scholarly journals Mathematical Modeling of Unsteady Gas Transmission System Operating Conditions under Insufficient Loading

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1325 ◽  
Author(s):  
Vasyl Zapukhliak ◽  
Lyubomyr Poberezhny ◽  
Pavlo Maruschak ◽  
Volodymyr Grudz ◽  
Roman Stasiuk ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Pressure Fluctuations ◽  
High Amplitude ◽  
Transmission System ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Amplitude Fluctuations ◽  
Pipeline Route ◽  
Main Gas Pipeline ◽  
System Operating

Under insufficient loading of a main gas transmission system, high-amplitude fluctuations of pressure may occur in it. A mathematical model is proposed to estimate the amplitude of pressure fluctuations in a gas pipeline along its length. It has been revealed that the shutdown of compressor stations along the gas pipeline route has a significant impact on the parameters of the unsteady transient operating conditions. The possibility of minimizing oscillation processes by disconnecting compressor stations is substantiated for the “Soyuz” main gas pipeline.

Intermittency in the Dynamics of Turbulent Combustors

2014 ◽  
Author(s):  
Vineeth Nair ◽  
R. I. Sujith
Keyword(s):  
Reynolds Number ◽  
High Speed ◽  
Bluff Body ◽  
Combustion Instability ◽  
Homoclinic Orbits ◽  
High Amplitude ◽  
Operating Conditions ◽  
Periodic Oscillations ◽  
Lean Blowout ◽  
Amplitude Fluctuations

The dynamic transitions preceding combustion instability and lean blowout were investigated experimentally in a laboratory scale turbulent combustor by systematically varying the flow Reynolds number. We observe that the onset of combustion-driven oscillations is always presaged by intermittent bursts of high-amplitude periodic oscillations that appear in a near random fashion amidst regions of aperiodic, low-amplitude fluctuations. The onset of high-amplitude, combustion-driven oscillations in turbulent combustors thus corresponds to a transition in dynamics from chaos to limit cycle oscillations through a state characterized as intermittency in dynamical systems theory. These excursions to periodic oscillations become last longer in time as operating conditions approach instability and finally the system transitions completely into periodic oscillations. Such intermittent oscillations emerge through the establishment of homoclinic orbits in the phase space of the global system which is composed of hydrodynamic and acoustic subsystems that operate over different time scales. Such intermittent burst oscillations are also observed in the combustor on increasing the Reynolds number further past conditions of combustion instability towards the lean blowout limit. High-speed flame images reveal that the intermittent states observed prior to lean blowout correspond to aperiodic detachment of the flame from the bluff-body lip. These intermittent oscillations are thus of prognostic value and can be utilized to provide early warning signals to combustion instability as well as lean blowout.

scholarly journals Forecasting rational working modes of long-operated gas-transport systems under conditions of their incomplete loading

2021 ◽  
Vol 4 (8(112)) ◽  
pp. 6-15
Author(s):  
Volodymyr Grudz ◽  
Yaroslav Grudz ◽  
Myroslav Iakymiv ◽  
Mykola Iakymiv ◽  
Pavlo Iagoda
Keyword(s):  
Mathematical Modeling ◽  
Energy Consumption ◽  
Transport System ◽  
Gas Transport ◽  
Pressure Fluctuations ◽  
Initial Pressure ◽  
High Amplitude ◽  
Nonstationary Process ◽  
Optimality Criteria ◽  
Transport Systems

