Method For Preliminary Design Research Articles

A Modeling and Simulation Method for Preliminary Design of an Electro-Variable Displacement Pump.

Electro-hydrostatic actuators (EHAs) have been considerably researched in academia, and their applications in various industrial fields are expanding. The variable-speed EHA has now taken priority over the variable-displacement EHA, but its driving motor and associated electronics encounter issues when applied in high-power applications: low-dynamics, high thermal dissipation, high price, etc. Therefore, a variable-displacement EHA equipped with an electro-variable displacement pump (EVDP) has been considered. The EVDP itself is a mechatronic system that integrates a piston pump, a ball screw, a gearbox, and a permanent magnet synchronous motor (PMSM). Consequently, the EVDP needs to be investigated to ensure its system-level performance when applied in an EHA. In addition to the previous research on the technical parameters of the EVDP, a dedicated design method is necessary for further reducing the cost of using the EVDP and exploring its performance potential. Here, a simulation based EVDP preliminary design method is selected for designing a 37 kW EVDP. Firstly, a previously proposed multidisciplinary model of the EVDP is extended by improving the parameter generation, including the EVDP life, reliability, control models, etc. Secondly, the proposed model is partially verified using a downsized prototype. Thirdly, the EVDP is simulated at a system level, supported by the proposed model. The EVDP performance is evaluated according to the specified design requirements. The temperature, bandwidth and accuracy, reliability and lifetime, etc., are all predicted for the EVDP. The simulation results demonstrate the EVDP's applicability in variable-displacement EHA. The proposed modeling and simulation method can be used to evaluate diverse EVDP performance and respond to general design requirements. The method can also support the resolution of the preliminary design challenges in terms of limited information and robustness. Therefore, the proposed method is appropriate for the realization of the simulation-based EVDP preliminary design method.

An Intelligent Optimization Method for Preliminary Design of Lead-Bismuth Reactor Core Based on Kriging Surrogate Model

To meet the numerous application demands of lead-bismuth reactors, different design optimization tasks need to be conducted on these reactors based on the existing reactor core solutions. However, the design optimization of lead-bismuth reactors is a challenging task because it is a complex, multi-dimensional, and nonlinear constrained problem. To resolve these issues and improve the efficiency of design optimization, a new method, called the KSM-OLHS-SEUMRE method, based on the Kriging surrogate model (KSM), orthogonal Latin hypercube sampling (OLHS), and space exploration and unimodal region elimination (SEUMRE) algorithm is proposed in this study. Based on this method, a design optimization program of lead-bismuth reactors (DOPPLER-K) is developed, which realizes functions like sample point generation, optimization analysis, pre-post processing of reactor calculation, coupling of the Reactor Monte Carlo (RMC) calculation code and the Steady-state Thermal-hydraulic Analysis Code (STAC). Further, taking lead-bismuth reactors SPALLER-4 and URANUS as prototypes, the proposed intelligent optimization method for preliminary design of lead-bismuth reactor core is verified. The results show that this method can rapidly and accurately find the target scheme satisfying the optimization conditions, and it is three orders of magnitude faster than pure Monte Carlo calculation. Compared with the initial core scheme of URANUS, the optimization rates of fuel loading, total core mass, active zone volume, and total core volume are reduced by 10.8, 11.5, 18.1, and 17.1%, respectively. These results validate the feasibility and efficacy of the proposed method for design optimization of lead-bismuth reactor core.

