80 research outputs found
Experimental assessment of the performance and emissions of a spark-ignition engine using waste-derived biofuels as additives
The use of biofuels for spark ignition engines is proposed to diversify fuel sources and reduce fossil fuel consumption, optimize engine performance, and reduce pollutant emissions. Additionally, when these biofuels are produced from low-grade wastes, they constitute valorisation pathways for these otherwise unprofitable wastes. In this study, ethanol and pyrolysis biogasoline made from low-grade wastes were evaluated as additives for commercial gasoline (RON95, RON98) in tests performed in a spark ignition engine. Binary fuel mixtures of ethanol + gasoline or biogasoline + gasoline with biofuel incorporation of 2% (w/w) to 10% (w/w) were evaluated and compared with ternary fuel mixtures of ethanol + biogasoline + gasoline with biofuel incorporation rates from 1% (w/w) to 5% (w/w). The fuel mix performance was assessed by determination of torque and power, fuel consumption and efficiency, and emissions (HC, CO, and NOx). An electronic control unit (ECU) was used to regulate the air–fuel ratio/lambda and the ignition advance for maximum brake torque (MBT), wide-open throttle (WOT)), and two torque loads for different engine speeds representative of typical driving. The additive incorporation up to 10% often improved efficiency and lowered emissions such as CO and HC relative to both straight gasolines, but NOx increased with the addition of a blend.This work was supported by FCT-Fundação para a Ciência e Tecnologia within the R&D
Units, MEtRICs Project Scope: UIDP/04077/2020. Joaquim da Costa was supported through a PhD
Grant from Fundo de Desenvolvimento Capital Humano of the Government of Timor Leste
Performance and emissions of a spark ignition engine operated with gasoline supplemented with pyrogasoline and ethanol
The partial replacement of fossil fuels by biofuels contributes to a reduction of CO2 emissions, alleviating the greenhouse effect and climate changes. Furthermore, fuels produced from waste biomass materials have no impact on agricultural land use and reduce deposition of such wastes in landfills. In this paper we evaluate the addition of pyrolysis biogasoline (pyrogasoline) as an additive for fossil gasoline. Pyrogasoline was produced from used cooking oils unfit to produce biodiesel. This study was based on a set of engine tests using binary and ternary mixtures of gasoline with 0, 2.5, and 5% pyrogasoline and ethanol. The use of ternary blends of gasoline and two different biofuels was tested with the purpose of achieving optimal combustion conditions and lower emissions, taking advantage of synergistic effects due to the different properties and chemical compositions of those biofuels. The tests were performed on a spark-ignition engine, operated at full load (100% throttle, or WOT—wide open throttle) between 2000 and 6000 rpm, while recording engine performance and exhaust gases pollutants data. Binary mixtures with pyrogasoline did not improve or worsen the engine’s performance, but the ternary mixtures (gasoline + pyrogasoline + ethanol) positively improved the engine’s performance with torque gains between 0.8 and 3.1% compared to gasoline. All fuels presented CO and unburned hydrocarbons emissions below those produced by this type of engine operated under normal (fossil) gasoline. On the other hand, NOx emissions from oxygenated fuels had contradictory behaviour compared to gasoline. If we consider the gains achieved by the torque with the ternary mixtures and reductions in polluting emissions obtained by mixtures with pyrogasoline, a future for this fuel can be foreseen as a partial replacement of fossil gasoline.This work was partially funded by Fundação para a Ciência e Tecnologia: UIDB/04077/2020
Improvement of biocomposite performance under low-velocity impact test - a review
2nd World Conference on Advanced Materials for Defense, AUXDEFENSE 2020Virtual, Online6 July 2020 through 7 July 2020Code 266239The study of the impact energy and the composite behaviour plays a vital role in the efficient design of composite structures. Among the various categories of impact tests, it is essential to study low-velocity impact tests as the damage generated due to these loads is often not visible to the naked eye. The internal damages can reduce the strength of the composites and hence the impact behaviour must be addressed specifically for improving their applications in the transport industry. The main aim of this paper is to provide a comprehensive review of the work focusing on the assessment of biocomposites performance under low impact velocity, the different deformations, and damage mechanisms, as well the methods to improve the impact resistance.(undefined
Compact automotive thermoelectric generator with embedded heat pipes for thermal control
