Detailed Thermal Characterization on a 48V Lithium-Ion Battery Pack during Charge-Discharge Cycles

This study experimentally investigates the temperature distribution and behavior of a 48V Lithium-Ion (Li-ion) battery pack during two charge-discharge cycles using 25 thermocouples. Results indicate that better convective heat transfer occurs at the external surfaces of the pack, while middle cells reach maximum temperatures. Differences are also observed in the behavior of the three modules. The discharge cycle shows a temperature rise of 5.8{\deg}C with a pack temperature gradient increasing from 1.3{\deg}C to 2.7{\deg}C. The study highlights the importance of assessing the thermal behavior of each module and the complexity of the Li-ion battery pack system. Findings on the battery cells, modules, and pack in the same study can provide valuable insights for designing efficient cooling systems for Li-ion battery packs.Comment: 11 pages, 4 figure

multiobjective optimization of the breathing system of an aircraft two stroke supercharged diesel engine

Abstract One of the factors limiting the utilization of piston internal combustion engines for aircraft propulsion is the performance decrease increasing the altitude of operation. This is due to the negative effect of air density reduction increasing the altitude on cylinder filling. A solution to this problem is represented by the engine supercharging. Unfortunately, in two stroke engines, the cylinder filling efficiency is antithetical to the cylinder scavenging efficiency. With the aim of guaranteeing an optimal balance between engine performance and specific consumption, an engine breathing system optimization is needed. In this work, the results obtained running a multi-objective optimization procedure aiming at performance increase and fuel consumption reduction of an aircraft two stroke supercharged diesel engine at various altitudes are analyzed. During the optimization procedure, several geometric parameters of the intake and exhaust systems as well as geometric and operating engine parameters have been varied. Then, a multi-objective optimization algorithm based on genetic algorithms has been run to obtain the configurations optimizing the engine performance at Sea Level (take-off conditions) and fuel consumption at 10680 m (cruise conditions)

Light-Induced ignition of Carbon Nanotubes and energetic nano-materials: a review on methods and advanced technical solutions for nanoparticles-enriched fuels combustion

Abstract Aim of the present manuscript is to provide an overview of all possible methods and light source typologies used by the different research groups for obtaining the energetic nano-materials' photo-ignition, showing the latest progress related to such phenomenon employing, also, alternative radiation sources to the common Xe lamp. In fact, the employment of a different source typology can open new usage prospects respect to those enabled by the Xe lamp, mainly due to its technological limitations. Therefore, several studies are faced to test light sources, such as lasers and LEDs, for igniting the nano-energetic materials (as CNTs mixed with metallic catalyzers, Al / CuO nano-particles, etc); these nano-materials are usefully employed for starting, in volumetric and controlled way, the combustion of air-fuel mixtures inside internal combustion engines, leading to significant benefits to the combustion process also in terms of efficiency, reliability, and emissions of pollutants. Several research works are presented in literature concerning the ignition of liquid / gaseous fuels, without nano-particles, employing laser sources (i.e laser-based plugs in place of the common spark plugs); therefore, an innovative solution is proposed that employs multi-point laser-plugs for inducing the ignition of nano-materials dispersed into the air-fuel mixture inside the cylinder, so further improving the combustion of the fuel in an internal combustion engine

Potential Application of Photo-thermal Volumetric Ignition of Carbon Nanotubes in Internal Combustion Engines

In internal combustion engines, an ignition source is required to initiate the combustion process. This is commonly obtained either through an electric spark generation or by physical act of compression-ignition. In order to improve performance and lower pollutants levels, researchers have proposed alternatives to conventional ignition or combustion processes, such as homogeneously-charge compression-ignition (HCCI) combustion, whose critical operational requirement is precise control of the autoignition timing within the engine operating cycle. In this work, an innovative volumetrically-distributed ignition approach is proposed to control the onset of the autoignition process, by taking advantage of the optical ignition properties of carbon nanotubes when exposed to a low-consumption light source. It is shown that this ignition method enhanced the combustion of methane, hydrogen, LPG, and gasoline (injected to chamber in liquid phase). The results for this new ignition method show that pressure gradient and combustion efficiency are increased, while combustion duration and ignition delay time are decreased. A direct observation of the combustion process indicates that these benefits are due to the spatially-distributed ignition followed by a faster initial consumption of the air/fuel mixture. The use of this ignition system is therefore proposed as a promising technology for the combustion management in internal combustion engines, specifically for the HCCI engines

