Numerical modeling of high efficiency multistage plasma thrusters for space applications

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Daniel Kahnfeld ◽  
Julia Duras ◽  
Paul Matthias ◽  
Stefan Kemnitz ◽  
Peter Arlinghaus ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
High Efficiency ◽  
Space Applications ◽  
Plasma Thrusters

Cycloid Drives With Machining Tolerances

1989 ◽  
Vol 111 (3) ◽  
pp. 337-344 ◽  
Author(s):  
J. G. Blanche ◽  
D. C. H. Yang
Keyword(s):  
High Efficiency ◽  
Dynamic Instability ◽  
Torque Ripple ◽  
Gear Train ◽  
Space Applications ◽  
Input Shaft ◽  
Epicyclic Gear ◽  
Speed Reducer ◽  
Planet Gear ◽  
Gear Mechanism

The cycloidal speed reducer, or cycloid drive, is an epicyclic gear train in which the profile of the planet gear is an epitrochoid and the annular sun gear has rollers as its teeth. The cycloid drive has very high efficiency and small size, in comparison with a conventional gear mechanism, making it an attractive candidate for limited space applications. On the other hand, in this type of transmissions there exist two major drawbacks, namely, backlash and torque ripple. Backlash, the angle through which the output shaft can rotate when the input shaft is held fixed, has a degrading effect on the output accuracy. Torque ripple, the variation in mechanical advantage as the input shaft rotates, causes vibrations and could lead to dynamic instability of the machinery. If the cycloid drive were manufactured to the ideal dimensions, there would be no backlash nor torque ripple. However, in reality, there will always be some machining tolerances. In this paper an analytical model is developed which models the cycloid drive with machining tolerances. Consequently, the effect of machining tolerances on backlash and torque ripple are investigated. It is found that both the backlash and the torque ripple are inherent periodic functions of the input crank angle.

scholarly journals 10 W high efficiency 14 V HBT power amplifier for space applications

2004 ◽  
Author(s):  
N. Le Galloul ◽  
J.F. Villemazet ◽  
B. Cogo ◽  
J.L. Cazaux ◽  
A. Mallet ◽  
...  
Keyword(s):  
Power Amplifier ◽  
High Efficiency ◽  
Space Applications

Pseudo-Capacitor Structure for Direct Nuclear Energy Conversion

2008 ◽  
Vol 1100 ◽  
Author(s):  
Liviu Popa-Simil
Keyword(s):  
Energy Conversion ◽  
Nuclear Power ◽  
Nuclear Energy ◽  
Nuclear Reactor ◽  
High Efficiency ◽  
Nuclear Reactors ◽  
Direct Conversion ◽  
Space Applications ◽  
Power Sources ◽  
Conversion Efficiencies

AbstractThe advanced space missions need for more power opened the way for advanced nuclear reactors and for alternative power conversion procedures. The most advanced power systems available in space are the fuel cells and nuclear reactors. Both systems manifest low efficiencies for converting the primary energy into electricity and as consequence are requiring high heat dump into space mainly by infrared radiation. The thermo-nuclear power generator also requires a high temperature gas turbine and a mechano-electric generator, finally driving to low conversion efficiencies. The new nano-materials offer the possibility of creating direct energy conversion devices able of achieving high conversion efficiencies up to 99% in the cryogenic versions. The interest for direct conversion of the nuclear energy into electricity appeared in early 1940th, by the invention of the thermo-ionic fission device by Linder. Then a series of patents and scientific papers improved gradually the designs and performances of the devices, up to the actual concepts of beta-voltaic and liquid-electronics. The most intuitive direct conversion device looks mainly like a super mirror- or a heterogeneous super-capacitor. The issues on its operation are related to global conversion efficiencies and the stable operation life-time in high radiation field. There are combinations of nano-structures and actinides assuring both the neutron flux stability, by meeting criticality conditions and the direct conversion or the nuclear energy into electricity. Achieving a high efficiency internal conversion of the nuclear energy into electricity is not enough if it is not completed by a high efficiency power extraction system from the nuclear reactor core into the outside load. The development of the new MEMS devices and micro electronics in the 40 nm technologies provides an excellent background for the production of the electric power harvesting and conversion devices embedded in the fuel. The new nano-structured materials may be produced as radiation energy harvesting tiles that are free of actinides, using them for harvesting the energy of radioactive sources and controlled fusion devices, or may include actinides in their structure achieving critical or sub-critical accelerator driven nuclear reactor assemblies. Another predictable advantage of the nano-structure is the property of self-repairing and self-organizing to compensate the radiation damage and improve the lifetime. Due to direct conversion the power density of the new materials may increase from the actual average of 0.2 kw/cm3 to about 1 kw/mm3 driving to miniaturization of nuclear power sources and reductions of the shield weight. At these dimensions and power densities of few thousands horse power per liter the nuclear power source becomes suitable for mobile applications as powering trains, strategic airplanes, etc. These new developments may drive to the production of high power solid-state compact nuclear battery for space applications, leading to a new development stage.

