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Shrub fuels are capable of extreme fire behaviour under conditions that are often moderate in other fuels. There is also a narrow range of conditions that determine fire success in these fuels, below which fires may ignite but hardly spread and above which they ignite and develop into fast moving and high intensity fires. This is due to the elevated dead fine fuels that dry rapidly and carry fire. Fire danger rating systems designed for forest and grassland fuels do not predict fire potential in shrub fuels very well. Fire management requires fire danger rating systems to provide accurate and timely information on fire potential for all important fuel types. Studies of fuel moisture, ignition and fire spread were carried out in the field in gorse (Ulex europaeus L.) shrub fuels to predict the moisture content of the elevated dead fuels and to define the conditions that govern fire development. The accuracy of the Fine Fuel Moisture Code (FFMC) of the Canadian Forest Fire Weather Index (FWI) System to predict moisture content of this layer was assessed. A bookkeeping method to predict moisture content was developed based on semi-physical models of equilibrium moisture content, fuel response time and the FFMC. The FFMC predicted moisture content poorly, because the FWI System is based on the litter layer of a mature conifer forest. The gorse elevated dead fuel layer is more aerated and dries faster than this conifer forest litter layer. The bookkeeping method was reliable and allowed adjustment of fuel response time based on weather conditions. Difficulties in modelling meteorological conditions under the gorse canopy limited its accuracy. Separate thresholds determined ignition and fire spread success, with both based on the elevated dead fuel moisture content. Options to improve the shrub fire danger rating system were presented based on these findings. The results are significant because they are based on data collected in the field under real conditions. Validation of these results and extension to other shrub fuels is required before the findings are used to change current models. However, the study has significantly advanced the knowledge of fire behaviour in shrub fuels and will contribute to safe and effective fire management in these fuels.

The Homogeneous Charge Compression Ignition (HCCI) engine is a promising engine concept that emits low concentrations of NOx and particulates and still has a high efficiency. Since the charge is auto-ignited, the auto-ignition quality of the fuel is of major importance. It has been shown in several studies that neither of the classical measures of auto-ignition quality of gasoline-like fuels, RON and MON, can alone describe this in all conditions in HCCI combustion. However, even in such cases it is possible to combine RON and MON into an octane index, OI, that describes the auto-ignition quality well in most conditions. The octane numbers are combined into the OI with the variable K according to the following equation: OI = (1-K)RON + K MON = RON – K S The OI of a sensitive fuel is the equivalent of the octane number of a primary reference fuel with the same resistance to auto-ignition in the tested condition. The K-value is dependent on the temperature and pressure history. A generic parameter Tcomp15, the temperature at 15 bar during the compression, was introduced to describe the temperature and pressure history. It was found that the K-value increases with increasing Tcomp15 and two linear equations have been suggested to describe this relationship. At high or low Tcomp15 it has been found that the sensitivity of the fuel octane quality on combustion phasing is small and the auto-ignition quality defined by the OI scale does no longer play a big role. NO affects the combustion phasing of gasoline-like fuels. This effect is most significant at low concentration where it advances the combustion phasing considerably. At higher conditions its influence is different for different fuels. A sensitive fuel is considered a good HCCI fuel since its OI changes in the same direction as the octane requirement of the engine, which would make the engine management easier. It is also likely that a sensitive fuel will enable a wider operating range. The auto-ignition quality of diesel-like fuels was studied in tests with three different strategies of mixture formation. In these tests it was found that the ignition delay increased with lower cetane number and that the cetane number described the auto-ignition quality well, even for fuels of significantly different physical properties. The experiments were, however, made at a limited range of operating conditions and low load. A good diesel-like HCCI fuel should be easy to vaporize to facilitate homogeneity. It should have a high resistance to auto-ignition, not necessarily the highest, one that allows both high and low loads at a given compression ratio. Finally, it should also function well with the injection system without a significant decrease in injection system life length. / QC 20100917

