Comparative Study of a Powerplant Life Consumption Rate When Installed in Two Different Aircraft Variants

The Hellenic Air Force (HAF) operates both EMB-145 and EMB-135 LR versions of Embraer aircraft, used in surveillance and civil missions respectively. These aircraft are equipped with the same version of Rolls Royce, AE 3007 turbofan engine. This study aims to quantify and compare the life consumption rate of this engine when installed in each of the two aircraft variants. Two typical missions, one for each variant, were constructed based on mission profile data dictated by the aircraft commanders. For each mission profile segment, corresponding engine data were matched out of the engine recordings archives held by the Hellenic Air Force. The life consumption rate was based on the Low Cycle Fatigue (LCF) and creep cumulative detrimental effect on the rotor blades of the 1st High-Pressure Turbine stage. For the LCF, the rainflow method was used to determine the respective loading cycles, whereas the Larson - Miller parameter method was used to determine the consumed life fractions due to creep. The main conclusion of the study was that the engine when installed in the EMB-145 military variant, is much more loaded. Despite the fact absolute life consumption values could hide a great level of uncertainty, the comparative outcomes wherein errors are, to a certain extent, cancelled out, could be used as a rule of thumb when monitoring engine life consumption rates.

Turboprop Engine Loading During High and Low Maneuver Intensity Flight Mode

The life consumption rate of the aircraft engine is a vital input for aircraft operators who aim to an efficient fleet management. T6 aircraft, propelled by the PT6 turboprop engine, is operated by the Hellenic Air Force, both for training and aerobatic purposes. The current study focuses on quantifying and comparatively assessing the engine life consumption rate for the following missions: i) An “aerobatic” mission which is a typical high intensity maneuver flight and ii) a “training for patrol” mission, representing a typical low intensity maneuver flight. Missions were selected with the criterion of setting the lowest and the highest possible engine loading during a certain mission. In other words, the goal of the study is to define the extent of the loading the engine can encounter as a propulsion system of the T-6 aircraft during a certain mission. This is the first step before proceeding in setting up a methodology for continuously monitoring the engine life consumption rate in support of the squadron flight management plan. The study was based on real time data recorded during the respective flights. An engine model built using “GasTurb” gas turbine simulation software was used to fill in engine operating data at stations where recordings have not been taken. Engine life consumption was based on creep and low cycle fatigue failure mechanisms of the first gas generator turbine stage. Creep life fractions were calculated based on the Larson-Miller parameter curves and the fatigue cycles were counted using the rainflow method. The study showed that the life consumption is about 10 times lower when the aircraft is operated at a low loading mode as opposed to a high loading mode.

The Dark Side of Transnational Mobility: Croatian Travel Writers in Hitler’s New Europe

This article analyses the use of Europeanizing discourses in the travel writing of Croat visitors to the Third Reich. Situating these visits in the context of transnational exchanges in Hitler’s new Europe and the war against the Soviet Union, it considers a number of specific case studies of travel between Croatia and Nazi Germany. It argues that the European discourse of writers, journalists, and youth activists in the Ustasha-led Independent State of Croatia served a number of specific purposes. First, they created a space of normality in an extremely violent state, providing an illusion of stability. By bringing the sights, sounds, and pleasures of travel to the near abroad back to Croatia in the form of books, magazine articles, and mobile film reels, they also gave citizens a glimpse of the good life, consumption, and materiality. As such, these travelogues and accounts of journeys overseas also aimed to persuade intellectuals and members of the cultural elite who did not support the Ustasha regime of the various material and professional “club goods” that might accrue to them by becoming active supporters of the regime. Furthermore, they served to create an impression of mobility in a surveillance state in which even internal travel was extremely restricted. Finally, in depicting Nazi-led war in the East and the struggle against the “East within”—in the form of the campaign of genocide against Serbs, Jews, Roma and so-called “asocials”—to building European brotherhood, modernization, and becoming an essential member of the new Europe, they became a source of regime legitimation, thereby telling us important things about the subjectivity of both the state and ideological tourists in a time of terror, war, and occupation.

