To promote use of Compressed Natural Gas (CNG) as a substitute for High Speed Diesel to create a clean environment in urban and semi-urban and to reduce cost of transportation while reducing dependence on imports.
Introduction
Natural Gas is fast becoming a fuel of choice by the industry due to its inherent characteristics of low emission, clean burning and increasingly easy transportability. For the same calorific value, NG emits less CO2, particulates and NOx. It is also economical compared to liquid fuels.
Government of India’s Policy
The government of India is promoting use of Natural Gas through incentives and liberal policies in import (OGL) and construction of pipelines. Building of international pipelines across Turkmenistan, Iran, Afghanistan and Pakistan are being explored to promote use of this cheap and clean energy source.
Indian Railways - Status
Indian Railways (IR) havetaken tentative steps in introduction of Natural Gas (in the form of CNG) as a fuel substitute on Diesel electric Multiple Units. There are nearly 700 Diesel Power Cars (DPC), which have the potential to be converted to dual-fuel mode.
Technology
Trials with up to 20% substitution of high speed diesel with CNG have been successfully carried out. This is based on the “fumigation technology”. Fumigation involves mixing of natural gas in the charge air before supercharging and is generally limited to 20%
In-port Injection Technology involves injection of natural gas just before the opening of the inlet valve. This permits substitution of up to 60-65%.
High Pressure Direct Injection (HPDI) technology permits up to 90-95% substitution. Gas is directly injected into the cylinder through an additional injector. A pilot injection of small quantity of high speed diesel is then made to initiate combustion.
IROAF has planned retrofits with all three technologies.
Natural Gas is safer than liquid fuels like diesel and petrol and LPG due to its smaller range of inflammability.
State of the Industry
Most of the technology and equipment for retrofits are imported. HPDI is nearly proprietary. Conversion of an existing engine to dual-fuel, using any of the three technologies, involves extensive trials, mapping of engine characteristics at various levels of power, fuel substitution and safety related issues.
Roadmap
IROAF will introduce natural gas as a diesel substitute in all DEMUs sheds on IR. In addition, CNG will also be increasingly used on shunting locomotives to curb pollution in urban centres. IROAF will explore all available technologies such as Fumigation, In-port Injection, High Pressure Direct Injection (HPDI) and other emerging technologies to achieve these objectives.
