Описание
viii Preface
engines is not covered, except that empirical information for such quantities as maximum tip
speed are used, based on experience. To cover the mechanical design of engines would have
required a much bigger book than this and would have required a mass of knowledge which I do
not possess.
In preparing the course it was necessary for me to learn new material and for this I
obtained help from many friends and colleagues in industry, in particular in Rolls-Royce. This
brought me to realise how specialised the knowledge has become, with relatively few people
having a firm grasp outside their own speciality. Furthermore, a high proportion of those with
the wide grasp are nearing retirement age and a body of knowledge and experience is being lost.
The idea therefore took hold that there is scope for a book which will have wider appeal than a
book for students – it is intended to appeal to people in the aircraft engine industry who would
like to understand more about the overall design of engines than they might normally have had
the opportunity to master. My ambition is that many people in the industry will find it useful to
have this book for reference, even if not displayed on bookshelves.
The original course, Chapters 1–10, was closely focused on an elementary design of an
engine for a possible (even likely) new large civil aircraft. Because the intention was to get the
important ideas across with the least complication, a number of simplifications were adopted,
such as taking equal and constant specific heat capacity for air and for the gas leaving the
combustor as well as neglecting the effect of cooling air to the turbines.
Having decided that a book could be produced, the scope was widened to cover
component performance in Chapter 11 and off-design matching of the civil engine in Chapter 12.
Chapters 13 – 18 look at various aspects of military engines; this is modelled on the treatment in
Chapters 1–10 of the civil engine, postulating the design requirement for a possible new fighter
aircraft. In dealing with the military engine some of the simplifications deliberately adopted in the
early chapters are removed; Chapter 19 therefore takes some of these improvements from
Chapters 13 – 18 to look again at the civil engine.
Throughout the book the emphasis is on being as simple as possible, consistent with a
realistic description of what is going on. This allows the treatment to move quickly, and the book
to be brief. But more important it means that someone who has mastered the simple formulation
can make reasonably accurate estimates for performance of an engine and can estimate changes in
performance with alteration in operating condition or component behaviour. Earlier books
become complicated because of the use of algebra; furthermore to make the algebra tractable
frequently forces approximations which are unsatisfactory. The present book uses arithmetic
much more – by taking advantage of the computer and the calculator the numerical operations are
almost trivial. The book contains a substantial number of exercises which are directed towards
the design of the civil engine in the early chapters and the military engine in the later chapters.
The exercises form an integral part of the book and follow, as far as possible, logical steps in the
design of first the civil engine and then later the military combat engine. Many of the insights are
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