This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Comparisons of Thermocouple, Time-Averaged and Mass-Averaged Exhaust Gas Temperatures for a Spark-Ignited Engine
ISSN: 0148-7191, e-ISSN: 2688-3627
Published February 01, 1982 by SAE International in United States
Annotation ability available
Accurate knowledge of engine exhaust gas temperatures is important for engine design and diagnostic efforts. To survive the harsh exhaust gas environment, most practical devices for determining exhaust gas temperatures are relatively large. Because of their size, these devices do not provide instantaneous gas temperatures but provide a single equilibrium temperature. This investigation compared computed thermocouple equilibrium temperatures of the exhaust gas to computed time-averaged and mass-averaged gas temperatures for nine different engine conditions. Mass-averaged gas temperatures are directly related to the exhaust gas energy whereas thermocouple and time-averaged gas temperatures are not directly related. For most of the engine conditions of this study, the exhaust gas energy based on time-averaged gas temperatures was about 10% lower than the energy based on mass-averaged temperatures and the energy based on thermocouple temperatures depended on the thermocouple properties.
The mass-averaged, time-averaged and thermocouple exhaust gas temperatures varied as a function of engine conditions. For a spherical thermocouple with a diameter of 0.076 cm and an emissivity of 0.85, the computed thermocouple equilibrium temperature was about 20 K lower than the time-averaged exhaust gas temperature for variations in engine speed, spark timing and equivalence ratio. Variations in engine load did not appreciably change the thermocouple equilibrium temperature, however the time-averaged gas temperature decreased for increasing engine loads.
The thermocouple temperature for a fixed engine condition was examined as a function of thermocouple emissivity, diameter and shape. The calculations resulted in thermocouple temperatures which increased for decreasing values of emissivity for all thermocouple diameters and for decreasing values of the thermocouple diameters for moderate to high emissivities. For low emissivities, decreasing thermocouple temperatures were obtained for decreasing values of the thermocouple diameter.
CitationCaton, J., "Comparisons of Thermocouple, Time-Averaged and Mass-Averaged Exhaust Gas Temperatures for a Spark-Ignited Engine," SAE Technical Paper 820050, 1982, https://doi.org/10.4271/820050.
- Mollenhauer, K. “Measurement of Instantaneous Gas Temperatures for Determination of the Exhaust Gas Energy of a Supercharged Diesel Engine,” SAE paper 670929 1967
- Kaneko, Y. Kuroda H. Tanaka, K. “Small Engine - Concept Vehicles,” SAE paper 710926 1971
- Eltinge, L. Marsee F.J. Warren, A.J. “Potentialities of Further Emissions Reduction by Engine Modifications,” Presented at the Automotive Engineering Congress, Society of Automotive Engineers Detroit, MI 1968
- Caton J.A. Heywood, J.B “Models for Heat Transfer, Mixing and Hydrocarbon Oxidation in an Exhaust Port of a Spark-Ignitea Engine,” SAE paper 800290 1980
- Heywood, J.B. Higgins, J.M. Watts P.A. Tabaczynski, R.J. “Development and Use of a Cycle Simulation to Predict SI Engine Efficiency and NOx Emissions,” SAE paper 790291 1979
- Benson R.S. Brundrett, G.W. “Development of a Resistance Wire Thermometer for Measuring Transient Temperatures in Exhaust Systems of Internal Combustion Engines,” in” “Temperature-Its Measurement and Control in Science and Industry,” Vol 3 631 653 1962
- Benson, R.S. “Measurement of Transient Exhaust Temperatures in I.C. Engines,” in” “The Engineer,” 376 383 1964
- Wendland, D. W. “The Effects of Periodic Pressure and Temperaure Fluctations on Unsteady Heat Transfer in a Closed System,” NASA-CR-72323 1968
- Caton, J.A. “Heat Transfer, Mixing and Hydrocarbon Oxidation in an Engine Exhaust Port,” M.I.T., Ph.D. Thesis 1980
- Lancaster, D.R. Krieger R.B. Lienesch, J.H. “Measurement and Analysis of Engine Pressure Data,” SAE paper 750026 1975
- Caton J.A. Heywood, J.B. “An Experimental and Analytical Study of Heat Transfer in an Engine Exhaust Port,” in” “International Journal of Heat and Mass Transfer,” 24 4 581 596 1981
- Holman, J.P. “Heat Transfer,” McGraw-Hill Book Company Second Edition 1968
- Mikic, B.B. personal communication 1979
- Moffat, R.J. “Gas Temperature Measurement,” “Temperature-Its Measurement and Control in Science and Industry,” 3 553 571 1962
- Whitaker, S. “Forced Convection Heat Transfer Correlations for Flow in Pipes, Past Flat Plates, Single Cylinders, Single Spheres and for Flow in Packed Beds and Tube Bundles,” A.I.Ch.E. 18 2 361 1972