An Overview of the French Research Program on Plasma Thrusters for Space Applications

2001 ◽  
Vol 41 (6) ◽  
pp. 573-588 ◽  
Author(s):  
André Bouchoule ◽  
Anne Cadiou ◽  
Anne Héron ◽  
Michel Dudeck ◽  
Michel Lyszyk
Keyword(s):  
Research Program ◽  
Space Applications ◽  
Plasma Thrusters

scholarly journals Numerical Modeling of High Conversion Efficiency Mo/CZTS/CdS/ZnO/ FTO Thin Film – Based Solar Cells

2021 ◽  
Author(s):  
Samer H. Zyoud ◽  
Ahed H. Zyoud ◽  
Naser M. Ahmed ◽  
Anupama R. Prasad ◽  
Sohaib Naseem Khan ◽  
...  
Keyword(s):  
Thin Film ◽  
Numerical Modeling ◽  
Solar Cells ◽  
Solar Cell ◽  
Conversion Efficiency ◽  
High Efficiency ◽  
Short Circuit ◽  
Photovoltaic Cells ◽  
Effect Of Temperature ◽  
Cell Parameters

This article describes in detail the numerical modeling of a CZTS (copper zinc tin sulfide) based kesterite solar cell. The Solar Cell Capacitance Simulator -one-dimension (SCAPS-1D) software was used to simulate MO/CZTS/CdS/ZnO/FTO structured solar cells. The parameters of different photovoltaic thin-film solar cells are estimated and analyzed using numerical modeling. The effects of various parameters on the performance of the photovoltaic cell and the conversion efficiency are discussed. Since the response of the solar cell is also contingent on its internal physical mechanism, J-V characteristic measures are insufficient to characterize the behavior of a device. Different features, as well as different potential conditions, must be considered for simulation, disregarding the belief in the modeling of a solar cell. With a conversion efficiency of 25.72%, a fill factor of 83.75%, a short-circuit current of 32.96436 mA/cm2 and an open-circuit voltage of 0.64V, promising optimized results have been achieved. The findings will be useful in determining the feasibility of fabricating high-efficiency CZTS-based photovoltaic cells. The efficiency of a CZTS-based experimental solar cell is also discussed. First, the effects of experimentally developed CZTS solar cells are simulated in the SCAPS-1D environment. The experimental results are then compared to the SCAPS-1D simulated results. The conversion efficiency of an optimized system increases after cell parameters are optimized. Using one-dimensional SCAPS-1D software, the effect of system parameters such as the thickness, acceptor and donor carrier concentration densities of absorber and electron transport layers, and the effect of temperature on the efficiency of CZTS-based photovoltaic cells is investigated. The proposed results will greatly assist engineers and researchers in determining the best method for optimizing solar cell efficiency, as well as in the development of efficient CZTS-based solar cells.

Effect of High Coolant Velocity on Heat Transfer in Compact Heat Exchangers

2006 ◽  
Author(s):  
P. L. Sathyanarayanan ◽  
N. Venkateswaran ◽  
R. Ramprabhu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Fluid Velocity ◽  
Small Diameter ◽  
Space Applications ◽  
Compact Heat Exchangers ◽  
Military Vehicle ◽  
Transfer Capability ◽  
Lower Fluid

Compact Heat Exchangers were developed to have very high efficiency in transfer of heat within a very small space or volume and are being used in the automotive, aircraft and space applications. In order to obtain much higher heat transfer, these Heat Exchangers uses closely packed fins, narrow or small diameter passages and turbulators or turbulence promoters. Though these arrangements result in much higher pressure drop for the fluids, this disadvantage is expected to be off-set with a larger increase in heat transfer capability. Generally it is known that turbulence enables better mixing of the fluid and results in enhancing the heat being transferred. However in practice it has been observed that there is a limit to this enhancement and the heat transfer does not improve beyond certain turbulence levels. The higher turbulence level probably results in carrying the heat away along with the fluid without transferring all the heat to the cooling medium. The presence of turbulence promoters was found to be beneficial at a lower fluid velocity level, where they conduct the heat away more by surface conduction than by convection in the fluid. Detailed experimental investigation and findings of this phenomenon using a compact heat exchanger for a military vehicle is described in this paper.

scholarly journals Numerical simulation of aerodynamics of a high-efficiency orthogonal balanced blade of a wind generator

2018 ◽  
Vol 251 ◽  
pp. 04063
Author(s):  
Valeriy Prokopiev ◽  
Irina Lantsova ◽  
Andrey Proskurin
Keyword(s):  
Numerical Simulation ◽  
Numerical Modeling ◽  
Turbulent Flow ◽  
High Efficiency ◽  
Two Dimensional ◽  
Wind Generator ◽  
Rotating Blade

The results of verification of numerical modeling of a rotating blade of a wind generator with a nonstationary turbulent flow around in a two-dimensional formulation are given. A design free from the drawbacks of a single-blade orthogonal high-efficiency turbine is considered (US Patent Victor Lyatkher, US 8007235 B1, August 30, 2011, RF Patent 2426911 C1).

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