Studying reliability of marine pump systems by using technical supervision data

The article describes the analysis of the ship systems’ reliability at the stage of the technical design, which is based on the reliability data of individual system elements and mathematical methods of reliability theory. During the ship operation maintenance deficiencies can lead to the equipment failure, which can be prevented by the methods of instrumental diagnostics of system elements, maintenance repairs regardless of the current technical condition, and classification inspection during the ship operation. Collecting the detailed data on changes in the functional reliability of ship mechanical systems, which could confirm or deny the advantages of each of the existing methods is not enough. There has been carried out collecting, processing and analyzing the actual data on the life cycles of various pumps of ship systems at different stages of service life, as well as beyond the designated service life or operating time. There are examined the general ship systems and auxiliary power units of icebreakers and floating structures. The examined equipment has standard pumps with different capacity and efficiency. Service life, assigned resource (operating time), frequency of repair are taken as the criteria of pump reliability and durability. There have been shown the actual life cycles of pumps in dependence of the service life in years on the operating time in hours; in addition, data on the passage of maintenance repairs, maintenance, inspection of the technical condition, as well as replacement or extension of the service life are plotted on the graphs. It has been inferred that some of the pumps in the ship's systems should be replaced before the full resource was developed, while the performance of the systems as a whole was preserved or restored as a result of repairs; some pumps have exceeded their specified resource, but during the technical inspection their operation was extended, the operability of the systems was also preserved.

The Use of Ethanol as an Alternative Fuel for Small Turbojet Engines

The use of alternative fuels to traditional kerosene-based ones in turbo-jet engines is currently being widely explored and researched. However, the application of alternative fuels in the area of small turbojet engines with thrust ratings up to 2 kilo-newtons, which are used as auxiliary power units or to propel small aircraft or drones, is not as well researched. This paper explores the use of ethanol as a sustainable fuel and its effects on the operation of a small turbojet engine under laboratory conditions. Several concentrations of ethanol and JET A-1 mixtures are explored to study the effects of this fuel on the basic parameters of a small turbojet engine. The influence of the different concentrations of the mixture on the start-up process, speed of the engine, exhaust gas temperature, and compressor pressure are evaluated. The measurements shown in the article represent a pilot study, the results of which show that ethanol can be reliably used as an alternative fuel only when its concentration in a mixture with traditional fuel is lower than 40%, yielding positive effects on the operating temperatures and small negative effects on the speed or thrust of the engine.

Analisis Proses Perawatan Auxiliary Power Units pada Pesawat Udara (Studi Kasus: Keterlambatan Pengembalian APU GTCP 131-9 di PT GAA Tbk)

PT. GAA is an international company that employs 4300 employees based in Tangerang, Banten, Indonesia. PT. GAA is able to maintain and repair aircraft, ranging from light repair maintenance to overhauls, maintenance and repair of engines, APU (Auxiliary Power Units) and aircraft components, and cabin modifications. The time to complete the repair of APU sometimes exceeds the Turnaround Time (TAT) that is determined which is 45 days. In fact, there are many delays that occur in returning APU to consumers. In this research report applying the Gantt chart, RCA and 5 Whys Analysis methods, to find out the main causes of delays in the repair process through 10 gates and to find out which gate has the longest delay. From the results of the study, it was found that after the 131-9 APU data collection amounted to 30 units, for 1 year, it was found that the gate which experienced the longest delay was Gate 5, Gate 3, Gate 8 and Gate. 7 and the main cause is the limited ability to repair the APU, the lack of personnel ready to work and the technical problems that occur during APU testing and limited assembly space, equipment for APU assembly and supplies.

Dynamic Performances of Foil Bearing Supporting a Jeffcot Flexible Rotor System Using FEM

Aerodynamic bearings have received considerable attention in recent decades and are increasingly being used in applications where high speed, low loads and high precision are required. Aerodynamic applications mainly concern auxiliary power units (APU) and air-conditioning machines (ACM). From the industrial point of view, the static and dynamic characteristics of these bearings rotating at very high speed must be determined. According to the literature, studies carried out on this type of bearing consider the elastic deformations of the foils due to the pressure generated in the air film. The linear approach is from time to time adopted for the prediction of the dynamic behavior of these bearings, which is not always justified. This paper aims to present a step towards a better mastery of the non-linear dynamic behavior of a flexible rotor-air bearing system. We will focus on finite element modeling (FEM) of the non-linear isothermal elasto-aerodynamic lubrication problem in the case of a radial bearing operating in a dynamic regime. We will present the effects of rotational speed, unbalance eccentricity, and rotor mass on the non-linear response of rigid and compliant bearings. We use a partitioned approach which treats fluid and structure as two computation domains solved separately; reducing the development time needed for a monolithic code which is difficult to manage when the geometries or the physical properties of the problem to be treated become complex.

