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Summary: Schuyler Witschi (EE) Lianna Dicke (EE) Luke McKean (ME) Selden Porter (ME) •As oil and gasoline prices continue to rise, along with their environmental concerns, the discovery of natural gas sources in the United States creates the opportunity to utilize natural gas as an alternative for transportation fuel •This project relates to the means for delivering a portion of Compressed Natural Gas (CNG) or any gaseous fuel for use in an internal combustion engine through the use of a mass flow distribution device •It is our goal to create a test fixture which involves the stepper motor provided by CTS Corp. that can control mass flow in a repeatable and accurate manner Gas Flow Theory: Design: Ball Actuator Seat Regulated Output Natural Gas Input Natural Gas Cam • The flow was determined to be choked due to its high pressure differential. The following formula was used to determine the effective valve throat area needed to meet the engineering requirements: • The final design integrates a ball and seal valve operated by a push rod that rides a cam. • The cam is driven by an automotive actuator that uses CAN protocol. Where A0 is the effective throat area, m* is the mass flow rate through the throat, T0 is the total temperature at the throat, P0 is the total pressure at the throat, R is the specific gas constant, and γ is the adiabatic ratio of the gas. This assumes the flow is isentropic meaning it neglects viscosity and assumes there is no heat transfer in or out of the flow. • Lifting the ball a known distance (a function of the cam profile and actuator position) results in a solvable choke area and mass flow rate. • The cam profile can be tuned for different applications with different flow control requirements. Results: • To prevent leak, the ball is pressed into the seat with a spring. • By measuring flow out of the device under certain conditions we could plot the position to lift graph of the device which can be used to tune it • The spring, combined with the force from the pneumatic pressure differential, makes a positive seal. • O-rings are used in all mating surfaces to prevent leak and provide adequate sealing. By 25% throttle opening, the lower value of target flow rate range for 60 psi was met. At the upper limit of the available flow measurement equipment, the flow was still in the target range. Eng. rqmt. # ER1 ER2 ER3 ER4 ER5 ER6 ER7 Importance 9 9 9 9 9 3 3 Description Accuracy of Position Repeatability of Position Leak Rate of Device Operating Voltage Dynamic Range of Position Steps Flow @ 4 bar-g (58 psig) Operating Inlet Pressure Range Unit of Measure % of commanded value % of previous value sccm volts # of motor steps g/s bar-g (psig) Target Value ±5 ±5 25 13.5 123 12-18 4 (58) Measured Value <2 <1 200 12 >100 16 1.7-4.1 (25-60) sccm ms ms 0 N/A NA 260 250 °C (°F) -40-85 (-40-185) bar-g (psig) TBD hrs 10,000 ✓ ✓ ✓ liters 5.7 ✓ Will be acknowledged in the design: ER8 ER9 ER10 9 9 9 Total Leak Open Response Time Close Response Time ER11 3 Operational Temperature Range ER12 3 Burst Pressure ER13 3 Operating life ER14 1 Compatible Engine Size ✓