Tail Shaft Research Articles

АНАЛІЗ КОНСТРУКТИВНО-ТЕХНОЛОГІЧНИХ ОСОБЛИВОСТЕЙ ХВОСТОВИХ БАЛОК ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

An analysis of the structural and technological features of the design of the tail beam of transport category helicopters was carried out. The main zones of probable fatigue failure of the tail girders were determined. Based on the analysis of the structural and technological features of the design of tail beams of transport category helicopters, the tail beam design of the physical model was developed. In the practice of world helicopter industry, single-screw helicopters, which are characterized by relative simplicity of design, control system and relatively low cost, have become the most widespread. The tail beam is the most complex part in the production of a helicopter. For a single-screw helicopter, the tail beam is a very critical part of the structure, the failure of which, in most cases, leads to an aviation incident. Ensuring strength requirements is an extremely important task; therefore it is regulated by mandatory airworthiness standards for designers, which are an integral part of the Aviation Rules. In these standards, the initial requirements for the calculation and experimental works to ensure strength are set, load conditions are established, and instructions are given for determining the magnitude of the loads. In the practice of helicopter construction, the experience accumulated in aircraft construction is used in the formation of structural and power schemes of frame units. The tail beam of helicopters is made according to beam, truss or mixed schemes. Optimization methods of compressed and stretched panels of frame units have a common criterion for aviation - the minimum weight of the structure while meeting the requirements of strength, rigidity, survivability, resource, manufacturability, operational efficiency, etc. The task of selecting a rational structural and force scheme of the tail beam is solved by indirect methods involving weight statistical data, parametric dependencies and information about the force schemes of previous structures. In most cases, the type of tail beam design is selected based on the requirements for the helicopter, operating conditions and production capabilities. The task is to find the best option within a given structural type. The helicopter tail beam is part of the structure of the helicopter, has the shape of a truncated cone and consists of a set of frames, stringers and skin. For ease of manufacturing, the tail beam has a longitudinal technological connector, which allows separate assembly of each half of the tail beam. The tail beam is connected to the central part of the fuselage by bolts that fasten the end power frames with the help of fittings at the ends of the stringers. The end part of the tail beam is connected to the keel, similar to the connection of the tail beam to the central part of the fuselage. The following are installed on the tail beam: stabilizers, rudder control rods, rudder drive system, intermediate and tail gear, navigation lights, assemblies and components of hydraulics and tail shaft. Modern transport helicopters are designed and manufactured with a specified resource and service life in mind, which range from 15,000 to 30,000 hours with a service life of 25-30 years. Increasing the fatigue life of the zones of structural irregularities of the tail beams of transport category helicopters is an urgent task, which is of great practical importance for ensuring the safety of flights during the operation of helicopters during the established resource, which in turn is an important indicator of the competitiveness of helicopters.

A new method for calculating hydrodynamics of corner-tube boiler based on differential pressure solution

Corner-tube boiler is widely used in the production of industrial steam. For this boiler, it is difficult to conduct hydrodynamic calculation and check due to unique water cycle structure. A new method for hydrodynamic calculation of corner-tube steam boiler based on differential pressure solution is proposed in this article. The frictional pressure drop in the lower header has been taken into consideration by adding a direction discriminant factor, which can solve the inherent problem about the balance point. Meanwhile, taking a corner-tube steam boiler of 75 tonne per hour as an example, the circulation flow rates in each riser under different working conditions were calculated, and the cycle reliability was also checked. The calculation results showed that the hydrodynamic characteristic is good enough under the condition of full heat load. However, the riser in the tail shaft will surf from flow stagnation or backflow once the heat load is at or below 50%, which is generally consistent with the change trend of monitoring wall temperature during actual operation. This method proposed in this article is more accurate, by comparing with the traditional method, in predicting whether there is a risk of flow stagnation or backflow in the riser of the corner-tube steam boiler under lower heat load.

Transmission diagnostics of single-rotor helicopters

The usage of instrumental methods to monitor the technical condition of mechanisms leads to improved efficacy in detecting and warning of malfunctions. Timely detection of malfunctions during aircraft operation allows to avoid sudden failures and, as a consequence, to increase flight safety. Detection of defects is possible both during maintenance and by using inbuilt systems on board the aircraft. This paper proposes the method of instrumental monitoring of tail shaft condition based on the Hall effect, following an analysis of applied methods of transmission element diagnostics in single-rotor helicopters. The research outcomes permit us to suggest the development of various forms of selective and continual monitoring systems for the helicopter transmission condition, and advise for their implementation.

