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Die pre-heating has a beneficial effect on die life, by reducing thermal shock and stress fluctuations on the die surface. The findings from this paper indicate that the die surface stress decreased by 44% when the die is pre-heated to 150°C, and decreases by 57% when the die is pre-heated to 200°C, in comparison to when the die is started "cold" with an initial temperature of 20°C. Changes to the die start-up procedure, by switching off the die internal water cooling for the first four casting cycles, results in the die heating to operating temperature in fewer casting cycles, resulting in fewer castings being scrapped before the die achieves steady state operating temperature. From this, a saving of four castings per start-up can be made, reducing scrap by 4.5%, leading to lower manufacturing costs, reduced energy usage and increased useful die life.

Turbocompounding is generally regarded as the process of recovering a proportion of the exhaust gas energy from a reciprocating engine and applying it to the output power of the crankshaft. In conventional turbocompounding, the power turbine has been mechanically connected to the crankshaft but now a new method has emerged. Recent advances in high speed electrical machines have enabled the power turbine to be coupled to an electric generator. Decoupling the power turbine from the crankshaft and coupling it to a generator allows the power electronics to control the turbine speed independently in order to optimize the turbine efficiency for different engine operating conditions. Some renewable electricity is presently being generated from compression ignition engines fuelled primarily on biogas using a small proportion of injected palm oil to initiate combustion. Spark ignition engines are being considered as an alternative lower cost option.

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.

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.

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 describes an experimental investigation into the surface heat transfer coefficient of finned metal cylinders in a free air stream. Eight cast aluminium alloy cylinders were tested with three different fin pitches and three different fin lengths. The cylinders and their fins were designed to be representative of those found on a small engine. Each electrically heated cylinder was mounted in a wind tunnel and subjected to a range of air speeds between 12 and 50 m/s. The surface heat transfer coefficient, h, was found primarily to be a function of the air speed and the fin separation, with fin length having little effect.

Previous papers from The Queen's University of Belfast have described a new non-isentropic branched pipe junction model for use in a one-dimensional gas dynamic simulation of a multi-pipe system subject to unsteady gas flow. Such assemblages are commonly found in the intake and exhaust systems of multi-cylinder engines. The model takes full account of the effect of pressure loss, due to change in flow direction, and tracks the properties and composition of gas mixtures through the junction. Although the validity of the model has previously been inferred by its use in a complete engine simulation, which accurately predicted parameter variation in a firing engine, the independent validation of the junction model by itself is only now demonstrated. To investigate the performance of the junction model a series of three-pipe junctions were tested by directing a single pressure wave through each of the previously quiescent junctions.

Reed valves are the most common method used to control the intake of fresh air and fuel into the crankcase of a high performance two-stroke engine. While they can be quite simple in terms of mechanical design, their operation is highly dynamic and can be influenced by many other components. Previous publications from The Queen's University of Belfast have shown the derivation of mathematical models and their verification by measurements from a firing engine at relatively high engine speeds, up to 9,500 rev/min. In this present paper, measured and predicted data for delivery ratio and reed tip lift are presented for a 125 cm3, single cylinder engine over a range of speeds up to 12,290 rev/min. Steady flow discharge coefficients are measured and used in the mathematical simulation. Four variations of reed valve material/thickness are investigated in the firing engine. Correlation between measured and predicted delivery ratio is good over the speed range and various reed specifications.

The gas exchange process of the two-stroke engine is such that the flow of fresh air into the cylinder and exhaust gas out of the cylinder occur substantially together. It is therefore the case that not all of the air delivered will be trapped during this scavenge process. Extensive research has already been conducted into optimising the porting layouts of two-stroke engine cylinders. One of the techniques developed at The Queen's University of Belfast for evaluating scavenging is a unique experimental method described as the ‘single cycle scavenge test’. Although the test does not reflect the actual scavenge process in a firing engine, it is a sufficiently useful procedure to have become an industrial standard for scavenge evaluation. This paper discusses the application of that test procedure in the development of a multicylinder, externally scavenged, two-stroke automotive engine.

This paper describes the preliminary stages in the design of a low emission, multi-cylinder two-stroke engine for application in a luxury passenger car. A crankshaft driven compressor is used to provide scavenge air, exhaust timing edge valves are specified and also a valve able to disable transfer ports. Fuelling is provided by injection directly into the cylinder head. Rationale is given for the choice of the engine configuration, the scavenge system used and the definition of key features. A parametric investigation, performed by gas dynamic simulation, is presented illustrating the influence on the engine of: compressor speed ratio, exhaust manifold branch lengths, exhaust pipe lengths, and transfer and exhaust port timings. Finally, details are given of the design of the cylinder block, the exhaust valve and the intake valve.