Preliminary Engineering Design Research Articles

Analytical Solution for Longitudinal Seismic Responses of Circular Tunnel Crossing Fault Zone

ABSTRACTThis paper proposes a simplified analytical solution for longitudinal seismic responses of a circular tunnel crossing a fault zone under longitudinally propagating shear waves. The transmissions and reflections of shear waves at two geological interfaces between the fault zone and intact rock are considered when calculating the free‐field displacement. An improved elastic foundation beam model considering different tangential contact conditions at the tunnel‒rock interface is also adopted. According to the continuous conditions at the two geological interfaces, explicit expressions for the tunnel displacement, bending moment, and shearing force are given. The effectiveness of the proposed analytical solution is validated via numerical simulations, and the importance of accounting for tangential contact conditions at the tunnel‒rock interface is emphasized. Moreover, parametric studies are performed to investigate the effects of the fault zone width, rock conditions, tunnel lining stiffness, tangential contact conditions, and earthquake frequency on the deformation and internal forces of tunnels subjected to seismic waves. This novel analytical solution can be utilized to quickly estimate the longitudinal seismic responses of circular tunnels crossing fault zones subjected to longitudinally propagating shear waves, particularly in the preliminary engineering design, and can be extended to geological conditions with multiple interfaces.

Thermal modeling of the multiple shattered pellet injection system for HL-3

In order to study the physical mechanism and control strategy of disruption mitigation, and to alleviate the destructive effects during disruption, a multiple shattered pellet injection system (multi-SPI) was designed for the HL-3 tokamak. This paper describes the preliminary engineering design of the multi-SPI, and the thermal analysis results of the pellet preparation system. In-situ condensation and propellant acceleration technologies are adopted for the multi-SPI. Three pellets can be prepared at one time and injected individually or simultaneously, one of which is 7 mm and the other two are 5.5 mm in diameter. As the key component of multi-SPI, thermal analysis of the pellet preparation system is given by ANSYS. Results show that the temperature distribution of the heat sink is relatively uniform, and the temperature of standby guns remains lower than the working gas triple point when the other guns were fired. The results verify that the structure design of the pellet preparation system can satisfy the design requirements.

Comparison of numerical and exact analyses in a neutron activation and decay chain

A method for solving a set of coupled linear first-order ordinary differential equations as it applies to neutron activation and subsequent radioisotope decay chains was developed that is easy to implement and accurate enough for most preliminary engineering design calculations. The method is applied to a specific radioisotope production scheme to evaluate the yield of the desired isotope as well as production of secondary and tertiary contaminant radioisotopes. An analytical closed-form solution was also derived for the same activation and decay chain to provide a basis for comparison; the analytical solution was benchmarked against several limiting cases to validate the equations. Results of the simulation involving the numerical approach were compared to the exact analytical solution. The numerical solution, while obviously not exact, is found to be close enough for engineering purposes. A discussion of the numerical precision of the result for the particular case are discussed.

Fluid-driven slow slip and earthquake nucleation on a slip-weakening circular fault

