AN EVALUATION OF A 2/4-STROKE SWITCHABLE SECONDARY EXPANSION INTERNAL COMBUSTION ENGINE

AN EVALUATION OF A 2/4-STROKE SWITCHABLE SECONDARY EXPANSION INTERNAL COMBUSTION ENGINE

Presented by, Nirmal Joy, M7B, 7412 Guided by, Prof. Leena R. Assistant Prof. Dept. of Mechanical Engineering Introduction The length of time for oil remaining to produce was only 52.9 years based on the current oil production rate.The vehicle IC engine is one of the main oil consumption products.Therefore it is necessary to develop and optimize IC engine working process for improving the total energy conversion efficiency to ease the oil crisis.The secondary expansion means the burned gas, after working in a traditional 4-stroke combustion cylinder, is transferred into another cylinder to expand again.

IntroductionThe 2/4-stroke switchable secondary expansion IC engine is a 4-cylinder engine with two combustion cylinders and two expansion cylinders. The expansion cylinder could switch its working mode between 2-stroke and 4-stroke to perform different secondary expansion modes just by varying the valve timing. The 2-stroke secondary expansion mode has great advantages in high load condition on both fuel efficiency and power output, but it is not suitable in low load condition The 4-stroke secondary expansion is applied to maintain the high energy conversion efficiency in the low load condition. The 2-stroke secondary expansion modeThe burned gas is transferred into a 2-stroke secondary expansion cylinder to expand again.The combustion cylinder works on the traditional 4-stroke working cycle.The expansion cylinder only concludes two strokes, intake and exhaust.One expansion cylinder needs to cooperate with two combustion cylinders to form a whole working cycle.The exhaust valves of the combustion cylinders and the intake valve of the expansion cylinder are connected by a chamber.

The 4-stroke secondary expansion modeThe burned gas is transferred into an expansion cylinder, in which the burned gas goes through four strokes without combustion .One combustion cylinder and one expansion cylinder could form a whole working cycle.The exhaust valve of the combustion cylinder is connected with the intake valve of the expansion cylinder by a connecting pipe directly.

The 4-cylinder 2/4-stroke switchable secondary expansion IC engine The 4-cylinder 2/4-stroke switchable secondary expansion IC engine 4-stroke secondary expansion IC engine.But the 2-stroke secondary expansion IC engine needs at least three cylinders.There are two combustion cylinders and two expansion cylinders.Both combustion cylinders work on the traditional 4-stroke cycle, and both expansion cylinders can switch its operation between 2-stroke and 4-stroke by just varying the valve timing. The exhaust valves of both combustion cylinders and the intake valves of both expansion cylinders are connected by a chamber to regulate the pressure during the burned gas transferring process.

Experiment 2-stroke & 4-stroke secondary expansion engine has been developed. Valve timing switching device not developed.A 1D simulation model was established by GT-Power for evaluating the 2-stroke and 4-stroke secondary expansion mode to complete the study. The results show reasonable agreements between simulation and experimental data.Results and analysis

The most fuel saving area mainly concentrated in the high load condition near 2000 RPM, which is the speed to shift for most passenger vehicles. In most area of the high load condition, the fuel saving rate was usually larger than 8%.

Most fuel saving area of the 4-stroke secondary expansion mode focused on the low load conditions below the speed of 2000 RPM.For a vehicle driving in the urban traffic, the engine speed below 2000 RPM is the most frequently-used working condition, because of the frequent stop and start. In such working condition, the 4-stroke secondary expansion engine could save fuel by over 10% compared with the traditional IC engine.

The fuel saving rate was over 10% in most working conditions for the 2/4-stroke switchable secondary expansion engine, which could cover most frequently-used condition for a general vehicle engine. The fuel saving rate was higher in the speed below 3000 RPM compared with the high speed conditions, which means the secondary expansion IC engine based on the burned gas transferring could obtain higher fuel economic performance in the low speed condition. Conclusion A traditional 4-cylinder gasoline IC engine can be transformed into a secondary expansion IC engine with two 4-stroke secondary expansion working units by just redesigning the camshaft, intake, and exhaust manifolds. For the 2-stroke secondary expansion mode, it is more responsive to operate in high load condition. For the 4-stroke secondary expansion mode, the engine could achieve high fuel economic performance in the load and low speed condition. By combining the advantages of the 2-stroke and 4-stroke working modes, the 2/4-stroke switchable secondary expansion IC engine could obtain high economic performance in most working condition, which covers all the frequently-used working conditions for a general vehicle. References [1] Yong Lu, Pucheng Pei, Yongfeng Liu, An evaluation of a 2/4-stroke switchable secondary expansion internal combustion engine, (2014). [2]R.H. Miller, Supercharging and internal cooling cycle for high output, Trans ASME, 69(1947) 453. [3]ILMOR Engineering, 5-Stroke Concept Engine, http://www.ilmor.co.uk/capabilities/5-stroke-engine, 2013.9.10. [4]J. Martinez, Ilmor engineering shows off 5-Stroke engine concept, http://www.motorauthority.com/news/1034099_ilmor-engineering-shows-off-5-strost-engine-concept, 2013.8.9. Thank You