The study of erosive wear of the shaped elements of compressor station manifold of a gas pipeline

Transcription

1 OIL AND GAS TRANSPORTATION The study of erosive wear of the shaed elements of comressor station manifold of a gas ieline Ya. V. Doroshenko *, Т. І. Мarko, Yu. І. Doroshenko Ivano-Frankivsk National Technical University of Oil and Gas; 15, Karatska str., Ivano-Frankivsk, 76019, Ukraine Received: Acceted: Abstract The research is made to identify the laces of intense strikes of liquid and solid articles to the wall of comressor station manifold of a gas ieline, their erosive wear and to calculate the erosion rate. There is carried out 3D modeling of comressor station iing and its shaed elements, where a comlex movement of multihase flows, change of their direction, swirl, strikes of discrete hases to the wall of a ieline as well as erosive wear of the ieline wall occur. Based on the Lagrangian aroach (the Discrete Phase Model) there were develoed methods for modeling the erosive wear of comressor station manifold shaed elements (bends, T-junctions) using ANSYS Fluent R17.0 Academic software. A mathematical model is based on solving the Navier Stokes, continuity, discrete hases motion and the Finney equations, two arameter k ε Launder Sharma turbulence model with aroriate initial and boundary itions. The simulation was erformed for different motion atterns of gas (gas moves through T-junction run-ie to the T-junction branch; gas moves through the branch of T-junction to the T-junction run-ie, in which a ortion of gas stream flows in one side of the run-ie, and the rest of the gas stream in the other one; gas moves through the T-junction branch to one side of the T-junction run-ie). The simulation results were visualized in ANSYS Fluent R17.0 Academic ostrocessor by building concentration fields of a discrete hase and erosion rate fields at shaed elements contours. Having studied the obtained results there were identified laces of intense strikes of liquid and solid articles to the wall of shaed elements of comressor station manifold, the intensive erosive wear of a ieline wall and there was calculated the erosion rate. Keywords: a bend, a discrete hase, concentration fields, Finney equation, T-junction, the Lagrangian aroach. Comressor station manifold of trunk gas ielines consists of straight ieline sections, curves (branches) of hot bending, T-junctions, reducers, covering fitting. A comlex turbulent motion of gas flow and the change in the direction of its movement, leading to strikes of liquid and solid articles (the discrete hase) in the flow of natural gas (a solid hase) to the wall of the ieline and resulting in erosive wear of a ie wall, occur in T- junctions and curves of hot bending. The erosive wear is a factor that reduces the residual life of ielines. If comressor station manifold is not roerly monitored, the erosive wear can lead to ieline rutures and loss of roducts, and these facts are life-threatening and can cause damage to buildings in the territory of comressor stations. The erosive wear of a ie wall is esecially dangerous for ielines with the service life exceeding years. The gas transortation system of Ukraine rimarily consists of such ielines. Therefore, a comrehensive study of the erosive wear of gas ielines wall is articularly relevant. * Corresonding author: ya.doroshenko@nung.edu.ua 2016, Ivano-Frankivsk National Technical University of Oil and Gas. All rights reserved. To assess the efficiency of erosively worn comressor station manifold and calculate their remaining resource it is necessary to know the erosion rate, laces of manifold erosive wear and a geometric shae of the defective inner surface. Such information also enables to imrove designs of the manifold for their long service life. It is very difficult to accurately redict the erosive wear of comressor station manifold because of the wide range of arameters that affect their lacement and size, including the flow rate of liquid and solid articles, concentration, diameter, articles density, the mode of flow, gas temerature, geometry of the shaed elements, material of wall, etc. Today these roblems can be solved in the shortest time by means of the software ackage ANSYS Fluent, which enables to simulate the erosive wear of gas ielines shaed elements and calculate the value of erosive wear. An analysis of recent domestic and foreign studies The erosive wear of shaed elements occurs in various ielines (gas ielines, oil ielines, nitrogen ielines, steam ielines of nuclear and thermal ower stations, neumatic transort, etc.). This causes interest of many researchers to study the rocesses of the erosive wear of ie walls. ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2 65

2 Ya. V. Doroshenko, Т. І. Мarko, Yu. І. Doroshenko Many modern scientists are involved in comuter modeling of the erosive wear of ieline shaed elements. Their studies confirm that these software systems are effective means for identifying laces and calculating the erosion rate of ieline shaed elements. In articular V. Abdolkarimi and R. Mohammadikhah [1] studied the erosive wear of the gas ieline bend with the outside diameter of 1420 mm and the angle of 90 under the ressure of 8 MPa by means of the comuter modeling in ANSYS Fluent 6.3. Mass flow of gas at the inlet was 3780 kg/s. The maximum erosive wear was found between 40 and 65 angles of the bend, the calculated maximum rate of erosive wear was m/s. Having comared the results of numerical calculations with the results of exerimental measurements, the authors concluded that CFD (comutational fluid dynamics) modeling is a owerful tool for assessing the erosive wear of various industrial facilities. In his master's thesis A. Abdua (Blekinge Institute of Technology Karlskrona, Sweden) [2] investigated the effect of the imact velocity of the and ensation dros uon the erosive wear of gas ielines bends of the inner diameter of 50.8 mm and the rotation angle of 90 by means of comuter simulation. There were set three different velocities of liquid and solid articles 12, 19 and 28 m/s. According to the simulation results there was determined that articles velocity was roortional to the rate of erosive wear and significantly affected the average and maximum rates of the erosive wear. It was also observed that the density of the liquid drolets affected the location of the maximum erosive wear. Thus the maximum erosive wear was found almost in the middle of the bend when the density of liquid drolets was low. If the density of liquid drolets increases, the location of the maximum erosive wear shifts toward the flow outlet of the bend and the beginning of the adjacent ie. M. Azimian and H. Bart [3] studied the rate of erosive