bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the number of enlarged pores according to site, age, and sex
Authors: Jung H.J. , Ahn J.Y. , Lee J.I. , Bae J.Y. , Kim H.L. , Suh H.Y. , Youn J.I. , Park M.Y.
Published: February 2018

Background

Increasing the number of enlarged pores causes cosmetic problems. The difference in the number of enlarged pores according to facial site, age, and sex is unclear.

Objective

To analyze the distribution of the number of enlarged pores according to facial site, age, and sex.

Methods and materials

We analyzed the number of the enlarged pores and the percentage of wrinkles in the nose, forehead, and cheek from 434 polarized images. The measurement results were analyzed according to site, age, and sex. Relationship between enlarged pore counts and wrinkle severity was also analyzed. The study was conducted by using DermaVision,™ which can take cross‐polarization, parallel polarization, and ultraviolet light images.

Results

The enlarged pores of the nose and forehead were more prominent than in the cheeks. Pore counts were increased with age, and the increment was significant between the 30's and 40's. There was no significant difference by gender. Enlarged pore counts were related to wrinkle severity.

Conclusions

The number of enlarged pores differs depending on body site and increased with age. The enlarged pore counts correlate with wrinkle severity and the correlation varies depending on the body site.
Correcting preoperative iron deficiency as part of patient blood management in the ‘real world’: results of an audit on an Australian cohort
Authors: Hong F. S. , Sieradzki N. , Pollock C. , Nasra F. , Churilov L. , Mo A. , Willcox A. , Ho W. K. , Smith C.
Published: February 2018

Background

The perioperative module of the Australian Patient Blood Management guidelines recommended preoperative iron therapy for surgical patients with, or at risk of, iron deficiency anaemia. After implementing a preoperative haemoglobin optimization programme in our institution, an audit was undertaken to evaluate the benefit of preoperative iron therapy in ‘real world’ clinical practice.

Methods

Elective major surgery patients assessed in surgical pre‐admission clinics from 1 July 2013 to 30 June 2014 were screened for iron deficiency and anaemia. Those who were iron deficient (ferritin <30 μg/l), regardless of haemoglobin level, received either daily oral iron supplementation until day of surgery or intravenous iron polymaltose 1 g preoperatively (intervention group). Control patients who were not iron deficient were matched to the intervention group using propensity scores based on age, sex and surgical unit. The primary end‐point was the proportion of patients requiring perioperative red cell transfusion in intervention and control groups.

Results

One hundred and fourteen patients (8·75%) had iron deficiency. Ninety‐three patients received preoperative iron therapy, 17 (18·3%) of whom required red cell transfusions postoperatively. Of the 332 control patients, 71 (21·4%) required red cell transfusion. After adjusting for preoperative haemoglobin and time from screening to surgery, the odds of red cell transfusion were significantly lower in the intervention group compared to controls (odds ratio: 0·512, 95% confidence interval: 0·268–0·977; P = 0·04).

Conclusion

Preoperative iron therapy was associated with reduced need for postoperative red blood cell transfusion in elective major surgery patients who were initially iron deficient.
Shakespeare in Shackles: Pedagogical Experiment and Cultural Activity in a French Prison
Authors: Evain Christine , Saurier Delphine , Hawkridge Spencer
Published: February 2018

As cultural activities in prisons expand, institutions are recognizing the need for research on impact in order to optimize these activities. In this article, our team presents findings on a recent teaching experiment concerning literature workshops that brought together male inmates and university students over an 18-month period at the Centre de Détention de Nantes in France. Our qualitative approach explores an ethical question: What are our responsibilities towards all the parties involved in this teaching experiment? Two important and apparently conflicting findings come to the fore. First, the responsibility of teachers is to accompany the desires of students and inmates in their permanent negotiation with the apparatus itself. Second, workshop organizers need to reflect on their own responsibility concerning the way the workshop contributes to the institutionalization of the prison.
Robust Proportional Integral Derivative Controller Design for Various Processes Using Novel Hybrid Metaheuristic Algorithms
Authors: Agees Kumar C. , Rajeshwaran Saranya , Ganapathy Kanthaswamy
Published: February 2018

This paper compares the effectiveness of the proposed hybrid metaheuristic algorithms for a class of unstable systems with time delay to that of the existing ones. The local search and global methods of optimization are combined to yield more effective hybrid metaheuristic algorithms. These algorithms are used to tune the proportional–integral–derivative (PID) controllers, satisfying the robust stabilizing vector gain margin (VGM). Six global heuristic algorithms namely ant colony optimization (ACO), particle swarm optimization (PSO), biogeography-based optimization (BBO), population-based incremental learning (PBIL), evolution strategy (ES), and stud genetic algorithms (StudGA) are combined with the local search property of derivative free optimization methods such as simplex derivative based pattern search (SDPS) and implicit filtering (IMF) to yield hybrid metaheuristic algorithms. The efficacy of the proposed control schemes in terms of various time domain specifications and stabilizing VGM are compared with some existing methods for unstable process with time delay (UPTD) systems. The performance of the proposed control schemes particularly in the context of uncertainty in the plant is demonstrated using a case study. The efficacy of the proposed control scheme is illustrated with a nontransfer function based multibody vehicle autosteer control design problem.
On Efficiently Obtaining Higher Order Accurate Discretization Error Estimates for Unstructured Finite Volume Methods Using the Error Transport Equation
Authors: Yan Gary K. , Ollivier-Gooch Carl
Published: February 2018

