Benefits of E85 versus gasoline as low reactivity fuel for an automotive diesel engine operating in reactivity controlled compression ignition combustion mode

[EN] This work shows the capabilities of E85 fuel to be used as low reactivity fuel in a high compression ratio light-duty diesel engine (17.1:1) running under reactivity controlled compression ignition concept. To do this, experimental steady-state engine maps are obtained in a single-cylinder engine with diesel-E85 fuel combination. The engine mapping was performed following the same procedure used in previous works with other fuel combinations to allow the results comparison. Considering the mechanical and emissions limits imposed during the engine mapping, it was found that with diesel-E85 the combustion concept is limited to the region defined from 2 to 7 bar at 1000 rpm, and from 1.5 to 9 bar indicated mean effective pressure at 3000 rpm. This operating region was satisfied with nitrogen oxides, soot and pressure rise rate levels below 0.4 g/kWh, 0.01 g/kWh and 10 bar/CAD, respectively. The reactivity controlled compression ignition maps with diesel-E85 were obtained taking as reference the total fuel energy used in a previous work to map the engine with diesel-gasoline. The direct comparison of both combustion concepts (diesel-E85 and diesel-gasoline) revealed that E85 allows to extend the engine map around 2 bar indicated mean effective pressure towards the high load region. Moreover, the minimum load achieved at high engine speeds was decreased down to 1.5 indicated mean effective pressure. Finally, the differences in terms of emissions and performance between both reactivity controlled compression ignition concepts are highlighted by doing the difference between the maps of several variables.The authors gratefully acknowledge General Motors Global Research & Development for providing the engine used in this investigation. The authors also acknowledge FEDER and Spanish Ministerio de Economia y Competitividad for partially supporting this research through HiReCo project (TRA2014-58870-R).Benajes, J.; García Martínez, A.; Monsalve-Serrano, J.; Villalta-Lara, D. (2018). Benefits of E85 versus gasoline as low reactivity fuel for an automotive diesel engine operating in reactivity controlled compression ignition combustion mode. Energy Conversion and Management. 159:85-95. https://doi.org/10.1016/j.enconman.2018.01.015S859515

Analysis of a series hybrid vehicle concept that combines low temperature combustion and biofuels as power source

