bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Analysis of an Electric Turbocompounding System for a Hybrid Vehicle Diesel Engine
Authors: Ding Zhanming , Zhuge Weilin , Zhang Yangjun , Yin Yong , Zhang Shuyong 
Published: August 2015

Waste heat recovery (WHR) is one of the main approaches to improve the internal combustion engine (ICE) overall efficiency and reduce emissions. The electric turbocompounding (ETC) technology is considered as a promising WHR technology for vehicle engines due to its compactness and light weight. In order to improve the overall fuel efficiency of the engine at practical operating conditions, the impacts of the implementation of the ETC system should be investigated not only at engine full load conditions, but also under practical driving cycles.
In this paper, an ETC system was designed for a 4.75 L diesel engine, in which a power turbine was installed down-stream to the turbocharger turbine. A performance simulation model of the ETC engine was developed on the basis of the diesel engine model, which was validated against engine performance experimental data. The control strategies of the wastegate of turbocharger turbine, the wastegate of power turbine and the operating torque of generator were determined. The relative variation in BSFC was studied under full range of operating conditions, and results show that the maximum improvement of fuel economy is 6.7% at an engine speed of 1000 rpm and 70% of full load, in comparison with the baseline diesel engine. Main factors lead to the performance differences between the ETC engine and the baseline engine were analyzed. Furthermore, the performance of the ETC engine under the C-WTVC driving cycle was investigated. Results show that the implementation of the ETC system resulted in a 1.2% fuel consumption reduction under the C-WTVC driving cycle.
Investigation of the Bottoming Cycle for High Efficiency Combined Cycle Gas Turbine System With Supercritical Carbon Dioxide Power Cycle
Authors: Cho Seong Kuk , Kim Minseok , Baik Seungjoon , Ahn Yoonhan , Lee Jeong Ik 
Published: August 2015

The supercritical CO2 (S-CO2) power cycle has been receiving attention as one of the future power cycle technology because of its compact configuration and high thermal efficiency at relatively low turbine inlet temperature ranges (450∼750°C). Thus, this low turbine inlet temperature can be suitable for the bottoming cycle of a combined cycle gas turbine because its exhaust temperature range is approximately 500∼600°C. The natural gas combined cycle power plant utilizes mainly steam Rankine cycle as a bottoming cycle to recover waste heat from a gas turbine. To improve the current situation with the S-CO2 power cycle technology, the research team collected various S-CO2 cycle layouts and compared each performance. Finally, seven cycle layouts were selected as a bottoming power system. In terms of the net work, each cycle was evaluated while the mass flow rate, the split flow rate and the minimum pressure were changed.
The existing well-known S-CO2 cycle layouts are unsuitable for the purpose of a waste heat recovery system because it is specialized for a nuclear application. Therefore, the concept to combine two S-CO2 cycles was suggested in this paper. Also the complex single S-CO2 cycles are included in the study to explore its potential. As a result, the net work of the concept to combine two S-CO2 cycles was lower than that of the performance of the reference steam cycle. On the other hand, the cascade S-CO2 Brayton cycle 3 which is one of the complex single cycles was the only cycle to be superior to the reference steam cycle. This result shows the possibility of the S-CO2 bottoming cycle if component technologies become mature enough to realize the assumptions in this paper.
Metal Temperature Prediction of a DLN1 Class Flame Tube by CFD CHT Approach
Authors: Da Soghe Riccardo , Bianchini Cosimo , Andreini Antonio , Mazzei Lorenzo , Riccio Giovanni , Marini Alessandro 
Published: August 2015

