Fundamentals of Turbomachinery Design

Turbomachinery: Turbomachinery refers to machines that convert mechanical energy into fluid energy or vice versa. It includes pumps, compressors, turbines, and fans, among others.

Axial-flow Turbomachinery: Axial-flow turbomachinery is a type of turbomachinery where the fluid flows parallel to the axis of rotation. This type is used in applications where high flow rates and moderate pressure rises are required, such as in gas turbines and compressors.

Radial-flow Turbomachinery: Radial-flow turbomachinery is a type of turbomachinery where the fluid flows perpendicular to the axis of rotation. This type is used in applications where high pressure rises and moderate flow rates are required, such as in centrifugal pumps and compressors.

Mixed-flow Turbomachinery: Mixed-flow turbomachinery is a type of turbomachinery where the fluid flows at an angle between the axial and radial directions. This type is used in applications where both high flow rates and high pressure rises are required, such as in mixed-flow pumps and compressors.

Stages: A stage is a single passage through a turbomachine, consisting of a row of rotating blades and a row of stationary blades.

Blades: Blades are the structures that direct the fluid flow in a turbomachine. Rotating blades are attached to the rotor, while stationary blades are attached to the casing.

Inlet and Outlet Triangles: The inlet and outlet triangles are geometric shapes used to analyze the flow of fluid in a turbomachine. The inlet triangle is used to analyze the flow entering the rotor, while the outlet triangle is used to analyze the flow leaving the rotor.

Absolute and Relative Velocities: Absolute velocity is the velocity of the fluid relative to a stationary observer, while relative velocity is the velocity of the fluid relative to the rotor blades.

Velocity Diagrams: Velocity diagrams are graphical representations used to analyze the flow of fluid in a turbomachine. They consist of vectors representing the absolute and relative velocities of the fluid.

Work: Work is the energy transferred between the fluid and the turbomachine. It is measured in joules (J) or newton-meters (Nm).

Power: Power is the rate at which work is done. It is measured in watts (W) or joules per second (J/s).

Efficiency: Efficiency is the ratio of the power output of the turbomachine to the power input. It is measured as a percentage.

Head: Head is the energy per unit weight of the fluid. It is measured in meters (m) or feet (ft).

Reaction Turbines: Reaction turbines are turbines where the fluid does work on both the rotor and the stator. They are used in applications where high efficiencies are required, such as in hydroelectric power plants.

Impulse Turbines: Impulse turbines are turbines where the fluid does work only on the rotor. They are used in applications where high-speed flows are required, such as in steam turbines.

Cavitation: Cavitation is the formation of vapor bubbles in a fluid due to a decrease in pressure. It can cause damage to the blades and reduce the efficiency of the turbomachine.

Surge: Surge is a phenomenon that occurs in compressors when the flow rate is reduced below a certain level. It can cause damage to the compressor and reduce its efficiency.

Stall: Stall is a phenomenon that occurs in turbines when the flow rate is increased beyond a certain level. It can cause damage to the turbine and reduce its efficiency.

Map: A map is a graphical representation of the performance of a turbomachine. It shows the relationship between the flow rate and the pressure rise or head for different speeds.

Off-design Operation: Off-design operation refers to the operation of a turbomachine outside of its design point. It can result in reduced efficiency and increased wear and tear on the machine.

Design Point: The design point is the operating condition at which the turbomachine is designed to operate at maximum efficiency.

Specific Speed: Specific speed is a dimensionless parameter used to compare the performance of different turbomachines. It is defined as the speed of a machine that would produce one unit of power at one unit of head and one unit of flow rate.

Affinity Laws: Affinity laws are equations used to predict the performance of a turbomachine when its size is changed. They are based on the principles of similarity and dimensional analysis.

Tip Speed Ratio: The tip speed ratio is the ratio of the tangential velocity of the rotor blades to the absolute velocity of the fluid. It is a dimensionless parameter used to describe the operating conditions of a turbomachine.

Degree of Reaction: The degree of reaction is the ratio of the static pressure rise in the rotor to the total pressure rise in the stage. It is a dimensionless parameter used to describe the operating conditions of a turbomachine.

Reynolds Number: Reynolds number is a dimensionless parameter used to describe the flow regime of a fluid. It is defined as the ratio of the inertial forces to the viscous forces in the fluid.

Mach Number: Mach number is a dimensionless parameter used to describe the compressibility of a fluid. It is defined as the ratio of the velocity of the fluid to the speed of sound in the fluid.

Compressible and Incompressible Flow: Compressible flow refers to the flow of fluids where the density changes significantly with pressure, such as in gas turbines. Incompressible flow refers to the flow of fluids where the density remains constant, such as in water pumps.

Steady and Unsteady Flow: Steady flow refers to the flow where the flow parameters do not change with time, such as in a pipeline. Unsteady flow refers to the flow where the flow parameters change with time, such as in a reciprocating pump.

Laminar and Turbulent Flow: Laminar flow refers to the flow where the fluid moves in smooth, parallel layers, such as in a narrow pipe. Turbulent flow refers to the flow where the fluid moves in a chaotic, disordered manner, such as in a wide pipe.

In conclusion, turbomachinery design is a complex and multidisciplinary field that involves the study of fluid mechanics, thermodynamics, and solid mechanics. This explanation has covered some of the key terms and vocabulary used in the field, including axial-flow, radial-flow, and mixed-flow turbomachinery, stages, blades, inlet and outlet triangles, absolute and relative velocities, velocity diagrams, work, power, efficiency, head, reaction turbines, impulse turbines, cavitation, surge, stall, map, off-design operation, design point, specific speed, affinity laws, tip speed ratio, degree of reaction, Reynolds number, Mach number, compressible and incompressible flow, steady and unsteady flow, and laminar and turbulent flow. Understanding these concepts is essential for the design and analysis of turbomachinery.