The effect of air/fuel ratio on the CO and NOx emissions for a twin-spark motorcycle gasoline engine under wide range of operating conditions

Natural gas/diesel dual fuel engines used in oil and gas drilling operations must be able to meet NOx emissions limits across a wide range of substitution percentage, which affects the air to natural gas ratio or gas lambda. In a dual fuel engine operating at high substitution, premixed, propagating natural gas flames occur and the NOx formed in such premixed flames is known to be a strong function of gas lambda. Consequently there is interest in understanding how NOx formation in a dual fuel engine is affected by gas lambda. However, NOx formation in a dual fuel engine is complicated by the interaction with the non-premixed diesel jet flame. As a result, previous studies have shown that enriching the air-fuel ratio can either increase or decrease NOx emissions depending on the operating conditions investigated. This study presents multi-dimensional combustion simulations of an air-fuel ratio sweep from gas lambda 2.0 to 1.5 at 80% substitution, which exhibited a minimum in NOx emissions at a natural gas lambda of 1.75. Images from the simulations are used to provide detailed explanations of the physical processes responsible for the minimum NOx trend with natural gas lambda.

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Ambient Condition Effects on NOx and CO Emissions From Process Heaters

Volume 3: Combustion Science and Engineering ◽

10.1115/imece2008-68284 ◽

2008 ◽

Author(s):

Wesley R. Bussman ◽

Charles E. Baukal

Keyword(s):

Atmospheric Pressure ◽

Ambient Air ◽

Operating Conditions ◽

Nox Emissions ◽

Ambient Conditions ◽

Fuel Gas ◽

Natural Draft ◽

Actual Operating ◽

Wide Range ◽

Pollution Emissions

Because process heaters are typically located outside, their operation is subject to the weather. Heaters are typically tuned at a given set of conditions; however, the actual operating conditions may vary dramatically from season to season and sometimes even within a given day. Wind, ambient air temperature, ambient air humidity, and atmospheric pressure can all significantly impact the O2 level, which impacts both the thermal efficiency and the pollution emissions from a process heater. Unfortunately, most natural draft process burners are manually controlled on an infrequent basis. This paper shows how changing ambient conditions can considerably impact both CO and NOx emissions if proper adjustments are not made as the ambient conditions change. Data will be presented for a wide range of operating conditions to show how much the CO and NOx emissions can be affected by changes in the ambient conditions for fuel gas fired natural draft process heaters, which are the most common type used in the hydrocarbon and petrochemical industries. Some type of automated burner control, which is virtually non-existent today in this application, is recommended to adjust for the variations in ambient conditions.

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A predictive combustion model for one-dimensional gasoline engine simulation

International Journal of Engine Research ◽

10.1177/1468087420945905 ◽

2020 ◽

pp. 146808742094590

Author(s):

Yoshihiro Nomura ◽

Seiji Yamamoto ◽

Makoto Nagaoka ◽

Stephan Diel ◽

Kenta Kurihara ◽

...

Keyword(s):

Gasoline Engine ◽

Early Stage ◽

Burning Velocity ◽

Turbulent Flame ◽

Operating Conditions ◽

Combustion Model ◽

One Dimensional ◽

Turbulent Reynolds Number ◽

Proposed Model ◽

Wide Range

A new predictive combustion model for a one-dimensional computational fluid dynamics tool in the multibody dynamics processes of gasoline engines was developed and validated. The model consists of (1) a turbulent burning velocity model featuring a flame radius–based transitional function, steady burning velocity that considers local quenching using the Karlovitz number and laminarization by turbulent Reynolds number, as well as turbulent flame thickness and its quenching model near the liner wall, and (2) a knock model featuring auto-ignition by the Livengood–Wu integration and ignition delay time obtained using a full-kinetic model. The proposed model and previous models were verified under a wide range of operating conditions using engines with widely different specifications. Good agreement was only obtained for combustion characteristics by the proposed model without requiring individual calibration of model constants. The model was also evaluated for utilization after prototyping. Improved accuracy, especially of ignition timing, was obtained after further calibration using a small amount of engine data. It was confirmed that the proposed model is highly accurate at the early stage of the engine development process, and is also applicable for engine calibration models that require higher accuracy.