wear of the bend and T-junction with a diameter of 25 mm by means of comuter simulation. The oerating environment was liquid with solid articles. Places of the shaed elements erosive wear, the maximum rate of erosive wear were found. It was also found that if the liquid with solid articles is transorted by the ieline, the erosive wear of the T-junction is greater than that of the bend. Q. Mazumder [4] and H. Zhang, Y. Tan and D. Yang [5] studied the deendence of the value and location of the erosive wear of the T-junction and the U-bend ie uon the velocity of transorted air and water, the velocity and size of articles by means of comuter simulation. It is found that the maximum erosive wear is about 40 below the lace of direct strikes of articles in the T-junction and the U-bend ie, and the lace of the maximum erosive wear of the T-junction deends on the discrete hase velocity. If the discrete hase velocity increases, the lace of the maximum erosive wear of the T-junction moves down the flow. If the air is transorted by the ieline, then with increasing the size of articles, the lace of the maximum erosive wear of the U-bend aroaches the flow inlet in the U-bend, and if the water is transorted by the ieline, then with increasing the size of articles, the lace of the maximum erosive wear of the U-bend moves away from the flow inlet in the U-bend. The same effects were observed for different velocities of oerating media. It was also discovered that air and water velocities do not have a significant imact on the location of the erosive wear of the U-bend. Z. Hongjun and L. Yuanhua [6] investigated the effects of ieline geometrical arameters, flow arameters and characteristics of a discrete hase () on the value of the erosive wear of nitrogen ielines bends by means of comuter simulation and the software ackage ANSYS Fluent. It is found out that the smaller the diameter of the ieline and the smaller the bending angle of the T-junction, the larger the flow rate; the greater the volume fraction of and the bigger diameter of the grain, the greater is the value of erosive wear of nitrogen ielines bends. I. Dorina [7] carried out similar studies in neumatic transort of anthracite owder, which is extremely abrasive. It is studied by means of comuter simulation that the value of the erosive wear of neumatic actuator bend deends on the ratio between the radius of its bending, the ie diameter and the air flow rate of anthracite owder. It is found out that the most significant factor that affects the value of erosion rate of the bend is the velocity of anthracite owder articles in the air flow. By means of comuter simulation H. Hadžiahmetović [8] and M. Tarek [9] comared the results of the erosive wear of neumatic actuator bends of round and square sections with exerimental data and made sure of their convergence in the laces of the maximum erosive wear. It was determined that a flow rate and article size have the greatest effect on the erosive wear. Very small articles (with the diameter less than 10 µm) move with the main flow and virtually do not hit the wall of the ieline because they are light. Usually they hit at small angles of attack and it does not lead to a significant erosive wear. Larger articles tend to hit the wall. Thus, the greater the flow rate and the larger articles, the greater the erosive wear. Information on the erosive wear of the shaed elements of comressor station manifold is received on the basis of the external insection by ultrasonic flaw detectors, requiring secial ermits, financial and time costs, excavation of underground sites of ielines. Erosive wear test of comressor station manifold shaed elements are not rovided by any Ukrainian regulations and exerts, who carry out these insections, define them based on their logical reasoning and their acquired exerience. These facts do not always allow revealing the laces of the maximum erosion that is no less imortant than the recise determination of the erosive wear. The objective of the study is to develo scientific and methodological foundations of comlex numerical modeling of erosive wear of comressor station manifold, identify laces of erosive wear of shaed elements and calculate the extent of erosive wear. 66 ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2

3 The study of erosive wear of the shaed elements of comressor station manifold of a gas ieline GCU GCU GCU 1 the internal flush-jointed T-junction with reinforcing atches ( OST [10]); 2 bend (Gas Secifications /1 [11]); 3 welded T-junction with reinforcing atches (OST [10]); 5 the ie ; 6 the ie ; 7 the ie Figure 1 Comressor station layout The largest number of ieline shaed elements (bends, T-junctions, reducers) is contained in comressor stations manifold (Fig. 1), underground gas storages, and gas distribution stations. The change in direction of roduct flow to 90º (excet for the bends at the inlet and outlet of the intube comartments) occurs in bends of comressor station manifold (Fig. 1). There are different schemes of gas movement in the T-junctions of comressor station manifold: gas moves through the T-junction 1 run-ie (Fig. 1) to the T-junction branch; gas moves through the T-junction 3 branch (Fig. 1) to the T-junction run-ie, where art of gas stream flows in one direction of the line, and the rest of gas in the oosite direction; gas moves through the T-junction 4 branch (Fig. 1) in either direction of the line. We know that natural gas transorted by ielines contains liquid and solid articles (contaminations). Gas ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2 67

4 Ya. V. Doroshenko, Т. І. Мarko, Yu. І. Doroshenko ensate, water, oil and other hydrocarbons belong to the liquid discrete hase. The rock,, slag, exfoliated from the inner wall of the ie and carried from well deosits, the roducts of in-tube corrosion belong to the solid discrete hase. There are different reasons for the resence of contaminants in the inner cavity of ielines. Firstly, it is the oor quality of gas urification in the fishery and comressor stations, liquids ensing from the gas stream at favorable thermodynamic itions while gas uming in the ieline, assing of bearing lubrication in gas uming units, oor cleaning of the inner cavity of the ieline before its exloitation. The chemical reaction between the ie metal and liquid ollution, accumulated in the lowered fields of ielines, lead to corrosion and formation of solid articles. When moving by the shaed elements of comressor station manifold, liquid and solid articles hit the wall of the ieline, leading to erosive wear of the ieline. For timely and quality insection of shaed elements of comressor stations manifold, and the imrovement of existing structures we should know