[edit] Classification

At one time the word, "engine" (from Latin, via Old French, ingenium, "ability") meant any piece of machinery—a sense that persists in expressions such as siege engine. A "motor" (from Latin motor, "mover") is any machine that produces mechanical power. Traditionally, electric motors are not referred to as, "engines"; however, combustion engines are often referred to as, "motors." (An electric engine refers to a locomotive operated by electricity).

However, many people consider engines as things which generate their power from within, and motors as requiring an outside source of energy to perform work.

Engines can be classified in many different ways: by the principles of operation: by the source of energy: by the use of the engine, or by the cooling system employed.

[edit] Principles of operation

A 1906 gasoline engine

Reciprocating:

• Crude oil engine
• Two-stroke cycle
• Four-stroke cycle
• Six-stroke engine
• Hot bulb engine
• Diesel engine
• Poppet valves
• Sleeve valve
• Atkinson cycle
• Free-piston engine

• Proposed
  • IRIS engine
  • Bourke engine
• Improvements
• Controlled Combustion Engine

Rotary:

• Demonstrated:
  • Wankel engine
  • Nutating disc engine
• Proposed:
  • Differential-Stroke Cycle (D-Cycle) Engine
  • Orbital engine
  • Quasiturbine
  • Rotary Atkinson cycle engine
  • Toroidal engine
  • Trochilic engine

Continuous combustion:

• Gas turbine
• Jet engine (including turbojet, turbofan, ramjet, Rocket etc.)

[edit] Engine cycle

[edit] Two-stroke

Main article: Two-stroke cycle

Engines based on the two-stroke cycle use two strokes (one up, one down) for every power stroke. Since there are no dedicated intake or exhaust strokes, alternative methods must be used to scavenge the cylinders. The most common method in spark-ignition two-strokes is to use the downward motion of the piston to pressurize fresh charge in the crankcase, which is then blown through the cylinder through ports in the cylinder walls.

Spark-ignition two-strokes are small and light for their power output and mechanically very simple; however, they are also generally less efficient and more polluting than their four-stroke counterparts. In terms of cubic centimeter for cubic centermeter, a single-cylinder small motor application like a two-stroke engine produces much more power than an equivalent four-strokes due to the enormous advantage of having one power stroke for every 360 degrees of crankshaft rotation (compared to 720 degrees in a 4 stroke motor).

Small displacement, crankcase-scavenged two-stroke engines have been less fuel-efficient than other types of engines when the fuel is mixed with the air prior to scavenging allowing some of it to escape out of the exhaust port. Modern designs (Sarich and Paggio) use air-assisted fuel injection which avoids this loss, and are more efficient than comparably sized four-stroke engines. Fuel injection is essential for a modern two-stroke engine in order to meet ever more stringent emission standards.

Research continues into improving many aspects of two-stroke motors including direct fuel injection, amongst other things. The initial results have produced motors that are much cleaner burning than their traditional counterparts. Two-stroke engines are widely used in snowmobiles, lawnmowers, weed-whackers, chain saws, jet skis, mopeds, outboard motors, and many motorcycles.

The largest compression-ignition engines are two-strokes and are used in some locomotives and large ships. These particular engines use forced induction to scavenge the cylinders; an example of this type of motor is the Wartsila-Sulzer turbocharged two-stroke diesel as used in large container ships. It is the most efficient and powerful engine in the world with over 50% thermal efficiency. For comparison, the most efficient small four-stroke motors are around 43% thermal efficiency (SAE 900648); size is an advantage for efficiency due to the increase in the ratio of volume to area.

[edit] Four-stroke

Main article: Four-stroke cycle

Engines based on the four-stroke or Otto cycle have one power stroke for every four strokes (up-down-up-down) and are used in cars, larger boats, some motorcycles, and many light aircraft. They are generally quieter, more efficient, and larger than their two-stroke counterparts. There are a number of variations of these cycles, most notably the Atkinson and Miller cycles. Most truck and automotive diesel engines use a four-stroke cycle, but with a compression heating ignition system. This variation is called the diesel cycle. The steps involved here are:

1. Intake stroke: Air and vaporized fuel are drawn in.
2. Compression stroke: Fuel vapor and air are compressed and ignited.
3. Combustion stroke: Fuel combusts and piston is pushed downwards.
4. Exhaust stroke: Exhaust is driven out. During the 1st, 2nd, and 4th stroke the piston is relying on power and the momentum generated by the other pistons. In that case, a four cylinder engine would be less powerful than a six or eight cylinder engine.

