A computational and experimental study of combustion chamber deposit effects on NOx emissions

W. M. Studzinski, P. M. Liiva, P. J. Choate, W. P. Acker, Thomas Litzinger, S. Bower, M. Smooke, K. Brezinsky

Research output: Contribution to conferencePaper

10 Citations (Scopus)

Abstract

The oxides of nitrogen (NOx) produced during combustion in an automobile engine play a major role in atmospheric chemistry and therefore need to be reduced by modifying vehicle engine designs and fuels of tomorrow. In a combustion chamber of a spark ignited engine, NOx is formed as atmospheric nitrogen competes with fuel molecules to couple with oxygen in the extremely hot burned gases behind the proceeding flame front (Zeldovich type) and as reactions occur directly in the combustion flame zone ("prompt" type). Since little nitrogen is present in the fuel, the fuel contribution to the overall NOx emissions is minor. Certain combustion chamber deposits have been shown to increase NOx emissions by thermally insulating the combustion chamber and taking up chamber volume, thus slightly increasing the compression ratio of the engine and raising the combustion gas temperature. For the Zeldovich NO production mechanisms, the reaction rates increase rapidly as the combustion temperature increases and therefore NO production is significantly larger at higher temperatures. For example, increasing the bulk gas temperature by 2.5%, from 2000°K to 2050°K, increases the NO produced by over 44%. The dependence of prompt NO production on temperature is more complicated because of the large number of intermediate reactions involving hydrocarbon free radicals. A perfectly stirred reactor (PSR) computer model and a thermodynamic engine model have been utilized to study the temperature dependence of NOx formation and deposit effects on temperature. The PSR model developed was run to investigate the oxidation mechanisms of toluene, isooctane and methane as neat hydrocarbon fuels with varying levels of beat transfer to the cylinder wall to simulate thermal insulation due to deposits. The results indicate that the prompt mechanisms play a significant role in the production of NOx, primarily at the lower end of the temperature range which is sufficiently high to produce NOx and that changes in fuel chemistry affect the NOx production rates. The modeled NOx emissions however, are primarily a function of the Zeldovich mechanisms and a given combustion temperature. Empirical results from a GM 2.0L dynamometer test stand show substantial increases in NOx levels for the test fuels pure isooctane and a 50/50 mix of isooctane and toluene at several test conditions when operating with combustion chamber deposits built with a deposit build-up cycle versus a clean combustion chamber. Using a combination of theoretical calculations, model predictions and empirical validations, a relationship between combustion chamber deposits and NOx emissions is demonstrated and investigated.

Original languageEnglish (US)
DOIs
StatePublished - Dec 1 1993
EventFall Fuels and Lubricants Meeting and Exposition - Philadelphia, PA, United States
Duration: Oct 18 1993Oct 21 1993

Other

OtherFall Fuels and Lubricants Meeting and Exposition
CountryUnited States
CityPhiladelphia, PA
Period10/18/9310/21/93

Fingerprint

Combustion chambers
Deposits
Temperature
Engines
Nitrogen
Toluene
Hydrocarbons
Gases
Atmospheric chemistry
Automobile engines
Compression ratio (machinery)
Reaction intermediates
Dynamometers
Thermal insulation
Engine cylinders
Free radicals
Electric sparks
Reaction rates
Methane
Thermodynamics

All Science Journal Classification (ASJC) codes

  • Automotive Engineering
  • Safety, Risk, Reliability and Quality
  • Pollution
  • Industrial and Manufacturing Engineering

