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{
"metadata": {
"name": "",
"signature": "sha256:4e8467c44185deda0f287a5fb2df2f33438b3eb316ab3092c4e75cf0fe34abd0"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chatper 11 : Four Stroke Spark Ignition Engine"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 11.1 Page no : 239"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"d = 0.0625\t\t\t\t\t#Diameter in m\n",
"L = 0.09\t\t\t\t\t#Stroke in m\n",
"nv = 0.75\t\t\t\t\t#Volumetric efficiency\n",
"p = 1.03\t\t\t\t\t#Pressure at N.T.P in kg/cm**2\n",
"T = 273\t\t\t\t\t#Temperature at N.T.P in K\n",
"R = 29.27\t\t\t\t\t#Characteristic gas constant in kg.m/kg.degree C\n",
"\n",
"\t\t\t\t\t\n",
"#Calculations\n",
"Vs = ((3.14/4)*d**2*L)\t\t\t\t\t#Swept volume in cu.m\n",
"V = (nv*Vs)\t\t\t\t\t#Volume of charge at N.T.P in cu.m\n",
"w = (p*10**4*V)/(R*T)\t\t\t\t\t#Weight of the charge in kg/cycle\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'The weight of the charge is %3.6f kg/cycle'%(w)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The weight of the charge is 0.000267 kg/cycle\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 11.2 Page no : 242"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"n = 9.\t\t\t\t\t#Number of cylinder\n",
"d = 0.145\t\t\t\t\t#Bore in m\n",
"l = 0.19\t\t\t\t\t#Stroke in m\n",
"r = 5.9\t\t\t\t\t#Compression ratio\n",
"bhp = 460.\t\t\t\t\t#Brake horse power in B.H.P\n",
"N = 2000.\t\t\t\t\t#Speed in r.p.m\n",
"x = 20.\t\t\t\t\t#Percentage rich in mixture\n",
"CV = 11200.\t\t\t\t\t#Calorific value in kcal/kg\n",
"pC = 85.3\t\t\t\t\t#Percentage of carbon\n",
"pH2 = 14.7\t\t\t\t\t#Percentage of Hydrogen\n",
"nv = 70.\t\t\t\t\t#Volumetric efficiency in percent\n",
"T = 15.+273\t\t\t\t\t#Temperature in K\n",
"nm = 90.\t\t\t\t\t#Mechanical efficiency in percent\n",
"wO2 = 23.3\t\t\t\t\t#Percentage of oxygen by weight in air\n",
"da = 1.29\t\t\t\t\t#Density of air in kg/m**3\n",
"mC = 12.\t\t\t\t\t#Molecular weight of carbon\n",
"mO2 = 32.\t\t\t\t\t#Molecular weight of O2\n",
"mH2 = 2.\t\t\t\t\t#Molecular weight of H2\n",
"\n",
"\t\t\t\t\t\n",
"#Calculations\n",
"hihp = ((bhp/(nm/100))*(4500./427))\t\t\t\t\t#Heat equivalent in kcal\n",
"Vs = ((3.14/4)*d**2*l*(N/2)*n)\t\t\t\t\t#Swept volume in c.m per min\n",
"cw = (Vs/da)\t\t\t\t\t#Charge weight of air per minute in kg\n",
"ma = (100/wO2)*((pC/100)*(mO2/mC)+(pH2/100)*(mO2/(2*mH2)))\t\t\t\t\t#Wt. of air required per kg of fuel in kg\n",
"mf = (cw/ma)\t\t\t\t\t#Minimum fuel inkg\n",
"ith = (hihp/(mf*(100+x)/100*CV))*100\t\t\t\t\t#Indicated thermal efficiciency in percent'\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'Indicated thermal efficiency of the engine is %3.1f percent'%(ith)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Indicated thermal efficiency of the engine is 27.1 percent\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 11.3 Page no : 244"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"n = 8.\t\t\t\t\t#Number of cylinders\n",
"d = 8.57\t\t\t\t\t#Bore in cm\n",
"l = 8.25\t\t\t\t\t#Stroke in cm\n",
