2Air Required to Burn Fuel 1 kg of H requires 8 kg O1 kg of C requires 2.66kg O1 kg of S requires 1kg O1 kg of O is contained in 4.35kg air
3Problem No 1A certain petrol consists of 84 % C and 16 % H by mass. What mass of air is required for complete combustion?
4Problem No 1 Data Carbon = 84 % C by mass Hydrogen = 16 % H by mass. To FindMass of air is required for complete combustion?SolutionO required to burn 1 kg of C = 2.66 kgO required to burn 0.84 kg of C = x 2.66 kg
5Problem No 1 Solution O required to burn 1 kg of H = 8 kg O required to burn 0.16 kg of H = x 8 kgThereforeO required = (0.84 x 2.66)kg + ( 0.16 x 8)kgAir required = (0.84 x 2.66)kg + ( 0.16 x 8)kg x 4.35 kgkg
6Problem No 2A fuel oil contains, by mass, 87 % C, 11 % H, 1 % S and 1 % O. What mass of air is required for complete combustion?
7Problem No 2 Data Carbon = 87 % C by mass Hydrogen = 11 % H by mass Sulphur = 1 % S by massOxygen = 1 % O by massTo FindMass of air is required for complete combustion?SolutionO required to burn 1 kg of C = 2.66 kgO required to burn 0.87 kg of C = x 2.66 kg
8Problem No 2 Solution O required to burn 1 kg of H = 8 kg O required to burn 0.11 kg of H = x 8 kgO required to burn 1 kg of S = 1 kgO required to burn 0.11 kg of S = x 1 kgFuel oil supplies 0.01 kg of O /kg of fuelActual mass of O required = kg kg= kgMass of Air required = x 4.35 kg= kgAir fuel ratio by mass is to 1
9Problem No 3What is mass of air is required to burn complete 1 kg of benzole C6 H6 ?
10Problem No 3 Data Benzole C6 H6 To Find Mass of air is required for complete combustion?SolutionMolecular mass of Benzole C6 H6(12 x 6) + ( 1 x 6) = = 78% of C by mass = (72/ 78) x 100 = 92% of H by mass = (6/ 78) x 100 = 8
11Problem No 3 O required C = 0.92 x 2.66 = 2.45 kg O required H = x 8 kg = 0.64Total = 3.09 kgAir required = x 4.35 kg= 13.4 kgAir fuel ratio by mass is 13.4 to 1
12Problem No 4What is mass of air is required to burn complete 1 kg of ethyl alcohol C2 H6O ?
13Problem No 4 Data ethyl alcohol C2 H6O To Find Mass of air is required for complete combustion?SolutionMolecular mass of ethyl alcohol H2 C6O( 12 x 2) + (1 x 6) + ( 16 x 1) = 46% of C by mass = (24/ 46) x 100 = 52% of H by mass = (6/ 46) x 100 = 13% of O by mass = (16/ 46) x 100 = 35
14Problem No 4Total = kgThe fuel supplies 0.35 kg of O per kg of fuel= = kgAir required = x kg= 9 kgAir fuel ratio by mass is 9 to 1
16LUBRICATION SYSTEMLubrication is the introduction of a substance, called a lubricant (e.g. oil to create an oil film, between two moving contact surfaces, to reduce friction.This reduction of friction greatly reduces the wear of the surfaces and thus lengthens their service life.It also reduces the energy required for the movement.Lubrication is important in all moving parts of the vehicle but the engine has the greatest need.
17LUBRICATION SYSTEMUnder a microscope, even the smoothest engine components have a surface that looks very rough.If these surfaces made contact they would rub together, overheat and destroy themselves.To prevent this happening, engines have a lubrication system that pumps or drips a constant supply of oil on all the moving metal components.
18LUBRICATION SYSTEM OTHER FUNCTIONS Although the BASIC FUNCTION of a lubricant is to reduce friction and wear.It carries off generated heatIt helps to form a gas-tight seal between piston rings and cylinders.It also carries away harmful combustion waste products.Lubrication helps to control corrosion by coating parts with a protective film.A detergent added to the lubricant helps to removes sludge deposits.
20The Lubrication System (Reasons for) To separate the moving parts of the engine, to prevent excessive wear and heat build up caused by friction, without this, the engine components would get so hot, they could start to melt and stick to together (seized engine)To protect the engine components from acids formed from the burning of the fuel.
