scholarly journals Development and validation of a reduced mechanism for methane using a new integral algorithm in a premixed flame

2014 ◽  
Vol 68 (5) ◽  
pp. 529-539
Author(s):  
Zuozhu Wu ◽  
Xinqi Qiao ◽  
Zhen Huang
Keyword(s):  
Reduction Process ◽  
Operating Conditions ◽  
Computational Domain ◽  
Fast Reaction ◽  
One Dimensional ◽  
Reduced Mechanism ◽  
Wide Range ◽  
Computational Singular Perturbation ◽  
Premixed Laminar ◽  
Development And Validation

A new algorithm based on Computational Singular Perturbation (CSP) is proposed to construct global reduced mechanism. The algorithm introduces species concentrations, species net production rates and heat release rates as integral weighting factors to integrate CSP-pointers, including radical pointers and fast reaction pointers, throughout the computational domain. A software package based on the algorithm was developed to make the reduction process more efficient. Input to the algorithm includes (i) the detailed mechanism, (ii) the numerical solution of the problem for a specific set of operating conditions, (iii) the number of quasi steady state (QSS) species. The proposed algorithm was applied to the reduction of GRI3.0 involving 53 species and 325 reactions leading to the development of a 15-species reduced mechanism with 10 lumped steps. Then the reduced mechanism was validated in a one-dimensional, unstretched, premixed, laminar steady flame over a wide range of equivalence ratio, and excellent agreements between results calculated with the detailed and the reduced mechanisms can be observed.

scholarly journals A criterion based on computational singular perturbation for the construction of reduced mechanism for dimethyl ether oxidation

2013 ◽  
Vol 78 (8) ◽  
pp. 1177-1188
Author(s):  
Zuozhu Wu ◽  
Xinqi Qiao ◽  
Zhen Huang
Keyword(s):  
Steady State ◽  
Singular Perturbation ◽  
Dimethyl Ether ◽  
Reduction Process ◽  
Operating Conditions ◽  
Quasi Steady State ◽  
Reduced Mechanism ◽  
Wide Range ◽  
Computational Singular Perturbation ◽  
Premixed Laminar

A criterion based on the computational singular perturbation (CSP) method is proposed in order to determine the number of quasi-steady state (QSS) species. This criterion is employed for the reduction of a detailed chemical kinetics mechanism for the oxidation of dimethyl ether (DME), involving 55 species and 290 reactions, leading to a 20 steps reduced mechanism which involves 26 species. A software package, named I-CSP, was developed to make the reduction process algorithmic. Input to the I-CSP includes (i) the detailed mechanism, (ii) the numerical solution of the problem for a specific set of operating conditions, (iii) the number of quasi steady state (QSS) species. The resulting reduced mechanism was validated both in homogenous reactor, including auto-ignition and PSR, over a wide range of pressures and equivalence ratios, and in a one-dimensional, unstretched, premixed, laminar steady DME/Air flame. Comparison of the results calculated with the detailed and the reduced mechanisms shows excellent agreement in the case of homogenous reactor, but discrepancies can be observed in the case of the premixed laminar flame.

A predictive combustion model for one-dimensional gasoline engine simulation

2020 ◽  
pp. 146808742094590
Author(s):  
Yoshihiro Nomura ◽  
Seiji Yamamoto ◽  
Makoto Nagaoka ◽  
Stephan Diel ◽  
Kenta Kurihara ◽  
...  
Keyword(s):  
Gasoline Engine ◽  
Early Stage ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Operating Conditions ◽  
Combustion Model ◽  
One Dimensional ◽  
Turbulent Reynolds Number ◽  
Proposed Model ◽  
Wide Range

