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2016-11-08
Journal Article
2016-32-0033
Tiago J. Costa, Mark Nickerson, Daniele Littera, Jorge Martins, Alexander Shkolnik, Nikolay Shkolnik, Francisco Brito
Abstract This paper describes predictive models and validation experiments used to quantify the in-chamber heat transfer of LiquidPiston’s rotary 70cc SI “XMv3” engine. The XMv3 engine is air cooled, with separate cooling flow paths for the stationary parts and the rotor. The heat transfer rate to the stationary parts was measured by thermal energy balance of that circuit’s cooling air. However, because the rotor’s cooling air mixes internally with the engine’s exhaust gas, a similar procedure was not practical for the rotor circuit. Instead, a CONVERGE CFD model was developed, and used together with GT-POWER to derive boundary conditions to estimate a ratio between rotor and stationary parts heat transfer, thus allowing estimation of rotor and total heat losses. For both cases studied (5000 and 9000 rpm under full load), the rotor’s heat loss was found to be ∼60% that of the stationary parts, and overall heat losses were less than 35% of supplied fuel energy.
2014-11-11
Technical Paper
2014-32-0104
Alexander Shkolnik, Daniele Littera, Mark Nickerson, Nikolay Shkolnik, Kukwon Cho
Abstract This paper describes the development of small rotary internal combustion engines developed to operate on the High Efficiency Hybrid Cycle (HEHC). The cycle, which combines high compression ratio (CR), constant-volume (isochoric) combustion, and overexpansion, has a theoretical efficiency of 75% using air-standard assumptions and first-law analysis. This innovative rotary engine architecture shows a potential indicated efficiency of 60% and brake efficiency of >50%. As this engine does not have poppet valves and the gas is fully expanded before the exhaust stroke starts, the engine has potential to be quiet. Similar to the Wankel rotary engine, the ‘X’ engine has only two primary moving parts - a shaft and rotor, resulting in compact size and offering low-vibration operation. Unlike the Wankel, however, the X engine is uniquely configured to adopt the HEHC cycle and its associated efficiency and low-noise benefits.
2012-05-10
Video
Combustion engines are typically only 20-30% efficient at part-load operating conditions, resulting in poor fuel economy on average. To address this, LiquidPiston has developed an improved thermodynamics cycle, called the High-Efficiency Hybrid Cycle (HEHC), which optimizes each process (stroke) of the engine operation, with the aim of maximizing fuel efficiency. The cycle consists of: 1) a high compression ratio; 2) constant-volume combustion, and 3) over-expansion. At a modest compression ratio of 18:1, this cycle offers an ideal thermodynamic efficiency of 74%. To embody the HEHC cycle, LiquidPiston has developed two very different rotary engine architectures ? called the ?M? and ?X? engines. These rotary engine architectures offer flexibility in executing the thermodynamics cycle, and also result in a very compact package. In this talk, I will present recent results in the development of the LiquidPiston engines. The company is currently testing 20 and 40 HP versions of the ?M?
2010-04-12
Technical Paper
2010-01-1110
Stephen Nabours, Nikolay Shkolnik, Ryan Nelms, Gnanaprakash Gnanam, Alexander Shkolnik
The High Efficiency Hybrid Cycle (HEHC) is a thermodynamic cycle which borrows elements of Diesel, Otto and Atkinson cycles, including: Air compression to a high ratio, followed by fuel injection and compression ignition (Diesel). Constant volume combustion (Otto) Over-expansion (Atkinson) Optionally, internal cooling heat recovery via steam generation (Rankine). Simple air standard analysis predicts this cycle to be 17% more efficient than diesel and 19% more efficient than Otto. The construction of a prototype rotary engine implementing this cycle is also described in detail. The main engine components consist of a rotor in pure rotation and two reciprocating gates directly driven by overhead cams. This combination separates the working mixture into three separate volumes. At a given rotor position each volume operates at a different part of the cycle. For instance, intake/compression, combustion, expansion/exhaust are occurring simultaneously in separate chambers.
2008-10-06
Technical Paper
2008-01-2448
Nikolay Shkolnik, Alexander Shkolnik
In this paper we discuss a rotary implementation of the High Efficiency Hybrid Cycle (HEHC) engine. HEHC is a thermodynamic cycle which borrows elements of Diesel, Otto and Atkinson cycles, characterized by 1) compression of air only (e.g. Diesel), 2) constant volume heat addition (e.g. Otto), and 3) expansion to atmospheric pressure (e.g. Atkinson). The engine consists of a compressor, an isolated combustion chamber, and an expander. Both compressor and expander consist of a simple design with two main parts: a rotor and an oscillating rocker. Compared to conventional internal combustion engines, in which all processes happen within the same space but at different times, in this engine, all processes are occurring simultaneously but in different chambers, allowing for independent optimization of each process. The result is an engine which may offer up to 57% peak efficiency, and above 50% sustained efficiency across typical driving loads.
Viewing 1 to 5 of 5