bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Study of Two and Three Blade Mini Propellers Aerodynamic Performance
Authors: Rajeevalochanam Prathapanayaka , Nanjundaiah Vinod Kumar , Sahadevan Santhosh Kumar , Sharma Narendra , Settisara Janney Krishnamurthy
Published: September 2016

Fixed wing Micro Air Vehicles (MAVs) are widely powered by miniature brushless DC motors and mini propellers. These motors have low efficiencies in the MAVs’ operating range; hence consume more power and penalizing the endurance of MAVs flight. Mini propellers also suffer with lower efficiencies due to low Reynolds number effect compared to bigger propellers. Based on the power requirement of MAV’s; generally two bladed different size propellers are used to power these MAVs. Effect of Propeller slipstream wash on the lift generating wings is significant and it is well reported for bigger propellers. The strength of slipstream wash depends on the number of blades, diameter of the propeller, rotational speed, flight speed and trajectory. The effect of slipstream wash could be lowered by increasing the number of blades and with smaller diameter propellers. CSIR-NAL has designed, developed, and fabricated, efficient, 6inch diameter, two and three blade, light-weight, mini propellers using latest state of the art technological advancements for CSIR-NAL fixed wing MAV code named as Black Kite. Apart from this, these propellers are assessed for its realistic propulsive efficiencies using CSIR-NAL configured sophisticated precision test bench manufactured and supplied by M/s MAGTROL, Switzerland. The specialty of this test bench is that it can measure thrust, propellers shaft torque, input power and rotational speeds simultaneously. In the present study CSIR-NAL developed 6 inch diameter two and three bladed propellers of identical plan form are compared for their performance. The three bladed propellers generate 30% higher thrust by marginal weight and efficiency penalty, whereas the noise levels are reduced.
Adiabatic Film Cooling Effectiveness Measurements Throughout Multi-Row Film Cooling Arrays
Authors: Natsui Greg , Little Zachary , Kapat Jay , Socotch Anthony , Wang Anquan , Dees Jason E.
Published: September 2016

Adiabatic film cooling effectiveness measurements are obtained using pressure-sensitive paint (PSP) on a flat film cooled surface. The effects of blowing ratio and hole spacing are investigated for four multi-row arrays comprised of 8 rows containing 52 holes of 3.8 mm diameter with 20° inclination angles and hole length-to-diameter ratio of 11.2.

The four arrays investigated have two different hole-to-hole spacings composed of cylindrical and diffuser holes. For the first case, lateral and streamwise pitches are 7.5 times the diameter. For the second case, pitch-to-diameter ratio is 14 in lateral direction and 10 in the streamwise direction. The holes are in a staggered arrangement. Adiabatic effectiveness measurements are taken for a blowing ratio range of 0.3 to 1.2 and a density ratio of 1.5, with CO2 injected as the coolant.

A thorough boundary layer analysis is presented, and data was taken using hotwire anemometry with air injection, with boundary layer and turbulence measurements taken at multiple locations in order to characterize the boundary layer. Local effectiveness, laterally averaged effectiveness, boundary layer thickness, momentum thickness, turbulence intensity and turbulence length scale are presented. For the cylindrical holes, at the first row of injection, the film jets are still attached at a blowing ratio of 0.3. By a blowing ratio of 0.5, the jet is observed to lift off, and then impinge back onto the test surface. At a blowing ratio of 1.2, the jets lift off, but reattach much further downstream, spreading the coolant further along the test surface. A thorough uncertainty analysis has been conducted in order to fully understand the presented measurements and any shortcomings of the measurement technique. The maximum uncertainty of effectiveness and blowing ratio is 0.02 counts of effectiveness and 3 percent respectively.
Effects of Film Hole Exit Radiusing on Film Cooling Performance
Authors: Abdala Antar M. M. , Elwekeel Fifi N. M. , Zheng Qun
Published: September 2016

In the present study, theoretical investigation of film cooling effectiveness and heat transfer behavior for radiusing of film hole exit was evaluated. Seven rounding radii of R=0.0D, 0.06D, 0.08D, 0.1D, 0.3D, 0.5D and 0.8D were investigated. The film cooling effectiveness, the heat transfer coefficient, net heat flux ratio and discharge coefficient were investigated. Four mass flow rates in the range of 0.00044: 0.0018[kg/s] were used to investigate the effects of coolant velocity on the film cooling performance. Results show that using the film hole exit radiusing helps in improvement the film cooling effectiveness. The radius of R=0.5D shows higher film cooling effectiveness among the other radii. The spatially average laterally film cooling effectiveness and net heat flux ratio of R=0.5D outperforms the case of R=0.0D at all mass flow rates except at higher rates the values are lower. Discharge coefficient of R=0.5D shows enhancement than R=0.0D with the pressure ratios. Interpretation of the low and high heat transfer coefficient regions for radii of R=0.5D and R= 0.0D depending on the flow structures was explained in detail.
NOx Correlation for an Industrial 10 MW Non-Premixed Gas Turbine Combustor for High Hydrogen Fuels
Authors: Kroniger Daniel , Wirsum Manfred , Horikawa Atsushi , Okada Kunio , Kazari Masahide
Published: September 2016

This paper describes a model to predict the nitric oxides (NOx) emissions for a dry non-premixed flame gas turbine combustor at full operation conditions. The NOx correlation considered the combustor pressure, the combustor outlet temperature and the fuel composition from natural gas (NG) to pure hydrogen (H2) fuel.

