汽车发动机中燃烧参数检测方案(粒子图像测速)

50 51 Refractive and diffractive micro-optics for the minimalinvasive acquisition of combustion parameters R. Reichle， C. Pruss， W. Osten For the optimization of the combustion in engines，the time-resolved acquisition of locally resolved infor-mation about combustion parameters like the injectedfuel/air mixture or the temperature is very important.To enable non-contact measurements in close-to-pro-duction engines (see fig. 1)， new minimal invasive opticalsystems have been introduced [1-4] and are actually fur-ther enhanced in cooperation with Prof. Schulz (IVG，University of Duisburg-Essen). The optics are customdesigned for modern analysis concepts such as UV laserinduced fluorescence (LIF)， using the specific UV fluo-rescence properties of different fuel tracers upon laserexcitation to determine the desired parameters. Point measurements without engine modificationsare enabled by our measurement spark plug， which stillprovides the ignition function and has additionally in-tegrated microoptics to serve as a LIF-sensor. In firedengine experiments the robustness and optical functionhas been demonstrated (fig. 2)， actually the sensor func-tion is further developed towards simultaneous meas-urements in multiple volumes. The wide angle keyhole optics for 2D-measure-ments images the UV-fluorescence of a measurementplane onto an image intensifier. The optics is dividedinto two main parts. A simple front endoscope with anentry diameter of 1 cm and fused silica lenses producesa chromatically uncorrected intermediate image， whichis then relayed onto the camera by stationary hybridoptics. Here the chromatic correction of the completesystem is realized by the strong negative dispersion of adiffractive component. So if different relays are placedbehind a beam splitter， each imaging channel can be op-timized to a different wavelength band using the sameentrance endoscope. To suppress unwanted diffraction orders the etching depth of each diffractive element isadapted to the individual spectral band. The positionsof the diffractive elements in the relays further help tominimize the negative effects of the unwanted diffrac-tion orders regarding the image quality. Fig. 2： Sspark plug sensor and UV-FARLIF signal measured withthe sensor inside a running engine [2，3]. A new simulation tool has been implemented on thebasis of the widely used ray tracing tool ZEMAX. Itaccounts for the behaviour of real diffractive optics inoptical systems， including fabrication errors dependenton the local grating constant and broadband illumina-tion effects. The simulation tool integrates seamlesslyinto ZEMAX and can also be used for optimization.This new capability further improves the design of hy-brid diffractive/refractive optical systems. For the characterization of diffractive elements andhybrid optical systems at wavelength we have set up atest bench that works from the NIR to the UV. It usesa double monochromator with automatically exchange-able gratings and an optional Ulbricht sphere for thedefined illumination of test charts. In our characterization experiments we could showthe expected performance in terms of resolutionand chromatic correction. Benchmarking our systemagainst a commercially available UV-endoscope， we Fig. 1： Setup for minimal invasive UV-LIF-measurements. could show a dramatically higher brightness and at thesame time a broader chromatic correction range. Ifa broad correction range is required， as is typical forfluorescence observation， our system delivers about30 times more brightness， for monochromatic applica-tions still about 10 times. Benchmarking our systemagainst the non-endoscop-ic UVNikkor objective (f = 105 mm) at the same imagemagnification， we found comparable values in terms ofbrightness， as can be seen in figure 3. The averaged im-ages show LIF of toluol for an excitation at 266 nmimaged with the non-endoscopic UV Nikkor lens andour system with the same camera settings. Fig.3：Comparison of a standard non-endoscopic UV imaginglens (UV Nikkor， (a)) with the hybrid endoscopic sys-tem (b) imaging LIF of toluol at 307 nm， measured atthe LaVision GmbH. In combination with our beamshaping optics with9 mm outer diameter， the high performance of the op-tical imaging system allowed first minimal invasive 2D-UV-LIF-measurements out of a running engine at IVG(fig. 4). Figure 5 shows the front piece that is attachedto the test engine. The diffractive/refractive imaging optics is commer-cialized by the LaVision GmbH. Fig. 5： FFront piece of the hybrid endoscopic system attached toa test engine. Supported by： BMBF (FKZ 13N9456) and the Landes-stiftung Baden-Wurttemberg Project："MIMODIA" The authors especially acknowledge the good coopera-tion with the group of Prof. Schulz (IVG， University ofDuisburg-Essen). References： [1] Reichle， R. et al.， “Hybrid excitation and imaging optics forminimal invasive multiple-band UV-LIF-measurements inengines”，VDI-Berichte 1959 (2006)， pages 223-235，VDIVerlag. [2] Reichle， R. et al，"Fiber optic spark plug sensor for UV-LIFmeasurements close to the ignition spark”， Proceedings ofSPIE -The International Society for Optical EngineeringVol. 5856，158-168(2005). [3] Zimmermann， F.；Gessenhardt， C.； Reichle， R.； Pruss， C.；Schulz， C. “Micro-Invasive LIF Diagnostics in Engines，”inLaser Applications to Chemical， Security and Environmen-tal Analysis， OSA Technical Digest (CD) (Optical Society ofAmerica， 2008)， paper LWB1. [4] Gessenhardt， C.； Zimmermann，F； Schulz，C.； Reichle， R.；Pruss， C.；Osten， W. ，，Hybrid endoscopes for laser-basedimaging diagnostics in IC engines"， SAE 2009-01-0655. INSTITUT FUR TECHNISCHE OPTIK， ANNUAL REPORT esearch projects For the optimization of the combustion in engines,the time-resolved acquisition of locally resolved informationabout combustion parameters like the injectedfuel/air mixture or the temperature is very important.To enable non-contact measurements in close-to-productionengines (see fig. 1), new minimal invasive opticalsystems have been introduced [1-4] and are actually furtherenhanced in cooperation with Prof. Schulz (IVG,University of Duisburg-Essen). The optics are customdesigned for modern analysis concepts such as UV laserinduced fluorescence (LIF), using the specific UV fluorescenceproperties of different fuel tracers upon laserexcitation to determine the desired parameters.