Piston engine
Piston machines are fluid energy machines with a working space , the volume of which is intermittently changed by a usually periodically moving displacer ( piston ) . The fluid flow and pressure differences between inlet and outlet are variable in piston machines due to the intermittent mode of operation , which distinguishes them from continuously operating flow machines such as gas turbines , in which the fluid flow and pressure curve remain stationary .
In general, it can be both working machines (from the point of view of hydraulics : "transmitter" ), as well as power machines (motors; in hydraulics: "slave" ), with some piston machines also being able to work reversibly in both directions, such as hydraulic cylinders as well as some hydraulic pumps that work in reverse as a hydraulic motor or a Stirling motor that is driven as a work machine to become a heat pump . There are two different kinematic principles:
- Reciprocating piston machines in which the displacer is a piston that moves back and forth in a cylinder . In the broadest sense , machines that work with a diaphragm ( diaphragm pump , diaphragm cylinder ) are also piston machines.
- Rotary piston machines in which specially shaped displacers either only rotate or also revolve on a circular path.
Reciprocating engines
In reciprocating piston engines which is the displacer , a more or less disc-shaped piston (engl. Piston ) extending in a cylinder reciprocates or a cylindrical plunger , which, for example, in a stuffing box is running. There are reciprocating piston machines both as work machines ( pump = transmitter ) and as prime movers ( slave ) that drive a load, such as a hydraulic cylinder . Similar principles apply in pneumatics , but the compressibility of the working gas with compression and expansion must then also be taken into account. A distinction must be made depending on the type of kinematics :
- Simple reciprocating piston machines that act directly with their linear movement via a push rod , such as simple pneumatic cylinders , hydraulic cylinders or a plunger pump :
- Reciprocating piston engines with crank mechanism in which the linear movement kinematically via a thrust crank in a rotational movement is implemented as reciprocating pumps and compressors ( compressor ) as a working machine , as well as reciprocating engines as the engine :
- Aviation piston machines, on the other hand, transfer the linear movement via a rack to a shaft ( rack and pinion drive ), like the aviation piston engine :
- Free-piston machines , in which the piston itselfacts directly with its linear movement, are usually free-piston motors such as explosion rams or free-piston linear generators or combined with a turbine such as the Pescara gas generator, in which a free-piston diesel engine works against gas springs and its exhaust gases are used in a turbine as a prime mover become
Double-acting combined reciprocating expander compressor
A reciprocating piston engine with a crank mechanism , the upper and lower dead point is determined and hence the one of the components, displacement and compression ratio affect
Free-piston engine : The Pescara gas generator combines a free-piston engine with a gas turbine driven by the exhaust gases
Rotary piston machines
In rotary piston machines rotation (physics) specially shaped displacers rotate so that the crank drive is not required. A distinction must be made here according to the type of kinematics :
- Rotary lobe machines with direct rotary movement of the piston are rotary lobe pumps , such as rotary vane pumps , gear pumps or Roots blowers , which conversely can also work as hydraulic motors : The rotary lobe pumps also include the liquid ring pumps .
- Rotary piston machines , especially rotary piston pumps or rotary piston engines with special kinematics such as the Wankel engine , which works as a periodically working fluid energy machine with a variable pressure curve with a rotating and rotating piston:
| designation | Abbreviation | Rotating inertial forces |
Oscillating mass forces |
example |
|---|---|---|---|---|
| Rotary piston machines | DKM | - | - | Roots blower |
| Rotary piston machines | KKM | + | - | Rotary engine |
| Rotary piston- type rotary piston machines | DUKM | - | + | |
| Rotary piston-type rotary piston machines | KUKM | + | + | Vane pump |
With DUKM and KUKM, the speeds are usually limited if the inertia forces cannot be balanced.
| Machine type | Working machines | Power machines |
|---|---|---|
| Hydraulic piston machines (≈ incompressible media) |
Piston pumps | Hydraulic motors |
| Thermal piston machines (compressible media) |
Reciprocating compressors |
Internal combustion engine, gas expansion engine, steam engine, Stirling engine |
See also
- Displacement machine
- Free piston machine
- Rotary piston pump
- Working machine
- Power machine
- Cylinder pressure indexing
literature
- Wolfgang Kalide: Pistons and flow machines. 1st edition, Carl Hanser Verlag, Munich Vienna, 1974, ISBN 3-446-11752-0
- DIN 1940 standard "Combustion Engines", various editions since July 1946
Web links
Individual evidence
- ↑ a b c d H. Tschöke, K. Mollenhauer, " Dubbel - Taschenbuch für den Maschinenbau ", 24th edition 2014, section P1.1 " Definition and classification of piston engines ", Springer-Verlag Berlin Heidelberg, ISBN 978-3- 642-38890-3
- ↑ [1]
Single cylinder engine | In-line engine | Boxer engine | V-engine | Underground motor | W motor | Y motor | VR engine | X engine | H engine | Δ motor
Radial engine | In-line radial engine | Multiple radial engine | Rotary motor | Swashplate motor
Double piston engine | Opposed piston engine | Free piston engine | Rotary piston engine | Spherical motor | Slide motor | Rotary engine | Glow head motor | Direct injection hot-bulb motor