Utilizing the Thermodynamic Properties of E85 to Increase the Specific Efficiency of a High Specific Output Single Cylinder Formula SAE Engine PDF Download

Author: Derek N. Duncan
Publisher:
ISBN:
Category : Automobiles, Racing
Languages : en
Pages : 46

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Formula SAE is a collegiate engineering competition that has participants from around the globe. Of the 1000 points available throughout the event, 100 (10%) are dedicated to the fuel efficiency of the student built race cars. Competition rules allow either gasoline or E85, a mix of 85% ethanol and 15% gasoline, to be used as the primary fuel source. Because of the reduced specific energy content of E85, scores are normalized by applying a 1.4 divider to the final consumed volume of E85. With the desire to earn more points, a quantifiable way to determine if E85 could be an advantage was needed. To measure fuel consumption on the race track where every gram added to the car matters, a way to characterize flow rate and dead time of the fuel injector in the car was devised by finding the static flow rate and the associated combination of opening and closing times, or dead time. The method devised was designed to be simple to perform and data analysis was automated to make post processing a simple matter of transferring flow rate and dead time numbers into the engine control unit. Data recorded on track at the Formula Student Germany 2013 event and on the Oregon State University engine dynamometer were compared, and a method to estimate fuel consumption on any recorded track from engine dynamometer data was created. The estimation was first compared with recorded results from competition with an error of 2.1%, indicating that the results were reasonable to use for different engine configurations. Engine data was recorded for E85 and run through the estimation to determine how much E85 fuel would have been required to run the same event. The estimation was also used to determine how much work was done on track by the engine, which is another indicator of total system efficiency. Four engine configurations were tested. The baseline engine was the configuration used in the 2013 Global Formula Racing car, consisting of a Honda CRF450X engine, 3.8 liter intake plenum, Bosch 945 fuel injector, 13.5:1 compression piston, and a Megacycle X2 camshaft. This configuration was running on gasoline. Configuration 2 switched to a Honda 16450-MEN-A51 fuel injector. Configuration 3 changed fuel from gasoline to E85. The last configuration increased the compression ratio to 14:1. Configuration 2 had the highest overall efficiency at 34%, with configuration 4 having the highest energy generation over the course of the FSG 2013 endurance at 29.4 MJ. After normalizing energy generation, configuration 4 required the least volume of fuel to complete endurance at 2.5 liters, a reduction from 2.7 liters that the baseline required. This resulted in an approximate point increase of about 4.4. While this is an increase in point, the was determined that it was not enough to justify the use of E85 at FSAE events due to increased procurement and handling difficulty, along with reduced engine starting reliability.

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Languages : en
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The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in mid-level alcohol-gasoline blends with 24% vol./vol. iso-butanol-gasoline (IB24) and 30% vol./vol. ethanol-gasoline (E30). A single-cylinder research engine is used with a low and high compression ratio of 9.2:1 and 11.85:1 respectively. The engine is equipped with hydraulically actuated valves, laboratory intake air, and is capable of external exhaust gas recirculation (EGR). All fuels are operated to full-load conditions with =1, using both 0% and 15% external cooled EGR. The results demonstrate that higher octane number bio-fuels better utilize higher compression ratios with high stoichiometric torque capability. Specifically, the unique properties of ethanol enabled a doubling of the stoichiometric torque capability with the 11.85:1 compression ratio using E30 as compared to 87 AKI, up to 20 bar IMEPg at =1 (with 15% EGR, 18.5 bar with 0% EGR). EGR was shown to provide thermodynamic advantages with all fuels. The results demonstrate that E30 may further the downsizing and downspeeding of engines by achieving increased low speed torque, even with high compression ratios. The results suggest that at mid-level alcohol-gasoline blends, engine and vehicle optimization can offset the reduced fuel energy content of alcohol-gasoline blends, and likely reduce vehicle fuel consumption and tailpipe CO2 emissions.