the laces of their maximum erosive wear and forecast the value of their erosive wear. The erosive wear of shaed elements of comressor station manifold can be studied at the most by comuter simulation of three-dimensional turbulent flows by means of the ANSYS Fluent R17.0 Academic software. Mathematical models and numerical algorithms of this comlex meet international standards. To simulate the erosive wear in ANSYS Fluent there is laid the Lagrangian Discrete Phase Model (DPM). The basis of the Lagrangian aroach is the consideration of the motion of individual articles (or grous of articles) of the discrete hase. The Lagrangian DPM enables us to exlore the trajectory of discrete hase articles in the solid hase by solving the differential equation of article motion. The discrete hase can be solid, as bubbles in the liquid or as gas dros. The model allows for the two-way exchange of mass, momentum and energy of articles with the solid hase. The DPM model is used for small values of articles volume concentration because the interaction of articles with each other is indirectly taken into account. The advantage of the DPM model is that it allows us to accurately take into account the nature of the interaction of the discrete hase with the wall. In the model of interaction between the discrete hase and the wall there is the additional model of the wall erosion. In addition, it is much easier to take into account the seary decay of the discrete hase (in case of dros or bubbles) within the DPM model. The disadvantage of the DPM model is the limit of the local volume concentration of articles (less than 10 %). An integrated numerical simulation has three stages: simulation of the gas flow (solid hase) in the shaed elements of ielines; simulation of liquid and solid articles motion with shaed elements of ielines in the gas stream; calculation of the erosive wear of ielines shaed elements. The motion of a solid hase in ANSYS Fluent is simulated by numerical solution of equations describing the general motion of the gaseous medium. These are the Navier-Stokes equation (1), which exresses the law of momentum conservation (or Reynolds (2) if the flow is turbulent) and the continuity equation (3), which exresses the law of mass conservation ( ρui ) + ( ρuu i j ) = + t xj xi (1) u u i j + µ + + fi, x j xj x i ( ρui ) + ( ρuiu j ) + ( ρu i u j ) = t x j x j (2) u u i j = + µ + + f, xi x j x j x i ρ + ( ρuj ) = 0, (3) t x j where x i, x j are the coordinates; t is time; u i, u j are velocity comonents; ρ is the density of gas; µ is molecular dynamic viscosity of the gas; f is a term i that takes into account the effect of mass forces; is the ressure; u i are time-averaged values of velocity; u i are the comonents of velocity ulsation [12]. Boundary itions usually include the distribution of all comonents of velocity in the inlet section and the vanishing of the first derivatives (in the direction of flow) of velocity comonents in the outlet section. Pressure is only the first derivative in the equations, so you only need to indicate the ressure at any one oint of the comutational geometry. These equations are closed by two-arameter k ε (where k is the turbulence energy, ε is the rate of dissiation of the turbulence energy) turbulence model, which involves solving the following equations in ANSYS Fluent: transort of the turbulence energy k ( ρ k) µ t + ( ρ uk) = µ + k + µ ρε σ tg ;(4) t k transort equation for dissiation rate of the turbulence kinetic energy ε ( ) ρε µ 2 t ε ε + ( ρuε ) = µ + ε + C µ ρ σ 1 tg C2,(5) t k k ε where u is the flow rate of gas; µ is the turbulent t σ, k dynamic viscosity of gas; G is the mass flow; σ, ε C, 1 C are exerimentally obtained numeric 2 constants ( σ =1, k σ =1.3, ε C =1.44, 1 C =1.92). 2 The turbulence model k ε is the so-called "high Reynolds" model created on the basis of averaging the Navier-Stokes equations and designed to calculate turbulent rocesses. 68 ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2

5 The study of erosive wear of the shaed elements of comressor station manifold of a gas ieline The substance, which is resent in solid hase flow in the form of a discrete hase, does not form a continuum, and some articles interact with the continuous hase flow and with each other. For simulation of the discrete hase flow in a continuous hase there is alied the Lagrangian aroach in ANSYS Fluent, i.e. the movement of individual articles is tracked under the influence of the forces of the solid hase flow. It is believed that articles of the discrete hase are sheres. The forces influencing the article are caused by the difference of the article velocity and flow rate of the solid hase, and the dislacement of the continuous hase medium with this article. The equation of motion for this article was derived in [13] and has the following form m du dt πdρdu = 3πµ dccor ( u u ) dt 3 3 du u e π d ρ d π d + + F ( ρ ρ ) ω ( ω r ) 12 dt dt 6 3 πd ρ ( ω u ), (6) 3 where m is the article mass, u is the velocity of the article; d is the diameter of the article; 3 ρ is the density of the article; C is the coefficient of viscous cor resistance; F e is the external force acting on the article (such as gravity or strength of the electric field); ω is the angular velocity; r is the radius of the vector (in case of considering the movement in the relative frame of reference). The right side of the equation (6) is the sum of all forces acting on the article, exressed in terms of mass and acceleration of the article. The article inhibition is the first term in the right side due to viscous friction to solid hase flow according to Stokes' law. The se term is the force alied to the article, caused by the ressure dro, accelerated solid hase flow in the continuous hase, which surrounds the article. The third term is the force required to accelerate the weight of the solid hase in the volume, which is reressed by the article. These two terms should be considered when the density of the main hase is greater than the articles density. The fourth term ( F e ) is the external force that influences directly uon the article, such as the gravity or strength of the electric field. The last two terms are the centrifugal force and the Coriolis force, which take lace only if the motion is considered in the relative frame of reference. In addition, some additional forces should be sometimes considered in the right side (6) (e.g. in case of significant temerature difference in the flow). The equation (6) is a differential equation of the first order, in which the only unknown quantity is the article velocity u, and the argument is time t. The flow rate of the solid hase u is considered as a known one and it is defined by solving the