Model of the expansion process for R245fa in an Organic Rankine Cycle (ORC)

An Organic Rankine Cycle (ORC) is considered as one of the most environmental-friendly ways to convert different kinds of low temperature energies, i.e. solar, geothermal, biomass and thermal energy of exhaust gases into electrical energy. Two important facts about the ORC must be considered: An organic fluid is selected as the working fluid and a high expansion ratio is usually presented in the machinery due to thermodynamic and efficiency factors. In the past, the pre-design of turbomachinery has been based on the usage of ideal fluid laws, but the real gas effects have a significant influence in the ORC working condition, due to its proximity to the saturation vapor line. In this article, the Equations of State (EoS) (Ideal gas, Redlich-Kwong-Soave and Peng-Robinson) have been evaluated in a typical ORC expansion in order to observe the inaccuracies of the ideal gas model with different thermodynamic variables. Finally an isothermal process followed by an isochoric process is proposed to reproduce the thermodynamic process of the organic fluid expansion by means of simpler equations. In the last point of this paper, several examples of this expansion process have been calculated, in order to analyze the proposed methodologies. It has been concluded that in typical expansion process of ORC (2.5 MPa-0.1 MPa and 1.6MPa-0.1MPa), the PR and RKS equations show deviations between 6% and 8% in specific energy. These deviations are very low compared with the ideal gas equation whose deviations are above 100 %.This work was partially funded by the "Programa de Formacion de Profesorado Universitario (F.P.U)", "Programa de Apoyo a la Investigacion y Desarrollo de la Universidad Politecnica de Valencia 2010", "Proyectos I+D para grupos de investigacion emergentes 2011" and "Programa de apoyo a la investigacion y desarrollo de la U.P.V (PAID-06-09)". The authors thanks to R. Gatzweiler for his help to improve the English grammar.Lujan Martinez, JM.; Serrano Cruz, JR.; Dolz Ruiz, V.; Sánchez Serrano, J. (2012). Model of the expansion process for R245fa in an Organic Rankine Cycle (ORC). Applied Thermal Engineering. 40:248-257. https://doi.org/10.1016/j.applthermaleng.2012.02.020S2482574

Methodology to design a bottoming Rankine cycle, as a waste energy recovering system in vehicles. Study in a HDD engine

This article describes a methodology for the optimization of a bottoming cycle as a waste heat recovering system in vehicles. The methodology is applied to two particular cases in order to evaluate the preliminary energetic and technical feasibility of the implementation of a bottoming cycle in a heavy duty diesel (HDD) engine considering two different criteria. Initially, a study of the different waste heat sources of the engine is described. In this study, the power and exergy of each heat source is quantified, in order to evaluate which sources are suitable to be used in the bottoming cycle. The optimum working fluids to run the cycles are selected (water and R245fa). Then, the ideal Rankine cycle is optimized for the two different working fluids and different sets of heat sources (all the available heat sources and the sources with high exergy respectively) throughout the engine operating range, reaching a maximum improvement of 15% of the fuel consumption of the engine. Later, a study of the minimum temperature difference between the hot and cold flow of the heat exchangers is described. The improvements in fuel consumption and the size of the installed heat exchanger are related to this temperature difference. Finally, the non-ideal behavior of the machines (pump and expander) is analyzed, obtaining a maximum improvement of 10% in brake specific fuel consumption (bsfc).This work was partially funded by the "Programa de Formacion de Profesorado Universitario (FPU)", "Programa de Apoyo a la Investigacion y Desarrollo de la Universidad Politecnica de Valencia 2010", "Proyectos I + D para grupos de investigacion emergentes 2011" and "Programa de apoyo a la investigacion y desarrollo de la U.P.V (PAID-06-09)". The authors thank J. Dahlqvist for his help in improving the English grammar.Macian Martinez, V.; Serrano Cruz, JR.; Dolz Ruiz, V.; Sánchez Serrano, J. (2013). Methodology to design a bottoming Rankine cycle, as a waste energy recovering system in vehicles. Study in a HDD engine. Applied Energy. 104:758-771. https://doi.org/10.1016/j.apenergy.2012.11.075S75877110

