Pmi = indicated mean effective pressure, in N/m2.
The power required to drive a blower or a compressor connected to the engine must be
subtracted from the engine output to obtain the net brake power of the supercharged engine.
For the mechanically driven blower or compressor,
brake power, bp = (ηmech× ip) — (power to drive the blower) (15.12)
In Figure 15.3(a) at point 4 the exhaust valve opens and the exhaust process starts at a
Pressure substantially greater than the ambient pressure, pa. The cylinder charge is suddenly
exhausted by a free expansion and a considerable amount of energy released during combustion is lost as it does not contribute to power output of the engine. The attraction of turbocharging is evident, as the energy lost in this way is used to drive a turbine wheel integral with a compressor wheel which delivers compressed air or charge to the cylinder. The additional work available from the gas is indicated, after continuing the reversible adiabatic expansion line 3-4 down to the pressure pa at 6, by the area 4-6-1-4. The physical arrangement is shown in Figure 15.2(b) and there is no mechanical connection to the engine. The turbocharger combination is a free running unit with approximately equal mass flow rates over the turbine and compressor wheels reaching an equilibrium speed in the range from 20,000 to 80,000 rpm.
The pressure in the intake manifold is pi which is increased from atmospheric pressure pa to pi in the compressor. The exhaust pressure in the exhaust manifold of the engine before entering the turbine is pe, such that pi > pe. The expansion process in the turbine reduces the pressure frompeto pa. The T-s diagram for the turbocharger is shown in Figure 15.4.
Pmi = indicated mean effective pressure, in N/m2.
The power required to drive a blower or a compressor connected to the engine must be
subtracted from the engine output to obtain the net brake power of the supercharged engine.
For the mechanically driven blower or compressor,
brake power, bp = (ηmech× ip) — (power to drive the blower) (15.12)
In Figure 15.3(a) at point 4 the exhaust valve opens and the exhaust process starts at a
Pressure substantially greater than the ambient pressure, pa. The cylinder charge is suddenly
exhausted by a free expansion and a considerable amount of energy released during combustion is lost as it does not contribute to power output of the engine. The attraction of turbocharging is evident, as the energy lost in this way is used to drive a turbine wheel integral with a compressor wheel which delivers compressed air or charge to the cylinder. The additional work available from the gas is indicated, after continuing the reversible adiabatic expansion line 3-4 down to the pressure pa at 6, by the area 4-6-1-4. The physical arrangement is shown in Figure 15.2(b) and there is no mechanical connection to the engine. The turbocharger combination is a free running unit with approximately equal mass flow rates over the turbine and compressor wheels reaching an equilibrium speed in the range from 20,000 to 80,000 rpm.
The pressure in the intake manifold is pi which is increased from atmospheric pressure pa to pi in the compressor. The exhaust pressure in the exhaust manifold of the engine before entering the turbine is pe, such that pi > pe. The expansion process in the turbine reduces the pressure frompeto pa. The T-s diagram for the turbocharger is shown in Figure 15.4.
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