bluuebunny/crossref_metadata_2025 huggingface dataset:
Detailed Cold-Flow Simulation to Estimate Mass Flow Distribution of Aircraft Combustor
Authors: Makida Mitsumasa , Nakamura Naoki , Nozaki Osamu
Published: May 2012

In the TechCLEAN project of JAXA, a combustor for a small aircraft engine has been developed. The combustor was tuned to show the behavior of the Rich-Lean combustion through combustion tests under atmospheric and practical conditions. Finally, the full annular combustor was successfully tuned to reduce NOx emissions to 38.1% of the ICAO CAEP4 standard under ICAO LTO cycles, also sustaining basic performances as an aircraft combustor. In the development process of the combustor, numerical simulation methods were also utilized as analysis tools to accelerate the development of the combustor. To use them in the screening process of the combustor design, we focused on cost-effective simulation methods adopting the cold-flow RANS simulation code UPACS which has been developed in JAXA. Moreover, to simplify the treatment of calculation grids of the combustor with complicated configuration, we also utilized combination of the overset grid method and the attached multi-block grid method. In the previous report, we introduced the overview of the application of the cold-flow simulation in the combustor development process. Subsequently, in this report, we focus on the effect of combustor configuration parameters to the air mass flow ratio among fuel nozzles, dilution air holes and cooling air holes on the combustor linear. Then we also show the estimation method of the effective open area of combustor liners, mass flow ratio between air holes, and total pressure loss of the combustor.
Fatigue Reliability Predictions for Crack Bridging Materials
Authors: Gallops S. , Kruzic Jamie J.
Published: May 2012

Many modern materials are reliant on crack bridging to achieve adequate fracture resistance. As they are used in more cyclic loading applications, there is a need to make accurate fatigue reliability predictions. In bridging materials, the fatigue threshold, or stress intensity range below which fatigue cracks will not propagate, increases with crack extension in a manner similar to the fracture resistance. Thus, fatigue thresholds can be plotted versus crack extension as a fatigue threshold R-curve. The fatigue threshold R-curve was measured for a 99.5% pure polycrystalline alumina. Crack growth was initiated from razor micro-notches (ρ < 10 μm) in compact tension specimens at a loading frequency of 25 Hz and a load ratio of R = 0.1. The fatigue threshold was determined as a function of crack size by 1) decreasing the cyclic load until the crack growth rate slowed to less than 10−10 m/cycle and 2) using varying initial crack length and load combinations to get varying final crack sizes. Using the measured fatigue threshold R-curve and fracture mechanics weight functions, the bridging stress profile, considered a true material property, was calculated. The accuracy of the bridging stress profile was verified by direct measurement of the bridging stresses using x-ray fluorescence spectroscopy. From the bridging stress profile, the fatigue threshold R-curve was calculated for more technically relevant crack geometries, such as a semi-elliptical surface crack. Finally, fatigue endurance strength predictions were made as a function of initial flaw size using the calculated fatigue threshold R-curve for a semi-elliptical surface crack.
Identification of Spinning Mode in the Unsteady Flow Field of a LP Turbine
Authors: Lengani Davide , Paradiso Berardo , Marn Andreas , Go¨ttlich Emil
Published: May 2012

This paper presents an experimental investigation of the vane-blade unsteady interaction in an unshrouded LP turbine research rig with uneven blade/vane count (72 blades and 96 vanes). The rig was designed in cooperation with MTU Aero Engines and considerable efforts were put on the adjustment of all relevant model parameters. In particular blade count ratio, airfoil aspect ratio, reduced massflow, reduced speed, Mach and Reynolds numbers were chosen to reproduce the full scale LP turbine at take off condition. Measurements by means of a fast-response pressure probe were performed adopting a phase-locked acquisition technique in order to provide the time resolved flow field downstream of the turbine rotor. The probe has been fully traversed both in circumferential and radial traverses. The rotor exit is characterized by strong perturbations due to the tip leakage vortex and the rotor blade wake. Circumferential non uniformities due to the upstream vane wake and to the downstream exit guide vane potential effects are also identified. Furthermore in the present configuration with an uneven blade/vane count the non-uniformities due to the stator and rotor row are misaligned along the whole turbine circumference and create a spinning mode that rotates in direction opposite to the rotor at a high frequency. The aeroacoustic theory is employed to explain such further unsteady pattern. The variations of the exit flow angle within a cycle of such pattern are not negligible and almost comparable to the ones within the blade passing period.
Gas Turbine Bottoming Cycles for Cogenerative Applications: Comparison of Different Heat Recovery Cycle Solutions
Authors: Bhargava Rakesh K. , Bianchi Michele , De Pascale Andrea
Published: May 2012