THIESEL 2022. Conference on Thermo-and Fluid Dynamics of Clean Propulsion Powerplants

The THIESEL 2022. Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines planned in Valencia (Spain) for 8th to 11th September 2020 has been successfully held in a virtual format, due to the COVID19 pandemic. In spite of the very tough environmental demands, combustion engines will probably remain the main propulsion system in transport for the next 20 to 50 years, at least for as long as alternative solutions cannot provide the flexibility expected by customers of the 21st century. But it needs to adapt to the new times, and so research in combustion engines is nowadays mostly focused on the new challenges posed by hybridization and downsizing. The topics presented in the papers of the conference include traditional ones, such as Injection & Sprays, Combustion, but also Alternative Fuels, as well as papers dedicated specifically to CO2 Reduction and Emissions Abatement.Papers stem from the Academic Research sector as well as from the IndustryXandra Marcelle, M.; Payri Marín, R.; Serrano Cruz, JR. (2022). THIESEL 2022. Conference on Thermo-and Fluid Dynamics of Clean Propulsion Powerplants. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thiesel.2022.632801EDITORIA

Assessment by means of gas dynamic modelling of a pre-turbo diesel particulate filter configuration in a turbocharged HSDI diesel engine under full-load transient operation

Diesel particulate filters (DPF) are becoming a standard technology in diesel engines because of the need for compliance with forthcoming regulations regarding soot emissions. When a great degree of maturity in management of filtration and regeneration has been attained, the influence of the DPF placement on the engine performance emerges as a key issue to be properly addressed. The novelty of this work leads to the study of an unusual location of an aftertreatment device in the architecture of the turbocharged diesel engine exhaust line. The problem of the pre-turbo DPF placement is tackled comparing the engine response under full-load transient operation as opposed to the traditional DPF location downstream of the turbine. The study has been performed on the basis of a gas dynamic simulation of the engine, which has been validated with experimental data obtained under steady-state and transient conditions. The DPF response has been simulated with a model able to deal with the characteristic highly pulsating flow upstream of the turbine. Several levels of DPF soot loading have been considered to represent fully the most exigent conditions in terms of performance requirements. As a result, the main physical phenomena controlling the engine and DPF response and interaction have been identified. Placing the DPF upstream of the turbine will lead to a number of important advantages, owing to the continuous regeneration mode at which the DPF will operate, the lower pressure drop in the DPF, and the thermal energy storage in the DPF, which is very useful to mitigate 'turbocharger lag' during engine transient operation. These three effects have been evidenced with calculations performed using the validated model and the results have been fully analysed and discussed.This work has been partially supported by the Spanish MCI grant DPI2010-20891-C02-02.Bermúdez, V.; Serrano Cruz, JR.; Piqueras, P.; García Afonso, Ó. (2011). Assessment by means of gas dynamic modelling of a pre-turbo diesel particulate filter configuration in a turbocharged HSDI diesel engine under full-load transient operation. PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AU. 225(9):1134-1155. https://doi.org/10.1177/0954407011402278S11341155225

