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Viewing 181 to 210 of 4781
2013-09-17
Technical Paper
2013-01-2238
Manoj Radle, Biswadip Shome
Liquid ring pumps are used in aircraft fuel systems in conjunction with main impeller pumps. These pumps are used for priming the pump system as well as to remove fuel vapor and air from the fuel. Prediction of cavitation in liquid ring pumps is important as cavitation degrades the performance of these pumps and leads to their failure. As test based assessment of cavitation risk in liquid ring pump is expensive and time consuming, recent approaches have been to assess and predict the risk of cavitation using Computational Fluid Dynamics (CFD) methods with the goal to quicken the design process and optimize the performance of these pumps. The present study deals with the development and assessment of a CFD methodology to simulate cavitation for a liquid fuel pump used in aircraft fuel systems. The study simulates the cavitation phenomena using a multi-phase flow model consisting of fuel vapor, air, and liquid fuel phases.
2013-09-17
Technical Paper
2013-01-2101
Ivana Durickovic, Mario Marchetti, Stephanie Poissonnier, Guillaume Casteran, Rachel Mansour, Nathalie Schweigert, Benoit Mars
Winter maintenance is based on the intervention of operating services, as well as the use of deicers. Each year, in France, thousands of tons of deicers are spread through runways and taxiways. On the airport sector, the main deicers are sodium or potassium acetates and formates. All these deicers aim to prevent ice formation (preventive strategy) and/or improve the ice melting of snow residual film (curative strategy) at temperatures below 0°C. The operating principle of these compounds is based on the lowering of the solution's freezing point once dissolved in water. The phase diagram's knowledge is predominant to determine the deicer's amount to be applied on the surface. It provides a way to optimize their amounts applied with respect to weather conditions, present or forecasted. The Center for Technical Studies of Equipment in East of France (CETE de l'Est) developed and implemented a method based on Raman spectroscopy to characterize aqueous solutions of airport de-icers.
2013-09-17
Journal Article
2013-01-2145
Jonathan L. Geisheimer, David Kwapisz, Thomas Holst, Michael Hafner
Blade tip clearance is a key design parameter for gas turbine designers. This parameter is often measured during engine testing and development phases as part of design validation but has yet to be utilized during normal engine fleet operation. Although blade tip clearance measurements are often mentioned for fleet operation in the context of active clearance control, the use of blade tip clearance measurements can provide an additional benefit for engine health monitoring. This paper explores the use of blade tip clearance sensors for engine condition monitoring of hot section blades. Blade tip clearance, especially in the first stage turbine, has an impact on exhaust gas temperature. The use of tip clearance measurements can provide supplementary information to traditional EGT measurements by providing a direct measurement of wear on the blade tips.
2013-09-17
Journal Article
2013-01-2219
Peter Foote
The first cross-industry guidelines for the implementation of structural health monitoring for aerospace applications have been created as a SAE International Aerospace Recommended Practices document: SAE ARP 6461 ‘Guidelines for Implementation of Structural Health Monitoring on Fixed Wing Aircraft’ [1]. These guidelines have brought together manufacturers, operators / users, systems integrators, regulators, technology providers and researchers to produce information on the integration of SHM into aircraft maintenance procedures, generic requirements and advice on validation, verification and airworthiness. The take-up of SHM in the aerospace industry has been slow, in part due to the lack of accepted industry practices surrounding not just the technology itself (sensors and sensor systems) but also the associated issues arising from the introduction of new methods into aircraft maintenance.
2013-09-17
Journal Article
2013-01-2183
Joao Pedro Pinheiro Malere, Luis Gustavo dos Santos
1 The current pressure across the entire aerospace industry to reduce operating costs and increase efficiency has arguably never been greater. Thus the need to improve parameters such as availability and reliability, and increase the tools and services associated with more efficient aircraft operations and sustainment is now paramount. Moreover, these improvements are seen by many as important factors that define the differentiation and competitiveness of not only current but also future aircraft fleets. The paper will focus on some of the opportunities for OEMs that arise from implementing Integrated Vehicle Health Management (IVHM) systems on their platforms and the challenges associated with evaluating the costs and benefits of their implementation and operation.
