| With the implementation of the more stringent exhaust emission regulations, the emission of light-duty vehicle is controlled effectively. And the emission of Heavy-Duty Vehicle (HDV) is become a focus of the Environmental protection and management departments. The bus is a heavy vehicle of large quantities and frequent used, and is an important factor of vehicle emissions in the cities. The main content of this research is testing complete-vehicle emissions of the bus on the chassis dynamometer. This project can provide theoretical basis for drafting the regulation of the complete-vehicle emissions and fuel economy.The paper focuses on the development of the test method for emissions of HDV and analyzes the advantages and disadvantages and technical characteristics of the engine-dynamometer,on-board measurement chassis-dynamometer test method. Compared with the engine-dynamometer and on-board measurement system, the chassis-dynamometer has obvious advantages in the test accuracy and stability. So it can become the primary method of assessing the emissions of HDV in the future.The current worldwide regulations and the researches on vehicle road-coast of HDV are introduced. The project Performs experiments on the test vehicle. The different road-load between actual travel and on the chassis dynamometer is analyzed. And the chassis-dynamometer reproduced the actual travel road-load on the dynamometer.For the performance evaluation of heavy vehicle emissions and fuel consumption, the current worldwide regulations and standards for HDV on the emissions and fuel efficiency are introduced and analyzed. The necessity is discussed and demonstrated to establish a complete-vehicle based test and appraisement system for HDV emission and fuel economy.The project's research results include the following aspect:(1) Research the emissions of different cycles on the test vehicle and analyze the influence of different cycles on emissions. The NOx,HC,CO,CO2 mileage emission factors and Hundred kilometers fuel consumption of CCBC are 1.91 times, 0.36 times,1.42 times,1.33 times,1.27 times of WTVC. Research the contribution of the different operating modes of different cycles including accelerate,decelerate,constant speed and idle. Contribution rates of accelerating models to gaseous pollutants are the highest. The contribution rates of CO and NOx is up to 67.1% and 65.4%. The emissions of different feature mileage of WTVC are studied. The experiment reveals that the emissions of downtown cycle are higher than other cycles.(2) Collect the operating modes and conditions of the engine of test vehicle and confirm the working range of different cycles. The test contrasts the difference of working range of the emission regulations cycles and actual travel cycles. The conclusion is that the emission regulations cycle can't reflect the complete-vehicle condition in use.(3)Contrast the influence of different technologies on the complete-vehicle emissions. Compared with diesel-powered vehicle, the hybrid electric city bus (HEB) has lower common emissions, equivalent CO2 emission and fuel consumption. The CNG vehicle has advantages on the emissions control of CO,NOx and PM but has higher THC emission and CO2eqv emission.(4) The state of complete-vehicle has a great influence on the emissions. Contrast the emissions of cold-start and hot-start by chassis dynamometer and provide the reference for drafting of the regulation.The aim of the project is researching the way of testing the complete-vehicle emission of bus by chassis-dynamometer, providing the data basis for estimating and controlling of actual emissions of the bus, and offering the cycle data for emission scalibration of the engines and vehicles. This article could help to improve the testing level of our country.
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