scholarly journals Dimensionless Numerical Approaches for the Performance Prediction of Marine Waterjet Propulsion Units

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Marco Altosole ◽  
Giovanni Benvenuto ◽  
Massimo Figari ◽  
Ugo Campora
Keyword(s):  
Performance Prediction ◽  
High Speed ◽  
Design Stage ◽  
Propulsion Systems ◽  
Mixed Flow ◽  
Early Design Stage ◽  
Hydraulic Machines ◽  
Performance Map ◽  
Key Issues ◽  
Numerical Approaches

One of the key issues at early design stage of a high-speed craft is the selection and the performance prediction of the propulsion system because at this stage only few information about the vessel are available. The objective of this work is precisely to provide the designer, in the case of waterjet propelled craft, with a simple and reliable calculation tool, able to predict the waterjet working points in design and off-design conditions, allowing to investigate several propulsive options during the ship design process. In the paper two original dimensionless numerical procedures, one referred to jet units for naval applications and the other more suitable for planing boats, are presented. The first procedure is based on a generalized performance map for mixed flow pumps, derived from the analysis of several waterjet pumps by applying similitude principles of the hydraulic machines. The second approach, validated by some comparisons with current waterjet installations, is based on a complete physical approach, from which a set of non-dimensional waterjet characteristics has been drawn by the authors. The presented application examples show the validity and the degree of accuracy of the proposed methodologies for the performance evaluation of waterjet propulsion systems.

Optimum Design of Radial-Flow Impellers

1989 ◽  
Vol 203 (4) ◽  
pp. 229-232
Author(s):  
G S Ray ◽  
B K Sinha ◽  
S Majumdar
Keyword(s):  
Optimum Design ◽  
Centrifugal Force ◽  
Computer Aided Design ◽  
High Speed ◽  
Radial Flow ◽  
Design Stage ◽  
Early Design ◽  
Early Design Stage ◽  
Computer Aided ◽  
Aided Design

The paper presents a procedure of computer aided design of high-speed impellers. The configurations are obtained using programs for the strength under the influence of centrifugal force within given constraints. The method provides a tool for optimizing stresses at an early design stage.

Maneuvering Predictions for Fast Monohulls in Early Design Stage

2015 ◽  
Author(s):  
F.H.H.A. Quadvlieg ◽  
F. van Walree ◽  
V. Barthelemy
Keyword(s):  
High Speed ◽  
Model Tests ◽  
Design Stage ◽  
Correct Prediction ◽  
Design Assessment ◽  
Early Design ◽  
Early Design Stage ◽  
Directional Stability ◽  
Pros And Cons ◽  
The Time Domain

The present paper discusses directional stability and course keeping of fast monohulls. Model tests and CFD were used for analysis. In itself these are great tools, but in early design stage they are often perceived as too elaborate. In comparison, design verification is often carried out during model testing., However, it is not common to use these model tests for systematic variation or multiple design variations. In addition to model tests, tools for early design assessment are also pursued. By using a 3D panel method, maneuvering coefficients and subsequently directional stability are found in an earlier stage of the design. The present paper describes which methods can be used in the design stage, and some pros and cons of these methods. A method of choice is selected and an example is elaborated. The example ship is a high speed monohull (Fn=0.8) propelled by waterjets. This paper illustrates that the forces acting on the ship while performing forced motions are predicted. A next step (not in the present paper) is to solve the equations of motions in the time domain as a system of ordinary differential equations. However, in order to correctly predict the motions and trajectories, the correct prediction of forces and moments is essential

Advanced noise modeling for future propulsion systems

2018 ◽  
Vol 17 (6-8) ◽  
pp. 576-599 ◽  
Author(s):  
Stéphane Moreau ◽  
Michel Roger
Keyword(s):  
Three Dimensional ◽  
Broadband Noise ◽  
Design Stage ◽  
Acoustic Analogy ◽  
Propulsion Systems ◽  
Modal Expansion ◽  
Early Design Stage ◽  
Strip Theory ◽  
Noise Models ◽  
Bypass Ratio