A new predictive combustion model for a one-dimensional computational fluid dynamics tool in the multibody dynamics processes of gasoline engines was developed and validated. The model consists of (1) a turbulent burning velocity model featuring a flame radius–based transitional function, steady burning velocity that considers local quenching using the Karlovitz number and laminarization by turbulent Reynolds number, as well as turbulent flame thickness and its quenching model near the liner wall, and (2) a knock model featuring auto-ignition by the Livengood–Wu integration and ignition delay time obtained using a full-kinetic model. The proposed model and previous models were verified under a wide range of operating conditions using engines with widely different specifications. Good agreement was only obtained for combustion characteristics by the proposed model without requiring individual calibration of model constants. The model was also evaluated for utilization after prototyping. Improved accuracy, especially of ignition timing, was obtained after further calibration using a small amount of engine data. It was confirmed that the proposed model is highly accurate at the early stage of the engine development process, and is also applicable for engine calibration models that require higher accuracy.

Analysis of Gas Turbine Rotating Cavities by an One-Dimensional Model

2009 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Luca Innocenti ◽  
Mirko Micio
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Design Tool ◽  
Operating Conditions ◽  
Outer Flow ◽  
One Dimensional ◽  
Wide Range ◽  
Air System ◽  
Secondary Air ◽  
Radial Outflow

Reliable design of secondary air system is one of the main tasks for the safety, unfailing and performance of gas turbine engines. To meet the increasing demands of gas turbines design, improved tools in prediction of the secondary air system behavior over a wide range of operating conditions are needed. A real gas turbine secondary air system includes several components, therefore its analysis is not carried out through a complete CFD approach. Usually, that predictions are performed using codes, based on simplified approach which allows to evaluate the flow characteristics in each branch of the air system requiring very poor computational resources and few calculation time. Generally the available simplified commercial packages allow to correctly solve only some of the components of a real air system and often the elements with a more complex flow structure cannot be studied; among such elements, the analysis of rotating cavities is very hard. This paper deals with a design-tool developed at the University of Florence for the simulation of rotating cavities. This simplified in-house code solves the governing equations for steady one-dimensional axysimmetric flow using experimental correlations both to incorporate flow phenomena caused by multidimensional effects, like heat transfer and flow field losses, and to evaluate the circumferential component of velocity. Although this calculation approach does not enable a correct modeling of the turbulent flow within a wheel space cavity, the authors tried to create an accurate model taking into account the effects of inner and outer flow extraction, rotor and stator drag, leakages, injection momentum and, finally, the shroud/rim seal effects on cavity ingestion. The simplified calculation tool was designed to simulate the flow in a rotating cavity with radial outflow both with a Batchelor and/or Stewartson flow structures. A primary 1D-code testing campaign is available in the literature [1]. In the present paper the authors develop, using CFD tools, reliable correlations for both stator and rotor friction coefficients and provide a full 1D-code validation comparing, due to lack of experimental data, the in house design-code predictions with those evaluated by CFD.

scholarly journals Development and Validation of a Reduced DME Mechanism Applicable to Various Combustion Modes in Internal Combustion Engines

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Gregory T. Chin ◽  
J.-Y. Chen ◽  
Vi H. Rapp ◽  
R. W. Dibble
Keyword(s):  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Detailed Mechanism ◽  
Reduced Mechanism ◽  
Hcci Combustion ◽  
Combustion Modes ◽  
Reduced Chemistry ◽  
Wide Range ◽  
Development And Validation

A 28-species reduced chemistry mechanism for Dimethyl Ether (DME) combustion is developed on the basis of a recent detailed mechanism by Zhao et al. (2008). The construction of reduced chemistry was carried out with automatic algorithms incorporating newly developed strategies. The performance of the reduced mechanism is assessed over a wide range of combustion conditions anticipated to occur in future advanced piston internal combustion engines, such as HCCI, SAHCCI, and PCCI. Overall, the reduced chemistry gives results in good agreement with those from the detailed mechanism for all the combustion modes tested. While the detailed mechanism by Zhao et al. (2008) shows reasonable agreement with the shock tube autoignition delay data, the detailed mechanism requires further improvement in order to better predict HCCI combustion under engine conditions.

