Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Ronald D. Matthews. Vita. Includes bibliographical references.

Modern vehicles have to ful ll new CO2 emission and additionally customer comfort requirements to stay competitive. A major impact to the fuel consumption of an internal combustion engine (ICE) has the starting period. An ICE equipped with a preconditioning system which heats up the ICE much faster than a common ICE. This procedure of preconditioning is called peak heating. The main benet of preconditioning of an ICE is less fuel consumption. Recently the only way to obtain a fast heating up of an ICE is the injection of a higher amount of fuel during the starting period. This heat up procedure can be changed if a heat reservoir is available to the ICE during the starting period. In this case the additional injection of fuel is redundant and therefore the consumption during the starting period can be reduced. The major advantages of this strategy are achieved in cold ambient conditions. During this project di erent preconditioning strategies and di erent points of interaction in the coolant circuit of an ICE have been investigated. The preconditioning concepts have been evaluated according to their heating up performance and their implementation into the engine compartment. The results obtained by this project highlight that a system layout which enables a preheating of the cylinder block by a heat reservoir located in a bypass-line to the heater core is the most e ective point of interaction. The best results have been achieved with a coolant ow of 10 l/min at a temperature of 90 C. Furthermore, this project points out that the implementation of a preconditioning system into the oil cooler will achieve similar results. This strategy of preconditioning the engine oil reduces the internal frictions of the ICE which leads to a decreasing consumption. This solution is much more energy e cient and technically easier to implement into a modern vehicle with its limited space. An additional side e ect of the preconditioning of the oil is a longer service life of the ICE.

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Thesis (Ph.D.)--University of Melbourne, Dept. of Mechanical and Manufacturing Engineering, 2006. / Typescript. Includes bibliographical references (p. 251-276).

Thesis: M.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1976 / Includes bibliographical references. / by Gordon D. Marsh. / M.S. / M.S. Massachusetts Institute of Technology, Department of Mechanical Engineering

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The design trend for light duty diesel engines is towards lower compression ratio and higher turbocharger boost. This can enable higher specific power and lower pollutant emissions to be achieved, but raises concerns that cold start operation might be adversely affected. This is investigated and quantified through the study of a modern light duty diesel engine at two compression ratios and temperatures down to -20ºC. Key indicators of cold start performance are the magnitude and cycle-to-cycle variation of indicated mean effective pressure. Initial studies were carried out at 300 rpm, a speed representative of post-first-fire conditions. Studies were then conducted at higher engine speeds representative of cold idle. The utility of different injection strategies, timings and quantities is investigated when varying test temperature and engine speed through a range of values encountered during the cold start phase of engine operation. The importance of the glow plug as a cold start aid is also investigated by varying its operating temperature and protrusion into the combustion chamber. The indicated mean effective pressure was used to assess the effects of varying input parameters, and gross heat release rate information is used to identify the phenomena responsible for desirable or undesirable characteristics. Reduction in compression ratio led to no deterioration of initial start performance from speeds just above cranking, provided an appropriate injection strategy was chosen. Higher indicated mean effective pressure was possible at low speeds using low compression ratio due to reduced losses and more complete combustion. Cycle-to-cycle variability in indicated mean effective pressure increased markedly for both compression ratios at engine speeds representative of cold idle, especially when test temperature was reduced. Stability reduction was more severe at low compression ratio. Multiple pilot injections at high compression ratio cold idle resulted in better cycle-to-cycle stability. Analysis of heat release profiles suggested that additional pilots assisted fuel mixing, a conclusion supported by a computational fluid dynamics model. Multiple pilots created a more homogeneous fuel distribution through the bowl at time of main injection. Multiple pilots could not stabilise operation at low compression ratio. Improvement in cold idle at low compression ratio was achieved by increasing glow plug temperature, which significantly increased the rate of fuel preparation. This increased the initial rate of heat release and resulted in significantly less variation in the heat release rate profiles. Small changes in glow plug protrusion rapidly degraded cold idle performance, indicating the importance of correct design.

Partially-premixed Charge Compression Ignition (PCCI) combustion is defined by increased levels of premixed charge whilst retaining control over combustion through injection timing. An experimental investigation has been carried out on a current generation DI diesel engine, equipped with High Pressure Common Rail (HPCR) fuel injection equipment and an external Exhaust Gas Recirculation (EGR) system. The aims of the investigation were to determine the constraints imposed on operating a PCCI combustion strategy with the aim of simultaneously reducing engine-out net soot and NOx emissions. The work was carried out at fully-warm steady-state conditions at engine speeds of 1500 rpm and 1800 rpm, predominantly using a single injection strategy. With a single injection the Start of Injection (SOI), fuel rail pressure, and rate of EGR have been examined with a view to realising PCCI combustion. Timing ranges of -20º to +3ºATDC, rail pressures of 500-1200 bar, and EGR rates of 0-60% have been investigated. The responses looked at have been engine-out soot, NOx, HC, and CO emissions, fuel consumption, and combustion noise. It is shown that variation of the parameters has allowed PCCI combustion to be achieved in a restricted operating region, offering improvement in the NOx-soot trade-off. This region is limited on the available test engine by oxygen availability due to the specifications of the turbocharger and EGR systems. Engine speeds up to 2000 rpm (at 2.5 bar BMEP), and loads of 4.4 bar gross IMEP (at 1500 rpm) have been found to be the limits, beyond which soot and CO emissions rise excessively. It is shown that enhancing the mixing time and intensity are both desirable in achieving PCCI combustion. The net soot reduction mechanism exploited with PCCI combustion strategies is reducing soot formation to outweigh the reduction in oxidation. Enhancing the mixing intensity by increasing injection pressure is highly effective at reducing soot output, but at the expense of brake specific fuel consumption. Increasing the mixing time can also be effective in reducing soot output, but careful parameter selection is required to avoid excessive soot output. Retarded or highly advanced injection timings are shown to reduce net soot output, but both have associated trade-offs and penalties. Retarding combustion is effective at lowering soot and NOx emissions with low associated noise, but a fuel economy penalty is paid. Advanced combustion phasing can result in large peak rates of increase of pressure, which have been shown to correlate well with combustion noise. Overall soot reductions of up to 97% were achieved, but with associated penalties. One of the most acceptable reductions of ~90% came at the cost of a 6% increase in fuel consumption, highlighting that improvements in emissions are achievable with PCCI strategies with acceptable trade-offs.

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