A Hybrid Semi-empirical Model for Lean Blow-Out Limit Predictions of Aero-engine Combustors

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Bin Hu ◽  
Yong Huang ◽  
Jianzhong Xu
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Empirical Model ◽  
The Other ◽  
Model Parameters ◽  
Model Parameter ◽  
Other Hand ◽  
Aero Engine ◽  
Semi Empirical

According to the Lefebvre's model and flame volume (FV) concept, an FV model about lean blow-out (LBO) was proposed by authors in early study. On the other hand, due to the model parameter (FV) contained in FV model is obtained based on the experimental data, FV model could only be used in LBO analysis instead of prediction. In view of this, a hybrid FV model is proposed that combines the FV model with numerical simulation in the present study. The model parameters contained in the FV model are all estimated from the simulated nonreacting flows. Comparing with the experimental data for 11 combustors, the maximum and average uncertainties of hybrid FV model are ±16% and ±10%.

scholarly journals Methods based on a semi-empirical model for simulating scroll compressors with HFC and HFO refrigerants

2021 ◽  
Vol 1 ◽  
pp. 148
Author(s):  
George Meramveliotakis ◽  
George Kosmadakis ◽  
Sotirios Karellas
Keyword(s):  
Empirical Model ◽  
The Other ◽  
Fine Tuning ◽  
Optimization Process ◽  
Computational Time ◽  
Small Subset ◽  
Model Parameters ◽  
The Third ◽  
Discharge Temperature ◽  
Semi Empirical

The aim of this work is to evaluate three methodologies regarding semi-empirical scroll compressor modeling for different refrigerants and conduct a comparative analysis of their results and accuracy. The first step is to improve a semi-empirical model for scroll compressors based on established techniques, and further enhance the physical background of some of its sub-processes leading to more accurate predictions. Focus is then given on the compressor operation when changing the refrigerant, proposing three methods in total. The first method refers to the standard model, requiring an optimization process for the calibration of all the model parameters. The second method relies on a reference refrigerant, and also uses optimization procedures, but for the fine-tuning of a small subset of the parameters. The third method is more generalized, without the need of any optimization process for the parameters identification, when fluid change occurs, leading to a very fast approach. Το evaluate the accuracy and verify the applicability of each method also related to the necessary computational time, two scroll compressors each with three different refrigerants are considered (HFCs and HFOs and their blends). The model is evaluated with the available manufacturer data, using R134a as reference refrigerant. The results show that the first method predicts the key indicators with a very high accuracy, with the maximum discrepancy of 2.06%, 4.17% and 3.18 K for the mass flow rate, electric power and discharge temperature respectively. The accuracy of the other two methods is dropping, but within acceptable levels in most of the cases. Therefore, in cases that reduced accuracy can be accepted, the third method is preferred for compressor performance prediction when changing the refrigerant, which provides results at a small fraction of time compared with the other two methods, once the parameters are calibrated for a reference case.

About lung surgery

1903 ◽  
Vol 3 (9-10) ◽  
pp. 548-549
Author(s):  
E. Board
Keyword(s):  
Experimental Data ◽  
Lung Tissue ◽  
Lung Surgery ◽  
Operative Intervention ◽  
The Other ◽  
Pulmonary Diseases ◽  
Other Hand

Lung surgery is one of the youngest departments of surgical science. The basis for the development of methods of operative intervention in pulmonary diseases lies in the 1st possibility of preventing the danger of pneumothorax, which (danger) is currently so insignificant that some surgeons consider it even necessary to cause preliminary pneumothorax. On the other hand, the experimental data have shown the possibility of the loss of parts of the lung tissue and the conditions for the healing of its wounds.

scholarly journals Effect of Spheroidization Annealing on Pearlite Banding

2019 ◽  
Vol 949 ◽  
pp. 40-47 ◽  
Author(s):  
Sergey Guk ◽  
Eva Augenstein ◽  
Maksim Zapara ◽  
Rudolf Kawalla ◽  
Ulrich Prahl
Keyword(s):  
Empirical Model ◽  
Initial Conditions ◽  
The Other ◽  
Experimental Investigations ◽  
Initial State ◽  
Ferritic Matrix ◽  
Other Hand ◽  
Initial States ◽  
Hot Rolled

