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USE OF A TURBOFAN ENGINE TO MEASURE ICE CRYSTAL CLOUD CONCENTRATION IN-FLIGHT

IP.com Disclosure Number: IPCOM000239243D
Publication Date: 2014-Oct-23
Document File: 8 page(s) / 234K

Publishing Venue

The IP.com Prior Art Database

Abstract

This paper discusses the use of typical sensors found in modern high bypass ratio turbofan engines to detect the presence of altitude ice crystals in-flight.

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USE OF A TURBOFAN ENGINE TO MEASURE ICE CRYSTAL CLOUD CONCENTRATION IN-FLIGHT

TECHNICAL FIELD

    This paper discusses the use of typical sensors found in modern high bypass ratio turbofan engines to detect the presence of altitude ice crystals in-flight.

BACKGROUND

    In recent years, the aviation industry has linked a number of jet engine power loss events to the ingestion of ice particles. These events consisted of rollback, flame out, compressor surge or stall, and in some cases mechanical damage to the compressor. All of these events have occurred during flight through strong convective weather and mostly at high altitude. Significant effort is currently underway to characterize the atmosphere believed to cause these events in order to revise certification regulations.

    Altitude ice crystals are known to exist in the convective updrafts of strong tropical and sub-tropical storms. When ingested into the air-data sensors, or the engines of the aircraft, these ice crystals have caused operational issues. High altitude clouds consisting entirely of glaciated crystals do not produce the reflectivity radar echoes that are characteristic of supercooled liquid water clouds. As a result of this, commercial aircraft have difficulty avoiding ice crystal encounters.

    Techniques for detecting the ingestion of water into the core of a gas turbine have been used for years primarily to detect the presence of hail. The ingress of hail can cause combustor quench, or flame-out, particularly when operating near idle conditions. Methods typically rely


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on commonly measured engine parameters such as core rotor speed, and various temperatures and pressures throughout the engine, or fuel flow.

    Early methods detected the presence of hail by sensing a change in operating point by measuring the temperature difference across the compressor. Liquid water could be detected in the combustion chamber when the air temperature in the combustor lining tends towards the saturation temperature of water, at the combustor operating pressure. More elaborate methods of hail detection utilize a blow-out map and measurements that are indicative of compressor airflow pressure and temperature. Hail or water can also be detected by examining the compressor discharge temperature and fuel flow.

    The detection parameter could be used to trigger automated engine response schedules to prevent issues. Moreover, it can be implemented to alert pilots of the presence of altitude ice crystals so they may take evasive maneuvers before air-data sensor readings are corrupted, or the engines experience operational issues. The magnitude of the detection parameter can be used to determine the severity, or atmospheric concentration of the ice crystal threat.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows the control volume used to define the core ingestion efficiency (Θ).

    Fig. 2 shows sample time traces of ice crystal cloud Total Water Content measured with a gas turbine engine.

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