bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced High Turning Compressor Airfoils for Low Reynolds Number Condition: Part 1 — Design and Optimization
Authors: Sonoda Toyotaka , Yamaguchi Yoshihiro , Arima Toshiyuki , Olhofer Markus , Sendhoff Bernhard , Schreiber Heinz-Adolf
Published: February 2009

A high performance compressor airfoil at a low Reynolds number condition (Re = 1.3×105) has been developed using evolutionary algorithms in order to improve the performance of the outlet guide vane (OGV), used in a single low pressure turbine (LPT) of a small turbofan engine for business jet aircrafts. Two different numerical optimization methods, the Evolution Strategy (ES) and the Multi-Objective Genetic Algorithm (MOGA), were adopted for the design process to minimize the total pressure loss and the deviation angle at the design point at low Reynolds number condition. Especially, with respect to the MOGA, robustness against changes of the incidence angle is considered. The optimization process includes the representation of the blade geometry, the generation of a numerical grid and a blade-to-blade analysis using a quasi-three-dimensional (Q3D) Navier-Stokes solver with a k-ω turbulence model including a newly implemented transition model to evaluate the performance. Overall aerodynamic performance and boundary layer properties for the two optimized blades are discussed numerically. The superior performance of the two optimized airfoils is demonstrated by a comparison with conventional controlled diffusion airfoils (CDA). The advantage in performance has been confirmed by detailed experimental investigations, which are presented in Part 2 of this paper.
LDV Measurements of Unsteady Midspan Flow in a Turbine Rotor at Low Reynolds Number
Authors: Matsunuma Takayuki , Tsutsui Yasukata
Published: February 2009

In this study, the unsteady flow field at midspan in an axial-flow turbine rotor at low Reynolds number (Reout,RT = 3.6×104) was investigated experimentally using a laser Doppler velocimetry (LDV) system. The time-averaged and time-dependent distributions of velocity, flow angle, vorticity, turbulence intensity, and Reynolds stress were analyzed in terms of both absolute and relative frames of reference. In the relative frame of reference, the nozzle wake had a slip velocity relative to the mean flow, which caused the wake fluid to migrate across the rotor passage and accumulate on the rotor suction surface. The effect of the nozzle wake on the flow field inside the rotor was determined qualitatively and quantitatively. The flow separation occurred at the rotor suction surface because of the low Reynolds number. The position of the separation onset fluctuated periodically as much as about 10% of the rotor axial-chord by the rotor-stator interaction. The turbulence in the wake region was anisotropy, and it exhibited strong Reynolds stress.
Generic Friction Models for Time-Domain Vibration Analysis of Bladed Discs
Authors: Petrov E. P. , Ewins D. J.
Published: February 2009

New efficient models have been developed to describe dynamic friction effects in order to facilitate analysis of the vibration of bladed discs in the time domain. These friction models describe friction forces occurring at contact interfaces under time-varying normal load variations, including cases of separation. The friction models developed allow one to take into account time-varying friction contact parameters, such as friction coefficient and contact stiffness coefficients. Anisotropy and variation of the friction characteristics over the contact surfaces are included in the proposed models. The capabilities of the new friction models are demonstrated. Analysis of the friction forces is performed for different motion trajectories and different time variations of the normal load, and the effects of anisotropy, variation in time of the friction characteristics and normal load variation are discussed. A numerical analysis of transient vibrations of shrouded blades using the new models is presented.
Two Phase Flow Downstream of a Multipoint Lean Direct Injection Low NOx Nozzle
Authors: Boutazakhti Mohamed , Yimer Ibrahim , Sullivan Pierre E. , Thomson Murray J.
Published: February 2009

This work examines the flow downstream of a Parker Hannifin low NOx LDI nozzle. The nozzle is a square matrix of 3 × 3 airblast simplex fuel ports. The air pressure drop was set to 5%, for a Reynolds number of 40,000. Liquid injection pressure was 2.28kPa. The nozzle is tested at atmospheric conditions without combustion. The objective of this work is twofold: first characterize the spray and the turbulent flow fields; and second examine the effect of the interaction between jets on turbulence and spray profiles. Jet-jet lateral impingement starts within ∼ 1–2 nozzle diameters downstream. The comparison of a single jet and the 3 × 3 matrix spray profiles shows some degree of coalescence due to the interaction between jets. Despite this, the Sauter mean diameter of the resulting spray field is in the 25–35 μm range. In the first few air swirl cup diameters downstream of the nozzle exit plane (down to z/D = 3), the droplets are still accelerating to the air velocity and turbulence is anisotropic. No–slip and turbulence isotropy assumption are accurate only well downstream of the exit plane (z/D = 7.5).
Comparative Assessment of Direct and Indirect Probabilistic Methods for Thermomechanical Analysis of Structural Components in Gas Turbines
Authors: Volovoi Vitali V. , Waters Mark , Mavris Dimitri N.
Published: February 2009

