An engine is a machine that converts fuel into energy in the form of mechanical work, which can be used to power other machines or vehicles. The most common types of engines are internal combustion engines and external combustion engines. Engines play a critical role in modern society, powering transportation, industry, and many other applications.
Nomenclature & Symbols
- Internal Combustion Engine - These work by burning fuel inside the engine, which creates high pressure and temperature, driving a piston or rotor that is connected to a mechanical system. This mechanical energy can be used to power cars, motorcycles, boats, generators, and other machines.
- Two Stroke Engine - A two stroke engine completes a power cycle in two strokes of the piston. In this engine, the crankcase and the combustion chamber are both integrated into one chamber, which is sealed by the piston.
- Four Stroke Engine - A four stroke engine completes a power cycle in four strokes of the piston. The four strokes are intake, compression, combustion, and exhaust.
- Thermodynamics Cycle
- Otto Cycle - Describes the functioning of a spark ignition piston engine.
- Diecel Cycle - Used in diesel engines. It is a combination of two isentropic processes (compression and expansion) and two constant pressure processes (heat addition and rejection).
- Dual Cycle - Used to model the operation of internal combustion engines, such as gasoline engines and diesel engines. It is a combination of two processes: a constant volume heat addition process and a constant pressure heat rejection process.
- Diesel - A type of liquid fuel used in diesel engines. It is made from crude oil and is heavier and less refined than gasoline. Diesel fuel is composed of hydrocarbons, which are molecules that contain only hydrogen and carbon atoms. The chemical composition of diesel fuel varies depending on the source and refining process, but it typically contains long chain hydrocarbons with between 10 and 20 carbon atoms.
- Gas - A gaseous fuel that is used as a source of energy. Natural gas, which is primarily composed of methane, is the most common type of gas fuel. Other types of gas fuel include propane, butane, and hydrogen.
- Petrol - Also known as gasoline, is a liquid fuel used in internal combustion engines. It is primarily derived from crude oil through a refining process. Petrol contains a mixture of hydrocarbons with different boiling points, which allows it to ignite and burn efficiently in a gasoline engine.
- Engine Speed
- High-speed Engine - An engine that is designed to operate at high speeds. High-speed engines typically have a higher power-to-weight ratio and a smaller size than low-speed engines, which makes them more suitable for applications where space and weight are at a premium. They can also be more fuel efficient and environmentally friendly than low-speed engines due to their ability to operate at higher speeds with lower fuel consumption.
- Medium-speed Engine - These engines that operate at medium speeds, typically ranging from 300 to 1000 revolutions per minute (RPM). Medium-speed engines can be further classified based on their fuel type, such as diesel or gas, and their ignition system, such as spark ignited or compression-ignited. Compared to high-speed engines, medium-speed engines are larger and heavier, but they offer better fuel efficiency and durability.
- Low-speed Engine - They are also known as slow-speed engines or two-stroke engines. These engines operate at a low speed of around 60 to 120 revolutions per minute (RPM) and are known for their fuel efficiency and reliability. They are designed to use heavy fuel oil (HFO) as their primary fuel, which is cheaper than other types of fuel.
- Arrangement of cylinder
- Horizontal Engine - An engine where the cylinders are arranged in a horizontal orientation. These engines are often used in applications where space is limited and a vertical engine cannot fit. Horizontal engines can be either two-stroke or four-stroke, and they may run on gasoline, diesel, or other fuels. One of the advantages of horizontal engines is that they have a lower center of gravity than vertical engines, which can make them more stable and easier to handle.
- Vertical Engine - An engine where the crankshaft is oriented vertically, with the cylinder block and piston moving up and down in a vertical direction. In a vertical engine, the valves are usually positioned at the top of the cylinder head, which can improve the engine's breathing and combustion efficiency. The main advantage of a vertical engine is its compact size, which makes it well-suited for use in applications where space is limited.
- Radial Engine - An engine in which the cylinders are arranged in a circular pattern around the crankcase, with the crankshaft at the center. The pistons are connected to the crankshaft by rods and the crankshaft is fixed to the airframe, while the cylinders rotate around it. The radial engine is known for its reliability and ability to produce high power output, but has largely been replaced by more modern engine designs in most applications.
