bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Small Scale Liquefied Natural Gas Production Process at Filling Stations: Thermodynamic Analysis and Parametric Investigation
Authors: Ancona M. A. , Bianchi M. , Branchini L. , De Pascale A. , Melino F. , Mormile M. , Palella M. 
Published: September 2016

In the last years, the increased demand of the energy market has led to the increasing penetration of renewable energies in order to achieve the primary energy supply. However, simultaneously natural gas still plays a key role in the energy market, mainly as gaseous fuel for stationary energy generation, but also as liquefied fuel, as an alternative to the diesel fuel, in vehicular applications. Liquefied Natural Gas (LNG) is currently produced in large plants directly located at the extraction sites.
In this study, the idea of realizing plug & play solutions to produce LNG directly at vehicle’s filling stations has been investigated. A novel process of LNG production for filling stations has been analyzed, consisting in a single stage Joule-Thompson isenthalpic expansion process, with intercooled compression. Furthermore, the presented layout has been developed with the purpose of optimizing the energy consumption of the plant, obtaining moderately pressurized LNG.
With the aim of investigating the feasibility of this novel LNG generation process, a thermodynamic analysis has been carried out and presented in this study. Moreover, the minimization of energy consumption has been investigated with a parametric analysis, in order to optimize the LNG production and to maximize the efficiency of the process. Furthermore, novel performance indicators have been defined, in order to account the efficiency of the LNG production process. Results of the optimization analysis show that, with the proposed layout, an energy consumption equal to about 1.9 MJ/kg of produced LNG can be achieved.
Experimental Study of the Influence of the Operating Parameters on the Performance and Capability of a Mixed-Flow Multiphase Pump
Authors: Serena Alberto , Bakken Lars E. 
Published: September 2016

Multiphase flow introduces many challenges in turbomachines analysis and operation, as each of the phases responds differently to the forces in the hydraulic channel, and the mechanical and thermal interaction among the phases has to be taken into account too. Especially when very high gaseous fractions need to be covered, due to the concurrent physics involved and transient phenomena, a proper machine characterization cannot be limited to an overall description of the performance, but it needs to rely on advanced analysis tools which can reveal the local phenomena responsible for performance degradation and instabilities.
The flow regimes vary from a homogeneous distribution of fine bubbles, evenly dispersed and carried away by the main flow, to more complex flow patterns, especially if bubbles coalesce and adhere to a wide portion of the channel wall.
Tests are performed on a multiphase pump facility recently designed by the authors, which allows a complete optical access to the pump channels and fine adjustments in the inlet configuration and the tip clearance gap.
The investigation focuses on the effect of the mixture inlet pressure and machine rotational speed on performance and stability. Increasing values of the inlet pressure reduce the density ratio between the phases, thus making them become more coupled; this results in a milder performance degradation and a wider stable operating range.
Accurate flow visualization through the pump transparent casing complements the study, allowing an immediate and detailed local phenomena description.
The results are presented under performance and surging curves, showing the gas-handling capability dependence on the actual conditions.
These analyses fully characterize the machine behavior, define the operating zones which should be avoided, and will serve later to implement a control strategy to keep the machine in a safe regime.
Gas Turbine Shutdown Thermal Analysis and Results Compared With Experimental Data
Authors: Reddy Vishnu Vardhan , Selvam Kathiravan , De Prosperis Roberto 
Published: September 2016

Gas turbines undergo transient operation during startup, load change and shutdown. Understanding transient behaviour is very critical as it has significant influence on the safety and life of turbine components. The transient thermal analysis of the gas turbine is one of the most important aspects to evaluate the clearances and life of various components of the unit. The understanding of the shutdown phenomena is very complex due to huge transient variation in the temperature inside the turbine. In the shutdown process natural convection plays an important role as there is very less flow inside the turbine, which is difficult to model and predict with the current state of art tools.
A Flange to Flange 2D axi-symmetric thermal model was considered for this analysis to predict the overall temperature distribution of the gas turbine components with suitable approximations. In this paper detailed experimental results of the GE frame 5 shut down are analysed and numerical modelling was attempted to match the experimental results. Several analytical studies are carried out to understand the various effects including the “heat soak” effect. These effects were captured in both experimental and analytical studies.
Heat Transfer Correction Methods for Turbocharger Performance Measurements
Authors: Schinnerl Mario , Seume Joerg , Ehrhard Jan , Bogner Mathias 
Published: September 2016

