This thesis presents research on upward pointing oil jets that provide cooling of downward facing heated surfaces. The specific purpose of this research is to improve understanding of the oil jet cooling of internal combustion engine pistons. In this research, the cooling of heated blocks with flat and concave surfaces was investigated. Temperature measurements were obtained using an array of thermocouples embedded inside the heated blocks. A flash illumination and high resolution CCD camera system was used to observe the liquid jet impingement. Observations identified a 'bell-sheet' flow pattern, jet interference, jet splatter and jet breakup which provided insights into the liquid jet impingement processes normally encountered on downwardfacing surfaces. Bespoke contracting-type nozzles were used to produce the jet flow structure. The data from these nozzles were used to generate new empirical correlations for oil jet cooling of downward-facing flat surfaces and for predicting the size 6f impingement. The results obtained from these tests were also used for comparison with cooling jets from production automotive piston cooling nozzles. The research has demonstrated that the effectiveness of oil jet cooling can be affected by preheating the oil and varying the injector size to alter the targeted cooling efficiency, and liquid loss due to jet breakup and splatter. Local heat transfer coefficients were observed to increase when the jet Reynolds number increased. Piston undercrown cooling was studied using a range of oil jet configurations. The cooling rates improved with optimised targeted jets. The results also indicated that the undercrown geometry designs such as crosshatched surfaces, undercrown-skirt and gudgeon-pin boss, were significant for enhancing the local rate of forced convective heat transfer. New empirical correlations were developed from the experimental results that enabled prediction of the heat transfer coefficient and jet impingement size for high Prandtl number liquid jets impinging onto downward-facing surfaces. The heat transfer correlations were developed for normal (θ = 90°) and inclined (θ = 75°, 60° and 45°) jet impingements.

In the automotive industry, there is a strong trend that has increased the electronics in cars for various functions like fuel injection, electric control of doors and windows, electric chair adjustment, air-conditioning, drive-by-wire, brake-by-wire, etc. For these “automotive” systems, so-called smart power ICs must be used. These are chips in which the power functionality, e.g. the control of a motor is integrated with the logic control. There is also a trend towards operation at high voltages and integrating more intelligence using a microcontroller’s RAM.ROM memory and several sensors and interfaces. The final goal is the integration of a complete system on a single chip, a so-called power System-on-Chip (SoC). The interest in accurately modelling high-voltage transistors has increased in recent years due to the compatibility of these devices with standard CMOS technology. However, existing LDMOS models are not accurate enough for this task and SPICE models are especially weak when modelling AC performance. The limitation of these models lies in their lack of any capability to physically model some of the characteristic phenomena observed in LDMOS devices. The increased difficulty is related to complex 2D effects, specific to modern high voltage device architectures. This thesis presents a new physically based macro-model. This model is based on the investigations done on the key phenomena occurring in an LDMOS transistor. These phenomena were investigated by TCAD simulations and were confirmed by newly developed test-structures. The model is accurate for wide geometry and temperature variations as well for DC and AC operation. A novel corner extraction methodology based on neural networks has been developed making it possible to easily generate worst-case corners. The model was verified on device level as well on circuit level yielding good results.

A study of the friction between styrene butadiene rubber and ice has been undertaken. The instrument used o perform the measurements (a tribometer) was designed, constructed and developed specifically for this task and so has been optimised for this tribosystem. The versatile and compact design is easily accommodated in a domestic freezer and has been utilised to measure friction in both steady-state and transient regimes. The experimental component of the study is comprised of two separate and novel parts. Firstly, steady-state (constant temperature, load and speed) measurements of the sliding friction are placed on a friction map in speed-temperature space. This enables the frictional behaviour of this complex system to be presented in a clear and uncomplicated fashion. As the frictional behaviour of both rubber and ice independently change with the prevalent environmental conditions, presentation of data in this format allows the changes to be observed for all conditions encompassed by the map. Reference to maps of this form is beneficial from both traction and sliding perspectives as the areas of high and low friction are clearly demonstrated. The second experimental section relates to the transient nature of friction as it changes from static to sliding regimes. This study uncovered the temperature and force rate dependencies that can be utilised to increase the (typically) very low friction on ice. Application of this aspect of rubber-ice friction is particularly important to the automotive industry where transient regimes are widely used in safety and performance enhancement systems such as anti-lock braking systems and stability control.

