bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Design and Performance Optimization of the ORC System for the Waste Heat Recovery in Refining Petroleum Industry
Authors: Li Yan , Song Jian , Gu Chunwei 
Published: September 2014

As the increase of the energy consumption and the deterioration of environment, a carbon tax will be imposed in China to reduce carbon emissions strictly and the industrial waste heat recovery has been getting more attention. The Organic Rankine Cycle (ORC) system has been proven to be a promising solution for the utilization of the low-grade heat sources.
There are five waste heat sources from a 1.2 million ton reforming and extraction unit in Shijiazhuang Refining & Chemical Company of China. The temperatures of the waste heat sources are 98∼80°C, 104∼80°C, 147∼80°C, 205∼80°C and 205∼80°C, and the heat loads are 6.5MW, 11.5MW, 8.6MW, 3.8MW and 2.2MW, respectively. This paper studies the thermal design and performance optimization of a comprehensive utilization system for these waste heat sources, using ORC technology. The selection of suitable organic fluid is studied and the working parameters are designed and optimized with the application of the first law and the second law of thermodynamics. When the ORC systems are designed separately for the recovery of five waste heat sources, and the total power output is 3338.89kW with different organic working fluids. However this kind of designs leads to a very complex recovery system which needs large investment and space occupation. To reduce the overall system complexity, a single ORC system is proposed to recover all five heat sources, and the total amount of output power will only be 2813.02kW, due to the large exergy loss. With the above results shown, and for the purpose of simple system with large power output, this paper further studies the dual ORC systems heat recovery plan, with R245fa as the top cycle working fluid and R141b as the bottom cycle working fluid. The total amount of power output to 3353.27kW. The dual systems with single working fluid heat recovery plan is also studied, and with R141b as the working fluid for both the top cycle and the bottom cycle, the total amount of power output is 3325.03kW, and the heat recovery system is simple and compact, with good economical benefit.
Development and Integration of Rain Ingestion Effects in Engine Performance Simulations
Authors: Roumeliotis I. , Alexiou A. , Aretakis N. , Sieros G. , Mathioudakis K. 
Published: September 2014

Rain ingestion can significantly affect the performance and operability of gas turbine aero-engines. In order to study and understand rain ingestion phenomena at engine level, a performance model is required that integrates component models capable of simulating the physics of rain ingestion. The current work provides, for the first time in the open literature, information about the set-up of a mixed-fidelity engine model suitable for rain ingestion simulation and corresponding overall engine performance results. Such a model can initially support an analysis of rain ingestion during the pre-design phase of engine development. Once components and engine models are validated and calibrated versus experimental data, they can then be used to support certification tests, the extrapolation of ground test results to altitude conditions, the evaluation of control or engine hardware improvements and eventually the investigation of in-flight events.
In the present paper, component models of various levels of fidelity are firstly described. These models account for the scoop effect at engine inlet, the fan effect and the effects of water presence in the operation and performance of the compressors and the combustor. Phenomena such as velocity slip between the liquid and gaseous phases, droplet break-up, droplet-surface interaction, droplet and film evaporation as well as compressor stages re-matching due to evaporation are included in the calculations. Water ingestion influences the operation of the components and their matching, so in order to simulate rain ingestion at engine level a suitable multi-fidelity engine model has been developed in the PROOSIS simulation platform. The engine model’s architecture is discussed and a generic high bypass turbofan is selected as a demonstration test case engine.
The analysis of rain ingestion effects on engine performance and operability is performed for the worst case scenario, with respect to the water quantity entering the engine. The results indicate that rain ingestion has a strong negative effect on high-pressure compressor surge margin, fuel consumption and combustor efficiency, while more than half of the water entering the core is expected to remain unevaporated and reach the combustor in the form of film.
Numerical Studies on Effect of Channel Orientation in a Rotating Smooth Wedge-Shaped Cooling Channel
Authors: Srinivasan Balamurugan , Dhamarla Anand , Jayamurugan Chandiran , Rajan Amarnath Balu 
Published: September 2014

