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Investigation of Diesel/Natural Gas RCCI Combustion Using Multiple Reaction Mechanisms at Various Engine Operating Conditions

FEV North America Inc.-Mufaddel Dahodwala, Satyum Joshi, Erik Koehler, Michael Franke, Dean Tomazic
Michigan Technological University-Jeffrey Naber
  • Technical Paper
  • 2020-01-0801
To be published on 2020-04-14 by SAE International in United States
Past experimental studies conducted by the current authors on a 13 liter 16.7:1 compression ratio heavy-duty diesel engine have shown that diesel /natural gas Reactivity Controlled Compression Ignition (RCCI) combustion targeting low NOx emissions becomes progressively difficult to control as the engine load is increased due to difficulty in controlling reactivity levels at higher loads. For the current study, CFD investigations were conducted using the SAGE combustion solver in Converge with the application of Rahimi mechanism. Studies were conducted at a load of 5 bar BMEP to validate the simulation results against RCCI test data. In the low load study, it was found that the Rahimi mechanism was not able to predict the RCCI combustion behavior for diesel injection timings advanced beyond 30bTDC. This behavior was found at multiple engine speed and load points. To resolve this, multiple reaction mechanisms were evaluated and a new reaction mechanism that combines the GRI Mech 3.0 mechanism with the Chalmers mechanism was proposed. This mechanism was found to accurately predict the ignition delay and combustion behavior with early…
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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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Study on the Effect of Manifold Induction of Acetylene in a Dual-fuelled CI Engine

NIT Rourkela-Rakesh Kumar Sahoo, Akshat Jaiswal, Murugan Sivalingam
  • Technical Paper
  • 2020-01-0817
To be published on 2020-04-14 by SAE International in United States
The utilization of gaseous fuels in internal combustion (IC) engines is receiving more significant greater interest in recent years because of their better fuel mixing characteristics. Apart from potential gaseous fuels such as liquefied natural gas (LPG), compressed natural gas (CNG) and hydrogen, other gaseous fuels are being explored for their utilization in IC engines. The reason for this exploration is mainly because of the durability and robust nature of compression ignition (CI) engines, more research focuses on the utilization of a variety of gaseous fuels in CI engines. However, gaseous fuels need to be used in CI engines on dual fuel mode only. In this investigation, a single-cylinder, four-stroke, air-cooled diesel engine was converted into Acetylene run dual-fuel CI engine by changing the intake manifold of the test engine. Acetylene at three flow rates viz., 2lpm, 4lpm, and 6lpm were introduced into the intake port by manifold induction technique while Jatropha biodiesel was injected directly into the cylinder. In this paper, the effect of manifold induction of Acetylene on the performance and emission characteristics…
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Numerical Investigation of Diesel-Spray-Orientated Piston Bowls on Natural Gas and Diesel Dual Fuel Combustion Engine

Zhaojie Shen
Brunel University-Xinyan Wang, Hua Zhao
  • Technical Paper
  • 2020-01-0311
To be published on 2020-04-14 by SAE International in United States
Low combustion efficiency and high hydrocarbon emissions at low load are key issues of natural gas and diesel dual fuel engines. For better engine performance, two diesel-spray-orientated (DSO) bowls were developed based on the existing diesel injector of a heavy-duty diesel engine with the purpose of placing more combustible natural gas/air mixture around the diesel spray jets. A bulge-ring was designed at the rim of the piston bowl to enhance the in-cylinder flame propagation. Numerical simulations were conducted for a whole engine cycle by using STAR-CD 4.22 at engine speed of 1200 r/min and indicated mean effective pressure (IMEP) of 0.6 MPa. ECFM-3Z combustion model with built-in soot emissions model was employed. In this paper, natural gas was considered as a mixture of 95% methane and 5% ethanol. Simulation results of the original piston bowl agreed well with the experimental data, including in-cylinder pressure and heat released rate, as well as soot and methane emissions. Turbulence kinetic energy, combustion efficiency and methane emissions of the DSO piston geometries were compared with that of the original…
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Optical Characterization of the Combustion Process Inside a Large-Bore Fual-Fuel Two-Stroke Marine Engine by Using Multiple High-Speed Cameras

