Adiabatic
Insulated; occurring with no external heat transfer.

Aspect Ratio
The ratio of the blade height to the chord.

Axial Chord
The length of the projection of the blade, as set in the turbine, onto a line parallel to the turbine axis. It is the axial length of the blade.

Axial Solidity
The ratio of the axial chord to the spacing.

Blade Exit Angle
The angle between the tangent to the camber line at the trailing edge and the turbine axial direction.

Blade Height
The radius at the tip minus the radius at the hub.

Blade Inlet Angle:
The angle between the tangent to the camber line at the leading edge and the turbine axial direction.

Blower
A rotary machine that produces a low-to-moderate pressure rise in acompressible fluid (usually air), usually incorporated in a duct. See "fan" and"compressor."

Bucket
Same as rotor blade.

Camber Angle:
The external angle formed by the intersection of the tangents to thecamber line at the leading and trailing edges. It is equal to the sum of the angles formed by the chord line and the camber-line tangents.

Camber Line
The mean line of the blade profile. It extends from the leading edge to the trailing edge, halfway between the pressure surface and the suction surface.

CBE
Compressor-burner-expander, or the "simple" gas-turbine "cycle."

CBEX
Compressor (heat exchanger)-burner-expander-heat exchanger, or the"regenerated," "recuperated," or "heat-exchanger" gas-turbine "cycle."

Chord
The length of the perpendicular projection of the blade profile onto the chord line. It is approximately equal to the linear distance between the leading edge and the trailing edge.

Chord Line
If a two-dimensional blade section were laid convex side up on a flatsurface, the chord line is the line between the points where the front and the rear of the blade section would touch the surface.

Compressor
A rotary machine that produces a relatively high pressure rise (pressureratios greater than 1.1) in a compressible fluid.

Deflection
The total turning angle of the fluid. It is equal to the difference between the flow inlet angle and the flow exit angle.

Deviation Angle
The flow exit angle minus the blade exit angle.

Diffuser
Aduct or passage shaped so that a fluid flowing through it will undergo anefficient reduction in relative velocity and will thereforeincrease in (static) pressure.

Effectiveness
A term applied here to define the heat-transfer efficiency of heatexchangers.

Efficiency
Performance relative to ideal performance. There are many types ofefficiency requiring very precise definitions (see section 2.8).

Entropy
A property of a substance defined in terms of other properties. Its change during a process is of more interest than its absolute value. In an adiabatic.

Process, the increase of entropy indicates the magnitude of losses occurring. Expander: a rotary machine that produces shaft power from a flow of compressible fluid at high pressure discharged at low pressure. In this book the only types of expander treated are turbines.

Flow Exit Angle
The angle between the fluid flow direction at the blade exit and the machine axial direction.

Flow Inlet Angle
The angle between the fluid flow direction at the blade inlet and the machine axial direction.

Head
The height to which a fluid would rise under the action of an incremental pressure in a gravitational field.

Hub
The portion of a turbomachine bounded by the inner surface of the flow annulus.

Hub-Tip Ratio
Same as hub-to-tip-radius ratio.
Hub-to-tip-radius ratio: the ratio of the hub radius to the tip radius.

Incidence Angle
The flow inlet angle minus the blade inlet angle.

Intensive Property
A property that does not increase with mass; for instance, the pressure and temperature of a body of material do not double if an equal mass at the same temperature and pressure is joined to it. (The energy, on the other hand, would double.)

Intercoolers
Heat exchangers that cool a gas after initial compression and beforesubsequent compression.

Isentropic
Occurring at constant entropy.