The increasing demands of better efficiency of modern advanced gas turbine require higher turbine inlet temperatures, which gives great challenges to turbine blade designers. However, the temperature limits of turbine blade material are not high enough to ensure its survival in such incredible operating temperature. Hence, both internal and external cooling approaches have been developed and widely used in today’s turbine blade. To internal cooling problems, a variety of cooling enhancement approaches, such as impingement and turbulators, are employed in order to meet the different needs in leading, middle and trailing region. One of the most critical parts in turbine blade is trailing edge where it is hard to cool due to its narrow shape. Pin-fins are widely used to cool the trailing edge of rotor and stator blades of gas turbine engine. Pin-fins offer significant heat transfer enhancement, they are relatively easy to fabricate and offer structural support to the hollow trailing edge region. The flow physics in a pin-fin roughened channel is very complicated and three-dimensional.
In this work, we have studied the effect of channel orientation on heat transfer in a rotating wedge-shaped cooling channel using numerical methods. Qiu [1] studied experimentally heat transfer effects of 5 different angles of wedge shaped channel orientation for the inlet Reynolds number (5100 to 21000) and rotational speed (zero to 1000 rpm), which results in the inlet Rotation number variation from 0 to 0.68. They observed that compared to the non-rotating condition, there is about 35% overall heat transfer enhancement under highest rotation number. The above said results are validated using current studies with Computational Fluid Dynamics (CFD) revealed that rotation increases significantly the heat transfer coefficient on the trailing surface and reduces the heat transfer coefficient on the leading surface. This is due to the higher velocities associated with the converging geometry near trailing surface.
A Numerical Study on the Influence of Hole Aspect Ratio on the Performance Characteristics of a Hole-Pattern Seal
Authors: Migliorini Patrick J. , Untaroiu Alexandrina , Wood Houston G. 
Published: September 2014

In turbomachinery, annular seals are used to reduce leakage between regions of high and low pressure. Many configurations of annular seals have been developed and studied in the literature including plain, labyrinth, pocket-damper, honeycomb, and hole-pattern. In machines experiencing stability issues, honeycomb and hole-pattern type seals have been used to replace labyrinth seals. Bulk-flow models are typically used to predict the leakage and dynamic coefficients of hole-pattern seals, relying on empirically derived friction factor coefficients. Previous experimental studies have shown that, for hole-pattern seals, the leakage and stator friction factor are strongly influenced by hole-depth. However, this behavior is not a monotonic function of hole-depth, a fact that might reduce confidence in future bulk-flow model predictions if not properly accounted for. A recent numerical study has highlighted the role of vortex formation in the holes which has a strong influence on the flow in the clearance region. Depending on the shape of the vortex, the flow in the hole can act much like a pinch valve, reducing the effective clearance of the jet flow.
In this paper, computational fluid dynamics simulations of several hole-pattern seal configurations have been performed to study the effect of hole-aspect ratio (depth versus diameter) on the leakage and friction factors. The Reynolds Averaged Navier Stokes (RANS) equations with k-ε turbulence model were solved using ANSYS CFX. It was found that the shape of the hole influences the vortex formation within the hole, effecting the jet flow in the clearance region and the seal leakage. The results show that the leakage is heavily dependent on the hole diameter in addition to the hole depth. The relationship between the friction factors and the geometry of the seal was found to be non-monotonic. It is therefore difficult to develop a friction factor model that will accurately encompass all configurations and it is recommended that friction factor data be interpolated from experimental or numerical results.
Endwall Contouring Optimization in a High Pressure Turbine Vane With Consideration of Rim Seal Flow
Authors: Hu Shuzhen , Luo Hualing 
Published: September 2014

