Marco A. R. Nascimento

Micro Gas Turbine Engine: A Review

Microturbines came into the automotive market between 1950 and 1970. The first microtur‐ bines were based on gas turbine designed to be used in generators of missile launching sta‐ tions, aircraft and bus engines, among other commercial means of transport. The use of this equipment in the energy market increased between 1980 and 1990, when the demand for distributed generating technologies increased as well (LISS, 1999).

Flammability limits of hydrated and anhydrous ethanol at reduced pressures in aeronautical applications

There is interest in finding the flammability limits of ethanol at reduced pressures for the future use of this biofuel in aeronautical applications taking into account typical commercial aviation altitude (<40,000 ft). The lower and upper flammability limits (LFL and UFL, respectively) for hydrated ethanol and anhydrous ethanol (92.6% and 99.5% p/p, respectively) were determined for a pressure of 101.3 kPa at temperatures between 0 and 200°C. A heating chamber with a spherical 20-l vessel was used. First, LFL and the UFL were determined as functions of temperature and atmospheric pressure to compare results with data published in the scientific literature. Second, after checking the veracity of the data obtained for standard atmospheric pressure, the work proceeded with reduced pressures in the same temperature range. 295 experiments were carried out in total; the first 80 were to calibrate the heating chamber and compare the results with those given in the published scientific literature. 215 experiments were performed both at atmospheric and reduced pressures. The results had a correlation with the values obtained for the LFL, but values for the UFL had some differences. With respect to the water content in ethanol, it was shown that the water vapor contained in the fuel can act as an inert substance, narrowing flammability.

Load Current Control Model for a Gas Micro-Turbine in Isolated Operation

Micro-turbines operation like power generator in oil facilities or rural industries, which are far away from generation and distribution services, is one of the most important applications for this generation device. This work presents a load current control model, for a 30 kW gas micro-turbine, fueled with natural gas, operating in isolated mode. A brief description of the isolated operation issues is performed, standing out the differences with power grid connected operation. Each model element is explained, emphasizing in the necessary modifications characteristic of isolated operation. It is explained the methodology for obtaining the model parameters, using the Toolbox Ident for systems identification of MatLab. Three types of models were tested: ARX, ARMAX and Box-Jenkins. The minimal square estimator is used to get the transfer function parameters in z domain. These functions were transformed into the frequency domain of s variable using zero order holder. Each model block was validated independently, explaining the nature of each variable and the reason for the correspondent error. In the end of this paper it was developed an application in Simulink-MatLab, using all the parameters obtaining for analyzing the whole model performance. Result graphics are shown with the conclusions. Recommendations for future developments are commented in the end

Radial Inflow Turbine One and Tri-Dimensional Design Analysis of 600 kW Simple Cycle Gas Turbine Engine

Microturbines have been developed as an important power unit for distributed generation (DG) or distributed energy resource (DER) options [1]. They have been established and are widely used in aircraft and power applications, due to their easy installation, reliability, high performance, multi-fuel capabilities and low emission [2]. However, the aerothermodynamic design of a radial turbine still poses a challenge due to its high rotational speed and high inlet temperature, which influence the centrifugal stress and the rotor structural integrity. This paper presents the numerical investigations on the aerothermodynamic design of the nozzle and the radial inflow rotor for a 600 kW simple cycle gas turbine engine using a One-dimensional Computer FORTRAN Code (OFC) [3], on the grounds of non-dimensional parameters aimed at computational and work time reduction. This program utilizes a one-dimensional solution of flow conditions through the turbine along the meanline. The referred computer program is an effective performance prediction tool mostly in the initial stage of the preliminary design and can be used to quickly investigate and calculate the number of design options prior to any details of the vane and blade geometry. In order to find the most promising design option, a computational fluid dynamics (CFD) simulation has been used to study the performance, the aerothermodynamic design and the flow characteristics of the turbine components. The OFC results were compared with the CFD simulation, a computer program for the design analysis of radial inflow turbines, and analytical results taken from specialized literature showed the results were in agreement.Copyright

Analyzing the Impact of Using Biodiesel in the Parameters of a 30 kW Micro-Turbine Control Model

This work presents the modifications in a 30 kW gas micro-turbine speed control model, when it was supplied with castor bean biodiesel in several proportions. The concern about using biodiesel as an alternative fuel is increasing in the Brazilian distributed generation market. For this analytics, a complete study was developed considering the effects of using this new fuel. Characteristics like chemical composition, physical and chemical properties of the different mixtures were analyzed, especially focusing on the kinematic viscosity of the fuel. The tests results performed with the micro-turbine, originally projected for diesel, are shown. Mixtures of 5, 10, 15, 20, 25, 30, 50 e 100% of biodesel were used, and several variables were measured in the whole range of power. The influence of the biodiesel characteristics in the model parameters are commented in the conclusions. The possible application of the proposed model in studies of electrical power network is suggested in the end of the article.Copyright

