OPTIMUM Power Technology: Low Cost Combustion Analysis for University Engine Design Programs Using ICEview and NI Compact DAQ Chassis World Headquarters (USA): European Sales Office: Japanese Office: 3117 Washington Pike Tel: 412-257-9070 P. O. Box 6094, Stewkley Tel: 44 (0) 1525 242130 Fluent Asia Pacific Co., LTD Tel: 81-3-5324-7306 Bridgeville, A 15017-1496 Fax: 412-257-9011 Leighton Buzzard LU7 0XW Fax: 44 (0) 1525 242140 Nittochi Nishi Shinjuku Bldg. 18F, Fax: 81-3-5324-7302 USA United Kingdom Tokyo, 160-0023, JAPAN URL: http://www.fluent.co.jp
Introduction Analysis and measurement of in-cylinder pressure traces, or indicator diagrams, are long established techniques, widely used in the development of internal combustion engines, particularly within the automotive industry. This approach of assessing indicated engine performance dates back to the earliest days of engine development and was used frequently by Rudolph Diesel and others over 100 years ago. In fact, indicator diagrams were used as early as 1796, when John Southern, an assistant to James Watt, invented a method of creating indicator diagrams on steam engines. In these early days, the measurements were simply used to calculate the indicated performance or indicated mean effective pressure (IMEP). In 1938, new techniques for pressure trace analysis were introduced by Rassweiler and Withrow who developed a very effective technique for determining burn rate from measured pressure data by estimating the apparent pressure rise due to combustion. This approach has now become the industry standard for burn rate analysis, and is simply known as the Rassweiler and Withrow method. More recently, with powerful computing becoming widely available, there has been increasing interest in this area with larger companies producing dedicated hardware and software packages. Others have considered the use of more sophisticated techniques, by applying a full first law analysis and even considering flame propagation, and many have investigated the various aspects of processing, measurement accuracy and error analysis. With the growing popularity of Formula SAE throughout the world, the need to gain a competitive edge over other Universities has become even more important. OPTIMUM already offers an FSAE version of its well respected Automated Design for engine simulation, which is now in use with over 50 universities world wide. While this is an invaluable tool in improving and optimizing performance and helping students understand areas of gas dynamics, fluid dynamics and thermodynamics, OPTIMUM has now enhanced its support of university and engine research programs with the release of ICEview, advanced combustion analysis and high speed data acquisition system. Combustion analysis is generally regarded as technically demanding, sophisticated and very expensive, beyond the budgets of universities, however it will always remain on the wish list of many. OPTIMUM, working in conjunction with our partner National Instruments have developed a solution that is PC based, intuitive, fast, accurate and most importantly of all, affordable for university programs. Background OPTIMUM has a pedigree in advanced engine design and analysis tools. ICEview was developed from our highly successful combustion analysis software known as PTrAn. This is a low cost suite that processes data from high end combustion acquisition hardware. It is this expensive hardware that prevented many universities from investigating how to improve the combustion characteristics of their engines and hence overall performance. This no longer the case. Using standard National Instruments hardware platforms, many of which are common place at universities, OPTIMUM have developed ICEview as a low-cost, user-friendly combustion acquisition package that incorporates PTrAn for fast and accurate postprocessing. The system is PC-based and offers high-speed, crankangle-based sampling for all sensors allowing advanced combustion analysis such as IMEP, burn rates and many other combustion parameters. ICEview also performs knock
analysis and has many flexible digital filters to remove common but difficult to detect signals such as aliasing. Powerful post processing of data and enhanced graphics allows information to be visualized both clearly and concisely: cycle-to-cycle variability, cylinder-to-cylinder comparision, statistical analysis and cross-correlation are just a few examples of how results may be displayed. As stated earlier, it is Optimum s intention to offer an affordable solution to combustion analysis. Even if your university does not have the NI hardware required to run ICEview, large discounts can be obtained from NI for educational establishments, try visiting their web site at www.ni.com to see what huge savings can be made. Also visit Optimum Power Technology s web site at www.optimum-power.com to see the discounts we are offering to any FSAE team. And don t forget that all Optimum s software is backed up by free technical advice and assistance on setting up all hardware from our team of experienced engineers. Optimum does not expect ICEview to be used just for your university s FSAE team, but we actively encourage lecturers and professors to build teaching modules around the software to give students hands on experience in combustion analysis, which will lead to a greater understanding in the theory of combustion and how different parameters this critical area of engine design. Also designed to work within the LabVIEW environment, the NI graphical interface, ICEview offers universities an ability to carry out professional combustion analysis at a price that will be within the means of all teams. Equipment A schematic of a typical set up is shown below. Piezoresistive pressure transducers are mounted in the cylinder head and connected to the NI Compact DAQ via a charge amplifier. The encoder is normally mounted directly onto the engine crankshaft and the output signals go straight into a digital I/O module in the DAQ system.. NI Compact DAQ e USB PC Amplifier Tran d Engine Encoder Figure 1. Schematic of a typical system
