In　order　to　meet　the　demand　of　small　expander　in　the　field　of　waste　heat　recovery,　distributed　renewable　energy,　gas　liquefaction　and　compressed　air　vehicles,　a　single　screw　expander　with　175　mm　diameter　rotor　is　developed　in　our　lab.　An　experimental　system　using　compressed　air　has　been　built　to　test　the　performance　of　single　screw　expanders.　The　experiments　were　conducted　for　different　intake　pressure,　and　important　parameters　were　measured,　such　as　flow　rate,　intake　and　exhaust　temperature,　output　power　and　rotating　speed.　The　influence　of　intake　pressure　on　the　performance　was　obtained.　Results　indicate　that　satisfactory　power　output　and　economic　performance　can　be　obtained　at　high　intake　pressure　and　high　rotational　speed,　meanwhile　a　good　working　efficiency　is　maintained.　The　speed　of　2800　rpm　is　considered　as　the　best　working　speed,　and　fitting　formulae　are　given　for　dynamic　performances　versus　intake　pressures.　The　highest　overall　efficiency　that　can　be　reached　is　55%　and　the　maximum　output　reached　is　22　kW.　The　preliminary　experimental　study　indicates　a　very　good　working　performance　for　the　first　generation　of　self-developed　single　screw　expanders.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.