The Hybrid Rich-Burn/Lean-Burn Engine

1997 ◽  
Vol 119 (1) ◽  
pp. 243-249 ◽  
Author(s):  
D. P. Meyers ◽  
J. T. Kubesh
Keyword(s):  
Carbon Monoxide ◽  
Natural Gas ◽  
Combustion Stability ◽  
Lean Burn ◽  
Lean Mixture ◽  
Combustion Limits ◽  
Lean Limit ◽  
The Rich ◽  
Engine Concept ◽  
Combustion Exhaust

This paper describes a new low-emissions engine concept called the hybrid rich-burn/lean-burn (HRBLB) engine. In this concept a portion of the cylinders of a multicylinder engine are fueled with a very rich natural gas-air mixture. The remaining cylinders are operated with a lean mixture of natural gas and air and supplemented with the rich combustion exhaust. The goal of this unique concept is the production of extremely low NOx (e.g., 5 ppm when corrected to 15 percent exhaust oxygen content). This is accomplished by operating outside the combustion limits where NOx is produced. In rich combustion an abundance of hydrogen and carbon monoxide is produced. Catalyst treatment of the rich exhaust can be employed to increase the hydrogen concentration and decrease the carbon monoxide concentration simultaneously. The hydrogen-enriched exhaust is used to supplement the lean mixture cylinders to extend the lean limit of combustion, and thus produces ultralow levels of NOx. Results to date have shown NOx levels as low as 8 ppm at 15 percent oxygen can be achieved with good combustion stability and thermal efficiency.

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 study of combustion strategy for jet ignition on a natural gas engine

2020 ◽  
pp. 146808742097775
Author(s):  
Ziqing Zhao ◽  
Zhi Wang ◽  
Yunliang Qi ◽  
Kaiyuan Cai ◽  
Fubai Li
Keyword(s):  
Experimental Study ◽  
Natural Gas ◽  
Efficient Points ◽  
Lean Burn ◽  
Gas Engine ◽  
Absolute Value ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Excess Air ◽  
Lean Limit

To explore a suitable combustion strategy for natural gas engines using jet ignition, lean burn with air dilution, stoichiometric burn with EGR dilution and lean burn with EGR dilution were investigated in a single-cylinder natural gas engine, and the performances of two kinds of jet ignition technology, passive jet ignition (PJI) and active jet ignition (AJI), were compared. In the study of lean burn with air dilution strategy, the results showed that AJI could extend the lean limit of excess air ratio (λ) to 2.1, which was significantly higher than PJI’s 1.6. In addition, the highest indicated thermal efficiency (ITE) of AJI was shown 2% (in absolute value) more than that of PJI. Although a decrease of NOx emission was observed with increasing λ in the air dilution strategy, THC and CO emissions increased. Stoichiometric burn with EGR was proved to be less effective, which can only be applied in a limited operation range and had less flexibility. However, in contrast to the strategy of stoichiometric burn with EGR, the strategy of lean burn with EGR showed a much better applicability, and the highest ITE could achieve 45%, which was even higher than that of lean burn with air dilution. Compared with the most efficient points of lean burn with pure air dilution, the lean burn with EGR dilution could reduce 78% THC under IMEP = 1.2 MPa and 12% CO under IMEP = 0.4 MPa. From an overall view of the combustion and emission performances under both low and high loads, the optimum λ would be from 1.4 to 1.6 for the strategy of lean burn with EGR dilution.

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.

