1. MARCO TEÓRICO
1.1. El enfoque lineal o causal
1.1.2. Análisis de accidentes: el árbol de causas
The engine governor operates either as an idle-maximum-speed governor or as a variable-speed governor. The selection is made via parameter 2.1010.001. Two 2D parameters (2.0401.010 and 2.0401.012) serve to establish the relation between voltage or current value and speed and torque, see table "2D parameters" in the chapter "2D parameters" (→ Page 185).
Parameter No. 2.1010.004 serves as a reference value, also refer to table "1D parameters" in the chapter "1D parameters" (→ Page 103).
Whereas the variable-speed governor controls to a specific speed, the idle-maximum-speed governor only controls to two values, between which specified fuel injection takes place, whereby the speed governor is bypassed. The setting is made via parameter 2.0401.026 and/or 2.0401.027, refer to table "2D parameters" in the chapter "2D parameters" (→ Page 185).
The (automatic) switchover between operation as a fuel injection governor to operation as a speed governor is always carried out via speed.
The (automatic) switchover between operation as a speed governor to operation as a fuel injection governor is always carried out via torque.
nsoll: Engine specified speed Speed droop
n: PI(DT1): Speed governor
MSoll: Specified torque
MMax: Torque limitation:
• M = f (speed)
• M = f (charge air pressure) • M = f (fuel temperature) • etc.
MSoll_eff: Effective specified quantity
ton, toff, php_max: Characteristics maps for start-of-injection/end-of-injection and high-pressure controllers ton: Start of injection toff: End of injection php_max: Specified fuel high pressure
ton/toff: Firing Sequence n: Engine speed
nist: Engine actual speed
PWM: Pressure controller p: PI(DT1) high-pressure controller pfuel_soll: Specified fuel high pressure
php: Fuel high pressure
f: Fuel
CR: Common Rail HP: High-pressure pump NW: Camshaft gear KW: Crankshaft gear
The speed setpoint (specified speed and speed droop) is compared by the speed governor with the actual engine speed. In case of deviations, it adapts its output signal (injection specified quantity). The PID characteristic guarantees a quick response to changes and an exact speed adjustment.
The dynamic quantity limitation independent of the operating point protects the engine against overloading. The specified quantity after quantity limitation is the input signal for the characteristics-map-controlled
start-of-injection/end-of-injection controller. The power electronics activates the individual cylinders according to its specifications. The engine governor also regulates the injection pressure of the Common Rail system.
Angle measurement/determination of injection timing
Injection timing is determined in the electronics using the information from inductive sensors on two measuring wheels. One measuring wheel is mechanically coupled to the crankshaft and the other to the camshaft. In normal operation, the crankshaft sensor supplies the exact angular position of the crankshaft for determining injection timing and, derived from this, the engine speed.
In normal operation, the camshaft sensor provides both the intake and ignition stroke.
Crankshaft:
The crankshaft measuring wheel rotates as a function of engine speed. In the inductive sensor, each tooth of the measuring wheel generates a pulse. This determines the engine speed. It is also used for determining the angle of the crankshaft. The count is synchronized by a tooth gap (i.e. missing pulse at the sensor) at a defined angular position.
Camshaft:
The camshaft measuring wheel rotates at half engine speed. In controlled operation, the engine governor only evaluates the tooth gap.
Using this tooth gap, the electronics can distinguish between the intake and ignition stroke of cylinder A1.
Adjustable speed droop
The following illustration shows the principle control area of the engine governor and the effect of the adjustable speed droop (load-dependent change in speed setpoint).
Among other things, the speed droop is required to achieve load equalization with coupled drive machines. The speed droop setting is dependent on the plant and can be altered via the dialog unit.
The speed droop is defined as a relative speed change during relief of the engine. The speed droop is based on the rated speed (= maximum speed at maximum power output). Every point of the operating range is influenced during a load change.
The speed droop is calculated by subtracting the rated speed nnennfrom the maximum speed (zero load)
L1: Load
DBR: Limitation curve
nL1: Resulting speed at load L1
n0: Zero load
nL: Idle speed
nsoll: Speed setpoint
nnenn: Rated speed
nNullMaximum speed at zero load
Speed droop n: Engine speed
Power limitations
Power limitations are effected via the Monitoring and Protection module and its specified settings (→ Page 218).
Exhaust turbocharger
The exhaust turbochargers (ETCs) supply the diesel engine with the air volume with excess pressure required for combustion. This achieves higher efficiency and a performance increase of the engine.
The ETC control ensures optimized turbocharging over a wide power range.
The number of turbochargers that can be connected is specified by a parameter (1.3011.090. unalterable). Turbochargers that can not be connected operate as basic turbochargers as soon as the engine runs. Overspeed protection:
To protect the turbochargers, the behavior of the engine is influenced during turbocharger overspeed in accordance with the settings of the Monitoring and Protection module (→ Page 218).
Connectable turbochargers are cut in/out by opening and closing a hydraulically actuated turbocharger control valve. Activation of the turbocharger control valve(s) is effected by solenoid valve(s) controlled by the governor.
Cylinder cutout
If the cylinder cutout is active, the engine governor will activate only one half of the injectors alternately. The cylinder cutout is only active in idle mode. It guarantees engine operation free of white smoke.
• Injection quantity is smaller than the max. injection quantity for operation with cylinder cutout. • The plant "Cylinder cutout Off" is not active.