Determination of Propeller-Ice Milling Loads

1987 ◽  
Vol 109 (2) ◽  
pp. 193-199
Author(s):  
T. Kotras ◽  
D. Humphreys ◽  
A. Baird ◽  
G. Morris ◽  
G. Morley
Keyword(s):  
Design Process ◽  
Open Water ◽  
Propeller Blade ◽  
Good Strength ◽  
Propeller Design ◽  
Blade Width ◽  
Ice Conditions ◽  
Ice Loads ◽  
Ship Speed

In designing ice transiting ships, a major concern is the design of the propeller to provide adequate strength to resist ice loads due to propeller ice milling while still providing good propeller efficiency for open water observations as well as high icebreaking thrust at slow advance speeds. As a result, propeller design is a compromise between strength and efficiency. This is especially true for ice transiting ships that must transit long distances on ice-free routes and then perform difficult ice-breaking operations. The geometric properties of a propeller blade that provide good strength are blade width and thickness. Unfortunately, increasing these properties does not provide the best efficiency. Propeller design for ice transiting ships in general has tended to favor strength and reliability over efficiency in design compromises. The purpose of this paper is to outline a methodology for determining propeller ice milling loads as a function of propeller characteristics, propeller speed, ship speed, ice conditions and depth of ice milling to help in the propeller design process.

A study on the effect of the rake angle on the performance of marine propellers

2011 ◽  
Vol 226 (4) ◽  
pp. 940-955 ◽  
Author(s):  
A N Hayati ◽  
S M Hashemi ◽  
M Shams
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Design Process ◽  
Flow Characteristics ◽  
Open Water ◽  
Rake Angle ◽  
Marine Propellers ◽  
Propeller Design ◽  
Open Water Performance ◽  
Dynamics Method

In this study, the open water performance of three propellers with diverse rake angles was investigated by computational fluid dynamics method. The objective of this study was to find out the influence of the rake angle on the performance of conventional screw propellers. For this purpose, first, the obtained results for three B-series propellers were validated against the empirical results and then by modifying the rake angle, different models were investigated by the same method. Flow characteristics were examined for the models and the evolvement of vortices on different planes around the propeller were compared. The results suggest that in case of conventional screw propellers with linear rake distribution, while the effect of the rake angle on the propeller efficiency is not significant, the augmentation of this parameter improves the propeller thrust, especially at high propeller loads, but at the same time, the required torque increases, which is not desirable for the propeller design process.

scholarly journals Profiling Sea Ice with a Multiple Altimeter Beam Experimental Lidar (MABEL)

2014 ◽  
Vol 31 (5) ◽  
pp. 1151-1168 ◽  
Author(s):  
R. Kwok ◽  
T. Markus ◽  
J. Morison ◽  
S. P. Palm ◽  
T. A. Neumann ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Laser Pulses ◽  
The Arctic ◽  
Ice Cloud ◽  
Ice Conditions ◽  
Arctic Coast ◽  
Background Photon ◽  
532 Nm

AbstractThe sole instrument on the upcoming Ice, Cloud, and Land Elevation Satellite (ICESat-2) altimetry mission is a micropulse lidar that measures the time of flight of individual photons from laser pulses transmitted at 532 nm. Prior to launch, the Multiple Altimeter Beam Experimental Lidar (MABEL) serves as an airborne implementation for testing and development. This paper provides a first examination of MABEL data acquired on two flights over sea ice in April 2012: one north of the Arctic coast of Greenland and the other in the east Greenland Sea. The phenomenology of photon distributions in the sea ice returns is investigated. An approach to locate the surface and estimate its elevation in the distributions is described, and its achievable precision is assessed. Retrieved surface elevations over relatively flat leads in the ice cover suggest that precisions of several centimeters are attainable. Restricting the width of the elevation window used in the surface analysis can mitigate potential biases in the elevation estimates due to subsurface returns at 532 nm. Comparisons of nearly coincident elevation profiles from MABEL with those acquired by an analog lidar show good agreement. Discrimination of ice and open water, a crucial step in the determination of sea ice freeboard and the estimation of ice thickness, is facilitated by contrasts in the observed signal–background photon statistics. Future flight paths will sample a broader range of seasonal ice conditions for further evaluation of the year-round profiling capabilities and limitations of the MABEL instrument.

