):  
Nadir Yilmaz ◽  
A. Burl Donaldson
Keyword(s):  
Large Scale ◽  
Reaction Rates ◽  
Field Trials ◽  
Engine Oil ◽  
Cylinder Pressure ◽  
Reactor Model ◽  
Compression Ignition Engine ◽  
Chemical Reaction Kinetics ◽  
Stirred Reactor ◽  
Partially Stirred Reactor

Methanol utilization in a compression ignition engine has held tentative promise for a number of years, and, in fact, the concept has seen large scale field trials intended to demonstrate this option as a precursor to commercial implementation. However, results from those tests have identified some of the practical problems encountered with this fuel, namely, (1) its difficulty of vaporization and (2) its high autoignition temperature. Luminosity promoting additives, which facilitate radiative transport as a component of flame spread (because pure alcohol burns with little luminosity, continuum radiation as a reaction transport mechanism is essentially absent), intake air heating, active and passive heat sources, etc., represent some of the attempts to overcome limitations of these two factors. Except for intake air preheat, these augmentation methods have been noted to result in poor off-load thermal cycle efficiency. Focusing on the case of intake air preheat (which can be achieved by elevated compression ratio), and to model the chemical reaction kinetics, the partially stirred reactor model in CHEMKIN was used. This approach provided examination of the chemistry and reaction rates associated with an actual trial in which methanol was the fuel under study. To initiate this simulation, literature available reaction mechanisms were obtained, and then the experimental cylinder pressure history was matched by control of heat release rate via the partially stirred reactor model. This is represented within the reactor model by changing the turbulent mixing intensity factor. The overall reaction sequence, which models cylinder pressure, and attendant extent of reaction were the major focus. The minor focus included production of emission gases, e.g., the aldehydes and unburned fuel. Not only are the model results consistent with actual findings, they also support a method for addressing causes of off-load inefficiency and engine failures due to engine oil dilution with fuel.

scholarly journals Numerical simulation of a backward-facing step combustor using reynolds-averaged navier–stokes / extended partially stirred reactor model

2019 ◽  
Author(s):  
N. Petrova ◽  
V. Sabelnikov ◽  
N. Bertier
Keyword(s):  
Chemical Mechanism ◽  
Navier Stokes ◽  
Backward Facing Step ◽  
Reactor Model ◽  
Experimental Database ◽  
Eddy Simulation ◽  
Stirred Reactor ◽  
Tabulated Chemistry ◽  
Reynolds Averaged Navier Stokes ◽  
Partially Stirred Reactor

The authors adapt recently developed a large eddy simulation / extended partially stirred reactor (LES/EPaSR) model by Sabelnikov and Fureby for simulation of turbulent combustion to Reynolds-averaged Navier–Stokes (RANS) equations. The proposed RANS/EPaSR model is validated against experimental database created at ONERA for an air–methane premixed flame stabilized by a backward-facing step combustor. The RANS/EPaSR model is compared also with the following RANSbased combustion models: (i) quasi-laminar model with reduced chemical mechanism (QL RCM); (ii) premixed flamelet tabulated chemistry (PFTC) without taking into account the turbulence–chemistry interaction (TCI); and (iii) a PFTC with a presumed β probability density function (PDF) for a progress combustion variable.

A Multidisciplinary Approach for the Comprehensive Assessment of Integrated Rotorcraft–Powerplant Systems at Mission Level

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Ioannis Goulos ◽  
Fakhre Ali ◽  
Konstantinos Tzanidakis ◽  
Vassilios Pachidis ◽  
Roberto d'Ippolito
Keyword(s):  
Environmental Impact ◽  
Fuel Consumption ◽  
Comprehensive Assessment ◽  
Pollutant Emissions ◽  
Operational Performance ◽  
Civil Aviation ◽  
Accurate Estimation ◽  
Nox Emissions ◽  
Reactor Model ◽  
Stirred Reactor

