Evaluation of friction heating in cavitating high pressure Diesel injector nozzles

[摘要] Variation of fuel properties occurring during extreme fuel pressurisation in Diesel fuel injectors relative to those under atmospheric pressure and room temperature conditions may affect significantly fuel delivery, fuel injection temperature, injector durability and thus engine performance. Indicative results of flow simulations during the full injection event of a Diesel injector are presented. In addition to the Navier-Stokes equations, the enthalpy conservation equation is considered for predicting the fuel temperature. Cavitation is simulated using an Eulerian-Lagrangian cavitation model fully coupled with the flow equations. Compressible bubble dynamics based on the R-P equation also consider thermal effects. Variable fuel properties function of the local pressure and temperature are taken from literature and correspond to a reference so-called summer Diesel fuel. Fuel pressurisation up to 3000bar pressure is considered while various wall temperature boundary conditions are tested in order to compare their effect relative to those of the fuel heating caused during the depressurisation of the fuel as it passes through the injection orifices. The results indicate formation of strong temperature gradients inside the fuel injector while heating resulting from the extreme friction may result to local temperatures above the fuel's boiling point. Predictions indicate bulk fuel temperature increase of more than 100°C during the opening phase of the needle valve. Overall, it is concluded that such effects are significant for the injector performance and should be considered in relevant simulation tools.

[发布机构] City University London, Northampton Square, EC 1V 0HB, United Kingdom^1;Caterpillar UK Engines Co. Ltd, Peterborough; PE1 5FQ, United Kingdom^2;Caterpillar Inc., Mossville; IL; 61552, United States^3;Dept. of Engineering and Applied Sciences, University of Bergamo, Viale Marconi 5, Dalmine (BG); 24044, Italy^4;School of Computing, Engineering and Mathematics, University of Brighton, Cockcroft Building, Lewes Road, Brighton; BN2 4GJ, United Kingdom^5

[关键词] Conservation equations;Diesel fuel injectors;Diesel injector nozzles;Engine performance;Eulerian-lagrangian;Injection temperature;Room-temperature conditions;Wall temperatures