Analysis of Local Vibration and Strength of Water Jet Propulsion Unit of High Speed Ship

2018 ◽  
Author(s):  
Xin Zhang ◽  
Huilong Ren ◽  
Guoqing Feng ◽  
Yifu Liu ◽  
Zhaonian Wu
Keyword(s):  
High Speed ◽  
Element Model ◽  
Lateral Force ◽  
Water Jet ◽  
Local Vibration ◽  
Jet Propulsion ◽  
Vibration Problem ◽  
Local Strength ◽  
Blade Frequency ◽  
Propulsion Unit

In recent years, water jet propulsion unit has been widely used in the field of high speed ship. Compared with traditional propeller, water jet propulsion unit has excellent maneuverability with high speed, and lateral force generated by water jet propulsion unit can reduce the radius of turning. High speed ship with water jet propulsion has higher efficiency, lower noise. However, water jet propulsion unit needs to be opened in stern transom plate, and it causes the water jet force when ship is operating, all of these will affect the local strength of stern. It remains to be researched whether the vibration generated by water jet excitation force has a significant influence. These problems are designers worried about. To solve these problems, this paper builds the finite element model of stern contains water jet propulsion unit, considering hull deck load, broadside load, bottom load, bulkhead load and water jet load, checking the local strength of stern. Analysis of vibration problem, considering the influence of added mass of entrained water, dividing stern into deck, bottom, water jet propulsion unit, stern transom plate and other local structure, calculating natural frequencies of plate, panel and grillage of each local structures. Comparing the results with shaft frequency and blade frequency, checking the reserve frequency, judging whether water jet propulsion unit on vibration problem meets standards, providing reference for the following hull design.

Water-Jet Propulsion for High-Speed Hydrofoil Craft

1966 ◽  
Vol 3 (2) ◽  
pp. 174-179 ◽  
Author(s):  
VIRGIL E. JOHNSON
Keyword(s):  
High Speed ◽  
Water Jet ◽  
Jet Propulsion

scholarly journals Research on Vibration Reduction Method of Nonpneumatic Tire Spoke Based on the Mechanical Properties of Domestic cat’s Paw Pads

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Haichao Zhou ◽  
Huiyun Li ◽  
Ye Mei ◽  
Guolin Wang ◽  
Congzhen Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Speed ◽  
Vibration Reduction ◽  
Element Model ◽  
Approximate Model ◽  
Structure Design ◽  
Peak Amplitude ◽  
Radial Excitation ◽  
Vibration Problem ◽  
Design Variables

Although there is no risk of puncture, the vibration problem caused by discontinuous structures limits nonpneumatic tire development (NPT). The vibration reduction of nonpneumatic tires is a solvable urgent problem. This current study analyzed the dynamic grounding characteristics and the vibration reduction mechanism of the cat’s paw pads and then applied the mechanical properties to the bionic design of nonpneumatic tire spokes to solve the vibration problem. Domestic cats’ paw pads’ dynamic grounding characteristics were determined using the pressure-sensitive walkway, high-speed camera, and VIC-2D. The results indicated that the mechanical characteristics of swing deformation of paw pads during the grounding process attenuated the grounding stress and buffered the energy storage to achieve the vibration reduction effect. According to the similarity transformation, a finite element model of NPT that could accurately reconstruct the structure and realistically reflect the load deformation was employed. The structure design of asymmetric arcs on the spokes’ side edges was proposed, and it can effectively reduce the radial excitation force of NPT. The three parameters, the asymmetric arc, the thickness, and the curvature of spokes, were used as design variables to maximize the vibration reduction. The orthogonal experimental, the Kriging approximate model, and the genetic algorithm were carefully selected for optimal solutions. Compared with the original tire, the results showed that peak amplitude 1, peak amplitude 2, and the root square of the optimized tire’s amplitudes were reduced by 76.07%, 52.88%, and 51.65%, respectively. These research results offer great potential guidance in the design of low-vibration NPT.

