qip ice 13 electronic injection systems

32

Click here to load reader

Upload: goutamtripacharjee

Post on 25-Nov-2015

164 views

Category:

Documents


22 download

TRANSCRIPT

  • 1Internal Combustion Engines

    Lecture-13

    Ujjwal K Saha, Ph.D.Department of Mechanical Engineering

    Indian Institute of Technology Guwahati

    Prepared underQIP-CD Cell Project

  • 2Gasoline Injection

    In a multi-cylinder engine with a carburetor, it is difficult to obtain a uniform mixture in each cylinder. The various cylinders receive the air-gasoline mixture in varying quantities and richness. This problem is called the mal-distribution and can be solved by the port injection system by having the same amount of gasoline injected at each intake manifold.

    By adopting gasoline injection each cylinder can get the same richness of the air-gasoline mixture and the mal-distribution can be avoided to a great extent.

  • 3Typical pattern of mixture distribution in a multi-cylinder engine

  • 4Reasons for Gasoline Injection

    To have uniform distribution of fuel in a multi-cylinder engine To improve the breathing capacity and hence the volumetric efficiency To reduce or eliminate detonation To prevent fuel loss during scavenging in case of two-stroke engines

    Gasoline direct injection (GDI) Port-Injection

    (a) Timed and (b) Continuous Manifold Injection

    Types of Injection Systems

  • 5Groupings

    The above fuel injection systems can be grouped under two heads,viz., single-point and multi-point injection. In the single point injection system, one or two injectors are mounted inside the throttle body assembly. Fuel sprays are directed at one point or at the center of the intake manifold. This type is also known as throttle body injection.Multipoint injection has one injector for each engine cylinder, where fuel is injected in more than one location. This is somewhat more common and is often called port injection system.

  • 6Continuous Injection Systems

    This system usually has a rotary pump. The pump maintains a fuel line gauge pressure of about 0.75 to 1.5 bar. The system injects fuel through a nozzle located in the manifold immediately downstream of the throttle plate. In a supercharged engine, fuel is injected at the entrance of the supercharger. The timing and duration of the fuel injection is determined by Electronic Control Unit (ECU) depending upon the load and speed.

  • 7Timed Injection Systems

    This system has a fuel supply pump which sends fuel at a low pressure of about 2 bar when the engine is running at maximum speed. A fuel metering or injection pump and a nozzle are the other parts of the system. The nozzle injects the fuel in the manifold or the cylinder head port at about 6.5 bar or into the combustion chamber at pressures that range from 16 to 35 bar. Timed injection system injects fuel usually during the early part of the suction stroke.

  • 8Gasoline injection in four-stroke engines

  • 9Fuel injection in two-stroke

    engines

  • 10

    Electronic Fuel Injection System Modern gasoline injection systems use engine sensors, a computer, and solenoid operated fuel injectors to meter and inject the right amount of fuel into the engine cylinders.

    These systems called electronic fuel injection (EFI) use electrical and electronic devices to monitor and control engine-operation.

    An electronic control unit (ECU) or the computer receives electrical signals in the from of current or voltage from various sensors. It then uses the stored data to operate the injectors, ignition system and other engine related devices. Typical sensors for an electronic fuel injection system includes the following:

  • 11

    Typical Sensors

    1. Exhaust gas or oxygen sensor - senses the amount of oxygen in the engine exhaust and calculates air fuel ratio. Sensor output voltage changes in proportion to air fuel ratio.

    2. Engine temperature sensor - senses the temperature of the engine coolant, and from this data the computer adjusts the mixture strength to rich side for cold starting.

    3. Air flow sensor - monitors mass or volume of air flowing into the intake manifold for adjusting the quantity of fuel.

  • 12

    Typical Sensors contd.

    4. Air inlet temperature sensor - checks the temperature of the ambient air entering the engine for fine-tuning the mixture strength.

    5. Throttle position sensor - senses the movement of the throttle plate so that the mixture flow can be adjusted for engine speed and acceleration.

    6. Manifold pressure sensor - monitors vacuum in the engine intake manifold so that the mixture strength can be adjusted with changes in engine load.

  • 13

    Typical Sensors contd.

    7. Camshaft position sensor senses rotation of engine camshaft/crankshaft for speed and timing of injection.

    8. Knock sensor microphone type sensor that detects ping or resignation noise so that the ignition timing can be retarded.

  • 14

    Electronic Fuel Injection System

    The injector pulse width is an indication of the period for which each injector is energized and kept open. The computer decides and controls the injector pulse width based on the signals received from the various sensors.