Analysis of the integration of the three-way catalyst thermal management in the on-line supervisory control strategy of a gasoline full hybrid vehicle

Full hybrid electric vehicles have proven to be a midterm viable solution to fulfil stricter regulations, such as those regarding carbon dioxide abatement. Although fuel economy directly benefits from hybridization, the use of the electric machine for propulsion may hinder an appropriate warming of the aftertreatment system, whose temperature is directly related to the emissions conversion efficiency. The present work evaluates the efficacy of a supervisory energy management strategy based on Equivalent Minimization Consumption Strategy (ECMS) which incorporates a temperature-based control for the thermal management of the Three-Way Catalyst (TWC). The impact of using only the midspan temperature of TWC is compared against the case where temperature at three different sampling points along the TWC length are used. Moreover, a penalty term based on TWC temperature has been introduced in the cost functional of the ECMS to allow the control of the TWC temperature operating window. In fact, beyond a certain threshold, the increase of the engine load, requested to speed up TWC warming, does not translate into a better catalyst efficiency, because the TWC gets close to its highest conversion rate. A gasoline P2 parallel full hybrid powertrain has been considered as test case. Results show that the effects of the different calibrations strategies are negligible on the TWC thermal management, as they do not provide any improvements in the fuel economy nor in the emissions abatement of the hybrid powertrain. This effect can be explained by the fact that the charge sustaining condition has a greater weight on the energy management strategy than the effects deriving from the addition of the soft constraints to control the TWC thermal management. These results hence encourage the use of simple setups to deal with the control of the TWC in supervisory control strategies for full hybrid electric vehicles

photo induced ignition phenomenon of carbon nanotubes by xenon pulsed light ignition tests analysis automotive and new potential applications future developments

Abstract The possibility to use carbon nanotubes (CNTs) enriched with a certain amount of metal nanoparticles for photo-inducing the combustion of liquid fuel sprays, gaseous and solid fuels was investigated in different research works. CNTs photo-ignition phenomenon has been used to trigger the combustion of different fuel typologies, demonstrating better features compared with those obtained by employing a traditional spark-plug. These improvements are due to the presence of distributed ignition nuclei inside the combustion chamber, so obtaining better values of the peak pressure, ignition delay and combustion duration. In this work, the CNTs photo-ignition phenomenon has been analyzed in order to find the minimum energy values needed to trigger the ignition, by varying the light pulse parameters and the nanoparticles concentration, Multi Wall CNTs (MWCNTs) – ferrocene, by weight. Afterwards, the results of combustion processes, triggered by using the nanoparticles, are shown comparing them with those obtained by means the spark plug and with results already published related to other fuel typologies. Hence, an overview of the possible applications of this photo-ignition phenomenon, beside that of the automotive field, is presented, also considering the disadvantages of the Xe-lamp based triggering system. Therefore, after a critical discussion on the light source typology until now used (Xenon lamp), by reporting the possible contraindications deriving from the use of this light source in most of the applicative fields, a solution is here proposed. It involves the substitution of the Xe lamp with LED sources, showing also the related experimental setup. This solution is also strengthened by the our experimental observations of CNTs photo-ignition by using high-power white LEDs as light source, never reported up to now in the literature, and by better characteristics of adaptability, robustness, easy driving and benefits provided by the LEDs rather than the Xenon lamp

Effects of low-grade gas composition on the energy/exergy performance of a polygeneration system (CH2HP) based on biomass gasification and ICE