Evaluation of a Lean-Burn Natural Gas Engine Operating on Variable Methane Number Fuel

2011 ◽  
Author(s):  
Cory J. Kreutzer ◽  
Daniel B. Olsen ◽  
Robin J. Bremmer
Keyword(s):  
Natural Gas ◽  
High Efficiency ◽  
Engine Performance ◽  
Combustion Stability ◽  
Lean Burn ◽  
Natural Gas Engines ◽  
Spark Timing ◽  
Gas Compression ◽  
Fuel Blending ◽  
Methane Number

Wellhead gas from which pipeline natural gas originates has significant variability in composition due to natural variations in deposits. Gas quality is influenced by relative concentrations of both inert and hydrocarbon species. Gas compression engines utilizing wellhead gas as a fuel source often require significant installation time and adjustment of stock configuration due to fuel compositions that vary with time and location. Lean burn natural gas engines are chosen as wellhead compression engines for high efficiency and low emissions while minimizing the effect of variable gas composition. Ideal engine conditions are maintained by operating within the knock and misfire limits of the engine. Additional data is needed to find engine operational limitations. In this work, experimental data was collected on a Cummins GTA8.3SLB engine operating on variable methane number fuel under closed-loop equivalence ratio control. A fuel blending system was used to vary methane number to simulate wellhead compositions. NOx and CO emissions were found to increase with decreasing methane number while combustion stability remained constant. In addition, the effects of carbon dioxide and nitrogen diluents in the fuel were investigated. When diluents were present in the fuel, engine performance could be maintained by spark timing advance.

scholarly journals Control-oriented analysis of a lean-burn light-duty natural gas research engine with scavenged pre-chamber ignition

2019 ◽  
Vol 176 (1) ◽  
pp. 42-53
Author(s):  
Severin HÄNGGI ◽  
Thomas HILFIKER ◽  
Patrik SOLTIC ◽  
Richard HUTTER ◽  
Christopher ONDER
Keyword(s):  
Natural Gas ◽  
Control Structure ◽  
Engine Performance ◽  
Combustion Stability ◽  
Performance Criteria ◽  
Transport Sector ◽  
Lean Burn ◽  
Fuel Ratio ◽  
Cng Engine ◽  
Lean Conditions

Natural gas is well-suited as a fuel in the transport sector. Due to its excellent combustion characteristics, engines operating with compressed natural gas (CNG) reach high efficiency, especially if operated at lean conditions. However, CNG engine research mainly focusses on stoichiometric conditions in order to use a three-way catalytic converter for the exhaust gas after treatment system. With the objective to explore the potential of CNG engines operated at lean conditions, a turbo-charged CNG engine with high com-pression ratio is developed and optimized for lean operation. In order to increase the ignition energy, the CNG engine is equipped with scavenged pre-chambers. A specific control structure is developed, which allows to operate the engine at a pre-defined (lean) air-to-fuel ratio. Further functionalities such as the combustion placement control and algorithms to estimate the conditions inside of the pre-chamber are implemented. The first part of this paper describes this engine control structure, which is specifically developed for the lean-burn CNG engine. In the second part, the effects of pre-chamber scavenging on engine performance criteria such as the combustion stability, engine efficiency or engine emissions are analyzed. With the objective to use pre-chamber scavenging to improve engine performance, a scavenging feed-back control strategy is proposed. In order to control the ignition delay, this strategy adapts the amount of CNG injected into the pre-chamber with a linear controller or an extremum seeking algorithm depending on the air-to-fuel ratio of the main chamber.

Extending the Lean Limit of Natural Gas Engines

2008 ◽  
Author(s):  
R. L. Evans
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Lean Burn ◽  
Stratified Charge ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Charge Mixture ◽  
Cyclic Variations ◽  
Lean Limit ◽  
The Stability

Two different methods to improve the thermal efficiency and reduce the emissions from lean-burn natural gas fuelled engines have been developed, and are described in this paper. One method used a “squish-jet” combustion chamber designed specifically to enhance turbulence generation, while the second method provided a partially stratified-charge mixture near the spark plug in order to enhance the ignition of lean mixtures of natural gas and air. The squish-jet combustion chamber was found to reduce Bsfc by up to 4.8% in a Ricardo Hydra engine, while the NOx – efficiency tradeoff was greatly improved in a Cummins L-10 engine. The partially stratified-charge combustion system extended the lean limit of operation in the Ricardo Hydra by some 10%, resulting in a 64% reduction in NOx emissions at the lean limit of operation. Both techniques were also shown to be effective in increasing the stability of combustion, thereby reducing cyclic variations in cylinder pressure.

