bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid System of Supercritical Carbon Dioxide Brayton Cycle and Carbon Dioxide Rankine Cycle Combined Fuel Cell
Authors: Bae Seong Jun , Ahn Yoonhan , Lee Jekyoung , Lee Jeong Ik
Published: September 2014

The Supercritical Carbon Dioxide (S-CO2) Brayton cycle has been receiving a lot of attention because it can achieve compact configuration and high thermal efficiency at relatively low temperature (450∼750 °C). However, to achieve high thermal efficiency of S-CO2 Brayton cycle, it requires a highly effective recuperator. Moreover, the temperature difference in the heat receiving section is limited for the S-CO2 Brayton cycle to achieve high thermal efficiency results in high mass flow rate and potentially high pressure drop in the cycle. Thus, to resolve these problems while providing flexibility to match with various heat sources, authors suggest a hybrid system of S-CO2 Brayton and Rankine cycle. This hybrid system utilizes the waste heat of the S-CO2 Brayton cycle as the heat input to the Carbon Dioxide (CO2) Rankine cycle. Thus, the recuperator effectiveness does not always have to be high to achieve high efficiency, which results in reduction of the recuperator volume reduction. By controlling amount of the heat transfer from the cooler of the S-CO2 Brayton cycle to the Rankine cycle, the total system can be compact and can achieve wider operating range. Thus, the hybrid system of S-CO2 Brayton cycle and CO2 Rankine cycle can be coupled to various heat sources with more flexibility without trading off the performance. In this paper, Molten Carbonate Fuel Cell (MCFC) system is selected to demonstrate the feasibility of the proposed hybrid cycle system while comparing the proposed system’s performance to that of other cycle layouts as well.
CCPP Performance Augmentation Using LNG Re-Gasification Cold Energy
Authors: Acharya Mihir , Pattanayak Lalatendu , Gajjar Hemant , Elbracht Frank , Asthana Sandeep
Published: September 2014

With gas becoming a fuel of choice for clean energy, Liquefied Natural Gas (LNG) is being transported and re-gasification terminals are being set up at several locations. Re-gasification of LNG leads to availability of considerable cold-energy which can be utilized to gain power and efficiency in a Gas Turbine (GT) based Power Plant. With a number of LNG Re-gasification Terminals coming up in India & around the globe, setting up of a high efficiency CCPP adjacent to the terminal considering utilization of the cold energy to augment its performance, and also save energy towards re-gasification of LNG, provides a feasible business opportunity.

Thermodynamic analysis and major applications of the LNG re-gasification cold energy in Gas Turbine based power generation cycle, are discussed in this paper. The feasibility of cooling GT inlet air by virtue of the cold energy of Liquefied LNG to increase power output of a Combined Cycle Power Plant (CCPP) for different ambient conditions is analyzed and also the effect on efficiency is discussed. The use of cold energy in condenser cooling water circulating system to improve efficiency of the CCPP is also analyzed. Air cooling capacity and power augmentation for a combined cycle power plant based on the advanced class industrial heavy duty gas turbine are demonstrated as a function of the ambient temperature and humidity. The economic feasibility of utilizing the cold energy is also deliberated.
Two-Phase Flow Modeling and Measurements in Low-Pressure Turbines: Part 2 — Turbine Wetness Measurement and Comparison to CFD-Predictions
Authors: Schatz M. , Eberle T. , Grübel M. , Starzmann J. , Vogt D. M. , Sürken N.
Published: September 2014

The correct computation of steam subcooling, subsequent formation of nuclei and finally droplet growth is the basic prerequisite for a quantitative assessment of the wetness losses incurred in steam turbines due to thermal and inertial relaxation. The same basically applies for the prediction of droplet deposition and the resulting threat of erosion.

Despite the fact that there are many CFD-packages that can deal with real-gas effects in steam flows, the accurate and reliable prediction of subcooling, condensation and wet steam flow in steam turbines using CFD is still a demanding task.

One reason for this is the lack of validation data for turbines that can be used to assess the physical models applied. Experimental data from nozzle and cascade tests can be found in the open literature; however, this data is only partly useful for validation purposes for a number of reasons. With regard to steam turbine test data, there are some publications, yet always without any information about the turbine stage geometries.

