bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution and Future Trend of Large Frame Gas Turbines: A New 1600 Degree C, J Class Gas Turbine
Authors: Hada Satoshi , Yuri Masanori , Masada Junichiro , Ito Eisaku , Tsukagoshi Keizo
Published: July 2013

MHI recently developed a 1600°C class J-type gas turbine, utilizing some of the technologies developed in the National Project to promote the development of component technology for the next generation 1700°C class gas turbine.

This new frame is expected to achieve higher combined cycle efficiency and will contribute to reduce CO2 emissions.

The target combined cycle efficiency of the J type gas turbine will be above 61.5% (gross, ISO standard condition, LHV) and the 1on1 combined cycle output will reach 460MW for 60Hz engine and 670MW for 50Hz engine.

This new engine incorporates:

1) A high pressure ratio compressor based on the advanced M501H compressor, which was verified during the M501H development in 1999 and 2001.

2) Steam cooled combustor, which has accumulated extensive experience in the MHI G engine (> 1,356,000 actual operating hours).

3) State-of-art turbine designs developed through the 1700°C gas turbine component technology development program in Japanese National Project for high temperature components.

This paper discusses the technical features and the updated status of the J-type gas turbine, especially the operating condition of the J-type gas turbine in the MHI demonstration plant, T-Point.

The trial operation of the first M501J gas turbine was started at T-point in February 2011 on schedule, and major milestones of the trial operation have been met. After the trial operation, the first commercial operation has taken place as scheduled under a predominantly Daily-Start-and-Stop (DSS) mode. Afterward, MHI performed the major inspection in October 2011 in order to check the mechanical condition, and confirmed that the hot parts and other parts were in sound condition.
The Potential of GT Combined Cycles for Ultra High Efficiency
Authors: Wettstein Hans E.
Published: July 2013

Gas turbine combined cycles (GTCC) using a steam bottoming cycle are a widely used technology for electric power generation. From [1] it is known that the best current large GTCC’s loose around 25% of the fuel exergy just by combusting the fuel while all other exergy losses sum up to around 15%. For the net efficiency of such plants 60% is remaining. This paper shows thermodynamic calculation results of GTCC’s with variable pressure ratio and turbine inlet temperature (TIT) aimed at understanding the efficiency potential associated with further increases of the TIT thus reducing the exergy loss by combustion. The assumptions of these calculations correspond to published industrial experience and standard assumptions in two different scenarios. The results are curves showing net efficiency and specific power as functions of TIT. Other data like the related pressure ratio and compressor exit temperature are shown too. The conclusion shows that a net efficiency of 63…65% is feasible with a hot gas temperature of around 1750°C based on the two scenarios. The winning cycle arrangement uses an adiabatic compressor. A GTCC with GT-compressor having one intercooling stage is clearly less favorable in several respects.
Analysis of an Integrated PEMFC/ORC Power System Using Ammonia for Hydrogen Storage
Authors: Borello Domenico , Del Prete Zaccaria , Marchegiani Andrea , Rispoli Franco , Tortora Eileen
Published: July 2013

The present work deals with a high temperature proton exchange membrane (SPEEK-type) fuel cell (HT-PEMFC) energy system fuelled with hydrogen obtained by reforming of ammonia (NH3) and coupled with a bottoming Organic Rankine Cycle (ORC) energy system. This system was designed for distributed electric power generation, mainly for production of electric power systems with potential future applications in smart-grid.

The use of ammonia as hydrogen rich gas source allows to avoid hydrogen tanking with metal hydrides, giving the opportunity to lighten and simplify the storage section of the system with respect to the pure hydrogen fed systems.

The hybrid fuel cell/ORC configuration allows to increase the efficiency of standard power generation technologies. In other words, the ORC subset represents the most appropriate solution, in terms of sustainability, for extracting the excess heat produced during the H2 combustion maintaining the PEMFC working temperature at 120°C and for reducing the temperature of the exhausts.

The objective of the work is to optimize the electric output of the system (PEMFC + ORC), thus improving the overall efficiency. To this end, a numerical model is implemented and tested. A validation of the numerical scheme is carried out comparing the prediction of the reforming phase with experimental results obtained by the authors. The thermal and electrical energy balance is also assessed. Furthermore, the operation conditions of the reformer are studied in detail to determine the settlements leading to a proper ammonia cracking to produce nitrogen and hydrogen. Furthermore, the calculations take into account also the auxiliary equipments such as pumps, compressors and heat exchangers.
Development of High Efficient 30MW Class Gas Turbine: The Kawasaki L30A
Authors: Tanaka Ryozo , Koji Take , Ryu Masanori , Matsuoka Akinori , Okuto Atsushi
Published: July 2013

