Lecture # 2-G fuel supply and carburator.pptx

Lecture # 2-G fuel supply and carburator.pptx

1. Lecture # 2 Fuel Supply and Carburetor 1

2. Components of the cylinder charge: Fresh gas Fuel can, on the other hand, be injected with the combustion process and metered precisely to the individual cylinder. Residual gas (inert gas) This no longer contains any oxygen and therefore does not participate in combustion during the following power cycle. However, it does delay ignition and slows down the course of combustion, which results in slightly lower efficiency but also in lower peak pressures and temperatures. In this way, a specifically used amount of residual gas can reduce the emission of nitrogen oxides (NOX). 2

3. Gas exchange: Volumetric efficiency and air consumption The success of the gas-exchange process is measured in the variables volumetric efficiency, air consumption and retention rate Pumping losses Work is expended in the form of pumping losses or gas-exchange losses in order to replace the exhaust gas with fresh gas in the gas-exchange process. (throttling losses and push-out losses) 3

4. Supercharging: Dynamic supercharging Supercharging can be achieved simply by taking advantage of the dynamic effects inside the intake manifold. Mechanical supercharging The intake-air density can be further increased by compressors which are driven mechanically from the engine’s crankshaft. Exhaust-gas turbocharging In contrast mechanical supercharging, the compressor of the exhaust-gas turbocharger is driven by an exhaust-gas turbine located in the exhaust-gas flow. 4

5. Torque and power: 5

6. Torque and power: Generation of torque Relationship between torque and power The physical quantity torque M is the pro - duct of force F times lever arm s 6 The engine’s power output P climbs along with increasing torque M and engine speed n .

7. Torque and power: 7

8. Cylinder-charge control systems Electronic throttle control (ETC) 8

9. Cylinder-charge control systems Function and method of operation 9 The Motronic ECU (2) – ME-Motronic for systems with manifold injection or DI-Motronic for gasoline direct injection – calculates the required air mass from the torque to be set and generates the triggering signals for the electrically actuated throttle valve. Using the feedback information from the throttle-valve angle sensor (3) regarding the current position of the throttle valve, it then becomes possible to adjust the throttle valve precisely to the required setting.

10. Cylinder-charge control systems Function and method of operation 10 A cruise-control function can also be easily integrated with ETC (Electronic Throttle Control). The ECU adjusts the torque in such a way that the vehicle speed preselected at the control element for cruise control is maintained. There is no need to press the accelerator pedal.

11. Cylinder-charge control systems Throttle device 11

12. Cylinder-charge control systems Throttle device 12 The use of plastic offers the following advantages over the aluminum housing: Weight saving Optimal throttle-valve geometry Corrosion resistance Low wear Less sensitivity to temperature influences Less tendency to icing (omission of water heater)

13. Cylinder-charge control systems Accelerator-pedal sensors 13 In Motronic systems with Electronic Throttle Control (ETC), the pedal-travel sensor records the travel or the angular position of the accelerator pedal. For this purpose, potentiometers are used in addition to proximity-type sensors.

14. Cylinder-charge control systems Accelerator-pedal sensors : Potentiometric pedal-travel sensor 14 The engine ECU receives the measured value picked off at the potentiometer wiper as a voltage. The ECU uses a stored sensor curve to convert this voltage into the relative pedal travel or the angular position of the accelerator pedal.

15. Cylinder-charge control systems Accelerator-pedal sensors : Potentiometric pedal-travel sensor 15 A second (redundant) sensor is incorporated for diagnosis purposes and for use in case of malfunctions. It is a component part of the monitoring system. One sensor version operates with a second potentiometer, which always delivers half the voltage of the first potentiometer at all operating points. Thus, two independent signals are available for fault-detection purposes. Instead of the second potentiometer, another version uses a low-idle switch, which signals the idle position to the ECU. The status of this switch and the potentiometer voltage must be plausible.

16. Cylinder-charge control systems Accelerator-pedal sensors : Potentiometric pedal-travel sensor 16 For vehicles with automatic transmissions, a further switch can be incorporated for an electrical kickdown signal. Alternatively, this information can also be derived from the rate of change of the potentiometer voltage. A further possibility is to trigger the kickdown function by means of a defined voltage value of the sensor curve; here, the driver receives feedback on a jump in force in a mechanical kickdown cell. This is the most frequently used solution.

17. Cylinder-charge control systems Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors 17 In this type of sensors, the magnetic flux of a roughly semicircular, permanent-magnetic disk is fed back via a pole shoe, two further conductive elements and the similarly ferromagnetic shaft to the magnet.

18. Cylinder-charge control systems Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors 18 Depending upon the angular setting, the flux is led to a greater or lesser degree through the two conductive elements, in the magnetic path of which a Hall-effect sensor is also situated. Using this principle, it is possible to achieve a practically linear characteristic in the measuring range of 90°.

19. Cylinder-charge control systems Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors 19 The magnet moves around the Hall-effect sensor in a circular arc. Only a relatively small section of the resulting sinusoidal characteristic curve features good linearity. If the Hall-effect sensor is located slightly outside the center of the circular arc, the characteristic curve increasingly deviates from the sinusoidal, and now features a short measuring range of almost 90°, and a longer measuring range of more than 180° with good linearity.

20. Cylinder-charge control systems Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors 20 A great disadvantage though is the low level of shielding against external fields, as well as the remaining dependence on the geometric tolerances of the magnetic circuit, and the intensity fluctuations of the magnetic flux in the permanent magnet as a function of temperature and age.

21. Cylinder-charge control systems Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors 21 In this type of Hall-effect angle-of-rotation sensor, it is not the field strength but rather the direction of the magnetic field which is used to generate the output signal. The field lines are recorded by four radially arranged measuring elements lying in one plane in the x- and y-directions. The output signals are derived in the ASIC from the raw data (cos and sin signals) using the arctan function. The sensor is positioned between two magnets to generate a homogenous magnetic field. The sensor is therefore insensitive to component tolerances and temperature-resistant.

22. Cylinder-charge control systems Accelerator-pedal sensors : 22