bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations of the Stabilities of Piloted Flames Using Blast Furnace Gas
Authors: Li Chunyan , Tang Haojie , Jing Liyue , Zhu Min
Published: August 2015

The effective utilization of low-grade energy sources generated from steel-making processes provides not only excellent opportunities for low cost power generation but also a significant means for the reduction of greenhouse gas emissions. In this paper, the work was carried out to study the static and dynamic combustion instabilities for gas turbine combustors burning low-calorific-value blast furnace gas (BFG). A burner was designed to stabilize the BFG flame with central pilot flames. A diagnostic system was set up to detect the characteristics of flame dynamics. In the experiments, the fuel ratio between the pilot and main burner and, the equivalence ratio of the main flame and the annular flow velocity were varied for the investigation of the combustion lean blowout (LBO) limits. The flame dynamics near LBO were investigated. The dynamic responses of the flame to flow perturbations were also measured. A network model was employed to study and validate the blowout mechanisms. The LBO limits were calculated and compared with experimental results for various equivalence ratios.
Influence of Rotation on Heat Transfer in a Two-Pass Channel With Impingement Under High Reynolds Number
Authors: Yang Li , Tyagi Kartikeya , Ekkad Srinath , Ren Jing
Published: August 2015

Effect of rotation on turbine blade internal cooling is an important factor in gas turbine cooling systems. In order to minimize the impact from the Coriolis force, cooling structures with less rotation-dependent cooling effectiveness are needed. This study presents an impingement design in a two pass channel to reduce impact of rotational forces on non-uniform heat transfer behavior inside these complex channels. A Transient Liquid Crystal(TLC) method was employed to obtain local heat transfer coefficient measurements in a rotating environment. The channel Reynolds number based on the channel diameter ranges from 25,000 to 100,000. The rotation number ranges from 0 to 0.14. A series of computational simulations with the SST model were also utilized to understand the flow field behavior that impacts the heat transfer distributions on the walls. A 1-D correlation of zone averaged Nusselt number distribution was derived from the measurements.

Results show that rotation reduces the heat transfer on both sides of the impingement, which is due to the Coriolis force and the pressure redistribution. The local change in the present study is about 25%. Rotation significantly enhances the heat transfer near the closed end because of the centrifugal force and the ‘pumping’ effect. Within the parameters of this test, the magnitude of enhancement is 25% to 75%. Compared to U-bended two pass channel, impingement channel has advantages in the upstream channel and the end region, but performance is not beneficial on the leading side of the downstream channel.
Experimental Investigation of Heat Transfer Dependency on Conjugate and Convective Thermal Boundary Conditions in Pin Fin Channel
Authors: Li Weihong , Chi Zhongran , Kan Rui , Ren Jing , Jiang Hongde
Published: August 2015

The present work experimentally quantifies the effects of thermal boundary conditions, i.e., conjugate and convective boundary conditions, on heat transfer performance for the pin fin channel in trailing edge of gas turbine blade. The geometry of pin fin arrays is typical of x/D=y/D=2.5 and H/D=1.

For conjugate case, model is constructed with a relatively high conductivity material so that the Biot number of the model matches engine condition. Uniform heat flux is imposed along the external wall of pin fin arrays and highly resolved temperature distributions of internal wall is obtained with steady liquid crystal, meanwhile external temperature is measured through thermocouples. For convective case, model is constructed with low thermal conductivity material to ensure the usage of transient liquid crystal to obtain heat transfer coefficients of the internal wall on the same configuration.

Both the measurements are used as boundary conditions to conduct simulation of solid part of pin fin array. Internal and external wall non-dimensional temperature distributions, as well as isothermal lines distribution, of the two cases are compared, results indicate that it will produce large errors in temperature predictions without considering conjugate effect. Further analysis are made about the mechanism of thermal boundary conditions in determining wall temperature, which demonstrates the necessity of taking conjugate heat transfer effect in turbine cooling design.
An Experimental Investigation on Transpiration Cooling Based on the Double-Laminated Sintered Woven Wire Mesh Structures
Authors: Jiandong Ma , Luo Xiang , Pin Lv , Yangpeng Liu , Haiwang Li
Published: August 2015

