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Experimental and Numerical Assessment of Active Pre-chamber Ignition in Heavy Duty Natural Gas Stationary Engine

Istituto Motori CNR-Gessica Onofrio, Carlo Beatrice
Lund University-Changle Li, Pablo Garcia Valladolid, Per Tunestal
  • Technical Paper
  • 2020-01-0819
To be published on 2020-04-14 by SAE International in United States
Gas engines (fuelled with CNG, LNG or Biogas) for generation of power and heat are, to this date, taking up larger shares of the market with respect to diesel engines. In order to meet the limit imposed by the TA-Luft regulations on heavy duty engines, lean combustion represents a viable solution for achieving lower emissions as well as efficiency levels comparable with diesel engines. Leaner mixtures however affect the combustion stability as the flame propagation velocity and consequently heat release rate are slowed down. As a strategy to deliver higher ignition energy, an active pre-chamber may be used. This work focuses on assessing the performance of two pre-chambers with different nozzle orifice diameters, in a stationary heavy-duty engine for power generation, operating at different loads, equivalence ratios and spark timings. The engine was originally a 6-cylinder compression ignition engine which is here employed as a single cylinder engine and then suitably modified to host the pre-chamber (with its natural gas injection system and spark plug) with a new bowl piston to decrease compression ratio. A…
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Performance of a Printed Bimetallic (Stainless Steel and Bronze) Engine Head Operating Under Stoichiometric and Lean Spark Ignited (SI) Combustion of Natural Gas

Argonne National Laboratory-Munidhar Biruduganti, Douglas Longman
Oak Ridge National Laboratory-Michael Kass, Brian Kaul, John Storey, Amelia Elliott, Derek Siddel
  • Technical Paper
  • 2020-01-0770
To be published on 2020-04-14 by SAE International in United States
The purpose of this study was to evaluate the durability and operational performance of a bimetallic (stainless steel and bronze) natural gas engine head. The performance was evaluated against a stock cast iron head for comparison. During manufacturing of the printed head, efforts were made to ensure that the internal features, including the fire deck geometry for the two head were identical. The engine was operated under two engine speeds (1200 rpm and 1800 rpm) and two Brake Mean Effective Pressures (6 bar and 10 bar). For each speed and BMEP combination, two equivalence ratios (0.7 and 1.0) were evaluated. In addition to emissions and engine performance data, the research team also took thermal images of both operating heads to ascertain heat transfer and thermal loss differences between the two head materials. The results showed that the brake efficiency, coolant and exhaust temperature were the same for both heads. However, unburned hydrocarbon emissions (methane) were higher, and the NOx emissions were lower for the printed head. Measurement of the compression ratio (CR) showed that the…
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Combustion Enhancement in a Gas Engine Using Low Temperature Plasma

Chiba University-Yasuo Moriyoshi, Tatsuya Kuboyama
Oita University-Kimitoshi Tanoue
  • Technical Paper
  • 2020-01-0823
To be published on 2020-04-14 by SAE International in United States
Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors’ previous study, lean burn limit could be extended by low temperature plasma ignition while a voltage drop during discharge, leading to the transition to arc discharge, was found. In this study, the structure of plug and power supply’s performance with steep voltage rising with time, dV/dt, are examined to investigate the effects on combustion performance. As a result, the following conclusions were deduced. (1) The lean combustion limit was extended when a four-pole plug with IES power source was used due to volumetric ignition. (2) A modified one-pole plug to improve the electric insulation, leading to prevent the voltage drop, could not extend the lean limit due to less volumetric ignitability. The specifications of plug must be improved to expand the ignition volume. (3) Using a variable dV/dt power source, the effect of dV/dt was tested. The combustion characteristics were not affected by dV/dt in this…
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Experimental Investigation of the Influence of Ignition System Parameters on Combustion in a Rapid Compression-Expansion Machine

Graz University of Technology-Andreas Nickl, Andreas Wimmer
HOERBIGER Wien GmbH-Georg Meyer
  • Technical Paper
  • 2020-01-1122
To be published on 2020-04-14 by SAE International in United States
Lean burn combustion concepts with high mean effective pressures are being developed for large gas engines so that future stringent emission limits are met while high engine efficiencies are maintained. Since these combustion concepts induce severe boundary conditions for ignition, applied research is focusing on the process of spark ignition and flame initiation in order to avoid misfiring and keep cycle-to-cycle combustion variability within reasonable limits. This paper conducts a fundamental investigation of early flame kernel development under different ignition system settings. The investigations are carried out on a rapid compression-expansion machine in which the spark ignition process can be observed under engine-like pressure and excess air ratio conditions while low flow velocities are maintained. The schlieren setup for high-speed optical investigations of the area of the spark plug electrodes is described and a suitable post-processing routine is introduced. The influence of different spark current durations on early flame kernel formation is investigated using a modulated capacitive discharge ignition (MCDI) system. The outcomes reveal that a short spark current duration results in a slower increase…
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Improving Heady Duty Natural Gas Engine Efficiency: A Systematic Approach to Application of Dedicated EGR

