The currently available technologies for controlling emissions in internal combustion engines may not be sufficient to achieve the very low emission levels imposed by future legislation. The utilisation of gaseous hydrogen (H-2) in CI engines is a viable option for simultaneously solving the problems of energy efficiency improvements and emissions reduction, including greenhouse gases (GHG). This paper is a part of a wider study devoted to the analysis of dual combustion (diesel-hydrogen) in internal combustion engines. In this paper, a diesel engine is modified to run using a hydrogen-diesel mixture as fuel, with diesel fuel used alone as the ignition source. This mode of operation is studied for two speeds and various injection strategies, with hydrogen as the main fuel and diesel for ignition, up to a hydrogen/diesel mass ratio of 1.75. In order to control NOx emissions, intake self-ignition and combustion knocking, water was injected into the intake manifold (WI). The test results show that smoke emissions decrease with an increase in the hydrogen/diesel ratio. Conversely, NOx emissions increase with the hydrogen fraction, but water injection produces a reduction in the NOx emissions of around 50%. An almost flat efficiency of close to 40% is observed. (C) 2019 Elsevier Ltd. All rights reserved.