Abstract

High temperature pressurized bleed air generated in the engine compressor is used for air conditioning in a jetliner. The engine bleed air must be regulated to a target temperature in the bleed air temperature control system using cold ram air before it can be used in the cabin or other low temperature area. The bleed air system is a control system that consists of sensors, and valve actuators. Potential faults associated with these components need to be considered in the design of the control system. This dissertation focuses on fault detection and diagnosis of the bleed air temperature control system. The faults in temperature sensors and valve actuators are detected using two unscented Kalman filters. The source of a fault is identified using the squared residuals. Nonlinear governing equations for the engine bleed air temperature control system are derived in state space form. Convergence analysis of the proposed fault detection and diagnosis methods is conducted. Heat exchanger is another core component in the bleed air temperature control system. A common fault associated with a heat exchanger is fouling which reduces the heat transfer efficiency, introduces additional resistance to flow, and increases fuel consumption. This dissertation presents a heat exchanger fouling detection method based on the valve control command of an engine bleed air temperature control system. Heat exchanger fouling is monitored by estimating the deviation of valve control command. A simulated bleed air temperature control system has been designed and built. Experiments have been conducted for temperature sensor fault, valve actuator fault, and heat exchanger fouling. Computer simulations for each of these cases are conducted and compared to experimental results.

Highlights

  • Simulation studies have been conducted for the bleed air temperature control system, using dynamic equations and the unscented Kalman filter (UKF) based fault detection and isolation method derived in the above sections

  • In the following figures (Fig. 3.3 to Fig. 3.7) the dashed line shows the real value of sensor or actuator fault, the dot-dashed line shows the threshold of εx, and the solid line is the value of fault detected by the proposed UKF algorithm or the value of εx

  • Temperature sensing elements, air flow control elements, and heat exchanging elements constitute the key components for proper functioning of the temperature control system

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Summary

Introduction

Bleed air is hot, compressed air taken from an aircraft engine, after the compressor stage(s) and before the fuel is injected in the burners This high-pressure, hightemperature engine bleed air is commonly used within the aircraft after cooling in several ways, including de-icing (Yeoman, 1994), pressurizing the cabin (Newman, et al, 1980) and air conditioning for passengers and avionics equipment (Ensign & Gallman, 2006). The ECS in today's jetliners is designed to provide a safe and comfortable cabin environment at cruising altitudes that can reach 40,000 feet. At those altitudes, the cabin must be pressurized to enable passengers and crew to breathe normally. The ECS controls air flow, filtration and temperature

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