RealVAMS: An R Package for Fitting a Multivariate Value-added Model (VAM)

We present RealVAMS, an R package for fitting a generalized linear mixed model to multimembership data with partially crossed and partially nested random effects. RealVAMS utilizes a multivariate generalized linear mixed model with pseudo-likelihood approximation for fitting normally distributed continuous response(s) jointly with a binary outcome. In an educational context, the model is referred to as a multidimensional value-added model, which extends previous theory to estimate the relationships between potential teacher contributions toward different student outcomes and to allow the consideration of a binary, real-world outcome such as graduation. The simultaneous joint modeling of continuous and binary outcomes was not available prior to RealVAMS due to computational difficulties. In this paper, we discuss the multidimensional model, describe RealVAMS, and demonstrate the use of this package and its modeling options with an educational data set

Numerical approach for assessing combustion noise in compression-ignited Diesel engines

[EN] Diesel combustion noise has become a crucial aspect for the engine manufacturers due to its impact on human health and influence on the customer purchasing decision. The interaction of the pressure waves after mixture self-ignition induces cavity resonances inside the combustion chamber. This complex phenomenon produces high-frequency pressure oscillations, hence traditional in-cylinder measurements do not provide enough information to characterise the in-cylinder acoustic field. In this paper, a numerical methodology is proposed for assessing the Diesel combustion as a noise source and to overcome measurement limitations. An optimisation procedure is also presented in order to determine the numerical calculation parameters, boundary conditions definition and initialization. Results show that local flow conditions at the start of combustion have a strong influence on the acoustic response of the in-cylinder noise source. These particular conditions are only achievable by the proposed methodology which considers entire engine cycle simulations with the complete cylinder domain. Therefore, traditional Computational Fluid Dynamic (CFD) approaches, such those used for predicting combustion stability or pollutant emissions, are not suitable for reproducing the physical mechanisms of noise generation and they cannot be used for acoustic purposes. The reliability of the proposed methodology to simulate the acoustic field accurately inside the combustion chamber has been validated by comparison with experiments.The equipment used in this work has been partially supported by FEDER project funds "Dotacion de infraestructuras cientifico tecnicas para el Centro Integral de Mejora Energdtica y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06)", framed in the operational program of unique scientific and technical infrastructure of the Spanish Ministerio de Economia y Competitividad. J. Gomez-Soriano is partially supported through the "Programa de Apoyo para la Investigacion y Desarrollo (PAID)" of Universitat Politecnica de Valencia [Grant No. FPI-S2-2016-1353].Torregrosa, AJ.; Broatch, A.; Gil, A.; Gómez-Soriano, J. (2018). Numerical approach for assessing combustion noise in compression-ignited Diesel engines. Applied Acoustics. 135:91-100. https://doi.org/10.1016/j.apacoust.2018.02.006S9110013

Numerical analysis of combustion noise in an atmospheric swirl-stabilized LDI burner through modal decomposition techniques

[EN] Combustion noise in gas turbine engines has recently become a relevant source of noise in the aircraft due to the appearance of new burner architectures that are intrinsically more unstable, and the optimization of other conventional noise sources in this mean of transport (e.g., jet, fan, airframe). In this work, a simulation setup for reactive conditions was prepared in the CONVERGE finite-volume package using the detailed chemistry SAGE solver to model the combustion of a benchmark case, which was solved using a LES approach with three different cell base sizes: 8,10,12 mm. A confined liquid-fueled swirl-stabilized burner located at the CORIA Laboratory, France, was used to validate the numerical results with the experimental measurements obtained at this facility. OH-PLIF measurements and PDA results for both phases were used to guarantee the accuracy of the numerical OH contours and the velocity profiles of both phases. These experimental measurements were collected at CORIA. After ensuring the stabilization of the numerical flame, the reactive simulations were extended with some adjustments in the time step to capture the acoustic motion. Several techniques like Fast Fourier Transform (FFT), Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) were used to analyze these results and confirm the presence of a Precessing Vortex Core (PVC) and a Vortex Breakdown Bubble (VBB) during the coupling of pressure, axial velocity and fuel mass fraction in reactive conditions. Furthermore, the acoustic analysis performed with a Helmholtz solver proved that the second longitudinal mode of the chamber (329 Hz) was present in the pressure signal (300 Hz in the LES calculations) and resonated with the Vortex Breakdown Bubble (VBB). However, this dominant frequency did not appear in the frequency distribution of the OH mass fraction and no feedback interaction between the acoustic and the combustion happened. Thus, only combustion noise was obtained.This work was supported by the institutional program of the Korea Institute of Science and Technology (KIST, Project No. 2E32582).Broatch, A.; Carreres, M.; Garcia Tiscar, J.; Rodríguez-Pastor, M. (2023). Numerical analysis of combustion noise in an atmospheric swirl-stabilized LDI burner through modal decomposition techniques. Aerospace Science and Technology. 137:1-17. https://doi.org/10.1016/j.ast.2023.10828111713