Kawasaki Heavy Industries (KHI) will launch the first unit of the L30A gas turbine, rated output of 30.9MW, and 41.2% of thermal efficiency. The L30A is a twin-shaft gas turbine designed for combined heat and power application (CHP) with lower emissions. The newly developed 14-stage compressor has a pressure ratio of 24.5 with an air flow of 86.5 kg/sec. KHI’s proven dry low emission (DLE) technologies are adapted to the combustion design, and NOx emission of 15 ppm (15% = O2) has been achieved. Also, the newly designed 2-stage gas generator turbine (GGT) employs the proven cooling design with conjugate heat transfer and flow (CHT) analysis, and 3-stage power turbine (PT) has the inter-locking type tip shroud which reduces vibration level for wide operating range of PT with lower pressure losses. The in-house verification tests have been conducted since 2010, to confirm design targets such as performance, emission, vibrations and temperatures were verified in exclusive test facility for the L30A. This paper describes the technical features of the L30A, the development activities and some verification test results.
Demonstration of Model Based, Off-Line Performance Analysis on a Gas Turbine Air Compressor (GTAC)
Authors: Wiese Ashley P. , Blom Matthew J. , Brear Michael J. , Manzie Chris , Kitchener Anthony
Published: July 2013

This paper presents a model based, off-line method for analysing the performance of individual components in an operating gas turbine. As with other studies, a least squares approach is employed. The component models are physics-based where possible. In its most general form, the method permits simultaneous inference of the combustor efficiency and stagnation pressure loss, the hot-end heat losses and associated heat transfer coefficients, the turbine inlet temperature and the turbine’s isentropic efficiency. As part of this, combustion of unburnt fuel within the turbine is modelled.

The method is demonstrated on a so-called ‘Gas Turbine Air Compressor (GTAC)’ test rig built by the group, a micro-turbine whose compressor supplies air for both the cycle and external applications, but produces no shaft work. The method is also formulated for other gas turbines. The highest order models are tested first, and then the model order is progressively reduced to determine adequate component model complexity. Since the GTAC is a micro-gas turbine, heat losses are found to be significant. It is also shown that care must be taken to distinguish between variations in the performance of different components, since the performance of several components can have similar effects on the complete, operating device.
Numerical Through Flow Simulation of a Gas Turbine Engine With Wet Compression
Authors: Sun Lanxin , Zheng Qun , Li Yijin , Luo Mingcong , Wang Jie , Bhargava Rakesh K.
Published: July 2013

In this paper, a thorough flow simulation of a small turbojet engine has been carried out to predict the engine performance as a result of water injected at the compressor inlet. Wet compression will not only change compressor performance characteristic map, but also has effects on both the combustor and the turbine sections. The match between the turbojet engine components, that is the compressor, combustor and turbine, will shift to a new operating point. In this paper, we present a steady-state numerical simulation of the entire gas turbine with wet compression in order to evaluate the effects on the gas turbine performance.

Compared with the dry case, the results of wet cases show increased values of compressor compression ratios, turbine expansion ratios, intake mass flowrates and engine thrusts including decreased amount of specific fuel consumption. The wet compression reduces NOx production in the combustor, which is also simulated and results presented. The study also indicates that the water mass flowrate and droplet diameter are key factors impacting the engine performance.
Creep Life Prediction for Aero Gas Turbine Hot Section Component Using Artificial Neural Networks
Authors: Ghafir M. F. Abdul , Li Y. G. , Wang L.
Published: July 2013

Accurate and reliable component life prediction is crucial to ensure safety and economics of gas turbine operations. In pursuit of such improved accuracy and reliability, model-based creep life prediction methods have become more and more complicated and therefore demand more computational time although they are more flexible in applications, in particular for new gas turbine engines. Therefore, there is a need to find an alternative approach that is able to provide a quick solution to creep life prediction for production engines while at the same time maintain the same accuracy and reliability as that of the model-based methods. In this paper a novel creep life prediction approach using Artificial Neural Networks is introduced as an alternative to the model based creep life prediction approach to provide a quick and accurate estimation of gas turbine creep life. Multilayer feed forward back propagation neural networks have been utilised to form three neural network-based creep life prediction architectures known as the Range Based, Functional Based and Sensor Based architectures. The new neural network creep life prediction approach has been tested with a model single spool turboshaft gas turbine engine. The results show that good generalisation can be achieved in all three neural network architectures. It was also found that the Sensor-Based architecture is better than the other two in terms of accuracy, with 98% of the post-test samples possessing prediction errors within ± 0.4%. Overall, it can be concluded that the proposed neural network approach in creep life prediction is able to provide a good alternative to the more complicated model-based creep life prediction algorithms and can be applied to different types of gas turbine engines.
Technical and Economic Analysis of the Gas Turbine Air Bottoming Cycle
Authors: Chmielniak Tadeusz , Czaja Daniel , Lepszy Sebastian
Published: July 2013

The gas turbine engine has many advantages such as low investment costs, low emissions and a low water consumption. This fact allows its application in many power engineering systems, for example as parts of gas and oil transport systems. It is possible to increase the efficiency of gas turbines through the use of combined cycles. For this purpose, the steam cycle is used most frequently. These systems are highly efficient in terms of energy, but they are very complex and have a high water consumption. An alternative to steam cycles are gas-air systems, referred to as the ABC’s (Air Bottoming Cycles), which use hot combustion gases as a heat source for the air cycle. ABC’s are composed of a gas turbine powered by natural gas, an air compressor and an air turbine coupled to the system by means of a heat exchanger, referred to as the AHX (Air Heat Exchanger).

