TECHNOLOGY EVALUATION SUMMARY SHEET OF

GAS TURBINES

By: Ebrahim Farahan, John P. Eudaly, ORNL

October, 1978

1 INTRODUCTION

This evaluation estimates the status, cost, and performance of currently available simple and regenerative cycle gas turbines. A brief theoretical analysis of reheat, intercooled, and compound cycles also has been included.

A simple-cycle gas turbine consists of a compressor, a combustor, and an expansion turbine. A regenerative-cycle gas turbine has these same components in addition to a regenerator. The function of the regenerator is to transfer heat from the exhaust gas to the air after the air leaves the compressor but before it enters the burners.

To facilitate transfer of performance data into the ICES computer simulation code, all performance functions have been presented uniformly. The algebraic relationship between operating conditions and the gas turbine output capacity and thermal efficiency is obtained by determining and then listing the value of coefficients for a generalized polynomial of the form:

Y = A + BX + CX²

(Eq. DS-1)

A performance factor, such as efficiency, is represented by the dependent variable Y in Eq. DS-1. The independent variable, X, represents a particular operating condition.

2 PERFORMANCE

2.1 RATING FACTORS

Standard ambient rating conditions are 59°F (15°C) and 50% relative humidity at sea level (1 atm). Atmospheric-based aerating factors include variation in altitude and ambient temperature. The effect of temperature and altitude on output can be expressed by the following two equations:

	% rated output = 124.2 - 0.41 (T) % rated output = 100 - 0.00333 (H)	(Eq. DS-2) (Eq. DS-3)
where:
	T = temperature, °F, and H = altitude, ft.

Units are normally given peak and continuous ratings; continuous rating is generally 10% less than peak rating.

2.2 SIZE RANGE

For simple-cycle units smaller than 10,000 SHP (Shaft-Horse-Power) the power density, SHP/ft³, varies from less than 1 to 132. Above 10,000 SHP, the power density is fairly constant at about 5 SHP/ft³.

The size of a regenerator varies considerably with the design configuration. A large regenerator with high effectiveness can occupy as much as 15,000 ft³.

The specific capacity, SHP/lb, varies from 0.08 to 5.5 for units less than 10.000 SHP: the average value for larger units is 0.6 SHP/lb.

2.3 FULL-LOAD EFFICIENCY

Currently available, simple-cycle units range from 80 to 134,000 SHP continuous duty capacity with a thermal efficiency* range from 11 to 38%. The regenerative cycle gas turbines are available from approximately 12,000 to 50,000 SHP with a full load thermal efficiency of about 34%.

*Defined as the ratio of shaft work output to fuel input (generally LHV) in consistent units.

2.4 PART LOAD EFFICIENCY AND PERFORMANCE

Generalized equation coefficients A, B, and C are provided in Table DS-1 for substitution into Eq. DS-1 to show algebraic relationships of part load performance.

Table DS-1 Generalized Coefficients, Part Load Performance

4 AVAILABILITY

Gas turbine availability compares favorably with availabilities of diesel engines and other prime movers. Maintenance procedures can be handled by those familiar with steam turbine maintenance.

5 COST CONSIDERATIONS

The estimated equipment and plant cost* for gas turbines has been graphically presented throughout this evaluation. To use these cost estimates in ICES computer models, the following generalized relationship expressing cost vs turbine capacity was formulated:

*In 1976$ unless otherwise indicated.

		(Eq. DS-4)
where:
	D = turbine or component (regenerator) cost D_n = nominal turbine cost (in 1976$ unless specified) Q = required turbine capacity Q_n = nominal turbine capacity n = predetermined exponent

The values of D_n Q_n, and n of Eq. DS-4 are tabulated in Table DS-2 for each particular turbine.

Table DS-2 Generalized Cost Equation Coefficients