Numerical Estimation of Wiebe Function Parameters Using Artificial Neural Networks in SI Engine

[EN] In modeling an Internal Combustion Engine, the combustion sub-model plays a critical role in the overall simulation of the engine as it provides the Mass Fraction Burned (MFB). Analytically, the Heat Release Rate (HRR) can be obtained using the Wiebe function, which is nothing more than a mathematical formulation of the MFB. The mentioned function depends on the following four parameters: efficiency parameter, shape factor, crankshaft angle, and duration of the combustion. In this way, the Wiebe function can be adjusted to experimentally measured values of the mass fraction burned at various operating points using a least-squares regression, and thus obtaining specific values for the unknown parameters. Nevertheless, the main drawback of this approach is the requirement of testing the engine at a given engine load/speed condition. Furthermore, the main objective of this study is to propose a predictive model of the Wiebe parameters for any operating point of the tested SI engine. For this purpose, an Artificial Neural Network (ANN) is developed from the experimental data. A criterion was defined to choose the best-trained network. Finally, the Wiebe parameters are estimated with the neural networks for different operating conditions. Moreover, the mass fractions burned generated from the Wiebe functions are compared with the respective experimental values from several operating points measured in the engine test bench. Small differences were found between the estimated and experimental mass fractions burned. Therefore, the effectiveness of the developed ANN model as a prediction tool for the engine MFB is verified.Torregrosa, AJ.; Broatch, A.; Olmeda, P.; Aceros, S. (2021). Numerical Estimation of Wiebe Function Parameters Using Artificial Neural Networks in SI Engine. SAE International. 1-10. https://doi.org/10.4271/2021-01-037911

Validation and Analysis of Heat Losses Prediction Using Conjugate Heat Transfer Simulation for an Internal Combustion Engine