The paper presents an application of gas-air systems with example configurations, together with thermodynamic characteristics. Two technological structures are taken into consideration — a simple system of the ABC and an ABC with air intercooling. A parametric analysis of these systems is performed using a special computer program with real gas properties for enthalpy and entropy calculations. A basic comparative analysis of gas turbine air bottoming cycle and combined gas-steam cycle has been also done. Other important calculations are related to the heat exchanger, which is one of the most important components in this system because it couples the gas and air parts. The efficiency of the whole cycle depends on a rationally designed heat exchanger. The calculations are performed for a shell-and-tube exchanger, as well as for a plate heat exchanger. For all investigations an purchase cost of machines and devices is also determined.
The Effective Positions to Inject Water Into the Cascade of Compressor
Authors: Wang Jie , Zheng Qun , Sun Lanxin , Luo Mingcong
Published: July 2013

Generally, droplets are injected into air at inlet or interstage of a compressor. However, both cases did not consider how to utilize the kinetic energy of these moving droplets. Under the adverse pressure gradient of compressor, the lower energy fluids of blade surfaces and endwalls boundary layers would accumulate and separate. Kinetic droplets could accelerate the lower energy fluids and eliminate the separation. This paper mainly investigate the effective positions where to inject water and how to utilize the droplets’ kinetic energy. Four different injecting positions, which located on the suction surface and endwall, are chosen. The changes of vortexes in the compressor cascade are discussed carefully. In addition, the influences of water injection on temperature, total pressure losses and Mach number are analyzed. Numerical simulations are performed for a highly loaded compressor cascade with ANSYS CFX software.
Economic Evaluation of Industrial Gas Turbines for Electrical Power Generation
Authors: Mohamed W. , Al-Abri B. , Pilidis P. , Nasir A.
Published: July 2013

This paper looks at some of the financial implications of generating electricity using a 165 MW gas turbine based power plant operating in a warm coastal environment. The engine performance model is developed using the Turbomatch in-house software package capable of simulating engine performance at both design and off-design conditions. Given the long operational life of the power plant, the economic model uses the Net Present Value (NPV) technique to simulate and account for the time value of money. This allows techno-economic comparisons between various modes of operation and variations in power demand to be made. The modelling will be used to optimise operation using key economic and performance parameters. The modelling is based on the Techno-Economic, Environmental and Risk Analysis (TERA) philosophy which allows for a broad and multidimensional analysis of the problem to aid plant operation and equipment selection. The analysis shows that 30 °C increase in ambient temperature above the design point results in 11.5% increase in the levelized cost of electricity (LCOE). The analysis also shows that the LCOE is increased by 4.3 as a result of 5% degradation in turbine compressor.
Numerical Simulation for the Preliminary Design of Fuel Flexible Stationary Gas Turbine Combustors Using Conventional and Alternative Fuels
Authors: Irrazabal Bohorquez Washington Orlando , Barbosa João Roberto , Bastiaans Rob Johan Maria , de Goey Philip
Published: July 2013

Currently, high efficiency and low emissions are most important requisites for the design of modern gas turbines due to the strong environmental restrictions around the world. In the past years, alternative fuels have been considered for application in industrial gas turbines. Therefore, combustor performance, pollutant emissions and the ability to burn several fuels became of much concern and high priority has been given to the combustor design.

This paper describes a methodology focused on the design of stationary gas turbines combustion chambers with the ability to efficiently burn conventional and alternative fuels. A simplified methodology is used for the calculations of the equilibrium temperature and chemical species in the primary zone of a gas turbine combustor. Direct fuel injection and diffusion flames, together with numerical methods like Newton-Raphson, LU Factorization and Lagrange Polynomials, are used for the calculations. Diesel, ethanol and methanol fuels were chosen for the numerical study.

A computer code sequentially calculates the main geometry of the combustor. From the numerical simulation it is concluded that the basic gas turbine combustor geometry, for some operating conditions and burning diesel, ethanol or methanol, are of similar sizes, because the development of aerodynamic characteristics predominate over the thermochemical properties.

It is worth to note that the type of fuel has a marked effect on the stability and combustion advancement in the combustor. This can be seen when the primary zone is analyzed under a steady-state operating condition. At full power, the pressure is 1.8 MPa and the temperature 1,000 K at the combustor inlet. Then, the equivalence ratios in the primary zone are 1.3933 (diesel), 1.4352 (ethanol) and 1.3977 (methanol) and the equilibrium temperatures for the same operating conditions are 2,809 K (diesel), 2,754 K (ethanol) and 2,702 K (methanol). This means that the combustor can reach similar flame stability conditions, whereas the combustion efficiency will require richer fuel/air mixtures of ethanol or methanol are burnt instead of diesel.

