Wyniki wyszukiwania - BazTech

1

Selected problems of transmission wear of the Mi-24 helicopter

Gębura A., Zientalski K.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2015

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nr 37

25--44

EN

The hypothesis of mutual, destructive impact of the worn upper bearing of the WR-24 transmission on the Mi-24 helicopter's gearbox was stated. The Mi-24 is the only helicopter operated in Poland, in which the gearbox is mounted outside the main transmission – in the centre of the transmission shaft, between the main gearbox and the tail rotor. Damage to the gears in the gearbox of power generators is equivalent to termination of the tail rotor's drive. Such a termination immediately causes rotation of the body in the direction opposite to the direction of rotation of the main rotor. It is associated with the loss of lift and steering. It may lead to a disaster. Such an incident occurred in January 2011 in Afghanistan – both authors participated in its investigation. The authors, taking into account very good, almost legendary combat properties of the Mi-24, and their research of the specifics of wear and tear of the transmission elements, they think that, first, funds for development and implementation of the drive unit monitoring system should be made available specially for this helicopter. For this purpose, the authors propose to use the FAM-C method. It is characterised with significant ergonomics. Thank to this, multiple kinematic pairs can be observed simultaneously, and, therefore, the relationships between them as well.

2

Selected aspects of wear affecting keyed joints and spline connections during operation of aircrafts

Gębura A., Szymczak J.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2014

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nr 35

85—103

EN

The paper deals with selected deficiencies of spline connections, such as angular or parallel misalignment (eccentricity) and excessive play. It is emphasized how important these deficiencies are for smooth operation of the entire driving units. The aim of the study is to provide a kind of a reference list with such deficiencies with visual symptoms of wear, specification of mechanical measurements for mating surfaces, mathematical description of waveforms for dynamic variability of motion in such connections and visualizations of the connection behaviour acquired with the use of the FAM-C and FDM-A. Attention is paid to hazards to flight safety when excessively worn spline connections are operated for long periods of time.

3

An Experimental Comparison of Three Probabilistic Approximations Used for Rule Induction

Clark P. G., Grzymala-Busse J.W.

Fundamenta Informaticae

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2013

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Vol. 127, nr 1-4

177--191

EN

In this paper we present results of experiments on 166 incomplete data sets using three probabilistic approximations: lower, middle, and upper. Two interpretations of missing attribute values were used: lost and “do not care” conditions. Our main objective was to select the best combination of an approximation and a missing attribute interpretation. We conclude that the best approach depends on the data set. The additional objective of our research was to study the average number of distinct probabilities associated with characteristic sets for all concepts of the data set. This number is much larger for data sets with “do not care” conditions than with data sets with lost values. Therefore, for data sets with “do not care” conditions the number of probabilistic approximations is also larger.

4

The monitoring of the bearing joints with excessive axial clearances using the FAM-C AND FDM-A methods

Gębura A., Tokarski T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2010

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nr 27

121-136

EN

The intended aim of the paper is to discuss issues resulting from the observation of thee bearing support elements/components in single-shaft turbine engines with excessive axial clearances. Described are parameters and symptoms of such a condition, probable hazards, as well as capabilities of determining it with the FDM-A1 and FAM-C2 methods. Presented are hypotheses formulated by the Authors on subsequent stages of the wearout of bearing support elements/components in an aircraft turbojet engine, which lead to that excessive axial clearances start to arise. Theory of the issue has been completed with results of diagnostic examination of engines and data from the mechanical inspection of the engines after their disassembly.

5

The FDM-A AND FAM-C methods with regard to effects associated with transmission of rf signals

Gębura A., Mroszkiewicz K.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2010

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nr 27

151-164

EN

The paper deals with issues related to analogies between methods used for conditioning, transmission and reception of diagnostic signals with use of the FAM-C1 and FDM-A2 techniques and corresponding phases that happen to phenomena associated with transmission of information in radio engineering. All these cases include modulation, transmission and demodulation of FM signals. The only difference is the content of information transmitted: for the diagnostic signal with use of FAM-C and FDM-A techniques it is the information about technical condition of kinematic pairs within the driving unit (demonstrated by defined modulation to angular velocity of kinematic pairs) whilst broadcast signals are used to transmit speech, music or specific sequences of sounds (acoustic signals). The transmission medium is also different. In case of RF signals conveyed between the transmitter and the receiver it can be air, vacuum or water whilst transmission with use of FAM-C and FDM-A techniques assumes signal propagation via rigid tension members of the transmission unit deployed between the monitored kinematic pairs and the electric current generator. The difference lies also in ranges of the carrier frequency - for broadcast transmission with FM modulation the carrier frequency is from a dozen of MHz to hundreds of MHz whilst FAM-C and FDM-A techniques assume the frequency from dozens of Hz to several kHz. The last major difference is also in the heterodyne3 frequency, which is from a dozen of MHz to hundreds of MHz for the RF transmission and from several hundreds of Hz up to several kHz for diagnostic purposes (depending on how the electric machine is designed).