Turbocharger performance maps used for the matching process with a combustion engine are measured on test benches which do not exhibit the same boundary conditions as the engine. However, these maps are used in engine simulations, ignoring that the compressor and turbine aerodynamic performance is rated on the basis of quantities which were measured at positions which do not coincide with the respective system boundaries of the turbomachinery.
In the operating range of low to mid engine speeds, the ratio between the heat flux and the work done by the turbine and the compressor is much greater than at high speeds where heat transfer phenomena on the compressor side can usually be neglected. Heat losses on the turbine side must be taken into account even at higher shaft speeds when dealing with isentropic turbine efficiencies.
Based on an extensive experimental investigation a one-dimensional heat transfer model is developed. The compressor and turbine side are treated individually and divided into sections of inlet, wheel, outlet, diffuser and volute. The model demonstrates the capability to properly account for the impact of heat transfer and thereby improves the predictive accuracy of temperatures relevant for the matching process.
Cryogenic Turboexpanders in LNG Liquefaction Applications
Authors: Taher Matt , Meher-Homji Cyrus B. 
Published: September 2016

Turboexpanders provide the most efficient solution when it is required to reduce the pressure of a fluid stream. By expanding high pressure fluid, energy in the high pressure fluid entering the turboexpander can be efficiently used for either driving a booster compressor or for electrical power generation. While the plants are designed to operate without the need for the power produced by turboexpander, the work recovered from the expansion is a bonus, which increases the plant thermal efficiency.
This paper is intended to explain the benefits of utilizing a turboexpander in LNG liquefaction applications. Also, in absence of a published API standard for a turboexpander-generator package, this paper provides recommendations on factory acceptance tests.
Experimental Investigation of Effusion Cooling Performance on the Liner of a Scaled Three Injector Annular Combustor
Authors: Ji Yongbin , Ge Bing , Zang Shusheng , Yu Jiangpeng , Zhang Ji 
Published: September 2016

Gas turbine combustors design nowadays is aimed at achieving extremely lower NOx emissions through involving more air into the combustor to perform lean combustion, which results in the reduction of cooling air ratio for the liner walls. In this context, effusion cooling, one of the most effective cooling strategies, is adopted on the liner for its advantages of providing well cooling protection with limited amount of air. The swirl flow structure generated by the injector to stabilize flame in most modern lean-burn combustor is very complex with recirculation and vortex breakdown. So the interaction between three dimensional main flow and jets issued from the effusion holes is significant when assessing effusion cooling performance on the liner.
In the present work, detailed effusion cooling feature on both inner and outer liners of a scaled annular combustor equipped with three axial swirlers has been provided under non-reactive and reactive conditions. The main flow is electrically heated for the non-reactive condition, while premixed combustion is realized after methane is fueled into the injectors and mixed with the air in the surrounding passage for the reactive condition. Temperature distribution on the target bended plate with 7 rows of discrete cooling holes in an in-line layout is captured by infrared thermography, and the cooling effectiveness is then analyzed. Effects of coolant to mainstream flow rate ratio and equivalence ratio are evaluated respectively. Results show that the macro rotational flow generated by the swirl flows interacts with cooling film and leads to non-symmetric cooling protection circumferentially on both liners. Additionally, averaged cooling effectiveness is found to increase with the flow rate ratio. At reactive conditions, stagnation of the high temperature swirl flow impinging on the liner wall locates at X/D range of 0.4–0.5, which has not been observed at non-reactive conditions. Also cooling effectiveness results indicate that outer liner obtains better cooling protection than inner liner when reaction is activated. Finally, the effect of most interested parameter for combustion process equivalence ratio is surveyed at Φ=0.7, 0.8 and 0.9. With experimental results, the importance of the combustion is highlighted in weighing the effusion cooling performance on the real annular combustor liners, which can’t be predicted comprehensively by non-reactive investigations. To obtain more knowledge of this issue, future work concerned with the flow field and flame visualization needs to be done through experimental techniques and numerical methods.
A Study of S-CO2 Power Cycle for Waste Heat Recovery Using Isothermal Compressor
Authors: Heo Jin Young , Ahn Yoonhan , Lee Jeong Ik 
Published: September 2016

As the demand to develop more efficient energy systems increases, ways to generate power from waste heat are under investigation. The supercritical carbon dioxide recovery cycle (S-CO2 cycle) has been considered a viable candidate as a bottoming cycle for “waste heat to power” (WHP) applications, such as the utilization of gas turbine outlet heat.
One major limitation to the system is that the S-CO2 cycle operates at a low expansion ratio, which leads to a higher turbine outlet temperature. This waste heat should be recuperated in order for the overall cycle efficiency to increase. Such limitation leads to a larger recuperator, higher volume flow rate, lower temperature gradient at the heater, and more complex cycle layouts for WHP applications. These constraints ultimately lead to the increase of hardware costs, which can degrade economics of the system.
To solve the existing problems regarding the use of S-CO2 cycle for WHP applications, the possibility of using an isothermal compressor in place of a conventional compressor in a simple Brayton cycle is investigated. This solution, named the iso-Brayton cycle, though the compressor technology is still under development, seems promising because it does not require an additional heat exchanger as one of the cycle components. Furthermore, the compressing work is minimized during an isothermal compression process.
To analyze the cycle performance of the iso-Brayton cycle, it is compared with a reference cycle, the simple recuperated Brayton cycle. The parameters of cycle net efficiency and cycle net work (or net usable work) are calculated using the KAIST-CCD in-house code.
Measurements and Modelling of Ingress in a New 1.5-Stage Turbine Research Facility
Authors: Patinios Marios , Scobie James A. , Sangan Carl M. , Owen J. Michael , Lock Gary D. 
Published: September 2016

In gas turbines, hot mainstream flow can be ingested into the wheel-space formed between stator and rotor discs as a result of the circumferential pressure asymmetry in the annulus; this ingress can significantly affect the operating life, performance and integrity of highly-stressed, vulnerable engine components. Rim seals, fitted at the periphery of the discs, are used to minimise ingress and therefore reduce the amount of purge flow required to seal the wheel-space and cool the discs.
This paper presents experimental results from a new 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disc. The fluid-dynamically-scaled rig operates at incompressible flow conditions, far removed from the harsh environment of the engine which is not conducive to experimental measurements. The test facility features interchangeable rim-seal components, offering significant flexibility and expediency in terms of data collection over a wide range of sealing-flow rates. The rig was specifically designed to enable an efficient method of ranking and quantifying the performance of generic and engine-specific seal geometries.
The radial variation of CO2 gas concentration, pressure and swirl is measured to explore, for the first time, the flow structure in both the upstream and downstream wheel-spaces. The measurements show that the concentration in the core is equal to that on the stator walls and that both distributions are virtually invariant with radius. These measurements confirm that mixing between ingress and egress is essentially complete immediately after the ingested fluid enters the wheel-space and that the fluid from the boundary-layer on the stator is the source of that in the core. The swirl in the core is shown to determine the radial distribution of pressure in the wheel-space.
The performance of a double radial-clearance seal is evaluated in terms of the variation of effectiveness with sealing flow rate for both the upstream and the downstream wheel-spaces and is found to be independent of rotational Reynolds number. A simple theoretical orifice model was fitted to the experimental data showing good agreement between theory and experiment for all cases. This observation is of great significance as it demonstrates that the theoretical model can accurately predict ingress even when it is driven by the complex unsteady pressure field in the annulus upstream and downstream of the rotor. The combination of the theoretical model and the new test rig with its flexibility and capability for detailed measurements provides a powerful tool for the engine rim-seal designer.
Experimental Investigation of Stall and Surge in a Multistage Compressor
Authors: Munari Enrico , Morini Mirko , Pinelli Michele , Spina Pier Ruggero , Suman Alessio 
Published: September 2016

Flow instability conditions, in particular during surge and stall phenomena, have always influenced the operational reliability of turbo-compressors and have attracted significant interest resulting in extensive literature. Nowadays, this subject is still one of the most investigated because of its high relevance on centrifugal and axial compressor operating flow range, performance and efficiency. Many researchers approach this important issue by developing numerical models, whereas others approach it through experimental studies specifically carried out in order to better comprehend this phenomenon. The aim of this paper is to experimentally analyze the stable and unstable operating conditions of an aeronautic turbo-shaft gas turbine axial-centrifugal compressor installed on a brand new test-rig properly designed for this purpose.
The test facility is set up in order to obtain i) the compressor performance maps at rotational speeds up to 25,000 rpm and ii) the compressor transient behavior during surge. By using two different test rig layouts, instabilities occurring in the compressor, beyond the peak of the characteristic curve, are identified and investigated.
These two types of analysis are carried out thanks to pressure, temperature and mass flow sensors located in strategic positions along the circuit. These measurement sensors are part of a proper control and acquisition system, characterized by an adjustable sampling frequency. Thus, the desired operating conditions of the compressor, in terms of mass flow and rotational speed and transient of these two parameters are regulated by this dedicated control system.
Comparison of Two Numerical Algorithms for Computing the Effects of Mistuning of Fan Flutter
Authors: Salles L. , Vahdati M. 
Published: September 2016

