Backpressure Control Research Articles

Methods and experiments for automatic control of surface back pressure based on dung beetle optimizer-PID controller

To ensure safer drilling and to prevent kicks and blowouts, Managed Pressure Drilling (MPD) technology has been proposed. However, conventional MPD necessitates manual operation of the choke within the choke manifolds by engineers, a task heavily reliant on their experience. This paper proposes a PID controller tuned using the Dung Beetle Optimizer (DBO) and details several laboratory experiments on automatic choke control utilising DBO-PID alongside a modified hydraulic control box. The experimental results demonstrate that DBO-PID can quickly and stably control the surface back pressure (SBP) to the desired level. Following extensive laboratory experiments validation, a field experiment implementing DBO-PID with a hydraulic control box was conducted on an offshore platform. The field experiment results indicate that DBO-PID is 29 % faster than manual control by an engineer in stabilising the SBP, with an overshoot of less than 4 % when nearing the target SBP. Additionally, during the control processes for both constant and variably targeted SBP, pressure fluctuation was 72 % and 63 % less, respectively, compared to manual operation. Both laboratory and field experiments have conclusively demonstrated that the automatic choke control system, comprising DBO-PID and a hydraulic control box, can efficiently manage SBP, thereby preventing kicks and blowouts. Furthermore, this system could replace manual operations in MPD, enhancing the safety of oil and gas resource development, protecting engineers' lives, and safeguarding the natural environment.

Dampening Humidifier Effects on Electrochemical Pressure Impedance Spectroscopy (EPIS) Fuel Cell Diagnostics

Fuel cells are versatile, low-emission alternative energy sources, but their optimization and failure analyses are complex due to their black-box nature. Conventional in-situ diagnostic techniques such as electrochemical impedance spectroscopy (EIS), are widely used to deconvolute transient processes within operating fuel cells. EIS is invaluable to understanding some of these processes, but other processes within the cell, such as mass transport and individual water fluxes, get overshadowed and are hard to detect.In an effort to provide information that is currently unattainable with conventional fuel cell diagnostic techniques, this project focuses on the further development of electrochemical pressure impedance spectroscopy (EPIS). EPIS is based on a pressure alternating frequency response analysis (pFRA). This diagnostic method is similar to EIS, except that it implements mechanical perturbations in the form of gas pressure oscillations, rather than voltage or current oscillations, to achieve an electrochemical response. Since EIS is based on electrical perturbations, the results are primarily based on the transport of electrons and provides electron-based performance metrics, including charge transfer, adsorption, diffusion, and double-layer behaviors. Conversely, the mechanical perturbations in EPIS enable the investigation of non-electron-based mechanisms, such as flow and gas transport resistances.This project builds from the work of Zang et al., who developed an experimental setup for EPIS and showed that pressure perturbations affect local reaction rates and transport phenomena within the cell, providing a sinusoidal voltage response.1 Prior work focused on the EPIS signal at the outlet, as the oscillation diminished by the time it reached the inlet of the cell. Shirsath et al. proposed that the excess volume of the humidifier before the fuel cell dampens the pressure oscillation signal and acts as an extra capacitor.2 To mitigate this, this project focused on the implementation of additional hardware between the humidifier and the cell inlet to act as a counter resistance and amplify the inlet pressure oscillation and subsequent EPIS response. The setup was fully explored through a series of targeted tests focused on identifying the most effective system parameters to validate the configuration and achieve optimal results. This hardware implementation aims to reduce the system effects and provide a more consistent pressure oscillation down the channel to further decouple the EPIS response and provide more accurate diagnostics of the cell. 1 Zhang, Q., Homayouni, H., Gates, B. D., Eikerling, M. H., & Niroumand, A. M. (2022). Electrochemical Pressure Impedance Spectroscopy for Polymer Electrolyte Fuel Cells via Back-Pressure Control. Journal of The Electrochemical Society, 169(4), 044510. 2 Shirsath, A. V., Raël, S., Bonnet, C., Schiffer, L., Bessler, W., & Lapicque, F. (2020). Electrochemical pressure impedance spectroscopy for investigation of mass transfer in polymer electrolyte membrane fuel cells. Current Opinion in Electrochemistry, 20, 82–87.

