scholarly journals Improved Atomization via a Mechanical Atomizer with Optimal Geometric Parameters and an Air-Assisted Component

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 584
Author(s):  
Inna Levitsky ◽  
Dorith Tavor
Keyword(s):  
Liquid Fuel ◽  
High Efficiency ◽  
Geometric Parameters ◽  
Supply Pressure ◽  
Swirl Chamber ◽  
Air Supply ◽  
Wide Range ◽  
Liquid Atomization ◽  
Atomization Characteristics ◽  
Geometrical Dimensions

Atomization of liquid media is a key aim in various technological disciplines, and solutions that improve spray performance, while decreasing energy consumption, are in great demand. That concept is very important in the development of liquid fuel spray atomizers in high-efficiency microturbines and other generator systems with low inlet pressure and a wide range of power supply. Here we present a study of the liquid atomization characteristics for a new mechanical atomizer that has optimal geometric parameters and a preliminary swirl stage. In our air-assisted atomizer, air is introduced through a swirl chamber positioned at the exit of the mechanical atomizer. The optimized mechanical atomizer alone can achieve D32 drop diameters in the range of 80 to 40 µm at water supply pressures of 2 to 5 bar, respectively. The addition of an air swirl chamber substantially decreases drop sizes. At an air–liquid ratio (ALR) equal to 1, water pressures of 2.5 to 3 bar and air supply pressures 0.35 to 1 bar, D32 drops with diameters of 20–30 µm were obtained. In an air-assisted atomizer the parameters of the mechanical atomizer have a much stronger influence on drop diameters than do characteristics of the air-swirl chamber. Using a mechanical atomizer with optimal geometrical dimensions allows limiting the liquid supply pressure to 5 bar; but when an air-assisted component is introduced we can recommend an ALR ≈ 1 and an air supply pressure of up to 1 bar.

Optimization of a Small Scale Pellet Boiler

2010 ◽  
Author(s):  
Jose´ Carlos Teixeira ◽  
Rui Ferreira ◽  
Manuel Eduardo Ferreira
Keyword(s):  
Heat Dissipation ◽  
High Efficiency ◽  
Raw Materials ◽  
Direct Conversion ◽  
Pollutant Emissions ◽  
Small Scale ◽  
Air Supply ◽  
Wide Range ◽  
Great Relevance ◽  
Secondary Air

Environmental concerns and the drive to reduce the dependence on petroleum based fuels brought the use of renewable energies to the forefront. Biomass appears as a very interesting option for direct conversion into heat. In this context, densified forms of biomass such as pellets are of great relevance because of their easy of use, high efficiency and low emissions. Expected trends in the biomass market suggest that equipments should operate over a wide range of thermal loads and with fuels derived from lower quality raw materials; simultaneously, a high efficiency and low emissions are taken for granted. Currently, biomass domestic boilers prove to be very sensitive to fuel characteristics and load conditions. This work reports on the development of a 15 kW net pellet boiler. A prototype was built that enables the independent control of the air supply into various regions of the combustion chamber and an accurate supply of fuel. The test rig also includes: boiler and flue gases extraction system; feeding system; heat dissipation system; flue gas analyzer; data acquisition system and all sensors. In order to optimize the combustion conditions, pollutant emissions and their relation with feeding conditions, primary and secondary air flow rate and excess of air was analyzed. The results suggest that this burner is a promising for implementation in domestic boilers. The advantages are: CO emissions well below those observed in similar equipments and the capacity to maintain the emissions level constant under different loading conditions.

scholarly journals Study and Analytical Modeling of the Influence of Technological and Geometric Parameters on the Performance of Ga0:67In0:33P=GaAs=Ga0:70In0:30As Tri-junction Photovoltaic Solar Cells

2020 ◽  
pp. 66-78
Author(s):  
N. Ndorere ◽  
B. Kounouhewa ◽  
M.B. Agbomahena
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
High Efficiency ◽  
Geometric Parameters ◽  
Cell Structures ◽  
In Doping ◽  
Wide Range ◽  
Proportional Increase ◽  
The One ◽  
Photovoltaic Solar Cells

