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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.

This paper describes an experimental investigation into the surface heat transfer coefficient of finned metal cylinders in a free air stream. Ten cylinders were tested with four different fin pitches and five different fin lengths. The cylinders and their fins were designed to be representative of those found on a motorcycle engine with an external cylinder diameter of 100mm and fin lengths of 10 to 50mm. The fins of each cylinder were gravity die cast in aluminium alloy. Each cylinder was electrically heated and mounted in a wind tunnel which subjected it to a range of air speeds between 2 and 20 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 a lesser effect. In addition to the determination of an overall heat transfer coefficient, the distribution of cooling around the circumference of each cylinder was also studied.

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).

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 four different fin pitches and five different fin lengths. The cylinders and their fins were designed to be representative of those found on a motorcycle engine. Each electrically heated cylinder was mounted in a wind tunnel and subjected to a range of air speeds between 2 and 20 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 a lesser effect. The coefficient increases with airspeed and as the fins are separated or shortened. It was also noted that a limiting value of coefficient exists, influenced only by airspeed. Above the limiting value the surface heat transfer could not be increased by further separation of the fins or reduction in their length.

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.

This paper describes an experimental investigation into the effect of bore/stroke ratio on a simple two-stroke engine. This was achieved with a special purpose engine of modular design. The engine allowed four combinations of bore and stroke to be contrived to yield a common swept volume of 400 cm3 with bore/stroke ratios of: 0.8, 1.0, 1.2 and 1.4. Other factors that might affect engine performance were standardised: the exhaust, intake and ignition systems were common, the combustion chamber designs were similar, scavenge characteristics were similar, port timings and time-areas were kept the same, and cylinder and crankcase compression ratios were also kept the same. The most important conclusions were: Engine power was greatest with the compromise bore/stroke ratio of 1.0 or 1.2. Combustion efficiency tended to decrease with increasing bore/stroke ratio. Mechanical efficiency tended to increase with increasing bore/stroke ratio.