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Feasibility of Multiple Piston Motion Control Approaches in a Free Piston Engine Generator

West Virginia University-Mehar Bade, Nigel Clark, Parviz Famouri, PriyaankaDevi Guggilapu
  • Technical Paper
  • 2019-01-2599
To be published on 2019-10-22 by SAE International in United States
The control and design optimization of a Free Piston Engine Generator (FPEG) has been found to be difficult as each independent variable changes the piston dynamics with respect to time. These dynamics, in turn, alter the generator and engine response to other governing variables. As a result, the FPEG system requires an energy balance control algorithm such that the cumulative energy delivered by the engine is equal to the cumulative energy taken by the generator for stable operation. The main objective of this control algorithm is to match the power generated by the engine to the power demanded by the generator. In a conventional crankshaft engine, this energy balance control is similar to the use of a governor and a flywheel to control the rotational speed. In general, if the generator consumes more energy in a cycle than the engine provides, the system moves towards a stall. If the generator consumes less energy, then the effective stroke, compression ratio and maximum translator velocity must rise steadily from cycle-to-cycle until the heat transfer losses stop the…
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Quantification of Windage and Vibrational Losses in Flexure Springs of a One kW Two-Stroke Free Piston Linear Engine Alternator

West Virginia University-Nima Zamani Meymian, Nigel Clark, Jayaram Subramanian, Gregory Heiskell, Derek Johnson, Fereshteh Mahmudzadeh, Mahdi Darzi, Terence Musho, Parviz Famouri
Published 2019-04-02 by SAE International in United States
Methods to quantify the energy losses within linear motion devices that included flexural springs as the main suspension component were investigated. The methods were applied to a two-stroke free-piston linear engine alternator (LEA) as a case study that incorporated flexure springs to add stiffness to the mass-spring system. Use of flexure springs is an enabling mechanism for improving the efficiency and lifespan in linear applications e.g. linear engines and generators, cryocoolers, and linear Stirling engines. The energy loss due to vibrations and windage effects of flexure springs in a free piston LEA was investigated to quantify possible energy losses. A transient finite element solver was used to determine the effects of higher modes of vibration frequencies of the flexure arms at an operational frequency of 65 Hz. Also, a computational fluid dynamics (CFD) solver was used to determine the effects of drag force on the moving surfaces of flexures at high frequencies. A parametric study was performed to understand the effects of geometrical and operational parameters including the diameter of flexures, gap width between flexure…
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Emissions from Low- and Mid-Level Blends of Anhydrous Ethanol in Gasoline

Future Fuel Strategies-Nigel Clark, Tammy Klein, David L. McKain
Thiggins Energy Consulting-Terry Higgins
Published 2019-04-02 by SAE International in United States
Typically ethanol is present in gasoline as a 10% blend by volume (E10), although E15, E85 (51 to 83%), and E0 are also available at selected stations. Numerous studies of tailpipe regulated emissions have been conducted to compare emissions from E10 and E0, and there is a growing body of literature addressing blends of E15 and higher. Isolating the effect of ethanol in a study is philosophically difficult, because the ethanol naturally displaces some hydrocarbons, because the ethanol interacts with the remaining gasoline, and because properties of mixing are often nonlinear. Some studies have used splash blending, simply mixing the ethanol with a reference gasoline to produce a blend for comparison to the reference. Others have used match blending, where the objective is to match selected properties of the blend to properties of a reference gasoline. Recent studies have examined both port injected and direct injected engines, the latter being both naturally aspirated and turbocharged, and differing test cycles have been used. In consequence, the conclusions of the studies are not uniform. This paper examines…
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Sensitivity Analysis and Control Methodology for Linear Engine Alternator