Effects of Fuel Cell Operating Conditions on Electrochemical Pressure Impedance Spectroscopy (EPIS) Diagnostics

Fuel cells are versatile, low-emission alternative energy sources, but their optimization and failure analyses are complex due to their black-box nature. Conventional in-situ diagnostic techniques such as electrochemical impedance spectroscopy (EIS), are widely used to deconvolute transient processes within operating fuel cells. EIS is invaluable to understanding some of these processes, but other processes within the cell, such as mass transport and individual water fluxes, get overshadowed and are hard to detect.In an effort to provide information that is currently unattainable with conventional fuel cell diagnostic techniques, this project focuses on the further development of electrochemical pressure impedance spectroscopy (EPIS). EPIS is based on a pressure alternating frequency response analysis (pFRA). This diagnostic method is similar to EIS, except that it implements mechanical perturbations in the form of gas pressure oscillations, rather than voltage or current oscillations, to achieve an electrochemical response. Since EIS is based on electrical perturbations, the results are primarily based on the transport of electrons and provides electron-based performance metrics, including charge transfer, adsorption, diffusion, and double-layer behaviors. Conversely, the mechanical perturbations in EPIS enable the investigation of non-electron-based mechanisms, such as flow and gas transport resistances.This project builds from the work of Zang et al., who developed an experimental setup for EPIS and showed that pressure perturbations affect local reaction rates and transport phenomena within the cell, providing a sinusoidal voltage response.1 This study focused on systematically analyzing the effects of varying fuel cell operating conditions to better understand the benefits and limitations of EPIS as a diagnostic technique. The EPIS response and subsequent flow resistances and gas transport resistances were monitored to understand the effects of variations in the cathode inlet relative humidity, the cell inlet temperatures, and the oxygen stoichiometry (stoic). The goal is to improve the metrics by which fuel cells are measured by providing new methods to assist in the real-time probing of processes and failure mechanisms within operating cells. 1 Zhang, Q., Homayouni, H., Gates, B. D., Eikerling, M. H., & Niroumand, A. M. (2022). Electrochemical Pressure Impedance Spectroscopy for Polymer Electrolyte Fuel Cells via Back-Pressure Control. Journal of The Electrochemical Society, 169(4), 044510.

Experimental and numerical investigation of the effects of porous bleed systems on a model scramjet inlet under high backpressure conditions

In this study, we conducted experimental and numerical investigations to assess the effects of backpressure and configurations of porous bleeds on a scramjet inlet's performance at Mach 5. Experiments in a high-enthalpy wind tunnel, using a backpressure controller and a porous bleed with 1 mm holes and 10 mm lateral spacing, were paired with Reynolds-averaged Navier-Stokes simulations to explore the mitigation of flow separation and the prevention of inlet unstart under various backpressure conditions. The simulations provided insights into how backpressure levels and porous bleed geometries impact internal flow structures, as well as the critical backpressure ratio at which inlet unstart occurs. Additional simulations varied the bleed system's hole diameter and spacing, identifying configurations that optimize aerodynamic performance by enhancing total pressure recovery and Mach number at the isolator exit, while reducing bleed mass flow rates. The study also quantified the impact of these configurations on engine thrust, determining that certain bleed system designs significantly improve thrust by efficiently suppressing the interaction between the core flow and corner recirculation zones. This study examined the internal three-dimensional flow structure characteristics under high back pressure and provided insights into porous bleed configuration capable of efficiently suppressing inlet unstart.