Preliminary design and performance analysis of the liquid turbine for supercritical compressed air energy storage systems

• The preliminary design method and experiment of the liquid turbine is presented. • The predicted and experimental performance of the turbine validates the method. • Reasonable parameter ranges for liquid turbines are different from other turbines. Liquid turbines can replace throttling valves to recover waste energy and reduce vaporization in various industrial systems, such as liquefied natural gas, air separation, supercritical compressed air energy storage (SC-CAES) systems, et al. However, there were few studies about differences in the preliminary design method between general radial inflow turbines and liquid turbines. In this paper, a preliminary design method of liquid turbines was presented, and the performance of liquid turbines was predicted using CFD methods which were validated with experimental results. The efficiency of the designed liquid turbine was 92% and the output power was 65.7 kW. The performance of the turbine predicted by the preliminary method could agree with simulation results of prototype and model turbines near the design working condition, while there was a certain deviation when the flow rate was less than 70%. Through analyzing the presented preliminary design method, it could be found that distinctive differences in thermal properties of working fluids caused that typical design parameters for liquid turbines, like ratios of the blade height, the hub radius and the area, should be selected differently from empirical values for gas radial turbines. The results obtained in this paper could help guide the design of liquid turbines for various systems to promote energy conservation and improve system efficiencies significantly.

A time-domain methodology to assess the dynamic positioning performances

This paper presents the procedure for designing a Dynamic Positioning system and evaluating its performance using a dynamic approach. Generally, static analysis is the standard preliminary design method for a Dynamic Position system; however, this has some drawbacks for a realistic representation of the system operating in real conditions since the transient behaviours are neglected. The proposed procedure provides results in a novelty manner, and they are named Time-domain Dynamic Positioning Capability Plots. They were obtained by a model-based design approach using a ship's dynamic simulator. The dynamic simulator is based on a fully actuated testing model. Indeed, the proposed tool has been designed on a tug vessel equipped with two azimuth thrusters and one bow-thruster. In particular, two force allocation logics for the station keeping manoeuvres have been developed; one is an optimised thrust allocation logic, the other is obtained with the primary goal to reduce as much as possible azimuth thrusters rotation. The two different allocations can fulfil both open-loop and closed-loop commands, but only the closed-loop has been discussed. Eventually, the comparison between static capability plots and the capability plots obtained by several dynamic simulations has been provided, presented, and discussed.

Benchmark of different aerodynamic solvers on wing aero-propulsive interactions

Distributed electric propulsion is a fertile research topic aiming to increase the wing aerodynamic efficiency by distributing the thrust over the wing span. The blowing due to distributed propulsors shall increase the wing lift coefficient for a given planform area and flight speed. This should bring several advantages as wing area, drag, and structural weight reduction, which in turn reduce fuel consumption, allowing airplanes to fly more efficiently. However, there are no consolidated preliminary design methods to size a distributed propulsion system. Numerical analysis is then performed at early stage, where many design variables have not been fixed yet. Therefore, the design space is vast and exploring all the possible combinations is unfeasible. For instance, low-fidelity methods (VLM, panel codes) have a low computational time, but usually they do not account for flow separation and hence they are unable to predict the wing maximum lift. Conversely, high-fidelity codes (CFD) provide more realistic results, but a single drag polar sweep can last days. This work provides a benchmark of different aerodynamic solvers for a typical regional turboprop wing with flaps and distributed propulsion, to better understand the limits of each software in the prediction of aero-propulsive effects.

Design method and performance analysis of a hybrid-electric power-train applied in a 30-passenger aircraft

Design methods to transform actual aircraft propulsion systems into hybrid, and to analyze the performance must be developed. Present work details the first approach of a preliminary design method and evaluation of a hybrid-electric power-train for a conventional airplane. High fidelity models of the components are developed based on the physical relations of the involved variables. The main characteristics of the chosen aircraft with conventional propulsion on a typical mission are the inputs of an application developed in SUAVE, which renders aerodynamic variables for the design process. The turboprop engines of the conventional and hybrid (in parallel architecture) systems are modeled in GasTurb. The propeller is modeled using blade element momentum theory (BEMT) on the software JBlade. The first simulation results are used to calculate the initial power-train electrical components characteristics. Modeling results in steady state conditions are inputs of a code developed in MatLab, a design optimization algorithm that calculates the base characteristics of the optimal hybrid motor components. The method was tested employing the gas turbine TR5000 on turbo-prop configuration as the engine of the hybrid set. The aircraft EMB–120 ‘Brasilia’ was the airplane of this application, aiming to characterize the most important outcomes from this multidisciplinary approach.

