bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational Analysis of Unsteady Flow in a Partial Admission Supersonic Turbine Stage
Authors: Tokuyama Yuki , Funazaki Ken-ichi , Kato Hiromasa , Shimiya Noriyuki , Shimagaki Mitsuru , Uchiumi Masaharu 
Published: September 2014

Turbines used in upper stage engine for a rocket are sometimes designed as a supersonic turbine with partial admission. This study deals with numerical investigation of supersonic partial admission turbine in order to understand influences on the unsteady flow pattern, turbine losses and aerodynamic forces on rotor blades due to partial admission configuration. Two-dimensional CFD analysis is conducted using “Numerical Turbine” code. Its governing equation is URANS (Unsteady Reynolds Averaged Navier-Stokes Simulation) and fourth-order MUSCL TVD scheme is used for advection scheme.
The unsteady simulation indicates that strongly non-uniform circumferential flow field is created due to the partial admission configuration and it especially becomes complex at 1st stage because of shock waves. Some very high or low flow velocity regions are created around the blockage sector. Nozzle exit flow is rapidly accelerated at the inlet of blockage sector and strong rotor LE shock waves are created. In contrast, at rotor blade passages and Stator2 blade passages existing behind the blockage sector, working gas almost stagnates. Large flow separations and flow mixings occur because of the partial admission configuration. As a result, additional strong dissipations are caused and the magnitude of entropy at the turbine exit is approximately 1.5 times higher than that of the full admission.
Rotor1 blades experience strong unsteady aerodynamic force variations. The aerodynamic forces greatly vary when the Rotor1 blade passes through the blockage inlet region. The unsteady force in frequency domain indicates that many unsteady force components exist in wide frequency region and the blockage passing frequency component becomes pronounced in the circumferential direction force. Unsteady forces on Rotor2 blades are characterized by a low frequency fluctuation due to the blockage passing.
Effect of the Compressor Discharge Casing Geometry on Combustor Exit Temperature Profiles in a Multi-Can Gas-Turbine Combustor
Authors: Agarwal Krishna Kant , Gori Stefano 
Published: September 2014

Temperature profile variations in gas turbine combustors are important from the considerations of thermal stresses and material fatigue. The specific profile being addressed in this study is the combustor exit gas temperature profile in radial direction at first stage nozzle entry (also called the combustor transition-piece (TP) exit profile). Normally, in multi-can combustor configurations, this profile is assumed to be constant along the circumferential direction or from one can to another. However, field test on one of the GE-MS5002D class machine revealed that the shape of the combustor TP exit temperature profile is varying across the different cans. It is important to assess the reason of this behavior in order to define thermal input for stage 1 nozzle thermal design and define an average temperature profile for turbine bucket verification.
For investigating the reasons of varying TP exit profiles across different cans, a reacting flow CFD study is performed for a combined multiple combustor-cans geometry. This is a challenging attempt considering that mesh for a single can liner is itself typically quite large (∼30 million) for capturing all flow features. The present multi-can study was made feasible with judicious simplification of combustor geometry, retaining only important flow features and using adequate mesh to capture system physics. Results indicate that the varying flame shape across different cans is indeed captured in the CFD. Hence, this effect could be something associated with the combustor design. Subsequent detailed post-processing of CFD results revealed the root cause to be associated with the presence of unsymmetrical arrangement of struts in the compressor discharge casing region. This effect is a slight flow-recirculation created much upstream due to the struts, which eventually results in asymmetric distribution of the flow across the combustor dilution holes. This leads to the flame shifting in different orientation for different cans with a systematic reference to the struts position. In conclusion, this paper describes the approach used for multi-can CFD analysis of the combustor, flow behavior in presence of unsymmetrical strut and its impact on the combustor exit temperature profile much downstream.
A Numerical and Experimental Assessment of the Use of a Turbine Utilizing Splitter Blades for an Automotive Variable Geometry Turbocharger
Authors: Walkingshaw Jason , Spence Stephen , Filsinger Dietmar , Thornhill David 
Published: September 2014

