Refrigerator With Linear Compressor Principle Prototype Development

The aim of the paper is to design and develop low cost, energy efficient, environmental linear compressors for use in refrigerator. Conventional refrigerator compressors are comprised of a rotary electric motor that in turn drives a reciprocating compressor through a crank-piston. Their overall efficiency is low owing to the inherently low efficiency of induction motors and the mechanical friction of the crank-driven piston movement. In a linear compressor, there is no side ways thrust on the piston because all the driving forces act along the line of motion, which allows oil-free lubrication and labyrinth seal. Operation of the linear compressor is at fixed frequency and modulated output. Capacity continuous modulation by adjustment of piston top dead center and stroke amplitude enables efficient operation throughout nearly all of its operation range and avoids the loss and surge from repeated on-off operation.This thesis focuses on a moving-coil type linear compressor for refrigerators, which magnetic field is generated by a permanent magnet. In this case, when the current is alternating and exists in the wires, the driven force is generated through the interaction between current and magnetic field. Dynamic model for its complete system is established and calculated by numeric method of Newmark integral calculus because gas force and friction force are nonlinear and complicated. Based on the theories of mechanical vibration, electromagnetics, thermodynamics and combination of numeric simulation, a prototype machine is designed and manufactured. Simulations and experiments about are done to acquire the characteristics of the compressor and the influence of factors, such as friction force, gas force, equivalent parameters of coil, additional capacitance, static position of piston, stiffness of resonant spring etc. Friction force leads to declination of capacity due to decrease of stroke and increase of clearance. Gas force makes the offset of piston as well as stroke decrease and clearance increase, so enough driven force is needed for certain compressed volume gas. It also can be found that the performance can be enhanced by increase of resonant-spring stiffness, equivalent coil-resistance, coil-inductance and reduce of piston's static position.