21Purpose of Lubrication System LubricateReduces Friction by creating a thin film(Clearance)between moving parts (Bearings and journals)
22Purpose of Lubrication System SealsThe oil helps form a gastightseal between piston ringsand cylinder walls(Reduces Blow-By)Internal oil leak (blow-by) willresult in BLUE SMOKE at thetale pipe.
23Purpose of Lubrication System CleansAs it circulates through the engine, the oil picks up metalparticles and carbon, and brings them back down to the pan.
24Purpose of Lubrication System CoolsPicks up heat when moving through the engine and thendrops into the cooler oil pan, giving up some of this heat.
25Purpose of Lubrication System Absorbs shockWhen heavy loads are imposed on the bearings, the oilhelps to cushion the load.Absorbs ContaminantsThe additives in oil helps in absorbing the contaminantsthat enter the lubrication system.
26VISCOSITY Viscosity is a measure of oil’s resistance to flow. A low viscosity oil is thin and flows easilyA high viscosity oil is thick and flows slowly.As oil heats up it becomes moreviscous (Becomes thin)
27VISCOSITYIf the oil is too thin(has very low viscosity) it will be forcedout from between the moving parts, resulting in rapid wear.If the oil is too thick(has very high viscosity) it will flow veryslowly to engine parts, especially when the engine and the oilare cold, resulting in rapid wear.Viscosity Index is the measure of how much the viscosity ofan oil changes with temperature. (20 W)Viscosity number is set by SAE (Society of AutomotiveEngineers)
28VISCOSITY Single viscosity oils SAE 5W, SAE 10W (Winter) and SAE 20, SAE30 … (Summer)Multiple viscosity oils SAE 10W-30.This means that the oil is same as SAE 10W when coldand SAE30 when hot.The higher the number the higher the viscosity(thickness) of oil.
29Properties of oil Corrosion and Rust Inhibitor: Displaces water from metal surfaces, to prevent corrosion.Foaming Resistance: Rotating crankshaft tends to causebubbles (Foam) in the oil and bubbles in oil will reduce theeffectiveness of oil to lubricate.Synthetic Oils: Made by chemical process and do notnecessarily come from petroleum.
30Service Rating of Oil SA, SB, SC, SD,…..SJ SA and SB oils are not recommended for use in today’sAutomobile engines.
31A.P.I. Ratings SA Straight mineral oil no additives. SB ’s motor oil with some detergent.SC ’s oil more additives.SD ’s enter multi-viscosity oils.SE 1970’s emission controls make heat is problem.SF 1980’s improves fuel economy.SG Late 1980’s wider viscosity ranges.SH ’s great stuff.SJ Late 1990’sSL 2000’sSM Current
34Parts Oil Pumps Driven by camshaft, crankshaft (Rarely rebuild by an auto technician)Rotor Pump(Two star shaped rotorspumps the oil)Gear oil Pump
35Parts Oil Pan Stores the oil and helps in cooling the oil Pan gasket splits if over tightened.
36Parts Pressure Relief Valve to prevent the buildup of high Pressure (Causes the oil filter to bulge, but not a commonproblem).Good oil pressure is40-60 psi
37Parts Oil Pressure Indicator Light or a Gauge The light turns on or gauge reads low whenthe pressure drops below 10psi.Good oil pressure is psi.Common causes of low oil pressure are:Low oil levelWorn out pumpLow oil pressure Safety system will shuts down the car bycutting the ignition System(Spark).
38Parts Oil Filter filters the oil Some particles are too small for the filter Element(paperin the filter ) to trap.
39Parts Oil Galleries Deliver the oil to top end and returning it To the oil pan.
40Parts Positive Crankcase ventilation Valve Pollution prevention Blow-by back into the intakePrevent sludge in the engine.
41Parts Oil Pressure sending unit electrically sends the signal to the Light or Gauge mounted on the dash.If the wires get shorted the light will come on orthe gauge will read high.
42OIL CHANGE Every 5000Km 3 months Ignoring regular oil change intervals will shortenengine life and performance.
43Selecting Motor OilPick proper viscosity as recommended by manufacturer.Pick proper service rating as recommended by the manufacturer.
44Automatic Transmission Fluid (ATF) Has red color to identify it from motor oil.Several kinds:Dexron/MerconType FA
45Gear LubeUsed in manual transmissions and differentials on rear drive cars.Heavy viscosity 90W.Looks like motor oil but smells real bad!
46Chassis Grease Conventional type of petroleum grease. Grease steering and suspension parts.