The test data for parametrizing the model was acquired with a high pressure combustion test rig for industrial 10 MWth reverse-flow gas turbine combustors. The experimental results confirm the typical dependencies of NOx emissions. As expected, higher NOx emissions occur with increasing combustor pressure, combustor outlet temperature and hydrogen content of the fuel.

The reference NOx model has been derived on the basis of physical approaches for the pressure and temperature effects. The substitution of natural gas with hydrogen is taken into account by a variable pressure exponent and a variable factor in the exponent of the exponential temperature correlation. As a result, the pressure exponent increases with increasing hydrogen. The temperature exponent factor decreases with increasing hydrogen. The model can describe the data set with limitations at high pressure and high hydrogen content fuel operation conditions.
On the Impact of Passive Tip-Injection on the Downstream Flow Field of a Shrouded LP-Turbine: CFD and Experimental Results
Authors: Ghaffari Pouya , Willinger Reinhard
Published: September 2016

Using shrouded blades with fins is a common method to reduce the leakage mass flow rate through the clearance between rotor and stator. A variety of methods have been developed improving the discharge behaviour of this sealing application. The leakage mass flow rate and its interaction with the main flow resulting in mixing losses and deviations in turning is also an important issue and has to be taken into consideration. The objective of this paper is to present a method aiming at reduction of tip-leakage mass flow rate and its high angular momentum by means of passive tip-injection. The results include analytical study followed by CFD calculations for compressible flow in a rotational frame of reference as well as experimental data. An uncooled low pressure air turbine with shrouded blades is considered for the CFD and the measurements. Three passive tip-injection configurations are investigated numerically out of which one configuration is also examined experimentally in the framework of this study.
Effect of Reynolds Number, Hole Patterns and Hole Inclination on Cooling Performance of an Impinging Jet Array: Part I — Convective Heat Transfer Results and Optimization
Authors: Li Weihong , Li Xueying , Ren Jing , Jiang Hongde , Yang Li , Ligrani Phillip
Published: September 2016

This study comprehensively illustrates the effect of Reynolds number, hole spacing, jet-to-target distance and hole inclination on the convective heat transfer performance of an impinging jet array. Highly resolved heat transfer coefficient distributions on the target plate are obtained utilizing transient liquid crystal over a range of Reynolds numbers varying between 5,000 and 25,000. Effect of streamwise and spanwise jet-to-jet spacing (X/D, Y/D: 4–8) and jet-to-target plate distance (Z/D: 0.75–3) are employed composing a test matrix of 36 different geometries. Additionally, the effect of hole inclination (θ: 0°–40°) on the heat transfer coefficient is investigated. Optical hole spacing arrangements and impingement distance are pointed out to maximize the area-averaged Nusselt number and minimize the amount of cooling air. Also included is a new correlation, based on that of Florschuetz et al., to predict row-averaged Nusselt number. The new correlation is capable to cover low Z/D∼0.75 and presents better prediction of row-averaged Nusselt number, which proves to be an effective impingement design tool.
Experiments on Front- and Aft- Disk Cavity Ingestion in a Subscale 1.5-Stage Axial Turbine
Authors: Balasubramanian J. , Michael M. , Roy R. P. , Kim Y. W. , Moon H. K.
Published: September 2016

This paper describes experiments performed in a subscale 1.5-stage axial air turbine in which ingestion of mainstream air into the front and aft disk cavities was measured. The front disk cavity is upstream of the rotor, the aft disk cavity is downstream of the rotor. Both disk cavities contain a labyrinth seal at a radially inboard location; this seal divides the cavity into a ‘rim cavity’ and an ‘inner cavity’. The front rim cavity features a double seal with radial clearance and axial overlap at its periphery; the aft rim cavity double seal possesses axial gap. Results are reported for three experiment sets, each set defined by the main air flow rate and rotor speed. Furthermore, each set comprises four different purge air flow rates. The initial step in each experiment was the measurement of time-average static pressure distribution in the main gas annulus and the disk cavities to establish the steady-state pressure differentials that contribute to ingestion into and egress from the cavities. This was followed by the measurement of tracer gas (CO2) concentration distribution in the disk cavities to quantify the ingestion. In addition to the pressure and concentration (in terms of sealing effectiveness) results, the mass flow rates of ingested main air into the front and aft rim cavities are reported for the various experimental conditions. Both inner cavities were found to be completely sealed against ingestion. Ingestion and egress discharge coefficients based on an orifice model are reported for the front and aft double rim seals; their trends are quite different from those of single rim seals with axial overlap and radial clearance reported earlier.
Investigation of Air Injection and Cavity Size Within a Circumferential Combustor to Increase G-Load and Residence Time
Authors: Cottle Andrew E. , Polanka Marc D. , Goss Larry P. , Goss Corey Z.
Published: September 2016

