Propulsion efficiency

Another important consideration for marine propeller design is cavitation, the rapid formation and then collapse of vacuum pockets on the blade surface at high speed, and its contributions to losses in propulsive efficiency. The phenomenon can cause serious damage to the propeller by eroding the blade surface and creating high frequency underwater noise. Cavitation first became a serious problem in the late nineteenth and early twentieth centuries... 

The most well-known propulsion efficiency is the amount of energy (fuel) required to move a vehicle a certain distance against opposing forces. Efficiencies of road vehicles, for instance, arc usually measured in miles per gallon. 

Propellers are the predominant propulsive devices driving ships, although water jets are now used in some high-speed ships. An experimental installation in a small ship of a magnetohydrodynamic propulsor has been tested, but it achieved rather low propulsive efficiency. Fish-like propulsion also has been examined for possible application to ships and underwater vehicles. 

Note that overall efficiency of all the above engines is primarily controlled by the cycle fuel efficiency the propulsive efficiency... 

NRI s main task in the Zemships project is to develop a simplified mathematical model of ship propulsion. This model has been used together with measurement data from typical driving loop to optimise a driving strategy with regards to achieving high propulsions efficiency. 

It is helpful to start with the ultimate and then back off to the achievable when analyzing the potential for lithium powered vehicles. Here is the ultimate. If an electric car had 100 percent efficiency of electricity utilization, zero tire and aerodynamic drag, and 100 percent energy recovery from braking, its propulsion efficiency would be perfect. Except for the electricity used for control, instruments, radio, and lights, the range would be infinite. 

Since the development and application of atomistic computational methods in recent years, our understanding of gas microfluidics and nanofluidics has been greatly improved. If the flow and thermal behavior can be correctly analyzed and accurately predicted, optimal design of microsystems is possible. Related work can be found in analyses of the performance of microscale air slide bearings in hard disk drives [16], the propulsion efficiency of micronozzles in... 

Rarefied analyses of thermal coupling between the micro-nozzle with the surrounding substrate have also been reported [10]. In this work, steady low Reynolds number gas flows were again modeled by the DSMC approach, and the substrate transient thermal response was governed by the heat conduction equation. It was shown that propulsive efficiencies of the micronozzle decreased with higher nozzle wall temperatures and vice versa. These results are in agreement with the continuum-based heat transfer results previously discussed. 

Propulsive Efficiency Ratio of work done by the propulsion system on the vehicle to the kinetic energy imparted by the system to the working fluid. 

The field of propulsion deals with the means by which aircraft, missiles, and spacecraft are propelled toward their destinations. Subjects of development include propellers and rotors driven by internal combustion engines or jet engines, rockets powered by solid- or liquid-fueled engines, spacecraft powered by ion engines, solar sails or nuclear reactors, and matter-antimatter engines. Propulsion system metrics include thrust, power, cycle efficiency, propulsion efficiency, specific impulse, and thrust-specific fuel consumption. Advances in this field have enabled hiunanity to travel across the world in a few hours, visit space and the Moon, and send probes to distant planets. 

Power delivered from alternator Alternator output required to meet spaceship electrical power needs, including propulsion, engineering, and science loads. Based on [(130 kW thrusters output/0.72 Electric Propulsion efficiency) + 5 kWe (Vehicle operation)]/ 0.95 PMAD efficiency =195 -200 kWe and on JPL document 982-00115, revision 2, Prometheus Project Multi-mission Project Derived Requirements, dated July 15,2005. 

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