For a centrifugal compressor, as found in most turbochargers on internal combustion engines, is there a noticeable change in flow rate versus a naturally aspirated flow rate? In other words, does the pump effectively increase the pressure of the gas only, or does it also increase the flow rate? Really what I'd like to know is how much of the work a turbocharger does goes into increasing the density of the fluid versus how much of it goes into raising its temperature, per the ideal gas law.
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Yes, there is a noticeable change in both flow rate and pressure when a centrifugal compressor is used in a turbocharger compared to a naturally aspirated engine. A turbocharger works by increasing the pressure of the intake air, which compresses it and consequently increases its density. Here’s how the work done by the turbocharger breaks down: Increased Density (Compression): The centrifugal compressor primarily increases the pressure of the air. According to the ideal gas law (PV=nRTPV=nRT), when the pressure increases while keeping the temperature constant, the density of the air increases. This leads to a denser intake charge, meaning more oxygen is available for combustion, which is the primary goal of a turbocharger. Increased Temperature: Compression of the air also causes its temperature to rise, as the process is thermodynamically adiabatic (without heat exchange) in an ideal compressor. In real-world conditions, some heat will be lost to the surrounding environment, but the temperature still increases significantly during compression. The ratio of work that goes into increasing the density versus raising the temperature depends on the design and efficiency of the turbocharger. In a typical turbocharger setup, much of the energy goes into increasing pressure and density, but this is accompanied by a significant increase in temperature. The effectiveness of the turbocharger depends on the balance between compressing the air (increasing density) for more air in the cylinders and the temperature rise that can reduce air intake efficiency if not managed. This is why many turbocharged systems use an intercooler to lower the temperature of the compressed air, improving air density and preventing knock or pre-ignition. In summary, a turbocharger increases both the pressure (density) and temperature of the air. The main goal is to increase the density (by compressing the air), but temperature rise is an inevitable side effect of the compression process. The compressor does not significantly increase the flow rate in the way a supercharger might; instead, it pushes more air into the engine at higher pressure, resulting in greater mass flow, but not necessarily higher volume flow at atmospheric conditions. enter link description here
