{
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"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"Chapter 18 : Super Charging"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 18.1 Page no : 327"
]
},
{
"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",
"d = 9.\t\t\t\t\t#Bore in cm\n",
"l = 10.\t\t\t\t\t#Stroke in cm\n",
"N = 2500.\t\t\t\t\t#Speed in r.p.m\n",
"Ta = 25.+273\t\t\t\t\t#Temperature of air entering the compressor in K\n",
"q = 16800.\t\t\t\t\t#Heat rate in kcal/hour\n",
"T = 60.+273\t\t\t\t\t#Temperature of air leaving the cooler in K\n",
"p = 1.6\t\t\t\t\t#Pressure of air leaving the cooler in kg/cm**2\n",
"t = 14.5\t\t\t\t\t#Engine torque in kg.m\n",
"nv = 75.\t\t\t\t\t#Volumetric efficiency in percent\n",
"nm = 74.\t\t\t\t\t#Mechanical efficiency in percent\n",
"R = 29.27\t\t\t\t\t#Characteristic gas constant in kg.m/kg.K\n",
"Cp = 0.24\t\t\t\t\t#Specific heat at constant pressure n kcal/kg.K\n",
"\n",
"\t\t\t\t\t\n",
"#Calculations\n",
"BHP = (2*3.14*N*t)/4500\t\t\t\t\t#Brake horse power in B.H.P\n",
"IHP = (BHP/(nm/100))\t\t\t\t\t#Indicated horse power in I.H.P\n",
"pm = ((IHP*4500)/((l/100)*(3.14/4)*d**2*(N/2)*n))\t\t\t\t\t#Mean effective pressure in kg/cm**2\n",
"Vs = (n*(3.14/4)*(d/100)**2*(l/100)*(N/2))\t\t\t\t\t#Swept volume in m**3/min\n",
"Va = (Vs*(nv/100))\t\t\t\t\t#Aspirated Volume of air into engine in m**3/min\n",
"ma = (p*10**4*Va)/(R*T)\t\t\t\t\t#Aspirated mass flow into the engine in kg/min\n",
"mcdT = ((BHP*4500/427)/Cp)\t\t\t\t\t#Product of mass flow rate and change in temperature\n",
"msdT = ((q/60)/Cp)\t\t\t\t\t#Product of mass flow rate and change in temperature\n",
"x = (mcdT/msdT)\t\t\t\t\t#Ratio\n",
"T2 = ((Ta-(x*T)))/(1-x)\t\t\t\t\t#Temperature in K\n",
"mc = (msdT/(T2-T))\t\t\t\t\t#Air flow in kg/min\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'a) the mean effective pressure is %3.2f kg/cm**2 \\\n",
"\\nb) the air consumption is %3.3f kg/min \\\n",
"\\nc) the air flow into the compressor is %3.2f kg/min'%(pm,ma,mc)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"a) the mean effective pressure is 6.45 kg/cm**2 \n",
"b) the air consumption is 5.871 kg/min \n",
"c) the air flow into the compressor is 30.14 kg/min\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 18.2 Page no : 328"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"IMEP = 10.\t\t\t\t\t#Indicated mean effective pressure in kg/cm**2\n",
"x = 20.\t\t\t\t\t#Mixture strength 20% richer math.tan chemically correct\n",
"pIMEP = 0.41\t\t\t\t\t#Pumping Indicated mean effective pressure in kg/cm**2\n",
"p1 = 0.97\t\t\t\t\t#Charge pressure at the beginning of compression in kg/cm**2\n",
"T1 = 100.+273\t\t\t\t\t#Charge temperature at the beginning of compression in K\n",
"pm = 0.91\t\t\t\t\t#Mean pressure during the conduction stroke in kg/cm**2\n",
"bn = 70.\t\t\t\t\t#Blower adiabatic efficiency in percent\n",
"T2 = 50.\t\t\t\t\t#Temperature of the charge after delivery by the blower in degree C\n",
"dp = 0.07\t\t\t\t\t#Pressure drop in kg/cm**2\n",
"pi = 1.47\t\t\t\t\t#Charge pressure in the cylinder during the induction stroke in kg/cm**2\n",