An online monitoring method for creep-fatigue life consumption with real-time damage accumulation

Online damage evaluation based on monitored complex cyclic loadings has become an important technique for reliability assessment, especially in high-temperature environments where creep occurs in addition to fatigue. Accuracy and rapidity of calculation are basic requirements for online damage evaluation methods. However, current creep damage evaluation methods seldom consider the fluctuation in stress, which leads to inaccuracy in life-consumption estimates. In addition, traditional cycle-counting methods are not applicable to online use. In this study, an online creep-fatigue damage evaluation method is proposed that accounts for the creep behavior that occurs under fluctuating loads. The cycle-counting method is modified from a rainflow-counting algorithm; it broadens the counting of half-cycles and adopts a new equivalent temperature in the stress-strain response calculation. The proposed method is explained in detail and demonstrated with a case study. The application of this method to a high-temperature, high-pressure pipe demonstrates its online applicability and accuracy. A time-matching algorithm is developed to display the damage evolution in real time, thus revealing the link between the incremental damage and the current load conditions, and yielding an intuitive demonstration of a given component’s state of health.

Drinking Water Preference among Students in UiTM Perlis using Fuzzy AHP

Due to the decrease in groundwater quality, as a result for Malaysia's to make the bottled water as their basic source of drinking water. It is a fact that each bottled water contains various types of minerals and each mineral will have its own benefits fo r general human health. Calcium, magnesium, zinc, iron, sodium, and more are common kinds of minerals found in bottled water. The type of minerals that are in the bottled drinking water depends on the water source. Many customers around the world, particul arly Malaysians, have turned to bottled water as their primary source of potable water. The research was performed to determine the best and most preferred brands of mineral bottled water available in UiTM Arau, Perlis in terms of its advantages and everyd ay mineral content. Fuzzy AHP is a hybrid method that combines Fuzzy Set Theory and AHP. It has been developed to take into account uncertainty and imprecision in the evaluations. The decision - making method used by multi - criteria is the FAHP method as an a pproach to the problem of selection bottled with mineral water. In this paper, the mineral water brands bottled namely "Spritzer," "Bleu" and "Ice Mountain" are analyzed and presented as sold in UiTM Perlis. The criterion given is price, availability, tast e, water source, and packaging. Comparison is made between these three brands to decide which of these brands is more favoured and desirable among UiTM Perlis students based on the weight of alternatives regarding the criteria. The results obtained were th at Spritzer has the greatest total score with a weight of 0.439. The analysis shows that the "Spritzer" brand is better compared to the other two daily life consumption brands, which weight is 0.439 with 5 criteria. Bleu, however, offers a better weighty f lavour, 0.386 of those two brands of mineral water bottles. This study can be a factor in influencing consumer behaviour and providing information to local bottled water companies' marketers. It will ultimately increase their profitability and revenue by n ew and better marketing techniques. In addition, bottled water producers can also produce bottled water that meets the needs of Malaysian consumers. In addition, this study will provide consumers with a greater understanding of the standard of bottled wate r that may affect the environment, such as pollution, etc. This study will also benefit both marketers and consumers by helping them make educated decisions on choosing the most appropriate mineral water bottled for consumption in keeping with their health concerns these days.