2013-09-17
Journal Article
2013-01-2201
Joshua Benhabib
Manufacturing operations introduce unreliability into hardware that is not ordinarily accounted for by reliability design engineering efforts. Inspections and test procedures normally interwoven into fabrication processes are imperfect, and allow defects to escape which later result in field failures. Therefore, if the reliability that is designed and developed into an equipment/system is to be achieved, efforts must be applied during production to insure that reliability is built into the hardware. There are various ways to improve the reliability of a product. These include: Simplification Stress reduction/strength enhancement Design Improvement Using higher quality components Environmental Stress Screening before shipment Process Improvements, etc. This paper concentrates on ‘Manufacturing Process Improvement’ effort through the use of design of experiments, (DOE). Hence, improved levels of reliability can be achieved.
2013-09-17
Journal Article
2013-01-2301
Yao Wang, Shon Grabbe
When the demand for either a region of airspace or an airport approaches or exceeds the available capacity, miles-in-trail (MIT) restrictions are the most frequently issued traffic management initiatives (TMIs) that are used to mitigate these imbalances. Miles-in-trail operations require aircraft in a traffic stream to meet a specific inter-aircraft separation in exchange for maintaining a safe and orderly flow within the stream. This stream of aircraft can be departing an airport, over a common fix, through a sector, on a specific route or arriving at an airport. This study begins by providing a high-level overview of the distribution and causes of arrival MIT restrictions for the top ten airports in the United States. This is followed by an in-depth analysis of the frequency, duration and cause of MIT restrictions impacting the Hartsfield-Jackson Atlanta International Airport (ATL) from 2009 through 2011.
2013-04-08
Technical Paper
2013-01-1705
Mohamed F. Aly
The engine fault detection problem is of special interest in the automotive industry due to its direct implementation in the diagnostics of typical engine problems as well as engine preventive and predictive maintenance measures. The procedure of identifying the type and location of an engine fault can be very costly and time consuming. This paper is dedicated to the identification of more than 26 different engine faults using multi-level signal processing technique and an exhaustive search in a predefined database. This database can be easily modified and/or updated to include new types of faults; it also gives the flexibility of providing warning signals of unidentified problems whenever it detects one.
2013-04-08
Journal Article
2013-01-0607
Mahdi Norouzi, Efstratios Nikolaidis
Estimation of the probability of failure of mechanical systems under random loads is computationally expensive, especially for very reliable systems with low probabilities of failure. Importance Sampling can be an efficient tool for static problems if a proper sampling distribution is selected. This paper presents a methodology to apply Importance Sampling to dynamic systems in which both the load and response are stochastic processes. The method is applicable to problems for which the input loads are stationary and Gaussian and are represented by power spectral density functions. Shinozuka's method is used to generate random time histories of excitation. The method is demonstrated on a linear quarter car model. This approach is more efficient than standard Monte Carlo simulation by several orders of magnitude.
2013-04-08
Journal Article
2013-01-0606
Vijitashwa Pandey, Zissimos Mourelatos
The classical definition of reliability may not be readily applicable for repairable systems. Commonly used concepts such as the Mean Time Between Failures (MTBF) and availability can be misleading because they only report limited information about the system functionality. In this paper, we discuss a set of metrics that can help with the design of repairable systems. Based on a set of desirable properties for these metrics, we select a minimal set of metrics (MSOM) which provides the most information about a system, with the smallest number of metrics. The metric of Minimum Failure Free Period (MFFP) with a given probability generalizes MTBF because the latter is simply the MFFP with a 0.5 probability. It also generalizes availability because coupled with repair times it provides a clearer picture of the length of the expected uninterrupted service. Two forms of MFFP are used: transient and steady state.
