MGT/HTFC Hybrid System Emulator Test Rig: Experimental Investigation on the Anodic Recirculation System

Author(s):  
Mario L. Ferrari ◽  
Matteo Pascenti ◽  
Loredana Magistri ◽  
Aristide F. Massardo

The Thermochemical Power Group (TPG) of the University of Genoa designed and installed a complete hybrid system emulator test rig equipped with a 100 kW recuperated micro gas turbine, a modular cathodic vessel located between recuperator outlet and combustor inlet, and an anodic recirculation system based on the coupling of a single stage ejector with an anodic vessel. The layout of the system was carefully designed, considering the coupling between a planar SOFC stack and the 100 kW commercial machine installed at TPG laboratory. A particular pressurized hybrid system was studied to define the anodic side properties in terms of mass flow rates, pressures, and temperatures. In this work, this experimental facility is used to analyze the anodic ejector performance from fluid dynamic and thermal points of view. The attention is mainly focused on the recirculation factor value in steady-state conditions. For this reason, a wide experimental campaign was carried out to measure the behavior of this property in different operative conditions with the objective to avoid carbon deposition in the anodic circuit, in the reformer, and in the fuel cell stack.

Author(s):  
Mario L. Ferrari ◽  
Matteo Pascenti ◽  
Loredana Magistri ◽  
Aristide F. Massardo

The aim of this work is the experimental analysis of a primary-surface recuperator, operating in a 100 kW micro gas turbine, as in a standard recuperated cycle. These tests, performed in both steady-state and transient conditions, have been carried out using the micro gas turbine test rig, developed by the Thermochemical Power Group at the University of Genova, Italy. Even if this facility has mainly been designed for hybrid system emulations, it is possible to exploit the plant for component tests, such as experimental studies on recuperators. The valves installed in the rig make it possible to operate the plant in the standard recuperated configuration, and the facility has been equipped with new probes essential for this kind of tests. A wide-ranging analysis of the recuperator performance has been carried out with the machine, operating in stand-alone configuration, or connected to the electrical grid, to test different control strategy influences. Particular attention has been given to tests performed at different electrical load values and with different mass flow rates through the recuperator ducts. The final section of this paper reports the transient analysis carried out on this recuperator. The attention is mainly focused on thermal transient performance of the component, showing the effects of both temperature and flow steps.


Author(s):  
Francesco Caratozzolo ◽  
Alberto Traverso ◽  
Aristide F. Massardo

This work presents the re-engineering of the TRANSAT 1.0 code which was developed to perform off-design and transient condition analysis of Saturators and Direct Contact Heat Exchangers. This model, now available in the 2.0 release, was originally implemented in FORTRAN language, has been updated to C language, fully coded into MATLAB/Simulink® environment and validated using the extensive set of data available from the MOSAT project, carried out by the Thermochemical Power Group of the University of Genoa. The rig consists of a fully instrumented modular vertical saturator, which is controlled and monitored with a LABVIEW® computer interface. The simulation software showed fair stability in computation and in response to step variation of the main parameters driving the thermodynamic evolution of the air and water flows. Considering the actual mass flow rates, a geometric similitude was used to avoid calculation instability due to flows under 100 g/s. Overall the model proved to be reliable and accurate enough for energy system simulations.


Author(s):  
Francesco Caratozzolo ◽  
Mario L. Ferrari ◽  
Alberto Traverso ◽  
Aristide F. Massardo

This study is based on a complete hybrid system emulator test rig developed at the University of Genoa (Savona laboratory) by the Thermochemical Power Group (TPG). The plant is mainly composed of a 100 kW recuperated micro gas turbine coupled with both anodic and cathodic vessels for high temperature fuel cell emulation. The test rig was recently equipped with a real-time model for emulating components not physically present in the laboratory (SOFC block, reformer, anodic circuit, off-gas burner, cathodic blower). This model is used to fully evaluate thermodynamic and electrochemical performance related to solid oxide fuel cell systems. Using a UDP based connection with the test rig control and acquisition software, it generates a real-time hardware-in-the-loop (HIL) facility for hybrid system emulation. Temperature, pressure and air mass flow rate at the recuperator outlet (downstream of the compressor) and rotational speed of the machine are inputs from the plant to the model. The turbine outlet temperature (TOT) calculated by the model is fed into the machine control system and the turbine electric load is moved to match the model TOT values. In this study various tests were carried out to characterize the interaction between the experimental plant and the real-time model; double step and double ramp tests of current and fuel provided the dynamic response of the system. The control system proved to be fast, compared to the slow thermal response of the SOFC stack, and also reliable. The hybrid systems operated at 90% of nominal power with electrical efficiency of about 56% based on natural gas LHV.


