A Case Study on Contrail Avoidance - Effects of Collection of Condensed Water from Engine Core Exhaust on Aircraft Performance

摘要

Aviation industry has experienced a constant growth over the last decades, and forecasts suggest that this trend will continue. In order to reduce its future environmental footprint, the aviation industry is constantly in pursuit of greener technologies and hence significant research has been done on aircraft emissions. This research has indicated that contrails and aircraft induced cirrus clouds formed by water vapour released in the exhaust have detrimental effects [1]. Consequently, several contrail avoidance strategies have been investigated during the last two decades. They all however present a significant drawback: a fuel overconsumption. One of these strategies consists in condensing the water vapour within the engine, so that it can be stored in the aircraft or released into the atmosphere in a controlled manner [2]. This technique is the foundation of the current work. The aim of this study is to investigate the feasibility of storing condensed water on board and to establish the effects it may have on the performance of an aircraft over a mission. To assess the penalties of increasing the aircraft weight, an analytical aircraft performance model was developed which could account for on-board water collection and storage and further estimate its effect on overall performance. These penalties were assessed in two ways: the reduced range for a given amount of fuel due to excess weight and the augmented fuel consumption for a given range. Once the penalties were determined, the net balance between the positive effect of contrail prevention and the negative effect of the additionally emitted CO_2 due to excess fuel consumption was established. From these analyses and based on current data available, it was concluded that aviation radiative forcing associated with water vapour, cirrus clouds and contrails might be significantly reduced through collection of water vapour from the exhaust of the aircraft engine. However, the aircraft configured for water storage would either be able to cover 23% shorter range than the baseline aircraft using the same amount of fuel or consume 17% more fuel to cover the same distance.