Concern remains regarding the efficacy of drink driving countermeasures to produce lasting change for repeat offenders, as a wide array of countermeasures have been developed that demonstrate varying levels of success in reducing re-offence rates. This thesis proposes that the collection and examination of repeat offenders' self-reported perceptions, experiences and behavioural changes that result from completing court-ordered interventions can provide valuable contributions to the development of effective sentencing strategies. As a result, the program of research implemented a mixed-method design to investigate the self-reported impact of legal sanctions, a drink driving rehabilitation program, and alcohol ignition interlocks on key outcome measures for a group of recidivist drink drivers.----- Study One incorporated a cross-sectional design to examine the deterrent effect of traditional legal sanctions (e.g., fines and licence disqualification periods), non-legal sanctions, alcohol consumption, recent offending behaviour(s), and the actual severity of sanctions on perceptual deterrence and intentions to re-offend. The study involved face-to-face and telephone interviews with 166 repeat offenders. The analysis indicated that participants perceived legal sanctions to be severe, but not entirely certain nor swift.----- In Study One, self-reported recent drink driving behaviours and alcohol consumption levels were identified as predictors of future intentions to drink and drive. The results suggest that habitual behaviours are difficult to change, and heavy alcohol consumption levels increase the probability of re-offending. At a bivariate level, three non-legal sanctions were negatively associated with intentions to re-offend but were not predictors of future intentions to drink and drive in the model. In addition, a relationship was not evident between: (a) the size of the penalties and perceptions of sanction severity or future intentions to drink and drive, and (b) the number of previous convictions and self-reported deterrence. The findings of the study confirm the popular assumption that some repeat offenders are impervious to the threat and application of legal sanctions.----- Study Two examined the stages of change and self-efficacy levels of 132 repeat offenders - who were all involved in Study One - while they completed an 11 week drink driving rehabilitation program. A repeated measures design was implemented to focus on the impact of the intervention on a number of salient program outcomes such as participants' motivations and self-efficacy levels to control and change their drinking and drink driving behaviour(s). Prior to program commencement, the majority of participants were motivated to change their drinking driving, but not their drinking. The sample also reported high self-efficacy levels to control the two behaviours, but did not have high expectations of the effectiveness of the program.----- Upon completion of the program, significant increases were evident in motivations to change drinking and drink driving behaviours, and a large percentage of participants reported a positive appraisal of the effectiveness of the intervention. Program completion also resulted in a reduction in self-reported alcohol consumption levels, yet the majority of the sample continued to consume harmful levels of alcohol. Self-efficacy levels remained high, although a notable finding was that participants reported higher levels of control over their drinking rather than drink driving behaviours. In general, Study Two provided a positive perspective of the capacity of a drink driving rehabilitation program to produce change for a group of repeat offenders.----- Study Two extended a small body of research and examined the effects that mandated program enrolment has on motivations to change, as well as expectations and appraisals of program effectiveness. Contrary to predictions, mandated participants did not report lower levels of motivation to change drinking and drink driving compared to voluntary attendees, but did indicate lower expectations of the effectiveness of the program, as well as being willing to engage in the program. Furthermore upon program completion, mandated participants also reported lower appraisals of the effectiveness of the program, but this factor was not associated with intentions to re-offend or non-program completion. Rather, not successfully completing the program appeared linked with being unwilling to change drinking behaviours.----- Study Three involved a longitudinal case-study design that utilised both quantitative and qualitative data to conduct one of the first examinations of the impact of alcohol ignition interlocks on a group of recidivist drink drivers from a users' perspective. The study investigated 12 participants' self-reported perceptions and experiences of using an interlock and the effect that the device had on key program outcomes such as drinking levels, operational performance, circumvention attempts and general beliefs regarding the effectiveness of the device in comparison to traditional legal sanctions.----- Participants reported positive appraisals regarding the effectiveness of the device as qualitative themes emerged concerning the educational and practical benefits of interlocks. However, closer examination of individual interlock performances revealed each participant had attempted to start their vehicle after consuming alcohol, and a smaller sample of three drivers were regularly attempting to start their vehicle after drinking. The combination and analysis of self-reported and downloaded interlock data revealed four main themes: (a) initial operational difficulties, (b) a general unwillingness to reduce alcohol consumption levels, (c) an unwillingness to acknowledge/recognise that interlock breath violations resulted from drinking, and (d) an overall decline in the frequency of interlock breath violations over the interlock installation period. Similar to Study Two, a notable finding was that half the sample was still consuming harmful levels of alcohol upon program completion.----- Taken together, the results of the program of research highlight that repeat offenders' entrenched behaviours, such as drinking and drink driving, are resistant to change and that multi-modal interventions are required if the drinking and driving sequence is to be broken for this population. The findings have direct implications for the sentencing and management of repeat offenders and the development of countermeasures that attempt to produce long-term behavioural change.