    Under full load, the computer will sense a wide-open throttle, high intake manifold pressure, and high inlet airflow. The ECU will then increase the injector pulse width to enrich the mixture, which will enable the engine to produce higher power.

  • 15

    Electronic Fuel Injection System Under low load and idling conditions, the ECU will shorten the pulse width by which the injectors are kept in the closed position over a longer period of time. Because of this, air-fuel mixture will become leaner and will result in better fuel economy.

    Electronic fuel injection system has a cold start injector too. This is an extra injector that sprays fuel into the center of the engine intake manifold, when the engine is cold. It serves the same purpose as the carburetor choke. The cold start injector ensures easy engine startup in very cold weather.

  • 16

    MPFI System The main purpose of the Multi-Point Fuel Injection (MPFI) System is to supply a proper ratio of gasoline and air to the cylinders. These system function under two basic arrangements viz.,

    (i) Port injection (ii) Throttle body injection

  • 17

    Port Injection In this system, the injector is placed on the side of the intake manifold near the intake port. The injector sprays gasoline into the air, inside the intake manifold.

    The gasoline mixes with the air in a reasonably uniform manner. This mixture of gasoline and air then passes through the intake valve and enters into the cylinder.

  • 18

    Port Injection contd.

    Every cylinder is provided with an injector in its intake manifold. If there are six cylinders, there will be six injectors. Figure shows simplified view of a port or multi point fuel injection (MPFI) system.

  • 19

    Throttle Body Injection Figure illustrates the simplified sketch of throttle body injection system (single point injection). This throttle body is similar to the carburetor throttle body, with the throttle valve controlling the amount of air entering the intake manifold.

  • 20

    Remark

    As already mentioned, fuel-injection systems can be either timed or continuous. In the timed injection system, gasoline is sprayed from the injectors in pulses. In continuous injection system, gasoline is sprayed continuously from the injectors.

  • 21

    Remark

    The port injection system and the throttle-body injection system may be either pulsed systems or continuous systems. In both systems, the amount of gasoline injected depends upon the engine speed and power demands.

    In some literature MPFI systems are classified into two types viz.,

    D-MPFI and L-MPFI.

  • 22

    D-MPFI System The D-MPFI system is the manifold fuel injection system. In this type, the vacuum in the intake manifold is first sensed. Further, it senses the volume of air by its density. Figure shows the block diagram regarding the functioning of the D-MPFI system.

    Air

    Intake manifoldvacuum sensor

    Injector

    ECU

    Gasoline

    Injectionvolume control

    Mixture ofair and gasoline

    Engine

    RPM sensor

    Injection intointake manifold

  • 23

    D-MPFI System contd.

    As air enters into the intake manifold, the manifold pressure sensor detects the intake manifold vacuum and sends the information to the ECU. The speed sensor also sends information about the rpm of the engine to the ECU.

    The ECU in turn sends commands to the injector to regulate the amount of gasoline supply for injection. When the injector sprays fuel in the intake manifold the gasoline mixes with the air and the mixture enters the cylinder.

  • 24

    L-MPFI System The L-MPFI system is a port fuel- injection system. Here, the fuel metering is regulated by the engine speed and the amount of air that actually enters the engine. This is called air-mass metering or air-flow metering. This block diagram of L-MPFI system is shown.

    Air

    Air flow sensor

    Injector

    ECU

    Gasoline

    Injectionvolume control

    Mixture offuel and air

    EngineRPMsensor

    Injectionnear port

  • 25

    L-MPFI System contd.

    As air enters into the intake manifold, the air flow sensor measures the amount of air and sends information to the ECU. Similarly, the speed sensor sends information about the speed of the engine to the ECU.

    The ECU processes the information received and sends appropriate commands to the injector to regulate the amount of gasoline supply for injection. When injection takes place, the gasoline mixes with the air and mixture enters the cylinder.

  • 26

    Functional Divisions of MPFI System

    The MPFI system can be functionally divided into the following there main components:

    (i) Electronic Control System (ii) Fuel System(iii) Air Induction System

  • 27

    MPFI Electronic Control System

    The MPFI- electronic control system is shown in the above block diagram. The sensors that monitor intake air temperature, the oxygen, the water temperature, the starter signal and the throttle position send signals to the ECU.

    Sensors(Input)

    To cold start injectorr

    Air flow meter Ignition signal

    cold start injectortime switch

    Electronic control unit (ECU)

    To injectors

    (Output)

  • 28

    MPFI Electronic Control System contd.