47Other Types of Grease Lithium grease or white lube. Used on mis. parts.
48Other Lubricants WD-40 is a light oil with graphite. Liquid wrench is a penetrating oil for dry and rusted bolts.
49Non Petroleum Lubricants Silicone spray is for rubber and plastic parts. Doesn’t work well on metal.Brake cleaner is like dry cleaning fluid. Cleans off grease and evaporates in seconds.
50Other Useful FluidsCarburetor choke and throttle body cleaner. Contains toluene.Starting fluid. Contains ether.
52Oil ContaminationBlow-by gases add raw gasoline and water to the oil causing deterioration.Excessive heat can cause thermal breakdown.Excessive cranking can dilute oil with gasoline.Cooling gasket leaks will ruin oil causing sludge.
53Things That Make Oil Deteriorate Faster Short distance driving. (which is most trips)Extensive idling.Cold weather operation.Trailer towing.Excessive heavy loadsDirty and dusty conditions.
54Proper Oil Disposal Waste motor oil is a controlled waste. Be sure to properly dispose of.Oil filters too!
73ENGINE PERFORMANCE PARAMETERS Inlet Value Mach IndexFuel Air RatioCalorific Value of the Fuel
74INDICATED THERMAL EFFICIENCY Indicated thermal efficiency is the ratio of energy in the indicated power ip, to the input fuel energy in appropriate unitsηith = ip [kJ/s]energy in fuel per second [kJ/s]ηith = ip [kJ/s]mass of fuel/s x calorfic value of fuel
75BRAKE THERMAL EFFICIENCY Brake thermal efficiency is the ratio of energy in the brake power bp, to the input fuel energy in appropriate unitsηbth = bp [kJ/s]energy in fuel per second [kJ/s]ηith = ip [kJ/s]mass of fuel/s x calorfic value of fuel
76MECHANICAL EFFICIENCY Mechanical efficiency is the ratio of bp (delivered power) to indicated power ( power provided to the piston)ηm = bp [kJ/s] = bpip [kJ/s] bp+fpfp = ip - bp
77VOLUMETRIC EFFICIENCY Volumetric efficiency is the ratio actual volume flow rate of air into the intake system to the rate at which the volume is displaced by the system.ηv = ma / ρaV disp N/2ρa = Inlet densitySI = 80 to 85 %CI = 85 to 90 %
78RELATIVE EFFICIENCY OR EFFICIENCY RATIO Relative efficiency is the ratio thermal efficiency of actual cycle to ideal cycle.ηrel = Actual Thermal EfficiencyAir Standard Efficiency
79MEAN EFFECTIVE PRESSURE ip = pim LAnK60 x 1000Ip = Indicated power [kW]pim = Indicated mean effective pressure [N/m2 ]L = Length of the stock [m]A = Area of the piston [m2]N = Speed in revolutions per minute [rpm]n = Number of stock N/2 & NK = Number of cylinderbp = pbm LAnK
80MEAN PISTON SPEED Sp = 2LN L = Length of the stock [m] N = Crank Speed in revolutions per minute [rpm]
81SPECIFIC POWER OUTPUTPs = bp/A= constant x pbm x Sp
82SPECIFIC FUEL CONSUMPTION sfc = Fuel Consumption per unit TimePower
83Important definitions Brake Power [B.P]: It is the power developed by the engine at the output shaft.Where, N = Speed of the crank shaft in rpm.T =Torque applied on the brake drum due to load “W”, (N-m)R = Radius of the brake drum (m)T = W x R kg-m= 9.81 x W x R N-m
84Frictional Power [F.P]: It is the difference between the indicated power and the brake power. F.P = [I.P – B.P] kW,Mechanical Efficiency [ηmech ]: It is the ratio of the brake power and the indicated power.
85Indicated Power [I.P]: It is the power developed inside the IC engine cylinder Where, n = No. of working cycles/ min.n = N/2, for 4 stroke engine= N, for 2 stroke engineL = Stroke length (m), D = Bore diameter (m)Pm = Indicated mean effective pressure (N/m2)A = Area of the cylinder,,
86Brake thermal Efficiency [ηbth ]: It is the ratio of the brake power to the heat supplied by the fuel.Indicated thermal Efficiency [ηith ]: It is the ratio of the indicated power to the heat supplied by the fuel.Where, mf = mass of the fuel supplied (kg/hr)CV = Calorific Value of the fuel (kJ/kg)