Concave Bump for Impinging-Shock Control in Supersonic Flows

In the present study, a novel concave bump for impinging-shock control in two-dimensional supersonic flows is investigated. An analytical method for preliminary bump design based on a generalized shape of a shock-canceling bump has been developed and verified numerically. An extensive proof-of-concept study was performed at a freestream Mach number ranging from 2.5 to 5.0 for shock-generator angles varying from 6 to 12 degrees. It could be demonstrated that a concave bump designed for a given flow-deflection angle is capable of significantly reducing the size of the separation bubble as well as the total pressure losses throughout the Mach number range investigated. The achievable gains depend on the Mach number, the flow-deflection angle, and the relative impingement position of the incident shock front on the bump. The highest values of separation-length reduction (up to 100%), momentum thickness reduction (up to 31%), and pressure recovery factor increase (up to 33%) were obtained at the optimum shock impingement position for the largest deflection angle studied. The concave bump is less effective, and in some cases even disadvantageous, when the incident shock wave does not optimally strike the bump crest.

Innovative small axial multistage turbine with partial admission for bottoming ORC

The expander is the key element of an organic Rankine cycle (ORC) and has a significant influence on the cycle efficiency. Therefore, in this study, an innovative small axial multistage turbine with partial admission for a bottoming ORC (ORBC) is investigated. The ORBC was used for the waste heat utilization of exhaust gases and jacket cooling water from a 537 kW biogas internal combustion engine (ICE) .The initial design of the turbine flow part was developed using a mean diameter two-dimensional (2D) preliminary design (PD) method. The high rotational speed of the axial turbine, which is its most critical characteristic, was overcome by employing partial admission. To achieve high isentropic efficiency, new (nonstandard) profiles of the nozzle and moving blades were designed using an analytical method. The initial full flow part of the turbine was further investigated by three-dimensional (3D) computational fluid dynamics (CFD) simulations, with the aim of improving its design. The simulations also provided a better insight into the physics of flow than the mean diameter 2D method. Both the 2D PD calculations and 3D CFD simulations were performed using real gas properties.The innovative axial action–reaction turbine with partial admission has 8 stages, a mean diameter of 140 mm, and a rotational speed of 9000 rpm. According to the CFD simulation results, a mass flow of isopentane as the working fluid of 1.171 kg/s achieves an effective power of 60.35 kW and isentropic efficiency of 74.8%. These represent an 11.2% increase in the overall power and a 4.5% increase in the overall thermodynamic efficiency by employing an ORBC on a 537 kW biogas ICE.Therefore, the new turbine is competitive with other expanders in this power range.

Progressive collapse mechanisms of post-tensioned reinforced concrete frames considering effect of infill walls

This study numerically investigates progressive collapse mechanisms of post-tensioned RC frames under column removal scenarios by using the finite element method. The primary objective of this study is to investigate the influences of infill walls on mechanical behavior of post-tensioned (PT) frames against progressive collapse. Three experimental conventional reinforced concrete (RC) frames are modified into PT reinforced concrete frames: PT bare frame, PT full infilled frame and PT partial infilled frame. The numerical study was performed and the applied vertical load, horizontal displacement, failure process, load redistribution mechanisms, and re-centering capacity of PT frames are investigated under middle column pushdown scenario. Parametric analyses are conducted to study influences of material properties, arrangement of PT tendons, and magnitude of PT forces. The results show that masonry infill walls enhance the resisting capacity; however, change the failure modes and reduce the re-centering capacity of the PT frames against progressive collapse. The presence of the opening reduces the contribution of the infill walls. The PT bare frame have better resilience performance compared with the conventional bare frame. The bed joints, strength of masonry bricks, arrangement of PT tendons and magnitude of PT force greatly influence the progressive collapse resisting capacity of PT frames. Finally, a preliminary design method is proposed to predict the progressive collapse resisting capacity of PT frames with good accuracy and efficiency.