This paper experimentally investigated a cooling performance of double-laminated sintered woven wire mesh structures with different porosities. Each double-laminated test piece was made up of two parts which had different porosities and same thickness, and the total thickness is 6mm. The porosities of test pieces include 25.6%, 37.1%, 46.9% and 55.1%. All the tests were performed with air. In the experiments, the flow rate of main flow kept at 300Kg/h, and the blowing ratio between the cooling air and main flow approximately varied from 1.2% to 9%. The average surface temperature of test pieces was captured by an infrared thermal imager. Temperature of the main flow was fixed at 100°C. The cooling effectiveness for each specimen was calculated and analyzed. Experimental results showed that the cooling efficiency increases as the increase of the average porosity. The results also indicated that the cooling efficiency of the double-laminated model is affected by two layers together; the porosity and arrangement of two parts influents the cooling efficiency coupled. At last, the cooling performance of specimen with single porosity is higher than the specimen with combined porosity when the test pieces had a same geometric size.
Real-Time, Advanced Electrical Filtering for Pressure Transducer Frequency Response Correction
Authors: Hurst Adam M. , Carter Steve , Firth Doug , Szary Alan , VanDeWeert Joe
Published: August 2015

The frequency response of a pressure transducer is influenced by the natural resonance of the sensor structure, the spatial resolution of the sensor due to its diaphragm size, the sensor packaging, signal conditioning and mounting at the measurement location. The resonance of the sensor and aerodynamically-driven resonances related to the sensor packaging and/or mounting, specifically, can distort dynamic pressure measurements within the range of greatest interest (10Hz–20kHz), typically resulting in erroneous amplification. Historically, correcting for such errors within the frequency response of a pressure transducer or measurement system has been challenging, because such errors are hard to quantify with unknown resonant frequencies and damping factors (quality factors). However, with the ability to fully characterize resonant frequencies that lie within 10Hz–50kHz using a previously demonstrated dynamic pressure characterization methodology, it is possible to apply electrical filtering to substantially extend the flat (0±2dB) frequency response of a transducer before any digital signal conversion. In this work, we present a real-time frequency response compensation scheme that uses electrical filtering to correct for aerodynamically driven packaging or mounting related resonances while at the same time preventing signal distortion caused by the sensor resonances. The compensation extends the useable, flat amplitude bandwidth of the transducer while also correcting the phase response to maintain constant time delay over the extended bandwidth. This real-time frequency response correction scheme can be similarly used to compensate for chip resonances, which can limit the frequency response in applications such as shock and blast testing. A theoretical model of the frequency response correction methodology is presented. We additionally present temperature dependent experimental results that compare the frequency response with and without the correction scheme. These results demonstrate that the usable bandwidth of pressure transducers can be increased when real time, analog frequency response correction is applied. This work shows that if the frequency response of a transducer is well characterized, advanced signal conditioning can be implemented to substantially extend the flat bandwidth of the transducer without changes to the sensor, packaging or mounting.
Experimental Study of Leakage Flow on Flow Field and Film Cooling of High Pressure Turbine Blade Platform
Authors: Takeishi Kenichiro , Oda Yutaka , Kozono Shintaro
Published: August 2015

An experiment has been conducted to study stator/rotor disc cavity leakage flow on the platform of a highly loaded stationary linear blade cascade. The linear cascade consists of a scaled-up model of the high-pressure turbine blades of an E3 (Energy efficient engine) and leakage slot models installed under the platform. Experiments have been conducted to investigate the effect of the slot injection angle, leakage flow rates, distance between the leading edge of the blade and the slot, and spacing of the blades. The film-cooling effectiveness was measured by pressure sensitive paint (PSP), and the temperature fields and flow fields were investigated using laser-induced fluorescence (LIF) and particle image velocimetry (PIV), respectively. It was observed from the experiments that the leakage flow covered the surface of the blade platform when the distance between the leading edge and the slot was zero; however, with increasing distance, the horseshoe vortex dominates near the junction of the blade leading edge, and the leakage flow could not cover the region. It was also found that the leakage flow has an effect that promotes the formation of the horseshoe vortex for some experimental conditions.
Effects of Hydrogen Addition on the Flame Speeds of Natural Gas Blends Under Uniform Turbulent Conditions
Authors: Ravi S. , Morones A. , Petersen E. L. , Güthe F.
Published: August 2015