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Languages : en
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Delphi Automotive Systems and ORNL established this CRADA to explore the potential to improve the energy efficiency of spark-ignited engines operating on ethanol-gasoline blends. By taking advantage of the fuel properties of ethanol, such as high compression ratio and high latent heat of vaporization, it is possible to increase efficiency with ethanol blends. Increasing the efficiency with ethanol-containing blends aims to remove a market barrier of reduced fuel economy with E85 fuel blends, which is currently about 30% lower than with petroleum-derived gasoline. The same or higher engine efficiency is achieved with E85, and the reduction in fuel economy is due to the lower energy density of E85. By making ethanol-blends more efficient, the fuel economy gap between gasoline and E85 can be reduced. In the partnership between Delphi and ORNL, each organization brought a unique and complementary set of skills to the project. Delphi has extensive knowledge and experience in powertrain components and subsystems as well as overcoming real-world implementation barriers. ORNL has extensive knowledge and expertise in non-traditional fuels and improving engine system efficiency for the next generation of internal combustion engines. Partnering to combine these knowledge bases was essential towards making progress to reducing the fuel economy gap between gasoline and E85. ORNL and Delphi maintained strong collaboration throughout the project. Meetings were held regularly, usually on a bi-weekly basis, with additional reports, presentations, and meetings as necessary to maintain progress. Delphi provided substantial hardware support to the project by providing components for the single-cylinder engine experiments, engineering support for hardware modifications, guidance for operational strategies on engine research, and hardware support by providing a flexible multi-cylinder engine to be used for optimizing engine efficiency with ethanol-containing fuels.

Author: Douglas Fehan
Publisher: SAE International
ISBN: 0768079861
Category : Technology & Engineering
Languages : en
Pages : 148

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This compendium is an update to two best-selling editions published by SAE International in 1995 and 2003. Editor Doug Fehan has assembled a collection of technical papers from the SAE archive that will inspire readers to use race engine development as an important tool in the future of transportation. He focuses on several topics that are important to future race engine design: electrification, materials and processes, and improved technology. Today’s electric hybrid vehicles and kinetic energy recovery systems embody what inventors envisioned in the early 1900s. First employed in trams and trains of that era, the technology was almost forgotten until racers resurrected their version in 2009 F-1 racing. The automotive industry has long admired the aircraft industry’s use of lightweight metals, advanced finishing processes, and composites. The use of these materials and processes has helped reduce overall mass and, in turn, improved speed, performance, and reliability of race engines. Their initial high cost was a limiting factor for integrating them into mass-produced vehicles. With racing leading the way, those limitations were overcome and vehicles today feature some amazing adaptations of those processes and materials. Engine power, efficiency, durability, reliability, and, more recently, emissions have always been of primary importance to the automotive world. The expanding use of electrification, biofuels, CNG, high-pressure fuel delivery systems, combustion air management, turbocharging, supercharging, and low-viscosity lubricants have been the focus of race engine development and are now turning up in dealer showrooms. The papers in this publication were selected for two reasons: they demonstrate the leadership that racing plays in the future of automotive engineering and design as it relates to engines; and they will be interesting to everyone who may be in racing and to those who may want to be in racing.

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Category :
Languages : en
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The use of biofuels for internal combustion engines has several well published advantages. The biofuels, made from biological sources such as corn or sugar cane, are renewable resources that reduce the dependence on fossil fuels. Fuels from agricultural sources can therefore reduce a countries energy dependency on other nations. Biofuels also have been shown to reduce CO2 emissions into the atmosphere compared to traditional fossil based fuels. Because of these benefits several countries have set targets for the use of biofuels, especially ethanol, in their transportation fuels. Small percentages of ethanol are common place in gasoline but are typically limited to 5 to 8% by volume. Greater benefits are possible from higher concentrations and some countries such as the US and Sweden have encouraged the production of vehicles capable of operating on E85 (85% denatured ethanol and 15% gasoline). E85 capable vehicles are normally equipped to run the higher levels of ethanol by employing modified fuel delivery systems that can withstand the highly corrosive nature of the alcohol. These vehicles are not however equipped to take full advantage of ethanol's properties during the combustion process. Ethanol has a much higher blend research octane number than gasoline. This allows the use of higher engine compression ratios and spark advance which result in more efficient engine operation. Ethanol's latent heat of vaporization is also much higher that gasoline. This higher heat of vaporization cools the engine intake charge which also allows the engine compression ratio to be increased even further. An engine that is optimized for operation on high concentrations of ethanol therefore will have compression ratios that are too high to avoid spark knock (pre-ignition) if run on gasoline or a gasoline/ethanol blend that has a low percentage alcohol. An engine was developed during this project to leverage the improved evaporative cooling and high octane of E85 to improve fuel economy and offset E85's lower energy content. A 2.0 L production Direct Injection gasoline, (DIg) engine employing Dual Independent Cam Phasing, (DICP) and turbo charging was used as the base engine. Modified pistons were used to increase the geometric compression ratio from 9.2:1 to 11.85:1 by modifying the pistons and adding advanced valvetrain to proved control of displacement and effective compression ratio through valve timing control. The advanced valvetrain utilized Delphi's two step valvetrain hardware and intake cam phaser with increased phasing authority of 80 crank angle degrees. Using this hardware the engine was capable of operating knock free on all fuels tested from E0-E85 by controlling effective compression ratio using a Late Intake Valve Closing, (LIVC) strategy. The LIVC strategy results in changes in the trapped displacement such that knock limited torque for gasoline is significantly lower than E85. The use of spark retard to control knock enables higher peak torque for knock limited fuels, however a loss in efficiency results. For gasoline and E10 fuels, full effective displacement could not be reached before spark retard produced a net loss in torque. The use of an Early Intake Valve Closing, (EIVC) strategy resulted in an improvement of engine efficiency at low to mid loads for all fuels tested from E0- E85. Further the use of valve deactivation, to a single intake valve, improved combustion stability and enabled throttle-less operation down to less than 2 bar BMEP. Slight throttling to trap internal residual provided additional reductions in fuel consumption. To fully leverage the benefits of E85, or ethanol blends above E10, would require a vehicle level approach that would take advantage of the improved low end torque that is possible with E85. Operating the engine at reduced speeds and using advanced transmissions (6 speeds or higher) would provide a responsive efficient driving experience to the customer. The vehicle shift and torque converter lockup points for high ethanol blends could take advantage of the significant efficiency advantage of down-speeding and operating at higher loads to deliver the required power.