Blind Dynamic Resource Allocation in Closed Networks via Mirror Backpressure

We study the problem of maximizing payoff generated over a period of time in a general class of closed queueing networks with a finite, fixed number of supply units that circulate in the system. Demand arrives stochastically, and serving a demand unit (customer) causes a supply unit to relocate from the “origin” to the “destination” of the customer. The key challenge is to manage the distribution of supply in the network. We consider general controls including customer entry control, pricing, and assignment. Motivating applications include shared transportation platforms and scrip systems. Inspired by the mirror descent algorithm for optimization and the backpressure policy for network control, we introduce a rich family of mirror backpressure (MBP) control policies. The MBP policies are simple and practical and crucially do not need any statistical knowledge of the demand (customer) arrival rates (these rates are permitted to vary in time). Under mild conditions, we propose MBP policies that are provably near optimal. Specifically, our policies lose at most [Formula: see text] payoff per customer relative to the optimal policy that knows the demand arrival rates, where K is the number of supply units, T is the total number of customers over the time horizon, and η is the demand process’ average rate of change per customer arrival. An adaptation of MBP is found to perform well in numerical experiments based on data from NYC Cab. This paper was accepted by Gabriel Weintraub, revenue management and market analytics. Funding: Y. Kanoria was supported by the National Science Foundation’s Division of Civil, Mechanical, and Manufacturing Innovation [Grant CMMI-1653477]. Supplemental Material: The data files and online appendices are available at https://doi.org/10.1287/mnsc.2023.4934 .

Control of Back-pressure During Wind Tunnel Testing of A Two Dimensional Ramjet Air-intake Model

For optimum utilization of available run-time in blowdown wind tunnels, the controls, instrumentation, data acquisition and various other related systems associated with measurements must be efficiently synchronized. Testing of the air-intake model is a typical example where large number of steady and unsteady pressure measurements need to be combined with control of back pressure at the exit plane of the intake. This paper presents the development of a PC-based control system for testing a ramjet air-intake model at supersonic Mach numbers in the 0.3m trisonic wind tunnel at CSIR-National Aerospace Laboratories, Bangalore. The back pressure of the two-dimensional ramjet air intake model was controlled using a rectangular butterfly valve driven by a stepper motor external to the test section. Commands to vary the valve position were programmed in a PC and the valve position acquired from a potentiometer. The motor control and pressure data acquisition were operated in a hand-shake mode to enable hands-off execution of tests and maximize the data throughput from each blowdown.

Chinese Few-Shot Named Entity Recognition and Knowledge Graph Construction in Managed Pressure Drilling Domain.

Managed pressure drilling (MPD) is the most effective means to ensure drilling safety, and MPD is able to avoid further deterioration of complex working conditions through precise control of the wellhead back pressure. The key to the success of MPD is the well control strategy, which currently relies heavily on manual experience, hindering the automation and intelligence process of well control. In response to this issue, an MPD knowledge graph is constructed in this paper that extracts knowledge from published papers and drilling reports to guide well control. In order to improve the performance of entity extraction in the knowledge graph, a few-shot Chinese entity recognition model CEntLM-KL is extended from the EntLM model, in which the KL entropy is built to improve the accuracy of entity recognition. Through experiments on benchmark datasets, it has been shown that the proposed model has a significant improvement compared to the state-of-the-art methods. On the few-shot drilling datasets, the F-1 score of entity recognition reaches 33%. Finally, the knowledge graph is stored in Neo4J and applied for knowledge inference.

Impact of Operating Parameters on the Production of Nanoemulsions Using a High-Pressure Homogenizer with Flow Pattern and Back Pressure Control