With all the advancements made in the gas turbine technologies in the last 7 decades, a large amount (approximately 60%) of the thermal energy in the gas turbine exhaust is released in to the environment. This discharged heat could be profitably used not only in thermal utilities but also as an intermediate temperature heat source for the bottoming cycles producing electric power. This paper provides a systematic thermodynamic performance evaluation and comparison among the three different waste heat recovery solutions, namely, the Inverted Brayton Cycle, the Bottoming Brayton Cycle and the Organic Rankine Cycle. The results obtained from the parametric analyses of the CHP systems clearly identify advantages and limitations of the gas turbine technology and its size when combined with the three bottoming cycles evaluated in this study. A detailed discussion on the obtained results is presented in this paper.
Extended Mean Line Theory for Axial Fans: Analytic Calculation of the Flow Characteristics for Off-Design Points
Authors: Semel Matthias , Epple Philipp , Miclea-Bleiziffer Mihai , Delgado Antonio , Smith Henrik
Published: May 2012

The use of axial fans is very common for industrial applications. The most common design case is the free vortex design. It ensures constant meridional velocity and hence an axi-symmetric and two-dimensional flow. Those designs have proved to be robust and to deliver good results. However, the free vortex model holds only at the design point. At off-design points the flow characteristics differ substantially from the free vortex model, whereby the extent of validity of a forced vortex model is obtained. Solving the equation of radial equilibrium for off-design points enables a more precise design prediction considering the impact of the variable meridional velocity and the angular momentum. This approach can be applied to free vortex models as well as forced vortex models. In the present work theoretical formulas for the flow characteristics at off-design points were developed and implemented. Three angular momentum profiles, one free vortex and two forced vortex models, were analyzed relative to the change in the meridional velocity and angular momentum profiles. The impact of these modifications on the performance characteristics of axial fans, such as pressure, efficiency, torque and hydraulic power was investigated. Comparing design prediction with numerical CFD validation leads to a precise and extensive analysis. The validity of the used approach is demonstrated. Thus a qualitative prediction of flow characteristics for any axial-impeller at off-design is obtained. This allows for a in depth understanding of the fundamental working principles and consequences of the radial equilibrium equation at the design and also at off design points.
Experimental Investigation of Forced Response Impeller Blade Vibration in a Centrifugal Compressor With Variable Inlet Guide Vanes: Part 1—Blade Damping
Authors: Zemp Armin , Abhari Reza S. , Ribi Beat
Published: May 2012

Forming the first part of a two-part paper, the quantification of the resonant response levels and the damping quantities for a centrifugal compressor impeller with variable inlet guide vanes under engine representative operating conditions is detailed in this work. The motivation for the investigation is the lack of experimental data that are needed to improve and validate computational tools used during the design phase. Measurements were performed during resonant blade vibrations with the inlet pressure, the inlet guide vane angle and the operating point as the varying parameters. The flow non-uniformity introduced into the inlet flow field was measured with an aerodynamic probe. These measurements showed an increase in flow distortion for increased guide vane angles. The response amplitudes were acquired with dynamic strain gauges. A curve-fit method was applied to estimate the critical damping ratios. The results showed a linear correlation of the aerodynamic damping with the inlet pressure. The mode dependent material damping was therefore derived using a linear extrapolation to vacuum conditions of the inlet pressure dependent overall damping. The resonant blade dynamics could be captured with a single degree of freedom model. The aerodynamic damping and the maximum strain response were found to significantly depend on the inlet guide vane angle setting and on the throttle setting of the compressor.
Dynamic Characteristic Analysis of a Rotor-Bearing System Using Global Assumed Mode Method With Different Polynomial Function
Authors: Shiau T. N. , Chang J. R. , Kang C. H. , Liao C. Y.
Published: May 2012

In this study, the dynamic analysis of a domestic high speed rotor bearing system in turbo machines by using global assumed mode with different polynomial is investigated. This system consists of rotating multi flexible shaft, rigid disks and stiffness bearing effects. The analysis includes the whirl speeds, critical speeds, and mode shapes. The Global Assumed Modes Method (GAMM) and Finite Element Method (FEM) are employed to model the rotor-bearing system, and the accuracy of the results is discussed. With the application of GAMM, similarity transformation of different types of polynomials and interval has been investigated. The results show that using different polynomial function in GAMM have similar results, and which are also be agreed with the FEM. The results also show that the number of polynomial can be increased as the interval of the assumed mode function is altered. Consequently, the convergence of higher order modes will be more accurate.
Experimental and Numerical Investigation of Different Rectangular Volute Geometries for Large Radial Compressors
Authors: Bartelt Michael , Kwitschinski Thomas , Ceyrowsky Thomas , Grates Daniel , Seume Joerg R.
Published: May 2012

