Dynamic Data-Driven Combustor Design for Mitigation of Thermoacoustic Instabilities

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Pritthi Chattopadhyay ◽  
Sudeepta Mondal ◽  
Asok Ray ◽  
Achintya Mukhopadhyay
Keyword(s):  
Experimental Data ◽  
Design Methodology ◽  
Performance Comparison ◽  
Operating Conditions ◽  
System Stability ◽  
Data Driven ◽  
Pressure Oscillations ◽  
Dynamic Data ◽  
Operating Condition ◽  
Thermoacoustic Instabilities

A critical issue in design and operation of combustors in gas turbine engines is mitigation of thermoacoustic instabilities, because such instabilities may cause severe damage to the mechanical structure of the combustor. Hence, it is important to quantitatively assimilate the knowledge of the system conditions that would potentially lead to these instabilities. This technical brief proposes a dynamic data-driven technique for design of combustion systems by taking stability of pressure oscillations into consideration. Given appropriate experimental data at selected operating conditions, the proposed design methodology determines a mapping from a set of operating conditions to a set of quantified stability conditions for pressure oscillations. This mapping is then used as an extrapolation tool for predicting the system stability for other conditions for which experiments have not been conducted. Salient properties of the proposed design methodology are: (1) It is dynamic in the sense that no fixed model structure needs to be assumed, and a suboptimal model (under specified user-selected constraints) is identified for each operating condition. An information-theoretic measure is then used for performance comparison among different models of varying structures and/or parameters and (2) It quantifies a (statistical) confidence level in the estimate of system stability for an unobserved operating condition by using a Bayesian nonparametric technique. The proposed design methodology has been validated with experimental data of pressure time-series, acquired from a laboratory-scale lean-premixed swirl-stabilized combustor.

Rotor Damped Natural Frequencies and Stability Under Reduced Oil Supply Flow Rates to Tilting-Pad Journal Bearings

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Bradley R. Nichols ◽  
Roger L. Fittro ◽  
Christopher P. Goyne
Keyword(s):  
Experimental Data ◽  
Natural Frequencies ◽  
Dynamic Performance ◽  
Operating Conditions ◽  
System Stability ◽  
Flow Rates ◽  
Oil Supply ◽  
Pressure Profiles ◽  
Tilting Pad ◽  
Identification Technique

Reduced oil supply flow rates in fluid film bearings can cause cavitation, or lack of a fully developed film layer, over one or more of the pads due to starvation. Reduced oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses; however, little experimental data are available on its effects on system stability and dynamic performance. The study looks at the effects of oil supply flow rate on dynamic bearing performance by comparing experimentally identified damped natural frequencies and damping ratios to predictive models. A test rig consisting of a flexible rotor and supported by two tilting pad bearings in flooded housings is utilized in this study. Tests are conducted over a range of supercritical operating speeds and bearing loads while systematically reducing the oil supply flow rates provided to the bearings. Shaft response measured as a magnetic actuator is used to perform sine sweep excitations of the rotor. A single-input, multiple-output system identification technique is then used to obtain frequency response functions (FRFs) and modal parameters. All experimental results are compared to predicted results obtained from bearing models based on thermoelastohydrodynamic (TEHD) lubrication theory. Both flooded and starved model flow assumptions are considered and compared to the data. Differences in the predicted trends of the models and the experimental data across varying operating conditions are examined. Predicted pressure profiles and dynamic coefficients from the models are presented to help explain any differences in trends.

