Experimental Investigation of a Heavy-Duty CI Engine Retrofitted to Natural Gas SI Operation

2018 ◽  
Author(s):  
Jinlong Liu ◽  
Hemanth Bommisetty ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Operating Conditions ◽  
Intake Manifold ◽  
Heavy Duty ◽  
Lean Burn ◽  
Engine Operation ◽  
Cycle Variation ◽  
Spark Timing ◽  
Ci Engine ◽  
Ci Engines

Heavy-duty compression-ignition (CI) engines converted to natural gas (NG) operation can reduce the dependence on petroleum-based fuels and curtail greenhouse gas emissions. Such an engine was converted to premixed NG spark-ignition (SI) operation through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector. Engine performance and combustion characteristics were investigated at several lean-burn operating conditions that changed fuel composition, spark timing, equivalence ratio, and engine speed. While the engine operation was stable, the reentrant bowl-in-piston (a characteristic of a CI engine) influenced the combustion event such as producing a significant late-combustion, particularly for advanced spark timing. This was due to an important fraction of the fuel burning late in the squish region, which affected the end of combustion, the combustion duration, and the cycle-to-cycle variation. However, the lower cycle-to-cycle variation, stable combustion event, and the lack of knocking suggest a successful conversion of conventional diesel engines to NG SI operation using the approach described here.

Experimental Investigation of a Heavy-Duty Compression-Ignition Engine Retrofitted to Natural Gas Spark-Ignition Operation

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Jinlong Liu ◽  
Hemanth Kumar Bommisetty ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Compression Ignition ◽  
Heavy Duty ◽  
Compression Ignition Engine ◽  
Engine Operation ◽  
Cycle Variation ◽  
Spark Timing ◽  
Ci Engines

Heavy-duty compression-ignition (CI) engines converted to natural gas (NG) operation can reduce the dependence on petroleum-based fuels and curtail greenhouse gas emissions. Such an engine was converted to premixed NG spark-ignition (SI) operation through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector. Engine performance and combustion characteristics were investigated at several lean-burn operating conditions that changed fuel composition, spark timing, equivalence ratio, and engine speed. While the engine operation was stable, the reentrant bowl-in-piston (a characteristic of a CI engine) influenced the combustion event such as producing a significant late combustion, particularly for advanced spark timing. This was due to an important fraction of the fuel burning late in the squish region, which affected the end of combustion, the combustion duration, and the cycle-to-cycle variation. However, the lower cycle-to-cycle variation, stable combustion event, and the lack of knocking suggest a successful conversion of conventional diesel engines to NG SI operation using the approach described here.

Lean-Burn Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition

2018 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Fuel Injector ◽  
Heavy Duty ◽  
Lean Burn ◽  
Spark Timing ◽  
Heavy Duty Diesel

Increased utilization of natural-gas (NG) in the transportation sector can decrease the use of petroleum-based fuels and reduce greenhouse-gas emissions. Heavy-duty diesel engines retrofitted to NG spark ignition (SI) can achieve higher efficiencies and low NOx, CO, and HC emissions when operated under lean-burn conditions. To investigate the SI lean-burn combustion phenomena in a bowl-in-piston combustion chamber, a conventional heavy-duty direct-injection CI engine was converted to SI operation by replacing the fuel injector with a spark plug and by fumigating NG in the intake manifold. Steady-state engine experiments and numerical simulations were performed at several operating conditions that changed spark timing, engine speed, and mixture equivalence ratio. Results suggested a two-zone NG combustion inside the diesel-like combustion chamber. More frequent and significant late burn (including double-peak heat release rate) was observed for advanced spark timing. This was due to the chamber geometry affecting the local flame speed, which resulted in a faster and thicker flame in the bowl but a slower and thinner flame in the squish volume. Good combustion stability (COVIMEP < 3 %), moderate rate of pressure rise, and lack of knocking showed promise for heavy-duty CI engines converted to NG SI operation.