Preliminary Optimization of Multi-Stage Axial-Flow Industrial Process Compressors Using Aero-Engine Compressor Design Strategy

Aero-engine core compressor preliminary design strategy has been successfully applied to the advanced design of gas turbines compressors. However, few researchers have addressed the application of the aero-engine core compressor preliminary design strategy in the preliminary optimal design of industrial process compressors. Here we embedded the aero-engine core compressor preliminary design strategy into a preliminary optimal design method, in which six types of design parameters widely used to define the aero-engine compressor configuration, i.e., aspect ratio, solidity, reaction, rotation speed, outlet axial Mach number, and inlet radius ratio, were used as the design variables. The 4-stage, 5-stage, 6-stage, and 7-stage compressor configuration with the same overall design requirements for a large-scale air separation main compressor were preliminarily optimized by the developed method, in which the 4-stage design has a stage pressure rise level of current aero-engine core compressors, whereas the 7-stage design has that of current industrial process compressors. The optimized compressor configurations were then refined with the throughflow-based detailed design method and finally verified with computational fluid dynamic simulations. It is found that the developed method can optimize design efficiency and accurately predict aerodynamic performance of compressors in a few minutes. Several design guidelines for the advanced industrial process compressors were also identified. This work is of significance in extending aero-engine core compressor design strategy to the design of advanced industrial process compressors.

Experimental study on bond and anchorage of steel bars in precast concrete structures with new-to-old concrete interface

In monolithic precast concrete structures, the connection between precast components with extended reinforcing bars usually encounters problems regarding conflicts in reinforcement placement. In particular, the problem of reinforcement conflicts is more prominent for precast slabs in China. In order to solve reinforcement conflicts encountered during practical construction, a novel connecting approach for precast members is proposed. This new approach involves setting notches at the end of precast components and anchoring reinforcing bars at the specially designed notches. This new approach ensures that the structural performance of the joints for precast members is similar to that of cast-in-place structures while minimizing the protrusion of reinforcement at the end of the member. In order to investigate the force transfer mechanism of the proposed method and its applicability to precast slabs, a total of 54 specimens with and without notches are designed and tested using pull-out experiments. Based on the experimental analysis, it is found that the existence of the new-to-old concrete interface changes the anchorage strength of steel bars in the notches. The effect of new-to-old concrete interface on the bond strength of steel bars and the desirable anchorage length of steel bars at the concrete interface are analyzed. The influences of steel bar diameter, anchorage length, concrete strength and reinforcement ratio of the concrete cover on the structural performance are discussed and compared in depth. Through the experimental results, the main factors affecting the bond strength of steel bar anchorage in the notched connection are identified. The physical mechanism of force transfer of the proposed method is developed and described. Preliminary calculation and design methods are presented to guide the practical application of the proposed method and to further facilitate the construction process of the precast structures.

A discontinuous cantilever beam analogy for quantifying higher mode demands in stacked rocking cores

SummaryStacked rocking core (SRC) combinations are innovative sustainable structural assemblies that mitigate seismic demands through uplift at the hinge joints and direct damage to replaceable fuses. The stacked segments curtail substantially higher mode effects by the relative motions between multilevel cores. Currently, few research studies have quantified the behavior of SRCs under earthquake shaking. This paper presents a novel closed‐form solution for quantifying the higher mode demands of stacked braced frames subjected to seismic excitation. The mathematical formulae for modal analysis are derived using the analogy of discontinuous cantilever beam and Euler–Bernoulli equation. The proposed equations provide a method for rapid analysis and preliminary design of low‐ to mid‐rise SRCs. A parametric study is carried out to investigate the influences of rotational restraint of segments and the location of the rocking joints. Results verified by time response analysis indicate the validity and accuracy of the suggested formulae.