The present paper deals with the influence of the duration of isothermal spheroidization annealing on the evolution of pearlite bands in various initial states. In this study, two initial conditions of the steel 16MnCrS5 are considered: a) industrially hot-rolled pearlite structures in their ferritic matrix and b) a specifically adjusted microstructure in the lab condition. Based on the experimental investigations and quantitative microstructural analyses, an empirical model for the prediction of pearlite banding within a broad range of annealing durations could be derived. Both, experiment and model, agree that pronounced pearlite bands in the initial state almost disappear after 25 h of spheroidization annealing. On the other hand, a marginal degree of pearlite banding in the initial state increases slightly during annealing. This fact could be explained by inhomogeneous cementite formation inside and outside the primary segregation regions of manganese.

scholarly journals Preparation and Thermal and Anti-UV Properties of Chitosan/Mica Copolymer

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Yih-Sheng Huang ◽  
Sheng-Haur Yu ◽  
Yea-Ru Sheu ◽  
Kuo-Shien Huang
Keyword(s):  
Experimental Data ◽  
Thermal Stability ◽  
Free Radical ◽  
Physical Properties ◽  
Ammonium Persulfate ◽  
Sodium Bisulfite ◽  
The Other ◽  
Other Hand

This experiment aims to produce a free radical while annoying the oxidizing-reducing reagent of the ammonium persulfate and the sodium bisulfite under nitrogen, then trigger copolymerization between modified-mica and chitosan to prepare a variety of copolymers. This experiment also aims to study the related properties of these copolymer materials. The experimental data shows that the copolymer has more thermal stability and better absorption of UV than chitosan. But the above physical properties will be less if the mica ratio in copolymer is more than 8%. On the other hand, the SEM photo of the microstructure also shows that the modified mica distributes homogeneously on the surface of the film of the copolymer.

scholarly journals Understanding the Interaction Modes and Reactivity of Trimedoxime toward MmAChE Inhibited by Nerve Agents: Theoretical and Experimental Aspects

2020 ◽  
Vol 21 (18) ◽  
pp. 6510
Author(s):  
Alexandre A. de Castro ◽  
Daniel A. Polisel ◽  
Bruna T. L. Pereira ◽  
Elaine F. F. da Cunha ◽  
Kamil Kuca ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mus Musculus ◽  
Active Site ◽  
Theoretical Calculations ◽  
Nerve Agents ◽  
The Other ◽  
Chemical Weapons ◽  
Reactivation Process ◽  
Other Hand

Organophosphorus (OP) compounds are used as both chemical weapons and pesticides. However, these agents are very dangerous and toxic to humans, animals, and the environment. Thus, investigations with reactivators have been deeply developed in order to design new antidotes with better efficiency, as well as a greater spectrum of action in the acetylcholinesterase (AChE) reactivation process. With that in mind, in this work, we investigated the behavior of trimedoxime toward the Mus musculus acetylcholinesterase (MmAChE) inhibited by a range of nerve agents, such as chemical weapons. From experimental assays, reactivation percentages were obtained for the reactivation of different AChE–OP complexes. On the other hand, theoretical calculations were performed to assess the differences in interaction modes and the reactivity of trimedoxime within the AChE active site. Comparing theoretical and experimental data, it is possible to notice that the oxime, in most cases, showed better reactivation percentages at higher concentrations, with the best result for the reactivation of the AChE–VX adduct. From this work, it was revealed that the mechanistic process contributes most to the oxime efficiency than the interaction in the site. In this way, this study is important to better understand the reactivation process through trimedoxime, contributing to the proposal of novel antidotes.

scholarly journals Yield Prediction of Renewable Diesel From Hydrocracking Process as a Function of Pressure and Temperature Using Analytical Semi Empirical Model (ASEM)

2018 ◽  
Vol 67 ◽  
pp. 02019
Author(s):  
Handrianto Wijaya ◽  
Bambang Heru Susanto
Keyword(s):  
Empirical Model ◽  
The Other ◽  
Yield Prediction ◽  
Trial And Error ◽  
Time Cost ◽  
Renewable Diesel ◽  
Renewable Fuel ◽  
Hydrocracking Process ◽  
Using Data ◽  
Semi Empirical

The development of renewable fuels from biomass is very rapid, and becomes the main alternative to replace petroleum-derived fuels that are limited in stock. There has been a lot of experiments to optimize the production of renewable diesel, but it takes time, cost and a lot of trial and error in order to produce a good result. On the other hand, optimization using simulation is more cost and time effective. One of the processes in the production of this renewable fuel is hydrocracking. This experiment aims to study the effect of pressure and temperature in the hydrocracking process using the Analytical Semi Empirical Model (ASEM) method in representing the yield of the product. Mathematical models will be modified and validated using data from existing research. The results show that Analytical Semi Empirical Model can be used to predict the yield of product from hydrocracking, with all of the models show R2 higher than 0.95 and SSE lower than 3.