scholarly journals Analysis of a Collision-Energy-Based Method for the Prediction of Ice Loading on Ships

2019 ◽  
Vol 9 (21) ◽  
pp. 4546 ◽  
Author(s):  
Sabina Idrissova ◽  
Martin Bergström ◽  
Spyros E. Hirdaris ◽  
Pentti Kujala
Keyword(s):  
International Association ◽  
Load Prediction ◽  
Practical Applications ◽  
Polar Code ◽  
Ice Load ◽  
Conservation Of Momentum ◽  
Ice Conditions ◽  
Ice Loads ◽  
Popov Method

Ships designed for operation in Polar waters must be approved in accordance with the International Code for Ships Operating in Polar Waters (Polar Code), adopted by the International Maritime Organization (IMO). To account for ice loading on ships, the Polar Code includes references to the International Association of Classification Societies’ (IACS) Polar Class (PC) standards. For the determination of design ice loads, the PC standards rely upon a method applying the principle of the conservation of momentum and energy in collisions. The method, which is known as the Popov Method, is fundamentally analytical, but because the ship–ice interaction process is complex and not fully understood, its practical applications, including the PC standards, rely upon multiple assumptions. In this study, to help naval architects make better-informed decisions in the design of Arctic ships, and to support progress towards goal-based design, we analyse the effect of the assumptions behind the Popov Method by comparing ice load predictions, calculated by the Method with corresponding full-scale ice load measurements. Our findings indicate that assumptions concerning the modelling of the ship–ice collision scenario, the ship–ice contact geometry and the ice conditions, among others, significantly affect how well the ice load prediction agrees with the measurements.

The Variable-pitch Marine Propeller

1946 ◽  
Vol 155 (1) ◽  
pp. 211-231
Author(s):  
J. Lockwood Taylor
Keyword(s):  
Sea Water ◽  
Operating Conditions ◽  
Engine Fuel ◽  
Variable Pitch ◽  
Blade Width ◽  
And Control ◽  
Propeller Performance ◽  
Ship Speed ◽  
Fixed Pitch

The author first discusses propeller performance, dealing in turn with the order of the possible gain in efficiency to be expected by adopting the variable-pitch type for different classes of ships working within a range of operating speeds. The maintenance of speed in heavy weather and with a foul hull is then considered, and reference is made to the possibility of feathering for economical cruising, to the special application of variable-pitch propellers to tugs and trawlers, and to engine fuel consumption characteristics at part load and varying propeller r.p.m. Details of manoeuvring and control are discussed, from the viewpoint of exploring the possibility of eliminating the engine reversing gear and the direct manipulation of the prime mover generally. Ship speed control from the bridge is considered, and an estimation is made of astern performance, followed by a comparison with the normal reversing of a fixed-pitch screw. Factors influencing blade design are then reviewed, e.g. type of root and size of boss, the effect of the type and number of blades on the efficiency; and reference is made to the calculation of pitch-changing moments and the possibility of balancing hydrodynamic and centrifugal components by suitable design and tilt of the blades. Various types of operating mechanism are then examined—hydraulic, electric, mechanical, and combinations of these—and mention is made of the sealing of the hub against sea water. The author also refers to the need for indicating the pitch at the control station. Lastly a comparison is made with aeronautical applications. The author shows that the range of operating conditions as affecting engine r.p.m., with a fixed pitch, is in general much less for marine screws; blade widths are much greater. In the author's conclusions it is suggested that full-scale determination of the optimum pitch setting may be valuable; consideration is also given to possible size and limitations of blade width, and to the effect of the costs involved.