Automotive manufacturers require improved part load engine performance to further improve fuel economy. For a swing vane VGS (Variable Geometry Stator) turbine this means a more closed stator vane, to deal with the low MFRs (Mass Flow Rates), high PRs (Pressure Ratios) and low rotor rotational speeds. During these conditions the turbine is operating at low velocity ratios. As more energy is available at high pressure ratios and during lower turbocharger rotational speeds, a turbine which is efficient at these conditions is desirable. Another key aspect for automotive manufacturers is engine responsiveness. High inertia designs result in “turbo lag” which means an increased time before the target boost pressure is reached. Therefore, designs with improved performance at low velocity ratios, reduced inertia or an increased swallowing capacity are the current targets for turbocharger manufacturers.
To try to meet these design targets a CFD (Computational Fluid Dynamics) study was performed on a turbine wheel using splitter blades. A number of parameters were investigated. These included splitter blade merdional length, blade number and blade angle distribution.
The numerical study was performed on a scaled automotive VGS. Three different stator vane positions have been analysed. A single passage CFD model was developed and used to provide information on the flow features affecting performance in both the stator vanes and turbine.
Following the CFD investigation the design with the best compromise in terms of performance, inertia and increased MFP (Mass Flow Parameter) was selected for manufacture and testing. Tests were performed on a scaled, low temperature turbine test rig. The aerodynamic flow path of the gas stand was the same as that investigated during the CFD. The test results revealed a design which had similar performance at the closed stator vane positions when compared to the baseline wheel. At the maximum MFR stator vane condition a drop of −0.6% pts in efficiency was seen. However, 5.5% increase in MFP was obtained with the additional benefit of a drop in rotor inertia of 3.7%, compared to the baseline wheel.
LES of Wall Bounded Turbulent Flows Using Unstructured Linear Reconstruction Techniques
Authors: Amirante Dario , Hills Nicholas J. 
Published: September 2014

Large-Eddy Simulations of wall bounded, low Mach number turbulent flows are conducted using an unstructured finite-volume solver of the compressible flow equations. The numerical method employs linear reconstructions of the primitive variables based on the least-squares approach of Barth. The standard Smagorinsky model is adopted as the subgrid term. The artificial viscosity inherent to the spatial discretization is maintained as low as possible reducing the dissipative contribution embedded in the approximate Riemann solver to the minimum necessary. Comparisons are also discussed with the results obtained using the implicit LES procedure.
Two canonical test-cases are described: a fully developed pipe flow at a bulk Reynolds number Reb = 44 × 103 based on the pipe diameter, and a confined rotor-stator flow at the rotational Reynolds number ReΩ = 4 × 105 based on the outer radius. In both cases the mean flow and the turbulent statistics agree well with existing DNS or experimental data.
Heat Transfer Enhancement for a Turbine Blade Leading Edge Passage Using Various Turbulator Geometries
Authors: Saxer-Felici H. , Naik S. , Gritsch M. , Sedlov A. 
Published: September 2014

The leading edge regions of first stages blades and vanes of heavy-duty gas turbines are subjected to high thermal loads. Efficient cooling allows the reduction of the coolant mass flow required to drive the metal temperatures to a range satisfying mechanical integrity requirements.
This paper investigates the heat transfer and pressure loss behavior for the internal cooling channel of a leading edge of a gas turbine blade. The geometrical profile of the blade leading edge and the operating conditions considered are representative of that normally found in a heavy-duty gas turbine.
The geometries investigated cover angled turbulators of various angles, pitches and heights. Partial and full length rib coverage as well as broken ribs are also considered. In addition, the impact of including fillets in the geometry is assessed.
The experimental and numerical studies are conducted at passage Reynolds numbers ranging from 7.5·104 to 1.3·105.
Experiments are performed using Perspex models at atmospheric conditions. The internal heat transfer coefficients on all internal surfaces are measured via thermochromic liquid crystal method and the pressure drop is measured via pressure taps distributed along the channel.
The predicted and experimental heat transfer enhancements are compared on the leading-edge, pressure, suction and web surfaces. The overall non dimensional cooling performance numbers are also compared for the various geometries.
The results show a large variation of heat transfer enhancement and pressure loss over the various turbulator geometries investigated. Also, the complex flow structures lead to highly differentiated results for leading edge, pressure, suction and web surfaces. Although some configurations with higher ribs lead to increased heat transfer, the associated pressure losses are also shown to increase substantially.
An Application of Metal Plasticity in Finite Element Modeling to Predict the Low-Cycle Fatigue Life of a High-Pressure Steam Turbine Casing
Authors: Dyer Zachary , Altland George C. 
Published: September 2014

