|Quoting 727EMflyer (Reply 1):|
I may be out to lunch here, but doesn't the combustion also increase the volume (mass may be a better word) of the gas at the same time as the heat increases the pressure, thereby adding even more energy potential?
No. Several things to address here.
1.) The only increase in mass in combustion is due to addition of fuel. The amount of mass added compared to the total airflow of a high bypass engine is less than 0.1%.
2.) Gas turbine engines operate using the Brayton cycle. Combustion occurs ideally at constant pressure. In a real combustor, pressure will drop slightly due to losses.
3.) In a gas turbine engine all you need is heat addition. Whether the heat comes from a combustor, nuclear reactor or electric coil, it doesn't really matter where the heat comes from. In the case of a combustor, the entire point is to convert the chemical energy in the fuel into thermal energy. That's it. There is no added benefit of mass flow or pressure increase.
Now, back to the original question, could an electric coil work in a gas turbine engine? Yes it could be done, however the problem with this method is the heat transfer effectiveness of the coil. Not very good at all. It would be very difficult to get this to work efficiently in large gas turbines. The one place where a electric coil would work, and in fact I believe it has been done, is in a micro turbine engine. I don't have time right now, but if no one gets to it before I do, I'm sure there are some sites on the web describing these engines.