Optimal alarm threshold under time-varying operating conditions

2018 ◽  
Author(s):  
Hao Xia ◽  
Zengle Li ◽  
Xiluo Yang
Keyword(s):  
Operating Conditions ◽  
Time Varying ◽  
Alarm Threshold

scholarly journals A SVDD and K-Means Based Early Warning Method for Dual-Rotor Equipment under Time-Varying Operating Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Zhinong Jiang ◽  
Minghui Hu ◽  
Kun Feng ◽  
Hao Wang
Keyword(s):  
Test Data ◽  
Early Warning ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Cluster Center ◽  
Time Varying ◽  
Fixed Threshold ◽  
Alarm Threshold ◽  
Rotor Equipment

Under frequently time-varying operating conditions, equipment with dual rotors like gas turbines is influenced by two rotors with different rotating speeds. Alarm methods of fixed threshold are unable to consider the influences of time-varying operating conditions. Hence, those methods are not suitable for monitoring dual-rotor equipment. An early warning method for dual-rotor equipment under time-varying operating conditions is proposed in this paper. The influences of time-varying rotating speeds of dual rotors on alarm thresholds have been considered. Firstly, the operating conditions are divided into several limited intervals according to rotating speeds of dual rotors. Secondly, the train data within each interval is processed by SVDD and the allowable ranges (i.e., the alarm threshold) of the vibration are determined. The alarm threshold of each interval of operating conditions is obtained. The alarm threshold can be expressed as a sphere, whose controlling parameters are the coordinate of the center and the radius. Then, the cluster center of the test data, whose alarm state is to be judged, can be extracted through K-means. Finally, the alarm state can be obtained by comparing the cluster center with the corresponding sphere. Experiments are conducted to validate the proposed method.

Using Sliding Mode Control to Adjust Drum Level of a Boiler Unit With Time Varying Parameters

2010 ◽  
Author(s):  
Hamed Moradi ◽  
Firooz Bakhtiari-Nejad ◽  
Majid Saffar-Avval ◽  
Aria Alasty
Keyword(s):  
Water Level ◽  
Transfer Functions ◽  
Sliding Mode ◽  
Operating Conditions ◽  
Model Parameters ◽  
Feed Water ◽  
Time Varying ◽  
Boiler Unit ◽  
Varying Parameters ◽  
Time Varying Parameters

Stable control of water level of drum is of great importance for economic operation of power plant steam generator systems. In this paper, a linear model of the boiler unit with time varying parameters is used for simulation. Two transfer functions between drum water level (output variable) and feed-water and steam mass rates (input variables) are considered. Variation of model parameters may be arisen from disturbances affecting water level of drum, model uncertainties and parameter mismatch due to the variant operating conditions. To achieve a perfect tracking of the desired drum water level, two sliding mode controllers are designed separately. Results show that the designed controllers result in bounded values of control signals, satisfying the actuators constraints.

Computer simulation of the reliability of the heat exchange surface of the steam turbine condenser

2022 ◽  
pp. 1748006X2110672
Author(s):  
Krzysztof Bernard Łukaszewski
Keyword(s):  
Heat Exchange ◽  
Steam Turbine ◽  
Cooling Water ◽  
Operating Conditions ◽  
Time Varying ◽  
Turbine Condenser ◽  
Heat Exchange Surface ◽  
Steam Turbine Condenser ◽  
The Relationship ◽  
Exchange Surface

The aim of the article is to demonstrate the relationship between the adaptive regulation of the heat exchange surface to specific operating conditions of a steam turbine condenser and the reliability and availability of this surface in a specific period of time. The article exemplifies the relationship between the settings of the condenser heat exchange surface and the resulting changes in the reliability structures of this surface. The method of creating a mathematical model of reliability estimation, which is characterized by the variability of the reliability structures of the heat exchange surface in relation to specific operating conditions in a specific period of time, was indicated. Then, exemplary simulations of the adaptation of reliability structures of specific pipe systems constituting the condenser’s heat exchange surface to specific processes of operation of this condenser are presented. The simulations refer to the time-varying thermal loads of the condenser, the time-varying mean thickness of the sediments, and changes in the temperature of the cooling water at the point of its intake over time. The adaptation of certain reliability structures consists in the adaptation of specific systems of pipes through which the cooling water flows to the currently existing operating conditions of the condenser in order to maintain the desired reliability of the heat exchange surface for a specified time. This is done by enabling or disabling the flow of cooling water through a given number of pipes in specific systems under given operating conditions. On the basis of computer simulations, the reliability functions, and the availability functions of the subsystem under consideration were estimated.

Nonlinear dynamic analysis of a microsegment gear system with a time-varying base circle

2020 ◽  
Vol 44 (2) ◽  
pp. 279-293
Author(s):  
Kang Huang ◽  
Fengwei Xu ◽  
Yangshou Xiong ◽  
Meng Sang ◽  
Yong Yi
Keyword(s):  
Dynamic Analysis ◽  
Nonlinear Dynamic ◽  
High Speed ◽  
Operating Conditions ◽  
Gear System ◽  
Resonant Peak ◽  
Time Varying ◽  
Heavy Load ◽  
Involute Gear ◽  
Base Circle

A systematic dynamic analysis of a microsegment gear system with a time-varying base circle, time-varying mesh stiffness, and gear backlash is carried out in this paper. By discretizing the meshing process, a six degree-of-freedom nonlinear dynamic model of a microsegment gear pair is established. To study the dynamic response of the microsegment gear and involute gear under various operating conditions, the numerical integration method is adopted. The dynamic transmission error (DTE) of the two gears is analysed in terms of time history charts, phase diagrams, fast Fourier transformation spectra, and Poincaré maps. The effects of support damping and support stiffness on radial vibration are also investigated. Results reveal that, compared with the involute gear system, the microsegment gear system is more stable at the high-speed condition and has a smaller amplitude of DTE under medium-speed and heavy-load, high-speed, and heavy-load conditions. The support damping and support stiffness have great effects on the resonant peak in the radial direction of the microsegment gear. Both the proposed model and numerical results are expected to provide a useful source of reference for the dynamic design of the microsegment gear system.

Dynamics of Hypoid Gear Transmission With Nonlinear Time-Varying Mesh Characteristics

2003 ◽  
Vol 125 (2) ◽  
pp. 373-382 ◽  
Author(s):  
Yuping Cheng ◽  
Teik C. Lim
Keyword(s):  
Response Spectra ◽  
Transmission Error ◽  
Operating Conditions ◽  
Time Varying ◽  
Analysis Model ◽  
Tooth Contact Analysis ◽  
3 Dimensional ◽  
Resonant Modes ◽  
Loaded Tooth Contact Analysis ◽  
Backlash Nonlinearity

The coupled translation-rotation vibratory response of hypoid geared rotor system due to loaded transmission error excitation is studied by employing a generalized 3-dimensional dynamic model. The formulation includes the effects of backlash nonlinearity as well as time-dependent mesh position and line-of-action vectors. Its mesh coupling is derived from a quasi-static, 3-dimensional, loaded tooth contact analysis model that accounts for the precise gear geometry and profile modifications. The numerical simulations show significant tooth separation and occurrence of multi-jump phenomenon in the predicted response spectra under certain lightly loaded operating conditions. Also, resonant modes contributing to the response spectra are identified, and cases with super-harmonics are illustrated. The computational results are then analyzed to quantify the extent of non-linear and time-varying factors.

A Dual-Loop EGR Engine Air-Path Oxygen Concentration Model With Time-Varying Transport Delays

2013 ◽  
Author(s):  
Xiangrui Zeng ◽  
Junmin Wang
Keyword(s):  
Oxygen Concentration ◽  
Dynamic Models ◽  
Operating Conditions ◽  
High Fidelity ◽  
Exhaust Gas ◽  
Time Varying ◽  
Transport Delay ◽  
Engine Model ◽  
Gas Recirculation ◽  
Transient Operations

Dual-loop exhaust gas recirculation (EGR) systems can provide control authorities for adjusting the engine in-cylinder gas conditions. However, the transport delay in the EGR air-path makes some simple oxygen concentration dynamic models perform poorly under the transient operating conditions. In this paper, a dual-loop EGR air-path oxygen concentration model considering the time-varying transport delays is developed and a method to calculate the delay time based on the continuity of gas velocity is presented. Simulation validations using a high-fidelity GT-Power 1-D computational engine model show that the developed model can capture the oxygen concentration dynamics during both steady-state and transient operations.