A new type of fuel injector, incorporating a steel, annular diaphragm as the open/close device has been designed. This design would avoid sliding contact between components and exhibit low wear when metering hydrogen fuel. Further, it has been shown by simulation that the injector can a designed to withstand cyclic stresses and deliver hydrogen fuel at a rate suitable for direct injection to the cylinder of an IC engine. Investigation of the possibility of incorporating a pump in the injector unit to provide elevated pressure shows that a minimum of 3.4% of the fuel energy supplied would be required to power hydrogen compression. Structural analysis of the clamped diaphragm component shows that bending stress would be at least 236 MPa when sufficient deflection is achieved. Material such as spring steel, with a high yield strength and fatigue endurance limit, would need to be used to avoid failure. CFD analysis of compressible flow models of two commercial injectors shows good agreement with published data, indicating the expected linear relationship of mass flow rate to supply pressure in the super-sonic range. A model of a commercial annular plate injector on which the new design is based indicates mass flow rate up to 50% lower than published data, and the model indicates a discharge coefficient of 22%. This is the result of key differences between actual and modelled injector geometries. Good agreement between results of a CFD model of the diaphragm injector geometry and compressible flow theory is obtained. These results show agreement of the relationship between back pressure and shock wave formation, and sub- and super-sonic mass flow rate-pressure relationship. The model suggests that 66 bar supply pressure would be required to achieve the highest design mass flow rate of 23 g/s, and that the discharge coefficient of the new injector design would be 90% under these conditions.

This work describes a feasibility study of a new concept in pneumatic turbomachinery. The concept has its origins in the Tesla turbine with a set of closely spaced, flat discs on a shaft. Fluid flows through the gaps between the discs and exerts a force on the disc faces by viscous shear. In this new concept, plates are positioned in the disc spaces to restrict the flow in one direction round the rotor. It is explained that this design offers certain advantages over conventional pneumatic drives for position control applications such as robotics and the feasibility study has focused on this application. A theoretical analysis is presented which indicated that the disc spaces need to be very small to limit the flowrate and a consequence of this is that the restrictor plates are flexible due to their thin size. A multiple disc motor and a single disc motor which were built are described and their performance compared with theoretical predictions. The plates in the multiple disc motor experienced instability and an experimental and theoretical investigation of this problem is presented. The developent of the theoretical analysis is described, beginning with static and quasi-steady models. The final formulation of the problem considers an unsteady, compressible, laminar flow through a straight, high aspect ratio rectangular duct containing a perfectly flexible membrane. The governing equations are solved by numerical methods. A two-step Lax-Wendroff method was employed but proved to be numerically unstable. The method of characteristics proved to be successful and is the solution method used in a computed survey of membrane stability in a thin duct. The implication of the theoretical and experimental results on the feasibility of the viscous shear torque motor for use in position control is discussed.

Hydrogen sulphide emission by catalytic converter-fitted automobiles is a problem, because the gas has an extremely unpleasant odour, which is detectable by the human nose at concentrations below 1 ppm. The problematic hydrogen sulphide emissions are produced by the "storage release" mechanism, in which the catalyst absorbs sulphur dioxide during net oxidising conditions and releases it very rapidly as hydrogen sulphide when the stoichiometry of the exhaust gas changes to net reducing. After a prolonged period of oxidative storage the peak emission of hydrogen sulphide by "storage release" can greatly exceed that possible by direct conversion of sulphur dioxide during net reduction conditions (termed the "steady state" mode of emission). Components of the formulation of typical TWCs (Three Way Converters), as well as iron, nickel and barium doped analogues, were prepared. Storage-release sequences were then simulated on the samples at a number of different temperatures on purpose-built 'catalyst test apparatus'. Temperature programmed reductions were performed in the same apparatus by dosing the samples with sulphur dioxide in oxidising conditions at 500°C (the temperature at which the emission of hydrogen sulphide is conventionally said to become a problem). The TPR spectra exhibited sulphur dioxide and hydrogen sulphide peaks, the hydrogen sulphide peak always occurring at the higher temperature. The addition of platinum to various oxides and oxide mixtures was shown to increase the proportion of stored sulphur emitted as hydrogen sulphide and to lower the temperature at which storage-release effects occur. These effects were evident in the lowered temperatures at which the TPR spectra peak maxima occurred and the increased size of hydrogen sulphide peaks relative to hose of sulphur dioxide.

No description available.

Steering feel and quality are terms commonly used in the automotive industry when describing passenger car steering systems. However, a procedure for the quantification of these terms does not exist, let alone a concise definition of what they constitute. This thesis puts forward a hypothesis by which steering quality and feel are described by the input/output relationships of the steering system and how they are perceived by the driver. Good control properties are postulated for these relationships and an experiment is conducted, where they are altered in a manner proposed to affect quality. A methodology for the objective assessment of the control properties is developed, employing vehicle dynamic testing and representation by a mathematical model. This is put into practice to evaluate the outcome of the experiment. It was found that the methodology was successful in detecting and quantifying the alteration in the vehicle control properties. A subjective evaluation was performed to assess the experiment in terms of the quality and feel perceived by the driver. The subjective judgement delivered a result, where the deviation in quality agreed with the objective quantities hypothesised to describe quality. The thesis provides a significant step in the understanding of what is termed steering feel and quality. The methodology, successful in quantifying the experimental results with respect to quality, constitutes a scientific advancement in the current procedures for the assessment of steering quality.

No description available.

No description available.