Currently, the automotive industry faces challenges to implement solutions that provide reductions in energy consumption, pollutants and greenhouse-gas (GHG) emissions. Exhaust heat recovery employing Thermoelectric generators (TEGs) enables the direct conversion of heat into electric energy without moving parts and little to no maintenance. On-board electrical production is especially useful given the growing electrification trend of road vehicles. The present work assesses the performance of a novel temperature-controlled thermoelectric generator (TCTG) concept in a light duty vehicle and its impact on fuel economy and GHG emissions under realistic driving conditions. The novel exhaust heat exchanger (HE) concept consists of corrugated pipes embedded in a cast aluminium matrix along with variable conductance heat pipes (VCHPs) acting as spreaders of excess heat along the longitudinal direction. This concept seems to have a quite good potential for highly variable thermal load applications, as it is able to avoid overheating by spreading heat instead of wasting it through by-pass systems. Furthermore, when compared to previous concepts by the group, it does not need gravity assistance and has a form factor similar to conventional generators. It also appears to be capable of delivering a breakthrough electric output for TEG systems in such light vehicles, with as much as 572 W and 1538 W of average and maximum electric powers during a driving cycle, respectively, and showing a quite promising reduction of 5.4% in fuel consumption and CO2 emissions.- This work has been supported by FCT e Fundacao para a Ciencia e Tecnologia within the R&D Units Project Scope: UIDP/04077/2020 within MEtRICs - Mechanical Engineering and Resource Sustainability Centre, Project Exhaust2Energy (PTDC/EMS-ENE/3009/2014) and M-ERA.net Project THERMOSS (M-ERA.net2_0011_2016), financed by European Regional Development Fund (ERDF) funds through P.O.F.C. e COMPETE and National funds through PIDDAC and FCT. The authors also wish to thank Dr. Helder Puga from the Casting Lab of the Mechanical Engineering Department of University of Minho, Paulo Moutinho and BorgWarner Emissions Systems (Spain Technical Center -Vigo, Spain)
The effect of ambient pressure on the heat transfer of a water spray
The present work is aimed at quantifying the effects of ambient pressure in the heat transfer at single injections of a full cone spray over a hot metal surface. The experimental configuration is that of a spray impinging down perpendicularly onto a flat surface located at 55 mm inside an injection chamber. The experiments were conducted for prescribed initial wall temperatures ranging from single phase to local nucleate boiling and transition regimes of heat transfer. Ambient pressures ranged from atmospheric to 30 bar. The analysis is based on spatial resolved measurements of the instantaneous surface temperature during the injection period. The measurements are then processed in order to obtain estimates of the time-averaged values of the local heat flux. The overall cooling rate is also obtained by integrating the local values within the total area of the spray impact Results show that the amount of heat extracted by the impinging spray increases 3.4 times when ambient pressure is increased from atmospheric to 20 bar at the same superheating degree at the wall of 45 degrees C. This corresponds to an increase from 13.3% to 47.7% in the ratio between the actual cooling and the theoretical maximum cooling, defined here as cooling efficiency. This is a result of a better spreading of the liquid film at the wall, covering a larger footprint upon impact. Instantaneous peak heat flux is also increased, as a clear indication of the improved heat transfer between the impinging droplets and the wall.The work presented herein derives from a broader research program devised to develop a system for in cylinder cooling of internal combustion engines using high pressure water sprays produced by gasoline direct injectors.The authors would like to acknowledge LiquidPiston INC. for providing all the laboratorial conditions to perform the experiments, MEtRICs - Mechanical Engineering and Resource Sustainability Centre (UID/EMS/04077/2019), and Diogo Ferreira for aiding in the highspeed visualization setup and experiments. T. Costa is supported by the Portuguese Foundation for Science and Technology (FCT) under the PhD grant PD/BD/105929/2014, MIT Portugal Program, and F.P. Brito is supported by FCT under the Post doctoral grant SFRH/BPD/89553/2012 and J. Martins is supported by the FCT grant SFRH/BSAB/142994/2018, financed by FEDER funds through Programa Operacional Fatores de Competitividade - COMPETE and National funds through PIDDAC and FCT
Using vanadium redox flow batteries for the electricity storage towards the electric vehicles fast charging process
