Decreasing NOx Emission Of Compression Ignition Engine Fueled With Diesohol By EGR

With the development of the national economy and increasing of automobile quantity, the shortage problem of petroleum is also increasingly serious, and the harmful emissions of automobiles have become the main pollution sources of the atmosphere environment. Ethanol is renewable resources of energy, and it is also a cleaning fuel. It is far important to study the application of ethanol fuel on internal combustion engines for moderating the shortage problem of petroleum, decreasing the emissions of exhaust and realizing the strategy of sustainable development. Currently, the automobile engines fueled with ethanol / diesel mixture have been included in our national brainstorm plans. All countries of the world have drawn up the increasingly strict emission regulations to limiting the pollution of exhaust gases of engines. The harmful compositions in the diesel engine mainly include the carbon monoxide (CO), unburned hydrocarbons (HC), the oxides of nitrogen (NOx) and particulate matters (PM), etc. Because the air/fuel ratio of the diesel engine is great, the CO and HC emissions are lower, and the main emissions are NOx and PM. So the regulations of all countries mainly limit emissions of the two exhaust gases. Test cycle of Euro â…¢ESC 13-mode was carried on a compression ignition engine of CY4102AZLQ fueled with E0 and E101 diesohol. Compared with the fuel of E0, the brake specific emissions of NOx and HC of the E101 fuel increased 5.7% and 35.1% respectively, and the CO and Rb decreased 13.0% and 17.7% respectively. At the same time, the weighted brake specific fuel consumption increased 10.3%. The brake specific emissions of HC and CO of the two kinds of fuels both meted their limits, but NOx both obviously exceeded its limit value. The formation conditions of the NOx in diesel engine are high temperature, rich oxygen and the residence time of oxygen and nitrogen under high temperature. The technology of exhaust gas recirculation (EGR) can decrease the density of oxygen in the intake gas and the max burnt temperature inside the cylinder effectively, so it can suppress the formation of NOx and it is one of the available methods which can decrease the emission of NOx. A low-pressure loop of EGR system was designed for lowering the NOx emission of the engine and making it also satisfy the Euro â…¢emission regulation. The exhaust gases flowed from front of the turbine to front of the compressor, through the EGR valve which limited its discharge and the EGR cooler, then mixed with the fresh air and entered into the compressor. EGR experiments under the whole work condition were studied using the fuel of E101 diesohol. The effects of EGR on the performance and emission behavior of the automobile were as follows: 1. With the increasing of EGR rate, the temperature before turbine (Tr) was gradually higher under the low load of all speeds. With the increasing of load, Tr presented uptrend, and it was more and more obvious with the increasing of the EGR rate. Under the whole work condition, air/fuel ratio was gradually lower along with the increasing of the EGR rate, and the decreasing level also enlarged gradually with the increasing of the load. The effect of speed on air/fuel ratio was not great. 2. The engine torque scarcely changed with the EGR rate at low load. Along with the increment of load, the engine torque descended with the increasing of EGR rate, and the load was higher, the drop range was also bigger. When the speed was fast, the influence of the increment of the EGR rate on the torque was bigger. Be hardly changed when added little EGR at low load; When the EGR rate was bigor the load was high, be increased with the increasing of the EGR rate, and when the value of the EGR rate is bigger, the increasing range is also bigger. 3. Under the whole work condition, the NOx emission decreased with the increasing of the EGR rate. When the load changed from low to high, the drop range of NOx emission was increased with the increasing of the EGR rate. The suppression effect of EGR on NOx emission was more effective at high load. When the speed was different, the drop range of NOx emission varied little with the increasing of the EGR rate. 4. When added little EGR at all loads of medium speed, the Rb scarcely varied. The Rb and its increasing range were gradually increased with the EGR rate from low to high load at other conditions. 5. Under the whole work condition, the CO emission increased with the increasing of the EGR rate, and the EGR rate was bigger, the increasing range was more obvious. At small EGR rate or high loads of all speeds, the HC emission hardly varied or decreased a little with the increasing of the EGR rate. HC emission increased with the increasing of EGR rate under other conditions, and it increased faster at low load. On the premise of guaranteeing the dynamical performance, economy and stability of the engine, the principle of establishing the optimum EGR rate under each mode was found according to the influence regulation of the variety of the EGR rate on the engine and the value of brake specific emission of each exhaust gas. Big EGR rate should be chose at medium load, small EGR rate should be chose at low/high load, and no EGR should be added at full load. While choose the optimum EGR rate, it should satisfy the request of decreasing NOx, compromise the variety of Rb, HC and CO and guarantee that the HC and CO still can meet their Euro â…¢limits.