Andrea De Pascale

CFD Simulation of Water Injection in GT Inlet Duct Using Spray Experimentally Tuned Data: Nozzle Spray Simulation Model and Results for an Application to a Heavy-Duty Gas Turbine

This study describes an application of Computational Flow Dynamics (CFD) to the two-phase flow problem of water injection into a compressor inlet duct for fogging systems. The paper addresses issues related to the CFD setup and the developed spray simulation model. Water injection is simulated by fitting experimental data on sprays obtained from industrial nozzles. In particular, the initial droplets size distribution is defined in accordance with results of laboratory tests on impaction-pin type nozzles. By using a commercial CFD software, 3D numerical simulations have been carried out on a typical gas turbine inlet duct. The effects of the duct geometry, filter and silencer on the duct internal air flow-field were analyzed. Finally, the effect of water injection carried out by means of an array of nozzles in the inlet duct is investigated. The paper presents the CFD two-phase results obtained for the application case under study; the analysis of the compressor bellmouth conditions due to the evaporation phenomenon is included in the paper.Copyright

CFD Simulation of a Microturbine Annular Combustion Chamber Fuelled With Methane and Biomass Pyrolysis Syngas: Preliminary Results

Micro gas turbines could be profitably used, for distributed energy production, also exploiting low calorific value biomass-derived fuels, obtained by means of integrated pyrolysis and/or gasification processes. These synthesis gases show significant differences with respect to natural gas (in terms of composition, low calorific value, hydrogen content, tar and particulate matter content) that may turn into ignition problems, combustion instabilities, difficulties in emission control and fouling. CFD simulation of the combustion chamber is a key instrument to identify main criticalities arising when using these gases, in order to modify existing geometries and to develop new generation combustion chambers for use with low calorific value gases. This paper describes the numerical activity carried out to analyze the combustion process occurring inside an existing microturbine annular combustor. A CFD study of the combustion process performed with different computational codes is introduced and some preliminary results are reported in the paper. A comparison of results obtained with the different codes is provided, for the reference case of methane combustion. A first evaluation of the pollutant emissions and a comparison with the available experimental data is also provided in the paper, showing in particular a good matching of experimental data on NOx emissions at different load conditions. Moreover, the carried out investigation concerns the case of operation with a syngas fuel derived from pyrolysis of biomass and finally the case of syngas and natural gas co-firing. This combustion condition is simulated with a simple reduced chemical kinetic scheme, in order to assess only the key issues rising with this fuel in comparison with the case of methane combustion. The analysis shows that in case of syngas operation the combustor internal temperature hot spots are reduced and the primary zone flame tends to stabilize closer to the injector, with possible implications on the emission release.Copyright

A feasibility study of an auxiliary power unit based on a PEM fuel cell for on-board applications

Proton exchange membrane (PEM) fuel cells show characteristics of high power density, low operating temperature, and fast start-up capability, which make them potentially suitable to replace conventional power sources (e.g., internal combustion engines) as auxiliary power units (APU) for on-board applications. This paper presents a methodology for a preliminary investigation on either sizing and operating management of the main components of an on-board power system composed by: (i) PEM fuel cell, (ii) hydrogen storage subsystem, (iii) battery, (iv) grid interface for the connection to an external electrical power source when available, and (v) electrical appliances and auxiliaries installed on the vehicle. A model able to reproduce the typical profiles of electric power requests of on-board appliances and auxiliaries has been implemented in a computer program. The proposed methodology helps also to define the sizing of the various system components and to identify the fuel cell operating sequence, on the basis of the above mentioned load profiles. Copyright

Numerical Simulation of Biomass Derived Syngas Combustion in a Swirl Flame Combustor

In this work a numerical investigation is carried out on a model combustor characterized by swirl flow conditions, fed with a biomass derived syngas fuel (which incorporates CH4 , CO and H2 ) and operated in laboratory at atmospheric pressure. The combustor internal aerodynamics and heat release in case of syngas combustion have been simulated in the framework of CFD-RANS techniques, by means of different available models and by adopting different levels of kinetic mechanism complexity. In particular, the applicability of reduced mechanisms involving CO and H2 species and also of detailed kinetic mechanisms are assessed. The results obtained by means of the CFD simulations on the model combustor and a comparison with available experimental data on flow field and thermal field are presented in the paper. In the test-case of syngas-air swirled flames, the turbulent non premixed combustion “flamelet” model with detailed non-equilibrium chemistry, originally developed for methane-air combustion, provides encouraging results in terms of temperature distribution. Nevertheless, a simpler chemical path including the main fuel species integrated in a general purpose, widely used in industry, turbulent combustion model still provides acceptable results.Copyright