We investigate the propagation of fluid-driven fault slip on a slip-weakening frictional interface separating two identical half-spaces of a three-dimensional elastic solid. Our focus is on axisymmetric circular shear ruptures as they capture the most essential aspects of the dynamics of unbounded ruptures in three dimensions. In our model, fluid-driven aseismic slip occurs in two modes: as an interfacial rupture that is unconditionally stable, or as the quasi-static nucleation phase of an otherwise dynamic rupture. Unconditionally stable ruptures progress through four stages. Initially, ruptures are diffusively self-similar and the interface behaves as if it were governed by a constant friction coefficient equal to the static friction value. Slip then accelerates due to frictional weakening while the cohesive zone develops. Once the latter gets properly localized, a finite amount of fracture energy emerges along the interface. The rupture dynamics is then governed by an energy balance of the Griffith’s type. In this stage, fault slip transitions from a large-toughness to a small-toughness regime due to the diminishing effect of the fracture energy in the near-front energy balance. Ultimately, self-similarity is recovered and the fault behaves again as having a constant friction coefficient, but this time equal to the dynamic friction value. This condition is equivalent to a fault interface operating to leading order with zero fracture energy. When slow slip is the result of a frustrated dynamic instability, slip also initiates self-similarly at a constant peak friction coefficient. The maximum size that aseismic ruptures can reach before becoming unstable can be as small as a critical nucleation radius (shear modulus divided by the slip-weakening rate) and as large as infinity when faults are close to a well-defined limit that separates the two modes of aseismic sliding. In the former case, earthquake nucleation occurs unaffected by the dynamic friction coefficient. In contrast, the latter case exhibits fracture-mechanics behavior, characterized by a finite influx of elastic strain energy being supplied to and dissipated at the rupture front. We provide analytical and numerical solutions for the problem solved over its full dimensionless parameter space, including expressions for relevant length and time scales characterizing the transition between different stages and regimes. Due to its three-dimensional nature, the model enables quantitative comparisons with field observations as well as preliminary engineering design of hydraulic stimulation operations. Existing laboratory and in-situ experiments of fluid injection into simulated and natural faults are briefly discussed in light of our results.

STATISTICAL METHOD FOR ESTIMATING SELECTED GEOTECHNICAL PROPERTIES OF QUATERNARY SEDIMENT

Quaternary sediments have characteristics that distinguish them from older soils. In engineering practice, these sediments are of particular interest to engineering geologists and geotechnical engineers because many engineering constructions have to be founded on, or in, them. This paper describes a method for rapidly estimating selected geotechnical properties of some Quaternary soil from the Mesopotamian Plain using statistical correlation equations. The paper explored an expedient statistical method to estimate some geotechnical properties (including total and dry unit weights, void ratio, porosity, Atterberg limits, and compression index) rapidly without running time-consuming and expensive laboratory tests. It was found that the selected properties showed a relatively moderate to high correlation with independent properties. Both the unit weight and void ratio depicted a high correlation with initial water content. while a moderate correlation existed between compression index and initial water content. Also, the plasticity index has a strong correlation with liquid limit values. The results of this study accord an additional usage as facultative engineering tools for geotechnical engineers to utilize for any preliminary engineering design.

Preliminary engineering design of vacuum thermal shielded Pb-Li loop section for potential nuclear fusion application

Nuclear fusion reactor design and engineering has reached into an advanced phase where the issues pertaining to radioactive tritium handling & accountability, divertor heat load mitigation, reactor size reduction & cost minimization are some of the core problems being addressed globally. Tritium breeding blanket is an important sub system of the reactor, which demands the most efficient design from many perspectives including that of tritium handling and accountability. Especially, Liquid Metal Breeder Blanket (LMBB) design consists of a complex network of heated pipes carrying Lead-Lithium (Pb-Li) Eutectic Alloy liquid metal. There are a few major issues with such pipes, namely (1) Large Space required due to substantial increase in diametric size of such pipes covered with heating elements and silica fibre based thermal insulation, (2) Loss of the bred tritium from liquid metal through permeation across the pipe wall and associated radioactive safety issues, and (3) Tritium retention in silica fibre based insulation resulting in tritium accountability problem and health hazard during maintenance duration. One possible solution to these problems could be putting a vacuum envelope over the loop pipe. The vacuum isolation will take care of thermal insulation for convection loss and at the same time, the pumping port of the envelope will collect all the lost tritium. In order to demonstrate the feasibility of the concept from thermal shielding point of view, we have prepared a conceptual and preliminary engineering design of such a vacuum envelope on a segment of the Pb-Li loop of 1 inch diameter. The loop segment includes a straight part as well as one 180° U bend too. The design is to maintain the envelop temperature less than 50 °C while the loop pipe is maintained at 350 °C. Basic calculation of thermal conductivity of low pressure air (vacuum) is done and compared with that of conventional insulation material silica based fibre felt. The fabrication, integration and maintenance schemes are also discussed in this report.