POPULATION DIVERSITY BASED ON MORPHOMETRIC MERISTIC ENDEMIC BUTINI FISH (Glossogobius matanensis) IN LAKE TOWUTI, SOUTH SULAWESI

Butini fish is a resource wealth of fauna found only in the East Complex Malili Luwu, South Sulawesi. The necessary information about the morphological characters (morphometric and meristic) to determine the management of fish resources. The purpose is to assess the diversity of populations based on morphometric meristik. Sampling is based on descriptive methods and fish samples taken to determine the diversity of phenotypes based on the depth of each morphometric character. Calculating morphometric characters using the main component analysis to obtain the correlation between the character and the grouping of individuals based on morphometric characters. Calculation meristik characters include the number of fingers, the number of fins and scales, namely the number of fingers of the dorsal fin, anal fin radius, the radius of the ventral fin, pectoral fin radius, the radius of the caudal fin, scales on the rib line, scales above the rib line, scales below the ribs, scales in front of the dorsal fins, scales on the cheeks, around the body scales, scales around the tail shaft. The analysis showed that the first two principal components contained the greatest information, with a cumulative range of 80%. All the characters' morphometric first role is a major component. The character who plays the main component of the length of the head in front of the eyes, long upper jaw, lower jaw length, high cheeks, and the length of the radius of a weak base ventral fins showed great correlation to the diversity of forms. Main components analysis also showed that butini fish, at any depth, showed no grouping. This suggests that the fish species observed was one (one unit of population). In calculating the value of phenotypic diversity of each character, butini generally fish in the lake Towuti show morphometric characters with the highest diversity value and the lowest given by the total length and high under the eyes. In the calculation of the formula derived characters meristik flipper fingers that D1, V-VI. D2. I, 8-11; dan D1, V-VI, D2. I, 8-10.

Simulation and Experiment Research on Abrasive Wear of the Ship Mechanical Seal

The wear of friction pair resulting from seawater particles will inevitably bring marine tail shaft mechanical seal in the process of work, and abrasive wear will increase the static ring wear, resulting in the leakage of the mechanical seal. In this paper, through finite element simulation analysis of abrasive wear with different particle sizes and abrasive wear tests under different static ring materials, it is concluded that larger abrasive particle sizes will increase the deformation and residual stress on the surface of static ring materials, thus increasing the amount of wear, and the surface of softer static ring materials will be more serious. Also, if the particle size is too large, the particle concentration of the friction surface will decrease, and the wear will decrease.

Assessing the Potential Replacement of Mineral Oil with Environmentally Acceptable Lubricants in a Stern Tube Bearing: An Experimental Analysis of Bearing Performance

Abstract This study compares the performance of a plain bearing, with a similar structure to a tail shaft stern bearing, lubricated with either mineral oil or an environmentally acceptable lubricant (EAL). The main characteristic of the bearing is its length/diameter ratio of <1. Measurements are carried out with the bearing operating under loads from 0.5 to 1 MPa and seven speeds ranging from 1 to 11 rev/s. The bearing lubricated with either mineral oil with a viscosity grade of 100 or an environmentally acceptable lubricant (EAL) with a viscosity grade of 100 or 150 is investigated according to the ISO standard. Bearing wear is simulated by increasing the clearance circle by 0.1 mm. According to the results obtained, the use of an EAL in place of mineral oil does not cause significant changes in the bearing performance, regardless of the value of the clearance radius. The pressure distribution in the oil film, bearing load carrying capacity, eccentricity and friction coefficient have similar values for the entire load and speed ranges considered, and the discrepancies in the results are within the range of the measurement errors. Only an increase in EAL viscosity causes significant changes in bearing performance and these changes comply with the general theory of lubrication.

