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Flow maldistribution of the exhaust gas entering a Diesel Particulate Filter (DPF) can cause uneven soot distribution during loading and excessive temperature gradients during the regeneration phase. Minimizing the magnitude of this maldistribution is therefore an important consideration in the design of the inlet pipe and diffuser, particularly in situations where packaging constraints dictate bends in the inlet pipe close to the filter, or a sharp diffuser angle. This paper describes the use of Particle Image Velocimetry (PIV) to validate a Computational Fluid Dynamic (CFD) model of the flow within the inlet diffuser of a DPF so that CFD can be used with confidence as a tool to minimize this flow maldistribution. PIV is used to study the flow of gas into a DPF over a range of steady state flow conditions. The distribution of flow approaching the front face of the substrate was of particular interest to this study.

The single shot apparatus creates a pressure wave (compression or rarefaction) by releasing a pressure or vacuum from a blowdown cylinder. The wave is contrived to be representative of cylinder blowdown or the suction wave that emanates from an engine intake valve during induction. Generated waves may be fired into a quiescent pipe or system of pipes that represent the ducts found on an engine. The most significant features that distinguish the new apparatus from any previous are that it uses a poppet valve to release the wave and that the apparatus is largely automatic, enabling the generation of a new wave every 15 seconds or so. The particular version of the apparatus described here has been conceived to allow a low speed background flow to be maintained in the pipe system between waves. The purpose of this is to allow microscopic particles to be kept in suspension in the air to facilitate flow studies using Particle Image Velocimetry (PIV) or Laser Doppler Anemometry (LDA).

A numerical study of the heat transfer from an air-cooled single-cylinder engine has been undertaken using computational fluid dynamics. The variation in heat transfer from and airflow around the cylinder, which was simplified to a stack of annular fins, was observed at different values of fin pitch and length. The simulation results were compared with experimental results obtained previously at Queen's University Belfast (QUB). The CFD prediction of the circumferential temperature distributions had a similar trend to the experimental analysis, offset from the experimental results by approximately 8 degrees Kelvin.

This paper presents a discussion of the difficulties in evaluating the discharge coefficients of ports in the cylinder wall of high performance two-stroke engines. Traditionally such evaluation requires the knowledge of the area of the port on a chord normal to the direction of flow through the port. However, due to the complex shape of ports in these engines, it is difficult to know the exact flow direction without some kind of flow analysis. Results of a study conducted on various methods of obtaining the port area either by assuming a flow direction or using geometrical information are presented. From the information presented it can be seen that the use of wall area is quite acceptable to determine discharge coefficients. This wall area requires no interpretation by the experimenter and therefore also permits a direct comparison with other ports.

Die cracking is one of the most important life-limiting tool failure mechanisms in high pressure die casting (HPDC). Cracking is caused by thermal shock from sudden heating and then cooling of the die surface. Injection of molten aluminium, transfers heat to the die which results in compressive stresses on the die surface. After the casting has been extracted, the die is sprayed with releasing agent which generates tensile stresses on the surface of the die. These stress fluctuations result in heat check cracking or gross cracking forming on the surface of the die. Casting simulation software was used to simulate the casting process; metal filling the die cavity, solidification and thermal stresses in the die. For this paper a comparison was made between a simulation analysis and a cracked die slide. When the die cracks due to thermal fatigue, aluminium penetrates into the cracks which results in visual defects being formed in the casting and will further reduce the die-life.