SAE International Journal of Advances and Current Practices in Mobility

West Virginia University-Mehar Bade, Nigel Clark, Parviz Famouri, PriyaankaDevi Guggilapu, Mahdi Darzi, Derek Johnson
  • Journal Article
  • 2019-01-0230
Published 2019-04-02 by SAE International in United States
Linear engine alternator (LEA) design optimization traditionally has been difficult because each independent variable alters the motion with respect to time, and therefore alters the engine and alternator response to other governing variables. An analogy is drawn to a conventional engine with a very light flywheel, where the rotational speed effectively is not constant. However, when springs are used in conjunction with an LEA, the motion becomes more consistent and more sinusoidal with increasing spring stiffness. This avoids some attractive features, such as variable compression ratio HCCI operation, but aids in reducing cycle-to-cycle variation for conventional combustion modes. To understand the cycle-to-cycle variations, we have developed a comprehensive model of an LEA with a 1kW target power in MATLAB®/Simulink, and an LEA corresponding to that model has been operated in the laboratory. This MATLAB®/Simulink numerical model has been used to examine the sensitivity of the LEA dynamics and performance parameters to changes in the design and operating inputs. The sensitivity analysis provides insight into the pathway for improving and optimizing the design, as well as…
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In-Use Efficiency of Oxidation and Three-Way Catalysts Used in High-Horsepower Dual Fuel and Dedicated Natural Gas Engines

SAE International Journal of Engines

West Virginia University-Derek Johnson, Mahdi Darzi, Nigel Clark, Andrew Nix, Robert Heltzel
  • Journal Article
  • 03-11-03-0026
Published 2018-07-01 by SAE International in United States
Directional drilling rigs and hydraulic stimulation equipment typically use diesel fueled compression ignition (CI) engines. The majority of these engines are compliant with US Environmental Protection Agency (EPA) Tier 2 standards. To reduce fuel costs, industry is investing in dual fuel (DF) and dedicated natural gas (DNG) engines. DF engines use diesel oxidation catalysts (DOCs) to reduce CO and NMHC emissions. DNG engines may be either lean-burn or rich-burn and the latter uses three-way catalysts (TWC) to reduce CO, NMHC, and NOx emissions. This research presents in-use catalyst efficiency data collected pre- and post-catalyst for three DF engines and two DNG engines. One DF engine was converted earlier and did not include a DOC. Data were collected from six Tier 2 engines, two CI drilling engines converted to operate as DF, two CI hydraulic fracturing engines converted to operate as DF, and two SI DNG drilling engines. DF engines with DOCs were able to reduce CO and NMHC during DF operation by >90 and >50%, respectively. The DOCs did not reduce methane and NOx emissions.…
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Continuously Varying Exhaust Outlet Diameter to Improve Efficiency and Emissions of a Small SI Natural Gas Two-Stroke Engine by Internal EGR

West Virginia University-Mahdi Darzi, Derek Johnson, Ramanjaneya Mehar Ba Bade, Christopher Ulishney, Nima Zamani Meymian, Nigel Clark, Gregory Thompson, Parviz Famouri
Published 2018-04-03 by SAE International in United States
With continuously increasing concern for the emissions from two-stroke engines including regulated hydrocarbon (HC) and oxides of nitrogen (NOx) emissions, non-road engines are implementing proven technologies from the on-road market. For example, four stroke diesel generators now include additional internal exhaust gas recirculation (EGR) via an intake/exhaust valve passage. EGR can offer benefits of reduced HC, NOx, and may even improve combustion stability and fuel efficiency. In addition, there is particular interest in use of natural gas as fuel for home power generation. This paper examines exhaust throttling applied to the Helmholtz resonator of a two-stroke, port injected, natural gas engine. The 34 cc engine was air cooled and operated at wide-open throttle (WOT) conditions at an engine speed of 5400 RPM with fueling adjusted to achieve maximum brake torque.Exhaust throttling served as a method to decrease the effective diameter of the outlet of the convergent cone. Throttling balanced energy and exergy flows by acting as a source of internal EGR and lowering combustion temperatures, which yielded lower heat transfer. Though exhaust throttling improved efficiency, it…
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Quantification of Energy Pathways and Gas Exchange of a Small Port Injection SI Two-Stroke Natural Gas Engine Operating on Different Exhaust Configurations

