GB778302A - Compound power plants - Google Patents

Abstract

778,302. Charge pumps; regulating. NAPIER & SON, Ltd., D. Sept. 6, 1955 [Sept. 17, 1954], No. 27052/54. Classes 7 (2) and 7 (6). [Also in Groups XXVI and XXIX] Charge air, supplied to a two-stroke diesel engine A Fig. 1, by axial flow and centrifugal compressors E, F in series and powered respectively by an exhaust-gas turbine D and the engine, is throttled under idling and/ or low load slow running conditions by a valve H, thus ensuring satisfactory compression ignition at such times. A blow-off valve S operating as described below is incorporated. The compressors E, F may be linked by a fluid coupling or an infinitely-variable gear as in Specification 663,296 to transmit power from the crankshaft or chankshafts of the engine A to the compressor E or vice versa. The valve H is operated by a piston J in a hydraulic cylinder J<SP>2</SP>. Under normal engine operating conditions a servo-motor piston M<SP>1</SP> acting on a boost control (not shown), such as a ratio-control of a variable-speed gear between the engine A and compressor E, is in a position such that a spring-loaded valve K<SP>2</SP> in a supply duct L, K to the cylinder J<SP>2</SP> is closed and a spring J<SP>3</SP> therefore holds the valve H open. Under idling or low load conditions, however, the piston M<SP>1</SP> moves upward sufficiently for its rod M<SP>2</SP> to open the valve K<SP>2</SP> and the consequent feed to the cylinder J closes the valve H to give the negative boost required by the setting of a spring P acting on the servo-motor valve N via a lever O and loaded by a cam Q on an engine control shaft also mounting a cam Q<SP>2</SP> controlling via tracks Q<SP>4</SP> and Q<SP>5</SP> (appropriate in the case of an aircraft engine to no-power flight and ground running conditions) the fulcrum of a lever R<SP>1</SP> in the normal fuel injection control mechanism. The boost pressure re-acts on the valve N via a diaphragm O<SP>1</SP> the atmospheric pressure on which is counter-balanced by that on an evacuated capsule O<SP>2</SP>. The blow-off valve S, Fig. 1, operates to prevent compressor surging under idling &c. conditions, the compressor delivery pressure acting via a duct X on a spring-loaded pilot piston V<SP>2</SP> to uncover ducts V<SP>3</SP> or V<SP>4</SP> as this pressure falls or rises and so vent or pressurize the space below a main valve piston V and correspondingly open or close the valve member U<SP>2</SP>.