Combustion at high G-loading offers the promise of higher flame speeds and shorter residence times. Ultra-Compact Combustors (UCC) make use of this phenomenon by injecting air and fuel into a circumferential cavity around the main core flow. Air is injected tangentially into the combustion cavity to induce bulk circumferential swirl. Swirl velocities in the cavity produce a centrifugal load on the flow that is typically expressed in terms of gravitational acceleration, or g-loading. The Air Force Institute of Technology (AFIT) has developed an experimental facility in which g-loads up to 2000 times the earth’s gravitational field (“2000 g’s”) can be established.

This paper investigates the flow within the combustion cavity to determine conditions that lead to the generation of higher g-loads and longer residence times. This is coupled with the desire to completely combust the fuel — ideally within the combustion cavity. These objectives have led to changes within the AFIT test setup to enable optical access into the primary combustion cavity. Particle Image Velocimetry (PIV), complemented by traditional high-speed video imagery, provided high-fidelity measurements of the velocity fields within the cavity. These experimental measurements were compared to a set of Computational Fluid Dynamics (CFD) solutions. Improved cavity air and fuel injection schemes were evaluated over a range of air flows and equivalence ratios. Increased combustion stability was attained by providing uniform distribution of air drivers. Lean cavity equivalence ratios at a high total airflow resulted in higher g-loads and complete combustion showing promise for utilizing the UCC as a main combustor.
A Novel Suction Side Winglet Design Method for High Pressure Turbine Rotor Tips
Authors: Zhou Chao , Zhong Fangpan
Published: September 2016

Winglet tips are promising candidates for future high pressure turbine rotors. Many studies found that the design of the suction side winglet is the key to the aerodynamic performance of a winglet tip, but there is no general agreement on the exact design method. In this paper, a novel suction side winglet design method will be introduced. The winglets are obtained based on the near tip flow field of the datum tip geometry. The suction side winglet aims to reduce the tip leakage flow particularly in the front part of the blade passage. It is found that on the casing endwall, the pressure increases in the area where the winglet is used. This reduces the tip leakage flow in the front part of the blade passage and the pitchwise pressure gradient on the endwall. As a result, the size of the tip leakage vortex reduces. A surprising observation is that the novel winglet tip design eliminates the scraping vortex and results in a further increasing of the efficiency. The tip leakage loss of the novel winglet tip is 23% lower than the datum cavity tip, with an increase of tip surface area by only 20%. The spanwise deflection of the winglet due to the centrifugal force is small. Numerical simulation shows that in a turbine stage, this winglet tip increases the turbine stage efficiency by 0.9% at a tip gap size of 1% span compared with a cavity tip.
Investigation of Performance of High Velocity Air Intake Wave-Plate Separators for Marine Gas Turbines
Authors: Luan Yigang , Ni Yang , Liu Huannan , Bu Shi , Sun Haiou
Published: September 2016

Due to the advantages of great power, small size and light weight, the application of gas turbines in marine power facilities has increased a lot over time. Concerning the factors of off-shore operating environments which include the huge air intake quantity, the massive mist marine circumstance and the precious vessel available capacity, this paper combined experimental study with numerical simulation to investigate the performance of a type of new air intake wave-plate separator which can be applied under high intake velocity conditions. The total pressure drop was measured in a small wind tunnel with the inlet velocities of the separators ranging from 1.0 to 15.0 m/s. The resistance characteristics of high velocity wave-plate separators were simulated under the same velocity range described above. The separation efficiencies of high velocity wave-plate separators were simulated under the inlet velocity of 14.0 m/s, and the liquid diameters were 5μm, 10μm, 15μm and 20μm respectively. By analyzing the results of experiments and simulations, this paper draws the conclusion that high velocity wave-plate separators can keep high separation efficiencies and acceptable total pressure drop under high inlet velocities.
Origins and Structure of Rotating Instability: Part 2 — Numerical Observations in a Transonic Axial Compressor Rotor
Authors: Wu Yanhui , An Guangyao , Chen Zhiyang , Liu Jun , Yang Guowei
Published: September 2016

Rotating instability (RI) is an obvious unsteady flow phenomenon occurring in the tip region of compressors, which is potentially linked to tip clearance flow noise, blade vibration and rotating stall/surge. The existing investigations for RI indicate the origins of RI are closely related to unsteady flow behaviors in given blade passages in the rotating reference frame, which depend on the design specifics of axial machines. However, no efforts are made to set up a quantitative link between the time scale of unsteady behavior in a given passage and the characteristic parameters of RI, let alone to define the fluid dynamic processes/events which are causally linked with the RI inception. This is the motivation for the current investigations.