A numerical estimation of discretization error for steady compressible flow solutions is performed using the error transport equation (ETE). There is a deficiency in the literature for obtaining efficient, higher order accurate error estimates for finite volume discretizations using nonsmooth unstructured meshes. We demonstrate that to guarantee sharp, higher order accurate error estimates, one must discretize the ETE to a higher order than the primal problem, a requirement not necessary for uniform meshes. Linearizing the ETE can limit the added cost, rendering the overall computational time competitive, while retaining accuracy in the error estimate. For the Navier–Stokes equations, when the primal solution is corrected using this error estimate, for the same level of solution accuracy the overall computational time is more than two times faster compared to solving the higher order primal problem. In addition, our scheme has robustness advantages, because we solve the primal problem only to lower order.
Nonlinear Vibrations of Axially Functionally Graded Timoshenko Tapered Beams
Authors: Ghayesh Mergen H.
Published: February 2018

This paper presents the coupled axial-transverse-rotational nonlinear forced vibrations of Timoshenko tapered beams made of an axially functionally graded (AFG) material subjected to an external harmonic excitation. Two sources of nonlinearities are considered in modeling and numerical simulations: (i) the geometric nonlinearities arising from induced nonlinear tension due to the clamped–clamped boundary conditions and large deformations, and (ii) nonlinear expressions to address the nonuniform geometry and mechanical properties of the beam along the length. More specifically, a nonlinear model is developed based on the Timoshenko beam theory accounting for shear deformation and rotational inertia. Exponential distributions are presumed for the cross-sectional area, moduli of elasticity, mass density, and Poisson's ratio of the AFG tapered Timoshenko beam. The kinetic and potential energies, the virtual work of the external harmonic distributed load, and the one done by damping are implemented into Hamilton's energy principle. The resultant nonuniform nonlinearly coupled partial differential equations are discretized into a set of nonlinear ordinary differential equations utilizing Galerkin's technique. In the discretization scheme, a large number of modes, both symmetric and asymmetric, are employed due to the asymmetric characteristic of the nonuniform beam with respect to its length. The effect of different parameters, including the gradient index and different taper ratios, on the force-vibration-amplitude and frequency-vibration-amplitude diagrams is examined; the effect of these parameters on the natural frequencies, internal resonances, and asymmetric characteristics of the AFG system is investigated as well.
Spatial Interpolation for Periodic Surfaces in Manufacturing Using a Bessel Additive Variogram Model
Authors: Yang Yuhang , Shao Chenhui
Published: February 2018

High-resolution spatial data are essential for characterizing and monitoring surface quality in manufacturing. However, the measurement of high-resolution spatial data is generally expensive and time-consuming. Interpolation based on spatial models is a typical approach to cost-effectively acquire high-resolution data. Conventional modeling methods fail to adequately model the spatial correlation induced by periodicity, and thus their interpolation precision is limited. In this paper, we propose using a Bessel additive periodic variogram model to capture such spatial correlation. When combined with kriging, a geostatistical interpolation method, accurate interpolation performance can be achieved for common periodic surfaces. In addition, parameters of the proposed model provide valuable insights for the characterization and monitoring of spatial processes in manufacturing. Both simulated and real-world case studies are presented to demonstrate the effectiveness of the proposed method.
Development of Fatigue Crack Growth Thresholds for Austenitic Stainless Steels Exposed to Air Environment for ASME Code Section XI
Authors: Hasegawa Kunio , Usami Saburo
Published: February 2018

Fatigue crack growth thresholds ΔKth define stress intensity factor range below which cracks will not grow. The thresholds ΔKth are useful in industries to determine durability lifetime. Although massive fatigue crack growth experiments for stainless steels in air environment had been reported, the thresholds ΔKth are not codified at the American Society of Mechanical Engineers (ASME) Code Section XI, as well as other fitness-for-service (FFS) codes and standards. Based on the investigation of a few FFS codes and review of literature survey of experimental data, the thresholds ΔKth exposed to air environment have been developed for the ASME Code Section XI. A guidance of the thresholds ΔKth for austenitic stainless steels in air at room and high temperatures can be developed as a function of stress ratio R.
Axial Compressor Rotor Optimization Using a Novel Ensemble of Surrogates-Based Infill Criterion
Authors: Kamenik Jan , Stramacchia Michele , Toal David J. J. , Keane Andy J. , Bates Ron
Published: February 2018