equations (1), (2), (3) at all oints of the medium. The initial data is the article osition at the initial time in addition to its size and roerties. There is also indicated what should occur when articles hit the wall or another article. The terms, which contain u, are moved on the left side of equation (6) to erform the calculation. The velocity and osition of the article in each successive moment of time is determined by numerical integration of all the other terms of the equation (6) over time with some ste t. The algorithms, imlemented in ANSYS Fluent, make it ossible to simulate the imact of the discrete hase on the flow of the continuous hase. In the first aroximation the density and viscosity of the continuous hase and some other values are multilied by (1 α ), where α is the secific volume occuied by the articles. In this case the changes in mass, momentum and energy of the articles are calculated at every ste of the time, and these changes are added according to the equation of mass conservation (2), ulse (1) and the energy for the flow of the continuous hase. Thus, the calculation of the continuous hase flow and article motion is erformed jointly. If the flow of the continuous hase is turbulent, the trajectory of articles is not deterministic, because it deends on the intensity and direction of turbulent fluctuations. Several boundary itions, which corresond to different events that occur when the articles hit the wall, are imlemented in modern software roducts: beating off as a result of elastic or inelastic hitting, sticking to the wall, sliding along the wall (deending on the hysical roerties and the angle of attack), assing through the wall (if the wall is orous), etc. Under certain itions, there is also the ossibility of slitting and merging simulation of water drolets or gas bubbles when they hit each other [14]. The calculation of the erosive wear is made using the Finney model, develoed for rigid lastic materials by analyzing the equations of motion of a article during its hitting the surface, by means of Ansys Fluent software. To estimate the amount of the surface material loss caused by the article hitting there is investigated the trajectory of the article motion. The following assumtions were made: cutting the surface is lastic deformation; cracks do not extend in front of the article, which cuts the surface; material delamination is caused by the cutting action of articles. This model can not be used for brittle materials. According to the Finney model, the secific erosion rate (the surface mass removed from a surface unit er a unit of time) on the surface equals n E = Ku f θ, (7) ( ) where K is the coefficient that deends on the elastic modulus of the wall material and the article density; n is the exonent, which deends on the wall material (it varies from 2.3 to 2.5 for steel); f ( θ ) is a dimensionless function that takes into account the ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2 69

6 Ya. V. Doroshenko, Т. І. Мarko, Yu. І. Doroshenko Figure 2 The comuted volumetric mesh imact of the angle of attack θ on the rate of the erosive wear. This function can be of different forms. For instance, it has the following form in [15] 2 Аθ + Вθ, if θ ϕ ; f ( θ ) = (8) 2 2 Хсos θ sin ( Wθ ) + Y sin θ + Z, if θ > ϕ, where А, B, W, X, Y, Z, ϕ are emirical coefficients. Three-dimensional models of the shaed elements of comressor station manifold, the design and geometric dimensions of which are identical to industrial designs (Fig. 1), are drawn in a Design Modeler geometric module of Ansys Fluent. Geometry of shaed elements meets the requirements of the standard OST [10] and Gas Secifications /1 [11], which are widely sread in the gas industry. Moreover, shaed elements were drawn with surrounding ies areas, geometric dimensions of which meet secifications. Pie wall thickness was calculated based on the ressure in the lace of shaed element location and in view of the fact that the ielines of comressor station manifold belong to the highest category. The estimated volumetric Automatic mesh was generated in Meshing Fluent's rerocessing technology the volume was filled with aralleleieds, and if it was found imossible triangular risms were alied. The size of mesh elements was set as 0.09 m (Fig. 2). To better describe the near-boundary layer there was created the near-wall Inflation Layer with the lattice height of 0.09 m and the number of lattice layers 3 (Fig. 2). The calculation results were qualitatively visualized for this size of mesh elements. When the rogram ANSYS Fluent was oened, double accuracy was set. A standard two-arameter model of turbulence k ε was chosen in the rogram ANSYS Fluent, Models menu, Viscous tab. This model has three versions (Standard, RNG and Realizable). Realizable modification was chosen in the field of otions of the turbulence models. The turbulence model k ε makes it imossible to fully simulate the nearwall effects. Therefore the near-wall functions were used for the quality modeling of flows in ANSYS Fluent. Enhanced Wall treatment was chosen. The natural gas was chosen from the data basis of ANSYS Fluent and given to the comuted mesh. To solve the roblems of gas dynamics we should consider gas comressibility. That is why the deendence of gas density on the flow arameters was set. For this urose, the item Real-gas is chosen in the Density list, Materials menu. Besides, the equation of energy is automatically added to the equations being solved and gas temerature should be secified when boundary itions are set. Steel is chosen as the material of the wall in the ANSYS Fluent database. The Lagrangian discrete hase model is chosen in the menu Models to secify features of the discrete hase. The Set Injection Proerties Window is oened in an Injection tab, where the surface of the articles suly (flow inut), articles velocity and temerature at the inlet, the mass flow of articles, the maximum and minimum diameter of article diameter range were chosen for each discrete hase (at first for the liquid and then for the solid one). The velocity and temerature of discrete hase articles at the inut of the shaed element was set as equal to the velocity and temerature of the continuous hase at the inlet. The velocity of the continuous hase at the shaed element inlet was determined by calculating the gas motion dynamics by shaed elements of comressor station manifold in ANSYS Fluent without accounting for the flow of the discrete hase [16]. The temerature of the continuous hase corresonds to the oerating itions of trunk gas ielines. Moisture content of natural gases deends on the temerature and ressure of gas and it is determined by nomogram given in [17, Fig. 7]. The mass flow rate of the liquid hase was calculated based on the values of natural gas moisture and continuous hase volume flow. According to [18] the mass flow of solids must not exceed g/m 3 in the natural gas. According to [19] the natural gas, which is fed into gas distribution oints, contain much more imurities than g/m 3. As the [20, Table 2] indicates, the weight of imurities can comrise to g/m 3 in the natural gas. The weight of imurities in the natural gas was assumed to be equal to g/m 3 at comressor station inlet before the urification system. The mass flow of the solid hase was calculated on the basis of the values of the mass of 70 ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2

