bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experiences on Project-Based-Classes for Turbomachine Design in an Aerospace Engineering Undergraduate Program
Authors: Tomita Jesuino Takachi , Barbosa João Roberto , Bringhenti Cleverson 
Published: September 2014

At Technological Institute of Aeronautics-ITA, the Flow Machines for Aerospace Applications course deals with turbopumps. It is offered to students of the second professional year in the undergraduate program. The objective of the course is to present enough information for the students to learn about machine preliminary design.
The theory involved in flow machines is multidisciplinary, so that the students must fully understand the principles of fluid mechanics, heat transfer, gas dynamics and thermodynamics, whose complete understanding is vital to start the design of such machine.
Lack of understanding the basic theory due to the problems like difficulty of associating the velocity triangles to blade angles, blade camber, incidence and deviation angles, makes the subject more complex than it really is. This problem is mitigated with hands-on activities during practical classes.
In this work, the syllabus of flow machines design course at ITA is presented, details of how the subjects are taught and the procedures used during the classes are reported, based on real life engineering project. After a period of theory and lab classes the students are requested to do a complete preliminary design of a turbomachine, using adequate numerical tools based on specs of a turbomachine. The instructor follows the class with discussions towards adjustments that could result in operational characteristics improvement. The project starts with meanline calculations to produce the base geometry and proceeds up to 3D CFD calculations to check the performance of the designed turbomachine and to subsidize design modifications. Experience exchanged with students are reported and commented aiming at course improvement.
Self Healing Fusion Welding Technology
Authors: Gontcharov Alexandre , Liburdi Joe , Lowden Paul , Nagy Douglas , Patel Nikesh 
Published: September 2014

The properties of laser, microplasma and GTAW welds on representative gas turbine blade materials are disclosed. Proprietary filler materials and technology were used to clad multipass welds onto IN738, RenéN5 and CMSX4 alloys which were then subject to vacuum heat treatment before testing.
It was found that welds with a bulk content of boron up to 0.6 wt. % demonstrated a capability to heal cracks adjacent to the fusion line (HAZ cracks) and they exhibited superior tensile and stress-rupture properties at a temperature of 982°C. Welds that comprised 1.5 to 2% silicon had superior oxidation resistance at a temperature of 995°C. Combined alloying of welds with moderate amount of boron and silicon produced a unique combination of both high mechanical and oxidation properties.
Healing of HAZ cracks took place during post weld heat treatment at a temperature exceeding the solidus temperature of the weld metal eutectics but below of a solidus temperature of the base material. It was found that boron and silicon additives reduced welding pool solidification temperature and increased the solidus–liquidus range. At this temperature a partial re-melt of eutectics occurred allowing healing of HAZ and weld solidification cracks while weld geometry was supported by a continuous framework of high temperature dendrites. This allows the tip repair of turbine blades manufactured of precipitation strengthened superalloys that are normally prone to weld cracking.
Heat Transfer in a Coupled Impingement-Effusion Cooling System
Authors: Miller Mark , Natsui Greg , Ricklick Mark , Kapat Jay , Schilp Reinhard 
Published: September 2014

