The development of short sea shipping in the United States : a dynamic alternative

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004.Includes bibliographical references (p. 122-128).Current projections show that U.S. international trade is expected to reach nearly two billion tons by 2020, approximately double today's level. With such a large forecasted growth in trade coming through the United States and growing problems associated with highway congestion, air pollution, and national security, building short sea shipping networks will be difficult, but possible, and potentially of great benefit to the nation. By bringing together shipping providers, customers, and with support from the federal government, short sea shipping can become a reality. This paper outlines the need for a change in our maritime transportation system. It takes a look at the current uses of short sea shipping in the United States as well as the system used in Europe. The technology associated with this concept is described and high-speed vessel design is investigated. Issues relating to the integration of short sea shipping are brought to light, including customer requirements, capital financing, and government policy. A computer-based simulation model calculates a total cost analysis for two modes of transporting goods, trucking and short sea shipping. The model is applied to a group of products of different size, weight, and value.(cont.) The quantitative results of the model show that in most cases, for lower value products, the savings in transportation costs from short sea shipping offset the increase in inventory costs. These results are then used to look at other commodities listed on the 2002 commodity flow survey to show the potential for short sea shipping use.by Peter H. Connor.S.M

A CFD and experimental investigation into a non-intrusive method for measuring cooling air mass flow rate through a synchronous generator

This paper presents a detailed methodology for a non-intrusive measurement of cooling air mass flow rate that enables an overall machine evaluation. This approach enables the simultaneous measurement of air mass flow with shaft torque at differing operating points, while minimising the change in air flow introduced by the measurement system. The impact of geometric parameters in the designed system are investigated using a detailed 180° CFD model. Special attention was paid to minimising their influence on pressure drop, mass flow rate through the machine and measurement uncertainty. Based on the results of this investigation, the system was designed and manufactured and the experimentally measured data was used to validate the CFD predictions. For the as optimal identified configuration, the flow rate is predicted to decrease by 2.2 % relative to unrestricted operation. The achieved measurement uncertainty is ±2.6 % at synchronous speed

Stator and rotor vent modelling in a MVA rated synchronous machine

An investigation into the solution dependence of a conjugate heat transfer computational fluid dynamics (CFD) model of a synchronous generator, with respect to meshing, has been carried out. Utilising CFD as a tool for investigating the airflow and thermal performance of electrical machines is increasing. Meshing is a vital part of the CFD process, but its importance is often misunderstood or overlooked in the context of electrical machine analyses; partly due to the relative mesh independency of the finite element analysis (FEA) numerical method. This paper demonstrates how a relatively complex, aircooled generator CFD model can be considerably influenced by changes in the mesh. Flow rate, velocity and windage effects are assessed as a function of the mesh adopted. Mesh changes have been shown to affect the mass flow rate through a single vent by up to 55% and the associated heat transfer coefficient by 128%

CFD optimisation of the thermal design for a vented electrical machine

Optimisation algorithms hold the potential to dramatically reduce computational time whilst ensuring the optimal solution is found. Within this paper, the feasibility of using this novel approach on complex 3-D Computational Fluid Dynamics models, which are required for thermal management of electrical machines, is proven. A model of a simplified generator is parameterised with the aim of minimising the peak stator temperature by varying the axial location of a single stator vent. By generating a single parameterised case, and automating the optimisation, the simulations are run independently after initial setup, hence reducing both computational and user time. Locating a vent in the optimal position reduced the peak stator temperature by 9.4 K. A sensitivity study linking peak temperature to vent position has been carried out developing a polynomial relationship between them for the aforementioned geometry. Mass flow and pressure distribution in the vent have been analysed in detail

Design and testing of electromechanical actuator for aerospace applications

Electromechanical actuators are gaining interest in the aerospace industry within the More Electrical Aircraft (MEA) architecture. The end-goal of fully electric aircraft includes Electromechanical actuation for flight control systems. The design and testing of a flight control system for helicopter swashplate is presented in this work. The mechanical system is driven by electrical machines and controlled by dedicated power electronics, both of which fit challenging space requirements and environmental conditions. The predicted performances are validated by experimental testing of prototypes

Analysis and Mitigation of AC Losses in High Performance Propulsion Motors

In this paper, the AC copper losses in classical random windings are investigated and mitigated using several techniques across a range of permanent magnet synchronous motor designs. At high operating frequencies, AC copper losses can represent a substantial share of the total loss in electrical machines, thus, reducing the machine's overall performance, and increasing the thermal loading. Recently, different approaches for modelling AC copper losses have been proposed. This paper utilises simulation software to quantify the expected AC losses in six different propulsion motor designs. The motor designs are then modified to reduce the AC winding losses through the implementation of five different methods. Using two-dimensional finite element analysis, the magnetisation direction, magnet to airgap ratio, copper stranding, magnetic wedges and the motor slot openings are modified to reduce AC losses. The paper considers distributed, fractional, slot and concentrated windings, and the results show promising reductions across these different winding configurations

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer has been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, whilst ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer have been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, while ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure