aircraft piston engine

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A SEMINAR ON AIRCRAFT PISTON ENGINE Presented by, Ambigapathy.M Karuppusamy.P Roland Clements.J Selvamani.M


AGENDA Introduction History of Piston engine Types of Piston engine Parts of Piston engine Piston engine working Piston engine systems Advantages of Piston engine Limitations of Piston engine

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Introduction In 1903, the Wright brothers made history with the first powered aeroplane that could carry a man. Their flying machine was powered by a piston engine – and today, a century later, piston engines are still used, in hundreds of thousands of aircraft, all over the world. 1903 1955 1991 1935 1916

History of Piston Engine:

History of Piston Engine Combustion Air Piston Steam Solid Fuel There are many types of piston engine where solid fuel is burnt externally in a fire box, to turn water into steam, which is piped to the engine to drive the pistons. But these engines are much too heavy for aviation.

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Combustion Air Connecting Rod Steam Crank Crank Crank Driven Wheel Driven Wheel Driven Wheel Solid Fuel Even though this type of engine is heavy, it is efficient; that is, more of the energy developed (power) is available for driving the vehicle through the connecting rod, crank and drive wheels , compared to other forms of power generation. Piston

Internal combustion engine:

Internal combustion engine Bottom Dead Centre (BDC). The combustion process takes place inside the engine. But there are some similarities between the two types of engine. Top Dead Centre (TDC). With the advent of flight, power supplies had to be more efficient - from smaller and lighter engines. Which is where the Internal Combustion Engine came to the fore. Connecting Rod Piston Crank Driven Wheel Crankshaft

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1903- 1940s: Propeller + Piston Engines Era From 1903 (Wright bros.) until the Early 1940s , all aircraft used the piston engine combined with propeller as their propulsion system. Piston engine is just similar with car engine except with several different. A propeller is essentially a type of fan which transmits power by converting rotational motion into thrust to propel the aircraft (move forward). Piston engine uses the energy produced by burning a mixture of air and fuel to drive the propeller.

Types of Piston engines:

Types of Piston engines Single Inline 3 Vee Twin Inline 4 Inline 5

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Vee 5 Vee 6 Vee 8 Piston Engine Types - Layouts

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Based on Cylinder Arrangements: In-Line: Cylinders in a straight line all facing same way Horizontally Opposed In-Line: Cylinders in a straight line, facing each other in p airs con-rods not joined

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V In-Line: Two rows of cylinders, matched in pairs angled to form a V when viewed along the crankshaft, con-rods joined Radial: Complex ‘Star’ cylinder arrangement, con-rods joined Radial “ V“ configuration

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Cut section of RADIAL engine

Parts of piston engine:

Parts of piston engine Cylinder Barrel Cylinder Walls Cylinder Heads Valve Guides Crankcase Piston Head Piston Rings Oil control Ring Oil Scraper Ring Piston Pins Connecting Rod Spark Plug

Cylinder Barrel :

Cylinder Barrel Chrome-molybdenum or nickel- molybdenum steel Used to guide and seal piston and to mount cylinder assembly to head Barrel threads into head to form cylinder assembly

Cylinder Walls :

Cylinder Walls Cylinder interior wall

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Inside surface of cylinder barrel is honed to a controlled amount of roughness Rough enough to hold oil film but smooth enough to minimize friction and wear Plain steel cylinder walls are not treated to prevent wear or corrosion Nitrided cylinder walls are hardened to reduce wear but still rust as easily as plain steel walls. Nitriding is exposing the cylinder wall to ammonia at high temperatures and it hardens the wall to a thickness of approximately .005”

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Chrome cylinder walls use chromium plating to resist wear and provide a corrosion resistant surface. Cylinders may be chromed back to standard inside dimensions if they become worn Chrome is too smooth to hold oil without etching or channeling during the overhaul process The cylinder wall is tapered inward towards the top so that as the engine warms up, the hotter top of the wall expands more than the bottom, creating a round barrel at operating temperature.

Cylinder heads :

Cylinder heads Constructed of cast aluminum Provides combustion chamber, and mounting areas for spark plugs and valve parts

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The cylinder head is designed to transfer heat by conduction to the fins and then from the fins to the air by convection The exhaust side of the head has the most fins as it runs the hottest The head also may incorporate a drain line fitting to allow excess oil to return to the crankcase (inter cylinder drain lines on radials)

Valve Guides :

Valve Guides Made of bronze Secured in the head by an interference (shrink) fit Made of chrome steel, stellite, or brass Secured by interference fit Valve Seats

Crankcase :

Crankcase The crankcase holds all of the engine parts in alignment and supports the cylinders and crankshaft

