scholarly journals Gas-Driven Fracture Propagation

1981 ◽  
Vol 48 (4) ◽  
pp. 757-762 ◽  
Author(s):  
R. H. Nilson
Keyword(s):  
Gas Flow ◽  
Oil And Gas ◽  
Elementary Function ◽  
Separation Of Variables ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Late Time ◽  
Shooting Methods ◽  
Uniform Compression ◽  
Penetration Length

A one-dimensional gas-flow drives a wedge-shaped fracture into a linearly elastic, impermeable half space which is in uniform compression, σ∞, at infinity. Under a constant driving pressure, p0, the fracture/flow system accelerates through a sequence of three self-similar asymptotic regimes (laminar, turbulent, inviscid) in which the fracture grows like an elementary function of time (exponential, near-unity power, and linear, respectively). In each regime, the transport equations are reducible under a separation-of-variables transformation. The integro-differential equations which describe the viscous flows are solved by iterative shooting methods, using expansion techniques to accomodate a zero-pressure singularity at the leading edge of the flow. These numerical results are complemented by an asymptotic analysis for large pressure ratio (N = p0/σ∞ → ∞) which exploits the disparity between the fracture length and penetration length of the flow. Since the seepage losses to a surrounding porous medium are shown to be negligable in the late-time long-fracture limit, the results have application to geologic problems such as: containment evaluation of underground nuclear tests, stimulation of oil and gas wells, and permeability enhancement prior to in situ combustion processes.

scholarly journals Synergetics of geological mediums and its impact on the effectiveness of the exploitation and exploration for mineral deposits

2019 ◽  
pp. 15-21
Author(s):  
Yu. I. Voitenko
Keyword(s):  
Gas Flow ◽  
Oil And Gas ◽  
Solid Phase ◽  
Dynamic Effect ◽  
Gas Production ◽  
Reservoir Properties ◽  
Uniform Compression ◽  
Reduced Pressure ◽  
Oil And Gas Production ◽  
Joint Influence

The mechanisms of joint influence of mountain and reservoir pressures, saturating fluid, structure elements of rocks and external dynamic effects on their behavior in natural conditions, in particular near of the well, are investigated. With specific examples, it is shown that the behavior of rocks with such a set of influencing factors is determined by the laws of synergetics and the combined action of external influences, uneven stress-strain state of the rocks, the pore pressure and chemo mechanical effects. Examples are the results of gas-flow and gas-metric studies of closed wells, as well as the results of explosive perforation and intensification of producing wellbores at different depths. Defects occurrence in minerals with a high modulus of elasticity is initiated by an external dynamic effect and independently under the action of the saturating fluid. Then, under volumetric non-uniform compression and reservoir pressure, gradual fracturing of terrigenous rocks occurs at the micro and macro level. The result of these processes is the formation of areas of the improved permeability near the wells during drilling, production and suspending. When drilling on traditional technology they will impair formation reservoir properties via infiltration of water and solid phase. In oil and gas wells and in closed wells - improve these properties. Analysis of the behavior of rocks from the synergetic position shows that the best mode of loading on the reservoir during wells drilling, wells completion and oil and gas production is depression (reduced pressure) on the reservoir. The known and new promising technologies for the intensification of oil and gas production are determined.

A method for shock train leading edge detection based on differential pressure

2016 ◽  
Vol 231 (1) ◽  
pp. 61-71 ◽  
Author(s):  
B Xiong ◽  
Z-G Wang ◽  
X-Q Fan ◽  
Y Wang
Keyword(s):  
Standard Deviation ◽  
Edge Detection ◽  
Detection Method ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Differential Pressure ◽  
Shock Train ◽  
Pressure Method ◽  
Operational Application ◽  
Deviation Method

In order to make the shock train leading edge detection method more possible for operational application, a new detection method based on differential pressure signals is introduced in this paper. Firstly, three previous detection methods, including the pressure ratio method, the pressure increase method, and the standard deviation method, have been examined whether they are also applicable for shock train moving at different speeds. Accordingly, three experimental cases of back-pressure changing at different rates were conducted in this paper. The results show that the pressure ratio and the pressure increase method both have acceptable detection accuracy for shock train moving rapidly and slowly, and the standard deviation method is not applicable for rapid shock train movement due to its running time window. Considering the operational application, the differential pressure method is raised and tested in this paper. This detection method has sufficient temporal resolution for rapidly and slowly shock train moving, and can make a real-time detection. In the end, the improvements brought by the differential pressure method have been discussed.

