Needle lift profile influence on the vapor phase penetration for a prototype diesel direct acting piezoelectric injector

In this study, Schlieren visualization tests have been performed for a prototype diesel common rail direct-acting piezoelectric injector, to understand the influence of fuel injection rate shaping on the vapor spray development under evaporative and non-reacting conditions. This state of the art injector presents a particular feature that permits full needle lift control through a parameter referred to as piezo stack charge level, enabling various fuel injection rate typologies. A fast camera and a two pass Schlieren visualization setup have been utilized to record high speed images of the injection event and later analyze, through the vapor phase, the transient evolution of the spray. The tests have been performed employing a novel continuous flow test vessel that provides an accurate control of ambient temperature and pressure up to 1000 K and 15 MPa respectively. The effect of ambient temperature, injection pressure, needle lift and needle lift profile were studied. Data obtained is correlated to previous liquid length and injection rate measurements of the same injector. Results show, as expected for all cases, that instant vapor penetration rate is closely related to instant injection rate. This is confirmed by the injection pressure test results, along with those obtained for the three different piezo stack charge levels, both affecting the vapor penetration in a similar way. Nevertheless, results obtained for the three different charge levels show that the influence of the charge level and the injection pressure differ in the very beginning of the injection event, where the spray development is largely determined by needle lift and not injection pressure. Ambient temperature alone seems not to have and important effect on vapor penetration. Finally, the effects of the needle lift profile in the instant injection rate and vapor penetration are presented, confirming the strong relation between these three parameters, and confirming also that the needle lift plays a determinant role in the spray development, especially at the early stages of the injection process. Both boot and ramp shaped injections proved the ability to strongly influence the vapor penetration rate. In comparison to the square shaped injection, the effect of the ramp shaped injection delays the vapor penetration right from the start of injection while the effect of the boot shaped injection takes considerably longer to become noticeable. From the results, the needle lift control feature has proven to be a very versatile tool for engine designers to control the injection process as desired, opening a new path with a plenty of room for improvement.he authors would like to thank general motors company for their financial support and its cooperation during the project and José Enrique del Rey* and Michele Bardi* for their collaboration in the experimental measurements and setup. (*) From CMT-Motores Térmicos. Universitat Politecnica de Valencia.Payri, R.; Gimeno, J.; Viera, JP.; Plazas Torres, AH. (2013). Needle lift profile influence on the vapor phase penetration for a prototype diesel direct acting piezoelectric injector. Fuel. 113:257-265. doi:10.1016/j.fuel.2013.05.057S25726511

Linking instantaneous rate of injection to X-ray needle lift measurements for a direct-acting piezoelectric injector

Internal combustion engines have been and still are key players in today's world. Ever increasing fuel consumption standards and the ongoing concerns about exhaust emissions have pushed the industry to research new concepts and develop new technologies that address these challenges. To this end, the diesel direct injection system has recently seen the introduction of direct-acting piezoelectric injectors, which provide engineers with direct control over the needle lift, and thus instantaneous rate of injection (ROI). Even though this type of injector has been studied previously, no direct link between the instantaneous needle lift and the resulting rate of injection has been quantified. This study presents an experimental analysis of the relationship between instantaneous partial needle lifts and the corresponding ROI. A prototype direct-acting injector was utilized to produce steady injections of different magnitude by partially lifting the needle. The ROI measurements were carried out at CMT-Motores Termicos utilizing a standard injection rate discharge curve indicator based on the Bosch method (anechoic tube). The needle lift measurements were performed at the Advanced Photon Source at Argonne National Laboratory. The analysis seeks both to contribute to the current understanding of the influence that partial needle lifts have over the instantaneous ROI and to provide experimental data with parametric variations useful for numerical model validations. Results show a strong relationship between the steady partial needle lift and the ROI. The effect is non-linear, and also strongly dependent on the injection pressure. The steady lift value at which the needle ceases to influence the ROI increases with the injection pressure. Finally, a transient analysis is presented, showing that the needle velocity may considerably affect the instantaneous ROI, because of the volume displaced inside the nozzle. Results presented in this study show that at constant injection pressure and energizing time, this injector has the potential to control many aspects of the ROI and thus, the heat release rate. Also, data presented are useful for numerical model validations, which would provide detailed insight into the physical processes that drive these observations, and potentially, to the effects of these features on combustion performance.The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (Argonne). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.Viera-Sotillo, JP.; Payri, R.; Swantek, AB.; Duke, DJ.; Sovis, N.; Kastengren, AL.; Powell, CF. (2016). Linking instantaneous rate of injection to X-ray needle lift measurements for a direct-acting piezoelectric injector. Energy Conversion and Management. 112:350-358. https://doi.org/10.1016/j.enconman.2016.01.038S35035811