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Unsteady Simulations of a Low NOx LDI Combustor for Environmentally Responsible Aviation Engines

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2015-43802 ◽

2015 ◽

Author(s):

Scott A. Drennan ◽

Gaurav Kumar ◽

Erlendur Steinthorsson ◽

Adel Mansour

Keyword(s):

Experimental Data ◽

Complex Geometry ◽

Mesh Refinement ◽

Operating Conditions ◽

Design Parameters ◽

Nox Emissions ◽

Fuel Injector ◽

Cfd Simulations ◽

Wide Range ◽

Environmentally Responsible

A key objective of NASA’s Environmentally Responsible Aviation (ERA) research program is to develop advanced technologies that enable 75% reduction of LTO NOx emissions of N+2 aviation gas turbine engines relative to the CAEP 6 standard. To meet this objective, a new advanced multi-point fuel injector was proposed and tested under the NASA ERA program. The new injector, called the three-zone injector, or 3ZI, uses fifteen spray cups arranged in three zones. Swirling air flows into each cup and fuel is introduced via pressure swirl atomizers within the cup. Multiple design parameters impact the performance of the injector, such as the location of the atomizer within the spray cup, the spray angle and cup-to-cup spacing. To fully understand the benefits and trade-offs of various injector design parameters and to optimize the performance of the injector, detailed CFD simulations are an essential tool. Furthermore, the CFD methodology must allow easy changes in design parameters and guarantee consistent and comparable accuracy from one design iteration to the next. This paper investigates the use of LES in reacting and non-reacting flows and compares against the NOx experimental data for the multi-point atomization strategy of the injector. The CFD simulations employ an automatically generated Cartesian cut-cell meshing approach with mesh refinement applied near complex geometry and spray regions. Adaptive Mesh Refinement (AMR) is used to refine mesh in regions of high gradients in velocity and temperature. The CFD simulations use boundary and operating conditions based on experimental data for air flow and spray atomization obtained from LDV and PDPA characterizations of the spray respectively. The results are extended to reacting flow using a detailed reaction mechanism and predictions of NOx emissions are compared to experimental data. Overall NOx predictions were consistently less than experimental values. However, the NOx prediction trends showed excellent agreement with experimental data across the wide range of equivalence ratios investigated.

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Air-fuel ratio and speed control for low emission vehicles based on sliding mode techniques

Proceedings of the Institution of Mechanical Engineers Part I Journal of Systems and Control Engineering ◽

10.1243/0959651021541480 ◽

2002 ◽

Vol 216 (2) ◽

pp. 117-124 ◽

Cited By ~ 5

Author(s):

P F Puleston ◽

G Monsees ◽

S K Spurgeon

Keyword(s):

Sliding Mode ◽

Speed Control ◽

Operating Conditions ◽

Robust Controller ◽

Automotive Engines ◽

Fuel Ratio ◽

Low Emission ◽

Wide Range ◽

Unknown Disturbances ◽

Set Up

This paper deals with the combined air-fuel ratio (AFR) and speed control of automotive engines. The robust controller is developed using dynamic sliding mode (SM) control design methods. The proposed controller set-up is tested under realistic operating conditions by means of computer simulation using a comprehensive non-linear model of a four-stroke engine, specifically provided by the automotive industry for these purposes. This accurate industrial model comprises extensive dynamics description and numerous look-up tables representing parameter characteristics obtained from experimental data. The SM controller set-up proves to be robust to model uncertainties and unknown disturbances, regulating effectively the engine speed for a wide range of set-points while maintaining the AFR at the stoichiometric value.

