Research on remote intelligent control technology of throttling and back pressure in managed pressure drilling

In order to reduce the non production time of drilling,improve the efficiency and safety of drilling,improve the economic effect of managed pressure drilling(MPD),and realize the intelligent control construction of digital oilfield.Based on the pressure control in MPD,this paper analyzes the pressure control drilling system,takes the wellhead back pressure as the controlled parameter,calculates the mathematical model of the throttle valve according to the characteristics of the throttle valve,the basic parameters and boundary conditions of pressure control drilling,and puts forward an improved particle swarm Optimization PID neural network(IPSO-PIDNN)model.By means of remote communication,VR technology can realize remote control of field control equipment.The real-time control results of IPSO-PIDNN are compared with those of traditional PID neural network(PIDNN)and traditional Particle Swarm Optimization PID neural network(PSO-PIDNN).The results show that IPSO-PIDNN model has good self-learning characteristics,high optimization quality,high control accuracy,no overshoot,fast response and short regulation time.Thus,the advanced automatic control of bottom hole pressure in the process of MPD is realized,which provides technical guarantee for the well control safety of MPD.

Effect of back pressure on the grinding performance of abrasive suspension flow machining

Abrasive suspension flow machining(ASFM)is an advanced finishing method that uses an abrasive suspension slurry for grinding and chamfering as well as the finishing of inaccessible components.This study examines the effect of back pressure on the grinding characteristics of an abrasive suspension flow during the grinding of slender holes.A numerical model was developed to simulate the abrasive suspension flow in a slender hole and was verified experimentally using injector nozzle grinding equipment under different grinding pressures and back pressures.It is shown that the ASFM with back pressure not only eliminates the cavitation flow in the spray hole,but also increases the number of effective abrasive particles and the flow coefficient.Increasing the back pressure during the grinding process can increase the Reynolds number of the abrasive suspension flow and reduce the thickness of the boundary layer in the slender hole.Moreover,increasing the back pressure can improve the flow rate of the injector nozzle and its grinding performance.

Effect of pressure evolution on the formation enhancement in dual interacting vortex rings

In the biological locomotion,the ambit pressure is of particular importance to use as a means of propulsion.The multiple vortex rings have been proved to generate additional thrust by interaction,but the mechanism of this thrust enhancement is still unknown.This study examines the effect of ambit pressure on formation enhancement in interacting dual vortex rings.The vortex rings,which have the same formation time,are successively generated in a piston-cylinder apparatus.The finite-time Lyapunov exponent(FTLE)visualizes the flow fields as an indication of Lagrangian coherent structures(LCSs),and the pressure field is calculated based on the digital particle image velocity(DPIV).We extract the back pressure of the rear vortex in dual vortices and the back pressure circulationΓ_(b),which is defined as a form of overpressure circulationΓ_(p).TheΓ_(b)has a positive linear relationship withΓ_(p).A critical interval distance d*_(cr)in a range of0.32-0.42 is found whereΓbandΓp reach the maximum synchronously,leading to a full-interaction mode.Moreover,an over-interaction mode and an under-interaction mode are proposed when the dimensionless interval distance d*_(is)smaller or larger than d*_(cr).To conclude,the high back pressure caused by vortex interaction can enhance the formation of vortex rings and lead to high thrust.

Influence of twist extrusion process on consolidation of pure aluminum powder in tubes by equal channel angular pressing and torsion

In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal channel angular pressing and torsion（ECAPT） was conducted via three-dimensional（3D） finite element simulation,experimental investigation and theoretical analysis.Simulation results revealed that during the consolidation of aluminum powder particles by ECAPT,TE process played a significant role of back pressure.Due to the torsional shear and high hydrostatic pressure exerted by twist channel,both the magnitude and homogeneity of the effective strain were increased markedly.After one pass of ECAPT process using a square channel with an inner angle of 90° and a twist slope angle of 36.5° at 200℃,commercial pure aluminum powder particles were successfully consolidated to nearly full density.Simulation and experimental results showed good agreement.In the microstructure observations,grains were greatly refined.At the same time,porosities were effectively eliminated by shrinking in size and breaking into small ones.Microhardness test indicated that strain distribution of ECAPT-processed billet was more homogeneous with respect to the ECAP-processed one.All these improvements may be attributed to the extreme intense shear strain induced during ECAPT and the increase in self-diffusion coefficient of aluminum due to the back pressure exerted by TE process.

