Nominal Design Research Articles

Analysis, Design, and Implementation of DC–DC IBBC-DAHB Converter With Voltage Matching to Improve Efficiency

The interleaved bidirectional buck–boost converter dual active half-bridge (IBBC-DAHB) dc–dc converter consists of two converters IBBC and DAHB and a coupled inductor. The IBBC-DAHB converter has significant features such as low ripple current at the low-voltage side, low current stress on the input inductors, voltage stress across the switches less than the high-voltage side, high voltage gain, and zero-voltage soft switching. The converter offers high efficiency using phase-shift modulation when it operates at a nominal design operating point. However, the efficiency decreases due to high circulating current, high current stress, and limited soft-switching range when the source and load voltages deviate from their nominal values. This paper employs both duty cycle and phase-shift modulation methods to improve the above mentioned shortcomings using voltage matching for the DAHB converter. The proposed converter is analyzed and a 500-W experimental prototype with 40–60 V input voltage and 400 V output voltage under 100 kHz switching frequency is implemented to verify the theoretical results. The maximum efficiency of 97.15% is achieved at 60 V and 400 W. A flat efficiency characteristic for the converter is derived by the proposed control method, where the efficiency at 20% of nominal load is 91% and much higher than the phase-shift control, which is 70.8%.

Design-Oriented Testing and Modeling of Reinforced Concrete Pile Caps

A new perspective in the design of reinforced-concrete pile caps is proposed in this paper, where the conventional approach leading to a reinforcing mesh is replaced by modelling the cap as a strut-and-tie system, in agreement with the strut-and-tie model, STM proposed by several design codes, ACI 318 included. Twelve RC pile-cap specimens were designed and manufactured. In the first group of 4 specimens the caps rest on two piles (Group A, axis-to-axis distance 300 mm), while in the second and third groups the piles are three and four, respectively (Groups B and C, axis-to-axis distance 400 mm). In each group, the first and third specimens were designed according to the traditional sectional method (reference specimens, with constant depth and lateral shoulders), while the design of the second and fourth specimens was based on the strut-and-tie method (no lateral shoulders; no corners opposite to the piles). Needless to say, the nominal design load was the same within each group. The tests clearly show that cap design based on strut-and-tie systems brings in a sizable reduction in terms of reinforcement amount and cost, accompanied by a less pronounced but still sizable extra bearing capacity.

Reliability of elastomeric-isolated buildings under historical earthquakes with/without forward-directivity effects

Deviations from nominal design values of mechanical characteristics of seismic isolators are inevitable due to uncertainties and/or errors in material properties, element dimensions, construction methods, quality control, and/or installation steps, etc. In addition, due to uncertainties existing in active fault mechanisms affecting the site and local soil conditions, earthquake ground motions show record-to-record variability. Moreover, environmental conditions and/or time-dependent factors such as aging, temperature, and travel, etc. may also cause additional deviations in nominal values of characteristics of seismic isolators and thus in structural responses over the service life of structures. Therefore, in order to capture the dynamic behavior of base-isolated buildings realistically and design reliable base-isolated buildings, influence of such uncertainty should be taken into account. In this study, seismic reliability of realistic fully three-dimensional benchmark multi-story buildings equipped with nonlinear isolation systems is investigated under historical near-fault earthquakes. In order to take into account the uncertainties in the isolation system characteristics, pre-yield stiffness, post-yield stiffness, and yield displacement parameters are assumed as random variables, while the record-to-record variability nature of the ground motions is considered by using large sets of historical near-fault ground motions with or without forward-directivity effects. Two different levels of nominal isolation periods are taken into account while three different levels of uncertainty are considered for the random isolator characteristics. The reliability of the buildings is investigated in terms of structural integrity, isolation system safety, and the safety of the vibration-sensitive contents of the buildings using the peak bearing displacements and the peak floor accelerations obtained from the nonlinear time history analyses conducted in the framework of the Monte Carlo simulations. The plots including the average reliabilities for the displacement and the acceleration limit values provide a comprehensive picture in terms of the reliability level of the structural systems and of the vibration sensitive contents.