Cite this

Studzinski, W. M., Liiva, P. M., Choate, P. J., Acker, W. P., Litzinger, T., Bower, S., ... Brezinsky, K. (1993). A computational and experimental study of combustion chamber deposit effects on NOx emissions. Paper presented at Fall Fuels and Lubricants Meeting and Exposition, Philadelphia, PA, United States. https://doi.org/10.4271/932815
Studzinski, W. M. ; Liiva, P. M. ; Choate, P. J. ; Acker, W. P. ; Litzinger, Thomas ; Bower, S. ; Smooke, M. ; Brezinsky, K. / A computational and experimental study of combustion chamber deposit effects on NOx emissions. Paper presented at Fall Fuels and Lubricants Meeting and Exposition, Philadelphia, PA, United States.
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abstract = "The oxides of nitrogen (NOx) produced during combustion in an automobile engine play a major role in atmospheric chemistry and therefore need to be reduced by modifying vehicle engine designs and fuels of tomorrow. In a combustion chamber of a spark ignited engine, NOx is formed as atmospheric nitrogen competes with fuel molecules to couple with oxygen in the extremely hot burned gases behind the proceeding flame front (Zeldovich type) and as reactions occur directly in the combustion flame zone ({"}prompt{"} type). Since little nitrogen is present in the fuel, the fuel contribution to the overall NOx emissions is minor. Certain combustion chamber deposits have been shown to increase NOx emissions by thermally insulating the combustion chamber and taking up chamber volume, thus slightly increasing the compression ratio of the engine and raising the combustion gas temperature. For the Zeldovich NO production mechanisms, the reaction rates increase rapidly as the combustion temperature increases and therefore NO production is significantly larger at higher temperatures. For example, increasing the bulk gas temperature by 2.5{\%}, from 2000°K to 2050°K, increases the NO produced by over 44{\%}. The dependence of prompt NO production on temperature is more complicated because of the large number of intermediate reactions involving hydrocarbon free radicals. A perfectly stirred reactor (PSR) computer model and a thermodynamic engine model have been utilized to study the temperature dependence of NOx formation and deposit effects on temperature. The PSR model developed was run to investigate the oxidation mechanisms of toluene, isooctane and methane as neat hydrocarbon fuels with varying levels of beat transfer to the cylinder wall to simulate thermal insulation due to deposits. The results indicate that the prompt mechanisms play a significant role in the production of NOx, primarily at the lower end of the temperature range which is sufficiently high to produce NOx and that changes in fuel chemistry affect the NOx production rates. The modeled NOx emissions however, are primarily a function of the Zeldovich mechanisms and a given combustion temperature. Empirical results from a GM 2.0L dynamometer test stand show substantial increases in NOx levels for the test fuels pure isooctane and a 50/50 mix of isooctane and toluene at several test conditions when operating with combustion chamber deposits built with a deposit build-up cycle versus a clean combustion chamber. Using a combination of theoretical calculations, model predictions and empirical validations, a relationship between combustion chamber deposits and NOx emissions is demonstrated and investigated.",
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Studzinski, WM, Liiva, PM, Choate, PJ, Acker, WP, Litzinger, T, Bower, S, Smooke, M & Brezinsky, K 1993, 'A computational and experimental study of combustion chamber deposit effects on NOx emissions' Paper presented at Fall Fuels and Lubricants Meeting and Exposition, Philadelphia, PA, United States, 10/18/93 - 10/21/93, . https://doi.org/10.4271/932815

A computational and experimental study of combustion chamber deposit effects on NOx emissions. / Studzinski, W. M.; Liiva, P. M.; Choate, P. J.; Acker, W. P.; Litzinger, Thomas; Bower, S.; Smooke, M.; Brezinsky, K.

1993. Paper presented at Fall Fuels and Lubricants Meeting and Exposition, Philadelphia, PA, United States.

Research output: Contribution to conferencePaper

TY - CONF

T1 - A computational and experimental study of combustion chamber deposit effects on NOx emissions

AU - Studzinski, W. M.

AU - Liiva, P. M.

AU - Choate, P. J.

AU - Acker, W. P.

AU - Litzinger, Thomas

AU - Bower, S.

AU - Smooke, M.

AU - Brezinsky, K.