For the case shown in Part I, a quantitative link between the time scale of tip flow unsteadiness and the characteristic parameters of RI has been set up. The consistency between experimental and numerical results also demonstrates that multi-passage computations with the circumferential extent larger than the length scale of RI could shed light on the flow mechanisms relevant to the emergence of RI. In this part, systematic multi-passage simulations were thus laid out for a tip-critical transonic rotor, NASA Rotor 35, to identify the fluid dynamic processes for the inception of RI in presence of shock wave. It is found that the flow field becomes unsteady when the mass flow rate is below a critical value close to the stability limit. The flow unsteadiness in specific passages originates from the rotor tip region, but it is not synchronous with the occurrence of the circumferential travelling wave similar to RI as is the case in Part I. The origin of flow unsteadiness attributes to the periodic oscillation of a new vortex structure is termed as tip secondary vortex (TSV). The TSV is essentially a vortex segment arising from the spiral-type breakdown of TLV. The underlying flow mechanism for the inception of a rotating wave similar to RI is that the periodic oscillation of TSV is capable of inducing the flow blockage transfer against the rotor rotation direction. In conjunction with the investigation results reported in Part 1, a local inception criterion for RI is thus identified, which could be depicted as the initiation of the flow blockage transfer induced by the unsteady flow behavior in blade passages near tip.
Study on Nonlinear Identification SOFC Temperature Model Based on Particle Swarm Optimization-Least Squares Support Vector Regression
Authors: Chen Jinwei , Zhang Huisheng , Weng Shilie
Published: September 2016

A nonlinear autoregressive network with exogenous inputs (NARX) identification model is employed for predicting the Solid oxide fuel cell (SOFC) operating temperature dynamics fast and accurately in a Solid oxide fuel cell–gas turbine (SOFC-GT) hybrid system. At the same time, the least squares support vector regression (LSSVR) method with radial basis kernel function (RBF) which uses particle swarm optimization (PSO) to optimize the LSSVR’s parameters is applied to establish the NARX model. The major factors which affect the cathode and anode outlet temperature of the SOFC-GT hybrid system are the inlet flow rate of cathode and anode. Therefore, the inlet flow rates of cathode and anode are taken as inputs of the NARX model, cathode and anode outlet temperature as outputs. With the training data sampled from the mechanism model which is derived from conservation laws, a SOFC temperature the NARX model based on the LSSVR is established. Investigations are conducted to analyze the effects of training data size and fitness function of PSO on the accuracy of the NARX model. And by comparing the temperature behaviors with the results collected form the mechanism model, the accuracy of the NARX model based on the LSSVR is verified with enough accuracy in predicting the dynamic performance of the SOFC temperature. Furthermore, in the aspect of simulation speed, the NARX model is much faster than the mechanism model because the NARX model avoids the internal complex computation process. For large size training data, the training time of the NARX model is only about 1.2s. For running all 20,000s of simulation, the predicting time of the NARX model is only about 0.2s, while the mechanism model is about 36s. In consideration of the high speed and accuracy of the NARX model, it can be applied to design valid multivariable model predictive control (MPC) schemes with high reputation.
Mechanism and Flow Control on the Mismatching of Impeller and Vaned Diffuser Caused by Inlet Prewhirl for Centrifugal Compressors
Authors: Huang Qiangqiang , Zheng Xinqian , Wang Aolin
Published: September 2016

Air often flows into compressors with inlet prewhirl, because it will obtain a circumferential component of velocity via inlet distortion or swirl generators such as inlet guide vanes. A lot of research has shown that inlet prewhirl does influence the characteristics of components, but the change of the matching relation between the components caused by inlet prewhirl is still unclear. This paper investigates the influence of inlet prewhirl on the matching of the impeller and the diffuser and proposes a flow control method to cure mismatching. The approach combines steady three-dimensional Reynolds-averaged Navier-Stokes (RANS) simulations with theoretical analysis and modeling. The result shows that a compressor whose impeller and diffuser match well at zero prewhirl will go to mismatching at non-zero prewhirl. The diffuser throat gets too large to match the impeller at positive prewhirl and gets too small for matching at negative prewhirl. The choking mass flow of the impeller is more sensitive to inlet prewhirl than that of the diffuser, which is the main reason for the mismatching. To cure the mismatching via adjusting the diffuser vanes stagger angle, a one-dimensional method based on incidence matching has been proposed to yield a control schedule for adjusting the diffuser. The optimal stagger angle predicted by analytical method has good agreement with that predicted by computational fluid dynamics (CFD). The compressor is able to operate efficiently in a much broader flow range with the control schedule. The flow range, where the efficiency is above 80%, of the datum compressor and the compressor only employing inlet prewhirl and no control are just 25.3% and 31.8%, respectively. For the compressor following the control schedule, the flow range is improved up to 46.5%. This paper also provides the perspective of components matching to think about inlet distortion.
Geometric Modeling and Analysis for Gooseneck
Authors: Tu Qiuye , Zhang Dongdong , Chen Jie , Cai Yuanhu
Published: September 2016