Another important result from the numerical study is that the concentration of the main pollutants (CO, CO2, NO, NO2) is reduced when ethanol or methanol are burnt, in place of diesel.
Design Criteria and Optimization of Heat Recovery Steam Cycles for High-Efficiency, Coal-Fired, Fischer-Tropsch Plants
Authors: Martelli Emanuele , Kreutz Thomas G. , Gatti Manuele , Chiesa Paolo , Consonni Stefano
Published: July 2013

In this work, the “HRSC Optimizer”, a recently developed optimization methodology for the design of Heat Recovery Steam Cycles (HRSCs), Steam Generators (HRSGs) and boilers, is applied to the design of steam cycles for three interesting coal fired, gasification based, plants with CO2 capture: a Fischer-Tropsch (FT) synthesis process with high recycle fraction of the unconverted FT gases (CTL-RC-CCS), a FT synthesis process with once-through reactor (CTL-OT-CCS), and an Integrated Gasification Combined Cycle (IGCC-CCS) based on the same technologies. The analysis reveals that designing efficient HRSCs for the IGCC and the once-through FT plant is relatively straightforward, while designing the HRSC for plant CTL-RC-CCS is very challenging because the recoverable thermal power is concentrated at low temperatures (i.e., below 260 °C) and only a small fraction can be used to superheat steam. As a consequence of the improved heat integration, the electric efficiency of the three plants is increased by about 2 percentage points with respect to the solutions previously published.
The Design of an Axial Flow Fan for Application in Large Air-Cooled Heat Exchangers
Authors: Louw Francois G. , Bruneau Phillipe R. P. , von Backström Theodor W. , van der Spuy Sybrand J.
Published: July 2013

The heat transfer characteristics of industrial air-cooled heat exchangers (ACHEs) are dependent on the ability of the fan system to deliver sufficient cooling air. However, under normal operating conditions, variable flow direction and strength often subject peripheral fans to distorted inlet conditions with an attendant reduction in overall volumetric flow rate and cooling capacity. In this paper, a design methodology for single-rotor axial flow fans, appropriate for use in large industrial ACHE’s is presented. The primary motivation for this work was to address the issues of robust off-design performance, in particular, distorted inlet flow tolerance. Using this methodology, two 8-bladed prototype fans (B1 and B2) were designed, built and tested in accordance with BS 848 (Type A) standards. The two B-fans have a hub-tip ratio of xh = 0.4 and employ the Clark Y and NASA LS airfoil profiles respectively. Measured performance characteristics were compared to commercial fan designs (V-, DL- and L-fan) used in existing ACHEs. Results indicate that the B-fans have a higher design point operating efficiency. The B-fans also show a steeper fan static pressure rise characteristic compared to the commercial fans, except for the DL-fan, implying a greater tolerance to pressure fluctuations caused by distorted inflows.
Comparing the Pressure Rise of Air and Supercritical Carbon Dioxide in Conical Diffusers
Authors: Monje B. , Sánchez D. , Chacartegui R. , Sánchez T. , Savill M. , Pilidis P.
Published: July 2013

The channels formed between adjacent blades in a turbine/compressor are nothing more than a variable section duct. Hence, the first step of turbomachinery design is to understand the physical processes experienced by a certain fluid when flowing through these nozzles and diffusers. In the main, nozzles are easier to understand since the fluid flows impelled by a favourable pressure gradient whereas for diffusers the flow has to face an adverse pressure gradient. This latter situation brings about the occurrence of stall (boundary layer detachment from the wall) which makes it more complicated to design and operate the component (both the individual stages and the entire compressor). It is thus essential to characterise the performance of diffusers of any type, which is influenced by several parameters such as geometry, Mach and Reynolds number, inlet total pressure and aspect of the boundary layer at the inlet section. Dolan and Runstadler generated very valuable information in 1973 (Pressure recovery performance of conical diffusers at high subsonic Mach numbers, NASA CR-2299) by providing performance maps for the flow of air in diffusers. This work is aimed at complementing the previous one by giving maps that apply to the flow of supercritical carbon dioxide in similar devices. By doing so, an important step towards the design of thermal turbomachinery specific of this singular fluid is taken.
Implementation of a Remote Pump Laboratory Exercise in the Training of Engineering Students
Authors: Monaco Lucio , Vogt Damian M. , Fransson Torsten H.
Published: July 2013

The use of laboratory exercises in the training of engineering students is of paramount importance to give the students the possibility to gain practical experience on real hardware and on real test data. Recent trends in the education of engineers at the Department of Energy Technology at KTH go towards an increasing share of distant-based education, which is put in place to educate students at different geographic locations, not only locally (such as for example with engineers in industry) but also internationally (i.e. with students in different countries). In order to provide the possibility to follow a course at a distance without compromising on learning objectives and learning quality, a number of remotely operated laboratory exercises have been developed and implemented in the engineering curriculum at the department. Among these, to mention the work carried out by Navarathna et al. [11] on a remotely operated linear cascade test facility. The present laboratory exercise is integrated in a course on turbomachinery and gives the students the possibility to interactively learn about the operation of pumps at various speeds, various mass flow rates, parallel operation and serial operation. Students access the laboratory exercise using a web-based interface, perform measurements and finally have test data sent to an initially specified email address for further analysis.
Discussion of Some Myths/Features Associated With Gas Turbine Inlet Fogging and Wet Compression
Authors: Wang Ting , Khan Jobaidur R.
Published: July 2013