6

The monitoring of the bearing nodes with excessive radial clearances using the FAM-C and FDM-A methods

Gębura A., Tokarski T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2009

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nr 25

109-127

EN

The paper has been intended to present findings resulting from the monitoring of the bear-ing support elements with increased radial clearances with the FAM-C1 and FDM-A2 meth-ods. The role the lubricant film plays in this type of the rolling-elements' wear has been described. Discussed are symptoms, parameters, and hazards to the resonant state in bearing nodes, as well as capabilities of diagnosing them with the FAM-C and FDM-A methods. Hypotheses about subsequent stages of the wearing process in aircraft turbojet engine's bearing support assemblies, including how the resonant state occurs, have been presented. The mechanism of the resonance in rolling-element bearings has been de-scribed, with particular attention paid to the effects of gyrostatic moments upon the bearing support elements, both in micro- and macro-scale. Theoretical analyses have been sup-plemented with findings resulting from the diagnostic work carried out by the Authors, and with data from the mechanical verification of engines in the course of the authorised dis-mantling thereof.

7

Diagnosing turbine engine bearing structures with the aid of FAM-C and FDM-A methods

Gębura A.

Polish Maritime Research

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2009

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nr 1

53-60

EN

The diagnostic method FDM-A [2], based on the measurement of the pulsation component frequency modulation, and the FAM-C method, making use of the alternating current frequency, were developed in the Air Force Institute of Technology. The essence of their accuracy consists in “natural” synchronisation of the sampling signal with the angular velocity of the observed kinematic links. These methods make it possible to determine the level of wear of a subsystem and its location during normal operation of the power unit. They provide opportunities for determining numerous parameters of bearings, bearing structures, and the rotor unit. Moreover, the FDM-A method makes it possible to detect resonances in particular elements and their parameters - among others, they provide opportunities for assessing the level of the mechanic quality factor of the examined structure, i.e. the time margin of structure operation until the structure reaches the state of resonance. On the other hand, the FAM-C method provides opportunities for defining numerous parameters of the phenomena connected with the rotor unit. The diagnostic system is connected to an arbitrary point of the electric network (electric junction, for instance) supplied with the direct voltage1 or the alternating voltage2 taken from the generators driven by the examined rotating system. The presented experimental material was recorded in operating investigations of the aircraft turbine engine unit, in which the role of “generators – observers” was played by: an aircraft DC generator and a threephase AC rate generator. Generators of this type are also used in rocket cutters with turbine engines, this way the conclusions presented in the article can be easily transferred to those objects. During the measurements, performed on the decks of the examined airplanes and on engine test beds, the ranges and locations of assembly and wear defects were determined. Successive stages of wear of the rolling bearings were also observed.

8

Metody FDM-A i FAM-C w wykrywaniu i monitorowaniu silnie zaciśniętych łożysk tocznych

Gębura A., Tokarski T.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2008

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nr 23

223-235

PL

W artykule przedstawiono badania eksploatacyjne z zastosowaniem metod diagnostycz-nych opartych na wykorzystaniu analizy modulacji częstotliwości prądnic FDM-A i FAM-C. Metod tych użyto do wykrywania i monitorowania ruchu zbyt silnie zaciśniętych łożysk tocznych w węzłach łożyskowych silników turboodrzutowych. Szczególną uwagę poświę-cono obserwacji ruchu tocznego poszczególnych elementów tocznych oraz płynności ruchu koszyka. W wyniku wykonanych badań i diagnoz stwierdzono, że z chwilą powstania zbyt silnego zacisku pierwszym i najważniejszym skutkiem, obserwowanym metodą FDM-A, jest względne zróżnicowanie stochastyczne płynności ruchu poszczególnych ele-mentów tocznych. W wymienionej metodzie zjawisko to obserwowane jest jako niestabil-ność szerokości pasma zbioru charakterystycznego danego łożyska tocznego.

EN

The paper has been intended to present performance tests with the FDM-A and FAM-C diagnostic methods based on the application of analyses of generators' frequency modula-tion. Both the methods have been used to detect and monitor too tightly fitted rolling-element bearings (i.e. bearings that show too large interference fits) in bearing nodes of turbine jet engines. Special attention has been paid to observations of the rolling motion of individual rolling elements and flexibility of motion of the bearing cage. Results of con-ducted tests and diagnosing work allow us to state that as soon as a too tight fit arises, the first and the most important effect observed with the FDM-A method is the relative stochas-tic differentiation of flexibility of motion of particular rolling elements. The phenomenon observed with this method is instability of the bandwidth of a characteristic set of a given rolling-element bearing.

9

The Diagnostic Of Technical Condition Of Turbine Engine's Bearing By Means Of Method Of Alternator Frequency Modulation

Gębura A., Tokarski T.