In this paper, non-axisymmetric endwall contouring optimizations in a high pressure turbine second vane passage were performed with and without including the rim seal flow. Aerodynamic performances of two contoured endwalls were studied and compared with the planar endwall case. The optimization was carried out with a commercial software package NUMECA Fine/Design 3D. A genetic algorithm was chosen as the optimization method. The objective was to minimize the total pressure loss in the high pressure turbine vane.
Without the rim seal flow, the contoured endwall decreased the strength of the passage vortex, and reduced the total pressure loss coefficient up to 10.4%. However, the benefit achieved by this contoured endwall was lost when the rim seal flow was included by adding a under platform section in the computation model. With the existence of the rim seal flow, the flow field near the endwall was significantly changed. After recontouring the endwall using the optimization procedure with including rim seal flow, a 9.8% decrease in total pressure loss coefficient was achieved with the reduction of the vortex strength.
Oil Whip Elimination Using Fuzzy Logic Controller
Authors: Dimitri A. S. , Mahfoud J. , El-Shafei A. 
Published: September 2014

Oil whip is a self-excited sub-synchronous vibration which limits the range of operating speed of Journal Bearings (JB). JB have wide range of applications due to their high loading capacity, simple geometry, and lubrication. When the speed of rotation increases, the oil whip instability is excited with a frequency corresponding to the rotor critical speed which causes excessive undesirable vibration.
A solution for this instability is implemented through this paper. The control action is implemented through a new integrated bearing device. The bearing consists of JB and Electromagnetic Actuator (EMA). The oil whip control action is applied through the EMA.
A fuzzy logic control algorithm is developed and experimentally applied to a rotor test rig. The fuzzy logic controller is suitable to deal with problems of uncertainties and non-linearity.
The experimental results show the ability of the developed fuzzy logic controller to eliminate the oil whip instability when applied to a test rig which simulates industrial rotor through an integrated bearing prototype which was designed and manufactured.
A Simple Corner Correction Technique for Transient Thermal Measurement
Authors: Chen W. , Jiang H. , Zhang Q. , He L. 
Published: September 2014

The 1D conduction analytical and semi-analytical approaches for a semi-infinite domain have been widely adopted in the data processing of transient thermal experiments. The convective heat transfer coefficient (HTC) calculated by the 1D approach contains large errors when lateral conduction effects are significant, especially near a corner of solid domain. The problems could be addressed by alternative full 3D numerical conduction analyses, which tend to be complex as well as requiring extra experimental efforts to obtain the full thermal boundary conditions around corners, in addition to an access to a 3D conduction solver (CFD or FEA).
In the present work, a simple and effective method is developed to correct such errors in the near-corner region without using any commercial tool. The present approach is based on the recognition that a temperature time trace in a 2D situation is the result of the accumulated heat conductions from the normal and lateral directions respectively and summatively. An equivalent semi-infinite 1D conduction temperature trace for a correct HTC can be generated by reconstructing and removing the lateral conduction effect at each discrete time step. This simple new correction procedure enables the standard 1D conduction analysis to be properly used to get the correct HTC, completely analytically without needing any aid of CFD or FEA solutions.
Two test cases of practical interest with turbine blade tip heat transfer and film cooling are used for validation and demonstration. It has been consistently shown that the errors of the conventional 1D conduction analysis in the near corner regions can be greatly reduced by the new corner correction method. The demonstrated validity, the simplicity and robustness of the present method makes it a good candidate for future applications in transient thermal experimental studies.
Automatic Design Optimisation of Profiled Endwalls Including Real Geometrical Effects to Minimize Turbine Secondary Flows
Authors: Shahpar Shahrokh , Caloni Stefano , de Prieëlle Laurens 
Published: September 2014