Methodology for Phase Doppler Anemometry Measurements on a Multi-Hole Diesel Injector

[EN] In this paper, a methodology for Phase Doppler Anemometry (PDPA) measurements on a multi-hole diesel injector is developed. Several key considerations were taken into account in this methodology: The windows for PDPA optical access must be clean, since fuel impregnated in these could preclude the droplets velocity acquisition. Some parts, including a device for spray isolation, were designed and manufactured to fulfill this goal. Taking into account that only one spray is measured, the isolation device captures all except three of the sprays (including the spray of interest). The two plumes accompanying the main spray were thought to conserve the actual air entrainment and thus the spray behavior. The spray of interest was aligned horizontally to ease the way that the PDPA measurements are carried out. The plume was lined up by means of the MIE-Scattering macroscopic optical technique. Images were acquired for several injection events and spray contours were detected and processed with a purpose-built Matlab tool. At each time step a spray axis inclination was estimated using the centroids from instantaneous contours. Also, preliminary droplet velocity measurements were made to check the effectiveness of the alignment and spray isolation strategies. Both geometrical characterization and spray alignment had very low measurement error. Radial velocity profiles show that PDPA measurements with this set-up configuration preserved the spray behavior.This research was performed in the frame of the project "Estudio de la interaccion chorro-pared en condiciones realistas de motor" reference TRA2015-67679-c2-1-R from Ministerio de Economia y Competitividad (Spanish Ministry of Economy). The equipment used in this work has been partially supported by FEDER Project funds "Dotacion de infraestructuras cientifico tectinas para el Centro Integral de Mejora Energetica y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06)", framed in the operation program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain. Jhoan S. Giraldo was supported by a research grant from Generalitat Valenciana (Programa Santiago Grisolia, GRISOLIA/2013/007).Payri, R.; Gimeno, J.; Marti-Aldaravi, P.; Giraldo-Valderrama, JS. (2017). Methodology for Phase Doppler Anemometry Measurements on a Multi-Hole Diesel Injector. Experimental Techniques. 41(2):95-102. https://doi.org/10.1007/s40799-016-0154-1S95102412Lee J, Kang S, Rho B (2002) Intermittent atomization characteristics of multi-hole and single-hole diesel nozzle. KSME Int J 16(12):1693–1701Lee BH, Song JH, Chang YJ, Jeon CH (2010) Effect of the number of fuel injector holes on characteristics of combustion and emissions in a diesel engine. Int J Automot Technol 11(6):783– 791Lee J, Kaug S, Rho B (2003) Atomization characteristics of intermittent multi-hole diesel spray using time-resolved pdpa data. KSME Int J 17(5):766–775Zhou L-Y, Dong S-F, Cui H-F, Wu X-W, Xue F-Y, Luo F-Q (2016) Measurements and analyses on the transient discharge coefficient of each nozzle hole of multi-hole diesel injector. Sensors Actuators A Phys 244:198–205Payri R, Salvador FJ, Manin J, Viera A (2016) Diesel ignition delay and lift-off length through different methodologies using a multi-hole injector. Appl Energy 162:541–550Payri R, García-Oliver JM, Bardi M, Manin J (2012) Fuel temperature influence on diesel sprays in inert and reacting conditions. Appl Therm Eng 35:185–195Payri F, Payri R, Bardi M, Carreres M (2014) Engine combustion network: Influence of the gas properties on the spray penetration and spreading angle. Exp Thermal Fluid Sci 53:236– 243Payri R, Gimeno J, Bardi M, Plazas AH (2013) Study liquid length penetration results obtained with a direct acting piezo electric injector. Appl Energy 106(0):152–162Soare V (2007) Phase Doppler Measurements in Diesel Dense Sprays: Optimisation of Measurements and Study of the Orifice Geometry Influence over the Spray at Microscopic Level. PhD thesis, Universitat Politècnica de ValenciaAraneo L, Tropea C (2000) Improving phase doppler measurements in a diesel spray. SAE paperCoghe A, Cossali GE (2012) Quantitative optical techniques for dense sprays investigation: A survey. Optics and Lasers in Engineering 50(1):46–56. Advances in Flow VisualizationPayri R, Araneo L, Shakal J, Soare V (2008) Phase doppler measurements: system set-up optimization for characterization of a diesel nozzle. J Mech Sci Technol 22(8):1620–1632Desantes JM, Payri R, Salvador FJ, Soare V (2005) Phase doppler measurements: system set-up optimization for characterization of a diesel nozzle. In: SAE Technical Paper. SAE International, 04Bracco FV, Reitz RD (1979) On the dependence of spray angle and other spray parameters on nozzle design and operating conditions. SAE Technical PaperGavaises M, Andriotis A (2006) Cavitation inside multi-hole injectors for large diesel engines and its effect on the near-nozzle spray structure. In: SAE Technical Paper. SAE International, 04Macian V, Payri R, Garcia A, Bardi M (2012) Experimental evaluation of the best approach for diesel spray images segmentation. Exp Tech 36(6):26–34Payri R, Gimeno J, Viera JP, Plazas AH (2013) Needle lift profile influence on the vapor phase penetration for a prototype diesel direct acting piezoelectric injector. Fuel 113:257– 265Koo Ja-Ye Hung C, Martin JK (1997) Injection pressure effects upon droplet behaviour in transient diesel sprays. SAE PaperLee J, Kang S, Rho B (2003) Time-resolved analysis of turbulent mixing flow characteristics of intermittent multi-hole diesel spray using 2-d pdpa. JSME International Journal Series B Fluids and Thermal Engineering 46 (3):425–433Sinnamon J, Lancaster D, Stiener J (1980) An experimental and analytical study of engine fuel spray trajectories. SAE Technical PaperDesantes JM, Salvador FJ, López JJ, De la Morena J (2011) Study of mass and momentum transfer in diesel sprays based on x-ray mass distribution measurements and on a theoretical derivation. Exp Fluids 50 (2):233–246Hinze (1975) Turbulence. McGraw-Hill, New YorkSchlichting H (1979) Boundary Layer Theory. McGraw-Hill, New YorkDesantes JM, Payri R, Salvador FJ, Gil A (2006) Development and validation of a theoretical model for diesel spray penetration. Fuel 85:910–91