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It provides a place to mount the engine to the aircraft Constructed of aluminum alloy Divided into sections (radial) Nose section - Houses prop shaft and bearings Power section - mount for cylinders Fuel induction section - intake tubes, blower, manifolds (supercharger) Accessory section - mounts for magnetos, pumps, generators (magnesium) Opposed crankcase: Sections are not as distinct as in the radial and the crankcase splits from front to rear instead of in radial sections

Pistons Head :

Pistons Head Constructed of aluminum alloy Parts include top, ring grooves, ring lands, skirt, and piston pin boss Cooling fins on the bottom help the oil carry heat away from the piston top

Cam ground pistons :

Cam ground pistons diameter of the piston is greater perpendicular to the piston pin boss This compensates for uneven expansion during operation (becomes round at operating temperature)

Piston head designs :

Piston head designs

Piston rings (general):

Piston rings (general) Provide seal between cylinder wall and piston Rings ride on a thin film of oil Conduct heat from the piston out to the cylinder and the fins Material is cast iron or chrome steel

Piston rings (type) :

Piston rings (type) Compression rings are located at the top of the piston and seal the combustion chamber Types include rectangular, tapered, wedge Compression rings:

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On bottom of piston below compression rings Regulates oil film thickness on cylinder wall Holes in ring and piston allow excess oil to drain back to crankcase Too much oil film and the engine will use excessive oil and too little oil causes heat and insufficient lubrication Oil control rings:

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Oil scraper rings: Directs the oil away from or towards the oil control rings depending upon the requirements of the engine. Piston Pins (wrist pins): Connects the piston to the end of the connecting rod Constructed of hardened steel The pin is retained in the piston with clips or plugs to prevent cylinder wall scoring Typical Lycoming and Continental pins are free-floating, meaning the pin is not secured to the piston or the rod.

Piston ring end gap:

Piston ring end gap The gap at the end of the rings allows for expansion and contraction and unevenness in the cylinder wall Always stagger the end gaps during ring installation to prevent losing compression. Butt, step and angle types

Connecting Rod Assembly:

Connecting Rod Assembly The link between the crankshaft and the piston Normally steel but some low powered engines use aluminum to save weight Cross section is an “H” or “I” Types include : Plain Rod Fork and blade rod Master and articulated

Spark Plug:

Spark Plug Electric power for the spark plugs is generated by the Magnetos , which work like a motor in reverse, by generating an electric current when their internal components are rotated

Basic working principles of Piston engine:

Basic working principles of P iston engine The piston engine and a bicycle pump are basically similar, in that both have a cylinder, inside which is a plunger or piston. Pull the piston back to force air in. Then push the piston up the cylinder, to push the air out. Air forced out A Bicycle Pump Air forced in Air forced in A Piston Engine CYLINDER PISTON Compressed charge of fuel and air Expanding gases force piston down CYLINDER PISTON

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Cylinder Piston Crank Shaft A piston engine has a crankshaft, which works the same way as the bicycle pedals and crank. The force on the bicycle pedal from leg muscles is equivalent to the force supplied by burning fuel and air. A B Crank Fuel and Air

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Cylinder Piston Connecting Rod Crank Shaft ‘Big-end’ Gudgeon Pin Fuel and Air The crankshaft is made-up of various parts. The piston connects to the crankshaft by a connecting (con) rod. The piston is attached to the conrod by a ‘ Gudgeon ’ pin. And the conrod itself is attached to the crankshaft by the ‘Big-end’ bearing.

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The piston movement now causes the crankshaft to rotate, so we can use the crankshaft rotation to drive a propeller, or the wheels of a car. The rotating crankshaft also provides a means of returning the piston to its starting point. So the piston produces linear thrusting movements time after time. Main Bearings Offset Bearing Counter Balance Weights Cylinder Piston Connecting Rod Crank Shaft ‘Big-end’ Gudgeon Pin Fuel and Air

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FRONT Crankshaft Timing Belt & Water Pump driving pulley location Flywheel attachment flange REAR The crankshaft is mounted in the engine via the main bearings; on the rotational centre of the crankshaft. At the rear there is a mounting flange for a flywheel. The timing gear and ancillaries (water pump and alternator) are driven from the front of the crankshaft, which is where the aircraft propeller is mounted.

Valve Operation :

Valve Operation The Exhaust Valve needs to be open, to allow the burnt gases out The Inlet Valve needs to be open, to allow the fuel/air mixture in Inlet Valve Exhaust Valve In order to compress the fuel air mixture in each cylinder, first it has to be able to get in, then it has to be sealed in or compression cannot take place. This is done through the operation of inlet and exhaust valves.

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Overhead Cam No Rocker Overhead Cam and Rocker Cam Shaft Return Spring Valve Rocker Arm The less parts there are, the more accurate the work with opening and closing times, and the more efficient the engine. Some engines feature a hydraulic system for valve opening (closing via a return spring), but driven by a cam. Some manufacturers now fit VARIABLE valve timing; to ensure that the valves operate at the optimum point at all rpm values to gain maximum efficiency from a piston engine.