Lean-Burn Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural-Gas Spark Ignition

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Fuel Injector ◽  
Heavy Duty ◽  
Lean Burn ◽  
Heavy Duty Diesel ◽  
Ci Engines

Increased utilization of natural gas (NG) in the transportation sector can decrease the use of petroleum-based fuels and reduced greenhouse gas emissions. Heavy-duty diesel engines retrofitted to NG spark ignition (SI) can achieve higher efficiencies and low NOX, CO, and hydrocarbon (HC) emissions when operated under lean-burn conditions. To investigate the SI lean-burn combustion phenomena in a bowl-in-piston combustion chamber, a conventional heavy-duty direct-injection CI engine was converted to SI operation by replacing the fuel injector with a spark plug and by fumigating NG in the intake manifold. Steady-state engine experiments and numerical simulations were performed at several operating conditions that changed spark timing (ST), engine speed, and mixture equivalence ratio. Results suggested a two-zone NG combustion inside the diesel-like combustion chamber. More frequent and significant late-burn (including double-peak heat release rate) was observed for advanced ST. This was due to the chamber geometry affecting the local flame speed, which resulted in a faster and thicker flame in the bowl but a slower and thinner flame in the squish volume. Good combustion stability (COVIMEP < 3%), moderate rate of pressure-rise, and lack of knocking showed promise for heavy-duty CI engines converted to NG SI operation.

Comparison of Emissions and Efficiency of a Turbocharged Lean-Burn Natural Gas and Hythane-Fueled Engine

1997 ◽  
Vol 119 (1) ◽  
pp. 218-226 ◽  
Author(s):  
J. F. Larsen ◽  
J. S. Wallace
Keyword(s):  
Natural Gas ◽  
Specific Energy Consumption ◽  
Oxides Of Nitrogen ◽  
Heavy Duty ◽  
Lean Burn ◽  
Clear Trend ◽  
Engine Operation ◽  
Spark Timing ◽  
Test Engine ◽  
Carbon Dioxide Co2

An experiment was conducted to evaluate the potential for reduced exhaust emissions and improved efficiency, by way of lean-burn engine fuelling with hydrogen supplemented natural gas (Hythane). The emissions and efficiency of the Hythane fuel (15 percent hydrogen, 85 percent natural gas by volume), were compared to the emissions and efficiency of pure natural gas using a turbocharged, spark ignition, 3.1 L, V-6 engine. The feasibility of heavy duty engine fueling with Hythane was assessed through testing conducted at engine speed and load combinations typical of heavy-duty engine operation. Comparison of the efficiency and emissions at MBT spark timing revealed that Hythane fueling of the test engine resulted in consistently lower brake specific energy consumption and emissions of total hydrocarbons (THC), carbon monoxide (CO), and carbon dioxide (CO2), at a given equivalence ratio. There was no clear trend with respect to MBT oxides of nitrogen (NOx) emissions. It was also discovered that an improved NOx-THC tradeoff resulted when Hythane was used to fuel the test engine. Consequently, Hythane engine operating parameters can be adjusted to achieve a concurrent reduction in NOx and THC emissions relative to natural gas fueling.

Multiple Combustion Stages Inside a Heavy-Duty Diesel Engine Retrofitted to Natural-Gas Spark-Ignition Operation

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Intake Manifold ◽  
Lean Burn ◽  
Spark Timing ◽  
Before And After ◽  
Heavy Duty Diesel ◽  
The One

Abstract Converting existing diesel engines to natural-gas (NG) spark-ignition (SI) operation can reduce the dependence on oil imports and increase energy security. NG-dedicated conversion can be achieved by the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector. Previous studies indicated that lean-burn NG inside the traditional diesel chamber (i.e., a bowl-in-piston geometry) is a two-stage combustion (i.e., a fast burn inside the bowl followed by a slower burn inside the squish). However, a triple-peak apparent heat release rate (AHRR) was seen at specific operating conditions (e.g., advanced spark timing (ST) at medium load and engine speed), suggesting that one of the two combustion stages may separate again. Specifically, the burn inside the squish region divided in two events before and after top dead center (TDC). This was due to the different flow motion inside the squish during the compression stroke compared to the one in the expansion stroke, which affected the combustion environments. The result was the apparition of two close peaks in pressure trace, which suggest larger gradients in pressure and temperature than at a more delayed ST. In addition, the phasing and magnitude of three peaks of the heat release changed cycle-to-cycle. As an advanced ST is the usual strategy used in lean-burn SI combustion, understanding phenomena such as the one presented here can be important for reducing engine-out emissions and increase engine efficiency.