"r = 7.\t\t\t\t\t#Compression ratio\n",
"N = 4000.\t\t\t\t\t#Speed in r.p.m\n",
"la = 53.35\t\t\t\t\t#Length of the arm in cm\n",
"t = 10.\t\t\t\t\t#Test duration in min\n",
"br = 40.8\t\t\t\t\t#Beam reading in kg\n",
"gas = 0.455\t\t\t\t\t#gasoline in kg. In textbook, it is given wrong as 4.55\n",
"CV = 11400.\t\t\t\t\t#Calorific value in kcal/kg\n",
"Ta = 21.+273\t\t\t\t\t#Temperature of air in K\n",
"pa = 1.027\t\t\t\t\t#Pressure of air in kg/cm**2\n",
"wa = 5.44\t\t\t\t\t#Rate of air in kg/min\n",
"J = 427.\t\t\t\t\t#Mechanical equivalent of heat in kg.m/kcal\n",
"R = 29.27\t\t\t\t\t#Characteristic gas constant in kg.m/kg.K\n",
"\n",
"\t\t\t\t\t\n",
"#Calculations\n",
"bhp = (2*3.14*N*br*la)/(4500*100)\t\t\t\t\t#Brake horse power in B.H.P\n",
"pb = (bhp*4500)/((n/2)*(l/100)*(3.14/4)*d**2*N)\t\t\t\t\t#Brake mean effective pressure in kg/cm**2\n",
"bsfc = (gas*60)/bhp\t\t\t\t\t#Brake specific fuel consumption in kg/b.h.p.hr\n",
"bsac = ((wa*60)/bhp)\t\t\t\t\t#Brake specific fuel consumption in kg/b.h.p.hr\n",
"nb = ((bhp*4500)/(J*gas*CV))*100\t\t\t\t\t#Brake thermal efficiency in percent\n",
"Vd = ((3.14/4)*d**2*l)\t\t\t\t\t#Piston print lacement in c.c/cycle\n",
"Pd = (Vd/10**6)*(N/2)*n\t\t\t\t\t#Piston print lacement in m**3/min\n",
"Va = ((wa*R*Ta)/(pa*10**4))\t\t\t\t\t#Volume of air used in m**3/min\n",
"nv = (Va/Pd)*100\t\t\t\t\t#Volumetric efficiency in percent\n",
"af = (wa/gas)\t\t\t\t\t#Air fel ratio\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'a) the B.H.P delivered s %3.0f h.p \\\n",
"\\nb) the b.m.e.p is %3.1f kg/cm**2 \\\n",
"\\nc) the b.s.f.c is %3.3f kg/b.h.p.hr \\\n",
"\\nd) the brake specific air consumption is %3.3f kg/b.h.p.hr \\\n",
"\\ne) the brake thermal efficiency is %3.1f percent \\\n",
"\\nf) the volumetric efficiency is %3.0f percent \\\n",
"\\ng) the air fuel ratio is %3.2f'%(bhp,pb,bsfc,bsac,nb,nv,af)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"a) the B.H.P delivered s 122 h.p \n",
"b) the b.m.e.p is 7.2 kg/cm**2 \n",
"c) the b.s.f.c is 0.225 kg/b.h.p.hr \n",
"d) the brake specific air consumption is 2.686 kg/b.h.p.hr \n",
"e) the brake thermal efficiency is 24.7 percent \n",
"f) the volumetric efficiency is 60 percent \n",
"g) the air fuel ratio is 11.96\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 11.4 Page no : 246"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"n = 4.\t\t\t\t\t#Number of cylinders\n",
"N = 2000.\t\t\t\t\t#Speed in r.p.m\n",
"m = 13.15\t\t\t\t\t#Mass of fuel in kg/hour\n",
"Vd = 655.5\t\t\t\t\t#Displacement volume in c.c\n",
"da = 1.2\t\t\t\t\t#Density of air in kg/m**3\n",
"d = 12.7\t\t\t\t\t#Manometer depression in cm\n",
"\t\t\t\t\t#Qa = 0.231*math.sqrt(ha); Qa is the flow rate in cu.m/min and ha is the pressure difference in metres\n",
"\n",
"\t\t\t\t\t\n",
"#Calculations\n",
"Qa = (0.231*math.sqrt(((d*1000)/da)/100))\t\t\t\t\t#Flow rate in cu.m/min\n",
"Wa = (Qa*da)\t\t\t\t\t#Weight of air in kg/min\n",
"Va = (Qa*(2/N)*(1/n))*10**6\t\t\t\t\t#Volume of air drawn in per cycle per cylinder in c.c\n",
"nv = (Va/Vd)*100\t\t\t\t\t#Volumetric efficiency in percent\n",
