Cruising Economy by Use of Water Injection

A STUDY of possible economic advantages to the aircraft operator of utilizing the internal cooling potentialities of water to assist aircraft-engine cooling and increase detonation limited powers is presented here.

Cost analysis is made of three methods of increasing airplane performance by water injection, namely:

1. 1.
   By increasing cruising bmep's while maintaining engine cooling requirements at the value for conventional cruising bmep's.
2. 2.
   By decreasing cruise power cooling requirements with the addition of water.
3. 3.
   By increasing cruise powers up to meto at a constant F/A ratio while maintaining low cooling requirements and avoiding detonation with the use of water.

It is concluded by the author that if the water to be used for cooling does not displace an equivalent weight of payload, a maximum saving of 7% at sea level and 18% at 25,000 ft can be realized in direct operating cost with water. At the same operating cost a performance increase of 3% at sea level and 12% at 25,000 ft can be realized. However, if the water carried results in an equivalent loss in payload, the operating cost may be doubled if water injection is used.