A preliminary design method for axisymmetric turbomachinery disks based on topology optimization

The topology optimization can be used to obtain preliminary turbomachinery disk designs which meet strength requirement. In order to eliminate enclosed holes which challenge manufacturing processes and to ensure distinct solid-void interface in the optimal result obtained by the topology optimization, a density distribution function is introduced for each element column in the design domain. Then, a parameter in each function is used to determine the disk’s thickness at corresponding radial position by controlling element densities. Once thicknesses at all radial positions are optimized, the shape of disk is thus determined. In this way, the optimization problem can be simplified by using these parameters as design variables. Illustrative examples are carried out to demonstrate the effectiveness of the proposed method in designing both compressor disks and turbine disks in comparison to the software T-Axis Disk and shape optimization method.

A novel preliminary design method for intermediate compressor/turbine ducts

In order to achieve a rapid design of intermediate compressor/turbine duct (ICD/ITD) geometries for turbofan engines, a novel preliminary design method is proposed in this paper. An arc-line-arc configuration is adopted to design diffused contour, which is the shroud for an ITD and the hub for an ICD. Then undiffused contour is built under a specified width along the duct mean line. It is also corrected by considering strut blockage effects. A parametric study is conducted for an ITD using two-dimensional (2D) axisymmetric CFD simulations to reasonably select arc radii of the diffused contour. Furthermore, an empirical formulation between the arc radii and flow Reynolds number is established. Finally, two cases, including an ICD and an ITD, are redesigned. The performance of designed geometries is compared to their baseline structures via 3D CFD simulations. Results indicate that the total pressure loss coefficient is decreased by 7.9% and 5.5% by the redesigned ICD and ITD, respectively, without sacrificing diffusion performance. Flow filed check reveals that mitigated pressure gradient is obtained for the two cases. This validates the effectiveness and feasibility of the proposed preliminary design method.

Higher mode effects of multistorey substructures on the seismic response of double-layered steel gridshell domes

The seismic response of gridshell roofs with substructures is strongly influenced by the relative mass and stiffness of the roof and substructure, and particularly by how close the periods of the dominant roof and substructure modes are. Multistorey substructures may exhibit a significant higher-mode acceleration response, primarily due to the contribution of the shorter second translational substructure mode to the roof response. This paper presents parametric studies conducted on steel gridshell domes with 60, 100 and 150 m spans and six-storey substructures to investigate the interaction between the higher substructure modes and dominant roof modes. The contribution of each substructure mode to the overall response was characterised by a newly proposed dominance response ratio. In contrast to previous studies of long-period single-storey substructures, which only minimally excited the roof modes, the higher modes of the long-period multistorey substructures investigated in this study significantly contributed to the roof response. The roof vertical accelerations were amplified by up to three times the substructure roofline acceleration, as the curved roof geometry couples the horizontal substructure and vertical roof response. The substructure higher-mode contribution was quantified using amplification factors and developed into equivalent static loads that were found to be in good agreement with response spectrum analysis results. The proposed equivalent static loads provide insight into the complex dynamic characteristics of gridshell roofs with multistorey substructures and offer an efficient method for preliminary seismic design.

A method for preliminary rotor design – Part 1: Radially Independent Actuator Disc model

Abstract. We present an analytical model for assessing the aerodynamic performance of a wind turbine rotor through a different parametrization of the classical blade element momentum (BEM) model. The model is named the Radially Independent Actuator Disc (RIAD) model, and it establishes an analytical relationship between the local thrust loading and the local power, known as the local-thrust coefficient and the local-power coefficient respectively. The model has a direct physical interpretation, showing the contribution for each of the three losses: wake rotation loss, tip loss and viscous loss. The gradient for RIAD is found through the use of the complex step method, and power optimization is used to show how easily the method can be used for rotor optimization. The main benefit of RIAD is the ease with which it can be applied for rotor optimization and especially load constraint power optimization as described in Loenbaek et al. (2021). The relationship between the RIAD input and the rotor chord and twist is established, and it is validated against a BEM solver.

