Experimental Study On Super-turbo Twin Charger Diesel Engine

The boost technology is the main technology to improve the power, reduce fuel consumption and exhaust emission for diesel engines. Currently the single turbocharge are widely used in China market, however, the single turbocharge always has the difficulty to balance high and low speed conditions, and turbo-lag is always an issue, which will make the diesel engine’s emission, fuel economy and transient performance worse at low speed and transient condition. Along with the new exhaust emission regulation, and to improve the diesel engine’s performance, fuel economy at low speed and transient condition, it is very important to upgrade current single turbocharge technology.The studies of domestic and overseas shows that two stages boost technology can resolve the issues above mentioned. There are two kind of two stages boost system: two stages turbocharge and super-turbo twin charger system. Among them, the two stages turbocharger has been used for mass production in foreign OEMs, but super-turbo twin charger system is seldom studied and reported on diesel engine, only has some application on gasoline engines. In this thesis the super-turbo twin charge system are studied on diesel engine, to explore the matching solution and the technology advantages for super-turbo system on diesel engine.The study probe details into the potentials of super-turbo twin charger system on improving fuel economy and emission at low speed, optimizing on response and emission at transient condition. Tests are based on YC4 D 4.2L diesel engine. First of all, calculate the overall air flow and air pressure demand based on the optimization target, then calculate the pressure ratio distribution between supercharger and turbocharger. Based on the calculation, matched the supercharger and turbocharger; After that, the super-turbo twin charger engine and bench test system are set up; Finally a series of engine tests are done, including the turbocharger re-matching test, super-turbo twin charger full load, part load, and BSFC test; optimize the bypass valve angle to improve fuel economy; and the study of improvement on response and emission at transient condition.The test result shows, at low-mid speed range, super-turbo twin charger system can obviously reduce smoke emission at all load, the lower speed, the more improvement; the super-turbo twin charger system’s influence to fuel economy is related to load: the fuel consumption is lower than original engine at mid-full load, the higher load, the more fuel consumption saving, but at low load, fuel economy is worse than original engine, the lower load, the worse fuel economy; For transient condition, the response and smoke emission are dramatically improved by using super-turbo twin charger system.