Prolonged operation of the gas-transport system in conditions of partial loading involves frequent changes in the volume of gas transportation, which necessitates prompt forecasting of system operation. When forecasting the modes of operation of the gas transport system, the main criterion of optimality implies the maximum volume of gas pumping. After all, in this case, the largest profit of the gas-transport company is achieved under the condition of full provision of consumers with energy. In conditions of incomplete loading of the gas-transport system caused by a shortage of gas supply, optimality criteria change significantly. First, the equipment is operated in ranges far from nominal ones which leads to growth of energy consumption. Secondly, changes in performance cause high-amplitude pressure fluctuations at the outlet of compressor stations. Based on mathematical modeling of nonstationary processes, amplitude and frequency of pressure fluctuations at the outlet of compressor stations which can cause the pipeline overload have been established. To prevent this, it was proposed to reduce initial pressure relative to the maximum one. Calculated dependence was obtained which connects the amplitude of pressure fluctuations with the characteristics of the gas pipeline and the nonstationary process. Reduction in energy consumption for transportation is due to the shutdown of individual compressor stations (CS). Mathematical modeling has made it possible to establish regularities of reduction of productivity of the gas-transport system and duration of the nonstationary process depending on the location of the compressor station on the route. With an increase in the number of shutdown compression stations, the degree of productivity decrease and duration of nonstationarity reduces The established patterns and proposed solutions will improve the reliability of a gas-transport system by preventing pipeline overload and reduce the cost of gas transportation by selecting running numbers of shutdown stations with a known decrease in productivity.

scholarly journals THE PREDICTION OF STATIONARY MODES OF OPERATION OF GAS SUPPLY SYSTEMS BY THE METHOD OF INTEGRAL COEFFICIENTS

2019 ◽  
pp. 71-76
Author(s):  
Ye. I. Kryzhanivskyi ◽  
V. Ya. Hrudz ◽  
V. Ya. Hrudz (jun.) ◽  
R. V. Tereshchenko
Keyword(s):  
Operation Mode ◽  
Resistance Coefficient ◽  
Transmission System ◽  
Gas Pipeline ◽  
Technological Parameters ◽  
Modes Of Operation ◽  
Additional Information ◽  
Input And Output ◽  
Output Information ◽  
Main Gas Pipeline

The authors present the methods of generating the system of the integral coefficients of influence for gas transmission systems aiming at the estimation of the parameters of its work on stationary operating modes. Each change of the technological parameters of the operation mode at the input of the gas transmission system will necessarily cause the reaction of the system which will manifest itself in changing the corresponding parameters at its output. Obviously, the parameters of the input and output of the system are interconnected by a complex system of equations, the implementation of which requires certain time costs and gathering additional information about the technical and hydrogasdynamic states of the system at each moment. Under the conditions of incomplete loading of the gas transmission system, which involves frequent changes in its operation modes, the accomplishment of the task is not always possible. It is suggested to create a system of integral coefficients of influence which characterize the ratio of input and output information in different stationary modes, and formally submit it in a matrix form. The processes characterized by integral coefficients of influence implicitly contain the technological parameters of the gas pipeline (length, diameter, hydraulic resistance coefficient, heat transfer to the environment, etc.) which can not always be determined with sufficient accuracy by the deterministic methods. The suggested methodology involves the creation of simple and effective methods of predicting which allow estimating the state of the gas pipeline by the costs and pressures at the inputs and outputs of the system, that is, by the operational data that are being monitored. On the basis of the proposed methodology, it is suggested to create an operational system that will allow managing the modes of operation of the main gas pipeline in cases of frequent changes in pumping volumes. When changing the technological scheme of the gas transmission system, there is a need to adapt the integral coefficients of influence. The application of the proposed methods is illustrated by the example of the main gas pipeline Soyuz.

scholarly journals IMPROVING THE EFFICIENCY OF FUNCTIONING OF REPAIR-OPERATING UNITS IN THE SYSTEM OF MAINTENANCE AND REPAIR OF MAGISTRALS

2019 ◽  
pp. 104-115
Author(s):  
V. Y. Grudz ◽  
V. V. Grudz ◽  
V. M. Bodnar ◽  
M. S. Chernetsky
Keyword(s):  
Linear Part ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Gas Pipelines ◽  
Maintenance And Repair ◽  
Technological Structure ◽  
Optimal Technology ◽  
Main Gas Pipeline ◽  
Operating Units

