Rankine Cycle

Rankine cycle.

Rankine Cycle is a model that is used to envisage the performance of combustion engines, mainly steam and chemical fuel engines. This model is used to predict the efficiency of heat energy converted to mechanical energy in a steam engine. This type was invented by Professor William John Macquorm Rankine, A Polymath professor at Glasgow University. These Rankine calculations were initially done manually but currently, they is an open source program that has simplified everything (Cycle Pad) the whole calculation has been simplified, and it can be completed in a flash. Here is an example of the software interface:

[pic 1]

The buttons on the left are simple buttons of components in a normal cycle. They have been coded with the relevant dimension hence all you need to do is drag them to the blue are which is the work are.

 In this report, I have reviewed a Rankine cycle problem, with reheat procedure, done necessary calculations both by hand and using the open source program. I consequently have included procedures of my calculations; this is pictures and screenshots (from the software). I also have in this report the results of the problem as found from Cycle Pad.

Before I get to the report, I have analyzed the problem below and found the appropriate variables that are to be assumed in the Cycle Pad. We are given several variables to choose from and in this case am selecting the a, A and 1. According to analysis, we have the boiler pressure to be 40kPa, the boiler output temperature at 450oC and the condenser pressure at 0.6 kPa. I started by standardizing the problem. I equated the boiler to the heater, the condenser to the cooler, and of course for a standard Rankine cycle; we have a turbine driven by the steam and the pressure pump. After that, I drew our cycle in the program and added to the cycle inlets and outlets appropriately. For my case, this is my cycle:

[pic 2]

Now I shift my focus to the data input after the design of the cycle. The program has three types of data; unknown data; assumed data; and known data. They are represented by black, green and blue respectively. So we input the data we are aware above into their respective components. This is the data Cycle Pad used to calculate the other data that we do not know. This is what it will look like after the input:

[pic 3][pic 4]

[pic 5]

After assuming the data into the program, it will perform a string of mathematical calculations in the background to give the final required answers. The manual formula for calculation of the thermal efficiency is [pic 6]

We also need to calculate the Net-Work. We cannot work it out directly, so we need to calculate the output work at the turbine and the work spent on the pumps and the subtract the work spent on the pumps from work produced by the turbines to get the net-work. The following are the formulas for finding them:

[pic 7]

Work spent on the pump=

Work output of the turbine= [pic 8]

Now we need to perform the reheating procedure. This process is done to increase the efficiency of the engine. A low-pressure turbine is added to the cycle, and some of the water is let to blow back to the heater without passing through the condenser. So after redesigning our cycle with the reheat added, this is what it looked like: -[pic 9]