Effect of Liquid Level on Gas Carry-Under in GLCC Compact Separators

2018 ◽  
Author(s):  
Srinivas Swaroop Kolla ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Swirling Flow ◽  
Flow Behavior ◽  
Operating Conditions ◽  
Liquid Level ◽  
Experimental Investigations ◽  
Level Control ◽  
Oil Flow ◽  
Control Configuration ◽  
Carry Over ◽  
The Stability

Gas Carry-Under (GCU) is one of the two undesirable phenomena that occurs in the GLCC©1 (Gas-Liquid Cylindrical Cyclone) separators. Initial studies have shown that maintaining liquid level below the inlet of the GLCC© under control configuration affects the GCU in GLCC©. Also, it has been hypothesized that effective formation of vortex that is formed in the lower part of the GLCC©, or a stable gas core enhances the separation of gas entrained in the liquid. However, there has not been a systematic study on the effect of liquid level and the stability of the vortex on the GCU. This detailed and extensive experimental study attempts to fill that gap, investigating the effect of different liquid levels maintained below the inlet on the GCU. These studies are performed under the NOC (Normal operating Conditions) below the OPEN for liquid carry-over using control configuration to maintain the liquid level in the GLCC©. This study focuses on measuring the cumulative GCU in the liquid leg of the GLCC© over a period of time. The experimental investigations for GCU are conducted in a state of the art experimental facility for air-water and air-oil flow incorporating pressure and level control configurations. The experiments were carried out using a 3″ diameter GLCC© equipped with gas trap sections to measure simultaneously the GCU in the liquid leg of the GLCC©. The equilibrium liquid level is controlled at 4 different settings starting at 6″ below the GLCC© inlet and increasing to 2 feet below the inlet. It has been observed that the liquid level has tremendous effect on the complex swirling flow behavior in the lower part of the GLCC© and vortex stability, which in turn affects the GCU in the liquid leg of the GLCC©. Also, it has been noted that the liquid level has a significant effect on the Gas Void-Fraction in the liquid leg of the GLCC©, which is a critical parameter for multiphase pump operations.

Gas Carry-Under in GLCC for Separated and Recombined Outlet Configurations

2018 ◽  
Author(s):  
Srinivas Swaroop Kolla ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Volume Fraction ◽  
Swirling Flow ◽  
Control Strategies ◽  
Flow Behavior ◽  
Jet Impingement ◽  
Test Facility ◽  
Experimental Investigations ◽  
Level Control ◽  
Complex Flow ◽  
Control Configuration

Gas Carry-Under (GCU) is one of the undesirable phenomena that exists in the GLCC©1 even within the Operational Envelope (OPEN) for liquid carry-over. Few studies that are available on GLCC© GCU have been carried out when the GLCC© is operated in a metering loop configuration characterized by recombined outlets. In such configurations the gas and the liquid outlets of the GLCC are recombined downstream which acts as passive level control. However, studies have shown that the GLCC© OPEN increases significantly when active control strategies are employed. There has not been a systematic study aimed at analyzing the effect of control on the GCU in the GLCC. This study compares the previously published GLCC GCU swirling flow mechanism under recombination outlet configuration with data taken under the separated outlet configuration (control configuration). Experimental investigations for GCU are conducted in a state-of-the-art test facility for air-water and air-oil flow incorporating pressure and level control configurations. The experiments are carried out using a 3″ diameter GLCC© equipped with 3 sequential trap sections to measure simultaneously the Gas Volume Fraction (GVF) and gas evolution in the lower part of the GLCC. Also, gas trap sections are installed in the liquid leg of the GLCC© to measure simultaneously the overall GCU. The liquid level was controlled at 6″ below the GLCC© inlet for all experiments using various control strategies. Tangential wall jet impingement is the cause for entrainment of gas, thereby leading to GCU. 3 different flow mechanisms have been identified in the lower part of the GLCC and have significant effect on the GCU. Viscosity and surface tension are observed to affect the GCU. The extensive acquired data shed light on the complex flow behavior in the lower part of the GLCC© and its effect on the GCU of the GLCC©.

