Diesel Engines

DIESEL ENGINES

INDEX

1.INTRODUCTION2.FUEL INJECTION3.COMBUSTION4.TURBOCHARGING5.COMBUSTION PRODUCTS AND EMISSION CONTROL6.IMPROVEMENTS IN ENGINE DESIGN

INTRODUCTION

• Diesel engines operate on the principle of ‘Compression Ignition’• The theoretical cycle of operation of a Diesel engine is known as the

‘Diesel Cycle’ after the German inventor Rudolf Diesel

THEORETICAL P-V DIAGRAM

• The fuel used is known as ‘Diesel Fuel’ or ‘Fuel Oil’• It is the collective name for hydrocarbons distilled between 204 ºC and

316 ºC• The main constituents of Diesel fuel are paraffins and naphthalenes• The international standards governing this fuel are mentioned in DIN

EN 590

FUEL INJECTION

• There are two types of fuel injection systems – Mechanical and Electromechanical

• The mechanical system was used previously and it was suitable for injection pressures upto 300 bar and for slow injection speed and slow overall engine speed

• New technical developments in order to reduce noise, engine size and weight and emissions along with higher speed and efficiency have given rise to the Electromechanical system

• In the electromechanical system, solenoid or piezoelectric operated injectors are used and the maximum injection pressure is upto 2000 bar

• The injection duration is also reduced to the order of a few microseconds

MECHANICAL INJECTION SYSTEMS• Mechanical injection systems depend heavily upon the injectors for the

following parameters – – Injection timing– Injection pressure– Duration of injection

• Various types of injectors have been developed to generate the appropriate spray pattern

• The main types of mechanical injectors are – Pintle, Pintaux, Single hole and Multi hole type

• The main components of any Diesel fuel injector are the high pressure supply line, needle pressure valve, retaining spring and nozzle

• Various types of nozzles offer different spray patterns and fuel drip characteristics

• Single hole type of nozzles give a highly penetrating type of spray, while Pintle and Multi hole type of nozzles give a more dispersed spray

• The different types of pumps used are – Inline Pumps, Rotary Distributor Pumps, and Unit Injectors/Pumps

• The Unit pumps were mainly used by Volkswagen and Caterpillar. Mercedes Benz also used Unit pumps in the Actros commercial vehicle before switching over to ‘Common Rail Direct Injection’

ELECTROMECHANICAL INJECTION SYSTEMS• In these systems the injector is actuated by an electric signal from the

ECU and not by fuel pressure• The injection parameters as mentioned previously are controlled by the

ECU by varying the electric signal

COMMON RAIL DIRECT INJECTION SYSTEM (BOSCH)

COMMON RAIL DIRECT INJECTION SYSTEM (DELPHI)

● There are three versions of CRDI systems used by Mercedes Benz – CDI I, CDI II, CDI III

● The injection pressures used are –

● CDI I : 900 bar

● CDI II : 1350 bar

● CDI III : 2000 bar

INJECTOR CODING

• Fuel Supply Pump

(image from engine)

• High Pressure Pump

(image from engine)

COMBUSTION● There are mainly two types of combustion chambers – Direct

Combustion and Indirect Combustion

● This is related to the type of injection

● The modern type uses Direct Injection in which the fuel is injected into the cylinder itself and the combustion chamber is actually a recess in the piston crown

ADVANTAGES OF DIRECT INJECTION● Very high efficiency of upto 45%

● Environmentally friendly

● Economical

TURBOCHARGING● Turbocharging is a technique to raise the intake air pressure and thus

allowing more quantity of air to enter the cylinder

● This increases the volumetric efficiency of the engine

● There are 3 types of modern turbocharging techniques

1. Waste Gate Turbocharging

2. Variable Turbine Geometry Turbocharging

3. 2 Stage Turbocharging

WASTE GATE TURBOCHARGING

VARIABLE TURBINE GEOMETRY

2 STAGE TURBOCHARGING

COMBUSTION PRODUCTS

REDUCTION OF EMISSIONS IS ACHIEVED BY -

● EXHAUST GAS RECIRCULATION

● PARTICUALTE FILTER

● UREA TREATMENT OF EXHAUST PRODUCTS

IMPROVEMENTS IN ENGINE DESIGN

● Pilot Injection

● Inlet Port Shutoff

● Aluminium Engines

● Aviation Diesel Engines

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Row 1 Row 2 Row 3 Row 40

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