[EN] This work evaluates the potential of a series hybrid vehicle concept that combines low temperature combustion (LTC) and biofuels as power source. To do this, experimental data from a previous work obtained in a singlecylinder engine running under ethanol-diesel dual-fuel combustion is used. Then, vehicle systems simulations are used to estimate performance and emissions of the LTC hybrid vehicle and compare them versus conventional diesel combustion (CDC). The vehicle selected to perform the simulations is the Opel Vectra, which equips the compression ignition engine used in the experimental tests. The results from the simulations used for the analysis are firstly optimized by combining design of experiments and the Kriging fitting method. The multi-objective optimization allows to determine some characteristics and controls of the hybrid vehicle. The comparison of the estimated performance and emissions of the LTC-hybrid concept versus CDC over the worldwide harmonized light vehicles test cycle (WLTC) and real driving cycle (RDE) revealed clear benefits in terms of energy consumption, CO2 and NOx and soot emissions. In this sense, the hybrid concept enabled a reduction of the final energy consumed of 3% in the RDE cycle and 6.5% in the WLTC as compared to CDC. In terms of engine-out emissions, the CO2 was reduced around 16% versus CDC, and engine-out NOx and soot were reduced below the levels imposed by the Euro 6 regulation. As a penalty, the engine-out HC and CO emissions increased to more than double than CDC. However, based on previous experimental results, it is expected that a conventional diesel oxidation catalyst can reduce the tail-pipe HC and CO levels below the Euro 6 limits.The authors gratefully acknowledge General Motors Global Research & Development for providing the engine used to acquire the experimental data shown in this investigation. The authors also acknowledge FEDER and Spanish Ministerio de Economía y Competitividad for partially supporting this research through TRANCO project (TRA2017- 87694-R).García Martínez, A.; Monsalve-Serrano, J. (2019). Analysis of a series hybrid vehicle concept that combines low temperature combustion and biofuels as power source. Results in Engineering. 1:1-12. https://doi.org/10.1016/j.rineng.2019.01.001S1121Kalghatgi, G. (2018). Is it really the end of internal combustion engines and petroleum in transport? Applied Energy, 225, 965-974. doi:10.1016/j.apenergy.2018.05.076Singh, S., & Kennedy, C. (2015). Estimating future energy use and CO2 emissions of the world’s cities. Environmental Pollution, 203, 271-278. doi:10.1016/j.envpol.2015.03.039Engel, M. S., Paas, B., Schneider, C., Pfaffenbach, C., & Fels, J. (2018). Perceptual studies on air quality and sound through urban walks. Cities, 83, 173-185. doi:10.1016/j.cities.2018.06.020Guanetti, J., Formentin, S., Corno, M., & Savaresi, S. M. (2017). Optimal energy management in series hybrid electric bicycles. Automatica, 81, 96-106. doi:10.1016/j.automatica.2017.03.021He, H., & Guo, X. (2018). Multi-objective optimization research on the start condition for a parallel hybrid electric vehicle. Applied Energy, 227, 294-303. doi:10.1016/j.apenergy.2017.07.082García Valladolid, P., Tunestål, P., Monsalve-Serrano, J., García, A., & Hyvönen, J. (2017). Impact of diesel pilot distribution on the ignition process of a dual fuel medium speed marine engine. Energy Conversion and Management, 149, 192-205. doi:10.1016/j.enconman.2017.07.023Wu, H.-W., Wang, R.-H., Ou, D.-J., Chen, Y.-C., & Chen, T. (2011). Reduction of smoke and nitrogen oxides of a partial HCCI engine using premixed gasoline and ethanol with air. Applied Energy, 88(11), 3882-3890. doi:10.1016/j.apenergy.2011.03.027Olmeda, P., García, A., Monsalve-Serrano, J., & Lago Sari, R. (2018). Experimental investigation on RCCI heat transfer in a light-duty diesel engine with different fuels: Comparison versus conventional diesel combustion. Applied Thermal Engineering, 144, 424-436. doi:10.1016/j.applthermaleng.2018.08.082Yao, M., Zheng, Z., & Liu, H. (2009). Progress and recent trends in homogeneous charge compression ignition (HCCI) engines. Progress in Energy and Combustion Science, 35(5), 398-437. doi:10.1016/j.pecs.2009.05.001Maurya, R. K., & Agarwal, A. K. (2011). Experimental investigation on the effect of intake air temperature and air–fuel ratio on cycle-to-cycle variations of HCCI combustion and performance parameters. Applied Energy, 88(4), 1153-1163. doi:10.1016/j.apenergy.2010.09.027Singh, A. P., & Agarwal, A. K. (2012). Combustion characteristics of diesel HCCI engine: An experimental investigation using external mixture formation technique. Applied Energy, 99, 116-125. doi:10.1016/j.apenergy.2012.03.060Yang, Y., Dec, J. E., Dronniou, N., & Sjöberg, M. (2011). Tailoring HCCI heat-release rates with partial fuel stratification: Comparison of two-stage and single-stage-ignition fuels. Proceedings of the Combustion Institute, 33(2), 3047-3055. doi:10.1016/j.proci.2010.06.114Benajes, J., García, A., Monsalve-Serrano, J., Balloul, I., & Pradel, G. (2017). Evaluating the reactivity controlled compression ignition operating range limits in a high-compression ratio medium-duty diesel engine fueled with biodiesel and ethanol. International Journal of Engine Research, 18(1-2), 66-80. doi:10.1177/1468087416678500García, A., Monsalve-Serrano, J., Rückert Roso, V., & Santos Martins, M. E. (2017). Evaluating the emissions and performance of two dual-mode RCCI combustion strategies under the World Harmonized Vehicle Cycle (WHVC). Energy Conversion and Management, 149, 263-274. doi:10.1016/j.enconman.2017.07.034Benajes, J., García, A., Monsalve-Serrano, J., & Villalta, D. (2018). Exploring the limits of the reactivity controlled compression ignition combustion concept in a light-duty diesel engine and the influence of the direct-injected fuel properties. Energy Conversion and Management, 157, 277-287. doi:10.1016/j.enconman.2017.12.028Benajes, J., García, A., Monsalve-Serrano, J., Balloul, I., & Pradel, G. (2016). An assessment of the dual-mode reactivity controlled compression ignition/conventional diesel combustion capabilities in a EURO VI medium-duty diesel engine fueled with an intermediate ethanol-gasoline blend and biodiesel. Energy Conversion and Management, 123, 381-391. doi:10.1016/j.enconman.2016.06.059Benajes, J., García, A., Monsalve-Serrano, J., & Boronat, V. (2016). Dual-Fuel Combustion for Future Clean and Efficient Compression Ignition Engines. Applied Sciences, 7(1), 36. doi:10.3390/app7010036Benajes, J., García, A., Monsalve-Serrano, J., & Boronat, V. (2017). An investigation on the particulate number and size distributions over the whole engine map from an optimized combustion strategy combining RCCI and dual-fuel diesel-gasoline. Energy Conversion and Management, 140, 98-108. doi:10.1016/j.enconman.2017.02.073Benajes, J., García, A., Monsalve-Serrano, J., & Boronat, V. (2017). Gaseous emissions and particle size distribution of dual-mode dual-fuel diesel-gasoline concept from low to full load. Applied Thermal Engineering, 120, 138-149. doi:10.1016/j.applthermaleng.2017.04.005Curran S, Hanson R, Wagner R. Reactivity controlled compression ignition combustion on a multi-cylinder light-duty diesel engine. Int. J. Engine Res. 13 (3), 216-225.Reitz, R. D., & Duraisamy, G. (2015). Review of high efficiency and clean reactivity controlled compression ignition (RCCI) combustion in internal combustion engines. Progress in Energy and Combustion Science, 46, 12-71. doi:10.1016/j.pecs.2014.05.003Olmeda, P., Martin, J., Garcia, A., Villalta, D., Warey, A., & Domenech, V. (2017). A Combination of Swirl Ratio and Injection Strategy to Increase Engine Efficiency. SAE International Journal of Engines, 10(3), 1204-1216. doi:10.4271/2017-01-0722Luján, J. M., Bermúdez, V., Dolz, V., & Monsalve-Serrano, J. (2018). An assessment of the real-world driving gaseous emissions from a Euro 6 light-duty diesel vehicle using a portable emissions measurement system (PEMS). Atmospheric Environment, 174, 112-121. doi:10.1016/j.atmosenv.2017.11.056OLIVER, M. A., & WEBSTER, R. (1990). Kriging: a method of interpolation for geographical information systems. International journal of geographical information systems, 4(3), 313-332. doi:10.1080/02693799008941549Benajes, J., García, A., Monsalve-Serrano, J., & Villalta, D. (2018). Benefits of E85 versus gasoline as low reactivity fuel for an automotive diesel engine operating in reactivity controlled compression ignition combustion mode. Energy Conversion and Management, 159, 85-95. doi:10.1016/j.enconman.2018.01.015García, A., Piqueras, P., Monsalve-Serrano, J., & Lago Sari, R. (2018). Sizing a conventional diesel oxidation catalyst to be used for RCCI combustion under real driving conditions. Applied Thermal Engineering, 140, 62-72. doi:10.1016/j.applthermaleng.2018.05.04

