Search

In this article, the results of an experimental investigation and a 1D modeling activity on the steady-state performance of a wastegated turbocharger turbine for spark ignition engines are presented. An experimental campaign to analyze the turbine performance for different waste-gate valve openings was conducted at the test bench for components of propulsion systems of the University of Genoa. Thanks to the experimental activity, a 1D model is developed to assess the interaction between the flow through the impeller and the by-pass port. Advanced modeling techniques are crucial for improving the assessment of turbocharger turbines performance and, consequently, enhancing the engine–turbocharger matching calculation. The initial tuning of the model is based on turbine characteristic maps obtained with the by-pass port kept closed. The study then highlights the waste-gate valve behavior considering its different openings. It was found that a more refined model is necessary to accurately define the mass flow rate through the waste-gate valve. After independently tuning the 1D models of the turbine and the waste-gate valve, their behavior is analyzed in parallel-flow conditions. The results highlight significant interactions between the two components that must be taken into account to reduce inaccuracies in the engine-turbocharger matching calculation. These interactions lead to a reduced swallowing capacity of the turbine impeller. This reduction has an impact on the power delivered to the compressor, the boost pressure, and, consequently, the engine backpressure. The results suggest that methods generally adopted that consider the by-pass valve and the turbine as two nozzles working in parallel under the same thermodynamic condition could be insufficient to accurately assess the turbocharger behavior. [ABSTRACT FROM AUTHOR]

A one-dimensional numerical overland flow model based on the cascade plane theory was developed to estimate rainfall-induced runoff and soil erosion on converging and diverging plane surfaces. The model includes three components: (i) soil infiltration using Horton's infiltration equation, (ii) overland flow using the kinematic wave approximation of the one-dimensional Saint-Venant shallow water equations for a cascade of planes, and (iii) soil erosion based on the sediment transport continuity equation. The model's performance was evaluated by comparing numerical results with laboratory data from experiments using a rainfall simulator and a soil flume. Four independent experiments were conducted on converging and diverging surfaces under varying slope and rainfall conditions. Overall, the numerically simulated hydrographs and sediment graphs closely matched the laboratory results, showing the efficiency of the model for the tested controlled laboratory conditions. The model was then used to numerically explore the impact of different plane soil surface geometries on runoff and soil loss. Seven geometries were studied: one rectangular, three diverging, and three converging. A constant soil surface area, the rainfall intensity, and the slope gradient were maintained in all simulations. Results showed that increasing convergence angles led to a higher peak and total soil loss, while decreasing divergence angles reduced them. [ABSTRACT FROM AUTHOR]

Source rock is one of the major components of the hydrocarbon system. Understanding the maturity of the source rock and the patterns of the basin would have led to proposing a suitable site for drilling an exploratory well. Simulation of the hydrocarbon system is an indirect approach to an estimate of the exploration potential of a site. The current research purposes are to evaluate the maturation of the hydrocarbon fluids, trace the hydrocarbon migration pathway, and identify the possible source rock characteristics in the Garmsar area, Central Iran Basin. To this purpose, 1D and 2D modeling of the area have been carried out using PetroMod software to measure kerogen maturation and hydrocarbon generation and expel, as well as to stimulate the production of oil and gas from a source rock, migration pathway, and accumulation respectively. Geochemical characteristics of the source rocks were examined to estimate the hydrocarbon generation; the obtained data have demonstrated that there are relatively good quantities of organic matter in the source rocks of Qom Formation in Garmsar Block, and the organic matter is mainly type II and III. In general, source rock from the Garmsar Block spreads a satisfactory perspective for hydrocarbon generation. Furthermore, based on the 2D modeling, hydrocarbon accumulation begins in the C4 member of the Qom Formation and, eventually to the present, increases in anticlines at the central part of the study area in the F member of the Qom Formation. [ABSTRACT FROM AUTHOR]

This study employed 1D numerical pseudo models to examine the Upper Jurassic carbonate succession, focusing on the Mikulov Formation in the Vienna Basin region. It addresses the protracted and complex history of the Jurassic source rock play, revealing a transition from rapid syn-rift (>200 m/Ma) to slower post-rift sedimentation/subsidence of the overlying layers during extensional deformation (up to 120 m/Ma with a thickness of 1300 m). This provides valuable insights into the rift-to-drift stage of the central Alpine Tethys margin. The Mikulov marls exhibit characteristics of a post-rift passive margin with slow sedimentation rates. However, a crustal stretching analysis using syn-rift heat flow sensitivity suggested that thermal extension of the basement alone cannot fully explain the mid-Jurassic syn-rift stage in this segment of the Alpine Tethys. The sensitivity analysis showed that the mid-late Jurassic differential syn-rift sequences were exposed to slightly cooler temperatures than the crustal stretching model predicted. Heat flow values below 120 mW/m2 aligned with measurements from deeply settled Mesozoic successions, suggesting cold but short gravity-driven subsidence. This may account for the relatively low thermal maturation of the primary source rock interval identified by the time-chart analysis, despite the complex tectonic history and considerable sedimentary burial. The post-Mesozoic changes in the compaction trend are possibly linked to the compressional thrusting of the Alpine foreland and postdating listric faulting across the Vienna Basin. [ABSTRACT FROM AUTHOR]