Increases on mass flow rates of modern radial process compressors result on larger machine components. In particular, the dimensions of the outlet volutes increase strongly, resulting in disproportionately large machines whose technical feasibility is restricted due to technological and economical reasons. A resulting aim is to design modern radial compressors much more compact, while improving the efficiency and the pressure ratio. Therefore, the present experimental investigation addresses the compressor behaviour for reduced dimensions of rectangular volutes. Furthermore, the experimental setups are numerically modelled and different operating points are simulated with a commercial CFD-Code. A rectangular, external reference volute is equipped with differently shaped blockage-inlays and the global compressor parameters are measured for all variants. Additionally, the pressure and velocity distributions of the local flow field are determined experimentally for varying mass flow ratios at different circumferentially distributed volute layers. The decrease of the volute cross-section results in a reduction of the compressor map width especially at high mass flow rates. Recommendations are given for designing compact volutes of large radial compressors.
Natural Frequency Shift in a Centrifugal Compressor Impeller for High-Density Gas Applications
Authors: Magara Yohei , Yamaguchi Kazuyuki , Miura Haruo , Takahashi Naohiko , Narita Mitsuhiro
Published: May 2012

In designing an impeller for centrifugal compressors, it is important to predict the natural frequencies accurately in order to avoid resonance caused by pressure fluctuations due to rotorstator interaction. However, the natural frequencies of an impeller change under high-density fluid conditions. The natural frequencies of pump impellers are lower in water than in air because of the added mass effect of water, and in high-pressure compressors the mass density of the discharge gas can be about one-third that of water. So to predict the natural frequencies of centrifugal compressor impellers, the influence of the gas must be considered. We previously found in the non-rotating case that some natural frequencies of an impeller decreased under high-density gas conditions but others increased and that the increase of natural frequencies is caused by fluid-structure interaction, not only the added mass effect but also effect of the stiffness of the gas. In order to develop a method for predicting natural frequencies of centrifugal compressor impellers for high-density gas applications, this paper presents experimental results obtained using a variable-speed centrifugal compressor with vaned diffusers. The maximum mass density of its discharge gas is approximately 300 kg/m3. The vibration stress on an impeller when the compressor was speeding up or slowing down was measured by strain gages, and the natural frequencies were determined by resonance frequencies. The results indicate that for high-density centrifugal compressors, some natural frequencies of an impeller increased in high-density gas. To predict this behavior, we developed a calculation method based on the theoretical analysis of a rotating disc. Its predictions are in good agreement with experimental results.
A Numerical and Experimental Investigation of the Effects of Flow Ratio on the Flow and Performance Characteristics of a Twin Entry Radial Turbine
Authors: Shahhosseini M. R. , Hajilouy-Benisi A. , Rajabian M.
Published: May 2012

In this paper, a numerical and experimental investigation of the performance and internal flow field characteristics of the twin-entry radial inflow turbine under full and partial admission conditions are presented. The turbine is tested on a turbocharger test facility which was developed for small and medium size turbochargers. The flow pattern in the volute and impeller of a twin-entry turbine is analyzed using a fully three-dimensional viscous program. The computational performance results are compared with the experimental results, and good agreement is found. The flow field at the outlet of the turbine is investigated using a five-hole pressure probe. Numerical and experimental results are obtained for both full and partial admission conditions. In the volute, results show that the highest entropy gain factor belongs to the tongue. In the inlet of the rotor, a large variation in the incidence angle is displayed at the extreme conditions, leading to large incidence losses. Entropy distribution contours at the rotor exit plane are evaluated. For full admission, the location of low entropy gain at this plane occupies a region near the shroud and near the hub pressure surface corner which corresponded to a region of high absolute flow angle. Results show that the entropy gain factor patterns do not have appreciable differences at full and partial admission conditions when more flow is located at the volute shroud side. However, in the extreme cases low entropy gain at the shroud side occupies a relatively large region, and this region is increased when shroud side volute is fully closed.
Application of a Multistage Casing Treatment in a High Speed Axial Compressor Test Rig
Authors: Kroeckel T. , Hiller S. J. , Jeschke P.
Published: May 2012

The subject of this paper is the experimental investigation of the overall performance and local aerodynamics of a 2.5 stage axial compressor test rig with a two stage casing treatment. Casing treatments are a well known method to aerodynamically stabilize the near stall compressor aerodynamics. However, in the past, casing treatments have only been applied to high aspect ratio front stages. This investigation puts the focus on the impact of advanced casing treatments applied to both rotors of a high speed compressor test rig. The rotors’ geometric and aerodynamic features are identical to those seen in the rear stages of aircraft engine high pressure compressors. Based on experimental results, we explain the casing treatment’s effect on the local flow phenomena as well as its influence on the compressor operability and performance. In order to clearly quantify the casing treatment’s influence, all measurements are conducted twice: for the rig without casing treatments and for an identical rig with casing treatments. The analysis of experimental data confirms that multistage casing treatments are able to significantly push the surge line towards higher pressure ratios and lower mass flow rates without any significant degradation of the peak efficiency. However, detailed flow analysis and the comparison of the configurations with and without casing treatments reveal that the flow is significantly redistributed by the effect of the casing. The present effort was conducted as part of the EU integrated program for New Aero Engine Core Concepts (NEWAC).
Integrated Combustor–Turbine Design for Improved Aerothermal Performance: Effect of Dilution Air Control
Authors: Basol A. M. , Regina K. , Kalfas A. I. , Abhari R. S.
Published: May 2012

