ラムジェットエンジンの研究 ＩＩ 限界高度比距離特性

Abstract

This paper presents a study on the flight range of a vehicle propelled by a ramjet engine from a view point of the vehicle-engine design trends. Of our interest is to know how far it can fly for a given amount of fuel, which strictly depends on the selection of fundamental design parameters of the vehicle-engine system and the component performance characteristics as well. A systematic parametric study was conducted to reveal the performance variable effects on the steady state flight range, such as the flight Mach number, altitude, lifting force, drag force, vehicle frontal projected areas, vehicle weight, pressure recovery at the inlet, energy density of fuel and so on. It was found that the flight altitude is the most predominant factor to determine the flight range and the higher altitude results in the longer flight distance because of the lower density effects. However, there exists a limit in the flight range, called the aerodynamic ceiling altitude, at which the vehicle lifting force must at least su port the vehicle weight, consequently determining the longest possible flight range attained. The aerodynamic ceiling altitude was found to increase almost linearly with respect to the flight Mach number up to the design value but remain nearly constant above it because of the constant mass flow capture area at the engine inlet. Another limitation is due to the combustion instability as discussed in Part 1 of the present paper which mostly restricts the flight range at the flight Mach numbers below the design value, although it depends on the vehicle lift-weight ratio. The aerodynamic ceiling altitude, therefore, limits the flight range at the higher flight Mach numbers than the design in most of the cases.