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Category :
Languages : en
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Ethanol is a very attractive fuel from an end-use perspective because it has a high chemical octane number and a high latent heat of vaporization. When an engine is optimized to take advantage of these fuel properties, both efficiency and power can be increased through higher compression ratio, direct fuel injection, higher levels of boost, and a reduced need for enrichment to mitigate knock or protect the engine and aftertreatment system from overheating. The ASTM D5798 specification for high level ethanol blends, commonly called E85, underwent a major revision in 2011. The minimum ethanol content was revised downward from 68 vol% to 51 vol%, which combined with the use of low octane blending streams such as natural gasoline introduces the possibility of a lower octane E85 fuel. While this fuel is suitable for current ethanol tolerant flex fuel vehicles, this study experimentally examines whether engines can still be aggressively optimized for the resultant fuel from the revised ASTM D5798 specification. The performance of six ethanol fuel blends, ranging from 51-85% ethanol, is compared to a premium-grade certification gasoline (UTG-96) in a single-cylinder direct-injection (DI) engine with a compression ratio of 12.9:1 at knock-prone engine conditions. UTG-96 (RON = 96.1), light straight run gasoline (RON = 63.6), and n-heptane (RON = 0) are used as the hydrocarbon blending streams for the ethanol-containing fuels in an effort to establish a broad range of knock resistance for high ethanol fuels. Results show that nearly all ethanol-containing fuels are more resistant to engine knock than UTG-96 (the only exception being the ethanol blend with 49% n-heptane). This knock resistance allows ethanol blends made with 33 and 49% light straight run gasoline, and 33% n-heptane to be operated at significantly more advanced combustion phasing for higher efficiency, as well as at higher engine loads. While experimental results show that the octane number of the hydrocarbon blend stock does impact engine performance, there remains a significant opportunity for engine optimization when considering even the lowest octane fuels that are in compliance with the current revision of ASTM D5798 compared to premium-grade gasoline.

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Category :
Languages : en
Pages : 25

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Basic engine thermodynamics predicts that spark ignited engine efficiency is a function of both the compression ratio of the engine and the specific heat ratio of the working fluid. In practice the compression ratio of the engine is often limited due to knock. Both higher specific heat ratio and higher compression ratio lead to higher end gas temperatures and increase the likelihood of knock. In actual engine cycles, heat transfer losses increase at higher compression ratios and limit efficiency even when the knock limit is not reached. In this paper we investigate the role of both the compression ratio and the specific heat ratio on engine efficiency by conducting experiments comparing operation of a single-cylinder variable-compression-ratio engine with both hydrogen-air and hydrogen-oxygen-argon mixtures. For low load operation it is found that the hydrogen-oxygen-argon mixtures result in higher indicated thermal efficiencies. Peak efficiency for the hydrogen-oxygen-argon mixtures is found at compression ratio 5.5 whereas for the hydrogen-air mixture with an equivalence ratio of 0.24 the peak efficiency is found at compression ratio 13. We apply a three-zone model to help explain the effects of specific heat ratio and compression ratio on efficiency. Operation with hydrogen-oxygen-argon mixtures at low loads is more efficient because the lower compression ratio results in a substantially larger portion of the gas to reside in the adiabatic core rather than in the boundary layer and in the crevices, leading to less heat transfer and more complete combustion.

