Engines & Power Electronics : Testing & monitoring


High Accuracy Angle Measuring Device for Industrial, Medical, Scientific or Recreational Use

A UW-Stout researcher has developed a high-accuracy angle measurement system that addresses the problems inherent to commercially available systems. In this novel device, a high accuracy rotary optical encoder is controlled by a microprocessor. The encoder consists of rotating optical disks and sensors that are precisely formed and placed to read angles with 0.001 arc second sensitivity (average) and better than ±0.1 arc second accuracy (single readings), which is comparable to the accuracy of the high-end commercial encoders currently on the market. This accuracy is maintained with strategies that combat the mechanical sources of error that are known disadvantages of other devices. The system can also be adjusted to compensate for any asymmetrical shifts that may occur. Mechanical sources of error and noise are further minimized by precision placement of disks and sensors, as well as low-friction reference points that keep components centered and level during rotation. In addition, multiple sensor heads eliminate major readout errors and remove the need for recalibration. All of these features and benefits are contained within a design that is both compact and portable. Beyond high accuracy and portability, the cost of this new angle measurement system is substantially lower than a high-end commercial system because it is easily constructed from readily available industrial grade components, bringing the production cost to roughly $2,000. Strikingly, this cost is comparable to the advertised price of other rotary position encoders that are less than one tenth as accurate. Its high accuracy, low cost, and portability make this new angle measurement system a strong option for use in virtually any of the current applications for absolute rotary encoders.

Internal Combustion Engine Exhaust Filtration Analyzer

UW-Madison researchers have developed an improved method and system for analyzing the performance of filtering materials used in DPFs and other exhaust filtration devices.  The new method is able to replicate actual in-use processes that occur during filling and regeneration of filtration devices.  The ability to accurately replicate realistic conditions and manipulate key system parameters sets the new method apart from previous techniques and allows for more accurate and complete analyses of exhaust filtration materials.

Control of the various operational parameters is provided by variable exhaust flow restriction with an actuating valve and orifice in the exhaust system.  In a diesel engine, the exhaust back pressure can be modulated to control the flow characteristics of the exhaust with an actuating value through feedback from a differential pressure sensor placed across the filtering material.  A mass flow controlled orifice may be incorporated downstream of the exhaust analyzer to control the filtration velocity independent of engine operating conditions.  The orifice also allows control of total downstream flow rate while diluting the sampled exhaust with a constant flow of air and provides a constant volume ratio of exhaust and air.  Both improve the evaluation of filter performance by reducing the number of dynamically changing parameters.  The exhaust also may be cooled in stages to control temperature-related characteristics of the exhaust, increasing the accuracy of results.

The implementation of exhaust filtration devices will continue to grow with increasing government regulation of emissions from mobile and stationary internal combustion engines.  As these regulations become more stringent and encompassing, exhaust filtration analysis will be an increasingly important tool in the filtration material development and certification of DPFs and other exhaust filtration devices.

Non-Intrusive Monitoring of Combustion Chambers

A UW–Madison researcher has developed an improved monitoring system for engine combustion chambers that is less expensive and requires fewer components than currently available systems. Rather than using sensors located within the combustion chambers, this monitoring system makes use of a valve that allows air and fuel to enter and exit the chamber. When the piston compresses the air/gas mixture, the valve seals the chamber to contain it for the combustion process. The high pressure exerted by the piston compression causes the valve head to bend slightly, displacing the valve stem. Because the stem extends out of the chamber, displacements as small as 1/1000 of an inch can be measured by a sensor located on the outside of the chamber. To calculate pressure, the displacement is compared to a plot of valve movement versus cylinder pressure. Then a control system uses that information to adjust engine operation.

Spectrographic Sensor for Precisely Measuring Gas Parameters in an Internal Combustion Engine

A UW-Madison researcher has developed a device capable of accurately and quantitatively measuring gas temperature and concentration within a cylinder. The device includes a fiber optic light source installed in a spark plug. The fiber optic source introduces a light signal into the combustion space within the cylinder. A high-speed spectrographic sensor, such as a spatial heterodyne spectrometer, analyzes the strength of the light after it interacts with the combustion gases. A computer can then use this information to automatically determine gas temperature and water concentration, and to measure the absorption spectra of the combustion gases.

Continuous-Wave Laser Source for High Speed Spectroscopy

UW-Madison researchers have devised a simple and inexpensive laser-based spectroscopy approach that is similar to FTIR in principle; however, because it has no moving parts, it offers many advantages, including the ability to produce spectra every microsecond or faster. The laser is generally fashioned as a fiber laser, which is a laser cavity composed primarily of fiber optic cable. To measure spectra, the continuous-wave fiber output is directed at the test article and onto a single photoreceiver. The photoreceiver signal is then digitally processed to produce the desired spectra.

Modeless Wavelength-Agile Laser

A UW-Madison researcher has developed an easily constructed modeless laser with a rapidly sweeping color that results in improved performance in many sensing applications. The laser changes its cavity length at a speed that prevents the formation of modes, resulting in a spectrally narrow, swept-wavelength light source that eliminates mode hopping. A pivoting mirror design provides the high rate of cavity length change.

High-Speed, Swept Frequency Spectroscopic System

A UW-Madison researcher has developed a wavelength-agile laser capable of rapidly scanning through a broad wavelength range, with superior light coupling and reduced light loss. It is particularly well suited to measure gas absorption in engines.

The invention consists of commercially available components that include an ultra-fast laser, a non-linear optical fiber and a frequency-spreading element. When these components are connected in series, the fiber optic cable receives a multi-frequency light pulse and spreads its frequency in time prior to transmitting it into a test cell. This approach significantly reduces losses involved in coupling light to the optic fiber and avoids the measurement of unwanted nonlinear processes. By directing the laser’s output through a test article of interest, the item’s properties can be determined by the recorded transmission spectrum.

Method and Apparatus for Simulating and Testing Internal Combustion Engines

UW-Madison researchers have developed a dynamometer for a single cylinder test engine (1CTE), which allows the 1CTE to simulate a multi-cylinder engine (MCE) by replicating its instantaneous engine dynamics. The dynamometer achieves this not only absorbing the torque output of the 1CTE (as in standard dynamometers), but also by delivering a motoring torque input to the 1CTE. Calculated in real-time by hardware and software-based methods, this input corresponds to the dynamic torque the 1CTE would receive from other cylinders if it were actually part of an MCE. Thus, the 1CTE acts dynamically as if interacting with other cylinders, allowing much more accurate simulation of MCE conditions over a wider range of speeds, including idling speeds.