Abstract: A radial flow centrifugal impeller comprising an even number of re-heat flow ports, a main engine flow port, and a drive shaft having a helical impeller arrangement provided on its circumference and impeller blades mounted on the circumference of the helical impeller arrangement, each impeller blade having a flat peripheral first portion adjacent each re-heat flow port and a flat peripheral second portion adjacent the main engine flow port, the ratio of the size of the first portions on all the impeller blades to the size of the second portions on all the impeller blades being effective to control the ratio of the fuel flowing through the re-heat flow ports and the main engine flow port, and the re-heat flow ports being symmetrically disposed about the radial flow centrifugal impeller.

Abstract: A method of recovering an underwater pipe comprises inserting a recovery line attachment into the pipe, explosively deforming the pipe so that it is mechanically secured to the attachment, and bringing the pipe to the surface by means of a lifting line secured to the attachment. The attachment may include a body insertable into the end of the pipe and a portion having a generally conical surface so that it forms a water tight seal with the pipe when the pipe is explosively deformed into engagement with it.

Abstract: A fluid cooled heat exchanger system comprising a heat exchanger, first conduit means connected to the heat exchanger, a pump for pumping a cooling fluid to the heat exchanger via the first conduit means, second conduit means for receiving fluid from the pump that is in excess of the heat exchanger requirements, and a valve which is so connected to the first and second conduit means that fluid that has passed through the heat exchanger via the first conduit means mixes in the valve with fluid that has by-passed the heat exchanger via the second conduit means, and the valve having a movable valve element which is moved off a valve seat by an amount dependent upon the flow of fluid in the second conduit means whereby the flow of fluid through the heat exchanger is maintained substantially constant.