The world is presently confronted with the twin crisis of fossil fuel depletion and environmental degradation. Indiscriminate extraction and lavish consumption of fossil fuels have led to reduction in underground based carbon resources. The search for an alternative fuel, which promises a harmonious correlation with sustainable development, energy conservation, management, efficiency, and environmental preservation, has become highly pronounced in the present context. For the developing countries of the world, fuels of bio-origin can provide a feasible solution to the crisis. In the present investigation, hydrogen-enriched air was used as intake charge in a Cl (compression ignition) engine. Experiments were conducted in a single-cylinder, four-stroke, air-cooled, stationary direct-injection diesel engine Kirlosker TAF1 with 1500 rpm and 4.4 kW capacity coupled to an electrical generator. The injection timings (18.5, 20, 21.5, 24.5, 27.5 degrees CA) and flow rates of hydrogen were varied (80, 120, 150 g/hr) to find out the optimum condition for hydrogen enrichment to meet the best performance. Experiment results showed that hydrogen enriched engine gave maximum brake thermal efficiency and minimum brake specific energy consumption at 16.4% H-2 or 120 g/h flow rate with 20 CA injection timing. (C) 2013 Elsevier Ltd. All rights reserved.