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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

MULTI-DIMENSIONAL MODELING OF A 1 kWe FREE PISTON LINEAR ALTERNATOR

Aimilios Sofianopoulos
Stony Brook University, Stony Brook, NY 11794, USA

Yingcong Zhou
Stony Brook University, Stony Brook, NY 11794, USA

Benjamin Lawler
Stony Brook University, Stony Brook, NY 11794, USA

Sotirios Mamalis
Stony Brook University, Stony Brook, NY 11794, USA

Abstract

Free Piston Linear Alternators (FPLA) have the potential to provide solutions for high efficiency distributed power generation by operating at low-temperature combustion modes and by reducing frictional losses compared to conventional crank-slider engines. The current study is focused on modeling, simulation, and analysis of a natural gas FPLA for small-scale Combined Heat and Power (CHP) applications. The objective of this study is to investigate combustion processes and quantify efficiency losses for operation at 1 kWe power output with low NOx emissions. The proposed FPLA operates in Homogeneous Charge Compression Ignition (HCCI) mode with dilute mixture (φ' = 0.25-0.5) at high compression ratio (~23:1). Mixture dilution is accomplished by residual gas trapping. Modeling results of closed cycle simulations indicated that gross indicated efficiency of 43.1% can be realized, while NOx emissions are kept below regulated standards. Effective equivalence ratio (φ') operating range was identified between φ' = 0.25-0.4 to achieve low pressure rise rates, high efficiency, and NOx emissions below regulated standards. Varying the operating frequency was found to introduce a tradeoff between heat losses and combustion efficiency, which led to maximum gross indicated efficiency occurring at 50 Hz. Reducing stroke to bore ratio (S/B) and increasing surface to volume ratio (S/V) at top dead center (TDC) led to increased heat transfer losses to the cylinder walls and lower combustion efficiency.

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