Effect of aging and manufacturing tolerances on multi-stage transonic axial compressor performance

The Axial compressor is an integrated part of a gas turbine. The central part of compressors is its blades. Blade aerodynamic has a significant effect on compressor performance. Because of the adverse pressure gradient in the compressor, any deviation in the blade profile has a significant influence on the flow field as well as the compressor performance. During the manufacturing and operation of a compressor, the blade profile may deviate from the nominal design. This deviation may happen within the manufacturing process, e.g., changing in stagger angle of the blade, changing in the maximum thickness of the blade profile or may occur in an operation process, e.g., increasing the blade surface roughness. By the way, these deviations affect the compressor performance. In this research, a numerical investigation is carried out to understand better the effects of geometry variability of the blades, including maximum thickness, blade surface roughness, and rotor blades stagger angle on the Transonic Axial compressor performance parameters, including the efficiency and pressure ratio. A CFD code, which solves the Reynolds-averaged Navier–Stokes equations, is employed to simulate the complicated 3D flow field of the axial compressor. The code is validated against experimental data for the axial compressor. The numerical result is in good agreement with the test dataand error at the design point for the efficiency was computed to be 0.3%, which shows high accuracy of the numerical method. Then, the effect of geometry variability on the axial compressor blade performance parameters is studied. Results show that increase in the surface roughness, blade thickness, and the rotor blades twist lowers the efficiency, pressure ratio and mass flow significantly in the compressor. Results show with a 10% increase of the blade installation angle at the design point, the mass flow rate decreases 1.93%, and the efficiency and pressure ratio decreases 0.35% and 1.8%, respectively. The blade surface roughness reduces the mass flow rate, total pressure ratio and efficiency of the compressor. The results show that imposing the roughness at the design point of the compressor, mass flow rate and efficiency is reduced 1.8% and 2.75 %, respectively. Meridional view of this compressor is shown in figure 1 in which the blade profiles for the first to fourth stages are DCA type [1].

Experimental beyond design and residual performances of full‐scale viscoelastic dampers and their empirical modeling

SummaryMost past researches relevant to viscoelastic (VE) dampers, regardless of analytical and experimental ones, aimed at their design (or pre‐damage) performance. In reality, however, under maximum considered or greater shaking caused by earthquakes, the shear deformation of the VE dampers installed in a structure may exceed or is even much larger than their nominal design range, thus leading to damage to the VE material. Under this circumstance, the structural design might become not conservative when the viscoelastically damped structure is a retrofit design or is not a supplemental damping design. Therefore, in this study, the beyond design and residual performances of the full‐scale VE dampers after suffering damage are experimentally probed and compared with their design (or pre‐damage) performance tested before. To have more engineering sense in practice, some suitable and conservative empirical post‐damage models through considering reduction factors in the Kelvin‐Voigt model for assessing the beyond design and residual performances of the full‐scale VE dampers after suffering damage are recommended.

Transmission and Reflection Characterization of Polarizing Beam Splitters at Submillimeter Wavelengths

This paper presents a comparison of the transmission and reflection performance of different free-standing wire grids and photolithographic polarizers. This study has been carried out in the frame of the development work of the submillimeter-wave instrument (SWI) as part of the JUpiter and ICy moons Explorer mission of the European Space Agency. SWI is a passive heterodyne radiometer that is operating in the frequency bands from 530 to 625 GHz and from 1080 to 1275 GHz. The optical coupling network of SWI includes a polarizing beam splitter to separate the signal into the two channels. Simulations of the transmittance and reflectance in copolarization and in cross polarization have been performed at different incidence angles and polarizations to support the selection of the optimum beam splitter for SWI. The nominal and actual design parameters of the investigated polarizing beam splitters, measured with a confocal laser microscope, have been considered in the simulations. Measurements of the transmission and reflection losses in co- and in cross polarization have been performed at 636.5 GHz to validate these numerical calculations. The very low losses of the beam splitters in copolarization were accurately measured by means of a free-space cavity resonator setup. These measurements are in very good agreement with the simulations and radiometric measurements of the transmission loss which were performed with a breadboard model of the SWI receiver unit at 590.0 GHz. The lowest transmission losses among the studied beam splitters are observed for a free-standing wire grid with a single plane of gold-coated wires. The highest reflectance in copolarization and the lowest levels of cross-polarization leakage are determined for the photolithographic polarizers.