The effect of low-solidity vaned diffusers on the performance of a turbocharger compressor

1997 ◽  
Vol 211 (5) ◽  
pp. 325-339 ◽  
Author(s):  
P A Eynon ◽  
A Whitfield
Keyword(s):  
Pressure Ratio ◽  
Leading Edge ◽  
Vaneless Diffuser ◽  
Peak Efficiency ◽  
Turning Angle ◽  
Edge Angle ◽  
Turbo Charger ◽  
Geometry Configuration ◽  
Vane Angle ◽  
Selection Of

The design of low-solidity diffuser vanes and the effect on the performance of a turbo-charger compressor is discussed. The effect of vane number and turning angle was investigated while maintaining a basic design with a solidity of 0.69 and a leading edge angle of 75°. This large leading edge angle was specifically chosen so that the vane would be aligned with the low flowrates close to surge. Tests were initially conducted with six, eight and ten vanes and a turning angle of 10°. Based on these results the ten-vane design was selected for further investigation with 15 and 20° of vane turning; this led to vane exit angles of 60 and 55° respectively. All results are compared with those obtained with the standard vaneless diffuser configuration and it was shown that all designs increased and shifted the peak pressure ratio to reduced flowrates. The peak efficiency was reduced relative to that obtained with the vaneless diffuser. Despite the low-solidity configuration none of the vane designs provided a broad operating range without the use of a variable geometry configuration. This was attributed to the selection of a large leading edge vane angle.

Stall Behavior in an Ultra-High-Pressure-Ratio Centrifugal Compressor: Backward-Traveling Rotating Stall

2021 ◽  
pp. 1-51
Author(s):  
Yingjie Zhang ◽  
Xingen Lu ◽  
Yanfeng Zhang ◽  
Ziqing Zhang ◽  
Xu Dong ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Shock Intensity ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Boundary Layer Separation ◽  
Rotating Stall ◽  
High Pressure Ratio ◽  
Ultra High Pressure

Abstract This paper describes the stall mechanism in an ultra-high-pressure-ratio centrifugal compressor. A model comprising all impeller and diffuser blade passages is used to conduct unsteady simulations that trace the onset of instability in the compressor. Backward-traveling rotating stall waves appear at the inlet of the radial diffuser when the compressor is throttled. Six stall cells propagate circumferentially at approximately 0.7% of the impeller rotation speed. The detached shock of the radial diffuser leading edge and the number of stall cells determine the direction of stall propagation, which is opposite to the impeller rotation direction. Dynamic mode decomposition is applied to instantaneous flow fields to extract the flow structure related to the stall mode. This shows that intensive pressure fluctuations concentrate in the diffuser throat as a result of changes in the detached shock intensity. The diffuser passage stall and stall recovery are accompanied by changes in incidence angle and shock wave intensity. When the diffuser passage stalls, the shock-induced boundary-layer separation region near the diffuser vane suction surface gradually expands, increasing the incidence angle and decreasing the shock intensity. The shock is pushed from the diffuser throat toward the diffuser leading edge. When the diffuser passage recovers from stall, the shock wave gradually returns to the diffuser throat, with the incidence angle decreasing and the shock intensity increasing. Once the shock intensity reaches its maximum, the diffuser passage suffers severe shock-induced boundary-layer separation and stalls again.

A Study of Influences of Inlet Total Pressure Distortions On Clearance Flow in an Axial Compressor

2021 ◽  
Author(s):  
Guoming Zhu ◽  
Xiaolan Liu ◽  
Bo Yang ◽  
Moru Song
Keyword(s):  
Total Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Leading Edge ◽  
Stall Margin ◽  
Flow Cells ◽  
Static Pressure Distribution ◽  
Speed Flow ◽  
Clearance Flow ◽  
The Stability

Abstract The rotating distortion generated by upstream wakes or low speed flow cells is a kind of phenomenon in the inlet of middle and rear stages of an axial compressor. Highly complex inflow can obviously affect the performance and the stability of these stages, and is needed to be considered during compressor design. In this paper, a series of unsteady computational fluid dynamics (CFD) simulations is conducted based on a model of an 1-1/2 stage axial compressor to investigate the effects of the distorted inflows near the casing on the compressor performance and the clearance flow. Detailed analysis of the flow field has been performed and interesting results are concluded. The distortions, such as total pressure distortion in circumferential and radial directions, can block the tip region so that the separation loss and the mixing loss in this area are increased, and the efficiency and the total pressure ratio are dropped correspondingly. Besides, the distortions can change the static pressure distribution near the leading edge of the rotor, and make the clearance flow spill out of the rotor edge more easily under near stall condition, especially in the cases with co-rotating distortions. This phenomenon can be used to explain why the stall margin is deteriorated with nonuniform inflows.