7 The study of erosive wear of the shaed elements of comressor station manifold of a gas ieline solids in the natural gas and continuous hase volume flow. When the natural gas asses through the urification system at the comressor station, the moisture and solid articles content is reduced. Accordingly, the mass flow of liquid and solid hases was reduced via shaed elements of a comressor station, located after the urification system in the flow direction. The maximum diameter of the liquid hase drolets equals according to [20] 2 5 max 2Din ρgas d =, 3 (9) ρ ( k We) 5 f where D in is the internal diameter of the gas ieline; k f is the drolet drag coefficient, k f = 0.4 ; ρ gas is the density of gas; ρ is the density of the liquid hase; We is a dimensionless arameter the Weber number ρ We = 2 gasu Din, (10) where is the surface tension force of the liquid hase on the brink of gas. The strength of the surface tension of the liquid hase-gas interface deends on the ressure and temerature of gas and it is determined by [21]. The maximum diameter of the solid hase articles was taken as equal to the grain size of fine. When natural gas asses through the urification system, diameter of liquid dros and solid hase articles reduces, that is why the maximum diameter of discrete hases was set smaller than it was calculated for the comressor station shaed elements, located after the urification system in the direction of the flow. The Discrete Random Walk Model otion was chosen in Turbulent Disersion tab, Set injection roerties window to account for the imact of the turbulent flow on the discrete hase. The Erosion/Accretion otion was marked in the Physical Models tab of the Lagrangian Discrete Phase model window to estimate the erosive wear. In the Materials menu a corresonding material was chosen for each discrete hase of the ANSYS Fluent database. Because ensate, water and dominate in the natural gas, transorted by ielines, we have chosen the ensate of density ρ = 960 kg/m for the liquid hase, and the of density 3 ρ = 2800 kg/m for solid articles. Having set materials and characteristics of each discrete hase, the following boundary itions were set in the Boundary Condition menu. Mass flow inlet was set at the inlet of the shaed element, and Pressure outlet was set at its outlet. When we set these boundary itions of turbulence at the inlet of the shaed element, gas flow distribution is even in the cross section with the tyical turbulent distribution diagram of gas flow rates. In addition to the values of the mass flow there were set the Turbulence Intensity 5%, Hydraulic 3 Diameter and gas temerature at the inlet in the Mass flow inlet window. When we set the ressure at the outlet, there were also set the Turbulence Intensity 5 %, Hydraulic Diameter and the gas temerature at the outlet in the Pressure outlet window. Tyically, the turbulence intensity does not exceed 20 %, but in most cases it is in the range of 1 to 10 %. The flow is considered comletely turbulent when the turbulence intensity equals 5 %. Wall boundary ition and the equivalent roughness coefficient of ies h s = 0.03 mm were also set. In DPM Tab of the Wall boundary ition we have chosen the tye of boundary ition for the Discrete Phase Reflection reflection of the discrete hase article from the wall (the angle of incidence equals to the angle of reflection). Having set boundary itions we tuned arameters of the solver. The Solution methods tab was chosen in the roject tree, where the connection algorithm of gas motion and continuity equations were chosen in the Pressure-Velocity Couling area. Then we chose Couled algorithm, which was considered a searate tye of the Couled ressure-based solver. To connect the fields of velocity and ressure there was alied the slitting algorithm, and for other arameters the setting algorithm. This algorithm makes it ossible to get qualitative consistent results for virtually all classes of roblems. To imrove the stability of solution, the Courant number should be reduced to 50. Also, when arameters of the solver were set, the se order of accuracy was chosen for all equations. The Navier-Stokes equations are solved by numerical method. Besides, differential equations are relaced by algebraic equations that describe the change in the variable between several neighboring oints in an arbitrary mesh comonent. Analogous equations are solved by iterative method. After each iteration, some values of variables are calculated. They are substituted into the original equations, written in the following form f (, T, ρ, x, y, z, v, w,...) = 0. Due to the fact that the solution is aroximate (since the algebraic analogue is solved, not the differential equation), there is obtained that f (, T, ρ, x, y, z, v, w,...) = R during the substitution of the calculation results. The value of R is called the discreancy and it is the criterion for the rocess of solution. Obviously, the closer the value of R is to zero, the closer the solution of the discrete analog to the solution of the outut differential equation. The solution of the roblem can be considered comleted if the following itions are met: the difference of the cost of a working body between inut and outut limits is close to zero and changes little from iteration to iteration; errors of all equations during calculation reach the values lower than the recommended limit; errors of all equations do not significantly change during the calculation. The error of all equations, excet energy equation, was set as R = The error for the energy equation was set as 7 R = ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2 71

