混合动力汽车的排放特性

© EVS-25 Shenzhen, China, Nov. 5-9, 2010 The 25th World Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition Research Emission Characteristic of Hybrid Electric Transit Bus Yanxin Nie 1, Mengliang Li 2, Junfang Xu 3, Hao Zhang 1 1 EV R&D Center, China Automotive Engineering Research Institue, No.101 Chaotiancun Chenjiaping.Hi-tech District, Chongqing, 400039, P.R.China 2 China Automotive Technology and Research Center, No.218 Chenglindao Dongli District, Tianjin, 300162, P.R.China 3 National NGV Engineering Research Institute, China Automotive Engineering Research Institue, No.101 Chaotiancun Chenjiaping.Hi-tech District, Chongqing, 400039, P.R.China E-mail: nieyanxin@evchina.org Abstract—The Vehicle emission test on Hybrid Electric Transit Bus and Conventional Transit Bus was conducted, using on-board test system, the relationship between emission rate and Vehicle Specific Power were analyzed, providing technical support for the development of hybrid control strategy and the forecast of emission. The results showed that, Hybrid Electric Bus had a obvious performance on saving energy and environmental protection. For the conventional bus, when VSP is less than 0, a certain sum of HC and CO were exhausted, and HC and CO emission rates increase with the decrease of VSP; and NOx, CO2, PM emission rates and fuel consumption rate are stable. For the Hybrid Electric Bus, various emission rates and fuel consumption rate increase with the increase of VSP. Keywords—Emission characteristic, Hybrid Electric Transit Bus, Vehicle Specific Power, Reasearch 1. Introduction With the continuous increase of automobiles and decrease of oil resources, energy-saving and environmental protection become the two major themes of the global auto industry development. Auto companies are competing to research and develope energy-saving and new energy vehicles, such as electric vehicles. Hybrid Electric Vehicle (HEV) has a set of engine system and a set of motor system, not only inherits pure Electric Vehicle (BEV) as a “green car” that has advantages of saving energy and ultra-low emission, but also makes up disadvantage, which is lack of driving mileage of BEV. The hybrid electric system is the most suitable and the most potential to apply to bus (Hybrid Electric Bus, HEB), especially the transit bus. Urban has congested public traffic, and bus stop-goes with driving slow. In this case, fuel consumption and emission of the conventional internal combustion engine vehicle are very poor, and hybrid electric systems are to bring into play to their strengths. So, now require technology and methods to evaluate energy saving and emission reduction effects of HEB. The paper by using on-board test system researches emission characteristic of Hybrid Electric Transit Bus as function over Vehicle Specific Power (VSP). The study can further help to achieve energy saving and emission decrease, as well as provides support for emission forecast. 2. Design of Experiment 2.1 Test System The on-board test system[1] is mainly composed of On- Broad Driving-Cycle Trace System (OBDCTS), Portable Emission Measurement System (PEMS). As shown on Figure 1. OBDCTS is used to follow and reproduce the appointed driving cycle (such as NEDC, Bus Driving Cycle of Chinese Typical Cities and so on) in the experimental field. OBDCTS is mainly composed of vehicle a signal processing instrument, a non-contact photoelectric speed sensor, and a computer with data signal processing software. Driver operates the experimental vehicle via following the appointed driving cycle. OBDCTS computer displays current speed, target speed and many other signals. PEMS is mainly composed of OBS-2200 and ELPI, and is used to test the emission. OBS-2200 can be used to measure the instantaneous concentration of CO、CO2、 H2O、NOx and THC, flow rate of emission, temperature, instantaneous emission pressure of vehicle. ELPI can be used to measure the instantaneous number concentration and mass concentration of different Particle Matter (PM) diameter. Figure 1 Test System 2.2 Test Vehicles In china, there is only a test method for fuel consumption of heavy-duty