bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards Use of Structural Equation Modelling in Enumerating Correlation of Qualitative and Quantitative Factors With Manufacturing Part Deviation
Authors: Srinivasan Karthik , Kumar G. V. V. Ravi 
Published: February 2024

Abstract
A typical gas turbine part that is fitted into an aero engine goes through many manufacturing processes spread across multiple supply chain organizations. Despite high precision standards in comparison to other industry segments, geometrically complex parts in gas turbine do end up deviating from design geometries. These parts go through visual inspection at every stage in addition to dimensional measurement of critical characteristic features. Operator involvement is un-avoidable at present and despite being process driven, operator level variances are not ignorable in manufacturing operations. With Industry 4.0 being adopted by many industries, and 5.0 emerging, user involvement is minimized, and a large amount of data is generated and captured throughout the process of manufacturing, testing, verification, assessment and sentencing of parts for use in aerospace industry. As data is becoming increasingly centralized by adoption of cloud technologies, it becomes more efficient to troubleshoot problems through mathematical modelling — the brain behind Artificial Intelligence (AI). Structural Equation Modelling (SEM) has been in use for long in management sciences and decision making involving ill-defined factors and that have strong interdependencies.
This article presents a methodology of leveraging SEM technique in identifying correlation of qualitative and quantitative factors with part deviation assessment. A framework for converting qualitative inspection information to quantitative information is presented to leverage SEM. The implementation is explained using a representative data for a turbomachinery airfoil to demonstrate the approach and considerations. Few use cases of SEM in the industry are also presented.
Inlet Distortion Studies on a Centrifugal Compressor
Authors: Jaiswal Sujeet Kumar , Bubanale Sadashiv , Keerthi M. C. 
Published: February 2024

Abstract
Centrifugal compressors can be subjected to non-uniformity in inlet flows due to complicated inlet pipe geometries arising from space constraints and the wakes of protruding instrumentation, impacting the compressor’s performance. Inlet distortion can cause premature stall initiation and surge, effectively reducing the operating range of the device. This motivates a detailed characterization of the performance for different types of inlet distortion. While the impact of distortion in axial compressors is studied extensively, there are relatively fewer studies for centrifugal compressors. The present study investigates the effects of inlet total pressure distortion on the performance of a centrifugal compressor. The rig employing a centrifugal compressor of a turbocharger is developed and built for the study to analyze full-speed compressor aerodynamics. The experimental setup comprises of a turbocharger, whose turbine is driven through flow-metered compressed air, enabling independent control of the shaft speed by adjusting the flow rate and pressure. The compressor section line is instrumented with pressure sensors, thermocouples, shaft RPM sensor, to enable the measurements required to generate the compressor characteristics. A typical operating point of the compressor with clean inflow at 130,000 RPM is a pressure ratio of 1.4 with a mass flow rate of 0.02 kg/s. Provision is added to include distortion screens to generate total pressure distortion at the inlet duct of the compressor. A PC-based data acquisition program is developed to acquire and monitor the compressor map data as well as monitor other parameters for the purposes of safety and maintenance. The distortion screens are fabricated and characterized as per the SAE ARP 1420 distortion descriptors to generate circumferential and radial total pressure distortion for different cases. The compressor performance with clean inflow is compared with different distortion screens in terms of the static pressure ratio, isentropic efficiency, for a given normalized mass flow rate and normalized RPM. In the presence of inflow distortion, the compressor performance is expectedly found to deteriorate, particularly with a lower pressure rise at the same RPM and flow rate. For a given RPM, the effect is substantial near choke compared to the near-surge region. The decrease in isentropic efficiency is more significant at higher RPMs and near choke. A detailed account of the impact of different types of distortion, in terms of their circumferential and radial distortion intensities, on the compressor global performance, along with insights gained from the local measurements, are presented.
Structural Validation of Portable Compressor Trailer Under Dynamic Conditions
Authors: Bhirud Mehul , Valand Bharatkumar , Rathod Ankit 
Published: February 2024