Experimental and Numerical Analysis of Pressure Pulsations and Mechanical Deformations in a Centrifugal Pump Impeller

2011 ◽  
Author(s):  
Stefan Berten ◽  
Sebastian Hentschel ◽  
Karin Kieselbach ◽  
Philippe Dupont
Keyword(s):  
Boundary Conditions ◽  
Flow Behavior ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Pressure Waves ◽  
Centrifugal Pumps ◽  
Pressure Pulsations ◽  
Load Pressure ◽  
Part Load

Deformations, mechanical stresses and vibrations in centrifugal pumps are the result of pressure fluctuations, which are acting as excitation forces. When a pump operates at its optimum, the pressure pulsations are at minimum, but for a pump operating in part-load, pressure pulsations increase and subsequent vibration and deformation levels increase. In a recent experimental research, the pressure pulsations and the resulting structural stresses in the last stage impeller of a multistage pump have experimentally investigated for different operating conditions [1]. The experimental investigations have been complemented by transient numerical simulations using a commercial CFD code and structural analysis using the pressure pulsations resulting from the CFD code as boundary conditions. In the present study, a validation of these CFD and FEM simulations is presented. The analysis has been performed in three steps. In the first step, the transient CFD results for different load cases are analyzed and compared with the experimental results in order to evaluate the CFD simulations. In the second step the time domain pressure pulsation data are post-treated and decomposed into a series of rotating pressure waves. These pressure waves are then applied as boundary conditions to an FEM model and one full impeller revolution is simulated as steady calculations for 72 angular positions. The pressure pulsations in the best efficiency point are regularly distributed in space and time and dominated by rotor-stator-interaction. For part-load operation, the pressure distribution becomes more and more unsteady. The CFD results for part load exhibit stationary stall in the diffuser for a flow rate relative to best efficiency point of q* = 0.9 and unsteady stall behavior for a q* = 0.8. While the numerical CFD results agree well with experimental data for q* = 1 and q* = 0.9, at lower part load (q* = 0.8) the CFD didn’t reproduce the experimentally observed flow behavior, especially the rotating stall. The FEM results at design conditions show relatively low tangential stresses at the impeller outlet, which agree well with the measured deformations and stresses.

Unsteady Aerodynamic Blade Excitation at the Stability Limit and During Rotating Stall in an Axial Compressor

2006 ◽  
Author(s):  
Ronald Mailach ◽  
Konrad Vogeler
Keyword(s):  
Gas Turbines ◽  
Axial Compressor ◽  
Stability Limit ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Momentum Exchange ◽  
Stall Inception ◽  
The Stability ◽  
Force Excitation

The stable operating range of axial compressors is limited by the onset of rotating stall and surge. These flow conditions endanger the reliability of operation and have definitely to be avoided in compressors of gas turbines. However, there is still a need to improve the physical understanding of these flow phenomena to prevent them while utilizing the maximum available working potential of the compressor. This paper discusses detailed experimental investigations of the rotating stall onset with the main emphasis on the aerodynamic blade excitation in the Dresden four-stage Low-Speed Research Compressor. The stall inception, which is triggered by modal waves, as well as the main flow features during rotating stall operation are discussed. To investigate the unsteady pressure distributions, both the rotor and the stator blades of the first stage were equipped with piezoresistive pressure transducers. Based on these measurements the unsteady blade pressure forces are calculated. Time-resolved results at the stability limit as well as during rotating stall are presented. For all operating conditions rotor-stator-interactions play an important role on the blade force excitation. Furthermore the role of the inertia driven momentum exchange at the stall cell boundaries on the aerodynamic blade force excitation is pointed out.