The main objective of this study was to establish the relative importance of the main operating parameters impacting the formation of food-grade oil-in-water nanoemulsions by high-pressure homogenization. The goal of this unit operation was to create uniform and stable emulsified products with small mean particle diameters and narrow polydispersity indices. In this study, we examined the performance of a new commercial high-pressure valve homogenizer, which has several features that provide good control over the particle size distribution of nanoemulsions, including variable homogenization pressures (up to 45,000 psi), nozzle dimensions (0.13/0.22 mm), flow patterns (parallel/reverse), and back pressures. The impact of homogenization pressure, number of passes, flow pattern, nozzle dimensions, back pressure, oil concentration, emulsifier concentration, and emulsifier type on the particle size distribution of corn oil-in-water emulsions was systematically examined. The droplet size decreased with increasing homogenization pressure, number of passes, back pressure, and emulsifier-to-oil ratio. Moreover, it was slightly smaller when a reverse rather than parallel flow profile was used. The emulsifying performance of plant, animal, and synthetic emulsifiers was compared because there is increasing interest in replacing animal and synthetic emulsifiers with plant-based ones in the food industry. Under fixed homogenization conditions, the mean particle diameter decreased in the following order: gum arabic (0.66 µm) > soy protein (0.18 µm) > whey protein (0.14 µm) ≈ Tween 20 (0.14 µm). The information reported in this study is useful for the optimization of the production of food-grade nanoemulsions using high-pressure homogenization.

A comparative analysis of moving average filter and Kalman filter for large diesel engine test cell back-pressure control

Diesel engine combustion releases many harmful components, thus there are continuous efforts into improving the efficiency of these engines and reducing the harmful gasses and particulates to meet the emission authorities targets. To develop and sell new engine-related products, these engines are required to run and to be audited in diesel engine test cells. A critical measurement for benchmark testing is the exhaust back-pressure, which is the resultant exhaust flow from the engine and a product of the air and fuel consumed. The back-pressure is controlled by restricting the flow of the exhaust using a butterfly valve and this pressure must be set to the defined limits to ensure engine compliance. Setting this limit takes time and consumes large volumes of fuel, which causes additional emissions. Therefore, a feedback control solution to regulate this back-pressure is desirable. In current practice, a moving average filter is used on two commercial standard engine softwares – SGS CyFlex® and AVL Puma 2® Data Acquisition and Control Systems to provide a useful signal for feedback control. Considering the presence of erratic noise associated with the back-pressure measurement, a Kalman Filter with tunable measurement uncertainty and process noise gains is also considered. By modifying the script in SGS CyFlex® and AVL PUMA 2®, a Kalman Filter is implemented for the first time on diesel engine test cells and a comparative analysis between the performance of the two filters is provided. Both filters effectively reduce the noise of the system, with the Kalman Filter showing a closer tracking to the desired system response. This demonstrates the potential of applying the Kalman Filter to provide the feedback signal for improved back-pressure control that could reduce the fuel consumption during testing, thereby makes testing process more economical and environment friendly. The script and results presented in this work will open up the opportunities of applying Kalman filtering method’s in various engine testing functions, which will have broader impact in the current industrial practice.

Annular Dump Diffuser and Deswirl System for Back-Pressure Control in Engine-Scale Transonic Annular Cascade

Abstract A common requirement for turbomachinery testing facilities is the ability to independently control Mach number and Reynolds number. In practice, this means independent control of the inlet total pressure and exit static pressure in a test facility. In this paper, we present a solution to this problem with particular applicability to large-scale annular test facilities. We describe the design and commissioning of a combined annular dump diffuser and deswirl system for back-pressure control in environments with high-whirl transonic flow. The particular application was an annular cascade of nozzle guide vanes from a current civil engine. The purpose was to provide independent control of Mach number and Reynolds number, by controlling the back-pressure in the intermediate annular plenum which forms the dump diffuser. The dump diffuser is necessary to facilitate optical and probe access (without interaction effects) and to reduce the risk of exit static pressure disturbances (due to particular duct design). The system has been installed and validated in the engine component aerothermal (ECAT) facility at the University of Oxford. In this implementation of the system, the high-whirl transonic flow from the nozzle guide vanes passes through a short, parallel annular duct, and is dumped into an annular plenum, before being re-accelerated into a deswirl vane ring. The deswirl ring turns the flow to the axial direction. The flow is then discharged through a variable choke plate into a silencer. Conditioning the flow to have zero whirl at the choke plate reduces the sensitivity of the choke plate effective blockage to the whirl angle. The design, deswirl vane aerodynamic performance, and overall system performance are assessed with detailed experiments and 3D unsteady computational fluid dynamics predictions. The control of high-whirl transonic flow is notoriously challenging, and the deswirl system has application to exhaust conditioning in a number of applications including annular cascade experiments and rocket turbo-pump exhaust systems.

