Turbomachine Turbomachine is a device in which energy exchange is accomplished by hydrodynamic forces arising between the moving fluid and the rotating and stationary elements of the machine - Daily Turbomachine is a device in which energy is transferred either to, or from a continuously flowing fluid by dynamic action of one or more moving bladed rows -Dixon Turbomachine A Turbomachine is characterised by dynamic action of one or several rotating elements and rapidly moving fluid -Wislicenus Turbomachine Turbomachine is a device in which energy transfer occurs between a continuously flowing fluid and a rotating element due to dynamic action and results in a change in pressure or momentum of fluid. Turbomachines -Three Types Power Generating Turbines Gas, Hydro, Steam, Wind Power Absorbing Pumps Fans, Blowers, Compressors Power Transmitting Hydraulic coupling Torque converter Compressors A typical Compressor System (CM4120 Julie King) Sectional View Compressors Compressors-Purpose Compressors used to increase the pressure of a gas (compressible fluid) Examples – Increase the pressure for instrument air systems (to get control valves to operate), transport gases such as hydrogen, nitrogen, fuel gas, etc. in a chemical plant 2 CLASSES of Compressors Positive Displacement : Operate by trapping a specific volume of gas and forcing it into a smaller volume (THESE ARE NOT TURBO MACHINES ! ) – 2 Basic Designs » Rotary » Reciprocating Non positive Displacement /ROTODYNAMIC : Operate by accelerating the gas and converting the energy to pressure (THESE ARE TURBO MACHINES ! ) – 2 Basic Designs » Centrifugal » Axial ROTARY & RECIPROCATING COMPRESSORS (Positive Displacement type) Positive Displacement (PD) Compressors: Rotary Design Rotary compressors (get their name from the rotating motion of the transfer element) compress gases with lobes, screws, and vanes into smaller volumes. 4 Primary Types of PD Rotary Compressors: – Rotary Screw – Sliding Vane – Lobe – Liquid Ring Rotary Screw Compressor Rotary Screw Compressors Commonly used in industry. It operates with 2 helical rotors that rotate toward each other, causing the teeth to mesh. As the left rotor turns clockwise, the right rotor rotates counterclockwise. This forces the gases to become trapped in the central cavity. The 2 rotors are attached to a drive shaft and drive that provide energy to operate the compressor. Have an inlet suction line and outlet discharge port. Sliding Vane Compressor Sliding Vane Compressors Uses a slightly off-center rotor with sliding vanes to compress gas. Inlet gas flows into the vanes when they are fully extended and form the largest pocket. As the vanes turn toward the discharge port, the gases are compressed. As the volume decreases, the pressure increases until maximum compression is achieved. Then the gas is discharged out of the compressor. Lobe Compressor Lobe Compressors Characterized by 2 bean shaped impellers used to trap and transfer gases. The 2 impellers move in opposite directions on parallel mounted shafts as the lobes sweep across the suction port. Compressed gases are released into the discharge line. The lobes do not touch each other. Very small clearance(of the order of a fraction of mm.) exists between the casing and lobes. Lobe Compressors Designed to have constant volume discharge pressures and constant speed drivers. Lobe Compressors can be used as compressors or vacuum pumps. Liquid Ring Compressors It has one moving transfer element and a casing that is filled with water or seal liquid. As the rotor turns, the fluid is centrifugally forced to the outer wall of the elliptical casing. An air pocket is formed in the center of the casing. As the liquid ring compressor rotates, a small % of the liquid escapes out through discharge port. Make up water or seal liquid is added to the compressor during operation. The liquid helps cool the compressed gases. Liquid Ring Compressors Used to compress hazardous and toxic gases as well as hot gases. Liquid Ring Compressor WORKING PRINCIPLE The rotor is positioned centrally in an oval-shaped body. Upon rotation, which proceeds without metal to metal contact, a ring of liquid is formed which moves with the rotor and follows the shape of the body. At the two points of the nearest proximity of the rotational axis and body, this completely fills the chambers of the rotor and as rotation proceeds, it follows the contour of the body and recedes again, leaving spaces to be filled by the incoming gas.These spaces are connected via the cone porting to the inlet of the compressor. Liquid Ring Compressor WORKING PRINCIPLE As a result of the suction action thus created, gas is pulled into the compressor. As the rotation progresses, the liquid is forced back into the chambers, This gas is forced out of the discharge port and then leaves the compressor via the outlet flange. The compressor is fed continuously with liquid which serves the clearances between inlet and discharge port and remove the heat of compression. This liquid together with the gas to be compressed and is separated from the discharge separator. Positive Displacement Reciprocating Compressors Most common type of compressors. Work by trapping and compressing specific volumes of gas between a piston and a cylinder wall. The back and forth motion incorporated by a reciprocating compressor pulls gas in on the suction (or intake) stroke and discharges it on the other. Spring-loaded suction and discharge valves open/close automatically as the piston moves up and down in the cylinder chamber. Positive Displacement Reciprocating Compressors Basic Parts of are: – – – – – – – – Piston Connecting Rod Crankshaft Driver Piston Rings Suction Line Discharge Line Spring -Loaded Suction and Discharge Valves Positive Displacement:Reciprocating Compressors Can have 1 to 4 cylinders. One shown only has one cylinder. Multi Stage Reciprocating Compressors Discharge from Stage 1 is suction for Stage 2. TURBO COMPRESSORS or ROTODYNAMIC COMPRESSORS ( Non-Positive Displacement type) Rotodynamic Compressors Centrifugal Compressor Centrifugal Compressor Centrifugal Compressor Centrifugal Compressor Centrifugal compressors accelerates the velocity of the gases (increases kinetic energy) which is then converted into pressure as the gas flow leaves the volute and enters the discharge pipe. Usually operate at speeds > 3,000 rpm. Deliver much higher flow rates than positive displacement compressors. Centrifugal Compressor 2 Types of Centrifugal Compressors – Single- Stage : Compress the gas once » Use for high gas flow rates, low discharge pressures – Multi- Stage : Take the discharge of one stage and pass it to the suction of another stage » Use for high gas flow rates, high discharge pressures Centrifugal Compressor Basic Components – Impellers, Vanes, Volutes, Suction Eyes, Discharge lines, Diffuser Plates, Seals, Shaft, Casing – Suction Vane Tips = Part of the impeller vane that comes into contact with gas first. – Discharge Vane Tips = Part of the impeller vane that comes into contact with gas last Axial Compressor Axial Compressor Axial Compressor Axial Compressor Axial Compressor Composed of a rotor that has rows of fan like blades. In industry, axial compressors are used a lot where high flow rates and pressures are needed. Gas flows along the shaft, axially. Rotating blades attached to a shaft push gases over stationary blades called stators. Stator blades are attached to the casing. Axial Compressor……... As the gas velocity is increased by the rotating blades, the stator blades slow it down. As the gas slows down, kinetic energy is converted into pressure. ( Diffuser action) Gas velocity increases as it moves from stage to stage until it reaches the discharge. Axial Compressor……... Multi-Stage axial compressors can generate very high flow rates and discharge pressures. Axial compressors are usually limited to 16 stages (due to temperature/material limitations) Axial compressors are lighter, more efficient, and smaller than centrifugal compressors.