Modeling of Formaldehyde Formation From Crevices in a Large Bore Natural Gas Engine

2007 ◽  
Author(s):  
Daniel B. Olsen ◽  
Ryan K. Palmer ◽  
Charles E. Mitchell
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Gas ◽  
Kinetic Modeling ◽  
The United States ◽  
Chemical Kinetic ◽  
Formation Mechanisms ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine

Formaldehyde emissions from stationary natural gas engines are regulated in the United States, as mandated by the 1990 Clean Air Act Amendments. This work aims to advance the understanding of formaldehyde formation in large bore (>36 cm) natural gas engines. Formaldehyde formation in a large bore natural gas engine is modeled utilizing computational fluid dynamics and chemical kinetics. The top land crevice volume is believed to play an important role in the formation mechanisms of engine-out formaldehyde. This work focuses specifically on the top land crevice volume in the Cooper-Bessemer LSVB large bore 4-stroke cycle natural gas engine. Chemical kinetic modeling predicts that the top land crevice volume is responsible for the formation of 22 ppm of engine-out formaldehyde. Based on a raw exhaust concentration of 80 ppm, this constitutes about 27% of engine-out formaldehyde. Simplifying assumptions made for the chemical kinetic modeling are validated using computational fluid dynamics. Computational fluid dynamic analysis provided confirmation of crevice volume mass discharge timing. It also provided detailed pressure, temperature and velocity profiles within the top land crevice volume at various crank angle degrees.

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.

The influence of the enrichment injection angle on the performance of a pre-chamber spark ignition natural-gas engine

2017 ◽  
Vol 232 (5) ◽  
pp. 679-694 ◽  
Author(s):  
Liyan Feng ◽  
Jun Zhai ◽  
Chuang Qu ◽  
Bo Li ◽  
Jiangping Tian ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Gas ◽  
Nitrogen Oxide ◽  
Spark Ignition ◽  
Nitrogen Oxide Emissions ◽  
Mixture Formation ◽  
Injection Angle ◽  
Gas Engine ◽  
Natural Gas Engine

Using an enriched pre-chamber is an effective way to extend the lean limit, to reduce the nitrogen oxide emissions and to avoid abnormal combustion in spark ignition natural-gas engines. Enrichment injection in the pre-chamber of a spark ignition natural-gas engine determines the flow field and the fuel–air mixture formation quality in the pre-chamber and has a profound influence on the combustion performance of the engine. In order to study the characteristics of enrichment injection in the pre-chamber of a natural-gas engine, two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics calculations were carried out. The influence of the enrichment injection angle on the engine performance was investigated with the aid of a computational fluid dynamics simulation tool. The results indicate that a change in the enrichment injection angle directly affects the gas motion, the fuel–air mixture formation, the flame propagation and the formation of nitrogen oxides in the pre-chamber and further influences the penetration of the flame jets, the combustion temperature distribution and the formation of nitrogen oxides in the main chamber. There is an optimal injection angle for this research engine. Of the four injection angles that were investigated, an injection angle of 14° results in the lowest nitrogen oxide emissions.

Railplug Design Optimization to Improve Large-Bore Natural Gas Engine Performance

2005 ◽  
Author(s):  
Hongxun Gao ◽  
Matt J. Hall ◽  
Ofodike A. Ezekoye ◽  
Ron D. Matthews
Keyword(s):  
Natural Gas ◽  
High Energy ◽  
Parameter Study ◽  
Transfer Model ◽  
High Speed Photography ◽  
Discharge Process ◽  
Ignition System ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine

It is a very challenging problem to reliably ignite extremely lean mixtures, especially for the low speed, high load conditions of stationary large-bore natural gas engines. If these engines are to be used for the distributed power generation market, it will require operation with higher boost pressures and even leaner mixtures. Both place greater demands on the ignition system. The railplug is a very promising ignition system for lean burn natural gas engines with its high-energy deposition and high velocity plasma jet. High-speed photography was used to study the discharge process. A heat transfer model is proposed to aid the railplug design. A parameter study was performed both in a constant volume bomb and in an operating natural gas engine to improve and optimize the railplug designs. The engine test results show that the newly designed railplugs can ensure the ignition of very lean natural gas mixtures and extend the lean stability limit significantly. The new railplug designs also improve durability.

