Propulsion

About: Propulsion is a research topic. Over the lifetime, 24977 publications have been published within this topic receiving 200311 citations.

Session - Power Title: Onboard DC Grid for Enhanced DP Operation in Ships

Abstract: Onboard DC Grid is a novel, new technology which is a further development of utilizing DC links that already exists in all propulsion and thruster drives, accomplishing for usually more than 80% of the electrical power consumption on electric propulsion vessels. This extension means that we keep all the good and well proven products used in today’s electric ships like AC generators, inverter modules, AC motors, etc. The main AC switchboard and transformers are not longer needed. The result is a more flexible power and propulsion system. Further Onboard DC Grid enables a combination of power sources and energy storage. Onboard DC Grid is suitable for vessels with total installed power of up to 20MW and operates at 1000V DC on the main bus. Typical target vessel is Offshore Support Vessels (OSVs), but any other vessel type using low voltage electric distribution would also be in the target range. For DP operation this approach gives several benefits. Firstly, the power network is no longer fixed at 60Hz. This means that an additional freedom of controlling the generator engine speed is present, giving the possibility to run engines efficiently even at 50% loading or lower. Today’s discussion of operating the power plant with open or closed bustie breakers can then be closed. Secondly, use of energy storage gives a possibility to level out the power variations on the engines even if the thruster loads are varying significantly due to vessel movements in bad weather conditions. This does not only contribute to increased fuel saving, but equally important would be the increased DP performance by the fact that the dynamic response of the thrusters would be independent from the engine dynamics. Today each thruster will experience ramp limits in power changes due to limitations in engines, however the energy storage take most of these power variations and hence reduce these limitations to a minimum. To conclude Onboard DC Grid is suited for vessels with total installed power up to about 20MW. It is flexible with respect to use of various power and fuel sources, and it gives clear benefits for vessels operating in DP, with respect to fuel consumption but also with respect to dynamic performance of the thruster system. Click below to:

Control device for hydraulically propelled work vehicle

Abstract: The current operational condition is discriminated as being the vehicle propulsion condition or the performing work condition. When the vehicle propulsion operational condition is discriminated, the maximum engine revolution speed is limited to a first revolution speed and the maximum displacement is limited to a first displacement value. When the performing work condition is discriminated, the maximum engine revolution speed is limited to a second revolution speed equal to or lower than the first revolution speed and the maximum displacement is limited to a second displacement value higher than the first displacement value. The first and second revolution speeds and the first and second displacement values are so determined that the first revolution speed multiplied by the first displacement value at least as relating to pressure for vehicle propulsion on level ground is less than the second revolution speed multiplied by the second displacement value as relating to the pressure for below the range of torque limitation control. By this, the pump output flow during vehicle propulsion on level ground is made lower than while performing work and, during vehicle propulsion, reduction of the pressure loss is made possible. Even with the identical pump pressure, the effective motor pressure is increased, so that its output torque can be increased. Because also the maximum displacement of the motor can be reduced according to the reduction of the maximum pump output flow amount, the construction of the hydraulic circuit can be made more compact.

Model of Ideal Electrohydrodynamic Thruster

Abstract: of thrust and thrust efficiency can be obtained from electrohydrodynamic thrusters, etc. In this paper, a simple onedimensional model of an ideal electrohydrodynamic thruster for calculating thrust efficiency and thrust of electrohydrodynamic thrusters is presented. The maximum current that can be achieved for an ideal electrohydrodynamicthrusteratagivenvoltageisalsocalculated.Thisallowsthecalculationofthemaximumthrust that can be obtained from the thruster and the corresponding thrust efficiency. It is shown that, with an increase in the voltage, the maximum thrust and the corresponding thrust efficiency move in opposite directions: the thrust efficiency decreases, while the thrust increases. It is also shown that, at high altitudes, the performance of electrohydrodynamic thrusters (thrust and thrust efficiency) drops very fast; therefore, using electrohydrodynamic thrusters at altitudes greater than 5 km is apparently unrealistic. The model shows that maximum thrust cannot exceed 20–30 N=m 2 at sea level, even at breakdown voltage. The model illuminates the physical limitations of electrohydrodynamic thrusters and provides reasonable estimates of the performance limits of real electrohydrodynamic thrusters.

Dc power system for marine vessels

Abstract: An embodiment of the invention is a power system for a marine vessel including a plurality of power sources (20). A propulsion power distribution unit is coupled to the plurality of primary power sources (20). A plurality of propulsion devices (30) are coupled to the propulsion power distribution unit. A weaponry power distribution unit is coupled to the propulsion power distribution unit. A plurality of directed energy weapons (50) are coupled to the weaponry power distribution unit.

Hybrid powertrain with an engine input clutch and method of control

Abstract: A powertrain is provided with a first input clutch and a second input clutch, each of which is selectively engageable to connect an engine with a transmission input member. Selective engagement of the first input clutch permits a motor to power the engine to start the engine. Selective engagement of the second input clutch permits the engine to power the transmission for propulsion.