Combustor liner of present gas turbine engines is subjected to high thermal loads as it surrounds high temperature combustion reactants and is hence facing the related radiative load. This generally produces high thermal stress levels on the liner, strongly limiting its life expectations and making it one of the most critical components of the entire engine. The reliable prediction of such thermal loads is hence a crucial aspect to increase the flame tube life span and to ensure safe operations.
The present study aims at investigating the aero-thermal behavior of a GE DLN1 (Dry Low NOx) class flame tube and in particular at evaluating working metal temperatures of the liner in relation to the flow and heat transfer state inside and outside the combustion chamber. Three different operating conditions have been accounted for (i.e. Lean-Lean partial load, Premixed full load and Primary load) to determine the amount of heat transfer from the gas to the liner by means of CFD. The numerical predictions have been compared to experimental measurements of metal temperature showing a good agreement between CFD and experiments.
Space-Time Gradient Method for Unsteady Bladerow Interaction: Part II — Further Validation, Clocking and Multi-Disturbance Effect
Authors: He L. , Yi J. , Adami P. , Capone L. 
Published: August 2015

For efficient and accurate unsteady flow analysis of blade row interactions, a Space-Time Gradient (STG) method has been proposed. The development is aimed at maintaining as many modelling fidelities (the interface treatment in particular) of a direct unsteady method as possible while still having a significant speed-up. The basic modelling considerations, main method ingredients and some preliminary verification have been presented in Part I by Yi and He [1]. In Part II, further case studies are presented to examine the capability and applicability of the method.
Having tested a turbine stage in Part I, here we first consider the applicability and robustness of the method for a 3D transonic compressor stage under a highly loaded condition with separating boundary layers. The results of the STG solution compare well with the direct unsteady solution while showing a speed up of 25 times. Attention is then directed to rotor-rotor/stator-stator interferences in a 2-stage turbine configuration. Remarkably for stator-stator and rotor-rotor clocking analyses, the STG method demonstrates a significant further speed-up. Also interestingly the 2-stage cases studied suggest a clearly measurable clocking dependence of blade surface time-mean temperatures for both stator-stator clocking and rotor-rotor clocking, though only small efficiency variations are indicated. Also validated and illustrated is the capability of the STG for efficient evaluations of unsteady blade forcing due to the rotor-rotor clocking.
Considerable efforts are directed to extending the method to more complex situations with multiple-disturbances. Several techniques are adopted to decouple the disturbances in the temporal term. The developed capabilities have been examined for turbine stage configurations with inlet temperature distortions (hot streaks), and for 3 blade-row turbine configurations with non-equal blade counts. The results compare well with the corresponding direct unsteady solutions.
Investigation on Cooling Effectiveness and Flow Resistance of Inlet Fogging Location in Gas Turbine Inlet Duct
Authors: Zhang Hai , Jiang Bin , Zheng Qun , Chaker Mustapha 
Published: August 2015

The output power and efficiency of gas turbines are reduced significantly during the hot weather, particularly in areas where the daytime temperature reaches as high as 50 °C. Gas turbine inlet fogging and overspray has been considered a efficient and cost-effective method to augment the power output. Therefore, the evaporation effect and the flow resistance performance in the inlet duct after the inlet fogging applied are the objectives of this paper.
The nozzles array mounted on channels and beams, and they have effects on the pressure drop. Installation site of the fogging nozzles which is relative to the silencers also have impact on the effectiveness of evaporation and cooling. For research the evaporative cooling effect in the duct, the whole inlet duct is meshed in this research to compute the pressure drop through the nozzles frames under fogging and none-fogging conditions with CFD method.
The results indicate that injection velocity and arrangement of nozzles have significant effects on the pressure drops and cooling effect, which will affect compressor performance. Gas turbine is sensitive not only to the inlet temperature, but also to the inlet pressure drop. This paper provides a comprehensive analysis of the pressure drop and evaporation of inlet fogging and will be of values to gas turbine inlet fogging system designers and users.
Variable Geometry Design of a High Endwall Angle Power Turbine for Marine Gas Turbines
Authors: Gao Jie , Zheng Qun , Yue Guoqiang , Wang Fukai 
Published: August 2015