Implosion performance of subscale beryllium capsules on the NIF

Many inertial fusion designs use capsules made of beryllium, as its high mass ablation rate is advantageous. We present the first systematic experimental study of indirectly driven beryllium capsules with a cryogenic deuterium-tritium fuel layer. “Subscale” capsules, 80% of the nominal National Ignition Facility point design radius, show optimal performance with the remaining mass of ∼6–7%. A buoyancy-drag mix model explains the implosion performance, suggesting that fuel-ablator mix is the dominant degradation mechanism. Increasing the capsule scale is predicted to reduce the impact of fuel-ablator mix and achieve high performance.

A study of vibro-acoustic behaviour variation of thin sheet metal components manufactured through deep drawing process

Deep drawing is one of the most widely used manufacturing methods in the automobile industry. Therefore, a thorough understanding of this method is very important. Only for certain kinds of materials the forming process knowledge to achieve the desired dimensional accuracy is currently available. With the advent of different kinds of steels—corrosion resistant, dent resistant and cost-effective alloys—in the market, the deep drawing manufacturing method gained a significant momentum in the recent past. Achieving the desired dimensional accuracy of a designed part still remains a challenge as complex phenomena including spring-back are associated with the manufacturing process. It is often seen that the deep drawing process results in both geometric profile and thickness variations as compared to the nominal part design. These deviations are important with respect to the geometrical dimensional accuracy, but in addition they can also have a significant effect on the vibro-acoustic behaviour of the manufactured components. Hence, most often the simulation results of a nominal CAD part design using Finite Element Analysis (FEA) do not represent the actual behaviour of the component. In this research paper, a variation analysis—using both simulation and experimental methods—of a component manufactured through deep drawing, starting from a blank sheet made of mild steel material, is presented in a systematic manner. After a thorough analysis of the dynamic behaviour of the blank, an industrial component—an oil pan look-a-like—with a high draw ratio is designed, manufactured and analysed for understanding the impact of geometrical deviations on it’s vibro-acoustic behaviour. The geometry of the actual component is obtained through a white-light scanning process. It is observed that a geometry profile deviation up to 5 mm and a thickness variation of 40% occurred in the actual manufactured part as compared to the nominally designed part. The eigenfrequencies of the actual part have deviations up to 14% as compared to that of the nominal part. The mode shape comparison—using the Modal Assurance Criterion (MAC)—between the experimental and the simulation results proves the necessity of incorporating geometric deviations. The acoustic simulation results obtained from the geometries of the nominal CAD design and the actual part are compared and it is found that the actual part design results are in good agreement with the experimental results. Hence, this paper focuses on establishing the importance of considering geometry and thickness deviations, that occur in the deep drawing process, when predicting vibro-acoustic properties. It is demonstrated that there is a significant increase in the accuracy of the simulation predictions by incorporating the manufacturing effects.