A novel infill criterion for so-called ensemble of surrogates-based optimization is proposed and applied in practice for an aerodynamic compressor rotor design optimization. The ensemble uses a combined approach based on different radial basis functions and aims to reduce prediction errors through weighted linear combinations of radial basis functions. The update strategy uses a new hybrid custom metric termed α, which incorporates information about each surrogate’s local agreement through correlation coefficients and also information about the global accuracy of each ensemble combination through the root-mean-square error. Surrogate models are searched using a hybrid optimizer, i.e., with a genetic algorithm and sequential quadratic programming, and proposed update points are evaluated using the high-fidelity black box function. The results are compared with established optimization approaches and the best design is analyzed further in terms of the flow physics. Results show that α-based ensemble of surrogates approaches are particularly efficient for large-scale cases, where other types of surrogates such as Kriging models are onerous to construct.
Gas Turbine Inlet Air Cooling Using Vapor-Adsorption Refrigeration Driven by Power Plant Exhaust
Authors: Panyam Varuneswara Reddy , Dandotiya Devendra , Banker Nitin
Published: February 2018

Turbine inlet air cooling (TIAC) has long been the most commonly used method to improve the performance of gas turbine based power plants. It is particularly effective in regions with high ambient temperatures. With growing energy demands and higher ambient temperatures around the globe, it is important to look beyond cooling cycles like vapor-absorption and vapor-compression which have certain limitations. It is prudent to use a vapor-adsorption cycle for TIAC since the waste exhaust heat can be utilized as the power source for adsorption compressor, resulting increase in thermal efficiency of the power plant. Also, the scalability of adsorption cooling from mere Watts to hundreds of kW and its ability to function using lower temperature heat sources (as low as 60 °C) render it highly suitable for TIAC. In this paper, a gas turbine power plant and a TIAC system running on vapor-adsorption cycle are mathematically modelled and thermal analysis involving comparison of performance of the power plant with and without inlet air cooling at various ambient and desorption temperatures is presented. Performance parameters analyzed include net power output and thermal efficiency of the power plant and the COP of the chiller. The results show that vapor-adsorption system has huge potential to be integrated with gas turbine power plant for inlet air cooling.
Turbomachinery-Based Vapor Pressure Amplifier for Refrigeration Energy Saving
Authors: Chennaoui Leila , Cerri Giovanni , Alavi Sayyedbenyamin
Published: February 2018

Vapor compression refrigeration plant power consumption can be heavily reduced for a definite cooling power by the adoption of a power regeneration process internal to the simple cycle. Such a process takes benefit from the adoption of turbomachinery based vapor pressure amplifier.

The selection of the wheel sizes, their machining to be adapted to the process and the addition of stator blades in the expander and a diffuser in the compressor path is discussed and tests results are presented.

Improvements of the power consumption and of the COP of about 23–24% for a specified cooling power have been demonstrated.
Development of LP Blade Module for High Back Pressure-Aerodynamic Design
Authors: Ambrish  , Singh Nand Kumar
Published: February 2018

In steam turbine power plants, the appropriate design of the last stage blades is critical in determining the plant efficiency and reliability. The development of LP module for desert applications is finding applications for a number of industrial steam turbine operating with air cooled condensers. The conventional LP Module for water cooled condenser operates at low back pressure (Pexit = 0.09 bar) and are generally not suitable for high back pressure application. This paper focuses on the aerodynamic design & optimization of last stages of LP blade module for high back pressure application and validation through 3D CFD. The guide and moving blade are designed with seven equally-spaced profiles section from hub to shroud through Axstream S/w. The profile and incidence losses are minimized for the design and off-design conditions.

Aeromechanical design of LP blade module consisting of 2 stages for 0.2 bar back pressure, 1.1 bar inlet static pressure and a mass flow of 61.2 kg/s is carried out. An optimization process through a streamline curvature code and design optimization software using Optimus is established and flow path contours is optimized thoroughly, a total to total efficiency of 81.4% is achieved for the rated condition. The off-design performance is investigated for a wide range of operating conditions, especially at low volume flow rate of steam condition.
Aero Engine Performance Evaluation During Missile Firing Test
Authors: Manoharan Sajath Kumar , Santhosh Kasram , Padwale Mahesh P. , Ravishankar G. P.
Published: February 2018

Evaluation of engine performance during armament firing in fighter aircraft is a vital qualification aspect for airframe engine integration. Ingestion of missile’s efflux into air intake results in rapid increase of engine inlet temperatures (temperature ramps) which cause flow disturbance to the compressor. Temperature distortion caused due to armament firing and its effect on compressor stability during flight testing is evaluated. Accordingly mitigation actions are recommended for stall/surge free operations. Distortion descriptors are assessed using simulation model (engine performance program) and results compared with engine distortion limits.
Identification of Geographical Locations to Operate Savonius Wind Turbine Rotor for Meeting a Desired Performance
Authors: Roy Sukanta , Das Ranjan , Saha Ujjwal K.
Published: February 2018

