Air compressor discharge pressure

Figure 4-6. Ammonia combustion and absorption at air compressor discharge pressure of 3-12 bar (Process 2, elevated pressure), a = medium pressure, 3-6 bar b = high pressure, 6-12 bar, with interceding or booster compressor.

Figure 4-9. Ammonia combustion at air compressor discharge pressure of 2-5 bar, absorption at nitrous gas compressor discharge pressure of 7-15 bar (Process 3, dual-pressure cycle).

Figure 16-13. Air compressor discharge pressure as a function of ih speed.

The work extracted from the expanding uid (HA-HC), may be utilized to generate electricity, compress gas, or just be dissipated in an ambient blower or oil friction brake (see Section 3.2.2.4). The net result is that as refrigeration is generated across the turbine, less refrigeration is needed from the incoming air and the air compressor discharge pressure can be run at much lower pressures. Cycles termed low-pressure cycles ensued from this development. 

Air compressor discharge pressure determination The discharge pressure required by the main air compressor is determined from individual equipment and line resistances of the plant. This is best illustrated by referring to Figure 3.19. The LP column top pressure is set by the waste exit pressure and the resistances in the waste circuit. These consist of piping and heat exchanger... 

Air enters the compressor of a simple gas turbine at 14.7 psia and 520 R, and has a volumetric flow rate of lOOOft /sec. (The compressor discharge pressure is 260 psia,) and the turbine inlet temperature is 2000 F. The turbine efficiency is 87% and the compressor efficiency is 83%. Determine (a) the thermal efficiency of the cycle, (b) the back-work ratio, and (c) the net power developed. 

This cycle is a variation of the Claude cycle. If air is the working fluid, the compressor discharge pressure is 200 bars (2885 psig) and the liquid fraction produced in the Joule-Thompson expansion is about 0.6, then the optimum temperature for the inlet to the expansion turbine is about ambi-... 

Compressor discharge pressure > design fouled condenser/insufficient air to the cooling tower/low flowrate of water to the condenser/air in the refrigerant/too much refrigerant, level too high. 

High wet gas compressor suction pressure. An increase in the pressure at the suction to the wet gas compressor backs up through the fractionator overhead condensers and trays, the vapor line, and the reactor cyclones to the riser. Now, for the operator to maintain a proper regenerator slide valve AP (i.e., at least 3 psi), he must pinch back on the flue gas slide valve to raise the regenerator pressure. This, of course, translates directly into an increase in air-blower discharge pressure. 

Compression ratio The compressor discharge pressure (in absolute pressure) divided by the suction pressure (also in absolute pressure). If Tm compressing air, the suction pressure is atmospheric pressure, and the discharge pressure is 29.4 psig, what is the compression ratio (Answer 3.)... 

Figure 2-21 show the effect of 5% by weight of steam injection at a turbine inlet temperature of 2400 °F (1316 °C) on the system. With about 5% injection at 2400°F (1316 °C) and a pressure ratio of 17 1, an 8.3% increase in work output is noted with an increase of about 19% in cycle efficiency over that experienced in the simple cycle. The assumption here is that steam is injected at a pressure of about 60 psi (4 Bar) above the air from the compressor discharge and that all the steam is created by heat from the turbine exhaust. Calculations indicate that there is more than enough waste heat to achieve these goals. 

The most simple combustor is a straight-walled duct connecting the compressor and turbine as seen in Figure 10-1. Actually, this arrangement is impractical because of the excessive pressure loss resulting from combustion at high velocities. The fundamental pressure loss from combustion is proportional to the air velocity squared. Since compressor discharge... 

Centrifugal compressors range in volumetric size from approximately 1,(X)0 to 150,000 cfm. In single-wheel configuration, pressures vary considerably. A common low pressure compressor may only be capable of 10 to 12 psi discharge pressure. In higher-head models, pressure ratios of 3 are available, which on air is a 30-psi discharge pressure when the inlet is at atmospheric conditions. 