[EN] New technologies are required to improve engine thermal efficiency. For this it is necessary to use all the tools available nowadays, in particular computational tools, which allow testing the viability of different solutions at reduced cost. In addition, numerical simulations often provide more complete and precise information than experimental tests. Such is the case for the study of the heat transfer through the walls of an engine. Conjugate Heat Transfer (CHT) simulations permit precise calculations of the heat transfer rate from gas to walls throughout the whole engine cycle, and thus it is possible to know such details as the instantaneous heat losses and wall temperature distribution on the walls, which no experiment can give. Nevertheless, it is important to validate CHT calculations, either with some experimental measurements or with some other reliable tool, such as 0D-1D modelling known to work well. The proposed work is based on the CHT simulation of the heat transfer to the walls of an engine piston during an entire cycle to determine the parameters that permit obtaining good results. This will be ascertained by comparison with the results of a lumped model previously validated for many applications. Another objective of this work is also to determine if it is significant to take into account the spatial and temporal variations of the wall temperature for the prediction of the heat losses during the engine cycle, as generally a mean and constant wall temperature (isothermal walls) is assumed for CFD combustion calculations.This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 724084. The authors wish to thank IFPEN for their permission to use their single cylinder engine geometry and pressure results. The authors want to express their gratitude to CONVERGENT SCIENCE Inc. and Convergent Science GmbH for their kind support for performing the CFD-CHT calculations using CONVERGE software.Broatch, A.; Margot, X.; Garcia Tiscar, J.; Escalona, J. (2019). Validation and Analysis of Heat Losses Prediction Using Conjugate Heat Transfer Simulation for an Internal Combustion Engine. SAE International. 1-8. https://doi.org/10.4271/2019-24-009118Leguille, M., Ravet, F., Le Moine, J., Pomraning, E. et al. , “Coupled Fluid-Solid Simulation for the Prediction of Gas-Exposed Surface Temperature Distribution in a SI Engine,” SAE Technical Paper 2011-24-0132 , 2011, doi:104271/2011-24-0132.Mohammadi, A. and Yaghoubi, M. , “Estimation of Instantaneous Local Heat Transfer Coefficient in Spark-Ignition Engines,” International Journal of Thermal Sciences 49(7):1309-1317, 2010.Babajimopoulos, A., Assanis, D.N., Flowers, D.L., Aceves, S. M., and Hessel, R.P. , “A Fully Coupled Computational Fluid Dynamics and Multi-Zone Model with Detailed Chemical Kinetics for the Simulation of Premixed Charge Compression Ignition Engines,” International Journal of Engine Research 6(5):497-512, 2005.Fischer, M. and Jiang, X. , “Numerical Optimisation for Model Evaluation in Combustion Kinetics,” Applied Energy 156:793-803, 2015.Xin, J., Shih, S., Itano, E., and Maeda, Y. , “Integration of 3D Combustion Simulations and Conjugate Heat Transfer Analysis to Quantitatively Evaluate Component Temperatures,” SAE Technical Paper 2003-01-3128 , 2003, doi:10.4271/2003-01-3128.Iqbal, O., Arora, K., and Sanka, M. , “Thermal Map of an IC Engine Via Conjugate Heat Transfer: Validation and Test Data Correlation,” SAE International Journal of Engines 7(1):366-374, 2014.Lee, S. and Bae, C. , “Design of a Heat Exchanger to Reduce the Exhaust Temperature in a Spark-Ignition Engine,” International Journal of Thermal Sciences 47(4):468-478, 2008.Kashdan, J. and Bruneaux, G. , “Laser-Induced Phosphorenscence of Combustion Chamber Surface Temperature on a Single-Cylinder Diesel Engine,” SAE Technical Paper 2011-01-2049 , 2011, doi:10.4271/2011-01-2049.Knappe, C., Algotsson, M., Andersson, P., Richter, M. et al. , “Thickness Dependent Variations in Surface Phosphor Thermometry during Transient Combustion in an HCCI Engine,” Combustion and Flame 160(8):1466-1475, 2013.Torregrosa, A.J., Olmeda, P., Degraeuwe, B., and Reyes, M. , “A Concise Wall Temperature Model for Di Diesel Engines,” Applied Thermal Engineering 26(11-12):1320-1327, 2006.Torregrosa, A.J., Olmeda, P., Martín, J., and Romero, C. , “A Tool for Predicting the Thermal Performance of a Diesel Engine,” Heat Transfer Engineering 32(10):891-904, 2011.Kundu, P., Scarcelli, R., Som, S., Ickes, A. et al. , “Modeling Heat Loss through Pistons and Effect of Thermal Boundary Coatings in Diesel Engine Simulations Using a Conjugate Heat Transfer Model,” SAE Technical Paper 2016-01-2235 , 2016, doi:10.4271/2016-01-2235.Senecal, P.K., Pomraning, E., Anders, J., Weber, M. et al. , “Predictions of Transient Flame Lift-Off Length with Comparison to Single-Cylinder Optical Engine Experiments,” Journal of Engineering for Gas Turbines and Power 136(11):111505, 2014.Som, S., Longman, D., Aithal, S., Bair, R. et al. , “A Numerical Investigation on Scalability and Grid Convergence of Internal Combustion Engine Simulations,” SAE Technical Paper 2013-01-1095 , 2013, doi:10.4271/2013-01-1095.Pei, Y., Shan, R., Som, S., Lu, T. et al. , “Global Sensitivity Analysis of a Diesel Engine Simulation with Multi-Target Functions,” SAE Technical Paper 2014-01-1117 , 2014, doi:10.4271/2014-01-1117.Andruskiewicz, P., Najt, P., Durrett, R., Biesboer, S. et al. , “Analysis of the Effects of Wall Temperature Swing on Reciprocating Internal Combustion Engine Processes,” International Journal of Engine Research 19(4):461-473, 2018.Woschni, G., Spindler, W., and Kolesa, K. , “Heat Insulation of Combustion Chamber Walls-A Measure to Decrease the Fuel Consumption of IC Engines?” SAE Technical Paper 870339 , 1987, doi:10.4271/870339.Kosaka, H., Wakisaka, Y., Nomura, Y., Hotta, Y. et al. , “Concept of “Temperature Swing Heat Insulation” in Combustion Chamber Walls, and Appropriate Thermo-Physical Properties for Heat Insulation Coat,” SAE International Journal of Engines 6(1):142-149, 2013.Fukui, K., Wakisaka, Y., Nishikawa, K., Hattori, Y. et al. , “Development of Instantaneous Temperature Measurement Technique for Combustion Chamber Surface and Verification of Temperature Swing Concept,” SAE 2016 World Congress and Exhibition, SAE International, 2016.Hartmann, F., Buhl, S., Hasse, C., Krost, P., Henke, M., and Hübner, W. , “Erschließung von wirkungsgradpotentialen durch reduzierung der wärmeverluste mittels innovativer kolbenbeschichtungen,” in 16th Conference, The Working Process of the Internal Combustion Engines, Graz, September 2017.Broatch, A., Olmeda, P., Margot, X., and Gomez-Soriano, J. , “Numerical Simulations for Evaluating the Impact of Advanced Insulation Coatings on H2 Additivated Gasoline Lean Combustion in a Turbocharged Spark-Ignited Engine,” Applied Thermal Engineering 148:674-683, 2019.Broatch, A., Olmeda, P., Margot, X., and Escalona, J. , “New Approach to Study the Heat Transfer in Internal Combustion Engines by 3D Modelling,” International Journal of Thermal Sciences 138:405-415, 2018.Wiedenhoefer, J.F. and Reitz, R.D. , “A Multidimensional Radiation Model for Diesel Engine Simulation with Comparison to Experiment,” Numerical Heat Transfer Part A 44(7):665-682, 2003.Urip, E., Liew, K.H., and Yang, S.L. , “Modeling IC Engine Conjugate Heat Transfer Using the KIVA Code,” Numerical Heat Transfer, Part A: Applications 52(1):1-23, 2007.Li, Y. and Kong, S.-C. , “Coupling Conjugate Heat Transfer with In-Cylinder Combustion Modeling for Engine Simulation,” International Journal of Heat and Mass Transfer 54(11):2467-2478, 2011.Patil, M.M., Pise, A., and Gokhale, N. , “Simulation of Conjugate Heat Transfer (CHT) between Engine Head and Cooling Medium of Diesel Engine,” SAE Technical Paper 2015-01-1662 , 2015, doi:10.4271/2015-01-1662.Bejan, A. and Kraus, A.D. , Heat Transfer Handbook. Vol. 1 (John Wiley & Sons, 2003).Broatch, A., Margot, X., Novella, R., and Gomez-Soriano, J. , “Impact of the Injector Design on the Combustion Noise of Gasoline Partially Premixed Combustion in a 2-Stroke Engine,” Applied Thermal Engineering 119:530-540, 2017.Convergent Science Inc. , CONVERGE 2.2 Theory Manual.O’Rourke, P. and Amsden, A.A. , “A Particle Numerical Model for Wall Film Dynamics in Port-Injected Engines,” SAE Technical Paper 961961 , 1996, doi:10.4271961961.Amsden, A. , “KIVA-3V: A Block-Structured KIVA Program for Engines with Vertical or Canted Valves,” Los Alamos, National Laboratory, 1997.Torregrosa, A.J., Broatch, A., Olmeda, P., and Martín, J. , “A Contribution to Film Coefficient Estimation in Piston Cooling Galleries,” Experimental Thermal and Fluid Science 34(2):142-151, 2010.Olmeda, P., Dolz, V., Arnau, F., and Reyes-Belmonte, M. , “Determination of Heat Flows inside Turbochargers by Means of a One Dimensional Lumped Model,” Mathematical and Computer Modelling 57(7-8):1847-1852, 2013.Broatch, A., Olmeda, P., García, A., Salvador-Iborra, J., and Warey, A. , “Impact of Swirl on In-Cylinder Heat Transfer in a Light-Duty Diesel Engine,” Energy 119:1010-1023, 2017.Kikusato, A., Terahata, K., Jin, K., and Daisho, Y. , “A Numerical Simulation Study on Improving the Thermal Efficiency of a Spark Ignited Engine---Part 2: Predicting Instantaneous Combustion Chamber Wall Temperatures, Heat Losses and Knock,” SAE International Journal of Engines 7(1):87-95, 2014

