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Engine fan with viscous drive. A fan clutch is a thermostatic engine cooling fan that can freewheel at low temperatures when cooling is not needed, allowing the engine to warm up faster, relieving unnecessary load on the engine. As temperatures increase, the clutch engages so that the fan is driven by engine power and moves air to cool the engine.
Engine cooling removes energy fast enough to keep temperatures low so the engine can survive. [2] Some high-efficiency engines run without explicit cooling and with only incidental heat loss, a design called adiabatic. Such engines can achieve high efficiency but compromise power output, duty cycle, engine weight, durability, and emissions.
Vehicle speed affects this, in rough proportion to the engine effort, thus giving crude self-regulatory feedback. Where an additional cooling fan is driven by the engine, this also tracks engine speed similarly. Engine-driven fans are often regulated by a fan clutch from the drivebelt, which slips and reduces the fan speed at low temperatures ...
Dieseling or engine run-on is a condition that can occur in spark-plug-ignited, gasoline-powered internal combustion engines, whereby the engine keeps running for a short period after being turned off, drawing fuel through the carburetor, into the engine and igniting it without a spark.
The tests require engine manufacturers to carry out at least two tests of the engine, to make sure that the engine can survive a compressor or fan blade breaking off within the engine and a turbine blade breaking off within the engine, without fragments being thrown through the outside enclosure of the engine, creating a contained engine failure.
Diesel engine runaway is an occurrence in diesel engines, in which the engine draws extra fuel from an unintended source and overspeeds at higher and higher RPM, producing up to ten times the engine's rated output until destroyed by mechanical failure or bearing seizure due to a lack of lubrication. [1]
In a geared turbofan, a planetary reduction gearbox between the fan and the LP shaft allows the latter to run at a higher rotational speed thus enabling fewer stages to be used in both the LP turbine and the LP compressor, increasing efficiency and reducing weight. However, some energy will be lost as heat in the gear mechanism and weight saved ...
The original engine contained a single stage fan driven by a 4-stage low pressure (LP) turbine, supercharging a 14-stage high pressure (HP) compressor driven by a 2-stage HP turbine, with an annular combustor. Later higher thrust versions of the CF34 feature an advanced technology core, with only 10 HP compressor stages.