Carbon Capture at the Kemper IGCC Power Plant

The Kemper County Project demonstrated Transport Integrated Gasification (TRIG™) technology at a 2 x 1 Integrated Gasification Combined Cycle (IGCC) facility in Kemper County, Mississippi. Capable of generating up to 582 MW during syngas operations, the facility represents the largest IGCC project undertaken, the first to use lignite as fuel, the first to capture and sell CO2, and the first to produce multiple byproducts from initial startup. Featuring UOP’s SELEXOL™ (also known as SeparALL™) process, the acid gas removal (AGR) system at the plant captured carbon dioxide from the syngas and diverted it for use in enhanced oil recovery (EOR), making the Kemper facility’s carbon emissions comparable to those of a similarly sized natural-gas-fired combined cycle power plant. In addition to producing carbon dioxide, the plant also generated other saleable byproducts, including ammonia and sulfuric acid. The UOP SELEXOL process uses a physical solvent to remove acid gases from synthetic gas for the selective removal of H2S and COS and/or CO2 to very low levels in the treated gas. Very low sulfur levels of below 1 ppmv can be achieved with variable and optimized CO2 capture levels. The AGR at Kemper was the first and the largest carbon capture facility for IGCC in the world and also removed sulfur from the syngas. The process H2S absorbers remove over 99% of the sulfur. The captured H2S is later stripped from the solvent using steam heat, producing a concentrated H2S acid gas for producing sulfuric acid, while the purified solvent is refrigerated and recycled to the absorption units. Following sulfur removal, the syngas flows into CO2 absorbers, where a large portion of the CO2 in the syngas is removed. The CO2-laden solvent is regenerated by lowering the pressure of the solvent, allowing the CO2 to evolve. The removed CO2 stream was dehydrated and compressed and sold as a byproduct for EOR. The plant successfully produced electricity and all associated byproducts, while maintaining excellent safety records both during construction and plant operation. The AGR operated for over 3000 hours, processing around 1 million metric tons of syngas before the project was suspended, primarily due to the dramatic decrease in the long-term price forecast for natural gas since the time that the project was approved. Despite changes in project economics, the plant operated as intended, and just under 100,000 metric tons of carbon dioxide was delivered to the pipeline and used for enhanced oil recovery. The AGR system performed well, even at turndown conditions, processing the air-blown syngas without difficulty and making Kemper the first SELEXOL facility to process syngas produced from air-blown gasification. Syngas processing rates in the AGR were as high as 90% of full load syngas capacity, and the plant achieved the nominal design carbon capture rate of 65%, while maintaining stringent CO2 product quality requirements. The AGR sulfur capture rates were also excellent, with syngas sulfur content consistently below 0.5 ppmv, allowing the plant to easily meet its sulfur emission requirements. Commissioning on the byproduct processing systems also saw great success. The CO2 compressors, the largest two in the world with a rated power consumption of 21 MW each, performed well at supplying the CO2 to the pipeline at pressures of up to 122 barg. This paper provides a description of the process technology deployed at the Kemper Facility and discusses plant operational experience, including some of the challenges associated with commissioning a facility of this size and novelty, as well as the extended operation of the Acid Gas Removal system and CO2 compression unit.

Energy from waste: Plant design and control options for high efficiency and emissions’ compliance under waste variability

Variations in composition and charging rates of waste constituents in energy-from-waste (EfW) plants disturb throughput and power output from nominal design (ND) levels. Offgas flowrates and composition are affected, impinging on operating expenses, profitability and emissions. State-of-the-art facilities claim improved efficiency and emissions' compliance, by controlling the combustor via fluegas recirculation, fluegas heat recovery, excess air and oxygen enrichment. The work investigates the mutual influence of plant ND and of the above controls. Given a ND, it assesses the concurrent effect on performance and pollution abatement efficacy, under variability in key waste constituents. Based on the combined mass and enthalpy balance and on necessary and sufficient conditions for emissions’ compliance, it determines appropriate manipulations (directions, gains and ranges) for high efficiency and reduced emissions under large waste variability (e.g., biodegradable fraction varying by 50%). It quantifies how heat integration and oxygen enrichment enable higher throughput of poor constituents (by boosting combustion), whereas higher fluegas recirculation and excess air suppress it, enabling higher throughput and power production from rich waste constituents. Concurrent action of the control variables enhances performance. ND affects the directions (increase or decrease) and manipulation ranges and provides safety margins ensuring compliance over the entire waste uncertainty range.

