[交通运输]AIRCRAFTDESIGN21.ppt

AIRCRAFT DESIGN ( 2 ): A Conceptual Approach Daniel P. Raymer Chapter 6 Initial Sizing CONTENTS 6.1 Introduction 6.2 Rubber-Engine Sizing 6.3 Fixed-Engine Sizing 6.4 Geometry Sizing 6.5 Control-Surface Sizing 6.1 Introduction(1) Aircraft sizing is the process of determining the takeoff gross weight and fuel weight required for an aircraft concept to perform its design mission. In Chapter 3 a quick method based on minimal information was introduced . This chapter presents a more refined method capable of detail with most types of aircraft-sizing problems. 6.1 Introduction(2) An aircraft can be sized using some existing engine or a new design engine. The existing engine is fixed in size and thrust, and is referred to as a “fixed-size-engine” or “fixed-engine”. The new design engine can be built in any size and thrust required, and is called a “rubber-engine”. The designer will use a rubber engine in the early stages of design, specially for a major military fighter, bomber program, or SST ( the second supersonic transport ). And then, with the customer, tell the engine company what characteristics the new engine should be have; 6.1 Introduction(3) When the engine company finalize the design for the new engine, it becomes fixed in size and thrust ( fixed-engine ); Developing a new jet engine costs several billion dollars. Developing and certifying a new piston engine is also very expensive. Most aircraft projects do not rate development of a new engine, and so must rely on selecting the best of the existing engines; 6.1 Introduction(4) Even projects that must use an existing engine may begin with a rubber-engine design study to determine what characteristics to look for in the selection of an existing engine. The rubber engine can be scaled to any thrust so the thrust-to-weight ratio can be held to some desired value even as the aircraft weight is varied. 6.1 Introduction(5) The