The effect of dilution air control in a combustor on the heat load distribution of an axial turbine with non-axisymmetric endwall profiling is examined. Endwall profiling is a more common design feature in new engine types, due to the effectiveness of the endwall profiling in reducing secondary flows, and their associated losses. In the present work, the effect of dilution air control is examined by using two different circumferentially non-uniform hot-streak shapes; the two cases differ in their spanwise extents either side of the stator, and therefore represent different approaches for dilution air control. This numerical study details the impact of these two different strategies for dilution air control on the rotor blade heat load distribution. The inlet boundary conditions simulate the experiment that is conducted in the axial research turbine facility “LISA” at ETH Zurich. A circumferential non-uniformity in the spanwise migration pattern of the hot streak inside the stator is observed. Even though this circumferential non-uniformity in the spanwise migration is alleviated by the non-axisymmetric endwall profiling, the two hot-streak cases result in considerably different heat load distributions on the rotor blade, emphasizing the importance of the integrated combustor–turbine approach. Finally, the implications for dilution air control on the liner are discussed for the realization of the simulated hot streak shapes in a real combustor.
Impact of Steam Injection and Turbine Exhaust Gas Bypass in the Recuperative Cycle Gas Turbine CHP System
Authors: Kang S. Y. , Kim T. S.
Published: May 2012

The capability of modulating power and heat productions by steam injection in a recuperative cycle gas turbine was investigated. A combined heat and power system using a current state-of-the-art recuperative cycle gas turbine was modeled. Variations in engine performance characteristics due to steam injection were examined. A full off-design analysis was carried out to investigate not only the performance change but also the variation in engine operation caused by the steam injection. Impact of injecting steam at different locations (recuperator and combustor) was investigated. A special attention was given to the change in the compressor surge margin, and a couple of operations that secures a minimum surge margin were comparatively analyzed. Bypass of turbine exhaust gas around the recuperator to increase steam generation was simulated and its usefulness in controlling heat to power ratio was demonstrated. Variations in electric power and thermal energy productions in response to the modulations of injection ratio and gas bypass were presented for a wide ambient temperature range.
Ultra Rich Combustion of Natural Gas to Syngas
Authors: Woolderink M. H. F. , Kok J. B. W.
Published: May 2012

In this paper the turbulent rich combustion process of perfectly premixed natural gas and oxidizer to syngas is investigated. Also an overview is given of an ultra rich combustion setup that is present at the Laboratory of Thermal Engineering of the University of Twente. The numerical investigation of the process is carried out as follows. The gaseous chemistry is described by a reaction progress variable based combustion model with detailed chemistry. The soot formation is described by the processes of nucleation, surface growth, agglomeration and oxidation. Also radiative heat loss of the gases and the soot particles is taken into account. The numerical model predicts the flow field, gaseous species, temperature, heat loss and soot mass fraction and number of soot particles. The combination of radiation and soot formation models with the combustion model will give a complete picture of the processes in the partial oxidation reactor. The numerical results will be validated with measurements on a reactor operating at pressures from 1 to 6 bar and at equivalence ratios 2 to 4. The measurements are to be done by taking samples from the reactor which are subsequently analyzed with a gas chromatograph and a Scanning Mobility Particle Sizer. The planned experiments will give valuable validation data for the performance of combustion and soot formation models at ultra rich conditions that are not yet available in literature.
Optimization of a Micro Gas Turbine Using Genetic Algorithm
Authors: Pourhasanzadeh Maryam , Bigham Sajjad
Published: May 2012

Distributed generation is an attractive way of producing energy, minimizing transport losses and enhancing energy efficiency. Micro gas turbines in distributed generation systems add other advantages such as low emissions and fuel flexibility. In the present work, a 100 kW micro gas turbine is considered. The optimization procedure is done by Genetic Algorithm method which is a new method in optimizing problems. The plant is comprised of an air compressor, recuperator, combustion chamber and gas turbine. The design Parameters of the plant, were chosen as: compressor pressure ratio, compressor isentropic efficiency, gas turbine isentropic efficiency, combustion chamber inlet temperature and the temperature of the combustion gas at the gas turbine inlet. In order to find the design parameters optimally, a thermo-economic approach has been followed. An objective function, representing the total cost of the plant in terms of dollar per second, was defined as the sum of the operating cost, related to the fuel consumption, the capital investment which stands for equipment purchase and maintenance cost. Subsequently, different parts of the objective function have been expressed in terms of design variables. Finally, the optimal values of design variables were obtained by minimizing the objective function using Genetic Algorithm code that is developed in Matlab software programming.
LES and RANS Assessment of Rib Cooled Channel Related to SGT-800 Combustor Liner
Authors: Lo¨rstad Daniel
Published: May 2012