Various sources of uncertainty greatly affect the life of structural components of gas turbines. Probabilistic approaches provide a means to evaluate these uncertainties; however, the accuracy of these approaches often remains unknown. Published quantitative studies of the effectiveness of various uncertainty quantification techniques are usually based on very simple examples. This is contrasted by the large-size finite element models that are used for complex geometries of critical structural parts such as turbine blades or nozzles. In such real-life applications the expenses of the “function calls” (runs of these models) preclude systematic studies of probabilistic methods. These expenses are attributed not only to the actual runs of the model, but to the difficulties in parametrically changing the model as well. Such a “complexity gap” leads to a justifiable concern over whether the trends identified in academic studies are relevant to these industrial applications. As a result, structural engineers end up with the number of function calls that they can afford rather than what would be needed for the required level of accuracy. The present effort intends to bridge this gap by studying a mid level problem: a simplified notional finite element model of a gas turbine component is presented. Despite its simplicity, the model is designed to reflect the major features of more realistic models. The parametric changes of the model are fully automated, which allows for performing an extensive set of benchmark tests that help to determine the relative merits of various existing probabilistic techniques for component life assessment. Several meta-modeling techniques are investigated and their performance compared based on direct sampling methods. In this context, various Design of Experiments (DoE) methods are studied. The results are used to construct the Response Surface Equations (RSE) as well as the kriging models. It is emphasized that changes in the relative locations of the critical points induced by variation of independent parameters can critically affect the overall fidelity of the modeling; the means of remedying such a degradation in precision are discussed. Finally, it is shown that when the ranges of independent variables are large, kriging generally provides precision that is an order of magnitude better than RSE for the same DoE.
Comparison of Linear and Non-Linear Gas Turbine Performance Diagnostics
Authors: Kamboukos Ph. , Mathioudakis K.
Published: February 2009

The features of linear performance diagnostic methods are discussed, in comparison to methods based on full non-linear calculation of performance deviations, for the purpose of condition monitoring and diagnostics. First, the theoretical background of linear methods is overviewed to establish a relationship to the principles used by non-linear methods. Then computational procedures are discussed and compared. The effectiveness of determining component performance deviations by the two types of approaches is examined, on different types of diagnostic situations. A way of establishing criteria to define whether non-linear methods have to be employed is presented. An overall assessment of merits or weaknesses of the two types of methods is attempted, based on the results presented in the paper.
Polymer-Derived Si-Al-C-N-O Ceramics for High Temperature Applications
Authors: Bharadwaj Lavanya , Dhamne Abhijeet , An Linan , Fookes Barry , Kapat Jay , Chow Louis
Published: February 2009

Polymer-derived ceramics are a new class of materials synthesized by thermal decomposition of polymeric precursors. The resultant materials are amorphous alloys of silicon, carbon, and nitrogen, which can be converted to crystalline materials by annealing at higher temperatures. This novel chemical-to-ceramic route offers a unique opportunity to tailor the structures and compositions, therefore the properties, of the resultant materials by designing the chemistry of the precursors. In this paper we report the studies on synthesis and oxidation behavior of polymer-derived SiAlCN materials. The precursor was synthesized by mixing a polysilazane and aluminum isopropoxide. The mixture was then pyrolyzed at 1000°C in Ar/N2 to convert to SiAlCNO ceramics. The oxidation studies revealed that the SiAlCNO possesses a lower oxidation rate than SiCN. It is believed that the better oxidation resistance exhibited by SiAlCN is due to the oxide layer containing Al, which makes oxygen diffusion more difficult than in pure SiO2. The materials are promising for many high temperature applications, e.g. environmental barrier coatings, high temperature fibers, matrixes for composites, and even monolithic components.
Effects of Coolant Density Ratio on Film Cooling Performance on a Vane
Authors: Cutbirth J. Michael , Bogard David G.
Published: February 2009

Film cooling performance was studied on a simulated turbine vane model with an objective of determining how much the coolant density ratio affects this performance. Experiments were conducted using coolant density ratios of 1.8 and 1.2. The purpose of the study was to determine if tests done at small density ratios (which is often more viable in a laboratory) can give reasonable predictions of performance at more realistic large density ratios. Furthermore, appropriate scaling parameters were determined. The mainstream flow was operated with low and high turbulence levels. Adiabatic effectiveness was measured in the showerhead region of the vane, and following the first row of coolant holes on the pressure side. Adiabatic effectiveness performance using small density ratio coolant gave performance trends similar to the large density ratio coolant, but quantitative values differed by varying amount depending on operating conditions.
Frequency Domains Identification of a MIMO AMB Rigid Rotor System Based on Measured Open-Loop Frequency Responses
Authors: Ahn Hyeong-Joon , Han Dong-Chul , Maslen Eric H.
Published: February 2009

