Thermodynamic investigation of a hydrogen enriched natural gas fueled HCCI engine for the efficient production of power, heating, and cooling

One of the primary concerns with fuel combustion in internal combustion engines is the significant quantity of energy that is dissipated as waste heat, which leads to thermal pollution and reduced engine efficiency. To address this issue, a new integrated system incorporating a natural gas fueled homogeneous charge compression ignition (HCCI) engine for different hydrogen fractions (0%-20%) in fuel blends and its exhaust heat is recovered to drive the NH3-H2O based absorption refrigeration cycle (ARC) and process heat exchanger has been developed, which encompasses the generation of electricity, heating, and cooling. A comprehensive energy-exergy model was built and the impact of some key operating variables on the performance of combined system are investigated. Simulation of the proposed system was performed using Engineering Equation Solver (EES) software and REFPROP toolbox library data. The energy and exergy efficiencies of HCCI engine resulted in an increase from 45.26% to 55.45% and from 41.15% to 46.14%, whereas the combined system efficiencies were increased by 15.90% and 10.13% when hydrogen addition is promoted from 0% to 20%. Utilization of 10% hydrogen resulted in energy efficiency of 49.57% for electrical, 11.89% for cooling, and 4.51% for heating. Illustration of exergy flow diagram identified HCCI engine (118.29 kW, 32.11%) as the most fuel exergy destructive component, followed by ARC cycle (30.86 kW, 8.37%), catalytic converter (27.24 kW, 7.39%) and process heat exchanger (11.103 kW, 3.01%). Impressive exergetic results from the system include a power exergy of 158.91 kW (43.14%), heating exergy 10.697 kW (2.90%), and cooling exergy 3.92 kW (1.06%).