Mohammad Reza Herfatmanesh

Characteristics of pressure wave in common rail fuel injection system of high-speed direct injection diesel engines

The latest generation of high-pressure common rail equipment now provides diesel engines possibility to apply as many as eight separate injection pulses within the engine cycle for reducing emissions and for smoothing combustion. With these complicated injection arrangements, optimizations of operating parameters for various driving conditions are considerably difficult, particularly when integrating fuel injection parameters with other operating parameters such as exhaust gas recirculation rate and boost pressure together for evaluating calibration results. Understanding the detailed effects of fuel injection parameters upon combustion characteristics and emission formation is therefore particularly critical. In this article, the results and discussion of experimental investigations on a high-speed direct injection light-duty diesel engine test bed are presented for evaluating and analyzing the effects of main adjustable parameters of the fuel injection system on all regulated emission gases and torque performance. Main injection timing, rail pressure, pilot amount, and particularly pilot timing have been examined. The results show that optimization of each of those adjustable parameters is beneficial for emission reduction and torque improvement under different operating conditions. By exploring the variation in the interval between the pilot injection and the main injection, it is found that the pressure wave in the common rail has a significant influence on the subsequent injection. This suggests that special attentions must be paid for adjusting pilot timing or any injection interval when multi-injection is used. With analyzing the fuel amount oscillation of the subsequent injections to pilot separation, it demonstrates that the frequency of regular oscillations of the actual fuel amount or the injection pulse width with the variation in pilot separation is always the same for a specified fuel injection system, regardless of engine speed, fuel amount, injection pulse, and injection pressure.

Experimental investigation of effects of dwell angle on fuel injection and diesel combustion in a high-speed optical CR diesel engine

In order to meet the ever-more stringent emission standards, significant efforts have been devoted to the research and development of cleaner internal combustion engines. Diesel combustion and the formation of pollutants are directly influenced by the spatial and temporal distribution of the fuel injected. This study investigated the effects of dwell angle of split injection on diesel combustion and emissions in a high-speed common rail direct injection optical diesel engine. The fuel injection system was characterized through the measurement of the fuel injection rate and quantity for the tested strategies on a fuel injection test rig. In particular, the interaction between the two injection events was identified. Effects of the split injection dwell angle and the interactions of the two consecutive injection events on diesel combustion and exhaust emissions were then investigated in the single cylinder optical engine using heat release analysis and optical diagnostic techniques. The fuel injection process was illuminated by a high repetition copper vapour laser and recorded synchronously by a high speed video camera. The combustion temperature and soot distribution during the combustion process were measured by a recently developed high speed two-colour system. The results indicated that this injection mode has the potential to improve fuel economy and engine performance while substantially reducing the combustion noise, provided that the injection timings are appropriately selected.

Experimental investigation of hydraulic effects of two-stage fuel injection on fuel-injection systems and diesel combustion in a high-speed optical common-rail diesel engine

In order to meet the ever more stringent emission standards, significant efforts have been devoted to the research and development of internal combustion engines. The requirements for more efficient and responsive diesel engines have led to the introduction and implementation of multiple injection strategies. However, the effects of such injection modes on the hydraulic systems, such as the high-pressure pipes and fuel injectors, must be thoroughly examined and compensated for since the combustion and the formation of pollutants in direct-injection engines are directly influenced by the spatial and temporal distribution of the injected fuel within the combustion chamber. This study investigated the hydraulic effects of two-stage fuel injection on diesel combustion and emissions. The fuel-injection system was characterised for all the tested strategies through the measurement of the fuel-injection rate and quantity. In particular, the interaction between the two injection events was identified. The effects of two-stage injection, dwell angle and the interactions between two consecutive injection events on the combustion process and the emissions were investigated in a high-speed direct-injection single-cylinder optical diesel engine using heat-release analysis and high-speed fuel spray and combustion visualisation techniques. The results indicated that the two-stage injection strategy has the potential for simultaneous reduction of nitrogen oxide, soot and unburned hydrocarbon emissions. The results suggested that an optimum fuel quantity in the first injection exists, 0–30%, with which simultaneous reduction of nitrogen oxide, soot and unburned hydrocarbon emissions can be achieved with the added benefits of improved engine performance, fuel economy and combustion noise. However, higher soot emissions were produced, mainly due to the interaction between the two consecutive fuel-injection events whereby the fuel sprays during the second injection were injected into burning regions, as well as reduced soot oxidation due to the continuation of the combustion into the expansion stroke.

In-cylinder studies of split injection in a single cylinder optical diesel engine

In order to meet the ever more stringent emission standards, significant efforts have been devoted to the research and development of cleaner IC engines. Diesel combustion and the formation of pollutants are directly influenced by spatial and temporal distribution of the fuel injected. This study investigates the effect of dwell timing on the in-cylinder combustion process and emissions through the application of 70%/30% split injection strategy in a single cylinder HSDI optical diesel engine. The fuel injection process was illuminated by a high repetition copper vapour laser and recorded synchronously by a high speed video camera. The combustion temperature and soot distribution during the combustion process were measured by a recently developed high speed two-colour system at the authors laboratory. The results indicated that this injection mode has the potential to improve fuel economy and engine performance while substantially reducing the combustion noise, provided that the injection timings are appropriately selected.