Arrival-Based Backpressure Traffic Signal Control

Fluctuations in arrival rates significantly affect the performance of traffic signal controls. In this paper, we propose an arrival-based distributed control algorithm based on the backpressure control framework, and show that this arrival-based backpressure (ABP) algorithm preserves the attractive features of backpressure control, including queue mitigation and global stability. Moreover, numerical results show that the ABP algorithm outperforms the fixed, actuated, and original backpressure signal controllers in low, medium, and heavy loading demand levels in increasing throughput, reducing queue length and waiting time.The benefits are evident under periodic traffic scenarios.

Electrochemical Pressure Impedance Spectroscopy for Polymer Electrolyte Fuel Cells via Back-Pressure Control

Electrochemical pressure impedance spectroscopy (EPIS) analyses the voltage response of a polymer electrolyte fuel cell (PEFC) as a function of an applied pressure signal in the frequency domain. EPIS is similar to electrochemical impedance spectroscopy (EIS) and its development was inspired by the diagnostic capabilities of the latter. The EPIS introduced in this work modulates the cathode pressure of a PEFC with a sinusoidal signal through the use of a back-pressure controller, and monitors the cell voltage while holding the cell at a constant current. A sinusoidal pressure wave propagates along the flow field channels because of this pressure modulation. This pressure wave impacts local reaction rates and transport properties in the cathode, resulting in a sinusoidal voltage response. The amplitude ratio and phase difference between these two sinusoidal waves entail diagnostic information on processes that take place within the PEFC. To demonstrate the utility of the EPIS technique, experiments have been carried out to measure and analyze the frequency response of PEFCs with two different flow fields. A parametric study has been conducted to characterize the effect of pressure oscillation amplitude, load, oxygen concentration, oxygen stoichiometry and cathode gas flow rate on the EPIS signal.

Well drilling with combined pressure control

The research deals with the analysis of new technologies for drilling oil and gas wells including the technology of managed pressure drilling (MPD). A consideration is given to the equipment for creating differential pressure in the wellreservoir system, which is supplied by the foreign companies Schlumberger, M-I SWACO, AKROS, etc. The analysis is given to the application of the basic complex of managed pressure drilling equipment, which includes the installation of back-pressure control, nitrogen compressor station, choke manifold, separator, rotary wellhead dock, flare tower with ignition system and hardware and software complex. The article also deals with the implementation options of the managed pressure drilling technology through the use of a sealed circulation system, which simplifies the well flushing scheme and ensures smooth adjustment of the flushing agent pressure at the bottomhole. A viable possibility of the presented basic MPD equipment and the attached software and hardware complex to determine the permissible values of reservoir fracturing pressure and formation pressure is studied in order to monitor the pressure profile in the casing annulus. It has been found that managed pressure drilling as a fundamentally new primary penetration technology for the hydrodynamic conditions of the reservoir allows to perform drilling in the zones with almost any initial absorption rate. That means that we do not stop sinking by boring (i.e. circulation) and do not increase the equivalent pressure on the horizon that depends on the equivalent circulating density. The adjustment involves the approximation of the equivalent pressure on the horizon to the formation pressure. The technological process of managed pressure drilling with the use of the discussed equipment will enable better understanding of the efficiency of this drilling technology by the drilling personnel and contribute to its more conscious application by domestic companies.

