Significance of biofilm activity in facultative pond design and performance

1995 ◽  
Vol 31 (12) ◽  
pp. 119-128 ◽  
Author(s):  
C. Polprasert ◽  
B. K. Agarwalla
Keyword(s):  
Substrate Utilization ◽  
Operating Conditions ◽  
Type Model ◽  
Diffusion Type ◽  
Substrate Removal ◽  
Proposed Model ◽  
Wide Range ◽  
Suspended Biomass ◽  
Side Walls ◽  
And Performance

Facultative ponds have found wide application in wastewater treatment as an economical systemwhere land area is available at reasonable cost. Different approaches are available in the literature for the design of facultative ponds. Most research have dealt with only suspended biomass and considered it as the major form of biomass responsible for substrate removal. However, the side walls and bottom of the facultative pond can provide support for the growth of attached (biofilm) biomass which also aids in the degradation of organic matters (substrate). This study demonstrates the significance of biofilm biomass growing on the side walls and bottom of these ponds to substrate utilization. A model for substrate utilization in facultative ponds is proposed which encompasses first-order reactions of both suspended and biofilm biomass. The biofilm activity is described with a diffusion type model, while the dispersed flow model is used for the pond hydraulics to include a wide range of pond dimensions and operating conditions. The proposed model, validated with observed data of two full-scale facultative ponds located in Bangkok, Thailand, and in New Mexico, U.S.A., was able to predict effluent BOD5 concentrations of these two ponds reasonably well.

scholarly journals CFD Study of Nozzle Configurations for Ultra High Bypass Engines

1993 ◽  
Author(s):  
H. Zimmermann ◽  
R. Gumucio ◽  
K. Katheder ◽  
A. Jula
Keyword(s):  
Engine Performance ◽  
Operating Conditions ◽  
Aerodynamic Design ◽  
Thrust Coefficient ◽  
Optimum Range ◽  
Installation Effects ◽  
Wide Range ◽  
And Performance ◽  
Aircraft Aerodynamics ◽  
Bypass Ratio

Performance and aerodynamic aspects of ultra-high bypass ratio ducted engines have been investigated with an emphasis on nozzle aerodynamics. The interference with aircraft aerodynamics could not be covered. Numerical methods were used for aerodynamic investigations of geometrically different aft end configurations for bypass ratios between 12 and 18, this is the optimum range for long missions which will be important for future civil engine applications. Results are presented for a wide range of operating conditions and effects on engine performance are discussed. The limitations for higher bypass ratios than 12 to 18 do not come from nozzle aerodynamics but from installation effects. It is shown that using CFD and performance calculations an improved aerodynamic design can be achieved. Based on existing correlations, for thrust and mass-flow, or using aerodynamic tailoring by CFD and including performance investigations, it is possible to increase the thrust coefficient up to 1%.

Uncertainty Analysis of Inflow Conditions on an HPT Gas Turbine Nozzle: Effect on Particle Deposition

2020 ◽  
Author(s):  
R. Friso ◽  
N. Casari ◽  
M. Pinelli ◽  
A. Suman ◽  
F. Montomoli
Keyword(s):  
Gas Turbine ◽  
Energy Efficient ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Operating Conditions ◽  
Wide Range ◽  
And Performance ◽  
Gas Turbine Nozzle ◽  
The Impact ◽  
Inflow Conditions

Abstract Gas turbines (GT) are often forced to operate in harsh environmental conditions. Therefore, the presence of particles in their flow-path is expected. With this regard, deposition is a problem that severely affects gas turbine operation. Components’ lifetime and performance can dramatically vary as a consequence of this phenomenon. Unfortunately, the operating conditions of the machine can vary in a wide range, and they cannot be treated as deterministic. Their stochastic variations greatly affect the forecasting of life and performance of the components. In this work, the main parameters considered affected by the uncertainty are the circumferential hot core location and the turbulence level at the inlet of the domain. A stochastic analysis is used to predict the degradation of a high-pressure-turbine (HPT) nozzle due to particulate ingestion. The GT’s component analyzed as a reference is the HPT nozzle of the Energy-Efficient Engine (E3). The uncertainty quantification technique used is the probabilistic collocation method (PCM). This work shows the impact of the operating conditions uncertainties on the performance and lifetime reduction due to deposition. Sobol indices are used to identify the most important parameter and its contribution to life. The present analysis enables to build confidence intervals on the deposit profile and on the residual creep-life of the vane.