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.

The scavenging timing of pre-chamber on the performance of a natural gas engine

2020 ◽  
pp. 146808742096087
Author(s):  
Xue Yang ◽  
Yong Cheng ◽  
Pengcheng Wang
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Injection System ◽  
Maximum Pressure ◽  
Ignition Process ◽  
Main Chamber ◽  
Ignition Timing ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine

The pre-chamber ignition system scavenged with natural gas can effectively improve the in-cylinder combustion process and extend the lean-burn limit of natural gas engines. The scavenging process affects the flow field and fuel-air mixture concentration distribution in the pre-chamber and affects the combustion process in the pre-chamber as well as the ignition process in the main chamber. This has a significant influence on the performance of natural gas engines. It is supposed that the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing affects the combustion process in the pre-chamber. To verify this suppose, an independent injection system for injecting natural gas into the pre-chamber is designed and experiments are carried out on a single-cylinder natural gas engine. The ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing is adjusted by changing the injection start angle of the scavenging process. The combustion process in the pre-chamber and the main chamber are analyzed using the in-cylinder pressures. The results indicate that, with the delay of the injection start angle, the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing increases, the combustion process in the pre-chamber is enhanced, the maximum pressure difference between two chambers increases and appears earlier. The energy of the hot jets and the penetration of the jets increase, which enhances the combustion process in the main chamber.

The Effect of Parametric Variations on Formaldehyde Emissions From a Large Bore Natural Gas Engine

2002 ◽  
Author(s):  
Daniel B. Olsen ◽  
Bryan D. Willson
Keyword(s):  
Natural Gas ◽  
Environmental Protection Agency ◽  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Air Pollutant ◽  
Formation Mechanisms ◽  
Combustion Engines ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Hazardous Air Pollutant

Formaldehyde is a hazardous air pollutant (HAP) that is typically emitted from natural gas-fired internal combustion engines as a product of incomplete combustion. The US Environmental Protection Agency (EPA) is currently developing national emission standards to regulate HAP emissions, including formaldehyde, from stationary reciprocating internal combustion engines under Title III of the 1990 Clean Air Act Amendments. This work investigates the effect that variations of engine operating parameters have on formaldehyde emissions from a large bore natural gas engine. The subject engine is a Cooper-Bessemer GMV-4TF two-stroke cycle engine with a 14″ (36 cm) bore and a 14″ (36 cm) stroke. Engine parameter variations investigated include load, boost, ignition timing, inlet air humidity ratio, air manifold temperature, jacket water temperature, prechamber fuel supply pressure, exhaust backpressure, and speed. The data analysis and interpretation is performed with reference to possible formaldehyde formation mechanisms and in-cylinder phenomena.

Laser Ignition of Natural Gas Engines Using Fiber Delivery

2005 ◽  
Author(s):  
Azer P. Yalin ◽  
Morgan W. Defoort ◽  
Sachin Joshi ◽  
Daniel Olsen ◽  
Bryan Willson ◽  
...  
Keyword(s):  
Natural Gas ◽  
Past Research ◽  
Spark Ignition ◽  
Laser Source ◽  
Laser Ignition ◽  
Ignition System ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Design Concepts

A practical impediment to implementation of laser ignition systems has been the open-path beam delivery used in past research. In this contribution, we present the development and implementation of a fiber-optically delivery laser spark ignition system. To our knowledge, the work represents the first demonstration of fiber coupled laser ignition (using a remote laser source) of a natural gas engine. A Nd:YAG laser is used as the energy source and a coated hollow fiber is used for beam energy delivery. The system was implemented on a single-cylinder of a Waukesha VGF 18 turbo charged natural gas engine and yielded consistent and reliable ignition. In addition to presenting the design and testing of the fiber delivered laser ignition system, we present initial design concepts for a multiplexer to ignite multiple cylinders using a single laser source, and integrated optical diagnostic approaches to monitor the spark ignition and combustion performance.

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