In the current market for large steam turbines, customers increasingly want to aggressively cycle their equipment to accommodate electrical grids that include fluctuating supplies of green energy. Increased and aggressive cycling leads to higher probability of low-cycle-fatigue cracking and provides motivation for the design of new steam turbines that are robust enough to withstand this demanding working environment yet still meet the operational and cost expectations of potential customers.
ASME BPVC Section III Subsection NH provides a calculation for fatigue damage assessment using either an elastic method or an inelastic method. This paper describes how the inelastic method can be applied to large steam turbines — calculating low-cycle fatigue damage by using commercial finite element software and plastic material models to directly determine elastic-plastic strains throughout the cycle, rather than approximating them using the results of an elastic analysis. The inelastic method is applied to a steam turbine casing during startup cycles — the total strain through the cycle is calculated directly by the elastic-plastic finite element analysis (FEA) then the delta equivalent total strain is calculated using equations in Subsection NH. For comparison, an elastic method is applied to the same analysis — the maximum elastic stress is calculated by the linear-elastic FEA then the delta equivalent total strain is approximated using Neuber’s rule.
The inelastic method calculates a smaller delta equivalent total strain, which leads to significantly increased fatigue life. This more sophisticated method could lead to steam turbine components with less cost, more durability, and better performance. This paper also discusses some issues in using the inelastic method, such as shakedown and ratcheting.
A New Risk and Reliability Model for Compressor and Pump Installations
Authors: Garcia-Hernandez Augusto , Delgado-Garibay Hector , Rivera Reyes Rubén , Martínez Jose Luis , Martínez Gomez Lorenzo 
Published: September 2014

Compression and pumping systems are constantly changing infrastructures, with many of the older compressor/pumping stations requiring updates, repairs and inspections to maintain safe and efficient operations. These stations operate over a wide range of pressures, flows, and working fluids under varying environmental conditions. Operating condition factors, as well as original design and materials, can significantly affect corrosion rates, structural integrity, and the flow capability of these compressor/pumping stations. Station equipment can be logically inter-related using failure trees and each critical sub-component be assigned a mean time between failure and failure probability using acceptable industry standards. These individual components are then allowed to interact to determine sub-system, system, and full station level failure probabilities. This type of analysis has historically not been utilized by the oil and gas industry but is common to other industries, such as the aerospace and nuclear power industries.
This paper presents a new, comprehensive, consistent, and effective process for predicting risk, integrity, and reliability of the compressor and pump stations as well as each major subsystem and component within these stations. The model considers predefined “threats” such as mechanical, materials, electrical, third party, environment and external forces, improper maintenance, and operation of all its components; thus, typical failures modes are included in these threats. A semi-quantitative methodology with factored risk indices is applied where weighting factors are used to adjust the model with operational data. These factors are generated from reliability data extracted from the station. Comparisons between the model predictions and the reliability data will allow tuning of the weighting factors. Weighting factors are defined for each of the identified threats. The probability of failure is computed at a component level; however, it can be obtained at any level in the system based upon the specified categorization. The probability of failure is represented as a function of three factors: exposure, resistance, and mitigation, while the consequence of failure is estimated using the same approach based on three factors: receptor, hazard, and reduction.
This predictive risk and failure model has been defined based on international specifications and is consistent with actual operating conditions, capacity planning, and remaining life expectations, while assuring that the stations meet the day-to-day operational demands of the system. The model also is able to predict each individual equipment failure probability within the station systems and provides for easy output of the data in graphical form for proper operating, maintenance, repair, and testing decisions.
An Experimental Study of Mist Film Cooling With Fan-Shaped Holes on an Extended Flat Plate: Part 1 — Heat Transfer
Authors: Ragab Reda , Wang Ting 
Published: September 2014

