Modification and Tuning of Multi-valve Diesel Bus Engine to Run On Biogas for Electricity Production

Abstract

This study is to modify and tune a multi-valve bus diesel engine for electricity production in a farm using biogas as fuel. The engine under study is a Hino Model K-13CTI 6 cylinder 13,000 cc 24 valves turbocharged with intercooler engine. The engine is coupled to an induction motor to work as a 3-phase 4-pole 132 kW generator to produce electricity at 50 Hz. Modifications include replacing the fuel injection system with spark ignition system, reduction of compression ratio from the original 16:1 to 8:1 by using a custom made cylinder head spacer, modification of the turbocharger waste gate so the boost pressure can be adjusted to find the optimal operating point, and an addition of biogas carburetor for proper air-fuel mixing. In this configuration when the generator is synchronized to the power grid, the system running speed is 1,500 rpm. When the system is finely tuned, optimal engine efficiency was achieved at 28.6% by setting the lambda factor at 1.097, ignition timing at 54^o before top dead center, and the turbocharger boost at 56 kPa. With this setting, the generator power output is 134.2 kilowatt with emission of CO and NO_X being 1,154 and 896 ppm respectively.