Variable geometry turbines are widely used to improve the part-load performance of gas turbine engines. However, there is a performance penalty associated with the vane-end clearance required for the movement of variable vanes. Especially for variable geometry turbines with high casing-endwall angles, greater vane-end clearances are necessary due to annulus slope, and then high endwall leakages would occur, which further deteriorates turbine efficiency.
The variable geometry design of the first stage stator vane in a four-stage power turbine featuring very high endwall angles has been carried out by proposed stepped spherical endwall concept. The vane endwalls are spherically shaped so as to maintain constant endwall clearance at all turning angles. And, downstream of the spherical endwall an endwall step is introduced, in order to match the original S-shaped endwall contour and to reduce the leakage loss. Meantime, the rotating shaft is inclined upstream to further match the original endwall contour, and cavity tip design has been used to further reduce the leakage loss. An efficient numerical method has been employed to validate the variable geometry design as mentioned, and the effect of a rotating shaft has been included in the calculations. Then, the four-stage variable geometry power turbine characteristics are evaluated.
Results show that the proposed stepped spherical endwall concept can be applied to the variable geometry design of the power turbine featuring very high endwall angles, and compared to the fixed geometry turbine, the efficiency of the new-designed variable geometry power turbine keeps nearly unchanged. Detailed results from this investigation are well presented and discussed in this paper.
Comparison of Steady and Unsteady Coupled Heat-Transfer Simulations of a High-Pressure Turbine Blade
Authors: Schmidt Markus , Starke Christoph 
Published: August 2015

This article presents results for the coupled simulation of a high-pressure turbine stage in consideration of unsteady hot gas flows.
A semi-unsteady coupling process was developed to solve the conjugate heat transfer problem for turbine components of gas turbines. Time-resolved CFD simulations are coupled to a finite element solver for the steady state heat conduction inside of the blade material. A simplified turbine stage geometry is investigated in this paper to describe the influence of the unsteady flow field onto the time-averaged heat transfer. Comparisons of the time-resolved results to steady state results indicate the importance of a coupled simulation and the consideration of the time-dependent flow-field.
Different film-cooling configurations for the turbine NGV are considered, resulting in different temperature and pressure deficits in the vane wake. Their contribution to non-linear effects causing the time-averaged heat load to differ from a steady result is discussed to further highlight the necessity of unsteady design methods for future turbine developments.
A strong increase in the pressure side heat transfer coefficients for unsteady simulations is observed in all results. For higher film-cooling mass flows in the upstream row, the preferential migration of hot fluid towards the pressure side of a turbine blade is amplified as well, which leads to a strong increase in material temperature at the pressure side and also in the blade tip region.
Wake Analysis of a Finite Width Gurney Flap
Authors: Holst D. , Bach A. B. , Nayeri C. N. , Paschereit C. O. , Pechlivanoglou G. 
Published: August 2015

The results of stereo Particle-Image-Velocimetry measurements are presented in this paper to gain further insight into the wake of a finite width Gurney flap. It is attached to an FX 63-137 airfoil which is known for a very good performance at low Reynolds numbers and is therefore used for small wind turbines and is most appropriate for tests in the low speed wind tunnel presented in this study. The Gurney flaps are a promising concept for load control on wind turbines but can have adverse side effects, e.g. shedding of additional vortices. The investigation focuses on frequencies and velocity distributions in the wake as well as on the structure of the induced tip vortices. Phase averaged velocity fields are derived of a Proper-Orthogonal-Decomposition based on the stereo PIV measurements. Additional hot-wire measurements were conducted to analyze the fluctuations downstream of the finite width Gurney flaps. Experiments indicate a general tip vortex structure that is independent from flap length but altered by the periodic shedding downstream of the flap.
The influence of Gurney flaps on a small wind turbine is investigated by simulating a small 40 kW turbine in Q-Blade. They can serve as power control without the need of an active pitch system and the starting performance is additionally improved. The application of Gurney flaps imply tonal frequencies in the wake of the blade. Simulation results are used to estimate the resulting frequencies. However, the solution of Gurney flaps is a good candidate for large scale wind turbine implementation as well. A FAST simulation of the NREL 5MW turbine is used to generate realistic time series of the lift. The estimations of control capabilities predict a reduction in the standard deviation of the lift of up to 65%. Therefore finite width Gurney flaps are promising to extend the lifetime of future wind turbines.
The Aerodynamic Response of Fuel Injector Passages to Incident Acoustic Waves
Authors: Su Jialin , Garmory Andrew , Carrotte Jon 
Published: August 2015

