How does a diesel locomitive works?

Question

How does a diesel locomitive works?

Answer 1

Here's the brief and simple explanation:

A diesel-electric locomotive has a diesel prime mover as it's primary source of power.  This prime mover acts as a big generator: it produces electricity, as well as being connected to a crankshaft that powers other equipment: air compressors, auxiliary generators, etc.

The electricity produced from the prime mover is fed to traction motors, usually one on each axle.  These traction motors are what actually moves the axles and wheels.  There's no transmission - just think of how your ceiling fan works, but about 10,000 times more powerful.

To stop, there are up to four types of brakes on a diesel locomotive:

-Handbrake: manually operated, chain-fed, pulls brake pistons out to push the brake shoes against the wheel.

-Independent brake: locomotive only brake, uses straight air fed into brake cylinders, pushing out pistons to press the shoes against the wheel.

-Automatic (train) brake: line of compressed air throughout entire train, uses changes in air pressure to trigger compressed air being fed into brake cylinders.

-Dynamic brake: uses traction motors to generate electrical resistance (motors can't be under power at the time), which slows the locomotive axles down, and thus, the rest of the train.

Answer 2

There is another type of diesel locomotive known as the diesel-hydraulic, in which the engine is coupled to the transmission via a fluid flywheel - that is, a flywheel consisting of an oil bath in which the motor shaft and transmission shaft have vanes opposing each other. Rotation of the motor shaft forces the vanes of the transmission shaft to rotate, thus driving the loco.

Also: electro-diesel, a hybrid locomotive capable of running on external power supply or its own generator;

Diesel-mechanical, where the diesel motor is coupled to the final drive via a conventional gearbox (largely obsolete and mainly used for small shunting locomotives).

Answer 3

Visit www.howstuffworks.com.  You will get complete details.

Answer 4

You have a very big diesel engine.  Typical is a "710", which is 710 cubic inches per cylinder.  You heard right.    Typically 12-16 cylinders, with some 20's.  

The diesel engine makes between 1500 and 6000 horsepower (depending on type) and this turns a very, very large generator.  

On Amtrak engines there's a second generator of around 750kw (1000hp) to provide AC power for the passenger coaches.  That's enough juice to run a small town.

The power from the generator runs through "switchgear" (a cabinet full of electrical equipment) and then on to large electric "traction motors".  The motors are hung off the axle and have a very simple gear drive.  They apply the force to the locomotive wheels.   There's usually a motor on every axle, with locomotives having 4 or 6 axles total.  

Why do they use electric drive?  Because it amounts to an "infinitely variable transmission".   The engine can run at maximum RPM and apply full power to the wheels starting from 0 MPH.  Nothing forces the engine speed to match the ground speed, as in a geared transmission. In fact, diesel locomotives develop their strongest tractive effort at 0 MPH.  

Now, the electric motors are bound to ground speed, and a slower turning motor takes more current (amps).  Current makes heat in the motor, so there's a practical limit to how long a locomotive can apply full power at very low speeds, before it overheats.  So it needs to get that train moving in fairly short order.  Once it gets over 15MPH, that's not much of a worry.   The engineer has ammeters to show the current in the motors, and marks on the ammeters tell him how long he can overcurrent them before overheating becomes an issue.

By the way, I see no reason why diesel locomotives can't run biodiesel, or with minor modification, SVO (straight vegetable oil).  That and electrification makes rail the easiest mode to get on alternative fuels.

Answer 5

A diesel engine - usually a V-16 or a V-20 - turns a 600 volt generator which, in turn, provides power to traction motors mounted on each axle.

Answer 6

Good to see some great answers. The only thing I'd add is that diesel-electric is still the preference for heavy freight locos. It has the added advantage of dynamic electric braking (running the electric motors as generators causes a braking effect, the electricity generated is dispersed through what are effectively electric heaters and are cooled by cooling grids).

Answer 7

known as a diesel -electric locomotive

the diesel engines run generators - which provide electric energy for the driving force for propulsion from electric motors

to slow down - they back off the juice and use air brakes

which are connected to every car in the train, and powered by the locomotive