Deriving analytical expressions of the spatial information entropy index on riverine water quality dynamics

Information entropy theory has been largely applied in hydrology and water resource engineering. Recently, entropy theory has received significant attention for describing reactive solute mixing and transport processes in ground water and surface water and for its applications in water quality management. However, analytical expressions of the entropy index of riverine water quality dynamics are often not included in the literature. In this study, the analytical expressions of the spatial information entropy index (Gx) in the 1D steady-state transport process under full-extent observation and tracking observations are derived after the definition of the system boundary and probability space. The expressions of Gx were successfully validated by field data from two tracer experiments, and the different characteristics of Gx under different riverine hydraulic situations were uncovered. The formula of Gx shows a reasonable linkage with the Peclet number (Pe) in hydrodynamics. This indicates that Gx is a physical quantity describing or linking to the real world more than a statistical index, and in practice, similar decision or management measurements based on entropy theory can be made for rivers with similar Pe conditions. Hydrologists will benefit in many ways from analytical expressions, such as theoretical analysis, quick calculation of the entropy index, preliminary engineering design, etc. A clearly defined example of maximum entropy time (tGmax) and its application in water quality evaluation, monitoring optimization and pollution source identification are demonstrated. These new findings will provide a convenient tool for catchment water quality management.

Two-phase flow pattern online monitoring system based on convolutional neural network and transfer learning

Two-phase flow may almost exist in every branch of the energy industry. For the corresponding engineering design, it is very essential and crucial to monitor flow patterns and their transitions accurately. With the high-speed development and success of deep learning based on convolutional neural network (CNN), the study of flow pattern identification recently almost focused on this methodology. Additionally, the photographing technique has attractive implementation features as well, since it is normally considerably less expensive than other techniques. The development of such a two-phase flow pattern online monitoring system is the objective of this work, which seldom studied before. The ongoing preliminary engineering design (including hardware and software) of the system are introduced. The flow pattern identification method based on CNNs and transfer learning was discussed in detail. Several potential CNN candidates such as ALexNet, VggNet16 and ResNets were introduced and compared with each other based on a flow pattern dataset. According to the results, ResNet50 is the most promising CNN network for the system owing to its high precision, fast classification and strong robustness. This work can be a reference for the online monitoring system design in the energy system.

Bi-objective Optimization for Rebar Cutting Plan Using Symbiotic Organisms Search

The construction industry is one of the biggest industries in the world. One of the most important materials in this industry is the reinforced steel bar. In construction site usually fabricated the reinforced steel bars into the form of one-dimensional stocks and designed according to the structural specification and installed in various structural components such as columns, beam, slab, and foundation. The purpose of cutting stock problems for reinforced steel bars (rebar cutting plan, RCP) is to satisfy the project requirements and also to minimize the cutting losses, which is the major contributor to the construction waste As there are two objective functions, we call the problem bi-objective rebar cutting plan (B-RCP). In the previous research, efforts developed the metaheuristics method to minimize the cutting losses in preliminary engineering designs but it few to consider about simplicity in order to achieve efficient work. Thus, this research applies the bi-optimization with epsilon constraint in order to find the trade-off solution between the material waste and number of cutting pattern for decision making. This study proposed the metaheuristic method Symbiotic Organisms Search (SOS) to solve B-RCP in one framework, to find the feasible cutting patterns along with the minimum total waste of the reinforced steel bar. To test the performance of the proposed SOS framework, the previous study case is set to be a benchmark, and then create a comparison with PSO. For real project instances of RCP are used to evaluate and validate the performance of SOS. The validation results from both cases of RCP show that SOS has better performance than PSO in both minimize the material waste along reducing the number of cutting patterns. Thus, it is validated that SOS is a competitive algorithm for solving the RCP.