Prediction of Travelling Time and Exhaust Gas Emission of Ships on the Northern Sea Route

2013 ◽  
Author(s):  
Nils Reimer ◽  
Quang-Tan Duong
Keyword(s):  
Fuel Consumption ◽  
Open Water ◽  
Exhaust Gas ◽  
Northern Sea Route ◽  
Exhaust Gas Emission ◽  
Speed Range ◽  
Travelling Time ◽  
Ice Conditions ◽  
The Impact

In order to simulate the impact of increased shipping activities to the arctic environment for a scenario with decreasing ice extent and ice volume, a simulation tool for ship travelling time was enhanced with regard to the determination of fuel consumption and exhaust emission on the Northern Sea Route (NSR). The tool was then used to investigate the impact of ships in different periods within the years 2000 and 2007 with various ice conditions. The transit speed is compared for different periods in the past and present by using ice records from different years together with route parameters and ship data as input for a simulation program. The program is able to calculate the ship resistance in open water and additional components due to wind, waves and ice within a speed range. By including specific propulsion data of the ship, a requested power is obtained for the speed range. The maximum speed is finally interpolated using the maximum available shaft power. The simulations are carried out for three different ship types with different hull shapes and propulsive power. The results show a significant decrease of travelling time for 2007 compared to 2000. Further in 2007 the season in which transport via the NSR is profitable is clearly extended to the winter months. In a second work task the program is further developed with respect to the determination of fuel oil consumption and exhaust gas emission. Due to increased resistance during ice breaking, high thrust has to be provided at low speed leading to an off design condition for propulsion arrangements which are optimised for service speed in open water. It can be found that the resulting actual fuel consumption is closely related to the operation profile of the ship. High values for fuel consumption thereby occur at service speed in ice free water but also at very low speeds in very tough ice conditions. For moderate ice conditions the fuel consumption and related emissions can be lower especially if the ship is forced to slow steaming for safety reasons.

scholarly journals Airborne River-Ice Thickness Profiling with Helicopter-Borne UHF Short-Pulse Radar

1987 ◽  
Vol 33 (115) ◽  
pp. 330-340 ◽  
Author(s):  
Steven A Arcone ◽  
Allan J Delaney
Keyword(s):  
Short Pulse ◽  
Hanging Wall ◽  
Open Water ◽  
High Water ◽  
High Water Content ◽  
Ice Thickness ◽  
Frazil Ice ◽  
Pulse Radar ◽  
Detailed Surface ◽  
Ice Conditions

AbstractThe ice-thickness profiling performance of a helicopter-mounted short-pulse radar operating at approximate center frequencies of 600 and 900 MHz was assessed. The antenna packages were mounted 1.2 m off the skid of a small helicopter whose speed and altitude were varied from about 1.8 to 9 m/s and 3 to 12 m. Clutter from the helicopter offered minimal interference with the ice data. Data were acquired in Alaska over lakes (as a proving exercise) and two rivers, whose conditions varied from open water to over 1.5 m of solid ice with numerous frazil-ice formations. The most readily interpretable data were acquired when the ice or snow surface was smooth. Detailed surface investigations on the Tanana River revealed good correlations of echo delay with solid ice depth, but an insensitivity to frazil-ice depth due to its high water content. On the Yukon River, coinciding temporally coherent surface and bottom reflections were associated with solid ice and smooth surfaces. All cases of incoherent surface returns (scatter) occurred over ice rubble. Rough-surface scattering was always followed by the appearance of bottom scattering but, in many cases, including a hanging-wall formation of solid frazil ice, bottom scattering occurred beneath coherent, smooth-surface reflections. Areas of incoherent bottom scattering investigated by drilling revealed highly variable ice conditions, including frazil ice. The minimum ice thickness that could be resolved from the raw data was about 0.2 m with the 600 MHz antenna and less than 0.15 m with the 900 MHz antenna.

scholarly journals Study on vibration and noise influence for optimization of garden mower