Segmentation of copper alloys processed by equal-channel angular pressing

This research provides experimental evidence for localized shear, billet cracking, and segmentation during the processing of various copper alloys. The results demonstrate that although many parameters affect the shear localization, there is a direct relation between segmentation and alloy strength （hardness） that is related to the alloying elements and constitutive phases. For instance, alpha brass is successfully processed by ECAP at room temperature, but alpha/beta brasses fail even at a temperature of 350 °C. Finite element simulation of cracking and segmentation was performed using DEFORMTM to investigate the influence of different parameters on segmentation. The results confirm that friction and processing speed have narrow effects on attaining a perfect billet. However, employing back pressure could be reliably used to diminish shear localization, billet cracking, segmentation, and damage. Moreover, diminishing the flow localization using back pressure leads to uniform material flow and the billet homogeneity increases by 36.1%, when back pressure increases from 0 to 600 MPa.

Filtration Features in the Base of the Bratsk HPP （Hydroelectric Power Station） Concrete Dam

The design protection of the base of the Bratsk HPP （Hydroelectric Power Station） dam from filtration coming from the water reservoir included the arrangement of several cement-grout curtains and the system of drainage holes in the 2nd and 4th columns. During operation, increased hydrostatic back pressure at the base of the dam was found, which indicated the low efficiency of the base design protection. To reduce back pressure B. E. Vedeneev Hydro Technic Institute proposed the device of “advanced” drainage holes from the cement-grout gallery near the upstream face. The implementation of the proposal in a number of sections of the dam has led to a decrease in back pressure, but affected filtration in the drainage system, increasing it significantly. The article examines filtration features of “advanced” drainage holes and their dependence on the severity of winters. The spread of the practice of “advanced” drainage in other sections of the dam requires caution and further investigations of the nature of filtration.

Improving Operational Flexibility of Integrated Energy Systems Through Operating Conditions Optimization of CHP Units

As a type of energy system with bright application prospects,the integrated energy system(IES)is environmentally friendly and can improve overall energy efficiency.Tight coupling between heat and electricity outputs of combined heat and power(CHP)units limits IES operational flexibility significantly.To resolve this problem,in this paper,we integrate operating mode optimization of the natural gas combined cycle CHP unit(NGCC-CHP)into dispatch of the IES to improve flexibility of the IES.First,we analyze operational modes of the CHP units from the perspectives of thermal processes and physical mechanisms,including the adjustable extraction mode,backpressure mode,and switching mode.Next,we propose an explicit mathematical model for full-mode operation of the CHP units,in which the heat-electricity feasible region,switching constraints,and switching costs are all formulated in detail.Finally,a novel economic dispatch model is proposed for a heat and electricity IES,which uses the full-mode operation of CHP units to improve operational flexibility.The Fortuny-Amat transformation is used to convert the economic dispatch model into a mixed-integer quadratic programming model,which can then be solved using commercial solvers.Case studies demonstrate the proposed method can reduce operational costs and obviously promotes wind power utilization.

Numerical investigation on flow nonuniformity-induced hysteresis in scramjet isolator

Numerical simulation and theoretical analysis were conducted to study the hysteresis inside scramjet isolator during the reciprocating process of back pressure variation.It is revealed that only a regular reflection is theoretically possible for two leading shocks when the inflow Mach number is greater than 2.0,and no hysteresis can occur in the transition between shock reflection types.Nevertheless,wall suction,gas injection,and background waves cause non-uniformity of the incoming flow and would make hysteresis possible.Besides the classical hysteresis in the transition between shock reflection,new kinds of hysteresis were found in both the deflection angle of separated boundary layer and the location of the shock train.Moreover,the occurrence of hysteresis in the deflection angle of the separated boundary layer is accompanied with the shock reflection hysteresis.In the case with background waves or gas injection,hysteresis in the starting position of leading shock was observed too.As back pressure decreases,the leading shock does not follow the same path as that as the back pressure increases,and it is anchored at the location where the background shock or the injection interacts with the leading shock.It is inferred that,if two strong adverse pressure gradient regions move towards and interact with each other,hysteresis will take place when they start to separate.

Influences of Lateral Double-Layered Deflectors on Cooling Performance of Air-Cooled Condenser

The cooling performance of air-cooled condenser(ACC)is susceptible to adverse impacts of ambient winds.In this work,three kinds of lateral double-layered deflectors installed under the ACC platform are proposed to weaken the unfavorable effects of cross winds.Through CFD simulation methods,the main parameters of thermo-flow performances of a 2×660 MW direct dry cooling system are obtained,by which it can be concluded that the deflectors can effectively reduce the inlet air temperatures while enhance the mass flow rates of upwind fans due to the guiding effect,especially at high wind speeds,while the improvement of cooling capacity of ACCs in the 0°wind direction is weak.The inclined-vertical deflectors are superior to others in performance improvement of ACCs for all cases,which can reduce the turbine back pressure by 12.15%when the wind speed is 12 m/s,so they can be applied to the performance enhancement of ACCs under windy conditions in practical engineering.