[edit] Five-stroke

Engines based on the five-stroke cycle are a variant of the four-stroke cycle. Normally, the four cycles are intake, compression, combustion, and exhaust. The fifth cycle is added by Delautour^[9] is refrigeration. Engines running on a five-stroke cycle are claimed to be up to 30% more efficient than equivalent four-stroke engines.

[edit] Six-stroke

The six stroke engine captures the wasted heat from the four-stroke Otto cycle and creates steam, which simultaneously cools the engine while providing a free power stroke. This removes the need for a cooling system making the engine lighter while giving 40% increased efficiency over the Otto Cycle.

Beare Head Technology combines a four-stroke engine bottom end with a ported cylinder which closely resembles that of a two-stroke: thus, 4+2 equals a six-stroke. It has an opposing piston that acts in unison with auxiliary low pressure reed and rotary valves, which allows variable compression and a range of tuning options.

[edit] IRIS Engine

Main article: IRIS engine

The IRIS design replaces the piston and cylinder architecture of conventional engines with a mechanism called the Internally Radiating Impulse Structure or, "IRIS". In an IRIS combustion chamber, a number of inverted segments of a circle or, "chordons", interact to create a continuously sealed chamber of variable volume. Instead of elongating during combustion—as a traditional engine does—the IRIS engines' chamber expands in diameter. This innovation may significantly enhance fuel efficiency by reducing waste heat and increasing the amount of surface area the engine has available to produce torque.

[edit] Bourke engine

Main article: Bourke engine

In this engine, two opposed cylinders are linked to the crank by a Scotch yoke. The Scotch yoke mechanism prevents side thrust which in turn prevents any piston slap allowing the operation as a detonation or "explosion" engine. This also greatly reduces friction between pistons and cylinder walls. The Bourke engine uses fewer moving parts and has to overcome less friction than conventional crank and slider engines with poppet valves, however no independent testing of this engine has ever expanded any of these claims.

[edit] Controlled Combustion Engine

Main article: Controlled Combustion Engine

These are also cylinder-based engines, which may be one or two-stroke but instead of a crankshaft and piston rods, use two gear-connected, counterrotating concentric cams to convert reciprocating motion into rotary movement. These cams practically cancel out sideward forces that would otherwise be exerted on the cylinders by the pistons greatly improving mechanical efficiency. The number of lobes of the cams (always an odd number not less than 3) determines the piston travel versus the torque delivered. In this engine, there are two cylinders that are 180 degrees apart for each pair of counterrotating cams. For single-stroke versions, there are as many cycles per cylinder pair as there are lobes on each cam and twice as many for two-stroke engines.

[edit] Wankel

Main article: Wankel engine

The Wankel engine (rotary engine) does not have piston strokes so it is more properly called a, "four-phase"—rather than a four-stroke engine. It operates with the same separation of phases as the four-stroke engine with the phases taking place in separate locations in the engine. While it is true that three power strokes typically occur per rotor revolution due to the 3/1 revolution ratio of the rotor to the eccentric shaft, only one power stroke per shaft revolution actually occurs; this engine provides three power 'strokes' per revolution per rotor giving it a greater power-to-weight ratio than piston engines. This type of engine is most notably used in the current Mazda RX-8, the earlier RX-7, and other models.

[edit] Gas turbine

Main article: Gas turbine

Gas turbine cycle engines employ a continuous combustion system where compression, combustion, and expansion occur simultaneously at different places in the engine—giving continuous power.

A gas turbine is a rotary machine similar in principle to a steam turbine and it consists of three main components: a compressor, a combustion chamber, and a turbine. The air after being compressed in the compressor is heated by burning fuel in it. About two-thirds of the heated air combined with the products of combustion is expanded in a turbine resulting in work output which is used to drive the compressor. The rest (about one-third) is available as useful work output.

[edit] Jet engine

Main article: Jet engine

Jet engines take a large volume of hot gas from a combustion process (typically a gas turbine, but rocket forms of jet propulsion often use solid or liquid propellants) and feed it through a nozzle which accelerates the jet to high speed. As the jet accelerates through the nozzle, this creates thrust and in turn does useful work.

From Wikipedia, the free encyclopedia

A colored automobile engine

The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber (or "cylinder"). This exothermic reaction creates gases at high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause the movement of solid parts of the engine: by acting on pistons, rotors, or even by pressing on and moving the entire engine itself.^[1][2][3][4]

The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating piston engines, Wankel engines, and similar designs in which combustion is intermittent. However, continuous combustion engines such as jet engines, most rockets, and many gas turbines are also classified as types of internal combustion engines.^[1][2][3][4]

Internal combustion engines contrast with external combustion engines such as steam engines and Stirling engines that use a separate combustion chamber to heat a separate working fluid—which then in turn does work. For example, by moving a piston or a turbine.