Development and Validation of a Submodel for Thermal Exchanges in the Hydraulic Circuits of a Global Engine Model

[EN] To face the current challenges of the automotive industry, there is a need for computational models capable to simulate the engine behavior under low-temperature and low-pressure conditions. Internal combustion engines are complex and have interconnected systems where many processes take place and influence each other. Thus, a global approach to engine simulation is suitable to study the entire engine performance. The circuits that distribute the hydraulic fluids -liquid fuels, coolants and lubricants- are critical subsystems of the engine. This work presents a 0D model which was developed and set up to make possible the simulation of hydraulic circuits in a global engine model. The model is capable of simulating flow and pressure distributions as well as heat transfer processes in a circuit. After its development, the thermo-hydraulic model was implemented in a physical based engine model called Virtual Engine Model (VEMOD), which takes into account all the relevant relations among subsystems. In the present paper, the thermo-hydraulic model is described and then it is used to simulate oil and coolant circuits of a diesel engine. The objective of the work is to validate the model under steady-state and transient operation, with focus on the thermal evolution of oil and coolant. For validation under steady-state conditions, 22 operating points were measured and simulated, some of them in cold environment. In general, good agreement was obtained between simulation and experiments. Next, the WLTP driving cycle was simulated starting from warmed-up conditions and from ambient temperature. Results were compared with the experiment, showing that modeled trends were close to those experimentally measured. Thermal evolutions of oil and coolant were predicted with mean errors between 0.7 °C and 2.1 °C. In particular, the warm-up phase was satisfactorily modeled.This research has been partially funded by the European Union’s Horizon 2020 Framework Programme for research, technological development and demonstration under grant agreement 723976 (“DiePeR”) and by the Spanish government under the grant agreement TRA2017-89894-R. Josep SalvadorIborra was supported by Universitat Politècnica de València through the contract FPI-S2-2016-1357 of the program PAID01-16. The authors wish to thank Renault SAS, especially P. Mallet and E. Gaïffas, for supporting this research. Jaime Monfort San Segundo is acknowledged for his helpful collaboration in the code implementationBroatch, A.; Olmeda, P.; Martín, J.; Salvador-Iborra, J. (2018). Development and Validation of a Submodel for Thermal Exchanges in the Hydraulic Circuits of a Global Engine Model. SAE Technical Papers. https://doi.org/10.4271/2018-01-0160