In order to meet noise specifications for future foreseen aircraft propulsion systems, such as for ultrahigh bypass ratio turbofans and contra-rotating open rotors, the dominant turbomachinery noise mechanisms need to be modeled accurately at an early design stage. Two novel methods are presented here, which could significantly improve the existing analytical noise models. For the high-solidity ultrahigh bypass ratio, a mode-matching technique based on a modal expansion of acoustic and vortical variables in each subdomain of a blade row is shown to accurately reproduce sound generation and propagation in two-dimensional bifurcated channels and in three-dimensional annular unstaggered flat-plate cascades. For the low solidity contra-rotating open rotors, several extensions to Amiet’s compressible isolated airfoil theory are coupled with Curle’s and Ffowcs Williams and Hawkings’ acoustic analogy in the frequency domain within a strip theory framework, to yield both far-field tonal and broadband noise. Including sweep in both tonal and broadband noise models is shown to significantly improve the comparison with experiments on a stationary swept airfoil in a uniform turbulent stream and on a realistic contra-rotating open rotor geometry at approach conditions.

A Dynamics Workstation

1989 ◽  
Author(s):  
J. K. Wu ◽  
M. A. Fogle ◽  
J. Y. Wang ◽  
J. K. Lu
Keyword(s):  
Mechanical System ◽  
Dynamic Simulation ◽  
High Speed ◽  
Mechanical Systems ◽  
Design Stage ◽  
Design System ◽  
Design Quality ◽  
Modeling Tool ◽  
Early Design Stage ◽  
System Models

Abstract The engineer’s modeling capability is the weakest link in the chain that supports the simulation of dynamic mechanical systems, due to the fact that engineers are forced to define mechanical system models in a way they are not familiar with. Advanced developments in computer techniques, computer graphics, and recursive computational algorithms for mechanical systems make the high speed dynamic simulation and graphic animation of mechanical systems feasible. But without a practical, useful modeling tool, the engineer has difficulty in using these advanced techniques. The Dynamics Workstation is a modeling tool developed to help the engineer define mechanical system models in a natural, practical way. The engineer can communicate with the workstation naturally and interactively, define the model in formats that meet the needs for both high speed dynamic simulation and conventional dynamic analysis, define and assemble the model body by body using a relative coordinate system, visualize the configuration of the model, carry out simple joint exercises to detect the errors of the model in the early design stage, graphically lock and unlock joints, and adjust the system configuration even after initial assembly. The workstation automatically generates the mechanical system model based on the engineer’s interactive input data. The model design system strengthens the engineer’s modeling capability; it not only improves the design quality, but also boosts productivity.

Elastodynamic Model-Based Vibration Characteristics Prediction of a Three Prismatic–Revolute–Spherical Parallel Kinematic Machine

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Jun Zhang ◽  
Yan Q. Zhao ◽  
Marco Ceccarelli
Keyword(s):  
Dynamic Characteristics ◽  
Lower Order ◽  
High Speed ◽  
Natural Frequencies ◽  
Eigenvalue Decomposition ◽  
Design Stage ◽  
Response Analysis ◽  
Early Design Stage ◽  
Synthesis Strategy ◽  
Parallel Kinematic

Parallel kinematic machines (PKMs) have been proposed as an alternative solution for high-speed machining (HSM) tool for several years. However, their dynamic characteristics are still considered an issue for practice application. Considering the three prismatic–revolute–spherical (3-PRS) PKM design as a typical compliant parallel device, this paper applies substructure synthesis strategy to establish an analytical elastodynamic model for the device. The proposed model considers the effects of component compliances and kinematic pair contraints so that it can predict the dynamic characteristics of the 3-PRS PKM. Based on eigenvalue decomposition of the characteristic equations, the natural frequencies and corresponding vibration modes at a typical configuration are analyzed and verified by numerical simulations. With an algorithm of workspace partitions combining with eigenvalue decompositions, the distributions of lower-order natural frequencies throughout the workspace are computed to reveal a strong dependency of dynamic characteristics on mechanism's configurations. In addition, the effects of the radii of the platform and the base along with the cross section of the limb on lower-order natural frequencies are analyzed to provide useful information during the early design stage. At last, frequency response analysis for the tool center point (TCP) is worked out based on the elastodynamic model to provide primary guideline for cutting chatter avoidance.

scholarly journals The Solution of Two-Dimensional Heat Conduction Problems for Predicting Operating Temperature and Power Handling Capabilities of Hybrid Circuits

