Chapter 4, Engine Basics
Internal combustion engine
A heat engine in which the combustion of fuel is contained with and a Cylinder. Differentiated From a steam engine and which the fuel is combusted outside of the engine.
Engine
A machine that converts one energy form to another form of energy .
Compression ratio
A measure of the cylinder volume when the piston is at BDC versus the cylinder volume when the piston is at TDC . Compression ratios and diesel engines fall between 14:1 and 24:1. Current high speed Turbo charged truck and bus diesel engines have compression ratios typically between 16:1 and 17:1.
After top dead center ATDC
A point of piston travel through its Downstroke.
Indirect injection IDI
ACI or in SI engine in which the fuel charge is introduced outside the engine cylinder to a pre combustion chamber, cylinder head and take tract, or intake manifold.
Spark ignited SI
An engine in which the airfield charge is ignited by a timed electrical spark. When diesel engine platforms are converted to run natural gas NG, they require an SI system.
Heat engine
An engine that converts the potential HEAT ENERGY of a combustible fuel into mechanical work the diesel is a heat engine that functions by combining the heat energy of diesel fuel into mechanical work at its fly wheel.
Diesel engine
An internal combustion engine in which the cylinder fuel air charge is ignited by the heat of compression.
Be for top dead center BTDC
Any point of piston travel through its up Stroke.
Compression ignition CI
CI is the acronym commonly used to describe any diesel engine and which the fuel charge is ignited by heat generated on the compression stroke.
Naturally aspirated NA
Describes an engine whose only means of inducing air or air fueled mixture into its cylinders is the low cylinder pressure created by the down stroke of the piston
Manifold boost
Describes the extent of charge pressure above at miss phyrric delivered to the cylinders in a Turbo charged engine .Most current truck and bus diesel engines are boosted ;That is ,They are turbocharged
Direct injection DI
Either ACI or an SI engine and which the fuel charge is injected directly into the engine cylinder rather than to a Pre combustion chamber or part of the intake manifold. Almost all current diesel engines use Di as well as a new generation of gasoline fueled, SI engines.
Mean effective pressure MEP
Everage pressure acting on a piston through its complete cycle, the net gain of which converts to work potential. it is usually calculated by disregarding the intake and exhaust strokes and subtracting the mean compression pressure from the mean combustion pressure.
Inertia
In physics, It describes the tendency of a body at rest or in motion to want to continue in that state unless influenced by an external force.
Thermal efficiency
Measure of how efficiently and engine converts the potential heat energy of a fuel into usable Mechanical energy, usually expressed as a percentage.
Boyle's Law
States that for a given, confined quantity of gas, pressure is inversely related to the volume, so as one value goes up, the other goes down. In compressing gas in an engine cylinder during piston upstroke, cylinder volume is reduced so cylinder pressure accordingly is increased.
Charles's Law
States that the volume occupied by a fixed quantity of gas is directly proportional to its temperature if the pressure remains constant.
Rejected Heat
That portion of the potential heat energy of a fuel not converted into useful kinetic energy.
Diesel Cycle
The 4 stroke compression a unison cycle parented by Rudolph diesel in 1892. Go the term diesel can be used to describe some two-stroke-cycle CI engines, The diesel cycle is necessarily a four-stroke-cycle.
Bore
The Diameter of a cylinder. Or is expressed as the piston sectional area over which cylinder pressures act.
Compassion pressure
The actual cylinder pressure developed on the compression stroke . Actual compression pressures developed range from 2.41 MPa 350 PSI to 4.82 MPa 700 PSI in Diesel Engines.
British Thermal Unit (BTU)
The amount of heat required to raise the temperature of 1 pound of water 1ﾟF at 60°F, the standard unit of heat energy measurement.
Static friction
The characteristic of a body at rest to attempt to stay that way.
Stroke
The distance through which a piston travels from BDC to TDC. Stroke is established by the crank throw offset; that is, The distance from the crankshafts inner line to the throw center line multiplied by 2 equals the stroke dimension.
Kinetic energy
The energy of motion. When a heat engine attempts to convert the energy available in a fuel to mechanical work some heat losses result. Kinetic energy describes that percentage of the potential energy of the fuel that actually gets converted to usable mechanical energy.
Calorific Value
The heating value of a fuel measured and BTU, calories, or joules.
Bottom dead center BDC
The lowest point of piston travel and the engine cylinder.
Combustion pressure
The peak pressure developed during the power .In today's alike tronic Li controlled truck diesel engines ,Compassion pressures may peak at up to 5 times the compression pressure
Ignition lag
The period between the entry of the 1st droplets of fuel into the engine cylinder in the moment of big nation based on the fuel chemistry and the actual temperatures of the engine components and the air charge.
Ratio
The quantitive relationship between 2 values expressed by the number of times 1 contains the other. The term is commonly used in automotive technology to describe the drive/driven relationship of 2 meshed gears, The mechanical advantage of levers, and the cylinder compression ratio.
Clearance volume
The remaining volume in an engine cylinder when the piston is at the top of its travel or TDC. Clearance volume influences actual compression temperatures and cylinder breathing efficiencies. The clearance volume on older indirect injection IDI Diesel engines was considerable, But it is much less on today's direct injected DI engines.
Friction
The resistance that an object or fluid encounters and moving over or through another.
Over square engine
The term used to describe an engine in which the cylinder bore diameter Is larger than the stroke dimension. A majority of spark ignited, Gasoline Fueled engines fall into this category, Know this could change as direct injected, gasoline fueled engines become popular.
Square engine
The term used to describe an engine in which the cylinder bore diameter is exactly equal to the piston stroke dimension. When bore and stroke values are expressed , bore always appears before stroke.
Under square engine
The term used to describe an engine in which the cylinder bore diameter is smaller than the stroke dimension. Most high compression diesel engines are undersquare.
Celander volume
The total volume in the cylinder when the piston is at BDC: Swept volume plus clearance volume.
Top dead center TDC
The uppermost point of the piston travel in an engine cylinder.
Swept volume
The volume displaced by the piston in the cylinder as it moves from BDC to TDC. It can be calculated if both stroke and born are known.
Joule
Unit of energy that describes the work done when an electrical current of one Ampere flows through a resistance of 1 ohm in 1 second or in mechanical terms the work that results when a force of 1 newton moves the point of application 1 meter.
Atkinson cycle
Variation on the Otto cycle by connecting the piston to the crankshaft with a double pivot linkage, it enables the 4 piston strokes of the Otto cycle to take place in one crankshaft revolution. it also permits a longer power stroke than compression stroke promising the theoretically higher efficiencies then the Otto cycle.
Miller cycle
Variation on the Otto cycle engine that uses a super charger and hold open the intake valve on for the 1st part of the compression stroke, providing higher efficiencies.
volumetric efficiency
the cylindrical fill efficiency of a vessel. In engine breathing, this refers to the actual quantity of air in the engine cylinder during operation compared to what it would contain at atmospheric pressure.