scholarly journals Numerical Simulation on Hydraulic Characteristics of Nozzle in Waterjet Propulsion System

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 915 ◽  
Author(s):  
Chuan Wang ◽  
Xiaoke He ◽  
Li Cheng ◽  
Can Luo ◽  
Jing Xu ◽  
...  
Keyword(s):  
Propulsion System ◽  
Dynamics Simulation ◽  
Transition Curve ◽  
Hydraulic Loss ◽  
Main Function ◽  
System Efficiency ◽  
Hydraulic Characteristics ◽  
Linear Contraction ◽  
Circular Nozzle ◽  
Inlet Duct

As an important over-current component of the waterjet propulsion system, the main function of a nozzle is to transform the mechanical energy of the propulsion pump into the kinetic energy of the water and eject the water flow to obtain thrust. In this study, the nozzle with different geometry and parameters was simulated based on computational fluid dynamics simulation and experiment. Numerical results show a good agreement with experimental results. The results show that the nozzle with a circular shape outlet shrinks evenly. Under the designed flow rate condition, the velocity uniformity of the circular nozzle is 0.26% and 0.34% higher than that of the elliptical nozzle and the rounded rectangle nozzle, respectively. The pump efficiency of the circular nozzle is 0.31% and 0.14% higher than that of the others. The pressure recovery and hydraulic loss of the circular nozzle are superior. The hydraulic characteristics of the propulsion pump and waterjet propulsion system are optimal when the nozzle area is 30% times the outlet area of the inlet duct. Thus, the shaft power, head, thrust, and system efficiency of the propulsion pump and waterjet propulsion system are maximized. The system efficiency curve decreases rapidly when the outlet area exceeds 30% times the outlet area of the inlet duct. The transition curve forms greatly affect thrust and system efficiency. The transition of the linear contraction shows improved uniformity, and the hydraulic loss is reduced. Furthermore, the hydraulic performance of the nozzle with a linear contraction transition is better than that of others.

scholarly journals Optimal Design of Inlet Passage for Waterjet Propulsion System Based on Flow and Geometric Parameters

2019 ◽  
Vol 2019 ◽  
pp. 1-21 ◽  
Author(s):  
Weixuan Jiao ◽  
Li Cheng ◽  
Di Zhang ◽  
Bowen Zhang ◽  
Yeping Su ◽  
...  
Keyword(s):  
Velocity Ratio ◽  
Optimization Method ◽  
Hydraulic Performance ◽  
Numerical Results ◽  
Propulsion System ◽  
Operating Conditions ◽  
Geometric Parameters ◽  
Hydraulic Characteristics ◽  
Design And Optimization ◽  
Ship Speed

As an important overcurrent component in a waterjet propulsion system, the inlet passage is used to connect the propulsion pump and the bottom of the propulsion ship. The anticavitation, vibration, and noise performance of the waterjet propulsion pump are significantly affected by the hydraulic performance of the inlet passage. The hydraulic performance of the inlet passage directly affects the overall performance of the waterjet propulsion system, thus the design and optimization method of the inlet passage is an important part of the hydraulic optimization of the waterjet propulsion system. In this study, the hydraulic characteristics of the inlet passage in the waterjet propulsion system with different flow parameters and geometric parameters were studied by a combination of numerical simulation and experimental verification. The model test was used to verify the hydraulic characteristics of the waterjet propulsion system, and the results show that the numerical results are in good agreement with the test results. The numerical results are reliable. The hydraulic performance of the inlet passage is significantly affected by the inlet velocity ratio. There is a certain correlation between the hydraulic performance of the inlet passage and ship speed, and the hydraulic performance of the inlet passage is limited by ship speed. The geometric parameters of the best optimization case are as follows: the inflow dip angle α is 35°, the length L is 6.38D0, and the upper lip angle is 4°. The optimal operating conditions are the conditions of IVR 0.69–0.87.