Lund University-Alexios Matamis, Mattias Richter
MAN Energy Solutions-Johan Hult, Eric Baudoin, Stefan Mayer
  • Technical Paper
  • 2020-01-0788
To be published on 2020-04-14 by SAE International in United States
Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine, with fuel injection from positions at the rim of the cylinder, the flame morphology becomes asymmetric. The optical spatial mapping and…
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Under-expanded Gaseous Jets Characterization for Application in Direct Injection Engines: Experimental and Numerical Approach

Istituto Motori CNR-Luigi Allocca, Alessandro Montanaro, Giovanni Meccariello
Università degli Studi de L'Aquila-Francesco Duronio, Stefano Ranieri
  • Technical Paper
  • 2020-01-0325
To be published on 2020-04-14 by SAE International in United States
In the last years, increasing concerns about environmental pollution and fossil sources depletion led transport sector’s research and development towards the study of new technologies capable to reduce vehicle’s emissions and fuel consumption. Direct-injection systems (DI) for internal combustion engines propose as an effective way to achieve these goals. This technology has already been adopted in gasoline engines (GDI) and, lately, a great interest is growing for its use in natural gas fuelling engines, so increasing efficiency with respect to port-fuel injection engines. Alone or in combination with other fuels, compressed natural gas (CNG) represents an attractive way to reduce exhaust emission (high H/C ratio), can be produced in renewable ways, and is more widespread and cheaper than gasoline or diesel fuels. Gas direct-injection process involves the occurrence of under-expanded jets in the combustion chamber. An accurate characterization of such phenomena is crucial for a consequent application in DI-CNG engines. In this paper an experimental and numerical analysis of methane under-expanded jets (as surrogate of CNG) has been carried out. The fuel has been injected…
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The Effect of Exhaust Gas Recirculation (EGR) on Fundamental Characteristics of Premixed Methane/Air Flames

Michigan State University-Berk Can Duva, Yen-Cheng Wang, Lauren Chance, Elisa Toulson
  • Technical Paper
  • 2020-01-0339
To be published on 2020-04-14 by SAE International in United States
Increasingly stringent regulations of internal combustion engines emissions have increased focus on alternative fuels for transportation and emission reduction techniques, such as exhaust gas recirculation (EGR). Natural gas is a promising alternative to conventional petroleum derived automotive fuels since it provides lower exhaust emissions, higher octane ratings, and better fuel economy. Although many studies have investigated fundamental combustion characteristics of methane/air flames diluted with either CO2, N2 or H2O in order to investigate the EGR effect, studies analyzing actual EGR content (CO2+N2+H2O) are very rare. In the present study, spherically expanding flames were employed to investigate the EGR effect on laminar flame speeds and burned gas Markstein lengths of premixed methane/air mixtures at 3 bar and 373 K through both experiments and numerical simulations. The EGR content was simulated with a mixture of 9.50 % CO2 + 71.49 % N2 + 19.01 % H2O and the EGR ratio was varied from 0% to 15%. Numerical results were obtained from CHEMKIN using the GRI-Mech 3.0, USC Mech II, and San Diego mechanisms. Numerical laminar flame speed…
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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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Impact of ethane enrichment on diesel-methane dual-fuel combustion

Aalto University-Zeeshan Ahmad, Ossi Kaario, Qiang Cheng, Martti Larmi
  • Technical Paper
  • 2020-01-0305
To be published on 2020-04-14 by SAE International in United States
Over the past few years, the growing concerns about global warming and efforts to reduce the engine-out emissions have made the dual-fuel (DF) engines more popular in marine and power industries. The use of natural gas as an alternative fuel in DF engines has both the environmental and economic advantages over the conventional diesel combustion. However, the misfire phenomenon at lean conditions limits the operating range of DF combustion and causes emissions of unburned hydrocarbon (UHC) and unburned CH4 (methane-slip) in the environment. The greenhouse effect of CH4 is considered 28 times greater than CO2 over a 100-year perspective, which raises concerns for the governments and marine engine manufacturers. In efforts to reduce the UHC and CH4-slip from DF engines, this study discusses ethane enrichment of diesel-methane DF combustion in a full-metal single-cylinder research engine at a constant load of approx. 12 bar IMEP under lean condition (λCH4 = 2.0) with a small pilot diesel (3% of total injected energy). The conditions at top-dead-center (TDC) are kept constant in all experiments i.e. motored peak pressure…