ME401 Part 3sub Sys

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Internal Combustion Engines Dr. Md. Ehsan 2009 ME 401

Engine Sub-Systems

Air Intake & Exhaust System

Fuel Supply System

Ignition System

Lubrication System

Cooling System

Starting System


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Intake Manifold

Takes air-fuel mixture from Carburettor/Mixer in to Cylinder

Objectives :

Maintain the A/F ratio -

Fineness of atomization of fuel in carburettor

Pressure drop (flow) in the manifold

Temperature of mixture in the Manifold

Uniform distribution of charge to all cylinders

Pipe layout Sharp bends (turbulent mixing)

Improved volumetric efficiency Prevent induction robbery

Economy

Manufacturing

Material : AL good heat conductivity, ductility, light weight

Process : Typically Casting.

Shape : To keep the mixture compositionunchanged and uniform as far as possible.


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Intake Manifold layouts for 4-Cylinder Inline Engines


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Air-Filter

Ensures dust free air going in the engine

Wet/Dry type

Pleated structure of dry filter Reducing noise of air entering

Pleated Filter Structure

Hot Air Intake System

Automatic hot air intake system

Under heated poor vaporization, freezing/ice formation

Over heated low density, poor volumetric efficiency, lowpower


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Exhaust System

Exhaust Manifold Exhaust Pipe Silencer

Exhaust manifold

Material Cast Iron/ Steel (about 700-800 C),

has to be corrosion resistive

Layout Prevent interference between cylinders,

independent cylinders/ pair of cylinders

Exhaust pipe

Material Steel pipe, corrosion protection

Construction Pipe is generally rigid and fixed to the frame

by flexible attachments to reduce vibration

Silencers (Mufflers)

Low frequency (Capacitive) Silencer air suction/ motoring

High frequency (absorption) Silencer rapid expansion of

exhaust gases

Combination type Silencer

Back pressure developed tuning construction Sheet metals

Corrosion


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TURBO CHARGER

250 kW Turbo-Charged After Cooled Diesel Generator

Exhaust

Manifold

IntakeManifold

Turbo

Charger


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Cooling System

Water Cooled System Very Common

Air Cooled System Less Common

Components :

Radiator Water-Air Heat Exchanger, Large

surface area, Cross flow from fan

Pressure Cap Maintains pressure, two-way valves

Expansion Tank Keeps radiator filled with water

hot and cold controlling volume

Hoses Fabric reinforced Rubber

Thermostatic Valve Maintains water temperature in the

water-jacket in certain desired level - by controlling flow

Water Jacket Water filled space around cylinders

Fan Electrical/Mechanical Drive Motor/Fan belt -

advantage/ disadvantages

Pump Centrifugal type low head


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Typical cooling water pump of engines

Operation of a wax-pellet type of cooling system


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Flow between the Expansion tank and Radiator, through the Cap


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Lubrication System

Lub Oil Sump(Chamber)

Strainer

Pump

(Cam operated gear/vanefitted with relief valve)

Filter

(Replaceable cartidge)

Main Oil Gallery

Holes/Passages/Channels(to valves, cam, crank-piston)

Return to sump(gravity feed)


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Flow of Lubricating Oil in an engine

Lubrication of Cylinder Wall


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Functions of Lubrication System

Reduce wear of mating components

Reduce frictional power losses

Serve as a cooling agent

Serve as a cleaning agent

Better sealing

Better cushion at bearings

Properties of Lubricating Oil

Correct viscosity less change in operating temp range(Viscosity Index), Multiple viscosity

Resistance to OxidationCarbon

Extreme pressure

Foam formation

Corrosion/Rust


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Designation of Lub Oil SAE 30, SAE 40(higher number more viscous)

SAE 10W-30, SAE 5W-20(Multiple viscosity)

Reasons of Loss of Lub oil

Leakage through valve stem-guide clearance

Leakage through piston ring-cylinder

Loss through crankcase ventilation(PCV =Positive crankcase ventilation)

Checking the Lub oil

Oil volume Deep stick (engine not running)

Oil pressure- Pressure switch/lamp (about 3-5 bar)

Pressure might not be developed due to -

lack of oil line leakage

faulty pump line blockagefaulty relief valve faulty pressure switch

Oil change - Every 3000-5000 km runOil Flushing

Better to change the filter with oil


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FUEL FILTER AND CAM DRIVEN FUEL PUMP


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TYPICAL FIRING ORDERS

4-Cylinder : 1-3-4-2

6-Cylinder : 1-4-2-6-3-5 or 1-5-3-6-2-4


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Functions of Mechanical Contact Breaker System

Trigger the system when spark is required

Interrupt the primary current flow to induce a high voltage inthe secondary circuit.

Limitations of Mechanical Contact Breaker System

Ignition timing varies from specification. Timing alters due toi. Wear at the heel, cam, spindle and erosion at contact facesii.Contact bounce and inability of the heel to follow the cam

at

high speed.

Dwell angle variations at high speed and wear of components.

Servicing requirements are frequent.

Cannot effectively control currents above 3 Amps.

Electronic Ignition / Breaker less Ignition / Solid State

Ignition

Inductive Pulse Generator

Optical Pulse Generator

Hull Effect IC

Electronic Control Module


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Starting System

Manual Electric Motor Pneumatic Motor Another Engine


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Electric Starter Motor and its Components


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Some gas turbine engines and Diesel engines, particularly on trucks, use a pneumatic

self-starter. The system consists of a geared turbine, an air compressor and a pressure

tank. Compressed air released from the tank is used to spin the turbine, and through a

set of reduction gears, engages the ring gear on the flywheel, much like an electric

starter. The engine, once running, powers the compressor to recharge the tank.

Another method, for large diesel engines, uses additional valves in cylinder heads.Compressed air (20-25 bar) is let in the cylinders so that its pressure pushes pistons

down when appropriate; at the upward piston movement, air is discharged through

normal exhaust valves.

Since large trucks typically use air brakes, the system does double duty, supplying

compressed air to the brake system. Pneumatic starters have the advantages of

delivering high torque, mechanical simplicity and reliability. They eliminate the need

for oversized, heavy storage batteries in prime mover electrical systems.

Documents

ME401 Part 3sub Sys