Design and Experimental Evaluation of PID Controller for Digital Electro-Pneumatic Cabin Pressure Control System

The performance of the designed digital electro-pneumatic cabin pressure control system for the cabin pressure schedule of transport aircraft is investigated.For the purpose of this study,an experimental setup consisting of a simulated hermetic cabin and altitude simulation chamber is configured for cabin pressure control system operation.A series of experimental tests are executed to evaluate the performance of the cabin pressure control system.The parameters of the PID controller are optimized.In the optimization process,the variation regularity of the rate of cabin pressure change under various conditions is considered.An approach to prioritize the control of the rate of change of cabin pressure based on the flight status model is proposed and verified experimentally.The experimental results indicate that the proposed approach can be adopted for the designed digital electro-pneumatic cabin pressure control system to obtain a better cabin pressure schedule and rate of cabin pressure change.

Experiment on Boiling Heat Transfer of Refrigerant R134a in Mini-channels

The flow boiling heat transfer characteristics of refrigerant R134 a flowing inside two different kinds of minichannels are investigated. One channel is multi-port extruded with the hydraulic diameter of 0.63 mm,and the other one is rectangular with offset fins and a hydraulic diameter of 1.28 mm. The experiments are performed with a mass flow rate between 68 and 630 kg/(m^2·s),a heat flux between 9 and 64 kW/m^2,and a saturation pressure between 0.24 and 0.63 MPa,under the constant heat flux heating mode. It is found that the effect of mass flow rate on boiling heat transfer is related to heat flux,and that with the increase of heat flux,the effect can only be efficient in higher vapor quality region. The effects of heat flux and saturation pressure on boiling heat transfer are related to a threshold vapor quality,and the value will gradually decrease with the increase of heat flux or saturation pressure. Based on these analyses,a new correlation is proposed to predict the boiling heat transfer coefficient of refrigerant R134 a in the mini-channels under the experimental conditions.

Three-Dimensional Numerical Simulation of Ice Crystal Melting in Jet Engine

A method was presented for calculating the melting rate of ice crystals in different axial positions in a compressor. The volume of fluid model and enthalpy-porosity model were used to simulate the melting process of single ice crystal. The result was validated by experimental data from literature. The change of the liquid fraction of the ice crystals with the axial position was obtained when the temperature distribution inside the compressor was introduced into the melting process. The liquid fraction of the spherical ice crystals was fitted with the ice crystal diameter as a variable, and the general distribution function for computing liquid fraction in any axial position in the compressor was obtained. The function of axial position as a variable for non-spherical ice crystal was also got.

Numerical simulation of a UAV impacting engine fan blades

A 3D digital model of a small Unmanned Aerial Vehicle(UAV)is obtained by using the method of scanning reverse modeling and joint mapping.A numerical simulation of a small UAV strikes on rotary engine blades,presented in this paper,was performed with a Transient Nonlinear Finite Element code PAM-CRASH software.A test of motor strike on plate was developed and the dynamic response of the plate were obtained to validate the numerical simulation method of a UAV strike on blades.Based on this,dynamic damage response caused by UAV on the engine blades were studied.It is indicated that the impact process between the UAV and a single blade can be divided into two typical stages:cutting and impact.Cutting mainly leads to the failure of the leading edge material,and impact mainly leads to the plastic deformation of the blade.At the same time,it is compared with the damage impacted by bird with the same mass.For the same mass of bird and UAV,the damage caused by UAV striking fan blade is more serious,and 1.345 kg UAV striking fan blade of typical civil aviation engine is enough to cause damage to flight safety.

Unmanned aerial vehicle strike on a flat plate:Tests and numerical simulations

The incursion of Unmanned Aerial Vehicles(UAVs)into airports often occurs due to the popularity of drones,which may lead to a threat to aircraft flight safety.Therefore,estimating the dynamic impact load caused by drone strikes is essential.This paper proposes a test method with high precision and low cost involving launching of a UAV to impact a flat plate specimen by using an air gun.The test results of UAVs impacting flat plates at different impact velocities,such as the UAV dam-age deformation captured by a high-speed camera and strain vs time dynamic response curves of plates,were obtained and analysed.At the same time,a corresponding numerical simulation was car-ried out by using the explicit finite element software LS-DYNA.The predicted damage to the UAV and strain on the flat plate during the strike process were compared with the test results.The overall trend of the simulation results is in good agreement with the test results,at least for the first three mil-liseconds of the event.This shows that the numerical simulation model established in this paper is rea-sonable.The UAV numerical method established in the present paper can be used to carry out numerical simulations and evaluations of the collision safety of UAVs against large aircraft and high-value ground targets.The results show that the local deformation of the impacted target is uneven due to the distribution of concentrated mass components such as motors,battery,and camera.As the impact velocity of the UAV increases,all parts of the UAV are seriously damaged and basically in a fragmented state,and the battery is greatly deformed.The interaction between the UAV and the flat plate specimen is approximately 2.7 ms,and the UAV numerical simulation model established in this paper can well simulate the real UAV impact process.