Limitations of Natural Gas Lean Burn Spark Ignition Engines Derived From Compression Ignition Engines

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Spark Ignition ◽  
High Energy ◽  
Intake Manifold ◽  
Compression Ignition ◽  
Primary Control ◽  
Heavy Duty ◽  
Lean Burn ◽  
Ci Engines

Abstract Converting existing diesel engines to the spark ignition (SI) operation can increase the utilization of natural gas (NG) in heavy-duty applications, which can reduce oil imports in the US and curtail greenhouse-gas emissions. The NG operation at lean-burn conditions was evaluated inside a retrofitted heavy-duty direct-injection compression-ignition (CI) engine, where the diesel injector was replaced with a high-energy spark plug and NG was mixed with air in the intake manifold. Steady-state engine experiments that changed combustion phasing were performed at 13.3 compression ratio, lean equivalence ratio, medium load, and low-speed conditions, fueled with pure methane as NG surrogate. Results suggested that NG combustion inside such retrofitted engines is different from that in conventional SI engines due to the geometric characteristics of the diesel combustion chamber. In detail, the different conditions inside the bowl and the squish partitioned the combustion process into two distinct events in terms of timing and location. Moreover, the squish region helped stabilize the extreme lean operation by creating a highly turbulent flow into the bowl during the compression stroke. However, combustion efficiency and unburned hydrocarbon emissions were significantly affected by the fuel fraction that burned inside the squish region under less than optimal conditions during the expansion stroke. As a result, despite the combustion phasing being the primary control of engine’s indicated thermal efficiency, the combustion strategy for CI engines converted to NG SI should optimize the slower burning inside the squish region.

Observation of Flame Propagation in a Heavy-Duty Natural-Gas Lean Burn Spark-Ignition Engine

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Low Cost ◽  
Turbulent Flame ◽  
Propagation Speed ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Heavy Duty ◽  
Lean Burn ◽  
Local Flow

Abstract Natural gas (NG) is an alternative combustible fuel for the transportation sectors due to its clean combustion, small carbon footprint, and, with recent breakthroughs in drilling technologies, increased availability and low cost. Currently, NG is better suited for spark-ignited (SI), as a gasoline replacement in conventional SI engines or as a diesel replacement in diesel engines converted to SI operation. However, the knowledge on the fundamentals of NG flame propagation at conditions representative of modern engines (e.g., at higher compression ratios and/or lean mixtures) is limited. Flame propagation inside an engine can be achieved by replacing the original piston with a see-through one. This study visualized flame activities inside the combustion chamber of an optically-accessible heavy-duty diesel engine retrofitted to NG SI operation to increase the understanding of combustion processes inside such converted engines. Recordings of flame luminosity throughout the combustion period at lean-burn operating conditions indicated that the fully-developed turbulent flame formed from several smaller-scale kernels. These small kernels varied with shapes and locations due to different flow motion around the spark location (including the effect of spark electrodes on the local flow separation), different local temperature, or different energy released in these regions. In addition, the turbulent flame was heavily wrinkled during propagation, despite it was grown from a relatively-circular kernel. Moreover, the intake swirl accelerated the flame propagation process while rotating the turbulent flame during its development. Furthermore, the flame propagation speed reduced dramatically when entering the squish region, while the direction from which the flame first touched the bowl edge changed with individual cycles. The results can help the CFD community to better develop RANS and/or LES simulations of such engines under lean-burn operating conditions.

Engine Performance and Emissions for a Heavy-Duty Diesel Engine Converted to Stoichiometric Natural Gas Operation

2020 ◽  
Author(s):  
Jinlong Liu ◽  
Christopher Ulishney ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Catalytic Converter ◽  
Combustion Process ◽  
Engine Performance ◽  
Intake Manifold ◽  
Heavy Duty ◽  
Indicated Mean Effective Pressure ◽  
Performance And Emissions ◽  
Heavy Duty Diesel ◽  
Ci Engines