"Ta = 15.+273\t\t\t\t\t#Atomspheric temperature in K\n",
"pa = 1.03\t\t\t\t\t#Atmospheric pressure in kg/cm**2\n",
"g = 1.4\t\t\t\t\t#Ratio of specific heats\n",
"\n",
"\t\t\t\t\t\n",
"#Calculations\n",
"T2x = ((((pi/pa)**((g-1)/g)-1)/(bn/100))+1)*Ta+T2\t\t\t\t\t#Temperature in K\n",
"rIMEP = ((pi/pa)*(T1/T2x))\t\t\t\t\t#Ratio of I.M.E.P\n",
"gIMEP = (rIMEP*IMEP)\t\t\t\t\t#Gross I.M.E.P in kg/cm**2\n",
"nsIMEP = (gIMEP+(pi-pa))\t\t\t\t\t#Net I.M.E.P supercharged in kg/cm**2\n",
"nuIMEP = (IMEP-pIMEP)\t\t\t\t\t#Net I.M.E.P unsupercharged in kg/cm**2 \n",
"iIMEP = (nsIMEP-nuIMEP)\t\t\t\t\t#Increase in I.M.E.P in kg/cm**2\n",
"pei = (iIMEP*100)/nuIMEP\t\t\t\t\t#Percentage increase\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'Percentage increase in the net I.M.E.P due to supercharging is %3.1f percent'%(pei)\n",
"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Percentage increase in the net I.M.E.P due to supercharging is 49.9 percent\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 18.3 Page no : 331"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"import math \n",
"\t\t\t\t\t\n",
"#Input data\n",
"l = 4.5\t\t\t\t\t#Capacity in litres\n",
"P = 20.\t\t\t\t\t#Power in H.P per m**3 of free air induced per minute\n",
"N = 1700.\t\t\t\t\t#Speed in r.p.m\n",
"nv = 75.\t\t\t\t\t#Volumetric efficiency in percent\n",
"Ta = 27.+273\t\t\t\t\t#Atomspheric temperature in K\n",
"pa = 1.03\t\t\t\t\t#Atmospheric pressure in kg/cm**2\n",
"pr = 1.75\t\t\t\t\t#Pressure ratio\n",
"ie = 70.\t\t\t\t\t#Isentropic efficiency in percent\n",
"nm = 75.\t\t\t\t\t#Mechanical efficiency in percent\n",
"g = 1.4\t\t\t\t\t#Ratio of specific heats\n",
"nb = 80.\t\t\t\t\t#Efficiency of blower in percent\n",
"R = 29.27\t\t\t\t\t#Characteristic gas constant in kg.m/kg.K\n",
"Cp = 0.24\t\t\t\t\t#Specific heat at constant pressure in kJ/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",
"Vs = (l/1000*(N/2))\t\t\t\t\t#Swept volume in m**3/min\n",
"uVs = ((nm/100)*Vs)\t\t\t\t\t#Unsupercharged swept volume in m**3/min\n",
"dp = (pr*pa)\t\t\t\t\t#Blower delivery pressure in kg/cm**2\n",
"Tc = (Ta*pr**((g-1)/g))\t\t\t\t\t#Temperature after isentropic compression in K\n",
"dT = (Ta+(Tc-Ta)/(ie/100))\t\t\t\t\t#Blow delivery temperature in K\n",
"Va = (Vs*(dp*Ta)/(pa*dT))\t\t\t\t\t#Equivalent volume at free air condition in m**3/min\n",
"iiv = (Va-uVs)\t\t\t\t\t#Increase in the induced volume in m**3/min\n",
"iIHP = (P*iiv)\t\t\t\t\t#ncrease in I.H.P \n",
"iBHP = (iIHP*(nm/100))\t\t\t\t\t#Increase in B.H.P\n",
"ma = (dp*10**4*Vs)/(R*dT)\t\t\t\t\t#Mass of air delivered by blower in kg/min\n",
"HP = (ma*Cp*(dT-Ta)*J)/(4500*(80./100))\t\t\t\t\t#H.P required for blower\n",
"nibhp = (iBHP-HP)\t\t\t\t\t#Net increse in engine b.h.p\n",
"pei = (nibhp/(P*uVs))*100\t\t\t\t\t#Percentage increase\n",
"\n",
"\t\t\t\t\t\n",
"#Output\n",
"print 'Percentage net increase in B.H.P is %3.1f percent'%(pei)\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Percentage net increase in B.H.P is 42.1 percent\n"
]
}
],
"prompt_number": 5
}
],
"metadata": {}
}
]
}