This publication is part of a two-part paper; whereas part 1 focuses on the numerical validation of wet steam models by means of condensing nozzle and cascade flows, the focus in this part lies on the comparison of CFD results of the turbine flow to experimental data at various load conditions. In order to assess the validity and reliability of the experimental data, the method of measurement is presented in detail and discussed. The comparison of experimental and numerical results is used for a discussion about the challenges in both modeling and measuring steam turbine flows, presenting the current experience and knowledge at ITSM.
PIV Measurements in a Two-Pass 90-Deg Ribbed-Wall Parallelogram Channel
Authors: Liou Tong-Miin , Chang Shyy Woei , Chan Shu-Po , Liu Yu-Shuai
Published: September 2014

A parallelogram channel has drawn very little or no attention in the open literature although it appears as a cross-sectional configuration of some gas turbine rotor blades. Particle Image velocimetry is presented of local flow structure in a two-pass 90-deg ribbed-wall parallelogram channel with a 180-deg sharp turn. The channel has a cross-sectional equal length, 45.5 mm, of adjacent sides and two pairs of opposite angles are 45-deg and 135-deg. The rib height to channel height ratio is 0.1. All the measurements were performed at a fixed Reynolds number, characterized by channel hydraulic diameter of 32.17 mm and cross-sectional bulk mean velocity, of 10000 and a null rotating number. Results are discussed in terms of the distributions of streamwise and secondary-flow mean velocity vector, turbulent intensity, Reynolds stress, and turbulent kinetic energy of the cooling air. It is found that the flow is not periodically fully developed in pitchwise direction through the inline 90-deg ribbed straight inlet and outlet leg. Pitchwise variation of reattachment length is revealed and comparison with reported values in square channels is made. Whether the 180-deg sharp turn induced separation bubble exists in the ribbed parallelogram channel is also documented. Moreover, the measured secondary flow results inside the turn are successively used to explain previous heat transfer trends.
Structural and Dynamic Optimization of a Single Axial Compressor Blade Using the Gradient-Based Method
Authors: Pugachev Alexander O. , Sheremetyev Alexander V. , Tykhomirov Viktor V. , Petrov Alexey V.
Published: September 2014

This paper describes the development of an in-house code for sizing optimization of blades with constraints imposed on blade’s natural frequencies and static stresses. The optimization environment includes a three-dimensional parametric model of the blade, interface functions for automated execution of the static and modal finite element analyses as well as post-processing of the results, and optimization algorithm. The blade geometry is represented by section profiles at a number of span-wise stations. Each blade section profile is parametrized by nine intuitive geometric parameters which control profile thickness distribution, chord, offset, and stagger angle. Three-dimensional finite element analysis of the blade is performed using ANSYS Mechanical software package. A sequential quadratic programming technique is used to solve the nonlinear optimization problem. Sensitivity analysis is performed using the finite-difference method. Several optimization problems with different objective functions and combinations of constraints are implemented. The aerodynamic constraints are not considered directly. The blade’s aerodynamic properties are sustained by imposing tight limits on the allowable changes of design variables. Sizing optimization is performed for an axial compressor blade of a gas turbine engine. The results show that the code can meet the defined objective and constraints for the most tested cases. A detailed comparison of optimized profiles with the baseline geometry is provided.
Gas Turbine Operation Offshore: On-Line Compressor Wash Operational Experience
Authors: Madsen Stian , Bakken Lars E.
Published: September 2014

On-line compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load (T5.4 control), hence production rate is limited by the available power from these engines. All the six engines analyzed run continuously without redundancy, hence gas turbine uptime is critical for the field’s production and economy. The performance and operational experience with online wash at different water-to-air ratios and engine loads, as well as economy potentials related to successful on-line washing are given.

