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.

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.

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.

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.

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.

Numerical Simulation of Re-Entrant Bowl Effects on Natural-Gas Spark-Ignition Operation

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Numerical Simulation ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Cfd Simulation ◽  
Engine Performance ◽  
Spark Ignition ◽  
Combustion Stability ◽  
Intake Manifold ◽  
Performance And Emissions ◽  
Ci Engines

Heavy-duty compression–ignition (CI) engines converted to natural gas (NG) spark ignition (SI) operation have the potential to increase the use of NG in the transportation sector. A three-dimensional (3D) numerical simulation was used to predict how the conventional CI combustion chamber geometry (i.e., re-entrant bowl and flat head) affects the combustion stability, performance, and emissions of a single-cylinder CI engine that was converted to SI operation by adding a low-pressure gas injector in the intake manifold and a spark plug in place of the diesel injector. The G-equation based 3D computational fluid dynamics (CFD) simulation investigated three different combustion chamber configurations that change the size of the squish region at a constant compression ratio (CR) and a clearance height. The results show that the different flame propagation speeds inside and outside the re-entrant bowl can create a two-zone combustion phenomenon. Moreover, a larger squish region increased the flame burning speed, which decreased late-combustion duration (DOC). All these findings support the need for further investigations of the combustion chamber shape design for optimum engine performance and emissions in 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
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