    The air-flow sensor sends signals to the ECU regarding the intake air volume. The ignition sensor sends information about the engine speed. The ECU processes all these signals and sends appropriate commands to the injectors to control the volume of the fuel for injection. When necessary the cold-start injector timing switch off the ECU operates the cold start injector which is a part of the fuel system.

  • 29

    MPFI Fuel System Here, fuel is supplied by the fuel pump. At the time of starting, the cold start injector is operated by the cold start injector time switch. The cold start injector injects fuel into the air intake chamber, thus enriching the air-fuel mixture.The pressure regulator regulates the pressure of the fuel. The injectors receive signals from the ECU and inject the fuel into the intake manifold.

  • 30

    MPFI Air Induction System

    Here, the air cleaner, the air-flow meter, the throttle body and the air valve supply a proper amount of air to the air intake chamber and intake manifold. The quantity of air supplied is just what is required for complete combustion.

  • 31

    1.1. Crouse WH, Crouse WH, andand Anglin DLAnglin DL, (1985), Automotive Engines, Tata McGraw Hill.2.2. Eastop TD, Eastop TD, andand McConkey A,McConkey A, (1993), Applied Thermodynamics for Engg.

    Technologists, Addison Wisley.3.3. Fergusan CR, Fergusan CR, andand Kirkpatrick ATKirkpatrick AT,, (2001), Internal Combustion Engines, John

    Wiley & Sons.4.4. Ganesan VGanesan V,, (2003), Internal Combustion Engines, Tata McGraw Hill.5.5. Gill PW, Smith JH, Gill PW, Smith JH, andand Ziurys EJZiurys EJ,, (1959), Fundamentals of I. C. Engines, Oxford

    and IBH Pub Ltd. 6.6. Heisler H,Heisler H, (1999), Vehicle and Engine Technology, Arnold Publishers.7.7. Heywood JB,Heywood JB, (1989), Internal Combustion Engine Fundamentals, McGraw Hill.8.8. Heywood JB, Heywood JB, andand Sher E,Sher E, (1999), The Two-Stroke Cycle Engine, Taylor & Francis.9.9. Joel R, Joel R, (1996),(1996), Basic Engineering Thermodynamics, Addison-Wesley.10.10. Mathur ML, and Sharma RP,Mathur ML, and Sharma RP, (1994), A Course in Internal Combustion Engines,

    Dhanpat Rai & Sons, New Delhi.11.11. Pulkrabek WW,Pulkrabek WW, (1997), Engineering Fundamentals of the I. C. Engine, Prentice Hall.12.12. Rogers GFC, Rogers GFC, andand Mayhew YRMayhew YR, (1992), Engineering Thermodynamics, Addison

    Wisley. 13.13. Srinivasan S,Srinivasan S, (2001), Automotive Engines, Tata McGraw Hill.14.14. Stone R,Stone R, (1992), Internal Combustion Engines, The Macmillan Press Limited, London.15.15. Taylor CF,Taylor CF, (1985), The Internal-Combustion Engine in Theory and Practice, Vol.1 & 2,

    The MIT Press, Cambridge, Massachusetts.

    References

  • 32

    1. http://www.mne.psu.edu/simpson/courses2. http://me.queensu.ca/courses 3. http://www.eng.fsu.edu4. http://www.personal.utulsa.edu5. http://www.glenroseffa.org/6. http://www.howstuffworks.com7. http://www.me.psu.edu 8. http://www.uic.edu/classes/me/ me429/lecture-air-cyc-web%5B1%5D.ppt9. http://www.osti.gov/fcvt/HETE2004/Stable.pdf10. http://www.rmi.org/sitepages/pid457.php11. http://www.tpub.com/content/engine/14081/css12. http://webpages.csus.edu13. http://www.nebo.edu/misc/learning_resources/ ppt/6-1214. http://netlogo.modelingcomplexity.org/Small_engines.ppt15. http://www.ku.edu/~kunrotc/academics/180/Lesson%2008%20Diesel.ppt16. http://navsci.berkeley.edu/NS10/PPT/ 17. http://www.career-center.org/ secondary/powerpoint/sge-parts.ppt18. http://mcdetflw.tecom.usmc.mil19. http://ferl.becta.org.uk/display.cfm20. http://www.eng.fsu.edu/ME_senior_design/2002/folder14/ccd/Combustion21. http://www.me.udel.edu22. http://online.physics.uiuc.edu/courses/phys14023. http://widget.ecn.purdue.edu/~yanchen/ME200/ME200-8.ppt -

    Web Resources