Gas turbine inlet fogging and overspray (high-fogging) have been considered the most cost-effective means of boosting a gas turbine’s total power output, especially under hot or dry weather conditions. The result of employing fogging or overspray is indisputably clear — total power output is increased; however, development of the theory and explanation of the phenomena associated with fogging and overspray are not always consistent and are sometimes misleading and incorrect. This paper focuses on reviewing several interesting features and commonly discussed topics, including (a) entropy production of water evaporation, (b) the effect of centrifugal force on water droplets, and (c) whether water droplets can survive the journey in the compressor and enter the combustor. Furthermore, three turbine myths: that fogging/overspray increases the air density in the compressor, reduces the compressor power consumption, and noticeably enhances the gas turbine efficiency, are examined and discussed.

Some common mistakes in describing the compressor work are identified and corrected. A newly constructed multiphase T-S diagram is used to explain the physics of water droplet evaporation process and corresponding entropy production during wet compression.
Podcasting the Whiteboard: A New Way of Teaching Engineers
Authors: Vogt Damian M. , Fransson Torsten H.
Published: July 2013

The education of engineers largely relies on traditional classroom teaching in which a teacher instructs a subject using a variety of techniques ranging from the traditional blackboard (nowadays also whiteboard), over overhead to computer-based presentations. In order to deepen knowledge and get hands-on experience, students are often given practical exercises or case studies to perform, be it individually or in group in the form of a seminar. It is experienced that black- (or white) board based lectures are having an advantage over overheads / slide shows as knowledge is built up instantaneously at a natural pace rather than confronting students with pages of prepared material. The present paper presents a new technique herein referred to as “podcasted whiteboard lectures” in which lectures are given in a traditional lecture hall setup but with having the teacher lecturing by means of an electronic whiteboard. A key advantage of this technique is that it can be recorded and made available to students afterwards, which is here done using podcasting. It is experienced that the technique is very efficient for maximizing the students’ learning experience as one is given the possibility to follow a subject ubiquitous and at preferred pace. Another advantage is that animations and simulations can be integrated right into the lecture and into the same medium used for lecturing. The technique is thereby equally applicable to campus as well as distance-based teaching.
Computational Modeling of Ligaments and Tendons: A Tribute to Dr. Savio Lau-Yuen Woo
Authors: An Kai-Nan
Published: July 2013

Tendons and ligaments are soft connective tissues that play an important role in the musculoskeletal system. The tendon transmits the concentrated tensions generated by the muscle to the bone, and the ligaments stabilize and guide the movement between bones connected at the articulating joints. To perform these tasks, these soft connective tissues are uniquely built to bear load transmission, but are flexible enough to allow the changing direction in their paths of alignment. To accomplish these requirements, the tendons and ligaments have a hierarchy of highly aligned collagen structures consisting of fibrils, fascicles and fibers, along with the ground substance of proteoglycans and glycolipids to form the tendon and ligament tissues.
Regional and Fiber Orientation Dependent Shear Properties and Anisotropic Modeling of Bovine Meniscus
Authors: Abraham Adam C. , Edwards Christian R. , Odegard Gregory M. , Haut Donahue Tammy L.
Published: July 2013

The meniscus is a multiphase material composed of interstitial water, collagen, glycosaminoglycans (GAGs), and fibrochondrocytes [2, 9]. The microstructure of the meniscus consists of superficial randomly orientated fibers providing a smooth lubricating surface, with the deep portion containing circumferentially oriented fibers intermixed with sparse radial tie fibers [12]. This layered morphology evokes an anisotropic material response with regard to axial, radial and circumferential directions relative to primary collagen fibril orientations [1, 4, 6, 8, 10, 13]. In addition to intrinsic fiber orientation influencing mechanical differences in meniscal tissue, GAG and water content have previously been shown to be regionally dependent within the meniscus, elucidating provincial specificity of the applied stress distribution within the joint.
The Use of Wavelets for Wall Removal and Scatter Enhancement in Ultrasound Blood Velocity Profile Measurements
Authors: Bijnens Nathalie , Koutsouridis Gregory , Rutten Marcel , van de Vosse Frans , Brands Peter
Published: July 2013

Ultrasound waves, transmitted by a transducer into a body, are reflected and scattered by the materials they encounter in the body. In case of blood flow measurements in an artery, the received signal will contain the information not only from the moving red blood cells, but the reflections from the vessel wall of other soft tissue structures as well. The discrimination between ultrasound signals originating from scattering of red blood cells and reflection of tissue is one of the major problems for blood velocity assessment. Traditionally, in Doppler processing, where the highest blood velocities in the middle of the vessel are estimated, this discrimination is obtained via a high pass filter with a static cut-off frequency related to the maximum frequency content of the reflections. This is illustrated in Fig.1 (top). As illustrated in Fig. 1 (bottom), problems occur for velocity estimation of slowly moving blood cells close to the vessel wall and in case of perpendicular insonification [1]. In these cases, there is no frequency shift in the signal received from scattering on blood cells. Furthermore, the intensity of the reflections from the vessel wall is highest in case of perpendicular insonification. Filtering in these cases is very challenging since it allows the assessment of blood velocity profiles without contrast agents.
Toward Improved Models for Hemodynamics in Stenotic Vessels: PIV and CFD Results Including Turbulence and Compliance
Authors: Stroud Rossmann Jenn
Published: July 2013