The Circle of Willis (CoW) describes the arterial system in the human brain enabling the neurovascular blood supply. Neurovascular diseases like intracranial aneurysms (IAs) can occur within the CoW and carry the risk of rupture, which can lead to subarachnoid hemorrhage. The assessment of hemodynamic information in these pathologies is crucial for their understanding regarding detection, diagnosis and treatment. Multi-dimensional in silico approaches exist to evaluate these hemodynamics based on patient-specific input data. The approaches comprise low-scale (zero-dimensional, one-dimensional) and high-scale (three-dimensional) models as well as multi-scale coupled models. The input data can be derived from medical imaging, numerical models, literature-based assumptions or from measurements within healthy subjects. Thus, the most realistic description of neurovascular hemodynamics is still controversial. Within this systematic review, first, the models of the three scales (0D, 1D, 3D) and second, the multi-scale models, which are coupled versions of the three scales, were discussed. Current best practices in describing neurovascular hemodynamics most realistically and their clinical applicablility were elucidated. The performance of 3D simulation entails high computational expenses, which could be reduced by analyzing solely the region of interest in detail. Medical imaging to establish patient-specific boundary conditions is usually rare, and thus, lower dimensional models provide a realistic mimicking of the surrounding hemodynamics. Multi-scale coupling, however, is computationally expensive as well, especially when taking all dimensions into account. In conclusion, the 0D–1D–3D multi-scale approach provides the most realistic outcome; nevertheless, it is least applicable. A 1D–3D multi-scale model can be considered regarding a beneficial trade-off between realistic results and applicable performance. [ABSTRACT FROM AUTHOR]

One-dimensional blood flow model accuracy has been verified in many studies. The topic of this work is introducing gravity into a one-dimensional model. For this purpose, gravitational force was introduced into an existing model. To account for gravity, the boundary conditions also must be adjusted to reflect the body's adaptation. For this purpose, a method for calculating the arterial resistance of the terminal arteries during gravity changes has been developed and presented in this article. The technique is based on the idea that the human body reacts to changes in gravity in such a way as to preserve the volume of blood delivered to the organs. Experiments have shown that not only the pressure, but also the flux waveform and the pressure waveform change when the flow is preserved. The method of adjusting the boundary conditions is such that the flow almost does not change after applying the gravity, but it is possible to estimate the change in pressure dynamics. This methodology can be used to study the blood flow in different cases related to gravity. [ABSTRACT FROM AUTHOR]

In this work, a reliable kinetic reaction mechanism was revised to accurately reproduce the detailed reaction paths of steam reforming of methane over a Ni/Al 2 O 3 catalyst. A steady-state fixed-bed reactor experiment and a 1D reactor catalyst model were utilized for this task. The distinctive feature of this experiment is the possibility to measure the axially resolved temperature profile of the catalyst bed, which makes the reaction kinetics inside the reactor visible. This allows for understanding the actual influence of the reaction kinetics on the system; while pure gas concentration measurements at the catalytic reactor outlet show near-equilibrium conditions, the inhere presented temperature profile shows that it is insufficient to base a reaction mechanism development on close equilibrium data. The new experimental data allow for achieving much higher quality in the modeling efforts. Additionally, by carefully controlling the available active surface via dilution in the experiment, it was possible to slow down the catalyst conversion rate, which helped during the adjustment of the reaction kinetics. To assess the accuracy of the revised mechanism, a monolith experiment from the literature was simulated. The results show that the fitted reaction mechanism was able to accurately predict the experimental outcomes for various inlet mass flows, temperatures, and steam-to-carbon ratios. [ABSTRACT FROM AUTHOR]

• A comprehensive 1D model is developed to couple hydrodynamics, oxygen transfer and autocatalytic manganese oxidation. • The transient axial 1D model is applied to a bubble column used for Mn(II) removal. • A two bubbles class model is implemented to represent the heterogeneous regime. • Simulated parameters are in good agreement with experimental measurements and very close to 3D CFD results. • Transient 1D model and experimental data are in good agreement for several operating conditions after the first 15 min. Modeling multiphase reactors requires an in-depth multidisciplinary analysis of various phenomena including the chemical kinetics, oxygen mass transfer, as well as the simulation of flows within these contactors. In this study, a 1D model of two-phase flow for Mn(II) removal from drinking water by aeration process is developed and validated. This model is based on the Eulerian description of two-phase gas–liquid flow with the comparison between a one-medium bubble size and a two-bubble class description to represent the bubble population in the heterogeneous flow regime. All the relevant chemical species are simulated by coupling hydrodynamics, gas–liquid mass transfer, and reaction kinetic. A pseudo-first-order model accounting for homogeneous and heterogeneous kinetics is considered for Mn(II) oxidation. The performance of the developed 1D model is compared and validated with experimental data. The 1D model was able to predict quantitatively Mn oxidation as a function of pH, initial Mn(II) and initial Mn(IV) concentrations. [ABSTRACT FROM AUTHOR]

Energy management in electrified vehicles is critical and directly impacts the global operating efficiency, durability, driveability, and safety of the vehicle powertrain. Given the multitude of components of these powertrains, the complexity of the proper control is significantly higher than the conventional internal combustion engine vehicle (ICEV). Hence, several control algorithms and numerical methods have been developed and implemented in order to optimize the operation of the hybrid powertrain while complying with the required boundary conditions. In this work, a model-based method is used for predicting the impacts of a set of possible control actions, choosing the one minimizing the associated costs. In particular, the energy management technique used in the present study is the equivalent consumption minimization strategy (ECMS). The novelty of this work consists of taking into account the thermal state of the ICE for optimization. This feature was implemented by means of an extensive experimental campaign at different coolant temperatures of the ICE to calibrate the additional fuel consumption due to operating the engine outside of its optimum temperature. The results showed significant gains in both WLTC and RDE cycles. [ABSTRACT FROM AUTHOR]

This study proposes 1D modeling that considers the noise and vibration of a vehicle window-brushed DC motor. The electrical and mechanical components of the brush DC motor are included, creating a model that considers noise and vibration. The model has a back electromagnetic force (EMF) including vibration components and is constructed based on an electric circuit and transfer functions. To ensure the reliability of the model, the back EMF, noise, and vibration experiment environment of the brushed DC motor were configured. The measured back EMF was applied to the model, and it was confirmed that the simulation results of the model were consistent with the measured noise and vibrations. [ABSTRACT FROM AUTHOR]

To address the increasing interest towards more environmentally friendly naval transportation and the introduction of IMO2020 restrictions on pollutant emissions onboard ships, the present work details the preliminary design of a mini gas turbine engine, i.e., a gas turbine engine with an output power up to 5 MW, for onboard energy generation. In comparison to conventional propulsion systems, gas turbine units benefit from known compactness, which can be further enhanced by employing single-stage uncooled radial machines, according to similar works in the field. As such, the present paper aims to set up a complete procedure that allows a reliable and fast (i.e., requiring a limited computational effort) preliminary design of one-stage centrifugal compressors and radial turbines operating at a high pressure ratio via the use of classical one-dimensional theory. The aerodynamic design outputs in terms of forces and torques are then used to perform a preliminary mechanical design of the shaft by means of a one-dimensional finite element model with commercial software to estimate the corresponding shaft line stress. Despite some necessary geometrical and modeling simplification of the design problem, which results in the unavailability of detailed information on individual components, the employed procedure nevertheless allows a comprehensive overview of the possibilities in terms of maximum machine performance achievable at an early design stage with the associated limited computational requirements. The design procedure and the geometry achieved for the application are presented along with aerodynamic and structural results. [ABSTRACT FROM AUTHOR]

Impending emission regulations of diesel engines for construction machineries would regulate nitrogen oxide emissions strictly in cold operating conditions. The urea-based selective catalytic reduction (urea-SCR) system coupled with the electrically heated catalyst (EHC) has been considered as a potential measure to meet the strict emission regulations by promoting evaporation and thermal decomposition of urea–water solution in cold operating conditions. Analyzing the thermal conditions in the EHC is crucial for the optimized operation and control of EHC-based urea-SCR systems under various engine operating conditions. In the current study, we introduce a simple one-dimensional analysis scheme to characterize the surface temperature distribution in the EHC based on energy conservation and the theories of forced internal convection. Since the EHC has a complicated internal structure with fine flow cells inside it, a flow cell in the EHC is extracted for the one-dimensional heat transfer analysis. EHC operation parameters such as exhaust gas flow rate and supplied electric power to the EHC are scaled to be applied for the flow cell analysis. The adequacy of the analysis scheme is then validated by surface temperature measurement results at the EHC outlet. The validation results showed over 95% prediction accuracy of the 1D analysis scheme in the operating conditions of a heavy-duty diesel engine. Based on proven reliability, the effects of geometric and operation parameters on the surface temperature distribution in the EHC were analyzed and discussed using the analysis results. [ABSTRACT FROM AUTHOR]

• The influence of annealing temperature on the n- region was thoroughly evaluated. • Junction depths were calculated through simulations and validated with experiments. • The transport rate of interstitials was determined by the 1D model and validated. • Reannealing experiments resulted in the pn junction moving back. • The diffusion coefficient of vacancies was determined and validated. The n− region is crucial to the performance of n-on-p HgCdTe devices. However, the underlying mechanisms governing its formation process remain insufficiently elucidated in current literature. In this work, the influence of annealing temperature on the n− region formation process was investigated systematically through experiments and one-dimensional (1D) simulation. The two key parameters, the transport rate of interstitials (Tr I) and the diffusion coefficient of vacancies (D V) were determined through the 1D model, and their accuracy was validated by experiments. The determination of Tr I and D V allows for more flexible and precise optimization of the n− region in HgCdTe, thereby providing valuable guidance for cost-effective, high performance, and reliable preparation of HgCdTe detectors. [ABSTRACT FROM AUTHOR]

