GB2051238A

GB2051238A - Fluid Operated Power Plant

Info

Publication number: GB2051238A
Application number: GB7920086A
Authority: GB
Original assignee: Sadek R M
Current assignee: Sadek R M
Priority date: 1979-06-08
Filing date: 1979-06-08
Publication date: 1981-01-14
Also published as: GB2051238B

Abstract

In the plant, incorporating, for example an open-cycle gas turbine engine (1, 2, 3), or a diesel engine, the intake air to the compressor (1) is cooled to a temperature of substantially 0 DEG C when the ambient temperature rises above 0 DEG C or a predetermined level, say 30 DEG C, the air intake temperature being maintained, preferably automatically, at substantially 0 DEG C regardless of subsequent fluctuations in ambient temperature above the lower limit set. The intake air is cooled by its passage through an evaporator (5) through which circulates a refrigerant fluid, itself cooled in a condenser (7) by a coolant fluid, e.g. subsoil water or water from a cooling tower spray pond (9). <IMAGE>

Description

SPECIFICATION Fluid Operated Power Plants Including, for Example Gas Turbine Engines or Diesel Engines This invention relates to fluid operated power plants, particularly power plants including, for example open cycle gas turbine engines or diesel engines.

It is known that a serious handicap in using power generating units such as gas turbines in hot and tropical climates is the adverse influence of high ambient temperatures on the power that can be developed by the unit under such conditions. A high ambient temperature can, in some instances, result in a reduction of 30% or more in the rated power output. This is illustrated in Figure 1 of the accompanying drawings which is a graph showing the relationship between the expected power output and ambient temperature for a standard power generating unit, in this case a Ruston TB 5000 gas turbine which has an ISO rating of 4900 horse power (hp) at 7900 rpm.

Figure 1 also includes a plot of the variation with ambient temperature of a ratio (KWto/KW1so)1 KW150 being the power output expected at 1 SOC ambient temperature and KWt being that expected at ambient temperature tOC. It is apparent from the graph of Figure 1 that the rated output at an ambient temperature of 450C is about 70% of that possible at an ambient temperature of OOC, which means a power reduction of about 43% of that to be generated from this same unit at an ambient temperature of 450C.This represents a great handicap in using gas turbines as power generating units in hot and tropical countries where usually the load demand increases as the ambient temperature rises, despite the fact that gas turbines are most suited for such areas, especially those areas having a limited supply of water for cooling.

This handicap is due to the inherent characteristics of gas turbine rotary compressors, whether of the axial or centrifugal type. Figure 2 of the accompanying drawings is a graph showing the relationship between ambient temperature and both the compression ratio r and the air mass flow rate M (in kg/sec) through a rotodynamic compressor.Figure 2 also illustrates plots of the variation with ambient temperature of both the ratio of the air mass flow rate at ambient temperature tOC (M t) to that at ambient temperature 500C (M 50), and the ratio of the compression ratio at ambient temperature tOC (rut) to that at ambient temperature 500C (rio). The reduction in both the air mass flow rate and the compression ratio with increasing ambient temperature are the main causes of the resultant reduction in the power output of the gas turbine with increasing ambient temperatures. Moreover, the increased ambient temperature and the resultant reduction in the compression ratio produce a reduction in the overall efficiency of the turbine.

According to the present invention, there is provided a method of operating a fluid operated power plant including the step of cooling the air intake to the compressor of the power plant to a temperature of substantially OOC when the ambient temperature is greater than OOC.

According to another aspect of the invention, there is provided a fluid operated power plant including a compressor requiring an intake of air, and incorporating refrigeration means operable when the ambient temperature is greater than OOC to cool the air intake to the compressor to a temperature of substantially OOC.

The refrigeration means may be adapted so as to be operable to cool the compressor air intake to OOC only when the ambient temperature reaches or exceeds 300C.

The power plant may incorporate an opencycle gas turbine engine a diesel engine, or the like.

Reference is now made to the accompanying drawings, which illustrate one embodiment of the invention, by way of example, in comparison to the Ruston TB 5000 gas turbine discussed above, in the drawings: Figure 1, as aforesaid, shows a graph of the relationship between expected power output and ambient temperature for the Ruston TB 5000 gas turbine; Figure 2, as aforesaid, shows a graph of the relationship with ambient temperature of both the air mass flow rate through a rotodynamic compressor and the resulting compression ratio therefor; Figure 3 shows schematically, one embodiment of the present invention; and Figure 4 shows a graph of the relationships with ambient temperature of the output of gas turbines having respectively refrigerated and nonrefrigerated compressor air intakes.

The embodiment of the invention shown in Figure 3 and described below incorporates an open-cycle gas turbine engine, but the invention is equally applicable to other types of fluid operated power plants, for example, diesel engines.