2021 ◽  
Vol 10 (1) ◽  
pp. 428-435
Author(s):  
Yimin Chen ◽  
Wenzhuo Zhang ◽  
Lu Dong ◽  
Korhan Cengiz ◽  
Amit Sharma
Keyword(s):  
Product Design ◽  
Design Process ◽  
Integrated Design ◽  
Frequency Level ◽  
Quality Life ◽  
Load Carrying ◽  
The World ◽  
Product Design Process ◽  
Safety And Environment

Abstract Advancement in engineering provides various improvement in quality life while taking consideration of important factors for safety and environment. The use of mower food maintenance of land it is very common across several parts of the world with some frequent noise generated through its operation. This article is an attempt to study the noise and frequency generated through the vibrations of mower blade. In this study, an integrated design for designing, testing and developing mower blade that generates less noise is presented. For designing efficient blade that produces less noise, we have implemented various engineering approaches such as rapid product design, process of re-engineering and reverse engineering. The simulation of the designed blade is carried out through CAD software where the design prototype is analysed for its performance. The outcomes of the prototype are tested through simulation and its performance is compared for the determination of success of proposed design at different variations in frequency level. It is observed through the experimentation that the noise and vibration differences are generated through load carrying vehicles, mowers with riding capacity and simple mowers. From the analysis, mower with riding capacity is observed as safest among all other types of machines.

Structural sizing for the weight estimation of a very light aircraft wing

2018 ◽  
Vol 232 (14) ◽  
pp. 2681-2687
Author(s):  
Abdelkader Benaouali ◽  
Robert Rogólski ◽  
Stanisław Kachel
Keyword(s):  
Finite Element ◽  
Design Process ◽  
Geometric Modeling ◽  
Optimization Techniques ◽  
Product Development Process ◽  
Optimization Strategy ◽  
Aircraft Wing ◽  
Lattice Method ◽  
Vortex Lattice Method

The design process is no longer a trial-and-error procedure due to the introduction of computer-aided tools and optimization techniques. The product development process is therefore accelerated, allowing to produce more in a relatively lesser time. Moreover, the best possible design, with regard to the performance, can hence be obtained. When applied to the design of an aircraft wing, the optimization objective is usually to minimize the structural weight under failure-based constraints. This paper presents an optimization strategy that allows the determination of the wing surface structural thicknesses corresponding to the minimal weight while keeping the structure safe in terms of strength and buckling. This strategy is applied for the wing sizing process of a new two-seater very light aircraft, currently under development. The design process goes through geometric modeling, aerodynamic calculations using vortex lattice method, and finite element modeling. Structural optimization is performed within MATLAB, and is based on the automatic execution of the finite element solver MSC.NASTRAN.

Facilitating rain-on-snow detection with satellite data

2021 ◽  
Author(s):  
Annett Bartsch
Keyword(s):  
Satellite Data ◽  
Open Water ◽  
The Arctic ◽  
Calibration And Validation ◽  
In Situ Data ◽  
Snow Properties ◽  
Structure Changes ◽  
Indirect Measures ◽  
Ice Conditions ◽  
Northern European Russia

<p>Rain-on-snow modifies snow properties and can lead to the formation of ice crusts which impact wildlife and also vegetation. Events in the Arctic have been recently linked to specific sea ice conditions (longer open water season) for Siberia. Specifically microwave satellite data have been shown applicable for identification of such events across the Arctic. Related snow structure changes can be observed specifically over Scandinavia, northern European Russia and Western Siberia as well as Alaska (Bartsch, 2010). Events which had severe impacts for reindeer herder herding have occurred several times in the last two decades.</p><p>Challenges further include the categorization of severity of events and attribution of observations to rain-on-snow events.</p><p>Calibration and validation of detection schemes have been largely based on indirect measures. Usually a combination of air temperature and snow height measurements, supported by reports of such events are analysed.</p><p>In this presentation, the utility of current calibration and validation approaches are discussed. Requirements towards in situ data from the viewpoint of satellite based retrievals are outlined.</p><p>Bartsch, A. Ten Years of SeaWinds on QuikSCAT for Snow Applications. Remote Sens. 2010, 2, 1142-1156.</p>

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