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.

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

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.

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.

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.

An Experimental Study of the Combustion Process in a Natural-Gas Spark-Ignition Engine

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu ◽  
Hemanth Bommisetty
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Spark Ignition ◽  
High Energy ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Intake Manifold ◽  
Spark Timing

Abstract The conversion of existing internal combustion engines to natural-gas operation can reduce U.S. dependence on petroleum imports and curtail engine-out emissions. In this study, a diesel engine with a 13.3 compression ratio was modified to natural-gas spark-ignited operation by replacing the original diesel injector with a high-energy spark plug and by fumigating fuel inside the intake manifold. The goal of this research was to investigate the combustion process inside the flat-head and bowl-in-piston chamber of such retrofitted engine when operated at different spark timings, mixture equivalence ratios, and engine speeds. The results indicated that advanced spark timing, a lower equivalence ratio, and a higher speed operation increased the ignition lag and made it more difficult to initiate the combustion process. Further, advanced spark timing, a larger equivalence ratio, and a lower speed operation accelerated the flame propagation process inside the piston bowl and advanced the start of the burn inside the squish. However, such conditions increased the burning duration inside the squish due to more fuel being trapped inside the squish volume and the smaller squish height during combustion. As a result, the end of combustion was almost the same despite the change in the operating conditions. In addition, the reliable ignition, stable combustion, and the lack of knocking showed promise for the application of natural-gas lean-burn spark-ignition operation in the heavy-duty transportation.

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.

Hydrogen Blended Natural Gas Operation of a Heavy Duty Turbocharged Lean Burn Spark Ignition Engine

2004 ◽  
Author(s):  
S. R. Munshi ◽  
C. Nedelcu ◽  
J. Harris ◽  
T. Edwards ◽  
J. Williams ◽  
...  
Keyword(s):  
Natural Gas ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Heavy Duty ◽  
Lean Burn

Improved Thermodynamic Model for Lean Natural Gas Spark Ignition in a Diesel Engine Using a Triple Wiebe Function

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Diesel Engines ◽  
Mass Fraction ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Spark Ignition ◽  
High Energy ◽  
Multi Stage ◽  
Stage Combustion ◽  
Wiebe Function

Abstract The use of natural gas (NG) in heavy-duty internal combustion engines can reduce the dependence on petroleum fuels and greenhouse gas emissions. Diesel engines can convert to NG spark ignition (SI) by installing a high-energy ignition system and a gas injector. The diesel combustion chamber affects the flow inside the cylinder, so some existing SI combustion models will not accurately describe the operation of converted diesels. For example, the single Wiebe function has difficulties in correctly describing the mass fraction burn (MFB) throughout the combustion process. This study used experiments from a 2L single-cylinder research engine converted to port fuel injection NG SI and operated with methane at 1300 rpm and equivalence ratio 0.8 (6.2 bars IMEP) to compare the standard Wiebe function with a triple Wiebe function. Results indicated that lean-burn engine operation at an advanced spark timing produced three peaks in the heat release rate, suggesting a multi-stage combustion process. A “best goodness-of-fit” approach determined the values of the key parameters in the zero-dimensional Wiebe function model. The triple Wiebe function described the mass fraction burn and combustion phasing more accurately compared with the single Wiebe function. Moreover, it provided the duration and phasing of each individual burning stage that can then characterize the combustion in such converted diesel engines. This suggests that a multiple Wiebe function combustion model would effectively assist in analyzing such a multi-stage combustion process, which is important for engine optimization and development.

Two-Stage Lean-Burn Combustion Inside a Natural-Gas Spark-Ignition Engine With a Bowl-in-Piston Chamber

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Intake Manifold ◽  
Hydrocarbon Emissions ◽  
Fuel Injector ◽  
Unburned Hydrocarbon ◽  
Piston Chamber

Abstract The conversion of existing diesel engines to spark ignition (SI) operation by adding a low-pressure injector in the intake manifold for fuel delivery and replacing the original high-pressure fuel injector with a spark plug to initiate and control the combustion process can reduce U.S. dependence on petroleum imports and increase natural gas (NG) applications in heavy-duty transportation sectors. Since the conventional diesel combustion chamber (i.e., flat-head-and-bowl-in-piston-chamber) creates high turbulence, the converted NG SI engine can operate leaner with stable and repeatable combustion process. However, existing literatures point to a long late-combustion duration and increased unburned hydrocarbon emissions in such retrofitted engines that maintained the original combustion chamber. Consequently, the main objective of this paper was to report recent findings of NG combustion characteristics inside a bowl-in-piston combustion chamber that will add to the general understanding of the phenomena. The new results indicated that the premixed NG burn inside the bowl-in-piston combustion chamber will separate into a bowl-burn and a squish-burn processes in terms of burning location and timing. The slow burning event in the squish region explains the low slope of the burn rate towards the end of combustion in existing studies (hence the longer late-combustion period). In addition, the less-favorable conditions for the combustion in the squish region explained the increased carbon monoxide and unburned hydrocarbon emissions.

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