Laser metrology — a diagnostic tool in automotive development processes

• Published in: Optics and lasers in engineering 2000-08, Vol.34 (2), p.101-120
• Main Authors: Beeck, Manfred-Andreas, Hentschel, Werner
• Format: Article
• Language: English
• Subjects: Applied sciences; Automotive application; Biological and medical applications; Brake noise; Car body resonances; Combustion analysis; Direct-injection engine; Double-pulse holography; Engine knocking; Exact sciences and technology; Fundamental areas of phenomenology (including applications); High-speed filming; High-speed techniques (microsecond to femtosecond); In-cylinder flow; Industrial metrology. Testing; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Interferometers; Laboratory procedures; Laser-induced fluorescence; Mechanical engineering. Machine design; Metrological applications; Metrology, measurements and laboratory procedures; Mie-scattering; Non-destructive testing: methods and equipments; Optical instruments, equipment and techniques; Optical metrology; Optics; Particle image velocimetry; Physics; Pulsed ESPI; Scanning vibrometry; Spray analysis; Transparent engine
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/S0143-8166(00)00077-4

Laser measurement techniques are widely used in automotive development processes. Applications at Volkswagen are presented where laser metrology works as a diagnostic tool for analysing and optimising complex coupled processes inside and between automotive components and structures such as the reduction of a vehicle's interior or outer acoustic noise, including brake noise, and the combustion analysis for diesel and gasoline engines to further reduce fuel consumption and pollution. Pulsed electronic speckle pattern interferometry (ESPI) and holographic interferometry are used for analysing the knocking behaviour of modern engines and for correct positioning of knocking sensors. Holographic interferometry shows up the vibrational behaviour of brake components and their interaction during braking, and allows optimisation for noise-free brake systems. Scanning laser vibrometry analyses structure-born noise of a whole car body for the optimisation of its interior acoustical behaviour.Modern engine combustion concepts such as in direct-injection (DI) gasoline and diesel engines benefit from laser diagnostic tools which permit deeper insight into the in-cylinder processes such as flow generation, fuel injection and spray formation, atomisation and mixing, ignition and combustion, and formation and reduction of pollutants. The necessary optical access inside a cylinder is realised by so-called ‘transparent engines’ allowing measurements nearly during the whole engine cycle. Measurement techniques and results on double-pulse particle image velocimetry (PIV) with a frequency-doubled YAG laser for in-cylinder flow analysis are presented, as well as Mie-scattering on droplets using a copper vapour laser combined with high-speed filming, and laser-induced fluorescence (LIF) with an excimer laser for spray and fuel vapour analysis.