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Marine Auxiliary Machinery 7E Episode 3

Tham khảo tài liệu 'marine auxiliary machinery 7e episode 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 70 Machinery service systems and equipment Figure 2.26 Homogenizer Vickers type Package boiler combustion system The elementary automatic combustion system based on a two flame burner Figure 2.27 is used for many auxiliary boilers. The burner is drawn oversize to show detail. Various different control systems are employed for the arrangement. The burner has a spring loaded piston valve which closes off the passage to the atomizing nozzle when fuel is supplied to the burner at low pressure. If the fuel pressure is increased the piston valve will be opened so that fuel passes through the atomizer. The system can supply the atomizer with fuel at three different pressures. The solenoid valves are two-way in that the fuel entering can be delivered through either of two outlets. The spill valves are spring loaded. When either one is in circuit it provides the only return path for the fuel to the suction side of the fuel pressure pump. The pressure in the circuit will be forced therefore to build up to the setting of the spill valve. A gear pump with a relief arrangement to prevent excessive pressure is used to supply fuel to the burner. Fuel pressure is varied by the operation of the system and may range up to 40 bar. Combustion air is supplied by a constant speed fan and a damper arrangement is used to change the setting. Machinery service systems and equipment 71 solenoid Figure 2.27 Flame change valve Solenoid operation System operation Control of the setup may be through various combinations of electrical electronic or mechanical systems. An electrical control scheme is employed in this description. Electrical circuits are arranged so that when the boiler is switched on assuming water level and other factors are correct the system will 72 Machinery service systems and equipment I heat up and circulate the fuel 2 purge the combustion space of unburnt gas and 3 ignite the flame and by controlling it maintain the required steam pressure. When the boiler is started .