Bio-hydrogen from sustainable biomass (i.e. agro-industrial residues) gasification can play a relevant role in the hydrogen economy, providing constant hydrogen from renewable sources. Nowadays, most hydrogen production systems integrate one or more water-gas shift (WGS) units to maximize the hydrogen yield that, however, needs additional syngas treatments, investment and operational costs. Besides, different electricity inputs are needed along the process to power the compression of raw syngas, shifted syngas, and pure hydrogen to the desired pressure. This common process integration with WGS generates a kind of off-gas from the hydrogen separation unit whose composition may or may not be suitable for power production, depending on the operating conditions of the gasification unit. In this regard, this work proposes a different approach in which no WGS reactors are involved and the off-gas is used to generate heat and power to provide the energy input needed by the system. In particular, the authors tested the bio-syngas and the corresponding off-gas in a 4-cylinders, spark ignition natural gas internal combustion engine operated in cogeneration mode with the aim to analyse the effect of removing the hydrogen from the original bio-syngas on mechanical/electric and thermal power, on fuel efficiency and CO2 specific emission

A comprehensive study on the effect of pilot injection, EGR rate, IMEP and biodiesel characteristics on a CRDI diesel engine

Although many studies have concerned effect of different kind of biodiesel fuel on engine, there are no information about the comparison between different biodiesels in a comprehensive study and with consideration of pilot injection and EGR system. Therefore, the aim of this study is to have a comprehensive investigation of the effect of pilot injection timing and EGR system, as common ways to reduce engine emissions, on engine combustion, emissions and performance while using of different kind of the biodiesel. The brassica, cardoon, coffee, waste cooking oil biodiesels and standard diesel fuels were evaluated fuels. However, the results of the study depicted that different characteristics of the considered fuels had changed the engine response to variation of injection strategy and EGR application. The maximum reduction of combustion duration compare to diesel fuel (17.7%) was related to coffee biodiesel. Moreover, Coffee biodiesel has lowest pressure rise rate. On the other hand, cardoon had shortest ignition delay and highest combustion temperature. In addition, maximum retardation of combustion position was for brassica biodiesel fuel (19.07%). Although the NOx emission has decreased due to application of EGR (up to 86%) and pilot injection (up to 29.3%), high EGR rate in high IMEP has changed the combustion quality due to sewer changes in the combustion quality. In this condition, CO and THC emission increased severely. Higher viscosity and lower oxygen content of the coffee and cardoon biodiesel than diesel fuel decreased combustion quality and caused the higher THC, CO and soot emissions and lower NOx emissions than brassica and WCO biodiesel fuels in higher EGR rates and IMEPs. It can be stated that pilot injection and EGR are two parameters which are effective significantly on the engine characteristics and the adjusting of these parameters should be done properly specially according to the used fuel properties

Investigating the impact of copper leaching on combustion characteristics and particulate emissions in HPCR diesel engines

© 2019 Elsevier Ltd Copper leaching in diesel fuel and its impact on combustion and emission characteristics of a Direct Injection High Pressure Common Rail (DI HPCR) diesel engine was investigated. This work was performed using a single cylinder Ricardo Hydra research engine fitted with a cylinder head, piston assembly, and crankshaft from a production 2.2 L DI diesel engine. A fuel conditioning device consisting of a helicoidally shaped copper duct and electromagnetic coils powered from the battery was installed along the fuel line just before the high pressure pump. A diesel fuel with a copper content of less than 0.2 ppm was used. Inductively coupled plasma mass spectrometry (ICP-MS) analysis showed an increase of copper content to 1 ppm when fuel flowed through the conditioning device prior to the injection and returned from the engine back to the fuel tank. Copper leaching from the conditioning device was confirmed using a bespoke test rig. Combustion characteristics were analysed via post-processing pressure measurements, while an AVL Smoke Meter was used to monitor particulate emissions. A pilot plus main strategy was used to achieve a target Brake Mean Effect Pressure (BMEP) typical of medium load. Soot reduction in the range of 7–14% was measured when the device was connected to the fuel line, compared to the baseline. The initiation and early development of combustion was also investigated using an unstirred, quiescent combustion chamber with optical access. High-speed photography showed that ignition probability was enhanced in presence of the fuel conditioning device