2013-04-08
Journal Article
2013-01-0946
Vicente Romero, Joshua Mullins, Laura Swiler, Angel Urbina
This paper discusses the treatment of uncertainties corresponding to relatively few samples of random-variable quantities. The importance of this topic extends beyond experimental data uncertainty to situations involving uncertainty in model calibration, validation, and prediction. With very sparse samples it is not practical to have a goal of accurately estimating the underlying variability distribution (probability density function, PDF). Rather, a pragmatic goal is that the uncertainty representation should be conservative so as to bound a desired percentage of the actual PDF, say 95% included probability, with reasonable reliability. A second, opposing objective is that the representation not be overly conservative; that it minimally over-estimate the random-variable range corresponding to the desired percentage of the actual PDF. The presence of the two opposing objectives makes the sparse-data uncertainty representation problem an interesting and difficult one.
2013-04-08
Journal Article
2013-01-1384
Zhen Jiang, Wei Chen, Yan Fu, Ren-Jye Yang
Reliability-based design optimization (RBDO) has been widely used to obtain a reliable design via an existing CAE model considering the variations of input variables. However, most RBDO approaches do not consider the CAE model bias and uncertainty, which may largely affect the reliability assessment of the final design and result in risky design decisions. In this paper, the Gaussian Process Modeling (GPM) approach is applied to statistically correct the model discrepancy which is represented as a bias function, and to quantify model uncertainty based on collected data from either real tests or high-fidelity CAE simulations. After the corrected model is validated by extra sets of test data, it is integrated into the RBDO formulation to obtain a reliable solution that meets the overall reliability targets while considering both model and parameter uncertainties.
2013-01-09
Technical Paper
2013-26-0094
R. P. Senthil Kumar, N. Jaya Kumar, Sajith Nair
BSR (Buzz, Squeak and Rattle) is one of the oldest concerns in automobiles which directly reflect the build, assembly and manufacturing quality of a vehicle. In a cabin all the areas where there is relative motion between two components, such as trims, instrument panel and seats, are prone to squeak. This paper explains the study of seat squeak measurement and diagnosis which is a major concern for one of the products which is already in the market. Since squeak is a friction induced non stationary phenomenon, lot of effort was required to generate squeak in both component as well as vehicle level. At component level, electrodynamic shaker was extensively used for generation of squeak signals. In Vehicle level, driving through different road patterns, pave track and forced excitation on four posters are performed for generation of squeak signals. In this paper usage of wavelet and Zwikker loudness are explained for the diagnosis of seat squeak to identify the problematic frequencies.
2013-01-09
Technical Paper
2013-26-0090
Venkateswararao Manchi, Prasath R, Mansinh Kumbhar
Ground clearance plays an important role in Sports Utility Vehicles (SUV). Designers are good in designing their own systems but when it comes to integration of systems, the impact of one system on others and cascading effects become the major problems in full vehicle development. The test vehicle is a monocoque construction with power train in transverse (east-west) direction. Vehicle shudder is observed in lateral direction exciting the steering column, floor during the low gear power train run up in Wide Open Throttle (WOT) condition. The shudder is felt predominantly on the front half of the vehicle. Being a low frequency phenomenon with high energy it becomes critical and the phenomenon is easily perceivable by passenger. The paper discusses the measurement and analysis procedures to identify the root cause of shudder. Different modifications are tried out based on the analysis and an optimum solution is selected.
2012-10-22
Technical Paper
2012-01-2097
Ginger Shao, David Goldstein, Kyusung Kim, Emmanuel Nwadiogbu, Rudy Proenza, My Tran, David Williams
An emerging emphasis for the design and development of vehicle condition-based maintenance (CBM) systems amplifies its use for conducting vehicle maintenance based on evidence of need. This paper presents a systems engineering approach to creating an integrated vehicle health management (IVHM) architecture which places emphasis on the system's ultimate use to meet the operational needs of the vehicle and fleet maintainer, to collect data, conduct analysis, and support the decision-making processes for the sustainment and operations of the vehicle and assets being monitored. The demand for a CBM system generally assumes that the asset being monitored is complex or that the operational use of the system demands complexity, timely response or that system failure has catastrophic results. Ground vehicles are such complex systems, which is the emphasis of this paper. Developing the system architecture of such complex systems demands a systematic approach.
