Optimization of Exhaust Port and Valves for Heavy duty engines

Abstract

The efficiency of combustion engines is crucial for their future development, prompting researchers to explore various factors to enhance performance. Among these factors, exhaust gases hold significant potential. Typically, exhaust gases carry about 30-40% of the engine's energy, which often remains underutilized. Although technologies like turbochargers have made progress in recovering some of this lost energy, a considerable amount is still lost due to the energy required to expel the exhaust gases from the combustion chamber.
This thesis aims to improve the flow in the exhaust port of a 13L Volvo engine by using optimization strategies. STAR CCM+ is used for steady state computational fluid dynamics (CFD) analysis, focusing on flow and pressure losses at various valve lifts.
Different optimization strategies were analyzed and among that parameter optimization was the best suited for this thesis. Parameter optimization aims at modifying parameters like radius, angle, area. Several parameters were modified to the exhaust port and valves and tested to identify the most effective improvements. Four cases were performed to analyze the performance. In case 1, aligning the valve face with the cylinder head showed flow improvement at certain valve lifts, but overall, the performance was similar to the base geometry. In case 2, with the port positioned above the cylinder head, resulted in deteriorated flow after a few lifts. Case 3, which involved enlarging the port neck area, and case 4, which involved smoothing the valve edges along with case 3, showed improvements in flow by 5.3% and 6.9%, respectively. However, the fourth modification posed complications due to a reduced valve seat area. The study also investigates the potential of a diffuser design to analyze the maximum exhaust flow.
The improvement in efficiencies is also analyzed and it proves that improving the exhaust flow does not lead to the expected improvement in efficiency. The findings demonstrate that while certain geometric changes can enhance exhaust flow, each modification presents unique challenges that must be carefully considered.

Popular Abstract

Internal combustion engines are majorly used in transportation sectors. Throughout the years ICE have undergone significant developments in terms of being more efficient, reliable and to reduce emissions. Even with this level of advancements, losses are still a huge factor. One such loss is pumping loss. Exhaust gases contain a significant portion of energy after combustion and need to be pushed out of the combustion chamber. Improper flow of exhaust gases can lead to combustion problems and drop in efficiency due to retention of exhaust gas in the chamber. However, the exhaust gases are not entirely able to move out of the combustion chamber which causes the piston to use some work to push the gases out. This work done by piston is the pumping work.
This master's thesis focuses on the optimization of the exhaust port geometry to improve the exhaust gas flow to reduce blowdown losses. Using advanced computational fluid dynamics (CFD) software Star CCM+, analysis of different designs and its influence on the flow of exhaust gases. The goal is to identify and implement design changes that maximize the exhaust gas flow and to analyze the improvements in efficiency.
Efficient exhaust gas flow is crucial for the performance and environmental impact of internal combustion engines. This project investigates how modifying the geometry of exhaust ports can enhance the flow of exhaust gases, reducing pressure losses and improving overall engine efficiency. By employing CFD simulations and optimization techniques, the study seeks to identify and implement design changes that offer significant performance improvements. The findings of this research could lead to the development of more advanced, cleaner engines.
The results indicate that modifying the exhaust port to have a gradual expansion area can lead to good improvement in exhaust flow. On the other hand, it is impossible to make a large improvement in flow without modifying the valve geometry. Also, even with the best improvement in exhaust flow the efficiency does not correspond to the same amount of improvement.

• author: Balakrishnan, Gokul Kanna
• supervisor: Per Tunestål
• organization: Department of Energy Sciences
• course: MVKM05 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• report number: LUTMDN/TMHP-24/5563-SE
• ISSN: 0282-1990
• language: English
• id: 9174060
• date added to LUP: 2024-09-11 11:16:23
• date last changed: 2024-09-11 11:16:23