Adaptive determination of cut-off frequencies for filtering the in-cylinder pressure in diesel engines combustion analysis

[EN] In-cylinder pressure analysis is a key tool for engine research and diagnosis and it has been object of study from the beginning of the internal combustion engines. One of its most useful application is combustion analysis on the basis of the First Law of Thermodynamics. However, heat release law calculations use the in-cylinder pressure derivative signal. Hence, the noise is increased and pressure filtering becomes necessary to remove high frequency noise, thus allowing for accurate combustion analyses. In this work, a methodology to set the cut-off frequency of a low-pass filter is proposed. Statistical criteria are used to separate the signal from the noise through the calculation of the Discrete Fourier Transform of several consecutive in-cylinder pressures cycles. Thus, only physically meaningful information is preserved. The proposed methodology is compared with some adaptive and non-adaptive algorithms used to select the cut-off frequencies, and it shows a good ability to adapt to different engine operating conditions. © 2011 Elsevier Ltd. All rights reserved.The authors thank the Universidad Politécnica de Valencia (PAID-06-09) and Generalitat Valenciana (GV/2010/045) for its valuable support to this work.Payri González, F.; Olmeda González, PC.; Guardiola García, C.; Martín Díaz, J. (2011). Adaptive determination of cut-off frequencies for filtering the in-cylinder pressure in diesel engines combustion analysis. Applied Thermal Engineering. 31:2869-2876. https://doi.org/10.1016/j.applthermaleng.2011.05.012S286928763