Aerodynamic Damping Predictions Using a Linearized Navier-Stokes Analysis

1999 ◽  
Author(s):  
Daniel Hoyniak ◽  
William S. Clark
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Operating Conditions ◽  
The Other ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Blade Loading ◽  
Operating Condition ◽  
Linear Cascade ◽  
Aerodynamic Damping

A recently developed two dimensional, linearized Navier-Stokes algorithm, capable of modeling the unsteady flows encountered in turbomachinery applications, has been benchmarked and validated for use in the prediction of the aerodynamic damping. Benchmarking was accomplished by comparing numerical simulations with experimental data for two geometries. The first geometry investigated is a high turning turbine cascade. For this configuration, two different steady operating conditions were considered. The exit flow for one operating condition is subsonic whereas the exit flow for the other operating condition is supersonic. The second geometry investigated is a tip section from a high speed fan. Again, two separate steady operating conditions were examined. For this fan geometry, one operating condition falls within an experimentally observed flutter region whereas the other operating condition was observed experimentally to be flutter free. For both geometries considered, experimental measurements of the unsteady blade surface pressures were acquired for a linear cascade subjected to small amplitude torsional vibrations. Comparisons between the numerical calculations and the experimental data demonstrate the ability of the present computational model to predict accurately the steady and unsteady blade loading, and hence the aerodynamic damping, for each configuration presented.

Dynamic Data-Driven Design of Lean Premixed Combustors for Thermoacoustically Stable Operations

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Pritthi Chattopadhyay ◽  
Sudeepta Mondal ◽  
Chandrachur Bhattacharya ◽  
Achintya Mukhopadhyay ◽  
Asok Ray
Keyword(s):  
Experimental Data ◽  
Design Method ◽  
High Amplitude ◽  
Critical Issue ◽  
Operating Conditions ◽  
Design Parameters ◽  
System Response ◽  
Thermoacoustic Instabilities ◽  
Lean Premixed ◽  
Combustion Systems

Prediction of thermoacoustic instabilities is a critical issue for both design and operation of combustion systems. Sustained high-amplitude pressure and temperature oscillations may cause stresses in structural components of the combustor, leading to thermomechanical damage. Therefore, the design of combustion systems must take into account the dynamic characteristics of thermoacoustic instabilities in the combustor. From this perspective, there needs to be a procedure, in the design process, to recognize the operating conditions (or parameters) that could lead to such thermoacoustic instabilities. However, often the available experimental data are limited and may not provide a complete map of the stability region(s) over the entire range of operations. To address this issue, a Bayesian nonparametric method has been adopted in this paper. By making use of limited experimental data, the proposed design method determines a mapping from a set of operating conditions to that of stability regions in the combustion system. This map is designed to be capable of (i) predicting the system response of the combustor at operating conditions at which experimental data are unavailable and (ii) statistically quantifying the uncertainties in the estimated parameters. With the ensemble of information thus gained about the system response at different operating points, the key design parameters of the combustor system can be identified; such a design would be statistically significant for satisfying the system specifications. The proposed method has been validated with experimental data of pressure time-series from a laboratory-scale lean-premixed swirl-stabilized combustor apparatus.

Detection of Thermoacoustic Instabilities Via Nonparametric Bayesian Markov Modeling of Time-Series Data

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Sihan Xiong ◽  
Sudeepta Mondal ◽  
Asok Ray
Keyword(s):  
Time Series ◽  
Real Time ◽  
Time Series Data ◽  
Data Driven ◽  
Series Data ◽  
Markov Modeling ◽  
Bayesian Nonparametric ◽  
Dynamic Data ◽  
Thermoacoustic Instabilities ◽  
And Control

Real-time detection and decision and control of thermoacoustic instabilities in confined combustors are challenging tasks due to the fast dynamics of the underlying physical process. The objective here is to develop a dynamic data-driven algorithm for detecting the onset of instabilities with short-length time-series data, acquired by available sensors (e.g., pressure and chemiluminescence), which will provide sufficient lead time for active decision and control. To this end, this paper proposes a Bayesian nonparametric method of Markov modeling for real-time detection of thermoacoustic instabilities in gas turbine engines; the underlying algorithms are formulated in the symbolic domain and the resulting patterns are constructed from symbolized pressure measurements as probabilistic finite state automata (PFSA). These PFSA models are built upon the framework of a (low-order) finite-memory Markov model, called the D-Markov machine, where a Bayesian nonparametric structure is adopted for: (i) automated selection of parameters in D-Markov machines and (ii) online sequential testing to provide dynamic data-driven and coherent statistical analyses of combustion instability phenomena without solely relying on computationally intensive (physics-based) models of combustion dynamics. The proposed method has been validated on an ensemble of pressure time series from a laboratory-scale combustion apparatus. The results of instability prediction have been compared with those of other existing techniques.

