废气再循环对压力波增压器平均价值建模的影响外文翻译(编辑修改稿)

废气再循环对压力波增压器平均价值建模的影响外文翻译(编辑修改稿)内容摘要：

ressure, ., the throttle reduces the level of ambient pressure by energy dissipation to the level of intake manifold pressure. The engine then works at partload conditions, which are characterized by a negative pressure difference over the engine: Pim— Pem0: throttled engine operation The negative pressure difference between intake and exhaust manifolds causes pumping losses for the engine. This is the main reason why naturally aspirated SI engines have a poor efficiency at partload conditions. Among various approaches toward improving this situation several possibilities are found: burn engines with direct injection of gasoline engine speed concept and supercharging for high engine speed only and supercharging over entire engine speed range The concept 1 tries to reduce the fuel consumption by a lean engine operating mode which is still a subject of current research and therefore not further discussed here. In contrast, the engine concepts 2, 3, and 4 try to avoid the pumping losses of the engine by reducing the engine displacement. Compared to a regular SI engine, the downsized engine more often operates at high loads where the throttling losses hardly occur. This leads to negligible pumping losses. The engine then operates near its most economical operating point. The engine power lost by downsizing may be recovered by: Increasing the engine speed. Increasing the intake manifold pressure above ambient pressure. The first concept is not a suitable choice for passenger cars due to the noise caused by an engine operating at high engine speeds. The second concept recovers the missing engine power by increasing the intake manifold pressure above ambient pressure. This may be realized by the adding a: mechanical charger turbocharger pressure wave supercharger A charger presses the fresh air either with the help of mechanical energy from the crankshaft of the engine (mechanical charger) or with the help of the exhaust gas enthalpy from the engine (turbocharger or pressure wave supercharger). In supercharged engine mode, the pressure difference over the engine bees zero or even positive (see , showing a turbocharged SI engine as an example): Pim— Pem≥0:supercharged engine operation Figure : SI engine supercharged with a turbocharger with a bypass valve。 a: ambient。 im: intake manifold。 em: exhaust manifold。 1: before pressor。 2: after pressor。 3: before turbine。 4: after turbine The downsized supercharged engine operates more economically in the range between lower and medium loads pared to a naturally aspirated engine due to smaller pumping losses in this load range. Therefore, supercharging an SI engine may reduce the fuel consumption. Supercharging an SI Engine with a Pressure Wave Supercharger In the SAVE project, a downsized small SI engine is supercharged with a pressure wave supercharger (PWS). The main reasons for choosing a PWS as the charging device in that project are briefly explained in the following: Leakage losses: The expected exhaust gas volume flow of a small SI engine is very low. A turbocharger would have relatively high leakage losses over the turbine as a result of the very small turbine geometry. Therefore, its efficiency decreases. For a given desired boost pressure p2, the lower turbine efficiency requires a higher exhaust gas pressure p3 pared to the case without leakage losses over the turbine (for the nomenclature of the pressures see ). This causes increased pumping losses for the engine. In contrast to a turbocharger, the expected leakage losses of a PW。