Inlet silencer

Lowering the inlet velocities and providing proper inlet silencers can reduce air noise. Considerable work by NASA on compressor casings has greatly reduced noise. 

Air is drawn into the compressor at atmospheric pressure Pi (in practice slightly lower due to the inlet silencer, filter and ducting) and atmospheric temperature Pi, and compressed adiabatically to a higher pressme P2 to reduce its volume to V2 and raise its temperatme to T2. The adiabatic compression is given by the following equations see standard textbooks e.g. References 1 to 5. 

FIG. A-53 Water penetration through the inlet silencer. (Source Altair Filters International Limited.)... 

The inlet and exhaust systems in gas turbines are described. The inlet and exhaust systems consist of an inlet filter, silencers, ducting, and expansion joints. The design of these systems can be critical to the overall design of a gas turbine. Proper filtration is a must, otherwise problems of blade contamination and erosion ensue. The standards are minimal for specifications. 

Silencers are also minimally specified. Work in this area has progressed dramatically in the past few years with the NASA quiet engine program. There are some good silencers now available on the market, and inlets can be acoustically treated. 

A mode curve exhibiting this shape could indicate that the motor mountings, or the baseplate under the motor, are loose and that the motor is moving vertically. In fact, in the example from which this figure was taken, this is exactly what was happening. The blower s baseplate floats on a one-inch thick cork pad, which is normally an acceptable practice. However, in this example, an inlet filter/silencer was mounted without support directly to the inlet located on the right end of the machine. The weight of the filter/silencer compressed the cork pad under the blower, which lifted the motor-end of the baseplate off of the cork pad. In this mode, the motor has complete freedom of movement in the vertical plane. In effect, it... 

With a reckless flair for drama, Midgley used an elaborate series of laboratory demonstrations to help sell the additive to executives and scientists. Holding a small, open bottle of tetraethyl lead up to the air inlet of a knocking engine, he liked to show how its fumes silenced knock s explosions. Midgley was versatile he could invent, devise a practical manufacturing process, and even sell the invention. 

After a gas turbine has been operating for a long time the inlet filter pressure drop may become high enough to indicate that the filter needs cleaning. The drop in pressure across silencers will remain almost constant the effect of ingress of particles or development of soot can be neglected. 

The amount of silencing and filtering of the inlet combustion air depends upon the site environment and the operational considerations. 

The amount of inlet and exhaust noise silencing will depend upon, the location of machine with respect to people in say offices or control rooms, how many machines will be in one group since... 

Inlet ducting and silencer pressure drop A Pi 125 mm of water... 

Air fans, blowers, compressors, and eductors must be monitored for vibration, change in sound, hot spots, lack of lubrication, and wear. Insist that inlet screens, filters, and silencers be kept in proper position, tightly, and that they be cleaned regularly with a nonflammable cleaning compound. 

Inlet vane controls on blowers and fans should be checked for looseness of linkages and bearings, and corrected or replaced before they cause more trouble. Make sure that inlet screens, filters, and silencers are in place, tight, and cleaned. Do not use any flammable cleaning compound. 

Air blower and compressor (positive displacement type) are preferable with silencer-cum-filter, dampers for primary (atomising) air, primary and secondary air piping, manometer, pressure regulators for air supply at burner inlet. The positive displacement-type combustion air blowers shall also be able to atomise the oil or separate compressors for atomisation of oil shall be provided. 

Compressors, pumps Vibration-isolated mounting in enclosed soundproofed rooms. Machines preferably separated from one another by partitions or with individual enclosures. Ventilation or air intake openings of such rooms should have louvred sound attenuators. Intake and outlet silencers for the compressors. Pressure pipelines to have sound-damping expansion joints and acoustically sealed wall inlets. Pressure release pipelines to have silencers. Additional sound insulation for compressed air pipelines to suppress rushing noises. Sound-insulated enclosed portable compressors represent the current "state of the art" for use in quarrying operations. 

The air inlets and outlets of the building, as well as the intake and discharge openings of the fans, should be provided with suitable sound attenuators (silencers) (see Funke, 1973). 

Electric motors Motors with low speeds are preferable. Big motors to be water-cooled rather than air-cooled. Direct drive by four-pole or variable-speed motors. Choose motor types with low noise emission. Fan blading to have irregular pitch. If necessary, motor enclosure to be provided with special silenced ventilation. Internal combustion engines (e.g., for driving quarry machinery) Exhaust noise can be reduced by using amply dimensioned absorption and reflection silencers. Enclosure of the engine with ventilation system equipped with inlet and outlet silencers and ducts lined with sound-absorbing material (see Funke, 1977). 

Fans are the quietest when operating near maximum efficiency, yet even then they may require sound attenuation at the inlet and ontlet. Silencers and/or a sufficient length of acoustically lined ductwork are commonly used to protect room air grilles nearest the fan. Noise through duct and fan sides must also be considered. In the United States, do not use acoustic duct lining in hospitals except as permitted by the U.S. Department of Health and Human Services (DHHS) Publication HRS-M-HF 84-1. 

The outer frame is a simple fabricated enclosure that supports either the air inlets and silencers if the unit is open-ventilated (Fig. 6.33) or the roof and cooler enclosure if the unit is totally enclosed water-to-air-cooled. The outer frame further acts as an air guide to complete the ventilation paths, and as a sonndproof enclosure to keep noise levels low. Since the rotor is pedestal mounted, the end shields are very simple structures. As with the inner frame, the outer frame is designed to be free of resonances in the range of operating frequencies. 

Inserting air filtration, silencing, evaporative coolers, chillers, and exhaust heat recovery devices in the inlet and exhaust systems causes pressure drops in the system. The effects of these pressure drops are unique to each design. Shown in Fig. 6.62 are the effects on the MS7001EA. 

This situation was further exacerbated by the choice of materials for the inlet system. While the filter housing was constructed of stainless steel, the downstream silencer and plenum used a stainless-steel perforated lining for acoustic attenuation, welded to a carbon steel base frame. 

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