Hydrogen Assisted Jet Ignition (HAJI) is an advanced ignition process that allows ignition of ultra-lean mixtures in an otherwise standard gasoline fuelled spark ignition engine. Under typical operating conditions, a small amount of H2 (~ 2 % ofthe main fuel energy or roughly the equivalent of 1 g/km of H2) is injected just before ignition in the region of the spark plug. By locating the spark plug in a small prechamber (less than 1 % of the clearance volume) and by employing a H2 rich mixture, the content of the prechamber is plentiful in the active species that form radicals H and OH on decomposition and has a relatively high energy level compared to the lean main chamber contents. Thus, the vigorous jets of chemically active combustion products that issue through orifices, which connect to the main chamber, burn the main charge rapidly and with almost no combustion variability (less than 2% coefficient of variation in IMEP even at λ = 2.5). / The benefits from the low temperature combustion at λ = 2 and leaner are that almost zero NOx is formed and there is an improvement in thermal efficiency. Efficiency improvements are a result of the elimination of dissociation, such as CO2 to CO, which normally occurs at high temperatures, together with reduced throttling losses to maintain the same road power. It is even possible to run the engine in an entirely unthrottled mode, but at λ = 5. / Although only a small amount of H2 is required for the HAJI process, it is difficult to both refuel H2 and store it onboard. In order to overcome these obstacles, the viability of a variety of more convenient fuels was experimentally assessed based on criteria such as combustion stability, lean limit and emission levels. The prechamber fuels tested were liquefied petroleum gas (LPG), natural gas, reformed gasoline and carbon monoxide. Additionally, LPG was employed as the main fuel in conjunction with H2 or LPG in the prechamber. Furthermore, the effects of HAJI operation under sufficient exhaust gas recirculation to allow stoichiometric fuel-air supply, thus permitting three-way catalyst application were also examined. / In addition to experiments, prechamber and main chamber flame propagation modeling was completed to examine the effects of each prechamber fuel on the ignition of the main fuel, which consisted of either LPG or gasoline. The modeling and experimental results offered similar trends, with the modeling results giving insight into the physiochemical process by which main fuel combustion is initiated in the HAJI process. / Both the modeling and experimental results indicate that the level of ignition enhancement provided by HAJI is highly dependent on the generation of chemical species and not solely on the energy content of the prechamber fuel. Although H2 was found to be the most effective fuel, in a study of a very light load condition (70 kPa MAP) especially when running in the ultra-lean region, the alternative fuels were effective at running between λ = 2-2.5 with almost zero NOx formation. These lean limits are about twice the value possible with spark ignition (λ = 1.25) in this engine at similar load conditions. In addition, the LPG results are very encouraging as they offer the possibility of a HAJI like system where a commercially available fuel is used as both the main and prechamber fuel, while providing thermal efficiency improvements over stoichiometric operation and meeting current NOx emission standards.