2012-10-22
Technical Paper
2012-01-2095
Kirby J. Keller, Jeanne Maggiore, Robab Safa-Bakhsh, William Rhoden, Michael Walz
The Sensory Prognostics and Management Systems (SPMS) program sponsored by the Federal Aviation Administration and Boeing developed and evaluated designs to integrate advanced diagnostic and prognostic (i.e., Integrated Vehicle Health Management (IVHM) or Health Management (HM)) capabilities onto commercial airplanes. The objective of the program was to propose an advanced HM system appropriate for legacy and new aircraft and examine the technical requirements and their ramifications on the current infrastructure and regulatory guidance. The program approach was to determine the attractive and feasible HM applications, the technologies that are required to cost effectively implement these applications, the technical and certification challenges, and the system level and business consequences of such a system.
2012-10-22
Technical Paper
2012-01-2173
Kevin McCarthy, Alex Heltzel, Eric Walters, Richard Deitrich, Justin Coffey, Sam Septembre, Michael McGonigle
Advanced tactical aircraft and their propulsion systems produce an order of magnitude more heat than legacy designs and offer fewer viable heat rejection opportunities. The current approach uses aircraft fuel as a primary heat sink which is either cooled by ram air and returned to the aircraft, or rejected off the aircraft when burned by the engine. Traditionally, aircraft have been limited in mission capability by the design performance and the available fuel quantity; however, potential thermal limitations have presented a new mission challenge. Joker and bingo range notifications based on fuel quantity remaining are common on modern fighters to ensure the pilot has the foresight to complete a mission segment and return to base before running out of fuel. Now, pilots may need to consider the possibility of a similar thermal joker/bingo concept until alternative LO heat rejection methods are discovered that remove limitations.
2012-10-22
Journal Article
2012-01-2106
Nayeff Najjar, Chaitanya Sankavaram, James Hare, Shalabh Gupta, Krishna Pattipati, Rhonda Walthall, Paul DOrlando
This paper addresses the issues of data reduction, visualization, clustering and classification for fault diagnosis and prognosis of the Liquid Cooling System (LCS) in an aircraft. LCS is a cooling system that consists of a left and a right loop, where each loop is composed of a variety of components including a heat exchanger, source control units, a compressor, and a pump. The LCS data and the fault correlation analysis used in the paper are provided by Hamilton Sundstrand (HS) - A United Technologies Company (UTC). This data set includes a variety of sensor measurements for system parameters including temperatures and pressures of different components, along with liquid levels and valve positions of the pumps and controllers. A graphical user interface (GUI) is developed in Matlab that facilitates extensive plotting of the parameters versus each other, and/or time to observe the trends in the data.
2012-10-22
Journal Article
2012-01-2233
Michael Ballas, Fred Potter
Aircraft-level health management requires effective management of data flow. As future aircraft adopt conditioned base maintenance (CBM) and/or integrated vehicle health management (IVHM) protocols, there is need to manage infinitely more data communication on and off the aircraft. This paper explores the idea of employing an Electronic Power Distribution System (EPDS) as a “network backbone” for aircraft-level prognostics. Using EPDS to capture and distribute this data provides a practical solution that minimizes system hardware on future CBM/IVHM enabled aircraft. Employing the Electronic Circuit Breaker (ECB) in a more enhanced sensor state and as a data communication tool, provides tremendous value given its multipurpose capability.
2012-10-22
Journal Article
2012-01-2234
Freeman Rufus, Ash Thakker, Sean Field, Nathan Kumbar
Electrical and mechanical failures (such as bearing, winding and rotating-diode failures) combine to cause premature failures of the generators, which become a flight safety issue forcing the crew to land as soon as practical. Currently, diagnostic / prognostic technologies are not implemented for aircraft generators where repairs are time-consuming and costly. This paper presents the development of feature extraction and diagnostic algorithms to 1) differentiate between these failure modes and normal aircraft operational modes; and 2) determine the degree of damage of a generator. Electrical signature analysis (ESA) based time-domain features were developed to distinguish between healthy and degraded generators while taking into account their operating conditions. Frequency-domain based ESA techniques are used to identify the degraded components within the generators.