Ethanol Mechanism Reduction Based on DRGEPSA Method at Various Operating Ranges

2020 ◽  
Author(s):  
Shrabanti Roy ◽  
Omid Askari
Keyword(s):  
Sensitivity Analysis ◽  
Error Propagation ◽  
Cfd Simulation ◽  
Reduction Process ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Computational Time ◽  
Wide Range ◽  
Relation Graph ◽  
Future Work

Abstract Reducing the size of a detail chemical kinetic is necessary in the prospect of numerical computation. In this work a skeleton reduction is done on a detail mechanism of ethanol. The detailed ethanol mechanism used here is developed through reaction mechanism generator (RMG). The generated mechanism is validated at wide range of engine relevant operating conditions using laminar burning speed (LBS), ignition delay time (IDT) and species mole fraction calculation at different reactor conditions. This detail mechanism consists of 67 species and 1031 reactions. Though the mechanism is in a very good agreement at various operating ranges with experimental data, it is costly to use a detail mechanism for 3D computational fluid dynamics (CFD) analysis. To make the mechanism applicable for CFD simulation further reduction of species and reactions is essential. In this work a skeleton mechanism is generated using directed relation graph technique with error propagation and sensitivity analysis (DRGEPSA). The DRGEPSA method, works based on error calculation at user defined condition. This technique is a combination of two methods, directed relation graph with error propagation (DRGEP) and directed relation graph with sensitivity analysis (DRGASA). To ensure the wide range of applicability of the skeleton mechanism, IDT is calculated at temperature, pressure, and equivalence ratio ranges from 700–2000 K, 1–40 atm and 0.6–1.4 respectively. A 10% error estimation is considered during the process. Initially DRGEP is applied on the detail mechanism to eliminate unimportant species. Further, sensitivity analysis helps to identify and reduce more unimportant species from the mechanism. Reactions related to the deleted species are automatically removed from the mechanism in each step. The final skeleton mechanism has 42 species and 464 reactions. This skeleton mechanism is validated and compared with different IDT data for the conditions not used in reduction technique. Results of LBS and different species concentration from reactor conditions is considered for validation. The skeleton mechanism can reduce computational time by 35% for LBS and 25% for IDT calculation. For future work, this skeleton mechanism will be considered in optimum reduction process.

scholarly journals Meander-Like Shape Optimization of the Stator-Rotor Platform Cavity

2018 ◽  
Author(s):  
Paht Juangphanich ◽  
Guillermo Paniagua
Keyword(s):  
Geometry Optimization ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Practical Implementation ◽  
Computational Domain ◽  
Optimization Strategy ◽  
Minimum Thickness ◽  
Ansys Fluent ◽  
Driving Mechanisms ◽  
Wide Range

Recent progress in additive manufacturing has enabled opportunities to explore novel stator rim geometries which can be implemented to improve cooling strategies in turbomachinery. This paper presents a simplified stationary geometry optimization strategy to produce enhanced stator-rotor cavity sealing and highlights main driving mechanisms. The stator and rotor rims were designed using a design strategy based on inspiration from the meandering of rivers. A minimum thickness of 2mm was maintained throughout the cavity to ensure a practical implementation. The computational domain comprised of the stator outlet, hub disk leakage cavity, and rotor platform was meshed using NUMECA Int. package, Hexpress. The numerical analysis required 3D Unsteady Reynolds Average Navier-Stokes to replicate vorticial structures using Ansys Fluent. The operating conditions were representative of engine-like conditions, exploring a wide range of massflow ratios from 1 to 3%. The optimization yielded designs that provide 30% reduction in rear platform temperature while minimizing coolant massflow. The applicability of the design was compared against 3D sector in both stationary and in rotation.

