Flow Modelling of Propulsion Nozzles for Nano-Satellites

2019 ◽  
Author(s):  
José Páscoa Marques ◽  
Gustavo Ribeiro ◽  
Francisco Brójo
Keyword(s):  
Numerical Model ◽  
Computational Model ◽  
Droplet Size ◽  
Electrostatic Field ◽  
Low Cost ◽  
Research Topic ◽  
Test Case ◽  
Propulsion Systems ◽  
Flow Modelling ◽  
Space Operation

Abstract The development of compact propulsion systems for nano and micro satellites is nowadays a growing research topic. Actually, the availability of low cost materials able to withstand space operation is now becoming widespread technology. This democratization on the access to space was not followed with a corresponding availability of critical propulsion technologies. However, the availability of propulsion systems for this class of satellites will provide them with new possibilities in what relates to mission profiles. In the present work an electrospray will be analysed, in particular the flow in the nozzle. This flow is controlled by a mix of pressure and electrostatic field. A full EHD (electrohydrodynamics) computational model is developed that is integrated in a classic CFD code using user specified functions. The proposed computational model was able to compute the flowfield for the electrospray test case under consideration. A benchmark against experimental results, by comparing spray thruster droplet size, concluded that the numerical model can predict their size within an error of 5%.

Low Order Modeling for Fan and Outlet Guide Vanes in Aero-Engines

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Jiahuan Cui ◽  
Rob Watson ◽  
Yunfei Ma ◽  
Paul Tucker
Keyword(s):  
Detailed Analysis ◽  
Immersed Boundary Method ◽  
Low Cost ◽  
Immersed Boundary ◽  
Test Case ◽  
Guide Vanes ◽  
Compression System ◽  
Aero Engine ◽  
Aero Engines ◽  
Low Order

Intakes of reduced length have been proposed with the aim of producing aero-engines with higher efficiency and reduced weight. As the intake length decreases, it is expected that stronger effects of the fan on the flow over the intake lip will be seen. If the effects of the fan cannot be ignored, a low-cost but still accurate fan model is of great importance for designing a short-intake. In this paper, a low order rotor/stator model, the immersed boundary method with smeared geometry (IBMSG), has been further developed and validated on a rig test case. The improved IBMSG is more robust than the original. The rig test case used for validation features a low-pressure compression system with a nonaxisymmetric inflow, which is representative of the inlet condition of an aero-engine at its cruise condition. Both the fan and the outlet guide vanes (OGVs) are modeled using IBMSG. A detailed analysis is carried out on the flow both upstream and downstream of the fan. After validating the IBMSG method against the rig test case, a short-intake case, coupled with a fan designed for the next generation of aero-engines, is further investigated. It is found that compared with the intake-alone case, the inflow distortion at the fan face is significantly reduced by the presence of fan. Due to this increased interaction between the fan and the flow over the intake lip, accounting for the effects of the downstream fan is shown to be essential when designing a short intake.

Numerical Study on the Effect of a Submerged Breakwater Seaward of an Existing Breakwater for Climate Change Adaptation

2018 ◽  
Author(s):  
Athul Sasikumar ◽  
Arun Kamath ◽  
Onno Musch ◽  
Arne Erling Lothe ◽  
Hans Bihs
Keyword(s):  
Climate Change ◽  
Numerical Model ◽  
Transmission Coefficient ◽  
Numerical Study ◽  
Protective Measure ◽  
Test Case ◽  
Relative Width ◽  
Optimal Dimension ◽  
Submerged Breakwater ◽  
Design Storm