This paper discusses frequency domain identification for a MIMO active magnetic bearing (AMB) rigid rotor system based on measured open-loop frequency responses. The frequency responses measured by a digital controller include the effects of sensor, amplifier, and discretization dynamics. These dynamics affect the identification of poles of the AMB system as well as the achievable performance of the controller. A new reduced order frequency domain identification of a multi-input/multi-output (MIMO) AMB rigid rotor system is proposed, which implicitly includes these dynamics along with the rest of the identified plant. The proposed identification scheme consists of three distinct steps: i) sensor, amplifier and delay dynamics; ii) rigid modes; and iii) flexible modes. The proposed scheme directly tackles the open-loop MIMO frequency data and is based on an explicit MIMO parameterization. An accurate reduced order model, suitable for advanced control synthesis, can be obtained through the proposed identification scheme.
The Determination of In-Situ Film Hole Flow Rates Using a Transient Thermal Inertia Method
Authors: Bunker Ronald S. , Osgood Sarah J. , Nirmalan Nirm V.
Published: February 2009

Film hole flow rates are conventionally characterized by a discharge coefficient relating the actual mass flow rate to the theoretical ideal flow rate based upon some measured effective hole diameter or flow area. These discharge coefficients are typically measured on controlled test plates that contain the particular size, shape, and fabrication method for an individual film hole type. Such discharge coefficients are then assumed to apply to all of the in-situ film holes of that type which are machined or formed in the as-fabricated cooled turbine component. The thermal-mechanical analysis of the component is then performed using these assumed values to calculate film hole flow rates. In practice however, every film hole in a cooled airfoil is different due to machine tool wear, surface curvatures, laser drift, coating variations, and local flow supply behavior. A new method has been developed and demonstrated which allows determination of the individual film hole flow rates in-situ for an as-fabricated component, thus avoiding the need for assumed discharge coefficients or highly detailed flow checks. This method uses the thermal transient characteristics of external surface points near an active film hole to determine the flow rate through the hole. An imaging Infrared system is used to record the component response to an induced thermal cooling transient in which the film hole internal heat transfer dominates the local thermal transient behavior. The characteristic of the non-dimensionalized thermal decay is related to the flow rate within each individual film hole using a limited calibration function. This method allows the rapid inspection and quantification of detailed film hole flows for actual parts, which data may then be used in the analysis and health monitoring of parts in operation.
Effect of Sector Mode Shape Variation on the Aerodynamic Stability of a Low-Pressure Turbine Sectored Vane
Authors: Chernysheva Olga V. , Fransson Torsten H. , Kielb Robert E. , Barter John
Published: February 2009

The paper presents a method to investigate the flutter appearance in a cascade, where blades are connected together in a number of identical sectors. The key parameters of the method are vibration amplitudes and mode shapes of the blades belonging to the same sector. The aerodynamic response from a sectored vane cascade is calculated based on the aerodynamic work influence coefficients of freestanding blades performed with two-dimensional inviscid linearized flow solver. A case study based upon the presented methodology shows that, despite stabilizing effect of tying blades together into sectors, a sectored vane consisting of six low-pressure turbine blades vibrating with real single modes, and identical amplitudes can be unstable at realistic design conditions.
Blade Forced Response Prediction for Industrial Gas Turbines: Part 1 — Methodologies
Authors: Moffatt Stuart , He Li
Published: February 2009

Forming the first part of a two-part paper, the methodology of an efficient frequency-domain approach for predicting the forced response of turbomachinery blades is presented. The capability and computational efficiency of the method are demonstrated in Part Two with a three-stage transonic compressor case. Interaction between fluid and structure is dealt with in a loosely coupled manner, based on the assumption of linear aerodynamic damping and negligible frequency shift. The Finite Element (FE) package ANSYS is used to provide the mode shape and natural frequency of a particular mode, which is interpolated onto the CFD mesh. The linearised unsteady Navier-Stokes equations are solved in the frequency domain using a single-passage approach to provide aerodynamic excitation and damping forces. Two methods of obtaining the single degree-of-freedom forced response solution are demonstrated: the Modal Reduction Technique, solving the modal forced response equation in modal space; and a new Energy Method, an alternative method allowing calculations to be performed directly and simply in physical space. Both methods are demonstrated in a preliminary case study of the NASA R67 transonic fan blade with excitation of the 1st torsion mode due to a hypothetical inlet distortion.
The Role of Forward Sweep in Subsonic Axial Fan Rotor Aerodynamics at Design and Off-Design Operating Conditions
Authors: Corsini A. , Rispoli F.
Published: February 2009

The role that forward sweep plays in the aerodynamics of subsonic axial fan rotor is herein discussed, with emphasis on the combined effects of non-uniform three-dimensional work distribution and modified stacking lines. To study blade forward sweep effects numerical investigations have been undertaken on highly loaded fans of non-free vortex design, with ideal total head rise coefficient typical of industrial application range. The results of two rotors with identical overall design parameters and, respectively, with 35-deg forward swept blades and unswept blades have been compared. The investigation has been carried-out using an accurate in-house developed multi-level parallel finite element RANS solver, with the adoption of a non-isotropic two-equation turbulence closure. The pay-off derived from the sweep technology has been assessed with respect to the operating range improvement. To this end the flow structure developing through the blade passages and downstream of the rotors as well as loss distributions have been analysed at three different operating conditions. The studies showed that the forward swept blade operates more efficiently in particular at low volume flows, with a delayed onset of stall. The analyses of three-dimensional flow structures showed that, sweeping forward the blade, the flow centrifugation on blade suction surface is reduced and non-free vortex spanwise secondary flows is attenuated. Moreover, reduced fluid mechanical losses have been also pointed out in rotor with swept blades.
Complex Identification Technique of Aircraft Gas Turbine Engine’s Health
Authors: Pashayev A. M. , Sadiqov R. A. , Abdullayev P. S.
Published: February 2009