Due to the mortality and morbidity of cardiovascular disease, there is great interest in the flow dynamics and fluid mechanical forces in stenotic vessels. Critical stress conditions both on [1–2] and within [3] atherosclerotic plaque deposits have been implicated in plaque rupture. The presence of atherosclerotic lesions constricting and accelerating blood flow changes the wall behavior, and can also trigger intermittent, unstable, or transitional flows [4–5]. The current work evaluates the effect of incorporating flow turbulence and wall compliance in hemodynamic models.
Enhanced Transmucosal Transport Using Osmolyte-Mediated Fluid-Matrix Interaction
Authors: Teo Ka Yaw , Ibrahim Basma , Park Seungman , Yoon Yeo , Han Bumsoo
Published: July 2013

Various drug delivery systems are developed to deliver therapeutic and diagnostic agents to tissues covered with mucus, such as airways, nasal cavity, or oral cavity [1]. However, the mucus, which present for protection of the tissues, significantly hinders the transport of these agents and ultimately mitigates their efficacy [2]. Several studies have been performed to improve the transmucosal transport by studying the transport rates of polymeric nanoparticles with various sizes and surface chemistry [3–5]. However, drug delivery systems with improved transmucosal transport capability are still highly desired.
The Influence of Tibial Insert Design on Posterior Stabilized Total Knee Arthroplasty Kinematics
Authors: Dharia Mehul A. , Muenchinger Marc , Siggelkow Eik , Bischoff Jeff E.
Published: July 2013

Posterior stabilization in PCL (Posterior Cruciate Ligament) sacrificing Total Knee Arthroplasty (TKA) can be achieved by two commonly used design concepts. Anteriorposterior (AP) stability can be provided either by the ultracongruent (UC) shape of the tibial articulation or by a posterior cruciate substitution with a central spine on the tibial insert which articulates with a transverse cam on the femoral component [1]. Clinical studies have indicated that the use of UC tibial insert design does not significantly compromise the TKA outcomes when compared with the use of posterior cruciate substituting design [2].
Mechanical Stimulation Provides the Key Induction Signal for Tenogenic Differentiation of Human Mesenchymal Stem Cells in Braided Nanofibrous Scaffolds
Authors: Handorf Andrew M. , Barber John G. , Allee Tyler J. , Vanderby Ray , Li Wan-Ju
Published: July 2013

Tendon injury frequently occurs to the people who actively participate in physical or recreational activities. For example, in the U.S., there are more than 250,000 Achilles tendon injuries annually. The orthopedic problem causes significant burdens on the health care system and the economy because of costly patient care and loss of patients’ work productivity.
Development of a Biofidelic Material Model for Brain Tissue
Authors: Kulathu Sandeep , Littlefield David L.
Published: July 2013

Computational simulations of brain injury mechanisms have advanced to a level of sophistication where in addition to capturing different anatomic regions, the computational mesh is capable of distinguishing white and grey matter in the brain. Brain tissue is typically modeled as an isotropic, viscoelastic material. Experiments have shown that the mechanical response of brain tissue to an external load varies depending on the location from which the tissue is harvested and also the direction of loading. Some researchers have developed anisotropic constitutive models by appealing to the composite material case wherein cylindrical axon fibers are immersed in a cellular matrix. Though such material models have been developed over a small sample, they have not been applied over the entire brain for simulation purposes.
Mechanics and Modeling of Postnatal Arterial Development in Wild-Type and Elastin-Insufficient Mice
Authors: Cheng Jeffrey K. , Le Victoria , Mecham Robert P. , Wagenseil Jessica E.
Published: July 2013

Large arteries in vertebrates serve as elastic reservoirs that store a portion of the blood volume with systole and discharge it during diastole. This function is made possible by the combination of extracellular matrix (ECM) proteins deposited by the smooth muscle cells (SMCs) in the arterial wall. Elastin and collagen expression in mice is first detectable around embryonic day 14 and peaks around postnatal day (P) 14, returning to baseline levels by P30. During this time, pressure and cardiac output increase significantly before leveling off ∼P30 [1]. Hence, the protein amounts and consequent mechanical properties of the arterial wall change simultaneously with the applied hemodynamic loads in a complicated and unknown feedback loop.
Mechanism of Injury in a High Ankle Sprain: A Simulation Study
Authors: Wei Feng , Braman Jerrod E. , Meyer Eric G. , Powell John W. , Haut Roger C.
Published: July 2013

