Week 6 - Data analysis

Objective: To extract the data from the output file and plot graphs.

Problem statement:

1. Data visualizer

• Script should take column numbers as the input and plot the respective columns.
• Each file should be saved by the name of the column.
• The plot labels should be extracted from the file and must appear as labels in the plots.

2. Compatibility check

• Code should exit gracefully, if a non-compatible file is provided as an input.

3. Basic performance calculation

• Calculate the area under the P-V diagram.
• Calculate the power output of this engine. Assume that RPM is 1500
• This engine consumed 20 micro grams of fuel (per 1 stroke cycle). Calculate its specific fuel consumption.

Solution Procedure:

1. Data visualizer

• Required libraries are imported.
• User is asked to eter the file name from which data has to be extracted.
• File is opened.
• Column numbers for x-axis and y-axis data are asked.
• Program enters a 'for' loop to extract the data.
• An 'if' statement is used to extract column labels.
• Another 'elif' statement is used to extract the data for each column and converted into 'float' class.
• Graph is plotted and saved by the column name.

2. Compatibility check

• Here 'try-except' statement is used to check if the file name is correct or not.
• If the file name is correct then the program moves to the next step.
• If the file name is incorrect, the program exits gracefully with a custom error message.

3. Basic performance calculation

• Area under P-V diagram is calculated only in case the volume (column 8) is chosen for x-axis and pressure (column 2) is chosen for y-axis.
• This is achieved using an 'if' statement.
• Area or Work is calculated using formula: area = P * change in volume.
• P is taken as average of two consecutive pressure values and change in volume is calculated by taking difference between two consecutive volume values.
• Power is calculated using formula: power = work * speed(in rad/s)
• Specific fuel consumption is calculated by dividing fuel consumed per second by power generated.

Results:

• The plots are successfully seved by the column names.

Discussion:

• The calculations given in basic performance calculations can only be perdormed using pressure and volume data therefore the calculated values are displayed only when column 8 (volume) is selected for x-axis and column 2 (pressure) is selected for y-axis.

Python code:

import matplotlib.pyplot as plt
import math

# initaliization

x_label = []
y_label = []
x_column = []
y_column = []

# asking the file name

print('Enter the file name containing the data:\n')
name = input()																# taking file name as input and storing it in 'name' variable

try:																		# try-except statement is used to modify the file name error message
	file = open(name)														# opening the file to extract data
	
	print('Please enter column number of data for x-axis of the plot:\n')
	x = int(input())														# taking input of column number for x axis
	print('Please enter column number of data for y-axis of the plot:\n')
	y = int(input())														# taking input of column number for y axis

	line_count = 1															# setting initial line count as 1
	for line in file:
		
		if line_count == 3:													# using if statement to extract the plot labels
			x_label = line.split()[x]
			y_label = line.split()[y]

		elif '#' not in line:												# using elif statement to extract the contents of x and y column
			x_column.append(float(line.split()[x-1]))
			y_column.append(float(line.split()[y-1]))

		line_count = line_count + 1

	# caluclation of area under P-V diagram
	if (x == 8) and (y ==2):												# area can only we calculated when we have pressure and volume data
		work = 0															# assigning initial work as zero
		for i in range(len(x_column)-1):
			p_avg = ((y_column[i+1] + y_column[i])/2) * pow(10,6)			# calculating average of two consecutive pressure values and converting to pascal from mega pascal
			v = x_column[i+1] - x_column[i]									# calculating change in volume
			work = work + (p_avg * v)										# area or work = p * change in volume
			i = i+1
		print('Area under P-V curve (work done) is ' + str(work) + ' joules\n')

		# power calculation
		speed = (1500 * 2 * math.pi) / 60									# converting speed from RPM to rad/sec
		power = work * speed												# power = work * speed in rad/sec
		print('Power output of the engine is ' + str(power) + ' watts\n')

		# specific fuel consumption calculation
		m_fuel = (20 * pow(10,-6) * speed) / (4 * math.pi)					# converting mass of fuel consumed to grams/sec
		sfc = m_fuel/power 													# specific fuel consumption = mass of fuel consumed / power generated
		print('Specific fuel consumption of engine is ' + str(sfc) + ' grams/joules\n')

	# saving the plot
	
	plt.figure()
	plt.plot(x_column,y_column)
	plt.xlabel(x_label)
	plt.ylabel(y_label)
	plt.title(y_label + ' vs ' + x_label + ' Plot')
	plt.savefig(y_label + '_vs_' + x_label + '.png')
	

except FileNotFoundError:
	print('File not recognized. Please provide a valid CONVERGE output file') # custom error message for incorrect file name

Plot:

Screenshots:

1. Comapatibility check

2. Performance values