Modern research on gas turbine cooling continues to focus on the optimization of different cooling designs, and better understanding of the underlying flow physics so that cooling schemes can be coupled together. The current study focuses on one particular coupled cooling design: an impingement-effusion cooling system, which combines impingement cooling on the backside of the cooled component and full coverage effusion cooling on the exposed surface.
The goal of this study is to explore a wide range of geometrical parameters outside the ranges normally reported in the available literature. Particular attention is given to the total coolant spent per unit surface area cooled. Through determination of impingement heat transfer, film cooling effectiveness, and film cooling heat transfer on the target wall, a simplified heat transfer model of the cooled component is developed to show the relative impact of each parameter on the overall cooling effectiveness.
The use of Temperature Sensitive Paint (TSP) for data acquisition allows for high resolution local heat transfer and effectiveness results. Impingement arrays with local extraction of coolant via effusion are able to produce higher overall heat transfer, as no significant cross flow is present to deflect the impinging jets. Low jet-to-target-plate spacing produces the highest yet most non-uniform heat transfer distribution; at high spacing the heat transfer rate is much less sensitive to impingement height.
Arrays with high hole-to-hole spacing and high jet Reynold’s number are more effective (per mass of coolant used) than tightly spaced holes at low jet Reynold’s number. On the effusion side, staggered hole arrangements provide significantly higher film cooling effectiveness than their in-line counterparts as the staggered arrangement minimizes jet interactions and promotes a more even lateral distribution of coolant.
Residual Life Assessment of a Critical Component of a Gas Turbine: Achievements and Challenges
Authors: Beres Wieslaw , Zhang Zhong , Dudzinski David , Chen W. R. , Wu X. J. 
Published: September 2014

The residual life assessment of a turbine spacer from a gas turbine engine is presented. The spacer has been identified as one of the safety critical components of the engine, therefore the useful life of this component significantly affects economic operation of the fleet.
Numerical analyses of fatigue crack propagation at one critical location of the spacer were performed using both three dimensional (3D) finite element based method and the weight function method. These results combined with the material data allowed for basic assessment of the damage tolerance of this component. Experimental validation of the spacer life was performed in a spin rig facility. During this validation, two sets of spacers were tested and the number of cycles to appearance of a detectable crack was recorded. Moreover, a fractographic study was conducted on the fracture surfaces of two spin rig tested spacers using scanning electronic microscopy techniques. It was found that crack nucleation occurred at multiple sites and crack propagation occurred by a mixed mode of striation formation and faceted fracture. Therefore it was concluded that the mixed mode interaction should be considered in predicting the fatigue life of the spacer.
Finally, the paper describes the challenges and pitfalls encountered during preparation and execution of the analyses and tests, including availability of engine and operational data and also uncertainties in interpretation of the results.
Development of an Innovative Multi-Sensor Waveguide Probe With Improved Measurement Capabilities
Authors: Lenzi Giulio , Fioravanti Andrea , Ferrara Giovanni , Ferrari Lorenzo 
Published: September 2014

Currently waveguide probes are widely used in several turbomachinery applications ranging from the analysis of flow instabilities to the investigation of thermoacoustic phenomena. There are many advantages to using a waveguide probe. For example, the same sensor can be adopted for different measurement points, thus reducing the total number of sensors or a cheaper sensor with a lower operating temperature capability can be used instead of a more expensive one in case of high temperature applications. Typically, a waveguide probe is made up of a transmitting duct which connects the measurement point with a sensor housing and a damping duct which attenuates the pressure fluctuations reflected by the duct end. If properly designed (i.e. with a very long damping duct), the theoretical response of a wave guide has a monotone trend with an attenuation factor that increases with the frequency and the length of the transmitting duct. Unfortunately, the real geometry of the waveguide components and the type of connection between them have a strong influence on the behavior of the system. Even the smallest discontinuity in the duct connections can lead to a very complex frequency response and a reduced operating range. The geometry of the sensor housing itself is another element which contributes to increasing the differences between the expected and real frequency responses of a waveguide since its impedance is generally unknown.
Previous studies developed by the authors have demonstrated that the replacement of the damping duct with a properly designed termination could be a good solution to increase the waveguide operating range and center it on the frequencies of interest. In detail, the termination could be used to balance the detrimental effects of discontinuities and sensor presence. In this paper an innovative waveguide system leading to a further increase of the operating range is proposed and tested. The system is based on the measurement of the pressure oscillations propagating in the transmitting duct by means of three sensors placed at different distances from the pressure tap. The pressures measured by the three sensors are then combined and processed to calculate the pressure at the transmitting duct inlet. The arrangement of the sensing elements and the geometry of the termination are designed to minimize the error of this estimation. The frequency response achieved with the proposed arrangement turns out to be very flat over a wide range of frequencies. Thanks to the minor errors in the estimation of pressure modulus and phase the probe is also suitable for the signal reconstruction both in frequency and time domain.
An Enhanced Off-Design Performance Model for Single Stage Fans
Authors: Kurzke Joachim 
Published: September 2014

