Strategies to Lower Load in Oxy-Fuel Compression Ignition Engines with Oxygen Separation Membranes

The possibility of applying oxy-fuel combustion to a compression ignition (CI) engine at different operating points regarding engine speed and load is studied in this work. To do so, a strategy is proposed to extend the load operation map range of a 2.2 L turbocharged and direct-injection CI engine under oxy-fuel combustion conditions using Mixed Ionic-electronic Conducting Membranes (MIEC) to acquire oxygen (O2) from the air, enabling forward carbon dioxide (CO2) capture and eliminating nitrogen oxides (NOx) emissions. The strategy consists of modifying exhaust gas temperature (Texh) and oxygen-fuel ratio (λ), generating temperature-lambda maps to decide the optimal combination in terms of engine performance. Thus, the system behavior is analyzed at three engine speeds (1250 rpm, 2500 rpm and 3500 rpm) with different load levels and compression ratio (CR) equal to 20. The baseline engine model is calibrated with experimental data within part-load operation ranges, and an apparent combustion time (ACT) model is applied to simulate a diffusion combustion process properly under oxy-fuel combustion conditions. Finally, many parameters are defined to verify whether the system produces enough energy to heat up the MIEC, generating the necessary oxygen. Indeed, those proposed parameters are essential for finding out oxy-fuel engine operation limits and estimating MIEC design features.