Application of GA-FNC in Crystallizer Liquid Level Control System

2011 ◽  
Vol 199-200 ◽  
pp. 1777-1780
Author(s):  
Ming Li ◽  
Da Yong Yang
Keyword(s):  
Control System ◽  
Control Strategy ◽  
Steel Casting ◽  
Fuzzy Controller ◽  
Liquid Level ◽  
Level Control ◽  
Intelligent Control System ◽  
Casting System ◽  
The Stability ◽  
Self Learning

This article discusses the control strategy of the steel casting system which possesses the characteristics of large inertia, time-varying and nonlinear. Aiming at getting the minimum deviation of liquid level, the control strategy uses the genetic algorithm to off-line optimize the parameters (cij,bj) of the Gaussian membership function and the network structure of fuzzy controller which affect the overall system firstly. Then, BP algorithm is used to online regulate and optimize the weight parameters of the control output which affect the system partly. Finally, the intelligent control system of the liquid level which is based on GA-FNC is simulated. The results show that the method can enhance the ability of self-learning and robustness of the system greatly and improve the stability of steel casting system significantly.

Experimental Investigations of Stall Flutter in a Transonic Cascade

1999 ◽  
Author(s):  
Karsten Ellenberger ◽  
Heinz E. Gallus
Keyword(s):  
Steady State ◽  
Gas Turbines ◽  
Flow Behavior ◽  
Dynamic Pressure ◽  
Experimental Investigations ◽  
Compressor Blades ◽  
Pressure Transducers ◽  
Oil Flow ◽  
Mach Numbers ◽  
Stall Flutter

The design of modern gas turbines is more and more based on flow simulations by numerical calculation models. Due to the different influence parameters the development and verification of these codes requires detailed data bases, which can only be provided by experimental investigations. The demand of increasing power density leads to higher Mach Numbers up to transonic ranges. Due to the thin blade profiles the risk of stall flutter becomes an extraordinary point of interest. Therefore, in a transonic wind tunnel a cascade of nine compressor blades designed by MTU Munich were investigated at different inlet Mach numbers and incidence angles. To get information about flow behavior at steady state, profile pressure distribution was measured at midspan with pressure taps on profile surface. In order to provide information about the overall flow field oil flow visualization and Schlieren technique were applied for the investigation at steady state. For flutter simulation the blade in the middle position of the cascade was forced to torsional oscillating movement by an electromagnetic shaker system with a frequency of f = 310.0 Hz. The flow behavior with oscillating and fixed center blade was investigated at midspan by means of dynamic pressure transducers and hot films glued on profile probes. The results of these investigations are presented in this paper especially up to the appearance of stall flutter.

Mechanistic Modeling of Dynamic Zero-Net Liquid Holdup (ZNLH) in Gas-Liquid Cylindrical Cyclone (GLCC©) Separator

2018 ◽  
Author(s):  
Srinivas Swaroop Kolla ◽  
Megharaj Praneeth Karpurapu ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Gas Flow ◽  
Mechanistic Model ◽  
Operating Conditions ◽  
Mechanistic Modeling ◽  
Experimental Investigations ◽  
Liquid Holdup ◽  
Technical Performance ◽  
The Past ◽  
Carry Over ◽  
Static Conditions

Over the past 2 decades, GLCC© compact separators have been replacing the conventional vessel type separators in the Oil & Gas Industry, because of its numerous advantages. Despite these advantages, GLCC separators face two critical problems affecting the performance under extreme operating conditions, namely, Liquid Carry Over (LCO) into the gas leg and Gas Carry Under (GCU) into the liquid leg. This study focuses on the LCO phenomenon. Having a deeper insight into the LCO flow phenomenon helps us to enhance the technical performance of GLCC at these extreme conditions. Several studies were presented in the past on experimental investigations and mechanistic modeling of LCO. In the above cases, mechanistic modeling of LCO was based on Zero Net liquid Holdup (ZNLH) parameter. The liquid holdup in the upper part of the GLCC before it is blown out by gas flow is referred to as ZNLH. ZNLH is an important phenomenon affecting the GLCC pressure behavior and performance characteristics. Above mentioned experimental investigations performed to calculate ZNLH were carried out under static conditions where the effects of superficial liquid velocities were neglected. Investigations have been carried out in this study under dynamic conditions to evaluate the effect of superficial liquid velocities on ZNLH. We found that Dynamic ZNLH results are different from static ZNLH data as they show lower liquid holdup for the same gas velocities. A mechanistic model is proposed in this study to predict dynamic ZNLH and this model is validated against the dynamic ZNLH experimental data. It may be noted that a suitable ZNLH model will help in improving the predictions of the LCO mechanistic model considerably.