PY - 1993/12/1

Y1 - 1993/12/1

N2 - The oxides of nitrogen (NOx) produced during combustion in an automobile engine play a major role in atmospheric chemistry and therefore need to be reduced by modifying vehicle engine designs and fuels of tomorrow. In a combustion chamber of a spark ignited engine, NOx is formed as atmospheric nitrogen competes with fuel molecules to couple with oxygen in the extremely hot burned gases behind the proceeding flame front (Zeldovich type) and as reactions occur directly in the combustion flame zone ("prompt" type). Since little nitrogen is present in the fuel, the fuel contribution to the overall NOx emissions is minor. Certain combustion chamber deposits have been shown to increase NOx emissions by thermally insulating the combustion chamber and taking up chamber volume, thus slightly increasing the compression ratio of the engine and raising the combustion gas temperature. For the Zeldovich NO production mechanisms, the reaction rates increase rapidly as the combustion temperature increases and therefore NO production is significantly larger at higher temperatures. For example, increasing the bulk gas temperature by 2.5%, from 2000°K to 2050°K, increases the NO produced by over 44%. The dependence of prompt NO production on temperature is more complicated because of the large number of intermediate reactions involving hydrocarbon free radicals. A perfectly stirred reactor (PSR) computer model and a thermodynamic engine model have been utilized to study the temperature dependence of NOx formation and deposit effects on temperature. The PSR model developed was run to investigate the oxidation mechanisms of toluene, isooctane and methane as neat hydrocarbon fuels with varying levels of beat transfer to the cylinder wall to simulate thermal insulation due to deposits. The results indicate that the prompt mechanisms play a significant role in the production of NOx, primarily at the lower end of the temperature range which is sufficiently high to produce NOx and that changes in fuel chemistry affect the NOx production rates. The modeled NOx emissions however, are primarily a function of the Zeldovich mechanisms and a given combustion temperature. Empirical results from a GM 2.0L dynamometer test stand show substantial increases in NOx levels for the test fuels pure isooctane and a 50/50 mix of isooctane and toluene at several test conditions when operating with combustion chamber deposits built with a deposit build-up cycle versus a clean combustion chamber. Using a combination of theoretical calculations, model predictions and empirical validations, a relationship between combustion chamber deposits and NOx emissions is demonstrated and investigated.

AB - The oxides of nitrogen (NOx) produced during combustion in an automobile engine play a major role in atmospheric chemistry and therefore need to be reduced by modifying vehicle engine designs and fuels of tomorrow. In a combustion chamber of a spark ignited engine, NOx is formed as atmospheric nitrogen competes with fuel molecules to couple with oxygen in the extremely hot burned gases behind the proceeding flame front (Zeldovich type) and as reactions occur directly in the combustion flame zone ("prompt" type). Since little nitrogen is present in the fuel, the fuel contribution to the overall NOx emissions is minor. Certain combustion chamber deposits have been shown to increase NOx emissions by thermally insulating the combustion chamber and taking up chamber volume, thus slightly increasing the compression ratio of the engine and raising the combustion gas temperature. For the Zeldovich NO production mechanisms, the reaction rates increase rapidly as the combustion temperature increases and therefore NO production is significantly larger at higher temperatures. For example, increasing the bulk gas temperature by 2.5%, from 2000°K to 2050°K, increases the NO produced by over 44%. The dependence of prompt NO production on temperature is more complicated because of the large number of intermediate reactions involving hydrocarbon free radicals. A perfectly stirred reactor (PSR) computer model and a thermodynamic engine model have been utilized to study the temperature dependence of NOx formation and deposit effects on temperature. The PSR model developed was run to investigate the oxidation mechanisms of toluene, isooctane and methane as neat hydrocarbon fuels with varying levels of beat transfer to the cylinder wall to simulate thermal insulation due to deposits. The results indicate that the prompt mechanisms play a significant role in the production of NOx, primarily at the lower end of the temperature range which is sufficiently high to produce NOx and that changes in fuel chemistry affect the NOx production rates. The modeled NOx emissions however, are primarily a function of the Zeldovich mechanisms and a given combustion temperature. Empirical results from a GM 2.0L dynamometer test stand show substantial increases in NOx levels for the test fuels pure isooctane and a 50/50 mix of isooctane and toluene at several test conditions when operating with combustion chamber deposits built with a deposit build-up cycle versus a clean combustion chamber. Using a combination of theoretical calculations, model predictions and empirical validations, a relationship between combustion chamber deposits and NOx emissions is demonstrated and investigated.

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Studzinski WM, Liiva PM, Choate PJ, Acker WP, Litzinger T, Bower S et al. A computational and experimental study of combustion chamber deposit effects on NOx emissions. 1993. Paper presented at Fall Fuels and Lubricants Meeting and Exposition, Philadelphia, PA, United States. https://doi.org/10.4271/932815