scholarly journals COLD FLOW NUMERICAL ANALYSIS OF GAS MICROTURBINE COMBUSTION CHAMBER THROUGH CFD TOOL

2019 ◽  
Vol 18 (1) ◽  
pp. 29
Author(s):  
G. K. Caetano ◽  
J. F. T. de Carvalho ◽  
J. S. Rosa
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Reverse Flow ◽  
Ideal Point ◽  
Random Motion ◽  
Design Data ◽  
Cold Flow

Gas turbines are equipment used mainly in the generation of electric energy. They have as one of their main components the combustion chamber. Therefore, it is relevant to study the characteristics of this component, in order to reach a satisfactory operation. In this context, this paper presents an analysis of a combustion chamber applied to a gas turbine with a cold flow approach using the numerical theoretical method, through the computational fluid dynamics technique. In this experiment, the software Abaqus CFD (computational fluid dynamics) – present in the 3DExperience platform – and the finite volume method are used. The objective was to evaluate the flow, pressure and velocity profiles during the single-phase flow. The gas turbine prototype is configured using a combustion chamber of reverse flow type in order to decrease flow velocity and increase the combustion efficiency. Based on input data obtained from practical experiments, the calculation of the number and Reynolds confirmed – according to the literature of fluid mechanics – the occurrence of a flow classified as turbulent, with chaotic and random motion, what allows defining the ideal point of injection from analysis of velocity plots with stream lines. In addition, a Mach number smaller than 0.3 confirms the theory of having an incompressible flow, in which compressibility effects can be disregarded. The analysis of mass flow rates of the combustion zones made it possible to evaluate maximum differences of 3% between the design data and the one found in the study. To determine the inherent error of the mesh in the CFD study was calculated through the grid conference method, the value found was around 2.68%.

Actuation Studies for Active Control of Mild Combustion for Gas Turbine Application

2014 ◽  
Author(s):  
Emilien Varea ◽  
Stephan Kruse ◽  
Heinz Pitsch ◽  
Thivaharan Albin ◽  
Dirk Abel
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Active Control ◽  
Gas Turbines ◽  
Reverse Flow ◽  
Air Flow ◽  
Combustion Regime ◽  
Nox Emissions ◽  
Low Oxygen ◽  
Mild Combustion

MILD combustion (Moderate or Intense Low Oxygen Dilution) is a well known technique that can substantially reduce high temperature regions in burners and thereby reduce thermal NOx emissions. This technology has been successfully applied to conventional furnace systems and seems to be an auspicious concept for reducing NOx and CO emissions in stationary gas turbines. To achieve a flameless combustion regime, fast mixing of recirculated burnt gases with fresh air and fuel in the combustion chamber is needed. In the present study, the combustor concept is based on the reverse flow configuration with two concentrically arranged nozzles for fuel and air injections. The present work deals with the active control of MILD combustion for gas turbine applications. For this purpose, a new concept of air flow rate pulsation is introduced. The pulsating unit offers the possibility to vary the inlet pressure conditions with a high degree of freedom: amplitude, frequency and waveform. The influence of air flow pulsation on MILD combustion is analyzed in terms of NOx and CO emissions. Results under atmospheric pressure show a drastic decrease of NOx emissions, up to 55%, when the pulsating unit is active. CO emissions are maintained at a very low level so that flame extinction is not observed. To get more insights into the effects of pulsation on combustion characteristics, velocity fields in cold flow conditions are investigated. Results show a large radial transfer of flow when pulsation is activated, hence enhancing the mixing process. The flame behavior is analyzed by using OH* chemiluminescence. Images show a larger distributed reaction region over the combustion chamber for pulsation conditions, confirming the hypothesis of a better mixing between fresh and burnt gases.

scholarly journals CFD Indications of Premix Flame Stability in a Gas Turbine Combustor

1996 ◽  
Author(s):  
J. Allan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Heating Rate ◽  
Flame Stability ◽  
Cfd Model ◽  
Gas Turbine Combustor ◽  
Flow Models ◽  
Cold Flow ◽  
Primary Zone

