This is a question we are often, well sometimes asked. Well. It’s a heat engine However, I hand you over to AI which is probably better than my RS (Real stupidity)
Triple expansion engines cannot run efficiently on compressed air for several reasons:
1. **Energy Density**: Steam contains much more energy per unit volume than compressed air. The high thermal energy of steam (due to both its temperature and phase change from water) provides a significant amount of work when expanding through the stages of a triple expansion engine. Compressed air, on the other hand, lacks the latent heat of vaporization and has a much lower energy density, leading to less work output.
2. **Thermodynamic Efficiency**: The efficiency of steam engines, relies on the thermodynamic properties of steam. Steam has a higher specific volume and undergoes significant expansion when converting from high-pressure to low-pressure stages. Compressed air does not undergo a phase change and has less expansive capability, resulting in lower thermodynamic efficiency in this type of engine.
3. **Heat Management**: Triple expansion steam engines are designed to handle high temperatures and the associated heat transfer processes. Steam, when expanding, cools significantly but remains at a relatively high temperature due to its latent heat. Compressed air cools rapidly during expansion, which could lead to freezing issues and reduced efficiency due to the Joule-Thomson effect, where expanding air can lead to significant temperature drops.
4. **Mechanical Design**: The mechanical design of triple expansion engines is optimized for steam’s properties. This includes considerations for steam’s lubricating properties and its specific heat capacity. Compressed air might require different materials and lubrication to prevent excessive wear and tear or different design parameters to handle the lower energy densities and different thermal characteristics.
5. **Economic and Practical Considerations**: Using compressed air would require significant infrastructure for generating and storing large quantities of high-pressure air. Steam is generated boilers that can generate steam on-demand using various fuel sources. In contrast, generating compressed air at the scale needed would be less efficient and more cumbersome, making it impractical.
