Investigations on thermodynamic processes of a novel pneumatic drive asymmetric Gifford-McMahon cycle cryorefrigerator

In this paper, a numerical and experimental investigation is conducted on a novel pneumatic-drive asymmetric Gifford-McMahon cycle cryorefrigerator for the first time. In the pneumatic-drive asymmetric Gifford-McMahon cycle cryorefrigerator, the duration of the assistance space exhaust process is kept higher than that of the assistance space intake process. Therefore, the displacer moves faster at the lower dead centre and slower at the upper dead centre inside the expander cylinder, which makes the duration of expansion process longer. The numerical model solves the governing equations of the refrigerant and dynamics of free-floating displacer iteratively to illustrate the refrigeration mechanisms. Additionally, the model computes the performance parameters of the cryorefrigerator, like refrigerating capacity, and specific refrigerating capacity. By adopting the numerical model, the impact of the loitering time on the thermodynamic processes is elaborated. It is perceived that, both refrigerating capacity and specific refrigerating capacity reduces with an increase in the loitering time. The experimental cooling characteristics are studied for different values of discharge to suction pressure ratios of helium compressor.

Dynamics of pneumatic drive of devices for udder massage of animals

The paper presents the results of theoretical developments on the deformation of flexible shells of the executive bodies of the means of stripping, the assessment of their mechanical impact on the udder of the heifer and first-calf, the dynamics of the pneumatic drive of the executive bodies. The design and technological parameters of the devices for milking first-calf heifers and massaging the udder of heifers are justified, the set and duration of technological operations for animal milking and the economic efficiency of their implementation are determined.

ANALYSIS OF ACTIVE BUCKET DESIGNS OF OPEN-PIT AND CONSTRUCTION EXCVATORS

The designs of active buckets are analyzed. It is revealed that dynamic impact of buckets on the rock mass can be vibrational or impact. The entire bucket, its front wall, or individual vibration impact devices mounted in the front wall can serve as a dynamic actuator. The drive of the active elements can be electromagnetic, hydromechanical, pneumatic or hydraulic. It is noted that the most successful design of the active bucket is the impact teeth built into the bucket with a pneumatic drive. It is concluded that the most productive idea is an active bucket with built-in impact devices and a hydraulic drive.

A high efficiency pneumatic drive system using vane-type semi-rotary actuators

A compressed air driven generator is proposed, where the pneumatic energy is converted into mechanical energy using two vane-type rotational actuators. The use of a second actuator with a higher displacement in order to produce a thermodynamic expansion allows to reach a better energetic efficiency in comparison to the classical operation of such actuators. The alternating movement of the angular actuators is transformed into a unidirectional rotational motion with the help of a mechanical motion rectifier. The paper analyses the enhancement of the energetic performance of the system. An experimental set-up is also described. The performance of the new system is described, and the limits of its realization is commented on the base of experimental recordings of the evolution of the pressure in the chambers.