1 Copyright © 2005 by ASME Proceedings of ICEF2005 ASME Internal Combustion Engine Division 2005 September 11-14, 2005, Ottawa, Canada ICEF2005-1221 HIGH EFFICIENCY HYBRID CYCLE ENGINE Nikolay Shkolnik, Ph.D. LiquidPiston, Inc. 77 Kirkwood Rd. West Hartford, CT 06117 Tel. (860) 236-9969 Fax. (413) 751-6070 Email: NShkolnik@LiquidPiston.com Alexander C. Shkolnik LiquidPiston, Inc. 77 Kirkwood Rd. West Hartford, CT 06117 Tel. (617) 939-4363 Fax. (413) 751-6070 Email: Shkolnik@mit.edu ABSTRACT A "High Efficiency Hybrid Cycle" (HEHC) thermodynamic cycle is explored. This four-stroke cycle borrows elements from Otto, Diesel, Atkinson, and Rankine cycles. Air is compressed into an isolated combustion chamber, allowing for true isochoric combustion, and extended duration for combustion to proceed until completion. Combustion products expand into a chamber with greater volume than intake. We provide details of a compact HEHC design implementation using rotary pistons and isolated rotating combustion chambers. Two Pistons simultaneously rotate and reciprocate and are held in position by two roller bearings. One Piston performs intake and compression, while the other performs exhaust and expansion. We predict a reduction of energy losses, moving part counts, weight and size over conventional engines. KEYWORDS: ENGINE, EFFICIENCY, HYBRID, THERMODYNAMIC CYCLE, ROTARY INTRODUCTION The internal combustion engine suffers from fairly low efficiency due to theoretical thermodynamic limitations of ideal cycles as well as additional energy losses due to deviations from ideal cycles and friction between moving parts. Typically, only ~30% of the chemical energy of fuel is converted into useful work; ~40% is removed as heat by cooling water, and another 30% is lost with exhaust gases. There are many different types of engines, operating on various thermodynamic cycles, and an even greater number of modifications within each type. These different types exist because each offers certain advantages over others. At the same compression ratio, Diesel cycle engines are slightly less efficient than Otto cycle engines, however the Diesel engine is capable of operating at higher compression ratios at which it becomes more efficient than the Otto engine. Stirling cycle engines are superior to both Otto and Diesel cycle engines because they allow part of the exhaust energy to be recuperated, but these engines are very cumbersome (and therefore expensive) to build and maintain. At the same time, Rankine cycle steam engines offer some advantages over internal combustions engines, but are very large and slow. The development of the patent pending High Efficiency Hybrid Cycle engine aims to combine the benefits of several thermodynamic cycles. In this paper we present the HEHC cycle, followed by a discussion of the thermodynamic model of the cycle, and conclude with a sample compact design implementing the HEHC cycle. NOMENCLATURE c v = specific heat at constant volume c p = specific heat at constant pressure k = c p /c v M air = Mass of air intake volume N = ratio of final expansion volume to intake volume p = pressure q out = heat rejected at constant pressure from state 4 to state 1 Q in = heat input due to fuel combustion per amount of air intake r = r C = compression ratio (V 1 /V 2 ) r E = expansion ratio (V 4 /V 3 ) R = universal gas constant T = temperature V = volume η th = thermal efficiency