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.

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.

Evaluation of Spark Plug and Timing Configurations on the Fuel Consumption, Combustion Stability, and Emissions of a Large-Bore, Two-Stroke, Natural Gas Engine

2016 ◽  
Author(s):  
Derek Johnson ◽  
Marc Besch ◽  
Nathaniel Fowler ◽  
Robert Heltzel ◽  
April Covington
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Combustion Engine ◽  
Engine Performance ◽  
Combustion Stability ◽  
Oxides Of Nitrogen ◽  
Natural Gas Engines ◽  
Fuel Delivery ◽  
Spark Plug ◽  
Trade Offs

Emissions compliance is a driving factor for internal combustion engine research pertaining to both new and old technologies. New standards and compliance requirements for off-road spark ignited engines are currently under review and include greenhouse gases. To continue operation of legacy natural gas engines, research is required to increase or maintain engine efficiency, while reducing emissions of carbon monoxide, oxides of nitrogen, and volatile organic compounds such as formaldehyde. A variety of technologies can be found on legacy, large-bore natural gas engines that allow them to meet current emissions standards — these include exhaust after-treatment, advanced ignition technologies, and fuel delivery methods. The natural gas industry uses a variety of spark plugs and tuning methods to improve engine performance or decrease emissions of existing engines. The focus of this study was to examine the effects of various spark plug configurations along with spark timing to examine any potential benefits. Spark plugs with varied electrode diameter, number of ground electrodes, and heat ranges were evaluated against efficiency and exhaust emissions. Combustion analyses were also conducted to examine peak firing pressure, location of peak firing pressure, and indicated mean effective pressure. The test platform was an AJAX-E42 engine. The engine has a bore and stroke of 0.216 × 0.254 meters (m), respectively. The engine displacement was 9.29 liters (L) with a compression ratio of 6:1. The engine was modified to include electronic spark plug timing capabilities along with a mass flow controller to ensure accurate fuel delivery. Each spark plug configuration was examined at ignition timings of 17, 14, 11, 8, and 5 crank angle degrees before top dead center. The various configurations were examined to identify optimal conditions for each plug comparing trade-offs among brake specific fuel consumption, oxides of nitrogen, methane, formaldehyde, and combustion stability.

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.

Combustion Characteristics of a Dual Fuel Diesel Engine With Natural Gas (Influence of Cetane Number of Ignition Fuel)

2011 ◽  
Author(s):  
Yasufumi Yoshimoto ◽  
Eiji Kinoshita
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Cetane Number ◽  
Engine Performance ◽  
Mean Value ◽  
Combustion Characteristics ◽  
Combustion Stability ◽  
Dual Fuel ◽  
Gas Oil ◽  
Performance And Emission

This paper investigates the performance, exhaust emissions, and combustion characteristics of a dual fuel diesel engine fueled by CNG (compressed natural gas) as the main fuel. The experiments used standard ignition fuels prepared by n-hexadecane and heptamethylnonane which are used to define the ignitability of diesel combustion, and focused on the effects of fuels with better ignitability than ordinary gas oil such as fuels with higher cetane numbers, 70 and 100. Compared with gas oil ignition, a standard ignition fuel with C.N. 100 showed shorter ignition delays, and lower NOx exhaust concentrations, and engine noise. The results also showed that regardless of ignition fuel, misfiring occurred when the CNG supply was above 75%. While the CNG ratio where misfiring occurs lowered somewhat with increasing C.N., the combustion stability (defined as the standard deviation in the cycle to cycle variation of IMEP divided by the mean value of IMEP) was little influenced. In summary, the results show that the influence of the ignitability on the engine performance and emission characteristics of the dual fuel operation is relatively small when the ignition fuel has C.N., and similar to or higher than ordinary gas oil.

Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines

2004 ◽  
Author(s):  
Chamila A. Tissera ◽  
Matt M. Swartz ◽  
Emre Tatli ◽  
Ramprabhu Vellaisamy ◽  
Nigel N. Clark ◽  
...  
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Injection System ◽  
Lean Burn ◽  
Desorption Process ◽  
Gas Engine ◽  
No Conversion ◽  
Natural Gas Engine ◽  
Fuel Ratio ◽  
Conversion Rates

NOx control in a lean burn natural gas engine is typically achieved with appropriate management of air/fuel ratio and ignition timing. A novel approach for further reduction involves the capture of NOx by first adsorbing the NOx from the exhaust stream, followed by the periodic desorption of NOx from an aftertreatment medium. Then, by passing the desorbed NOx gas into the intake air stream and back through the engine, a percentage of the NOx will be converted to harmless gases during the combustion process. The objective of this paper is to report the NOx conversion phenomenon during a lean combustion process. The results of this testing will be used to develop an optimal system for the conversion of NOx with a NOx adsorber. A 1993 Cummins L10-G spark ignited natural gas engine was used to conduct the experiments. Commercially available nitric oxide (NO, 98.8% purity) was injected into the engine intake to mimic the NOx stream from the desorption process to obtain NO conversion rates at various steady-state engine operating points. The NO injection system was capable of injecting NO at varying flow rates and time intervals. NO was injected into the intake manifold for ten and twenty second periods, and the conversion rates were calculated. When the injected NO amount increased from 0.22 g/s to 1.2 g/s and engine loads varied from 200ft-lb to 400ft-lb at 800 RPM, the NO conversion rates increased from 5% to 47%. It was observed that the air/fuel ratio, injected NO quantity and the engine load greatly effected the NO conversion rates. It was also noted that engine speed had a negligible affect when the intake NO concentration was held constant.

