Effect of HHO addition on combustion and emission in SI engine with butanol direct injection and gasoline port injection

As a renewable biofuel fuel with similar properties to gasoline, butanol can not only reduce the consumption of fossil energy, but also effectively improve the performance of engine. However, when the mixture ratio of butanol is large, the combustion of the mixture will deteriorate due to the high latent heat of butanol vaporization. In order to solve this problem, the HHO supply system was innovatively built on the basis of butanol/gasoline compound injection system. The HHO produced by the HHO supply system is sucked into the cylinder by the way of negative pressure in the cylinder. This system also forms a new intake system with the original intake system. In this research, the engine speed is 1500 rpm, manifold absolute pressure (MAP) is 42 kPa, and lambda is 1. Five butanol direct injection ratio (BDIr), five HHO flux and six direct injection timing (DIT) are studied to observe the combination effects of butanol and HHO. The results show that under all test conditions, with the increase of HHO flux, indicated mean effective pressure (IMEP), peak in-cylinder pressure (Pmax) and NO increase, CA 0-10, CA 10-90, CO and HC decrease. When HHO flux increases from 0 to 16 L/min, IMEP increases by 4.84% and CO emission decreases by 22.52%. It is worth noting that this improvement is more obvious when BDIr >40%. HHO can effectively offset the negative impact of large proportion of butanol vaporization latent heat and improve the engine's tolerance to BDIr. Moreover, the engine performance gap between different DIT is also shortened with the addition of HHO, which reduces the engine's sensitivity to DIT. In addition, it can also be found that butanol can improve the surge of NO emission caused by HHO. When BDIr >= 60%, the NO emission after the introduction of HHO can be maintained at the original level or even lower. In general, biofuel butanol and clean fuel HHO can work together well and 16 L/min HHO +40% BDIr +60% GPIr +300 degrees CA BTDC DIT is the optimal combination of the BDI + GPI + HHO engine.

Automated summary

This study innovatively built an HHO supply system on the basis of the butanol/gasoline compound injection system to solve the combustion deterioration caused by the high latent heat of butanol vaporization. The results showed that HHO can effectively offset the negative impact of butanol and improve the engine's tolerance to butanol direct injection ratio (BDIr). In addition, butanol can improve the surge of NO emission caused by HHO.