In the context of global energy consumption, the production of photovoltaic solar energy remains very low. One solution to this problem is to use multi-junction solar cells with high efficiency. Efforts are being made to increase the efficiency of solar cells and reduce their cost of production. In order to optimize the performance of multi-junction solar cells, this paper presents an analytical model allowing to study and model the influence of technological and geometric parameters on the performance of tri-junction solar cells Ga0:67In0:33P=GaAs=Ga0:70In0:30As. These parameters are the thickness, doping and Gap energy of the three sub-cells making up the tri-junction solar structure. The thicknesses and doping of the emitters (bases) of the sub-cells are varied and chosen in order to optimize the efficiency of the Trijunction Solar Cell (TJSC) Ga0:67In0:33P=GaAs=Ga0:70In0:30As. The one hand, the base doping (emitter) is selected so as to minimize the dark current and the other hand,to reduce the resistive losses in this region. As for the thickness, it is chosen so as to minimize the recombination phenomena. The simulation results show that for a given thickness, the sub-cell efficiencies have maximums which evolve with the increase in doping. If the doping of the base (or emitter) of the sub-cells increases, there follows a proportional increase in the efficiency. In addition, when the optimal doping and thickness of the bases (or emitters) are reached, above these, they can vary over a wide range without considerably modifying the efficiency of the solar cell. This point about the tolerance ranges is very important for the practical realization of Photovoltaic solar cell structures. These results also show that the optimal performance of the Tri-junction Solar Cell are obtained for the relatively low thicknesses of the bases (or emitters) (100nm-700nm) with high doping values(Nb = 8e + 18cm

scholarly journals Experimentally Validated Extension of the Operating Range of an Electrically Driven Turbocharger for Fuel Cell Applications

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 331
Author(s):  
Markus Schoedel ◽  
Marco Menze ◽  
Joerg R. Seume
Keyword(s):  
Fuel Cell ◽  
High Efficiency ◽  
Numerical Study ◽  
Leading Edge ◽  
Point Of View ◽  
Rotor Blades ◽  
Maximum Efficiency ◽  
Operating Range ◽  
Air Supply ◽  
Wide Range

From an aerodynamic point of view, the electric turbocharger for the air supply of an automotive fuel cell faces difficult requirements: it must not only control the pressure level of the fuel cell, but it also has to operate with very high efficiency over a wide range. This paper explores features for the compressor and the turbine of an existing electric turbocharger, which are intended to meet the specific requirements of a fuel cell in an experimentally validated numerical study. Adjustable diffuser or nozzle vanes in the compressor and turbine achieve wider operating ranges but compromise efficiency, especially because of the necessary gaps between vanes and end walls. For the turbine, there are additional efficiency losses since the pivoting of the nozzle vanes leads to incidence and thus to flow separation at the leading edge of the nozzle vanes and the rotor blades. An increase in the mass flow and a slight efficiency improvement of the turbine with the low solidity nozzle vanes counteracts these losses. For the compressor, a reduction in the diffuser height and its influence over the operating range and power consumption yields an increase in surge margin as well as in maximum efficiency.

Synthesis of Elaborate Benzofuran-2-Carboxamide Derivatives Through a Combination of 8-Aminoquinoline Directed C–H Arylations and Transamidations

2019 ◽  
Author(s):  
Michael Oschmann ◽  
Linus Johansson Holm ◽  
Oscar Verho
Keyword(s):  
Small Molecule ◽  
High Efficiency ◽  
Synthetic Strategy ◽  
Small Molecule Screening ◽  
Physiological Properties ◽  
Wide Range ◽  
Directing Group ◽  
Synthetic Sequence

Benzofurans are everywhere in nature and they have been extensively studied by medicinal chemists over the years because of their chemotherapeutic and physiological properties. Herein, we describe a strategy that can be used to access elaborate benzo-2-carboxamide derivatives, which involves a synthetic sequence of 8-aminoquinoline directed C–H arylations followed by transamidations. For the directed C–H arylations, Pd catalysis was used to install a wide range of aryl and heteroaryl substituents at the C3 position of the benzofuran scaffold in high efficiency. Directing group cleavage and further diversification of the C3-arylated benzofuran products were then achieved in a single synthetic operation through the utilization of a two-step transamidation protocol. By bocylating the 8-aminoquinoline amide moiety of these products, it proved possible to activate them towards aminolysis with different amine nucleophiles. Interestingly, this aminolysis reaction was found to proceed efficiently without the need of any additional catalyst or additive. Given the high efficiency and modularity of this synthetic strategy, it constitute a very attractive approach for generating structurally-diverse collections of benzofuran derivatives for small molecule screening.