8 Ya. V. Doroshenko, Т. І. Мarko, Yu. І. Doroshenko The simulation results were visualized in ANSYS Fluent Academic ostrocessor, which heled to identify the laces of the most intense liquid and solid articles hits of the walls of shaed elements and laces for maximum erosive wear at shaed elements contours. For a better understanding of erosive wear of shaed elements of comressor station manifold one should read the study of the motion dynamics of multihase flows through shaed elements of gas ieline comressor station manifold [22] and studies of the gas motion dynamics by shaed elements of comressor station manifold [16]. Let us consider the comressor station manifold at its inlet where the welded T-junction with reinforcing atches is installed (Fig. 1), and where the gas is moving by the T-junction 1 run-ie (Fig. 1) to the T-junction branch. The internal flush-jointed T-junction has an outside diameter of the run-ie and the branch Dout. r. = Dout. b = 1420 mm, the nominal wall thickness of the run-ie and the branch δ. = δ = 28 mm. The inner diameter of the run-ie and the branch equal Din. r. = Din. b = 1364 mm. Geometry of the T-junction meets the requirements of the standard OST [14]. The shaed element was drawn with the 3 meter surrounding areas of the ieline and the outer diameter D out = 1420 mm. Pie wall thickness was calculated, and then the ies were chosen from the technical secifications, the nominal thickness of which equals δ = 18.7 mm. The inner diameter of the ie is D = mm and it is equal to the hydraulic in diameter, which was set in ANSYS Fluent. To study the erosive wear of the T-junction 1 comressor station manifold (Fig. 1), where the gas is moving by the T-junction run-ie to the T-junction branch, there were set the following boundary itions for the continuous hase in ANSYS Fluent rerocessor (Fig. 3, a) 1) inlet: mass flow r М in = kg/s; hydraulic diameter D in = m; gas temerature Т in = 297 К; 2) outlet: ressure Р out = Pа; hydraulic diameter D out = m; gas temerature Т out = 297 К. There were set characteristics of every Discrete Phase at the inlet in Set injection roerties Windows of the Discrete Phase Model (Fig. 3, а): 1) liquid hase (ensate): velocity υ = 13.1 m/s; temerature Т = 297 К; mass flow М = 0.58 kg/s (according to nomogram given in [17, Fig. 7] moisture content of the 3 natural gas is 0.6 g/m when the ressure of the solid b hase equals 4.9МPа and the temerature 297 К. The mass flow of the liquid hase is calculated based on the volume flow rate of the continuous hase); max min maximum diameter d = 0.34 mm; minimum diameter d = 3 mm; 2) solid hase (): velocity υ = 13.1 m/s; temerature Т = 297 К; mass flow М = kg/s (mass of solids in the natural gas at a comressor station inlet before the 3 urification system is assumed to be equal g/m. The mass flow of the solid hase is calculated based on the volume flow rate of the continuous hase max maximum diameter d = 0.12 mm; min 3 minimum diameter d = 0.1 mm. When the gas flow asses through the internal flush-jointed T-junction with discrete hases, it changes its direction and flows from the T-junction run-ie to the T-junction branch (Fig. 3). The simulation results were visualized in ANSYS Fluent Academic ostrocessor by constructing concentration fields of the discrete hase (Fig. 3, b) and the fields of erosive wear rate (Fig. 3, c, d) on T-junction contours. As can be seen from concentration fields of the discrete hase on T-junction contours (Fig. 3, b), liquid and solid articles hit most intensively the wall of the uer art of the T-junction run-ie to the right of the branch and the walls of the T-junction branch and the adjacent ie to the right (lace of discrete hases hittings extends from the mid of the T-junction branch to more than 3 meters from the annular weld in the direction of the roduct`s motion by the ie adjacent to the branch). The maximum concentration of the discrete hase on contours of the T-junction run-ie and branch equals 1.7 kg/s. It is clear from the erosive wear fields on T-junction contours (Fig. 3, c, d) that the most intensive erosive wear of the T-junction is in the uer art of its rine-ie, to the right of the branch at the distance of 0.1m from the T-junction branch. The maximum rate 8 2 of erosive wear is equal to kg/(m s). At this rate of erosive wear the wall becomes thinner at the seed of 0.158mm/year. The erosive wear of less intensity is on the right of the branch and the run-ie. The lace of erosive wear extends from the mid of the branch at the distance of 1.5 m from the annular weld in the direction of the roduct`s motion by the ie adjacent to the branch. The maximum rate of erosive 8 2 wear is equal kg/(m s) at this oint. The wall becomes thinner at the seed of 0.099mm/year at this erosion rate. Let us consider the comressor station manifold at its inlet where the bend with the rotation angle of 90 is installed (Fig. 1). An outside diameter of the ie bend is D out. bend = 1420 mm, the nominal wall thickness of 72 ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2

9 The study of erosive wear of the shaed elements of comressor station manifold of a gas ieline 1 the internal flush-jointed T-junction with reinforcing atches (ОST [10]); 2 ie ; а design diagram; b concentration fields of the discrete hase on contours; c, d erosive wear fields on contours Figure 3 Simulation results of the erosive wear of the T-junction at the comressor station inlet, where the gas flows through the T-junction run-ie to the T-junction branch the ie bend is δ = 24 mm, and the inner diameter bend of the ie bend equals D in. bend = 1372 mm. Geometry of the bend meets the requirements of Gas Secifications /1 [11]. The shaed element was drawn with the surrounding areas of the ieline 3 meters in length and the outer diameter D out = 1420 mm. Pie wall thickness was calculated, and then the ies were chosen from the technical secifications, the nominal thickness of which equal δ = 18.7 mm. The inner diameter of the ie is D in = mm and it is equal to the hydraulic diameter, which was set in ANSYS Fluent. To study the erosive wear of the bend 2 of comressor station manifold (Fig. 1), there were set the following boundary itions in ANSYS Fluent rerocessor: 1) inlet: mass flow М in = kg/s; hydraulic diameter D in = m; gas temerature Т in = 297 К; 2) outlet: ressure Р out = 4.93 МPа; hydraulic diameter D out = m; gas temerature Тout = 297 К. Due to the fact that the bend 2 was laced near the internal flush-jointed T-junction 1 (Fig. 1), characteristics of every Discrete Phase at the bend inlet 2 (Fig. 4, a), which were set in Set injection roerties Windows of the Discrete Phase Model, were the same as at the inlet of these T-junction. The simulation results were visualized in ANSYS Fluent Academic ostrocessor by constructing concentration fields of the discrete hase (Fig. 4, b) and the fields of erosive wear rate (Fig. 4, c, d) on the bend contours. As can be seen from concentration fields of the discrete hase on bend contours (Fig. 4, b), liquid and solid articles hit most intensively the wall on its convex side. The lace of hit extends from the mid of the bend to the distance of 1.5 m meters from the annular weld in the direction of the roduct`s motion through the ie adjacent to the bend. The most intensive hitting occurs on the convex side of the bend where the gas flows and at the beginning of the adjacent ie (the maximum concentration of the discrete hase on contours equals 1.4kg/s ). It is clear from the erosive wear fields on T-junction contours (Fig. 4, c, d) that the most intensive ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2 73

