Piston Machines. 1 Celkový obraz. O modulu Pomůcky a nástroje Pravidla a konvence Strana 2/14

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Renata Krausová
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2 1 Celkový obraz O modulu Pomůcky a nástroje Pravidla a konvence Strana 2/14

3 2 Obsah 1. Celkový obraz 2 2. Obsah 3 3. Piston Pumps Piston Pumps 4 4. Piston Compressors Piston Compressors 5 5. Spark-ignition Engines Spark-ignition Engines 7 6. Compression-ignition Engines Compression-ignition Engines Rejstřík Strana 3/14

4 3 Piston Pumps 3.1 Piston Pumps Piston pumps are a type of water pumps which cause the liquid to flow using one or more oscillating pistons. Types according to number of cylinders Piston pumps belong among the reciprocating pumps. They need a system of suction and discharge valves, thank to which the fluid is moved in a required direction. There are various types some of them have just one cylinder (called simplex-cylinder pump), others may have up to four cylinders (quad-cylinder pump) or even more. Most reciprocating pumps are duplex- or "triplex-cylinder types (with two or three cylinders). Types according to the way of suction and discharge They can also differ according to the direction of suction and discharge. Single acting piston pumps have independent suction and discharge strokes, while double acting pumps perform suction and discharge in both directions. Application Piston pumps are usually driven by air or steam, or by a belt drive from an independent engine. Piston pumps were very popular in the times of the industrial revolution in the 19 century, but nowadays they are used less often. Their usual application is for pumping fluids with high resistance, where high flow rate is not needed. Typical pumped materials include for example concrete and heavy oils Strana 4/14

5 4 Piston Compressors 4.1 Piston Compressors Description Piston compressors (often also called reciprocating compressors) are a type of positive-displacement compressors, driven by a crankshaft. They convey gases at high pressure. The intake gas flows through the suction manifold into the compression cylinder. Here a piston, which is driven by a crankshaft, compresses the gas, which is then discharged. Application Reciprocating compressors are used in many kinds of industries. We can find them in gas pipelines and natural gas processing plants, oil refineries, chemical factories and refrigeration plants. Plastic bottles made of polyethylene terephthalate (PET) are also manufactured by blowing with the use of piston compressors. Portable compressors Piston compressors can be made as a portable tool, which can power various machines. In the past they were used to drive for example pneumatic drills. Such a unit was usually mounted on a trailer and the compressor was driven through a centrifugal clutch by an engine, usually diesel. The engine had a speed limiter (or a governor), which enabled it to run at two speeds: idling, the clutch was disengaged maximum, the clutch was engaged and the compressor was running However, nowadays these portable piston compressors have been replaced by rotary compressors. piston compressor, reciprocating compressor pístový kompresor positive-displacement compressor objemový kompresor Vocabulary driven poháněný crankshaft kliková hřídel convey dopravit pressure tlak intake gas nasávaný plyn suction manifold sběrné sací potrubí compression cylinder vzduchový válec piston píst Strana 5/14

6 compress stlačit discharge vytlačit application využití industry průmysl gas pipeline plynovod natural gas processing plant továrna na zpracování zemního plynu, plynárna oil refinery ropná rafinérie refrigeration plant chladící zařízení polyethylene terephthalate polyethylentereftalát blowing vyfukování portable přenosný tool nástroj power pohánět pneumatic drill pneumatická sbíječka unit stroj, agregát mounted upevněný, namontovaný trailer přívěs centrifugal clutch odstředivá spojka diesel engine naftový motor speed limiter, governor omezovač otáček, omezovač rychlosti idling volnoběh engaged clutch zapnutá spojka disengaged clutch vypnutá spojka rotary compressor rotační kompresor, kompresor s otočnými písty Strana 6/14

7 5 Spark-ignition Engines 5.1 Spark-ignition Engines Spark-ignition engines are a type of internal combustion engines. Unlike the compression-ignition engines, where the heat resulting from compression ignites the fuel mixture, in spark-ignition engines it is ignited with an electrically produced spark. Division There are two types of spark-ignition engines: two-stroke engine: the thermodynamic cycle is completed in two movements of the piston four-stroke engine, also known as Otto cycle engine: the thermodynamic cycle is completed in four movements of the piston Wankel engine: the four piston strokes do not follow one after another, instead they take place simultaneously in different parts of the engine Strana 7/14