Motivated by the need to further improve film cooling in terms of both cooling effectiveness and coolant coverage area, the mist/air film cooling scheme is investigated through experiments using fan-shaped holes over an extended downstream length in this study. Both an existing wind tunnel and test facility, used in previous work, have been retrofitted. The first modification was extending the length of the flat plate test section to cover longer distances downstream of the injection holes, up to X/D = 100, in order to investigate whether mist cooling can be harnessed farther downstream where single-phase film cooling is not effective. The second modification was to incorporate a fan-shaped diffusion hole geometry in order to investigate whether mist can further enhance the film cooling performance of the already highly effective fan-shaped holes. A Phase Doppler Particle Analyzer (PDPA) system is employed to measure droplet size, velocity, and turbulence information. An infrared camera and thermocouples are both used for temperature measurements. Part 1 is focused on the heat transfer result on the wall, and Part 2 is focused on the two-phase droplet multiphase flow behavior. Three blowing ratios are investigated.
The results show that, at low blowing ratios when the film is attached to the surface, the enhancement of the mist film cooling effectiveness, compared to the air-only case, on the centerline of the hole ranges from 40% in the near hole region to over 170% at X/D = 100. Due to the diffusive nature of the fan-shaped hole, the laterally-averaged enhancement is on par with that on the centerline. The significant enhancement over the extended downstream distance from X/D = 40–100 is attributed to the evaporation time needed to evaporate all of the droplets. Each droplet acts as a cooling sink and flies over a distance before it completely vaporizes. This “distributed cooling” characteristic allows controlled cooling by manipulating the size distribution of the water droplets to extend the cooling effects of the droplets farther downstream from the injection location. At higher blowing ratios, when the cooling film is lifted off from the surface, the cooling enhancement drops below 40%. Although the enhancement in the near hole region X/D < 40 is about 20% lower than that achieved by using the cylindrical holes, the magnitudes of the mist adiabatic film cooling effectiveness using fan-shaped holes are still much higher than those of the cylindrical holes.
Experimental Studies of Supersonic Steam Flow in the Flat Nozzle Blade Cascade at Different Initial Steam Conditions
Authors: Gribin Vladimir , Tishchenko Aleksandr , Gavrilov Ilya , Tishchenko Victor , Khomyakov Sergey , Popov Vitaliy 
Published: September 2014

The results of experimental studies of supersonic steam flow downstream the flat turbine nozzle blade cascade has been considered. The investigations were carried out in a broad range of steam initial conditions (superheated, dry saturated) and isentropic Mach (M1t) number downstream the object of study. The schlieren method was used to obtain the visual information about shock waves structure. The flow parameters oscillations were measured by pressure transducers situated at different locations downstream the object of study.
It is shown that the occurrence of condensing shock at conditions of superheated steam upstream the nozzle blade cascade leads to the sufficient unsteadiness of shock waves system. This is due to the complex relationship between the boundary layer and a shock wave system. With changing of initial steam conditions the rearrangement of static pressure frequency spectra is observed.
A Comparative Study of Combined Heat and Power Systems for a Typical Food Industry Application
Authors: Saidi Karim , Orth Ulrich , Boje Sven , Frekers Christian 
Published: September 2014

In the food industry, there is typically a requirement for electric power, process steam as well as cooling capability. Based on actual requirements of a specific site, a study was performed to define two different Combined Heat and Power (CHP) options and to compare them over a one year period regarding the extent to which they satisfy the operator’s needs.
CHP is defined as the sequential generation of two different forms of usable energy from a single fuel source. It is mechanical energy and thermal energy. The mechanical energy may be used either to drive a generator to produce electricity, or to drive rotating equipment such as a compressor. Thermal energy can be used either directly for process applications or indirectly to produce steam, hot water (district heating), or chilled water for cooling purposes. Combined Heat and Power technologies are proven, reliable and cost-effective. MAN can offer different CHP concepts adapted to specific customer requirements.
This paper presents the results of a comparative study based on the typical requirements of the food industry. The CHP system has to cover the demand for power, saturated steam at two pressure levels, and cooling. Two different CHP options were studied and compared regarding technical and economic considerations.
The first system proposed is based on a MAN’s gas turbine (model: THM1304-10N) in the 10 MW class, a Waste Heat Recovery Unit for steam production and one Absorption Chiller (ammonia/water) for cooling process. A share of the steam produced is used for driving the chiller.
The second system includes a combined cycle with MAN’s new MGT6100 gas turbine in the 6 MW class. A Waste Heat Recovery Unit and a back pressure steam turbine with two extractions at two intermediate pressure levels are used. A part of the saturated steam at the outlet of the steam turbine drives the absorption chiller and the remainder is used for the third steam process.
For both options, a supplementary firing is also considered. A technical and economical comparison between the two solutions is provided in order to show the advantages and the disadvantages of each system with regard to the requirements of the specified application.