The encoder provides the NI DAQ unit with the necessary pulses to acquire data on an angular basis. Other than that, all that s required is a PC to run ICEview. The typical NI hardware required is reviewed below: Chassis 9172 The NI CompactDAQ chassis comes with everything you need to connect C Series I/O modules to your PC, including an AC power supply and a 6 ft USB cable. An NI CompactDAQ chassis operates with as few as one C Series I/O module or as many as eight, so you can configure your measurement system to meet your needs now and have slots left for future expansion. Digital I/O Modules National Instruments C Series modules for NI CompactDAQ work with multiple logic level types and have multiple connector options for switches, encoders, and transducers. The NI 9401 is an 8-channel, high-speed, bidirectional I/O module using 5 V/TTL logic. It can be configured to have 8 inputs or 8 outputs or 4 inputs and 4 outputs. With an I/O delay time of only 100 ns, the 9401 is ideal for use with an angle encoder or to read or send trigger signals from/to other equipment. Analog Input Modules National Instruments C Series analog input modules provide high-performance measurements for a wide variety of signal types on the NI CompactDAQ and CompactRIO platforms. Each module features built-in signal conditioning and direct signal connection via screw-terminal, BNC, D-Sub, or RJ-50 connectors. Modules are available to accept signals from accelerometers, strain gages, thermocouples or voltage sources. The NI 9215 is a 4-channel module with simultaneous sampling up to 100 ks/s on each channel. With a voltage range of ±10 V and 16-bit resolution, the 9401 is well suited to data acquisition for combustion analysis.
System Review Optimum Power have designed ICEview to be user friendly and intuitive. A new user can have the system up and running in a surprisingly short time. Once the hardware is installed, only three files need to be created before the collection of useful data can begin. These files are created in a straightforward graphical interface. The Engine File contains the engine details such as engine type, bore, stroke, con rod length, compression ratio etc. The Test File contains information on ambient conditions, sampling details (internal clock or external encoder), and the level of software filtering to be applied. The Trace File contains information on the method of pressure referencing, the encoder offset relative to tdc, and the calibration of the transducers being used. With these three files completed, the system is ready to go. Optimum use National Instruments LabVIEW to collect the raw data in real time either on a time basis or on an angle basis when using an encoder. The user can view the data in the online mode or collect the data in the record mode. Figure 2 shows a typical LabVIEW screen with two cylinder pressure traces - one firing and one non-firing. Figure 2
Once data collection is complete, the LabVIEW screen disappears and the ICEView screen appears displaying the unconverted or raw data as shown in Figure 3. This particular data shows the output of cylinder pressure transducers installed in a 45-degree V-twin engine. Figure 3 The same data, now converted, is shown in Figure 4. The y-axis is now in pressure units (bar, in this case) and both cylinder traces have been corrected for the encoder offset. Figure 4
Once the user is satisfied that the data are correct, he can switch to PTrAn the combustion analysis package within ICEView. Before calculating any of the combustion parameters, PTrAn checks the signals for signs of thermal shock or drift in the pressure transducers. This alerts the user to any potential problems with the test set up before proceeding with the analysis. Figure 5 shows the default screen in PTrAn. The upper plot displays cylinder pressure vs. crank angle while the lower plot shows Log P vs. Log V. The green lines represent the indices of compression and expansion. The major combustion events, such as start of burn and end of burn, are shown in blue on the plots. On the extreme right side of the screen are displayed 28 results calculated for this particular cycle. The user can use the spin buttons to move from trace to trace and from cycle to cycle. Figure 5
By right clicking in the plot area the user can change the plots to show other parameters derived from the pressure data. Figure 6 shows the burn rate and mass fraction burned while Figure 7 shows the knock signature. Figure 6 Figure 7
Summary ICEView is a professional combustion analysis package, and through the university discount system operated by both National Instruments and Optimum Power, offers the quality and performance of similar systems but at a fraction of the cost. The software will give students the opportunity to carryout combustion analysis to the highest level giving an excellent grounding and understanding of exactly how to obtain optimum results. The choice of Optimum to work in partnership with NI and their LabVIEW system gives universities the possibility of using existing NI hardware, or purchasing low-cost general-purpose hardware form NI. Due to its modular design, and the fact that the hardware is not specific to ICEview, it can easily be used on other projects or in other areas of the department. ICEView has been targeted at universities and priced at a level we believe to be well within typical budgets. We believe that ICEView could easily be incorporated into teaching modules and be used as a frame work for all automotive engineering students wishing to study combustion analysis. Buying ICEView will enhance your results and offer a great way to enter the technically demanding area of combustion analysis at a very competitive price For further information visit our web site at www.optimum-power.com or contact our offices at the numbers given on the front page