Investigation of changes in the arrangement of water molecules and salt ions surrounding different atoms of the DNA molecule during the melting process: a molecular dynamics simulation study

2015 ◽  
Vol 93 (3) ◽  
pp. 348-361 ◽  
Author(s):  
C. Izanloo
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Double Helix ◽  
Melting Process ◽  
Minor Groove ◽  
Dynamics Simulation ◽  
Transition Curve ◽  
Water Molecules ◽  
Major Groove ◽  
Dna Duplex

A molecular dynamics simulation was performed on a B-DNA duplex (CGCGAATTGCGC) at different temperatures. The DNA was immerged in a saltwater medium with 1 mol/L NaCl concentration. The arrangements of water molecules and cations around the different atoms of DNA on the melting pathway were investigated. Almost for all atoms of the DNA by double helix → single-stranded transition, the water molecules released from the DNA duplex and cations were close to single-stranded DNA, but this behavior was not clearly seen at melting temperatures. Therefore, release of water molecules and cations approaching the DNA by the increase of temperature does not have any effect on the sharpness of the transition curve. Most of the water molecules and cations were found to be around the negatively charged phosphate oxygen atoms. The number of water molecules released from the first shell hydration upon melting in the minor groove was higher than in the major groove, and intrusion of cations into the minor groove after melting was higher than into the major groove. The hydrations of imino protons were different from each other and were dependent on DNA bases.

scholarly journals Modeling and Simulation to Improve the Efficiency of Transportation Systems: A Tool for Decision Support

2020 ◽  
Author(s):  
Erma Suryani ◽  
Rully Agus Hendrawan ◽  
Philip Faster Eka Adipraja ◽  
Rarasmaya Indraswari ◽  
Ervina Ahyudanari ◽  
...  
Keyword(s):  
Decision Support ◽  
Transportation System ◽  
Transportation Systems ◽  
Dynamics Simulation ◽  
Time Lags ◽  
System Efficiency ◽  
Transport Planning ◽  
Complex Decision Making ◽  
Development Route ◽  
Use Of Models

Abstract This paper addresses problem solving and complex decision making in the management of transportation operations under environmental dynamics through the use of models and scenarios. A system dynamics simulation was used to model and analyze the efficiency of transportation systems as a tool for decision support to improve efficiency. Transportation systems are complex because they involve a number of different stakeholders, resulting in feedback with different time lags between the responses of all entities. Data and information were collected from the Transportation Department of Surabaya city. Several scenarios to improve the efficiency of transportation systems were developed by modifying the structure and parameters of the model. Several factors influence the efficiency of transportation system: traffic network, conventional roadway, accessibility based transport planning, multi modal transport, planning efficiency, and resources efficient modes (economic category). By implementing a number of strategies (such as the improvement of planning efficiency; multimodal transport development; route-based performance improvement), transportation system efficiency in Surabaya was predicted to be improved from 56% in 2019 to 66% in 2040. The novel contributions of this research are: formulating relationships among several variables, modeling dynamic behavior of transportation system efficiency, and building scenario models to improve transportation operation efficiency. This research contributes to the literature by investigating these relationships through the use of models and experimental scenarios.

scholarly journals The Effect of Hull Biofouling on Parameters Characterising Ship Propulsion System Efficiency

2015 ◽  
Vol 21 (4) ◽  
pp. 27-34X ◽  
Author(s):  
Wiesła Tarełko
Keyword(s):  
Rotational Speed ◽  
Operating Performance ◽  
Propulsion System ◽  
System Efficiency ◽  
Friction Resistance ◽  
Ship Propulsion ◽  
Different Types ◽  
Research Experiment

Abstract One of most important issues concerning technical objects is the increase of their operating performance. For a ship this performance mainly depends on the efficiency of its main pro-pulsion system and the resistance generated during its motion on water. The overall ship re-sistance, in turn, mainly depends on the hull friction resistance, closely related with the pres-ence of different types of roughness on the hull surface, including underwater part biofouling. The article analyses the effect of hull biofouling on selected parameters characterising the efficiency of the ship propulsion system with adjustable propeller. For this purpose a two-year research experiment was performed on a sailing vessel during its motor navigation phases. Based on the obtained results, three groups of characteristics were worked out for different combinations of engine rotational speed and adjustable propeller pitch settings. The obtained results have revealed that the phenomenon of underwater hull biofouling affects remarkably the parameters characterising propulsion system efficiency. In particular, the development of the biofouling layer leads to significant reduction of the speed of navigation.

