Measuring Internal Combustion Engine In-Cylinder …

1 USER SOLUTIONS timing adjusting these parameters toobtain optimum performance is a considerable observing the measured in-cylinderpressure and the location of the peak pres-sure with respect to the top-dead-centerpiston position (TDC), the Engine operator can quickly tune the Engine foroptimum performance. Most conventionalengines exhibit optimum performancewhen the peak pressure occurs 12 to 15 deg after TDC and the combustionevent occurs during the nearly constantvolume condition near TDC, as indicatedby the mass fraction burned. For a givencompression ratio and fuel octane num-ber, the spark advance needed for peakperformance may lead to overheating ofthe pistons because of severe spark , during the performance optimiza-tion process, the operator needs to monitor the cylinder pressure for sparkknock between 10 and 40 deg after knock is detected, the spark advancemust be reduced to avoid piston DescriptionWe chose LabVIEW for the OPTIMIZER because of its flexibility in integrating dataacquisition and analysis functions withoutthe need for additional software.

2 Wedesigned the system to measure and Measuring Internal Combustion Engine In-Cylinder Pressure with LabVIEWby William Doggett, Creative TechnicalSolutions, Challenge: Creating an affordable in-cylinderpressure measurement and analysissystem to optimize Internal combus-tion Engine design and Solution: Developing theOPTIMIZER, a flexible, low-cost PC-based In-Cylinder pressure mea-surement and analysis system based on a DAQ board controlled byLabVIEW who has worked on the design ofan Internal Combustion (IC) Engine willunderstand the tremendous advantagethat an inexpensive, accurate device formeasuring and analyzing In-Cylinder pressure would offer a designer.

3 CreativeTechnical Solutions, Inc. has used aNational Instruments DAQ board andLabVIEW to build the OPTIMIZER, a PC-based system for use by enginebuilders, research laboratories, small racing shops, and performance of an IC Engine , dependson a number of variables. For a givencompression ratio, optimum horsepowerand Engine torque are generated when: Each cylinder receives the maximum amount of air from the inlet and intake valve assembly The fuel/air ratio is adjusted properly for the operation conditions The fuel and air are well mixed The spark advance is adjusted for incipient knock Because the pressure resulting fromcombustion of the fuel/air mixture gener-ates torque and power, the most funda-mental parameter to examine duringengine development is the magnitude andtiming of the In-Cylinder pressure duringthe compression and power strokes.

4 Benchtesting of an inlet manifold will documentthe flow for a given pressure drop understeady-flow conditions. But when installedon an Engine , the inlet manifold flow is anonsteady-flow process driven by the pis-ton motion, inlet valves area, valve timing,and overlap and runner geometry. Thecoupling of these parameters often resultsin unequal charging of different cylindersin a multicylinder first step in optimizing Engine per-formance is to design the inlet manifoldand valve train to deliver maximum andequal masses of air to the cylinders. For agiven compression ratio and air inlet tem-perature, the operator can derive thischarging information from the level of thecylinder pressure during the compressionstroke prior to ignition.

5 Because combus-tion of the fuel/air mixture is a complexfunction of a number of combustionchamber geometric variables, as well asmany other variables such as localfuel/air mixing, octane number, localequivalence ratio, Engine temperature,air temperature and humidity, and sparkWe chose LabVIEW for the OPTIMIZER because of its flexibility in integrating data acquisition and analysis functionusing same TestnLabVIEWTMnDAQLog-Log Plot of Pressure versus Headquarters Tel:(512) 794-0100 Fax:(512) 683-9300 Offices:Australia03 9879 5166 Austria0662 45 79 90 0 Belgium02 757 00 20 Brazil000811 781 0559 Canada905 785 0085 Denmark45 76 26 00 Finland09 725 725 11 France01 48 14 24 24 Germany089 741 31 30 Hong Kong2645 3186 Israel03 6120092 Italy02 413091 Japan03 5472 2970 Korea02 596 7456 Mexico001 800 0100 793 Netherlands0348 433466 Norway32 84 84 00 Singapore2265886 Spain91 640 0085 Sweden08 730 49 70 Switzerland056 200 51 51 Taiwan02 2377 1200 523545 Copyright 1998 NationalInstruments rights and company names listed are trademarks or trade names oftheir respective 111198To develop a low-cost

6 PC-based dataacquisition (DAQ) system for in-cylinderpressure measurements,we selectedOptrand fiber-optic-based pressure relatively low cost gaugeshave been used successfully in a number ofdevelopment and monitoring gauges have accumulatedmore that 800 million cycles to date inengine operation and control addition to providing 5 V full scale,thegauges have a sense signal that you canmonitor to ensure that the pressure signalis measured the pressure trans-ducer signals with the NationalInstruments PCI-MIO-16-E-1 DAQboard,triggered from an optical encoderwith deg ensure thatthe encoder index pulse is properly aligned with Engine TDC,we used aPhiltec fiber-optic displacement sensor to accurately determine TDC duringmotoring technique eliminatesthe need to use indexed wheels and mark-ers to estimate ArchitectureWithin the LabVIEW-based measurementsystem,the Engine operator uses a numberofsubroutines to set up the Engine para-meters,enter gauge parameters,determineTDC,capture data as a function ofenginespeed.

7 And present the measured andderived results in a number ofuseful Engine setup screen is shown inthe adjacent developed a low-cost PC-based dataacquisition and analysis system using aDAQ board and LabVIEW to acquire and analyze In-Cylinder pressure for IC engines,for the purpose ofoptimizingengine used low-costfiber-optic-based pressure transducers anda fiber-optic displacement sensor to deter-mine optical encoder triggersand clocks the DAQ gasolineand diesel Engine versions ofthe systemare development plansinclude upgrading to simultaneous sam-pling for very high rpm operation andaccurate pumping mean effective pressure(MEP) more information,contact CreativeTechnical Solutions,Inc.

8 ,30 Research Drive,Hampton,VA 23666,tel (757) 865-1400,fax(757) 865-8177,e-mail present In-Cylinder pressure measure-ments in a number ofgraphical formats sothe Engine operator can assess the effectsofdesign changes and operating condi-tions on performance as a function ofengine operating speed and distributions for each cylindercan be averaged for any desired number ofengine cycles and at several Engine figure on the previous page shows alog-log plot ofpressure volume for derived parameters that resultfrom analysis ofthe pressure recorded as afunction ofcrank angle are tabulatedalong with their standard can record the dynamometertorque on one ofthe low-speed channelsand

9 Use it to compare the brake horsepow-er with the indicated power derived fromthe pressure differences in these values are a measure ofthe friction andpumping the LabVIEW-based measurement system,the engineoperator uses a number ofsub-routines to set up the Engine parameters,enter gauge parameters,determine TDC,capture data as afunction ofengine speed,and presentthe measured and derived results in a number ofuseful Setup Scr