Injury to the tibiofibular syndesmosis ligaments, which bind together the distal ends of the tibia and fibula, is commonly referred to as a high ankle sprain [8]. While lateral ankle sprains are the most common injury, high ankle sprains represent a more disabling problem and require a longer recovery period [1] and different treatment [4]. The mechanism associated with a high ankle sprain is primarily thought to involve external rotation of the foot [1,7]. However, both a cadaver study [6] and a simulation study [5] show that tibiofibular syndesmosis ligaments are not stretched the most during an excessive, pure external foot rotation.
Cervical Disc Height During Dynamic In Vivo Flexion-Extension
Authors: Anderst William J. , Lacek Thomas P. , Donaldson William F. , Lee Joon Y. , Kang James D.
Published: July 2013

Cervical disc degeneration is a common and potentially debilitating disease. Over 100,000 surgical procedures are performed per year in the US to treat degenerative cervical spines1. However, the in vivo kinematics and arthrokinematics of the cervical spine have yet to be adequately characterized due to the inability to precisely track vertebral movement during dynamic motion. We have recently established the validity of a set of tools, including a biplane x-ray system, a model-based tracking technique and custom software, to precisely measure in vivo cervical spine kinematics and arthrokinematics with sub-millimeter accuracy2. Consequently, we can now begin to investigate the interdependent relationship between cervical vertebral kinematics and disc morphology and mechanical properties.
Development and Preliminary Validation of a Parametric Pediatric Head Finite Element Model for Population-Based Impact Simulations
Authors: Hu Jingwen , Li Zhigang , Zhang Jinhuan
Published: July 2013

Head injury is the leading cause of pediatric fatality and disability in the United States (1). Although finite element (FE) method has been widely used for investigating head injury under impact, there are only a few 3D pediatric head FE models available in the literature, including a 6-month-old child head model developed by Klinich et al (2), a newborn, a 6-month-old and a 3-year-old child head model developed by Roth et al. (3, 4, 5), and a 1.5-month-old infant head model developed by Coats et al (6). Each of these models only represents a head at a single age with single head geometry. Nowadays, population-based simulations are getting more and more attention. In population-based injury simulations, impact responses for not only an individual but also a group of people can be predicted, which takes into account variations among people thus providing more realistic predictions. However, a parametric pediatric head model capable of simulating head responses for different children at different ages is currently not available. Therefore, the objective of this study is to develop a fast and efficient method to build pediatric head FE models with different head geometries and skull thickness distributions. The method was demonstrated by morphing a 6-month-old infant head FE model into three newborn infant head FE models and by validating three morphed head models against limited cadaveric test data.
Modeling the Inflation Response of C57BL/6 Mouse Sclera
Authors: Myers Kristin M. , Nguyen Thao D.
Published: July 2013

Small rodent models have become increasingly useful to investigate how the mechanical properties of soft tissues may influence disease development. These animal models allow access to aged, diseased, or genetically-altered tissue samples, and through comparisons with wild-type or normal tissue it can be explored how each of these variables influence tissue function. The challenges to deriving meaningful material parameters for these small tissue samples include designing physiologically-relevant mechanical testing protocols and interpreting the experimental load-displacement data in an appropriate constitutive framework to quantify material parameters. This study was motivated by determining the possible role of scleral material properties in the development of glaucomatous damage to the retinal ganglion cells (RGC). Glaucoma is one of the leading causes of blindness in the United States and in the world with an estimate of 60 million people affected by this year [1]. Through exploring mouse models, the overall goal of our work is to determine the role of scleral material properties and scleral tissue microstructure in the pathogenesis of glaucoma.
Comparison of a Novel Nonlinear Viscoelastic Finite Ramp Time Correction Method to a Heaviside Step Assumption
Authors: Troyer Kevin L. , Puttlitz Christian M.
Published: July 2013

Connective soft tissues exhibit time-dependent, or viscoelastic, behavior. In order to characterize this behavior, stress relaxation experiments can be performed to determine the tissue’s relaxation modulus. Theoretically, the relaxation modulus describes the stress relaxation behavior of the tissue in response to an instantaneous (step) application of strain. However, a step increase in strain is experimentally impossible and a pure ramp load is intractable due to the inertial limitations of the testing device. Even small deviations from an instantaneous strain application may cause significant errors in the determination of the tissue’s relaxation modulus.
In-Vivo Dynamic Strains of the Ovine Anterior Mitral Valve Leaflet
Authors: Rausch Manuel , Bothe Wolfgang , Escobar-Kvitting John-Peder , Goktepe Serdar , Miller Craig , Kuhl Ellen
Published: July 2013

Throughout the cardiac cycle the Mitral Valve (MV) experiences complex mechanical and hemodynamic loading [1]. Dysfunction of the MV may have devastating consequences and has been associated with high morbidity and mortality. Surgical repair techniques are available to treat malfunctioning MVs [2]. However, it is likely that interventions such as surgical repair may cause alterations in the loading conditions and associated deformations of the MV. In consequence such alterations could result in detrimental remodeling and disturb normal valve function. It is therefore essential to characterize the MV under in-vivo conditions as accurately as possible and thereby establish a baseline of the normal valve. Even though excellent research has been conducted in-vivo [3], in-vitro [4], as well as in-silico [5], the Anterior Mitral Valve Leaflet (AMVL) has never been characterized from a mechanical perspective across its entire surface. The goal of this study is, hence, to provide a more complete picture of the deformations across the entire AMVL in the beating heart.
Human Coronary Microcalcifications: 3D High Resolution Characterization of Frequency Size and Distribution
Authors: Maldonado Natalia , Kelly Adreanne , Vengrenyuk Yuliya , Fallon John T. , Virmani Renu , Cardoso Luis , Weinbaum Sheldon
Published: July 2013

