Search Results (3)

As a critical system of onboard aircraft equipment, the environmental control system (ECS) has an essential impact on flight safety. The performance of the ECS is usually tested using the thermal test facility. The facility comprises temperature and pressure simulation units to simulate the engine bleed air. Currently, the ECS often fails due to the dynamic and rapid changes in the temperature and pressure of bleed air. To achieve the dynamic bleed air simulation, the most critical problem is to simulate the bleed air’s rapid heating and boost process during the actual engine working process. However, the temperature simulation unit has the characteristics of nonlinear and large inertia. Moreover, temperature and pressure control are strongly coupled. These characteristics usually lead to temperature and pressure dynamic control failure. This paper introduces a novel facility that adopted the hot and cold blending method to realize the rapid response of the temperature. Furthermore, it used a particular system structure to reduce pressure and temperature control coupling. In addition, it adopted the lookup-table-based PID (LPID) controller to acquire the rapid response and good steady-state performance of temperature and pressure control. Experimental control results are presented and discussed. The results showed that the facility could meet ECS’s dynamic and steady-state test requirements. The novel facility makes up for the insufficient dynamic test capacity of the previously developed ECS test facilities. Full article

The aircraft engine bleed air simulation thermodynamic laboratory simulation parameters include the bleed air pressure and temperature. However, existing laboratories cannot carry out the dynamic test of the engine bleed air simulation. In the engine bleed air simulation dynamic test, the temperature control has the characteristics of strong coupling and nonlinear and large inertia. The conventional control strategy cannot solve the contradictions of the response speed and stability of the system. Moreover, the dynamic control of the pressure and temperature involve strong coupling. That often leads to the failure of control decisions. Therefore, there is still no relevant report on the laboratory equipment used for the engine dynamic bleed air simulation. According to the above problem, this study adopted heat exchangers for indirect heating to reduce the coupling of dynamic control between temperature and pressure. Specifically, to take into account the rapid response and stability of the system, this study used the lookup table-based PID (LPID) controller to control the temperature and pressure of the bleed air simulation test. The dynamic test errors were within 10%, and the steady-state accuracies were within ±2%. The simulation software results and the engine bleed air simulation test results showed that temperature and pressure control systems based on the LPID controller have advantages: high control precision, a low overshoot amount, a fast response, and a high stability. Full article

In this study, the inter-stage dynamic performance of a multistage axial compressor is simulated through a semi-empirical model constructed in the Matlab Simulink environment. A semi-empirical 1-D compressor model developed in a previous study has been integrated with a 0-D twin-shaft gas turbine model developed in the Simulink environment. Inter-stage performance data generated through a high-fidelity design tool and based on throughflow analysis are considered for the development of the inter-stage modeling framework. Inter-stage performance data comprise pressure ratio at various speeds with nominal variable stator guide vane (VGV) positions and with hypothetical offsets to them with respect to the gas generator speed (GGS). Compressor discharge pressure, fuel flow demand, GGS and power turbine speed measured during the operation of a twin-shaft industrial gas turbine are considered for the dynamic model validation. The dynamic performance of the axial-compressor, simulated by the developed modeling framework, is represented on the overall compressor map and individual stage characteristic maps. The effect of extracting air through the bleed port in the engine center-casing on transient performance represented on overall compressor map and stage performance maps is also presented. In addition, the dynamic performance of the axial-compressor with an offset in VGV position is represented on the overall compressor map and individual stage characteristic maps. The study couples the fundamental principles of axial compressors and a semi-empirical modeling architecture in a complementary manner. The developed modeling framework can provide a deeper understanding of the factors that affect the dynamic performance of axial compressors. Full article