Natural gas is the primary fuel for stationary, powergeneration gas turbines, and it is necessary to understand its combustion characteristics under engine-relevant (turbulent) conditions. Since its composition varies depending on the fuel source, a natural gas surrogate (NG 18% C2+) and admixtures with H2 have been utilized recently by the authors to aid chemical kinetics modeling using ignition delay times and laminar flame speed experiments. The present study focused on measuring turbulent flame speeds (displacement speeds) of natural gas (NG2) and methane with H2 using a fan-stirred flame bomb. The apparatus is a closed, cylindrical chamber fitted with four radial impellers that generate a central spherical volume of homogeneous and isotropic turbulence with negligible mean flow. Schlieren imaging was used to visually track the growth of the spherically expanding turbulent kernels during the constant-pressure period. The turbulence levels were fixed at an average RMS intensity level of 1.5 m/s and at an integral length scale of 27 mm. Turbulent flame speeds (ST,0.1) of NG2 blends were measured over a wide range of equivalence ratios between 0.7 and 1.3. ST,0.1 for the natural gas surrogate closely matched with those of methane for near-stoichiometric mixtures. However, preferential-diffusion effects (fuel effects) were observed under turbulent conditions for off-stoichiometric cases. The effects of hydrogen addition on the turbulent flame speeds of NG2 (25/75 and 50/50 (by volume) blends of H2/NG2) were also investigated and were compared with the flame speeds reported in a recent paper by the authors (ASME GT2014-26742) on the effects of hydrogen addition to turbulent flame speeds of methane. The effect of the hydrogen addition was to increase the turbulent flame speed (by about a factor of two for 50% H2 addition), although this effect was much more pronounced for the lean and stoichiometric mixtures. Interestingly, the flame speeds (both laminar and turbulent) of the CH4 blends with H2 were slightly larger than those for the NG2 blend at equivalent conditions, or about 10–20% larger at 50% H2 addition. This behavior can be explained kinetically by the increased importance of the inhibiting reaction CH3 + H (+M) ↔ CH4 (+M), where ethane oxidation produces more CH3 radicals than methane at similar conditions.
Numerical Investigations of Flow Features in a Low Pressure Steam Turbine Last Stage Under Different Mass Flow Rates
Authors: Liu Bo , Yang Jiandao , Zhou Daiwei , Zhu Xiaocheng , Du Zhaohui
Published: August 2015

In steam turbine plants, the last stages of the low pressure (LP) turbines can deliver up to 20% of the overall power of the plant. It poses lots of challenges to designers especially when the last stages are operated under low volume flow conditions. In the current paper, numerical simulations are conducted to investigate the flow features in a LP steam turbine.

In steady calculations, flows under six different mass flow rates are simulated. Performances and flow patterns in last stage rotor (LSR) in low mass flow rates are highlighted. Since the last stage is modeled as a full blade annulus, flow patterns and blade force in circumferential distribution are examined. Results show that under low mass flow rate conditions, vortices occur in the last stage and the diffuser. The LSR acts like a compressor. The periodical distributions of pressure in LSR passages are broken. High amplitude aerodynamic force fluctuations are found on LSR blades in low mass flow cases.

By conducting unsteady simulations, the time series of aerodynamic force are demonstrated to have the similar trend and magnitude of that in steady spatial sequence. The mechanism for aerodynamic force excitation is discussed in the current paper. Unsteady pressure fluctuation in tip section of LSR at low mass flow rates seems to have a significant correlation with the aerodynamic force fluctuation level rise.
Theoretical and Numerical Investigations of Acoustic Response of a Multiperforated Plate for Combustor Liners
Authors: Popie V. , Piot E. , Tordeux S. , Vuillot F.
Published: August 2015

Multiperforated plates are used in combustion chambers for film cooling purpose. As the knowledge of the acoustic response of the chamber is essential for preventing combustion instabilities, the acoustic behaviour of the perforated plates has to be modeled. This can be done either by considering the transmission impedance of the plates, or their Rayleigh conductivity.

In this paper, the link between these two values is given in the frame of matched asymptotic expansions. Especially the far-field or near-field nature of the physical quantities used in the definition of the impedance and Rayleigh quantity is enlighted. Direct numerical simulations of the propagation of an acoustic plane wave through a perforated plate are performed and post-treated so that the assumptions underlying the definitions of impedance and Rayleigh conductivity are checked.
Field Conversion of a Low-Firing Frame 7B Gas Turbine Power Plant to Ultra-Low Emission Combustion
Authors: Demougeot Nicolas , Benoit Jeffrey A.
Published: August 2015

The search for power plant sustainability options continues as regulating agencies exert more stringent industrial gas turbine emission requirements on operators. Purchasing power for resale, de-commissioning current capabilities altogether and repowering by replacing or converting existing equipment to comply with emissions standards are economic-driven options contemplated by many mature gas turbine operators.