The new approach to identification of the aviation GTE technical condition is considered (examined) at an fuzzy, limitation and uncertainty of the information. This approach is based on applicability of fuzzy logic and artificial neural networks (Soft computing).
Experimental Study of Surface and Interior Combustion Using Composite Porous Inert Media
Authors: Marbach T. L. , Agrawal A. K.
Published: February 2009

Combustion using silicon carbide coated, carbon-carbon composite porous inert media (PIM) was investigated. Two combustion modes, surface and interior, depending upon the location of flame stabilization, were considered. Combustion performance was evaluated by measurements of pressure drop across the PIM, emissions of NOx and CO, and the lean blow-off limit. Data were obtained for the two combustion modes at identical conditions for a range of reactant flowrates, equivalence ratios, and pore sizes of the PIM. Results affirm PIM combustion as an effective method to extend the blow-off limit in lean premixed combustion.
Probabilistic Surface Damage Tolerance Assessment of Aircraft Turbine Rotors
Authors: Enright Michael P. , Lee Yi-Der , McClung R. Craig , Huyse Luc , Leverant Gerald R. , Millwater Harry R. , Fitch Simeon H. K.
Published: February 2009

This paper describes some of the new surface damage capabilities in DARWIN™, a probabilistic fracture mechanics software code developed to evaluate the risk of fracture associated with aircraft jet engine titanium rotors/disks. An initial framework is presented in which a graphical user interface (GUI) is used to explicitly define the stresses and temperatures at the crack location for several crack geometries. A summary of the approach used to develop new stress intensity factor solutions for these geometries is also presented, including selected validation results.
Selection, Development and Testing of Stainless Steels and Alloys for High-Temperature Recuperator Applications
Authors: Maziasz Philip J. , Pint Bruce A. , Swindeman Robert W. , More Karren L. , Lara-Curzio Edgar
Published: February 2009

Compact recuperators/heat-exchangers are essential hardware that increases the efficiency of microturbines and smaller industrial gas turbines. There are several different kinds of recuperator technology (primary surface, plate and fin, spiral, and others), but they all have several common materials needs. Most commercial recuperators today are made from 347 stainless steel sheet or foil. Increased engine size, higher exhaust temperatures and alternate fuels all require greater performance (strength, corrosion resistance) and reliability than 347 steel, especially as temperatures approach or exceed 750°C. To meet these needs, the Department of Energy (DOE) has sponsored programs at the Oak Ridge National Laboratory (ORNL) to measure properties of commercial sheet and foil materials, to analyze recuperator components, and to identify or develop materials with improved performance and reliability, but which also are cost-effective. This paper summarizes high-temperature creep and corrosion testing of commercial 347 used for current recuperators, testing of HR 120 and modified 803 alloys, and development of modified 347 stainless steels.
Detailed Chemistry Simulations of a Trapped Vortex Combustor
Authors: Goldin Graham M. , Madsen Jens , Straub Douglas L. , Rogers William A. , Casleton Kent H.
Published: February 2009

Steady simulations of a Trapped Vortex Combustor are performed with the Strained Laminar Flamelet model, the Eddy Dissipation Concept (EDC) model and the Composition PDF Transport model using an accurate 19 species Augmented Reduced Mechanism. CO predictions are reasonable, although the EDC model over-predicts CO since the reaction time in the fine scales is less than the residence time in the combustor. The PDF Transport model over-predicts NO by a factor of four for reasons that are not well understood at present. In-situ Adaptive Tabulation (ISAT) accelerates chemistry calculations by two to three orders of magnitude, making 3D CFD calculations with detailed chemistry computationally feasible.
Modelling and Measurements of Combustor Cooling Tile Flows
Authors: Denman Paul A. , Barker Ashley G. , Jayatunga Charith W. , McGuirk James J.
Published: February 2009