Abstract
Portable air screw compressors are the most reliable, effective, and well-suited for the unique needs of building roads, performing restoration work, conducting civil engineering, mining, sandblasting, oil and gas exploration etc. This compressors must be designed to withstand tough site circumstances and difficult-to-reach site locations that may have challenging topography. Compressed air at remote locations is also used to power tools on the site, such as power hammers, drills, saws, wrenches, nail guns etc. These portable compressors are exposed to higher load such as dynamic load, lifting/towing load and random vibration load during their operation such as towing/lifting and transportation from one location to another. Fatigue life, stability and performance of majority of the structures and systems depend significantly on dynamic loadings applied on them. In order to guarantee effective product performance without trolley base frame failure over product life, it is crucial to examine the structural strength of the compressor base frame under such dynamic loading scenarios.
Ingersoll Rand India is equipped a portable compressor unit using cutting-edge technology to meet the requirements of the business. The Modal and random vibration analysis of the portable compressor trolley base frame has been analyzed in the current study to evaluate the compressor trolley base frame. To verify dynamically, the unit’s Natural Frequency has been computed using modal analysis. According to SAE J 2380 standard, random vibration analysis has been performed to examine the base frame’s strength and its fatigue life against random loading for 92.6 hours of testing duration. Successful validation of a given equipment implies 100000 miles of life with 90% success probability without any random vibration fatigue failure. A thorough investigation of modal and random vibrations analysis was performed using ANSYS 2020 R2. Random vibration analysis was performed by applying PSD G acceleration at support base as per SAE J 2380 standard. The strength of the trolley base frame has been evaluated through a number of parameters, such stress accumulation, natural frequencies, fatigue life, and damage factor.
According to the results of the investigation, estimated system natural frequency was found away from the operating frequency of the system which ensure the system will operate without critical resonance and high stresses while in operation. Under the random vibration analysis, random fatigue life, random fatigue damage factor and equivalent stress were found to be acceptable. According to the numerical investigation, the compressor’s base frame was unlikely to fail during its service life against the dynamic loads random in nature. Physical test of the compressor unit was also carried out for various road profiles and found the system structurally strong enough & having good degree of agreement with virtual validation.
Application of Machine Learning Based Meta Models for Predicting Film Cooling Effectiveness in Gas Turbine Blades
Authors: Grover Amit , Shrivastava Rishabh 
Published: February 2024

Abstract
In Large Gas Turbines, turbine components in particular blades and vanes operate at significantly high temperatures. As a result, cooling of these components becomes one of the prime objectives during the design phase. There are different cutting-edge internal cooling techniques such as convection cooling - internal ribbed surface heat transfer only, serpentine passage, impingement cooling, film cooling and combination of all these methods are used to meet the heat transfer design requirements. Among all methods, film cooling plays a vital role in the improvement of heat transfer and is extensively applied to ensure thermal protection of hot gas path components especially blades and vanes. A precise estimation of film cooling effectiveness is critical for evaluating external heat transfer and metal temperature. Conventional approach based on heat transfer correlations and finite element method with varied film cooling scheme is highly resource intensive which involves setting up different cooling schemes. The model setup process includes geometrical modeling, meshing of model, boundary conditions application and performing thermal simulation to achieve optimal design. This constrained the number of film cooling hole configuration which could be evaluated, resulting in sub-optimal design in terms of cooling effectiveness.
In this work Machine learning approach is explored for establishing optimal film cooling hole configuration with minimal time and efforts and can be applied during early design phase. Film cooling effectiveness is influenced by several factors like coolant & mainstream conditions, cooling hole arrangement and other geometrical parameters such as cooling hole diameter, inclination, pitch, breakout, coverage, and location on the airfoil geometry etc. In current scope cooling hole diameter, pitch, cooling hole count, and surface angle is used as input feature to the Machine Learning model and cooling effectiveness as target variable. The input to the Machine learning model is derived from physics-based heat transfer calculations. A comparative study is introduced between linear regression, K-nearest neighbour, random forest, and gradient boost Machine learning methods using root mean square values as an evaluation metrics. Optimal hyperparameter were calculated for each model using grid search method. It was observed that gradient boost method shows minimum error, additionally cooling hole count is the most significant factor in predicting cooling effectiveness.
Application of Advanced Sampling Techniques to Handle Class Imbalance in GT Blade Failure Prediction
Authors: Shrivastava Rishabh , Lalchandani Rohan , Pohekar Advait , Sharma Krishnandu , Vodnala Pavan 
Published: February 2024