Modern high bypass turbofan engines have single stage fans with a low hub-tip radius ratio. The fan map is a very important element for off-design performance simulations. Such a map consists of tables with corrected mass flow, pressure ratio and efficiency for a range of corrected spool speeds.
Applying the data read from a fan map to both the core and the bypass stream is inaccurate because the transonic flow field of the bypass stream is very different to the subsonic flow field of the core stream. A better approximation of reality is to use a hybrid map with total mass flow, bypass pressure ratio and efficiency. Constant factors are employed to derive the core stream pressure ratio and efficiency.
For more accurate simulations two maps may be employed, one for the core and another one for the bypass stream. The total mass flow of the fan is the same in these two maps while pressure ratio and efficiency are different for the two streams. The data for each point in this so-called “Split Map” are valid for a pre-defined bypass ratio.
This paper describes an alternative to the split map methodology which takes the variability of the bypass ratio into account in a different way. The hypothesis is that the overall fan performance is not affected by variations in bypass ratio. The fan performance map is completed by an additional table with core stream efficiency.
This enhanced map is used as follows. When scaling the map, the bypass ratio as well as the pressure ratio and efficiencies for the core and bypass streams are known. Assumed values for fan tip speed, hub-tip radius ratio and fan inlet Mach number yield the core stream velocity triangle. The rotor blade exit flow angle from this triangle remains the same in all other operating conditions.
The core flow velocity triangle analysis with known rotor blade exit angle yields the work done on the core stream during off-design. The pressure ratio is calculated from this work and the efficiency read from the core stream efficiency table mentioned above.
Finally, the bypass stream pressure ratio and efficiency are calculated from the overall map and the core stream data applying the actual bypass ratio.
Design and Development of Advanced Three-Dimensional Non-Periodic Diffusers for Centrifugal Compressors
Authors: Grigoriev Mikhail , Swiatek Chet , Hitt Jim 
Published: September 2014

Recent changes in the global economy have significantly impacted the air separation market. Companies traditionally focused upon initial capital expenditures, have shifted their mindset towards total life cycle costs. As a primary component in the air separation process, the compressor has been recognized as a significant contributor to life cycle costs of an air separation facility. Accordingly, market expectations have shifted towards more efficient compressor designs to reduce the overall power consumption.
This paper highlights the development efforts at Cameron’s Compression Systems to design advanced 3D cascade diffusers, leading to the development of compressors with higher aerodynamic efficiencies.
While the concept of matching the diffuser design towards the local flow field is not new, the implementation of this concept has been significantly hindered by a lack of understanding with regard to impeller discharge conditions. Furthermore, the tools necessary to explore these specifics either did not exist, or where prohibitive in terms of both cost and time.
Over the past 20 years, great advances have been made in the area of computational engineering. The advancements in Computational Fluid Dynamics (CFD) tools have led to a better understanding of the transitional impeller flow fields. Furthermore, the dramatic progress in cheaper high-end computers has facilitated the design and development of sculpted three-dimensional diffusers within reasonable time frames and at relatively low cost.
Recently, Cameron has deployed advanced sculpted 3D diffusers on limited production designs. This process involves a heavy utilization of STAR-CCM+ for performance analyses of centrifugal stages with various diffuser geometries. The CFD analyses vary from relatively simple steady state analyses with single impeller and single diffuser passages using indirect (mixing plane) interfaces to full stage unsteady simulations involving full inlet, impeller, diffuser and volute with a discharge pipe. This paper discusses a range of issues involved in performing CFD analyses for complex diffuser geometries. We show how CFD analyses are used to improve the aerodynamic performance of stages with respect to the regular low solidity cascade 2D diffusers. The paper provides results of comparative studies of the computational analyses with the aerodynamically tested data for the stages using both the regular low solidity 2D diffusers and sculpted non-periodic 3D diffusers. The test results confirm predicted improvements in compressor efficiency using sculpted non-periodic 3D diffusers over regular 2D diffusers by as much as 2% for peak efficiency. The paper discusses stage improvements due to use of 3D sculpted non-periodic diffusers.
Numerical Investigation of Influence of Radial Inlet Distortion on Compressor Performance in 2-Stage Turbocharging System
Authors: Chen Jinke , Zheng Xinqian , Wang Chenfang , Zhuge Weilin , Zhang Yangjun 
Published: September 2014