10 Ya. V. Doroshenko, Т. І. Мarko, Yu. І. Doroshenko 1 bend (Gas Secifications /1 [11]); 2 ie ; а design diagram; b concentration fields of the discrete hase on contours; c, d erosive wear fields on contours Figure 4 Simulation results of the erosive wear of the bend at the comressor station inlet erosive wear is on the convex side of the bend where the gas stream flows between an angle of 60 and 90 of the bend and at the beginning of the ie, which is welded to the bend, at the distance of 0.1 m in the direction of the roduct motion. The maximum rate of erosive wear 8 2 is equal to kg/(m s). At this rate of erosive wear the wall becomes thinner at the seed of 0.08 mm/year. The rate of erosive wear significantly decreases at the beginning of the ie welded to the bend, although the intensive hittings of liquid and solid articles take lace at the distance of 1.5 m from the annular weld. It is caused by the decrease of the angle of attack when the lace of hitting moves away from the annular weld. Let us consider the comressor station manifold at the outlet of the gas treatment unit where the welding T-junction 3 with reinforcing atches is installed (Fig. 1), and where gas moves by the T-junction branch and directs in two sides of the T-junction run-ie (gas comressor unit GCU 1 and GCU 2). An outside diameter and the nominal wall thickness of the run-ie and branch equal D out. r. = 1020 mm, D. = 529 mm, out b δ r. = 18 mm, δ b = 10 mm, resectively. In this case the inner diameter of the run-ie and branch equal D in. r. = 984 mm, D in. b = 509 mm, resectively. Geometry of the T-junction meets the requirements of the standard ОSТ [14]. The shaed element was drawn with the surrounding areas of the ieline. The length of the ieline area, adjacent to the branch, is 1.7 m, and the outer diameter, the nominal wall thickness and the inner diameter are D = 529 mm, δ = 7 mm, D in = 515 mm, resectively. The inner diameter of the ieline areas adjacent to the T-junction is equal to the hydraulic diameter secified in ANSYS Fluent. To study the erosive wear of the T-junction 3 of comressor station manifold (Fig. 1), where gas moves by the T-junction branch and directs in two sides of the T-junction run-ie, there were set the following boundary itions in ANSYS Fluent rerocessor: 1) inlet: mass flow М in = 119 kg/s; hydraulic diameter D in = m; gas temerature Т in = 297К; 2) outlet 1: ressure Р out1 = Pa; out 74 ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2

11 The study of erosive wear of the shaed elements of comressor station manifold of a gas ieline 1 the internal flush-jointed T-junction with reinforcing atches (ОST [10]); 2 ie ; а design diagram; b concentration fields of the discrete hase on contours; c, d erosive wear fields on contours Figure 5 Simulation results of the erosive wear of the comressor station manifold T-junction at the urification unit outlet, where the gas flows through the T-junction branch in two directions of the T-junction run-ie hydraulic diameter D out1 = m; gas temerature Тout1 = 297 К; 3) outlet 2: ressure Р out 2 = Pa; hydraulic diameter D out2 = m; gas temerature Т out 2 = 297 К. To determine the ressure at the outlet of the T-junction (Fig. 5, a) there was calculated the art of the flow (mass flow), which is directed toward the GCU 1, and which toward GCU 2 (Fig. 1). Based on the values of the mass flow at the outlet of the T-junction run-ie (Fig. 5, a) there were calculated the following values in ANSYS Fluent rogram comlex: the T-junction for various ressures at the outlet 1 and outlet 2 of the T-junction run-ie until there were determined the ressures, for which mass flows were equal to the re-calculated at the T-junction run-ie outlet. The ressures were equal to Р out1 = Pa, Р out2 = Pa. Corresonding mass flows amounted M out1 = 70.4 kg/s, M out2 = 48.6 kg/s. There were set characteristics of every Discrete Phase at the inlet in Set injection roerties Windows of the Discrete Phase Model (Fig. 5, а): 1) liquid hase (ensate): velocity υ = 16.6 m/s; temerature Т = 297 К; mass flow М = kg/s; max min maximum diameter d = 0.1 mm; minimum diameter d = 0.1 mm; 2) solid hase (): velocity υ = 16.6 m/s; temerature Т = 297 К; mass flow М 4 = kg/s; max min maximum diameter d = 0.1 mm; minimum diameter d = 0.1 mm. During the movement of gas with discrete hases by the T-junction 1 (Fig. 5), there occurs bifurcation of gas flow and it is directed in two oosite directions of the T-junction run-ie. The calculation results are visualized in ANSYS Fluent ost-rocessor by constructing concentration fields of the discrete hase (Fig. 5, b) and the fields of erosion rate (Fig. 5, c, d) on the T-junction contours. As can be seen from concentration fields of the discrete hase on the T-junction contours (Fig. 5, b), the lace of the most intensive hitting of liquid and solid ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2 75

12 Ya. V. Doroshenko, Т. І. Мarko, Yu. І. Doroshenko 1 the internal flush-jointed T-junction with reinforcing atches (ОST [10]); 2 ie ; а design diagram; b concentration fields of the discrete hase on contours; c, d erosive wear fields on contours Figure 6 Simulation results of the T-junction erosive wear at the outlet of the gas treatment unit 1, where the gas flows through the T-junction branch in one direction of the T-junction run-ie articles has the form of a ring with a width of t =1.5 m, curved by the inner surface of the T-junction run-ie and adjacent ies. The maximum concentration of a discrete hase is insignificant on the T junction run-ie contours, because the discrete hase is disersed uon a large internal surface area and is 0.064kg/s in the T-junction run-ie. As can be seen from concentration fields on the T-junction contours (Fig. 5, c, d), the lace of the most intensive T-junction erosive wear is in the T-junction run-ie, oosite to the branch and also has an annular form with a width of b = 1.5 m, curved by the inner surface of the T-junction run-ie. The maximum erosive wear is insignificant and equals kg/(m s). At this rate of erosive wear the wall becomes thinner at the seed of mm/year. Let us consider the comressor station manifold at the outlet of the gas treatment unit 1 where the welding T-junction 4 with reinforcing