Generally, water/air ratios are 1-5:100 by weight. The quantity of water carried is usually sufficient for ONE "wet" take-off only.Take off thrust can be increased by 10 to 30% by the use of water injection.Water/Methanol Injection TheoryIt can be seen that the fuel control system schedules more fuel into the engine to increase the engine RPM. If the fuel was mixed with the water then there would not need to be any adjustment to the fuel control system, as the fuel in the water would ignite and therefore turn the turbines with greater speed. Why methanol?Methanol is used for two reasons; the first is that it acts as an anti-freeze for the water in the water tank, and secondly, it is the only fuel that will mix completely with water. As it is a fuel it will increase the power output if it is burnt in the combustion chamber, albeit not by a lot as methanol has a low calorific value. Note that the prime purpose of Methanol is anti-freeze not increase in fuel for burning.Types of SystemThe water or water/methanol may be injected either into the compressor inlet, or the combustion chamber inlet. The latter is more suitable for engines with an axial flow compressor. This is because a more even distribution can be obtained and a greater quantity of coolant can be satisfactorily injected. Also, the greatest advantage of the water injection system is the cooling of the turbine components. The gain due to reduction of inlet air temperature can usually be neglected. In the combustion chamber inlet injection system, a non return valve must be fitted in the water delivery pipe to prevent Compressor Delivery Pressure entering the water injection system components. Note: Demineralised water is used to avoid fouling the compressor or turbine blades, etc. with the impurities normally found in household drinking water. The water should contain no more than 10 parts per million of solids or the life of the engine may be seriously reduced. Note: Methyl/ethyl mixtures will generally be a blend of 35 to 50 percent alcohol in either demineralised or distilled water. Figure 15.7: Simplified Water Injection System
Part 66 Training Syllabus Module 15 –Gas Turbine Engine Issue: 1 Issue Date: 15.04.2010 Amdt. / Date: Doc No: BM1_01 Copyright © 2010 - Unpublished Work Part 66 Module 1 Page 220 Figure 15.8: Water injection schematic Figure 15.09 : Turbo jet thrust restoration
Part 66 Training Syllabus Module 15 –Gas Turbine Engine Issue: 1 Issue Date: 15.04.2010 Amdt. / Date: Doc No: BM1_01 Copyright © 2010 - Unpublished Work Part 66 Module 1 Page 221 Figure 15.10: Turbo-propeller power boost Module 15.16 - Turbo-prop EnginesIntroductionA turbine engine can drive a propeller by extracting some of the energy that remains in the exhaust gases after they have driven the compressor. This can be done by connecting the propeller to the compressor through a set of reduction gears. But the propeller can be more efficiently driven through appropriate reduction gears by a turbine separate from the core engine, the portion of the engine that drives the compressor. An engine that uses a separate turbine to drive the propeller is called a free-turbine engine.
- Fall '17
- gas turbine engine, engine inlet, Compressor Inlet Pressure