{ "metadata": { "name": "" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Chapter9:Carburettors and Fuel Injection in SI Engines " ] }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.1 page no: 279" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "ma=5 #Mass flow rate of air per min for a simple jet carburettor in kg/min\n", "mf=0.4 #Mass flow rate of fuel in kg/min\n", "df=780 #Density of the fuel in kg/m**3\n", "p1=1.013 #The initial pressure of air in bar\n", "t1=27 #The initial temperature of air in degree centigrade\n", "C2=90 #The air flow velocity in m/s\n", "Cva=0.8 #The velocity coefficient for the venturi\n", "Cdf=0.6 #The coefficient of discharge of the main fuel jet \n", "Cpd=0.75 #The pressure drop across the fuel metering oriface\n", "Cp=1005 #The specific heat of gas in J/kgK\n", "g=1.4 #Adiabatic index\n", "R=287 #Real gas constant in J/kgK\n", "\n", "#Calculations\n", "import math\n", "p2=p1*(1-(C2**2/(Cva**2*2*Cp*(t1+273))))**(g/(g-1))\n", "da1=((p1*10**5)/(R*(t1+273)))\n", "da2=((da1)*(p2/p1)**(1/g))\n", "A2=((ma/60.0)/(da2*C2))*10**4\n", "d2=(4*A2/math.pi)**(1/2.0)\n", "pv=p1-p2\n", "pj=Cpd*pv\n", "Aj=((mf/60.0)/(Cdf*(2*df*pj*10**5)**(1/2.0)))*10**6\n", "dj=(4*Aj/math.pi)**(1/2.0)\n", "\n", "#Output\n", "print\"The throat diameter of the choke = \",round(d2,3),\"cm\" \n", "print\"The oriface diameter = \",round(dj,1),\"mm\" \n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The throat diameter of the choke = 3.251 cm\n", "The oriface diameter = 2.2 mm\n" ] } ], "prompt_number": 1 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.2 page no: 281" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "Vs=0.002 #The swept volume in m**3\n", "nv=75.0 #Volumetric efficiency in percent\n", "N=4500.0 #The engine rpm\n", "p1=1.013 #The initial pressure of air in bar\n", "R=287.0 #Real gas constant in J/kgK\n", "t1=15.0 #The atmospheric temperature in degree centigrade\n", "Cp=1005.0 #The specific heat of gas in J/kgK\n", "g=1.4 #Adiabatic index\n", "C2=100.0 #The air flow velocity at choke in m/s\n", "Cda=0.85 #The velocity coefficient for the venturi\n", "Cdf=0.66 #The coefficient of discharge of the main fuel jet \n", "sf=0.75 #The specific gravity of fuel\n", "d=0.4 #The ratio of the diameter to choke diameter\n", "af=14.0 #The air fuel ratio\n", "gf=9.81 #The gravitational force constant in m/s**2\n", "Z=0.006 #The petrol surface below the choke in m\n", "df=750.0 #The density of the fuel in kg/m**3\n", "\n", "#Calculations\n", "import math\n", "Va=((nv/100.0)*Vs*N)/(2.0*60.0)\n", "V1=Va/2.0\n", "ma=(p1*10**5*V1)/(R*(t1+273))\n", "p2=p1*(1-(C2**2/(2*Cp*(t1+273))))**(g/(g-1))\n", "da1=((p1*10**5)/(R*(t1+273)))\n", "da2=da1*(p2/p1)**(1/g)\n", "A2=(ma/(da2*C2*Cda))*10**6\n", "D=((A2*4)/(math.pi*0.84))**(1/2.0)\n", "mf=ma/af\n", "pm=(p1-p2-(gf*Z*df/10.0**5))*10**5\n", "Aj=(mf/(Cdf*(2*df*pm)**(1/2.0)))*10**6\n", "dj=(4*Aj/math.pi)**(1/2.0)\n", "\n", "#Output\n", "print\"The diameter of the choke = \",round(D,2),\"mm\" \n", "print\"The diameter of the jet in = \",round(dj,2),\"mm\" \n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The diameter of the choke = 22.89 mm\n", "The diameter of the jet in = 1.26 mm\n" ] } ], "prompt_number": 1 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.3 page no: 283" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "d=0.08 #The diameter of the bore in m\n", "L=0.09 #The length of the stroke in m\n", "N=4000.0 #The engine rpm\n", "C=84.0 #The carbon content in the fuel by mass in percent\n", "H=16.0 #The hydrogen content in the fuel by mass in percent\n", "nv=80.0 #The volumetric efficiency of the engine in percent\n", "p1=1.0 #The pressure at ambient condition in bar\n", "t1=25.0 #The temperature at ambient condition in degree centigrade\n", "p=0.06 #The depression at venturi throat in bar\n", "ma=0.95 #The actuat quantity of air supplied\n", "Ra=287.0 #Real gas constant in J/kgK\n", "Rf=98.0 #Real gas constant in J/kgK\n", "n=4.0 #Number of cylinders\n", "Cp=1005.0 #The specific heat of gas in J/kgK\n", "g=1.4 #Adiabatic index\n", "\n", "#Calculations\n", "import math\n", "V=(math.pi/4.0)*d**2*L*(nv/100.0)*(N/(2.0*60.0))*n\n", "Af=(100/23.0)*((C*(32/12.0))+(H*8))/100.0\n", "mfa=Af*ma\n", "Aaf=mfa\n", "da=(p1*10**5)/(Ra*(t1+273))\n", "dv=(p1*10**5)/(Rf*(t1+273))\n", "ma1=V/((1/da)+(1/(mfa*dv)))\n", "mf1=ma1/mfa\n", "p2=p1-p\n", "C2=(2*Cp*(t1+273)*(1-(p2/p1)**((g-1)/g)))**(1/2.0)\n", "T2=(t1+273)*(p2/p1)**((g-1)/g)\n", "d2=(p2*10**5)/(Ra*T2)\n", "A2=(ma1/(d2*C2))*10**4\n", "d2=(A2*4/math.pi)**(1/2.0)\n", "\n", "#Output\n", "print\"The fuel flow rate = \",round(mf1,5),\"kg/s\" \n", "print\"The velocity of air at throat = \",round(C2,1),\"m/s\" \n", "print\"The throat diameter = \",round(d2*10,2),\"mm\" \n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The fuel flow rate = 0.00379 kg/s\n", "The velocity of air at throat = 102.5 m/s\n", "The throat diameter = 24.75 mm\n" ] } ], "prompt_number": 2 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.4 page no: 285" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "d=0.1 #The diameter of the bore in m\n", "L=0.12 #The length of the stroke in m\n", "N=3000 #The engine rpm\n", "d2=0.035 #The throat diameter of carburettor venturi in m\n", "nv=80 #The volumetric efficiency of the engine in percent\n", "Cda=0.82 #The coefficient of discharge of air flow \n", "p=1.013 #The ambient pressure in bar\n", "T=298 #The ambient temperature in K\n", "ar=15 #The air fuel ratio \n", "Z=0.005 #The top of the jet above the petrol level in the float chamber in m\n", "Cdf=0.7 #The coefficient of discharge for fuel flow \n", "df=750 #The specific gravity of the fuel in kg/m**3\n", "R=287 #Real gas constant in J/kgK\n", "g=9.81 #The gravitational constant in m/s**2\n", "n=4 #Number of cylinders \n", "\n", "#Calculations\n", "import math\n", "V=(math.pi/4.0)*d**2*L*(nv/100.0)*(N/(2.0*60.0))*n\n", "da=(p*10**5)/(R*T)\n", "ma=V*da\n", "A2=(math.pi/4.0)*d2**2\n", "P=(ma**2/(Cda**2*A2**2*2*da))/10.0**5\n", "mf=ma/ar\n", "Aj=(mf/(Cdf*(2*df*((P*10**5)-(g*Z*df)))**(1/2.0)))*10**6\n", "dj=(Aj*4/math.pi)**(1/2.0)\n", "\n", "#Output \n", "print\"The depression of the throat = \",round(P,3),\"bar\" \n", "print\"The diameter of the fuel jet of a simple carburettor = \",round(dj,3),\"mm\" \n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The depression of the throat = 0.054 bar\n", "The diameter of the fuel jet of a simple carburettor = 1.953 mm\n" ] } ], "prompt_number": 3 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.5 page no:286" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "mf=(6/3600.0) #The mass flow rate of fuel in kg/s\n", "df=750 #The density of fuel in kg/m**3\n", "Z=0.003 #The level in the float chamber below the top of the jet in m\n", "p=1.013 #The ambient pressure in bar\n", "T=294 #The ambient temperature in K\n", "dj=0.0012 #The jet diameter in m\n", "Cdf=0.65 #The discharge coefficient of the jet \n", "Cda=0.8 #The discharge coefficient of air \n", "A=15.3 #The air fuel ratio \n", "g=9.81 #The gravitational constant in m/s**2\n", "R=287 #Real gas constant in J/kgK\n", "dh=1000 #The density of water in kg/m**2\n", "\n", "#Calculations\n", "import math\n", "da=(p*10**5)/(R*T)\n", "Ca2=Cda*((2*g*Z*df)/da)**(1/2.0)\n", "Aj=(math.pi/4.0)*dj**2\n", "P=((mf**2/(Cdf**2*Aj**2*2*df))+(g*Z*df))/10.0**5\n", "h=(P*10**5)/(dh*g)\n", "h1=(P*10**5)/g\n", "ma=mf*A\n", "A2=(ma/((Cda*(2*da*(P*10**5))**(1/2.0))))*10**4\n", "d2=((A2*4/math.pi)**(1/2.0))*10\n", "\n", "#Output \n", "print\"The critical air velocity = \",round(Ca2,1),\"m/s\" \n", "print\"The depression at the throat = \",round(h1,1),\"mm of H2O\" \n", "print\"The effective throat diameter \",round(d2,2),\"mm\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The critical air velocity = 4.9 m/s\n", "The depression at the throat = 351.6 mm of H2O\n", "The effective throat diameter 21.12 mm\n" ] } ], "prompt_number": 4 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.6 page no: 287" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "d2=22 #The venturi throat diameter of a simple