Correlation Between Engine and Aircraft Loadings for Several Mission Types

Fighter aircraft constitutes a well-defined class of aircraft. Their extensive use on a daily basis by operators stands as a strong motive behind studies that concern their rate of “exhaustion ”. For an aircraft operator either civil or military, it is very important at any point in time to have a clear view of the engines’ and the aircrafts’ operating condition. This is valuable information in order to foresee undesired incidences and in order to schedule missions in accordance to the actual and anticipated maintenance needs. For the latter, the operator would also need to know the rate of the engine and the aircraft life consumption per mission. The current study concerns the F-16 Block 52M aircraft, powered by the Pratt and Whitney F100-PW-229 engine. Aircraft is continuously subjected to crack growth mechanisms while flying. On the other hand, engines also go through Low Cycle Fatigue (LCF) cycles and creep prominent conditions while being in operation. The engine and the aircraft structural condition are continuously monitored, based on real time data recordings. To the extent of the authors’ knowledge, that is a common practice for most F-16 users. However, what was found to be missing from the international literature was a study to quantify any potential correlation between the aircraft loading and the engine loading for all typical mission types an aircraft of this type undertakes. For users that have already installed an aircraft loading monitoring system like “Aircraft Structural Integrity Program” (ASIP) it would be very useful to set a “rule of thumb” aside regarding the degree of correlation between aircraft and engine loading. Engine life consumption rate was estimated based on the creep and LCF failure mechanisms applied on the most critical engine section, the turbine. Engine recordings were picked from an arbitrary sample of 200 flights of a certain aircraft, wherein most typical mission types could be found. Turbine and subsequently blade temperature as well as blade stress were calculated using a very narrow time step. These data along with blade material data were fed in the Larson Miller model, to set an algorithm for estimating life consumption due to creep. Engine Total Accumulated Cycles (TACs) which account for LCF loading, are directly measured by the engine recorder, based on an embedded algorithm. Aircraft loading is calculated based on the accelerations the aircraft structures encounter during flight. These are also recorded under a very narrow time step. Last step was the correlation of the engine life consumption against the aircrafts’ loading for typical mission types. Scatter diagrams and statistical measures were used, in order to define the degree of correlation between them.

Augmented Kalman filter with a reduced mechanical model to estimate tower loads on a land-based wind turbine: a step towards digital-twin simulations

This article presents an application of the Kalman filtering technique to estimate loads on a wind turbine. The approach combines a mechanical model and a set of measurements to estimate signals that are not available in the measurements, such as wind speed, thrust, tower position, and tower loads. The model is severalfold faster than real time and is intended to be run online, for instance, to evaluate real-time fatigue life consumption of a field turbine using a digital twin, perform condition monitoring, or assess loads for dedicated control strategies. The mechanical model is built using a Rayleigh–Ritz approach and a set of joint coordinates. We present a general method and illustrate it using a 2-degrees-of-freedom (DOF) model of a wind turbine and using rotor speed, generator torque, pitch, and tower-top acceleration as measurement signals. The different components of the model are tested individually. The overall method is evaluated by computing the errors in estimated tower-bottom-equivalent moment from a set of simulations. From this preliminary study, it appears that the tower-bottom-equivalent moment is obtained with about 10 % accuracy. The limitation of the model and the required steps forward are discussed.

Codes and Standards for Managing Degradation of Boilers in Service

Degradation of pressure equipment is becoming an important issue due to increasing asset service time in process and power plants across Europe. For this reason it is important to assess life consumption of these assets to avoid catastrophic failures. Therefore it is necessary to refer to national/international normative on this subject. At present time the Italian thermotechnical committee (CTI) has drawn up a comprehensive set of norms which help the user to set up an inspection plan to investigate and assess degradation of pressure vessels and boilers. In the first part of this paper creep damage of Steam Generators is analyzed. For this purpose results of INAIL (Istituto Nazionale per l’ Assicurazione contro gli Infortuni sul Lavoro) database of steam boilers with 100’000 service hours or more is illustrated. Critical components are identified with reference to materials, geometry and operating parameters (pressure, temperature and time). At the end of the design life cycle, components of pressure equipment operated in creep regime must subjected to specific checks to estimate their residual life and the suitability for further use in safety conditions. The procedure allows to define reinspection intervals keeping acceptable the risk associated with the further use of the component related to creep even in evidence of defects in progress. The first check must be performed after 100,000 hours of effective use. Then, residual life evaluations must be repeated according to period of time that are defined as function of the results of all the checks carried out. In the second part of this paper boiler degradation is discussed with reference to NDT results and in-field inspection campaigns which are carried out traditionally after 45 years of service time, to minimize the risk of pressure components failures. In this paper results of different case studies are discussed with reference to degradation mechanisms and applicable standards.