In this paper, feasible geographical locations in India have been identified to meet a desired performance criterion from a Savonius wind turbine rotor involving semicircular blades. The identification is based upon the average wind speed prevailing at the relevant location. For a given turbine geometry, in order to simultaneously satisfy the required power and torque characteristics over a particular range of tip speed ratio, an inverse problem is solved with the aid of golden section search method (GSSM)-based optimization algorithm to predict the required local wind speed. For this, the minimization of the sum of least square errors between the target power and torque coefficients is done with respect to some initially-guessed power and torque values. Thereafter, based on the estimated wind speed, the reconstructed power and torque characteristic curves are validated with the experimental wind tunnel data. The necessary blockage corrections have been considered during the inverse analysis for which pertinent correlations reported in the available literature are used. The variations of the estimated parameter and the pertinent objective function are studied at different iterations of the GSSM. The effect of the initial guess on the estimated value of wind velocity is also reported and it is found that a unique solution occurs for a particular set of power and torque characteristics. The present work avoids the conventional hit and trial method based nonlinear analysis along with repetitive field tests which are otherwise needed to simultaneously generate a given power and torque performance from the Savonius wind turbine. The proposed inverse method thus can be extremely useful to determine the feasible Indian geographical locations directly from any required torque and power data.
Evaluation of Impulse Turbines for a Wave Energy Converter
Authors: George A. , Ranjith Balakrishnan , Samad A. , Dudhgaonkar P. V.
Published: February 2018

The extraction of wave energy through self-rectifying air turbine is one of the emerging technologies for oscillating water column (OWC) based wave energy devices. In the present effort, a bi-directional impulse (BDI) turbine is designed and the performance parameters were found numerically and compared with an existing unidirectional impulse (UDI) turbine. A brief analytical formulation through similarity laws, to find a dynamically similar BDI turbine using pressure drop vs flow characteristics, gives the approximate diameter range equivalent to the reference UDI turbine. The results are used to reduce the range of diameters and it is found that the characteristics are matching with the reference UDI turbine. The maximum and minimum diameters among the selected range are considered for detailed computational fluid dynamics (CFD) analysis. These two BDI turbines are modeled and meshed in ICEM CFD 14.5. The commercial CFD code CFX 14.5 is used for the numerical simulations. The Reynolds-averaged Navier-Stokes (RANS) equations with the standard k-ϵ scalable wall function model are solved to obtain the performance parameters. A detailed flow physics of the BDI turbines has also been included.
Surrogate Based Design Optimisation of Combustor Tile Cooling Feed Holes
Authors: Nagabandi K. , Mills S. , Zhang X. , Toal D. J. J. , Keane A. J.
Published: February 2018

Gas turbine operating temperatures are projected to continue to increase and this leads to drawing more cooling air to keep the metals below their operational temperatures. This cooling air is chargeable as it has gone through several stages of compressor work. In this paper a surrogate based design optimization approach is used to reduce cooling mass flow on combustor tiles to attain pre-defined maximum metal surface temperatures dictated by different service life requirements.

A series of Kriging based surrogate models are constructed using an efficient GPU based particle swarm algorithm. Various mechanical and manufacturing constraints such as hole ligament size, encroachment of holes onto other features like side rails, pedestals, dilution ports and retention pins etc. are built into the models and these models are trained using a number of high fidelity simulations. Furthermore these simulations employ the proprietary Rolls-Royce Finite Element Analysis (FEA) package SCO3 to run thermal analysis predicting surface heat transfer coefficients, fluid temperatures and finally metal surface temperatures.

These temperature predictions are compared against the pre-defined surface temperature limits for a given service life and fed back to the surrogate model to run for new hole configuration. This way the loop continues until an optimized hole configuration is attained. Results demonstrate the potential of this optimization technique to improve the life of combustor tile by reducing tile temperature and also to reduce the amount of cooling air required.
Numerical Investigations on Influence of Uniform Blade Surface Roughness on the Performance Characteristics of a Transonic Axial Flow Compressor Stage
Authors: Chotalia Ravi J. , Alone Dilipkumar Bhanudasji
Published: February 2018

