Why is steam used in turbines

A Steam Turbine is a mechanical device that extracts thermal energy from pressurized steam and transforms it into mechanical work. Thank you for visiting the Energy System Map. Visit bit. Sir Charles A. Parsons invented the first modern turbine, a reaction turbine, in Connected to a dynamo, the turbine produced 7.

Large turbines are used to generate electricity. As the name implies, a steam turbine is powered by steam. This steam spins the blades continuously. The turbine is then used to run a generator, producing electricity.

The basic parts of stream turbines are blades and rotors. A set of blades is known as a stage. They also have steam inlets usually a set of nozzles and outlets. Two independent mechanisms, known as governors, are used to ensure safe operation of the turbine. Steam turbines use high-pressure steam to turn electricity generators at incredibly high speeds, so they rotate much faster than either wind or water turbines.

For example, a typical power plant steam turbine rotates at — repetitions per minute RPM ; about — times faster than the blades spin on a typical wind turbine, which needs to use a gearbox to drive a generator quickly enough to make electricity 2. A steam turbine is also significantly more compact than a steam engine, one reason why steam turbines were quickly adopted for powering ships where space was very limited.

Superheated Steam — Regular, saturated steam can be expanded into even more steam by superheating it. The remaining water droplets that are suspended in saturated steam can themselves become steam. Superheated steam is important because it increases the efficiency of the boiler. It is important that dry steam is used for power generation because water droplets could damage the power-generating turbines. Supercritical Steam Generation — Another process often used in the production of electricity is subcritical steam generation.

Standard boilers function at subcritical levels, defined as less than 3, psi. Below the critical level boiling bubbles will form as the water is converted to steam. Supercritical generation occurs at pressure levels above the critical threshold of 3, psi.

At this level the liquid water instantly becomes steam without ever going through the bubbling and boiling phase. An advantage of supercritical steam generation is that it ultimately uses less fuel and releases less greenhouse gas emissions. If the feed water contains too many suspended solids or dissolved impurities this can cause corrosion or a buildup of sediment and sludge in the boiler. Moving on, non-ideal considerations will make a difference. Basically, a turbine isn't a perfect ideal expansion process.

These factors are related to the working fluid, but probably not like you think. Some losses come from the fact that the fluid works its way around the blades in the turbine altogether, so it doesn't make energy. Some losses are just due to aerodynamics of the blades itself.

Some losses are even because the temperatures are so high that blades require active cooling, necessitating some mixing that harms cycle efficiency. Some losses are because thrown away kinetic energy at the end of a turbine, to move it into a pipe to go to the next turbine.

Are all of these affected by the fluid? Yes, but how can you say that one is better than another? That's quite difficult. Water is obviously abundant, so a good question might be to ask why we don't just use air which is also abundant.

In a sense we do for direct cycle oil and natural gas cycles can't for coal because it would muck up the turbine. But we could also build a closed cycle based on Nitrogen gas. One good argument for water over air is component cost. The condenser is a very expensive component, and with water Rankine cycles, you get a lot of cost reduction because there are tons of little droplets of water flying around, aiding heat transfer.

Also, you have smaller pumps to move liquid water, as opposed to lukewarm air. EDIT: arbitrarily through reading I stumbled on some good images of the non-ideal turbine losses.

This is only one small part of what I was talking about, of course. This is also for a compressor, so I'm kind of lying when I say the above stall condition eddies are relevant. It still has aerodynamic losses, which are similar. The first question is, why use a steam engine rather than an air engine? The most efficient thermodynamic process is the Carnot Cycle - though no one has built a Carnot Engine yet. Take a look at it's T-S Diagram found there.

An important feature of the Carnot-Cycle are the isothermal expansions and compressions happening. Now, a Rankine Cycle is in Theory as efficient. This cycle uses steam, the evaporation and condensation of the steam are isothermal processes in the ideal case. Rankine Engines can theoretically achieve Carnot efficiency. However, if only lower temperature heat sources are available, other liquids with lower boiling points may be used in then so called organic rankine processes.

The question is fundamentally incorrect, given that the ideal gas law does not apply with steam. In order to be considered an ideal gas, the fluid has to be far away from the liquid vapor dome.