Influence of diesel surrogates on the behavior of simplified spray models

Numerous experimental investigations make use of diesel surrogates to make the computational time reasonable. In the few studies where measured (surrogate and real diesel) and computed (surrogate only) results have been compared, the selection methodology for the surrogate constituent compounds and the measures taken to validate the chemical kinetic models are not discussed, and the range of operating conditions used is often small. Additionally, most simplified models use tuning variables to fit model results to measurements. This work makes the comparison between some frequently used diesel surrogates using a simple 1D vaporizing spray model, with the spray cone angle as the tuning parameter. Results show that liquid length and fuel fraction strongly depend on the physical properties of the used fuel for a fixed spray angle. These parameters are important for modeling auto-ignition and pollutant formation. The spray angle is varied till the spray length is the same for each surrogate. Results show important differences between other spray parameters such as local mixture fraction and axial velocity

Effect of in-cylinder swirl on engine efficiency and heat rejection in a light-duty diesel engine

[EN] During the last years, the growing awareness about the impacts of climate change lead to an increase in the importance of the efficiency over other criteria in the design of internal combustion engines. In this framework, the heat transfer to the combustion chamber walls can be considered as one of the main sources of indicated efficiency diminution. Hence, the main objective of this research is to thoroughly assess the effect of the swirl ratio on the heat rejection to the chamber walls, and thus on the efficiency, of a fully instrumented four-cylinder direct-injection diesel engine with variable swirl ratio (covering the range from 1.4 to 3). The analysis, based on the engine global energy balance, includes a combination of theoretical and experimental tools such as thermal flow measurement and dedicated thermocouples in the cylinder head and liner. Considering the results, it is shown that an increase in swirl ratio leads to a heat transfer enhancement, along with important changes on the combustion development. As a result of the combination of these two effects, it is shown that intermediate swirl ratios can slightly improve engine efficiency at low load, while increasing swirl worsens the combustion process and efficiency at high load. However, convective heat transfer increases about 3% of the fuel energy in the chamber when swirl ratio increases from 1.4 to 3. The heat rejection characterization is completed with the analysis of the wall temperatures. Despite the observed trends, heat transfer does not seem to be the only key issue for explaining the indicated and brake efficiencies, thus the pumping work plays an important role due to the effect of reducing the intake section to generate the swirl motion.This work was supported by GM Global R&D and the Spanish Ministry of Economy and Competitiveness (TRA2013-41348-R).Olmeda, P.; Martín, J.; Blanco-Cavero, D.; Warey, A.; Domenech, V. (2017). Effect of in-cylinder swirl on engine efficiency and heat rejection in a light-duty diesel engine. International Journal of Engine Research. 18(1-2):81-92. https://doi.org/10.1177/1468087417693078S8192181-

Experimental theoretical methodology for determination of inertial pressure drop distribution and pore structure properties in wall-flow diesel particulate filters (DPFs)

Wall-flow particulate filters have been placed as a standard technology for Diesel engines because of the increasing restrictions to soot emissions. The inclusion of this system within the exhaust line requires the development of computational tools to properly simulate its flow dynamics and acoustics behaviour. These aspects become the key to understand the influence on engine performance and driveability as a function of the filter placement. Since the pressure drop and the filtration process are strongly depending on the pore structure properties - permeability, porosity and pore size - a reliable definition of these characteristics is essential for model development. In this work a methodology is proposed to determine such properties based on the combination of the pressure drop rement in a steady flow test rig and two theoretical approaches. The later are a lumped model and a one-dimensional (1D) unsteady compressible flow model. The purpose is to simplify the integration of particulate filters into the global engine modelling and development processes avoiding the need to resort to specific and expensive characterisation tests. The proposed methodology was validated against measurements of the response of an uncoated diesel particulate filter (DPF) under different flow conditions as cold steady flow, impulsive flow and hot pulsating flow. © 2011 Elsevier Ltd.This work has been partially supported by the Spanish Ministerio de Ciencia e Innovacion through grant number DPI2010-20891-C02-02.Payri González, F.; Broatch Jacobi, JA.; Serrano Cruz, JR.; Piqueras Cabrera, P. (2011). Experimental theoretical methodology for determination of inertial pressure drop distribution and pore structure properties in wall-flow diesel particulate filters (DPFs). Energy. 36(12):6731-6744. https://doi.org/10.1016/j.energy.2011.10.033S67316744361

A computational methodology to account for the liquid film thickness evolution in Direct Numerical Simulation of prefilming airblast atomization

