Rapid and automated measurement of biofuel blending using a microfluidic viscometer Sanket Goel a,⇑ , P.S. Venkateswaran a , Rahul Prajesh b , Ajay Agarwal b a University of Petroleum and Energy Studies (UPES), Energy Acres, VPO Bidholi, PO Prem Nagar, Dehradun 248007, Uttarakhand, India b CSIR – Central Electronics Engineering Research Institute (CEERI), Pilani 333031, Rajasthan, India highlights  Multiphysics simulation to study viscosity based flow inside a microfluidic device.  Design and fabrication of a microfluidic device to work as a micro-viscometer.  Microfluidic device for real-time detection and monitoring of bio-fuel blend-ratio.  Comparison and analysis of the experimental results and the computational studies. article info Article history: Received 2 January 2014 Received in revised form 20 August 2014 Accepted 20 August 2014 Available online 2 September 2014 Keywords: Viscosity Biofuel-blending COMSOL Microfluidics Laminar flow abstract As the fossil fuels are depleting with time, the research work in the biofuels domain is rapidly growing. The blends of biofuel can be used as automobile fuel and the existing methods to detect the blending ratio have heavy one-time test cost, need controlled environment and require experienced operators. It is well observed that fuel mixture affects lubricating properties of the fuel and thereby the engine performance. As lubricating properties are related to physical properties, developing a sensor, based on this, can provide a reliable and effective solution to detect and monitor fuel blending. This work describes the computational and the comparative experimental analysis of a microfluidic-device which performs blending studies by analyzing the interface position of the fluid occupancy in a micro-channel and its variations. The device was fabricated in acrylic using a well-established micro-fabrication technique, and is re-usable, re-calibrated and can be integrated with the existing microcontrollers of automobiles. The viscosity of the various bio-diesel blends can be used to indicate the fraction of bio-diesel in the fuel sample based on the best fit curve of the percentage of channel fraction occupied by the samples. The interface shift is because of the greater occupancy rate of a higher viscous sample in the channel. The best fit curve was determined based on an extensive testing of various oils including the hair oils, machine oils etc. of different densities to confirm the interface shifting phenomenon. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Biodiesel is an alternative for diesel fuel that is obtained by trans-esterification of vegetable oils or other materials that are largely composed of tri-glycerols [1,2]. Biodiesel is composed of fatty acid chains that are chemically bonded to one methanol molecule. The non-edible oil plants like Jatropha, Karanja, and Putranjiva etc. are economical as their consumption in biodiesel is lower. Biodiesel decreases the emission of hydrocarbon, carbon monoxide, particulate matter and sulfur-di-oxide. The viscosity of aforementioned oil plants are more than diesel. Amongst these three vegetable oils, Jatropha shows better results in terms of vis- cosity, cetane number, and pour point. Biodiesel have low calorific value than diesel so rate of increase of NOx is low in case of load hence less exhaust gas temperature. Smoke, CO, and particulates of three biodiesels are better than diesel fuels that indicate good impact on the environment and living beings [3]. The viscosity of biodiesel is slightly greater than petro diesel but less than that of parent vegetable oil or fats [4–7]. There is a mis- conception that density is directly related to viscosity but equally dense substance may have a wide range of viscosities. The conduc- tivity of a fuel is the measure of the ability of the fuel to dissipate static electric charges because in low conductive fuel, electric charges accumulate and lead to dissipation in the form of sparks. Blends of biodiesel at or above 20% level would not require any http://dx.doi.org/10.1016/j.fuel.2014.08.053 0016-2361/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: sgoel@ddn.upes.ac.in, sanketgoel@gmail.com (S. Goel). Fuel 139 (2015) 213–219 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel