Validation Of Dynamic Model Research Articles

Dynamical modeling and experimental validation for tooth pitting and spalling in spur gears

Abstract Dynamical modeling of a gear system with faults has been an important research topic for understanding fault features and their associated fault vibration mechanisms. Due to the complicated structures and intricate interactions between the components of the gear system, the fault vibration features and corresponding vibration mechanisms due to tooth pitting and spalling remain mostly unknown. This paper proposes a novel spur gear dynamical model, validated by various experimental tests, to analytically investigate the effects of tooth pitting and spalling on the vibration responses of a gear transmission. The proposed dynamical model considers the effects of tooth surface roughness changes and geometric deviations due to pitting and spalling, and also incorporates Time Varying Mesh Stiffness (TVMS), a time-varying load sharing ratio, as well as dynamic tooth contact friction forces, friction moments and dynamic mesh damping ratios. The proposed gear dynamical model is validated by comparison with responses obtained from experimental test rig under different conditions. Comparisons indicate that the responses of the proposed dynamical model are consistent with experimental results, in both time and frequency domains under different rotation speeds and fault severity conditions.

Effects of external perturbations on dynamic performance of carbon dioxide transcritical power cycles for truck engine waste heat recovery

Carbon dioxide transcritical power cycle (CTPC) systems are dynamically tested on a constructed test bench using an expansion valve. Effects of external perturbations of pump speed, expansion valve opening and engine conditions on dynamic performance of the CTPC systems are investigated with step changes. Dynamic characteristics are identified with rise time, settling time and overshoot. Results show that both a basic CTPC system and a CTPC system with a recuperator (R-CTPC) behave as a second-order underdamped system with the perturbations of pump speed and expansion valve opening. Overshoot or undershoot tends to appear in pressures when pump speed changes, while overshoot or undershoot occurs more noticeably in temperatures when expansion valve opening varies. Although the CTPC systems respond slowly with the perturbations of engine conditions, they have the ability to operate safely and produce power continuously. Therefore, the CTPC systems are robust when facing narrow fluctuations of heat sources while swift when required to make adjustments, showing great potential for truck engine waste heat recovery. Overall, current research gives a full understanding of the dynamic performance of the CTPC systems, which will provide references for dynamic model validation and possible control strategy identification.

Validation of Computational Fluid Dynamics Models for Evaluating Loose-Fitting Powered Air-Purifying Respirators.

Loose-fitting powered air-purifying respirators (PAPRs) are used in healthcare settings to reduce exposure to high-risk respiratory pathogens. Innovative computational fluid dynamics (CFD) models were developed for evaluating loose-fitting PAPR performance. However, the computational results of the CFD models have not been validated using actual experimental data. Experimental testing to evaluate particle facepiece leakage was performed in a test laboratory using two models of loose-fitting PAPRs. Each model was mounted on a static (non-moving) advanced headform placed in a sodium chloride (NaCl) aerosol test chamber. The headform performed cyclic breathing via connection to a breathing machine. High-efficiency particulate air (HEPA)-filtered air was supplied directly to the PAPR facepiece using laboratory compressed supplied-air regulated with a mass-flow controller. One model was evaluated with six supplied-air flowrates from 50-215 L/min (Lpm) and the other model with six flowrates from 50-205 Lpm. Three different workrates (minute volumes) were evaluated: low (25 Lpm), moderate 46 (Lpm), and high 88 (Lpm). Manikin penetration factor (mPF) was calculated as the ratio of chamber particle concentration to the in-facepiece concentration. Overall, data analyses indicated that the mPF results from the simulations were well correlated with the experimental laboratory data for all data combined (r = 0.88). For data at the three different workrates (high, moderate, low) for both models combined, the r-values were 0.96, 0.97, and 0.77, respectively. The CFD models of the two PAPR models were validated and may be utilized for further research.

Dynamic analysis and experimental verification of the carbon–carbon composite finger seal under complex working states

The finger seal has an important influence on the performance of the aero-engine, and the effect of complex working states on the performance of the finger seal, which is located in the aero-engine, is also prominent. But so far, the finger seal performance under complex working states, which include the incline of the rotor, assembly condition, temperature effect, and impact effect, has not been investigated yet. Based on this, an equivalent dynamic model of finger seal is presented under complex working states, and the dynamic performance analysis of the finger seal is carried out by the model. The results show that the complex working states have larger influence on the finger seal performance. Meanwhile, an experimental research is carried out and the results are compared with the theoretical results. And then the validity of the equivalent dynamic model of the finger seal under complex working states is proved. The present work is conducive to improve the theoretical research system of finger seal, and promote the dynamic analysis technology to engineering application as well.

Analysis of flow field design on vanadium redox flow battery performance: Development of 3D computational fluid dynamic model and experimental validation

Homogeneous distribution of the electrolyte over the porous electrode is a critical issue hindering the commercialization of vanadium redox flow batteries, owing to increased overpotential at high current and limited power density of the system. Therefore, an understanding of the physical phenomena regulating mass transport of the electrolyte is crucial to improving system performance. The present work describes the development and experimental validation of a 3D computational fluid dynamic model of a vanadium redox flow battery in a half-cell configuration with an active area of 25 cm2. The model simulates the influence of a single serpentine and an interdigitated flow field. The adoption of the half-cell configuration allows the negative electrode to be considered as a pseudo-reference electrode with zero potential loss, leading to a reduction in computation time and the number of fitting parameters, which can be determined with reduced uncertainty. The developed model includes a traditional fluid dynamic analysis of the electrolyte in the flow field and in the porous electrode, coupled with the electrochemistry of the reactions involved. In both the experiments and the simulations, the single serpentine distributor exhibits better performance and higher pressure drops compared to those of the interdigitated geometry under all the investigated operating conditions. In the analysis of the local reaction rate, both distributors experienced increased reaction rates under the rib, induced by a by-pass flow between adjacent channels. The reaction rate shows a highly heterogeneous distribution in the serpentine geometry, while it is more uniform in the interdigitated configuration.

Compact steam bottoming cycles: Model validation with plant data and evaluation of control strategies for fast load changes

Power plants installed on offshore oil and gas installations need to be operated in a flexible manner in order to accommodate the variability in heat and power demands. The present paper describes steady-state process model validation based on data from an actual offshore oil and gas installation, dynamic model validation, and evaluation of control strategies for fast load changes. The offshore process configuration consisted of two gas turbines with a once-through heat recovery steam generator located downstream of each gas turbine. One steam turbine received the combined steam mass flow from the two steam generators. The validation data, focusing on the steam bottoming cycle, consisted of one year of operation. Subsequently, a dynamic process model based on a simplified process layout was developed in the open physical modeling language Modelica and validated with reference steady-state and transient software data. The results from the evaluation of control strategies showed the benefits in utilizing feedforward control for the operation of the heat recovery steam generator under fast load changes, and the effectiveness of attemperation to avoid excessive excursions of live steam temperature during transients.

Darrieus wind turbine prototype: Dynamic modeling parameter identification and control analysis

This paper details the process required to develop a linear dynamic model and control of a Darrieus wind turbine equipped with a Permanent Magnet Synchronous Generator. The turbine is to be integrated in a smart grid for future installation in urban context. An active control system is integrated in such a way that, even in the presence of non-ideal phenomena and disturbances, optimal operation is achieved. For the class of linear (or linearized) systems such optimal control solution corresponds to the Linear Quadratic Regulator (LQR). A set of tests were performed on a wind tunnel, data was acquired allowing the application of well rooted identification techniques, leading to the deduction and validation of several low order dynamic models. Optimal control solutions were implemented to guarantee that close to ideal operational conditions are maintained. As such, efficiency is improved without jeopardizing the integrity of the wind turbine in a broad set of operational conditions.