NRG’s Gilbert power plant based in Milford, NJ began commercial operation in 1974 and is fitted with four (4) natural gas fired GE’s 7B gas turbine generators with two each exhausting to HRSG’s feeding one (1) steam turbine generator. The gas turbine units, originally configured with diffusion flame combustion systems with water injection, were each emitting 35 ppm NOx with the New Jersey High Energy Demand Day (HEED) regulatory mandate to reduce NOx emissions to sub 10 ppm by May 1st, 2015. Studies were conducted by the operator to evaluate the economic viability & installation of environmental controls to reduce NOx emissions. It was determined that installation of post-combustion environmental controls at the facility was both cost prohibitive and technically challenging, and would require a fundamental reconfiguration of the facility. Based on this economic analysis, the ultra-low emission combustion system conversion package was selected as the best cost-benefit solution.

This technical paper will focus on the ultra low emissions technology and key features employed to achieve these low emissions, a description of the design challenges and solution to those, a summary of the customer considerations in down selecting options and an overview of the conversion scope. Finally, a technical discussion of the low emissions operational flexibility will be provided including performance results of the converted units.
The Effect of Compressor Shaft Geometry on Shaft Thermal Bow due to Natural Convection
Authors: Smith E. O. , Neely A. J.
Published: August 2015

This study builds upon previous work by the authors, using a combination of 3D conjugate heat transfer (CHT) computational fluid dynamics (CFD) and finite element analysis (FEA) to characterise the thermal bow behaviour of a simple compressor shaft and case model under natural cooling. As with previous studies by the authors, body temperatures obtained from 3D CHT CFD solutions at set time intervals are transferred to FEA, where the physical distortion associated with the asymmetric thermal load is measured. The current study examines the influence of a range of shaft design parameters on the severity and duration of the shaft deformation. The parameters of interest include shaft length, annulus geometry, degree of shaft ventilation, and shaft internal cavity geometry. Each time the baseline model is modified to analyse the contribution of a parameter, the model is allowed to cool down from representative operational temperatures for a period of 180 minutes, over which time the shaft thermal bow, and shaft-to-case clearance, are measured. The results of this study indicate that the shaft’s thermal bow response and shaft-to-case clearance over time are highly sensitive to changes to its geometry, whereas the change in 180-degree out-of-phase shaft-to-case clearance is more sensitive to the case geometry, rather than the shaft. These results indicate that increasing the length of the shaft, reducing its wall thickness, or introducing a rising-line annulus, will increase the severity of the shaft thermal bow phenomenon; whereas introducing disc geometry inside the shaft will reduce the severity of the bow.
Estimation of Damping for Turbine Blades in Non-Stationary Working Conditions
Authors: Carassale Luigi , Marrè-Brunenghi Michela , Patrone Stefano
Published: August 2015

Turbine blades are critical components in thermal power plants and their design process usually includes experimental tests in order to tune or confirm numerical analyses. These tests are generally carried out on full-scale rotors having some blades instrumented with strain gauges and usually involve a run-up and/or a run-down phase. The quantification of damping in these conditions is rather complicated, since the finite sweep velocity produces a distortion of the vibration amplitude in contrast to the Frequency-Response Function that would be expected for an infinitely slow crossing of the resonance. In this work, we show through a numerical simulation that the usual identification procedures lead to a systematic overestimation of damping due both to the finite sweep velocity, as well as to the variation of the blade natural frequency with the rotation speed. An identification procedure based on the time-frequency analysis is proposed and validated through numerical simulations.
Sensitivity Analysis for Simulation-Based Optimization via Metamodeling Techniques
Authors: Liu Haitao , Ma Ying , Xu Shengli , Wang Xiaofang , Song Yang
Published: August 2015