Abstract
The Blades of a Gas Turbine Engine are subjected to an exceedingly high temperature, pressure, and centrifugal load during its operation. Consequently, they exhibit a heightened susceptibility to failure modes such as creep, crack initiation and growth, HCF, Flutter, and Oxidation. Attaining accuracy in the prediction of these failure modes is of paramount importance. Traditionally this has been achieved by Finite element packages, discretizing the problem into finite elements, applying the necessary boundary conditions, and solving a mathematical equation for each of these finite elements. The process involves a numerical solution of differential equations that govern these physical phenomena. However, this pursuit is not without tradeoff, as it demands a significant investment of temporal, human, and computational resources. To minimize mentioned efforts, advanced data-driven techniques can be implemented to predict the creep failure instances. Machine learning is gaining significant traction for solving these kinds of problems because of advances in storage and computational power. Machine learning focuses on using data and algorithms to learn the pattern and make prediction on unseen data with substantial accuracy. Generally, machine learning can be classified into supervised and unsupervised learning. In this work we are developing a machine learning based classification model (supervised learning) to capture the failure instances. Failure prediction using Machine learning is generally encountered with higher prediction error because of imbalanced dataset (minority class is the focus of attention — less than 5% of data). This paper deals with the approach of improving turbine failure prediction using various sampling techniques. Random Oversampling, Synthetic Minority Oversampling Technique – SMOTE, Tomek Links and combine SMOTE-Tomek links sampling methods are utilized to generate a balanced dataset for improving Machine Learning model performance. Coolant mass flow rate, Hot gas mass flow rate, Coolant Temperature, Turbine Inlet Temperature and Blade Material are provided as an input to the Machine Learning model, and on the other hand, a binary variable indicating creep failure instances is set to be the target variable for the model. The Machine Learning models used for prediction are Naïve Bayes classifier, Random Forest, Adaboost and gradient boost methods. The results demonstrate that among all the sampling technique mentioned above, combined SMOTE-Tomek link sampling method resulted in maximum improvement of recall and F1 score.
Characteristics of Laminar Separation Bubble With Varying Leading-Edge Shapes and Deflections of the Trailing-Edge Flap
Authors: Sarvankar Sumit S. , Sarkar Drik , Sureshbhai Mistry Chetankumar , Rao Vadlamani Nagabhushana 
Published: February 2024

Abstract
A series of Implicit Large Eddy Simulations (ILES) is carried out to examine the characteristics of a leading edge (LE) separation bubble. The test case comprises a flat plate with an elliptic leading edge which is equipped with a trailing edge flap. Simulations are carried out (a) at three different flap angles (20°, 30°, 90°) and (b) using two different geometries of Elliptic Leading Edge (ELE) where the ratio of the semi-major to semi-minor axis is set to either 2:1 or 4:1. The flap is modeled using the immersed boundary method which is computationally economical as it avoids regenerating the grid for varying flap angles. The results show that (a) the flow separates at lower flap deflection angles with a decrease in the aspect ratio of the ELE from 4:1 to 2:1 (b) an increase in the flap angle promotes separation at the LE due to an increase in the blockage in the bottom passage and a subsequent increase in the flow incidence at the leading edge. Simulations are also carried out using the γ – Reθ transition model and comparisons are drawn against ILES and experiments. Although the qualitative trends predicted using both ILES and Reynolds Averaged Navier-Stokes (RANS) are in agreement with the experiments, both approaches predict relatively shorter separation bubbles. This is attributed to the excess flow blockage in experiments due to the support plates which are not modeled in the simulations. Nevertheless, the results demonstrate the superior accuracy of ILES over the Reynolds Averaged Navier Stokes (RANS) model.
Aerodynamic Design Aspects for Small-Size Transonic Contra-Rotating Fan Stage
Authors: Pasupula Manideep , Mistry Chetan S. 
Published: February 2024

Abstract
Contra-Rotating fan stage presents a potential solution to address the demand for sustainable and efficient aircraft requirements. The objective of this work is to design and investigate numerically a contra-rotating axial fan stage for a compact transonic engine. The design process begins with the use of mean-line analysis and fundamental work balance method to determine the initial design parameters. This design is then optimized through computational fluid dynamics (CFD) analysis. The fan stage is designed using a constant-tip design approach with a tip diameter of 300 mm. To design the rotors, the double circular arc (DCA) airfoil is utilized with an elliptical leading edge and a cut-off trailing edge. The front rotor is designed with an aspect ratio of 0.8, while the aft rotor has an aspect ratio of 0.6. The overall pressure ratio of the contra-rotating fan stage is 3.5. The study investigates various pressure loading ratios between the front and aft rotors, with a tip-loaded configuration for both rotors. The SST k-ω and BSL turbulence models are used for numerical investigation, with the γ-θ model used to capture the transitional turbulence. The CFD analysis reveals that the flow reaches supersonic speeds in the front rotor’s upper half and the aft rotor’s entire span. This suggests that the design and optimization of the blade for the fan stage must take into account the effects of supersonic flow on the performance and efficiency of the fan stage. Many parameters are considered while designing the blade such as blade thickness, chord length, leading edge radius, trailing edge radius. Varying the blade thickness moves the contact point of the adjacent blade’s leading edge bow shock towards the trailing edge thus ensuring acceleration of the flow on the most of suction surface and reducing the risk of flow detaching & stall. The maximum relative Mach number for the front rotor is 1.3 and for the aft rotor is 2.7. The flow physics of the aft rotor is much more complex and unconventional than the front rotor’s, as the rotor’s whirl velocity is relatively much higher due to the opposing rotation. Results indicate that in the aft rotor, the blade throat is shifted significantly due to the high stagger, causing shock interactions and increasing the complexity of the downstream flow.
Design of a Facility for Testing Centrifugal Compressors
Authors: C. Kishore Kumar , Anand Jaiprakash , S. Ganesan , Govardhan Raghuraman N. 
Published: February 2024