Behavior of an IC Engine Turbocharger in Critical Conditions of Lubrication

Problems in the turbocharger lubrication system can cause serious deterioration in their overall performance and even their complete destruction. The paper describes several tests with different critical lubrication conditions, in order to determine the thresholds at which the operation may be appropriate. In an IC engine, these problems can be produced mainly by several factors: the decreasing in the supply pressure of the oil, a delay in the lubrication oil pressure and an intermittent lubrication interruption. A turbocharger test bench and an IC engine test bench has been used to test the turbocharger, in order to reproduce the conditions and cycles similar to the operation of the turbocharger in an IC engine (pressures, temperatures, mass flows, accelerations, etc..). Thermodynamic variables and mechanic variables measured in the tests help to identify some of the operating limits of lubrication in critical conditions. In addition, optical techniques have been combined with accelerometer measurements, in order to detect modifications in the movement of the turbocharger shaft. The main conclusions obtained from these tests are that accelerations from low rotational speed to 100krpm, without lubrication oil in the bearing system, don’t cause significant problems in the turbocharger, for 20 sec. However, the accelerations to 150krpm can cause critical problems depending on the lubrication delay and the bearing configuration. Finally, higher acceleration rates to 200krpm, without lubrication, cause the turbocharger destruction in a few seconds. By other hand, a low oil inlet pressure given by an oil column, of about 1m in height, allows to the turbo survive during accelerations from low rotational speed to 150 krpm.Galindo, J.; Serrano Cruz, JR.; Dolz Ruiz, V.; López Hidalgo, MA.; Bouffaud, F. (2013). Behavior of an IC Engine Turbocharger in Critical Conditions of Lubrication. SAE International Journal of Engines. 6(2):1-9. doi:10.4271/2013-01-0921S196

Study of the turbocharger shaft motion by means of infrared sensors

This work describes a technique for measuring the precession movement of the shaft of small automotive turbochargers. The main novelty is that the technique is based on infrared light diode sensors. With presented technique it is possible to perform secure mounting of electronics and also to measure, with good accuracy, far enough from the turbocharger shaft. Both advantages allow applying it even in critical lubrication conditions and when blade contact occurs. The technique's main difficulties arise from the small size of the turbocharger shaft and the high precession movement in critical conditions. In order to generate the optimum albedo reflection for infrared measurement, a special cylindrical nut with larger diameter than the original one is assembled at the shaft tip in the compressor side. Following, shaft balancing, the calibration of the sensors and the compensation of errors from different sources are needed steps before the method is able to identify the main frequencies of shaft motion. Once synchronous and sub-synchronous frequencies have been obtained it is possible to reconstruct the instantaneous position of the shaft to determine its precession movement.This research has also been partially supported by the Programa de Desarrollo del Talento Humano de la Secretaria Nacional de Educacion Superior, Ciencia, Tecnologia e Innovacion del Gobierno Ecuatoriano No. 20100289.Serrano Cruz, JR.; Guardiola, C.; Dolz García, VM.; López, M.; Bouffaud, F. (2015). Study of the turbocharger shaft motion by means of infrared sensors. Mechanical Systems and Signal Processing. 56-57:246-258. https://doi.org/10.1016/j.ymssp.2014.11.006S24625856-5

Brayton cycle for internal combustion engine exhaust gas waste heat recovery

An average passenger car engine effectively uses about one-third of the fuel combustion energy, while the two-thirds are wasted through exhaust gases and engine cooling. It is of great interest to automotive industry to recover some of this wasted energy, thus increasing the engine efficiency and lowering fuel consumption and contamination. Waste heat recovery for internal combustion engine exhaust gases using Brayton cycle machine was investigated. The principle problems of application of such a system in a passenger car were considered: compressor and expander machine selection, machine size for packaging under the hood, efficiency of the cycle, and improvement of engine efficiency. Important parameters of machines design have been determined and analyzed. An average 2-L turbocharged gasoline engine's New European Driving Cycle points were taken as inlet points for waste heat recovery system. It is theoretically estimated that the recuperated power of 1515 W can be achieved along with 5.7% improvement in engine efficiency, at the point where engine power is 26550 W.Galindo, J.; Serrano Cruz, JR.; Dolz Ruiz, V.; Kleut, P. (2015). Brayton cycle for internal combustion engine exhaust gas waste heat recovery. Advances in Mechanical Engineering. 7(6):1-9. doi:10.1177/16878140155903141976Bredel, E., Nickl, J., & Bartosch, S. (2011). Waste Heat Recovery in Drive Systems of Today and Tomorrow. MTZ worldwide, 72(4), 52-56. doi:10.1365/s38313-011-0042-0Freymann, R., Strobl, W., & Obieglo, A. (2008). The turbosteamer: A system introducing the principle of cogeneration in automotive applications. MTZ worldwide, 69(5), 20-27. doi:10.1007/bf03226909Freymann, R., Ringler, J., Seifert, M., & Horst, T. (2012). The Second Generation Turbosteamer. MTZ worldwide, 73(2), 18-23. doi:10.1365/s38313-012-0138-1Glavatskaya, Y., Podevin, P., Lemort, V., Shonda, O., & Descombes, G. (2012). Reciprocating Expander for an Exhaust Heat Recovery Rankine Cycle for a Passenger Car Application. Energies, 5(6), 1751-1765. doi:10.3390/en5061751Song, B., Zhuge, W., Zhao, R., Zheng, X., Zhang, Y., Yin, Y., & Zhao, Y. (2013). An investigation on the performance of a Brayton cycle waste heat recovery system for turbocharged diesel engines. Journal of Mechanical Science and Technology, 27(6), 1721-1729. doi:10.1007/s12206-013-0422-2Dolz, V., Novella, R., García, A., & Sánchez, J. (2012). HD Diesel engine equipped with a bottoming Rankine cycle as a waste heat recovery system. Part 1: Study and analysis of the waste heat energy. Applied Thermal Engineering, 36, 269-278. doi:10.1016/j.applthermaleng.2011.10.02