Modeling and dynamic analysis of spiral bevel gear coupled system of intermediate and tail gearboxes in a helicopter

The coupled dynamic model of the intermediate and tail gearboxes’ spiral bevel gear-oblique tail shaft-laminated membrane coupling was established by employing the hybrid modeling method of finite element and lumped mass. Among them, the dynamic equation of the shaft was constructed by Timoshenko beam; spiral bevel gears were derived theoretically by the lumped-mass method, where the effects of time-varying meshing stiffness, transmission error, external imbalance excitation and the like were considered simultaneously; laminated membrane coupling was simplified to a lumped parameter model, in which the stiffness was obtained by the finite element simulation and experiment. On this basis, the laminated membrane coupling and effects of several important parameters, including the unbalance value, tail rotor excitation, oblique tail shaft’s length and transmission error amplitude, on the system’s dynamic characteristics were discussed. The results showed that the influences of laminated membrane coupling and transmission error amplitude on the coupled system’s vibration response were prominent, which should be taken into consideration in the dynamic model. Due to the bending-torsional coupled effect, the lateral vibration caused by gear eccentricity would enlarge the oblique tail shaft’s torsional vibration; similarly, the tail rotor’s torsional excitation also varies the lateral vibration of the oblique tail shaft. The coupled effect between the eccentricity of gear pairs mainly hit the torsional vibration. Also, as the oblique tail shaft’s length increased, the torsional vibration of the oblique tail shaft tended to diminish while the axis orbit became larger. The research provides theoretical support for the design of the helicopter tail transmission system.

Research on the influence of the normal vibration on the friction-induced vibration of the water-lubricated stern bearing

During the slow voyage of ships, the friction-induced vibration noise often occurs in the contact region of the water-lubricated stern bearing and the tail shaft. The lateral vibration can impact the normal motion of the contact surface, then change the dynamic friction force, finally affect the behaviour of the friction-induced vibration. By adding the movement of the stern shaft journal into the normal load description of the dynamic friction, the equation of friction-induced vibration considering the effect of normal vibration was established. Then the effect law of normal vibration on friction-induced vibration was discussed by numerical simulation and test. The results show that the normal vibration would make the friction-induced vibration appear quasi-periodic, chaotic trend, and narrow the speed range in which the noise of friction-induced vibration appears.

Research on Dynamic Characteristic of Marine Shafting-Oil Film-Stern Structure System

The working conditions of the propulsion system of ships are affected by many factors and partially by hull deformations and lubricating oil film. In order to solve the problem of engineering application of reliability assessment and control of ship propulsion system on heavy sea, a mechanical model of ship shafting-oil film-stern structure coupled system is established. The hull and shafting are studied as a whole, and a test rig with the wave loads system is assembled. By carrying out the integrative analysis and physical experiment, the motion characteristics of the system are analyzed. According to the various types of wave loads which ship faces on ocean, the influence of the stern structure on the vibration characteristics of the shafting is obtained. It is concluded that the coupling degree of shafting and stern structure is correlated with the natural frequency of the coupled system, and the wave-induced loads response is correlated with wave encountering frequency. The characteristics of the shafting-oil film-stern structure system, such as the maximum amplitude of tail shaft and the minimum oil film thickness of bearing, are significantly modified under the influence of stern structure.

Marine Propulsion System Vibration Sensor Heads

Abstract Vibration symptoms are the main symptoms used for diagnosing machines. This applies mainly to vibrations of non-rotating machines. Symptoms of rotating element vibrations are used in a limited scope, while mostly used are the symptoms of radial vibrations of rotating shafts. Across industries, the use of technical vibration diagnosis varies. Marine propulsion systems are poorly equipped with diagnostic equipment of that type. One of the main reasons is lack of appropriate sensors. The study presents two solutions of sensor heads. One solution applies to a sensor head built into the free end of the crankshaft of a reciprocating machine. The shaft free end sensor allows measurement of torsional and longitudinal vibration accelerations of the free end as a function of shaft rotation. The other solution refers to a sensor head built into sealed slide bearing of a straight shaft. The slide bearing head enables measurement of the eccentricity to the journal relative to the shell. Sensor heads under consideration are particularly suitable to be built in the ship’s propulsion system and integrated with the ship’s maintenance system. Sensors of the ship’s maintenance system equipped with these heads will allow the operator to draw conclusions concerning the wear margins of the propulsion engine and that of the tail shaft.