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A Study on the Performance of Combustion in a HCCI Engine Using n-Heptane by a Multi-Zone Model

ASME 2009 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2009-14117 ◽

2009 ◽

Cited By ~ 5

Author(s):

Hongsheng Guo ◽

Hailin Li ◽

W. Stuart Neill

Keyword(s):

Numerical Simulation ◽

Numerical Simulations ◽

Chemical Species ◽

Numerical Data ◽

Operating Conditions ◽

Zone Model ◽

Nox Emissions ◽

Hcci Engine ◽

Operation Conditions ◽

Wide Range

A study of n-heptane combustion in an HCCI engine was carried out by a multi-zone numerical simulation that covers a complete engine cycle. A reaction mechanism that includes 177 chemical species and 1638 reactions was used. The results of the numerical simulations were compared to existing experimental data for a range of air/fuel ratios, compression ratios and engine speeds. It is shown that the numerical simulation is able to reasonably capture the experimental cylinder pressure data over a wide range of operation conditions. It also provides a qualitative trend of CO emissions. The numerical simulation overpredicted the combustion at some operating conditions, such as at extremely high air/fuel ratios and higher engine speeds. Some differences were observed between the experimental and numerical data for NOX emissions. The numerical simulation predicted a monotonic decrease in NOX emissions as air/fuel ratio increased or compression ratio decreased, while an increase in NOX emissions was observed experimentally when combustion became very weak at extremely high air/fuel ratios or low compression ratios. It is suggested that further experiments and numerical simulations should be performed to explain this discrepancy.

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Optimization of Design and Operational Parameters Using Genetic Algorithm for a Spark Ignition Engine With CNG/H2 Mixtures

Energy Conversion and Resources ◽

10.1115/imece2005-82145 ◽

2005 ◽

Author(s):

G. Anand ◽

R. Balamurugan

Keyword(s):

Genetic Algorithm ◽

Spark Ignition ◽

Operating Conditions ◽

Spark Ignition Engine ◽

Nox Emissions ◽

Engine Fuel ◽

Operational Parameters ◽

Si Engine ◽

Engine Efficiency ◽

Wide Range

The present contribution describes the potential of using gaseous fuels like Hythane (CNG/H2 mixtures) as a spark ignition (SI) engine fuel. Genetic Algorithm (GA) is used to optimize the design and operational parameters of a CNG/H2 fueled spark ignition engine for maximizing the engine efficiency subjected to NOx emission constraint. This research deals with quasi-dimensional, two-zone thermodynamic simulation of four-stroke SI engine fueled with CNG/H2 blended fuel for the prediction of the combustion and emission characteristics. The validity of the model has been carried out by comparing the computed results with experimental data obtained under same engine setup and operating conditions. A wide range of engine parameters were optimized using a simple GA regarding both engine efficiency and NOx emissions. The five parameters chosen were compression ratio, engine speed, equivalence ratio, H2 fraction in the fuel, and spark plug position in cylinder head. The amount of NOx emissions was being kept under the constrained value of 750 ppm (< 5 g/kWh), which is less than permissible limit for heavy-duty engines.

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Lean Blowout Limits and NOx Emissions of Turbulent, Lean Premixed, Hydrogen-Enriched Methane/Air Flames at High Pressure

Volume 1: Combustion and Fuels, Education ◽

10.1115/gt2006-90490 ◽

2006 ◽

Cited By ~ 2

Author(s):

P. Griebel ◽

E. Boschek ◽

P. Jansohn

Keyword(s):

High Pressure ◽

Nox Reduction ◽

Flame Temperature ◽

Operating Conditions ◽

Flame Stability ◽

Nox Emissions ◽

Lean Blowout ◽

Wide Range ◽

Pure Methane ◽

Lean Premixed

Flame stability is a crucial issue in low NOx combustion systems operating at extremely lean conditions. Hydrogen enrichment seems to be a promising option to extend lean blowout limits of natural gas combustion. This experimental study addresses flame stability enhancement and NOx reduction in turbulent, high-pressure, lean premixed methane/air flames in a generic combustor, capable of a wide range of operating conditions. Lean blowout limits (LBO) and NOx emissions are presented for pressures up to 14 bars, bulk velocities in the range of 32–80 m/s, two different preheating temperatures (673 K, 773 K), and a range of fuel mixtures from pure methane to 20% H2/80% CH4 by volume. The influence of turbulence on LBO limits is discussed, too. In addition to the investigation of perfectly premixed H2-enriched flames, LBO and NOx are also discussed for hydrogen piloting. Experiments have revealed that a mixture of 20% hydrogen and 80% methane, by volume, can typically extend the lean blowout limit by roughly 10% compared to pure methane. The flame temperature at LBO is approximately 60 K lower resulting in the reduction of NOx concentration by ≈ 35% (0.5 → 0.3 ppm/15% O2).