The Regression Rate-Based Preliminary Engineering Design of Hybrid Rocket Combustion System

The paper presents a useful engineering model for the design of preliminary hybrid rocket engines. This model involves the experimentally obtained equation regarding the speed of the burning interface between solid fuel and gaseous phase, called the regression rate. This regression rate characterizes the mass rate of the burning fuel and additionally the mass rate of the oxidizer through the imposed ratio of these mass rates during combustion. The preliminary design is applied to combustion using pure HTPB and gaseous oxygen and was developed for three cases, constant regression rate, constant oxygen mass flow rate and constant O/F (ratio of mass rates of oxygen and of fuel). The design evaluates the initial fuel port geometry, the initial mass of fuel and oxygen, the combustion time, the thrust at sea level, and the time-dependent functions of regression rate, of fuel and oxygen mass rates, and of thrust. It was assumed that the regression rate formula applies at any time of combustion. These evaluations can also be applied for other fuel/oxygen couples by knowing the correct formula for the regression rate.

Mathematical Modeling & Engineering Design of Wastewater Treatment Unit for Al-Kut Gas Filling Company

New talented treatment method without chemicals and with minimum operational cost was performed to treat industrial waste water discharged by a hydrostatic test performed on the gas bottles maintenance workshops to reuse it. A common method by Tarleton and Wakeman was used to select the general treatment philosophy, The implementation of this study was carried out on three stages, water sample analysis, simulates the proposed preliminary design and detailed engineering designing for the first stage, a sample of waste water was brought from Al-Kut Gas Filling Company - maintenance section and tested for settling, aeration, and filtration. The experiments showed that the most of sediments were insoluble but rather than suspended in water and can be removed by settling. Furthermore, aeration test showed that concentrated Thiophene odor in water was removed at 50 C of water with diffused air bubbling. On the other hand, filtration of using 10 Micron filter paper was achieved to eliminate the rest of tiny sedimentation. Secondly, general dimension of equipment was calculated by engineering design equation according to qualitative and quantitative analyses of waste water. Accordingly, a set of experiments of simulation using ANSYS V19.0 and Eulerian – Eulerian as mathematical model were performed for the 3D two phase flow sedimentation tank with capacity of 5 m3/hr to find the optimum sedimentation performance by testing of the modifications on the tank geometry (baffle depth, distance between baffle and inlet, hooper). Simulation results showed that the optimum tank geometry (0.86 m Baffle depth with inclined part, 2.5m distance between baffle and inlet, hooper within V type geometry W=1.67m/0.29 m, D=1.03 m and tank dimension (L=10m, W=2.5, H=2.5 with slope angle = 2o) with 49.5 volume % in sediment layer with a minimum sediment layer height. 
 The third stage included an accomplishment of the Preliminary and detailed engineering design of the entire unit by SOLIDWORKS software to be ready for prototyping.

Progress of engineering design of CFETR cryogenic system

The China Fusion Engineering Test Reactor (CFETR) is the next magnetic confinement fusion device in China’s roadmap for realizing commercial fusion energy, aiming to bridge the gaps between the experimental reactor and the demonstration reactor DEMO. As a key subsystem of utilizing fusion power, the CFETR cryogenic system is required to create and maintain low temperature operation conditions for superconducting magnets, CP system and other users. The preliminary engineering design of the CFETR cryogenic system has been proposed. The system has a capacity of 125 kW@4.5 K, 1700 kW@80 K, 6 kW@15 K and 2.5 kW@1.8 K (optional). The dimension of cryodistirbution system has been carried with the length of 85.5 m, width of 82.9 m and height of 40.2 m. The cryogenic control system is based on the CODAC and controlled by PLC.

