Turbomachinery { pumps, fans and turbines
Fluid machinery
Eciency
Characteristic curves Turbomachinery { pumps, fans and turbines Pump/pipe systems SOE2156: Fluids Lecture 4 Pump/pipe systems
Pump/pipe systems Turbomachinery { pumps, fans and turbines Fluid machinery
Fluid machinery Fluid machine { a device exchanging energy (work) between a Eciency uid and a mechanical system. Characteristic curves In particular : a turbomachine is a device using a rotating
Pump/pipe mechanical system. systems
Pump/pipe The ow of energy can be in either direction : systems 1 Turbine ! the ow does work on the mechanical system Pump/pipe systems (i.e. energy is transmitted from the uid to the mechanical system)
2 Pumps, fans, compressors, blowers ! the mechanical system does work on the ow (i.e. energy is transmitted from the rotor to the uid) Contact between the mechanical and uid parts is via an impeller Turbomachinery { pumps, fans and turbines Types of turbine Fluid machinery Impulse turbine { e.g. Pelton wheel. Free jet of water impinges Eciency on revolving impeller (runner) and is de ected. Characteristic Change of momentum of water change of curves momentum (torque) for impeller. Pump/pipe systems Total available head converted into kinetic energy Pump/pipe systems head ! work done on impeller. Pump/pipe Reaction turbine { e.g. centrifugal, Kaplan turbine. Turbine systems completely enclosed in water, which can be pressurised. Shape of blades forces change in momentum of water { torque on blades { power. Reaction turbine uses available pressure head directly, without conversion to k.e. Turbomachinery { pumps, fans and turbines
Fluid machinery Eciency Contact between the mechanical and uid parts is via an Characteristic curves impeller Pump/pipe 1 Axial ow : uid approaches and leaves impeller along the systems axis of rotation Pump/pipe systems 2 Centrifugal ow : uid approaches axially, leaves radially Pump/pipe systems (in plane of impeller)
3 Mixed ow : part axial, part radial Turbomachinery { pumps, fans and turbines Centrifugal pumps/turbines
Fluid machinery
Eciency
Characteristic curves
Pump/pipe systems
Pump/pipe systems
Pump/pipe systems Turbomachinery { pumps, fans and turbines Kaplan turbine (axial ow)
Fluid machinery
Eciency
Characteristic curves
Pump/pipe systems
Pump/pipe systems
Pump/pipe systems Turbomachinery { pumps, fans and turbines Eciency
Fluid machinery Eciency De ne the eciency of a turbine Characteristic curves Actual power generated by turbine Pump/pipe = systems Head available to turbine Pump/pipe systems Power generated by turbine will be reduced by a number of Pump/pipe systems losses : Mechanical losses { bearing friction etc. Hydraulic losses, including : Impeller power loss { ineciencies in the impeller design Leakage power loss { some ow evades the impeller Casing power loss { friction with casing Turbomachinery { pumps, fans and turbines For a turbine, supplied with water ow rate Q at head H, the Fluid machinery power generated will be
Eciency
Characteristic P = gQH curves
Pump/pipe systems Reaction turbines will also operate as pumps { mechanical work Pump/pipe used to increase energy of uid. systems
Pump/pipe For a pump, pumping ow rate Q against head H, the power systems necessary will be gQH P = Eciencies, power, head etc. will depend on design of system and operating conditions. Turbomachinery { pumps, fans and turbines Characteristic curves
Fluid machinery
Eciency For a pump, we are interested in how the developed head H, Characteristic curves power P and eciency vary as ow rate Q changes. Plot Pump/pipe these against Q : systems
Pump/pipe systems
Pump/pipe systems
Head H Power P Efficiency
Flow rate Q Turbomachinery { pumps, fans and turbines
Fluid machinery
Eciency For a turbine, plot power P, ow rate Q, eciency against
Characteristic turbine speed N. curves
Pump/pipe systems Pumps, turbines designed to work at a particular point on the
Pump/pipe characteristic curve { hopefully at the most ecient point. systems Usually quote the performance at this design point. Pump/pipe systems What determines the conditions that the pump operates under? How do we couple the pump to the surrounding pipes? 3 Pump characteristic inverted
4 System will function where head and ow both match
Turbomachinery { pumps, fans and turbines Pump/pipe systems
Fluid machinery
Eciency 1 For pipes in series, head Characteristic losses sum curves Pipe Pump/pipe 2 Head losses have the form network systems Q2 Pump/pipe h = K systems l 2gA2 Pump/pipe H systems { i.e. quadratic curve
Q 4 System will function where head and ow both match
Turbomachinery { pumps, fans and turbines Pump/pipe systems
Fluid machinery
Eciency 1 For pipes in series, head Characteristic losses sum curves Pipe Pump/pipe 2 Head losses have the form network systems Pump Q2 Pump/pipe h = K systems l 2gA2 Pump/pipe H systems { i.e. quadratic curve
3 Pump characteristic inverted Q Turbomachinery { pumps, fans and turbines Pump/pipe systems
Fluid machinery
Eciency 1 For pipes in series, head Characteristic losses sum curves Pipe Pump/pipe 2 Head losses have the form network systems Pump Q2 Pump/pipe h = K systems l 2gA2 Pump/pipe H systems { i.e. quadratic curve
3 Pump characteristic inverted Q 4 System will function where head and ow both match