Author: Jon-Russell J. Groenewegen
Publisher:
ISBN:
Category : Biomass energy
Languages : en
Pages : 136

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This thesis research was conducted in pursuit of the DoD's plan for the universal use of a heavy, low volatility hydrocarbon fuel, and the increased interest in bio-derived fuels for small Unmanned Aircraft Systems (UAS's). Currently a majority of small UAS's use small spark ignition engines for their high power densities. Typically, these systems use commercial off-the-shelf power plants that are not optimized for fuel efficiency. Increased fuel efficiency is being pursued alongside the ability to utilize military heavy fuels. A test stand using a 33.5 cc four-stroke, spark ignition, air-cooled, single cylinder engine was constructed. Research was conducted to establish the feasibility of converting the existing system to utilize JP-8 with the stock mechanical carburetion. The stock carburetion had difficulty maintaining a consistent air/fuel ratio across the entire engine operating range. To resolve this, an electronic fuel injection system was developed to gain greater control over fuel mixture. An air-assisted electronic fuel injector was sourced from a scooter and adapted to work with the 33.5cc four-stroke engine. An aluminum injector mount was designed and machined and electronic controls were employed. Sensors on the valvetrain and crankshaft were developed as control signals for the injection system. The injector was characterized for flow rates and droplet size. The test stand consisted of a small dynamometer coupled to the engine. Servo throttle actuation was designed and throttle position was monitored with a throttle position sensor. The air-assisted injector was supplied with regulated shop air, and the fuel pressurized using regulated nitrogen. A fuel flowmeter and mass air flowmeter monitored equivalence ratio. Work was done to facilitate smooth measurement of unsteady air flow intrinsic to single-cylinder engines. Performance testing showed a decrease in brake specific fuel consumption (BSFC) while utilizing the injection system for the baseline fuel (Avgas 100LL), as greater mixture control (closer to stoichiometric) was realized. The engine was started using gasoline. Heavy fuel testing showed the ability to achieve required torque values at certain engine speeds. JP-8 was tested on the carbureted engine and fuel injected engine, showing a decrease in BSFC over baseline (carbureted avgas) with the carburetor and a further decrease in BSFC for the injected system. Biofuels that were tested were plant-based Camelina (carbureted and injected) and a UDRI grown and extracted algae-based fatty acid methyl ester (FAME) biofuel blended with D2 diesel in a 20% algae/80% diesel blend. Performance results for the Camelina showed a decrease in BSFC for the carbureted engine and the largest decrease of all the test fuels for the injected Camelina fuel. The algae blend showed less decrease in BSFC than the 100% diesel fuel. Emissions data were recorded as well. The injection system demonstrated less CO emissions for the injected fuels over the carbureted fuels due to closer to stoichiometric mixtures. Similarly, unburned hydrocarbon emissions decreased when injection was employed. NOx emissions were higher for the fuel injected engine, as peak NOx emissions will typically occur at slightly lean conditions and the injected fuels were closer to peak NOx emission conditions.

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Languages : en
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Ethanol offers significant potential for increasing the compression ratio of SI engines resulting from its high octane number and high latent heat of vaporization. A study was conducted to determine the knock limited compression ratio of ethanol gasoline blends to identify the potential for improved operating efficiency. To operate an SI engine in a flex fuel vehicle requires operating strategies that allow operation on a broad range of fuels from gasoline to E85. Since gasoline or low ethanol blend operation is inherently limited by knock at high loads, strategies must be identified which allow operation on these fuels with minimal fuel economy or power density tradeoffs. A single cylinder direct injection spark ignited engine with fully variable hydraulic valve actuation (HVA) is operated at WOT conditions to determine the knock limited compression ratio (CR) of ethanol fuel blends. The geometric compression ratio is varied by changing pistons, producing CR from 9.2 to 13.66. The effective CR is varied using an electro-hydraulic valvetrain that changed the effective trapped displacement using both Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC). The EIVC and LIVC strategies result in effective CR being reduced while maintaining the geometric expansion ratio. It was found that at substantially similar engine conditions, increasing the ethanol content of the fuel results in higher engine efficiency and higher engine power. These can be partially attributed to a charge cooling effect and a higher heating valve of a stoichiometric mixture for ethanol blends (per unit mass of air). Additional thermodynamic effects on and a mole multiplier are also explored. It was also found that high CR can increase the efficiency of ethanol fuel blends, and as a result, the fuel economy penalty associated with the lower energy content of E85 can be reduced by about a third. Such operation necessitates that the engine be operated in a de-rated manner for gasoline, which is knock-prone at these high CR, in order to maintain compatibility. By using EIVC and LIVC strategies, good efficiency is maintained with gasoline, but power is reduced by about 34%.