Demands on the high by-pass ratio of modern civil engine, an increasing radial offset between the booster and the high pressure compressor highlights the importance of S-shaped gooseneck. A desirable balance between the length and the radial offset by optimizing inner-wall and outer-wall for gooseneck will save the length of low pressure rotor and improve the situation to deliver the flow through it.

This paper presented a geometric modeling method which adopted polynomial curves to construct inner-wall and section area distribution for goosenecks. With the given boundary dimensions of gooseneck, the location of inflection point served as a variable to control the inner-wall curve, and the peak value and its location served as the other two variables to control the area distribution curve. A series of 3-D models were built from the baseline gooseneck model in order to analyze the relationships between the geometric parameters and the aerodynamic performance.

The 3-D numerical simulation results indicated that the peak value of area distribution has the most important effects on the total pressure loss of gooseneck. An appropriate peak value of area distribution could be obtained by changing the normalized Mach number at peak point to weaken the flow separation near the outer-wall and after the struts. Inner-walls with large curvature near the entrance of gooseneck, and area distributions with an appropriate peak location, would improve the streamline of outer-wall and restrain the flow separation. Subsequently, the relationships between the geometric control variables and the total pressure loss were established.

Moreover, taking the constructional blocking effects of struts into account, a series of simplified 2-D flow paths were modeled and the relationships were reestablished. The 2-D results indicated that the simplified model could also reveal the flow field near the inner-wall address the correct peak value. But the optimum peak location and the inner-wall inflection point were not consistent with the 3-D results due to the geometric changes on the outer-wall. The equivalent method will be further improved in the future research.
Numerical Analysis and Design Optimization of a Low Pressure Cylinder Control Valve Block of a High-Power Steam Turbine
Authors: Arkhipova Liubov , Bogachev Anton , Tyukhtyaev Alexey
Published: September 2016

A problem of energy losses reduction in the steam flows through different channels and flow paths of steam turbines is one of the issues of the day in turbo machinery.

In the report a comparative numerical analysis of two design options of control valve blocks and two different confuser pipes located upstream the control valves are presented. The aim of the research was minimization of energy losses in the control valve blocks and confuser pipes. The investigation consists of two parts.

In the first part a numerical study of steam flow through two alternative designs of the low pressure control valve block is discussed.

Another investigation presented in the report aims to selection of the optimum design of confuser pipes supplying steam to the control valve block. The cone angle and length of the pipe were varied in the study.

As a result of the work optimal design of confuser pipe and control valve block was chosen in respect to energy losses decrease.
Unified Thermodynamic Evaluation of Radical Aero Engine Cycles
Authors: Kaiser Sascha , Seitz Arne , Vratny Patrick , Hornung Mirko
Published: September 2016

The Joule-/Brayton thermodynamic cycle is the base cycle of all major contemporary aero engines. Over the decades, the achievement of further significant improvements has become progressively challenging, and the increase of efficiency approaches physical limitations. In order to meet the ambitious long-term emission reduction targets, the introduction of radical new propulsion system concepts is indispensable. Various cycles promising significant efficiency improvements over the conventional Joule-/Brayton-cycle are being examined by the engine community. However, as no clear favorite has emerged from these potential technical solutions, a transparent methodological approach for the consistent evaluation of the concepts is necessary.

Consistent thermodynamic description and performance metrics for three engine cycles are presented in this paper: The turbofan as reference and two radical engine cycles, namely the composite cycle and the cycle-integrated parallel hybrid. Laws for the estimation of component performance for large parametric variations are introduced. A method for the estimation of power plant system mass for the investigated engine cycles is proposed to evaluate fuel burn reduction. The studies substantiated that the turbofan improvement potential is saturating. The composite cycle engine offers a tremendous potential for fuel burn improvement of 24.5% over state of the art turbofan engines, which allows meeting the emission reduction targets in 2035. The cycle-integrated parallel hybrid engine improves the turbofan moderately with year 2035 technology, but is not capable of meeting the corresponding emission reduction targets on a short-to-medium range aircraft platform.
Turbine Vane Endwall Film Cooling With Slashface Leakage and Discrete Hole Configuration
Authors: Chowdhury Nafiz H. K. , Shiau Chao-Cheng , Han Je-Chin , Zhang Luzeng , Moon Hee-Koo
Published: September 2016

