The process of separating carbon dioxide by absorption requires a pressure higher than atmospheric. To avoid re-compression, we virtually designed a reciprocating engine which instead of relying on the expansion of the working medium to atmospheric pressure, uses the residual pressure at the end of the power stroke to supply the pressure for downstream processing of exhaust gases. This means that the exhaust gases are not expanded to atmospheric pressure, as is usually the case with reciprocating engines, but rather the pressure at the outlet is elevated according to the requirements of the absorption process. Since any manipulation of the work process can have a significant impact on the engine's performance, we evaluated the impact of direct compression of exhaust gases with AVL Cruise M software to simulate how the exhaust stroke outlet pressure affects the engine's performance and the composition of the exhaust gases. The results reveal that a direct compression approach for exhaust gas treatment can indeed exploit the residual pressure up to a certain level depending on the operating point. If valve timings, turbocharger characteristics and operating point of the engine are kept unchanged, this severly impacts the performance of the engine, indicating that optimization of the engine would be required to make the direct compression approach viable.
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