Development of a technology for the manufacturing of parts/components of an internal combustion engine involving additive manufacturing methods

Introduction: the article considers a strategic objective consisting in reduction of the Russian companies’ dependence on highly sought-after imported power engineering equipment, including internal combustion engines used as part of auxiliary power units. In the article, the co-authors propose to integrate additive manufacturing methods into technologies used to produce internal combustion engines, their parts and components, which are temporarily or permanently impossible to import. The co-authors have proven the feasibility of advanced additive technologies in respect of casting molds and castings designated for internal combustion engines. An alloy of cast iron featuring an advanced chemical composition was developed. It enables the use of complex shape castings free from any non-metallic inclusions to produce engine parts and components; these castings demonstrate higher values of strength and wear resistance, they are a must for an internal combustion engine operating in severe conditions. The co-authors demonstrate the casting mold production process using ExOne’s S-MAX 3D printer.Methods: the study is based on the analysis of strengths, weaknesses and peculiarities of established casting methods, with account for faster production cycles and a higher quality of final products.Results and discussion: in the article, the co-authors analyze the proposed technology used to manufacture castings for “a block of cylindersˮ and “a head of the block of cylindersˮ.Conclusion: the newly developed technology for production of parts/assemblies of an internal combustion engine, including an advanced alloy having a new chemical composition, enables manufacturers to make high quality parts/ assemblies for an internal combustion engine in the most economical and productive way.

Aircraft auxiliary power unit performance assessment and remaining useful life evaluation for predictive maintenance

Modern commercial aircraft are usually configured with aircraft condition monitoring system to collect the operating data of subsystems and components, which can be used for airborne system health monitoring and predictive maintenance. This paper presents a baseline model based aircraft auxiliary power unit performance assessment and remaining useful life prediction method using aircraft condition monitoring system reports data, which can facilitate a cost-effective management of auxiliary power units of aircraft fleet. Firstly, the performance baseline model for auxiliary power unit is established using random forest method. Then a health index characterizing the performance degradation of in-service auxiliary power units is obtained based on the performance baseline model. Finally, the performance degradation trend is predicted using Bayesian dynamic linear model. To improve the prediction accuracy, four performance baseline models are established from the data of auxiliary power units under different operating conditions, among which an optimal model is determined. This data-driven baseline model can be used to quantify the performance degradation of auxiliary power units in service, and can be further used to evaluate the remaining useful life of auxiliary power unit using a Bayesian dynamic model. The developed approach is applied on a real data set from 22 auxiliary power units of a commercial aircraft fleet. The results show that the computed health index can effectively characterize the auxiliary power units performance degradation and the remaining useful life relative prediction errors are less than 4% when auxiliary power unit enters the rapid degradation stage. This would allow operators to accurately assess the performance degradation for the auxiliary power units and further proactively plan future maintenance events based on remaining useful life prediction.

Effects of ported shroud casing treatment on the acoustic and flow behaviour of a centrifugal compressor

Centrifugal turbomachines of smaller sizes operating at higher speeds have become pervasive due to the increased specific power and reliability achieved by improvements in manufacturing, materials and computational methods. The presence of these small turbomachines, specifically compressors, in helicopters, unmanned aerial vehicles, auxiliary power units, turbochargers and micro gas turbines necessitates superior aerodynamic performance over a broad operational range, which is widely achieved by ported shroud casing designs. In addition to aerodynamic performance, acoustic emissions have become a critical aspect of design for these small centrifugal compressors due to high operational speeds. Furthermore, the literature on the acoustic effects of the casing treatment is rather limited. Therefore, the impact of ported shroud casing treatment on the acoustic and flow features of the compressor operating at the design and near-surge conditions have been quantified by numerically modelling the open and blocked configuration of the compressors. Upon comparing with experimental results, the numerical spectra are shown to capture the differences between the two configurations at the investigated operating points with reasonable accuracy. Although the casing treatment is generally seen to decrease the overall acoustic emission of the compressor at both operating conditions, increased propagation of tonal content in the direction upstream to the impeller is observed, particularly for design operation. Broadband characteristics in the lower and medium frequency regions usually associated with near-surge operation including ‘whoosh’ noise are observed to be alleviated by the ported shroud casing treatment.