Limits of compression ratio in spark-ignition combustion with methanol

2021 ◽  
pp. 146808742110433
Author(s):  
Christian Wouters ◽  
Patrick Burkardt ◽  
Stefan Pischinger
Keyword(s):  
Compression Ratio ◽  
Direct Injection ◽  
Spark Ignition ◽  
Combustion Stability ◽  
High Compression Ratio ◽  
Lean Burn ◽  
Promising Alternative ◽  
Excess Air ◽  
High Compression ◽  
Lean Limit

A shift toward a circular and [Formula: see text]-neutral world is required, in which rapid defossilization and lower emissions are realized. A promising alternative fuel that has gained traction is methanol, thanks to its favorable and clean-burning fuel properties as well as its ability to be produced in a carbon-neutral process. Especially methanol’s high knock resistance and its combustion stability offer the opportunity to operate an engine at both a high compression ratio and a high excess air dilution. Although methanol has been investigated in series-production engines for passenger car applications, there is a lack of investigations on a dedicated engine that can operate at methanol’s knock limit. In this paper, methanol’s knock limitation is experimentally assessed by applying high compression ratios to a direct injection spark-ignition single-cylinder research engine. To that end, four compression ratios were investigated: 10.8, 15.0, 17.7, and 20.6. With compression ratios of 15.0 and 17.7, the lean-limit was increased to excess air ratios of 2.0 and 2.1, respectively, compared to 1.7 at a compression ratio of 10.8. For the highest compression ratio of 20.6, the maximum lean burn limit was increased to an excess air ratio of 1.9 due to achieving the maximum cylinder pressure limit. Despite the minor increase in lean-limit, a maximum indicated efficiency of 48.7% was achieved with the highest compression ratio of 20.6. However, even at this high compression ratio, methanol did not show a knock limitation. The investigations in this work provide profound knowledge for future engine investigations with methanol.

Lean Limit Extension for High BMEP Gas Engines via Novel Electronic Ignition and Prechamber Plug: Higher Efficiency and Lower NOx in Open Chamber Engines

2011 ◽  
Author(s):  
Domenico Chiera ◽  
David Ahrens ◽  
Nolan Polley ◽  
David Petruska ◽  
Mike Riley ◽  
...  
Keyword(s):  
Natural Gas ◽  
High Performance ◽  
Fuel Efficiency ◽  
Combustion Stability ◽  
Ignition System ◽  
Trade Off ◽  
Spark Plug ◽  
Engine Knock ◽  
Lean Limit ◽  
Lean Conditions

Large bore natural gas engines have the perennial challenge to achieve ever higher efficiency with ever lower NOx emissions, while maintaining stable combustion, avoiding misfire and engine knock. A primary strategτy to achieve these goals is to run leaner and leaner. However, leaner mixtures lead to reduced combustion stability and the operating space between misfire and engine knock shrinks. Leaner operation requires a high performance ignition system. This report will highlight the fundamental challenges related to lean operation and the progress Woodward has made to create a novel high performance prechamber spark plug to achieve good combustion stability in a passive prechamber spark plug under lean conditions. The spark plug in combination with the appropriate ignition system enables faster and more stable combustion under increasingly lean conditions, improving fuel efficiency and emissions. Engine simulation modeling is used to demonstrate the benefits of lean gas mixtures and reduced combustion duration to enhance the NOx versus fuel consumption trade-off for a range of air fuel ratios. With this database available, a design requirements flow-down is performed such that combustion performance requirements can be specified a priori, which if met would ensure the high level engine emissions and performance targets would be met. With combustion requirements in hand, CFD simulations are used to identify the mechanisms by which flame propagation is improved with prechamber spark plugs in general, and by the Lean Quality Plug (WW-LQP) prechamber spark plug under development at Woodward. Experimental validation was carried out to confirm the benefits of lean operation and improvement of combustion stability (COV) on the NOx-efficiency trade-off. Operation with Woodward’s WW-LQP spark plug and IC1100 AC ignition system showed improved fuel efficiency at constant NOx on a high BMEP engine. Additionally, the enhanced stability and low COV of the WW-LQP enables extension of the natural gas lean limit closer to λ = 2.00 for an open chamber engine.

