A LOW COST PRESSURE WAVE GENERATOR USING DIAPHRAGMS

Abstract

The high cost of Pressure Wave Generators (PWGs) is a major barrier to the more widespread use of high-efficiency pulse tube and Stirling cryocoolers. This paper describes the development and testing of a low-cost industrial-style PWG which employs metal diaphragms. The use of diaphragms removes the need for rubbing or clearance seals, and eliminates contamination problems by hermetically separating the gas circuit and the lubricated driving mechanism. A conventional low-cost electric motor is used for power input, via a novel high-efficiency kinematic linkage. A first prototype of the diaphragm PWG produced 3.2 kW of PV power with a measured electro-acoustic efficiency of 72%. Accelerated testing predicts a diaphragm life time in excess of 40,000 hours. An additional advantage of the use of diaphragms is the ability to directly cool the gas in the compression space. This eliminates or significantly reduces the requirement for an after cooler, and further decreases the cost of the whole cryocooler system. A pulse tube cryocooler has been successfully run at Industrial Research Ltd to 59K with the diaphragm PWG and no aftercooler. Another pulse tube cryocooler with the diaphragm PWG is undergoing development at Cryomech, the results of which will be given in another presentation.