Journal of Polish CIMAC

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2007

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Vol. 2, no 2

123-131

EN

The paper has been intended to discuss an application of a diagnostic method based on measurements and analyses of frequency modulation. The method has been developed at Instytut Techniczny Wojsk Lotniczych – ITWL (Air Force Institute of Technology, Warszawa, Poland). It has been based on measurements of pulse-frequency modulation of a DC generator or that of an AC alternator. The method has been intended to determine the usual wear-and-tear of a subassembly under examination and to locate defects, both of them in the course of normal operation of an aircraft power plant. The diagnostic system is connected to any terminal supplied with DC or AC voltage. Results of performance tests of the turbine engine have been presented. An airborne D.C. generator and a threephase rate A.C. alternator were used as generators-observers. Subsequent stages of the wear-and-tear of rolling bearings, the turbine unbalance, and the misalignment were observed while taking measurements during both flight and bench tests. What was observed first was some increase in the amplitude of braking the bearing induced by the increasing resistance to motion due to the wear-and-tear of the bearing’s components. Then, the amplitude was observed to decrease due to the wearing-in of the bearing’s components. At the beginning of operation, the rolling-friction coefficient was 0.4, then this value kept increasing with time until some rapid decrease beyond any mathematical meaning. This decrease resulted from the extension of radial clearances. Such being the case, the bearing’s operation had to be stopped to avoid intense destructive effects.

10

Pulsacje napięcia wyjściowego prądnicy pokładowej prądu stałego źródłem informacji diagnostycznej o stanie układu napędowego.

Gębura A.

Zagadnienia Eksploatacji Maszyn

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2003

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Vol. 38, nr 1

187-201

PL

W pracy omówiono opracowaną przez autora i wdrożoną pod jego kierunkiem metodę diagnostyczną opartą na pomiarze i analizie parametrów składowej pulsacji prądu stałego. Zastosowanie tej metody wymagało zgłębienia fizyki zjawisk powstawania składowej przemiennej sygnału wyjściowego prądnicy komutatorowej - część niniejszego opracowania jest poświęcona pewnym zjawiskom stwierdzonym podczas badań. Przedstawiono materiał badawczy otrzymany z badań laboratoryjnych zespołu napędowego LUZES-III, w którym rolę "prądnicy-obserwatora" pełniła lotnicza prądnica GSR-ST-12000WT. Równocześnie wykazano, że zmiany częstotliwości składowej pulsacji prądnicy prądu stałego są dyskretnym odzwierciedleniem zmian prędkości kątowej badanych par kinematycznych napędów lotniczych.

EN

The author is keen on exchanging experience relating to a method described scientifically and developed in Air Force Institute of Technology. The method has been named FDM-A (F-frequency, M-modulation, D-direct current, A-level of method advance). Power transmission tracks of various aircrafts usually exhibit different degrees of wear and tear. A diagnostic method based on the measurement of D.C. generator's frequency modulation varying component pulsation has been developed at the Air Force Institute of Technology. This method makes it possible to qualify the level of usual wear-and-tear of subassemblies and locate the defects during operation of the aircraft power transmission tracks. Algorithms of a quick and effective analysis of wear-and-tear for particular kinematic couples have been worked out. Basing on this method, a few prototypes of pocket the size testers were produced six years ago. They are combined with aircraft electric network and indicate the most worn subassemblies, as well as the level of wear-and-tear. At present, the diagnostic system based on measurements taken with these testers and furnished with a suitable computer database would increase the reliability of the whole aircraft systems. Until now, a diagnostic level has been qualified only on the basis of the so-called negative standard power transmission track, with at least one extremly worn-out element, and only for one aircraft type. Theoretical and experimental works go on simultaneously, with the aim to establish a more universal method. An airborne D.C. generatoris used as a converter. Diagnostic equipment is connected to a live terminal which provides the diagnosis of elements in a few minutes.

11

Diagnosis of aircraft power transmission tracks based on the analysis of generator's frequency

Gębura A.

Journal of Technical Physics

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2002

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Vol. 43, no 1

61-68

EN

Power transmission tracks of various aircrafts usually exhibit different degrees of wear and tear. A diagnostic method based on the measurement of alternator's frequency modulation has been developed at the Air Force Institute of Technology. This method makes it possible to qualify the level of usual wear-and-tear of subassemblies and locate the defects during operation of the aircraft power transmission tracks. Algorithms of a quick and effective analysis of wear-and-tear for particular kinematic couples have been worked out. Basing on this method, a few prototypes of pocket-size testers were produced six years ago. They are combined with the aircraft electric network and indicate the most worn subassemblies, as well as the level of wear-and-tear. At present, the diagnostic system based on measurements taken with these testers and furnished with a suitable computer database would increase the reliability of the whole aircraft systems. Until now, a diagnostic level has been qualified only on the basis of the so-called negative standard power transmission track, with at least one extremely worn-out element, and only for one aircraft type. Theoretical and experimental works go on simultaneously, with the aim to establish a more universal method.