As the result of strict emission regulations and the demand of fuel reduction, an increasing number of engines are highly boosted with complex two-stage turbocharging systems.
In a two-stage turbocharging system, an additional intercooler between LP compressor and HP compressor is usually used to reduce the inlet temperature of the HP compressor for extending its life and reducing the compression work. Spatial restrictions of the turbocharging system lead to reduced distances between different components of the two-stage turbocharging system. Consequently, each component’s performance is influenced by the upstream and downstream ones. The high pressure compressor performance is affected by the inlet flow condition, which is significantly distorted by the intercooler.
In this paper, the characteristics of flow distortion caused by the intercooler and its evolution process are analyzed. Performances of the downstream high pressure compressor under uniform inlet condition and distorted inlet condition caused by the intercooler are analyzed and compared. The results show that the inlet distortion caused by intercooler deteriorates the compressor pressure ratio, flow range, and efficiency.
Effect of Vaned Diffuser on a Small Centrifugal Impeller Performance
Authors: Chen Jie , Yue Yang , Huang Guoping 
Published: September 2014

A small transonic centrifugal compressor with 3D vaned diffuser has been developed for a turbine engine by Nanjing University of Aeronautics and Astronautics. The centrifugal impeller’s diameter is approximately 80 mm. The impeller was improved by reducing the static pressure gradient in spanwise direction. But the improvement is reduced by the interaction between the impeller and the diffuser, when it works with the diffuser. So, the effect of the vaned diffuser on the performance and flow structure of the impeller was studied by steady and unsteady numerical simulations.
The total pressure ratio and efficiency of the impeller with a vaned diffuser are lower than those with a vaneless diffuser. Further, the difference decreases as the operation point moves from the surge to the choke. Analysis of steady flow proves that the meridional bend and the vanes in the 3D vaned diffuser are the main causes. When the impeller operates with the vaned diffuser, the vortex at the shroud of the impeller exit is pushed toward the trailing edge of the impeller blade, which leads to an altered flow structure in the impeller passages. As a result, the loss of the impeller increases, and consequently the efficiency as well as the pressure ratio drops. On the other hand, the unsteady analysis shows that the flow pattern at the impeller exit is circularly affected by features of the stagnation, the local acceleration, and the shock wave in the semi-vaneless space of the diffuser. The flow at the different spanwise location in the trailing edge of the impeller blade can be influenced by the different flow feature, therefore, the spanwise distributions of the flow parameters is disturbed.
Computational Study of a Transonic Turbine Cascade: Validation and Comparison of Griding Approaches and Challenges
Authors: Abo El Ella H. M. , Kibsey M. , Sjolander S. A. 
Published: September 2014

