San Diego, CA– Continental Controls Corporation, a manufacturer of controls and components for Gas Turbine and Reciprocating engines, has announced the release of a new design in Air/Fuel ratio control to minimize NOx, CO, and HC emissions.
The Continental Controls Emissions Control Valve is a computerized valve that precisely controls the fuel injection pressure to the carburetor or mixing bowl. It functions as an electronic zero pressure regulator. The computer in the valve measures the voltage from the O2 sensor located in the engine exhaust, and adjusts the pressure at the valve discharge to maintain the proper air fuel ratio. The closed loop operation precisely controls the fuel mixture, which is optimized for natural gas and the catalytic converter.
The ECV5 is a full authority valve, it includes a very low range differential pressure sensor to measure the differential pressure between discharge pressure of the valve and the inlet pressure to the carburetor or mixing bowl. The range of the pressure transducer is -0.5PSID to +1.5PSID. This differential pressure is sensed and compared to the internal pressure demand signal. The valve becomes a very fast acting and precise pressure regulator that maintains the gas injection pressure. The supply pressure required at the inlet to the ECV5 is very low and depends on the fuel flow required and turbo boost pressure for the application.
Zirconium Oxide Oxygen Sensor
The oxygen sensor provides a measure of the oxygen content in the exhaust, its output voltage is fed back to the computer in the valve. The O2 sensor voltage is compared to a set point and a difference or error signal is generated. The error signal is the input to an integral controller in the valve software and is used to adjust the pressure regulator set point to control the oxygen content in the exhaust. The O2 set point is set with the display unit. The voltage from the oxygen sensor is connected to one of the analog inputs to the valve. This signal is digitized and compared to an adjustable set point.
The oxygen sensor output, after a short warm-up period, will increase to about 800 millivolts if the mixture is a little rich, meaning very little oxygen is present. This voltage will transition to a low value when the fuel pressure is reduced, causing the mixture to be leaner, and excess oxygen to be present in the exhaust gas. The O2 sensor does not function until it is heated by the exhaust gas, the valve detects when the sensor is operational and then permits the O2 sensor output to trim the gas injection pressure.
Monitor and Display Unit (TCA)
The TCA Control Unit provides the user interface with the system. It also monitors the operation of the system and displays all data available. The TCA also provides the means for changing the set points for the starting pressure and certain control set points and selected parameters. Some of the adjustments are not available by the TCA without password authorization.
The TCA includes graphic display in the form of bar graphs with numeric values. The operation of the system is monitored by selecting one of the following parameters to be displayed:
-Gas injection pressure and its set point
-Oxygen Sensor Voltage and its set point
The TCA also is provided with a serial port for MOD-BUS communication with other control and data logging systems.
Advantages of the ECV5 Control System
Electronic Pressure Regulator – The electronic regulator is a feedback system that uses a pressure sensor and a controller with proportional and integral control. The gains of the controller are software adjustments that allow the regulator to be tuned to the application. The big difference here is the CCC system operates with a higher gain and therefore is more accurate and much more responsive to load changes than the other systems.