This work is based on long-term operation with on-line washing, where operational data is collected and performance analyzed, over a 4–5 year period. All engines are operated with four month intervals between maintenance stops, where off-line crank-wash is performed as well as other necessary maintenance and repairs. On-line wash is performed daily between the maintenance stops at full load (i.e. normal operating load for the subject engine). To keep the engine as clean as possible and reduce degradation between maintenance stops, both an effective on-line water wash system as well as effective air intake filter system, are critical factors. The overall target is to maintain high engine performance, and extend the interval between maintenance stops through effective on-line washing.

It is of vital importance to understand the gas turbine performance deterioration. The trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine’s condition. Engine response to water injection at different loads and water-to-air ratios, as well as engine response to compressor deterioration is documented and analyzed.

Instrument resolution and repeatability are key factors required in order to obtain reliable performance analysis results. Offshore instrumentation on older installations is often limited to the necessary instruments for machine control/protection, and additional instruments for effective performance monitoring and analysis are often missing or, if installed, have less accuracy. As a result of these analyses, a set of monitoring parameters is proposed for effective diagnosis of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and of the gas turbine performance and response.
Quantitative CFD Analyses of Particle Deposition on a Transonic Axial Compressor Blade: Part I — Particle Zones Impact
Authors: Suman Alessio , Kurz Rainer , Aldi Nicola , Morini Mirko , Brun Klaus , Pinelli Michele , Spina Pier Ruggero
Published: September 2014

Solid particle ingestion is one of the principal degradation mechanisms in the turbine and compressor sections of gas turbines. In particular, in industrial applications, the micro-particles not captured by the air filtration system cause fouling and, consequently, a performance drop of the compressor. This paper presents three-dimensional numerical simulations of the micro-particle ingestion (0–2 μm) on an axial compressor rotor carried out by means of a commercial computational fluid dynamic code. Particles of this size can follow the main air flow with relatively little slip, while being impacted by flow turbulence. It is of great interest to the industry to determine which areas of the compressor airfoils are impacted by these small particles.

Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separate from the continuous phase. Then, the NASA Rotor 37 is considered as a case study for the numerical investigation. The compressor rotor numerical model and the discrete phase treatment have been validated against the experimental and numerical data available in literature. The number of particles, sizes, and concentrations are specified in order to perform a quantitative analysis of the particle impact on the blade surface.

The results show that micro-particles tend to follow the flow by impacting at full span with an higher impact concentration on the pressure side. The suction side is affected only by the impact of the smaller particles (up to 1 μm). Particular fluid-dynamic phenomena such as separation, stagnation point and tip leakage vortex strongly influence the impact location of the particles.
Unbalance Identification and Balancing of Nonlinear Rotodynamic Systems
Authors: Torres Cedillo Sergio G. , Bonello Philip
Published: September 2014

This paper is devoted to the unbalance identification and balancing of an aircraft engine rotor running on Squeeze Film Damper (SFD) bearings that show highly nonlinear features. The high pressure (HP) rotor in a twin-spool assembly cannot be accessed under operational conditions because of the restricted space for instrumentation and temperatures that are beyond the safe operating limits of the sensors. This motivates the use of a non-invasive procedure, requiring prior knowledge of the structure. The only such method for rotating machinery with non-linear bearings reported in the literature is highly limited in its application (e.g. assumes circular centred orbits). The methodology proposed in this paper is aimed at overcoming such limitations. It uses the Receptance Harmonic Balance Method (RHBM) to generate the backward operator using vibration measurements taken from sensors installed on the engine casing. The operator is then inverted using either Least Squares Fit (LSF) or Singular Value Decomposition (SVD). The resulting solution is the equivalent unbalance distribution in prescribed unbalance planes of the HP rotor which are consequently used to balance it. This method is validated using two distinct rotordynamic systems and simulated casing vibration readings corrupted by different noise levels.
Tribological Optimization of Thrust Bearings Operated With Lubricants of Spatially Varying Viscosity
Authors: Pavlioglou S. K. , Mastrokalos M. E. , Papadopoulos C. I. , Kaiktsis L.
Published: September 2014