This work was later revised, extended and published as a full journal paper in ENERGY. Please use the journal version for citation purposes: Álvaro Cunha, Jorge Martins, Nuno Rodrigues, Vítor Monteiro, João L. Afonso, Paula Ferreira, F. P. Brito, Assessment of the use of Vanadium Redox Flow Batteries for Energy Storage and Fast Charging of Electric Vehicles in Gas Stations, Energy, 115-2, (2016), 1478–1494, DOI:10.1016/j.energy.2016.02.118. journal article available at: http://www.sciencedirect.com/science/article/pii/S0360544216301803The multitude and magnitude of the problems deriving from the use of fossil fuels for road transport is widely known. Therefore, electric mobility associated with renewable energy sources seems to be a good solution for minimizing these problems. However, the time required to charge the batteries of Electric Vehicles (EVs) and the availability of charging stations are seen as critical factors for their market viability. The use of fast charging stations is a possibility to mitigate the long time required to charge the batteries, but the high cost for power availability makes their operation very expensive. Moreover, it might be difficult to find suitable and affordable locations for installing these stations, so gas stations seem to be good candidates for this purpose. This paper assesses the use of fast charging stations for EVs in conjunction with Vanadium Redox Flow Batteries (VRFBs). Taking into account the low energy density of VRFBs, they are especially suited for situations where volume and weight are not limiting factors. Moreover, their liquid nature allows their installation inside deactivated underground fuel tanks located at gas stations. A preliminary assessment of a VRFB system for EVs fast charging stations taking advantage of existing gas stations infrastructures is presented. An energy and cost analysis of this concept is outlined, including a sensitivity analysis which shows that the project is technologically and economically viable for the conditions tested, although with long payback times.MOBI-MPP (MIT-Pt/EDAM-SMS/0030/2008) supported by the MIT Portugal Program and FEDER funds through the Programa Operacional Factores de Competitividade e COMPETE and National Funds through FCT e Foundation for Science and Technology. Post-doctoral grants SFRH/BPD/ 51048/2010 and SFRH/BPD/89553/2012 supported by the MIT Portugal EDAM and FCT, respectivelyinfo:eu-repo/semantics/publishedVersio
Analysis and design of a silicide-tetrahedrite thermoelectric generator concept suitable for large-scale industrial waste heat recovery
Industrial Waste Heat Recovery (IWHR) is one of the areas with strong potential for energy efficiency and emissions reductions in industry. Thermoelectric (TE) generators (TEGs) are among the few technologies that are intrinsically modular and can convert heat directly into electricity without moving parts, so they are nearly maintenance-free and can work unattended for long periods of time. However, most existing TEGs are only suitable for small-scale niche applications because they typically display a cost per unit power and a conversion efficiency that is not competitive with competing technologies, and they also tend to rely on rare and/or toxic materials. Moreover, their geometric configuration, manufacturing methods and heat exchangers are often not suitable for large-scale applications. The present analysis aims to tackle several of these challenges. A module incorporating constructive solutions suitable for upscaling, namely, using larger than usual TE elements (up to 24 mm in diameter) made from affordable p-tetrahedrite and n-magnesium silicide materials, was assessed with a multiphysics tool for conditions typical of IWHR. Geometric configurations optimized for efficiency, power per pair and power density, as well as an efficiency/power balanced solution, were extracted from these simulations. A balanced solution provided 0.62 kWe/m2 with a 3.9% efficiency. Good prospects for large-scale IWHR with TEGs are anticipated if these figures could be replicated in a real-world application and implemented with constructive solutions suitable for large-scale systems.Fundação para a Ciência e a Tecnologia, European Regional Development Fund (ERDF),
P.O.F.C.—COMPETE, European and National Funds: M-ERA.net Project THERMOSS (M-ERANET2/0011/2016), MEtRICs—Mechanical Engineering and Resource Sustainability Centre (UIDB/
04077/2020), C2TN—Center for Nuclear Sciences and Technologies (UID/Multi/04349/2019), Project
Exhaust2Energy (PTDC/EMS-ENE/3009/2014)
Assessment of an exhaust thermoelectric generator incorporating thermal control applied to a heavy duty vehicle
The road transport industry faces the need to develop its fleet for lower energy consumption, pollutants and CO2 emissions. Waste heat recovery systems with Thermoelectric Generators (TEGs) can directly convert the exhaust heat into electric energy, aiding the electrical needs of the vehicle, thus reducing its dependency on fuel energy. The present work assesses the optimisation and evaluation of a temperature-controlled thermoelectric generator (TCTG) concept to be used in a commercial heavy-duty vehicle (HDV). The system consists of a heat exchanger with wavy fins (WFs) embedded in an aluminium matrix along with vapour chambers (VCs), machined directly into the matrix, that grant the thermal control based on the spreading of local excess heat by phase change, as proposed by the authors in previous publications and patents. The TCTG concept behaviour was analysed under realistic driving conditions. An HDV with a 16 L Diesel engine was