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LDV is used to measure steady flow in a two port loop scavenged model two-stroke engine cylinder. The model cylinder, machined from acrylic for maximum optical access, is geometrically identical to that used in a previous dynamic study of transfer port efflux vectors. The measured flow field is compared with a CFD prediction which employs experimentally measured velocity, mass flow rate, and turbulence intensity as the inlet boundary condition at the transfer port. The finite volume prediction, using the PHOENICS general purpose code recreates the global flow pattern well, but shows some local discrepancies in flow direction and magnitude. Levels of turbulent kinetic energy were poorly recreated using a k-ϵ model of turbulence, especially around impingement of the incoming jets where local errors of up to 60% were seen.

The measurement of transfer port efflux velocities using laser doppler velocimetry (LDV) in a motored model two-stroke engine is described. The single cylinder engine used is of two port loop scavenged design, externally blown to provide scavenge flow into the cylinder during the entire port open period. LDV measurements were taken along a vertical path, central to the transfer duct, at the port exit over a range of crankangles at motoring speeds of 225rpm, 600rpm, and 900rpm. At 225rpm further measurements were taken for a range of delivery ratios from 0.7 to 2.0. Relatively uniform velocity profiles indicate plug like flow issuing from the port under most conditions. The resultant flow direction is seen never to align with the transfer duct walls, but to vary as a function of crankangle. Quantitative analysis of angles defining mean flow direction reveal that dynamic efflux behaviour is essentially similar for all tested speeds and delivery ratios.

The importance of exhaust system design for three cylinder two-stroke engines is demonstrated using a thermodynamic model developed at The Queen's University of Belfast. The influence of the major exhaust parameters on wide open throttle power and bmep is investigated. In addition, the potential benefits of reed valve induction over piston port induction at low engine speeds are demonstrated for one particular engine configuration.

A thermodynamic model developed at The Queen's University of Belfast is used to demonstrate the importance of exhaust system design for four cylinder two-stroke engines. The investigation considers two exhaust layouts for in-line engines and also a V or opposed piston layout. The influence of the major exhaust parameters on wide open throttle power and bmep is investigated.

A three cylinder two-stroke cycle diesel engine is proposed for automotive use. The engine is of the simple loop or cross-scavenging type with a crosshead seal and under piston scavenging pump. This paper records the initial investigations of this concept using a purpose built single cylinder engine. Results from different combustion systems are presented together with tests with the same engine when using an external air supply. Measurements from a parallel investigation using a laser doppler anemometer to measure air swirl motion within one of the chambers are also presented.