Pressure to reduce available cooling air in modern combustors has driven recent interest in cooling technology based on double-skinned combustor liners, i.e. tiles containing multiple pin-type pedestals to enhance heat transfer. The design of such systems is, however, hampered by the multiplicity of parameters needing optimisation: feedhole configuration, pedestal configuration, tile configuration (e.g. tile overlap). Much experimental testing is currently needed. In addition, the simulation of flow and heat transfer in cooling tile geometries using RANS-based CFD is made particularly difficult by the impossibility of resolving every individual pin in the pedestal matrix whilst retaining an overall CFD problem of reasonable size. The present paper describes a mixture of experimental and computational work undertaken to explore cooling tile flows. On the experimental side, a large-scale Perspex aerodynamic rig of a cooling tile was constructed. Measurements at representative Reynolds numbers were possible and delivered information on discharge coefficients, pressure drops and flow splits for various tile configurations. The same tile geometries were subsequently modeled using a RANS-based CFD approach. The novelty in these simulations was the use of a ‘sub-grid-scale’ model for the pedestal flow and heat transfer. This approach has previously been used in combustor heatshield predictions; it is demonstrated in the present work how it may also be applied to cooling tiles.
Economic and Performance Evaluation of Heat Sink Options in Combined Cycle Applications
Authors: Tawney Rattan , Khan Zahid , Zachary Justin
Published: February 2009

Because of the current environmental requirements for zero discharge from power plants and scarcity of water, the cooling tower—a proven and industry-recognized conventional option for combined cycle application heat sinks—is being scrutinized by designers, developers, operators, and regulatory agencies. This paper is a guideline to selecting the most appropriate solution for the plant heat sink based on water availability, site location, and wastewater disposal requirements. The paper discusses wet as well as dry cooling systems and evaluates the impact of heat sink selection for cogeneration applications and merchant power plant cycling operation mode. For each proposed option, the performance, relative costs, and noise issues will be presented.
A Review of W501G Engine Design, Development and Field Operating Experience
Authors: Bancalari Ed , Diakunchak Ihor S. , McQuiggan Gerry
Published: February 2009

At the end of 2002 there were nine W501G engines in commercial operation, with the lead engine having accumulated 13,000 operating hours and the total fleet about 50,000 operating hours. By the end of 2003 we expect to double the number of operating engines. This paper describes the advanced design features incorporated into the W501G engine, technology/component verification programs carried out in its development, extensive field verification tests, and engine operational experience since its introduction in 1999. The W501G is the latest in a series of successful heavy duty frames developed by Siemens Westinghouse. It is the most powerful and most efficient operating 60 Hz gas turbine, with combined cycle net LHV based efficiency of 58%. Its design is based on viscous 3-D aerodynamics, advanced cooling and sealing, ultra lean premixed combustion, and proven aero engine materials and coatings. It is the first operating engine with closed-loop steam cooling in the transition. Its compressor aerodynamics and mechanical integrity were verified in a full scale test. Numerous rig tests were carried out on its cooling designs, sealings, combustion system, and coatings. An extensive field test program, including telemetry, pyrometry and thermal paint tests, was carried out to verify its performance, emissions and mechanical integrity.
Dynamic Fatigue of CVD-Mullite Coated SN88 Silicon Nitride
Authors: Lin H.-T. , Ferber M. K. , Kirkland T. P. , Zemskova S. M.
Published: February 2009

Studies of dynamic fatigue were carried out on CVD-mullite coated and uncoated of SN88 silicon nitride at 850°C and at 30 MPa/s and 0.003 MPa/s in air. The objective of the studies was to evaluate the effect of thin CVD-mullite coatings on the mechanical reliability and lifetime performance of SN88 subjected to mechanical loading conditions. Mechanical results showed that the CVD-mullite coated SN88 samples exhibited similar strength degradation and lifetime performance to those uncoated samples under similar test conditions. SEM examinations of both coated and uncoated samples after mechanical testing also showed similar development of damage zone (i.e., pores and cracking were generated in SN88 surface region) due to oxidation reaction. Results of mechanical testing and SEM examinations indicated that the CVD-mullite coating could not environmentally protect SN88 to ensure a long-term mechanical performance and lifetime in gas turbine environments.
Sizing Incineration for Base-Load Energy
Authors: Beyene Asfaw
Published: February 2009

Many state and country codes require that Volatile Organic Compounds (VOC) are either captured or destroyed before they are emitted to the atmosphere. This measure requires designing and operating refrigeration systems that would evaporate, condense and separate the VOC from air stream, or more commonly, install afterburners to combust the VOCs. Both condensation and combustion related abatement technologies involve large capital and maintenance costs. In the case of combusting the VOC, fuel is usually added to the air/VOC mixture for proper air/fuel ratio and effective combustion. The resulting high temperature gas free from VOC is often emitted to the ambient with little or no value captured from the energy intensive process. Regulations limiting the emission of VOCs continue to grow. Paint and coating lines and manufacturing processes that involve emission of chemical vapors such as carpet manufacturing, produce large amounts of VOC that needs to be oxidized. Other incinerators that do not necessarily involve VOCs, such as kiln systems also produce large energy waste. Thermodynamically, the VOC destruction combustion process is simply a total waste of energy unless it allows some waste recovery. Afterburners are typically designed for environmental reasons, ignoring the energy cost, which is accepted as an inevitable penalty. This paper discusses the feasibility of selecting incinerators as a Gas Turbine Oxidizer (GTO) sized for the base-energy load. So sized GTO could produce process heat, generate electric power, shave energy peaks, and reduce air pollution without compromising the primary intent of effectively destroying VOCs.
Advances in Direct Fuel Cell/Gas Turbine Power Plants
Authors: Ghezel-Ayagh Hossein , Daly Joseph M. , Wang Zhao-Hui
Published: February 2009