2012-10-22
Journal Article
2012-01-2239
John E. James
Aviation battery maintenance is continuing to evolve. Much recent effort has been devoted to battery redesign to totally maintenance free or non-maintainable batteries. These batteries are placed into service and replaced at predetermined intervals. Still, some batteries are failing before their scheduled replacement period. For this reason attention is being focused on methods to transition batteries to an on-condition maintenance status. Nickel-Cadmium (NiCd) and Valve Regulated Lead-Acid (VRLA) are used to start engines, provide emergency back-up power, and assure ground power capability for maintenance and pre-flight checkout. Various Lithium-based battery chemistries are also now being developed and considered for use in these applications. As these functions are mission essential, State of Health (SoH) recognition is critical. SoH includes information regarding battery energy, power and residual cycle life.
2012-10-22
Journal Article
2012-01-2109
Laurence Wesson
Successful use of fiber optic interconnects in high-performance platforms and applications depends on viable technologies for their repair and installation. Splicing is often desirable, either to repair a damaged interconnect or to install it, particularly where it is difficult or impossible to access all necessary locations for complete removal and replacement. However, reliable aerospace cable splices must endure conditions as adverse as those for which the original cable was specified. In addition, the splicing technology must be usable with a high degree of reliability under difficult aerospace working conditions. Mechanical splices have shown some promise for the repair of multi-mode aerospace fiber cables, but they face daunting difficulties in splicing single mode fiber cables, which are being ever more seriously considered for new and upgraded systems.
2012-10-22
Technical Paper
2012-01-2096
Chris Hickenbottom, Kyusung Kim, Onder Uluyol
This paper discusses recent improvements made by Honeywell's Condition-Based Maintenance (CBM) Center of Excellence (COE) to Mechanical Health Management (MHM) algorithms. The Honeywell approach fuses Condition Indicators (CIs) from vibration monitoring and oil debris monitoring. This paper focuses on using MHM algorithms for monitoring gas turbine engines. First an overview is given that explains the general MHM approach, and then specific examples of how the algorithms are being refined are presented. One of the improvements discussed involves how to detect a fault earlier in the fault progression, while continuing to avoid false alarms. The second improvement discussed is how to make end of life thresholds more robust: rather than relying solely on the cumulative mass of oil debris, the end of life indication is supplemented with indicators that consider the rate of debris generation.
2012-09-24
Technical Paper
2012-01-2056
Rod Huisinga, Kurt Rottier, John Baertlein, Alex Kaye
The designers of heavy-duty off-road vehicles have been facing increasing pressure to reduce the cost and time required for assembly and maintenance. While the requirement to reduce assembly times is mainly an OEM driven objective, the requirement to reduce maintenance times is frequently driven by the customer. The design team is usually faced with the challenge of balancing functional requirements with what are often viewed as wish lists of easy assembly and maintenance, under the pressure of ever shorter development cycles. As a result, vehicle maintainability and ease of assembly are often overlooked early in the design cycle which can lead to less than desired results. This paper explores the design objectives and resultant solutions which were developed in the creation of the power-pack of a heavy-duty off-road vehicle.
2012-09-24
Technical Paper
2012-01-2032
Mahesh J Pardeshi, Ravindra Rajhans, M Srinivas, Shailesh Patil, Gautam Pingle
Designing a cabin tilting system for Light Commercial Vehicles using a single torsion bar becomes challenging considering the operator safety and stringent design weight targets. Performance of a good tilting system entirely depends on cabin mass and location of centre of gravity with respect to (w.r.t) to tilting pivot point. Cabin Mass and COG location are very difficult to estimate while designing a new cabin as it is dependent on the maturation of all other cabin aggregates and also the accessories added by the customer. Incorporation design parameter changes like increasing cab tilting angle and increasing torsion bar length, in the later stages of product development, becomes expensive. The objective of this paper is to come up with an optimum design of a single torsion bar tilting employing “Taguchi optimization” for deciding the optimum levels of control factors, which ensures desired performance (i.e tilting effort vs.