In coastal areas, climate change is causing mean sea level rise and more frequent storm surge events. This means the breakwaters are expected to withstand the action of more severe incident waves and larger overtopping rates than they were designed for. Therefore, these impacts may have a negative effect on the functionality such as overtopping above the acceptable limits, in addition to stability of these structures. A breakwater which has been partly damaged by a storm stronger than the design storm has weak spots that can easily be damaged further. One way of protecting these breakwaters subjected to climate change is to build a submerged breakwater on the seaward side. This study focuses on the use of numerical model for optimal dimension of a submerged breakwater to be used as a protective measure for an existing structure. Comparisons are made between transmission coefficient predicted in the numerical model and those calculated from different formulae in literature. The variation in transmission coefficient due to different relative submergence and relative width parameters for waves with different steepness is studied and curves showing the dependence of these parameters on wave transmission are made. These results are then used for a test case in Kiberg, Norway where a submerged breakwater is proposed in front of a existing damaged rubble mound breakwater. The optimal geometry generated on the basis of curves is then implemented in the local-scale finite element wave prediction model, CGWAVE.

Design and Optimization of Multi-Stage Centrifugal Compressors With Uncertainty Quantification of Off Design Performance

2017 ◽  
Author(s):  
A. Romei ◽  
R. Maffulli ◽  
C. Garcia Sanchez ◽  
S. Lavagnoli
Keyword(s):  
Uncertainty Quantification ◽  
Oil And Gas ◽  
Low Cost ◽  
Design Procedure ◽  
Design Tool ◽  
Test Case ◽  
Centrifugal Compressors ◽  
Design Performance ◽  
Leading Role ◽  
Multi Stage

The use of multi-stage centrifugal compressors carries out a leading role in oil and gas process applications. Green operation and market competitiveness require the use of low-cost reliable compression units with high efficiencies and wide operating range. A methodology is presented for the design optimization of multi-stage centrifugal compressors with prediction of the compressor map and estimation of the uncertainty limits. A one-dimensional (1D) design tool has been developed that automatically generates a multi-stage radial compressor satisfying the target machine requirements based on a few input parameters. The compressor performance map is then assessed using the method proposed by Casey-Robinson [1], and the approach developed by Al-Busaidi-Pilidis [2]. The off-design performance method relies on empirical correlations calibrated on the performance maps of many single-stage centrifugal compressors. An uncertainty quantification study on the predicted performance maps was conducted using Monte Carlo method (MCM) and generalized Polynomial Chaos Expansion (gPCE). Finally, the design procedure has been coupled to an in-house optimizer based on evolutionary algorithms. The complete design procedure has been applied to a multi-stage industrial compressor test case. A multi-objective optimization of a multi-stage industrial compressor has been performed targeting maximum compressor efficiency and flow range. The results of the optimization show the existence of optimum compressor architectures and how the Pareto fronts evolve depending on the number of stages and shafts.

scholarly journals Numerical Model for Prediction of Indoor COVID-19 Infection Risk Based on Sensor Data

2021 ◽  
Vol 2069 (1) ◽  
pp. 012189
Author(s):  
J Virbulis ◽  
M Sjomkane ◽  
M Surovovs ◽  
A Jakovics
Keyword(s):  
Numerical Model ◽  
Low Cost ◽  
Infection Risk ◽  
Sensor Data ◽  
Effect Of Temperature ◽  
Indoor Environments ◽  
Building Management ◽  
Building Management System ◽  
Predicted Risk ◽  
Droplet Transmission

Abstract In addition to infection with SARS-CoV-2 via direct droplet transmission or contact with contaminated surfaces, infection via aerosol transport is a predominant pathway in indoor environments. The developed numerical model evaluates the risk of a COVID-19 infection in a particular room based on measurements of temperature, humidity, CO2 and particle concentration, the number of people and instances of speech, coughs and sneezing using a dedicated low-cost sensor system. The model can dynamically provide the predicted risk of infection to the building management system or people in the room. The effect of temperature, humidity and ventilation intensity on the infection risk is shown. Coughing and especially sneezing greatly increase the probability of infection in the room; therefore distinguishing these events is crucial for the applied measurement system.