This paper presents a novel optimisation methodology based on both Adjoint sensitivity analysis and trust-based dynamic response surface modelling to improve performance of a modern turbine of a large civil aero-engine in the presence of high-fidelity geometry configurations. The system has been applied to the non-axisymmetric hub and tip endwall optimisation of a high-pressure turbine stage making use of multi-row 3D simulations, parametric modelling and rapid meshing of real geometry features such as rim seals and modelling of film cooling flows.
It has been shown in previous papers that improvements gained using simplified models of the stage are lost when applying the high-fidelity geometry configuration. New results presented in this paper indicate that controlling the purge flow that exits the disc space through the rim seal at the hub of the main annulus is more significant than the reduction of secondary flows in the main passage. For a given rim sealing mass flow rate and whirl velocity, the non-axisymmetric endwalls are optimised such that the detrimental impact of the sealing flow on the turbine performance is reduced, and hence the stage efficiency is significantly increased. The traditional optimisation approaches based on evolutionary methods or even sequential modifications for defining the endwalls shape are computationally demanding. Since, turbomachinery industry continuously strive to reduce the design cycle time, in particular when high fidelity 3D CFD is used, the main body of this paper outlines the novel methods developed to produce a practical design in a very aggressively short design cycle time.
Numerical Investigation on the Flow Characteristics of a Supercritical CO2 Centrifugal Compressor
Authors: Zhao Hang , Deng Qinghua , Zheng Kuankuan , Zhang Hanzhen , Feng Zhenping 
Published: September 2014

Supercritical CO2 closed-loop Brayton cycles offer the potential of better economical and practical efficiency due to its compact size and smaller compression work as compared with some traditional working fluids cycles, in which compressor is the key component. In this paper, the aerodynamic design and impeller aerodynamic optimization were conducted for a single stage centrifugal compressor with a combined vaneless and vaned diffuser, operating with CO2 slightly above the vapor-liquid critical point. The NIST REFPROP database was used for the computation of supercritical CO2 properties in design analysis and numerical investigation. The flow characteristics of the supercritical CO2 compressor were investigated by NUMECA FINE/Turbo. In order to weaken the low pressure regions, a vaneless diffuser was applied in this design, which would control and reduce the distribution differences of fluid thermodynamic states and increase fluid static pressure. The results indicate that there are no obvious low pressure regions occurring close to the leading edge of vaned diffuser. So it is observed in the design process that the vaneless diffuser could improve the aerodynamic performance of supercritical CO2 compressor.
Compared with the operating conditions of the compressor only under centrifugal force, the pressure load from the aerodynamic analysis and the centrifugal load due to high speed of rotation were considered in the study of the stress and deformation of the structure of impeller by ANSYS/Mechanical. It can be concluded that supercritical CO2 provides unique properties for the compressor working process, which have a significant influence on finite element modeling in structural analysis. For the present design the maximum von Mises stress and total deformation are shown much smaller than the maximum allowable values, and thus the compressor could work in a wide range of operating conditions.
A Reactor Model for the NOx Formation in a Reacting Jet in Hot Cross Flow Under Atmospheric and High Pressure Conditions
Authors: Hoferichter Vera , Ahrens Denise , Kolb Michael , Sattelmayer Thomas 
Published: September 2014

Staged combustion is a promising technology for gas turbines to achieve load flexibility and low NOx emission levels at the same time. Therefore, a large scale atmospheric test rig has been set up at the Institute of Thermodynamics, Technical University of Munich to study NOx emission characteristics of a reacting jet in hot cross flow. The premixed primary combustion stage is operated at ϕ = 0.5 and provides the hot cross flow. In the second stage a premixed jet at ϕ = 0.77 is injected perpendicular to the first stage. In both stages natural gas is used as fuel and air as oxidant. This paper presents a reactor model approach for the computation of the resulting NOx concentrations. The mixing and ignition process along the jet streamline of maximum NOx formation is simulated using a perfectly stirred reactor with Cantera 1.8. The reactor model is validated for the ambient pressure case using experimental data. Afterwards, a high pressure simulation is performed in order to investigate the NOx emission characteristics under gas turbine conditions.
The NOx formation is divided into flame NOx and post flame NOx. The reactor model reveals that the formation of post flame NOx in the second combustion stage can be efficiently suppressed due to fast mixing with cross flow material and the corresponding temperature reduction. Compared to single stage combustion with the same power output, no NOx reduction was observed in the experiment. However, the results from the reactor model suggest a NOx reduction potential at gas turbine conditions caused by the increased influence of post flame NOx production at high pressure.
Automatic Three-Dimensional Optimisation of a Modern Tandem Compressor Vane
Authors: Schlaps R. C. , Shahpar S. , Gümmer V. 
Published: September 2014