Reduced Kinetic Mechanism for Reactive Flow Simulation of Syngas/Methane Combustion at Gas Turbine Conditions

2006 ◽  
Author(s):  
P. Gokulakrishnan ◽  
S. Kwon ◽  
A. J. Hamer ◽  
M. S. Klassen ◽  
R. J. Roby
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Kinetic Mechanism ◽  
Operating Conditions ◽  
Reactive Flow ◽  
Reduced Mechanism ◽  
Wide Range ◽  
Model Predictions ◽  
Reduced Kinetic Mechanism

The reduced kinetic mechanism for syngas/methane developed in the present work consists of a global reaction step for fuel decomposition in which the fuel molecule breaks down into CH2O and H2. A detailed CH2O/H2/O2 elementary reaction sub-set is included as the formation of intermediate combustion radicals such as OH, H, O, HO2, and H2O2 is essential for accurate predictions of non-equilibrium phenomena such as ignition and extinction. Since the chemical kinetics of H2 and CH2O are the fundamental building blocks of any hydrocarbon oxidation, the inclusion of detailed kinetic mechanisms for CH2O and H2 oxidation enables the reduced mechanism to predict over a wide range of operating conditions provided the reaction rate parameters of fuel-decomposition reaction is optimized over those conditions. Therefore, the rate coefficients for the fuel-decomposition step are estimated and optimized for the ignition delay time measurements of CH4, H2, CH4/H2, CH4/CO and CO/H2 mixtures available in the literature over a wide range of pressures, temperatures and equivalence ratios that are relevant to gas turbine operating conditions. The optimized reduced mechanism, consisting of 15 species and around 40 reactions, is able to predict the ignition delay time and laminar flame speed measurements of CH4, H2, CH4/H2, CH4/CO and CO/H2 mixtures fairly well over a wide range conditions. The model predictions are also compared with that of GRI3.0 mechanism. The reduced kinetic mechanism predicts the ignition delay time of CH4 and CH4/H2 mixtures far better than GRI mechanism at higher pressures. To demonstrate the predictive capability of the model in reactive flow systems, the reduced mechanism was implemented in Star-CD/KINetics commercial code using a RANS turbulence model to simulate CH4/air premixed combustion in a backward facing step. The CFD model predictions of the stable species in the exhaust gas agree well with the GRI mechanism predictions in a chemical reactor network modeling by approximating the backward facing step with a series of perfectly-stirred reactor and plug-flow reactor.

scholarly journals One-dimensional modeling of the interaction between close-coupled injection events for a ballistic solenoid injector

2018 ◽  
Vol 20 (4) ◽  
pp. 452-469 ◽  
Author(s):  
Raul Payri ◽  
Joaquin De la Morena ◽  
Vincenzo Pagano ◽  
Ali Hussain ◽  
Gilbert Sammut ◽  
...  
Keyword(s):  
Dwell Time ◽  
Dynamic Pressure ◽  
Injection Pressure ◽  
Operating Conditions ◽  
One Dimensional ◽  
Dimensional Modeling ◽  
Custom Made ◽  
Wide Range ◽  
Common Rail Injector ◽  
Injection Strategies

In this article, an investigation of a solenoid common-rail injector has been carried out to understand the hydraulic interactions between close-coupled injection events. For this purpose, a one-dimensional model of the injector was developed on GT-SUITE software. The geometrical and hydraulic characteristics of the internal elements of the injector, needed to construct the model, were obtained by means of different custom-made experimental tools. The dynamic behavior of the injector was characterized using an EVI rate of injection meter. The hydraulic results from the model show a good alignment with the experiments for single injections and a varied degree of success for multiple injections. Once the model was validated, it has been used to understand the injector performance under multiple-injection strategies. The mass of a second injection has shown to highly depend on the electrical dwell time, especially at low values, mostly due to the dynamic pressure behavior in the needle seat. The critical dwell time, defined as the minimum electrical dwell time needed to obtain two independent injection events, has been numerically obtained on a wide range of operating conditions and correlated to injection pressure and energizing time of the first injection. Finally, the increase in the needle opening velocity of the second injection compared to the single-injection case has been analyzed for close-coupled injection events.