West Virginia University-Mahdi Darzi, Derek Johnson, Christopher Ulishney, Ramanjaneya Mehar Ba Bade, Nima Zamani Meymian, Gregory Thompson, Parviz Famouri
West Virginia University Foundation Inc.-Nigel Clark
Published 2018-04-03 by SAE International in United States
This paper examines the energy pathways of a 29cc air-cooled two-stroke engine operating on natural gas with different exhaust geometries. The engine was operated at wide-open-throttle at a constant speed of 5400 RPM with ignition adjusted to yield maximum brake torque while the fueling was adjusted to examine both rich and lean combustion. The exhaust configurations examined included an off-the-shelf (OTS) model and two other custom models designed on Helmholtz resonance theory. The custom designs included both single and multi-cone features. Out of the three exhaust systems tested, the model with maximum trapping efficiency showed a higher overall efficiency due to lower fuel short-circuiting and heat transfer. The heat transfer rate was shown to be 10% lower on the new designs relative to OTS model. The fuel slip rate was in the range of 20-30% with custom designs showing 15% higher fuel slip rates on average, whereas the exhaust thermal energy was in the range of 12-18% of total input fuel energy and found to be 20% lower on custom designs relative to OTS model.…
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Fundamental Analysis of Spring-Varied, Free Piston, Otto Engine Device

SAE International Journal of Engines

West Virginia University-Matthew C. Robinson
West Virginia University Foundation Inc.-Nigel Clark
  • Journal Article
  • 2014-01-1099
Published 2014-04-01 by SAE International in United States
Conventional crank-based engines are limited by mechanical, thermal, and combustion inefficiencies. The free piston of a linear engine generator reduces frictional losses by avoiding the rotational motion and crankshaft linkages. Instead, electrical power is generated by the oscillation of a translator through a linear stator. Because the free piston is not geometrically constrained, dead center positions are not specifically known. This results in a struggle against adverse events like misfire, stall, over-fueling, or rapid load changes. It is the belief that incorporating springs will have the dual benefit of increasing frequency and providing a restoring force to aid in greater cycle to cycle stability. For dual free piston linear engines the addition of springs has not been fully explored, despite growing interest and literature. This investigation reviews the current modeling literature and advances the fundamental understanding of the free piston linear engine with springs by developing an idealized, nondimensional model. The model combines the dynamics of a damped, spring mass system with in-cylinder thermodynamic expressions. Simplifying assumptions are made to represent perfect springs, ideal gases,…
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Investigation of On-Road Crosswinds on Interstate Tractor-Trailer Aerodynamic Efficiency

West Virginia Univ.-Bharadwaj Sathiamoorthy, Matthew C. Robinson, Evan Fedorko, Nigel Clark
Published 2014-04-01 by SAE International in United States
Heavy duty tractor-trailers under freeway operations consume about 65% of the total engine shaft energy to overcome aerodynamic drag force. Vehicles are exposed to on-road crosswinds which cause change in pressure distribution with a relative wind speed and yaw angle. The objective of this study was to analyze the drag losses as a function of on-road wind conditions, on-road vehicle position and trajectory. Using coefficient of drag (CD) data available from a study conducted at NASA Ames, Geographical Information Systems model, time-varying weather data and road data, a generic model was built to identify the yaw angles and the relative magnitude of wind speed on a given route over a given time period. A region-based analysis was conducted for a study on interstate trucking operation by employing I-79 running through West Virginia as a case study by initiating a run starting at 12am, 03/03/2012 out to 12am, 03/05/2012. Results showed that vehicles which travelled the route on 03/04/2012 after 2pm were subjected to higher yaw angles (9 - 14 degrees) compared to vehicles travelling between…
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Trailer Technologies for Increased Heavy-Duty Vehicle Efficiency: Technical, Market, and Policy Considerations

SAE International Journal of Commercial Vehicles

MJ Bradley & Associates-Dana Lowell
The Intl. Council on Clean Transportation-Benjamin Rodriguez Sharpe
  • Journal Article
  • 2014-01-1622
Published 2014-04-01 by SAE International in United States
This paper reviews fuel-saving technologies for commercial trailers, provides an overview of the trailer market in the U.S., and explores options for policy measures at the federal level that can promote the development and deployment of trailers with improved efficiency. For trailer aerodynamics, there are many technologies that exist and are in development to target each of the three primary areas where drag occurs: 1) the tractor-trailer gap, 2) the side and underbody of the trailer, and 3) the rear end of the trailer. In addition, there are tire technologies and weight reduction opportunities for trailers, which can lead to reduced rolling resistance and inertial loss. As with the commercial vehicle sector, the trailer market is diverse, and there are a variety of sizes and configurations that are employed to meet a wide range of freight demands. Despite this great diversity, box-type vans represent more than two-thirds of the sales market and likely constitute a large percentage of total trailer miles traveled. In terms of manufacturing and sales, the trailer market is fairly consolidated, with…
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