Turbine vanes are typically assembled as a section containing single or double airfoil units in an annular pattern. First stage guide vane assembly results in two common mating interfaces — a gap between combustor and vane endwall and another resulted from the adjacent sections, called slashface. High pressure coolant could leak through these gaps to reduce the ingestion of hot gas and achieve certain cooling benefit. As vane endwall region flow field is already very complicated due to highly three-dimensional secondary flows, then a significant influence on endwall cooling can be expected due to the gap leakage flows. To determine the effect of leakage flows from those gaps, film cooling effectiveness distributions were measured using Pressure Sensitive Paint (PSP) technique on the endwall of a scaled up, mid-range industrial turbine vane geometry with the multiple rows of discrete film cooling holes inside the passages. Experiments were performed in a blow-down wind tunnel cascade facility at the exit Mach number of 0.5 corresponding to Reynolds number of 3.8 × 105 based on inlet conditions and axial chord length. Passive turbulence grid was used to generate freestream turbulence level about 19% with an integral length scale of 1.7 cm. Two parameters, coolant-to-mainstream mass flow ratio and density ratio were studied. The results are presented as two-dimensional film cooling effectiveness distribution on the vane endwall surface and the corresponding spanwise averaged values along the axial direction are also demonstrated.
Generation of the Equations for the Profile Losses Calculation in Blade Row of Axial Turbines in Design Analysis
Authors: Baturin Oleg , Kolmakova Daria , Gorshkov Aleksey , Popov Grigorii
Published: September 2016

The paper proposes a method for evaluating the reliability of models for estimating the energy losses in the blade rows of axial turbines, based on the statistical analysis of the experimental data deviation from the calculated. It was shown that these deviations are subject to the normal distribution law and can be described by mathematical expectations μΔξ and standard deviation σΔξ.

The values of profile losses were calculated by five well-known models for 170 different axial turbines cascades, representing the diversity of turbines used in aircraft gas turbine engines. The findings were compared with experimental data. Comparison results were subjected to statistical analysis. It was found that the best model to describe the profile losses in axial turbines is model that has been developed in Central Institute of Aviation Motors (Russia). It allows the calculation of profile losses deviating from the actual values of losses by −8±84% with a probability of 95%.

Taking into account the mentioned statistical criteria, a new equation was proposed based on the analysis of the profile losses nature and using mathematical optimization techniques. This equation makes possible to define the profile loss of axial turbine more accurate than the investigated models. It allows the calculation of profile loss values in the axial turbine that differ from the actual value by 10±61% with a probability of 95%. The proposed new equation takes into account more geometric and operational factors affecting the value of losses.
Study of Development of a Novel Dual Phase Airblast Injector for Gas Turbine Combustor
Authors: Li Jianing , Hamza Mahmoud , Kumaran Arul , Bhayaraju Umesh , Jeng San-Mou
Published: September 2016

A novel airblast injector is designed for gas turbine combustors. Unlike standard pressure swirl and prefilming/non-prefilming air blast atomizers, the novel injector is designed to improve the fuel injection delivery to the injector and improve atomization of the fuel by using a porous stainless steel tube. There are three swirling air streams in the injector. The liquid fuel is injected through the porous tube, with 7 micron porosity, between the swirling air streams, viz. an inner swirling air through the tube and the other two swirling air streams merging downstream of the tube. The swirl vane angles and the air split ratio are selected to increase the amount of air through the injector and facilitate the atomization process. The liquid fuel is injected through the outer surface of the porous tube, due to the permeability of the tube, produces a thin liquid sheet on the inner surface of the tube. The atomization occurs by surface stripping of the liquid sheet. The advantage of such an injector is that it produces a liquid sheet with uniform thickness around the circumference of the tube under all liquid loading. The porous tube also increases the surface area of contact between the fuel and air and produces a fine spray at engine idle conditions. An experimental approach is adopted in the present study to characterize the spray and aerodynamics of the injector for Jet-A and Gas-To-Liquid (GTL) fuels at atmospheric conditions. The effect of flare height on the Sauter Mean Diameter (SMD) is also studied. Spray characterization, droplet size and volume flux are investigated with PDI measurements. The effect of pressure drop and fuel properties on SMD distribution is analyzed. Velocity profiles at downstream of the injector are obtained from LDV measurements, and the velocity profile at the exit of the injector is also analyzed. A central toroidal recirculation zone (CTRZ) is observed at the exit of the injector. The effect of different configurations of the injector on spray characteristics is studied. A correlation for SMD is obtained.
Performance Metric for Turbine Stage Under Unsteady Pulsating Flow Environment
Authors: Lee Jinwook , Tan Choon S. , Sirakov Borislav T. , Wilkins Chris , Im Hong-Sik , Babak Martin , Tisserant Denis
Published: September 2016