Application of surface roughness to rotating mechanical bodies will result into performance degradation. In Aviation Industry, one of the most affecting causes for performance or efficiency degradation of gas turbine engine is the blade surface roughness. The aerosols which are very small particles in the atmosphere having diameters in the microns, impinges to the compressor blade inside the aircraft engine at higher altitudes. The aerosols damages surfaces of the compressor blades. Despite of having small dimensions, due to higher velocity of the aircraft, aerosol’s impinging creates roughened surfaces and fouling. This paper is an attempt to numerically evaluate the performance degradation of the single stage transonic axial flow compressor due to uniform roughness created by the aerosols. Various cases with different roughness on various sections of the blades are analyzed to study and identify which section of the blade is more influenced by roughness. The transonic axial flow compressor has a capability of producing 1.36 stage total pressure ratio, swallowing air mass flow rate of 23 kg/s at rated design speed of 12930 rpm is used for the steady state numerical analysis. A systematic steady state 3-dimensional numerical study using solver with SST k-ω turbulence model has been carried out to evaluate the impact of blade surface roughness on the performance of compressor stage. Moreover, cases with the aerosols having different dimensions and their resulting effect is also studied to find out how performance varies when the aircraft enters into atmosphere having big aerosols from the atmosphere having smaller one and vice-e-versa.
Dynamics of Cracked Viscoelastic Beam: An Operator Based Finite Element Approach
Authors: Ganguly Krishanu , Nahak Pradeep , Roy Haraprasad
Published: February 2018

The presence of crack introduces local flexibilities and changes physical characteristics of a structure which in turn alter its dynamic behavior. Crack depth, location, orientation and number of cracks are the main parameters that greatly influence the dynamics. Therefore, it is necessary to understand dynamics of cracked structures. Predominantly, every material may be treated as viscoelastic and most of the time material damping facilitates to suppress vibration. Thus present study concentrates on exploring the dynamic behavior of damped cantilever beam with single open crack. Operator based constitutive relationship is used to develop the general time domain, linear viscoelastic model. Higher order equation of motion is obtained based on Euler-Bernoulli and Timoshenko beam theory. Finite element method is utilized to discretize the continuum. Higher order equation is further converted to state space form for Eigen analysis. From the numerical results, it is observed that the appearance of crack decreases the natural frequency of vibration when compared to an uncracked viscoelastic beam. Under cracked conditions, the viscoelastic Timoshenko beam tends to give lower frequency values when compared to viscoelastic Euler-Bernoulli beam due to shear effect.
Characteristic Parameter Estimation of AMB Supported Coupled Rotor System
Authors: Kuppa Sampath Kumar , Lal Mohit
Published: February 2018

In this article, a rotor–bearing–coupling system supported by Active Magnetic Bearings (AMBs) is numerically simulated to estimate the characteristic parameters of AMB, residual unbalance, and misalignment parameters. The system is modeled with two rigid massless rotors each having a rigid disc and an AMB at its mid-span, mounted on flexible bearings and connected together with a flexible coupling. Proportional–Differential–Integrator (PID) is used to control the controlling current in AMB. Lagrange’s equation is used to obtain the linear equations of motion (EOMs) of the system. The developed EOM is solved by the fourth order Runga–Kutta method to generate the displacement and current responses. The time domain responses are converted into frequency domain by using Fast Fourier Transform (FFT) and full spectrum analysis is carried out to estimate the characteristic parameters of rotor AMB system. The estimation of parameters is performed based on least squares approach in frequency domain. The proposed methodology is tested against different levels of measurement error and modelling error to check the robustness of the algorithm.
Flashback and Lean Blow Out Study of a Lean Premixed Pre-Vaporized Can Combustor
Authors: Verma Harendra K. , Kumar Arvind , Kumar Keshav , Mohammed Rinaz
Published: February 2018

The latest trend in aero engine industry is to reduce the emission levels to a maximum extent as well as to improve the combustion efficiency. One of the ways to reduce the emission levels and improve the combustion efficiency in gas turbine combustors is to operate with lean premixed conditions. However, design modifications are required in conventional combustors to operate at lean premixed conditions.

A new combustor configuration was studied for lean premixed pre-vaporized (LPP) combustion. To arrive at LPP configuration a simple gas turbine Can-combustor geometry is modified by attaching a fuel air premixer chamber at upstream of the flame tube of basic diffusion combustor [1]. Reactive flow analysis was performed with both the LPP and conventional diffusion combustor using commercial CFD tool Fluent. Significant improvements were obtained from LPP combustor in terms of emission reduction. However, there are limitations for lean burning of fuel such as flashback and lean blow out. Present work is focused on studying these issues on the LPP combustor. These methodologies can be extended for other type of combustors after further studies.
Numerical Simulation of Cluster of Small Vertical Axis Wind Turbine to Develop a Wind Tree for Low Wind Speed Regime
Authors: Thomai Micha Premkumar , Thangaraj Mohan , Palanivel Silambarasan , Sivamani Seralathan
Published: February 2018