The Interaction of Carbon Black with Sulfur, MBT and TMTD in Vulcanization

1961 ◽  
Vol 34 (2) ◽  
pp. 588-599 ◽  
Author(s):  
G. A. Blokh ◽  
Ch. L. Melamed
Keyword(s):  
Experimental Data ◽  
Carbon Black ◽  
Chemical Reactions ◽  
The Other ◽  
Considerable Importance ◽  
Physical Aspect ◽  
Active Centers ◽  
Other Hand ◽  
The One

Abstract The experimental data collected on the interaction of active centers of carbon black with the rubber on the one hand and of the active centers of carbon black with the sulfur and accelerators, and also with the antioxidants, on the other hand, provide a sound basis for belief that the problem of reinforcement of rubber by active fillers in the process of vulcanization cannot be explained from the physical aspect alone. The facts indicate the considerable importance of the chemical reactions between the active groups of carbon black and the compounding ingredients in the course of vulcanization.

Fluid Forces Induced by Vortex Shedding

1976 ◽  
Vol 98 (1) ◽  
pp. 19-24 ◽  
Author(s):  
R. D. Blevins ◽  
T. E. Burton
Keyword(s):  
Experimental Data ◽  
Vortex Shedding ◽  
Model Parameters ◽  
Amplitude Dependence ◽  
Fluid Forces ◽  
At Resonance ◽  
Elastic Cylinders ◽  
Random Vibration Theory ◽  
Semi Empirical ◽  
Good Agreement

A semi-empirical, dynamic model for investigating the fluid forces induced on a bluff cylinder by vortex shedding is developed using random vibration theory. The model includes both spanwise correlation effects and the amplitude dependence of the correlated vortex forces. Model parameters are determined by experimental data. The results are then applied to determine the forces exerted on elastic cylinders at resonance with vortex shedding. The predictions are in good agreement with experimental data.

scholarly journals The Computation of Adjacent Blade-Row Effects in a 1.5 Stage Axial Flow Turbine

1997 ◽  
Author(s):  
Rolf Emunds ◽  
Ian K. Jennions ◽  
Dieter Bohn ◽  
Jochen Gier
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Boundary Conditions ◽  
Axial Flow ◽  
The Other ◽  
Navier Stokes ◽  
Blade Row ◽  
Flow Through ◽  
The University

This paper deals with the numerical simulation of flow through a 1.5 stage axial flow turbine. The 3-row configuration has been experimentally investigated at the University of Aachen where measurements behind the first vane, the first stage and the full configuration were taken. These measurements allow single blade row computations, to the measured boundary conditions taken from complete engine experiments, or full multistage simulations. The results are openly available inside the framework of ERCOFTAC 1996. There are two separate but interrelated parts to the paper. Firstly, two significantly different Navier-Stokes codes are used to predict the flow around the first vane and the first rotor, both running in isolation. This is used to engender confidence in the code that is subsequently used to model the multiple bladerow tests, the other code is currently only suitable for a single blade row. Secondly, the 1.5 stage results are compared to the experimental data and promote discussion of surrounding blade row effects on multistage solutions.

NUMERICAL SIMULATION ON THE EXISTENCE OF FLUCTUATION OF INSTANTANEOUS AVAILABILITY

2016 ◽  
Vol 40 (5) ◽  
pp. 703-713 ◽  
Author(s):  
Yang Yi ◽  
Ren Si Chao ◽  
Fan Guimei ◽  
Kang Rui
Keyword(s):  
Numerical Simulation ◽  
Numerical Methods ◽  
Failure Rate ◽  
The Other ◽  
Repairable System ◽  
Repair Rate ◽  
Trapezoidal Formula ◽  
Other Hand ◽  
Increasing Functions

This paper considers the fluctuation of the instantaneous availability by numerical methods for a one-unit repairable system. The choices of the failure rate and repair rate are linear or cubic increasing functions. For the equation of instantaneous availability composing of two convolutions, the following numerical methods are used: the composite Simpson formula and the trapezoidal formula. That is to say, the simulated curves of instantaneous availability under any condition are obtained. Through the simulated results, when the failure rate and repair rate are selected as increasing functions, the extremum of simulated curve exists so fluctuation exists. On the other hand, if parameters of increasing functions become smaller, the fluctuation weakens.

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