This paper presents an integrated methodology for the comprehensive assessment of combined rotorcraft–powerplant systems at mission level. Analytical evaluation of existing and conceptual designs is carried out in terms of operational performance and environmental impact. The proposed approach comprises a wide-range of individual modeling theories applicable to rotorcraft flight dynamics and gas turbine engine performance. A novel, physics-based, stirred reactor model is employed for the rapid estimation of nitrogen oxides (NOx) emissions. The individual mathematical models are implemented within an elaborate numerical procedure, solving for total mission fuel consumption and associated pollutant emissions. The combined approach is applied to the comprehensive analysis of a reference twin-engine light (TEL) aircraft modeled after the Eurocopter Bo 105 helicopter, operating on representative mission scenarios. Extensive comparisons with flight test data are carried out and presented in terms of main rotor trim control angles and power requirements, along with general flight performance charts including payload-range diagrams. Predictions of total mission fuel consumption and NOx emissions are compared with estimated values provided by the Swiss Federal Office of Civil Aviation (FOCA). Good agreement is exhibited between predictions made with the physics-based stirred reactor model and experimentally measured values of NOx emission indices. The obtained results suggest that the production rates of NOx pollutant emissions are predominantly influenced by the behavior of total air inlet pressure upstream of the combustion chamber, which is affected by the employed operational procedures and the time-dependent all-up mass (AUM) of the aircraft. It is demonstrated that accurate estimation of on-board fuel supplies ahead of flight is key to improving fuel economy as well as reducing environmental impact. The proposed methodology essentially constitutes an enabling technology for the comprehensive assessment of existing and conceptual rotorcraft–powerplant systems, in terms of operational performance and environmental impact.

Coherent Flame Model to Predict Formation Pollutants in Turbulent Premixed Flame

2010 ◽  
Author(s):  
Abdelhalim Bentebbiche ◽  
Denis Veynante
Keyword(s):  
Kinetic Scheme ◽  
Turbulent Flames ◽  
Premixed Flame ◽  
Reactive Flow ◽  
Reactor Model ◽  
Turbulent Premixed Flame ◽  
No Formation ◽  
Stirred Reactor ◽  
Good Issue ◽  
Turbulent Premixed

The objective of this work is to analyze and to model the turbulent flames in the context of coherent flame model. We present a detailed description of equations and the flamelet regimes in turbulent premixed flame. A surface density models proposed here represents a good issue for numerical simulation. Extension of coherent flame model and homogenous stilled reactor model is proposed to consider the dynamics behavior of flame and pollutants formation. From the results of this work it is concluded that the coherent flame model allows surpassing difficulties of the turbulent reactive flow modeling. Calculations based on a semi-global kinetic scheme and flamelet formulation combined with a well stirred reactor analysis of the burnt gases are used and provided reasonably accurate values of CO and NO formation. Also, we have observed that CO is formed near the reaction zone (front flame) but emission of CO2, H2O and NO are formed in the hot gases.

Micro-Kinetic Study of Reduction of NO on Pt Group Catalysts

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Dinesh B Mantri ◽  
Preeti Aghalayam
Keyword(s):  
Reaction Mechanism ◽  
Surface Coverage ◽  
No Reduction ◽  
Catalytic Reduction ◽  
Effect Of Temperature ◽  
Exponential Potential ◽  
Reactor Model ◽  
Reduction Activity ◽  
Stirred Reactor ◽  
High Durability

Catalytic reduction using CO has significant potential for the control of NOx using Pt group catalysts as CO is already present in the exhausts and Pt group catalysts have high durability in the presence of SO2 and H2O. Different reaction mechanisms are given in the literature for this reaction based on NO dissociation, -NCO formation and so on, but the exact reaction mechanism capable of capturing experimentally observed features is as yet unavailable. To determine the kinetics and reaction mechanism, we propose here an elementary reaction mechanism based on NO dissociation applicable to Pt group catalysts and simulated with CHEMKIN 4.0.2 using single and multiple PSR (Perfectly Stirred Reactor) model. The activation energies of the elementary steps are found from the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. Excellent agreement between literature experiments and our simulation results are observed for the NO-CO reaction on Pt and Rh catalysts and for the NO-CO-O2 reaction on Ir catalyst. The effect of temperature on the NO reduction activity is captured well by the model. Additionally the simulations can also point towards importance of particular reactions, selectivity to N2, effects of surface coverage, effects of residence time and catalytic surface area on NO reduction.

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