Despite major advances in treatment of coronary heart disease, apparently healthy patients die suddenly. Rupture of vulnerable fibroatheroma plaques in coronary arteries cause more than 250,000 deaths a year, yet the mechanisms as to why some caps rupture and some others do not, remain unknown. The current criterion to consider a fibroatheroma as “vulnerable” or prone to rupture is the thickness of its fibrous cap. However, available screening techniques and the cap thickness criterion have been shown to be insufficient to identify the victims before the event occurs.
Inhomogeneity of Bone Mineral Distribution in 2D Projection Images of Trabecular Bone is Associated With Its Micro-Architecture and Biomechanical Properties
Authors: Dong X. Neil , Huang Ning , Shirvaikar Mukul V. , Wang Xiaodu
Published: July 2013

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to apply a novel stochastic model [1] to characterize and quantitatively describe the spatial variation of bone properties such as mineralization.
Patient-Specific Modelling of Intracranial Aneurysm Evolution
Authors: Watton Paul N. , Homer Marc , Penrose Justin , Thompson Harry , Chen Haoyu , Selimovic Alisa , Ventikos Yiannis
Published: July 2013

Intracranial aneurysms appear as sac-like outpouchings of the cerebral vasculature wall; inflated by the pressure of the blood that fills them. They are relatively common and affect up to 5% of the adult population. Fortunately, most remain asymptomatic. However, there is a small but inherent risk of rupture: 0.1% to 1% of detected aneurysms rupture every year. If rupture does occur there is a 30% to 50% chance of fatality. Consequently, if an aneurysm is detected, clinical intervention may be deemed appropriate. Therapy is currently aimed at pre-rupture detection and preventative treatment. However, interventional procedures are not without risk to the patient. The improvement and optimization of interventional techniques is an important concern for patient welfare and is necessary for rationalisation of healthcare priorities. Hence there is a need to develop methodologies to assist in identifying those ICAs most at risk of rupture. We focus on the mathematical modelling and computational simulation of ICA evolution. Models must take into consideration: (i) the biomechanics of the arterial wall; (ii) the biology of the arterial wall and (iii) the complex interplay between (i) and (ii), i.e. the mechanobiology of the arterial wall. The ultimate ambition of such models is to aid clinical diagnosis on a patient-specific basis. However, due to the significant biological complexity coupled with limited histological information such models are still in their relative infancy. Current research focuses on simulating the evolution of an ICA with an aim to yield insight into the growth and remodelling (G&R) processes that give rise to inception, enlargement, stabilisation and rupture. We present a novel Fluid-Structure-Growth computational framework for modelling aneurysm evolution.
MMP and Matrix Degradation in Tendon
Authors: Riley Graham
Published: July 2013

Tendons are often affected by chronic pain and rupture, particularly in the middle-aged and elderly, but also in the sporting and physically active younger population. Although not life threatening, these conditions (‘tendinopathy’) are major causes of morbidity, and estimated to cost tens of millions of pounds every year in lost productivity. I have previously shown that the organisation and composition of the tendon extracellular matrix (ECM) are substantially altered in tendinopathy, and that these changes may predispose to tendon pain and rupture. I have also shown that most tendinopathy is degenerative, with changes in fibroblast activity and increased ECM turnover. ECM degradation, in both normal physiology and pathology, is largely mediated by metalloproteinase enzymes: the matrix metalloproteinases (MMP) and the ‘A Disintegrin And Metalloproteinase with ThromboSpondin motifs’ (ADAMTS). I have previously shown that there are differences in MMP activity in chronic tendinopathy compared to acute tendon injuries, as well as differences in collagen turnover between tendons. Thus, although it is not known which enzymes are implicated, perturbation of the balance of metalloproteinase activities is a potential cause of tendinopathy.
Fibroblast Behavior on Tunable Gels With Decreasing Elasticity
Authors: Previtera Michelle L. , Trout Kevin , Chippada Uday , Schloss Rene , Langrana Noshir A.
Published: July 2013

Cells sense and react to various extracellular matrix (ECM) cues including chemical and physical cues. Previous studies in our laboratory and others have used static substrates, where the elastic properties remain unchanged throughout the culture period, to examine the effects of mechanical stiffness on neuron and fibroblast behavior [1–4]. However, in vivo, the ECM is dynamic and alters due to pathological, developmental, and external factors [5]. To study the effects of dynamic ECM changes on cell behavior, we developed a DNA-crosslinked, polyacrylamide gel (DNA gel) that allows us to study how dynamic changes in ECM stiffness affect cell behavior [6, 7].