A predictive combustion model for one-dimensional gasoline engine simulation

2020 ◽  
pp. 146808742094590
Author(s):  
Yoshihiro Nomura ◽  
Seiji Yamamoto ◽  
Makoto Nagaoka ◽  
Stephan Diel ◽  
Kenta Kurihara ◽  
...  
Keyword(s):  
Gasoline Engine ◽  
Early Stage ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Operating Conditions ◽  
Combustion Model ◽  
One Dimensional ◽  
Turbulent Reynolds Number ◽  
Proposed Model ◽  
Wide Range

A new predictive combustion model for a one-dimensional computational fluid dynamics tool in the multibody dynamics processes of gasoline engines was developed and validated. The model consists of (1) a turbulent burning velocity model featuring a flame radius–based transitional function, steady burning velocity that considers local quenching using the Karlovitz number and laminarization by turbulent Reynolds number, as well as turbulent flame thickness and its quenching model near the liner wall, and (2) a knock model featuring auto-ignition by the Livengood–Wu integration and ignition delay time obtained using a full-kinetic model. The proposed model and previous models were verified under a wide range of operating conditions using engines with widely different specifications. Good agreement was only obtained for combustion characteristics by the proposed model without requiring individual calibration of model constants. The model was also evaluated for utilization after prototyping. Improved accuracy, especially of ignition timing, was obtained after further calibration using a small amount of engine data. It was confirmed that the proposed model is highly accurate at the early stage of the engine development process, and is also applicable for engine calibration models that require higher accuracy.

scholarly journals Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

Inventions ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 16 ◽  
Author(s):  
Zine Aidoun ◽  
Khaled Ameur ◽  
Mehdi Falsafioon ◽  
Messaoud Badache
Keyword(s):  
Heat Pumps ◽  
Operating Conditions ◽  
Industrial Processes ◽  
Experimental Investigations ◽  
Mixing Enhancement ◽  
Data Generation ◽  
Two Phase ◽  
Wide Range ◽  
Potential Applications ◽  
And Performance

Two-phase ejectors play a major role as refrigerant expansion devices in vapor compression systems and can find potential applications in many other industrial processes. As a result, they have become a focus of attention for the last few decades from the scientific community, not only for the expansion work recovery in a wide range of refrigeration and heat pump cycles but also in industrial processes as entrainment and mixing enhancement agents. This review provides relevant findings and trends, characterizing the design, operation and performance of the two-phase ejector as a component. Effects of geometry, operating conditions and the main developments in terms of theoretical and experimental approaches, rating methods and applications are discussed in detail. Ejector expansion refrigeration cycles (EERC) as well as the related theoretical and experimental research are reported. New and other relevant cycle combinations proposed in the recent literature are organized under theoretical and experimental headings by refrigerant types and/or by chronology whenever appropriate and systematically commented. This review brings out the fact that theoretical ejector and cycle studies outnumber experimental investigations and data generation. More emerging numerical studies of two-phase ejectors are a positive step, which has to be further supported by more validation work.