Swirling Flow Regimes and Gas Carry-Under in Gas–Liquid Cylindrical Cyclone Separator in a Separated Outlet Configuration

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Srinivas Swaroop Kolla ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Volume Fraction ◽  
Swirling Flow ◽  
Flow Behavior ◽  
Jet Impingement ◽  
Test Facility ◽  
Complex Flow ◽  
Cylindrical Cyclone ◽  
Oil Flow ◽  
Flow Mechanisms ◽  
Operational Envelope

Abstract Gas carry-under (GCU) and the corresponding gas volume fraction (GVF) in the gas–liquid cylindrical cyclone (GLCC©)2 liquid outlet occurs even within its normal operational envelope (OPEN). Few studies are available on GLCC, GCU, and GVF, which have been carried out in a GLCC operated in a metering loop configuration. This study focuses on GLCC GCU and GVF in swirling flow under separated outlet configuration with active control, which increases the GLCC OPEN significantly. A state-of-the-art test facility is used to acquire extensive GCU and GVF data for both air–water and air–oil flow in a 3″ diameter GLCC. The GLCC is equipped with three sequential trap sections to measure the instantaneous GVF and gas evolution in its lower part below the inlet. Also, gas trap sections are installed in the GLCC liquid outlet leg to measure the overall time-averaged GCU and GVF. The extensive acquired data shed light on the complex flow behavior in the lower part of the GLCC and its effect on the GCU and GVF in the GLCC. Tangential wall jet impingement from the GLCC inlet is the cause of gas entrainment and swirling in the lower GLCC body. The swirling flow mechanisms in the lower part of the GLCC are identified, which affect the GCU and GVF. The liquid viscosity and surface tension also affect the results. The GCU and GVF in the GLCC liquid outlet reduce as the superficial liquid velocities are increased for both air–oil and air–water flows, whereby the superficial gas velocities do not have a significant effect. The GCU and GVF for air–water flow are three orders of magnitude lower as compared to the air–oil flow.

Numerical Investigation of Two Phase Flow in a Dual Drive Booster (DDB)

2019 ◽  
Author(s):  
Arun Prabhakar ◽  
Stephen Ambrose ◽  
Herve Morvan
Keyword(s):  
Power Systems ◽  
Flow Behavior ◽  
Operating Conditions ◽  
Multiphase Model ◽  
Computational Domain ◽  
Two Phase ◽  
Ansys Fluent ◽  
Oil Flow ◽  
Gear Box ◽  
Polyhedral Grid

Abstract Recent efforts have been devoted in developing cutting edge methods and technologies to overcome the complications involved in extracting power from the spools in turbofan engines to drive the power systems in aircraft. In a contemporary turbofan engine design, a Dual Drive Booster turbofan (DDBTF) summation gear box is employed to derive power from the low pressure (LP) and high pressure (HP) spools. This paper aims to investigate the scavenging of lubrication oil from the Dual Drive Booster gearbox. It is essential that that the scavenging of oil from the gearbox is efficient to eradicate risks that may arise when oil resides in the gear box for prolonged durations. Longer residence times of oil in the gearbox can lead to rapid oil degradation. Simulations were conducted on a previously optimized geometry and the work in this paper will focus on investigating the effect of different operating conditions on the scavenging performance of the scavenge chamber. The effect of attitude, altitude and the inlet flow rate of oil have been simulated to understand their influence on the oil flow behavior. Emphasis is given on the predicting potential oil churning, recirculation and pooling behaviors in the scavenge chamber that encloses the gear box. Numerical Investigations are carried out using ANSYS Fluent. The Volume of Fluid (VOF) multiphase model is employed to model the multiphase flow arising between air and oil in the system and the effects of turbulence are modelled using the standard k-ϵ model. The computational domain is discretized using a polyhedral grid comprising of 4 million cells which was adopted based on grid independency tests that were conducted prior to the main simulations. Validation against published experimental data for similar flow regimes was also carried out. Results indicate that the scavenging performance is not affected significantly under the various operating conditions and scenarios that were investigated. This is because the effects of the windage outweigh the effects caused by the different operating conditions that are imposed to the scavenge chamber. The windage in the system drives the oil efficiently out from the chamber with the aid of the tangential sump (shown in Figure 4). Oil is distributed in an axially central section of the chamber and the total residence mass of oil is compared and under 0.5 kg for all the cases presented in this paper.