Effect of Preheating on Flame Structure of a Swirl Stabilized Combustor With Porous Insert to Control Thermoacoustics

2016 ◽  
Author(s):  
Daniel L. Depperschmidt ◽  
John A. Kornegay ◽  
James C. Allen ◽  
Ajay K. Agrawal
Keyword(s):  
Flame Structure ◽  
Operating Conditions ◽  
Nitric Oxides ◽  
Pressure Oscillations ◽  
Time Resolved ◽  
Porous Insert ◽  
Thermoacoustic Instabilities ◽  
Air Temperatures ◽  
Planar Laser ◽  
Swirl Stabilized Combustion

Lean premixed (LPM) combustion is a common strategy in the turbine industry for power generation to reduce emissions of nitric oxides and other pollutants. LPM combustion tends to produce thermoacoustic instabilities under specific conditions. Previously we have shown that an appropriately designed ring-shaped porous insert located on the dump plane can mitigate thermoacoustic instabilities in LPM swirl-stabilized combustion for a range of operating conditions, and explained results based on time-resolved flowfield measurements. In this study, experiments are conducted at higher inlet air temperatures than used before, and the flame structure in the combustor without and with porous insert is investigated for the first time using time-resolved OH planar laser-induced fluorescence technique operated at 10 kHz. Large pressure oscillations in the fuel-air mixing tube demonstrate the existence of thermoacoustic instabilities without the porous insert. The pressure oscillations diminish with the porous insert, which is attributed to the changes in the flow field and flame structure.

Reliability and Optimal Replacement via Coefficient of Variation

1980 ◽  
Vol 102 (4) ◽  
pp. 761-768 ◽  
Author(s):  
S. M. Pandit ◽  
A. K. Shiekh
Keyword(s):  
Experimental Data ◽  
Coefficient Of Variation ◽  
Cutting Tools ◽  
Operating Conditions ◽  
Limited Data ◽  
Operating Condition ◽  
Numerical Examples ◽  
Optimal Replacement ◽  
Fatigue Failures

The paper presents an approach to obtaining reliability and optimal replacement policies at different operating conditions, based on limited data at one operating condition. Guidelines for the choice of a distribution based on the behavior of sample functions of deterioration processes such as wear and fatigue are provided. The importance of the coefficient of variation is delineated to show how it provides a dimensionless format of the distributions and optimal replacement strategies. Simple graphical solutions of the otherwise complicated optimal replacement equations are illustrated by numerical examples based on experimental data in diverse forms from the areas of cutting tools and fatigue failures.

scholarly journals Review and performance comparison of mechanical-chemical degradation models for lithium-ion batteries

2019 ◽  
Author(s):  
Jorn Reniers ◽  
David Howey ◽  
Grietus Mulder
Keyword(s):  
Experimental Data ◽  
Lithium Ion Batteries ◽  
Lithium Ion ◽  
Large Data ◽  
Performance Comparison ◽  
Operating Conditions ◽  
Chemical Degradation ◽  
Model Framework ◽  
Data Set ◽  
Degradation Models

The maximum energy that lithium-ion batteries can store decreases as they are used because of various irreversible degradation mechanisms. Many models of degradation have been proposed in the literature, sometimes with a small experimental data set for validation. However, a thorough comparison betweendifferent model predictions is lacking, making it difficult to select modelling approaches which can explain the degradation trends actually observed from data. Here various degradation models from literature are implemented within a single article model framework and their behaviour compared. It is shown that many different models can be ?fitted to a small experimental data set. The interactions between different models are simulated, showing how some of the models accelerate degradation in other models, altering the overall degradation trend. The effects of operating conditions on the various degradation models is simulated. Thisidentifies which models are enhanced by which operating conditions and might therefore explain specific degradation trends observed in data. Finally, it is shown how a combination of different models is needed to capture different degradation trends observed in a large experimental data set. Vice versa, only a large data set enables to properly select the models which best explain the observed degradation.