In order to increase the performance of a modern gas turbine, compressors are required to provide higher pressure ratio and avoid incurring higher losses. The tandem aerofoil has the potential to achieve a higher blade loading in combination with lower losses compared to single vanes. The main reason for this is due to the fact that a new boundary layer is generated on the second blade surface and the turning can be achieved with smaller separation occurring. The lift split between the two vanes with respect to the overall turning is an important design choice.
In this paper an automated three-dimensional optimisation of a highly loaded compressor stator is presented. For optimisation a novel methodology based on the Multipoint Approximation Method (MAM) is used. MAM makes use of an automatic design of experiments, response surface modelling and a trust region to represent the design space. The CFD solutions are obtained with the high-fidelity 3D Navier-Stokes solver HYDRA. In order to increase the stage performance the 3D shape of the tandem vane is modified changing both the front and rear aerofoils. Moreover the relative location of the two aerofoils is controlled modifying the axial and tangential relative positions. It is shown that the novel optimisation methodology is able to cope with a large number of design parameters and produce designs which performs better than its single vane counterpart in terms of efficiency and numerical stall margin.
One of the key challenges in producing an automatic optimisation process has been the automatic generation of high-fidelity computational meshes. The multi block-structured, high-fidelity meshing tool PADRAM is enhanced to cope with the tandem blade topologies. The wakes of each aerofoil is properly resolved and the interaction and the mixing of the front aerofoil wake and the second tandem vane are adequately resolved.
Assessment of Aero-Thermal Design Methodology for Effusion Cooled Lean Burn Annular Combustors
Authors: Andreini A. , Facchini B. , Mazzei L. , Bellocci L. , Turrini F. 
Published: September 2014

Increasingly stringent limitations imposed on aircraft engine emissions have led many manufacturers toward lean combustion technology, which involves a relevant increase in mass flow rate dedicated to primary combustion, leading as a consequence to a reduction of air dedicated to cooling of liners. One of the most promising cooling techniques in such conditions is represented by effusion cooling, which consists of an array of closely spaced discrete film cooling holes. This cooling method is based on a protective layer of cooling flow on the hot side of the liner, enhancing at the same time the heat removal within the holes. In the latest years many aero engine manufacturers have increased the research and technology investment on this combustion technology. Working in partnership with the University of Florence, specific component design tools and experimental techniques have been improved by Avio Aero for combustor gas turbine investigation.
From a design perspective, CFD analysis has become a key tool up to the early stages of novel combustor design process, producing affordable direct 3D optimization of combustor aerodynamics. Nevertheless, a RANS simulation of even only a single sector of an annular combustor still presents a challenge when the cooling system is taken into account. This issue becomes more critical in case of modern effusion cooled combustors, which may contain up to two thousand holes for the single sector. For this reason, many efforts have been devoted to develop methodologies based on film cooling modeling. Among the approaches published in the literature, models based on local sources represent a good compromise between simplicity and accuracy, with the capability to automatically perform a Conjugate Heat Transfer analysis. This type of methodology has been already defined and validated by the authors, with comparison on effusion cooled plates in terms of experimental overall effectiveness measurements as well as the application on a tubular combustor test case. In the context of this work, the proposed approach has been applied to the analysis of a lean annular combustor with the purpose of investigating pressure losses, flow split and metal temperature field. The results obtained have been compared to experimental data and different numerical tools exploited during the preliminary design of these devices.