Unsteady Aerodynamic Blade Excitation at the Stability Limit and During Rotating Stall in an Axial Compressor

2006 ◽  
Vol 129 (3) ◽  
pp. 503-511 ◽  
Author(s):  
Ronald Mailach ◽  
Konrad Vogeler
Keyword(s):  
Gas Turbines ◽  
Axial Compressor ◽  
Stability Limit ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Momentum Exchange ◽  
Stall Inception ◽  
The Stability ◽  
Force Excitation

The stable operating range of axial compressors is limited by the onset of rotating stall and surge. These flow conditions endanger the reliability of operation and definitely have to be avoided in compressors of gas turbines. However, there is still a need to improve the physical understanding of these flow phenomena to prevent them while utilizing the maximum available working potential of the compressor. This paper discusses detailed experimental investigations of the rotating stall onset with the main emphasis on the aerodynamic blade excitation in the Dresden four-stage low-speed research compressor. The stall inception, which is triggered by modal waves, as well as the main flow features during rotating stall operation are discussed. To investigate the unsteady pressure distributions, both the rotor and the stator blades of the first stage were equipped with piezoresistive pressure transducers. Based on these measurements the unsteady blade pressure forces are calculated. Time-resolved results at the stability limit as well as during rotating stall are presented. For all operating conditions rotor–stator interactions play an important role on the blade force excitation. Furthermore the role of the inertia driven momentum exchange at the stall cell boundaries on the aerodynamic blade force excitation is pointed out.

Investigation on the control of multiphase flow behavior in a continuous casting tundish during ladle change

2020 ◽  
Vol 117 (6) ◽  
pp. 619
Author(s):  
Rui Xu ◽  
Haitao Ling ◽  
Haijun Wang ◽  
Lizhong Chang ◽  
Shengtao Qiu
Keyword(s):  
Multiphase Flow ◽  
Flow Behavior ◽  
Rolled Strip ◽  
Impact Zone ◽  
Steel Cleanliness ◽  
Carry Over ◽  
Slag Carry Over ◽  
Hot Rolled ◽  
Turbulence Inhibitor ◽  
The Impact

The transient multiphase flow behavior in a single-strand tundish during ladle change was studied using physical modeling. The water and silicon oil were employed to simulate the liquid steel and slag. The effect of the turbulence inhibitor on the slag entrainment and the steel exposure during ladle change were evaluated and discussed. The effect of the slag carry-over on the water-oil-air flow was also analyzed. For the original tundish, the top oil phase in the impact zone was continuously dragged into the tundish bath and opened during ladle change, forming an emulsification phenomenon. By decreasing the liquid velocities in the upper part of the impact zone, the turbulence inhibitor decreased considerably the amount of entrained slag and the steel exposure during ladle change, thereby eliminating the emulsification phenomenon. Furthermore, the use of the TI-2 effectively lowered the effect of the slag carry-over on the steel cleanliness by controlling the movement of slag droplets. The results from industrial trials indicated that the application of the TI-2 reduced considerably the number of linear inclusions caused by ladle change in hot-rolled strip coils.

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