- V-type Engine - An engine configuration in which the cylinders are arranged in a "V" shape, typically at an angle of 60 or 90 degrees to each other, and mounted on a common crankshaft. The V-shape design allows for a more compact engine size and can also provide a better balance of the reciprocating parts, resulting in less vibration.
- Spark Ignition - A method of igniting a fuel-air mixture in the combustion chamber of an internal combustion engine. It is the most common type of ignition system used in gasoline engines, where a spark is generated by an ignition system to ignite the fuel-air mixture in the combustion chamber. In a spark ignition engine, the fuel and air mixture is compressed by the piston, and then a spark plug generates a spark to ignite the mixture, causing it to combust and drive the piston down.
- Compression Ignition - A method of igniting a fuel-air mixture in the combustion chamber of an internal combustion engine. It is the most common type of ignition system used in diesel engines, where the fuel-air mixture is ignited by the heat generated by the compression of the air in the combustion chamber. In a compression ignition engine, the fuel is injected into the combustion chamber at the end of the compression stroke, and the heat generated by the compressed air ignites the fuel.
- Air Cooling - It is cooled by air rather than by liquid coolant. In an air-cooled engine, the hot air generated by the combustion process is directed over and around the engine components, and the heat is dissipated into the surrounding air. They are generally simpler and lighter than liquid cooled engines, as they do not require a radiator, coolant pump, or other complex cooling system components. They are also less prone to leaks and other cooling system failures.
- Water Cooling - An engine that is cooled by a liquid coolant, usually a mixture of water and antifreeze. In a water cooled engine, the coolant is circulated through the engine block and cylinder head, where it absorbs heat generated by the combustion process, and then flows through a radiator to dissipate the heat into the surrounding air. They are generally more efficient than air cooled engines, as they can maintain a more consistent operating temperature, which can improve fuel efficiency and reduce emissions.
- Stationary Engine - It is used to power equipment that is fixed in place, rather than being mounted on a vehicle or mobile equipment. Stationary engines are used in a wide variety of applications, including generators, water pumps, compressors, sawmills, and industrial machinery. Stationary engines can be either gasoline or diesel-powered, and they can be air cooled or water cooled.
- Automobile Engine - It is used to power a vehicle. Automobile engines are typically designed to run on gasoline, diesel, or alternative fuels such as compressed natural gas or electric power. Automobile engines can be classified based on their configuration, such as inline, V-shaped, or horizontally opposed. They can also be classified based on their number of cylinders, with four-cylinder and six-cylinder engines.
- Portible Engine - Is designed to be easily moved and transported from one location to another. Portable engines can be powered by gasoline, diesel, propane, or other fuels, and they are commonly used for a wide range of applications, including powering small equipment and tools, providing backup power, and running small generators. Portable engines are typically lightweight and compact, and they may be air-cooled or water-cooled.
- Aero Engine - Also known as an aircraft engine, is an internal combustion engine that is designed and used to propel an aircraft through the air. Aero engines can be classified into different types based on their design, size, and the aircraft they are used on.
- External Combustion Engine - This work by heating a fluid, such as steam or gas, outside the engine, which generates pressure and causes mechanical movement. Examples of external combustion engines include steam engines, Stirling engines, and gas turbines.
Heat Source - Require a heat source to produce the heat that will be used to generate power. This heat source can be a variety of fuels, including coal, wood, oil, or natural gas.
Working Fluid - A substance that absorbs the heat from the heat source and converts it into mechanical energy. The working fluid can be a gas, such as air or helium, or a liquid, such as water.
Heat Exchanger - Is the device that transfers heat from the heat source to the working fluid. This can be done through direct contact between the heat source and the working fluid, or through a separate device, such as a boiler or a heat exchanger.
Engine Components - They have various components, such as pistons, turbines, and generators, that work together to convert the heat from the working fluid into mechanical energy.
Control Systems - They require control systems to regulate the flow of heat and working fluid through the engine, as well as to monitor and adjust the engine's performance.