2012-04-16
Technical Paper
2012-01-1036
Richard A. Scholer, Michael Bourton, Dan Mepham, Arindam Maitra, Tim Godfrey, Doug Oliver, Donthy Venkatesh, Eloi Taha, Michael Muller, Cliff Fietzek
This paper is the third in the series of documents designed to record the progress on the SAE Plug-in Electric Vehicle (PEV) communication task force. The initial paper (2010-01-0837) introduced utility communications (J2836/1™ & J2847/1) and how the SAE task force interfaced with other organizations. The second paper (2011-01-0866) focused on the next steps of the utility requirements and added DC charging (J2836/2™ & J2847/2) along with initial effort for Reverse Power Flow (J2836/3™ & J2847/3). This paper continues with the following: 1. Completion of DC charging's 1st step publication of J2836/2™ & J2847/2. 2. Completion of 1st step of communication requirements as it relates to PowerLine Carrier (PLC) captured in J2931/1. This leads to testing of PLC products for Utility and DC charging messages using EPRI's test plan and schedule. 3. Progress for PEV communications interoperability in J2953/1.
2012-04-16
Technical Paper
2012-01-1342
Dimitrios T. Hountalas, Antonis A. Antonopoulos, Georgios N. Zovanos, Roussos G. Papagiannakis
High efficiency, power concentration and reliability are the main requirements from Diesel Engines that are used in most technical applications. This becomes more important with the increase of engine size. For this reason the aforementioned characteristics are of significant priority for both marine and power generation applications. To guarantee efficient engine operation and maximum power output, both research and commercial communities are increasingly interested in methods used for supervision, fault-detection and fault diagnosis of large scale Diesel Engines. Most of these methods make use of the measured cylinder pressure to estimate various critical operating parameters such as, brake power, fuel consumption, compression status, etc. The results obtained from the application of any diagnostic technique, used to assess the current engine operating condition and identify the real cause of the malfunction or fault, depend strongly on the quality of these data.
2012-04-16
Journal Article
2012-01-0064
Vijitashwa Pandey, Zissimos Mourelatos
In this article we present an approach to identify the system topology using simulation for reliability calculations. The system topology provides how all components in a system are functionally connected. Most reliability engineering literature assumes that either the system topology is known and therefore all failure modes can be deduced or if the system topology is not known we are only interested in identifying the dominant failure modes. The authors contend that we should try to extract as much information about the system topology from failure or success information of a system as possible. This will not only identify the dominant failure modes but will also provide an understanding of how the components are functionally connected, allowing for more complicated analyses, if needed. We use an evolutionary approach where system topologies are generated at random and then tested against failure or success data. The topologies evolve based on how consistent they are with test data.
2012-04-16
Technical Paper
2012-01-0125
Seyed Ehsan Samadani, Roydon A. Fraser, Michael Fowler
Due to the high power and energy density and also relative safety, lithium ion batteries are receiving increasing acceptability in industrial applications especially in transportation systems with electric traction such as electric vehicles and hybrid electric vehicles. In this regard, to ensure performance reliability, accurate modeling of calendar life of such batteries is a necessity. In fact, potential failure of Li-ion battery packs remains a barrier to commercialization. Battery pack life is a critical feature to warranty and maintenance planning for hybrid vehicles, and will require adaptive control systems to account for the loss in vehicle range, and loss in battery charge and discharge efficiency. Failure not only results in large replacement costs, but also potential safety concerns such as overheating or short circuiting which may lead to fires.
2012-04-16
Journal Article
2012-01-0070
Jing Li, Zissimos Mourelatos, Amandeep Singh
Reliability is an important engineering requirement for consistently delivering acceptable product performance through time. It also affects the scheduling for preventive maintenance. Reliability usually degrades with time increasing therefore, the lifecycle cost due to more frequent failures which result in increased warranty costs, costly repairs and loss of market share. In a lifecycle cost based design, we must account for product quality and preventive maintenance using time-dependent reliability. Quality is a measure of our confidence that the product conforms to specifications as it leaves the factory. For a repairable system, preventive maintenance is scheduled to avoid failures, unnecessary production loss and safety violations. This article proposes a methodology to obtain the optimal scheduling for preventive maintenance using time-dependent reliability principles.
Viewing 181 to 210 of 4781