CFR’s XCP Platform Provides Functional System Control
CFR’s expandable control platform (XCP) provides a powerful means of controlling the functional systems of the CFR F1/F2 and F5 engines as well as capturing process data and storing it in a readily accessible database for later retrieval. CFR Engines process capability ensures conformance to ASTM D2699, D2700, D2885 and D613. With the necessity of today’s labs to comply with the requirements of ISO/IEC 17025, it is ever more important to accurately control process parameters and to ensure that systems are calibrated in a timely manner with accurate records of calibration.
As an example, maintaining a steady mixture manifold temperature is important to obtain repeatable octane ratings on the F2 (MON) engines. From temperature tuning, it is understood that changing the mixture manifold temperature by 2°F can change the octane number by 0.1 when using
an analog meter. If the temperature is not well maintained to the setpoint, the engine may not pass fit-for-use testing.
To meet the requirements, engineers commonly turn to PID controllers. PID stands for Proportional, Integral, and Derivative. The PID controller will have a value, referred to as gain, assigned to each term. While these values could be determined theoretically, if an accurate mathematical model of the system existed, this is rarely the case, and instead, empirical methods are used to “tune” the controller to meet the desired performance. The mixture manifold temperature should heat to its setpoint and reach steady state quickly with minimal steady state error. Error is simply the difference between the set point and the measured value. The controller will run in a continuous loop with the following steps:
• Measure the value
• Calculate the error and new output value • Update the output • Wait some amount of time…and then repeat
While the amount wait time will vary for each application, one simple rule is not to run the controller faster than the input can be measured or the output can be set. In the case of XCP, the hardware input has a refresh rate of 1.25 Hz, therefore, the control loop should be programmed to execute at a maximum rate of 1 Hz. Each time the control loop executes, how the controller responds to each of the gain values can be thought of as follows:
• Proportional – What is the error right now?
• Integral – What has the error been over the previous N number of loops? • Derivative – How quickly is the error changing?
With an understanding of these elements, the temperature controller can be tuned with relative ease.
There is always the inescapable formula of garbage in equals garbage out. Regardless of how well the controller is tuned, if the sensor is not producing accurate values, the temperature will not be accurately controlled. The controller should be programmed to respond appropriately and safely if issues with the sensor (RTD) or actuator (heater) are detected. The mixture temperature should never change more than a few degrees every second, even with the heater on full power. If the temperature is changing rapidly, it would indicate a faulty RTD or a fault in the wiring. In either case, the controller should respond by removing power from the heater and signaling an error to the operator. The same idea applies to the heater. If the controller is set to full power, yet the temperature is not increasing, either the heater is bad, there is a fault in the wiring, or the actual temperature is unreliable. One simple example is when two RTDs are connected to the incorrect input receptacles. The controller should recognize this as a fault, turn off the power to the heater, and report the condition to the operator.
The XCP panel from CFR Engines, Inc. includes the capabilities outlined above to control the three heaters of the CFR engine. Using the XCP software has the additional benefit of automatically including the temperature set points and measured values into the rating report.
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CFR (IQT) is the leading cetane instrument for scientific research applications
The CFR Ignition Quality Tester (IQT) is widely used by the petroleum industry to measure the cetane value of commercial diesel fuels in certification and quality control applications. These uses cover petroleum diesel at a variety of cetane levels (often containing FAME and/or cetane improver additive) and ultra-high cetane renewable diesel (where IQT test method EN 15195 is the referee test method for cetane in the CEN paraffinic diesel specification, EN 15940). Less well known within the petroleum industry are the IQT’s capabilities for scientific research, a field where historically universities and government research entities engage in studies of fundamental combustion processes and fuel chemistry effects. These studies present unique challenges for the instrument in terms of the severity of the operating conditions and the flexibility needed for configuring special experiments.
The IQT is, by a large margin, the leading cetane instrument
for scientific research on fuel ignition and combustion processes. Since its introduction to the market in 1998, the use of the IQT has been cited in hundreds of published scientific papers. It is common for these researchers to make ignition delay measurements while operating the instrument at pressures and temperatures that are much greater than those specified in the standard test methods. The IQT’s thick-walled combustion chamber and rugged construction have proven to provide many years of reliable service despite the mechanical and thermal stresses imposed by such conditions.
IQT research units can be equipped with features such as user-configurable research software, enhanced data acquisition systems, dynamic injection pressure instrumentation and custom, variable displacement fuel injection equipment. High speed combustion pressure data from every injection event is recorded and maintained by the IQT computer for the service life of the instrument. Injector needle lift data and injection pressure data are also stored. The high-speed data is easily exported for analysis such as the Rate of Heat Release (RHR), the determination of physical and chemical ignition delay, and the development of new autoignition detection algorithms.
Like all CFR IQT customers, IQT researchers can depend on expert technical support directly from the engineers who design and build the instruments.
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The Volumetric Blending System… a new solution for perfecting your Reference Fuel Blending
The precise blending of primary, secondary, and standard fuels per ASTM D2699, D2700, and D613 is essential for the calibration and standardization of the CFR engines used for the determination of the research octane number, motor octane number, and cetane number. To support reference fuel blending accuracy, CFR Engines Inc. (CFR) has developed a Volumetric Blending System (VBS).
The VBS system has a unique design that utilizes pneumatic technology instead of electric pumps to minimize set-up requirements, minimize fuel handling, and enable flexibility of unit placement. It also includes an added distribution valve that can be used for either a warm-up fuel or calibration fuel.
System operation is simple, with fuels being pumped by using the latest pneumatic technology direct from the fuel drum to the calibrated burettes found on the distribution panel positioned in your laboratory. This removes the use of header tanks or the requirement for manual handling of the primary or secondary reference fuels. ASTM specification burettes are equipped with zero calibration devices and minimum diameter calibration sections for exact data reading. The flow-limited distribution valve ensures optimum mixture accuracy and service safety allowing you to always be ASTM compliant.
Like all CFR Engines Inc. products, the Volumetric Blending System (VBS) is designed and manufactured in the USA. The VBS is offered either as a wall mounted or cabinet mounted system with the flexibility to add amber burettes to either configuration.
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