The Atgram-1X well is located at the Zakiganj structure of the Eastern Folded Belt within the Bengal Basin. It is the second deepest well in Bangladesh and encounters Jenam Formation at target depth. It is a dry well, but a robust gas show was recorded at 3832 m within the Lower Bhuban Formation. So many gas field discoveries in the Eastern Folded Belt of the Bengal Basin indicate an active petroleum system in the Zakiganj structure. This research aims to understand the source rock potentiality and hydrocarbon generation, migration, and accumulation possibilities in the Zakiganj structure based on the 1D petroleum system modeling technique. There are four potential source rocks present in the studied well. These are the Jenam shale, Renji-3 shale, Renji-1 shale, and Lower Bhuban-2 shale. The maximum burial of this studied well was 5860 m at 0.5 ma years ago. The major upliftment occurred 2.6 to 1.6 million years ago. The maturity model shows that the source rock is early oil to wet gas maturity stage. These source rocks and gas and oil generation potential are about 103 mg HC/gm TOC and 30 mg HC/gm TOC, respectively. The potentiality of the kerogen transformed to hydrocarbon is about 77% which was started 7.81 million years ago. The critical moment of the source rock was 4.52 million years ago. The model shows that the possibility of forming a structural trap during the major upliftment started 2.6 million years ago and is a good prospect for accumulating wet gas. [ABSTRACT FROM AUTHOR]

Three-dimensional cardiovascular fluid dynamics simulations typically require computation of several cardiac cycles before they reach a periodic solution, rendering them computationally expensive. Furthermore, there is currently no standardized method to determine whether a simulation has yet reached that periodic state. In this work, we propose the use of an asymptotic error measurement to quantify the difference between simulation results and their ideal periodic state using open-loop lumped-parameter modeling. We further show that initial conditions are crucial in reducing computational time and develop an automated framework to generate appropriate initial conditions from a one-dimensional model of blood flow. We demonstrate the performance of our initialization method using six patient-specific models from the Vascular Model Repository. In our examples, our initialization protocol achieves periodic convergence within one or two cardiac cycles, leading to a significant reduction in computational cost compared to standard methods. All computational tools used in this work are implemented in the open-source software platform SimVascular. Automatically generated initial conditions have the potential to significantly reduce computation time in cardiovascular fluid dynamics simulations. [ABSTRACT FROM AUTHOR]

The combination of a growing number of complex technologies in internal combustion engines (ICE) is commonplace, due to the need of complying with the tight pollutant regulations and achieving high efficiencies. Hence the work of calibration engineers is led by a constant increase in degrees of freedom in ICE design. In this research work, a wide analysis on the optimization of combined variable valve timing (VVT) and exhaust gases recirculation (EGR) strategies is developed, in order to reduce fuel consumption in a EURO 6 1.3l 4-stroke 4-cylinder, gasoline, turbocharged, direct-injection engine, also equipped with a variable nozzle turbine (VNT). For that purpose, a methodology which combines 1D engine simulations with limited experimental work was applied. First, the data from 25 experimental tests distributed into three steady engine operating conditions was used to calibrate a 1D model. Then, modeling parametric studies were performed to optimize VVT and EGR parameters. A total of 150 cases were simulated for each operating point, in which VVT settings and EGR rate were varied at iso-air mass flow and iso-intake manifold temperature. The optimization was based on finding the configuration of VVT and EGR systems which maximizes the indicated efficiency. All different cases modeled were also evaluated in terms of pumping and heat losses. Moreover, a deep assessment of instantaneous pressure traces and mass flows in intake and exhaust valves was given, to provide insights about the optimization procedure. Finally, the findings obtained by simulation were compared with the results from a design of experiments (DOE) composed of more than 300 tests, and the impact on engine fuel consumption was analyzed. [ABSTRACT FROM AUTHOR]

This study proposes 1D modeling that considers the noise and vibration of a vehicle window-brushed DC motor. The electrical and mechanical components of the brush DC motor are included, creating a model that considers noise and vibration. The model has a back electromagnetic force (EMF) including vibration components and is constructed based on an electric circuit and transfer functions. To ensure the reliability of the model, the back EMF, noise, and vibration experiment environment of the brushed DC motor were configured. The measured back EMF was applied to the model, and it was confirmed that the simulation results of the model were consistent with the measured noise and vibrations.

Early Cretaceous and Jurassic sequences in the southwestern Iran host some of the largest hydrocarbon reservoirs in the globe. This study is aimed at evaluating the maturity of hydrocarbon fluids, migration paths, and characteristics of Pabdeh, Kazhdumi, Garu and Sargelu source rocks in this region. For this purpose, 27 samples of Pabdeh and Kazhdumi Formations from wells in the northern part of Dezful Embayment were chemically evaluated by Rock–Eval pyrolysis. OpenFlow™ software was utilized to analyze the burial history, conduct 1D thermal modeling in four oilfields and perform 2D modeling on a section to estimate the maturity and extension of sediments. Results of the 1D modeling showed that the kerogens of Sargelu, Garu and Kazhdumi Formations were properly matured, leading to some hydrocarbon outflow, although the organic matter content of Pabdeh Formation was too immature to produce any hydrocarbon. Based on the plot of hydrogen index (HI) versus Tmax, it was found that the studied formations were dominated by type II kerogen and a mixed species of type II and type III kerogens. Results of the migration path modeling showed some leakage from the Kazhdumi Formation up to an overlying seal that prevented the hydrocarbons from seeping out to surface. The Early and Middle Cretaceous oil systems were found to be connected through geometrical features or faults, with the Kazhdumi Formation separating the two systems. The results further showed the migration of hydrocarbons, at a relatively high rate, into the Abadan Plate through the sub-Kazhdumi reservoirs.The Early and Middle Cretaceous petroleum systems were found to be connected through particular geometry features or possibly faults, with the two systems separated by Kazhdumi Formation. For most part, the intensity of the maturation processes was found to decrease from east to west of the study area. [ABSTRACT FROM AUTHOR]