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The NOx and N2O Emission Characteristics of an HCCI Engine Operated With n-Heptane

Journal of Energy Resources Technology ◽

10.1115/1.4005243 ◽

2011 ◽

Vol 134 (1) ◽

Cited By ~ 6

Author(s):

Hailin Li ◽

W. Stuart Neill ◽

Hongsheng Guo ◽

Wally Chippior

Keyword(s):

N2o Emission ◽

Combustion Efficiency ◽

Operating Conditions ◽

N2o Emissions ◽

Emission Characteristics ◽

Nox Emissions ◽

Oxides Of Nitrogen ◽

Incomplete Combustion ◽

Hcci Combustion ◽

Wide Range

This paper presents the oxides of nitrogen (NOx) and nitrous oxide (N2O) emission characteristics of a Cooperative Fuel Research (CFR) engine modified to operate in homogeneous charge compression ignition (HCCI) combustion mode. N-heptane was used as the fuel in this research. Several parameters were varied, including intake air temperature and pressure, air/fuel ratio (AFR), compression ratio (CR), and exhaust gas recirculation (EGR) rate, to alter the HCCI combustion phasing from an overly advanced condition where knocking occurred to an overly retarded condition where incomplete combustion occurred with excessive emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO). NOx emissions below 5 ppm were obtained over a fairly wide range of operating conditions, except when knocking or incomplete combustion occurred. The NOx emissions were relatively constant when the combustion phasing was within the acceptable range. NOx emissions increased substantially when the HCCI combustion phasing was retarded beyond the optimal phasing even though lower combustion temperatures were expected. The increased N2O and UHC emissions observed with retarded combustion phasing may contribute to this unexpected increase in NOx emissions. N2O emissions were generally less than 0.5 ppm; however, they increased substantially with excessively retarded and incomplete combustion. The highest measured N2O emissions were 1.7 ppm, which occurred when the combustion efficiency was approximately 70%.

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Prediction of NOx Emissions for a Range of Engine Hardware Configurations Using Artificial Neural Networks

ASME 2020 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2020-2911 ◽

2020 ◽

Author(s):

Nick Papaioannou ◽

XiaoHang Fang ◽

Felix Leach ◽

Martin H. Davy

Keyword(s):

Experimental Data ◽

Neural Networks ◽

Artificial Neural Networks ◽

Operating Conditions ◽

Data Accuracy ◽

Nox Emissions ◽

Ann Model ◽

Baseline Training ◽

Wide Range ◽

Artificial Neural

Abstract The predictive ability of artificial neural networks where a large number of experimental data are available, has been studied extensively. Studies have shown that ANN models are capable of accurately predicting NOx emissions from engines under various operating conditions and different fuel types when trained well. One of the major advantages of an ANN model is its ability to relearn when new experimental data is available, thus continuously improving its accuracy. The present work explored the potential of an ANN model to predict NOx emissions for various engine configurations outside its training envelop. This work also looked into quantifying the amount of new data required to improve the accuracy of the model when exposed to unknown conditions. The chosen ANN model was constructed using data from a high-speed direct injection diesel engine and is capable of accurate NOx emissions over a wide range of operating conditions. The optimized network utilized 14 input parameters and is using 6 neurons in a single hidden layer feed-forward neural network. Experimental data from the various engine configurations tested, were then used to predict NOx from the existing ANN model. The results indicate that when the new data are within the baseline training envelop, the ANN model is capable of accurate NOx prediction even when there are substantial changes in engine configuration such as piston material. Similar results were also observed when the injector nozzle is changed. However, the model’s performance drops significantly when new data, outside the baseline training envelop, were employed indicating that additional training is required. As such, various methods for retraining the ANN model were explored with the selected method showing the best compromise between new-data accuracy and old-data accuracy retention. The retrained ANN model developed was found to be an effective tool in predicting NOx emissions for different engine configurations and operating conditions.

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