The Development And Research For The CNG Mono-fuel Engine YC6112ZLQ

With the world economy continuously increasing, the problem of the energy sources increasingly becomes the focus of every country government. Furthermore, with the quantity of the automotives retain, its emissions have become the most fearful pollutant. Nevertheless, the automotives combustion with the natural gas, one of which advantages is much cleaner and its exhaust emission is lower than the common automotives. On the development of future, the natural gas will be the best fuel "which bring on low emission". Therefore, it's greatly significant to solve the problem of the energy sources and environment by developing the natural gas engine. On the type of YC6112ZLQ, turbocharged and intercooled diesel engine, by improving the combustion system, adding the natural gas supply system, ignition system and control system, the compression ignition engine will be transferred to the spark ignition engine, and the single fuel of natural gas engine is designed, which is electronic controlled, turbocharged and intercooled, lean burning and single spraying, and its engine has good performances of power, economy and emission. The improving work process on the base engine is introduced in this thesis. The electronic control natural gas engine is transformed from the diesel engine. And its improving works could be summarized as follows: 1. Improving the air intake and the burn systems. The type of the combustion chamber is transformed from the reentrant ωto the tub, the compression ratio is decreased from 17.5 to 10.5, and the spray nozzle hole on the cylinder cap is changed into the spark plug hole. 2. Improving on the material of the valve and valve retainer. Add some material which is able to bear high temperature and has good lubricated into the material of the valve and valve retainer, which could enhance their wearability on high temperature. 3. Design the setting position of temperature and pressure sensors. 4. Add the natural gas supply system, igniting system and engine control system which are made by WOODWARD Company in America. 5. Reduce the diesel provide system such as the high pressure fuel injection pump and the fuel spray nozzle. Additional, the matching and optimizing demarcating tests of the key accessories is carried on. Such as follows. Choose the appropriate turbocharger to meet the design demand on the full load characteristic curve, the exhaust gas bypass valve of turbocharger should have appropriate angle. At high speed, the bypass valve should open at certain angle, which would make the boosted pressure decrease and the torque of engine decrease to the designing need. Choose the appropriate compression ratio and combustion chamber. The compression ratio should meet the demand of the power performance and a wide ignition range. The type of the combustion chamber must be enhancing combustion and could be shortening the combustion duration. By the tests of the engine parameters such as fuel-air ratio (phi)and spark advance angle (adv), and considering the economy performance, exhaust temperature and emission and etc. Onevery operating conditions, we can choose the appropriate fuel-air ratio and spark advance angle, which will optimize the engine performance. By using the two-way catalyst apparatus, the exhaust emission could meet Europe II level, and the reliability level could meet the design demand. Conclusions could be summarized by the test results as follows: 1. From the view of the technique and the cost of development, developing the natural gas engine is a good method on the diesel engine. The technique of single injecting and lean burning, could improve the power and economy performances meanwhile. Its cost is acceptable for consumer because of using the original accessories. 2. From the result of the test, the tub combustion chamber could not only improve fuel and air mixture combustion, but also could maintain combustion stability and improve the thermal efficiency and decrease the NOx emission if making the mixture leaner. 3. Comparing with the turbocharged and intercooled diesel engine, the maximum combustion pressure decreases much on the CNG engine. So removing the first compression piston ring groove austenitic carrier, which could advance the piston intensity and heat transferring capability. Because of the combustion temperature of CNG engine is much higher than the diesel engine, to avoid the piston ring blocked by heat expanding, the first piston ring glove clearance should be appropriately increased. 4. To shorten flame travel, the combustion chamber center should depart the piston center and close to the spark plug, which could make the combustion better.