Modern low emission combustion systems are more prone to combustion instabilities due to operation at lean conditions. The response of the airflow passing through the injector to incident acoustic waves is therefore of interest. Airflow fluctuations can initiate, for example, perturbations in stoichiometry and velocity that are subsequently delivered into the heat release region. In the case of liquid fuelled gas turbines the atomisation process will also be affected. Such effects can lead to further unsteady heat release and the generation of acoustic waves, thereby leading to combustion instability. This paper describes experimental measurements and the development of a numerical methodology by which the unsteady airflow response of complex, modern, low emission fuel injectors can be characterised.
Single and two passage injector configurations have been investigated which broadly capture many of the features associated with modern fuel injectors. Although targeted at low emission (lean burn) liquid fuelled injector geometries, the methodology developed is thought applicable to a wide range of injector configurations. Initially experimental measurements were used to characterise the overall acoustic impedance of each injector design over a range of frequencies. Such information is also required for the low order thermo-acoustic network models, as typically used in the design process, to predict the stability of the combustion system. In addition to the experimental measurements a methodology was developed using unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations in which acoustic boundary conditions were implemented to reproduce the experimental scenarios. Interrogation of the pressure field enabled similar data analysis techniques to be applied to the numerical data for determining the injector acoustic characteristics. Fidelity of the numerical simulations is confirmed by the excellent agreement between the experimental data and numerical simulations. Furthermore, the unsteady flow field within the passages is difficult to access experimentally, but can be examined in more detail from the simulation results. In this way an improved understanding of the passage flows and their individual responses to the incident acoustic pressure waves can be obtained. The numerical approach is aimed at providing a computationally efficient and economic tool for predicting the acoustic characteristics of the complex geometries typical of modern fuel injector designs. Using this tool injector designs with different acoustic response characteristics can be developed relatively quickly.
Enlarging Fuel Flexibility for Frame 5 DLN: Combustor Operability and Emissions With High C2+ Content
Authors: Zucca Alessandro , Forte Annalisa , Giannini Nicola , Romano Christian , Modi Roberto 
Published: August 2015

Fuel flexibility is a key feature for Dry Low NOx (DLN) combustors, which shall be capable of accepting a wider range of fuel compositions to meet more and more challenging requests from the Oil and Gas market segment (upstream and downstream applications). Non-methane hydrocarbons (C2+) are one of the main targets of GE Oil & Gas efforts to enlarge the fuel flexibility of DLN combustors, as they are often present in high concentration in fuel gas streams that customers would like their gas turbine to be fed with. The main concerns with such fuel gases in DLN combustor are: the risks of flashback, hardware overheating, increased combustion dynamics and NOx emission, ignition in unexpected locations (with potential damage of the combustor, operability issues and impact on durability).
In order to assess the capability of the current Frame 5 DLN1 hardware design with high C2+ fuels, a single can full pressure test campaign was conducted on a full size DLN1 combustor at Sesta Combustion Lab (Italy).
The combustion chamber was successfully tested in premix mode up to 50%v. of ethane content, observing safe and reliable operation with regard to the above mentioned risks. Special tests were carried out in both Premix and Lean-Lean operating modes, in order to verify the ability of the combustor to maintain a stable and harmless flame and assess the operability margins in the different operating conditions of the combustor. Tests demonstrated a good margin already with the current design. After optimizing the air flow path, the expected performances also in terms of NOx and CO emissions and combustion dynamics were achieved in the investigated ethane content range. These tests outcomes allowed a paramount enlargement of the Frame 5 DLN1 capability in terms of acceptable C2+ concentration in fuel gas.
Unsteady CFD Analysis of Erosion Mechanism in the Coolant Channels of a Rotating Gas Turbine Blade
Authors: Borello Domenico , Anielli Davide , Rispoli Franco , Salvagni Alessandro , Venturini Paolo 
Published: August 2015