Calculation and analysis of the loss and heat on damper bars in large tubular hydro-generator

2013 ◽  
Vol 62 (1) ◽  
pp. 43-54 ◽  
Author(s):  
Yong Liao ◽  
Zhen-Nan Fan ◽  
Li Han ◽  
Li-Dan Xie
Keyword(s):  
Electromagnetic Field ◽  
Temperature Field ◽  
Heat Conduction ◽  
Heat Dissipation ◽  
Operating Conditions ◽  
Fe Model ◽  
Time Varying ◽  
Rotor Core ◽  
Anisotropic Heat Conduction ◽  
Generator Design

Abstract In order to research the losses and heat of damper bars thoroughly, a multislice moving electromagnetic field-circuit coupling FE model of tubular hydro-generator and a 3D temperature field FE model of the rotor are built respectively. The factors such as rotor motion and non-linearity of the time-varying electromagnetic field, the stator slots skew, the anisotropic heat conduction of the rotor core lamination and different heat dissipation conditions on the windward and lee side of the poles are considered. Furthermore, according to the different operating conditions, different rotor structures and materials, compositive calculations about the losses and temperatures of the damper bars of a 36 MW generator are carried out, and the data are compared with the test. The results show that the computation precision is satisfied and the generator design is reasonable.

Dynamic Model of a Sac-Type Pneumatically Driven Artificial Ventricle

1977 ◽  
Vol 99 (1) ◽  
pp. 14-19 ◽  
Author(s):  
D. B. Geselowitz ◽  
G. E. Miller ◽  
W. M. Phillips
Keyword(s):  
Dynamic Model ◽  
Circulatory System ◽  
Operating Conditions ◽  
Time Varying ◽  
Outlet Port ◽  
Mock Circulatory System ◽  
Linear Resistance ◽  
Wide Range ◽  
Artificial Ventricle ◽  
Nonlinear Resistance

Inlet and outlet pressures and flows were obtained over a wide range of operating conditions for a pneumatically driven sac-type artificial ventricle connected to a mechanical mock circulatory system. The load presented to the ventricle by the mock circulatory system was found to be characterized by a linear resistance and capacitance. A dynamic model for the ventricle which accounted for instantaneous pressures and flows was developed. The outlet port is characterized by an inertance and square law resistance; the inlet port is characterized by a nonlinear resistance dependent on the type of valve. The input to the model is the time varying sac pressure. The model predicts the fill-limited and ejection-limited modes of the artificial ventricle.

scholarly journals A Flexible Top-Down Data-Driven Stochastic Model for Synthetic Load Profiles Generation

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 269
Author(s):  
Enrico Dalla Maria ◽  
Mattia Secchi ◽  
David Macii
Keyword(s):  
Stochastic Model ◽  
Power Flow ◽  
Distribution Systems ◽  
Control Strategies ◽  
Flow Analysis ◽  
Gaussian Mixture Models ◽  
Gaussian Mixture ◽  
Operating Conditions ◽  
Time Varying ◽  
Top Down

The study of the behavior of smart distribution systems under increasingly dynamic operating conditions requires realistic and time-varying load profiles to run comprehensive and accurate simulations of power flow analysis, system state estimation and optimal control strategies. However, due to the limited availability of experimental data, synthetic load profiles with flexible duration and time resolution are often needed to this purpose. In this paper, a top-down stochastic model is proposed to generate an arbitrary amount of synthetic load profiles associated with different kinds of users exhibiting a common average daily pattern. The groups of users are identified through a preliminary Ward’s hierarchical clustering. For each cluster and each season of the year, a time-inhomogeneous Markov chain is built, and its parameters are estimated by using the available data. The states of the chain correspond to equiprobable intervals, which are then mapped to a time-varying power consumption range, depending on the statistical distribution of the load profiles at different times of the day. Such distributions are regarded as Gaussian Mixture Models (GMM). Compared with other top-down approaches reported in the scientific literature, the joint use of GMM models and time-inhomogeneous Markov chains is rather novel. Furthermore, it is flexible enough to be used in different contexts and with different temporal resolution, while keeping the number of states and the computational burden reasonable. The good agreement between synthetic and original load profiles in terms of both time series similarity and consistency of the respective probability density functions was validated by using three different data sets with different characteristics. In most cases, the median values of synthetic profiles’ mean and standard deviation differ from those of the original reference distributions by no more than ±10% both within a typical day of each season and within the population of a given cluster, although with some significant outliers.

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