Synergetic Synthesis of Nonlinear Laws of Throttle Control of a Pneumatic Drive

Currently, a significant trend in control in robotic systems is developing and improving linear and nonlinear control algorithms to improve the overall quality of production with high accuracy and adaptability. The present study considers a synergistic synthesis of throttle control of a pneumatic distributor valve and backpressure control for piston rod positioning. The article presents the synthesis of control laws for the position of a pneumatic cylinder piston using the method of analytical design of aggregated regulators (ADAR) of synergetic control theory (STC), which allows operation with nonlinear mathematical models, eliminating the loss of information about the object during linearization. A comparative calculation of the energy efficiency of backpressure control and throttle control methods was carried out, while the numerical value of the total airflow with throttle control is 0.0569 m3⁄s and, with backpressure control, it is 0.0337 m3⁄s. Using a P controller in a linear model gives a transient oscillatory process damped in 2–2.5 s. When using a PID controller, the process has an overshoot equal to 11.5%, while the synergistic controller allows you to smoothly move the drive stem to a given position without overshoot. The parametric uncertainty analysis of the considered mathematical model is carried out. The model’s main parameters are identified, which change the actual functioning of the system under study. The inconsistency of applying classical control laws based on typical controllers to parametrically indeterminate mathematical models is shown.

Model-Predictive Control for Discrete-Time Queueing Networks With Varying Topology

In this article, we equip the conventional discrete-time queueing network with a Markovian input process which, in addition to the usual short-term stochastics, governs the mid- to long-term behavior of the links between the network nodes. This is reminiscent of the so-called Jump–Markov Systems in control theory, allowing the network topology to change over time and, thus, facilitating to model a plethora of useful applications in wireless communication, traffic, or logistics. We argue that the common back-pressure control policy is inadequate to control such network dynamics and propose a novel control policy inspired by the paradigms of Model-Predictive Control . Specifically, by defining a suitable but arbitrary prediction horizon, our policy takes into account future network states and possible control actions. This stands in clear contrast to most other policies which are myopic, i.e., only consider the immediate next state. We show numerically that such an approach can significantly improve the control performance and introduce several variants of the policy, thereby trading off performance versus computational complexity. In addition, we prove so-called throughput optimality of our policy, which guarantees stability for all network flows that can be maintained by the network topology. Interestingly, in contrast to general stability proofs in model-predictive control, our proof does not require the assumption of a terminal set, i.e., the prediction horizon is not required to be large enough as to reach a predetermined set of states with special properties. Finally, we provide several illustrating examples, one of which being a network of assembly-queues. This network, in particular, constitutes an interesting system class for which our policy exerts superiority over general backpressure policies, with the latter ones even losing their throughput optimality.

Optimization of back pressure control of direct air-cooling unit based on GPC

In view of the fact that the actual back pressure is difficult to track the set value quickly and stably, this paper applies the predictive control algorithm (GPC) which can respond quickly, has good robustness and is easy to realize in the industrial production site to optimize the back pressure control. The control performance of the back pressure control system with PID, fuzzy PID and GPC is compared and analyzed through the simulation test. The simulation results show that the GPC algorithm has better dynamic performance than PID and fuzzy PID control in the case of set point disturbance and internal disturbance, and has stronger robustness in the face of model mismatch. To sum up, GPC algorithm is more suitable for the back pressure control system under complex working conditions, and the optimization control method has a certain guiding significance for the actual production site back pressure control strategy improvement.

Thermal performance of an absorption-assisted two-stage ejector air-to-water heat pump

A gas-fired air-to-water ejector heat pump (EHP) for domestic hot water production is proposed and analyzed thermodynamically. The COP of the EHP is improved by using binary fluids (HFE7500 and water), and the high backpressure in the primary ejector (first-stage) is actively controlled by either a second-stage ejector and/or a LiBr-H2O absorption subsystem. A thermodynamic model is established for analysis and performance evaluation. A case study shows the backpressure of the first-stage ejector is reduced by 53.5%, and the backpressure control using the second-stage ejector increases the system COP by 21.0% compared with that using LiBr-H2O absorption. Parametric studies are conducted to investigate the roles of the first-stage ejector, the second-stage ejector, and the LiBr-H2O absorption subsystem. The first-stage ejector plays a dominant role in the EHP system performance. The EHP’s heating COP can reach 2.0 with an entrainment ratio of 0.12 in the first-stage ejector. EHP performance can be improved with a high entrainment ratio and a low-temperature primary working fluid in the first-stage and second-stage ejectors, a low condensation temperature in the first-stage ejector, and a high generating temperature and a low concentration of the LiBr-H2O solution.