The sensitivity information of objective and constraint functions is required in gradient-based optimization algorithms. Usually the more accurate the gradients are estimated, the faster the convergence speed will be. Commonly used gradient estimation methods, e.g., the finite differences, either have low estimate accuracy or require much computing budget. This paper presents a metamodel-based gradient estimation (MGE) method. In our numerical investigations, the proposed MGE method achieves more accurate estimates of the sensitivity information than the forward difference method (FDM) with only one more point. This article explores the sensitivity of the proposed method to the sampling strategy, the metamodel type, the finite difference step on the metamodel and the dimensionality of the design space, and offers some recommendations. Finally, we combine the new MGE method with the method of moving asymptotes (MMA) and apply them to the shape design of a turbine disc and an axial compressor blade. The results from the two engineering examples confirm the utility of proposed method.
Short Helical Combustor: Concept Study of an Innovative Gas Turbine Combustor
Authors: Ariatabar B. , Koch R. , Bauer H.-J.
Published: August 2015

An innovative design of a gas turbine annular combustor is investigated analytically and numerically. Its principal feature is the helical arrangement of the burners around the turbine shaft. Hence, a shorter combustor with lower aerodynamical losses and cooling air demand might be realized. A generic model of the combustor is developed and analyzed by means of a parametric study. Scaling laws for the geometry of the flame tube and the burners are derived. Thereby, the relevant similarity parameters for fluid flow, combustion and heat transfer are maintained constant. Subsequently, non-reacting and reacting flow regimes of selected design variants are numerically investigated. It is shown that a double annular configuration with a tilting angle of β = 45°, where circumferentially adjacent swirls are co-rotating and radially are counter-rotating, is the superior design in terms of

1. Maintaining the relevant similarity rules

2. Size and location of the recirculation zones and swirl flames

3. Flow pattern at the combustor exit

The deflection angle of the NGV as well as the axial length of such a Short Helical Combustor could be reduced by approx. 30%.
Optimization of a Large Injection System for Steam Turbines
Authors: Nettis Leonardo , Imparato Enzo , Cosi Lorenzo
Published: August 2015

Steam turbines are applied in production plants characterized by very large injections of low pressure steam. For this reason the design and optimization of the injection section is fundamental to obtain an adequate level of turbine efficiency and ensure uniform flow at the inlet of the low pressure stages downstream the injection.

This paper illustrate the optimization performed on a Steam Turbine injection system for a unit in which injection flow is 80% of the total outlet mass flow. Optimization was performed varying the shape of the original steam guide with the twofold objective of minimizing the total pressure loss and uniform the circumferential flow distribution.

The analysis has been performed using RANS 2D and 3D CFD solver. The design process has been structured in 3 different steps: i) Axisymmetric CFD screening based on DOE ii) 3D-CFD verification of the profile shape previously obtained with the additional estimation of the flow uniformity on 360° iii) 3D-CFD of the injection module including the reaction stage upstream and the first LP stage downstream, with the stator modeled on 360°.

The main outcomes are presented in terms of total pressure loss and uniformity of circumferential flow, both strongly reduced with respect to the original design. Moreover in order to characterize the excitation associated with flow non-uniformity an analysis in the frequency domain of the flow distribution has been performed.
The Effect of Rotor Casing on Low Pressure Steam Turbine and Diffuser Interactions
Authors: Singh Gursharanjit , Singh Gurnam , Wheeler Andrew P. S.
Published: August 2015

The present study aims to investigate the interaction between a last-stage steam turbine blade row and diffuser. This work is carried out using CFD simulations of a generic last stage low pressure (LP) turbine and axial-radial exhaust diffuser attached to it. In order to determine the validity of the computational method, the CFD predictions are first compared with data obtained from an experimental test facility. A computational study is then performed for different design configurations of the diffuser and rotor casing shapes. The study focuses on typical flow features such as effects of rotor tip leakage flows and subsequent changes in the rotor-diffuser interactions. The results suggest that the rotor casing shape influences the rotor work extraction capability and yields significant improvements in the static pressure recovery.
Investigation on Pressure Fluctuation Related to Mild Surge in Multi-Stage Centrifugal Blower With Inlet Guide Vane
Authors: Hiradate Kiyotaka , Sakamoto Kiyohide , Shinkawa Yasushi , Joukou Satoshi , Uchiyama Takeshi
Published: August 2015

Centrifugal blowers are widely used for gas compression in various industrial fields. Wider operating range is required in these machines. Investigations on the generation mechanism of unsteady flow (i.e., surge) are very important to improve the operating range of these machines. Purpose of this study is to clarify the generation mechanism of pressure fluctuations in a multi-stage centrifugal blower equipped with inlet guide vanes (IGVs) upstream of the first stage under the IGVs partially open condition.