This paper summarizes the recent progress in the development of hybrid power systems based on Direct FuelCell/Turbine® (DFC/T®). The DFC/T system is capable of achieving efficiencies well in excess of state-of-the-art gas turbine combined cycle power plants but in much smaller size plants. The advances include the execution of proof-of-concept tests of a fuel cell stack integrated with a microturbine. The DFC/T design concept has also been extended to include the existing gas turbine technologies as well as more advanced ones. This paper presents the results of successful sub-MW proof-of-concept testing, sub-MW field demonstration plans, and parametric analysis of multi-MW DFC/T power plant cycle.
Tubular SOFC Hybrid Power System Status
Authors: Veyo Stephen E. , Lundberg Wayne L. , Vora Shailesh D. , Litzinger Kevin P.
Published: February 2009

Power generation systems of exemplary efficiency can be configured through the synergistic thermal-hydraulic coupling of a solid oxide fuel cell (SOFC) generator module with a gas turbine engine electric generator. Analysis indicates that hybrid cycle power systems have the potential to achieve electrical generation efficiencies ranging from over 50% for 300 kWe atmospheric pressure hybrid systems to near 70% for pressurized fuel cell reheat gas turbine hybrid systems. Analysis results are reviewed. Siemens Westinghouse has fabricated two simple-cycle proof-of-concept designs for pressurized SOFC/micro gas turbine generator (PSOFC/MTG) hybrid systems. The efficiency horizon for simple-cycle PSOFC/MTG systems is 60%. The world’s first SOFC Pressurized Hybrid of 200 kWe capacity [PH200] was built for Southern California Edison (SCE) and is installed at the National Fuel Cell Research Center at the University of California – Irvine. The unit has operated for over 2000 hours with an indicated efficiency of 53%. Although operation has been troubled by SOFC stack nonconformance problems, this unit has demonstrated the technical feasibility of the PSOFC/MTG hybrid technology. Following the most recent stack repair, the unit was restarted in November, 2002. System operation and performance information is reviewed. A second proof-of-concept unit, a PH300 built for a consortium led by RWE, a German utility, is nearing completion and is scheduled for initial operation in early 2003, and another PH300 will be installed at an Edison S.p.A site in Italy later in 2003. PH300 project status information is presented.
The Analysis and Design of Saturators for Power Generation Cycles: Part 1 — Thermodynamics
Authors: Aramayo-Prudencio A. , Young J. B.
Published: February 2009

The introduction of water into a gas turbine circuit is known to provide benefits of increased efficiency and specific work output. There are several methods of humidification but the use of a pressurised saturator in an evaporative cycle offers many attractive features. This two-part paper presents an in-depth study of the saturator, in Part 1 via a thermodynamic approach and in Part 2 via a heat and mass transfer analysis. In Part 1, the pinch condition is shown to be the key reference state and an analytical expression is obtained for the pinch variables. Saturators with a given pinch condition form a family whose members have the same pressure, flow and enthalpy invariants. Each member has different outlet conditions which can be found computationally or analytically. The analytical approach gives insight into the effects of parameter changes. Minimisation of the entropy production rate is considered and the paper includes discussion on constraints on the operation of saturators and problems of scaling.
Hybrid Power: A 2003 Perspective for the Decade
Authors: Dennis Richard , Burch Gary , Williams Mark , Hoffman Pat , Gross Robert , Samuelsen Scott
Published: February 2009

Hybrid power generation systems are evolving as attractive candidates for high-efficiency production of electric energy and a near-zero emission of primary pollutants. Hybrids, by definition, are a combination of two or more power generation technologies that create a synergistic value greater than the sum of the individual parts. Examples include fuel cells integrated with gas turbines, fuel cells integrated with photovoltaics, and heat engines integrated with wind generation. This paper describes the evolution of hybrid systems for both distributed power generation and central power generation as anticipated for this decade, the development requirements and application opportunities, and strategies that utilize both fossil and renewable fuels to achieve the dramatic increase in electrical efficiency that hybrid systems portend.
Application of CFD Analysis for Rotating Machinery: Part 2 — Labyrinth Seal Analysis
Authors: Hirano Toshio , Guo Zenglin , Kirk R. Gordon
Published: February 2009