An approach for predicting the relative tendency for weak extinction among similar gas turbine premix combustors is presented. The method involves analyzing CFD (computational fluid dynamics) solutions so as to evaluate the recirculating masses in the primary zone and the resulting potential heating rate of incoming fresh mixture. Results are illustrated for two combustor geometries which look similar but have very different behaviour. The comparison between the combustors agrees with test data when the CFD model incorporates a simulation of the flame. The inadequacy of cold flow models for the purpose is shown.

scholarly journals Ensuring Adequate Coolant Purity for Advanced Gas Turbines

1995 ◽  
Author(s):  
D. E. Woodmansee ◽  
A. K. Tolpadi ◽  
T. H. Hwang ◽  
A. D. Maddaus
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Particulate Contaminants ◽  
Accelerating Flows

The role of particulate contaminants in advanced gas turbine coolants is discussed, especially in light of the extremely high G-field regions they will experience in service. Predictions of sedimentation in both laminar and highly turbulent accelerating flows using a computational fluid dynamics code are made for a range of particulate sizes to show that particles over 0.5 µm are of concern. Possible techniques for limiting access of these particulates to the gas turbines themselves are presented. Overall, contaminant deposition appears controllable, limiting required cleaning of coolant channels to regularly scheduled inspections.

scholarly journals Cold Flow Experiments in a Sub-Scale Model of the Diffuser-Combustor Section of an Industrial Gas Turbine

1996 ◽  
Author(s):  
J. S. Kapat ◽  
T. Wang ◽  
W. R. Ryan ◽  
I. S. Diakunchak ◽  
R. L. Bannister
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Reverse Flow ◽  
Outer Region ◽  
Weighted Average ◽  
Scale Model ◽  
Complex Flow ◽  
Flow Measurements ◽  
Cold Flow ◽  
Industrial Gas Turbine

This paper describes the experimental facility and flow measurements in a sub-scale, 360-degree model of the diffuser-combustor section of an advanced developmental industrial gas turbine. The experiments were performed under cold flow conditions which can be scaled to actual machine operation through the use of a conventional flow parameter. Wall pressure measurements were used to calculate the static pressure recovery in the annular pre-diffuser. A five-hole probe was used to measure the complex three-dimensional flow in the dump diffuser. Mass-weighted average total pressures were calculated to examine the loss characteristics of the annular and the dump diffuser. The “sink” effect caused by the combustors induces a nonuniform velocity profile and pressure distribution at the exit of the annular pre-diffuser, thereby reducing the effectiveness of the annular pre-diffuser. The outer region of the dump diffuser effectively diffuses the flow while recirculation in other areas of the dump diffuser lowers diffuser effectiveness. Partially nonuniform flow distribution was observed at the entrance to the annular passage between the combustors and the combustor housing (top hat). The existence of circumferential flow in this annular passage tends to increase air flow uniformity into the combustor. Although a specific geometry was selected for the present study, the results provide sufficient generality for improving understanding of the complex flow behaviors in the reverse flow diffuser-combustor sections of industrial gas turbines.

Gas Turbines and Uncertainty Quantification: Impact of PDF Tails on UQ Predictions, the Black Swan

2013 ◽  
Author(s):  
Francesco Montomoli ◽  
Michela Massini
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Uncertainty Quantification ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Black Swan ◽  
Probability Of Occurrence ◽  
Hot Gas ◽  
Black Swans ◽  
Input Parameters