Thermal Analysis of Elemental Sulfur in a Shell-and-Tube Configuration for Thermal Energy Storage Applications

2016 ◽  
Author(s):  
Mitchell Shinn ◽  
Karthik Nithyanandam ◽  
Amey Barde ◽  
Richard Wirz
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Energy Storage ◽  
Numerical Model ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Elemental Sulfur ◽  
Low Cost ◽  
High Energy ◽  
Shell And Tube

Currently, concentrated solar power (CSP) plants utilize thermal energy storage (TES) in order to store excess energy so that it can later be dispatched during periods of intermittency or during times of high energy demand. Elemental sulfur is a promising candidate storage fluid for high temperature TES systems due to its high thermal mass, moderate vapor pressure, high thermal stability, and low cost. The objective of this paper is to investigate the behavior of encapsulated sulfur in a shell and tube configuration. An experimentally validated, transient, two-dimensional numerical model of the shell and tube TES system is presented. Initial results from both experimental and numerical analysis show high heat transfer performance of sulfur. The numerical model is then used to analyze the dynamic response of the elemental sulfur based TES system for multiple charging and discharging cycles. A sensitivity analysis is performed to analyze the effect of geometry (system length), cutoff temperature, and heat transfer fluid on the overall utilization of energy stored within this system. Overall, this paper demonstrates a systematic parametric study of a novel low cost, high performance TES system based on elemental sulfur as the storage fluid that can be utilized for different high temperature applications.

Impact of Duty-Cycling

2020 ◽  
pp. 1557-1579
Author(s):  
Nassima Bouadem ◽  
Rahim Kacimi ◽  
Abdelkamel Tari
Keyword(s):  
Sensor Node ◽  
Low Cost ◽  
Research Topic ◽  
Wireless Sensor ◽  
Energy Availability ◽  
Duty Cycling ◽  
Save Energy ◽  
Fruitful Research ◽  
The Impact

Wireless Sensor Networks (WSNs) became omnipresent in our daily life. As a result, they have emerged as a fruitful research topic, because of their advantages, especially their low cost and easy deployment. However, these attractive merits imply that available resources, especially energy, in each sensor node have to be wisely used through different network dynamics. Beside other techniques, duty-cycling (DC) is the first widely used one to save energy in WSNs. However, due to the continuous changes, mainly in the energy availability, the nodes have to operate in a very low DC which is a required strategy in many applications in order to keep the network operational. This article presents a detailed survey that provides an interesting view of different DC schemes which are proposed to tackle the specific WSN challenges, and it also gives a novel classification of DC schemes that includes the most recent techniques. The last part aims to investigate the impact of the low DC on both the network and the application layer.

scholarly journals Recent Advances and Applications of Semiconductor Photocatalytic Technology

2019 ◽  
Vol 9 (12) ◽  
pp. 2489 ◽  
Author(s):  
Fubao Zhang ◽  
Xianming Wang ◽  
Haonan Liu ◽  
Chunli Liu ◽  
Yong Wan ◽  
...  
Keyword(s):  
Photocatalytic Performance ◽  
Low Cost ◽  
Research Topic ◽  
Living Standards ◽  
Photocatalytic Reaction ◽  
Large Specific Surface Area ◽  
Photocatalytic Efficiency ◽  
Comprehensive Information ◽  
Full Utilization

Along with the development of industry and the improvement of people’s living standards, peoples’ demand on resources has greatly increased, causing energy crises and environmental pollution. In recent years, photocatalytic technology has shown great potential as a low-cost, environmentally-friendly, and sustainable technology, and it has become a hot research topic. However, current photocatalytic technology cannot meet industrial requirements. The biggest challenge in the industrialization of photocatalyst technology is the development of an ideal photocatalyst, which should possess four features, including a high photocatalytic efficiency, a large specific surface area, a full utilization of sunlight, and recyclability. In this review, starting from the photocatalytic reaction mechanism and the preparation of the photocatalyst, we review the classification of current photocatalysts and the methods for improving photocatalytic performance; we also further discuss the potential industrial usage of photocatalytic technology. This review also aims to provide basic and comprehensive information on the industrialization of photocatalysis technology.

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