In a turbine stage for a vehicular turbocharger or a PDE (Pulse Detonation Engine) system, the power extraction process is inherently unsteady due to a highly pulsating flow delivered from the upstream combustor. Characterizing the operating performance of such a turbine stage would call for defining unsteady efficiency on a physically rigorous basis. Since the instantaneous efficiency can be calculated as the fraction of the actual power to the unsteady ideal power, an expression for the unsteady ideal power from the turbine stage is first derived by applying mass conservation and the First/Second Law of thermodynamics for the turbine stage. The newly derived expression elucidates the distinction from the quasi-steady situation in that the storage effect of mass/energy/entropy over the turbine stage is no longer negligible compared to the flux of mass/energy/entropy at the inlet and outlet. The storage effect resolves the previously reported physical inconsistency that the instantaneous efficiency can be a value of above unity or below zero; an erroneous result associated with defining the efficiency based on a quasi-steady basis. As the reduced frequency of the inlet pulsation of the turbine stage becomes larger than unity, the mass/energy/entropy accumulation rate over the turbine stage becomes significant compared to the mass/energy/entropy influx rate. Then, the definition of the efficiency based on a quasi-steady assumption loses its applicability. In this paper, the role of mass/energy/entropy storage rate in the unsteady ideal power is assessed in order to underpin the inconsistency in the previous quasi-steady approach. The utility of the unsteady efficiency definition is elucidated for the case of a turbocharger turbine stage subjected to high inlet flow pulsation.
A Taylor Series Expansion Approach for Nonlinear Blade Forced Response Prediction Considering Variable Rotational Speed
Authors: Heinze Torsten , Panning-von Scheidt Lars , Wallaschek Jörg , Hartung Andreas
Published: September 2016

In the field of turbomachinery, great efforts are made to enhance computational tools to obtain reliable predictions of the vibrational behavior of friction-damped bladed disks. As a trade-off between computational burden and level of simplification, numerous methods were developed to reduce the nonlinear systems dimension. Using component mode synthesis methods (CMS), one is capable to describe the systems motion by interface and modal coordinates. Subsequently or alternatively, the dynamic compliance matrix can be evaluated efficiently by means of modal superposition to avoid the inversion of the dynamic stiffness matrix. Only the equations corresponding to the degrees of freedom (DOF) subject to localized nonlinear contact forces need to be solved simultaneously, whereas the solution of the linear DOF is obtained by exploiting the algebraic character of the set of equations. In this paper an approach is presented to account for rotational speed-dependent stiffness in the subset of nonlinear DOF without the need to re-evaluate the associated eigenvalue problem (EVP) when rotational speed is changed. This is done by means of a Taylor series expansion of the eigenvalues and eigenvectors used for the modal superposition to re-construct the dynamic compliance matrix. In the context of forced response predictions of friction-damped blisks the expansion is performed up to different order for a simplified blisk model with nonlinear contact interfaces. The results are compared to the solution obtained by direct evaluation of the EVP at selected rotational speeds and the solution when dynamic compliance matrix is built up by direct inversion of the dynamic stiffness matrix. Finally, the proposed methods computational performance is analyzed.
Modeling and Simulation of Common Core Gas Turbine Engine Variant Applications
Authors: Sands Jonathan S. , Karl Alexander H. , Mavris Dimitri N.
Published: September 2016

The development of a clean sheet gas turbine engine program can be a multi-billion dollar undertaking. The decision to take on such a program can place the company at great risk. In order to distribute this capital risk among a large quantity of products, the engine core should be utilized across a family of products. However, common core engine variant designs must also achieve performance levels that are competitive and economically viable options for likely customers.

Common engine core design decisions should be made with knowledge of how a candidate core definition will impact initial and future product applications. Implications must be drawn to estimate the impacts on performance, weight, and cost when employing a single core definition across a variety of likely product applications. This introduces an immense computational challenge. If commonality were enforced via post processing of simulation data, a large portion of the design space would not represent common core applications, making the associated data useless to the designer. Therefore, engine commonality should be implicitly imposed across the various product applications being considered. To further reduce the computational burden of simulating multiple applications, design space exploration of the core and corresponding variant applications must also be done in an efficient manner.

This research aims to develop and demonstrate a computationally efficient method for modeling and simulating a variety of common core engine variant applications simultaneously. The modeling approach to enforce commonality will first be shown. Additionally, the method will be shown to enable design space exploration of multiple common core engine applications simultaneously. Through the use of surrogate models, the relationship between a common engine core definition and corresponding variant application will be captured in mathematical form. This mathematical relationship will then be duplicated for each product application, tying all applications to a single baseline engine core definition. The approach allows core design implications to be drawn instantaneously to each product application considered.