Index-Based Performance Assessment and Condition Monitoring of a Mobile Working Machine

2005 ◽  
Author(s):  
Vesa Ho¨ltta¨ ◽  
Matti Repo ◽  
Lauri Palmroth ◽  
Aki Putkonen
Keyword(s):  
Performance Assessment ◽  
Condition Monitoring ◽  
Operating Conditions ◽  
Multidimensional Data ◽  
Technical Performance ◽  
Machine Performance ◽  
Wide Range ◽  
Data Driven Approach ◽  
And Performance ◽  
Mobile Working

Real-time performance assessment and condition monitoring are potential new features in mobile working machines that have to run in a wide range of operating conditions. Condition monitoring and performance assessment are needed to be able to proactively correct impending faults before severe failures or machine stoppage occur. This paper presents a data-driven approach for machine performance assessment and condition monitoring based on indices representing the performance of a subsystem. Instead of adding new sensors, the indices are computed using existing data from the machine control system. Metrics for machine performance follow-up are derived from these multidimensional data, which have strong nonlinear correlations in certain measurement variables. Although the indices describe primarily the technical performance of the machine, they have proven to be valuable also in terms of condition monitoring of various machine functions. The indices summarize in a concise and easily comprehensible manner changes in performance.

scholarly journals A Variable-Geometry Combustor Used to Study Primary and Secondary Zone Stoichiometry

1983 ◽  
Author(s):  
Daniel Briehl ◽  
Donald F. Schultz ◽  
Robert C. Ehlers
Keyword(s):  
Operating Conditions ◽  
Fuel Quality ◽  
Variable Geometry ◽  
Gas Temperature ◽  
Reference Velocity ◽  
Primary Zone ◽  
Wide Range ◽  
Secondary Zone ◽  
And Performance ◽  
Exhaust Gas Temperature

A combustion program is underway to evaluate fuel quality effects on gas turbine combustors. A rich-lean variable geometry combustor design was chosen to evaluate fuel quality effects over a wide range of primary and secondary zone equivalence ratios at simulated engine operating conditions. The first task of this effort, was to evaluate the performance of the variable geometry combustor. The combustor incorporates three stations of variable geometry to control primary and secondary zone equivalence ratio and overall pressure loss. Geometry changes could be made while a test was in progress through the use of remote control actuators. The primary zone liner was water cooled to eliminate the concern of liner durability. Emissions and performance data were obtained at simulated engine conditions of 80 percent and full power. Inlet air temperature varied from 611 to 665 K, inlet total pressure varied from 1.02 to 1.24 MPa, reference velocity was 18.0 m/sec and exhaust gas temperature was a constant 1400 K.

An Automatic Car Heater System-Description and Performance Prediction

1968 ◽  
Vol 183 (1) ◽  
pp. 125-135
Author(s):  
A. G. Plackett
Keyword(s):  
Performance Prediction ◽  
Digital Computer ◽  
System Parameter ◽  
Operating Conditions ◽  
Comfort Level ◽  
System Description ◽  
Wide Range ◽  
System Components ◽  
Overall Performance ◽  
And Performance

The objective of the system is to control the car heater temperature to ensure an optimum comfort level, without the need for periodic adjustment, despite variations in ambient temperature and vehicle usage. Reasons for choosing a particular type of system are explained. The operation is analysed, and expressed in terms of an equation. Difficulties in solution due to non-linear terms are overcome with the aid of a digital computer. Test data on the system components and vehicle characteristics are used in the computer program to obtain a prediction of the accuracy of temperature control over a wide range of operating conditions. Predicted performance is compared with actual road tests results for an installation. Design optimization is facilitated by using the computer to examine the effect of system parameter changes on the overall performance.

scholarly journals Generalized Behavioral Modelling Methodology of Switch-Diode Cell for Power Loss Prediction in Electromagnetic Transient Simulation

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1500
Author(s):  
Yanming Xu ◽  
Carl Ngai Man Ho ◽  
Avishek Ghosh ◽  
Dharshana Muthumuni
Keyword(s):  
Power Loss ◽  
Process Analysis ◽  
Operating Conditions ◽  
Transient Simulation ◽  
Oxide Semiconductor ◽  
Model Parameters ◽  
Electromagnetic Transient ◽  
Proposed Model ◽  
Wide Range ◽  
Electromagnetic Transient Simulation