Energy performance progress of the Dutch non-profit housing stock: a longitudinal assessment

Worldwide, buildings consume a large part of the total energy delivered. In the context of all the end-use sectors, buildings represent the largest sector with 39% of the total final energy consumption, followed by transport in the EU (European Union ). Policy targets and regulations are in force at the EU level to ensure the energy efficiency improvement of the building stock. This research seeks to provide insight into the energy performance progress, of the existing non-profit housing stock in the Netherlands, through the application of energy renovations. The non-profit housing stock comprises 30% of the housing market in the Netherlands and a large part of the policies towards a more efficient housing stock rely on the non-profit housing sector. To that end, we determine the energy renovation rate of the stock and the impact of the applied renovations on both the predicted and actual energy consumption. The difference of predicted and actual energy savings is analysed through longitudinal statistical modelling in renovated and non-renovated dwellings. Based on the knowledge gained on the renovation rates of the non-profit housing stock we compare and evaluate future renovation rates through dynamic building stock modelling and empirical data validation. In essence, we examine the effect that the improvement of thermo-physical characteristics of dwellings has on efforts to make the existing housing stock almost emission-neutral by 2050, as advocated by the European Commission since 2011. The renovation activity is expected to be greater than the construction and demolition activity in the future and as such we need to bring awareness to the actual impact and effectiveness of energy renovations.

P2‐032: Derivation and validation of a novel dynamic model for predicting outcome in patients with hepatitis B virus related acute‐on‐chronic liver failure

P2‐032: Derivation and validation of a novel dynamic model for predicting outcome in patients with hepatitis B virus related acute‐on‐chronic liver failure

Calibration and validation of a simulation-based dynamic traffic assignment model for a large-scale congested network

Deployment of a simulation-based dynamic traffic assignment (DTA) model requires calibration of a large number of demand and supply input parameters. In this paper, we present a data-intensive framework for deployment, calibration, and validation of a simulation-based DTA model of Melbourne, Australia as a large-scale congested network. The model consists of 55,719 links and 24,502 nodes and simulates almost 2.1 million commuters in a 4-h morning peak period. We propose a machine learning based technique to classify and calibrate the traffic flow fundamental diagrams against empirical data obtained from a large number of freeway loop detectors across the network. An optimization framework for estimating the time-dependent origin-destination (TDOD) demand is also presented. To enhance the quality of the TDOD demand estimation, we apply a departure time profiling technique to account for the spatial differences between OD pairs. The paper also demonstrates the impact of adaptive driving on the quality of the DTA calibration. A comparison between the simulated and observed link volumes over 1,250 locations across the entire network shows that the calibration procedure generates an approximately 30% improvement in the root mean square error (RMSE). The impact of pedestrians and cyclists on the vehicular traffic is also implicitly considered in the central business district (CBD) area to improve underestimation of the simulated travel times. Validation results suggest that the calibrated DTA model successfully replicates traffic patterns in the network and support the future applications of the model for various transportation operations and planning purposes.

Multi-objective optimization of microclimate in museums for concurrent reduction of energy needs, visitors’ discomfort and artwork preservation risks

In museums, hygrothermal conditions must be carefully controlled by HVAC system to avoid artwork degradation. Higher energy requirements are needed for the maintenance of the suitable thermal environment. Moreover, a comfortable thermal sensation is needed for a positive museum experience. In light of current policies on energy efficiency, we propose an original procedure for the concurrent achievement of three goals: artwork preservation, energy efficiency, and human thermal comfort. This procedure is based on the application of multi-objective optimization and aims at correctly choosing temperature and relative humidity setpoints, through the use of dynamic simulations and evaluation of three indexes as objectives. This strategy can be particularly effective in museums hosted in historic buildings, where envelope and HVAC refurbishment is often forbidden or discouraged due to the architectural constraints. Furthermore, the retrofit action is almost costless. A case study is presented: first, a monitoring campaign in an Italian museum has been used for the validation of dynamic simulation models of the building-HVAC system; then, the validated models have been used to show that improvements of artwork lifetime, human thermal comfort and reduction of energy requirements of the HVAC system are possible, if currently-used hygrothermal setpoints (based on technical standards and guidelines) are replaced with those identified by the optimization problem.

Vibration response characteristics of a dual-rotor with unbalance-misalignment coupling faults: Theoretical analysis and experimental study

In order to improve energy efficiency and compact structure, the dual-rotor structure, with low-pressure rotor and high-pressure rotor, has been widely used in aero-engines. In severe operation conditions, the high rotating speed dual-rotor structure is vulnerable to some faults, such as misalignment, which may cause strong vibration and even catastrophic accidents. Perfect balance of the dual-rotor system cannot be obtained in practice, and some amount of unbalance is almost always present. The rotors’ centrelines are not co-linear in the couplings and the rotors run in improper axial positions in a dual-rotor system. The differential equations of rotor system is derived by using modern nonlinear dynamics and dual-rotor dynamics principles. The governing equations of the dual-rotor system with unbalance-misalignment coupling faults are solved numerically by the Runge–Kutta method. The complicated vibration responses influenced by different rotational angular speeds, mass eccentricity, misalignment angle and parallel misalignment are analyzed by the cascade plot, time waveform and frequency spectrum. Second harmonic frequency and rotational frequency components of dual rotors are observed. To verify the validity of the dual-rotor system dynamic model, the unbalance-misalignment coupling faults are carried out on a dual-rotor test rig by adjusting the height and quantity of gaskets and installing a screw on the disk of the inner rotor. The simulation results are found to agree with the experimental results. These results provide important theoretical and engineering references for the safe operation of dual-rotor system and the exact identification of coupling faults.

Experimental characterization of dynamic heat exchanger behavior

The transient response of heat exchangers plays a significant role in the time-dependent performance of thermal management systems, particularly in resource-limited situations with high power density and fast-acting heat sources. A scaled thermal management testbed with a plate-frame heat exchanger was built to emulate a thermal subsystem. This paper describes a methodology for dynamically characterizing the behavior of a commercial, off-the-shelf plate-frame heat exchanger both experimentally and computationally. Statistical design of experiments principles was used to develop a test plan composed of 20 test cases for dynamic model validation. The dynamic performance of the heat exchanger was evaluated with a physics-based model, and statistical surrogate models were derived from the experimental results. Additionally, a lumped mass model was employed to determine the dynamic parameters of the heat exchanger using the experimental data. The model efficiently and accurately predicts the experimental results across the entire experimental exploration space. The lumped mass model predicts the transient response without using computationally expensive resources such as a full numerical, thermo-fluid dynamic solvers. This approach has significant implications for developing practical models of thermal components particularly for the field of thermal controls.

Development and validation of a comprehensive dynamic mathematical model for hybrid PV/T solar collectors

In this paper, a model for the simulation of a hybrid photovoltaic-thermal collector under transient regime is developed and validated. The model is built using a control volume approach, the collector is divided into small elemental volumes where energy equation is solved using a bi-dimensional finite difference method. The model is validated against experimental data obtained from a two weeks testing in real environmental weather conditions on two hybrid PV/T solar tiles connected in series. An agreement between the experimental and numerical values of the instantaneous power production and the water outlet temperature within ±4 W and within ±0.5 K respectively is found. On a daily basis, the calculated electrical and thermal energies agree within −2.64% to +1.73% and within −4.90% to +7.37% with experimental data, allowing to state that the developed model is quite a reliable tool both for short-term and long-term yield analysis at component or system level.

Multi-objective optimization of chassis integrated system for electric wheel vehicle

In order to improve the overall performance of the electric wheel vehicle, this paper researches the multi-objective optimization method of the chassis integrated system. The dynamic models of integrated system including differential steering system, differential brake system, and active suspension system are established. In order to verify the validity of the vehicle dynamic model and ensure the correctness of the optimization analysis results, the model validation is implemented. Considering the coupling relationship among subsystems, the performance evaluation indexes of steering road feel, steering sensitivity, and suspension ride comfort are deduced under steering and braking conditions. To alleviate the subjectivity in the selection of objective weighting, the deviation sort polymerization method is used to convert the multi-objective model into a single-objective one based on the linear weighted polymerization. Aiming at the optimization characteristic of chassis integrated system, an adaptive weight particle swarm optimization algorithm is proposed to improve the optimization efficiency and convergence. The optimization results show that the optimized chassis integrated system can obtain favorable steering road feel, better steering sensitivity, and suspension ride comfort.

Development and Validation of a Reduced-Index Dynamic Model of an Industrial High-Purity Column

A depropanizer column is a high purity distillation unit, whose modeling is challenging due to its high nonlinear behavior and intricate dynamics. Also, depending on the assumptions, a differential algebraic equation (DAE) system of high index can arise in the modeling of the column. Such systems create significant difficulties to numerical simulation. Phenomenological hydraulic relationships can be used to avoid the index problems. However, these relationships may rely on unknown and arbitrarily assumed parameters and project details. This paper presents an alternative modeling approach called dynamic design using proportional action (DDPA), which is used to simplify the hydraulic and pressure drop relation for a distillation unit. The DDPA approach generates a reduced index dynamic model by adding equations similar to a proportional controller with arbitrarily large gain. A depropanizer column was modeled using DDPA, and the model was validated with real process data obtained in an industrial-scale depr...

Thermal energy storage for CSP hybrid gas turbine systems: Dynamic modelling and experimental validation

Integration of Thermal Energy Storage (TES) is one of the promising features of Concentrated Solar Power (CSP) technology which allows the Renewable Energy Sources (RES) to provide uninterrupted and dispatchable power supply, and thus facilitates the RES grid integration. Hybrid Solar Gas Turbine (HSGT) systems along with TES integration have gained great attention for the last decades. Numerical modelling and simulation tools are essential for the TES design optimization and analysis of its thermal behaviour during charging and discharging phases. This paper deals with the dynamic modelling and experimental validation of a TES at laboratory scale, which is part of the HSGT system. The TES is modelled with two different approaches: the CFD model using a commercial tool and a reduced-order model using the in-house transient simulation tool TRANSEO, which has been developed by Thermochemical Power Group (TPG) for the energy system dynamic analysis. The validation of both model results against the data obtained by the Authors through experimental investigation has highlighted that 2D discretization of the TES through the CFD model gives accurate representation of the thermal behaviour of the system, but it causes a significant computational expense. On the other side, 1D dynamic model reasonably predicts the time dependent thermal behaviour of TES, except some deviations from the experiments which are related to the simplified discretization scheme. However, due to its fast approach, the TRANSEO model can be effectively used to perform both TES initial design and sensitivity analysis, and also to develop or verify the control system at a later stage of HSGT system development.

P-HS-SFM: a parallel harmony search algorithm for the reproduction of experimental data in the continuous microscopic crowd dynamic models

ABSTRACTFinding the optimal parameters that can reproduce experimental data (such as the velocity–density relation and the specific flow rate) is a very important component of the validation and calibration of microscopic crowd dynamic models. Heavy computational demand during parameter search is a known limitation that exists in a previously developed model known as the Harmony Search-Based Social Force Model (HS-SFM). In this paper, a parallel-based mechanism is proposed to reduce the computational time and memory resource utilisation required to find these parameters. More specifically, two MATLAB-based multicore techniques (parfor and create independent jobs) using shared memory are developed by taking advantage of the multithreading capabilities of parallel computing, resulting in a new framework called the Parallel Harmony Search-Based Social Force Model (P-HS-SFM). The experimental results show that the parfor-based P-HS-SFM achieved a better computational time of about 26 h, an efficiency improvement of 54% and a speedup factor of 2.196 times in comparison with the HS-SFM sequential processor. The performance of the P-HS-SFM using the create independent jobs approach is also comparable to parfor with a computational time of 26.8 h, an efficiency improvement of about 30% and a speedup of 2.137 times.

Energy performance progress of the Dutch non-profit housing stock: a longitudinal assessment

Worldwide, buildings consume a large part of the total energy delivered. In the context of all the end-use sectors, buildings represent the largest sector with 39% of the total final energy consumption, followed by transport in the EU (European Union ). A considerable percentage of this energy consumption is attributed to the residential sector. The building sector plays a major role in order to meet the energy saving targets set in the EU and in the Netherlands. This is particularly true for existing buildings, because they will constitute the major part of the housing stock over several decades. The renovation activity is expected to be greater than the construction and demolition activity in the future. Policy targets and regulations are in force at the EU level to ensure the energy efficiency improvement of the building stock. The Energy Performance of Buildings Directive ([EPBD] 2002, recast 2010) is the main legislative and policy tool in EU and focuses on both new and existing buildings. At the same time, the building sector plays a prominent role in the Energy Efficiency Directive ([EED] 2012). Relatedly, in the Netherlands, the foundation of energy efficiency policy has been a number of national cross-cutting measures and EU derived policies that play a large role; like the strengthening of standards for new buildings or dwellings and energy labels for existing ones. The focus of this research is the existing dwelling stock and its energy performance progress. Throughout Europe, national approaches to building stock monitoring have evolved separately. Nevertheless, monitoring the building stocks’ energy performance is gaining attention. Information about the progress of energy performance improvements is not only needed to track the progress of policy implementation, but also better information and data are necessary to help the development of roadmaps towards a more energy efficient building stock. This research seeks to provide insight into the energy performance progress, of the existing non-profit housing stock in the Netherlands, through the application of energy renovations. The non-profit housing stock comprises 30% of the housing market in the Netherlands and a large part of the policies towards a more efficient housing stock rely on the non-profit housing sector. To that end, we determine the energy renovation rate of the stock and the impact of the applied renovations on both the predicted and actual energy consumption. The difference of predicted and actual energy savings is analysed through longitudinal statistical modelling in renovated and non-renovated dwellings. Based on the knowledge gained on the renovation rates of the non-profit housing stock we compare and evaluate future renovation rates through dynamic building stock modelling and empirical data validation. In essence, we examine the effect that the improvement of thermo-physical characteristics of dwellings has on efforts to make the existing housing stock almost emission-neutral by 2050, as advocated by the European Commission since 2011.

Dynamic process behavior and model validation of reactive dividing wall columns

Reactive dividing wall columns (RDWC) are a highly integrated column type. The coupling of a reactive distillation and a dividing wall column leads to complex interactions between vapor-liquid mass transfer, chemical kinetics and component split around the dividing wall. In simulation studies such interactions have been shown to lead to complex dynamics and the occurrence of multiple steady states. However, experimental investigations are still missing to verify the theoretical findings. In this work the first comprehensive experimental study of the dynamic behavior of RDWCs is presented. The reference system of enzymatic catalyzed butyl acetate transesterification with hexanol has been employed to investigate the start-up and open loop behavior under different operating conditions. Two different start-up strategies are tested and compared. The experiments demonstrate the reliable and secure start-up and stable operation of a RDWC. Additionally, a developed rigorous dynamic RDWC model is presented that considers the dynamic influence on the vapor distribution in the dividing wall section. A detailed model validation is carried out using the obtained experimental data. The comparison of simulation results and experimental values show good agreement over a wide range of operating conditions.