Labyrinth seals are used in various kinds of turbo machines to reduce internal leakage flow. The working fluid or, the gas passing through the rotor shaft labyrinth seals, often generates driving force components that may increase the unstable vibration of the rotor. It is important to know the accurate rotordynamic force components for predicting the instability of the rotor-bearing-seal system. The major goals of this research was to calculate the rotordynamic force of a labyrinth seals utilizing a commercial CFD program and to further compare those results to an existing bulk flow computer program currently used by major US machinery manufacturers. The labyrinth seals of a steam turbine and a compressor eye seal are taken as objects of analysis. For each case, a 3D model with eccentric rotor was solved to obtain the rotordynamic force components. The leakage flow and rotor dynamics force predicted by CFX TASCFlow are compared with the results the existing bulk flow analysis program DYNLAB. The results show that the bulk flow program gives a pessimistic prediction of the destabilizing forces for the conditions under investigation. Further research work will be required to fully understand the complex leakage flows in turbo machinery.
Stabilizing Excessive EGR With an Oxidation Catalyst on a Modern Diesel Engine
Authors: Zheng Ming , Irick David K. , Hodgson Jeffrey
Published: February 2009

For diesel engines (CIDI) the excessive use of exhaust gas recirculation (EGR) can reduce in-cylinder oxides of nitrogen (NOx) generation dramatically, but engine operation can also approach zones with high instabilities, usually accompanied with high cycle-to-cycle variations and deteriorated emissions of total hydrocarbon (THC), carbon monoxide (CO), and soot. A new approach has been proposed and tested to eliminate the influences of recycled combustibles on such instabilities, by applying an oxidation catalyst in the high-pressure EGR loop of a turbocharged diesel engine. The testing was directed to identifying the thresholds of stable operation at high rates of EGR without causing cycle-to-cycle variations associated with untreated recycled combustibles. The elimination of recycled combustibles using the oxidation catalyst showed significant influences on stabilizing the cyclic variations, so that the EGR applicable limits are effectively extended. The attainability of low NOx emissions with the catalytically oxidized EGR is also evaluated.
Investigation of a Novel Fuel Injection Technology Aimed to Reduce Cold-Start Emissions in SI Engines
Authors: Reese Brian T. , Guezennec Yann G. , Oljaca Miodrag
Published: February 2009

A novel fuel atomization device (Nanomiser™) was evaluated under laboratory conditions with respect to its ability to reduce SI engine cold-start hydrocarbon emissions. First, comparisons between the level of atomization using the conventional, pintle-type fuel injector and the novel atomizer were carried out using flow visualization in a spray chamber and particle size distribution. The novel atomizer is capable of producing sub-micron fuel droplets, which form an ultra-fine mist with outstanding non-wetting characteristics. To capitalize on these atomization characteristics, this device was compared to a conventional fuel injector in a small, two-cylinder, SI engine under a number of operating conditions. Results show a slightly enhanced combustion quality and lean limit under warm operating conditions and a dramatic reduction in unburned HC emission under cold operating conditions, with cold emissions with the Nanomiser™ matching those with a conventional injector under fully warm conditions.
A Combined Optimization Method for Common Rail Diesel Engines
Authors: de Risi Arturo , Carlucci Paolo , Donateo Teresa , Ficarella Antonio
Published: February 2009

The optimization method proposed in the present study consists of a multi-objective genetic algorithm combined with an experimental investigation carried out on a test bench, by using a DI Diesel engine. The genetic algorithm selects the injection parameters for each operating condition whereas the output measured by the experimental apparatus determines the fitness in the optimization process. The genetic algorithm creates a random population, which evolves combining the genetic code of the most capable individuals of the previous generation. Each individual of the population is represented by a set of parameters codified with a binary string. The evolution is performed using the operators of crossover, mutation and elitist reproduction. This genetic algorithm allows competitive fitness functions to be optimized with a single optimization process. For the determination of the overall fitness function the concept of Pareto optimality has been implemented. In this work, the input variables used for the optimization method are injection parameters like start of pilot and main injection, injection pressure and duration. The engine used is a FIAT 1929 cc DI diesel engine, in which the traditional injection system has been replaced by a common rail high pressure injection system. The competitive fitness functions were determined based on the measured values of fuel consumption, emissions levels (i.e. NOx, soot, CO, CO2, HC); combustion noise and overall engine noise, for each operating conditions. The optimization was performed for different engine speed and torque conditions typical of the EC driving cycles.
First Test Results of a Novel Large High-Efficiency Reciprocating Piston Engine
Authors: Coney Mike W. , Linnemann Claus , Greenwood Anna L. , Hogg Carl R.
Published: February 2009

A new type of high-efficiency reciprocating internal combustion engine — called the “isoengine” — is being developed, which has separate cylinders for compression and combustion. The fully developed engine is predicted to generate electricity at net electrical plant efficiencies of up to 60% with unit sizes in the range of about 5–20 MWe. The specific capital cost and overall engine size are expected to be similar to those of conventional large engines. The construction of a first 3 MW prototype engine has now been fully completed and in October 2002 the first fuel was injected. The present paper focuses on the experience and test results obtained during the commissioning and early test stage of the prototype engine. The testing of this Engineering Demonstrator will contribute significantly to the development of a Commercial Demonstrator and first commercial isoengines, which should be available in the second half of this decade.   NOTE: This paper was presented at the ASME 2003 Internal Combustion Engine Division Spring Technical Conference but was printed in the ASME 2003 Internal Combustion Engine and Rail Transportation Divisions Fall Technical Conference proceedings, pages 409–418. It should appear under the Engine Design heading.
Development of Pre-Turbo Catalyst for Natural Gas Engines
Authors: Leprince Thierry , Aleixo Joe , Chowdhury Kamal , Naseri Mojghan , Williams Shazan
Published: February 2009