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Pre-Commissioning Lead Mechanical / Rotating Equipment Engineer

Reference: 1216042058

ERS have a Client actively seeking to appoint a Pre-Commissioning Lead Mechanical / Rotating Equipment Engineer to be based in Saudi Arabia.

Location:

Al-Jubail, Saudi Arabia

Salary

Competitive salary depending on qualifications and experience

Job Responsibilities

Supervise the day-to-day administration of the commissioning of all static and rotating machinery, e.g. towers, vessels, drums, sumps, pumps, compressors, fans, etc., including those fitted as part of a unit.

Ensure work of contractors is carried out safely and efficiently in a competent manner and that they adhere to the Permit to Work System.

Assist compilation of punch lists in conjunction with the contractor and client.

Assist in the resolution of interface problems with other contractors.

Ensure safety and security of all commissioning activities and workers under his/her control.

Progress and direct Discipline Supervisors and Contractors to ensure work is completed in a timely manner.

Ensure that all equipment listed is preserved and maintained in accordance with the guarantee requirements of all Vendors.

Supervise the commissioning of all mechanical equipment, including organization and monitoring of vendor representatives´ site visits.

Accountability to Commissioning Site Manager.

Tel: +44 (0) 1454 203 460

cv@energyrs.co.uk

Injector pada sebuah steam turbine generator bisa di rupakan seperti sebuah pompa yang menggunakan ' venturi effect ' dari sebuah ' converging - diverging nozzle ' dengan tujuan meng-convert energi tekanan (pressure energy) dari sebuah 'fluida yang bergerak' menjadi sebuah energi percepatan (velocity energy) yang pada akhirnya akan menciptakan suatu area yang bertekanan rendah yang mampu menarik fluida pengisi untuk di mampatkan kembali kemudian di rubah lagi dari energi percepatan menjadi energi tekanan.
Fluida yang bergerak tersebut bisa sebuah uap air, cairan atau gas. Sedangkan zat yang masuk ke dalam nozzle penghisapan bisa sebuah gas, sebuah fluida, bubur/slurry atau debu gas (dast-laden gas stream).
Diagram damping melukiskan sebuah in/ejector yang sudah cukup modern. Ini menggambarkan sebuah 'motive fluid nozzle & converging-diverging outlet nozzle'. Air, udara, uap air atau bentuk fluida lainya pada tekanan yang tinggi akan menimbulkan sebuah gaya gerak (motive force) pada inlet.Efek Venturi, bagian dari prinsip bernoulli tersebut teraplikasikan pada teknologi in/ejector ini. Fluida yang bertekanan tinggi dirubah menjadi energi percepatan (high velocity jet) pada leher converging-diverging nozzle yang mana hal ini akan menyebabkan terjadinya area bertekanan rendah pada daerah tersebut. Area bertekanan rendah tersebut kemudian menghisap fluida pada suction ke converging-diverging nozzle sehingga bercampur dengan motive fluid.

Kesimpulannya adalah, energi tekanan yang ada pada inlet motive fluid dirubah menjadi energi kinektik dalam bentuk percepatan pada leher converging-diverging nozzle, kemudian ter-expand di dalam divergent diffuser, energi kinetik ini di rubah kembali menjadi energi tekanan pada diffuser outlet (seperti aturan pada prinsip bernoulli).

Sebagai rancangan parameter, maka formula berikut sangat penting :

• The compression ratio of the injector, P2 / P1, is defined as ratio of the injectors's outlet pressure P2 to the inlet pressure of the suction fluid P1.
• The entrainment ratio of the injector, Ws / Wv, is defined as the amount of motive fluid Ws (in kg/hr) required to entrain and compress a given amount Wv (in kg/hr) of suction fluid.
• The compression ratio and the entrainment ratio are key parameters in designing an injector or ejector.

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Industry leader - privately held OEM of power protection equipment is looking for leadership in the Mechanical Eng dept - TREMENDOUS opportunity - BSME expected

Simon Turner of leading Specialist Nuclear Recruitment firm Energy Recruitment Solutions Ltd, reports that ERS is enjoying unprecedented demand from their substantial base of industry leading UK and International firms, all actively seeking to engage quality personnel on a Permanent basis, thus enjoying cost savings over third party Contracting costs, Security Checking, etc.

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Details of current vacancies can be found via http://www.ersjobs.co.uk or feel free to contact Simon Turner direct for an informal chat about your career objectives. More information about ERS is available on  http://www.nuclear-energy.co.uk

To discuss how to best leverage your skillset and enjoy the best possible terms of engagement, contact Simon Turner of ERS on +44(0) 1454 203 460 or submit a CV to cv@energyrs.co.uk to register your interest or request a Job Search.

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