"af = (Wa/(m/60))\t\t\t\t\t#Air fuel ratio\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'a) the weight of air drawn is %3.3f kg/min \\\n",
"\\nb) volumetric efficiency taking air into account is %3.1f percent \\\n",
"\\nc) the air-fuel ratio is %i'%(Wa,nv,af)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"a) the weight of air drawn is 2.852 kg/min \n",
"b) volumetric efficiency taking air into account is 90.6 percent \n",
"c) the air-fuel ratio is 13\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 11.5 Page no : 248"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"d = 10.\t\t\t\t\t#Diameter in cm\n",
"l = 15.\t\t\t\t\t#Stroke in cm\n",
"r = 6.\t\t\t\t\t#Compression ratio\n",
"ihp = 20.\t\t\t\t\t#Indicated horse power in h.p\n",
"N = 1000.\t\t\t\t\t#Speed in r.p.m\n",
"n = 4.\t\t\t\t\t#Number of cylinders\n",
"nt = 30.\t\t\t\t\t#Thermal efficiency in percent\n",
"CV = 10000.\t\t\t\t\t#Calorific value in kca/kg\n",
"g = 1.4\t\t\t\t\t#Ratio of specific heats\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"Vs = ((3.14/4)*d**2*l)\t\t\t\t\t#Swept volume in c.c\n",
"Vc = (Vs/(r-1))\t\t\t\t\t#Clearance volume in c.c\n",
"na = (1-(1/r)**(g-1))*100\t\t\t\t\t#Air standard efficiency in percent\n",
"pm = ((ihp*4500)/((l/100)*(3.14/4)*(d/100)**2*(N/2)*n))\t\t\t\t\t#Pressure in kg/cm**2\n",
"pc = (ihp*4500*60)/(427*(nt/100)*CV)\t\t\t\t\t#Petrol consumption in kg/hr\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'Clearance volume is %3.1f c.c \\\n",
"\\nThe air standard efficiency is %3.1f percent \\\n",
"\\nPetrol consumption is %3.2f kg/hr'%(Vc,na,pc)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Clearance volume is 235.5 c.c \n",
"The air standard efficiency is 51.2 percent \n",
"Petrol consumption is 4.22 kg/hr\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 11.6 Page no : 253"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"n = 6.\t\t\t\t\t#Number of cylinders\n",
"P = 62.\t\t\t\t\t#Power in HP\n",
"N = 3000.\t\t\t\t\t#Speed in r.p.m\n",
"nv = 85.\t\t\t\t\t#Volumetric efficiency in percent\n",
"nt = 25.\t\t\t\t\t#Thermal efficiency in percent\n",
"CV = 10500.\t\t\t\t\t#Calorific value in kcal/kg\n",
"af = 15.\t\t\t\t\t#Air fuel ratio\n",
"T = 273.\t\t\t\t\t#standard atmosphere temperature in K\n",
"p = 1.03\t\t\t\t\t#standard atmosphere pressure in kg/cm**2\n",
"R = 29.27\t\t\t\t\t#Characteristic gas constant in kg.m/kg.K\n",
"J = 427.\t\t\t\t\t#Mechanical equivalent of heat in kg.m/kcal\n",
"\n",
"\t\t\t\t\t\n",
"#Calculations\n",
"q = (P*4500)/(J*(nt/100))\t\t\t\t\t#Heat supplied in kcal/min\n",
"F = (q/CV)\t\t\t\t\t#Fuel supplied per minute in kg\n",
"Fc = (F/N)*(2/n)\t\t\t\t\t#Fuel supplied per cycle per cylinder in kg\n",
"wt = (af*Fc)\t\t\t\t\t#Weight of air supplied per cycle in kg\n",
"d = ((((wt)*R*T)/(p*10**4*(3.14/4)*(nv/100)))**(1./3))*100\t\t\t\t\t#Diameter in cm\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'Cylinder bore = stroke = %3.2f cm'%(d)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Cylinder bore = stroke = 7.84 cm\n"
]
}
],
"prompt_number": 7
}
],
"metadata": {}
}
]
}
|