The classification of failures and damages of the linear part and its separate elements is carried out, variants of technology of carrying out of preventive and repair-restoration works and modular-technological structure of repair and maintenance units are formulated. Particular attention is paid to improving the efficiency of the operation of a separate repair and maintenance unit during maintenance and repair with a known layout scheme and a certain mode of control and restoration works by choosing the optimal technology of work and rational equipment of units and crews leaving for the route. On the basis of the analysis of the technology of work execution it is shown that only a small part of the repair and maintenance measures requires the use of powerful machinery and equipment, which include the first level of priority work on the replacement of gas pipeline sections, work, damage elimination, work on elimination of significant pipeline displacements, work for restoration of soil collapse of the main gas pipeline. In addition, each type of work on the objects of the linear part requires the use of the same vehicles. The type and number of vehicles depend on the particular operating conditions, as well as on the possibility and feasibility of purchasing and operating a particular type of equipment. The method of estimation of indexes of maintenance of linear part of main gas pipelines and efficiency of functioning of repair and maintenance units during maintenance and repair is developed.

Intermittency route to thermoacoustic instability in turbulent combustors

2014 ◽  
Vol 756 ◽  
pp. 470-487 ◽  
Author(s):  
Vineeth Nair ◽  
Gireeshkumaran Thampi ◽  
R. I. Sujith
Keyword(s):  
Bluff Body ◽  
Combustion Instability ◽  
Signal Amplitude ◽  
High Amplitude ◽  
Operating Conditions ◽  
Combustion Noise ◽  
Continuous Measure ◽  
Periodic Oscillations ◽  
Thermoacoustic Instability ◽  
Amplitude Fluctuations

AbstractThe dynamic transition from combustion noise to combustion instability was investigated experimentally in two laboratory-scale turbulent combustors (namely, swirl-stabilized and bluff-body-stabilized backward-facing-step combustors) by systematically varying the flow Reynolds number. We observe that the onset of combustion-driven oscillations is always presaged by intermittent bursts of high-amplitude periodic oscillations that appear in a near-random fashion amidst regions of aperiodic low-amplitude fluctuations. These excursions to periodic oscillations last longer in time as operating conditions approach instability and finally the system transitions completely into periodic oscillations. A continuous measure to quantify this bifurcation in dynamics can be obtained by defining an order parameter as the probability of the signal amplitude exceeding a predefined threshold. A hysteresis zone was observed in the bluff-body-stabilized configuration that was absent in the swirl-stabilized configuration. The recurrence properties of the dynamics of intermittent burst oscillations were quantified using recurrence plots and the distribution of the aperiodic phases was examined. From the statistics of these aperiodic phases, robust early-warning signals of an impending combustion instability may be obtained.

scholarly journals Injector-coupled transverse instabilities in a multi-element premixed combustor

2020 ◽  
Vol 12 ◽  
pp. 175682772093283
Author(s):  
John J Philo ◽  
Rohan M Gejji ◽  
Carson D Slabaugh
Keyword(s):  
Equivalence Ratio ◽  
Pressure Fluctuations ◽  
High Amplitude ◽  
Operating Conditions ◽  
Combustion Instabilities ◽  
Combustion Dynamics ◽  
Thermoacoustic Instabilities ◽  
Transverse Modes ◽  
Additional Mode ◽  
The Relationship

Combustion instabilities in a high-pressure, multi-element combustor are studied in order to understand the relationship between the chamber and injector dynamics. A linear array of seven injectors supplies premixed natural gas and air into a rectangular combustion chamber designed to promote high-frequency, transverse thermoacoustic instabilities. The effect of equivalence ratio on the combustion dynamics was investigated for two injector lengths, 62.5 and 125 mm. For all operating conditions, the 125 mm injectors promote high-amplitude instabilities of the fundamental transverse (1T) mode, which has a frequency of 1750–1850 Hz. Reducing the injector length significantly lowers the instability amplitudes for all operating conditions and, for lower equivalence ratio cases, excites an additional mode near 1550 Hz. The delineating feature controlling the growth of the instabilities in each injector configuration is the coupling with axial pressure fluctuations in the injectors that occur in response to the transverse modes in the chamber.

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