Potential of using OMEx as substitute of diesel in the dual-fuel combustion mode to reduce the global CO2 emissions

[EN] To achieve the targets of extreme low emissions values for the transport sector, several technologies emerged in the last few years. In this sense, advanced combustion modes as the dual-fuel low temperature combustion showed great advantages in terms of NOx and soot emissions reduction. At low and medium engine load, the operation is stable with virtually zero emissions. However, the exhaust gas recirculation rates at high load need to be increased to avoid excessive in-cylinder peaks, which leads to higher soot emissions. At these conditions, the use of non-sooting fuels as the oxymethylene dimethyl ethers (OMEx) allows avoiding the NOx-soot trade-off. In addition, the e-fuel consideration of the OMEx makes it suitable to reduce the global GHG emissions. This paper assesses the potential of using OMEx as high reactivity fuel to reduce the CO2 well-to-wheel emissions, and NOx and soot tailpipe emissions, in a medium-duty truck operating under dual-fuel combustion in transient conditions. The cargo mass was varied between 0% and 100% (18 ton) in the World Harmonized Vehicle Cycle. The tank-to-wheel analysis shows slightly higher CO2 production with OMEx-gasoline than with diesel-gasoline due to the ratio between the lower heating value and the carbon content. However, the well-to-wheel analysis shows the benefits of using OMEx to reduce the carbon dioxide footprint, which ranges from 13% (at full cargo mass) to 19% (at low cargo mass) compared to diesel-gasoline dual-fuel mode. This benefit is due to the large gains in terms of fuel production due to the carbon capture and the clean electric energy source necessary to produce the OMEx.The authors acknowledge FEDER and Spanish Ministerio de Economía y Competitividad for partially supporting this research through TRANCO project (TRA2017-87694-R). The authors also acknowledge the Universitat Politècnica de València for partially supporting this research through Convocatoria de ayudas a Primeros Proyectos de Investigación (SP20180148)Benajes, J.; García Martínez, A.; Monsalve-Serrano, J.; Martínez-Boggio, SD. (2020). Potential of using OMEx as substitute of diesel in the dual-fuel combustion mode to reduce the global CO2 emissions. Transportation Engineering. 1:1-6. https://doi.org/10.1016/j.treng.2020.01.001S16