In the last five years Uncertainty Quantification (UQ) techniques became popular to predict gas turbine performances. Taking into account the uncertainties in the input parameters it is possible to evaluate the impact of random variations and to overcome the limitations of deterministic studies. These methods, that only recently have been widely used in computational fluid dynamics, have some limitations that must be considered. One of the most important limitations is that these models cannot predict a “Black Swan” (BS) event. In probability a Black Swan is an event rare, possible and with serious consequences. A reliable design requires a correct evaluation of the probabilities of occurrence of the Black Swan that could strongly affect the life of the turbine. Black Swans are generated by the variability of the input parameters in the “tail” of the statistical distributions. Being far from the mean value design geometry/condition, these events have a low probability of occurrence. In this paper is shown that the use of the Gaussian distribution for the input parameters could strongly underestimate the probability of occurrence of a Black Swan event. Despite that most of the models used in UQ for aerodesign are neglecting the problem. As an example of Black Swan, the hot gas ingestion across a stator is analysed. The gaps have been assumed to be affected by uncertainty with a variation of +/-50% of the nominal value. By using a Monte Carlo simulation with 108 realizations and a Gauss distribution as input, the configuration is initially considered reliable. The six sigma criterion is also satisfied and the probability to have a failure is only 2.54 10−4%. However if a “fat tail” for the input distribution is used instead, the probability to have hot gas ingestion becomes 2.33%, 104 times higher. Most of the methods used in literature aim to have an accurate reproduction of the PDF moments such as mean, standard deviation, skew and kurtosis. However the “tail” of the distribution affects the gas turbine life and must be considered. In particular “fat tails”, the mathematical origin of Black Swans events, can have serious consequences, but in modern stochastic models used for computational fluid dynamics they are not accounted for.

Use of computational fluid dynamics to model reservoir mixing and destratification

1998 ◽  
Vol 37 (2) ◽  
pp. 227-234
Author(s):  
Julian D. Cox ◽  
Martin B. Padley ◽  
Joe Hannon
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reverse Flow ◽  
Dynamics Model ◽  
Artificial Mixing ◽  
Effective Operation ◽  
Different Types ◽  
Blade Mixer ◽  
Perforated Pipe ◽  
Better Than

Destratification of reservoirs by the use of artificial mixing is a method of improving the impounded water quality. In order to design a destratification device at Stocks Reservoir, NW England, a Computational Fluid Dynamics model was used to trial different types and sizes of mixing device. It was found that a perforated pipe bubble mixing device performed far better than a large banana blade mixer at destratifying Stocks Reservoir. Two important criteria for the effective operation of a mixing device were established. These were a minimum upflow velocity of entrained water through the reservoir, and the need for a reverse flow along the surface of the reservoir away from the abstraction point. These criteria have been incorporated into design equations which can be extended to use at other reservoirs. A bubble mixer was installed at Stocks Reservoir, and has been shown to fully destratify the reservoir and to reduce the levels of dissolved manganese in the water by more than 50%.

A Fully Integrated Approach to Component Zooming Using Computational Fluid Dynamics

2004 ◽  
Vol 128 (3) ◽  
pp. 579-584 ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Fabien Talhouarn ◽  
Anestis Kalfas ◽  
Ioannis Templalexis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Engine Performance ◽  
Integrated Approach ◽  
High Fidelity ◽  
Performance Simulation ◽  
Fully Integrated ◽  
Engine Component ◽  
Simulation Strategy

Background . This study focuses on a simulation strategy that will allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. Approach. The technique described in this paper utilizes an object-oriented, zero-dimensional (0D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3D) computational fluid dynamics (CFD) component model. The work investigates relative changes in the simulated engine performance after coupling the 3D CFD component to the 0D engine analysis system. For the purposes of this preliminary investigation, the high-fidelity component communicates with the lower fidelity cycle via an iterative, semi-manual process for the determination of the correct operating point. This technique has the potential to become fully automated, can be applied to all engine components, and does not involve the generation of a component characteristic map. Results. This paper demonstrates the potentials of the “fully integrated” approach to component zooming by using a 3D CFD intake model of a high bypass ratio turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The high-fidelity model can fully define the characteristic of the intake at several operating condition and is subsequently used in the 0D cycle analysis to provide a more accurate, physics-based estimate of intake performance (i.e., pressure recovery) and hence, engine performance, replacing the default, empirical values. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the coupled, high-fidelity component is presented in this paper. The analysis carried out by this study demonstrates relative changes in the simulated engine performance larger than 1%. Conclusions. This investigation proves the value of the simulation strategy followed in this paper and completely justifies (i) the extra computational effort required for a more automatic link between the high-fidelity component and the 0D cycle, and (ii) the extra time and effort that is usually required to create and run a 3D CFD engine component, especially in those cases where more accurate, high-fidelity engine performance simulation is required.

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