Air-turbine performance - Coursework Example

Firstly, the turbine may experience some heating for the atmosphere and if it operates at a temperature less than that of the atmosphere, the heating process will result to a transfer of energy to the turbine hence an increase in the shaft work output. Secondly, the turbine may experience effects of friction from either the air-stream or shaft bearings and this will lead to a reduction to the shaft work output. The magnitude of these two heating processes are rather difficult to measure hence for the purpose of this experiment, such effects will be noted so as to help in explaining the trends of the measurements obtained.

The diagram below shows a schematic arrangement of an air-turbine A high pressure from station 1 passes through a turbine and is exhausted at station 2 under a low pressure. Consequently, temperature T1 at station 1 falls to T2 at station 2 and these are measured using a thermocouple. Due to energy extraction, shaft work Wx is produced and this can be measured by use of brake-dynamometer. Therefore, in the plot of a graph of Wx against Cp (T2 -T1), any deviation from a straight line gradient passing through the origin will be attributed to factor - Wf + Q hence an evaluation of these two terms may result in either a negative, positive or zero value.

Theoretically, the rotational speed of the turbine is expected to vary. Also the percentage of the energy extracted from the air stream that is converted to useful shaft will vary with the rotational speed and will reach an optimum at the design speed of the turbine. d) The turbine speed was measure through the help of the tachometer once the turbine speed and inlet and outlet temperatures had stabilized. This speed values were recorded alongside the values of T2 and T1. The two graphs are nearly straight line graphs but with a negative gradient. However,