Refer to the Journal of Engineering for Gas Turbines and Power (Jan. 2005) study of gas turbines augmented with high-pressure inlet fogging, Exercise 8.29. The researchers classified gas turbines into three categories: traditional, advanced, and aero derivative. Summary statistics on heat rate (kilojoules per kilowatt per hour) for each of the three types of gas turbines in the sample are shown in the MINITAB printout on the next page.

a. Is there sufficient evidence of a difference between the mean heat rates of traditional augmented gas turbines and aero derivative augmented gas turbines? Test using α = .05.

b. Is there sufficient evidence of a difference between the mean heat rates of advanced augmented gas turbines and aero derivative augmented gas turbines? Test using α = .05.

Data from exercise 8.29

During periods of high electricity demand, especially during the hot summer months, the power output from a gas turbine engine can drop dramatically. One way to counter this drop in power is by cooling the inlet air to the gas turbine. An increasingly popular cooling method uses high-pressure inlet fogging. The performance of a sample of 67 gas turbines augmented with high-pressure inlet fogging was investigated in the Journal of Engineering for Gas Turbines and Power (Jan. 2005). One measure of performance is heat rate (kilojoules per kilowatt per hour). Heat rates for the 67 gas turbines are listed in the table on the bottom of page. Suppose that a standard gas turbine has, on average, a heat rate of 10,000 kJ/kWh.

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Descriptive Statistics: HEATRATE Variable ENGINE Mean StDev Minimum Maximum HEATRATE Advanced 21 9764 639 9105 11588 Aeroderiv Traditional 7 12312 2652 8714 16243 39 11544 1279 10086 14796