Distributed power generation is an efficient method for reducing CO2 emissions through the elimination of transmission losses. Co-generation has similar benefits with higher thermal efficiency. Natural gas engines are very popular for these applications. Unfortunately, these engines emit significant levels of methane, which is a greenhouse gas. Reduction of methane emissions would greatly improve the environment and provide greenhouse gas emissions credits. The exhaust temperature downstream of the turbocharger in a natural gas engine is typically below 500°C. At these temperatures, methane is difficult to oxidize with current oxidation catalysts. It would be a much better option to install the oxidation catalyst before the turbocharger where temperatures are 100–150°C higher. Pressures upstream of the turbocharger are higher than downstream and also affect catalyst conversion efficiencies. Misfiring events are common in natural gas engines. During misfiring events, the catalyst will see a sudden increase in hydrocarbon (methane). When this pulse of hydrocarbon hits the catalyst, it will be oxidized and generate a large exotherm which could lead to catalyst failure (mechanical and/or chemical). This issue is critical for a pre-turbo catalyst: 1) Mechanical failure of the catalyst could lead to catastrophic turbocharger failure, a result of the turbine blades being damaged. 2) Misfiring with catalyst installed before the turbocharger is more likely to ignite the methane pulse because of the higher temperatures in this location. High exotherms from ignition could negatively affect catalyst performance. Through careful catalyst design, one can minimize this risk and this paper will address these issues.
Visualization of the Effects of Post Injection and Swirl on the Combustion Process of a Passenger Car Common Rail DI Diesel Engine
Authors: Helmantel Arjan , Somhorst Joop , Denbratt Ingemar
Published: February 2009

The effects of variations in injection strategy and swirl on a DI Diesel engine performance and emissions were tested. The cylinder head was fitted with a small diameter endoscope, coupled with a triggered CCD camera, in order to study the effect of these variations on the combustion process. The images that were taken of the combustion process were used to calculate the spatial and temporal distribution of flame temperature and soot kks factor by using the 2-color method. The engine used in the experiments is a single cylinder version of a modern, passenger car type, common rail Diesel engine with a displacement of 480 cc. The fitted endoscope caused very little interference with the combustion chamber due to its small dimensions. The 65 degree angle view of the endoscope allowed coverage of a large portion of the entire combustion chamber. The combustion images and derived temperatures and soot concentrations were used to study the influence of post injection and high swirl. Adding a third (post) injection to the pilot and main injection increases the mixing and the flame temperature during the second half of the combustion process, thereby improving soot oxidation. The fuel efficiency was not negatively affected by the later phasing of part of the heat release. Increased swirl of the intake air was also studied. An 80% increase in swirl-ratio was achieved by closing off one of the two intake ports with a butterfly valve. The improved mixing gave significant reductions in soot emissions, with a small increase in NOx formation.
Analysis of Combustion Process in a Transparent Common Rail Diesel Engine by 2D Digital Imaging and Flame Emission Spectroscopy
Authors: Merola Simona S. , Vaglieco Bianca M. , Mancaruso Ezio
Published: February 2009

Spectroscopic measurements and 2D digital imaging were used in single cylinder, four-stroke DI diesel engine, optically accessible. It was equipped with a four-valve head and fully flexible electronic controlled ‘Common Rail’ injection system. Three fuel injection strategies, descriptive of the CR diesel engine, were considered. They consisted of a main, a pilot and main and finally pilot, main and post injections. Fuel spray and visible flame propagation were evaluated by digital imaging at high temporal resolution. Autoignition and combustion processes were analysed by broadband ultraviolet-visible flame emission spectroscopy. Radical species such as OH and C2 allowed to characterise the ignition process and pollutant formation. Soot temperature and mass concentration were evaluated by two-colour pyrometry. The presence of C2 and OH radicals strongly characterised CR diesel combustion process during soot formation and evolution. In particular, the high presence of OH concentration for the whole process, from the autoignition to the soot formation and successive phases, contributed to lower the soot levels.
CO-PM Modeling for Particulate Matter Emission of Diesel Engines
Authors: Tan Pi-Qiang , Lu Jia-Xiang , Deng Kang-Yao
Published: February 2009

In this study, a phenomenological model, that predicts the particulate matter emission (PM) of diesel engines, has been formulated. The CO-PM model is based on the formation mechanisms of PM and carbon monoxide (CO) of diesel engines. It can predict the emission concentration of PM via the emission concentration of CO. The calculation method of the model is simple and quick. To validate the model, experiments were carried out in two research diesel engines. Comparisons of the model results with the experimental data show good agreement. The model is useful for computer simulations of electronically controlled diesel engines, as well as electronic control unit (ECU) designs for diesel engines.