Расчет мощности электродвигателя компенсации потерь стенда испытаний хвостового вала вертолёта

Расчет мощности электродвигателя компенсации потерь стенда испытаний хвостового вала вертолёта

Effect of visible implant elastomers on the growth, survival and tag retention in juvenile Atlantic sturgeon (Acipenser oxyrinchus ) in laboratory conditions

This study identifies the possibility of using visible implant elastomers (VIE) to tag juvenile Atlantic sturgeon (Acipenser oxyrinchus). The mean body weight was 2.4 ± 0.4 g, and mean body length 5.5 ± 0.5 cm. Markers in three colours were used: blue, orange and green. Implant elastomers were injected in the rostrum and in the tail shaft. The experiment was conducted over a period of 10 weeks and included also a control group, that is, no tagging. No significant effect of tagging on the specific growth rate, feed conversion ratio and condition factor of juvenile Atlantic sturgeon was observed. The fish in all groups increased their body weight more than 10 times, reaching body weight of 25–28 g. The final survival in all of the groups was approximately 40%. The final tag retention varied depending on the implant colour. The highest retention of 100% was obtained with orange VIE and was significantly different from blue and green. Tag retention was dependent on the place of marking (P > 0.05). A correlation was observed between the applied dye and the place of marking (P = 0.0166). The best results were obtained when marking with orange VIE in the rostrum as all markers were visible after 70 days even without the use of UV light. According to our research, marking with VIE does not negatively affect growth and survival of juvenile Atlantic sturgeon and can be recommended for fish with an initial body weight of approximately 2.5 g in the case of short-term research.

Analysis of the Influence Factors on the Efficiency of Marine Tail Shaft Transmission System

The transmission efficiency of the marine tail shaft was calculated with the finite element method and experiment validated the rationality and feasibility of finite element models. The research conclusions as follows: power consumption increases with the shaft length, shaft diameter and speed increase. The results can provide a theoretical support for further research andit is also helpful for engineering applications.

Analysis of Pre-Tightening Strength of Ship Tail Shaft Coupling Based on Workbench Software

Coupling is mostly used for the connection of two shafts, widely in ship machinery. Because the vibration and impact of propeller under alternating load, the tail shaft work conditions are harsh, pre-tightening force plays an important role in the performance of tail shaft coupling. In this paper, based on conventional coupling, achieve pre-tightening by applying pre-tightening lock bolt at the circumference of pre-tightening nut, determine the pre-tightening force according to empirical formula, analyse the pre-tightening strength by using of Workbench finite element software, get the stress distribution of related parts, to explore the effect of pre-tightening force on the stress of related parts of coupling.

Chaperone–Protein Interactions That Mediate Assembly of the Bacteriophage Lambda Tail to the Correct Length

Bacteriophage λ makes two proteins with overlapping amino acid sequences that are essential for tail assembly. These two proteins, gpG and gpGT, are related by a programmed translational frameshift that is conserved among diverse phages and functions in λ to ensure that gpG and the frameshift product gpGT are made in a molar ratio of approximately 30:1. Although both proteins are required and must be present in the correct ratio for assembly of functional tails, neither is present in mature tails. During λ tail assembly, major tail protein gpV polymerizes to form a long tube whose length is controlled by the tape measure protein gpH. We show that the “G” domains of gpG and gpGT bind to all or parts of tail length tape measure protein gpH and that the “T” domain of gpGT binds to major tail shaft subunit gpV, and present a model for how gpG and gpGT chaperone gpH and direct the polymerization of gpV to form a tail of the correct length.

Calculation of Nature Frequency for Ship’s Tail Shaft Flexural Vibration Based on Genetic Algorithm

Analysis of the nature frequency of flexural vibration is vital to be able to provide effective shock absorption for a ship’s tail shaft. The paper built mathematic model of ship’s tail shaft flexural vibration by transfer matrix method, and put forward an effective method for calculating the natural frequency of vibration system: a genetic algorithm (GA). Through example calculation compared with Prohl method under conditions bearing isotropic supporting, the result showed that the method can meet the requirements of engineering calculation, and overcome the disadvantage that initial value of calculation is difficult to be obtained with other methods. Then the method has advantage especially when the degrees of frequency equation increase.