Experimental investigation on the efficiency of a diesel oxidation catalyst in a medium-duty multi-cylinder RCCI engine

[EN] Reactivity controlled compression ignition (RCCI) combustion is one of the most promising low temperature combustion (LTC) techniques, as it is able to provide ultra-low NOx and soot emissions together with higher thermal efficiency than conventional diesel combustion (CDC) in a wide range of operating conditions. However, the unburned hydrocarbon (UHC) and carbon monoxide (CO) emission levels are orders of magnitude higher than CDC, which can result in a major problem for implementing the RCCI concept in real engines. In this sense, the high levels of UHC and CO emissions together with the low exhaust temperatures during RCCI operation could compromise the diesel oxidation catalyst (DOC) conversion efficiency. The objective of this work is to evaluate the efficiency of a conventional DOC in oxidizing the UHC and CO emissions from RCCI combustion. To do this, a medium-duty multi-cylinder diesel engine equipped with its original after treatment system has been used. First, the DOC conversion efficiency is evaluated under some steady-state conditions. Later, the influence of the thermal inertia on the DOC response has been evaluated by means of transient tests. In this sense, different engine load-speed steps as well some simplified conditions from the worldwide harmonized vehicle cycle (WHVC) and the supplemental engine transient cycle (SET) are evaluated. In steady-state conditions, with DOC-inlet temperatures of 200-300 degrees C, the results show conversion efficiencies of 100% for CO and 85-95% for HC. At 10% and 25% load, the DOC-outlet UHC levels are unacceptable considering the EURO VI regulation, while at 50% load the tailpipe emissions fulfill the emissions standard. The results in transient conditions are more promising thanks to effect of the thermal inertia, showing 100% conversion efficiency for CO and greater than 90% for UHC during large periods of engine operation.The authors thanks VOLVO Group Trucks Technology and ARAMCO Overseas Company for supporting this research. The authors also acknowledge FEDER and Spanish Ministerio de Economia y Competitividad for partially supporting this research through TRANCO project (TRA2017-87694-R).Benajes, J.; García Martínez, A.; Monsalve-Serrano, J.; Lago-Sari, R. (2018). Experimental investigation on the efficiency of a diesel oxidation catalyst in a medium-duty multi-cylinder RCCI engine. Energy Conversion and Management. 176:1-10. https://doi.org/10.1016/j.enconman.2018.09.016S11017

Sizing a conventional diesel oxidation catalyst to be used for RCCI combustion under real driving conditions

[EN] Reactivity controlled compression ignition (RCCI) combustion has demonstrated to be able to avoid the NOx-soot trade-off appearing during conventional diesel combustion (CDC), with similar or better thermal efficiency than CDC under a wide variety of engine platforms. However, a major challenge of this concept comes from the high hydrocarbon (HC) and carbon monoxide (CO) emission levels, which are orders of magnitude greater than CDC, and similar to those of port fuel injected (PFI) gasoline engines. The high HC and CO emissions levels combined with the low exhaust temperatures during RCCI operation could present a challenge for the current exhaust aftertreatment technologies. The objective of this work is to evaluate the potential of a conventional diesel oxidation catalyst (DOC) for light-duty diesel engines when operating under dual-fuel RCCI diesel-gasoline combustion and to define its necessary size to accomplish with the current emissions standards. For this purpose, a 1-D model has been developed and calibrated through gas emissions measurements upstream and downstream the DOC under different engine steady-state conditions. After that, the DOC response in transient conditions has been evaluated by means of vehicle systems simulations under different driving cycles representative of the homologation procedures currently in force around the world. The results show that the HC and CO levels at the DOC outlet are unacceptable considering the different emissions regulations. By this reason, a dedicated study to define the DOC size needed to accomplish the different emissions standards is carried out. The results suggest that, the DOC volume needed to fulfill the type approval regulation limits ranges from four to six times the original volume.The authors gratefully acknowledge General Motors Global Research & Development for providing the engine used in this investigation. The authors also acknowledge FEDER and Spanish Ministerio de Economia y Competitividad for partially supporting this research through TRANCO project (TRA2017-87694-R).García Martínez, A.; Piqueras, P.; Monsalve-Serrano, J.; Lago-Sari, R. (2018). Sizing a conventional diesel oxidation catalyst to be used for RCCI combustion under real driving conditions. Applied Thermal Engineering. 140:62-72. https://doi.org/10.1016/j.applthermaleng.2018.05.043S627214