In the present work, a CFD-based optimization study of thrust bearings lubricated with spatially varying viscosity lubricants is presented, with the main goal of minimizing friction coefficient. In practice, spatial variation of viscosity could be achieved by utilizing electrorheological or magnetorheological fluids. The bearings are modeled as two-dimensional channels, consisting of a smooth moving wall (rotor), and a parallel or inclined stationary wall (stator), which can be (i) smooth, (ii) partially textured with rectangular dimples, and (iii) smooth and partially hydrophobic. The bearings are considered to be operated with an ideal lubricant that exhibits different values of viscosity in two distinct regions of the fluid domain: a high viscosity area is considered at the channel inflow, with the viscosity acquiring a reference (low) value farther downstream. The flow field is calculated from the numerical solution of the Navier-Stokes equations for two-dimensional incompressible isothermal flow. The bearing geometry is defined parametrically. Three optimization problems are formulated, corresponding to: (I) a conventional smooth converging slider, (II) a parallel slider with artificial surface texturing at part of the stator surface, and (III) a parallel or converging slider with hydrophobic properties at part of the stator surface. Here, the geometry parameters, as well as the increased viscosity value and the corresponding application regime, form the problem design variables. Bearings are optimized for maximum load capacity and minimum friction coefficient. Optimal solutions are compared against corresponding ones for operation with constant viscosity. It is demonstrated that, by using spatially-varying viscosity, a substantial reduction of friction coefficient can be achieved, for all optimization problems considered. This decrease is shown to be a consequence of a sharp pressure rise in the high viscosity regime, resulting in a corresponding rise in load capacity, accompanied by a less pronounced increase in wall shear stress, and thus in total friction force.
Development and Experimental Evaluation of Endothermic Fuel for Better Combustion and Life of Combustor: In Realistic Test Setup
Authors: Ganapuram Venu , Jangam Srinivas , Pulumathi Manjunath , Iyengar Venkat , Thippareddy Aruna Singanahalli , Rajaram Kannan
Published: September 2014

The concept of endothermic fuels is not a strange thing to the aeronautical community. Research is going on, globally, to achieve these kinds of fuels experimentally; but restricted to laboratory scale test setup. This is because of the stringent and controlled method of cracking the fuel thermally as well as catalytically. In this research work we have followed a systematic approach, i.e, developed a laboratory scale reactor for the preliminary feasibility studies and a realistic experimental set up, for the development and analysis of the cracked fuel by simulating the conditions of combustor walls. Developing this technology indigenously involves many steps, namely identification of the suitable catalysts, developing the technology of preparation of catalytically active coatings and then the design and fabrication of the catalytic cracking core. Finally the catalytic cracking core has to be integrated to the test combustor with the experimental setup. To carry out the catalytic cracking reaction, a high pressure and high temperature catalytic reactor was designed and developed. The reactor can heat kerosene up to 725 K and maintain pressures up to 10 bar. The catalytic coatings were prepared with ZSM-5 and molecular sieves (20:80); coated on aluminum cylinders. A temperature drop of 114 K was obtained when kerosene fuel was passed through the catalytic system. This clearly shows the cooling effect by the endothermic fuel. A mixed bed catalytic system (Molecular sieves, Reformax-100 and ZSM-5) was also developed for the in-situ generation of Hydrogen gas along with the catalytic cracking process. The presence of Hydrogen gas in the cracked fuel is confirmed by gas chromatographic (GC) Retention time Vs Voltage investigation.

The experimentation in test rig was carried out in two modes, one is for thermal cracking (absence of catalyst) of kerosene fuel and the other one is catalytic cracking. In both the cases, the combustor duct is heated by hot air to 1200 K. Skin temperatures were measured to study the cooling effect of the endothermic fuel and the results are reported in this paper. It is noticed that the chemical composition of the kerosene fuel has been changed and fragmented into lighter chains. It is evident in the Gas Chromatography results that the catalytically cracked kerosene samples (gaseous and liquid samples) are having 30% higher of lighter chains (Ethane, Propane and Butane) of chemical compounds than thermally cracked kerosene samples. As expected, the fuel has got cracked thermally and catalytically while cooling the wall of the duct (simulating the actual flight conditions to realize the practical feasibility of generating endothermic fuels rather than restricting it to laboratory scale experiments).
Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals: Part II — Effects of Partition Wall Type, Partition Wall Number and Cavity Depth
Authors: Li Zhigang , Li Jun , Feng Zhenping
Published: September 2014

