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Investigating Humidity Effects on Small Offroad Engine SI Performance and Emissions
Technical Paper
2021-01-1224
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Collaborative research outlined in this paper documents recent engine and emission performance of a newer, more robust small SI engine across a sweeping range of relative humidity (RH) having fixed intake air temperature and pressure. The experimental results will show that power correction references to SAE J1349 as well as humidity correction (Kh) reference in EPA 40 CFR §1065 may generically be applied, but do not accurately compensate for the extent of correction required. The test results shared from this particular performance testing of a Kohler KT745 carbureted engine develops the case for a more diverse and less conservative approach to a one-size-fits all strategy related to humidity corrections within the small SI testing community. Moreover, humidity effects for both observed and corrected power, as well as emission corrected constituents (not just NOx) are generally greater than would otherwise be assumed from the literature. From these results, facilities without intake air humidity management may unknowingly bias brake specific emissions of both HC+NOx and CO family emission limits (FELs). Moreover, in defining family emission limits with NOx only correction, general performance repeatability in certifications as well as production line testing (PLT) results throughout the year may contribute to a wider deviation in engine-to-engine emission variability and power than might normally be expected. The following results are specifically for rich engine operation of an air-cooled engine, and subsequent results for stoichiometric air-cooled engine relative humidity effects would need to be discussed separately.
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Citation
Olmos Jr, A., Griffin, S., Price, G., Beilke, N. et al., "Investigating Humidity Effects on Small Offroad Engine SI Performance and Emissions," SAE Technical Paper 2021-01-1224, 2021, https://doi.org/10.4271/2021-01-1224.Also In
References
- SAE International: Surface Vehicle Standard J1349 - Engine Power Test Code - Spark Ignition and Compression Ignition - As Installed Net Power Rating Sept 2011 https://doi.org/10.4271/J1349_201109
- Title 40 (EPA) CFR §1054 - Control of Emissions from New, Small Nonroad Spark-Ignition Engines and Equipment 2020
- Title 40 (EPA) CFR §1065 -Engine-Testing Procedures 2020
- Sodré , J.R. and Soares , S.M.C. Comparison of Engine Power Correction Factors for Varying Atmospheric Conditions Journal of the Brazilian Society of Mechanical Sciences and Engineering 25 3 September 2003 279 284 10.1590/s1678-58782003000300010
- Lindhjem , C. , Chan , L. , Pollack , A. , AND Kite , C. 2004, June Applying Humidity and Temperature Corrections to On and Off-Road Mobile Source Emissions EPA 13th International Emission Inventory Conference: Working for Clean Air in Clearwater Clearwater, FL 8 10
- Husaboe , T.D. , Polanka , M.D. , Rittenhouse , J.A. , Litke , P.J. et al. Dependence of Small Internal Combustion Engine’s Performance on Altitude Journal of Propulsion and Power 30 2014 1328 1333