How does a fuel engine convert heat into mechanical work?

In summary: You have a container of liquid that is heated up. 2) The liquid starts to change phase, turning into a gas. 3) The gas occupies a greater volume, which means it has a higher velocity. 4) The gas passes through a turbine, which produces mechanical energy.
  • #1
fawk3s
342
1
Seems like a stupid question, to me. But well, I am stupid aswell, so it fits me.

Its something I've been thinking about lately. How is the heat/buring of the fuel transformed into mechanical work?
I've had some ideas but they are mainly stupid and the loss of energy would be massive in those.

So how do fuel/steam engines work?

Thanks in advace,
fawk3s
 
Science news on Phys.org
  • #2
In an internal combustion engine, the release of stored chemical energy creates thermal energy. The combustion products in the form of hot gas produced a greater volume, or greater pressure, than the products. The pressure pushes a piston, or pushes through a turbine to the lower pressure exit downstream. Pressure on an area produces a force. The force on a piston is transmitted to a crackshaft, which produces a torque, or the force on a set of turbine blades causes moment on the blade, which tranmits a torque to the shaft of the turbine.

In addition, the expansion of hot gases in a jet or rocket engine also represents a change in momentum. The thrust or force of a jet/rocket is related to the exhaust (exit) velocity of the hot gases.

A steam cycle works much the same way. Liquid water is pumped into a heat exchanger (boilder) where it absorbs heat and changes phase going from liquid to gas. The gas occupies greater volume, and by virtue of the conservation of mass (continuity), the gas, which is constrained on one or two dimensions expands. That expansion means the gas has a higher velocity/momentum than the liquid. The steam flow passes through a turbine, and the momentum/energy of the flow pushes on the turbine blades, which like the example of the combustion turbine blade above, causes a torque on the turbine shaft.

A rotating shaft can be used via a transmission system to turn wheels of a vehicle (car, truck, motorcycle) or propeller (aircaft or ship) or generator shaft (electrical generator) or a motor or mill machinery.

So it goes something like thermal energy -> mechanical rotational energy, and optionally mechanical energy -> electrical energy
 
Last edited:
  • #3
Hm, I wasnt so wrong after all..
Thanks, helped much !
 
  • #4
The efficiency of the process is quite variable.

Commercial nuclear power plants based on the steam (Rankine) cycle have thermal efficiencies of ~32-37% depending largely on the turbine designs (particularly the blade designs).

Fossil (coal, oil, gas - fired) power plants have efficiencies of 34-40% depending on the amount of superheat.

Gas fired (Brayton, combustion turbine) can achieve ~42% efficiency. Aeroderivative combusion turbines have become quite efficient compared to combustion turbines of 30 to 40 years ago.

Adding a steam (Rankine) cycle to a gas-fired combustion turbine cycle can yield 53-62% thermal efficiency.
 
  • #5

FAQ: How does a fuel engine convert heat into mechanical work?

How does a fuel engine convert fuel into energy?

A fuel engine converts fuel into energy through a process called combustion. Fuel, typically gasoline or diesel, is mixed with air and ignited by a spark or compression. This creates a controlled explosion that pushes pistons, which in turn, rotates the crankshaft and creates motion.

What is the role of the carburetor in a fuel engine?

The carburetor is responsible for mixing the appropriate amounts of fuel and air to create the optimal air-fuel ratio for combustion. It controls the amount of fuel that enters the engine, based on the amount of air that flows through it. This ensures efficient combustion and maximizes the engine's power output.

How does the ignition system work in a fuel engine?

The ignition system provides the spark needed to ignite the fuel-air mixture in the engine. It consists of a battery, ignition coil, distributor, and spark plugs. When the spark plugs receive an electric current from the ignition coil, they create a spark that ignites the fuel, starting the combustion process.

What is the function of the pistons in a fuel engine?

Pistons are an essential component of a fuel engine as they are responsible for converting the energy from combustion into mechanical motion. As the fuel-air mixture ignites, it expands and pushes the piston downward, rotating the crankshaft and creating motion. The piston then moves back up to compress the mixture and prepare for the next combustion cycle.

How does a fuel engine regulate its speed?

A fuel engine regulates its speed through a device called a throttle. The throttle controls the amount of air that enters the engine, which in turn, controls the amount of fuel that is burned. By adjusting the throttle, the engine can increase or decrease its speed, depending on the demand for power.

Similar threads

Back
Top