Southwest Research Institute-Michael C. Kocsis, Robert Mitchell, Ahmed Abdul Moiz, Vickey Kalaskar, D. Ryan Williams, Scott Sjovall
  • Technical Paper
  • 2020-01-0818
To be published on 2020-04-14 by SAE International in United States
The worldwide trend of tightening CO2 emissions standards and desire for near zero criteria pollutant emissions is driving development of high efficiency natural gas engines for a low CO2 replacement of traditional diesel engines. A Cummins Westport ISX12 G was previously converted to a Dedicated EGR ™ (D-EGR™) configuration with two out of the six cylinders acting as the EGR producing cylinders. Using a systems approach, the combustion and turbocharging systems were optimized for improved efficiency while maintaining the potential for achieving 0.02 g/bhp-hr NOX standards. A prototype variable nozzle turbocharger was selected to maintain the stock torque curve. The EGR delivery method enabled a reduction in pre-turbine pressure as the turbine was not required to be undersized to drive EGR. A high energy Dual Coil Offset (DCO®) ignition system was utilized to maintain stable combustion with increased EGR rates. High compression ratio, reduced squish pistons were designed to maintain MBT combustion phasing and fast burn rates along the torque curve. The final engine configuration was tested on the Heavy-Duty Supplemental Emissions Test (SET), a…
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Predicting the Influence of Charge Air Temperature Reduction on Engine Efficiency, CCV and NOx-Emissions of a Large Gas Engine using a SI Burn Rate Model

Caterpillar Energy Solutions GmbH-Stefan Palaveev, Matthias Veltman
FKFS-Sebastian Hann, Michael Grill
  • Technical Paper
  • 2020-01-0575
To be published on 2020-04-14 by SAE International in United States
In order to meet increasingly stringent exhaust emission regulations, new engine concepts need to be developed. Lean combustion systems for stationary running large gas engines can reduce raw NOx-emissions to a very low level and enable the compliance with the exhaust emission standards without using a cost-intensive SCR-aftertreatment system. Experimental investigations in the past have already confirmed that a strong reduction of the charge air temperature even below ambient conditions by using an absorption chiller can significantly reduce NOx emissions. However, test bench operation of large gas engines is costly and time-consuming. To increase the efficiency of the engine development process, the possibility to use 0D/1D engine simulation prior to test bench studies of new concepts is investigated using the example of low temperature charge air cooling. In this context, a reliable prediction of engine efficiency and NOx-emissions is important. Furthermore, restrictions to the engine operation like increase of cycle-to-cycle fluctuations due to high excess air ratio or late combustion need to be predicted as well in the engine simulation. For this purposes, a combustion…
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Study for Higher Efficiency and Lower Emissions in Turbo Charged Small Gas Engine Using Low Caloric Biomass Model Gas

Doshisha University-Kenta Shiomi, Ryogo Kato, Eriko Matsumura, Jiro Senda
Yanmar Co.,Ltd-Ryoichi Hagiwara, Yuta Watanabe, Toru Nakazono
  • Technical Paper
  • 2019-32-0620
Published 2020-01-24 by Society of Automotive Engineers of Japan in Japan
In recent years, depletion of energy resources and increasing CO2 emission have been concerned. As this solution, the use of biofuels from garbage is focused. In this research, higher efficiency and lower emissions in the gas engine for power generation using biomass gas are aimed. However, the biomass gas is low caloric value and the output is low and the combustion is unstable. Therefore, a turbocharged spark ignition gas engine is used as the test institution. As a result, it is found that combustion stability and high efficiency of biomass gas can be realized.
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Experimental analysis of engine cooling capacity at different altitudes: a case study for biarticulated gas engine bus at high altitude

Scania Latin America-Gabriel Prado de Oliveira, Bruno Afonso Garcia
  • Technical Paper
  • 2019-36-0272
Published 2020-01-13 by SAE International in United States
The demand for mass public transportation is growing on the major urban areas worldwide along with stricter demands on exhaust gas emission levels driven by society’s concern on the environment, leading to the development of sustainable transport solutions. Some of the solutions to reduce emission levels, such as electrified powertrains, may not be affordable for emergent markets due to the necessity of investments on infrastructure as well as high costs of some technologies. Bogotá city in Colombia is renewing its bus rapid transit (BRT) fleet and aims to reduce emission levels in its operation. Therefore, the development of a biarticulated bus driven by a compressed natural gas (CNG) Otto engine can be a sustainable solution for such application reducing both emission levels and fuel costs (compared to a Diesel model). However, the development of a cooling system for such bus becomes a challenge due to several factors that have a negative impact on cooling performance such as: high gross train weight (GTW); high altitude application; CNG Otto engine (compared to a Diesel model) and limited…
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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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A Study on PCCI Combustion Control in Medium Speed Dual-Fuel Engine

Yanmar Co., Ltd.-Kazuteru Toshinaga, Masaki Kuribayashi
  • Technical Paper
  • 2019-01-2176
Published 2019-12-19 by SAE International in United States
To achieve simultaneous reduction of CO2 and NOx emission from the Dual-Fuel (DF) engine using natural gas and diesel fuel, Premixed Charge Compression Ignition (PCCI) type combustion is a promising technology. However, to apply this technology to the practical operation of the DF engine, combustion control is key challenge because the ignition of PCCI type combustion is governed by chemical reaction of natural gas/air and diesel fuel premixture and not controlled by direct control parameter such as spark timing of spark-ignition natural gas engine or diesel fuel injection timing of micro-pilot type DF engine. The focus of this study is to understand the effect of engine control parameters on DF-PCCI combustion characteristics to establish the combustion control strategy in medium speed DF engine. Engine experiments using a 4-stroke medium speed single cylinder engine were carried out. Firstly, early two stage diesel pilot injection was applied to realize DF-PCCI combustion. As a result, brake thermal efficiency was successfully improved by 2%pt compared with conventional micro-pilot combustion while achieving low NOx emission to meet the stringent emission…
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