Abstract: In order to reduce NOx in diesel tail gas without reducing the thermal efficiency, NOx formation mechanism and existing technology of diesel tail gas purification are researched, a NOx purification technology is presented, in which the liquid ammonia is injected into a cylinder in the engine-house, without catalyst, when the diesel engine burning temperature lowers to an effective reaction temperature range. This new technology is tested on a typical automotive diesel 4102BZLQ, its feasibility is verified, and the NOx content value is measured under rated operating condition, it is below the Euro V standard value. The innovations are: ① No limit to the burning temperature. ② No catalyst is used and the liquid ammonia is injected directly. The activation energy of oxidation reduction matter in the waste gas of diesel engine itself is utilized fully, and the efficiency, structure, life and reliability problems unable to be solved by other technologies are solved.

Key words: Diesel engine, Direct injection of ammonia, Engine matching test, Inside the cylinder, New technology, NOx purification, Continuous optimization, Discrete optimization, Geometrical configuration, Virtual work principle, Flexure hinge