Investigations and Analysis of Working Processes of Two-Stroke Engines with the Focus on Wall Heat Flux

Piecha, Pascal; Bruckner, Philipp; Schmidt, Stephan; Kirchberger, Roland; Schumann, Florian; Meyer, S. S.; Gegg, Tim; Leiber, S.

doi:10.4271/2016-32-0028

Cited by 7 publications

(3 citation statements)

References 11 publications

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“…Research was conducted on a microgeneration unit that produced 10 kW of electrical powerwell above the power required for most residential applications. effective or useful, 18% scavenging losses, 14% wall heat transfer, and 3% friction [107]. In other research, Orbaiz showed peak thermal efficiency for NG SI engines occurred during lean operation when in-cylinder heat loss and incomplete combustion were at a minimum [108].…”

Section: Chp Systemsmentioning

confidence: 83%

A Framework for Energy Optimization of Small, Two-Stroke, Natural Gas Engines for Combined Heat and Power Applications

Darzi¹

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A Framework for Energy Optimization of Small, Two-Stroke, Natural Gas Engines for Combined Heat and Power Applications Mahdi Darzi This research was focused on the development of a framework for the energy optimization a natural gas engine for small combined heat and power (CHP) applications operating with lowpressure natural gas (NG) available at homes. The required targets of the ARPA-E GENSETS program for 1 kW electric power generation and previous GENSETS simulation at West Virginia University, suggested a design space for the engine which is currently dominated by simple twostroke designs. Hence this research focused on screening, modeling, and experimentally evaluation of cost-effective technologies to achieve a system design that maximized thermal efficiency and utilization factor, while reducing emissions. A baseline engine was selected which started with 8% brake thermal efficiency (BTE) on natural gas operation. By implementing intake and exhaust optimization BTE increased up to around 12% and with head design optimization and exhaust backpressure, the engine reached 15% BTE. Though the initial optimization methods almost doubled efficiency, it was realized that further increases in BTE must be achieved for a commercially competitive design. The engine was redesigned to utilize modified porting for enhanced breathing and scavenging and a method to deploy low-pressure direct injection (LPDI) was developed. With these enhancements, BTE increased to around 24%. A second round of optimization was performed then, by modeling the whole system in a 1D platform and using a genetic algorithm and experimental data to further optimize scavenging which increased the efficiency up to around 26%. Finally, a 3D computational fluid dynamics (CFD) was developed to investigate the stratification effects of LPDI and determine the optimal spark plug location. This effort increased the BTE to around 27.5%. To assess issues with commercial deployment, three different NG compositions and propane operation were investigated. With an energy balance and exergy distribution analysis for each fuel, fuel quality effects on the CHP system performance were determined. At the end, with combination literature review, experiments, 1D and 3D simulations, a framework for optimization of micro-CHP systems operating on gaseous fuels was developed that can serve industry to highlight methods that can more than triple brake thermal efficiency of small two-stroke engines while improving the energy distribution for CHP systems. iii Acknowledgment Special thanks to Dr. Johnson for his support and mentorship throughout my PhD program. I thank my dedicated PhD committee members for their guidance and valuable feedback to improve this dissertation. I would like to thank Mr.

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Section: Chp Systemsmentioning

confidence: 83%

A Framework for Energy Optimization of Small, Two-Stroke, Natural Gas Engines for Combined Heat and Power Applications

Darzi¹

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“…scavenging losses, 14% wall heat transfer, and 3% friction. The engine was noted to have lower scavenging losses than normal due to excellent porting [24]. Also, energy balances conducted under the engine warm-up phase revealed increased miscellaneous losses partly attributed to the transient heating of metal components [25].…”

Section: Energy Balancementioning

confidence: 97%

“…The flow rate of the specific gas blend was corrected to MFC standard gas selection using Equations (24) and (25).…”

Section: =̇̇=mentioning

confidence: 99%

Experimental Design, Testing, and Evaluation of Methods to Improve the Efficiency and Reduce Emissions from a Small Two-stroke Natural Gas Engine

Ulishney¹

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Decentralized power generation is a research area of interest due to possible improvements in electrical generation efficiency and grid resilience. Two-stroke engines are simple, inexpensive, power dense systems that could serve as the prime-movers for combined heat and power (CHP) systems. In addition, such systems could be fueled on natural gas (NG) that is readily available to serve as a reliable fuel source in most households. However, most two-stroke engines are inefficient and produce excessive emissions. This research focused on methods to simultaneously improve engine efficiency and decrease emissions from a 34 cc air-cooled, two-stroke engine retrofitted to operate on NG. The engine type and size were selected for decentralized household power generation at the 1-kilowatt (kW) level. The engine utilized resonant intake and exhaust systems designed for operation at a fixed frequency of 90 Hz (5400 RPM) using Helmholtz resonance theory. Testing was conducted at wide open throttle (WOT) with electronic injection timing and ignition timing set for maximum brake torque (MBT). Two different fueling strategies and two variations in resonant exhaust systems were examined. The engine was first tested with port injection (PI) of NG with a near optimum baseline exhaust, then using low pressure direct injection (LPDI) with the near optimum exhaust, and finally with LPDI and an optimized resonant exhaust. Maximum indicated efficiency was 31.2% for the optimized LPDI system. Using PI as a baseline, LPDI increased efficiency by a relative 81% and 70% for the optimized and near optimum exhausts, respectively. Brake specific fuel consumption (BSFC) decreased by 33% and 32%, while indicated power increased by 46% and 25%, respectively. Emission levels met EPA standards for non-methane hydrocarbon plus nitrogen oxides (NMHC+NOx) and carbonmonoxide (CO) under all test configurations. At the most efficient points LPDI operation decreased NMHC+NOx by 46% for both exhausts as compared to PI, while CO increased under LPDI. This research validates that a resonance tuned, LPDI, NG, two-stroke engine could be incorporated into an emissions compliant decentralized power generation system with high efficiency at the 1 kW level. The findings will support future efforts in designing efficient, economically competitive, and clean CHP systems. I would like to thank Dr. Thompson for having selected me as an undergraduate applied thermodynamics grader, since this position led me on a direct path for graduate school. I would also like to thank Dr. Thompson for his recommending me to the new thermodynamics instructor, Dr. Derek Johnson. My utmost thanks go to Dr. Johnson for all his efforts in taking me under his wing as a new graduate student and aiming me toward success. Dr. Johnson orchestrated the engine team research, aiding in selection of components, designs, and technologies used for engine efficiency improvement. I would like to thank all the members of the WVU ARPA-E GENSETS project. Mehar Bade performed engine simulation and assi...

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Low pressure direct injection strategies effect on a small SI natural gas two-stroke engine’s energy distribution and emissions

et al. 2018

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Investigations and Analysis of Working Processes of Two-Stroke Engines with the Focus on Wall Heat Flux

Cited by 7 publications

References 11 publications

A Framework for Energy Optimization of Small, Two-Stroke, Natural Gas Engines for Combined Heat and Power Applications

A Framework for Energy Optimization of Small, Two-Stroke, Natural Gas Engines for Combined Heat and Power Applications

Experimental Design, Testing, and Evaluation of Methods to Improve the Efficiency and Reduce Emissions from a Small Two-stroke Natural Gas Engine

Low pressure direct injection strategies effect on a small SI natural gas two-stroke engine’s energy distribution and emissions

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