atches is installed (Fig. 1), and where gas moves through the T-junction branch and directs in one side of the T-junction runie. An outside diameter of the run-ie and branch is Dout. r. = Dout. b = 1020 mm, and the nominal wall thickness of the run-ie and branch equal δr. = δb = 20 mm. The inner diameter of the run-ie and the branch equals D.. = D. = 980 mm. in r Geometry of the T-junction meets the requirements of the standard ОSТ [14]. The shaed element was drawn with the surrounding areas of the 3-meter ieline and the outer diameter D out = 1020 mm. The ie wall thickness was calculated, and then the ies were chosen from the technical secifications, the nominal thickness of which equals δ = 12.3 mm. The inner diameter of the ies is D in =995.4mm and it is equal to the hydraulic diameter, which was set in ANSYS Fluent. To study the gas motion dynamics through the T-junction 4 of the comressor station manifold (Fig. 1), where the gas moves through the T-junction branch to one direction of the T-junction run-ie, there were set the following boundary itions in ANSYS Fluent rerocessor (Fig. 6, a): 1) inlet: mass flow М in = kg/s; hydraulic diameter D in = m; gas temerature Т in = 313К; 2) outlet: ressure Р out = 6.61 МPа; in b 76 ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2

13 The study of erosive wear of the shaed elements of comressor station manifold of a gas ieline hydraulic diameter D out = m; gas temerature Т out = 313К. The Discrete Phase Model was set with characteristics of every Discrete Phase at the inlet in Set injection roerties Windows (Fig. 6, а): 1) liquid hase (ensate): velocity υ = 10 m/s; temerature Т = 297 К; mass flow М = kg/s; max min maximum diameter d = 0.1 mm; minimum diameter d = 1 mm; 2) solid hase (): velocity υ = 10 m/s; temerature Т = 297 К; mass flow М 4 = 5 10 kg/s; max min maximum diameter d = 0.1 mm; minimum diameter d = 0.1 mm. When the gas flow with a Discrete Phase runs through the T-junction 4 of the comressor station manifold, laced at the outlet of the gas treatment unit 1 (Fig. 1), it changes its direction and runs from the branch to the right side of the T-junction run-ie (Fig. 6). The simulation results were visualized in ANSYS Fluent Academic ostrocessor by constructing concentration fields of the discrete hase (Fig. 6, b) and the fields of erosive wear rate (Fig. 6, c, d) on the T-junction contours. As can be seen from concentration fields of the discrete hase on T-junction contours (Fig. 6, b), liquid and solid articles hit most intensively the wall of the T-junction run-ie oosite to the branch. The lace of hit is ear shaed. The annular art of the ear shaed lace of hit almost coincides with the rojection of the T-junction branch on the inner wall of the run-ie. An elongated art of the ear-shaed lace of hit extends in the direction of the roduct`s motion through the T-junction line, aroximating to internal flush-jointed ie at the distance of 0.3 m. The maximum concentration of a discrete hase on the T-junction contours is 0.21 kg/s. It is clear from the erosive wear fields on T-junction contours (Fig. 6, c, d) that the lace of the most intensive erosive wear of the T-junction coincides with the lace of the most intensive hit of liquid and solid articles to the wall and is ear shaed and of the same size. The maximum rate of erosive wear is equal 9 2 to kg/(m s). At this rate of erosive wear the wall becomes thinner at the seed of mm/year. Conclusions Based on the Lagrangian aroach there was studied for the first time the erosive wear of shaed elements of comressor station manifold of the gas ieline, the design and geometric dimensions of which are identical to roduction rototyes, using ANSYS Fluent Academic software. There are identified the laces of intensive hits of ensate drolets and solid articles, carried by the gas flow, to the ieline wall, laces of the maximum erosive wear of bends, T-junctions of comressor station manifold and adjacent ieline sections, and there is calculated the erosion rate. It was found out that the most intensive erosive wear of the bends is on their convex side where the gas stream flows between an angle of 60 and 90 of the bend and at the beginning of the ie, which is welded to the bend. The lace of erosive wear deends on the scheme of the gas motion through the T-junction. If gas flows through the T-junction run-ie to the T-junction branch, the most intensive erosive wear is in the uer art of the run-ie in the side of the branch oosite to the inlet cross section, and it is oosite to the inlet cross section side in the branch and adjacent ie. If gas flows through the T-junction branch to the two sides of the T-junction run-ie, the most intensive erosive wear is in the T-junction run-ie in the oosite to the inlet cross section side of the branch and it is of the annular form curved by the inner surface of the T-junction runie. If gas flows through the T-junction branch in one direction of the T-junction run-ie, the most intensive erosive wear of the T-junction is ear shaed and laced oosite to the T-junction branch. These studies oen the rosect for a full and comrehensive investigation on the shaed elements strength of comressor station manifold. References [1] Abdolkarimi, V & Mohammadikhah, R 2013, CFD modeling of articulates erosive effect on a commercial scale ieline bend, ISRN Chemical Engineering, vol. 2013, [2] Abdua, A 2011, Estimating erosion in oil and gas ie line due to resence, Karlskrona, Sweden. [3] Azimian, M & Bart, H 2014, Investigation of hydroabrasion in slurry ieline elbows and T junctions, Journal of Energy and Power Engineering, no. 8, [4] Mazumder, Q 2012, Effect of Liquid and Gas Velocities on Magnitude and Location of Maximum Erosion in U Bend, Journal of Fluid Dynamics, no. 2, [5] Zhang, H, Tan, Y & Yang, D 2012, Numerical investigation of the location of maximum erosive wear damage in elbow: Effect of slurry velocity, bend orientation and angle of elbow, Powder Technology, no. 217, [6] Hongjun, Z, Yuanhua, L & Guang, F 2013, Numerical analysis of flow erosion on discharge ie in nitrogen drilling, Advances in Mechanical Engineering, vol. 2013, [7] Dorina, I 2012, Reduction of ie wall erosion by creating a vortex flow in anthracite owder neumatic transort for ower lants, International conference on renewable energies and ower quality (ICREPQ 12), Santiago de Comostela: Euroean Association for the Develoment of Renewable Energies, Environment and Power Quality (EA4EPQ). [30 March 2012]. [8] Hadžiahmetović, H, Hodžić, N, Kahrimanović, D & Džaferović, E 2014, Comutational fluid dynamics (CFD) based erosion rediction model in elbows, Technical Gazette 21, no. 2, ISSN Journal of Hydrocarbon Power Engineering. 2016, Vol. 3, Issue 2 77