Insights into degradation mechanisms, lifetime prolongation, and efficiency boost-up of proton-exchange membrane (PEM) electrolytic cells (ECs) is crucial for a quick technology ramp up. Besides experiments, macro-scale modeling can contribute to the better understanding of complex mechanisms in PEM electrolytic cells (PEMECs). Modeling of PEMECs is subjective to uncertainties in operating conditions, material and design properties. Uncertainty quantification (UQ) and sensitivity analysis (SA) can highlight how uncertainties propagate from the input parameters to the output of PEMEC models. However, UQ has not found its way into PEMEC modeling yet. Thus, we apply a quasi-Monte Carlo (QMC) and polynomial chaos expansions (PCEs) framework to quantify uncertainty in a highly nonlinear PEMEC model. Specifically, we implement a fast 1D python solver, which solves a system of six nonlinear coupled ordinary differential equations (ODEs) in PEMECs. The solver robustness is an asset for the conducted UQ and global SA study since the computational model needs to be evaluated several times. The UQ and SA analysis underlines how stochastic simulations improve the prediction accuracy of PEMEC models. It also enlightens the function of PEMECs. For example, the predicted cell voltage is very sensitive to the thickness of PEM, especially when the current density increases. [Display omitted] • A robust 1D computational model of PEM electrolytic cells is developed. • The implementation is in python. • Forward uncertainty propagation and global sensitivity analysis are carried out. • SA highlighted the layer thicknesses' impact on the polarization behavior of PEMECs. • The PEM thickness mostly impacts the polarization behavior at high current densities. [ABSTRACT FROM AUTHOR]

For LNG-fueled ships, estimating the rate of self-pressurization is critical because the pressure limit of an LNG storage tank and the specifications of the boil-off gas processing system depend on the pressure rise rate. However, estimation using a non-equilibrium model exhibits deviated prediction on the pressure increase when thermal stratification is occurred in LNG. Therefore, in this study, a new numerical model is proposed for estimating the self-pressurization of LNG by considering the nonuniform one-dimensional fluid temperature distribution at varying LNG levels. The suggested model was verified using a pilot-scale experiment with a 150 m3 LNG tank capacity. The results show that the proposed model can explain the limited evaporation at a higher level and the vigorous evaporation at a lower level. Furthermore, the suggested model exhibits that the temperature profile in LNG can be determined by the evaporation at the liquid surface according to different levels and can successfully predict the increasing rate of pressure by excluding the assumption of a homogeneous LNG temperature. [Display omitted] • One dimensional model for predicting self-pressurization is developed. • The free convection in the boundary layer and the phase interaction are considered. • The pressure increase at different liquid level is measured. • Thermal stratification in liquid phase accelerates the pressure increase. [ABSTRACT FROM AUTHOR]

The turbine, a key component of a turbocharger, is usually characterized by steady flow solutions. This method seems to be physically unrealistic as the fluid flow within a turbine is strongly unsteady due to the pulsating nature of the flow in the exhaust manifold of a reciprocating engine. This paper presents a new 1D gas dynamic code, written in the FORTRAN language, to characterize a radial turbine of one turbocharger embedded to a small gasoline engine. This code presents the novelty of meanline-1D coupling and the feature of numerical schemes choice. In this study, the turbocharger turbine is simulated with six different finite difference schemes. The computed distribution of the downstream mass flow rate, from the different cases, is compared to test data in order to choose the most suitable scheme. Test data are gathered from a developed test facility. Based on the computed results, unsteady performance of the turbine has been computed and discussed for the different schemes at two engine frequencies of 50 and 83.33 Hz. The results showed a significant impact of the numerical scheme on the 1D prediction of the turbine performance. Results indicated that the MR2LW finite-difference scheme has led to the minimum deviation of the numerical results to test data compared to the other considered schemes. [ABSTRACT FROM AUTHOR]

Microwave plasma in the liquid is initiated inside a gas bubble formed at the end of the electrode-antenna, through which microwave energy is introduced into the liquid. A 1D model a set of gas phase kinetic reactions describes the evolution processes of ionization, heat transfer and formation of gas and solid products inside the plasma bubble. The code is based on joint solution of the Boltzmann equation for free electrons of the plasma, a simplified equation for the microwave field, the heat conduction equation, the balance equation for the electron density and the balance equations for the weight fraction for all gas and solid products of n-heptane pyrolysis. The Joule heat released in the plasma is expended on the evaporation of liquid n-heptane into the bubble and the decomposition of the n-heptane molecules. The model includes both the description of gas phase processes and formation of solid carbon-containing particles. The growth mechanism for generation of solid particles describes simultaneous processes of the initial nucleation, surface growth and coagulation of soot particles. The results of calculations are compared with known experimental results. [ABSTRACT FROM AUTHOR]