Inlet-injection was motivated by the possibility for skin-friction reduction in the combustion chamber of a flight style, three-dimensional, scramjet engine. High Mach number flight, where skin friction in the combustion chamber is a significant proportion of the overall drag, is the regime of interest for this type of reduction. This is a result of high Mach number supersonic flow within the combustion chamber, coupled with high densities due to the compression process. The flight condition of interest was chosen to be Mach 8.0 at an altitude of 30km. This choice was dictated by near-term flight-testing capabilities. The approach was to design an inlet with a reduced contraction ratio. This would produce a relatively low-density combustion-chamber flow, that would, in turn, lead to lower viscous drag. Due to low temperatures in the combustion chamber, as a result of the reduced compression, a novel method of ignition was required. This fluid-dynamic ignition technique made use of inlet injection together with flow non-uniformities generated by the inlet. The inlet chosen for this purpose was a rectangular-to-elliptical-shape-transition inlet or REST inlet. The focus of the investigation, was therefore, to determine the potential for performance improvement using inlet injection of fuel. The general approach to the investigation was experimental, using a scramjet model consisting of inlet, combustion chamber and a truncated nozzle. Flow-path thrust-potential was used as the primary performance parameter, where the term `thrust-potential' is used to indicate the lack of full expansion. A secondary performance metric was combustion efficiency, determined by matching one-dimensional analysis to experimental pressure distributions. In addition to inlet-injection, conventional injection into the combustion-chamber was tested as the performance baseline. Based on findings from these tests, two additional methods of injection were investigated both having a combination of inlet and combustion-chamber injection. The general findings showed that inlet injection, in comparison to combustion-chamber injection, produced an increase in performance in terms of thrust-potential and combustion efficiency for supersonic combustion. This occurred over a range of equivalence ratios up to 1.0. However, the maximum thrust developed by inlet injection was limited by engine unstart. In terms of the maximum thrust-potential, combustion-chamber injection exceeded that of inlet injection but significantly higher fuelling was required and poor combustion efficiency persisted. In order to offset the limit in thrust production due to unstart, an alternative fuelling method was implemented. This took the form of partial injection of the fuel in the combustion chamber in combination with inlet injection. An increase in thrust-potential and combustion efficiency as a result of increased fuel coverage in areas of the combustion chamber, which were fuel lean under inlet-injection. A thrust potential level similar to that of combustion-chamber injection was achieved with significantly higher combustion efficiency and consequently a lower fuelling level. This type of combined-injection is an attractive option for fuel delivery at the nominal flight condition. An additional finding for combustion-chamber and combined injection was that very high equivalence ratios led to separated flow in the combustion chamber and isolator. This was a result of excessive heat release producing an adverse pressure gradient in the engine. This mode of operation showed high levels of thrust-potential at equivalence ratios in excess of 1.0. Although interesting, these findings were outside the scope of the investigation since the flow within the combustion chamber is no longer purely supersonic.

The process of shock-induced ignition has been investigated both computa- tionally and experimentally, with particular emphasis on the concept of radical farming. The first component of the investigation contained Computational Fluid Dynamic (CFD) calculations of an ignition delay study, a 2D pre-mixed flow over flat plate at a constant angle to the freestream, and through a generic 2D scramjet model. The focal point of the investigation however examined the complex 3D flow through a generic scramjet model. Five experimental test conditions were ex- amined over flow enthalpies from 3.4 MJ/kg to 6.4 MJ/kg. All test conditions simulated flight at 21000 metres ([symbol=almost equal to] 70000 ft), while the equivalent flight Mach number varied from approximately 8.5 at the lowest enthalpy, to approximately Mach 12 at the highest enthalpy condition. The presence of H2 fuel injected in the intake caused a separated region to form on the lower surface of the model at the entrance to the combustor. A fraction of the total mass of fuel was entrained in this separated region, providing long residence times, hence increased time for the chemical reactions that lead to ignition to occur. In addition, extremely high temperatures were found to exist between each fuel jet. Both fuel and air are present in these regions, therefore the chance of ignition in these regions is high. Streamlines passing through the recirculation zone ignited within this zone, while streamlines passing between the fuel jets ignited soon after entry into the combustor. The first instance of a pressure rise from combustion was observed on the centreline of the model where the reflected bow shock around the fuel jets crossed the centreline of the combus- tor. Upstream of this location the static pressure of the flow was too low for the chemical reactions that release heat to occur. The comparison between the experimental and computational results was lim- ited due to inaccuracies in modelling the thermal state of the gas in the CFD calculations. The gas was modelled as being in a state of thermal equilibrium at all times, which incorrectly models the freestream flow from the nozzle of the shock tunnel, and also the flow downstream of oblique shock wave within the scramjet model. As a result combustion occurs sooner in the CFD calculations than in the experimental result.