8 Fuel mixture Because the fuel mixture typically consists of air and petrol (gasoline or gas in American English), they are usually referred to as petrol engines (gasoline engines or gas engines in American English). However, other fuels can be used as well, such as autogas (LPG), compressed natural gas (CNG), methanol, ethanol or hydrogen. Cars in drag racing usually use nitromethane. Mixing process Spark-ignition engines were traditionally distinguished from compression-ignition engines also according to the place, where the fuel is mixed with air. While the compression-ignition engines blend fuel inside the cylinders, in spark-ignition engines it was done outside the cylinders, in a carburettor. However, in modern engines highly pressurized fuel is injected directly into the cylinders, which improves the efficiency of the engines. This process is called gasoline direct injection (GDi) Strana 8/14

9 Vocabulary spark-ignition engine zážehový motor internal combustion engine motor s vnitřním spalováním compression-ignition engine vznětový motor heat teplo compression stlačení ignite zažehnout fuel palivo fuel mixture palivová směs spark jiskra two-stroke engine dvoudobý motor four-stroke engine, Otto cycle engine čtyřdobý motor Wankel engine Wankelův motor piston píst simultaneously současně petrol (American English: gasoline, gas) benzín petrol engine (American English: gasoline engine, gas engine) benzínový motor blend smíchat cylinder válec carburettor (American English: carburetor) karburátor pressurized pod tlakem Strana 9/14

10 inject vstřikovat efficiency výkon direct injection přímé vstřikování autogas, LPG (Liquefied petroleum gas) zkapalněný ropný plyn natural gas zemní plyn hydrogen vodík drag racing závody dragsterů cat-away průřez Obrázky a fotografie použité v této kapitole pochází ze stránek {Wikimedia Commons XH kde byly zveřejněny pod licencí {GNU FDL XH Strana 10/14

11 6 Compression-ignition Engines 6.1 Compression-ignition Engines Compression-ignition engine is a type of an internal combustion engine. Because it converts heat into work, it belongs among heat engines. Unlike spark-ignition engines, the fuel mixture is ignited by the heat resulting form the compression of the mixture. The fuel is injected into the combustion chamber in the final stage of the compression. Operation Compression-ignition engines are often also called Diesel engines, after the European inventor and mechanical engineer Rudolf Christian Karl Diesel. It operates using the so called Diesel cycle. The picture on the right shows a p-v diagram for the diesel cycle, which follows four distinct processes. 1 to 2: compression (blue) 2 to 3: constant pressure heating (red) 3 to 4: expansion (yellow) 4 to 1: constant volume cooling (green) Strana 11/14

12 Types There are two sorts of compression-ignition engines, divided by the type of the combustion cycle: four-stroke cycle: the most common diesel engines, used for many motor vehicles, especially buses, trucks and often also for cars. two-stroke cycle: used especially for large engines for locomotives or boats. They have better power-to-weight ratio, and lower fuel consumption. Vocabulary compression-ignition engine, Diesel engine vznětový motor spark-ignition engine zážehový motor internal combustion engine motor s vnitřním spalováním convert přeměnit heat teplo heat engine tepelný stroj fuel mixture palivová směs ignite zažehnout compression stlačení inject - vstříknout combustion chamber spalovací komora Strana 12/14

13 combustion cycle spalovací takt four-stroke čtyřdobý two-stroke dvoudobý motor vehicle motorové vozidlo locomotive lokomotiva power-to-weight ratio poměr výkonu k hmotnosti fuel consumption spotřeba paliva clockwise proti směru hodinových ručiček Obrázky a fotografie použité v této kapitole pochází ze stránek {Wikimedia Commons XH kde byly zveřejněny pod licencí {GNU FDL XH Strana 13/14

14 7 Rejstřík Strana 14/14

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