These pressure fluctuations occur at flowrates when the slope of total system head curve is steeply negative. According to our previous study on the detailed unsteady pressure measurements, this pressure oscillation is supposed to be the mild surge caused by the positive slope of the head curves at the second to the last stages. The slope of the total system head curve was kept negative due to the steeply negative slope of the head curve at the first stage. Thus, the whole compression system seemed to be stable.

To confirm the validity of this hypothesis, system dynamic simulations based on Greitzer’s lumped-parameter model were conducted using newly measured static-pressure-rise characteristic curves of each stage in a four-stage centrifugal blower. In these simulations, the pressure-rise characteristic curves of the first stage and the second to last stages were modeled as two different actuator disks, and the stabilization/destabilization effects of each stage on the system dynamic characteristics were separately taken into account under the IGVs partially open condition.

The system dynamic simulation reproduced the mild surge behavior of the system under the IGVs partially open condition when the slope of the total system head curve was still kept steeply negative. The calculated amplitude and frequency of the pressure fluctuations caused by the mild surge showed satisfactory agreement with the measured ones. However, the inception flowrate of the system instability in the simulation was approximately 7% smaller than that in the measurement.

From these results, we confirmed that the pressure fluctuation occurred under the IGVs partially open condition was caused by the mild surge due to the positive slope of the pressure-rise characteristic at the second to the last stages. In addition, we found that this mild surge was caused by the stall of the vaned diffusers at the second to the last stage.
Application of Pinniped Vibrissae to Aeropropulsion
Authors: Shyam Vikram , Ameri Ali , Poinsatte Philip , Thurman Douglas , Wroblewski Adam , Snyder Christopher
Published: August 2015

Vibrissae (whiskers) of Phoca Vitulina (Harbor Seal) and Mirounga Angustirostris (Elephant Seal) possess undulations along their length. Harbor Seal Vibrissae have been shown to reduce vortex induced vibrations and reduce drag compared to appropriately scaled cylinders and ellipses. Samples of Harbor Seal vibrissae, Elephant Seal vibrissae and California Sea Lion vibrissae were collected from the Marine Mammal Center in California. CT scanning, microscopy and 3D scanning techniques were utilized to characterize the whiskers. Leading edge parameters from the whiskers were used to create a 3D profile based on a modern power turbine blade. The NASA SW-2 cascade wind tunnel facility was used to perform hotwire surveys and pitot surveys in the wake of the ‘Seal Blades’ to provide validation of Computational Fluid Dynamics simulations. Computational Fluid Dynamics simulations were used to study the effect of incidence angles from −37 to +10 degrees on the aerodynamic performance of the Seal blade. The tests and simulations were conducted at a Reynolds number of 100,000 based on inlet conditions and blade axial chord. The Seal blades showed consistent performance improvements over the baseline configuration. It was determined that a fuel burn reduction of approximately 5% could be achieved for a fixed wing aircraft.
Design of an Air-Starter Turbine and Starting Performance Prediction Through the Numerical Analysis
Authors: Park JaeHyeon , Park Sooyoung , Baek JeHyun
Published: August 2015

To get the required power, a procedure for starting an engine is required. For an engine of the large ship or land-based power plant, two kinds of mechanisms exist: one is to use an electric motor and the other air-starter. As one of the starting methods of heavy-duty engines, the air-starter gives rotating power from the blade lifting force by the compressed air flow through the turbine to rotate the stopped engine. Since the air turbine has a large weight-to-power ratio, simple structure and is spark-free, many heavy-duty engine are equipped with this device for their starting process. In order to get high enough power required to rotate the engine up to sufficient speed in a short time, high instantaneous torque is required. An impulsive supersonic turbine can be applied for this purpose. In this case, an one-stage air turbine with a minimum length convergent-divergent nozzle and transition arc shaped rotor was utilized to reduce shock loss. The performance of the desired turbine is evaluated numerically and compared with experimental results. The spin-down test is performed to estimate the performance of the designed turbine and numerical analysis is performed using the commercial tool ANSYS CFX.
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.
Unsteady Structure and Development of a Row of Impingement Jets, Including Shear Layer and Vortex Development: Part 2 — Laminar Jets
Authors: Yang L. , Ren J. , Jiang H. , Ligrani P. M.
Published: August 2015