High Efficiency Gas Turbine Based Power Cycles — A Study of the Most Promising Solutions: Part 1 — A Review of the Technology

Commercially available gas turbines have been mostly designed based on the simple Brayton cycle and despite the enormous advancements made in their components design, materials technology, blade cooling methods, etc., thermodynamic performance achievable for this simple cycle is limited. Numerous variants to the basic Brayton cycle viz., Recuperated (REC), Inter-Cooled (IC), Re-Heat (RH), steam injected (STIG) and their combinations have been proposed, extensively discussed in the literature since the early stages of gas turbine development and few of them have been successfully implemented. New variants not yet implemented in commercial engines and still in various stages of the development with potential for additional performance improvement are: advanced Steam Injected cycle and its variants (such as Inter-cooled Steam Injected, (ISTIG)), Recuperated Water Injection cycle (RWI), Humidified Air Turbine (HAT) cycle and Cascaded Humidified Advanced Turbine (CHAT) cycle, Brayton cycle with high temperature fuel cells (Molten Carbonate Fuel Cells (MCFC) and Solid Oxide Fuel Cells (SOFC)) and their combinations with the available modified Brayton cycles. The main objective of this paper (Part 1 of the two-part paper) is to provide a comprehensive review of high performance (with most promising solutions) complex gas turbine cycles, describing their main characteristics, benefits and drawbacks in comparison with the simple Brayton cycle. Detailed parametric thermodynamic cycle analyses for the selected high efficiency cycles under development are presented in Part 2 of this paper.Copyright

High Efficiency Gas Turbine Based Power Cycles—A Study of the Most Promising Solutions: Part 2—A Parametric Performance Evaluation

In general, two approaches have been used in the gas turbine industry to improve Brayton cycle performance. One approach includes increasing Turbine Inlet Temperature (TIT) and cycle pressure ratio (β), but it is quite capital intensive requiring extensive research and development work, advancements in cooling (of turbine blades and hot gas path components) technologies, high temperature materials and NOx reducing methods. The second approach involves modifying the Brayton cycle. However, this approach did not become very popular because of the development of high efficiency gas turbine (GT) based combined cycle systems in spite of their high initial cost. This paper discusses another approach that has gained lot of momentum in recent years in which modified Brayton cycles are used with humidification or water/steam injection, termed “wet Cycles”, resulting in lower cost/kW power system, or with fuel cells, obtaining “hybrid Cycles”; the cycle efficiency can be comparable with a corresponding combined cycle system including better part-load operational characteristics. Such systems, that include advanced Steam Injected cycle and its variants (STIG, ISTIG, etc.), Recuperated Water Injection cycle (RWI), humidified air turbine cycle (HAT) and Cascaded Humidified Advanced Turbine (CHAT) cycle, Brayton cycle with high temperature fuel cell, Molten Carbonate Fuel Cell (MSFC) or Solid Oxide Fuel Cells (SOFC) and combinations of these with the modified Brayton cycles, have not yet become commercially available as more development work is required. The main objective of this paper is to provide a detailed parametric thermodynamic cycle analysis of the above mentioned cycles and discussion of their comparative performance including advantages and limitations.Copyright

Performance Evaluation of the Integration Between a Thermo-Photo-Voltaic Generator and an Organic Rankine Cycle

The present study deals with the integration between a Thermo-Photo-Voltaic generator (TPV) and an Organic Rankine Cycle (ORC) named here TORCIS (Thermo-photo-voltaic Organic Rankine Cycle Integrated System). The investigated TORCIS system is suitable for CHP applications, such as residential and tertiary sector users. The aim of the research project on this innovative system is the complete definition of the components design and the pre-prototyping characterization of the system, covering all the unresolved issues. This paper shows the results of a preliminary thermodynamic analysis of the system. More in details, TPV is a system to convert into electric energy the radiation emitted from an artificial heat source (i.e., combustion of fuel) by the use of photovoltaic cells; in this system, the produced electric power is strictly connected to the thermal one, as their ratio is almost constant and cannot be changed without severe loss in performance; the coupling between TPV and ORC allows to overcome this limitation and to realize a cogenerative system which can be regulated with a large degree of freedom changing the electric-to-thermal power ratio. The paper presents and discusses the TORCIS achievable performance, highlighting its potential in the field of distributed generation and cogenerative systems.© 2012 ASME