Author(s):  
Martina Hohloch ◽  
Jan Zanger ◽  
Axel Widenhorn ◽  
Manfred Aigner

For the development of efficient and fuel flexible decentralized power plant concepts a test rig based on the Turbec T100 micro gas turbine is operated at the DLR Institute of Combustion Technology. This paper reports the characterization of the transient operating performance of the micro gas turbine by selected transient maneuvers like start-up, load change and shut-down. The transient maneuvers can be affected by specifying either the electrical power output or the turbine speed. The impact of the two different operation strategies on the behavior of the engine is explained. At selected stationary load points the performance of the gas turbine components is characterized by using the measured thermodynamic and fluid dynamic quantities. In addition the impact of different turbine outlet temperatures on the performance of the gas turbine is worked out. The resulting data set can be used for validation of numerical simulation and as a base for further investigations on micro gas turbines.


Author(s):  
Luca Larosa ◽  
Mario L. Ferrari ◽  
Loredana Magistri ◽  
Aristide F. Massardo

In this paper an innovative SOFC hybrid system is proposed, equipped with ejector-based cathodic recirculation. The cathodic flow is preheated by recirculating hot exhausts. However, this approach needs higher pressure values than those available with commercial micro gas turbines (mGT): a possible but expensive solution could be to design a completely new mGT. Another option could be to use a booster with the function of re-compressor installed between the mGT compressor and the ejector (in order to increase ejector inlet pressure). This choice allows the use of commercial machines with a substantial cost reduction by comparison with designing a new micro gas turbine. Moreover, this layout is able to separate the compressor ratio of the mGT from the ejector inlet pressure, generating more flexibility from the point of view of the control system. In this paper, a thermodynamic study of this machine coupling is carried out considering the hybrid system emulator developed by TPG at the University of Genoa. For this purpose, three different boosting approaches were examined with a steady-state model built in Matlab-Simulink environment. The results presented here were obtained to show emulator performance and flexibility. Available power and thermal aspects are discussed in detail.


Author(s):  
Mario L. Ferrari ◽  
Matteo Pascenti ◽  
Loredana Magistri ◽  
Aristide F. Massardo

The aim of this work is the experimental analysis of a primary-surface recuperator operating in a 100 kW micro gas turbine, as in a standard recuperated cycle. These tests, performed in both steady-state and transient conditions, have been carried out using the micro gas turbine test rig developed by TPG at the University of Genoa, Italy. Even if this facility has mainly been designed for hybrid system emulations, it is possible to exploit the plant for component tests, such as experimental studies on recuperators. The valves installed in the rig make it possible to operate the plant in the standard recuperated configuration, and the facility has been equipped with new probes essential for this kind of tests. A wide-ranging analysis of the recuperator performance has been carried out with the machine operating in stand-alone configuration, or connected to the electrical grid, to test different control strategy influences. Particular attention has been given to tests performed at different electrical load values and with different mass flow rates through the recuperator ducts. The final section of this paper reports the transient analysis carried out on this recuperator. The attention is mainly focused on thermal transient performance of the component, showing the effects of both temperature and flow steps.


