A Low Cost Pressure Wave Generator Using Diaphragms

Industrial Research Ltd has developed a unique diaphragm-based pressure wave generator technology for employment in pulse tube and Stirling cryocoolers. The system uses a pair of metal diaphragms to separate the clean cryocooler gas circuit from a conventionally lubricated mechanical driver, thus producing a clean pressure wave with a long-life drive. We have now extended the same diaphragm concept to support and seal the displacer in a free piston Stirling expander. The diaphragms allow displacer movement without rubbing or clearance gap seals, hence allowing for the development of costeffective long-life and efficient Stirling cryocoolers. Initial modeling, operating in conjunction with a 200 cc swept volume pressure wave generator, predicted in excess of 300 W cooling at 77 K with a Carnot efficiency of over 25%. A proof-of-concept prototype has achieved cryogenic temperatures. Details of the concept, modeling, and testing will be presented.

Section: A Free Piston Stirling Expander With Diaphragmsmentioning

confidence: 86%

“…Metallic diaphragm pressure wave generators (PWG) developed by Industrial Research Ltd [1] have matured to provide a useful alternative to linear motor pressure wave generators for Stirling and pulse tube cryocoolers. The metallic diaphragm pressure wave generator employs two opposed diaphragms that balance each other's average gas forces.…”

Section: Introductionmentioning

confidence: 99%

Novel diaphragm based Stirling cryocooler

Caughley¹,

Tucker²,

Gschwendtner³

et al. 2012

“…This pressure wave generator (CHC200) had a swept volume of 200ml. The CHC200 delivered 3.2kW of acoustic power at an electro-acoustic efficiency of 72% when directly coupled to the AMSC pulse tube [4]. This machine has proved reliable, having accumulated over 2000 hours running in our laboratory.…”

Section: Introductionmentioning

confidence: 96%

“…That approach is to separate the cryocooler's working gas from a conventional mechanical drive mechanism at ambient pressure with a metal diaphragm. A key feature of the design is the employment of a second opposed diaphragm to balance out the average gas force which can be very high [4]. A lever mechanism was used to convert the long stroke, low force movement suitable for a crank to a high force / short stroke required by the diaphragm.…”

Section: Introductionmentioning

confidence: 99%

Diaphragm Pressure Wave Generator Developments at Industrial Research LTD

Caughley¹,

Emery²,

Glasson³

et al. 2010

Self Cite

Industrial Research Ltd (IRL) have been developing a unique diaphragm based pressure wave generator technology for pulse tube and Stirling cryocoolers. Our system uses a metal diaphragm to separate the clean cryocooler gas circuit from a conventionally lubricated mechanical driver, thus producing a clean pressure wave with a long life drive that does not require the precision manufacture and associated costs of large linear motors. The first successful diaphragm pressure wave generator produced 3.2kW of acoustic power at an electro-acoustic efficiency of 72% with a swept volume of 200ml and a prototype has now accumulated over 2500 hours running. This paper describes recent developments in the technology. To explore scaling, a small diaphragm pressure wave generator with a swept volume of 20ml has been constructed and has delivered 454W of acoustic power at an electro-acoustic efficiency of 60%. Improvements have been made to the hydraulic force amplifier mechanism for driving the diaphragms resulting in a cheaper and lighter mechanism than the mechanical linkage originally used. To meet a customer's specific requirements, the 200ml pressure wave generator's stroke was extended to achieve 240ml of swept volume thereby increasing its acoustic power delivery to 4.1 kW without compromising efficiency.

“…A series of prototypes have been made. The first machines had a swept volume of 200 cc and produced up to 3.2 kW of acoustic, or P-V, power with an electro-mechanical efficiency of 72% [1] at 50 Hz. This PWG was successfully coupled to a pulse tube refrigerator that achieved 108 W @ 77 K [2].…”

Section: Introductionmentioning

confidence: 99%

30 kW metal diaphragm pressure wave generator

Caughley¹,

Branje²,

Klok³

2014

Abstract. Callaghan Innovation has been developing a metal-diaphragm pressure wave generator technology for pulse tube or Stirling cryocoolers since 2005. A series of successful pressure wave generators have been designed, fabricated and demonstrated ranging in swept volume from 20 to 240 cc driven by commercially available induction motors of powers from 0.5 kW to 7.5 kW respectively. A number of pulse tubes have also been design and successfully trialed with these pressure wave generators. Cooling powers up to 600 W at 120 K have been achieved. We have now scaled the pressure wave generator technology to 1000cc swept volume, powered by a 30 kW induction motor with the intention of providing over 20 kW of acoustic power to either pulse tube or Stirling expanders. The aim is to develop a cryocooler with more than 1000 W of refrigeration at 77 K. Target applications include liquefaction and High Temperature Superconducting devices. Initial results from testing the 1000 cc pressure wave generator are presented and we will discuss the challenges and advantages involved in scaling the metal diaphragm technology to higher acoustic powers.