- nth is the thermal efficiency of the Seiliger process. This process considers heat losses occurring in the ideal process and is mainly dependent on compression ratio and excess-air factor. As the diesel run at a higher compression ratio than a gasonline engine and high excess-air factor, it achieves higher efficiency.- ng : efficiency of cycle factor - ng specifies work done in the real high-pressure work process as a factor of the thearetical work of the Seiliger process. Deviations between the real and the ideal processes mainly result from use of the real working gas, the finite velocity of heat propagation and dissipation, the position of heat propagation, wall heat loss, and flow losses during the gas-exchange process.- nb : fuel conversion factor- nb considers losses occurring due to incomplete fuel combustion in the sylinder.- nm : mechanical effciency- nm includers friction losses and losses arising from driving ancillary assemblies. Frictional and power-tranmission losses increase with engine speed. At nominal speed, frictional losses are composed of the following:+ Pistons and piston rings approx. 50%+ Bearing approx. 20%+ Oil pump approx. 10%+ Coolant pump approx. 5%+ Valve-gear approx. 10%+ Fule-injection pump approx. 5%If the engine has a supercharger, this must also be included. - ni : efficiency indexThe efficiency index is the ratio between ‘indexed’ work present at the piston Wi and the calorific value of the fuel supplied.Work effectively avilable at the crankshaft We results from indexed work taking mechanical losses into consideration:
We = Wi . nm
C. Operating statuses
• Starting
Staring an engine involves the following stages: cranking, ignition and running up to self-sustained operation
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