Effects of partition wall type, partition wall number and cavity depth on the leakage and rotordynamic characteristics of the pocket damper seal (PDS) were numerically investigated using a presented 3D transient CFD method based on the multi-frequency elliptical whirling orbit model. The accuracy and availability of this transient CFD method and the multi-frequency elliptical whirling orbit model were demonstrated with the experimental data of the experimental eight-bladed fully-partitioned pocket damper seal (FPDS). The leakage flow rates and frequency-dependent rotordynamic coefficients of PDS were computed for two types of partition wall (namely conventional PDS and fully-partitioned PDS), four partition wall numbers including the labyrinth seal (no partition wall) and six cavity depths including the plain smooth seal (zero cavity depth) at operational conditions with or without inlet preswirl and 15000rpm rotational speed. The numerical results show that the FPDS has the similar leakage performance and more superior stability capacity than the conventional PDS. The FPDS possesses slightly larger leakage flow rate (∼2.6–4.0% larger) compared to the labyrinth seal. Eight is a preferable value for the partition wall number to gain the best leakage performance of the FPDS with the least manufacturing cost. The FPDS possesses significantly larger stiffness and damping than the labyrinth seal. Increasing partition wall number results in a significant increase in the direct stiffness but limited desirable effect on the effective damping. The FPDS possesses the lowest leakage flow rate when the cavity depth is about 2.0mm. Compared to the plain smooth seal, the FPDS possesses larger positive direct stiffness and significantly less direct damping and effective damping. Increasing cavity depth results in a significant decrease in the stabilizing direct damping and the magnitude of the destabilizing cross-coupling stiffness. H = 3.175mm is a preferable value of the cavity depth for which the effective damping of the FPDS is largest, especially for the concerned frequencies (80–120Hz) where most multistage high-pressure centrifugal compressors have stability problem.
Dynamic Analysis of Anisotropic Asymmetric Rotor-Bearing System Based on Three-Dimensional Finite Element Method
Authors: Ma Weimeng , Wang Jianjun
Published: September 2014

3D finite element modeling is a promising method, but it is not well extended to the dynamic analysis of anisotropic asymmetric rotor bearing systems. This paper is aimed at proposing a dynamic analysis method of anisotropic asymmetric rotor bearing systems based on 3D finite element method. In the proposed approach, the advantages of 3D finite element modeling are used to accurately simulate the dynamic characteristics of the asymmetric rotor. The asymmetric characteristics of the stator are considered and simplified as time-varying bearing stiffness parameters in the rotating frame. The time-varying coefficient differential equation of motion of the rotor bearing system is established in a rotating frame by taking consideration of the bearing characteristics. Floquet theory and Hill expansion method are adopted to obtain the set of equivalent linear time-invariant equations of the original time-varying coefficient differential equations. Frequency characteristics and stability of the system were obtained by solving the equivalent linear time-invariant equations. Two numerical examples are analyzed. The results of the two examples show that the proposed 3D finite element method is a good tool for dynamic analysis of anisotropic asymmetric rotor bearing systems.
On Predicting the Phenomenon of Surface Flow Convergence in Wind Farms
Authors: Selvaraj Suganthi , Sharma Anupam
Published: September 2014

A systematic analysis of a single-rotor horizontal axis wind turbine aerodynamics is performed to obtain a realistic potential maximum efficiency. It is noted that by including the effects of swirl, viscosity and finite number of blades, the maximum aerodynamic efficiency of a HAWT is within a few percentage points of the efficiency of commercially-available turbines. The need for investigating windfarm (as a unit) aerodynamics is thus highlighted.

An actuator disk model is developed and implemented in the OpenFOAM software suite. The model is validated against 1-D momentum theory, blade element momentum theory, as well as against experimental data. The validated actuator disk model is then used to investigate an interesting microscale meteorological phenomenon called “flow convergence” caused by an array of wind turbines. This phenomenon is believed to be caused by the drop of pressure in wind farms. Wind farm numerical simulations are conducted with various approximations to investigate and explain the flow convergence phenomenon.