The main parts of the annular combustor liner walls of the Siemens gas turbine SGT-800 are convectively cooled using rib turbulated cooling. Due to the serial system of cooling and combustion air there is a potential of further reduction of total combustor pressure drop by improvements of the cooling system. Apart from the rib cooling, also the cooling channel bypass entrance is related to a significant part of the total cooling system pressure drop. In this study, an investigation is performed for a rib cooled channel which is related to the considered combustor liner and where empirical correlations are available in order to evaluate the methodology used. The study includes an assessment of the Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models available within commercial Computational Fluid Dynamics (CFD) codes and includes also an investigation of model size when using periodic boundaries for LES simulations. It is well known that a small geometrical distance in the direction of the periodic boundaries may have a strong effect on the flow field but is often neglected in practice in order to speed up LES calculations. Here the effect is assessed in order to show what size is required for accurate results, both for time averaged and transient results. In addition too small domains may be affected by spurious low frequencies originating from the periodic boundaries requiring additional simulation time for time converged statistics, but also the averages may be significantly affected. In addition the simulation period for time converged statistics is evaluated in order to show that larger model size in the periodic direction does not necessarily require longer practical simulation time, due to the fact that larger volumes may be used for the combined time and space averaging. The aim is to obtain practical guidelines for LES calculations for internal cooling flows. Then the study is extended step by step to investigate the importance due to high Reynolds number, variable fluid properties and large temperature gradients in order to cover the ranges and specifics required for SGT-800 engine conditions.
Combustor Design Optimisation Using Co-Kriging of Steady and Unsteady Turbulent Combustion
Authors: Wankhede Moresh J. , Bressloff Neil W. , Keane Andy J.
Published: May 2012

In the gas turbine industry, computational fluid dynamics (CFD) simulations are often used to predict and visualize the complex reacting flow dynamics, combustion environment and emissions performance of a combustor at the design stage. Given the complexity involved in obtaining accurate flow predictions and due to the expensive nature of simulations, conventional techniques for CFD based combustor design optimisation are often ruled out, primarily due to the limits on available computing resources and time. The design optimisation process normally requires a large number of analyses of the objective and constraint functions which necessitates a careful selection of fast, reliable and efficient computational methods for the CFD analysis and the optimization process. In this study, given a fixed computational budget, an assessment of a co-Kriging based optimisation strategy against a standard Kriging based optimisation strategy is presented for the design of a 2D combustor using steady and unsteady Reynolds-averaged Navier Stokes (RANS) formulation. Within the fixed computational budget, using a steady RANS formulation, the Kriging strategy successfully captures the underlying response, however with unsteady RANS the Kriging strategy fails to capture the underlying response due to the existence of a high level of noise. The co-Kriging strategy is then applied to two design problems, one using two levels of grid resolutions in a steady RANS formulation and the other using steady and unsteady RANS formulations on the same grid resolution. With the co-Kriging strategy, the multi-fidelity analysis is expected to find an optimum design in comparatively less time than that required using the high-fidelity model alone since less high-fidelity function calls should be required. However, using the applied computational setup for co-Kriging, the Kriging strategy beats the co-Kriging strategy under the steady RANS formulation whereas under the unsteady RANS formulation, the high level of noise stalls the co-Kriging optimisation process.
Supersonic Ejectors for Hydrocarbon Emissions Capture
Authors: Biba Yuri , Kidd H. Allan , Peifer Stephen , Scott Christopher , Sloof Brian , Tse Anthony
Published: May 2012

Supersonic ejectors can be applied to capture low-pressure leakage gas from the gas seal vents of a centrifugal compressor. This captured gas can be re-injected into the fuel gas line of the gas turbine driver or the captured gas can be used as a fuel for gas fired utility heaters. By capturing the gas that is normally emitted to the atmosphere the operator can reduce operating cost and enjoy a reduction in hydrocarbon foot print. Because the supersonic ejector does not have moving parts, the system operating and maintenance costs are lower than functionally comparable traditional systems. In this study, a prototype of a supersonic ejector system was developed and tested at a pipeline compressor station. The obtained test data were used for developing and tuning a mean-line aerodynamic analysis tool, which predicts the ejector’s operating map. A family of three ejectors was designed to cover a range of operating conditions associated with gas turbine driven pipeline compressors. These ejectors were built, installed on a specially designed panel, described as the ejector system, and tested on inert gas at the original equipment manufacturer’s (OEM’s) facility. A comparison of predicted and as-tested supersonic ejector performance maps is discussed and conclusions are made about the system operating range.
Stability Analysis of an Industrial Gas Compressor Supported by Tilting-Pad Bearings Under Different Lubrication Regimes
Authors: Varela Alejandro Cerda , Santos Ilmar Ferreira
Published: May 2012