PMSM and 5-level CSI based boat electrical propulsion system efficiency analysis

2012 ◽  
Author(s):  
Bruno S. Dupczak ◽  
Marcelo L. Heldwein ◽  
Arnaldo J. Perin ◽  
Carlos A. Martins ◽  
Jerome Cros
Keyword(s):  
Efficiency Analysis ◽  
Propulsion System ◽  
System Efficiency ◽  
Electrical Propulsion

Multibody Dynamics Simulation and Bogie Structure Evaluation for Active-Bogie Steering Truck

2007 ◽  
Author(s):  
N. Miyajima ◽  
A. Matsumoto ◽  
Y. Suda ◽  
Y. Sato ◽  
H. Ohno ◽  
...  
Keyword(s):  
Traffic Safety ◽  
High Speed ◽  
Dynamics Simulation ◽  
Transition Curve ◽  
Steering Control ◽  
Active Steering ◽  
Steering Mechanism ◽  
Curving Performance ◽  
Hunting Stability ◽  
Structure Evaluation

Railway truck is necessary to have excellent curving performance as well as high speed hunting stability, but generally they are contrary to each other. In order to realize the compatibility, many trucks with passive steering mechanism have been studied, and some of them are realized on service operation. In order to realize further improvement of bogie steering ability on sharp curve, active steering control can give effective performance, and is considered as the latest topic. As an example of the active steering bogie, the bogie with actuators between wheelsets and bogie frame is considered. The bogie mechanism realizes effective steering but requires many actuators results in complex mechanism. The truck treated here has simple but effective mechanism: Actuators are attached only between car body and truck frame. When railway trucks negotiate sharp curve running, the rolling radius difference between inside and outside wheels cannot be obtained sufficiently, and the attitude of the truck becomes so-called “insufficient steering condition”. Considering the phenomena, if the truck frame is steered by actuators toward “radial steering position of the truck”, the improvement of curving performance of the truck can be realized. This is the first concept of active-bogie-steering (ABS) truck. In this paper, detailed study and evaluation for ABS (Active-Bogie-Steering) bogie will be presented. Validity tests were carried out with the bogie on rolling test stand in NTSEL (National Traffic Safety and Environment Laboratory), which can simulate curve-running condition including transition curve. Bogie parameters and steering actuator characteristics are elaborately identified in order to compare the experimental results with multi-body dynamics simulation. According to the test results and numerical simulation, the effectiveness of the proposed bogie mechanism and control are proved.

Fluidic Control of a Hydrostatic Transmission in a Vehicle Propulsion System

1973 ◽  
Vol 95 (2) ◽  
pp. 114-123
Author(s):  
K. N. Reid ◽  
R. L. Woods
Keyword(s):  
Engine Speed ◽  
Propulsion System ◽  
System Efficiency ◽  
Systematic Method ◽  
Hydrostatic Transmission ◽  
Vehicle Propulsion ◽  
Wide Range ◽  
Fluidic Control ◽  
Speed Engine ◽  
Steady State Performance

A vehicle propulsion system is considered which consists of an engine, hydrostatic transmission, and automatic controller. Control requirements are established for optimum or near optimum operation based on a steady-state performance index. Various controller classes are identified and a systematic method for synthesis of the “best” controller is outlined. A unique fluidic controller is discussed which adjusts the transmission ratio to maintain a specified engine speed-engine load relationship which maximizes overall system efficiency for a wide range of external load conditions.

scholarly journals Hydraulic Characteristics and Measurement of Rotating Stall Suppression in a Waterjet Propulsion System

2019 ◽  
Vol 42 (4) ◽  
pp. 85-100 ◽  
Author(s):  
Chenzhi Xia ◽  
Li Cheng ◽  
Can Luo ◽  
Weixuan Jiao ◽  
Di Zhang
Keyword(s):  
Rotating Stall ◽  
Propulsion System ◽  
Hydraulic Characteristics
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