Author(s):  
Mario L. Ferrari ◽  
Matteo Pascenti ◽  
Loredana Magistri ◽  
Aristide F. Massardo

The aim of this work, focused on natural gas fired distributed power systems, is the experimental analysis of the start-up and shutdown for high temperature fuel cell hybrid systems. These critical phases have been emulated using the micro gas turbine test rig developed by TPG at the University of Genoa, Italy. The rig is based on the coupling of a modified commercial 100 kWe recuperated gas turbine with a modular volume designed to emulate fuel cell stacks of different dimensions. It is essential to test the dynamic interaction between the machine and the fuel cell, and to develop different operative procedures and control systems without any risk to the expensive stack. This paper shows the preliminary experimental results obtained with the machine connected to the volume. The attention is mainly focused on avoiding surge and excessive stress on the machine components during the tests. Finally, after the presentation of the valve control system, this paper reports the emulation of the hybrid system start-up and shutdown phases. They have been performed to produce a gradual heating up and cooling down of the fuel cell volume, using the cold bypass line, three high temperature valves, and the machine load control system. This approach is necessary to avoid high thermal stress on the cell material, extremely dangerous for the plant life.


Author(s):  
Gianluca Annunziata ◽  
Maria Cristina Cameretti ◽  
Roberta De Robbio ◽  
Raffaele Tuccillo

The purpose of the paper is the investigation of the combustion development in a Lean Premixed Prevaporized (LPP) combustor supplied with liquid fuels of a Micro Gas Turbine. The injection system is equipped by an airblast atomizer with three air inlets. In such a study the analysis is performed by a CFD tool that can simulate the injection conditions, by isolating and studying some specific phenomena. A 3-D fluid dynamic code (the FLUENT® flow solver) has been used to simulate the spray pattern in the chamber fuelled by kerosene fuel. Preliminarily, the numerical simulation refers to cold flow conditions, in order to validate the estimation of the fundamental spray parameters, such as the spray angle and Sauter Mean Diameter of the droplets; in a second step, the calculations employ boundary conditions close to those occurring in the actual combustor operation, in order to predict the fuel vapour distribution throughout the premixing chamber. In particular, the fuel is injected under the typical conditions that occur in the injection system of a gas turbine LPP combustor and in all cases examined, the boundary information is introduced in terms of air and fuel mass flow rates and of inlet characteristics of the air flow entering the revalorizing chamber, in order to estimate the fuel vapour formation and its distribution. In a third phase the combustion phenomenon is simulated and the NO emissions calculated. Finally, the best solution obtained is also tested by using a bio-fuel to compare the combustion performance and NO amount.


Author(s):  
D. P. Bakalis ◽  
A. G. Stamatis

A hybrid system based on an existing recuperated microturbine and a pre-commercially available high temperature tubular solid oxide fuel cell is modeled in order to study its performance. Individual models are developed for the microturbine and fuel cell generator and merged into a single one in order to set up the hybrid system. The model utilizes performance maps for the compressor and turbine components for the part load operation. The full and partial load exergetic performance is studied and the amounts of exergy destruction and efficiency of each hybrid system component are presented, in order to evaluate the irreversibilities and thermodynamic inefficiencies. Moreover, the effects of various performance parameters such as fuel cell stack temperature and fuel utilization factor are investigated. Based on the available results, suggestions are given in order to reduce the overall system irreversibility. Finally, the environmental impact of the hybrid system operation is evaluated.


Author(s):  
Ji Ho Ahn ◽  
Tong Seop Kim

Owing to the increasing consumption of fossil fuels and emission of greenhouse gases, interests in highly efficient and low carbon emitting power systems are growing fast. Several research groups have been suggesting advanced systems based on fuel cells and have also been applying carbon capture and storage technology to satisfy the demand for clean energy. In this study, the performance of a hybrid system, which is a combination of a molten carbonate fuel cell (MCFC) with oxy-combustion carbon capture and an indirectly fired micro gas turbine (MGT) was predicted. A 2.5MW MCFC system that is used in commercial applications was used as the reference system so that the results of the study could be applicable to practical situations. The ambient pressure type hybrid system was modeled by referring to the design parameters of an MGT that is currently being developed. A semi-closed type design characterized by flow recirculation was adopted for this hybrid system. A part of the recirculating gas is converted into liquefied carbon dioxide and captured for storage at the carbon separation unit. Almost 100% carbon dioxide capture is possible with this system. In these systems, the output power of the fuel cell is larger than in the normal hybrid system without carbon capture because the partial pressure of carbon dioxide increases. The increased cell power partially compensates for the power loss due to the carbon capture and MGT power reduction. The dependence of net system efficiency of the oxy-hybrid on compressor pressure ratio is marginal, especially beyond an optimal value.


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