The importance of renewable energy has increased continuously in the recent years due to the growth in the energy demand and a decrease in the fossil fuel resources. Harnessing the low rated wind energy is the promising source so that the wind turbine can be used all year round. Deploying sequence of small turbine is efficient than single bigger size turbine in extracting the low rated wind energy. Hence, in this work, sequence of small vertical axis wind turbine is arranged in the tree like structure and named it as wind tree. The vertical axis type of turbine would be able to perform more efficiently at minimum wind velocity. So, the Helical Savonius vertical axis rotor is deployed in the wind tree which gives the relatively high torque and self-starting even at low wind speeds. The main aim of this work is to analyze numerically the cluster of vertical axis wind turbine in order to improve the average output of the wind tree. In this study, the vertical axis turbines are arranged in the branches of the tree at different plane, so that the wake of one turbine will not affect the turbine in the downstream. The numerical simulation has been studied by using commercially available software ANSYS CFX©. The single helical vertical axis wind turbine is fabricated and tested in the open jet wind tunnel and this experimental result is used for validating the numerical results. In addition to the validation, sensitive study for the grid and the turbulence model has been carried out to improve the simulation quality. Vertical axis wind can accept wind from any direction without any yaw mechanism, so the average performance of this type of turbine in cluster is analyzed by changing the flow (α = 0°, 45° and 90°) of the wind turbine cluster. It is observed from this study that the average power coefficient of the cluster of turbine at the flow angle of 45° has better performance than the other pattern. Moreover, its average power coefficient is 2.3 times higher than the isolated vertical axis wind turbine. These results of the cluster simulation are used to develop an efficient wind tree to harness the low rated wind energy.
Mean-Line Modelling of a Variable Geometry Turbocharger (VGT) and Prediction of the Engine-Turbocharger Coupled Performance
Authors: Thomas Anand Mammen , Samuel Jensen , Ramesh A.
Published: February 2018

Mean-line modelling approach which has generally been applied to fixed geometry turbocharger turbines has been extended to predict the performance of the variable geometry turbine for different inlet blade angles. The model uses an initial assumption of turbine inlet pressure which was iteratively corrected based on outlet pressure boundary condition. The model was implemented in MATLAB and stable and convergent solutions were obtained using relaxation techniques for different operating conditions. Experiments were done on a state of the art transient diesel engine test bed using the same VGT turbine in the turbocharger at different engine torques and speeds. Using experimental data the model was calibrated for the aerodynamic blockage in the fixed nozzle and rotor blade passages. Results revealed that turbine overall pressure ratio can be predicted accurately if a blockage factor varying with nozzle blade orientation is used in the model.
Application of Cold Expansion Process to Dovetail Slots of Compressor Disc: A Numerical Study
Authors: Kumar Sudhakar Anil , Babu Neelakantanahally Channaiah Mahendra
Published: February 2018

Dovetail slots are essential structural cut-outs made in compressor disc to assemble blades. Under in-service centrifugal loading and inherent vibrations, the root regions of these dovetail slots are prone to fatigue failures. Surface treatment methods like shot peening, low plasticity burnishing and laser shock peening are employed to achieve fatigue life extension of dovetail slots. Another method commonly employed in aerospace industry for fatigue life extension of circular holes is the cold expansion process. This cold expansion process is a proven surface treatment method capable of achieving highest fatigue life enhancement benefits compared to other surface treatment methods, particularly for circular holes. Considering the efficacy of circular hole cold expansion process, an attempt is made in this work to study the suitability of cold expansion process for dovetail slots.

In this work, a three dimensional, non-linear Finite Element simulation has been carried out to explore the application of cold expansion process for dovetail slot of a compressor disc. This Finite Element simulation involves two main steps namely, cold expansion of holes and machining process between holes. Two circular holes of appropriate radius at root locations of dovetail slot are cold expanded to introduce beneficial compressive residual stresses and further, portion between the two holes is machined-off to obtain the required dovetail shape. Complete distributions of beneficial compressive residual stresses retained after machining of dovetail slot are captured to assess the efficacy of cold expansion. The predicted results indicate that the proposed cold expansion process for dovetail slots is capable of significantly enhancing the fatigue life of dovetail slots.
Multiple Low Velocity Impact on Twisted Composite Stiffened Blade: A Finite Element Approach
Authors: Rout Mrutyunjay , Hota Sasank Shekhar , Karmakar Amit
Published: February 2018

This paper presents the numerical modeling of a twisted stiffened cylindrical shell employing finite element approach to investigate the transient response due to impact of multiple masses, wherein the shell and the stiffener are modeled as 8 noded isoparametric shell element with five degrees of freedom per node and 3 noded isoparametric curved beam element having four degrees of freedom per node, respectively. The stiffener element is considered as a discrete beam element and its nodal degrees of freedom are transferred to the corresponding degrees of freedom of the shell element considering curvature and eccentricity. The impact force is predicted by employing modified Hertzian contact law relating the contact force to local indentation. As indentation takes place the impactor induces damage and permanent deformation in the contact zone of stiffened panel, as a result the loading and unloading curves are different. Different mathematical equations are considered for both loading and unloading cases in the stiffened panel during low-velocity impact. The accuracy and effectiveness of the finite element approach is verified by comparing the results with the corresponding solutions of analytical as well as standard computational methods available in the open literature. The optimum design of a structure can only be obtained by understanding the impact behavior and the roles of various parameters affecting the response. Hence, parametric study has been carried out to predict the time histories of contact force, displacement of the impact point and in-plane stresses during low-velocity concurrent/delayed impact at multiple locations of the stationary and rotating stiffened shell.
Numerical and Experimental Investigations on Liner Heat Transfer in an Aero Engine Combustion Chamber
Authors: Narayana Rao Korukonda Venkata Lakshmi , Prasad B. V. S. S. S. , Kanna Babu Ch. , K. Degaonkar Girish
Published: February 2018