HEV, and no test method for pollutant emission now. Based on the references of GB/T19754-2005 Fuel Consumption Test Method of Heavy HEV and SAE J2711 Recommended Practice for Measuring Fuel Economy and Emission of Hybrid- Electric and Conventional Heavy-Duty Vehicles, the paper uses the on-board test system to measure the instantaneous emission of transit bus. The test vehicles include a parallel hybrid electric bus (HEB) and a conventional bus(CB). The parallel hybrid electric bus is no external charging HEV, and batteries are Gas Sampling and Flow Measuring Device OBDCTS Computer Host Computer ELPI Photoelectric Speed sensor OBS 2200 PM Sampling Pipe © EVS-25 Shenzhen, China, Nov. 5-9, 2010 The 25th World Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition mainly used to balance the engine power and vehicle driving demand power. The basic parameters of vehicles are shown in table 1. During the test, should weigh the experimental vehicles and the load is 65% of maximum capacity. During the test, Vehicles use the experimental Europe III diesel. Table1 Parameters of Test Vehicles Type HEB CB Dimensions length*width*height 1198 cm*254 cm *318 cm 1198 cm *254 cm *305cm Curb Weight 12190kg 11200kg Max Weight 17800kg 17700kg Maximum Speed 80km/h 80km/h Engine Type ISBE 185 32 ISBE 220 31 Engine State Europe III Europe III Engine Displacement 5.9L 5.9L Engine Rated Power 136kW 162kW Motor Rated Power 65kW / Battery Pack Type Super Capacitor / Voltage Range 260～380V / Capacity 41.25Ah / 2.3 Test Driving Cycle Table2 Parameters of Chinese Typical Cities Bus DC Running Time Running Distances Average Running Speed Maximum Speed 2628s 11.6 km 15.9km/h 60km/h Maximum Acceleration Maximum Deceleration Idle Time Proportion of Idle Time 0.914m/s2 1.543m/s2 762s 29.0% 0 10 20 30 40 50 60 0 500 1000 1500 2000 2500 Time s Sp ee d km /h Figure 2 Test Cycle The study uses Chinese Typical Cities Bus Driving Cycle[2] as the indicated Driving Cycle. The basic parameters of the Driving Cycle are shown as table 2, and velocity versus time curve is shown as figure 2.The Driving Cycle is developed based on buses run features in Beijing, Shanghai and Guangzhou, so the driving cycle is very suitable for the research of bus fuel consumption and emission performances. 3. Test processing and analysis 3.1 Test Preprocessing In accordance with the design of experiment, test vehicles were conduced vehicle exhaust testing. And acquired operation data (velocity, acceleraiton, etc) and instantaneous emission data (emission rate, exhaust temperature, exhaust pressure, etc.). The instantaneous emission data and operation data were matched the time synchronization. Then, these data required quality control (e.g., interpolation of missing values, etc.) to ensure data accuracy. Afer the series of preprocessing, NOx emission rate and speed of HEB versus time curve was showed Figure 3.When the vehicle speed is below 20km/h, NOx emission are relatively stability. And other emission and fuel consumption were the same. Analysis that the engine is idling in such speeds, and the motor drives vehicle. 0 10 20 30 40 50 60 70 0 50 100 150 200 250 300 Time s Sp ee d km /h 0 0.05 0.1 0.15 0.2 0.25 0.3 NO x g/ s Speed NOx Figure 3 NOx emission rate and speed of HEB versus time curve On each test, acquires correlation analysis of track speed and target speed. Through the correlation analysis, correlation coefficient R2 of each test condition is high (up to 0.98 above).This indicates that following of driving cycle is effective. And then test results can reflect the emission condition of buses in the application of China cities. 3.2 Comparison of emission and fuel consumption factors Table3 Comparison of emission and fuel consumption factors (g/km) THC CO NOx PM2.5 FC HEB 0.2084 13.28 12.68 0.268 248.3 CB 0.9157 9.858 14.506 0.558 303.8 Reduction rate 77.2% -34.7% 12.59% 51.97% 18.3% Emission factors and FC factor of HEB were lower CB, except CO factor. The HEB by using braking energy recovery technology and efficient control strategies can save 18.3% of fuel consumption compared with conventional vehicles, while reducing emission produced © EVS-25 Shenzhen, China, Nov. 5-9, 2010 The 25th World Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition from use of 18.3% diesel. As the optimization of combustion, resulted that NOx reduction rate was lower than fuel consumption, THC and PM2.5 reduction rates were higher. Author analyses and believes that HC emission may be excessive reduced resulted that CO reduction rate was negative. HEB still need to optimize the engine control strategy to reduce pollutants emission. 