A method for preliminary rotor design – Part 2: Wind turbine Optimization with Radial Independence

Abstract. A novel wind turbine rotor optimization methodology is presented. Using an assumption of radial independence it is possible to obtain an optimal relationship between the global power (CP) and load coefficient (CT, CFM) through the use of Karush–Kuhn–Tucker (KKT) multipliers, leaving an optimization problem that can be solved at each radial station independently. It allows solving load constraint power and annual energy production (AEP) optimization problems where the optimization variables are only the KKT multipliers (scalars), one for each of the constraints. For the paper, two constraints, namely the thrust and blade root flap moment, are used, leading to two optimization variables. Applying the optimization methodology to maximize power (P) or annual energy production (AEP) for a given thrust and blade root flap moment, but without a cost function, leads to the same overall result with the global optimum being unbounded in terms of rotor radius (R̃) with a global optimum being at R̃→∞. The increase in power and AEP is in this case ΔP=50 % and ΔAEP=70 %, with a baseline being the Betz optimum rotor. With a simple cost function and with the same setup of the problem, a power-per-cost (PpC) optimization resulted in a power-per-cost increase of ΔPpC=4.2 % with a radius increase of ΔR=7.9 % as well as a power increase of ΔP=9.1 %. This was obtained while keeping the same flap moment and reaching a lower thrust of ΔT=-3.8 %. The equivalent for AEP-per-cost (AEPpC) optimization leads to increased cost efficiency of ΔAEPpC=2.9 % with a radius increase of ΔR=17 % and an AEP increase of ΔAEP=13 %, again with the same, maximum flap moment, while the maximum thrust is −9.0 % lower than the baseline.

Adjoint State of Nonlinear Vortex-Lattice Method for Aerodynamic Design and Control

The adjoint state of a nonlinear vortex-lattice method, coupled with sectional polars obtained with an infinite swept-wing (2.5D) Reynolds-averaged Navier–Stokes (RANS) solver, is presented as an interactive method for preliminary aerodynamic design and control of moderate-to-high aspect ratio wings in subsonic and transonic flows. First, the nonlinear vortex-lattice method is described, augmented with a Prandtl–Glauert compressibility correction and regularized so that poststall solutions can be recovered. The linearization of the coupled system of equations is formulated using a Newton method, and the adjoint state is obtained for lift, drag, and inverse design functionals. Numerical results show that the aerodynamic model approximates well the forces predicted by three-dimensional (3D) RANS simulations for the Common Research Model wing, and that the adjoint-state gradients agree well with finite difference tests for a plethora of test cases. More interesting examples are shown, ranging from the optimal unstalling of wings to the assimilation of 3D RANS data into the present model, as well as its ability to extrapolate.

Optimization of Powertrain in EV

The method for preliminary powertrain design is presented in the paper. Performance of the EV is realized by motor torque–speed curve and gear ratio optimization. The typical two-zone mechanical characteristic of a PMSM traction motor is included in the optimization program. The longitudinal vehicle model is considered in the paper. Some examples try to show the calculation possibilities in application to existing vehicles: Tesla Model S and Mini Cooper SE.

Preliminary design of the control needed to achieve underwater vehicle trajectories

This paper presents a method for preliminary design of the control which is needed to achieve underwater vehicle trajectories. The proposed way allows one to evaluate dynamics of underwater vehicle using a trajectory tracking control algorithm. At the first stage, we propose the controller, and at the second, we test dynamics of the system based on the properties resulting from the transformed equations of motion and the selected indexes. The controller, which is applicable for fully actuated vehicles, contains the system dynamics in the control gains. It takes into account not only model of the vehicle but also model of disturbances. The way for the dynamics investigation uses the transformed equations obtaining from the inertia matrix decomposition. Consequently, thanks to the observed properties, it is possible to estimate dynamics using the criteria set. The method is useful before real experiment to test various models of the vehicle, disturbances, and the control task. The procedure is based on simulation tests and the proposed criteria. Effectiveness of the approach is shown on two examples of 6 DOF underwater vehicle model and its modifications.