Development and validation of a radial turbine efficiency and mass flow model at design and off-design conditions

Turbine performance at extreme off-design conditions is growing in importance for properly computing turbocharged reciprocating internal combustion engines behaviour during urban driving conditions at current and future homologation cycles. In these cases, the turbine operates at very low flow rates and power outputs and at very high blade to jet speed ratios during transitory periods due to turbocharger wheel inertia and the high pulsation level of engine exhaust flow. This paper presents a physically based method that is able to extrapolate radial turbines reduced mass flow and adiabatic efficiency in blade speed ratio, turbine rotational speed and stator vanes position. The model uses a very narrow range of experimental data from turbine maps to fit the necessary coefficients. By using a special experimental turbocharger gas stand, experimental data have been obtained for extremely low turbine power outputs for the sake of model validation. Even if the data used for fitting only covers the turbine normal operation zone, the extrapolation model provides very good agreement with the experiments at very high blade speed ratio points; producing also good results when extrapolating in rotational speed and stator vanes position.The authors of this paper wish to thank M.A. Ortiz for his invaluable help during the experimental setup and to Arnau Blasco for his hard data fitting work. This work has been partially supported by the Spanish Ministry of Economy and Competitiveness through Grant No. TRA2013-40853-R.Serrano Cruz, JR.; Arnau Martínez, FJ.; García-Cuevas González, LM.; Dombrovsky, A.; Tartoussi, H. (2016). Development and validation of a radial turbine efficiency and mass flow model at design and off-design conditions. Energy Conversion and Management. 128:281-293. https://doi.org/10.1016/j.enconman.2016.09.032S28129312