Oscillatory porewater bioadvection in marine sediments induced by hydraulic activities of Arenicola marina

We employed real‐time pressure recording and high temporal resolution two‐dimensional oxygen imaging to characterize the porewater bioadvection related to hydraulic activities of Arenicola marina, a widespread representative of benthic macrofauna. Behavior‐specific positive and negative pressure oscillations and hydraulic pulses resulted in bidirectional porewater flow and highly dynamic redox oscillations on the scale of minutes. Pumping of water by the worm into its blind‐ending burrow pressurized the sediment and caused sediment oxygenation at depth and the exit of anoxic porewater into the overlying water. The sediment volume that was affected by bioadvective transport of oxygen and the porewater flow patterns varied strongly among sediment types. In low‐permeability sediments, localized plumes of anoxic porewater ascended from the sediment, presumably through sedimentary cracks, while porewater flowed evenly through highly permeable sediments. Hydraulic behaviors that moved water out through the open tail shaft caused a reduction of porewater pressures below the hydrostatic baseline which resulted in the collapse of plumes and enhanced oxygen penetration into the surficial sediments. Porewater bioadvection and the related perfusing and oscillatory phenomena will affect a variety of biogeochemical and ecological processes, including organic matter mineralization, benthic recruitment, and prey localization. We suggest that bidirectional porewater bioadvection and the associated transient geochemical conditions are prevalent features of biogenically active sediments.

Comparative Genome Analysis ofListeriaBacteriophages Reveals Extensive Mosaicism, Programmed Translational Frameshifting, and a Novel Prophage Insertion Site

The genomes of six Listeria bacteriophages were sequenced and analyzed. Phages A006, A500, B025, P35, and P40 are members of the Siphoviridae and contain double-stranded DNA genomes of between 35.6 kb and 42.7 kb. Phage B054 is a unique myovirus and features a 48.2-kb genome. Phage B025 features 3' overlapping single-stranded genome ends, whereas the other viruses contain collections of terminally redundant, circularly permuted DNA molecules. Phages P35 and P40 have a broad host range and lack lysogeny functions, correlating with their virulent lifestyle. Phages A500, A006, and B025 integrate into bacterial tRNA genes, whereas B054 targets the 3' end of translation elongation factor gene tsf. This is the first reported case of phage integration into such an evolutionarily conserved genetic element. Peptide fingerprinting of viral proteins revealed that both A118 and A500 utilize +1 and -1 programmed translational frameshifting for generating major capsid and tail shaft proteins with C termini of different lengths. In both cases, the unusual +1 frameshift at the 3' ends of the tsh coding sequences is induced by overlapping proline codons and cis-acting shifty stops. Although Listeria phage genomes feature a conserved organization, they also show extensive mosaicism within the genome building blocks. Of particular interest is B025, which harbors a collection of modules and sequences with relatedness not only to other Listeria phages but also to viruses infecting other members of the Firmicutes. In conclusion, our results yield insights into the composition and diversity of Listeria phages and provide new information on their function, genome adaptation, and evolution.

Analysis of the flexural vibration of ship’s tail shaft by transfer matrix method

A ship’s tail shaft has serious flexural vibration due to the cantilevered nature of the propeller’s blades. Analysis of the nature frequency of flexural vibration is vital to be able to provide effective shock absorption for a ship’s tail shaft. A mathematic model of tail shaft flexural vibrations was built using the transfer matrix method. The nature frequency of flexural vibration for an electrically propelled ship’s tail shaft was then analyzed, and an effective method for calculating it was proposed: a genetic algorithm (GA), which calculates the nature frequency of vibration of a system. Sample calculations, with comparisons by the Prohl method under conditions bearing isotropic support, showed this method to be practical. It should have significant impact on engineering design theory.

The pKO2 linear plasmid prophage of Klebsiella oxytoca.

Temperate bacteriophages with plasmid prophages are uncommon in nature, and of these only phages N15 and PY54 are known to have a linear plasmid prophage with closed hairpin telomeres. We report here the complete nucleotide sequence of the 51,601-bp Klebsiella oxytoca linear plasmid pKO2, and we demonstrate experimentally that it is also a prophage. We call this bacteriophage phiKO2. An analysis of the 64 predicted phiKO2 genes indicate that it is a fairly close relative of phage N15; they share a mosaic relationship that is typical of different members of double-stranded DNA tailed-phage groups. Although the head, tail shaft, and lysis genes are not recognizably homologous between these phages, other genes such as the plasmid partitioning, replicase, prophage repressor, and protelomerase genes (and their putative targets) are so similar that we predict that they must have nearly identical DNA binding specificities. The phiKO2 virion is unusual in that its phage lambda-like tails have an exceptionally long (3,433 amino acids) central tip tail fiber protein. The phiKO2 genome also carries putative homologues of bacterial dinI and umuD genes, both of which are involved in the host SOS response. We show that these divergently transcribed genes are regulated by LexA protein binding to a single target site that overlaps both promoters.