João Roberto Barbosa

Methodology for gas turbine performance improvement using variable-geometry compressors and turbines

Abstract Poor part-load performance is a well-known undesirable characteristic of gas turbines. Running off-design, both compressor and turbine lose performance. Flow misalignment at the various rows causes losses to increase sharply, thereby decreasing net output faster than decreasing fuel consumption. To bring the flow to alignment with the blade passages, it is required to restagger the blades both at the compressor and at the turbine. To avoid mechanical complexities, it is generally accepted to restagger only the stators. This work deals with a numerical approach to the simulation of a gas turbine equipped with variable stators at the compressor and at the turbine, enabling the search for better-performance operation. A computer program has been developed to simulate virtually any gas turbine having variable stators at the compressor stages and turbine nozzle guide vanes. Variable-inlet guide vanes (VIGVs), variable-stator vanes (VSVs), variable-nozzle guide vanes (VNGVs), variable-geometry compressors (VGCs) and variable-geometry turbines (VGTs) are the focus in this work, which analyses a one-shaft free power turbine for power generation in the search for performance improvement at part load.

An insight on intercooling and reheat gas turbine cycles

Abstract The current drive for high efficiencies and low emissions has resulted in the examination and development of advanced power systems based on complex gas turbine cycles. Reheat and intercooling are two such schemes. The basic objective of introducing intercooling and reheat is to sources of loss in a gas turbine engine are those arising from the turbomachinery and the need to cool the turbine blades. In this paper the concepts of intercooling and reheat for gas turbines are assessed, in a systematic way, using a model that includes the above losses in order to evaluate their effects on the engine performance. Also examined is the choice of the position where intercooling or reheat is implemented which can have a large effect on the engine output. A comparison is made with the simple cycle and it is shown that these schemes show much promise. Some of the development difficulties are also outlined. Intercooling promises large improvements in efficiency over the simple cycle, especially at high pressure ratios. Reheat on the other hand is much more suited to combined cycles.

Gas Turbine Transients With Controlled Variable Geometry

A small 5-kN thrust gas turbine, designed and manufactured having in mind a thorough source of validation data, serves as basis for the study. The engine is an uncooled turbine, 5:1 pressure ratio axial flow compressor, delivering 8.1 kg/s air mass flow, whose control is made by a FADEC. Cold runs of the jet engine version have already been completed. The engine characteristics are being developed using the technology indicated in the paper. Accelerations and decelerations from idle to full power in a prescribed time interval and positive surge margin are the limitations imposed to the control system. In order to accomplish such requirements, a proportional, integral and derivative (PID) has been implemented to control the variable geometry transients, which proved to drive the engine to the required operating points. Compressor surge is avoided during accelerations or decelerations, imposing operation limits to the surge margin. In order to simulate a jet engine under transient operation, use was made of high-fidelity in-house developed software. The results presented in the paper are related to the compressor inlet guide vane (VIGV) transients. The engine transient calculations were predicted with the IGV settings varying with time, and the results are being used for the initial calibration of the transfer functions for the real time control.© 2012 ASME

The boundary element method applied to incompressible viscous fluid flow

An Integral equation formulation for steady flow of a viscous fluid is presented based on the boundary element method. The continuity, Navier-Stokes and energy equations are used for calculation of the flow field. The governing differential equations, in terms of primitive variables, are derived using velocity-pressure-temperature. The calculation of fundamental solutions and solutions tensor is showed. Applications to simple flow cases, such as the driven cavity, step, deep cavity and channel of multiple obstacles are presented. Convergence difficulties are indicated, which have limited the applications to flows of low Reynolds numbers.

A step further in gas turbine dynamic simulation

Abstract Non-proprietary gas turbine transient performance models that deal with volume dynamics in the open literature usually do not consider heat transfer effects and friction existing in the volume walls. Such models are more than satisfactory for the analysis of aero gas turbines because the associated volumes of their components are inherently small and therefore treated as adiabatic, frictionless and passing low Mach number flows. When focusing upon gas turbines with heat exchangers, such as those working on regenerative cycles, on the other hand, these simplifying hypotheses may not be valid. The analysis model suggested in this work takes account of non-adiabatic volume dynamics with friction and high Mach number flows. The model is applied to the study of a regenerative-cycle gas turbine, through which the need for a more complete analysis model is demonstrated. The result of the study showed that the regenerator cold section volume has a greater influence on the dynamics than the hot section volume, this causing the power output. Friction has little influence on the dynamic response but causes a decrease in the steady state power output, as expected. Heat exchange also reduces the power output and lowers the transient engine surge margin.

Operation Analysis and Thermoeconomic Evaluation of a Cogeneration Power Plant Operating as a Self-Generator in the Ecuadorian Electrical Market and Sugar Industry

This study evaluates the integral use of the sugarcane bagasse on the productive process of a cogeneration power plant in an Ecuadorian Sugar Company. Thermoelectric power plants burning biomass require a large initial investment and, for example, this initial investment requires

Numerical Tools for High Performance Axial Compressor Design for Teaching Purpose

800/kW, which is double the initial investment of a conventional thermoelectric power plant that is

CFD and CAA Analysis of Single Stream Isothermal Jets with Noise Suppression Devices

400/kW, and almost similar to the initial cost of a hydroelectric power plant that is

Analysis of Turbofan Empirical Noise Prediction Methods

1000/kW. A thermoeconomic study was made on the production of electricity and the sales of the exceeding 27 MW average. From the results, it was concluded that generated electricity costs are

Numerical Simulation for the Preliminary Design of Fuel Flexible Stationary Gas Turbine Combustors Using Conventional and Alternative Fuels

0.0443/kW h, in comparison with the costs of the supplied electricity through fossil power plants with values in the range