Push rod mechanism:

Inlet Valve Open Rocker Rocker Shaft Return Spring Valve Seat Push Rod Cam Shaft Valve Lift Inlet Valve Closed The valve opening motion comes from a rotating cam shaft. A cam has a raised portion that lifts the cam follower or push rod, which either operates a rocking lever or the cam bears directly on the top end of the valve stem, to open the valve. When the valve is forced open, the return spring is compressed, so when the cam rotates to a none raised section, the spring pushes the valve closed. Push rod mechanism

Cam drive mechanism:

Modern Engines use a toothed rubber belt to drive the cam shafts Cam Drive Mechanism Pistons and Crank Shaft Twin Cam System Chain Tensioners Cam drive mechanism

Major engine Assemblies:

Major engine Assemblies Flywheel Pistons and Crankshaft Sump (Oil Tank) Cylinder Block Cylinder Head Assembly Valve Gear ‘Rocker Box’ Cover The Cylinder Head Assembly houses the valve gear mechanism and the top of the cylinders. The spark plugs, inlet and exhaust manifolds are bolted to the head. The Cylinder Block houses the cylinders and the pistons. Also the oil pump and filter (inside), and externally the water pump, and the alternator. The Rocker Box Cover shields the valve mechanism and contains the lubricating oil. The Sump keeps the oil in and can double as an oil tank.

Chemistry of Power :

Chemistry of Power A Heat Engine is one that uses Combustion to create Heat Energy, which it then converts into Mechanical Energy The Combustion occurs when a compressed Fuel/Air mixture is ignited by a spark The Fuel, Aviation Gasoline (Petroleum Spirit, a Fossil Fuel), is mixed with Air in the Carburetor, then injected into the cylinder and compressed

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The ‘ideal’ Fuel/Air mixture is 1/15 , called Stoichiometric More Fuel = Rich Mixture, More Air = Lean Mixture Normally Rich at start-up, then reduced to typically 1/12 Compression begins the chemical combination process, and makes the combustion more efficient When ignited, the mixture Oxidizes, releasing Energy BANG! After ignition, waste gases such as Carbon Dioxide, and Carb

Piston Engine Working:

Piston Engine Working Intake Valve - fuel/air mixture enters here The Cylinder - fuel is compressed and burned inside Exhaust Valve - Exhaust gasses out here Piston - Forced down by explosion, then pushes up and forces exhaust gasses out of the cylinder Connecting Rod (Con-Rod) - connects piston to crankshaft Crankshaft - translates piston up/down into shaft rotation, complex shape allows all pistons to work together in sequence

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The 4-Stroke Cycle

Piston engine systems:

Piston engine systems Fuel System Starting System Cooling System Lubrication System

Fuel Systems: Aircraft Carburetor :

Fuel Systems: Aircraft Carburetor Air is drawn into the engine through the carburetor (due to piston suction), and flows through a Venturi The Venturi causes the air to accelerate, and thus, due to Bernoulli's principle, the pressure drops The pressure drop sucks gasoline into the airflow

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Mixture Control ensures that the mixture which enters the cylinder is the correct mix of fuel and air Nozzle ‘Atomizes’ the mixture (very fine mist), which makes combustion much more efficient Throttle opens/closes a valve to control the amount of mixture which can enter the cylinders When necessary, the Carburetor Heat function uses Hot Exhaust gasses to melt any ice in the Venturi Throttle and Mixture can be controlled from the cockpit

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The Starting System

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The Cooling System A water-cooled cooling system

Air-cooled cooling system:

Air-cooled cooling system Air-cooled engine (notice fins on the head and block)

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The Lubrication System

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The differences between piston aircraft engines and car engines Crankshaft – The crankshaft in an piston aircraft engine turns a propeller , crankshaft in car engine is used to move the wheels of the car. Weight – the piston aircraft engine must be lightweight compare to car engine. Power demand to run the engines- the piston aircraft engine demands high power for very long times compare to car engines Numbers of engine parts - an aircraft engine has at least two sets for every parts, including ignition system (spark plugs and magnetos) and fuel pumps compare to car engine that only have one set. Operating environment different- an aircraft engine no need radiator for air-cooling compare to the car.

Advantages of A/C Piston engine:

Advantages of A/C Piston engine From a manufacturing and engineering perspective, the reciprocating engines found in piston aircraft are far less complex Piston engines are indeed a more simple design W ell suited for relatively short missions of 300 miles or less Consumes less fuel, thus cheaper and much more economic than jets. Quiet, but fly at lower speeds. The best option for people who need to transport a few passengers and/or small amounts of cargo. Best choice for pilots who wish to own their own aircraft.

Limitations of A/C Piston engine:

Limitations of A/C Piston engine Lower load capacity compared to similar sized jet powered aircraft. Propellers are not used on high speed aircraft.

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The End of the seminar

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