Optimization of the inlet air line of an automotive turbocharger

This paper presents different aspects of air inlet behaviour near the inducer of a radial compressor and shows how the geometry can contribute to its stability and performance. Unfortunately, the space reserved for installation of an automotive turbocharger in a vehicle is constantly being reduced, so it is necessary to study the effects that elbows and abrupt changes in flow directions originate on the compressor performance. The work presented in this paper studies the effect that different 90 degrees elbows have on the compressor with respect to its ideal, straight, no-elbow configuration, in order to obtain the best possible elbow configuration. The methodology followed has been to, initially, study different geometries in computational fluid dynamics code in order to obtain the best possible configuration. Then, several 90 degrees elbows were constructed and characterized on a continuous flow test bench in order to validate the computational fluid dynamics results and to obtain optimum results. The elbows were then installed on a radial compressor and tested on a hot, continuous turbocharger test bench, where the compressor was characterized and maps were obtained with each different elbow. The results were compared with respect to the ideal, no-elbow configuration, which was taken as the base performance. After analysing the results obtained, it is possible to observe that in most of the cases, the elbows have a negative effect on the compression ratio, which tends to be reduced, especially at high rotor velocities and high air mass flow. On the other hand, the effect on the surge limit seems to be positive, as the surge line shifts to lower air mass flows, although the maximum mass flow allowed is reduced. It seems as if the compressor map shifts to the left with a reduction in compression ratio. From theoretical and experimental studies, it has been concluded that flow uniformity index and pressure loss are the most important factors affecting the performance of the compressorSerrano Cruz, JR.; Margot, X.; Tiseira Izaguirre, AO.; García-Cuevas González, LM. (2013). Optimization of the inlet air line of an automotive turbocharger. International Journal of Engine Research. 14(1):92-104. doi:10.1177/1468087412449085S92104141Soranna, F., Chow, Y.-C., Uzol, O., & Katz, J. (2005). The Effect of Inlet Guide Vanes Wake Impingement on the Flow Structure and Turbulence Around a Rotor Blade. Journal of Turbomachinery, 128(1), 82-95. doi:10.1115/1.2098755Engeda, A., Kim, Y., Aungier, R., & Direnzi, G. (2003). The Inlet Flow Structure of a Centrifugal Compressor Stage and Its Influence on the Compressor Performance. Journal of Fluids Engineering, 125(5), 779-785. doi:10.1115/1.1601255Elder, R. L., & Gill, M. E. (1985). A Discussion of the Factors Affecting Surge in Centrifugal Compressors. Journal of Engineering for Gas Turbines and Power, 107(2), 499-506. doi:10.1115/1.3239759Canova, M. (2004). Development and validation of a control-oriented library for the simulation of automotive engines. International Journal of Engine Research, 5(3), 219-228. doi:10.1243/1468087041549625Kyrtatos, N. P., Tzanos, E. I., & Papadopoulos, C. I. (2003). Diesel engine control optimization for transient operation with lean/rich switches. International Journal of Engine Research, 4(3), 219-231. doi:10.1243/146808703322223333Mattarelli, E. (2009). Virtual design of a novel two-stroke high-speed direct-injection diesel engine. International Journal of Engine Research, 10(3), 175-193. doi:10.1243/14680874jer02509Galindo, J., Serrano, J. R., Margot, X., Tiseira, A., Schorn, N., & Kindl, H. (2007). Potential of flow pre-whirl at the compressor inlet of automotive engine turbochargers to enlarge surge margin and overcome packaging limitations. International Journal of Heat and Fluid Flow, 28(3), 374-387. doi:10.1016/j.ijheatfluidflow.2006.06.002Galindo, J., Serrano, J. R., Guardiola, C., & Cervelló, C. (2006). Surge limit definition in a specific test bench for the characterization of automotive turbochargers. Experimental Thermal and Fluid Science, 30(5), 449-462. doi:10.1016/j.expthermflusci.2005.06.00

Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications

[EN] Nowadays turbocharging the internal combustion engine has become a key point in the reduction on pollutant emissions and the improvement on engine performance. The matching between the turbocharger and the engine is vital due to the highly unsteady flow the turbocharger works with. In the present paper the importance of the heat transfer phenomena inside small automotive turbochargers will be analyzed. This phenomenon will be studied from the point of view of both the turbine and the compressor in one-dimensional modelling. The goodness of the model will be demonstrated predicting turbine and compressor outlet temperatures. An accurate prediction of these parameters will be key designing the intercooler and the after treatment devices. A series of tests in a gas stand with steady and pulsating hot flow in the turbine side will be modeled to show the good agreement in turbocharger enthalpies prediction.This paper is partially supported by the Universitat Politècnica de València PAID-06-11 2034.Serrano Cruz, JR.; Olmeda González, PC.; Arnau Martínez, FJ.; Reyes Belmonte, MA.; Lefebvre, A. (2013). Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications. SAE International Journal of Engines. 6(2):1-13. doi:10.4271/2013-01-0576S1136