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A nozzle for a supersonic flow must increase in area in the flow direction, and a diffuser must decrease in area, opposite to a nozzle and diffuser for a subsonic flow. So, for a supersonic flow to develop from a reservoir where the velocity is zero, the subsonic flow must first accelerate through a converging area to a throat, followed by ...
Steam leaves the boiler and reaches the condenser after passing through the main valve, regulating valves, nozzles, clearance spaces between nozzles and moving blades, diaphragm and rotating shaft, and other passages. Further, there is a large pressure difference between the inside of a steam turbine and the ambient atmosphere and also from one ...
A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, and it can be used to direct or modify the flow of a fluid (liquid or gas). Nozzles are frequently used ...
A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube which is pinched in the middle, with a rapid convergence and gradual divergence. It is used to accelerate a compressible fluid to supersonic speeds in the axial (thrust) direction, by converting the thermal energy of the flow into kinetic energy .
It is done by the fixed blades which act as nozzles. The steam expands equally in all rows of fixed blade. The steam coming from the boiler is fed to the first set of fixed blades i.e. the nozzle ring. The steam is partially expanded in the nozzle ring. Hence, there is a partial decrease in pressure of the incoming steam.
The flow through a venturi nozzle achieves a much lower nozzle pressure than downstream pressure. Therefore, the pressure ratio is the comparison between the upstream and nozzle pressure. Therefore, flow through a venturi can reach Mach 1 with a much lower upstream to downstream ratio. [9]
The nozzles have to be of the convergent-divergent type for generating high (supersonic) steam velocity. This results in a more expensive and difficult design of the nozzle blade rows. High velocity at the nozzle exit leads to higher cascade losses. Shock waves are generated if the flow is supersonic which further increase the losses.
An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic pump with no moving parts except a valve to control inlet flow.