A one-dimensional (1D) numerical model has been previously developed to investigate the hemodynamics of blood flow in the entire human vascular network. In the current work, an experimental study of water-glycerin mixture flow in a 3D-printed silicone model of an anatomically accurate, complete circle of Willis (CoW) was conducted to investigate the flow characteristics in comparison with the simulated results by the 1D numerical model. In the experiment, the transient flow and pressure waveforms were measured at 13 selected segments within the flow network for comparisons. In the 1D simulation, the initial parameters of the vessel network were obtained by a direct measurement of the tubes in the experimental setup. The results verified that the 1D numerical model is able to capture the main features of the experimental pressure and flow waveforms with good reliability. The mean flow rates measurement results agree with the predictions of the 1D model with an overall difference of less than 1%. Further experiment might be needed to validate the 1D model in capturing pressure waveforms. [ABSTRACT FROM AUTHOR]

This study mainly touches on natural gas fueled combi boiler appliances having space and water heating functions. The hot water demanded in any type of building for daily activities such as personal hygiene, cleaning, and bathing is referred to as domestic hot water (DHW) . Since high efficiency targets have been already reached with respect to the space heating, most of the research and development activities are now focusing on the DHW heating function. Therefore, the subject of this study is concerned with only DHW heating function and the basic objective is making a comprehensive comparison between two mathematical models via different approaches for the same DHW circuit. In the first approach, basic heat transfer equations for DHW heating function are established by means of one-dimensional and time dependent differential equations. Later on, those transient energy equations were discretized by finite-difference method implicitly and solved simultaneously in Matlab ® . The second model has been constructed with the help of commercial software, Flowmaster ® which is one-dimensional thermo-fluid simulation tool. Then, the numerical results have been compared with the experimental data and the validity of the models has been discussed separately on the basis of the agreement between them. The advantages of both models have been evaluated as the distinctive contributions to the literature from DHW circuit modeling viewpoint. Among the intensive research and development activities of the combi boiler manufacturers to achieve high DHW comfort scores for high selling rates in the market, decreasing the time and money spent on the laboratory tests of the appliances is a challenging issue. Number of the laboratory tests is proposed to be decreased due to the preliminary results obtained from properly working numerical models for the performance analyses of completely new appliance concepts or design modifications on the regular appliances. [ABSTRACT FROM AUTHOR]

The multiple injection performance of Common Rail injectors has been analyzed at a hydraulic test rig as the dwell time was varied. The dependence of the injected volume on the dwell time has been investigated for direct acting piezoelectric and hydraulically-controlled (or indirect-acting) servo injectors. The injected fuel volumes in the long dwell-time range have been shown to be affected by the pressure waves that travel along the high pressure circuit for hydraulically-controlled servo injectors. On the other hand, the influence of pressure-wave-induced disturbances on multiple injection performance has been shown to be negligible for direct acting piezoelectric injectors. An analysis of closely-coupled injections has been conducted on a solenoid injector. When the dwell time is progressively reduced below a critical value, an increase in the fuel quantity that is injected in the second shot is observed. Injection fusion phenomena occur as the dwell time is diminished below a certain threshold and a maximum in the fuel volume, which is injected during the joint injections, is eventually detected for a very short electric dwell time value close to 100 μs. The cycle-to-cycle dispersion around this dwell time value results to be reduced significantly. A previously developed 1D model of the fuel injection system has been applied to analyze the injector transients. Detailed knowledge of the injection dynamics in the short dwell time region is of fundamental importance to optimize the implementation of both discontinuous and continuous rate shaping strategies. At present, there is a great deal of interest in these advanced schedules, since they can allow a minimization of soot emissions, fuel consumption and combustion noise to be achieved in diesel engines equipped with indirect-acting injectors. [ABSTRACT FROM AUTHOR]

In the continuous improvements of the safety of nuclear power plants, the study of natural circulation is of primary importance for developing passive safety systems and Generation-IV reactors, such as the Molten Salt Fast Reactor (MSFR). In particular, removing the decay heat during the shutdown of the MSFR involves dealing with a circulating fuel driven by natural circulation; as such, the development and validation of natural circulation models are of primary importance. To validate models and provide experimental data on natural circulation with a distributed heat source, the DYNASTY (DYnamics of NAtural circulation for molten SalT internallY heated) natural circulation loop has been built on the premises of Politecnico di Milano. This paper focuses on improving the 1D modeling of natural circulation phenomena in the DYNASTY facility and validating them against the results (also reported in this work) found in the first experimental campaign, carried out with water as the working fluid. The modeling of DYNASTY is based on a 1D approach using DYMOLA®, a modeling environment based on the MODELICA simulation language. The models used are improved versions of the ones available in the literature, which better model the experimental facility as they now include the mass flow rate meter, the heat loss between the facility and the environment, and a more realistic cooler. The improved model was then used to study the outcomes of the model simulations and verify the influence of the different numerical integration algorithms on the simulation results. The first DYNASTY experimental campaign provides in-depth testing of its behavior, with different cooling fan speeds and considering all possible heating configurations. The collected results for the heating and cooling transients are the mass flow rate and four fluid temperatures measured by thermocouples placed at the beginning and the end of the four DYNASTY legs. The experimental results were compared with the model simulations, showing the good predicting capabilities of the latter one following the tuning of the heat exchange model. In particular, the comparison showed an excellent match between the model and the experimental results for the heating transient while showing improving margins for the cooling transient. • Development of a 1D Modelica model for simulating natural circulating fluids. • 1D model parametric performance analysis. • Experimental analysis of the DYNASTY natural circulation loop. • Preliminary model comparison against experimental campaign results. • Promising comparison results in the heating transient. [ABSTRACT FROM AUTHOR]

