The effects of swirling flow and spark locations on the specific rate of growth of flame area, the flame speed and the convection velocity are investigated experimentally in a constant volume vessel near the lean misfire limit for an equivalence ratio of 0.645 using the shadowgraph technique. The circular and the elliptical models are used as flame contours to calculate the flame speed and the convection velocity. The circular model indicates that the flame speed decreases as the swirl flow decays and as the spark location is moved towards the center of the combustion chamber. The modified elliptical model shows the same result for the average flame speed $S\sb{ws}$. Both models show an overlap in convection velocity when comparison is made at a given spark location for different swirl levels because of cyclic variation; even though the average is higher for higher swirl level. The specific rate of growth of flame area (${1\over A}{dA\over dt}$) is obtained using three models for flame area A: (i) 2-D flame area $A\sb{f}$ measured from the photographs, (ii) spherical flame geometry model, and (iii) ellipsoidal geometry model. The stretch factor $K=({\delta\sb{l}\over u\sb{l}}) ({1\over A}{dA\over dt})$ at 0.5 ms from ignition time for the 2-D and the spherical models at ${r\over R}=0.68$ was within the range 0.63-0.97 and at ${r\over R}=0.55$ was within the range 0.5-0.59. The stretch factor for the ellipsoidal model at ${r\over R}=0.68$ was within the range 0.53-1.05 and at ${r\over R}=0.55$ was within the range 0.46-0.53. All three models for flame area indicate that the specific rate of growth of flame area and stretch factor at 0.5 ms from ignition time decrease as the swirl flow decays and as the spark location approaches the center of the combustion chamber.

Experimental measurements and model predictions of ignition delay times for single component and two-component liquid fuels are presented. The methodology used is the suspended-droplet/moving-furnace technique, in which a droplet of fuel is suspended from the tip of a thin quartz fibre. A preheated electric furnace moves towards and encompasses the droplet locality, producing a sudden rise in ambient temperature, and thus initiating the ignition process. The entire apparatus is enclosed in a pressure vessel and is remotely operated. Data were collected for pressures up to 18 atm absolute and in a temperature range of 773 K to 973 K. Fuels tested comprised n-paraffins (decane, dodecane, and hexadecane), aromatics (mesitylene, o-xylene, and isobutylbenzene) and a cycloparaffin (decalin), as well as selected binary combinations: n-decane/n-dodecane, n-dodecane/n-hexadecane, n-decane/decalin, n-decane/isobutylbenzene, n-decane/mesitylene, and n-decane/o-xylene. Paraffin measurements at low pressures and high temperature revealed a monotonic decrease in ignition times with increasing pressure. However, higher pressure ignitions at lower temperatures showed more complex behaviour by the measurement of two or "twinned" ignition times for the same pressure and temperature condition, indicating a change in reaction mechanism, possibly from one-stage to two-stage ignition. Aromatic fuels did not show "twinned" ignition time behaviour and responded with a slight increase in ignition times with increasing pressure, owing to a weaker reaction rate dependence on pressure. The cycloparaffin behaved analogously to the n-paraffin family. The behaviour of mixtures was largely controlled by the more volatile component. (Abstract shortened by UMI.)

abstract: In large modern urban areas, traffic congestion and fatality have become two serious problems. To improve the safety and efficiency of ground mobility, one promising solution is the cooperative control of connected and automated vehicle (CAV) systems, which can avoid human drivers’ incapability and errors. Taking advantage of two-dimensional (2D) vehicular control, this dissertation intends to conduct a thorough investigation of the modeling, control, and optimization of CAV systems with flocking control. Flocking is a dynamic swarm congregating behavior of a group of agents with self-organizing features, and flocking control of CAV systems attempts to achieve the maintenance of a small and nearly constant distance among vehicles, speed match, destination cohesion, and collision and obstacle avoidance. Concerning artificial multi-agent systems, such as mobile robots and CAV systems, a set of engineering performance requirements should be considered in flocking theory for practical applications. In this dissertation, three novel flocking control protocols are studied, which consider convergence speed, permanent obstacle avoidance, and energy efficiency. Furthermore, considering nonlinear vehicle dynamics, a novel hierarchical flocking control framework is proposed for CAV systems to integrate high-level flocking coordination planning and low-level vehicle dynamics control together. On one hand, using 2D flocking theory, the decision making and motion planning of engaged vehicles are produced in a distributed manner based on shared information. On the other hand, using the proposed framework, many advanced vehicle dynamics control methods and tools are applicable. For instance, in the low-level vehicle dynamics control, in addition to path trajectory tracking, the maintenance of vehicle later/yaw stability and rollover propensity mitigation are achieved by using additional actuators, such as all-wheel driving and four-wheel steering, to enhance vehicle safety and efficiency with over-actuated features. Co-simulations using MATLAB/Simulink and CarSim are conducted to illustrate the performances of the proposed flocking framework and all controller designs proposed in this dissertation. Moreover, a scaled CAV system is developed, and field experiments are also completed to further demonstrate the feasibility of the proposed flocking framework. Consequently, the proposed flocking framework can successfully complete a 2D vehicular flocking coordination. The novel flocking control protocols are also able to accommodate the practical requirements of artificial multi-agent systems by enhancing convergence speed, saving energy consumption, and avoiding permanent obstacles. In addition, employing the proposed control methods, vehicle stability is guaranteed as expected. / Dissertation/Thesis / Doctoral Dissertation Systems Engineering 2020

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Nowadays, occupant safety becomes one of the most important research area and the automotive industry increased their efforts for enhancing the safety of the vehicles. The aim of this research is to investigate the effect of vehicle dynamics control systems (VDCS) on both the collision of the vehicle body and the kinematics behaviour of the vehicle’s occupant. In this work, a novel vehicle dynamics/crash mathematical model is proposed and developed to co-simulate the crash event with the VDCS. This model is achieved using the novel approach of integrating front-end structure and vehicle dynamics mathematical models. The proposed mathematical model integrates both anti-lock braking systems (ABS) and active suspension control (ASC) systems alongside with crash structure modelling. This model is developed by generating its equations of motion and solving them numerically, this approach is used due to its quick and accurate analysis. In addition, a new multi-body occupant mathematical model is developed to capture the occupant kinematics before and during the collision. Validations of the proposed mathematical models are achieved to ensure their accuracy by comparing the simulated results with other real crash test data and former models results. The validation analysis of the vehicle and occupant models shows that the comparison results are well matched and the models are valid and can be used for different crash scenarios. The numerical simulation results are divided into two parts for vehicle and occupant models, respectively. Related to the vehicle model, it is shown that the mathematical model is flexible and useful for optimization studies. The results show that the deformation of the front-end structure is reduced, the vehicle body pitching and yawing angles are notably reduced, and the vehicle pitching acceleration is greatly reduced. Related to the occupant model, it is shown that the VDCS does have a significant effect on the rotations of the occupant's chest and head owing to its effect on the vehicle pitching. In addition, the occupant's deceleration is also slightly decreased and the occupant safety is improved.