Fuel and Emissions Control - Must meet environmental regulations regarding emissions of pollutants, such as nitrogen oxides and particulate matter. This requires the use of control systems that limit the production of these pollutants and ensure compliance with regulatory standards.
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- Air Filter - The air filter sits at the front of the air intake system, where it catches dirt, dust and debris that can hinder engine performance. Filters are disposable, and should be replaced regularly to guarantee optimum engine health.
- Air Flow Rate - The amount of air that passes through an opening or a device over a given time period, and is typically measured in units of volume per unit time.
- Alternator - In modern automobiles to charge the battery and to power the electrical system when its engine is running. Until the 1960s, automobiles used DC dynamo generators with commutators. With the availability of affordable silicon diode rectifiers, alternators were used instead.
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- Bearing - A curved metal piece that allows motion between components with minimum wear and friction. A bearing that surrounds a shaft may be circular in shape, or semi-circular.
- Bearing Cap - A retainer, held in place by nuts and bolts, which secures bearing shells in place.
- Belt Horsepower - It is the power of the engine measured at the end of a suitable belt, receiving drive from the PTO shaft of the tractor.
- Bore - For the internal combustion engines, the bore is the inner diameter of the engine cylinder.
- Bore Stroke Ratio - It is the ratio of the bore diameter of the engine to the stroke length.
- Bottom Dead Center - The piston’s point of maximum transit in the direction of the cylinder base. In other words, the piston will not travel further towards the cylinder base than the BDC reference point.
- Bottom End - The bottom end includes the cylinder block with all of its internal parts installed. The pistons, rods, crankshaft, and bearing would be in the block. The term short block is often used to mean the same thing as bottom end.
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- Camshaft - A shaft with cams installed on it is named a camshaft. A cam is a piece of equipment that converts the camshaft’s rotating motion into the follower’s linear motion. The valves are opened by the action of a camshaft. There are several cams along the length of this part of the car’s engine, two for each cylinder, one for the inlet valve, and one for the exhaust valve. The camshaft also contains an eccentric to run the fuel pump and gear to run the oil pump and ignition distributor.
- Camshaft Plug - A cup shaped seal that’s pressed into the back of the engine block where the rear of the camshaft is located. This prevents external oil leaks from a camshaft.
- Camshaft Pully - An engine’s timing system uses a cam pulley to regulate the camshaft’s rate of rotation, which in turn regulates the poppet valves that control air intake and exhaust in the cylinders. The timing chain and cam pulley work together to synchronize the crankshaft and camshaft rotation.
- Carburetor - It is the fuel system engine component that meters and mixes fuel and air in the proper proportion. The carburetor also atomizes this mixture and directs it to the intake manifold that distributes it through passages to each combustion chamber in engine.
- Carnot Efficiency - The theroetical maximum efficiency of any heat engine depending only on the temperatures it operates between.
- Combustion - A chemical reaction between a fuel and an oxidizing agent, typically oxygen in the air, that produces heat and light.
- Combustion Chanber - The area within the Cylinder where the fuel/air mix is ignited. As the Piston compresses the fuel/air mix and makes contact with the Spark Plug, the mixture is combusted and pushed out of the Combustion Chamber in the form of energy.
- Compression Ratio - The ratio of the maximum volume to the minimum volume in a cylinder.
- Compression Ring - The piston ring which forms a seal with the cylinder wall to prevent compression loss or gas blow-by (also see piston rings).
- Connecting Rod - This is used to connect piston to crankshaft. It has two ends. one is small end and other one is big end. Small end is connected by piston through gudgeon pin and big end is connected by the crankshaft.
- Connecting Rod Cap - Bolts to the bottom of the connecting rod body. It can be removed to for disassembly of the engine.
- Crankcase - The fuel/air mixture often passes through the crankcase before entering the cylinder in two-stroke engines, which typically employ a crankcase compression arrangement. There is no oil sump in the crankcase in this engine’s design. The majority of the oil in four-stroke engines is stored inside the crankcase, which normally has an oil sump at the bottom.
- Crankcase Ventilation - It is the process that removes the blow-by gases from the engine crankcase and feeds into the intake manifold of the engine.