Development of Continuous-Flow Total Artificial Heart for Use in Infants

Purpose Heart transplantation in infants and children is an accepted therapy for congenital heart disease, but donor organ availability remains unstable. Mechanical circulatory support is another standard option, but there is a lack of implantable devices due to size and functional range. The purpose of this study was to evaluate in vivo performance of the initial prototype of an infant continuous-flow total artificial heart (I-CFTAH) with one motor and one rotating assembly supported by a hydrodynamic bearing. Methods The I-CFTAH was designed to cover a range of 3 kg infant to 9 kg child (flange diameter - 26.9 mm; length - 44 mm), with nominal design point was matched to a 6 kg child, requiring 1.0 L/min of flow. I-CFTAH was tested using in silico virtual simulation mock loop (VML; MATLAB; MathWorks®) and simulated the hemodynamics as they surge through the system implanted with blood pump (run at 0.5 L/min for 3 kg infant). Lumped-parameter model including systemic/pulmonary circulation, values for impedance, beat rate, and blood volume was used. Results The in silico experiments showed intended performance of scaled down pump (left and right pump flows - 0.5 L/min at 4380 RPM). The difference between the left and right atrial pressures was maintained within ± 5-15 mm Hg. Simulation of I-CFTAH was successfully performed and allowed creating arterial pulsation with this device. Conclusion The present simulation-based approach showed feasibility of I-CFTAH design. The I-CFTAH met the proposed requirements for self-regulation, performance and pulse modulation. Further in vitro validation and in vivo implantation will be necessary to explore this technology in more detail.

Pump as turbine applied to micro energy storage and smart water grids: A case study

The need of energy storage in micro scale is recently emerging and becoming more relevant in the rising era of decentralised renewable energy production. This paper provides a technical overview of the design and the outcomes of a first-of-its-kind Pumped Hydro Energy Storage (PHES) micro facility. The described micro-PHES is integrated in a smart grid and it is designed to store energy produced by the connected renewable energy sources. Interestingly, this micro-PHES runs with a single centrifugal pump for both pumping and generating phases. Variable speed regulation allows the pump to constantly operate at the maximum hydraulic efficiency in order to deal with load variations. In the same way, the pump running in reverse, namely Pump as Turbine (PaT), runs at the most suitable speed and it keeps high efficiency (near to 0.71%) over a range of 40–120% of the nominal load design. The pump/PaT is selected according to the presented methodology and it is experimentally characterized in the current case study. The PHES implementation is defined in relation with the smart grid consumption and renewable energy production and it reaches a total round-trip yield up to 42%. In addition, this paper defines the techno-economic parameters for a micro-PHES cost-effective solution and provides an important dataset for micro-PHES feasibility breakdown. The use of a storm-water basin as reservoir produces an expense cut greater than 28% of the total direct cost. This constitutes a valid economic advantage to be integrated in future smart water grid’s designs. Also, the system with the described features can reach a Levelised Cost of Energy (LCOE) of 0.58–1.06 €/kWh in micro-PHES.

Optimizing the 8Li yield for the IsoDAR Neutrino Experiment

The focus of this paper is on optimizing the electron-antineutrino source for the IsoDAR (Isotope Decay at Rest) experimental program. IsoDAR will perform sensitive short-baseline neutrino oscillation and electroweak measurements, among other Beyond Standard Model searches, in combination with KamLAND and/or other suitable detectors. IsoDAR will rely on the high-Q β− decay of the 8Li isotope for producing electron-antineutrinos, created mainly via neutron capture in an isotopically enriched 7Li sleeve surrounding the Be target. In particular, this paper examines the performance, defined in terms of absolute 8Li (or, equivalently, electron-antineutrino) production rate, of various candidate sleeve materials, including a lithium-fluoride, beryllium-fluoride mixture (“FLiBe”) sleeve and a homogeneous mixture of lithium and beryllium (“Li-Be”). These studies show that the 8Li yield can be increased substantially by employing a Li-Be sleeve and therefore motivate significant changes to the nominal IsoDAR design.