Performances of Water Jet Propulsion with PD Pump

2014 ◽  
Vol 602-605 ◽  
pp. 539-545
Author(s):  
You Sheng Yang ◽  
Peng Sun ◽  
Yang Fu ◽  
Chao Chao Zhao
Keyword(s):  
High Performance ◽  
High Efficiency ◽  
Low Noise ◽  
Water Jet ◽  
Speed Ratio ◽  
Jet Propulsion ◽  
Constant Flow Rate ◽  
Positive Displacement ◽  
Displacement Pump ◽  
Propulsion Unit

Water jet propulsion (WJP) with positive displacement pump (PD pump), in which the suction thrust of PD pump (Due to the effect of pump suction and the influence of the suction boundary layer) and the reaction thrust of water jet are used to push watercraft forward, has many advantages like high efficiency,low noise, high maneuverability, good adaptability to variable working conditions, simple transmission mechanism over traditional propulsion methods. A mathematical model is developed and the WJP theory with PD pump is analyzed. Numerical studies are carried out to study the suction thrust, reaction thrust, and propulsion efficiency of the thruster with Bernoullihyperbolic suction inlet-PD pump-Bernoulli hyperbolic nozzle. The results show that: 1) in the conditions of no cavitation in suction inlet and constant flow rate, the suction thrust is inversely proportional to the inlet diameter and reaches around 8.5% of the total thrust; 2) the reaction thrust increases with the decrease of the nozzle diameter; 3) the pump-suction coefficientvis proportional to the speed ratioμ; 4) the efficiency of WJP with PD pump is higher than with negative displacement pump under the same speed ratio. The related conclusions provide a basis for the design of high performance water propulsion unit.

Vibration Survey Techniques

1971 ◽  
Vol 8 (01) ◽  
pp. 58-68
Author(s):  
William H. Knopfle
Keyword(s):  
Longitudinal Vibration ◽  
Performance Characteristics ◽  
Fundamental Vibration ◽  
Local Vibration ◽  
Vibration Measurements ◽  
Hull Girder ◽  
Survey Techniques ◽  
Vibration Problem ◽  
The Subject ◽  
Blade Frequency

The paper presents fundamental vibration survey considerations and discusses classical hull girder vibration and main propulsion machinery longitudinal vibration. The results of a typical hull girder vibration survey are presented. Elementary considerations of the effect, on blade-frequency hull girder vibration, of changing the number of blades on the propeller are discussed. The SNAME Bulletin No. C–1 "Code for Shipboard Vibration Measurements by Panels HS–7 and M–20 (1969)" is summarized with emphasis on the instrumentation aspect. The subject of local vibration is treated by means of some typical examples and the instrumentation requirements for this type of study are discussed. The performance characteristics of the Askania Hand Vibrograph are outlined. A vibration survey conducted by the author on a river towboat in order to investigate a rather unusual vibration problem is described.

scholarly journals Utilization of Open-Source OpenFOAM Code to Examine the Hydrodynamic Characteristics of a Linear Jet Propulsion System with or without Stator in Bollard Pull Condition

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Parviz Ghadimi ◽  
Negin Donyavizadeh ◽  
Pouria Taghikhani
Keyword(s):  
High Speed ◽  
Water Jet ◽  
Propulsion System ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Propulsion Systems ◽  
Thrust Coefficient ◽  
Jet Propulsion ◽  
Marine Industry ◽  
Total Thrust

With the development of high-speed crafts, new propulsion systems are introduced into the marine industry. One of the new propulsion systems is linear jet which is similar to pump jet and has a rotor, a stator, and a duct. The main difference between this system and pump jet is the placement of linear jet system under the hull body and inside a tunnel. Since this system, like a water jet, is inside the tunnel, the design idea of this system is a combination of a water jet and pump jet. In this paper, hydrodynamic performance of linear jet propulsion system is numerically investigated. To this end, the OpenFOAM software is utilized and RANS steady equations are solved using a k - ε turbulent model. The linear jet geometry is produced by assembling a Kaplan rotor, stator with a NACA 5505 cross section, and a decelerating duct. The results of numerical solution in the form of thrust, torque coefficient, and efficiency are compared with available experimental data for a ducted propeller, and good agreement is displayed. Subsequently, the hydrodynamic parameters are computed in two conditions: with a stator and without a stator. By comparing the results, it is observed that the total thrust coefficient of the propulsion system with a stator at all advance ratios increases by at least 40%. It is further observed that addition of a stator also improves its efficiency.

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