simulated in AVL Cruise to obtain the exhaust gas temperature and mass flow rate for each point of two cycle runs. A model proposed in previous publications was adapted to the new fin geometry and vapour chamber configuration and used the AVL Cruise data as input. It was possible to predict the thermal and thermoelectric performance of the TCTG along the corresponding driving cycles. The developed system proved to have a good capacity for applications with highly variable thermal loads since it was able to uncouple the maximisation of heat absorption from the regulation of the thermal level at the hot face of the TEG modules, avoiding both thermal dilution and overheating. This was achieved by the controlled phase change temperature of the heat spreader, that would ensure the spreading of the excess heat from overheated to underheated areas of the generator instead of wasting excess heat. A maximum average electrical production of 2.4 kW was predicted, which resulted in fuel savings of about 2% and CO2 emissions reduction of around 37 g/km.This article was partially supported by projects COOLSPOT PTDC/EME-TED/7801/2020,
UIDB/00481/2020 and UIDP/00481/2020 (Centre for Mechanical Technology and Automation—TEMA)
and UIDB/04077/2020 (MEchanical Engineering and Resource Sustainability Center—MEtRICs)—
Fundação para a Ciência e a Tecnologia (FCT); CENTRO-01-0145-FEDER-022083 (Centro2020),
Norte2020, Compete2020, under the PORTUGAL 2020 Partnership Agreement, through Portuguese
national funds of FCT/MCTES (PIDDAC) and the European Regional Development Fund
Exploratory research analysis on emissions generated in internal combustion engines
It is common knowledge that internal combustion engines have the function of transforming thermal energy into useful mechanical work. During the combustion process of the fuel and air mixture (heat generation) a quantity of gases are produced and released into the environment by the exhaust system of these engines. When these machines were invented, their creators might not have had the notion that the generated gases would be aggressors to nature. The constant population growth, the increasing demand for the use of these engines and observations of the impact in nature, among them the health and greenhouse effects, evidenced mainly from the end of the last century, led scientists to study the problem related to gaseous emissions from these machines. The present work aims to study and evaluate the emissions of internal combustion engines, their consequences both to the human health and to the environment, the evolution of government legislation and also the control mechanisms implemented to reduce these pollutants. The applied methodology is a qualitative and exploratory study of bibliographic character of theoretical and experimental works that were presented in master's dissertations, doctoral theses, scientific articles and websites of companies specialized in the subject
Complex fluid flow in microchannels and heat pipes with enhanced surfaces for advanced heat conversion and recovery systems
This paper addresses a multiscale approach for heat recovery systems, used in two distinct applications. In both applications, a microscale approach is used (microchannel heat sinks and heat pipes) for macroscale applications (cooling of a photovoltaic—PV cell), and the thermal energy of exhaust gases of an internal combustion engine is used for thermoelectric generators with variable conductance heat pipes. Several experimental techniques are combined such as visualization, thermography with high spatial and temporal resolution, and the characterization of the flow hydrodynamics, such as the friction losses. The analysis performed evidences the relevance of looking at the physics of the observed phenomena to optimize the heat sink geometry. For instance, the results based on the dissipated heat flux and the convective heat transfer coefficients obtained in the tests of the microchannel-based heat sinks for cooling applications in PV cells show an improvement in the dissipated power at the expense of controlled pumping power, for the best performing geometries. Simple geometries based on these results were then used as inputs in a genetic algorithm to produce the optimized geometries. In both applications, the analysis performed evidences the potential of using two-phase flows. However, instabilities at the microscale must be accurately addressed to take advantage of liquid phase change. In this context, the use of enhanced interfaces may significantly contribute to the resolution of the instability issues as they are able to control bubble dynamics. Such an approach is also addressed here.Authors acknowledge to Fundação para a Ciência e a Tecnologia¸ FCT and PORTUGAL
2020 Partnership Agreement, through the European Regional Development Fund, for partially financing this project through projects PTDC/EME-TED/7801/2020, JICAM/0003/2017, UIDB/00481/2020,
UIDP/00481/2020, and CENTRO-01-0145-FEDER-022083 (Centro2020) and for funding the scholarship of Pedro Pontes, ref. SFRH/BD/149286/2019
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