The La Baja Guajira Basin is South America's northernmost part that extends from onshore Colombia into the Caribbean Sea and represents an important gas-producing region in Colombia. The dataset used in this study consists of twenty-four (24) regional 2D seismic-reflection lines integrated with information from nine (9) boreholes across the basin. We present seismic interpretations of key stratigraphic and structural features constrained by 1D basin modeling. This allows us to describe the Neogene-Quaternary evolution of the basin, and understand the possible implications for the hydrocarbon potential. We have interpreted eight (8) seismic units within the La Baja Guajira Basin (acoustic basement to U7) affected by three fault groups: 1) NW-SE-striking basement normal faults, 2) inverted normal faults, and 3) strike-slip faults. Considering the evidence, we propose four tectonic phases along the basin's evolution. The basement was affected by normal faulting as the result of extensional tectonics prior to the deposition of the sedimentary infill (Paleogene?). Another extensional interval occurred during the Early Miocene, triggering a moderate accommodation within the proximal area. Subsequently, extension migrated westwards resulting in the formation of the main La Baja Guajira Basin depocenter. In the Middle Miocene (post-extension), sedimentation was controlled by exhumation pulses in adjacent areas to the basin, which resulted in significant sediment input contemporaneous with rapid tectonic subsidence. Yet, local inversion of NW-SE-oriented basement-rooted faults affected today's offshore domain until the Late Miocene. This inversion can be associated with regional compressive deformation linked to the activity of the Oca and Cuiza faults. A second episode of rapid tectonic subsidence happened in the Early Pliocene. In the south of the basin, rocks were subjected to maximum burial and highest temperatures in recent times, conditions that might lead to hydrocarbon generation. The high Neogene to recent sedimentation rates calculated for the La Baja Guajira Basin support microbial gas generation; structural reactivation in this time supported trap formation, particularly in the offshore parts of the basin. • Basement's configuration and Andean exhumation controlled the sedimentation. • The Early Miocene extension is associated with activity of the Oca and Cuiza faults. • Middle Miocene: first peak of rapid tectonic subsidence and maximum temperature. • Inversion affected today's offshore areas until the Late Miocene. • High overall sedimentation rates have contributed to microbial gas generation. [ABSTRACT FROM AUTHOR]

A sizing and simulation platform has been developed for the optimization of advanced configurations for aircrafts including, but not limited to, more electric, hybrid-electric, turbo-compound piston engines and fuel cell systems. In the present investigation the software has been applied to the simulation of a medium-altitude, medium-endurance unmanned aerial vehicle (UAV) equipped with a two-stroke diesel engine with a single stage turbo-compressor. The engine was simulated with a 1D code (AVL-Boost) taking into account several values of speed, air-fuel ratio and flight altitude. The behavior of the waste-gate valve at the different flight levels was also accounted for. The Willans line method is used to obtain the seal level and in flight performance map of scaled engines with the same configuration. The power requests of a reference 128kW engine and two scaled engines along the mission have been compared with the available power to discuss the potentiality of hybrid electric and turbo-compound configurations. [ABSTRACT FROM AUTHOR]

In this work, experimental data, carried out on a twin-cylinder turbocharged engine at full load operations and referred to a spark advance of borderline knock, are used to characterize the effects of cyclic dispersion on knock phenomena. 200 consecutive in-cylinder pressure signals are processed through a refined Auto-Regressive Moving Average (ARMA) mathematical technique, adopted to define the percentage of knocking cycles, through a prefixed threshold level. The heuristic method used for the threshold selection is then verified by 1D and 3D analyses. In particular, a 1D model, properly accounting for cycle-by-cycle variations, and coupled to a reduced kinetic sub-model, is used to reproduce the measured cycles, in terms of statistical distribution of a theoretical knock index. In addition, few individual cycles, representative of the whole dataset, are selected in a single operating condition in order to perform a more detailed knock analysis by means of a 3D CFD approach, coupled to a tabulated chemistry technique for auto-ignition modeling. Outcomes of 1D and 3D models are compared to the ARMA results and a substantial coherence of the numerical and experimental results is demonstrated. The integrated 1D and 3D analyses can hence help in supporting the choice of the experimental threshold level for knock identification, following a more standardized theoretical approach. [ABSTRACT FROM AUTHOR]

00857.2014.--Patient-specific one-dimensional (1D) blood flow modeling requires estimating model parameters from available clinical data, ideally acquired noninvasively. The larger the number of arterial segments in a distributed 1D model, the greater the number of input parameters that need to be estimated. We investigated the effect of a reduction in the number of arterial segments in a given distributed 1D model on the shape of the simulated pressure and flow waveforms. This is achieved by systematically lumping peripheral 1D model branches into windkessel models that preserve the net resistance and total compliance of the original model. We applied our methodology to a model of the 55 larger systemic arteries in the human and to an extended 67-artery model that contains the digital arteries that perfuse the fingers. Results show good agreement in the shape of the aortic and digital waveforms between the original 55-artery (67-artery) and reduced 21-artery (37-artery) models. Reducing the number of segments also enables us to investigate the effect of arterial network topology (and hence reflection sites) on the shape of waveforms. Results show that wave reflections in the thoracic aorta and renal arteries play an important role in shaping the aortic pressure and flow waves and in generating the second peak of the digital pressure and flow waves. Our novel methodology is important to simplify the computational domain while maintaining the precision of the numerical predictions and to assess the effect of wave reflections. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the main hypotheses and equations which lead to the design of the Hydres platform, a 1D code developed to evaluate liquefying fuel regression rates in hybrid propulsion and the engine propulsive performances. This code is based on an integral description of the aerothermochemical flow coupled to a one equation model for the liquid film. The validation of this numerical code was performed thanks to the Hycom facility, a lab-scale hybrid engine instrumented, among others, with ultrasonic sensors to follow the ablation of the fuel grain and hence its instantaneous regression rate. Measurements performed during the hybrid engine firing tests also provide the instantaneous regression law of the oxidizer/fuel pair and experimentally highlight the existence of a regression rate limit. [ABSTRACT FROM AUTHOR]

