Calculation of turbine efficiency

This condition cannot be calculated; it might be that the method is incorrect

1 Based on the parameters: inlet steam pressure of 3.53 MPa (a), temperature of 410℃； Thermal calculations were carried out using parameters such as a pumping pressure of 1.275 MPa(a) and a temperature of 296°C, resulting in an adiabatic efficiency of 76.64%. If the efficiency is 81.4%, then, with the aforementioned parameters remaining unchanged, the exhaust temperature is approximately 290°C. Using the steam enthalpy drop to calculate the same 76.64% efficiency yields identical results. According to the description provided by a friend on the first floor, these are operating parameters rather than design parameters; so which set of parameters corresponds to an efficiency of 81.84%?

81.4% is the design efficiency, while the efficiency calculated from the actual given parameters is 76.64%

Using the data from the table above, the efficiencies of the high-pressure cylinder under the rated, 1A, 1B, 3B operating conditions are 73.51, 71.91, 71.91, 71.91, 72.71, and 72.71 respectively. Based on the given shaft power, and without taking into account the energy loss due to bearings, these efficiencies are higher than those of the high-pressure cylinder; yet in reality, the efficiency of the low-pressure cylinder is even lower. How can this be explained?

Discussion with Yang*Aobo: 1. Describe the first sentence: 81.4% represents the design efficiency; the second sentence: The efficiency of the high-pressure cylinders under conditions 1A, 1B, and 3B is between 71-73, which is higher than the calculated efficiency for those high-pressure cylinders. Question: What exactly is the data for 81.4? What is the design calculation efficiency of the high-pressure cylinder? 2. Based on the steam parameters, the efficiency of the high-pressure cylinder (defined as from the inlet to the extraction section) is roughly consistent with the values calculated by the original poster, while the efficiency of the low-pressure cylinder (defined as from the extraction section to the exhaust section) is between 53 and 56%. 3. Since the exhaust steam is at saturated temperature, steam humidity has a significant impact on efficiency; the efficiency values of 53–56 are based on a steam dryness degree of 1. Assuming that the exhaust parameters used in the turbine design are taken from a point slightly away from the final impeller, allowing some wet steam to be present, the efficiency figures for the low-pressure cylinder will increase slightly, but this seems to have little practical significance. 4. Considering the distribution of steam volume, in the high-pressure cylinder section with higher efficiency, the steam used for work accounts for over 80% of the total steam volume; even when efficiency is calculated on a weighted basis, the low efficiency of the low-pressure cylinder has little impact on the overall efficiency of the turbine.

81.4% is the efficiency of the first unit; I’ve understood it now. I have calculated the efficiency of the high-pressure cylinder for each operating condition using the table provided, but the efficiency calculated from the given shaft power and the isentropic expansion work of the steam is higher than that of the high-pressure cylinder. In actual situations, the efficiency of the low-pressure cylinder is lower; this is something that puzzles me. Hehe