Effects of Sports Compression Socks on Performance, Physiological, and Hematological Alterations After Long-Haul Air Travel in Elite Female Volleyballers

Broatch, JR, Bishop, DJ, Zadow, EK, and Halson, S. Effects of sports compression socks on performance, physiological, and hematological alterations after long-haul air travel in elite female volleyballers. J Strength Cond Res 33(2): 492-501, 2019-The purpose of this investigation was to assess the merit of sports compression socks in minimizing travel-induced performance, physiological, and hematological alterations in elite female volleyball athletes. Twelve elite female volleyballers (age, 25 ± 2 years) traveled from Canberra (Australia) to Manila (Philippines), and were assigned to 1 of 2 conditions; compression socks (COMP, n = 6) worn during travel or a passive control (CON, n = 6). Dependent measures included countermovement jump (CMJ) performance, subjective ratings of well-being, cardiovascular function, calf girth, and markers of blood clotting, collected before (-24 hours, CMJ; -12 hours, all measures), during (+6.5 and +9 hours, subjective ratings and cardiovascular function), and after (+12 hours, all measures except CMJ; +24 hours and +48 hours, CMJ) travel. When compared with CON, small-to-large effects were observed for COMP to improve heart rate (+9 hours), oxygen saturation (+6.5 hours and +9 hours), alertness (+6.5 hours), fatigue (+6.5 hours), muscle soreness (+6.5 hours and +9 hours), and overall health (+6.5 hours) during travel. After travel, small-to-moderate effects were observed for COMP to improve systolic blood pressure (+12 hours), right calf girth (+12 hours), CMJ height (+24 hours), mean velocity (+24 hours), and relative power (+48 hours), compared with CON. COMP had no effect on the markers of blood clotting. This study suggests that compression socks are beneficial in combating the stressors imposed by long-haul travel in elite athletes, and may have merit for individuals frequenting long-haul travel or competing soon after flying

Impact of simple surge-enhancing inlet geometries on the acoustic behaviour of a turbocompressor

[EN] This paper reports the results of an experimental campaign where four different inlet geometries for the compressor of an automotive turbocharger were acoustically characterized. These four geometries (a straight pipe for reference, a tapered duct, a 90º elbow and a reservoir) were selected for their potential for deep surge margin enhancement, while being simple enough to be commonly found in production vehicles. A detailed measurement of this surge margin enhancement was performed, together with acoustic measurements of both radiated and orifice noise at design conditions of best isentropic efficiency and also close to the deep surge limit. Results demonstrated that while all the proposed geometries indeed enlarged the usable air mass flow range, changes in the acoustic behaviour of the system could be positive, neutral, or even negative. It is therefore important to carefully consider accurate noise measurements before implementing these geometric solutions in production vehicles, and to further pursue research on the link between the characteristic flow pattern produced by each inlet geometry and the noise emission of the turbocompressor.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The equipment used in this work has been partially supported by FEDER project funds ‘‘Dotacio´n de infraestructuras cientı´fico te´cnicas para el Centro Integral de Mejora Energe´tica y Medioambiental de Sistemas de Transporte (CiMeT)’’ (grant number FEDER-ICTS-2012-06), framed in the operational program of unique scientific and technical infrastructure of the Spanish Government.Broatch, A.; Margot, X.; Garcia Tiscar, J.; Roig-Villanueva, F. (2018). Impact of simple surge-enhancing inlet geometries on the acoustic behaviour of a turbocompressor. International Journal of Engine Research. https://doi.org/10.1177/1468087418784125