of this exemplary rotation the remaining blocking portions just begin to occlude their associated nozzles to slightly throttle them down but not so far as to substantially adversely affect performance in this particular implementation each blocking portion has a leading surface 156 and a trailing surface 158 the exemplary trailing surfaces are at uniform circumferential separation so that in the initial fig5 orientation each is adjacent the nozzle one before the nozzle to be occluded by that blocking portion e g the trailing surface of blocking portion 154 a is adjacent opening 152 h the exemplary ring has an inner surface at an inner diameter which seals against an outer surface of the ring containing the nozzles for example the nozzles may be machined or cast as a ring the ring 150 may be throttled to or toward the closed condition in response to a part load condition where mass flow is reduced for example the ring position may be adjusted in response to or with a change in compressor speed e g known by the controller which may provide the speed of a variable frequency drive of the compressor or the output of a refrigerant flow sensor not shown e g at condenser gas cooler outlet conditions along the line 36 the goal may be to maintain a high tangential velocity entering the ejector for example a control map preprogrammed into the controller may cause the ring to provide particular restrictions associated with particular speeds or flow rates or ranges thereof similarly in the situation of valves fully opening or closing individual nozzles the map may associate the desired number of open nozzles with such ranges of speed or flow rate similarly the angle and area ratio of the outlet diffusers may be made adjustable.