This work is aimed at theoretically study the dynamic behavior of a rotor-tilting pad journal bearing system under different lubrication regimes, namely thermohydrodynamic (THD), elastohydrodynamic (EHD) and hybrid lubrication regime. The rotor modeled corresponds to an industrial compressor. Special emphasis is put on analyzing the stability map of the rotor when the different lubrication regimes are included into the TPJB modeling. Results show that, for the studied rotor, the inclusion of a THD model is more relevant when compared to an EHD model, as it implies a reduction on the instability onset speed for the rotor. Also, results show the feasibility of extending the stable operating range of the rotor by implementing a hybrid lubrication regime.
Gas Turbine Emission Characteristics in Perfectly Premixed Combustion
Authors: Elkady A. M. , Kalitan D. M. , Herbon J. , Leonard G. , Akula R. , Karim H. , Hadley M.
Published: May 2012

In the present study, a simple perfectly premixed research burner was utilized at temperatures, pressures and residence times representative of an industrial gas turbine cycle to identify the lower limit of NOx and CO emissions, and to establish an emissions benchmark for practical gas turbine combustors. In addition to experimental data, a chemical reactor model has been utilized for the prediction of the NOx and CO, based on detailed chemical reaction mechanisms. Several current kinetics mechanisms were evaluated and subsequently compared to the experimental data. In addition, sensitivity analysis was performed to identify important reactions at the conditions tested, and will be discussed.
The Role of Simple and Combined Cycles in Renewable Applications Deployment
Authors: Zachary Justin
Published: May 2012

The integration of intermittent renewable energy technologies within the operating constraints of utility requirements provides gas turbine and combined cycle (CC) suppliers and designers with an opportunity to play a significant role. In particular, the large penetration of wind power affects the existing grid terms of system capacity, harmonics, safety, and protection. The deployment of gas turbines in simple and CCs could facilitate the process and help in achieving the Renewable Portfolio Standards (RPS) goals. Initially, the paper reviews the grid requirements and how each of the renewable sources of generation (solar thermal, wind, and solar photovoltaic) is capable of responding based on its unique attributes and characteristics. It goes on to address the benefits of CC with emphasis on the design challenges for repeated fast startups and plant size optimization. It discusses the drivers to increase equipment efficiency at a wide range of part-load operation while maintaining stringent emissions levels. Special emphasis is given to an economic comparison between use of simple and CC versus several solutions involving state-of-the-art energy storage. The discussion covers the integration from an engineering, procurement, and construction (EPC) contractor’s perspective.
Turbulence and Heat Transfer Measurements in an Inclined Large Scale Film Cooling Array: Part I—Velocity and Turbulence Measurements
Authors: El-Gabry Lamyaa A. , Thurman Douglas R. , Poinsatte Philip E. , Heidmann James D.
Published: May 2012

A large-scale model of an inclined row of film cooling holes is used to obtain detailed surface and flow field measurements that will enable future computational fluid dynamics code development and validation. The model consists of three holes of 1.9-cm diameter that are spaced 3 hole diameters apart and inclined 30° from the surface. The length to diameter ratio of the coolant holes is about 18. Measurements include film effectiveness using IR thermography and near wall thermocouples, heat transfer using liquid crystal thermography, flow field temperatures using a thermocouple, and velocity and turbulence quantities using hotwire anemometry. Results are obtained for blowing ratios of up to 2 in order to capture severe conditions in which the jet is lifted. This first part of the two-part paper presents the detailed velocity component and turbulence stresses along the centerline of the film-cooling hole and at various streamwise locations.
Combustion Hardware Extendor Kit III Enhancement Kit for MS5002C and D Heavy Duty Gas Turbine for Oil and Gas Applications
Authors: Ceccherini Gianni , Del Puglia Eugenio , Provenzale Michele , Mastromatteo Francesco , Cappuccini Filippo , Bianucci David
Published: May 2012

The continuous increase of both energy demand and oil and gas prices has driven gas turbine operators to seek improvements in both the durability and performances of their machines. The maintenance interval still represents one of the most critical issues related to durability and has a strong impact on production costs, especially in oil and gas applications. To address this issue, specific development programs were introduced by GE Oil & Gas, aimed at extending the mean time between maintenance (MTBM) of its entire heavy-duty fleet. These programs basically consist of identifying the most probable failure modes, strategies to remedy problems and finally delivering new technology. The success of such programs starts with the introduction of the new product, after it has gone through a rigorous and well-proven design process which includes conceptual, preliminary and detailed design reviews. Due to both high temperature environment and combustion dynamic frequencies, the combustor hardware is prone to different failure modes, limiting, in some cases, the MTBM to a relatively small number of hours. This paper describes the design process followed to deliver Extendortm III, which is a modification kit for the LHE (Lean Head End) combustion system of the MS5002C & D heavy duty gas turbines, aimed at enhancing MTBM. The development strategy is described in detail and the results of numerical dynamic analyses and validation testing are shown.
Noise Prediction of Pressure-Mismatched Jets Using Unstructured Large Eddy Simulation
Authors: Khalighi Yaser , Ham Frank , Moin Parviz , Lele Sanjiva K. , Schlinker Robert H.
Published: May 2012