- Crankshaft - The part of the engine from which power is drawn is the crankshaft. All engine parts use it as one of their primary sources of power transmission. The main component of the power transmission system where the piston’s reciprocating motion is turned into a rotational motion with the aid of a connecting rod is the crankshaft.
- Crank Web - The crankshaft is connected to the piston rod via the crank webs and crank pins. Crank webs allow the reciprocating piston motion to be converted to a rotary motion.
- Cubic Inch Displacement - Is the size of the engine. It is a unit of measurement used to describe the volume of the combustion chamber in an internal combustion engine.
- Cylinder - Cylinders are the main part of an engine, and the space in which the piston travels. Cylinders are normally arranged side by side.
- Cylinder Block - It is actually housing where all engine components reside. It is a metal casting containing the cylinders and cooling ducts of an engine. The cylinder block is extremely strong so it can withstand the rigors of engine torque and vibration, while supporting all attached engine accessories and the transmission. Cylinder block is a complicated component at the heart of the engine, with adoptions to attach the cylinder head, crankcase, engine mounts, drive housing and engine ancillaries, with passages for coolants and lubricants.
- Cylinder Block Deck - A flat machined surface for the cylinder head. Bolt holes are drilled and tapped in the deck for heat bolts. Coolant and oil passages allow fluids through the block, head gasket, and cylinder heads.
- Cylinder Head - Cast iron and an aluminum alloy are typically used to create the cylinder head. Gaskets are used to provide a tight, leak-proof connection between the cylinder head and block, which are connected by studs mounted to the block. Above each cylinder, the cylinder head contains a combustion chamber. Additionally, it has threaded holes for spark plugs as well as valve guides, valve seats, ports, and coolant jackets. It includes channels for the circulation of cooling water.
- Cylinder Liner - The cylinder liner is a thin-walled sleeve made up of hard material and fitted inside a bore made in the cylinder block. It acts as a smooth surface for the reciprocating of the piston and sustains the higher temperature stresses during combustion.
- Direct Injection - Direct injection is the type of fuel injection system in which the fuel is directly injected into the main combustion chamber.
- Distributor - An enclosed rotating shaft used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route secondary, or high voltage, current from the ignition coil to the spark plugs in the correct firing order, and for the correct amount of time.
- Drivetrain - The system of components that enable a car to move, including the engine, clutch assembly, transmission and wheels.
- Engine Balance Shaft - They are geared to the crankshaft or camshaft. The balance shaft has bob weights that spin in the opposite direction of crankshaft rotation. This cancels out torsional vibrations created by the crankshaft, providing a smoother engine idle.
- Engine Block - A cylinder block is the structure which contains the cylinder, plus any cylinder sleeves and coolant passages. In the earliest decades of internal combustion engine development, cylinders w ere usually cast individually, so cylinder blocks were usually produced individually for each cylinder.
- Engine Valvse - Engine valves are necessary to regulate the timing of the entry of the air-fuel mixture into the cylinder and the exit of the combustion products from the cylinders. These are situated at the engine cylinder’s inlet and outlet openings. When closed, the valves are snug against the valve seats.
- Exhaust Manifold - The exhaust manifold, which collects engine exhaust gas from several cylinders and sends it to the exhaust pipe, is often a straightforward cast iron or stainless steel unit. It’s linked to the exhaust valves. Its design is identical to that of the inlet manifold.
- Exhaust Valve - The exhaust valve is the component of four-stroke engines that controls the opening between the engine cylinder and exhaust manifold. During the exhaust stroke, the exhaust valve opens to remove the exhaust gases outside of a cylinder and it remains closed during the suction stroke, compression stroke, and expansion stroke.
- Flywheel - It is a large and heavy metal wheel. Flywheel is attached to the back of the crankshaft to smooth out the firing impulses. It provides inertia to keep the crankshaft turning smoothly during the periods when no power is being applied. It also forms a base for the starter ring gear and in manual transmission, for the clutch assembly.
