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Optimal Sizing and Control of Battery Energy Storage Systems for Hybrid Turbo-Electric Aircraft

Georgia Institute of Technology-Christopher Perullo
Ohio State University-Aaronn Sergent, Michael Ramunno, Matilde D'Arpino, Marcello Canova
  • Technical Paper
  • 2020-01-0050
To be published on 2020-03-10 by SAE International in United States
Hybrid-electric gas turbine generators are considered a promising technology for more efficient and sustainable air transportation. The Ohio State University is leading the NASA University Leadership Initiative (ULI) Electric Propulsion: Challenges and Opportunities, focused on the design and demonstration of advanced components and systems to enable high-efficiency hybrid turboelectric powertrains in regional aircraft to be deployed in 2030. Within this large effort, the team is optimizing the design of the battery energy storage system (ESS) and, concurrently, developing a supervisory energy management strategy for the hybrid system to reduce fuel burn while mitigating the impact on the ESS life. In this paper, an energy-based model was developed to predict the performance of a battery-hybrid turboelectric distributed-propulsion (BHTeDP) regional jet. A study was conducted to elucidate the effects of ESS sizing and cell selection on the optimal power split between the turbogenerators (TGs) and ESS. To this extent, the supervisory energy management strategy is formulated into a discrete time optimal control problem and solved via dynamic programming. The performance of BHTeDP was compared to a turboelectric…
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Effects of Engine Speed on the Performance at Extreme Vehicle Driving Conditions

FCA LATAM, Universidade Federal de Minas Gerais-Fabrício Thomaz, José Guilherme Coelho Baeta
  • Technical Paper
  • 2019-36-0297
Published 2020-01-13 by SAE International in United States
Nowadays, improvements in engine fuel economy and reduction in pollutant emissions have been much discussed. Downsizing and downspeeding are methods widely used in the automotive market, used to increase internal combustion engine efficiency. Fuel consumption is commonly measured through a specific cycle that could differ between countries. Federal Test Procedure (FTP-75) for Latin America and New European Driving Cycle (NEDC) for Europe are some examples. These cycles include normal driving conditions, low vehicle load and mild environmental conditions. The style of gear shifting is one of the main factors affecting fuel efficiency and performance of motor vehicles. At extreme diving conditions, parameters like coolant and air charge temperature could reach limit durability values of the system. In order to avoid knocking and maintain structural reliability, it becomes mandatory to control the engine speed. An increase in engine speed reduces engine load requirements and thus, turbocharger loads. Lower turbocharger requirements reduce ACT and, consequently, reduce knocking. This process allows an advanced ignition timing, enabling more chamber pressure and improving fuel conversion efficiency. However, a higher engine…
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Right Shifting for Fuel Economy

VW do Brasil / Centro Universitário FEI-Fernando Fusco Rovai
  • Technical Paper
  • 2019-36-0095
Published 2020-01-13 by SAE International in United States
Fuel economy is one of the main drivers of the automotive industry. This subject is becoming more and more important showing a clear upraising relevance tendency. The automotive community is researching and developing many solutions and trending technologies to improve the internal combustion engine, realizing its existence is under risk due to strong greenhouse gas impact. Some innovative technologies focus on the internal combustion engines replacement by other energy conversion systems. Other new technologies improve internal combustion engines efficiency but, in most of the cases, impacts on its costs and consequently on its viability, especially considering the entry level passenger cars. In these applications, the cost impact is hardly acceptable by the customers and this market represents a considerable part of the global automotive industry. Any opportunity to improve the vehicle efficiency with minimum cost is welcome. This paper intends to assess the development and application of a gear shift indicator in an entry level passenger car. This technology represents a very low cost impact because the engine control unit should add just an improved…
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Investigations on Pre-chamber Ignition Device Using Experimental and Numerical Approaches