The process of shock-induced ignition has been investigated both computa- tionally and experimentally, with particular emphasis on the concept of radical farming. The first component of the investigation contained Computational Fluid Dynamic (CFD) calculations of an ignition delay study, a 2D pre-mixed flow over flat plate at a constant angle to the freestream, and through a generic 2D scramjet model. The focal point of the investigation however examined the complex 3D flow through a generic scramjet model. Five experimental test conditions were ex- amined over flow enthalpies from 3.4 MJ/kg to 6.4 MJ/kg. All test conditions simulated flight at 21000 metres ([symbol=almost equal to] 70000 ft), while the equivalent flight Mach number varied from approximately 8.5 at the lowest enthalpy, to approximately Mach 12 at the highest enthalpy condition. The presence of H2 fuel injected in the intake caused a separated region to form on the lower surface of the model at the entrance to the combustor. A fraction of the total mass of fuel was entrained in this separated region, providing long residence times, hence increased time for the chemical reactions that lead to ignition to occur. In addition, extremely high temperatures were found to exist between each fuel jet. Both fuel and air are present in these regions, therefore the chance of ignition in these regions is high. Streamlines passing through the recirculation zone ignited within this zone, while streamlines passing between the fuel jets ignited soon after entry into the combustor. The first instance of a pressure rise from combustion was observed on the centreline of the model where the reflected bow shock around the fuel jets crossed the centreline of the combus- tor. Upstream of this location the static pressure of the flow was too low for the chemical reactions that release heat to occur. The comparison between the experimental and computational results was lim- ited due to inaccuracies in modelling the thermal state of the gas in the CFD calculations. The gas was modelled as being in a state of thermal equilibrium at all times, which incorrectly models the freestream flow from the nozzle of the shock tunnel, and also the flow downstream of oblique shock wave within the scramjet model. As a result combustion occurs sooner in the CFD calculations than in the experimental result.

The process of shock-induced ignition has been investigated both computa- tionally and experimentally, with particular emphasis on the concept of radical farming. The first component of the investigation contained Computational Fluid Dynamic (CFD) calculations of an ignition delay study, a 2D pre-mixed flow over flat plate at a constant angle to the freestream, and through a generic 2D scramjet model. The focal point of the investigation however examined the complex 3D flow through a generic scramjet model. Five experimental test conditions were ex- amined over flow enthalpies from 3.4 MJ/kg to 6.4 MJ/kg. All test conditions simulated flight at 21000 metres ([symbol=almost equal to] 70000 ft), while the equivalent flight Mach number varied from approximately 8.5 at the lowest enthalpy, to approximately Mach 12 at the highest enthalpy condition. The presence of H2 fuel injected in the intake caused a separated region to form on the lower surface of the model at the entrance to the combustor. A fraction of the total mass of fuel was entrained in this separated region, providing long residence times, hence increased time for the chemical reactions that lead to ignition to occur. In addition, extremely high temperatures were found to exist between each fuel jet. Both fuel and air are present in these regions, therefore the chance of ignition in these regions is high. Streamlines passing through the recirculation zone ignited within this zone, while streamlines passing between the fuel jets ignited soon after entry into the combustor. The first instance of a pressure rise from combustion was observed on the centreline of the model where the reflected bow shock around the fuel jets crossed the centreline of the combus- tor. Upstream of this location the static pressure of the flow was too low for the chemical reactions that release heat to occur. The comparison between the experimental and computational results was lim- ited due to inaccuracies in modelling the thermal state of the gas in the CFD calculations. The gas was modelled as being in a state of thermal equilibrium at all times, which incorrectly models the freestream flow from the nozzle of the shock tunnel, and also the flow downstream of oblique shock wave within the scramjet model. As a result combustion occurs sooner in the CFD calculations than in the experimental result.