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Many computational methods have been suggested for the solution of this theoretical situation, such as Riemann variables, Lax-Wendroff and other finite difference procedures. The basic approach adopted here is to re-examine the fundamental theory of pressure wave motion and adapt it to a mesh method interpolation procedure. At the same time the boundary conditions for inflow and outflow, such as the filling and emptying of engine cylinders, has been resolved for the generality of gas properties and in terms of the unsteady gas flow which controls those processes. The same generality of gas property and composition is traced throughout the pipe system. This change of gas property is very significant in two-stroke engines where the exhaust blowdown is followed by short-circuited scavenge air.

This Address is concerned with the work carried out by an engineering academic at The Queen's University of Belfast over the last 26 years. It describes the motivation which impelled the author towards a career in mechanical engineering and into a specialist field from which he has never strayed. It describes research and development into the design of the two-stroke cycle engine, which today is identified as a potential candidate for automobile powerplant production within the decade. At the same time the Address illustrates that much of this research and development, including the design, manufacture, build, test, and development of prototype automotive engines, has been heavily contributed to by both undergraduate and postgraduate students as part of their education and training at the university. It is contended that this approach is a vital component of a relevant university education and training for student and academic alike.

The design and development of high performance racing engines is greatly facilitated by the use of accurate simulation of their performance characteristics. The reverse is true if the simulation is inaccurate. This paper reports on certain aspects concerning the accuracy of engine modelling and simulation. The aspect considered is the coefficient of discharge of poppet valves in the engine cylinder head. It is required to know such discharge coefficients, as a function of lift and pressure ratio, so that, in the mathematical modelling process at each juncture during the open cycle, accuracy can be obtained for the mass flow rates of gases, the magnitude of pressure waves created, and the in-cylinder thermodynamics. The discharge coefficients, Cd, are required for both valves and for inflow and outflow at each valve and are measured for each set of valves in a four-valve pent-roof cylinder head of a 600 cm3 high performance motorcycle engine.

Previous papers from The Queen's University of Belfast have shown the application of digital computers in simulating the unsteady gas flow and thermodynamic processes in single cylinder engines having various types of exhaust systems. This paper outlines the results of an investigation of twin cylinder engines of the outboard motor type where compact and complex exhaust systems are used to optimise the performance characteristics within a specified package size. Measured and predicted pressure-time histories for the exhaust and open cycle cylinder are presented for a 350cm3, twin cylinder test engine, which has been extensively modified to emulate the porting configuration and performance characteristics of two production outboard motor engines. Also compared are the measured and predicted output performance data for the engines, where all of the predicted data is produced by a new twin cylinder simulation program incorporating a simple constant pressure junction model.