The Gas turbine combustion chamber is the highest thermally loaded component where the temperature of the combustion gases is higher than the melting point of the liner that confines the gases. Combustor liner temperatures have to be evaluated at all the operating conditions in the operating envelope to ensure a satisfactory liner life and structural integrity. On experimental side the combustion chamber rig testing involves a lot of time and is very expensive, while the numerical computations and simulations has to be validated with the experimental results. This paper is mainly based on the work carried out in validating the liner temperatures of a straight flow annular combustion chamber for an aero engine application. Limited experiments have been carried out by measuring the liner wall temperatures using k-type thermocouples along the liner axial length. The experiments on the combustion chamber testing are carried out at the engine level testing. The liner temperature which is numerically computed by CHT investigations using CFX code is verified with the experimental data. This helped in better understanding the flow characterization around and along the liner wall. The main flow variables used are the mass flow rate, temperature and the pressure at the combustor inlet. Initially, the fuel air ratio is used accordingly to maintain the same T4/T3 ratio. The effect of liner temperature with T3 is studied. Since T4 is constant, the liner temperature is only dependent on T3 and follows a specific temperature distribution for the given combustor geometry. Hence this approach will be very useful in estimating the liner temperatures at any given T3 for a given combustor geometry. Further the liner temperature is also estimated at other fuel air ratios (different T4/T3 ratios) by using the verified CHT numerical computations and found that TL/T3 remains almost constant for any air fuel ratio that is encountered in the operating envelope of the aero engine.
Numerical Analysis of Direct Type Greenhouse Dryer
Authors: Gupta Vishal , Sharma Abhishek , Gupta Khushboo Sabharwal
Published: February 2018

For food preservation, drying techniques is most widely used. Earlier drying was done openly in sun. But now with increased awareness, drying of agricultural produce is done with care. Greenhouse dryers are being mostly used. Good greenhouse dryers are considered one which can dry products in short span of time. For obtaining good quantity of dried products, the design of greenhouse dryer should be such that the air circulation is good and high temperature can be achieved near the crops. In present work, Computational Fluid Dynamics (CFD) approach has been used to visualize the air flow pattern and temperature distribution near the crops i.e., inside the direct type greenhouse dryer. Experimentally obtained data has been used as boundary conditions and numerically obtained results are helpful in understanding local parameters which cannot be found out experimentally.
Methods to Reduce Hot Return Condensate Temperature Without Compromising Plant Efficiency for Combined Heat and Power Plants
Authors: Addanky Anil Kumar
Published: February 2018

This paper describes five methods to achieve effective heat transfer and higher plant efficiency when condensate return temperature is high and treatment is needed to improve water quality in the water treatment plant before sending it to the deaerator for a combined heat and power plant.
Sub Modeling in Dynamic Analysis
Authors: Devadoss Gnanaraj , Thokala Anil , Kumar Avinash , Bysani Prasanth Kumar
Published: February 2018

In design of components, it is more convenient to analyze the component alone by modeling all the interface loads / displacements as boundary conditions rather than modeling the entire assembly. This process of analyzing at component level is referred as sub model analysis. Most of the assembly level model consists of several components and each component may have different owners. In cases where the entire assembly level model cannot be shared with component owners due to confidentiality, Sub model analysis is the preferred approach. Sub-model analysis also reduces overall model size and in turn the solution time.

Sub modeling is widely used approach in static structural analysis. In dynamic analysis, response of any system is a function of its stiffness, damping and inertia properties along with the applied loads. Sub model will have different inertia, stiffness and damping representations when compared with the assembly level model (also known as full model). The effect of these differences on sub model responses compared to full model needs to be investigated to validate sub modeling approach in dynamic analysis.

In this paper it is shown mathematically and also using finite element analyses that the dynamic response of a component is same between sub-model analysis and full model analysis. In sub-model analysis, dynamic behavior of the remaining system is captured by applying interface loads at component interfaces (with remaining model) which in turn is obtained from full model analysis. Frequency domain finite element model with harmonic excitations is considered to validate the sub modeling approach in dynamic analysis. The observations and conclusions inferred from this frequency domain analysis are also applicable for time domain analysis.