Considered is a cylinder channel with a single row of 10 aligned impinging jets, with exit flow in the axial direction at one end of the channel. For the present predictions, each jet is laminar with a Reynolds number of 200. An unsteady RANS solver is employed for predictions of flow characteristics within and nearby the 10 impingement jets. Spectrum analysis of different flow quantities shows frequencies associated with laminar jet and vortex oscillations, and evidence more orderly flow for Re=200, without the chaos and broad-band mixing associated with the turbulent flow when Re=15,000. Laminar flow spectra also evidence increased flow unsteadiness as cross-flows accumulate within the impingement channel with streamwise development as Z/D increases. In some cases, this increased unsteadiness manifests itself through the formation of multiple spectral peaks, in place of single peak spectra. As for the turbulent jet arrangements, unsteady, local static pressure gradient variations along interfaces between laminar jets and cross flow are also a key flow feature, which is connected to the initiation and development of the Kelvin-Helmholtz instability induced vortices.
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.
The Performance Analysis of a Combined Power Plant Implementing Technologies for Enhancing Power and Efficiency
Authors: Won Jumok , Son Changmin , Kim Changju
Published: August 2015

Combined Cycle Power (CCP) plant using Liquefied Natural Gas (LNG) plays a key role in electric supply including nuclear and coal power generation systems. There is growing demand for enhancing power and efficiency of existing CCP plants. Typically, the power reduction of gas turbine during summer can be recovered if gas turbine intake cooling system can be implemented in existing LNG based CCP plants. Possible approaches for power and efficiency enhancement are being widely studied in global gas turbine society. The present study aims to investigate net benefit of implementing selected technologies for enhancing power and efficiency of an existing LNG based CCP. For a comparative study, selected technologies such as (1) gas turbine intake cooling system, (2) wet cycle (steam injection), and (3) turbine cooling air precooling are implemented to Busan LNG based CCP plant, Republic of Korea. The complete CCP plant is modeled using Gatecycle and its validation against field operation data showed the differences in the generated power and efficiency at the base load condition within 0.5% and the difference in the turbine inlet temperature value less than 3%. Among the selected technologies, the wet cycle (steam injection) showed the most promising result. Its system composition is relatively simple in comparison to the other technologies. Furthermore, it is advantageous to use within a reasonable limit when higher power is required for peak demand of electric power.
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.
Investigation of Performance and Flow Field of a Centrifugal Compressor Under Negative Pre-Swirl
Authors: Zhao Jiayi , Wang Zhiheng , Xi Guang , Zhang Xiaohong , Lan Aiqing , Gong Wuqi
Published: August 2015

In the paper the effect of negative pre-swirl on the performance and the flow in a centrifugal compressor stage are investigated by both the experimental and numerical methods. The results show that, at a negative pre-swirl, whether the pressure ratio of compressor is increased or not is determined by the contest between the increased energy transfer and flow losses. At a large negative pre-swirl, the flow losses in the IGV and the impeller are increased obviously, which makes the pressure ratio and efficiency reduced dramatically. The further flow analysis show that, the enhanced separation area in the IGV and the depravation of the inlet flow condition of the impeller are the main sources of the losses, while there is almost no influence of the pre-swirl on the diffuser losses. Additionally, at a large negative pre-swirl there exist vortexes shedding from the separation region at impeller leading edge, which causes severe excited force on the impeller leading edge.
Design Method and Performance Effects of Curvature-Smooth Centrifugal Compressor Blades
Authors: Bi Qingzhen , Chen Hua , Tong Ding , Lu Yaoan , Zou Xueqi
Published: August 2015

Blade curvature has an important effect on the pressure distribution over the blade surface as well as the quality of airfoil machining, but curvature smoothing method in design environments is little studied. A new geometry generator is developed for the design of curvature-smooth airfoils. The sections of an airfoil can be initially designed by a conventional method, and each of the sections is then regenerated by fitting a fifth order B-spline curve. The first order differential of the curvature with respect to arc length of the blade surface is used as a curvature smoothness measure. The distance between discrete points and the curve, and the integral of the square of the first derivative along the streamwise section curve are simultaneously minimized in the fitting process. The design of a transonic centrifugal compressor for turbocharger application is presented to study the effects of the curvature-smooth blade on centrifugal compressor performance. A numerical study was carried out and the results are discussed.
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.