1. Active Reciprocating Compressor Valve Assembly P16452
Team Members:
Negar Salehi– Mechanical Engineer
Ian Nanney– Mechanical Engineer
Robert Osborn– Mechanical Engineer
Keith Leung – Electrical Engineer
Chris Reynolds – Electrical Engineer
Faculty Advisors:
William Nowak
Dr. Jason Kolodziej
Project Overview
Active Valve + Vessel Assembly
Background:
Standard compressors operate with passive mechanical valves that utilize springs to direct airflow based on the pressure difference. Significant gains on efficiency and wear are possible if these valves are actively controlled (limiting impact velocities, chattering, etc.). The design, build, and test an active compressor valve assembly is necessary to investigate different technologies that can be used to actuate the valve under the appropriate conditions (speed, temperature, pressure, etc).
Project Goal:
Design and build an active reciprocating compressor valve assembly that controls flow of air through the compressor. The demonstration will require instrumentation to prove the design is meeting reciprocating compressor like specifications. The final assembly consists of two major subsystems:
A designed test pressure vessel that mimics the presence of a compressor
The active valve assembly consisting of four solenoid actuated poppets and displacement measurement system
The complete vessel assembly consists of four poppets, each housed by a brass component wrapped and with 38 AWG wire. The brass components are then placed inside a white plastic piece that gets mated to a square aluminum body. Together this sub assembly is an valve that is attached to the open end of the pressure vessel. The Active Valve Assembly is then signaled using Labview to control inlet and outlet valves to allow pressurized air to flow into and out of the vessel. 1
Customer Requirements:
Primary customer requirements include but are not limited to the following:
Closing and opening of valves are controlled actively
Test facility simulates compression cycle
Active valve assembly is interchangeable with passive valve assembly
Compatible with LabView
Valves operate at 4 Hz
Theory
Displacement Measurement System
Concept to the right illustrates the selected system with a regulator valve that introduces the pressurized air into the assembly, an actuator that releases the air to atmosphere and a vacuum valve that sets the pressure back to 0 psi in the tank. Within the tank is a pressure sensor to monitor the pressure. The external control system signals the vacuum valve, regulator and actuator so that the vessel maintains a sinusoidal like pressure curve.
To ensure that the poppets are opening and closing properly, the displacement of the poppets had to be measured. The team was experiencing issues with the regular displacement measurement systems that use laser or Eddie current sensors. To use both type of sensors, they would have to face the poppets. There was no way of setting the sensors up within the vessel or anywhere outside the vessel in a way that they face the poppets.
The team decided to use hall effect sensors in designing a displacement measurement system to monitor the movement of poppets. The Hall Effect sensor consist of a thin piece of semiconductor material passing a continuous current through itself. When the device is placed in a magnetic field, the flux lines exert a force on the semiconductor material which as a result will produce a voltage. This voltage reading can be converted into a displacement measurement.
The application of the hall effect sensor for our project was to measure the magnetic field of the magnet inside the poppets and as a result, the displacement of them while the system is running.
One of the important customer requirements is pressurizing the vessel in a way that it follows a compression cycle. Simscape simulations were generated based on the combination of valves and tanks determined in system level concept selection. The simulations assisted the team in better understanding the flow of air through the system and combination of orifice areas that can result in a compression cycle pattern. The simulation results shown in the plot are close to ideal.
Results
System Design
The plot shows the displacement of one poppet that was measure while running the system. To obtain this graph, a hall effect sensor was used to measure the change in the magnetic field caused by the movement of the magnet inside the poppet. The voltage output was then converted to displacement. When the poppet is fully open, its position is approximately at 0.02 inches and when it’s fully closed, its position is at approximately 0.14 inches.
Below is the AutoCAD drawing of the final design of the system. It consists of the active valve assembly top and bottom section, sealed on the open side of a designed pressure vessel with an O-ring. The inlet and vacuum valves are also drawn in pink.
The picture on the bottom right, shows the airflow movement inside the valve assembly. The active actuation system utilizes solenoids. The light brown piece shows the solenoid cover. The wires are wrapped around this cover to build a solenoid, and inside is a cylindrical magnet fitted into a poppet. When the system is turned on, the solenoids create a magnetic field that moves the magnet inside the poppet and as a results the poppets open and close the exit orifice.
The final system architecture including all the controls system is shown to the right.