14. starptautiskÄ konference 2012 - Latvijas JÅ«ras akadÄmija

More documents

Recommendations

Info

Proceedings of 14th International conference „Maritime Transport and Infrastructure - <strong>2012</strong>”Fig. 1. Electric compressing installationFig. 2. Theoretical indicating pV diagramTheoretical indicative pV diagram of the double-stage compressor is demonstrated in fig.2.[1], [2].At a single-stage adiabatic compressing the expended work would be equal to the square 6-8-1-2-6, that is larger than the square of isothermal compressing 6-7-4-1-2-6. At the double-stagecompressing the work of the adiabatic compressing of the first stage is characterised with square 3-9-1-2-3. After being compressed to intermediate pressure Р 1 the gas goes to intermediate refrigerator 7(fig.1) according to adiabatic curve 1-9, where it is cooled at constant pressure Р 1 till the initial26
Proceedings of 14th International conference „Maritime Transport and Infrastructure - <strong>2012</strong>”temperature. Cooling results in the decreasing of the gas volume for value 9-4 equal to the differenceV 3 -V 2 . The initial point of pressure is back to the initial isotherm 1-4-7. The adiabatic pressure at thesecond stage will be represented with adiabatic curve 4-5 (straight line).Work of compressing indicated with square 6-5-4-3-6. Therefore at the double-stagecompressing we gain work equal to the square 5-8-9-4-5, shaded in the diagram. The work for gascompressing and movement in the double-stage compressor during one turn of the crankshaftcorresponds to the indicating diagram square F i and indicating work L i on a scale k 0 of pV -diagram.(Fig.2)L k F(1)iwhere k 0 - is a scale factor; F i – square of indicating diagram (Fig.2).Indicating power N i is numerically equal to the indicating work per second.Ni Lin(2)where n - is a rotation frequency of the crankshaft, sec -1 .The operation processes in the piston compressors take place with the period equal to one turnof the crankshaft. The position of the compressor piston and changing of the cylinder volume isaccording to the law of a crank gear:3dV cil/ d 0.785[sin sin 2](Dcil/ 2)(3)2According to the rotation angle φ the cylinder volume V cil will be equal to3V 0,785 ( / 2) [2a 1 cos cil D cos 2](4)4 4where S ; r ; S - is a piston stroke, r - is a radius of the crank, l - length of theD lconnecting rod, φ - angle of rotation of the electro compressor shaft.The angle of rotation of the crankshaft φ is measured by means of sensor 19 (fig.1), the instantvalues of the pressure in the compressor cylinders - by means of sensors 6 and 15 (fig.1). Using theobtained values the current volume of the compressor cylinders is calculated and a real pV-diagram iscreated. The diagnostics of the compressor is realised comparing the obtained pV-diagram with thereference one - comparing of the squares, calculation of its squares, actual location of the points 1-9 inthe reference frame «р» and «V» (fig.2). The difference between the real and ideal pV-diagrams isfixed and input for the comparison into the diagnostic matrix of failures. The matrix forms a report onthe current technical condition of the compressor.The instant resistive torque on the compressor shaft is not constant and depends on the shaftrotation angle φ. Therefore the rotation torque of the induction motor is not constant. The inductionmotor operates in dynamic mode the parameters of which are strictly connected with the dynamicparameters of the compressor. It is convenient to connect the mathematical model of the pistoncompressor with that of three-phase induction motor.oi2. Mathematical model of three-phase induction motor with squirrel-cage rotor in dynamicregimes.The investigation and analysis of the induction motors behaviour in dynamic regimes result inthe necessity to develop so called vector models of these machines. Mathematical description ofelectromechanical transformation of power in electrical machines is based on the development ofKirchhoff's differential equations and their solutions [5]. In matrix type the equations of voltages forthree phases of stator A, B, C and three phases of rotor a, b, c for the model (fig.3) can be written as:[ R][i(t)] d[ ( t)][U(t)] 0,(5)dt27
Page 1 and 2: LATVIJAS JŪRAS AKADĒMIJALJA PĒTN
Page 3: Proceedings of 14th International c
Page 7 and 8: Proceedings of 14th International c
Page 21 and 22: 20002001200220032004200520062007200
Page 51 and 52: KEMPINSKItNt>...... /1--":-...... I
Page 71 and 72: Concentration, mg/m 3Proceedings of
Page 73 and 74: 0:001:002:003:004:005:006:007:008:0
Page 77 and 78:
Proceedings of 14th International c
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Air temperature, deg CWater tempera
Page 125 and 126:
Water level (+/-), centimetreProcee
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Mln. LtMln. LtProceedings of 14th I
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
show all

14. starptautiskÄ konference 2012 - Latvijas JÅ«ras akadÄmija

Create successful ePaper yourself

Delete template?

Save as template?

14. starptautiskÄ konference 2012 - Latvijas JÅ«ras akadÄmija