Prefilming airblast atomization is widely used in aero engines. Fundamental studies on the annular configuration of airblast atomizers are difficult to realize. For this reason, researchers focused on planar configurations. In this regard, the Karlsruhe Institute of Technology (KIT) developed a test rig to conduct experimental activities, conforming a large database with results for different conditions. Such data allow validation of two-phase flow calculations concerning primary atomization on these devices. The present investigation proposes a Direct Numerical Simulation (DNS) on the KIT planar configuration through the Volume of Fluid (VOF) method within the PARIS code. The novelty compared to DNS reported in the literature resides in the use of a boundary condition that accounts not only for the gas inflow turbulence but also for the spatio-temporal evolution of the liquid film thickness at the DNS inlet and its effect on turbulence. The proposed methodology requires computing precursor single-phase and two-phase flow Large-Eddy Simulations. Results are compared to DNS that only account for a constant (both timewise and spanwise) liquid film thickness at the domain inlet, validating the workflow. The proposed methodology improves the qualitative description of the breakup mechanism, as its different stages (liquid accumulation behind the prefilmer edge, bag formation, bag breakup, ligament formation and ligament breakup) coexist spanwise for a given temporal snapshot. This implies more continuous atomization than the one predicted by the constant film thickness case, which showed the same breakup stage to be present along the prefilmer span for a given instant and led to a more discretized set of atomization events. The proposed workflow allows quantifying the influence of the liquid film flow evolution above the prefilmer on primary breakup frequency and atomization features.Comment: Preprint submitted to International Journal of Multiphase Flo

Improvement and application of a methodology to perform the Global Energy Balance in internal combustion engines. Part 1: Global Energy Balance tool development and calibration

[EN] The increasingly stringent internal combustion engines emissions regulations, has led to the extended use of after-treatment systems, giving progressively more importance to the engine efficiency optimization. In this framework, the combined modelling and experimental methodologies to perform and analyse the energy balance are key to evaluate the potential of different engine strategies aimed at the consumption optimization and the identification of the improvement paths. This work has been divided into two parts, dealing separately with the development and application of a Global Energy Balance tool. This article corresponds to the first part, which comprises the description of the models required to perform a detailed energy balance and the calibration methodologies followed to achieve accurate energy terms estimation. The models are calibrated based on experimental information, thus, a thermodynamic analysis aimed at defining comparable quantities between experimental and modelled terms is performed. The uncertainty analysis of the tool shows a deviation in the determination of the heat transfer to the coolant and the oil of about ±2%, and in terms of fuel energy about ±1%.This work was partially funded by the Government of Spain through Project TRA2013-41348-R. In addition, the authors acknowledge that some equipment used in this work has been partially supported by FEDER project funds (FEDER-ICTS-2012-06), framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain.López, JJ.; Payri, F.; Martín, J.; Carreño-Arango, R. (2018). Improvement and application of a methodology to perform the Global Energy Balance in internal combustion engines. Part 1: Global Energy Balance tool development and calibration. Energy. 152:666-681. https://doi.org/10.1016/j.energy.2018.03.118S66668115

ECU-oriented models for NOx prediction. Part 2: adaptive estimation by using an NOx sensor

The implantation of nitrogen oxide sensors in diesel engines is necessary in order to track emissions at the engine exhaust line for diagnosis and control of the after-treatment devices. However, the use of models is still necessary since the sensor outputs are delayed and filtered. The present paper deals with the problem of the nitrogen oxide estimation in two parts; Part 1 deals with a control-oriented model for the nitrogen oxide estimation, while Part 2 presents data fusion of the model and the sensor to improve the estimation, which is presented in the following. The use of models for the nitrogen oxide estimation is an alternative but the drift and the ageing are still issues. In order to overcome this problem, the fusion of different signals can be carried out in a smart way by means of a Kalman filter. There exist different ways of presenting this fusion, from directly tracking the bias to updating the model parameters. For this, different algorithms are proposed in this paper with the aim of correcting the model output. Furthermore, the estimation of the actual nitrogen oxide concentration, by preventing sensor delay and filtering, is also integrated in the algorithm, which is a suitable strategy for combining nitrogen oxide sensors and models on an onboard basis.Guardiola, C.; Climent, H.; Pla Moreno, B.; Blanco-Rodriguez, D. (2015). ECU-oriented models for NOx prediction. Part 2: adaptive estimation by using an NOx sensor. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. 229(10):1345-1360. doi:10.1177/0954407014561278S134513602291