Backpressure control with estimated queue lengths for urban network traffic

Backpressure (BP) control was originally used for packet routing in communications networks. Since its first application to network traffic control, it has undergone different modifications to tailor it to traffic problems with promising results. Most of these BP variants are based on an assumption of perfect knowledge of traffic conditions throughout the network at all times, specifically the queue lengths (more accurately, the traffic volumes). However, it has been well established that accurate queue length information at signalized intersections is never available except in fully connected environments. Although connected vehicle technologies are developing quickly, we are still far from a fully connected environment in the real world. This paper test the effectiveness of BP control when incomplete or imperfect knowledge about traffic conditions is available. We combine BP control with a speed/density field estimation module suitable for a partially connected environment. We refer to the proposed system as a BP with estimated queue lengths (BP-EQ). We test the robustness of BP-EQ to varying levels of connected vehicle penetration, and we compared BP-EQ with the original BP (i.e., assuming accurate knowledge of traffic conditions), a real-world adaptive signal controller, and optimized fixed timing control using microscopic traffic simulation with field calibrated data. Our results show that with a connected vehicle penetration rate as little as 10%, BP-EQ can outperform the adaptive controller and the fixed timing controller in terms of average delay, throughput, and maximum stopped queue lengths under high demand scenarios.

Transient two-phase flow behavior in wellbores and well control analysis for sour gas kick with high H2S content

ABSTRACT Complex two-phase flow phenomena in wellbores after sour gas kick may lead to severe well control incidents. By bridging the gas solubility, H2S phase transition and flow equations, a two-phase flow model is established under conditions of transient and non-isothermal states in wellbores, which is well validated against the two-phase flow experimental data. The following conclusions are drawn in the article: (1) a higher dissolved quantity and larger density of invaded sour gas containing H2S and CH4 in drilling fluids makes the detection of gas influx with high H2S content more difficult at an early stage; (2) when the mixed fluids move up to the wellhead, the release of the dissolved gas, the sharp decline of density of sour gas and the phase transition of H2S reduce the annulus pressure and induce complicated well control risks; (3) during H2S and CH4 influx, there are five major parameters that impact the bottom-hole pressure, which are evaluated for well control analysis. The proposed model shows a strong capacity to exhibit proper control of the wellhead back pressure, which can help to prevent the phase transition of H2S and reduce risks to well control.

Electrochemical Pressure Impedance Spectroscopy As a Diagnostic Method for Hydrogen-Air Polymer Electrolyte Fuel Cells

This work introduces a novel in-situ diagnostic method for polymer electrolyte fuel cells (PEFCs) referred to as electrochemical pressure impedance spectroscopy (EPIS). Inspired by electrochemical impedance spectroscopy (EIS), EPIS is a spectroscopic technique that analyses correlations between frequencies in an applied pressure signal and the corresponding voltage response signal in the frequency domain. In EPIS, cathode cell pressure is modulated as a sinusoidal wave by the back-pressure controller (BPC), and the cell voltage is monitored as the response signal. Cell voltage response originates from the membrane electrode assembly (MEA) and, therefore, EPIS can be used to probe cathode transport properties and is sought to develop tools that can be used to study water transport as a function of changes in structure and operating conditions. The cathode reactant gas flows through channels with a pressure drop and, thus, the pressure signal is not identical in different sections of the flow channel. Before studying the relationships between pressure and voltage, it is important to consider the impact of the flow channel on oscillations in the pressure response. The response of the system as a function of correlations between the cathode inlet pressure and the cathode outlet pressure is examined in this work to probe the contributions of the flow channel. Due to instrumental limitations, the BPC can only perform tests at a frequency of 0.1 Hz. Experimental limitations like cathode stoichiometry ratio, cathode flow rate, oxygen partial pressure at cathode, and pressure oscillation amplitude are intensively studied, and therefore, EPIS experimental formalism is defined in this work. Figure 1