Predictions of the WFIRST Microlensing Survey. I. Bound Planet Detection Rates

The Wide Field InfraRed Survey Telescope (WFIRST) is the next NASA astrophysics flagship mission, to follow the James Webb Space Telescope (JWST). The WFIRST mission was chosen as the top-priority large space mission of the 2010 astronomy and astrophysics decadal survey in order to achieve three primary goals: to study dark energy via a wide-field imaging survey, to study exoplanets via a microlensing survey, and to enable a guest observer program. Here we assess the ability of the several WFIRST designs to achieve the goal of the microlensing survey to discover a large sample of cold, low-mass exoplanets with semimajor axes beyond roughly one AU, which are largely impossible to detect with any other technique. We present the results of a suite of simulations that span the full range of the proposed WFIRST architectures, from the original design envisioned by the decadal survey, to the current design, which utilizes a 2.4-m telescope donated to NASA. By studying such a broad range of architectures, we are able to determine the impact of design trades on the expected yields of detected exoplanets. In estimating the yields we take particular care to ensure that our assumed Galactic model predicts microlensing event rates that match observations, consider the impact that inaccuracies in the Galactic model might have on the yields, and ensure that numerical errors in lightcurve computations do not bias the yields for the smallest mass exoplanets. For the nominal baseline WFIRST design and a fiducial planet mass function, we predict that a total of ${\sim}1400$ bound exoplanets with mass greater than ${\sim}0.1~M_{\oplus}$ should be detected, including ${\sim}200$ with mass ${\lesssim}3~M_{\oplus}$. WFIRST should have sensitivity to planets with mass down to ${\sim}0.02~M_{\oplus}$, or roughly the mass of Ganymede.

Off-design operation of ORC engines with different heat exchanger architectures in waste heat recovery applications

Abstract Organic Rankine cycle (ORC) engines in waste-heat recovery applications experience variable heat-source conditions (i.e. temperature and mass flow-rate variations). Maximising ORC system performance while accounting for off-design operation in response to such variations is of crucial importance for the financial viability and wider adoption of this technology. In this paper, the off-design performance of an ORC engine is investigated in a heat-recovery application from a stationary internal combustion engine (ICE), employing a screw expander and two heat exchanger (HEX) architectures. Unlike previous studies where the ORC expander and HEX performance are assumed fixed during off-design operation, here we consider explicitly the time-varying characteristics of these system components. Nominal system sizing results indicate that the screw expander isentropic efficiency exceeds 80%, and that the heat transfer area requirements of plate HEXs (PHEXs) are 50% lower than those of double-pipe HEXs (DPHEX). Following nominal system design, the ORC engine operation is optimised at conditions relating to part-load (PL) operation of the ICE. Although, the heat transfer coefficients in the evaporator decrease by 30% at PL, the HEX effectiveness increases by up to 20% due to higher temperature differences between the working fluid and the heat source, and the performance of the PHEX appears less sensitive to off-design operation conditions. The optimum PL screw expander efficiency maps reveal only a minor reduction of the expander efficiency (by 2%) relative to the design conditions. Optimum off-design maps indicate that the power output of the ORC engine reduces to 72% of full-load for an ICE at 60% of full-load, and that ORC engines with PHEXs generate slightly more power for the same heat-source conditions. Overall, the tool developed predicts ORC performance over an operating envelope and allows the selection of optimal HEX and expander designs. The findings can be used by ORC plant operators to optimise the ORC engine power output given varying on-site heat-source conditions, and by ORC vendors to inform HEX and expander design decisions.

Shell-and-tube or packed bed thermal energy storage systems integrated with a concentrated solar power: A techno-economic comparison of sensible and latent heat systems