Author: Flavio Dal Forno Chuahy
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Dual fuel reactivity controlled compression ignition (RCCI) combustion is a promising method to achieve high efficiency with near zero NOx and soot emissions; however, the requirement to carry two fuels on-board has limited practical applications. Advancements in catalytic reforming have demonstrated the ability to generate syngas (a mixture of CO and hydrogen) from a single hydrocarbon stream. The reformed fuel mixture can then be used as a low reactivity fuel stream to enable RCCI out of a single parent fuel. Beyond enabling dual-fuel combustion strategies out of a single parent fuel, fuel reforming can be endothermic and allow recovery of exhaust heat to drive the reforming reactions, potentially improving overall efficiency of the system. Previous works have focused on using reformed fuel to extend the lean limit of spark ignited engines, and enhancing the control of HCCI type combustion. The strategy pairs naturally with advanced dual-fuel combustion strategies, and the use of dual-fuel strategies in the context of on-board reforming and energy recovery has not been explored. Accordingly, the work presented in this dissertation attempts to fill in the gaps in the current literature and provide a pathway to "single" fuel RCCI combustion through a combination of experiments and computational fluid dynamics modeling. Initially, a system level analysis focusing on three common reforming techniques (i.e., partial oxidation, steam reforming and auto-thermal reforming) was conducted to evaluate the potential of reformed fuel. A system layout was proposed for each reforming technique and a detailed thermodynamic analysis using first- and second-law approaches were used to identify the sources of efficiency improvements. The results showed that reformed fuel combustion with a near TDC injection of diesel fuel can increase engine-only efficiency by 4% absolute when compared to a conventional diesel baseline. The efficiency improvements were a result of reduced heat transfer and shorter, more thermodynamically efficient, combustion process. For exothermic reforming processes, losses in the reformer outweigh the improvements to engine efficiency, while for endothermic processes the recovery of exhaust energy was able to allow the system efficiency to retain a large portion of the benefits to the engine combustion. Energy flow analysis showed that the reformer temperature and availability of high grade exhaust heat were the main limiting factors preventing higher efficiencies. RCCI combustion was explored experimentally for its potential to expand on the optimization results and achieve low soot and NOx emissions. The results showed that reformed fuel can be used with diesel to enable RCCI combustion and resulted in low NOx and soot emissions while achieving efficiencies similar to conventional diesel combustion. Experiments showed that the ratio H2/(H2+CO) is an important parameter for optimal engine operation. Under part-load conditions, fractions of H2/(H2+CO) higher than 60% led to pressure oscillations inside the cylinder that substantially increased heat transfer and negated any efficiency benefits. The system analysis approach was applied to the experimental results and showed that chemical equilibrium limited operation of the engine to sub-optimal operating conditions. RCCI combustion was able to achieve "diesel like" system level efficiencies without optimization of either the engine operating conditions or the combustion system. Reformed fuel RCCI was able to provide a pathway to meeting current and future emission targets with a reduction or complete elimination of aftertreatment costs. Particle size distribution experiments showed that addition of reformed fuel had a significant impact on the shape of the particle size distribution. Addition of reformed fuel reduced accumulation-mode particle concentration while increasing nucleation-mode particles. When considering the full range of particle sizes there was a significant increase in total particle concentration. However, when considering currently regulated (Dm>23nm) particles, total concentration was comparable. To address limitations identified in the system analysis of the RCCI experiments a solid oxide fuel cell was combined with the engine into a hybrid electrochemical combustion system. The addition of the fuel cell addresses the limitations by providing sufficient high grade heat to fully drive the reforming reactions. From a system level perspective, the impact of the high frequency oscillations observed in the experiments are reduced, as the system efficiency is less dependent on the engine efficiency. From an engine perspective, the high operating pressures and low reactivity of the anode gas allow reduction of the likelihood of such events. A 0-D system level code was developed and used to find representative conditions for experimental engine validation. The results showed that the system can achieve system electrical efficiencies higher than 70% at 1 MWe power level. Experimental validation showed that the engine was able to operate under both RCCI and HCCI combustion modes and resulted in low emissions and stable combustion. The potential of a hybrid electrochemical combustion system was demonstrated for high efficiency power generation