Fuel injectors

FUEL INJECTORS

A PRESENTATION BY PUSHPAJEETA2326215006

WHAT IS A FUEL INJECTOR?• Fuel injectors are electromechanical valves,

usually one per cylinder, situated so that they deliver fuel either directly into the engine’s combustion chamber (direct injection) or into the intake plenum port (indirect port injection).

REQUIREMENT?• Atomization• Distribution of fuel• Prevention of impingement on walls• Mixing

NOZZLES• Nozzle is the part of an injector through which the liquid fuel

is sprayed into the combustion chamber.

DESIGNE OF NOZZLE

• The design of the nozzle must be such that the liquid fuel forced through the nozzle will be broken up into fine droplets .

• It must spray fuel in such a manner as to minimize the quantity of fuel reaching the surrounding walls.

• The non turbulent type of combustion chamber depends almost entirely on both the nozzle design and injection pressure .

TYPES OF NOZZLES 1. SINGLE HOLE NOZZLE• This is simplest type of nozzle and is used in open combustion

chambers.• It consists of a single hole bored centrally through the nozzle body

and closed by the needle valve . It’s size is usually larger than 0.2mm.

• It’s spray cone angle varies from 5 deg to 15 deg.

ADVANTAGES• Simple in construction and operation.

DISADVANTAGES• High injection pressure required • Tendency to dribble • Not good mixing due to narrow cone angle.

2. MULTI HOLE NOZZLE• Extensive use in open combustion chamber as fuel gets properly mixed

even there is slow movement of air .• Number of holes varies from 4 to 18 , diameter lies between 0.25 to 0.35

mm and hole angle lies between 20 to 45 degree . ADVANTAGES• Good atomization • Proper distribution of fuel . DISADVANTAGES • Holes are small and liable to clogging.• Dribbling between injections.• Very high injection pressure .• Close tolerance in manufacture and costly.

3.PINTLE NOZZLE• The stem of the nozzle valve is extended to form a pin or pintle which

protrudes through the mouth of the nozzle body.• Spray cone angle is generally 60 degree ,and spray is hollow conical.

ADVANTAGES• Self cleaning type and avoid carbon deposits at end.• Avoids dribbling.• Good atomization DISADVANTAGES • Distribution and penetration is poor hence not suitable in open

combustion chamber

4. PINTAUX NOZZLE• It’s a type of pintle nozzle with an auxiliary hole.• Small amount of fuel come from auxiliary hole before main injection. ADVANTAGES• Good cold starting characteristics DISADVANTAGES • Tendency of auxiliary hole to choke.• Less effective than multi hole nozzle

ELECTRONIC UNIT INJECTOR • the Delphi Diesel Systems electronic unit injector

(EUI) both the quantity and the timing of injection are controlled electronically through a Colenoid actuator.

• The Colenoid is a solenoid of patented construction that can respond very quickly (injection periods are of the order 1 ms), to control very high injection pressures (up to 1600 bar or so).

• The Colenoid controls a spill valve, which in turn controls the injection process.

• The pumping element is operated directly from a camshaft (or indirectly via a rocker), and the whole assembly is contained within the cylinder head.

Benefits• High speed dual valve operation for accurate

control of injection events• High pressure injection for optimized

combustion and reduced after treatment• Lightweight, compact design for enhanced

efficiency• Available with a wide range of high pressure

nozzle options• Multiple injection capability with

programmable shot-to-shot injection control• Programmable variable nozzle opening and

closing pressure• On board diagnostic and dynamic trimming

capability (glitch control)• Cost effective technology• Proven reliability and durability• Target emissions: Euro IV, V, and VI; US 07 and

US 10 and beyond; Tier IV; Japan NLTR and post-Japan NLTR

HYDRAULIC ELECTRONIC UNIT INJECTOR• It uses a hydraulic pressure intensifier system

with a 7: 1 pressure ratio to generate the injection pressures• The hydraulic pressure is generated by pumping

engine lubricant to a controllable high pressure.• The HEUI uses a two-stage valve to control the oil

pressure, and this is able to control the rate at which the fuel pressure rises, thereby controlling the rate of injection, because a lower injection rate can help control NOx emissions.• The HEUI uses engine oil under high pressure to

power the plunger rather than a fuel injection pump camshaft lobe to power the plunger.• The HEUI fuel system provides infinite control of

injection pressure.

REFERENCE • Automobile Engineering , by R.K RAJPUT• I C ENGINE by V GANESHAN• Automotive engineering fundamental by RICHARD STONE &

JEFFREY K.BALL• DELPHI E3 fuel injector : http://

www.delphi.com/manufacturers/cv/powertrain/injection-systems-and-components/e3-diesel-electronic-unit-injector

• HEUI : http://generators.tpub.com/TM-9-6115-729-24/TM-9-6115-729-240063.htm

• Kamo R, Bryzik W, Reid M, Woods M. Coatings for improved engine performance. SAE technical paper 970204; 1997.

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