The aim of this paper is to study the effects of mistuning on fan flutter and to compare the prediction of two numerical models of different fidelity. The high fidelity model used here is a three-dimensional, whole assembly, time-accurate, viscous, finite-volume compressible flow solver. The Code used for this purpose is AU3D, written in Imperial College and validated for flutter computations over many years. To the best knowledge of authors, this is the first time such computations have been attempted. This is due to the fact that, such non-linear aeroelastic computations with mistuning require large amount of CPU time and cannot be performed routinely and consequently, faster (low fidelity) models are required for this task. Therefore, the second model used here is the aeroelastic fundamental mistuning model (FMM) and it based on an eigenvalue analysis of the linearized modal aeroelastic system with the aerodynamic matrix calculated from the aerodynamic influence coefficients. The influence coefficients required for this algorithm are obtained from the time domain non-linear Code by shaking one blade in the datum (tuned) frequency and mode. Once the influence coefficients have been obtained, the computations of aero damping require minimal amount of CPU time and many different mistuning patterns can be studied. The objectives of this work are to:
1. Compare the results between the two models and establish the capabilities/limitations of aeroelastic FMM,
2. Check if the introduction of mistuning would bring the experimental and computed flutter boundaries closer,
3. Establish a relationship between mistuning and damping.
A rig wide-chord fan blade, typical of modern civil designs, was used as the benchmark geometry for this study. All the flutter analyses carried out in this paper are with frequency mistuning, but the possible consequences of mistuned mode shapes are briefly discussed at the end of this paper. Only the first family of modes (1F, first flap) is considered in this work. For the frequency mistuning analysis, the 1F frequency is varied around the annulus but the 1F mode shapes remain the same for all the blades. For the mode shape mistuning computations, an FE analysis of the whole assembly different mass blades is performed.
The results of this work clearly show the importance of mistuning on flutter. It also demonstrates that when using rig test data for aeroelastic validation of CFD codes, the amount mistuning present must be known.
Finally, it should be noted that the aim of this paper is the study of mistuning and not steady/unsteady validation of a CFD code and therefore minimal aerodynamic data are presented.
Numerical Investigation of Boundary Layers in Wet Steam Nozzles
Authors: Starzmann Jörg , Hughes Fiona R. , White Alexander J. , Grübel Marius , Vogt Damian M. 
Published: September 2016

Condensing nozzle flows have been used extensively to validate wet steam models. Many test cases are available in the literature and in the past a range of numerical studies have dealt with this challenging task. It is usually assumed that the nozzles provide a one- or two-dimensional flow with a fully turbulent boundary layer. The present paper reviews these assumptions and investigates numerically the influence of boundary layers on dry and wet steam nozzle expansions.
For the narrow nozzle of Moses and Stein it is shown that the pressure distribution is significantly affected by the additional blockage due to the side wall boundary layer. Comparison of laminar and turbulent flow predictions for this nozzles suggests that laminar-turbulent transition only occurs after the throat. Other examples are the Binnie nozzle and the Moore nozzles for which it is known that sudden changes in wall curvature produce expansion and compression waves that interact with the boundary layers. The differences between two- and three-dimensional calculations for these cases and the influence of laminar and turbulent boundary layers are discussed.
The present results reveal that boundary layer effects can have a considerable impact on the mean nozzle flow and thus on the validation process of condensation models. In order to verify the accuracy of turbulence modelling a test case that is not widely known internationally is included within the present study. This experimental work is remarkable because it includes boundary layer data as well as the usual pressure measurements along the nozzle centreline. Predicted and measured boundary layer profiles are compared and the effect of different turbulence models is discussed. Most of the numerical results are obtained with the in-house wet steam RANS-solver, Steamblock, but for the purpose of comparison the commercial program ANSYS CFX is also used, providing a wider range of standard RANS-based turbulence models.
Experimental Investigation on Swirl and Heat Transfer Within a Rotor-Stator Cavity
Authors: Massini Daniele , Facchini Bruno , Micio Mirko , Da Soghe Riccardo 
Published: September 2016

A rotating test rig, reproducing a rotor-stator cavity with an axial admission system, has been exploited for an experimental investigation on the internal flow field and its effect on heat transfer on the stator side.
Working conditions were varied in a wide range of rotating velocities and superposed mass flow rates.
2D PIV flow measurements were performed in order to obtain a radial distribution of the tangential velocity, results were used to validate numerical simulations aimed at understanding the admission system effect on the swirl distribution.
Heat transfer coefficient distribution along the stator disk has been evaluated performing a steady state technique exploiting Thermo-chromic Liquid Crystals (TLC).
Tests have been performed varying the superposed mass flow rate up to reaching the condition of cavity completely sealed, further increase of the mass flow rate showed to reduce the effect of the rotation.
Working conditions were set in order to investigate cases missing in open literature, however few tests performed in similarity with other researches provided comparable results.