Basic terminology use for engine- Compression Ratio, Horse Power., Bore and Stroke etc.

Terminology For Engine:-

• BORE AND STROKE:- Thediameter of the cylinder is known as bore and the displacement of the piston, i.e. its travel from top dead centre (TDC) to bottom dead centre (BDC) is called stroke (Fig. 1). In old engines, the stroke wasalways greater than the bore but the recent trend is towards a shorter piston stroke. This is becausein the short piston stroke, the less of power due to friction is minimized. Also, the inertia and  centrifugalload on the bearings are reduced. In the square engine, which is the latest in technology, thebore and strokes are equal. 
  
•  PISTON DISPLACEMENT (SWEPT VOLUME)  Thisis the volume that the piston displaces during its movement from BDC to TDC (Fig. 2).Suppos D is the bore dia. and L is the stroke length. The piston displacement is given as (π/4) D2L. Example For a four-cylinder engine with a 10 cm bore dia. and 8 cm stroke length, the piston displacement (v) will be = (π/4) x 102 x 8 x 4= 2512cm3
• COMPRESSION RATIO :- The compression ratio (CR) of an engine is a measure of how much the air/air-fuel mixture is compresse in the cylinder. It is the volume of air when the piston is at BDC divided by its volume of air when the piston is at TDC. The volume above the piston is called clearance volume.The CR of an engine is an important factor in its performance. By increasing only the compression ratio, the engine power increases, the other factors remaining unchanged.
• HORSE POWER :-Power is the rate at which work is done. The rate at which the engine can do work is measured in horse power (HP). One HP is equivalent to 4500 kg m per min. The various methods of defining horsepower are described below. 
• Indicated Horse Power :- The amount of power that can be measured on the flywheel is always less than the power generated in the engine on account of expansion of the combusted fuel. The power that is actually develop in the cylinder is called indicated horse power and is given by         1HP=PLAN/4500           where,.                              

◆ P- means effective pressure in kg/cm2

◆L - stroke length in m 

◆A - area of cylinder in cm2

◆N - power stroke per min (for a four stroke engine N = rpm/2 and for a two-stroke engine N = rpm) Brake

•  Horse Power :-It is the horsepower available on the crankshaft and is measured by a suitable dynamometer. 
• SAE Horse Power (Taxable Horse Power)  :- The SAE (Society of Automotive Engineers) horse power rating is used to compare engines on a uniform basis, usually for tax purposes. The formula is   HP =D2N/2.5
• where 
• D - diameter of cylinder in inches 
• N- number of cylinders 
• Belt Horse Power 
• It is the power of the engine. measured at the end of a suitable belt, receiving drive from the PTO 
• shaft of the tractor. 
• Power Take Off Horse Power 
• It is the power delivered by a tractor through its PTO shaft. In general the belt and PTO horse power 
• of a tractor will approximately be the same and is measured by either a hydraulic or an electrical 
• dynamometer. 
• Drawbar Horse Power 
• It is the power of a tractor measured at the end of the drawbar. It is that power which is available to 
• pull loads.