Mechanical fuel systems:Timers and Diaphragm controls

Timers

Moving fuel through an open injector requires time and, once injected, additional time is needed for the fuel to ignite. As engine speeds increase, less time is available to accommodate these delays, and the start of injection must occur earlier.

The drawing back at Fig. 5-10 shows the VE hydraulic timer in cross-section. Pressure developed by the feed pump rises in an almost linear fashion with engine speed. As pressure increases, the piston moves to the right, compressing its return spring. A roller transfers this motion to the drive cam, turning it few degrees against direction of shaft rotation.

Mechanical timers are similar to SI advance mechanisms, in that they employ centrifugal weights to sense engine speed and advance the cam (Fig. 5-27). Spring tension on the weights determines the cut-in speed and shims fix the travel limit.

Mechanical fuel systems-0196

Mechanical fuel systems-0197

To check timer operation, connect a timing light to an injector pipe and run the engine up to speed. Injection should advance smoothly without hesitation as the rack is extended. Specifications vary, but most applications require 5–7.5° of total advance.

Diaphragm controls

Injector pumps often include a diaphragm-operated control that reduces fuel delivery at high altitudes and/or increases fuel at wide throttle angles for tur- bocharged applications. Diaphragms are tested with a vacuum gauge.

Related posts:

Transient-Suppression Devices:Voltage-Clamping Devices.
The switched reluctance motor.
Measurements and instrumentation:Temperature.
Direct-Current Voltage Testing of Electrical Equipment:Evaluation of Test Data Readings
Medium-Voltage Switchgear and Circuit Breakers:Short-Circuit Considerations and Power Circuit Breake...
Power Quality, Harmonics, and Predictive Maintenance:Effects of Harmonic on Power System Equipment a...
Fundamentals of Distribution Systems:The Past and the Future
Engine mechanics:Special considerations
COAL-FIRED POWER PLANTS:COMBINED SULFUR AND NITROGEN OXIDE REMOVAL AND PARTICULATE (DUST) REMOVAL
FUEL CELLS:FUEL CELL EFFICIENCY
Another Groups of Thermal Optimized Modulation Methods of Three-Level Neutral-Point-Clamped Inverter...
NUCLEAR POWER:NUCLEAR FISSION REACTOR DESIGNS
The Current Situation and Perspectives on the Use of Wind Energy for Electricity Generation:Belgium
The Current Situation and Perspectives on the Use of Biomass in the Generation of Electricity:Belgiu...
Introduction to Energy Hub Management with Intermittent Wind Power

Leave a comment

Your email address will not be published. Required fields are marked *