- Fuel Injector - It sprays fuel into a car's engine using electronic controlled valves, capable of opening and closing many times a second. They have an atomising nozzle that distributes the petrol or diesel evenly, for optimum combustion and efficiency. A car generally has one fuel injector per cylinder.
- Full Pressure Lubrication with Oil Filter - Is similar to an automobile engine that continuously delivers oil under pressure to critical engine components for maximum lubrication and long engine life. A high efficiency pump in the oil sump supplies lubricant to the crankshaft and connecting rod bearing surfaces.
- Glow Plug - The electric heater used in a diesel engine that increases the temperature of the air inside a combustion chamber thus it helps for starting the diesel engine during the cold season.
- Gudgeon Pin - It connects small end of connecting rod to a piston.
- Head Gasket - It is the gasket fitted between the engine block and cylinder head. Its main job is to prevent the leakage of the combustion gases outside of the combustion chamber.
- Head Gasket Volume - The volume of the head gasket refers to the amount of space that it occupies between the cylinder head and the engine block.
- Horsepower - A measure of power or the rate of doing work. In the context of engines, horsepower is used to measure the power output of an engine.
- Idle Speed - It is the speed of the engine when there is no load is acting on the engine.
- Ignition Coil - An electronic engine management component that are a part of the vehicle's ignition system. The ignition coil functions as an induction coil that converts the vehicle's 12 volts into the several thousand that are required to jump the spark plug gap and ignite the engine's air-fuel mixture.
- Indirect Injection - Indirect injection is the type of fuel injection system in which the fuel is injected into the pre-combustion chamber. In this, the combustion process starts in the pre-combustion chamber, and then this mixture is spread into the main combustion chamber.
- Injection Pump - The device that pumps diesel into the cylinders of a diesel engine. Traditionally, the injection pump was driven indirectly from the crankshaft by gears, chains or a toothed belt that also drives the camshaft. It rotates at half crankshaft speed in a conventional four-stroke diesel engine.
- Inlet Valve - The inlet valve is the component of a four-stroke engine that controls the opening between the engine cylinder and intake manifold. During the suction stroke, the intake valve opens to allow the flow of air-fuel mixture inside a cylinder and it remains closed during the compression stroke, expansion stroke and exhaust stroke.
- Intake Manifold - The part of the engine that divides the airflow between the cylinders of an automobile is called the intake manifold. The throttle valve (also known as the throttle body) and other parts are frequently housed in an intake manifold.
- Main Cap - They are blot to the bottom of the cylinder block and form one-half of the main bore. Large main cap bolts screw into holes in the block to secure the caps to the block.
- Manifold - The air-fuel mixture and exhaust gases are carried by separate sets of pipes that are connected to the cylinder head and are known as manifolds. To be able to withstand the high temperature of exhaust gases, it is typically made of cast iron. It comprises the carburetor flange, intake manifold flange for the tailpipe, throttle body flange, and air intake flange.
- Mean Effective Pressure - The average pressure that acts on the piston of an engine during a complete combustion cycle.
- Mean Piston Speed - It is the average speed of the piston while performing reciprocating motion into the engine cylinder.
- Oil Filter - To keep the engine in your automobile operating smoothly, it filters the motor oil to remove dangerous dirt, metal shavings, and debris. Without an oil filter, dangerous contaminants could enter your motor oil and ruin the engine. Your engine oil will stay cleaner and last longer if you filter out the trash.
- Oil Pan - It is attached to the bottom of the engine with bolts and is the reservoir for oil that gets pumped throughout the engine to lubricate, clean and cool moving parts. The pan is usually made of steel or aluminum and typically holds from four to six quarts of oil, depending on the engine
- Piston - A cylindrical plug that rotates inside a cylinder. It contributes to the conversion of fuel combustion’s pressure energy into useful mechanical power, which is then sent to the crankshaft via the connecting rod.
- Piston Deck Volume - Refers to the volume of the combustion chamber that is created by the space between the top of the piston and the cylinder head when the piston is at top dead center.
- Piston Pin - Allows the piston to swing on the connecting rod. The pin fits through the hole in the piston and the connecting rod small end.
- Piston Ring - Automotive pistons normally use three rings, two compression rings and one oil ring.