1980 ◽  
Vol 7 (1-3) ◽  
pp. 97-105 ◽  
Author(s):  
G. P. Ferraris ◽  
M. Tudanca
Keyword(s):  
Heat Conduction ◽  
Theoretical Calculations ◽  
Two Dimensions ◽  
Design Stage ◽  
Early Design ◽  
Early Design Stage ◽  
Power Handling ◽  
Accurate Design ◽  
The Stability ◽  
Numerical Approaches

The problems of heat conduction in hybrid thin and thick film circuits have been investigated using both analytical and numerical approaches.The calculations were restricted to two dimensions by assuming zero temperature gradient across the thickness of the substrate (slightly more than half millimeter).All normally recognized parameters were taken into consideration, such as film temperature, power dissipated, substrate area, etc.Allowances have also been made for lead conduction and connection technology, for horizontal or vertical circuit assembly, and for flush or stand-off mounting on the mechanical support.The measured results for practical cases show close agreement with the theoretical calculations.This approach provides a simple tool for the calculation, at an early design stage of power handling capacities of hybrid circuits using composite resistive configurations.Very little difference was found between temperatures predicted from the theoretical approach and those measured in practical cases of circuits under load.The availability of such accurate design information means that the stability, life, and reliability of hybrid circuits can be predicted with considerable accuracy at an early design stage.

scholarly journals TRACING THE EMERGENCE OF DESIGN PROBLEMS AND THEIR IMPACTS ON THE COMPLEXITY OF ENGINEERING SOLUTIONS

2021 ◽  
Vol 1 ◽  
pp. 3229-3238
Author(s):  
Torben Beernaert ◽  
Pascal Etman ◽  
Maarten De Bock ◽  
Ivo Classen ◽  
Marco De Baar
Keyword(s):  
Large Scale ◽  
Fusion Reactor ◽  
Design Stage ◽  
Engineering Model ◽  
Design Problems ◽  
Nuclear Fusion Reactor ◽  
Early Design Stage ◽  
Iterative Design ◽  
Problems And Solutions ◽  
Emergent Design

AbstractThe design of ITER, a large-scale nuclear fusion reactor, is intertwined with profound research and development efforts. Tough problems call for novel solutions, but the low maturity of those solutions can lead to unexpected problems. If designers keep solving such emergent problems in iterative design cycles, the complexity of the resulting design is bound to increase. Instead, we want to show designers the sources of emergent design problems, so they may be dealt with more effectively. We propose to model the interplay between multiple problems and solutions in a problem network. Each problem and solution is then connected to a dynamically changing engineering model, a graph of physical components. By analysing the problem network and the engineering model, we can (1) derive which problem has emerged from which solution and (2) compute the contribution of each design effort to the complexity of the evolving engineering model. The method is demonstrated for a sequence of problems and solutions that characterized the early design stage of an optical subsystem of ITER.

scholarly journals Reliability-Oriented Design of Inverter-Fed Low-Voltage Electrical Machines: Potential Solutions

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4144
Author(s):  
Yatai Ji ◽  
Paolo Giangrande ◽  
Vincenzo Madonna ◽  
Weiduo Zhao ◽  
Michael Galea
Keyword(s):  
Power Density ◽  
High Speed ◽  
High Performance ◽  
Low Voltage ◽  
Electrical Machines ◽  
Design Stage ◽  
Switching Frequency ◽  
Special Focus ◽  
Electrical Machine ◽  
Engineering Approach

Transportation electrification has kept pushing low-voltage inverter-fed electrical machines to reach a higher power density while guaranteeing appropriate reliability levels. Methods commonly adopted to boost power density (i.e., higher current density, faster switching frequency for high speed, and higher DC link voltage) will unavoidably increase the stress to the insulation system which leads to a decrease in reliability. Thus, a trade-off is required between power density and reliability during the machine design. Currently, it is a challenging task to evaluate reliability during the design stage and the over-engineering approach is applied. To solve this problem, physics of failure (POF) is introduced and its feasibility for electrical machine (EM) design is discussed through reviewing past work on insulation investigation. Then the special focus is given to partial discharge (PD) whose occurrence means the end-of-life of low-voltage EMs. The PD-free design methodology based on understanding the physics of PD is presented to substitute the over-engineering approach. Finally, a comprehensive reliability-oriented design (ROD) approach adopting POF and PD-free design strategy is given as a potential solution for reliable and high-performance inverter-fed low-voltage EM design.

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