Abstract
Centrifugal compressors are key elements in turbochargers and small gas turbines, making their performance evaluation essential for system efficiency and energy savings. This paper outlines creating and validating a specialized experimental setup designed for in-depth research on centrifugal compressors. The setup allows for the study of various impeller and diffuser configurations, flow-field analysis using Particle Image Velocimetry, and the investigation of inlet distortions, among other future research topics. The paper details the approach used to build the setup and validates its functionality through a case study featuring a research compressor with a vaneless diffuser. A characteristic map generated using Computational Fluid Dynamics (CFD) is used as a benchmark for comparison with experimental data. Initial results show a strong correlation between the CFD and experimental data in terms of flow rate and pressure ratio, validating the setup’s effectiveness. The overall performance aligns with existing research, confirming the setup’s value as a reliable platform for future studies on centrifugal compressors.
Effects of Recess Length of Bluff Body on Lean-Premixed Swirl-Stabilized CNG-Air Flame Structure
Authors: Huda Noorul , Soni Surendra Kumar , De Santanu 
Published: February 2024

Abstract
The stability of lean premixed turbulent swirl flames has been investigated using a laboratory-scale swirl-stabilized gas turbine combustor by varying the position of the bluff body inside the premixing tube. The relative location of the bluff body with respect to the dump plane is characterized in terms of a recess length, which is varied during the experiment. The resultant flame structure and dynamics have been studied for different bluff body recess lengths and bluff body shapes based on highspeed OH*-chemiluminescent images. Herein, we employ two different tapered bluff body shapes of an area ratio of 40% (B40) and 60% (B60). For the bluff body B40, a stable flame is mainly attached to the burner at a higher equivalence ratio. For a lower equivalence ratio, a lifted and elongated flame is formed. The increase in the recess length brings the flame closer to the burner surface, and a stable and intense flame is observed. For the bluff body B60, a less stable elongated and columnar type of flame is formed, and the flame stability slightly improves with the increase in recess length. The change in recess length significantly improves combustor performance when B40 is used instead of B60.
The increase in recess length is supposed to bring the recirculation created in the wake of the bluff body close to the exit of the premixing tube, resulting in better mixing of the inlet reactants and hot combustion products. This effect is less prominent for the B60 case, and high bulk velocity squeezing from the edges of B60 may not result in the effective mixing of inlet reactants and hot combustion products. The high bulk velocity for the B60 case may result in the delayed expansion of the inflow reactants, and all these combined effects may render ineffective for the B60 case.
Exploring the Effects of Synthetic Gaseous Fuels on the Performance, Combustion, and Emission Characteristics of a Dual Fuel Diesel Engine
Authors: Das Samar , Kalita Pankaj 
Published: February 2024

Abstract
This current experimental investigation attempts to explore the engine performance, combustion behaviour, and exhaust emission of a 3.5 kW capacity diesel engine utilizing synthetic-biogas (SBG), synthetic producer gas (SPG), and SBG-SPG mixture under dual fuel (DF) mode. SBG is prepared by mixing methane (CH4) and carbon dioxide (CO2) at 60:30 ratio. Similarly, hydrogen (H2) and carbon monoxide (CO) are also mixed at a 50:50 ratio for the preparation of SPG. Again, H2 and CO at a 50:50 ratio is mixed with a 60:30 ratio of CH4 and CO2 to simulate the SBG-SPG mixture. Engine experiments were executed at standard engine conditions of injection timing (IT) of 23° BTDC and compression ratio (CR) of 17.5 with five different engine loading conditions viz. 20%, 40%, 60%, 80%, and 100%. Maximum brake thermal efficiency (BTE) and pilot fuel replacement (PFR) were obtained at full engine loading condition. At this operating condition, SBG, syngas, and SBG-SPG mixture showed a BTE of 18.2%, 15.92%, and 18.89% respectively. Similarly, PFR of 84%, 78.74%, and 82.92% was found in case of SBG, SPG, and SBG-SPG mixture respectively. The combustion data indicated a decrement in ignition delay (ID) and increment in cylinder pressure with higher engine load. At 100% engine load, minimum ID of 20, 21 and 22° crank angle (CA) was obtained for SBG, SPG, and SBG-SPG mixture respectively. Again, highest peak cylinder pressure (PCP) was obtained for SBG-SPG mixture. It has also been observed that on an average, SPG resulted in higher emission including oxides of nitrogen (NOx), hydrocarbon (HC) and carbon monoxide (CO) compared to SBG. However, mixture of SBG-SPG resulted in 57.48, 0.09 and 5.6% reduction in NOx, HC and CO emissions respectively as compared to SPG.