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Design and Development of a Dual Fuel Diesel-LPG Controller
Abstract
Towards the effort of reducing pollutant emissions from direct injection (DI) Diesel engines. The use of Liquefied Petroleum Gas (LPG) as an alternative fuel is a promising solution. After scrutinizing the results, a Dual fuel Diesel-LPG Controller was developed for optimizing the performance on different loads (20% to 120%) without making any modifications in the engine design.
Key Words: Duel Fuel Genset, Diesel-LPG Controller, LPG.
1. Introduction
Diesel-LPG is a proven technology in case of vehicles. The potential benefits of using LPG in diesel engines are both economical and environmental [1]. They provide a relatively easy and inexpensive option to higher polluting. Diesel engines in a wide range of vehicles. Dong Jian et al. have developed new type of dual-fuel supply system, which could able to convert conventional diesel engines into dual-fuel engines like LPG/Diesel engines and CNG/Diesel engines [2].The degree of sophistication of these engines varies depending upon fuel control strategies; however, they have proved reliable in many parts of the world and continue to expand their market share, particularly in regions where Diesel pollution is a major concern and health hazard. Ghazi Karim has underlined the importance of understanding combustion process in dual-fuel engines with regard to enhanced performance and reduced pollution [3]. Blended fuel combustion using LPG is a promising technique for controlling both NOx and smoke emissions even on existing DI. Diesel engines and requires only a slight modification of the engine structure. BTE improved by 3% in the glow plug assisted dual fuel mode, especially at low loads and also reduced the hydrocarbons, carbon monoxide [4]. Compared with Diesel, the output performance of dual fuel was not
reduced, while smoke emissions of the duel fuel were reduced [5]. The DLC system was designed to activate the LPG solenoid valve when the load reached 2000W and it got deactivated when the load on the Dual fuel Genset is reduced below 2000W and it got deactivated when the load on the Dual fuel Genset is reduced below 2000W. Modification to the Genset had been made in such a way that the Genset runs on 100% diesel and also on Dual fuel mode with LPG and diesel. For idling, the Genset has to be operated on 100% diesel. The Dual fuel Genset was made to run on Dual fuel mode by connecting LPG to the intake manifold with the help of retrofitted LPG kit. The kit consisted of an LPG tank, vaporizer and a coolant circulation system. The LPG kit required 12V DC for its operation. This was provided with the help of 12V-3A DC eliminator. The cut off load was controlled with the help of DLC at 80% of load. An AVL five gas analyzer meter were used to measure emission parameters from exhaust manifold of the engine.
Initially, the engine was tested using diesel at loads 0%, 20%, 40%, 60%, 80%, 100%, and 120% to measure the engine operating characteristics and pollutant emissions. The test was conducted on five different Diesel-LPG modes i.e., (84%- 16%), (76%-24%), (68%-32%), (60%- 40%), and (52%-48%) to find the optimize Diesel-LPG mode. The engine can be run in the dual fuel mode without any major modification, but is usually associated with poor brake thermal efficiency and high HC and CO emissions at low loads [6]. Diesel- LPG modes were selected by the mass fraction of Diesel and LPG (Z) which is defined by Equation 1.
Through the initial experiments, it was found that the LPG fuel is beneficial only at higher loads thus the cut off at 80% was selected through the DLC in Diesel-LPG mode
2. Development of dual fuel controller
The Dual fuel Diesel-LPG Controller (DLC) works on the principle of current transformer. When current is passed through the primary coil i.e., alternator; voltage propositional to the alternator current is induced in the secondary winding i.e., Current to voltage converter (I/V convector). The core of the converter has been made out of laminated silicon steel sheets to reduce the effect of eddies. This voltage is then sent to the rectifier through the diodes. The function of the rectifier is to convert alternating voltage into direct voltage. The converted direct voltage has some alternating component which was nullified with the help of a capacitor. Direct voltage from capacitor was then sent to relay. The relay consisted of (NC) Normally Closed and (NO) Normally Open circuit. The DLC system was designed to activate the LPG solenoid valve when the load reached 80% of load and it got deactivated when the load on the Dual fuel Genset is reduced below it. But a provision has been made in the DLC circuit to set the cut off load as per the requirements Figure1 shows the schematic diagram of the Engine DLC.