After establishing the unique modeling and simulation approach, the method will be demonstrated for a multiple application common core design problem. The process will be used to arrive at an engine core definition that can be employed across multiple high bypass turbofan applications. In order to enumerate the amount of compromise made by employing a single baseline core definition across multiple applications, each resultant common core variant design will be compared to corresponding clean sheet designs selected for each individual application. The knowledge gained from this modeling and simulation approach allows the designer to make performance, weight, and cost trades efficiently across a family of products earlier in the development process.
Aerodynamic Turbine Design for an Oxy-Fuel Combined Cycle
Authors: Dahlquist Adrian , Genrup Magnus
Published: September 2016

The oxy-fuel combined cycle (OCC) is one of several carbon capture and sequestration (CCS) technologies being developed to reduce CO2 emissions from thermal power plants. The OCC consists of a semi-closed topping Bryton cycle, and a traditional bottoming Rankine cycle. The topping cycle operates with a working medium mixture of mainly CO2 and H2O. This CO2-rich working fluid has significantly different gas properties compared to a conventional open gas turbine cycle, which thereby affects the aerodynamic turbine design for the gas turbine units. The aerodynamic turbine design for oxy-fuel gas turbines is an unexplored research field. The topic of this study was therefore to investigate the aerodynamic turbine design of turbines operating with a CO2-rich working fluid. The investigation was performed through a typical turbine aero-design loop, which covered the 1D mid-span, 2D through-flow, 3D blade profiling design and the steady-state 3D analysis. The design was performed through the use of conventional design methods and criteria in order to investigate if any significant departures from conventional turbine design methods were required.

The survey revealed some minor deviations in design considerations, yet it showed that the design is feasible with today’s state-of-the-art technology by using conventional design practice and methods.

The performance of the oxy-fuel combined cycle was revised based on the performance figures from the components design. The expected total performance figures for the oxy-fuel combined cycle were calculated to be a net electrical power of 119.9 MW and a net thermal efficiency of 48.2%. These figures include the parasitic consumption for the oxygen production required for the combustion and the CO2 compression of the CO2 bleed stream.
Installation and Performance Analysis of 125 kW Organic Rankine Cycle for Stationary Fuel Cell Power Plant
Authors: Huh Kwanghak , Mirmobin Parsa , Imani Shamim
Published: September 2016

Installation and performance analysis of Thermapower™ 125MT Organic Rankine Cycle (ORC) System for recovery of waste heat from an existing Molten Carbonate Fuel Cell (MCFC) plant are presented. Over the last three years, about 100 MWe of new FC stationary power plants are in operation in Korea and more FC stationary power plants are on order and planned. The success of these fuel cell plants is their capability to supply both electricity and heat to customers. In order to promote renewable energy in Korea, the Korean Government is enforcing large power plants to supply electricity generated by renewable energy. The Korea Power Exchange (KPX) buys fuel cell generated electricity as renewable energy with higher price than other fossil fuel power plants [1].

Most of these FC plants supply electricity to power companies with their full capability, however valuable heat is wasted due to the limited demand, especially in summer season and off working hours or lack of heat pipe infrastructures. Due to the recent decrease in electricity price for renewable energy in Korea, the need for efficient utilization of waste heat is ever more demanding.

In this study, 125 kWe ORC system is installed to 11.2 MWe FC power plant to demonstrate cost saving benefits. This FC Power plant has 4 units of 2.8 MWe fuel cell in operation and has capacity of producing 6.0 ton/h of 167°C steam. In order to install an ORC system to existing FC plant, their Balance of Plant (BoP) has to be modified since only excess steam is allow to be utilized by the ORC system, after supplying steam to their prime customer. Furthermore, site has distinctly hot and cold seasons, thus affecting condensing conditions and therefore ORC performance. Design considerations to accommodate varying ambient conditions as well as steam flow rate variation are presented and discussed.
Differential Equation-Based Specification of Turbulence Integral Length Scales for Cavity Flows
Authors: Jefferson-Loveday Richard J.
Published: September 2016

A new modeling approach has been developed that explicitly accounts for expected turbulent eddy length scales in cavity zones. It uses a hybrid approach with Poisson and Hamilton-Jacobi differential equations. These are used to set turbulent length scales to sensible expected values. For complex rim-seal and shroud cavity designs, the method sets an expected length scale based on local cavity width which accurately accounts for the large-scale wake-like flow structures that have been observed in these zones. The method is used to generate length scale fields for three complex rim-seal geometries. Good convergence properties are found and a smooth transition of length scale between zones is observed. The approach is integrated with the popular Menter Shear Stress Transport (MSST) RANS turbulence model and reduces to the standard Menter model in the mainstream flow. For validation of the model, a transonic deep cavity simulation is performed. Overall the Poisson-Hamilton-Jacobi model shows significant quantitative and qualitative improvement over the standard Menter RANS model for both velocity and Reynolds stress measurements. In its current development, the approach has been extended through the use of an initial stage of length scale estimation using a Poisson equation. This essentially reduces the need for user objectivity. A key aspect of the approach is that the length scale is automatically set by the model and not by the modeler. Notably, the current method is readily implementable in an unstructured, parallel processing computational framework.