Thermodynamic analysis of medium pressure reciprocating natural gas expansion engines

Abstract

Natural gas pressure has to be reduced from medium pressure of 1.724 MPa (250 psia) to lower pressure of 0.414 MPa (60 psia) at Town Border pressure reduction Station (TBS). Currently, the pressure reduction is carried out by throttling valves while considerable amount of pressure energy is wasted. One of the equipment which could be used to recover this waste energy is the reciprocating expansion engine. The purpose of this research is to simulate one-sided reciprocating expansion engine thermodynamically for TBS pressure range. The simulation is based on first law of thermodynamics, conversation of mass and ideal gas assumptions. The model could predict in-cylinder pressure and in-cylinder temperature at various crank angles. In addition, the effects of the engine geometrical characteristics, such as intake and exhaust port area and ports timing on the Indicated work per cycle output are investigated.

Exergy Analysis of a Turbo Expander: Modeling and Simulation

“…6 For energy recovery purposes, the pressure drop can be exploited through dynamic or volumetric expanders by obtaining mechanical energy and thus electricity. [7][8] There are several studies on recovering physical exergy of high pressure natural gas during pressure reduction pro-cess most of them focus on the pressure exergy recovering devices such as turboexpander. [9][10][11] Researchers have developed case studies to estimate the amount of exergy recovery and the economics of turboexpander installations in NG pressure reduction stations.…”