To the 70th anniversary of World Meteorological Organization. Scientific and technical cooperation of Hydrometeorological Center of the USSR/Russia in the Programs of World Meteorological Organization

2020 ◽  
pp. 117-138
Author(s):  
S.V. Borshch ◽  
◽  
R.M. Vil’fand ◽  
D.B. Kiktev ◽  
V.M. Khan ◽  
...  
Keyword(s):  
Environmental Monitoring ◽  
High Efficiency ◽  
World Meteorological Organization ◽  
70Th Anniversary ◽  
Technical Level ◽  
Technical Cooperation ◽  
Wide Range

The paper presents the summary and results of long-term and multi-faceted experience of international scientific and technical cooperation of Hydrometeorological Center of Russia in the field of hydrometeorology and environmental monitoring within the framework of WMO programs, which indicates its high efficiency in performing a wide range of works at a high scientific and technical level. Keywords: World Meteorological Organization, major WMO programs, representatives of Hydrometeorological Center of Russia in WMO

Integrated Design and Multi-Objective Optimization of a Single Stage Heat-Pump Turbocompressor

2013 ◽  
Author(s):  
J. Schiffmann
Keyword(s):  
Design Optimization ◽  
High Efficiency ◽  
Integrated Design ◽  
Heat Pumps ◽  
Small Scale ◽  
Multi Objective Optimization ◽  
Design Constraints ◽  
Multi Objective ◽  
Wide Range ◽  
Standard Design

Small scale turbomachines in domestic heat pumps reach high efficiency and provide oil-free solutions which improve heat-exchanger performance and offer major advantages in the design of advanced thermodynamic cycles. An appropriate turbocompressor for domestic air based heat pumps requires the ability to operate on a wide range of inlet pressure, pressure ratios and mass flows, confronting the designer with the necessity to compromise between range and efficiency. Further the design of small-scale direct driven turbomachines is a complex and interdisciplinary task. Textbook design procedures propose to split such systems into subcomponents and to design and optimize each element individually. This common procedure, however, tends to neglect the interactions between the different components leading to suboptimal solutions. The authors propose an approach based on the integrated philosophy for designing and optimizing gas bearing supported, direct driven turbocompressors for applications with challenging requirements with regards to operation range and efficiency. Using previously validated reduced order models for the different components an integrated model of the compressor is implemented and the optimum system found via multi-objective optimization. It is shown that compared to standard design procedure the integrated approach yields an increase of the seasonal compressor efficiency of more than 12 points. Further a design optimization based sensitivity analysis allows to investigate the influence of design constraints determined prior to optimization such as impeller surface roughness, rotor material and impeller force. A relaxation of these constrains yields additional room for improvement. Reduced impeller force improves efficiency due to a smaller thrust bearing mainly, whereas a lighter rotor material improves rotordynamic performance. A hydraulically smoother impeller surface improves the overall efficiency considerably by reducing aerodynamic losses. A combination of the relaxation of the 3 design constraints yields an additional improvement of 6 points compared to the original optimization process. The integrated design and optimization procedure implemented in the case of a complex design problem thus clearly shows its advantages compared to traditional design methods by allowing a truly exhaustive search for optimum solutions throughout the complete design space. It can be used for both design optimization and for design analysis.

scholarly journals Low Power Cusped Field Thruster Developed for the Space-Borne Gravitational Wave Detection Mission in China

2021 ◽  
Vol 11 (14) ◽  
pp. 6549
Author(s):  
Hui Liu ◽  
Ming Zeng ◽  
Xiang Niu ◽  
Hongyan Huang ◽  
Daren Yu
Keyword(s):  
Low Power ◽  
Gravitational Wave ◽  
Attitude Control ◽  
High Efficiency ◽  
Experimental Investigations ◽  
Attitude Control System ◽  
Gravitational Wave Detection ◽  
Wave Detection ◽  
Wide Range ◽  
Institute Of Technology