A detailed techno-economic comparison—using annual, transient integrated system modelling—was conducted for sensible and latent heat thermal energy storage (TES) systems. As the most viable near-term competitors, thermocline/packed-bed and shell-and-tube configurations were compared to the conventional two-tank molten salt system. Concrete and a range of phase change materials (PCMs) were considered as the storage mediums in this study. All analyses were conducted for 15 h of storage capacity for the 19.9 MWe Gemasolar concentrated solar power (CSP) plant as a real-world case study.It was found that when the CSP plant is constrained to the operational within the tight bounds of the standard two-tank system, the dual-media thermocline (DMT) system with concrete or encapsulated PCM shows the best performance. Imposing rigid operational boundaries significantly disadvantages shell-and-tube (ST) systems (e.g. resulting in up to ∼50% less annual electricity production than a CSP plant with two-tank system). However, the results of this study reveal that extending the TES charge and discharge cut-off temperatures closer to the plant’s maximum and minimum operating range (i.e. 800 K and 650 K) can maximize the potential of dual-media TES alternatives. Under these loose operational conditions, the CSP plant will be required to occasionally operate at conditions which are far from its nominal design point (i.e. up to 75% variation). This flexibility allows all the TES alternatives considered in this study to achieve similar CSP annual electricity output as the two-tank system. In this case (e.g. all TES systems achieve the same annual output), the TES alternatives can be compared based on their specific costs rather than their levelized cost of electricity. Compared to the specific cost of two-tank molten salt systems, ∼24.5 US$ kWhth−1, a 62% reduction of specific storage cost was found to be achievable with concrete storage a dual-media thermocline (DMT) system, representing the best techno-economic option. This was followed by 49% cost reduction for a pipeless shell-and-tube (ST) system incorporating concrete or a PCM with 1 mm pipe thickness. Without minimizing the capsule thickness to 0.1 mm, the packed bed system with PCM would never have economic justification. Overall, this study reveals that if CSP systems can be designed to have more flexibility in their operational temperature range, a significant cost savings is available in moving to alternative TES systems.

Radial Basis Functions Update of Digital Models on Actual Manufactured Shapes

In the mechanical engineering world, there is a growing interest in being able to create so-called “digital twins” to assess the impact to performance or response. Part of the challenge is to be able to include and assess manufactured geometries as opposed to nominal design intent, particularly for components that are sensitive to small shape variations. In this paper, we show how the update of digital models adopted in computer aided engineering (CAE) can be conducted according to a mesh morphing workflow based on radial basis functions (RBF). The CAE mesh of the nominal design is updated onto the actual one as acquired from surveying a manufactured individual. The concept is demonstrated on a practical application, the wing structure of the RIBES experiment, showing how the new proposed method compares with a traditional one based on the reconstruction of the geometrical model.

Nominal model selection and guidance computer design for antitank guided missile

Nominal model selection and guidance computer design for antitank guided missile

Nominal model selection and guidance computer design for antitank guided missile

The great developments in applied mathematics and computational capabilities facilitate the design and implementation of robust control. Among the real applications are the guided missiles especially the antitank guided missile systems which are commanded to the line of sight (CLOS) against ground and short-range targets. The present work is concerned with improving the performance of an antitank guided missile system belonging to the first generation via robust synthesis of guidance systems. The selection of nominal model is required to design the guidance computer for the system. This paper is devoted to the quantitative analysis to select a nominal plant which used to design a guidance computer that has a successful flight path trajectory against different types of uncertainties. The design and analysis necessitate somehow accurate model with different uncertainties for the system. The flight path is evaluated considering the HIL environment.

CAEUp - Update of CAE models on actual manufactured shapes

Engineering fields with high technological contents involve manufacturing requirements in which the control of the margins of tolerance, as well as the verification of the manufactured components, has economic impacts in the relationships with customers. The verification of the actual geometry after manufacturing then acquires paramount importance, and it can be substantially improved by adopting the digital twin approach: the CAE model of the system is adapted onto the actual manufactured shape making the numerical prediction individual manufactured component specific. CAEUp aims at implementing a cloud-based software tool whose core is the comparison of the structural performances between the CAE model relative to the nominal design of a certain product and the digital twin of the real product as built. The digital twin is updated on High Performance Computing (HPC) cloud infrastructure and the performance prediction recomputed adopting a variation of the CAE model shaped like the actual manufactured part. The process is demonstrated adopting a specific example: the structural assessment of a simplified turbine blade geometry. The baseline geometry, available as a CAD model, is adopted to define the reference FEA model for the ANSYS® MechanicalTM solver so that key performance indexes can be computed (stress level and stiffness). The actual manufactured shape is surveyed and available as a tesselated surface (the standard STL format is herein adopted). The projection and adaption using mesh morphing allows to morph the baseline FEA model onto the actual manufactured shape; finally the updated FEA model is run again to extract performance indexes and decide whether the component fulfills the design specifications.