Operating range extension of RCCI combustion concept from low to full load in a heavy-duty engine

Fuel reactivity controlled compression ignition (RCCI) concept has arisen as a solution to control premixed combustion (PCI) strategies, which avoids soot and NOx formation by promoting a lean air fuel mixture and low temperature combustion. Thus, this study is focused on investigating the effects of different engine operating variables over combustion, to be able to suggest suitable strategies for extending the RCCI operation from low to full load, in a HD single-cylinder research engine. Different strategies are implemented at low, medium and high load, varying fuel and air reactivity, by means of parametrical studies. Performance and emissions results are analyzed combining engine testing with 3D-CFD modeling. Based on those results, an overlimit function is used to select the best engine settings for each operating point. Finally, engine emissions and performance results from that RCCI operation are compared with conventional Diesel combustion (CDC). Results suggest that double injection strategies should be used for RCCI operation from low to mid load. However, from high to full load operation, single injection strategies should be used, mainly to avoid excessive in-cylinder pressure gradients. In addition, it is confirmed the suitability of RCCI combustion to overcome the soot NOx trade-off characteristic of CDC, from 6 to 24 bar of BMEP, while improving fuel consumption.The authors would like to recognize the technical support from VOLVO Group Trucks Technology and to express their gratitude to CONVERGENT SCIENCE Inc. and IGNITE3D Engineer-ing GmbH for their kind support for performing the CFD calculations using CONVERGE software. In addition, thank the Spanish Ministry of Economy and Competitiveness for the financial support through Eduardo Belarte's grant (BES-2011-047073). The authors would also like to thank Gabriel Alcantarilla for the management of the facility and his assistance in data acquisition.Molina Alcaide, SA.; García Martínez, A.; Pastor Enguídanos, JM.; Belarte Mañes, E.; Balloul, I. (2015). Operating range extension of RCCI combustion concept from low to full load in a heavy-duty engine. Applied Energy. 143:211-227. https://doi.org/10.1016/j.apenergy.2015.01.035S21122714

The potential of RCCI concept to meet EURO VI NOx limitation and ultra-low soot emissions in a heavy-duty engine over the whole engine map

This work investigates the potential of RCCI concept to achieve ultra-low NOx and soot emissions over a wide range of engine speed and loads. For this purpose, a detailed experimental methodology has been defined and applied in a heavy-duty single-cylinder engine fueled with diesel and gasoline. In addition, to assess the influence of the engine compression ratio on RCCI capabilities two different compression ratios, 14.4:1 and 11:1, have been tested. Results suggest that a low compression ratio allows to fulfill all the self-imposed constraints (maximum cylinder pressure rise rate of 25 bar/CAD, NOx < 0.4 g/kW h and soot* < 0.01 g/kW h) from idle to full load and engine speeds from 900 to 1800 rpm. However, the use of higher compression ratio requires a delayed injection strategy to avoid excessive knocking levels, which results in unacceptable soot emissions at loads higher than 50%, even when gasoline fractions around 90% are used.The authors would like to acknowledge VOLVO Group Trucks Technology for supporting this research and to express their gratitude to Spanish economy and competitiveness ministry for partially funding this research under the project HiReCo TRA2014-58870-R.Benajes Calvo, JV.; Pastor Soriano, JV.; García Martínez, A.; Monsalve Serrano, J. (2015). The potential of RCCI concept to meet EURO VI NOx limitation and ultra-low soot emissions in a heavy-duty engine over the whole engine map. Fuel. 159:952-961. https://doi.org/10.1016/j.fuel.2015.07.064S95296115

