Study on leakage characteristics of ammonia fuel in high-pressure pump

Ammonia fuel plays a critical role in the achieving zero carbon emission in the field of internal combustion engines, and its physical properties different from traditional fuels put forward higher requirements for the supply performance and reliability of ammonia fuel high-pressure pumps. As the key to affecting the efficiency of ammonia pumps, the issue of fuel leakage has received considerable critical attention. A combination of experiment and simulation methods was used in study to obtain leakage characteristics of high-power ammonia fuel pump. The effects of fuel properties, working conditions and structure of ammonia pump on leakage characteristics are analyzed. The results indicate that ammonia fuel exhibits a slower pressure buildup rate compared to diesel, and leaks significantly more—over ten times as much. High pressure can cause the pump parts to deform, increasing plunger pair gap and leading to further leakage. When the gap is too large, the ammonia pump stops supplying liquid before the plunger reaches the maximum lift, resulting in an inefficient liquid supply process. Moreover, when the plunger pair gap exceeds 0.005 mm, leakage significantly impacts performance. Fuel temperature also affects leakage, showing a nonlinear relationship with it. The change in the volume efficiency of the ammonia pump under various operating conditions is mainly due to the loss of leakage volume efficiency. The motor control pump system achieves high volume efficiency for high-pressure ammonia pumps, ranging from 83.2% to 98.9% under full operating conditions. Through the analysis of the ammonia inlet boundary conditions, it is concluded that the ammonia inlet temperature only affects the volumetric efficiency of the ammonia pump, and the ammonia inlet pressure only affects the temperature rise of the ammonia pump system. Thus, the temperature and pressure of inlet ammonia can be managed to optimize pump performance independently.