13

Compression n0- 2 Expansion frJfv T... = in K -JT^^ÎiSS^v,

Compression n0- 2 Expansion frJfv T... = in K -JT^^ÎiSS^v,

Figure 1. Temperature Profile adjacent to combustion chamber wall at various times in the cycle. Motoring operation.

(From: Ikegami. SAE 860467)

Figure 1. Temperature Profile adjacent to combustion chamber wall at various times in the cycle. Motoring operation.

(From: Ikegami. SAE 860467)

Ikegami went on to demonstrate the impact of such phenomena on an insulated engine. An increase in wall temperature of 300 degrees C was calculated to result in a reduction in peak heat flux slightly over ten percent. This compares with values on the order of 50 percent predicted with classical models for the same wall temperature increase.

Although this type of computation is in its infancy, and several questions remain about the legitimacy of assumptions employed in the necessary turbulence sub-models, these results do demonstrate the plausibility of effects not considered by classical analysis techniques -effects for which experimental evidence has also been shown. Furthermore, it is instructive to note that Lawton [21], using different computational techniques, demonstrated the same phenomena as Ikegami. Recent boundary layer measurements of Farrell [22] also show evidence of such phenomena.

Concluding Recommendations In the material just reviewed, one conclusion comes to the fore again and again. Through cycle simulations. insulated engine testing, instantaneous heat flux measurements. and in-cylinder computational analysis, the conclusion which continues to emerge is that the future of the low heat rejection engine concept is dependent on a more firmly based understanding of the fundamentals of in-cylinder heat transfer. This conclusion points the direction of future research needs. These needs involve fundamental studies aimed at resolution of the thermal boundary layer through both analysis and experimentation.

References

1. Griffiths, W. J., "Thermodynamic Simulation of the Diesel Engine Cycle to show the Effect of Increasing the Combustion Chamber Wall Temperatures on Thermal Efficiency and Heat Rejection," Wellworthy Topics. No. 63. 1976.

2. "Heat Losses and Insulation in Reciprocating Engines." Ricardo. DP 76/82. 1976.

3. Kamo. R.. Bryzik, W., "Adia-batic Turbocompound Engine Performance Prediction." SAE 780068, 1978.

4. Wallace, F. J.. Way, R.J.B., Vollmer, H.. "Effect of Partial Suppression of Heat Loss to Coolant on the High Output Diesel Engine Cycle," SAE 790823, 1979.

5. Watson, N., Kyratatos, N. P.. Holmes. K.. "The Performance Potential of Limited Cooled Diesel Engines," Proc. Instn. Mech. Engrs., Vol. 197A. 1983.

6. Wallace. F. J.. Kao, T. K.. Tarabad, M. , Alexander. W.D.. Cole, A.. "Thermally Insulated Diesel Engines." Proc. Instn. Mech. Engrs., Vol. 198A. No. 5. 1984.

7. Morel. T.. Fort. E. F.. Blumberg. P. N.. "Effect of Insulation Strategy and Design parameters on Diesel Engine Heat Rejection and Performance." SAE 850506. 1985.

8. Hoag. K. L.. Brands. M. C.. Bryzik, W.. "Cummins/TACOM Adiabatic Engine Program." SAE 850356. 1985.

15. Moore, C. H.. Hoehne, J. L.. "Combustion Chamber Insulation Effect on the Performance of a Low Heat Rejection Cummins V-903 Engine." SAE 860317, 1986.

16. Hoag. K. L., "Measurement and Analysis of the Effect of Wall Temperature on Instantaneous Heat Flux." SAE 860312. 1986.

17. Enomoto. Y. . Furuhama. S.. "Heat Transfer into Ceramic Combustion Chamber Wall of Internal Combustion Engines." SAE 861276. 1986.

9. Bennethum. J.E., Hakim, N.S., "The Low Heat Rejection (Adiabatic) Reference Engine Design for On-Highway Applications," Proceedings of the Twenty-Third Automotive Technology Development Contractors' Coordination Meeting. DOE. pp. 63-79, 1985.

10. Assanis, D.N., "A Computer Simulation of the Turbocharged Turbocompound Diesel Engine System for Studies of Low Heat Rejection Engine Performance," Ph.D. Thesis. Massachusetts Institute of Technology, 1985.

18. Huang. J. C.. Borman. G. L.. "Measurements of Instantaneous Heat Flux to Metal and Ceramic Surfaces in a Diesel Engine." SAE 870155. 1987.

19. Woschni. G., Spindler, W. . Kolesa, K.. "Heat Insulation of Combustion Chamber Walls -A Measure to Decrease the Fuel Consumption of I. C. Engines?." SAE 870339, 1987.

20. Ikegami, M.. Kidoguchi. Y. . Nishiwaki. K.. "A Multidimensional Model Prediction of Heat Transfer in Non-fired Engines." SAE 860467. 1986.

11. Coers. R. B., Fox. L. D. . Jones. D. J.. "Cummins Uncooled 250 Engine." SAE 840459. 1984.

12. Toyama. K.. Yoshimitsu. T.. Yamaguchi. H. . Shimauchi. T. . Nakagaki. T. . "Heat Insulated Turbocompound Engine." SAE 831345. 1983.

13. Wade. W. R.. Havstad. P. H.. Ounsted. E.J.. Trinker. F.H.. Garwin. I.J., "Fuel Economy Opportunities with an Uncooled DI Diesel Engine," I Mech E C432/84, 1984.

14. Walzer, P., Heinrich. H. . Langer, M., "Ceramic Components in Passenger Car Diesel Engines," SAE 850567, 1985.

21. Lawton, B.. "Effect of Compression and Expansion on Instantaneous Heat Transfer in Reciprocating Internal Combustion Engines," Proc. Instn. Mech. Engrs.. Vol. 201. NO. A3. 1987.

22. Farrell. P. V.. Verhoeven. D.D., "Heat Transfer Measurements in a Motored Engine Using Speckle Interferome-try." SAE 870456. 1987.

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