Simulation perspective of upgrading biomass producer gas through a shift-methanation reaction coupled with cyclic CO2 capture

Reducing the CO content and improving the lower heating value (LHV) of biomass producer gas are essential for transforming it into a reliable energy source. The present work strives to provide a simulation perspective for a biomass producer gas upgrading process containing integrated shift-methanation and cyclic CO2 capture, where the CO2 by product from the shift-methanation reactor is separated by cyclic mono-ethanolamine (MEA) scrubbing. Equilibrium calculations via the Gibbs energy minimization method reveal that the appropriate temperature and pressure window for the shift-methanation reaction is 300–450 °C and 1–5 bar, respectively. The simulation results show that the optimal stage number for both the absorber and stripper is 10. The desired value of absorber and stripper efficiency can be obtained by balancing the MEA flow rate and reboiler duty. The original biomass producer gas with a 44.4% CO content and LHV of 9.45 MJ/Nm3 is upgraded to a CO content below 10% and LHV over 14 MJ/Nm3, reaching the national classification standard of Grade I gas. The preliminary engineering design in this work combines the shift-methanation reaction with CO2 absorption–desorption, demonstrating much potential for industrial-scale applications.

Progress of engineering design of CFETR magnet feeder system

The engineering design project of the China Fusion Engineering Test Reactor (CFETR) was almost done by the end of 2020. The superconducting magnets system of CFETR is significantly different from International Thermonuclear Experimental Reactor (ITER), so as a lifeline of Tokamak system, a new magnet feeder system needs to be designed to meet the CFTER operation requirement. According to the operating requirements of the CFETR magnet system, 23 feeder lines were designed for different coils. In this paper, the progress of the preliminary engineering design of the CFETR magnet feeder system was presented. Combined with the overall design consideration of the CFETR's buildings and other auxiliary systems, the overall layout of feeder system has been completed. The engineering design of main substructures and components were almost completed, including CTB (Coil Terminal Box, 100 kA HTSCL (High Temperature Superconducting Current Lead), CFT (Cryostat Feed-through), ICF (In-Cryostat-Feeder), etc. And some important analysis results were presented to give discussion and conclusion support for the design.

Design of the Test Section for the Experimental Validation of Antipermeation and Corrosion Barriers for WCLL BB

Tritium permeation into the Primary Heat Transfer System (PHTS) of DEMO and ITER reactors is one of the challenging issues to be solved in order to demonstrate the feasibility of nuclear fusion power plants construction. Several technologies were investigated as antipermeation and corrosion barriers to reduce the tritium permeation flux from the breeder into the PHTS. Within this frame, alumina coating manufactured by Pulsed Laser Deposition (PLD) and Atomic Layer Deposition (ALD) are two of the main candidates for the Water Cooled Lithium Lead (WCLL) Breeder Blanket (BB). In order to validate the performance of the coatings on relevant WCLL BB geometries, a mock-up was designed and will be characterized in an experimental facility operating with flowing lithium-lead, called TRIEX-II. The present work aims to illustrate the preliminary engineering design of a WCLL BB mock-up in order to deeply investigate permeation of hydrogen isotopes through PHTS water pipes. The permeation tests are planned in the temperature range between 330 and 500 °C, with hydrogen and deuterium partial pressure in the range of 1–1000 Pa. The hydrogen isotopes transport analysis carried out for the design and integration of the mock-up in TRIEX-II facility is also shown.

Compressive local buckling of integrated fluted-core sandwich composite panels

Fluted-core sandwich structures, consisting of fiber-reinforced plastics, are frequently utilized in the aerospace industry owing to their excellent strength-to-weight ratio. However, the thin-walled structures are prone to local buckling, which reduces their load-bearing capacity and eventually leads to material failure. The current study presents analytical models for predicting the local buckling of fluted-core sandwich panels subjected to uniform compressive load. The proposed method is based on a discrete plate analysis approach, which considers the face-sheets between two webs as rotationally-restrained plates, wherein the rotational restraint stiffness is determined based on the geometric configuration and material properties. Herein, two boundary conditions, i.e., simply-supported and clamped, along the loaded edges were studied. Several deflection functions were proposed based on the classical Rayleigh–Ritz method, satisfying the boundary conditions. The experimental tests and finite element simulations were carried out to analyze the local buckling behavior, rendering excellent consistency and demonstrating the reliability of the proposed method. The effects of geometric parameters on the local buckling behavior were systematically studied and the results revealed that the current analytical models with high computational efficiency are reliable, exhibiting promise of eventual success in the optimization of preliminary engineering designs.