- Piston Skirt - A cylindrical surface of the piston below piston rings is known as a piston skirt.
- Pressure - A measure of the force exerted per unit area on a surface. It is defined as the force per unit area perpendicular to the surface over which the force is distributed.
- Pressure Lubrication with Oil Filter - Pressure lubrication provides a controlled flow of clean oil to bearings for less wear and longer engine life. A high efficiency pump in the oil sump supplies lubricant to the crankshaft and connecting rod bearing surfaces. The pressure lubrication system incorporates a premium spin-on oil filter.
- Push Rod - Transfers motion between the lifters and the rocker arms. They are needed when the camshaft is located in the cylinder block.
- Rocker Arm - Used to transfer motion from the push rods to the valves. They can be used in both OHC and OHV engines. In any engine, the rockers mount on top of the cylinder head by various methods; rocker shaft, rocker stud, or rocker pedestal. There are two types of rocker arms; adjustable rocker arms, and nonadjustable rocker arms. Adjustable rocker arms provide a means of changing valve train clearance. Nonadjustable rocker arms provide no means of changing valve clearance. They are only used with some hydraulic lifters.
- Spark Plug - Plugs have two primary functions. Engine spark plug ignites the air/fuel chamber and removes the heat from engine combustion chamber.
- Splash Lubrication - In splash lubrication, a gear-driven dipper or slinger in the crankcase distributes oil to components, preventing clogging of small passages. On horizontal crankshaft engines, the dipper is attached to the connecting rod. It picks up oil from the reservoir and spreads it across bearing surfaces as the piston travels through the cylinder. On vertical crankshaft engines, a spinning gear with paddles is immersed in oil and slings lubricant throughout the crankcase.
- Starter - A device used to rotate an internal combustion engine so as to initiate the engine's operation under its own power. Starters can be electric, pneumatic, or hydraulic. In the case of very large engines, the starter can even be another internal combustion engine.
- Stroke - The stroke represents a measurement of the total distance travelled by the piston. The reference point is measured from the top of the piston crown.
- Supercharger - A compressor that is run by the crankshaft to feed compressed air into the engine cylinder to increase the power output.
- Timing Belt/Chain - A cogged belt, usually of reinforced rubber. The purpose of a timing belt component is to provide a quiet, flexible connection between the camshaft and crankshaft to keep the engine valves opening and closing in phase with the movement of the engine pistons.
- Timing Gear - Allows the camshaft and crankshaft to turn the timing chain. The crankshaft turns to move pistons up and down inside the cylinders. The camshaft turns to allow intake and exhaust valves on the cylinders to open and close. These components are important for proper engine timing.
- Torque - A type of force that is applied to an object that results in the object rotating around an axis. It is a measure of how much twisting is applied to an object.
- Total Displacement - The combined volume displaced by all cylinders in an internal combustion engine.
- Transfer Port - In a two-stroke engine the transfer port connects the engine crankcase to the cylinder. Thus during the downward movement of the piston, the air-fuel mixture present in the crankcase is pushed into the engine cylinder through the transfer port.
- Turbocharger - A turbocharger is a turbine-driven compressor unit that is run by the exhaust gases and forces extra compressed air into the engine cylinder to increase power output from the engine.
- Valve Seat - Prevents oil from entering the cylinder head ports through the valve guides.
- Voltage Regulator - Regulates the charging voltage that the alternator produces, keeping it between 13.5 and 14.5 volts to protect the electrical components throughout the vehicle.
- Volumetric Efficiency - A measure of how effectively an engine can move air in and out of the cylinders during the intake and exhaust strokes.
- Water Passage - The flow of water divides in the water outlet manifolds, goes to the exhaust manifolds, and through the jacket water outlet. The majority of the water is discharged to the jacket water outlet. Water from the exhaust manifolds enters cored passages in the engine front cover and returns to the pump.
- Water Pump - The water pump in a car is a belt driven device that receives power from the engine’s crankshaft. The water pump pulls the cooled fluid from the radiator through the pump’s center inlet and is constructed as a centrifuge. The fluid is then returned to the cooling system of the car after being circulated outward into the engine.