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Historically, when valve springs were wound with round wire and the coils were nominally equally spaced, it was relatively easy for the engineer to calculate the virtually-linear load carrying capacity, the almost non-varying stiffness and the relatively-constant natural frequency of the spring. This was the design data that was required then for some simplistic but effective calculations of the valvetrain dynamic stability. In recent times, valve springs have come to be commonly wound with other wire sections such as ovate and with coil-coil spacings that are unequal, giving the spring a variable load carrying capacity, variable stiffness and a variable natural frequency with deflection. Such springs are known as progressive wound springs. The computation of these spring characteristics is no longer a simple matter and neither is their incorporation within the calculation of the dynamic stability of the entire valvetrain. The technical literature is very sparse on these topics.

Engine cycle simulation is an essential tool in the development of modern internal combustion engines. As engines evolve to meet tougher environmental and consumer demands, so must the analysis tools that the engineer employs. This paper reviews the application of such a tool, VIRTUAL 4-STROKE [1], in the modelling of a benchmark 1.9 Litre TDI engine. In an earlier paper presented to the Society [2] the authors presented results of a validation study on the same engine under full load operation. This paper expands on that work with validation of the simulation model against measured data over a full range of part load operation.

Recent environmental legislation to reduce emissions and improve efficiency means that there is a real need for improved thermodynamic performance models for the simulation of direct-injection, turbocharged diesel engines, which are becoming increasingly popular in the automotive sector. An accurate engine performance simulation software package (VIRTUAL 4-STROKE) is employed to model a benchmark automotive 1.9-litre Turbocharged Direct Injection (TDI) diesel engine. The accuracy of this model is scrutinised against actual test results from the engine. This validation includes comparisons of engine performance characteristics and also instantaneous gas dynamic and thermodynamic behaviour in the engine cylinders, turbocharger and ducting. It is seen that there is excellent agreement in all of these areas.

The paper discusses the design of a racing motorcycle engine to compete in World Superbike racing. This class of motorcycle racing is based on production machines with four-stroke engines only. The rules allow three engine variants to be used, a 750 cm3 four-cylinder engine, a 1000 cm3 twin-cylinder engine, and a 900 cm3 three-cylinder engine. To date only the first two variations have been employed but this paper shows that the 900 cm3 engine has the highest potential power output of the set. This is demonstrated using engine simulation software and the finest detail of the design of the engine and its ducting are supplied within the discussion. The input data for the engine simulation is provided by empiricism so that the design is initially well-matched from the intake bellmouth to the end of the exhaust system. The outcome of this empirical process is confirmed by the engine simulation to be a relevant initial design procedure.

The paper discusses briefly the development of the theory of unsteady gas flow from a position of being totally misunderstood from the turn of this century until the 1940's, developed in the 1950's, and from which juncture the advent of the digital computer has turned such theory into a comprehensive design tool by the present day. While the most extensive use of this design method is for engines with a high performance specification, its employment as a design tool for industrial engines has been largely ignored. In the paper, a design for a small generating set engine at 3600 rpm is examined in great detail and the use of pressure wave effects is shown to enhance the engine performance considerably, either in terms of power gain, reduction of fuel consumption, reduction of hydrocarbon emissions, or reduction of noise levels.

This book provides design assistance with the actual mechanical design of an engine in which the gas dynamics, fluid mechanics, thermodynamics, and combustion have been optimized so as to provide the required performance characteristics such as power, torque, fuel consumption, or noise emission.

Design and Simulation of Two-Stroke Engines is a unique hands-on information source. The author, having designed and developed many two-stroke engines, offers practical and empirical assistance to the engine designer on many topics ranging from porting layout, to combustion chamber profile, to tuned exhaust pipes. The information presented extends from the most fundamental theory to pragmatic design, development, and experimental testing issues. Chapters cover: Introduction to the Two-Stroke Engine Combustion in Two-Stroke Engines Computer Modeling of Engines Reduction of Fuel Consumption and Exhaust Emissions Reduction of Noise Emission from Two-Stroke Engines and more