Preliminary design of the COMPASS upgrade tokamak

COMPASS Upgrade is a new medium size, high magnetic field tokamak (R = 0.9 m, Bt = 5 T, Ip = 2 MA) currently under design in the Czech Republic. It will provide unique capabilities for addressing some of the key challenges in plasma exhaust physics, advanced confinement modes and advanced plasma configurations as well as testing new plasma facing materials and liquid metal divertor concepts.This paper contains an overview of the preliminary engineering design of the main systems of the COMPASS Upgrade tokamak (vacuum vessel, central solenoid and poloidal field coils, toroidal field coils, support structure, cryostat, cryogenic system, power supply system and machine monitoring and protection system). The description of foreseen auxiliary plasma heating systems and plasma diagnostics is also provided as well as a summary of expected plasma performance and available plasma configurations.

Prediction of Solvatochromic Polarity Parameters for Aqueous Mixed-Solvent Systems

Solvent polarity is important data being used in solvent selections for preliminary engineering design of chemical processes. In this work, a predictive model is proposed for estimating the solvatochromic polarity of electronic transition energy (ET) of Reichardt indicator for aqueous mixtures. To validate the model, the ET values of eighteen aqueous mixtures collected from the literature were used. The predictive model provided a good estimation of ET values with an overall deviation of 2.1%, compared with an ideal model (5.1%) from the mole fraction average. The linear relationship of the contribution factor of hydrogen bond donor interactions (CFHBD) in the predictive model with Kamlet–Taft acidity was newly proposed in order to extend the model for other aqueous mixtures. The predictive model is applicable to many aqueous mixtures and simply requires three properties of pure components as: (i) ET values, (ii) gas-phase dipole moment and (iii) Kamlet–Taft acidity.

Improvement Model for the Proposal Accuracy of Security System Design at Industrial Facilities

The research develops an improvement model for industrial preliminary security system design (PSSD) projects at an engineering design company (EDC). The improvement model’s aim is to increase the accuracy of preliminary design Material Take-Off (MTOs) lists to reduce their non-compliance rate by clients in comparison to as-built design MTOs. The EDC’s design requirements allow an estimation error range of ±15% between preliminary design quantities and final as-built material quantities and equipment types/specifications. Also known as bills of quantity, the MTOs of PSSD projects at the EDC are investigated because their preliminary design error (PDE) rates exceed the 15% acceptable error margin that factor into a lower overall quality performance score. The study analyzes the entire population of noncompliant (NC) PSSD projects at the EDC consisting of 13 projects. The improvement model comprises of the procedural application of seven developed solutions during preliminary engineering design to mitigate critical errors identified from analyzed non-compliant PSSD projects. The application of solutions reduces the quantities of NC PSSD projects from thirteen to eight across all security project classifications. This indicates a 38.46% reduction in NC PSSD projects.

Simulation of cyclonic wave conditions in the Gulf of Oman

This study presents a detailed assessment of wave conditions in the Gulf of Oman based on numerical simulations during the passage of three cyclones that have caused severe impacts to the coastal communities. The cyclone-generated waves for Gonu (2007), Phet (2010) and Kyarr (2019) are validated against satellite altimeter data and offshore wave buoy measurements. Simulation results obtained at four locations indicate that significant wave heights decrease as waves propagate into the Gulf. The maximum significant wave heights occurred during cyclone Gonu with values between 4.0 and 7.2 m within the Gulf of Oman whilst for the other two cyclones were just over 2.0 m. Longer peak wave periods were obtained for cyclone Kyarr (12.9 s). Although wave heights tend to decrease with increasing distance from the entrance of the Gulf of Oman, peak wave periods remain constant. The study provides valuable information on cyclonic-wave conditions for coastal management and planning, risk assessment studies and preliminary engineering design. The cyclone model, together with additional marine observation buoys, is an essential set of tools in measuring and forecasting wave conditions for future cyclones and, consequently, to increase safety of coastal populations and infrastructure.