Criteria S.I. Engine (Petrol or Spark Ignition Engine) C.I. Engine (Diesel or Compression Ignition Engine) Working Cycle Works on Otto Cycle or Constant Volume Cycle. Works on Diesel Cycle. Mixture During Suction Stroke Takes a mixture of air and petrol during the suction stroke. Takes only air during the suction stroke. Fuel Used Uses petrol as fuel. Uses diesel as fuel. Compression Ratio Has a compression ratio that varies from 6 to 10. Has a compression ratio that varies from 16 to 20. Engine Weight and Cost S.I. engines are lighter and cheaper. C.I. engines are heavier and costlier. Initial Cost Initial cost is lower compared to C.I. engines. Initial cost is high due to high compression ratio. Starting Starting is easy. Starting is difficult, especially in cold conditions. ...
There are various properties of fluid
1.) MASS DENSITY- It is defined as mass of fluid per unit volume. It is generally denoted by ρ (Rho).
S.I unit = kg/m³
The mass density of water is taken as 1000 kg/ m³ at 4°C
2.) SPECIFIC WEIGHT. - It may be defined as the weight of fluid per unit volume.It is generally denoted by w.
S.I unit = N/m³
It is increase with increase in pressure. The specific weight of water is taken as 9810 N/m³ at 4°C.
IMPORTANT NOTE:-
*Relationship between specific weight and mass density:-
w = ρ× g
Specific weight = (mass density × Acceleration due to gravity)
3.) SPECIFIC VOLUME - It may be defined as the volume occupied by the fluid per unit mass. It is generally denoted by v.
OR
It may be defined as the reciprocal of mass density. It commonly applied to gasses.
v = 1/p
Specific volume = 1/ Rho
S.I unit = m³/kg
4.) Specific gravity - it may be defined as the ratio of specific weight of fluid to the specific weight of a standard fluid at a standard temperature.
It is generally denoted by S.
Specific gravity is also known as relative density.
5.) VISCOSITY - it is a property of fluid by virtue of which it offers resistance to flow or internal friction of an fluid.
Viscosity is measured by VISCOMETER. The unit of Viscosity is given as 'SAYBOLTS UNIVERSAL SECONDS' OR 'REDWOOD SECOND' etc.
τ ∝ dv/ dy
τ = μ.dv/dy ...(1.)
Where μ is the constant of proportionality and is called coefficient of dynamic Viscosity or simple Viscosity or absolute Viscosity.
From eq 1
μ = τ /( dv/ dy)
μ = ( N./m² )/ ( m/s /m)
μ = N.s/ m²
N.s/ m² = pa.s
S.I unit = pa.s ( Pascal × second)
pa.s. = 1N.S/ m²
1N.S/m² = 10 poise = 1000 centipoise
The Viscosity decrease with increase in temperature.
EXAMPLE :-
1. HIGH VISCOSITY -( Glycerine , Honey etc.)
2. LOW VISCOSITY - ( Water , Gasoline etc.)
IMPORTANT POINT S :-
* KINEMATIC VISCOSITY - The ratio of dynamic Viscosity to the mass density of a fluid. It is generally denoted by v (Nu).
v = μ/p
S.I unit = m²/s
The another unit of kinematics Viscosity is Stokes.
1m²/s = 10000 stokes
6.) VAPOUR PRESSURE - It is the liquid partial pressure exerted on its surface by the vapours of the same liquid gathers into the container which containing the liquid, above the surface of liquid due to evaporation.
The vapour pressure increases with increase in temperature.
7.) COHESION - it is the property of liquid by virtue of which it can withstand slight tension. This property of liquid due to internal molecular attraction between the molecules of the liquid.
The property of surface tension is also sir to cohesion.
8.) ADHESION - It is the property of liquid by virtue of which it adheres ( sticks) to the solid body with which it is in contact.
This property of liquid due to the force of attraction between the molecules of the liquid and the molecules of the solid body.
9.) SURFACE TENSION - The property of liquid by virtue of which the free surface of the liquid acts as a stretched elastic membrane capable of bearing a slight amount of tension.
Eg:- the paper boat travel on water due to surface tension. And insects sit on water due to this phenomenon.
S.I unit = N/m
10.) CAPILLARITY- It is the phenomenon by which a liquid rises up or falls down in a thin glass tube in comparison to the general level in the vessel, when the glass tube dipped in liquid.
* The rise of liquid is known as capillary rise.
* The fall of liquid is known as capillary Depression.
it is generally expressed in terms mm or cm of liquid.
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EXPRESSION FOR CAPILLARY RISE :- Let us consider a thin glass tube open at both ends. This glass tube dipped in water and the water will rise in the glass tube above the level of the liquid.
Let. d = diameter of glass tube
h = Height of liquid in the tube
σ = surface tension of liquid
θ = Angle of contact between liquid and glass tube
ρ = mass density of liquid
Weight of liquid of height h in the tube = ( Area of the tube × h) ×ρ×g
=(π/4)×d²×h×ρ×g. ....(1)
Tensile force on vertical component= ( σ ×cicumference of tube ) × cosθ
= σ × πd × cosθ. .....(2)
From eq 1 and 2
(π/4)×d²×h×ρ×g = σ × πd × cosθ
Now we get:-
h = (4σ × cosθ/ ρ×g×d)
The value of θ between water and clean glass tube is approximately equal to zero.
EXPRESSION FOR CAPILLARY FALL - in this case we use mercury in place of water.
Procedure is same for capilly rise
h = (4σ × cosθ/ ρ×g×d)
The value of θ for mercury and glass tube is 128°.
11.) COMPRESSIBILITY - it may be defined as the reciprocal of bulk modulus of elasticity (K).
COMPRESSIBILITY - 1/ K
S.I unit = m²/N
BULK MODULUS - It may be defined as the ratio compressive stress to volumetric strain.
K = N/m²