It is our premise that significant new advances in the understanding of noise generation mechanisms for jets and realistic methods for reducing this noise can be developed by exploiting high-fidelity computational fluid dynamics: namely large eddy simulation (LES). In LES, the important energy-containing structures in the flow are resolved explicitly, resulting in a time-dependent, three-dimensional realization of the turbulent flow. In the context of LES, the unsteady flow occurring in the jet plume (and its associated sound) can be accurately predicted without resort to adjustable empirical models. In such a framework, the nozzle geometry can be included to directly influence the turbulent flow including its coherent and fine-scale motions. The effects of propulsion system design choices and issues of integration with the airframe can also be logically addressed.
Test Conditions for Performance Characterization of Dielectric Barrier Discharge (DBD) Plasma Actuators for Active Flow Control in Jet Engines
Authors: Ashpis David E. , Thurman Douglas R.
Published: May 2012

Dielectric Barrier Discharge (DBD) plasma actuators for active flow control in the jet engine need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which in turn depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. It is usually impractical to simultaneously set engine pressures and temperatures in a chamber, and a simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density. Other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in engine operating flight conditions. Engine data was obtained from four generic engine models; 300-, 150-, and 50-Passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and altitude cruise, and the chamber pressures needed to test the actuators were calculated. The results show that testing has to be performed over a wide range of pressures from 12.4 to 0.03 atm, depending on the application. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it has to be tested at 12.4 atm for takeoff, and 6 atm for cruise conditions. If it is to be placed at the low-pressure turbine, it has to be tested at 0.5 and 0.2 atm, respectively. These results have implications for the feasibility and design of DBD plasma actuators for jet engine flow control applications. In addition, the distributions of unit Reynolds number, Mach number, and velocity along the engine are provided. The engine models are non-proprietary and this information can be used for evaluation of other types of actuators and for other purposes.
Performance Modeling of a Power Generation Gas Turbine With Wet Compression
Authors: Montalvo-Catano German , O’Brien Walter F.
Published: May 2012

In the last 15 years more than 1000 power generation gas turbines have been modified with an OEM or aftermarket module to generate the wet compression phenomenon where “Hot Day” conditions are present on the site. This modification to the gas turbine increases power, but can produce performance problems including reduced compressor surge margin and possibly a shorter maintenance cycle because of resulting problems present in the compressor such as blade vibration and erosion with impingement of water droplets on the surface of the compressor blades[1]. In the last few years researchers in academia and the private sector have worked to understand the principles behind the wet compression process in order to know in depth how to use the application to best advantage with gas turbines. The main areas of the research on wet compression are thermodynamic analyses, computer fluid dynamic analysis, and the use of operational data. Because present technology is unable to obtain detailed operational data on the evaporation process within the compressor, researchers rely on computer simulations based upon aerothermodynamics and physical measurements of the gas turbines, and assumptions based upon available information. These computer simulations are typically aimed toward explaining the performance data from a specific gas turbine model. Most of these computer simulations are cycle analyses of the gas turbine [2–7], although a few are CFD analyses for a specific compressor using either in-house computer programs or commercial CFD software [8–10]. CFD analysis takes into account the fact that an evaporation model should be used in order to predict how the evaporation of the water droplets occurs through the stages of the compressor. Many of the CFD simulations that have been performed for wet compression assume that the mixture of air, liquid water, and water vapor is at equilibrium throughout the compressor. Also, a single water droplet size is sometimes used for the simulation instead of a size distribution for the droplets. These assumptions simplify the calculations for the software. The results of these simulations may over-forecast the effect of the wet compression and the power output of the gas turbine because of incorrect predictions of evaporation models, or because of the lack of a proper droplet size distribution affecting the calculation. An analysis that properly forecasts the power output of a gas turbine with wet compression is important for design, performance prediction, and operation. The intention of this paper is to show how performance predictions for a power generation gas turbine is affected by applying several evaporation models [2, 4, 5, 7] in a gas turbine model with a detailed, stage-by-stage compressor model. Model predictions are compared with available operational performance data. Conclusions are provided regarding the best evaporation model assumptions for accurate predictions of gas turbine performance with wet compression.
Computational Investigation of the Three-Dimensional Flow Structure and Losses in a Low Reynolds Number Microturbine
Authors: Omri M. , Fre´chette L. G.
Published: May 2012