scholarly journals Stochastic Air-Fuel Ratio Control of Compressed Natural Gas Engines Using State Observer

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Jun Yang ◽  
Jian Wang ◽  
Xuesheng Zhou ◽  
Yanxiao Li
Keyword(s):  
Natural Gas ◽  
State Observer ◽  
Disturbance Attenuation ◽  
Accuracy Control ◽  
Compressed Natural Gas ◽  
Natural Gas Engines ◽  
Fuel Ratio ◽  
Cng Engine ◽  
Residual Gas ◽  
Engine Dynamic

In this paper, the air-fuel ratio regulation problem of compressed natural gas (CNG) engines considering stochastic L2 disturbance attenuation is researched. A state observer is designed to overcome the unmeasurability of the total air mass and total fuel mass in the cylinder, since the residual air and residual fuel that are included in the residual gas are unmeasured and the residual gas reflects stochasticity. With the proposed state observer, a stochastic robust air-fuel ratio regulator is proposed by using a CNG engine dynamic model to attenuate the uncertain cyclic fluctuation of the fresh air, and the augmented closed-loop system is mean-square stable. A validation of the proposed stochastic robust air-fuel ratio regulator is carried out by the numerical simulation of two working conditions. The accuracy control of the air-fuel ratio is realized by the proposed stochastic robust air-fuel ratio regulator, which in turn leads to an improvement in fuel economy and emission performance of the CNG engines.

Performance Characterization of Alternative Ignition Systems Using Optical Tools in Natural Gas Engines

2018 ◽  
Author(s):  
Bipin Bihari ◽  
Munidhar S. Biruduganti ◽  
Roberto Torelli ◽  
Dan Singleton
Keyword(s):  
Natural Gas ◽  
Engine Performance ◽  
Lean Burn ◽  
Natural Gas Engines ◽  
Reciprocating Engine ◽  
Optical Tools ◽  
Discharge Ignition ◽  
Performance And Emissions ◽  
Engine Performance And Emissions

Lean-burn combustion dominates the current reciprocating engine R&D efforts due to its inherent benefits of high BTE and low emissions. The ever-increasing push for high power densities necessitates high boost pressures. Therefore, the reliability and durability of ignition systems face greater challenges. In this study, four ignition systems, namely, stock Capacitive discharge ignition (CDI), Laser ignition, Flame jet ignition (FJI), and Nano-pulse delivery (NPD) ignition were tested using a single cylinder natural gas engine. Engine performance and emissions characteristics are presented highlighting the benefits and limitations of respective ignition systems. Optical tools enabled delving into the ignition delay period and assisted with some characterization of the spark and its impact on subsequent processes. It is evident that advanced ignition systems such as Lasers, Flame-jets and Nano-pulse delivery enable extension of the lean ignition limits of fuel/air mixtures compared to base CDI system.

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.

A Reduced Chemical Kinetic Mechanism for CFD Simulations of High BMEP, Lean-Burn Natural Gas Engines

2012 ◽  
Author(s):  
David Martinez-Morett ◽  
Luigi Tozzi ◽  
Anthony J. Marchese
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Chemical Kinetic ◽  
Cfd Simulations ◽  
Lean Burn ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Kinetic Mechanisms ◽  
Lean Conditions

Recent developments in numerical techniques and computational processing power now permit time-dependent, multi-dimensional computational fluid dynamic (CFD) calculations with reduced chemical kinetic mechanisms (approx. 20 species and 100 reactions). Such computations have the potential to be highly effective tools for designing lean-burn, high BMEP natural gas engines that achieve high fuel efficiency and low emissions. Specifically, these CFD simulations can provide the analytical tools required to design highly optimized natural gas engine components such as pistons, intake ports, precombustion chambers, fuel systems and ignition systems. To accurately model the transient, multi-dimensional chemically reacting flows present in these systems, chemical kinetic mechanisms are needed that accurately reproduce measured combustion data at high pressures and lean conditions, but are of sufficient size to enable reasonable computational times. Presently these CFD models cannot be used as accurate design tools for application in high BMEP lean-burn gas engines because existing detailed and reduced mechanisms fail to accurately reproduce experimental flame speed and ignition delay data for natural gas at high pressure (40 atm and higher) and lean (0.6 equivalence ratio (ϕ) and lower) conditions. Existing methane oxidation mechanisms have typically been validated with experimental conditions at atmospheric and intermediate pressures (1 to 20 atm) and relatively rich stoichiometry. These kinetic mechanisms are not adequate for CFD simulation of natural gas combustion in which elevated pressures and very lean conditions are typical. This paper provides an analysis, based on experimental data, of the laminar flame speed computed from numerous, detailed chemical kinetic mechanisms for methane combustion at pressures and equivalence ratios necessary for accurate high BMEP, lean-burn natural gas engine modeling. A reduced mechanism that was shown previously to best match data at moderately lean and high pressure conditions was updated for the conditions of interest by performing sensitivity analysis using CHEMKIN. The reaction rate constants from the most sensitive reactions were appropriately adjusted in order to obtain a better agreement at high pressure lean conditions. An evaluation of this adjusted mechanism, “MD19”, was performed using Converge CFD software. The results were compared to engine data and a remarkable improvement on combustion performance prediction was obtained with the MD19 mechanism.

Sign in / Sign up

Export Citation Format

Share Document