Research On The Technique Of Emission Measurement System To Fulfill Update Light-Duty Passenger Vehicle Regulation

Due to low accuracy and repeatability problem of pollutants mass emission measurenent happen while measuring ULEV/EURO4, SULEV/EURO5or chinese Level4vehicle emission, conventional CVS emission system was pushed to be upgraded. In order to fulfill measurement requirement of extreme low emission exhaust, emission system suppliers and vehicle companies, Government work together to develop new generation exhaust emission analysis system. This paper was part of the research work.The main factors which affect the accuracy in super ultra-Low emission measurement include the original exhaust concentration, same pollutant conponents in the ambient air which is involved in emission mass calculation, water vapor in the exhaust, outgasing in sampling system, inaccuracy compensation of DF calculations, improper dilution ratio be used and so on。Two solutions were defined aiming at improving emission measurement accuracy. The first is still using traditional CVS principle but improving structure and optimizing analyzer, the other is developing an alternative sampling system, named bag mini-dilition (BMD) system to replace CVS sampling system. The sampling principle of constant volume sampler is clear and simple, thus the CVS structure is reliable. CVS has been defined as only sampling syslem of legal emission mass test together with vehicle model driving cycle method for decades. There are large amount of CVS users now all over the world. But, traditional structure of CVS has some limitation, especial used for beyond ULEV emission test. The data repeatability is shown unacceptance..There is argument in keeping CVS structure but some modification or using a new sampling principle as alternative sampling method, such as BMD system. Bag Mini-Diluter has performed excellent behavior in emission test of engine test bed, it has good correlation with exsiting huge CVS. Now, it maybe is time to discuss whether replacing CVS in the SULEV exhaust gas measurement. Up to now, try to upgrade CVS to fulfill EURO V is still main idea in Europe. The paper presents more validating test to compare CVS and BMD with different engines and optimzing BMD product to market.This paper analyses error sources and validates test result of emission system. The information and research work is based on participating R&D of new genaration of exhaust emission analysis system in AVL-Pierburg.Main contents and structure of the paper list as below. Chapter one:Review of vehicle emission regulations implementation course in USA, EU and China. The vehicle emission limit value shows clearly more stringent control action in future. Lower emission level means more complicate and higher precision system is needed. How to using one analysis system to cover high concentration in cold start model and even lower concentration than ambient level become challenge task for emission sampling system and analysis system. Whether traditional CVS could meet requirement has become question mark. It’s pointed out that updating standard CVS is an urgent, necessary but a hard job.Chapter two:In order to improve performance of CVS, the theory of CVS and category were introduced. Some detail of CFV-CVS was summarized. Error analysis was used to deduce the contribution of instrument error to system error. One set of exhaust data of an SULEV were used to break down contribution of each influence factors. It’s gotten that the error rising from exhaust concentration took as main portion of system measurement error. Total error was grouped by DF calculations error, contaminant mass calculation error and the imperfect process in measuring. And some improvement idea was given corresponding to part. These improvement idea or scheme was verified though testing one medium duty vehivle. These test results also showed that the modified CVS was competent for measuring ULEV/EURO4level vehicles, but further optimization method and improment had to be done for measuring SULEV/EURO5level vehicles.Chapter three:To verify gas anti-background noise, An prototype detect cell of FID is built. An "low range" FID analyzer is tuned with different burning fuel, span gas and assistance burn air. Nominated a detect limit evaluation method, and then measured the real FID detector performation. After adjusting each flow rate, to get a ideal physical FID burning cell demission. The specifications of "Low Range" shows lower detect limit data. In order to combine4range into a whole range, and amplify electronic current signal of THC analyzer, one24-bit A/D converter was used to substitute416-bit A/D converters. Thus only one signal amplifier can assure all measurement in one range which avoids the data jump in range switching. It’s gotten from comparative experiment those parameters like detect limit, zero drift, responding times and so on were improved signifitly.Chapter four and chapter five focus on BMD system. Descript operation theory of AVL BMD and some testing with SULEV was introduced firstly. Error sourcing for BMD system was conducted. One propane sparge installation was set up to simulate vehicle exhaust and assess the error of BMD exhaust emission testing system. It’s shown that repeatability of AVL BMD relies on the extent of attenuation of tailpipe pressure fluctuation and the precision of direct vehicle exhaust volume system is key technology to realize high precision BMD. A pressure management unit was designed to maintain low pressure fluctuation in the entry of UFM. Pulsation muffler and resonating type of damper based on sonic interference principle to attenuate the pulsation were introduced to the test bench. Experimental results of flow rate tested by UFM were compared between with and without pulsation management system. It’s gotten that UFM with pulsation management system satisfied the request on precision in ULEV and SULEV level exhaust emission measurement.