• Two-way coupled 1D model successfully implemented for CO 2 reactive absorption. • 1D model yields excellent agreement with experimental and literature data. • Asymptotic model unravels the governing parameters at each pH zone. • Sensitivity analyses show the importance of k L in capturing the transient process. This work aims to investigate reactive bubbly flow using a comprehensive spatio-temporal 1D model. The work of Darmana et al. (2007) who conducted experimental and numerical study on CO 2 chemisorption in NaOH solution is used as the reference case. The gas–liquid hydrodynamics are well captured using a drift-flux loop model. During the transient process, bubble diameter d b shrinkage from 5.5 mm at the inlet to 3.7 mm at the outlet is captured by the 1D model. The pH evolution is also well predicted by the 1D model provided that appropriate closures are applied, including the recently proposed enhancement factor and reaction pathway by Krauβ & Rzehak (2017). An asymptotic 0D model is proposed to highlight the key parameters involved during the transient chemisorption process which are enhancement factor E , mass transfer coefficient k L , and interfacial area a. Sensitivity analyses on liquid axial dispersion coefficient, enhancement factor and mass transfer coefficient are then performed to elucidate their impact on reactive mass transfer. As the process is controlled by interfacial mass transfer, the most important parameters are k L and d b description. [ABSTRACT FROM AUTHOR]

Abstract: Turbocharging technique is more and more widely employed on compression ignition and spark ignition internal combustion engines, as well, to improve performance and reduce total displacement. Experimental studies, developed on dedicated test facilities, can supply a lot of information to optimize the engine-turbocharger matching, especially if tests can be extended to the typical engine operating conditions (unsteady flow). A specialized components test rig (particularly suited to study automotive turbochargers) has been operating since several years at the University of Genoa. The test facility allows to develop studies under steady or unsteady flow conditions both on single components and subassemblies of engine intake and exhaust circuit. In the paper the results of an experimental campaign developed on a turbocharger waste-gated turbine for gasoline engine application are presented. Preliminarily, the measurement of the turbine steady flow performance map is carried out. In a second step the same component is tested under unsteady flow conditions. Instantaneous inlet and outlet static pressure, mass flow rate and turbocharger rotational speed are measured, together with average inlet and outlet temperatures. A numerical procedure, recently developed at the University of Naples, is then utilized to predict the steady turbine performance map, following a 1D approach. The model geometrically schematizes the component basing on few linear and angular dimensions directly measured on the hardware. Then, the 1D steady flow equations are solved within the stationary and rotating channels constituting the device. All the main flow losses are properly taken into account in the model. The procedure is able to provide the sole “wheel-map” and the overall turbine map. After a tuning, the overall turbine map is compared with the experimental one, showing a very good agreement. Moreover, in order to improve the accuracy of a 1D engine simulation model, the classical map-based approach is suitably corrected with a sequence of pipes that schematizes each component of the device (inlet/outlet ducts, volute and wheel) included upstream and downstream the turbine to account for the wave propagation and accumulation phenomena inside the machine. In this case, the previously computed “wheel-map” is utilized. The turbine pipes dimensions, are automatically provided by the geometrical module of the proposed procedure to correctly reproduce the device volume and the flow path length. [Copyright &y& Elsevier]

Abstract: A simple and fast 1D effective medium simulation model for polycrystalline silicon thin film solar cells was defined, by using the device simulator AFORS-HET. The model was calibrated with current–voltage measurements of solar cells under illumination and in t he dark. The experimentally determined variation of the solar cell characteristics with varying absorber doping and absorber thickness can be reproduced by the model. Through inverse modeling, the effective defect density in the absorber layer was determined and it was shown that the open circuit voltage of the cell is limited by defects localized in the bulk of the absorber layer. Using the calibrated simulation model for sensitivity analyses, different optimization strategies for this type of solar cells have been assessed. Firstly, the optimum absorber thickness as a function of absorber doping and defect densities has been determined and secondly, the when using a layer of hydrogenated amorphous silicon (a-Si:H) to form a heterojunction back surface field has been simulated as a function of the absorber defect density. [Copyright &y& Elsevier]

This article discusses a study which hypothesized that rereflection of reflected waves leads to wave entrapment, preventing distal waves being seen in the proximal aorta. Researchers believed that wave reflection is important in the augmentation of blood pressure. They measured reflected waves along the aorta to quantify how the reflected wave timing and magnitude change at differing locations along the aorta.