Modeling Mixture Formation in a Gasoline Direct Injection Engine

2005 ◽  
Vol 73 (6) ◽  
pp. 931-939 ◽  
Author(s):  
Rossella Rotondi
Keyword(s):  
Flow Field ◽  
Fuel Injection ◽  
Direct Injection ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Injection System ◽  
Fuel Spray ◽  
Computational Domain ◽  
Mixture Formation ◽  
Wide Range

Mixture formation and combustion in a gasoline direct injection (GDI) engine were studied. A swirl-type nozzle, with an inwardly opening pintle, was used to inject the fuel directly in a four stroke, four cylinder, four valves per cylinder engine. The atomization of the hollow cone fuel spray was modeled by using a hybrid approach. The most important obstacle in the development of GDI engines is that the control of the stratified-charge combustion over the entire operating range is very difficult. Since the location of the ignition source is fixed in SI engines the mixture cloud must be controlled both temporally and spatially for a wide range of operating conditions. Results show that the volume of the spark must be considered when discretizing the computational domain because it highly influences the flow field in the combustion chamber. This is because the volume occupied by the plug cannot be neglected since it is much bigger than the ones used in port fuel injection engines. The development of a successful combustion system depends on the design of the fuel injection system and the matching with the in-cylinder flow field: the stratification at part load appears to be the most crucial and critical step, and if the air motion is not well coupled with the fuel spray it would lead to an increase of unburned hydrocarbon emission and fuel consumption

Analysis of Gas Turbine Rotating Cavities by a One-Dimensional Model: Definition of New Disk Friction Coefficient Correlations Set

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Luca Innocenti ◽  
Mirko Micio
Keyword(s):  
Gas Turbine ◽  
Axisymmetric Flow ◽  
Operating Conditions ◽  
Dimensional Model ◽  
Outer Flow ◽  
One Dimensional ◽  
Wide Range ◽  
Air System ◽  
Secondary Air ◽  
Radial Outflow

Reliable design of a secondary air system is one of the main tasks for the safety and unfailing performance of gas turbine engines. To meet the increasing demands of gas turbine designs, improved tools in the prediction of secondary air system behavior over a wide range of operating conditions are needed. A real gas turbine secondary air system includes several components, therefore, its analysis is not carried out through a complete computational fluid dynamics (CFD) approach. Usually, those predictions are performed using codes based on simplified approach, which allows to evaluate the flow characteristics in each branch of the air system requiring very poor computational resources and few calculation time. Generally, the available simplified commercial packages allow to correctly solve only some of the components of a real air system, and often, the elements with a more complex flow structure cannot be studied; among such elements, the analysis of rotating cavities is very hard. This paper deals with a design tool developed at the University of Florence for the simulation of rotating cavities. This simplified in-house code solves the governing equations for steady one-dimensional axisymmetric flow using experimental correlations, both to incorporate the flow phenomena caused by multidimensional effects such as heat transfer and flow field losses, and to evaluate the circumferential component of velocity. Although this calculation approach does not enable a correct modeling of the turbulent flow within a wheel space cavity, the authors tried to create an accurate model, taking into account the effects of inner and outer flow extraction, rotor and stator drag, leakages, injection momentum, and finally, the shroud/rim seal effects on cavity ingestion. The simplified calculation tool was designed to simulate the flow in a rotating cavity with radial outflow, both with the Batchelor and/or Stewartson flow structures. A primary 1D-code testing campaign is available in the literature (2008, “Analysis of Gas Turbine Rotating Cavities by a One-Dimensional Model,” ISROMAC Paper No. 12-2008-20161). In the present paper, the authors developed, using CFD tools, reliable correlations for both stator and rotor friction coefficients and provided a full 1D-code validation, due to the lack of experimental data, comparing the in-house design-code predictions with those evaluated by CFD.

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