OPERATIONAL STATE OF BRIDGES OF UKRAINE

2019 ◽  
pp. 57-68
Author(s):  
Larysa Bodnar ◽  
Petro Koval ◽  
Sergii Stepanov ◽  
Liudmyla Panibratets
Keyword(s):  
Management System ◽  
The State ◽  
Operating Conditions ◽  
Bridge Management ◽  
Bridge Management System ◽  
Program Complex ◽  
Operating Condition ◽  
Software Complex ◽  
Automatic Mode ◽  
The Status

A significant part of Ukrainian bridges on public roads is operated for more than 30 years (94 %). At the same time, the traffic volume and the weight of vehicles has increased significantly. Insufficient level of bridges maintenance funding leads to the deterioration of their technical state. The ways to ensure reliable and safe operation of bridges are considered. The procedure for determining the predicted operational status of the elements and the bridge in general, which has a scientific novelty, is proposed. In the software complex, Analytical Expert Bridges Management System (AESUM), is a function that allows tracking the changes in the operational status of bridges both in Ukraine and in each region separately. The given algorithm of the procedure for determining the predicted state of the bridge using a degradation model is described using the Nassie-Schneidermann diagram. The model of the degradation of the bridge performance which is adopted in Ukraine as a normative one, and the algorithm for its adaptation to the AESUM program complex with the function to ensure the probabilistic predicted operating condition of the bridges in the automatic mode is presented. This makes it possible, even in case of unsatisfactory performance of surveys, to have the predicted lifetime of bridges at the required time. For each bridge element it is possible to determine the residual time of operation that will allow predict the state of the elements of the structure for a certain period of time in the future. Significant interest for specialists calls for the approaches to the development of orientated perspective plans for bridge inspection and monitoring of changes in the operational status of bridges for 2009-2018 in Ukraine. For the analysis of the state of the bridge economy, the information is available on the distribution of bridges by operating state related to the administrative significance of roads, by road categories and by materials of the structures. Determining the operating state of the bridge is an important condition for making the qualified decisions as regards its maintenance. The Analytical Expert Bridges Management System (AESUM) which is implemented in Ukraine, stores the data on the monitoring the status of bridges and performs the necessary procedures to maintain them in a reliable and safe operating condition. An important result of the work is the ability to determine the distribution of bridges on the public roads of Ukraine, according to operating conditions established in the program complex of AESUM, which is presented in accordance with the data of the current year. In conditions of limited funding and in case of unsatisfactory performance of surveys, it is possible to make the reasonable management decisions regarding the repair and the reconstruction of bridges. Keywords: bridge management system, operating condition, predicted operating condition, model of degradation, bridge survey plan, highway bridge.

Application of vacuum belt press filters for cane mud filtration and performance comparison with rotary filters

2014 ◽  
pp. 298-301 ◽  
Author(s):  
Arnaud Petit
Keyword(s):  
Electricity Consumption ◽  
Performance Comparison ◽  
Operating Conditions ◽  
Vacuum Filter ◽  
Sugar Mill ◽  
Belt Press ◽  
Vacuum Belt ◽  
And Performance ◽  
Mud Filtration ◽  
The Impact

Bois-Rouge factory, an 8000 t/d cane Reunionese sugarcane mill, has fully equipped its filtration station with vacuum belt press filters since 2010, the first one being installed in 2009. The present study deals with this 3-year experience and discusses operating conditions, electricity consumption, performance and optimisation. The comparison with the more classical rotary drum vacuum filter station of Le Gol sugar mill highlights advantages of vacuum belt press filters: high filtration efficiency, low filter cake mass and sucrose content, low total solids content in filtrate and low power consumption. However, this technology needs a mud conditioning step and requires a large amount of water to improve mud quality, mixing of flocculant and washing of filter belts. The impact on the energy balance of the sugar mill is significant. At Bois-Rouge mill, studies are underway to reduce the water consumption by recycling low d.s. filtrate and by dry cleaning the filter belts.

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