IFP Energies nouvelles-O. Laget, S. Chevillard, G. Pilla, X. Gautrot, T. Colliou
  • Technical Paper
  • 2019-01-2163
Published 2019-12-19 by SAE International in United States
Nowadays Spark Ignition (SI) engine efficiency is mainly limited by abnormal combustion (knock) and stability issues at high dilution rate (both EGR and air). Increasing the combustion velocity is a relevant way to overcome these limitations. Main strategy to increase the combustion velocity is to enhance the flow motion in the cylinder (tumble motion) in order to increase the turbulence during the combustion. Such approach is mainly performed by working on intake port design which lead to engine volumetric efficiency penalties. Another approach to increase the combustion velocities is to have multiple ignition kernels in the chamber. This can be obtained thanks to Turbulent Jet Ignition (TJI) which uses a pre-chamber to spread the initial flame kernel throughout the combustion chamber. To achieve pre-chamber optimization a deep understanding of the complex phenomena involved in TJI as well as validated numerical tools is required. The present paper aims at providing such understanding using both numerical simulations and experimental investigations. First, dedicated experimental methodology is deployed on an optical engine providing a characterization of the flame jets…
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Use of Predictive Engine and Emission Model for Diesel Engine Model Based Calibration

ISUZU Technical Center of America-Yifan Wei, Lakshmidhar R. Uppalapati, Bruce Vernham
  • Technical Paper
  • 2019-01-2227
Published 2019-12-19 by SAE International in United States
The GHG and emissions regulations are becoming more and more stringent every year. To fulfill legislation requirements and potential future challenges, increasing number of technologies and actuators have been developed and implemented into powertrain systems. This trend poses new challenges on engine development process by harmonizing early stage technology implementation, hardware selection and performance evaluation with late stage calibration and validation works. Frontloading feedbacks to design and development team enable better decision making, hardware selection and calibration optimization. Seamless powertrain simulation toolchains can realize such frontloading tasks to reduce development cost and provide late stage information at early development period.However, frontloading virtualized development remains a large challenge for model developers with limited data during early phase of development. For various usages of simulations and models, especially robust calibration usage purpose, the models need to have high level of accuracy, reasonable simulation runtime and predictability over wide range of operating conditions at the same time; meanwhile there is limited quantity of test data available to generate data driven and statistical models and to perform optimizations. Therefore,…
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Experimental Investigation on the Influence of Brake Mean Effective Pressures up to 30 bar on the Behavior of a Large Bore Otto Gas Engine

Technical University of Munich-Stefan Eicheldinger, Tomas Bartkowski, Alexander Schröder, Dr.-Ing. Maximilian Prager, Prof. Dr.-Ing. Georg Wachtmeister
  • Technical Paper
  • 2019-01-2224
Published 2019-12-19 by SAE International in United States
For large bore Otto gas engines a high specific power output and therefore high engine load promises a rise in engine efficiency on one hand and on the other hand a reduction of the performance-related investment. However, this can negatively affect the emissions performance, operating limits especially in regards to knocking, and component life. For this reason at the Chair of Internal Combustion Engines (LVK) of the Technical University of Munich (TUM) experiments with a 4.77 l single-cylinder research engine were carried out to investigate the boundary conditions, potentials and downsides of combustion processes with a brake mean effective pressure beyond current series engines and higher than 30 bar. The objective in this investigations was to achieve BMEP > 30 bar with an engine configuration that widely represents the current series-production status. Hence, an unscavenged prechamber spark plug, a series Piston and Valve timing were used. To shift the knocking limit to more fuel-efficient operating points, different intake air temperatures were used. The engine behavior was measured in engine maps with a variation of the…
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Comparison of heat losses at the impingement point and in between two impingement points in a diesel engine using phosphor thermometry

Lund University, Division of Combustion Physics-Alexios Matamis, Mattias Richter
Scania CV AB-Christian Binder, Daniel Norling
  • Technical Paper
  • 2019-01-2185
Published 2019-12-19 by SAE International in United States
In-cylinder heat losses in diesel engines reduce engine efficiency significantly and account for a considerable amount of injected fuel energy. A great part of the heat losses during diesel combustion presumably arises from the impingement of the flame. The present study compares the heat losses at the point where the flame impinges onto the piston bowl wall and the heat losses between two impingement points. Measurements were performed in a full metal heavy-duty diesel engine with a small optical access through a removed exhaust valve. The surface temperature at the impingement point of the combusting diesel spray and at a point in between two impingement points was determined using phosphor thermometry. The dynamic heat fluxes and the heat transfer coefficients which result from the surface temperature measurements are estimated. Simultaneous cylinder pressure measurements and high-speed videos are associated to individual surface temperature measurements. Thus each surface temperature measurement is linked to a specific impingement and combustion events. An analysis of the surface temperature in connection with the high speed images reveals the great impact of…
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Enhancing Peak Firing Pressure Limit for Achieving Better Brake Thermal Efficiency of a Diesel Engine

