Simulation of The Effects of Valve Timing Misalignment on Performance in Spark Ignition Engines

Abstract

Engine performance can be improved by changing the valve opening (or closing) timing without any cam profile changes. In this study, a simple simulation model was created for valve timing misalignment, which is an assembly defect in the engine. Due to misalign, the opening angles of the valves have been changed between +20 degrees and −20 degrees compared to the normal opening angles. The engine performance resulting from this advanced and retarded valve timing was examined for a four-stroke, spark ignition, single-cylinder engine with an engine volume of 393 cc. In this study conducted for the 1000-7000 rpm engine speed range, first the in-cylinder pressure data were examined in detail and then the general engine performance parameters were examined. Accordingly, opening the valves earlier than necessary at low and medium engine speeds increases the maximum in-cylinder pressure, and at high engine speeds, it reduces the maximum in-cylinder pressure due to excessive decrease in volumetric efficiency. It was observed that the volumetric efficiency, which was 0.89 at medium speeds, decreased to 0.70 due to misalignment. Regardless of whether the misalignment is positive or negative, pressure fluctuations increase during the valve lapping process. Maximum braking torque occurs at medium engine speeds. Positive misalignment reduces braking torque, especially for low and high engine speeds. However, especially at high speeds, negative misalignment reduces the pumping torque. While the pumping torque for high engine speeds was −3.78 Nm, it increased up to −5.04 Nm due to positive misalignment. Whether it is positive misalignment or negative misalignment, brake specific fuel consumption tends to increase in both cases. At low and medium engine speeds, negative misalignment or positive misalignment always increases residual gas fraction. As a result of the study, it was seen that misalignment negatively affected engine performance. However, it is seen that the value accepted as reference is the optimum value for the operating speed range of the engine. With this study, it has been understood that valve timing, as well as valve system design, is vital for engine performance.

Keywords

• Engine simulation
• misalignment
• performance
• valve timing

References

1. 1. Ferguson, C. R., & Kirkpatrick, A. T. (2015). Internal combustion engines: applied thermosciences. John Wiley & Sons.
2. 2. Alagumalai, A. (2014). Internal combustion engines: Progress and prospects. Renewable and Sustainable Energy Reviews, 38, 561-571.
3. 3. Grenning, W. (1991). History of the Otto–Langen Engine. Gas engine magazine. Febrery.
4. 4. Reitz, R. D. (2013). Directions in internal combustion engine research. Combustion and Flame, 160(1), 1-8.
5. 5. Merker, G. P., Schwarz, C., Stiesch, G., & Otto, F. (2005). Simu-lating Combustion: Simulation of combustion and pollutant for-mation for engine-development. Springer Science & Business Media.
6. 6. Rajput, R. K. (2009). Engineering thermodynamics: A computer approach (SI units version). Jones & Bartlett Publishers.
7. 7. Caton, J. A. (2015). An introduction to thermodynamic cycle simulations for internal combustion engines. John Wiley & Sons.
8. 8. Babagiray, M., Solmaz, H., Ipci, D., & Aksoy, F. (2022). Model-ing and validation of crankshaft speed fluctuations of a single-cylinder four-stroke diesel engine. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engi-neering, 236(4), 553-568.

9. 9. Babagiray, M., Kocakulak, T., Ardebili, S. M. S., Solmaz, H., Çınar, C., & Uyumaz, A. (2022). Experimental and statistical in-vestigation of different valve lifts on HCCI combustion, perfor-mance and exhaust emissions using response surface method. Energy, 244, 123184.
10. 10. Çınar, C., Uyumaz, A., Polat, S., Yılmaz, E., Can, Ö., & Solmaz, H. (2016). Combustion and performance characteristics of an HCCI engine utilizing trapped residual gas via reduced valve lift. Applied Thermal Engineering, 100, 586-594.
11. 11. Qiang, Y., Ji, C., Wang, S., Xin, G., Hong, C., Wang, Z., & Shen, J. (2024). Study on the effect of variable valve timing and spark timing on the performance of the hydrogen-fueled engine with passive pre-chamber ignition under partial load conditions. Ener-gy Conversion and Management, 302, 118104.
12. 12. Gupta, H. N. (2012). Fundamentals of internal combustion en-gines. PHI Learning Pvt. Ltd.
13. 13. White, C. M., Steeper, R. R., & Lutz, A. E. (2006). The hydrogen-fueled internal combustion engine: a technical review. Interna-tional journal of hydrogen energy, 31(10), 1292-1305.
14. 14. Wang, Y., Zu, B., Xu, Y., Wang, Z., & Liu, J. (2016). Perfor-mance analysis of a Miller cycle engine by an indirect analysis method with sparking and knock in consideration. Energy Con-version and Management, 119, 316-326.
15. 15. Agarwal, A. K. (2007). Biofuels (alcohols and biodiesel) applica-tions as fuels for internal combustion engines. Progress in energy and combustion science, 33(3), 233-271.
16. 16. Heywood, John B. (1988). Internal combustion engine funda-mentals. New York :McGraw-Hill,
17. 17. Liu, F., Shi, Z., Hua, Y., Kang, N., Li, Y., & Zhang, Z. (2019). Study on the intake valve close timing misalignment between the maximum volume efficiency and the none backflow on a single cylinder diesel engine. Journal of Engineering for Gas Turbines and Power, 141(2), 021026.
18. 18. Bücker, I., Karhoff, D. C., Klaas, M., & Schröder, W. (2013). Engine in-cylinder flow control via variable intake valve timing (No. 2013-24-0055). SAE Technical Paper.
19. 19. Abidin, S. F. Z., Zulkefli, M. H., Ja’at, N. M., & Hassan, M. N. (2021). Effect of Camshaft Degreeing towards Performance of a Passenger Car. Fuel, Mixture Formation and Combustion Process, 3(1), 1-7.
20. 20. Sher, E., & Bar-Kohany, T. (2002). Optimization of variable valve timing for maximizing performance of an unthrottled SI engine—a theoretical study. Energy, 27(8), 757-775.
21. 21. Claywell, M., Horkheimer, D., & Stockburger, G. (2006). Investi-gation of intake concepts for a formula SAE four-cylinder engine using 1D/3D (Ricardo WAVE-VECTIS) coupled modeling tech-niques (No. 2006-01-3652). SAE Technical Paper.