Study on the Measurement Technology of Temperature Field at the Outlet of the Precooler in the Bleed air system of Civil Aircraft

In view of the phenomenon of uneven temperature field in the hot side outlet pipe of the precooler in the Bleed air system of civil aircraft, three thermocouple layout schemes were put forward. By comparing and analyzing the changes of the flow field in the pipe before and after the installation of the three schemes, the most effective scheme was determined. At the same time, the temperature uniformity before and after the mixing device at the outlet of the precooler is compared and analyzed, and the method of increasing the turbulence device to improve the accuracy of the average temperature measurement of the precooler is put forward.

Theoretical and Experimental Study on the Transmission Loss of a Side Outlet Muffler

Vibration and noise reduction methods are important research directions in many industries. Mufflers are widely used in pipelines to reduce noise and vibration transmission. A theoretical analysis is conducted to determine the noise reduction mechanism of a muffler with a side outlet, and the results are verified with experiments. The quadrupole parameters of the muffler are obtained using transfer matrix analysis, and sensitivity analysis of the quadrupole parameters is conducted. The influence of the side outlet location on the transmission loss of the muffler is investigated experimentally using an impedance tube. The key factors affecting the transmission loss are analyzed. The theoretical calculation results of the transmission loss of the side outlet muffler are in good agreement with the experimental results.

JUSTIFICATION OF HOPPER’S BOTTOM PROFILE WITH SIDE OUTLET, ENSURING STABLE AND COMPLETE OUTFLOW OF THE GRAIN

During the outflow of the bulk material from the hopper, the particles interact with each other, the walls of hopper, forming a so-called arches. Arching is a common phenomenon at the end of bulk materials. A large number of authors fight against arches, a lot of theories and models were designed. The use of arch destroyers is the most effective way to combat by arching process. The parameters of such devices are calculated on existing methods, where the frequency and impact on the bulk material is selected. Constructions for arch destroying are a large number, but each is present lack of expressed in constant maintenance and outer energy consumption. Therefore, an optimization of the hopper parameters, under arch creating conditions, at the design stage, is an urgent task for the theoretical description. In the analysis of the hopper with a side outlet, it was established, that the arches are formed in the least section, during the movement of bulk material. Such a section is called arch-making section. If arch-making section is too small, relative to the diameter of the bulk material, a static arch will formed, and the outflow will be terminated. To continue outflow can be only if you deduced an arch from the equilibrium state by external forces. This paper proposes a curved profile of the bottom profile so as to increase the height of arch-making section, retaining a predetermined pitch, thereby reducing the impact of the arch, keeping the specified feed of grain material. It was revealed that due to the new profile of the bottom at the lowest feeds of bulk material, more stable expiration is observed.