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Technical Paper

Some Techniques to Improve Performance of Si Engine At Part Loads - A Numerical and Experimental Approach

2003-08-22
2003-28-0026
Work in this paper involves the computer simulation and experimental investigations on a single-cylinder, four-stroke, spark-ignition engine in which inlet valve closure timing and clearance volume are optimized for better part -load performance. The simulation procedure involves thermodynamic and global modeling techniques. Many sub-models have been used for predicting heat transfer, friction and gas exchange processes. A two-zone model is adopted for combustion process. The combustion model used here predicts mass burning rates, ignition delay and combustion duration, etc. Sub-models for calculating flame-front area, flame -speed and chemical equilibrium composition of ten product species are used in combustion analysis. Measured valve -displacement along with suitable coefficient of discharge is used in the analysis of gas exchange processes. Unburned hydrocarbons and carbon monoxide emissions have been predicted.
Technical Paper

Flow Field Behind the Flame Holders in an Isothermal Model of an Afterburner - A Theoretical Study

2001-11-01
2001-28-0024
The flow in a gas turbine afterburner is highly complex since it is three dimensional and turbulent with major design requirements depending to a greater extent on the internal aerodynamics. The aim of this work is to carry out flow field analysis in an isothermal model of an afterburner using a computational fluid dynamics method. The calculations are performed using SIMPLE (Semi Implicit Method for Pressure Linked Equations) based algorithm with unstructured grid arrangement. The standard k-ε model is used for turbulence modeling. The three-dimensional velocities and turbulent kinetic energy have been predicted for the model afterburner and the flow field predictions agree satisfactorily well with the measurements. The velocity vector plots drawn along different longitudinal and cross sectional planes provide a wealth of information for different representative cases of afterburners.
Technical Paper

Modeling of Reacting Flows in an Afterburner

2001-11-01
2001-28-0025
Reacting flows in a gas turbine afterburner is a highly complex phenomenon since it is three dimensional, turbulent, having vitiated air at the inlet. Major design requirements depend to a great extent on the internal aerodynamics. Even though the afterburner configuration is basically similar to that of a gas turbine combustor, the additional components like diffuser, flame stabilizer, fuel manifold rings and variable area nozzle make the system more complex. The aim of the present investigation is to numerically predict the flow and combustion inside the afterburner using Computational Fluid Dynamics (CFD). In the present work a three-dimensional study of the afterburner system has been carried out. The configuration is modeled using unstructured grid arrangement. The numerical calculations are performed using SIMPLE (Semi Implicit Method for Pressure Linked Equations) based algorithm. The standard k-ε model is used for turbulence modeling.
Technical Paper

Simulation of Isothermal Flow Field Structure in a Gas Turbine Combustor

2001-11-01
2001-28-0026
The flow in a gas turbine combustor is comprised of regions of recirculating flow, strong streamline curvature, adverse pressure gradient, developing boundary layers and impingement flow. Such a flow structure coupled with complex geometric configuration makes the analysis of combustor flows quite difficult especially by experimental methods. The difficulties have led to the development of multidimensional computational methods for analyzing such complex flows, using powerful computers. The main aim of this work is to carry out a 2-D flow field analysis inside an annular gas turbine combustor using a general-purpose computer package called FLUENT. The numerical calculations are performed using Semi Implicit Method for Pressure linked Equation (SIMPLE) based algorithm with body fitted coordinates and unstructured grid arrangement. The general structure of the flow field has been compared with the available experimental results from flow visualization studies.
Technical Paper

Modelling of Combustion In a Gas Turbine Combustion System

2001-11-01
2001-28-0027
The main aim of this work is to carry out a 3D flow field analysis of an annular gas turbine combustor using finite volume method. The numerical calculations are performed using Semi Implicit Method for Pressure Linked Equations (SIMPLE) algorithm with unstructured grid arrangement. The turbulence models tried are k-ε (RNG) and k-ε (REALIZABLE) model. Two-phase calculations are performed using liquid droplet spray combustion model. The trajectory computation of the fuel provides the source terms for all the gas phase equation. The fuel used is JET-AG, and the combustion chamber is annular. The distribution of velocity field and distribution of temperature field are predicted for the combustor under consideration. From the temperature distribution it is possible to calculate the radial and circumferential pattern factors. It is found that the present prediction procedure is capable of handling complex flow and combustion quite satisfactorily.
Technical Paper

NUMERICAL PREDICTIONS AND EXPERIMENTAL INVESTIGATIONS ON EXTENDED EXPANSION ENGINE PERFORMANCE AND EXHAUST EMISSIONS

2000-01-15
2000-01-1415
This paper deals mainly with the computer simulation and experimental investigations on a single cylinder, four stroke, spark ignited, extended expansion engine. The simulation procedure involves thermodynamic and global modeling techniques. Submodels for predicting gas exchange processes, heat transfer and friction are used. Two-zone model is adopted for combustion process. The combustion model predicts mass burning rate, ignition delay and combustion duration. It uses sub-models for calculating flame-front area, flame-speed and chemical equilibrium composition of ten product species. Experimentally measured valve-lift data along with suitable coefficient of discharge is used in the analysis of gas exchange process. Unburned hydrocarbons, carbon monoxide and nitric oxide emissions have also been predicted. Experiments have been conducted on a single cylinder, air cooled, four stroke, spark ignition engine. A production engine was modified to run as extended expansion engine.
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