Week 6 - Data analysis

AIM: To script a program that reads through a file and performs the following operations

• Take column information as input and display, save the plot
• Inform the user if the data file isn’t present in the working directory
• Calculate the work done, power output and the specific fuel consumption

DATASET:

The given dataset has 17 columns containing thermodynamic data of a fuel injected engine. Text data that helps the user understand the data set begins with a # symbol. Hence all lines starting without a # has to be stored to different arrays.

SPECIAL FUNCTIONS:

simps() is used to calculate the area of PV diagram as per the third objective.

It is a part of scipy.integrate library and the following command has to be used in the initial code

from scipy.integrate import simps

This function works on the simpsons rule where it uses a quadratic polynomial on each subinterval of a partition to approximate the function f(x) and to compute the definite integral.

Simpsons rule is an improvement over the trapezoid rule.

Syntax: simps(dependent variable, independent variable)

If f(x) has to be integrated over x, then, simps(f(x), x is to be used).

FORMULAE REQUIRED:

Power output = Work done x No. of power strokes

For 2 stroke engine, No. of power strokes= rpm of engine

For 4 stroke engine, No. of power strokes= rpm of engine/2

Specific fuel consumption = Fuel consumption per unit time / Power

CODE:

import math
import matplotlib.pyplot as plt
import numpy as np
from scipy.integrate import simps


#Compatibilty check
try:
	open('engine_data.out')

except:
	print('File not recognized. Please provide a valid CONVERGE output file')


else:
	
	line_ctr = 1 #Counter variable
    #Arrays to store the parameter details
	column_number = []
	coloumn_name = []
	units =[]
	X = []
	Y = []

	#Taking user input
	x = int(input("Enter x axis parameter"))
	y = int(input("Enter y axis parameter"))

	for line in open('engine_data.out'): 

		for i in range(0, 19):
			if i >= 2: 
				if line_ctr == 2:
					column_number.append(int(line.split()[i]))

		for j in range(0, 18):	
			if j >= 1: 
				if line_ctr == 3:
					coloumn_name.append(line.split()[j])

				elif line_ctr == 4:
					units.append(line.split()[j])

		if '#' not in line:

			if line_ctr >= 6:
				X.append(float(line.split()[x]))
				Y.append(float(line.split()[y]))
		line_ctr += 1


	#Plotting 
	plt.figure()
	plt.plot(X, Y, color = 'r', linewidth = 2)
	plt.title('Plot of ' + str(coloumn_name[y]) + ' versus ' + str(coloumn_name[x]), color = 'k')
	plt.xlabel(str(coloumn_name[x]) + " " + str(units[x]))
	plt.ylabel(str(coloumn_name[y]) + " " + str(units[y]))
	plt.savefig(str(coloumn_name[y]) + ' vs ' + str(coloumn_name[x]) + '.png')
	plt.show()

	#------------------------------------------------------------#
	#Constant parameters for engine
    #Speed of engine (RPM)
	N = 1500
	#Fuel consumption (micro gram/stroke)
	fc = 20
	#Number of cylinders
	n = 1
	#Engine Specifications
	no_of_fc = 4
        
    #Calculation of area under PV diagram
	#Workdone in joule
	area = simps(Y, X)*pow(10, 6) #using simps function
	print('Area of PV diagram(work done) calculated using simpsons rule, W = ' + str(area) + ' J','\n')	
	#Power Output (KW)
	power = n*area*N/(60*1000)
	print('Power Output at 1500 RPM, Power output= ' + str(power) + ' KW')
	print('\n')
	#Speed of engine (rph)
	N_hr = N*60
	#Fuel consumption (kg/rev)
	fc_hr = fc*pow(10,-9)/2
	#Fuel consumption (kilogram per hour)
	fc_kg_hr = N_hr*fc_hr

	#Specific fuel consumption
	SFC = fc_kg_hr/power
	print('Specific Fuel Consumption, SFC = ' + str(SFC) + ' (kg/hr)/KW')
	print('\n')

FORMULAE REQUIRED:

Power output = Work done x No. of power strokes

For 2 stroke engine, No. of power strokes= rpm of engine

For 4 stroke engine, No. of power strokes= rpm of engine/2

Specific fuel consumption = Fuel consumption per unit time / Power

CODE:

EXPLANATION OF CODE:

• Import all libraries
• Use try: except: else: (Exception handling tool) to confirm that the file is present in the working directory. If not present, display an error
• Define variables to store the line number, column data, unit data, column thermodynamic information
• Request the user to enter the columns he/she wants to visualize
• Read through the file data and check if the data belongs to column number/name/units and split and write into the corresponding arrays.
• If the compiler does not encounter a # at the beginning, write the data into their respective arrays
• Plot the figure and save it with column names

For calculating the work done, power output and specific fuel consumption

• Define variables for all engine parameter inputs and assign value
• Calculate the area of PV diagram as explained in the earlier section
• Convert all the parameters to a single unit system (kW, h etc.)
• Calculate the specific fuel consumption as per the above described formula
• Display the values

RESULTS:

Output console

Input was x=7 and y=1

The PV diagram is plotted

The user can enter other values for input also, which will produce different plots

1. When x=0, y=1

2. When x=0, y=7

3. When x=0, y=4

4. When x=7, y=4

5. When x=7, y=1

ERRORS:

No errors were displayed in the console.