The microthruster is the crucial device of the drag-free attitude control system, essential for the space-borne gravitational wave detection mission. The cusped field thruster (also called the High Efficiency Multistage Plasma Thruster) becomes one of the candidate thrusters for the mission due to its low complexity and potential long life over a wide range of thrust. However, the prescribed minimum of thrust and thrust noise are considerable obstacles to downscaling works on cusped field thrusters. This article reviews the development of the low power cusped field thruster at the Harbin Institute of Technology since 2012, including the design of prototypes, experimental investigations and simulation studies. Progress has been made on the downscaling of cusped field thrusters, and a new concept of microwave discharge cusped field thruster has been introduced.

scholarly journals A general approach to high-efficiency perovskite solar cells by any antisolvent

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alexander D. Taylor ◽  
Qing Sun ◽  
Katelyn P. Goetz ◽  
Qingzhi An ◽  
Tim Schramm ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Perovskite Solar Cells ◽  
Precursor Solution ◽  
Microstructural Characterization ◽  
Application Rate ◽  
Perovskite Layer ◽  
Highly Efficient ◽  
Application Procedure ◽  
Wide Range

AbstractDeposition of perovskite films by antisolvent engineering is a highly common method employed in perovskite photovoltaics research. Herein, we report on a general method that allows for the fabrication of highly efficient perovskite solar cells by any antisolvent via manipulation of the antisolvent application rate. Through detailed structural, compositional, and microstructural characterization of perovskite layers fabricated by 14 different antisolvents, we identify two key factors that influence the quality of the perovskite layer: the solubility of the organic precursors in the antisolvent and its miscibility with the host solvent(s) of the perovskite precursor solution, which combine to produce rate-dependent behavior during the antisolvent application step. Leveraging this, we produce devices with power conversion efficiencies (PCEs) that exceed 21% using a wide range of antisolvents. Moreover, we demonstrate that employing the optimal antisolvent application procedure allows for highly efficient solar cells to be fabricated from a broad range of precursor stoichiometries.

scholarly journals Octane Index Applicability over the Pressure-Temperature Domain

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 607
Author(s):  
Tommy R. Powell ◽  
James P. Szybist ◽  
Flavio Dal Forno Chuahy ◽  
Scott J. Curran ◽  
John Mengwasser ◽  
...  
Keyword(s):  
High Efficiency ◽  
National Laboratory ◽  
Operating Conditions ◽  
Dominant Factor ◽  
Compression Ignition ◽  
Oak Ridge ◽  
Operating Modes ◽  
Wide Range ◽  
Thermodynamic Conditions ◽  
Si Engines

Modern boosted spark-ignition (SI) engines and emerging advanced compression ignition (ACI) engines operate under conditions that deviate substantially from the conditions of conventional autoignition metrics, namely the research and motor octane numbers (RON and MON). The octane index (OI) is an emerging autoignition metric based on RON and MON which was developed to better describe fuel knock resistance over a broader range of engine conditions. Prior research at Oak Ridge National Laboratory (ORNL) identified that OI performs reasonably well under stoichiometric boosted conditions, but inconsistencies exist in the ability of OI to predict autoignition behavior under ACI strategies. Instead, the autoignition behavior under ACI operation was found to correlate more closely to fuel composition, suggesting fuel chemistry differences that are insensitive to the conditions of the RON and MON tests may become the dominant factor under these high efficiency operating conditions. This investigation builds on earlier work to study autoignition behavior over six pressure-temperature (PT) trajectories that correspond to a wide range of operating conditions, including boosted SI operation, partial fuel stratification (PFS), and spark-assisted compression ignition (SACI). A total of 12 different fuels were investigated, including the Co-Optima core fuels and five fuels that represent refinery-relevant blending streams. It was found that, for the ACI operating modes investigated here, the low temperature reactions dominate reactivity, similar to boosted SI operating conditions because their PT trajectories lay close to the RON trajectory. Additionally, the OI metric was found to adequately predict autoignition resistance over the PT domain, for the ACI conditions investigated here, and for fuels from different chemical families. This finding is in contrast with the prior study using a different type of ACI operation with different thermodynamic conditions, specifically a significantly higher temperature at the start of compression, illustrating that fuel response depends highly on the ACI strategy being used.

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