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Summary A novel cascade configuration consisting of one standing wave unit and one travelling wave unit arranged in series is studied in this paper. Theoretically, a straight‐line cascade engine provides an efficient energy conversion, reduces the difficulties of fabrication and allows no Gedeon streaming. In order to achieve such a powerful cascade thermoacoustic engine, the regenerator of the travelling wave unit must be operated in high impedance and travelling wave phasing region. Various techniques of phase adjustment by modifying the configurations and geometrical dimensions of the system are investigated both numerically and experimentally in order to adjust the position of the sweet spot as well as to promote the acoustic impedance in the regenerator. It is found that the effective tuning methods with less modification here are accomplished by changing the volume of down‐cavity and reducing the flow area of down‐resonator by inserting the pencil. The exploration also shows that the acoustic field in the system is quite sensitive to the effect of down‐resonator length. The performance of the proposed system is clearly improved after the phase‐adjustment schemes are completely implemented, in which the regenerator works within the sweep spot zone with high acoustic impedance. Copyright © 2016 John Wiley & Sons, Ltd.

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Rural communities in developing countries often require small cold storage for vital medicines while having no access to electricity. The utilization of waste heat-produced in biomass burning cookstoves during daily cooking routines-to power a thermoacoustic engine driving a thermoacoustic refrigerator is investigated. The simplicity and affordability is met by the use of atmospheric air as working medium, cheap PVC ducting for acoustic waveguides and locally available blacksmithing technologies for simple heat exchangers. This paper describes DeltaEC modelling, fabrication and experimental evaluation of a laboratory concept demonstrator. The travelling-wave, looped-tube engine/cooler configuration is powered by a propane gas burner to mimic cookstove flue gases. A matching stub is used to match the acoustic impedances of engine and cooler. The optimum location of the cooler is investigated experimentally. The device achieves the minimum temperature of-8.3°C and up to 7 W of cooling power at a storage condition of +8°C.

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