Modern wide-bandgap (WBG) devices, such as silicon carbide (SiC) or gallium nitride (GaN) based devices, have emerged and been increasingly used in power electronics (PE) applications due to their superior switching feature. The power losses of these devices become the key of system efficiency improvement, especially for high-frequency applications. In this paper, a generalized behavioral model of a switch-diode cell (SDC) is proposed for power loss estimation in the electromagnetic transient simulation. The proposed model is developed based on the circuit level switching process analysis, which considers the effects of parasitics, the operating temperature, and the interaction of diode and switch. In addition, the transient waveforms of the SDC are simulated by the proposed model using dependent voltage and current sources with passive components. Besides, the approaches of obtaining model parameters from the datasheets are given and the modelling method is applicable to various semiconductors such Si insulated-gate bipolar transistor (IGBT), Si/SiC metal–oxide–semiconductor field-effect transistor (MOSFET), and GaN devices. Further, a multi-dimensional power loss table in a wide range of operating conditions can be obtained with fast speed and reasonable accuracy. The proposed approach is implemented in PSCAD/ Electromagnetic Transients including DC, EMTDC, (v4.6, Winnipeg, MB, Canada) and further verified by the hardware setups including different daughter boards for different devices.

scholarly journals Effect of Rain Distribution Alteration on Splash Dispersal of Colletotrichum acutatum

1997 ◽  
Vol 87 (6) ◽  
pp. 649-655 ◽  
Author(s):  
N. Ntahimpera ◽  
L. V. Madden ◽  
L. L. Wilson
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Selective Medium ◽  
Drop Size Distribution ◽  
Colletotrichum Acutatum ◽  
Type Model ◽  
Strawberry Fruit ◽  
Diffusion Type ◽  
Splash Dispersal ◽  
Wide Range

Splash dispersal of Colletotrichum acutatum conidia from infected strawberry fruit was assessed using a rain simulator to determine the properties of rain (e.g., intensity [millimeters/hour] or drop size distribution) most related to dissemination. Dispersal with a simulated rain corresponding to a natural rain of about 11 mm/h was compared with dispersal of three other simulated rains that had larger and smaller drop sizes, on average, than idealized natural rains. Splash droplets were collected in sheltered petri plates with a selective medium for Colletotrichum, and colonies formed from conidia entrained in the droplets were counted and used as the measure of dispersal. Colonies were mostly confined to a 27-cm radius from the source, and density of colonies decreased exponentially with the distance squared, as indicated by the fit of a diffusion-type model to the data. Splash dispersal was more affected by drop size distribution than rain intensity or other properties of the generated rains. That is, there was a direct positive relationship between total colonies over 61 min of rain for a circular area with a 72-cm radius (Σ) and the mass (volume) median diameter of impacting drops (D0') for four rain-simulation treatments. In a separate study, strawberry fruit were exposed to the same four simulated rains at two distances from a point source and for two rain durations. Although the proportion of infected fruit (y) increased with time and decreased with distance, rain treatment did not significantly affect y, as predicted based on past work with a wide range of intensities of simulated rains.

scholarly journals Voltage H∞ Control of a Vanadium Redox Flow Battery

Electronics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1567
Author(s):  
Alejandro Clemente ◽  
Germán Andrés Ramos ◽  
Ramon Costa-Castelló
Keyword(s):  
Large Scale ◽  
Great Accuracy ◽  
Operating Conditions ◽  
Vanadium Redox Flow Battery ◽  
Redox Flow Battery ◽  
Open Research ◽  
Wide Range ◽  
And Performance ◽  
Storage Technologies ◽  
Vanadium Redox

Redox flow batteries are one of the most relevant emerging large-scale energy storage technologies. Developing control methods for them is an open research topic; optimizing their operation is the main objective to be achieved. In this paper, a strategy that is based on regulating the output voltage is proposed. The proposed architecture reduces the number of required sensors. A rigorous design methodology that is based on linear H∞ synthesis is introduced. Finally, some simulations are presented in order to analyse the performance of the proposed control system. The results show that the obtained controller guaranties robust stability and performance, thus allowing the battery to operate over a wide range of operating conditions. Attending to the design specifications, the controlled voltage follows the reference with great accuracy and it quickly rejects the effect of sudden current changes.

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