Abstract Converting existing compression ignition (CI) engines to spark ignition (SI) operation can increase the use of natural gas (NG) in heavy-duty engine applications and reduce the reliance on petroleum fuels. Gas fumigation upstream of the intake manifold and the addition of a spark plug in place of the diesel injector to initiate and control the combustion process is a convenient approach for converting existing diesel engines to dedicated NG operation. Stoichiometric operation and a three-way catalytic converter can help the engine to comply with increasingly strict emission regulations. However, as the CI-to-SI conversion usually maintains the conventional geometry of a CI engine (i.e., maintains the flat cylinder head and the bowl-in piston), the goal of this study was to observe some of the effects that the diesel conversion to stoichiometric NG SI operation will have on the engine’s performance and emissions. Dynamometer tests were performed at a constant engine speed at 1300 rpm but various spark timings. The experimental results for a net indicated mean effective pressure ∼ 6.7 bar showed that ignition timing did not affect the end of combustion due to the slow-burn inside the squish. Moreover, the less-optimal conditions inside the squish led to increased carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions. While the combustion event was stable with no signs of knocking at the medium load conditions investigated here, the results suggest that the engine control needs to optimize the mass fraction trapped inside the squish region for a higher efficiency and lower emissions.

The Application of a Thermal Efficiency Maximizing Control Strategy for Ignition Timing and Equivalence Ratio on a Natural Gas-Fueled Hercules G1600

1996 ◽  
Vol 118 (4) ◽  
pp. 872-879
Author(s):  
M. L. Franklin ◽  
D. B. Kittelson ◽  
R. H. Leuer
Keyword(s):  
Control System ◽  
Natural Gas ◽  
Thermal Efficiency ◽  
Equivalence Ratio ◽  
Three Dimensional ◽  
Control Process ◽  
Operating Conditions ◽  
Optimization Process ◽  
Lean Burn ◽  
Spark Timing

A two-dimensional optimization process, which simultaneously adjusts the spark timing and equivalence ratio of a lean-burn, natural gas, Hercules G1600 engine, has been demonstrated. First, the three-dimensional surface of thermal efficiency was mapped versus spark timing and equivalence ratio at a single speed and load combination. Then the ability of the control system to find and hold the combination of timing and equivalence ratio that gives the highest thermal efficiency was explored. NOx, CO, and HC maps were also constructed from our experimental data to determine the tradeoffs between efficiency and emissions. The optimization process adds small synchronous disturbances to the spark timing and air flow while the fuel injected per cycle is held constant for four cycles. The engine speed response to these disturbances is used to determine the corrections for spark timing and equivalence ratio. The control process, in effect, uses the engine itself as the primary sensor. The control system can adapt to changes in fuel composition, operating conditions, engine wear, or other factors that may not be easily measured. Although this strategy was previously demonstrated in a Volkswagen 1.7 liter light duty engine (Franklin et al., 1994b), until now it has not been demonstrated in a heavy-duty engine. This paper covers the application of the approach to a Hercules G1600 engine.

Lean-Burn Stationary Natural Gas Reciprocating Engine Operation With a Prototype Fiber Coupled Diode End Pumped Passively Q-Switched Laser Spark Plug

2009 ◽  
Author(s):  
Dustin L. McIntyre ◽  
Steven D. Woodruff ◽  
John S. Ontko
Keyword(s):  
Natural Gas ◽  
Optical Fiber ◽  
Optical Power ◽  
Boost Pressure ◽  
Lean Burn ◽  
Engine Operation ◽  
Pump Source ◽  
Spark Plug ◽  
Spark Timing ◽  
Laser Spark

An end pumped passively Q-switched laser igniter was developed to meet the ignition system needs of large bore lean burn stationary natural gas engines. The laser spark plug used an optical fiber coupled diode pump source to axially pump a passively Q-switched Nd:YAG laser and transmit the laser pulse through a custom designed lens. The optical fiber coupled pump source permits the excitation energy to be transmitted to the spark plug at relatively low optical power, less than 250 watts. The Q-switched laser then generates as much as 8 millijoules of light in 2.5 nanoseconds which is focused through an asymmetric biconvex lens to create a laser spark from a focused intensity of approximately 225 GW/cm2. A single cylinder engine fueled with either natural gas only or hydrogen augmented natural gas was operated with the laser spark plug for approximately 10 hours in tests spanning 4 days. The tests were conducted with fixed engine speed, fixed boost pressure, no exhaust gas recirculation, and laser spark timing advance set at maximum brake torque timing. Engine operational and emissions data were collected and analyzed.

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