+44 (0)1509 263171
Please use this identifier to cite or link to this item:
|Title: ||An experimental and theoretical study into nitric oxide production at elevated pressures and temperatures|
|Authors: ||Woolridge, Stephanie|
|Issue Date: ||2007|
|Publisher: ||© Stephanie Woolridge|
|Abstract: ||An investigation has been carried out into the formation of nitric oxide in high pressure
combustion environments. Experiments have been conducted using a constant volume
combustion bomb, which enabled the effect of pressure to be decoupled from the effect of
temperature. Experiments have also been performed using a single cylinder spark-ignition
engine to provide data for comparison. A thermodynamic and multi-reaction chemical
kinetics model has been developed to calculate burned gas temperatures and NO
concentrations. The model has been used to assess the effects of thermochemical data,
kinetic rate data, radical concentrations and various chemical reactions on predicted NO
concentrations, and the results have been compared to measured NO data.
A search of the literature revealed that existing models describing NO formation in engines
often fail to predict measured concentrations of NO, especially under high load conditions.
Although the effect of pressure on NO formation has previously been subject to theoretical
study, the mechanisms of NO formation at high pressure remain subject to uncertainty and
in some cases empirical modifications to theoretical data have been used to obtain
agreement with experimental results.
The combustion bomb experimental results showed clear evidence that an increase in
pressure causes a decrease in NO concentrations under lean conditions. However, this
effect was not observed in the engine owing to the high temperatures that were generated
under high load conditions. It was found that the pressure effect was less significant under
stoichiometric and rich conditions in the combustion bomb.
The model showed that the commonly-used extended Zeldovich mechanism was unable to
accurately predict NO concentrations in non-stoichiometric conditions in either the bomb or
the engine. It was found that the time evolution of temperature had a significant effect on
calculated NO emissions, with high temperatures at the end of combustion generating
much higher NO concentrations than high temperatures earlier in the combustion process.
An existing comprehensive model of NO kinetics, the super-extended Zeldovich mechanism,
has been subject to a sensitivity study which found that only a small number of reactions
play a significant role in NO formation and destruction under the conditions tested here.
calculations showed that reactions involving N02 made a significant contribution to NO
formation and destruction under lean conditions, and accurately predicted NO
concentrations under lean conditions in the bomb. However, the same reactions were found
to accelerate NO formation in the engine.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Mechanical, Electrical and Manufacturing Engineering)|
Files associated with this item:
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.