Referring to Figure 3, an open-cycle gas turbine engine incorporates a compressor 1 to which is supplied atmospheric air, the air being thereby compressed and then passed to a combustion chamber 2 to facilitate combustion of a suitable fuel in a known fashion. The gaseous products of the combustion are passed in known manner to a gas turbine 3 to rotate the blades thereof and thereby drive a generator 4.

Before entering the compressor 1, the atmospheric air passes through an evaporator 5 in which it can be cooled to a temperature of substantially OOC by a circulating refrigerant fluid such as Freon 12. The temperature of the atmospheric air entering the evaporator 5 is likely to vary from, say, 200C to 500C, depending on the situation of the power plant. The system may be adapted for the automatic operation of a rotary compressor 6, which circulates the refrigerant fluid through the evaporator 5 and also through a condenser 7 which cools the refrigerant fluid, when the ambient temperature of the air entering the evaporator reaches a convenient level, say at least 300C.Alternatively, the compressor 6 may be operated to circulate the refrigerant fluid to cool the air intake to OOC whatever the ambient temperature of the air entering the compressor.

So long as the refrigerant fluid circulates through the evaporator 5, the temperature of the air intake to the compressor 1 can be maintained at substantially OOC regardless of subsequent fluctuations in the ambient temperature.

The rotary compressor 6 may be driven directly by the output shaft of the gas turbine 3, if the power generating unit is relatively small, or indirectly by A.C. motors where the power generating unit is relatively large or where several gas turbine engines are installed in one power plant.

To cool the refrigerant fluid in the condenser 7, a coolant such as water is circulated through the condenser 7. If available, subsoil water may be used, since the temperature of the subsoil water will be much lower than the ambient temperature of air entering the evaporator 5. Alternatively, as illustrated a cooling tower spray pond may be used as a source of coolant water.

In addition to cooling the compressor air intake, the refrigeration system 5 to 8 may be used to provide cooling air for the turbine blades, alternator windings and, possibly, also the power plant office air conditioning. In any case, the low compressor air intake temperature will result in a larger air mass flow rate through the compressor, a higher compression ratio and moreover a greater thermal efficiency than would be experienced if the refrigeration system 5 to 8 were omitted, which will allow for better cooling of the turbine blades and the alternator windings.

Refrigeration of the compressor air intake results in the generation of enough power to cover the power requirements of the refrigeration system and still provide appreciable net output power for external use which is greater than if no refrigeration of the compressor air intake was performed. Figure 4 illustrates the required refrigerating effect (Re) in tons, the power (KWr) in kilowatts required for such refrigeration to cool the compressor air intake to OOC, and the available net output power (KWn) in the kilowatts, at different ambient temperatures. It also shows the variation with ambient temperature of the surplus output power (KWs) available from the gas turbine with the refrigerated compressor air intake as a percentage of the power output (KWt) available from a turbine which does not have a refrigeration system for cooling the compressor air intake, the value of KWs being given by KWs=(KWnKWt) It will be apparent that for an ambient temperature of, say, 450C the power required for refrigeration of the compressor air intake leaves a net output power (KWn) which includes a surplus (KWs) of about 15% to 20% of the power output (KWt) developed at 450C by a gas turbine with a non-refrigerated compressor air intake.

Claims

1. A method of operating a fluid operated power plant including the step of cooling the air intake to the compressor of the power plant to a temperature of substantially OOC when the ambient temperature is greater than 0 C.

2. A method of operating a fluid operated power plant such as a gas turbine or diesel engine, including the step of cooling the air intake to the compressor of the power plant to substantially OOC when the ambient temperature is or exceeds 300 C.

3. A fluid operated power plant including a compressor requiring an intake of air, and incorporating refrigeration means operable when the ambient temperature is greater than OOC to cool the air intake to the compressor to a temperature of substantially OOC.

4. A fluid operated power plant as claimed in claim 3, in which said refrigeration means is operable to cool the air intake to the compressor as aforesaid when the ambient temperature is or exceeds 300C.

5. Afluid operated power plant as claimed in claim 3 or claim 4, in which said refrigeration means comprises a refrigerant flow circuit including an evaporator through which passes said air intake to the compressor, and a condenser, and a coolant flow circuit arranged so that a coolant fluid can flow through the condenser and thereby cool the refrigerant fluid.

6. A fluid operated power plant as claimed in claim 5, in which said coolant flow circuit includes as a source of coolant fluid a cooling tower spray pond.

7. A fluid operated power plant as claimed in claim 5, in which said coolant flow circuit is adapted to receive, as a coolant fluid, subsoil water.

8. A fluid operated power plant as claimed in any of claims 3 to 7, incorporating a diesel engine.

9. A method of operating a fluid operated power plant substantially as hereinbefore described with reference to and as illustrated in Figures 3 and 4 of the accompanying drawings.

10. A fluid operated power plant substantially as hereinbefore described with reference to and as illustrated in Figures 3 and 4 of the accompanying drawings.

11. A fluid operated power plant as claimed in any of claims 3 to 7 or claim 10, incorporating an open-cycle gas turbine engine.