The two-phase flow in a rotating wedge mimicking the final portion of a blade turbine internal cooling channel is here presented and discussed focusing on unsteady motion and erosion mechanisms. The rotation axis is placed to properly reproduce a configuration with a very strong deviation (90°).
The flow field was modelled by using the well known k-ε-ζ-f unsteady-RANS model based on the elliptic-relaxation concept. The model was modified by some of the authors to take into account the influence of turbulence anisotropy as well as rotation. The model was applied to the well-established and fully validated T-FlowS code.
A systematic comparison of rotating and non-rotating case was carried out to show the influence of Coriolis force on flow and erosion mechanisms.
The rotational effects strongly changed the flow behaviour within the channel, affecting both the unsteady flow and the particles trajectories. In the rotating case, there is no recirculation on the tip region; besides, position of the small recirculation regions above each pedestals change. These, and other minor effects, affect the particle motion thus resulting in a different erosion pattern.
Aeroelastic Investigation of an Annular Transonic Compressor Cascade: Experimental Results
Authors: Chenaux Virginie Anne , Zanker Achim , Ott Peter 
Published: August 2015

A reliable determination of the unsteady aerodynamic loads acting on the blades is essential to predict the aeroelastic stability of vibrating compressor cascades with accuracy. At transonic flow conditions, the vibration of the shock may change the blade aeroelastic behavior. Numerical tools still have difficulties to capture the physics associated to this effect. In order to increase the prediction’s accuracy, high quality experimental data at high spatial resolution is therefore required to enable the calibration and validation of these tools.
Within the frame of the European project FUTURE, experimental aeroelastic investigations were performed on a transonic compressor cascade in the Non-Rotating Annular Test Facility at EPFL. Associated to the measurements, the numerical flutter prediction procedure was applied.
This paper focuses on the experimental results. The experimental database gained during the project is presented and aims at helping the aeroelastic community to develop and improve their flutter prediction capabilities.
The test model consists of twenty prismatic blades. Each blade of the cascade assembly was mounted on an elastic spring element enabling harmonic bending vibrations in the twenty possible cascade’s travelling wave modes. Large efforts were made to improve the measuring techniques and to provide high quality data at relatively high spatial resolution. For various sub- and transonic flow conditions, steady-state and unsteady blade surface pressure distributions were measured to evaluate the local contributions to the blade stability in terms of local aerodynamic work. The blade global aerodynamic stability is determined applying an integration of all unsteady pressure signals measured over the airfoil.
Competing 3D Mechanisms in Compressor Flows
Authors: Taylor James V. , Miller Robert J. 
Published: August 2015

Even though three-dimensional design is central to all modern compressor design systems, many of these methods still rely, at the their core on a two-dimensional, sectional, view of blade aerodynamics. This paper argues that this view fundamentally limits design by not correctly considering the way in which pressure gradient transverse to the flow direction affects both separation and loss.
The first part of the paper details how 3D blade stacking and the transverse pressure gradient fundamentally alters the behaviour of the corner separations and trailing edge separations. By controlling this design parameter it is possible to switch between the two. The transverse pressure gradient is also shown to be responsible for a substantial increase in profile loss.
In the second part this understanding is used to explore the uncertainty of the design space by simultaneously varying pitch-chord ratio and 3D stacking. It is shown that the design space is split in half by two different levels of risk.