UBC Theses and Dissertations

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UBC Theses and Dissertations

Design and development of a high pressure CNG intensifier Touchette, Alain


A two-Stage, variable-stroke rotary-reciprocating intensifier was built in order to provide high pressure natural gas to a diesel engine. In this application, the intake pressure is variable (20 to 200 bar), as is the mass flow (2 to 50 kg/hr) and the delivery pressure is constant (200 bar). The main feature of this intensifier is that it can provide any mass flow in this range regardless of intake pressure or operating speed. The mechanism used to provide the variable mass flow uses a variable stroke. This mechanism, as well as the intensifier configuration, was chosen after investigating the alternative design concepts. This investigation showed that the variable stroke would be an energy efficient method of controlling the intensifier mass flow. The specific intensifier dimensions were determined using a graphical design optimization technique. Prototype testing was limited to speeds below its design operating range because of component failures due to inadequate cooling. In this speed range, the variable stroke proved to be capable of controlling the intensifier mass flow. The rotary-reciprocating geometry was not as energy efficient as originally expected. This shOrtfall is due to large frictional losses in the rotary gas seals and roller bearings. These frictional losses are essentially constant for all strokes which results in low efficiencies at low mass flows. It is suggested that a new intensifier design be considered: a configuration which retains the variable stroke capability of the rotary reciprocating design but eliminates the main sources of frictional losses by using non-rotating pistons.

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