scholarly journals An Experimental Investigation on the Combustion and Emissions Performance of a Natural Gas–Diesel Dual Fuel Engine at Low and Medium Loads

2015 ◽  
Author(s):  
Hongsheng Guo ◽  
W. Stuart Neill ◽  
Brian Liko
Keyword(s):  
Carbon Monoxide ◽  
Particulate Matter ◽  
Natural Gas ◽  
Diesel Fuel ◽  
Fuel Combustion ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Dual Fuel ◽  
Particulate Matter Emissions ◽  
Dual Fuel Combustion

Natural gas is an abundant and inexpensive fuel in North America. It produces lower greenhouse gas emissions than diesel fuel when burned in an internal combustion engine. It is also considered to be a clean fuel because it generates lower particulate matter emissions than diesel fuel during combustion. In this study, an experimental study was conducted to investigate the combustion and emissions performance of a natural gas – diesel dual fuel engine at low and medium loads. A single cylinder direct injection diesel engine was modified to operate as the dual fuel engine. The diesel fuel was directly injected into the cylinder, while natural gas was injected into the intake port. The operating conditions, such as engine speed, load, intake temperature and pressure, were well controlled during the experiment. The effect of natural gas fraction on energy efficiency, cylinder pressure, exhaust temperature, and combustion stability were recorded and analyzed. The emissions data, including particulate matter, nitric oxides, carbon monoxide, and methane at various natural gas fractions and operating conditions were also analyzed. The results showed that natural gas – diesel dual fuel combustion slightly decreased brake thermal efficiency at low and medium load conditions and significantly reduced carbon dioxide and particulate matter emissions. Methane and NOx emissions increased in dual fuel combustion mode compared to diesel operation. The variation of carbon monoxide emissions in dual fuel mode depended on load and speed conditions.

Precombustion Chamber Design for Emissions Reduction From Large Bore NG Engines

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Dean J. Simpson ◽  
Daniel B. Olsen
Keyword(s):  
Natural Gas ◽  
Combustion Stability ◽  
Nozzle Geometry ◽  
Oxides Of Nitrogen ◽  
Lean Burn ◽  
Engine Operation ◽  
Chamber Volume ◽  
Fuel Delivery ◽  
Design Variables ◽  
Partial Load

Precombustion chambers (PCCs) are an ignition technology for large bore, natural gas engines, which can extend the lean operating limit through improved combustion stability. Previous research indicates that the PCC is responsible for a significant portion of engine-out emissions, especially near the lean limit of engine operation. In this work, six concept PCC designs are developed with the objective of reducing engine-out emissions, focusing on oxides of nitrogen (NOx). The design variables include chamber geometry, chamber volume, fuel delivery, nozzle geometry, and material thermal conductivity. The concepts are tested on a single cylinder of a large bore, two-stroke cycle, lean burn, natural gas compressor engine, and the results are compared with stock PCC performance. The pollutants of interest include NOx, carbon monoxide, total hydrocarbons, and volatile organic compounds (VOCs). The results indicate that PCC volume has the largest effect on the overall NOx–CO tradeoff. Multiple nozzles and electronic PCC fuel control were found to enhance main chamber combustion stability, particularly at partial load conditions. The PCC influence on VOCs was insignificant; rather, VOCs were found to be heavily dependent on fuel composition.

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