Characterisation of Static Strip Seal Flow

2007 ◽  
Author(s):  
Arash Farahani ◽  
Peter Childs
Keyword(s):  
Gas Flow ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Main Stream ◽  
Cfd Modelling ◽  
Height Range ◽  
And Performance ◽  
Nozzle Guide ◽  
The Cost ◽  
Cooling Air

Strip seals are used in gas turbine engines between two static elements or between components which do not move relative to each other, such as Nozzle Guide Vanes (NGVs). The key role of a strip seal between NGV segments is sealing between the flow through the main stream annulus and the internal air system, a further purpose is to limit the inter-segmental movements. In general the shape of the strip seal is a rectangular strip that fits into two slots in adjacent components. The minimum clearance required for static strip seals must be found by accounting for thermal expansion, misalignment, and application, to allow correct fitment of the strip seals. Any increase in leakage raises the cost due to an increase in the cooling air use, which is linked to specific fuel consumption, and it can also alter gas flow paths and performance. The narrow path within the seal assembly, especially the height has the most significant affect on leakage. The height range of the narrow path studied in this paper is 0.01–0.06 mm. The behaviour of the flow passing through the narrow path has been studied using CFD modelling and measurements in a bespoke rig. The CFD and experimental results show that normalized leakage flow increases with pressure ratio before reaching a maximum. The main aim of this paper is to provide new experimental data to verify the CFD modelling for static strip seals. The typical flow characteristics validated by CFD modelling and experiments can be used to predict the flow behaviour for future static strip seal designs.

Flow With Shock Waves in a Transonic Centrifugal Compressor With a Low-Solidity Cascade Diffuser Using PIV

2004 ◽  
Author(s):  
Hiroshi Hayami ◽  
Masahiro Hojo ◽  
Norifumi Hirata ◽  
Shinichiro Aramaki
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Centrifugal Compressor ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Transonic Centrifugal Compressor ◽  
Image Velocimetry ◽  
Rotor Stator Interaction ◽  
Rotating Impeller ◽  
Low Solidity Cascade Diffuser

A single-stage transonic centrifugal compressor with a pressure ratio greater than six was tested in a closed loop with HFC134a gas. Flow at the inducer of a rotating impeller as well as flow in a stationary low-solidity cascade diffuser was measured using a double-pulse and double-frame particle image velocimetry (PIV). Shock waves in both flows were clearly observed. The effect of flow rate on a 3D configuration of shock wave at the inducer and a so-called rotor-stator interaction between a rotating impeller and a stationary cascade were discussed based on a phase-averaged measurement technique. Furthermore, the unsteadiness of inducer shock wave and the flow in a cascade diffuser during surge were discussed based on instantaneous velocity vector maps.

scholarly journals Multiphase gas-flow model of an electrical submersible pump

2018 ◽  
Vol 73 ◽  
pp. 29
Author(s):  
Diana Marcela Martinez Ricardo ◽  
German Efrain Castañeda Jiménez ◽  
Janito Vaqueiro Ferreira ◽  
Pablo Siqueira Meirelles
Keyword(s):  
Gas Flow ◽  
Oil And Gas ◽  
Learning Algorithm ◽  
Estimation Error ◽  
Oil And Gas Industry ◽  
Support Vector ◽  
System Response ◽  
Submersible Pump ◽  
Two Phase ◽  
Electrical Submersible Pump

Various artificial lifting systems are used in the oil and gas industry. An example is the Electrical Submersible Pump (ESP). When the gas flow is high, ESPs usually fail prematurely because of a lack of information about the two-phase flow during pumping operations. Here, we develop models to estimate the gas flow in a two-phase mixture being pumped through an ESP. Using these models and experimental system response data, the pump operating point can be controlled. The models are based on nonparametric identification using a support vector machine learning algorithm. The learning machine’s hidden parameters are determined with a genetic algorithm. The results obtained with each model are validated and compared in terms of estimation error. The models are able to successfully identify the gas flow in the liquid-gas mixture transported by an ESP.

scholarly journals Effect of Discrete Surface Disturbances on Vane External Heat Transfer

1997 ◽  
Author(s):  
R. S. Bunker
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
External Heat ◽  
Freestream Turbulence ◽  
External Heat Transfer ◽  
Enhancement Factors ◽  
Surface Disturbances

A transonic linear vane cascade has been utilized to assess the effects of localized surface disturbances on airfoil external heat transfer coefficient distributions, such as those which may be created by the spallation of thermal barrier coatings. The cascade operates at an overall pressure ratio of 1.86, with an inlet total pressure of about 5 atm. Cascade Reynolds numbers based on axial chord length and exit velocity range from 2.2 to 4.8 · 106. Surface disturbances are modeled with the use of narrow trip strips glued onto the surface at selected locations, such that sharp forward facing steps are presented to the boundary layer. Surface locations investigated include the near leading edge region on either side of the stagnation point, the midchord region of the pressure side, and the high curvature region of the suction side. Heat transfer enhancement factors are obtained for disturbances with engine representative height-to-momentum thickness ratios, as a function of Reynolds number. Enhancement factors are compared for both smooth and rough airfoil surfaces with added disturbances, as well as low and high freestream turbulence intensity. Results show that leading edge heat transfer is dominated by freestream turbulence intensity effects, such that enhancements of nearly 50% at low turbulence levels are reduced to about 10% at elevated turbulence levels. Both pressure and suction side enhancement factors are dominated by surface roughness caused effects, with large enhancements for smooth surfaces being drastically reduced for roughened surfaces.

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