New A.C.E. Institute Co., Ltd.-Kenji Enya, Noboru Uchida
  • Technical Paper
  • 2019-01-2180
Published 2019-12-19 by SAE International in United States
An increased cycle expansion ratio is beneficial from a thermodynamic viewpoint to increase the engine efficiency. In this study, the target compression ratio and corresponding thermodynamic cycle layout were investigated by means of a new ideal combustion cycle. To model the experimental pressure traces, the combustion was divided into three parts; constant volume combustion, early expansion combustion and late combustion. This study discussed optimal parameter values for compression ignition combustion under PFP constraints. These parameters included compression ratio, pressure ratios as well as cut-off ratios. Furthermore, this study experimentally investigated the limitation of thermal efficiency and the variation of energy losses under different geometric compression ratios, boosting pressure and degree of constant volume combustion. These experiments utilized a supercharged single-cylinder heavy duty diesel engine with PFP-capability of up to 30 MPa. In conclusion, it is confirmed that improvement in the indicated thermal efficiency and BTE was achieved by increasing the compression ratio. The trade-off between increased compression ratio and higher losses was also established and an optimum compression ratio found.
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Effects of Prechamber on Efficiency Improvement and Emissions Reduction of a SI Engine Fuelled with Gasoline

Istituto Motori CNR-Paolo Sementa, Francesco Catapano, Silvana Di Iorio, Bianca Maria Vaglieco
Published 2019-10-07 by SAE International in United States
The permanent aim of the automotive industry is the further improvement of the engine efficiency and the simultaneous pollutant emissions reduction.The aim of the study was the optimization of the gasoline combustion by means of a passive prechamber. This analysis allowed the improvement of the engine efficiency in lean-burn operation condition too. The investigation was carried out in a commercial small Spark Ignition (SI) engine fueled with gasoline and equipped with a proper designed passive prechamber.It was analyzed the effects of the prechamber on engine performance, Indicated Mean Effective Pressure, Heat Release Rate and Fuel Consumption were used. Gaseous emissions were measured as well. Particulate Mass, Number and Size Distributions were analyzed. Emissions samples were taken from the exhaust flow, just downstream of the valves. Four different engine speeds were investigated, namely 2000, 3000, 4000 and 5000 rpm. Stoichiometric and lean conditions at full load were considered in all tests. The results were compared with those obtained with the engine equipped with the standard spark plug. The results indicated that both performance and emissions were…
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Analysis of the Impact of the WLTP Procedure on CO2 Emissions of Passenger Cars

European Commission Joint Research-Biagio Ciuffo, Georgios Fontaras
Politecnico di Torino-Giuseppe DiPierro, Federico Millo, Claudio Cubito
Published 2019-10-07 by SAE International in United States
Until 2017 in Europe the Type Approval (TA) procedure for light duty vehicles for the determination of pollutant emissions and fuel consumption was based on the New European Driving Cycle (NEDC), a test cycle performed on a chassis dynamometer. However several studies highlighted significant discrepancies in terms of CO2 emissions between the TA test and the real world, due to the limited representativeness of the test procedure. Therefore, the European authorities decided to introduce a new, up-to date, test procedure capable to closer represent real world driving conditions, called Worldwide Harmonized Light Vehicles Test Procedure (WLTP). This work aims to analyze the effects of the new WLTP on vehicle CO2 emissions through both experimental and simulation investigations on two different Euro 5 vehicles, a petrol and a diesel car, representatives of average European passenger cars. The study also considers the effect of the engine warm-up and the impact of the start-stop technology in this new TA scenario. Since the WLTP imposes higher test mass and Road Loads (RLs), as well as higher driving cycle dynamics,…
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