Power requirements and discharge temperatures are calculated using the same relationships as used with the other rotary compressors already discussed. The efficiency is. 80 for air service and pressure in the 30 psig range. The mechanical losses are higher than the other rotaries. The mechanical loss is variable and dependent on gas, lubrication, and other factors. For an estimate, use. 15 of the gas horsepower. This approxuna tion should be close enough for an estimate. 

For the numerical example the cooled efficiency becomes 0.4205, a reduction of 0.0237 from (tj)ru = 0.4442. The extra loss in efficiency for throttling the cooling air from compressor discharge to the appropriate pressure at the LP turbine entry is thus 0.0052 for the numerical example, which is again quite small. 

Figure 12-2D. Standard air compressor cyiinder for 125 psig discharge pressure. Suction vaive unioaders for automatic capacity con-troi. (Used by permission Bui. L-679-BiA, 1957. Dresser-Rand Company.)...

Figure 12-95. Axial compressor Type AV100-16, during erection. Note stationary and rotating blades. Two identical steam turbine-driven machines supply air to blast furnace at steel works. Suction volume = 560,000 NmVh discharge pressure = 6.2 bar power input = 52,000 kW each. (Used by permission Bui. 26.13.10.40-Bhj. Sulzer Turbo Ltd.)...

Figure 14-40. Basic simple gas-turbine consists of three principal pieces of equipment (1) compressor that raises pressure of atmospheric air and discharges it to (2) combustion chamber or furnace where the burning of fuel raises air temperature before it enters (3) turbine through which the heated gas expands and does work on the turbine blades. Major part of turbine output goes to drive compressor remainder is available power to drive shaft-connected mechanical equipment such as centrifugal compressor or other. (Used by permission Rowley, L. N. and B. G. A. Skrotzki. Gas Turbines, Power, p. 79, Oct. 1946. McGraw-Hill, Inc. All rights reserved.)...

If the back-pressure is too high or demand too low, the compressor will generate a discharge pressure higher than designed. It will continue to compress the air or gas until it reaches the unload setting on the system s relief valve or until the brake horsepower required exceeds the maximum horsepower rating of the driver. 

This type of compressor will continue to compress the air volume in the down-stream system until (1) some component in the system fails, (2) the brake horsepower exceeds the driver s capacity, or (3) a safety valve opens. Therefore, the operator s primary control input should be the compressor s discharge pressure. If the discharge pressure is below the design point, it is a clear indicator that the total down-stream demand is greater than the unit s capacity. If the discharge pressure is too high, the demand is too low and excessive unloading will be required to prevent failure. 

Most state laws and safe practice require a safety relief valve ahead of the first stop valve in every positive displacement compressed air system. It is set to release at 1.25 times the normal discharge pressure of the compressor or at the maximum working pressure of the system, whichever is lower. The relief valve piping system sometimes includes a manual vent valve and/or a bypass valve to the suction to facilitate startup and shutdown operations. Quick line sizing equations are (1) line connection, (i/1.75 (2) bypass, ii/4.5 (3) vent, dl63 and (4) relief valve port, cU9. 

A Brayton engine receives air at 15psia and 70°F. The air mass rate of flow is 4.08 Ibm/sec. The discharge pressure of the compressor is 78psia. The maximum cycle temperature is 1740°F and the air turbine... 

A Braysson cycle (Fig. 4.32) uses air as the working fluid with 1 kg/sec mass flow rate through the cycle. In the Brayton cycle, air enters from the atmospheric source to a compressor at 20° C and 1 bar (state 1) and leaves at 8 bars (state 2) air enters an isobaric heater (combustion chamber) and leaves at 1100°C (state 3) air enters a high-pressure isentropic turbine and leaves at 1 bar (state 4). In the Ericsson cycle, air enters a low-pressure isentropic turbine and leaves at 0.04 bar (state 5) air enters a first-stage compressor and leaves at 0.2 bar (state 6) air enters an isobaric intercooler and leaves at 20°C (state 7) air enters a second-stage compressor and leaves at 1 bar (state 8) and air is discharged to the atmospheric sink. Assume all compressors have 85% efficiency. 

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