Evaluation of massive exhaust gas recirculation and Miller cycle strategies for mixing-controlled low temperature combustion in a heavy duty diesel engine

The future of compression ignition engines depends on their ability for keeping their competitiveness in terms of fuel consumption compared to spark-ignition engines. In this competitive framework, the Low Temperature Combustion (LTC) concept is a promising alternative to decrease NOx and soot emissions. Thus, this research focuses on implementing the LTC concept, but keeping the conventional mixing-controlled combustion process to overcome the well-known drawbacks of the highly-premixed combustion concepts, including load limitations and lack of combustion control. Two strategies for implementing the mixing-controlled LTC concept were evaluated. The first strategy relies on decreasing the intake oxygen concentration introducing high rates of cooled EGR. The second strategy consists of decreasing the compression temperature by advancing the intake valves closing angle to reduce the effective compression ratio, compensating the air mass losses by increasing boost pressure (Miller cycle). These strategies were tested in a single-cylinder heavy-duty research engine. Additionally, 3D-CFD modeling was used to give insight into local in-cylinder conditions during the injection-combustion process. Results confirm the suitability of both strategies for reducing NOx and soot emissions, while their main drawback is the increment in fuel consumption. However, they present intrinsic differences in terms of local equivalence ratios and temperatures along combustion.The authors of this paper thank the Spanish Ministry of Economic and Competitively for the financial support of this research through the project TRA2010-20271 (LOWTECOM).Benajes Calvo, JV.; Molina Alcaide, SA.; Novella Rosa, R.; Belarte Mañes, E. (2014). Evaluation of massive exhaust gas recirculation and Miller cycle strategies for mixing-controlled low temperature combustion in a heavy duty diesel engine. Energy. (71):355-366. https://doi.org/10.1016/j.energy.2014.04.083S3553667

In-cylinder soot radiation heat transfer in direct-injection diesel engines

The efficiency and CO2 are one of the main concerns of automotive manufacturers. There are several strategies under investigation to solve this problem. In the present work, the research effort has been focused on improving knowledge of in-cylinder heat transfer and its impact on engine efficiency. In particular, soot radiation was studied since it can be considered a significant source of the efficiency losses in modern diesel engines. Considering previous studies, the portion of total chemical energy released during combustion lost due to radiation heat transfer varies widely from 0.5% up to 10%, depending on engine parameters and combustion process. Thus, the main objective of this work was to evaluate the amount of energy lost to soot radiation relative to the input fuel chemical energy during the combustion event under different operating conditions in a completely controlled environment provided by an optical engine. Under these simplified conditions, two-color method was applied by using high speed imaging pyrometer with cameras (two dimensional results) and optoelectronic pyrometer (zero dimensional results). Once a detailed comparison between both diagnostics was performed, optoelectronic pyrometer was used to characterize radiant energy losses in a fully instrumented 4-cylinder direct-injection lightduty diesel engine. In particular swirl ratio, 'EGR and combustion phasing effects on radiation heat transfer were evaluated.The authors acknowledge General Motors Global R&D for supporting this research and to express their gratitude to Spanish economy and competitiveness ministry for partially funding this research under the project HiReCo TRA2014-58870-R.Benajes Calvo, JV.; Martín Díaz, J.; García Martínez, A.; Villalta Lara, D.; Warey, A. (2015). In-cylinder soot radiation heat transfer in direct-injection diesel engines. Energy Conversion and Management. 106:414-427. https://doi.org/10.1016/j.enconman.2015.09.059S41442710

Arracades de Pollentia al Museu d'Arqueologia de Barcelona

El present article és només una part d'un estudi exhaustiu sobre la col·lecció de joies exposades a la sala XII del Museu d'Arqueologia de Barcelona. S'hi analitzen detalladament deu exemplars d'arracades d'un conjunt inventariat com a pertanyents al jaciment arqueològic de Pollentia, a Alcúdia (Mallorca). Mitjançant la comparació d'aquestes peces amb unes altres de paral·leles, s'hi extreuen conclusions referents a la cronologia, la tipologia i l'estil, i s'hi plantegen noves hipòtesis.This article is just a part of a comprehensive study of the collection of jewels on display in Room XII Archaeology Museum of Barcelona. We focus on ten copies of a set of earrings inventoried as belonging to the archaeological site Pollentia, in Alcudia (Mallorca). By comparing these pieces with other parallel, drawn conclusions regarding the chronology, typology and style, and new hypothesis