This paper presents a computational study, with some experimental validation, of a low-turning transonic turbine cascade. A comparison is presented between the time-consuming and difficult to generate hexa-structured meshing approach, and the mostly automated tetra-unstructured meshing approach. The paper compares the predicted flow physics and losses, with discussion of the challenges in griding and convergence between both approaches.
Computations were carried out using a commercial RANS solver (ANSYS CFX 12) using the Shear Stress Transport turbulence model, and the Gamma-Theta transition model. The computational domain encompassed a half blade span, and one blade pitch with periodic boundary conditions; griding for both approaches was done using ANSYS ICEM CFD. Computational results from both griding approaches were compared to corresponding experimental data. The outlet Mach number was 0.90. The experiment was carried out using a linear cascade in a blow-down type wind tunnel. Downstream seven-hole pressure probe measurements at 1.8 axial chord lengths from the leading edge provided loss, streamwise vorticity, and secondary kinetic energy distributions and integrated coefficient values.
It was found that both griding approaches predicted similar downstream endwall flow structures to those observed in the experiment. The tetra-unstructured mesh solution predicted higher losses, but both predicted lower losses than the experiment. Overall results suggest that for capturing of the basic flow physics, both approaches suffice, with the tetra-unstructured being the much easier approach, but with limitations on the level of grid refinement. For more accurate capturing of the flow physics, the time-consuming and difficult to generate hexa-structured meshing approach can be justified.
Effects of Gas-Ingestion Through Turbine Rim Seals on Flow and Heat Transfer in the Wheel-Space
Authors: Tian Shuqing , Zhang Ying , Su Wei 
Published: September 2014

This paper presents numerical simulations of the gas-ingress into turbine wheel-space through the rim seal. The objective is to reveal the physical mechanism of gas-ingress flow in the wheel-space and its effects on the heat transfer in the cavity. Firstly, the wheel-space without mainstream passage is simulated to get the baseline of the case without ingress, and the windage heat in the cavity is investigated. Secondly, the gas-ingestion is conducted, and its effects on the flow and heat transfer in the wheel-space are studied.
The results reveal that in the absence of ingress into the wheel-space, the windage heating pays an important contribution to the stator/rotor temperatures because of the high rotational speed of the engine. When ingress occurs, the ingested gas mixes with the sealing air at the seal clearance and then inward flows into the wheel-space along the stator wall, and thus leads to the stator wall heated. The rotor wall is relatively less heated by the invaded gas than the stator wall because of the thermal buffering of the sealing air on the rotor wall. The thermal buffer ratio, which is defined as the ratio of the sealing effectiveness on the stator wall to that on the rotor wall, is shown dependent on the sealing flow rate. It is increased as the sealing flow rate increases.
Performance of IGFC With Exergy Recuperation
Authors: Iki Norihiko , Kurata Osamu , Tsutsumi Atsushi 
Published: September 2014

The Integrated coal Gasification Combined Cycle (IGCC) is considered to be a very clean and efficient system for coal-fired power generation. And given the development of 100 MW-scale solid oxide fuels cells (SOFCs), the integrated coal Gasification Fuel Cell combined cycle (IGFC) would be the most efficient coal-fired power generation system. However, more energy efficient power generation systems must be developed in order to reduce CO2 emissions over the middle and long term. Thus, the authors have proposed the Advanced Integrated coal Gasification Combined Cycle (A-IGCC) and Advanced IGFC (A-IGFC) systems, which utilize exhaust heat from solid oxide fuel cells (SOFCs) and/or gas turbines as a heat source for gasification (exergy recuperation).
The A-IGCC and A-IGFC systems utilize a twin circulating fluidized bed coal gasifier consisting of three primary components: a pyrolyzer, steam reformer and partial combustor. The temperature of the steam reformer is 800 °C, and that of the partial oxidizer is 950 °C. Since the syngas, produced by pyrolysis and the reforming process involving volatile hydrocarbons, tar and char, contains carbon monoxide and hydrogen, the A-IGCC technology has considerable potential for higher thermal efficiency while utilizing low-grade coals. The coal types utilized in the study were bituminous Taiheiyo, sub-bituminous Adaro and Loy Yang coal. Milewski’s formula was used to model the circuit voltage of the SOFC.
Cool gas efficiency increases, in order, from Taiheiyo coal to Adaro coal to Loy Yang coal. The A-IGFC system has the potential to achieve high thermal efficiency using various coals, with Loy Yang coal achieving the highest thermal efficiency. However, the drying process for Loy Yang and Adaro coal is an important issue.