Use this URL to cite or link to this record in EThOS:
Title: Modelling of an automotive natural gas engine for A/F control investigations
Author: Thomas, Alister Julian
ISNI:       0000 0001 3517 3057
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1995
Availability of Full Text:
Access from EThOS:
Access from Institution:
In this thesis, the problem of A/F ratio control in a natural gas, internal combustion engine is addressed, with the global objective of reducing exhaust emission pollutants. A review of some mechanical approaches to exhaust pollutant reduction are assessed. It is found that many techniques aid the reduction of exhaust pollutants, but the most effective is the 3-way catalytic converter. To maintain conversion efficiency, the A/F ratio must be strictly controlled within the catalyst window limits around the stoichiometric operating point. In order to investigate possible control techniques, a mathematical model is developed to simulate the physical behaviour of the engine processes. This approach allows a quick turn-around in terms of cost and time, for control investigations. The model demonstrates close trend-wise approximation of the engine states with previous modelling studies, however, a full validation study was not possible. The model is then used to conduct investigations into A/F ratio control through the process of simulation. Conventional Pl-closed-loop control is assessed for steady-state and transient engine conditions, and for varying microprocessor sampling rates. It is found that Pi-control effectively removes state estimation errors, but is unable to remove A/F ratio excursions under transient operation. An open-loop compensation control structure is then developed as an extension to the IM-controller action. Simulation results show this approach to drastically reduce A/F ratio excursions for a number of typical driving scenarios. Potential problems that could well be encountered in the “real” engine environment are then investigated, and the practicality of the new controller assessed. A new approach to control is simulated that affords the most appropriate state estimation for the modelled system. This is shown to improve A/F ratio control upon that of the conventional approach but cannot match the compensation controller ability.
Supervisor: Jones, R. Peter ; Kerbyson, Kay ; Goodhart, Sean Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TL Motor vehicles. Aeronautics. Astronautics