3.3 Based VSP test analysis 3.3.1 Methodology Vehicle Specific Power(VSP) concept was proposed by Jimenezt[3]. VSP takes into account aerodynamic drag, tire rolling resistance and road grade. VSP is generally defined as power per unit mass of the vehicle and is a function of vehicle speed, acceleration, and road grade. VSP for transit buses were estimated based on typical coefficient values that are representative of the types of buses that are analyzed here.Now, there is no uniform calculation formula of heavy-duty vehicle VSP[3]~[6].The paper uses the following formula: 3*049081.3)096403.0sin*807.9( v M avVSP +++∗= θ (1) where VSP is the Vehicle Specific Power (kw/ton); v is instantaneous speed at which the vehicle is traveling (m/s); a is instantaneous acceleration of the vehicle (m/s2); M is vehicle mass (ton); θ is instantaneous road grade; 0.096403 is rolling resistance term coefficient. VSP was estimated for each second of measured in-use data. Related research shows that VSP and Emission have a strong correlation. Mengliang Li[7] researched based-va mode emission characteristic, and cosidered that conventional bus average emission rate change with va is relatively simple, as a whole V-shaped with the lowest point in the va=0; Hybrid electric bus average emission change with va is more complicated, which may be because the hybrid electric bus with complicated control strategies. Because VSP can better reflect the vehicle loading situation than va. The Paper researches based-VSP mode emission characteristic. Analysis of the emission rates and fuel consumption rate compared with VSP curve, it will -20 ~ 20kw/ton VSP (over range part of the data assigned to the border interval) to be divided into 18 interval Bin by 2.5kw/ton increments, then average emission rates and fuel consumption rate of each Bin, and thus research emission and fuel consumption rate of transit bus as function over VSP[8]. 3.3.2 Conventional Bus After test data were preprocessed, the joint distribution of emission rate, fuel consumption rate of conventional vehicle compared with VSP was showed Figure 4. Further deals with the data, obtains conventional bus emission rate, fuel consumption rate curves with VSP. As shown on Figure 5.When VSP is less than 0, which means that acceleration is at least less than -0.0964m/s2, a certain sum of HC and CO were exhausted, and HC and CO emission rates increase with the decrease of VSP; and NOx, CO2, PM emission rates and fuel consumption rate are stable, which HC, CO, NOx, CO2, PM emission rate and fuel consumption rate remaine at 0.018 g /s, 0.032 g/s, 0.030 g/s, 0.50 g/s, 0.95mg/s and 0.14 g/s. When the vehicle is greater than 0, various emission rates and fuel consumption rate increase with the increase of VSP, and are much larger than when the vehicle is less than 0. Figure 4 The joint distribution of emission rate, fuel consumption rate of conventional vehicle and VSP Figure 5 Conventional bus emission rate, fuel consumption rate curves with VSP 3.3.3 Hybrid Electric Bus Figure 6 the joint distribution of emission rate, fuel consumption rate and VSP The paper used the same approach to deal with the date of HEB. The joint distribution of emission rates, fuel consumption rate of HEB compared with VSP is showed Figure 6. The joint distribution of HEB was seen more © EVS-25 Shenzhen, China, Nov. 5-9, 2010 The 25th World Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition decentralized compared with conventional bus, this is because HEB has more complex engine control. Further deals with the data, obtains hybrid electric bus emission rates, fuel consumption rate curves with VSP. As shown on Figure 