carburettor in mm\n", "Cda=0.82 #The coefficient of air flow \n", "dj=1.2 #The fuel orifice diameter in mm\n", "Cdf=0.7 #The coefficient of fuel flow\n", "Z=0.004 #The petrol surface below the throat in m\n", "g=9.81 #The gravitational constant in m/s**2\n", "da=1.2 #The density of air in kg/m**3\n", "df=750 #The density of fuel in kg/m**3\n", "P=0.075 #The pressure drop in bar\n", "\n", "#Calculations\n", "A=(Cda/Cdf)*(d2**2/dj**2)*(da/df)**(1/2.0)\n", "A1=(Cda/Cdf)*(d2**2/dj**2)*((da*P)/(df*(P-(g*Z*df)/10.0**5)))**(1/2.0) \n", "Ca2=(2*g*Z*df/da)**(1/2.0)\n", "\n", "#Output\n", "print\" (a) The air fuel ratio when the nozzle lip is neglected = \",round(A,2)\n", "print\"(b)The air fuel ratio when the nozzle lip is considered = \",round(A1,3)\n", "print\"(c) The critical air velocity or minimum velocity required to start the fuel flow = \",round(Ca2,1),\"m/s\" \n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ " (a) The air fuel ratio when the nozzle lip is neglected = 15.75\n", "(b)The air fuel ratio when the nozzle lip is considered = 15.78\n", "(c) The critical air velocity or minimum velocity required to start the fuel flow = 7.0 m/s\n" ] } ], "prompt_number": 22 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.7 page no: 289" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "h=4000 #The altitude of the airplane engine carburettor in m\n", "A=14.7 #The air fuel ratio at sea level\n", "ts=22 #The temperature at sea level in degree centigrade\n", "R=287 #Real gas constant in J/kgK\n", "\n", "#Calculations\n", "ta=ts-(0.0065*h)\n", "p=1.013/10.0**0.2083\n", "da=(p*10**5)/(R*(ta+273))\n", "ds=(1.013*10**5)/(R*(ts+273))\n", "Aa=A*(da/ds)**(1/2.0)\n", "\n", "#Output\n", "print\"The air fuel ratio at altitude = \",round(Aa,2)\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The air fuel ratio at altitude = 12.11\n" ] } ], "prompt_number": 23 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.8 page no: 289" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "A=14.5 #The air fuel ratio\n", "p2=0.825 #The pressure at the venturi throat in bar \n", "p1=1.013 #The atmospheric pressure in bar\n", "pd=37.5 #The pressure drop to the air cleaner in mm of Hg\n", "ma=260 #The mass flow rate of air in kg/h\n", "\n", "#Calculations\n", "pa=p1-p2\n", "p21=p1-(pd/750)-pa\n", "pf=pa\n", "pf1=p1-p21\n", "Af=A*(pf/pf1)**(1/2.0)\n", "\n", "#Output\n", "print\"(a) The throat pressure when the air cleaner is fitted = \",p21,\"bar\" \n", "print\"(b) The air fuel ratio with the air cleaner fitted = \",round(Af,3)\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "(a) The throat pressure when the air cleaner is fitted = 0.775 bar\n", "(b) The air fuel ratio with the air cleaner fitted = 12.887\n" ] } ], "prompt_number": 17 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 9.9 page no: 291" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#given\n", "bp=8 #The brake power of the petrol engine in kW\n", "nb=30 #The brake thermal efficiency in percent\n", "CV=44000 #The calorific value of the fuel in kJ/kg\n", "p1=1.013 #The suction condition of engine pressure in bar\n", "T1=300 #The temperature at suction condition in K\n", "Aj=2.5*10**-6 #The area of jet in m**2\n", "Z=0.008 #The nozzle lip in m\n", "g=9.81 #The gravitational force constant in m/s**2\n", "A=15 #The air fuel ratio\n", "Cda=0.9 #The coefficient of air flow\n", "Cdf=0.7 #The coefficient of fuel flow\n", "df=750 #The density of fuel in kg/m**3\n", "va=0.8 #The specific volume of air in m**3/kg\n", "\n", "#Calculations\n", "import math\n", "va1=va*T1/273.0\n", "da=1/va\n", "mf=bp/((nb/100.0)*CV)\n", "Cf=mf/(Cdf*df*Aj)\n", "P=((Cf**2*df)/2.0)+(df*g*Z)\n", "Ca=(2*P/da)**(1/2.0)\n", "ma=mf*A\n", "A2=(ma/(Cda*da*Ca))*10**4\n", "d2=(A2*4/math.pi)**(1/2.0)\n", "\n", "#Output\n", "print\"The venturi throat diameter of the carburator = \",round(d2,2),\"cm\" \n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The venturi throat diameter of the carburator = 2.63 cm\n" ] } ], "prompt_number": 1 } ], "metadata": {} } ] }