{ "metadata": { "name": "", "signature": "sha256:faffd56df5ff320ba3aaf8ef0438e5c3fd03dbfd20ea0e30132ca53319ffe641" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Chapter 8: Engine Cycles" ] }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 8.1, page no. 154" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "#initialization\n", "ratio = 7.0\n", "Q = 300.0 #B/lbm\n", "T1 = 60+460.0 #R\n", "P1 = 14.7 #lb/in^2\n", "cv = 0.1715 #B/lvm F\n", "g = 1.4\n", "\n", "#calculation\n", "Tratio = (ratio)**(g-1)\n", "T2 = Tratio*T1\n", "T3 = T2+Q/cv\n", "eta = round(1- 1/Tratio,2)\n", "WbyJ = eta*Q\n", "print WbyJ*778\n", "W = 778*WbyJ\n", "\n", "#result\n", "print \"Final temperature = %d R\" %T3\n", "print \"Thermal efficiency = %.3f\" %eta\n", "print \"Work done = %d ft-lb/lbm\" %W\n", "#difference in answer due to internal rounding off in Python" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "126036.0\n", "Final temperature = 2881 R\n", "Thermal efficiency = 0.540\n", "Work done = 126036 ft-lb/lbm\n" ] } ], "prompt_number": 17 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 8.2, page no. 157" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "import math\n", "\n", "#initialization\n", "cydia = 3.0 #in\n", "crdia = 5.0 #in\n", "ratio = 7.0\n", "rpm = 3000.0 #rpm\n", "hp = 50.0 #hp\n", "w = 24.2 #lbm\n", "Q = 18000.0 #B/lbm\n", "P1 = 14.7 #lb/in^2\n", "T1 = 60+460.0 #R\n", "g = 1.4\n", "cv = 0.1715\n", "\n", "#calculation\n", "eta = hp*550*3600/(778*w*Q)\n", "vol = math.pi*(cydia/12)**2 *(crdia/12)*6/4\n", "vdot = vol*rpm/(60*2)\n", "v1 = 53.3*T1/(144*P1)\n", "wdot = vdot/v1\n", "Qdot = w*Q/3600\n", "Qdash = Qdot/wdot\n", "T2 = T1*(ratio)**(g-1)\n", "T3 = T2+Qdash/cv\n", "eta2 = 1- 1/(ratio)**(g-1)\n", "WbyJ = eta2*Qdot\n", "Wdot = WbyJ*778/550.0\n", "\n", "#result\n", "\n", "print \"Part a\"\n", "print \"Thermal efficiency = %.3f \" %eta\n", "\n", "print \"part b\"\n", "print \"Temperature at the end of compression = %d R\" %T2\n", "print \"Power developed = %.1f hp\" %Wdot" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Part a\n", "Thermal efficiency = 0.292 \n", "part b\n", "Temperature at the end of compression = 1132 R\n", "Power developed = 92.6 hp\n" ] } ], "prompt_number": 2 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 8.3, page no. 161" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "#initialization\n", "Pi = 14.0 #lb/in^2\n", "T1 = 70+460.0 #F\n", "ratio = 13.0\n", "T3 = 2500+460.0 #F\n", "cv = 0.171\n", "cp = 0.23\n", "R = 53.3\n", "g = 1.4\n", "\n", "#calculation\n", "T2 = T1*(ratio)**(g-1)\n", "v3ratio = T3/T2\n", "cutoff = (v3ratio-1)/(ratio-1)\n", "v1ratio = ratio/v3ratio\n", "T4 = T3*(1/v1ratio)**(g-1)\n", "eta = 1.0- cv*(T4-T1)/(T3-T2)/cp\n", "percent = eta*100\n", "\n", "#result\n", "print \"cut off ratio = %.4f\" %cutoff\n", "print \"T end expansion = %d R\" %T4\n", "print \"Thermal efficiency = %.1f\" %percent, \"%\"\n", "#difference in % due to internal rounding off in Python" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "0.563104145624\n", "cut off ratio = 0.0835\n", "T end expansion = 1400 R\n", "Thermal efficiency = 56.3 %\n" ] } ], "prompt_number": 20 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 8.4, page no. 167" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "#initialization\n", "Pratio = 6.0\n", "P = 14.7 #lb/in^2\n", "Tt1 = 60+460.0 #R\n", "Tt3 = 1600+460.0 #R\n", "w = 60.0 #lb/sec\n", "cp = 0.24 #B/lbm F\n", "g = 1.4\n", "R = 53.3 #ft-lb/lbm R\n", "\n", "#calculation\n", "Tt2 = Tt1*(Pratio)**((g-1)/g)\n", "Tratio = Tt2/Tt1\n", "Q = cp*(Tt3-Tt2)\n", "eta = 1- 1/Tratio\n", "W = eta*778*Q\n", "Wdot = w*W/550.0\n", "\n", "#result\n", "print \"Thermal efficiency = %.3f\" %eta\n", "print \"Horsepower output = %d hp\" %Wdot" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Thermal efficiency = 0.401\n", "Horsepower output = 9731 hp\n" ] } ], "prompt_number": 5 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Example 8.5, page no. 169" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "#initialization\n", "P = 14.7 #lb/in^2\n", "T = 60+460 #R\n", "e1 = 0.8\n", "P2 = 3 #lb/in^2\n", "T2 = 1600+460 #R\n", "Pt4 = 15.6 #lb/in^2\n", "w = 60 #lbm/sec\n", "e2 = 0.85\n", "\n", "#calculation\n", "# from table 6, initial conditions are\n", "ht1 = 124.3\n", "Prt1 = 1.215\n", "Prt2s = 6*Prt1\n", "ht2s = 207.6\n", "ht2 = ht1+(ht2s-ht1)/e1\n", "dht1 = round((ht2s-ht1)/e1, 1)\n", "ht3 = 521.4\n", "Prt3 = 196.2\n", "Pt3 = 6*P-P2\n", "Pratio = Pt3/Pt4\n", "Prt4s = Prt3/Pratio\n", "ht4 = 326.5\n", "dht3 = round(e2*(ht3-ht4), 1)\n", "W = 778*(dht3-dht1)\n", "Q = ht3-ht2\n", "etaf = W/778.0/Q\n", "Wdot = w*W/550.0\n", "\n", "#result\n", "print \"Thermal efficiency = %.3f\" %(round(W))\n", "print \"Horsepower output = %d hp\" %Wdot\n", "#difference due to internal rounding off in Python." ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Thermal efficiency = 47925.000\n", "Horsepower output = 5228 hp\n" ] } ], "prompt_number": 11 }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Exmaple 8.6, page no. 172" ] }, { "cell_type": "code", "collapsed": false, "input": [ "\n", "#initialization\n", "g = 1.4\n", "Tt4 = 2060 #R\n", "cp = 0.24\n", "\n", "#calculation\n", "Tt5 = Tt4/1.67\n", "Tt2 = 868 #R\n", "Tt3s = 1234\n", "dTt3 = (Tt3s-Tt2)/2.0\n", "Tt3 = Tt2+dTt3\n", "Q = cp*(Tt4-Tt3)\n", "eta = 286*0.401/Q\n", "\n", "#result\n", "\n", "print \"Heat Added is \", round(Q),\"B/lbm\"\n", "print \"eta is \", round(eta, 3)\n", "print \"Improvement is around 6.2 percent in overall efficiency\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Heat Added is 242.0 B/lbm\n", "eta is 0.474\n", "Improvement is around 6.2 percent in overall efficiency\n" ] } ], "prompt_number": 1 } ], "metadata": {} } ] }