In this work, three dimensional numerical studies of the aerodynamics in laminar subsonic cascades at relatively low Reynolds numbers (Re < 2500) are presented. The stator and rotor blade designs are those for a MEMS-based Rankine microturbine power-plant-on-a-chip with 100 micron chord blades. Blade passage calculations in 2D and 3D were done for different Reynolds numbers, four different tip clearances (0%, 5%, 10% and 20%) and four incidences (0°, 5°, 10° and 15°) to determine the flow patterns and compute losses. These conditions are applied to a blade passage without rotation (stator) and with rotation (rotor), both for a stationary and moving outer casing. The 3D blade passage (without tip clearance) indicates the presence of two large symmetric vortices due to the interaction between flow curvature and hub/casing boundary layers. With tip clearance, a secondary vortex appears due to tip flow. This so-called tip vortex becomes dominant in the case of tip clearance above 10%. Relative wall motion also impacts the 3D flow patterns due to the important tangential drag at these low Reynolds numbers. Two dimensional calculations characterize well the flow at the mid-height plane, but are not sufficient for loss predictions due to the omission of the 3D flow structures. The 3D total losses increase dramatically for Re<500, which is similar to 2D studies. This suggests an operating Reynolds number greater than this to obtain efficiency levels necessary to operate a heat engine. The losses also increased monotonically with increasing tip clearance and incidence.
A Pb/Zn Based Chemical Looping System for Hydrogen and Power Production With Carbon Capture
Authors: McGlashan Niall R. , Childs Peter R. N. , Heyes Andrew L.
Published: May 2012

This paper describes an extension of a novel, carbon-burning, fluid phase chemical looping combustion system proposed previously. The system generates both power and H2 with ‘inherent’ carbon capture using chemical looping combustion (CLC) to perform the main energy release from the fuel. A mixed Pb and Zn based oxygen carrier is used, and due to the thermodynamics of the carbothermic reduction of PbO and ZnO respectively, the system generates a flue gas which consists of a mixture of CO2 and CO. By product H2 is generated from this flue gas using the water-gas shift reaction (WGSR). By varying the proportion of Pb to Zn circulating in the chemical loop, the ratio of CO2 to CO can be controlled, which in turn enables the ratio between the amount of H2 produced to the amount of power generated to be adjusted. By this means, the power output from the system can be ‘turned down’ in periods of low electricity demand without requiring plant shutdown. To facilitate the adjustment of the Pb/Zn ratio, use is made of the two metal’s mutual insolubility, as this means they form in to two liquid layers at the base of the reduction reactor. The amount of Pb and Zn rich liquid drawn from the two layers and subsequently circulated around the system is controlled thereby varying the Pb/Zn ratio. To drive the endothermic reduction of ZnO formed in the oxidiser, hot Zn vapour is ‘blown’ into the reducer where it condenses, releasing latent heat. The Zn vapour to produce this ‘blast’ of hot gas is generated in a flash vessel fed with hot liquid metal extracted from the oxidiser. A mass and energy balance has been conducted for a power system, operating on the Pb/Zn cycle. In the analysis, reactions are assumed to reach equilibrium and losses associated with turbomachinery are considered; however, pressure losses in equipment and pipework are assumed to be negligible. The analysis reveals that a power system with a second law efficiency of between 62% and 68% can be constructed with a peak turbine inlet temperature of only ca. 1850 K. The efficiency varies as the ratio between power and H2 production varies, with the lower efficiency occurring at the maximum power output condition.
An Experimental Study of Thermal Barrier Coatings and Film Cooling on an Internally Cooled Simulated Turbine Vane
Authors: Davidson F. Todd , Dees Jason E. , Bogard David G.
Published: May 2012

This study investigated the interaction of thermal barrier coatings (TBC) and various film cooling configurations to provide a detailed assessment of the thermal protection on a first stage turbine vane. The internally cooled, scaled-up turbine vane used for this study was designed to properly model the conjugate heat transfer effects found in a real engine. The TBC material was selected to properly scale the thicknesses and thermal conductivities of the model to those of the engine. External surface temperatures, TBC-vane interface temperatures and internal temperatures were all measured over a range of internal coolant Reynolds numbers and mainstream turbulence intensities. The blowing ratio of the various film-cooling designs was also varied. The addition of TBC on the vane surface was found to increase the overall effectiveness of the vane surface just downstream of the coolant holes by up to 0.25 when no film cooling was present. The presence of the TBC significantly dampened the variations in overall effectiveness due to changes in blowing ratio which mitigated the detrimental effects of coolant jet separation. It was also discovered that with the presence of TBC standard round holes showed equivalent, if not better, performance when compared to round holes embedded in a shallow transverse trench.