Case Studies of Distributed Generation Projects With Microturbines in Brazil

Microturbines have showed good perspectives for the distributed generation of the electricity in low capacity range, because they have high reliability and simple design (high potential for a cheap manufacture and in large scale). Besides, this technology must have a great application in systems of cogeneration of the public service (malls, hotel, hospital, etc.) and in the distributed generation of the electricity in the developing countries in order to get a reliable operation system, in a range of power compatible with the isolated communities. In Brazil, The Thermal Systems Study Group (NEST) of Federal University of Itajuba (UNIFEI) sponsored by The Energy Company of Minas Gerais (CEMIG), are developing a project of experimental valuation of the system with microturbines for electricity generation fueled with natural gas and diesel. The objective of this paper is to show an economic evaluation which presents the generation costs and the payback period with the Capstone 30 kW natural gas microturbines business in three cases: microturbines operating on base load in gas station, microturbines operating on peak shave in the industry and a microturbine cogeneration system operating in the residential segment. It was considered the cost of microturbines at this moment and the projection for the future, as well as the cost of electricity and natural gas in Brazil. An economical analysis was carried out for different variables involved and the results show the Capstone 30 kW natural gas microturbines business are feasible firstly in cogeneration cases which is possible to get until 3 years of payback period. Besides, the return on the investment have shown improvements with the incentive of the natural gas distributing companies and with the rises in the electricity price of Brazilian utilities.Copyright

ONE AND THREE-DIMENSIONAL ANALYSIS OF CENTRIFUGAL COMPRESSOR FOR 600 KW SIMPLE CYCLE GAS TURBINE ENGINE

Currently, industrial countries generate most of their electricity in large centralized plants. These plants have excellent economies of scale, however, they usually transmit electricity through long distances and can affect the environment. Distributed generation is another approach that reduces the amount of lost energy during transmission as the electricity is generated closely to where it is used, this way reducing the size and number of power lines to be constructed. The current technologies in DG include small gas turbine engines, internal combustion reciprocating engines, photovoltaic panels, fuel cells, solar thermal conversion and Stirling engines using fossil fuels and bio-fuels. Among them, small gas turbine engines are a promising technology for the implementation of distributed generation systems in the near future. This work presents the results of the preliminary compressor design of a simple cycle gas turbine engine, obtained with the use of a straightforward one-dimensional FORTRAN code, which enables to calculate the main characteristics of a centrifugal compressor by means of the application of non-dimensional parameters, with a vast reduction of computational time. The results obtained were compared with a CFD analysis and with experimental results taken from specialized literature; therefore a reasonable agreement was reached. The main contribution of this paper is to demonstrate that by the use of a simple code it is feasible to obtain fairly close results in comparison with those which can be obtained by laborious iterative processes such as those developed through the analysis using CFD techniques.Copyright

Numerical Meanline Analysis and Overall Performance Prediction of Radial-Inflow Turbine for a 600 kW Cycle Gas Engine

Radial-inflow turbines have been developed as one important power generation systems for distributed generation options, because they have demonstrated higher levels of efficiency than small axial flow turbine [1]. Radial-inflow turbine is a key part of microturbines and its aerodynamic performance affects directly on characteristics of whole microturbine system [2]. This paper presents the numerical meanline analysis and overall performance prediction of radial-inflow turbine for a 600 kW cycle gas engine using a One-dimensional Computer FORTRAN Code (OFC) [3]. This program was based mainly in non-dimensional parameters and it uses a one-dimensional solution of flow conditions through the turbine along the meanline. Comparison of predicted with analytical results determined performance for this turbine showed good agreement.Copyright

Aerodynamic Analysis Using CFD for Gas Turbine Combustion Chamber

In the past few years, with the development of advanced numerical computational codes, numerical simulation became a promising option to developing and improving the technology in different fields. The obtained results by simulations are used to get important information during the design phase or optimization of industrial equipment. Its employment generates reliable results at low cost due to the reduced number of experiments as well as the opportunity to develop new products and perform many simulations before its production. However, the numerical simulation credibility can only be verified when compared to the obtained results by experiments. This work aims to present and evaluate different aerodynamics models applied to combustion chambers using a CFD tool. In addition, aerodynamic analysis is made in a model of combustion chamber, where the flow is simulated with successive refining of the mesh as part of its validation process. For it, it is used a Low Nox Emission Combustion Chamber from Floxcom project as reference to validate turbulence models. Once that it is done, the selected turbulence model with satisfactory precision is used to describe the aerodynamic behavior of an annular combustion chamber from velocity and pressure distribution, which are important parameters to set load losses and recirculation intensity, which can affect the complex phenomenon of combustion.Copyright

Experimental Evaluation and Comparison of the Performance and Emissions of a Regenerative Gas Microturbine Using Biodiesel From Various Sources as Fuel

Biodiesel is an alternative fuel that has become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. As it can be blended in any proportion with mineral Diesel, and there are several reports which presented substantial reductions in emissions of unburned hydrocarbons, carbon monoxide and particulate in IC engines without reducing the output power significantly. The aim of this work was to perform an emissions and performance experimental analysis to evaluate and compare the use of Biodiesel obtained from different sources, Castor, Soy and Palm Oil, on a 30 kW regenerative gas micro turbine engine installed in the laboratories of the Federal University of Itajuba – Unifei, Brazil, at different power levels at steady state condition. All the fuels were characterized in terms of its viscosity and heat value, and the thermal performance and the emissions were measured. In all cases, it was performed a comparison between the obtained results with Biodiesel and Diesel. None of the fuels presented any problem related to atomization process in the related tests, and have shown no significant changes in performance of the microturbine reaching levels of around 26% of thermal efficiency. The minimum Heat Rate obtained at full load, was for the Biodiesel from Palm oil case, and the maximum was for Castor oil with a value 8.38% higher than when operated with Diesel. In Addition, when measuring pollutants emissions in the exhaust gases, it was observed a slightly increment in CO and a reduction in NOx concentration.Copyright