This paper discusses jet engine powerloss and damage due to ingestion of ice particles. In the mid-90s several commercial airplane jet engines experienced more frequent powerloss in ice particle conditions, resulting in a focused investigation, and a greater awareness that led to recognition of similar events on other aircraft. Since the mid-90s, events have been more numerous, and costly, and have generated greater industry interest. These events have been predominately associated with flight at high altitude near deep convective systems, often in tropical regions. Data are presented from flight-testing and an event data base to support the contention that the events are caused by ingestion of high concentrations of ice particles, and that supercooled liquid water is either of secondary importance or not required. The basic theory of how ice accretes in the engine by this process is described. Complex issues facing industry to mitigate the problem, and simulation of the ice particle environment are discussed.
The aviation industry has now connected a number of engine power-loss events to the ingestion of atmospheric ice crystals. Ice crystals are believed to penetrate to and eventually accrete on surfaces in the engine core where local air temperatures are warmer than freezing. Research aimed at understanding the accretion and shedding of ice crystals within the engine is being conducted industry-wide. Although this specific icing condition is readily produced inside an operating engine, rig testing is the preferred research tool because it has the advantage of good visibility of the ice accretion process and easy access for video documentation. This paper presents one of the first efforts to simulate the warm air/cold ice conditions occurring inside the engine core using a test rig. The test section contains geometry simulating the transition duct between the low and high compressors in a typical jet engine and an airfoil simulating the engine strut connecting the inner and outer surfaces. Test results showed ice formed on the airfoil and other surfaces in the test section at air temperatures warmer than freezing. However, when both the air and surface temperatures were held below freezing, the injected ice did not melt and no ice accretion was observed. Ice only formed on the airfoil when mixed phase conditions (liquid and ice) were produced, by introducing the ice into a warm airflow. This test concludes that a rig-level ice crystal icing test is feasible and capable of producing ice accretion in a simulated engine environment. As it was the first test of its kind, reporting of these preliminary test results are expected to benefit future experimenters.
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