This study is carried out using MSC Nastran.
Sensor Data Validation in a Developmental Aero Gas Turbine Engine
Authors: Srinivasan Usha , Nagalingam Muthuveerappan
Published: February 2018

Diagnosis, isolation and corrective action of incipient faults in a developmental Aero Gas Turbine Engine, mandates advanced warning of the emerging faults by apt and timely degradation monitoring in order to mitigate catastrophic failure. This calls for cautious performance monitoring during the test runs by instrumenting the engine under test with multiple sensors to acquire the physical parameters like temperature, pressure, flow and speed which are indicative of the engine degradation. Sensor reliability is critical to engine control and performance monitoring. Sensor data which serves as the primary key for assessing the engine behaviour needs to be validated before its use in determining the degradation. Particularly in a developmental engine under test, the accuracy and reliability of measurements creates the basis for understanding the engine behaviour, in order to evaluate its performance. This paper targets to develop validation tool to ensure that only trusted sensor measurements are used for engine performance computation by weeding out the erroneous data. The pre-processing of data to ensure its accuracy also serves as a “need for maintenance indicator” to warn the operator for sensor breakdowns, wearing or deterioration and detect calibration needs. Development and validation of the LabVIEW based “Sensor Data Validation Tool (SDVT)” using the actual test run data constitutes the main body of this paper along with concluding remarks which brings out the validation results and the required maintenance action.
Analysis of Infinitely Short and Infinitely Long Hydrodynamic Journal Bearings Under Micro-Polar Fluid by Direct Integration Method
Authors: Routh Bikash
Published: February 2018

In the present paper Reynolds equation of lubrication under micro-polar fluid for journal bearing is solved by direct-integration method under infinitely long and infinitely short journal bearing assumptions [1]. Infinitely long-bearing and infinitely short bearing solutions are the two available approximate closed form solutions for journal bearings. In the present investigation, solution of Reynolds equation i.e. pressure profile is compared with pressure profile obtained by previously used approximate method like finite difference method (FDM). Mentionable here that any approximation method needs lots of calculation and computer programing to get the result. In the present work it has been found that direct-integration method leads the almost same result as the conventionally used complex finite difference method. CFD analysis is also presented in the present work to justify the profile obtained by direct numerical method. It has seen here that theoretical and simulation results are in good agreement to each other’s.
Reliability of Ti/SiC Metal Matrix Composites
Authors: Mishra Ashish , Mahesh Sivasambu
Published: February 2018

Components such as bladed rings, and bladed disks fabiricated out of titanium matrix composites were extensively explored in the two decades since about 1990 as light weight replacements for conventional superalloy blades and disks in the intermediate hot stages of gas turbines. One of the challenges, which has hindered their adoption is the relative unreliability of the composite components; nominally identical Ti composite specimen display a much larger variability in strength than their superalloy counterparts.

In the present work, we have quantified the reliability of Ti matrix composites by developing a detailed micromechanical-statistical model of their failure. The micromechanical model resolves fibres, matrix, and the interface, and accounts for such failure modes as fibre breakage, matrix cracking, matrix plasticity, interfacial sliding, and debonding. It also accounts for mechanical interaction between these various failure modes. The mechanical model’s predictions are validated against synchotron X-ray measurements reported in the literature, both after loading, and unloading. Using the detailed micromechanical model, Ti matrix composite was simulated following a Monte Carlo framework. These simulations yield the empirical strength distribution of the Ti matrix composite, and insights into the dominant failure mode. The latter allows the construction of a stochastic model of composite failure. The stochastic model can be used to determine safe working loads as a function of composite size for any desired reliability level.
Suction Mode Start Characteristics of a Turbofan Engine for a Windmill Relight
Authors: Bhatt Ashish , Balaji B. , Tyeb Abdullah , Gupta Amit , Padwale Mahesh P. , Ravishankar G. P.
Published: February 2018

Wind-milling occurs when air flowing through the flamed out engine results in increasing spool rotation. Aircraft forward speed and dive angles play an important role in achieving sustainable spool rotation for relight. Aircraft fuel pump connected to power take-off shaft of Engine shuts when engine rpm falls below design speed and cannot deliver pressurized fuel to Engine during wind-milling. Under this condition, engine has to suck the fuel from aircraft using its own fuel pump. The atmospheric pressure available on the aircraft fuel tank assists the engine to operate in suction mode. The datum height between engine inlet and fuel tank outlet changes with the dive angle of the aircraft.

A test set up was established in the engine test bed to vary the datum between aircraft fuel tank and Engine inlet. The datum was varied to simulate various dive angles of the aircraft. The negative gravity head (Engine fuel inlet above fuel tank outlet) between engine and fuel tank was varied in steps. Total four test cases were carried out in an engine test bed located at an altitude of 920 m above sea level. The engine was successfully started in suction mode without external assistance of fuel pump. This paper presents the test setup, comparison of engine start cycle under various dive angles of the aircraft to evaluate optimum flight conditions to attempt windmill relight.

These tests show that as the negative gravity head is increased, the time taken to start the engine increases. The slope of N2 build up becomes shallower with increase in gravity head.