7.Various emission rates and fuel consumption rate increases with the increase of VSP. when VSP is lower than 0, various emission rates and fuel consumption rate are stable, which HC, CO, NOx, CO2, PM emission rate and fuel consumption rate remaine at 0.001 g/s, 0.045 g/s, 0.019 g/s, 1.81 g/s, 0.50 mg/s, 0.59 g/s. When VSP is lower than 0, HC, CO, NOx and PM emission rates of the HEB are more than conventional bus.And CO2 emission and fuel consumption rate is higher than conventional bus because the engine is still in a stable status and charges batteries. Figure 7 Hybrid Electric bus emission rate, fuel consumption rate curves with VSP 4. Conclusion By using on-board test system, it helpes well to understand and study that real world performances, control strategy of vehicles. Emission factors and FC factor of the HEB were lower the CB.The HEB has about 20% the effects of energy- saving and emission reduction. The conventional bus: When VSP is less than 0, a certain sum of HC and CO were exhausted, and HC and CO emission rates increase with the decrease of VSP; and NOx, CO2, PM emission rates and fuel consumption rate are stable. The Hybrid Electric Bus: The joint distribution of hybrid electric bus is seen more decentralized compared with conventional bus, this is because HEB has more complex engine control. Various emission rates and fuel consumption rate increases with the increase of VSP. when VSP is lower than 0, various emission rates and fuel consumption rate are stable. By repeating the above method, can get various emission rates and fuel consumption rate of the same type of conventional bus with VSP curves.And then, can predict emission and fuel consumption of this type of vehicle under different driving cycle. 5. References [1] LI Mengliang and NIE Yanxin, Emission characteristics of parallel hybrid electric bus as a function of the instantaneous degree of hybridization, 5th IEEE Vehicle Power and Propulsion Conference, VPPC '09, September.2009, pp: 330-334 [2] GB/T19754-2005 Fuel Consumption Test Method of Heavy HEV [3] Jimenez, Understanding and Quantifying Motor Vehicle Emissions with Vehicle Specific Power and TILDAS Remote Sensing. Cambridge US: Massachusetts Institute of Technology, 1999. [4] Frey, H., N. Rouphail and H. Zhai. Link-based Emission Factors for Heavy-duty Diesel Trucks Based on Real-World Data . Transportation Research Record: Journal of the Transportation Research Board, Vol.2058, No.2008, 2008, pp: 23-32. [5] Koupal, J., M. Cumberworth, and H. Michaels, et al. Draft Design and Implementation Plan for EPA’s Multi-Scale Motor Vehicle and Equipment Emission System (MOVES) (EPA420-P- 02-006). Washington: U.S. Environmental Protection Agency, 2002. [6] Zhai, H., H. Frey, and N. Rouphail. A Vehicle-Specific Power Approach to Speed- and Facility-Specific Emissions Estimates for Diesel Transit Buses [J]. Environmental Science Technology, Vol. 42, No. 21, 2008, pp: 7985–7991. [7] LI Mengliang, NIE Yanxin, GAO Jidong and LI Wei, GUO Xuexun, A comparative study on emission of Hybrid Electric Bus and Conventional Bus, Automotive Engineering magazine, Vol. 32, No. 3, March. 2010, pp: 193-197. [8] nieyanxin, Based PEMS Characteristics of Heavy-duty Hybrid Electric Transit Bus Emission. Wuhan china: WuHan technology university, 2009 6. Author Engineer.Yanxin Nie Electric Vehicle Research & Development Center, China Automotive Engineering Research Institute, No.101 Chaotiancun Chenjiaping.Hi-tech District, Chongqing, P.R.China Tel: 86-23-68662112 Fax: 86-23-68662112 Email:nieyanxin@evchina. org Yanxin Nie, born in 1985, Master’s degree Researcher. Mengliang Li China Automotive Technology and Research Center, No.218 Chenglindao Dongli District, Tianjin, P.R.China Tel: 86-22-84771906 Fax: 86-22-84771906 Email: mengliang_li@163.com Mengliang Li, born in 1964, Master’s degree Engineer. Junfang Xu National NGV Engineering Research Institute, China Automotive Engineering Research Institute Co., Ltd. No.101 Chaotiancun Chenjiaping.Hi-tech District, Chongqing, P.R.China Tel: 86-23-68651392 Fax: 86-23-68829330 Email:xujunfang2003@163.com Junfang Xu, born in 1985, Master’s degree