Development and Experimental Evaluation of Port Fuel Injected

HCNG Engine

Abstract

Depleting petroleum reserves and stringent emission legislations demand introduction of alternative automotive fuelsin order to reduce global emissions and lower the consumption of conventional fuels such as gasoline and diesel. Several alternative fuels have emerged such as alcohol, biodiesel and LPG but none of them are available commercially/ are widely successful except natural gas. Natural gas is used in the form of compressed natural gas

(CNG) or liquefied natural gas (LNG). Over last couple of decades, number of on-road CNG vehicles has drastically increased and several surveys project further increase.

Most important quality of CNG is its lower emissions and it is accepted as a clean fuel.

However CNG suffers from severe shortcomings because of its properties such as lower diffusivity, poor lean limit, high ignition energy, high COV, low flame speed and high flame quenching distance. These adverse properties of CNG can be improved by addition of hydrogen.This mixture is known as hydrogen enriched compressed natural gas (HCNG/

H2CNG or Hythane). Pure hydrogen has serious safety concerns for its implementation in internal combustion engines due to its low ignition energy and wide flammability range, which causes backfire and engine knocking. However many of the excellent properties of hydrogen can be effectively utilized in Hydrogen-CNG mixtures. Since, application of hydrogen in IC is technically extremely challenging and not feasible at present. In this scenario, HCNG emerges as feasible path for using hydrogeninIC engines and it can be immediately implemented usingcurrent infrastructure in existing engines with minor hardware modifications.

A single cylinder diesel engine is modified for operation on HCNG in this study. Several modifications are done, such as ignition system modifications, cylinder head modifications, reduction of compression ratio and development of fuel injection system and safety devices.

Several sensors were mounted on the modified engine such as lambda sensor, fuel flow meter, precision optical shaft encoder, piezoelectric pressure transducer, TDC sensor etc.

Experiments were performed at different loads using different HCNG mixtures (0%, 10%,

20% and 30%). Effect of hydrogen addition on engine performance, combustion and emissions was analyzed. Effect of compression ratio variation was also investigated.

Hydrogen addition to methane improved brake thermal efficiency and enhanced combustion stability. Brake specific fuel consumption (BSFC) and brake specific energy consumption reduced at a constant BMEP for HCNG mixtures. Lower amount of HCNG was required to produce same power compared to CNG. Combustion parameters such as in-cylinder pressure, rate of pressure rise, heat release rateand combustion duration improved with addition of hydrogen. Emissions such as HC, CO and CO2 reduced with increasing BMEP and increasing hydrogen fraction in HCNG. This was primarily due to lower C/H ratio of

HCNG mixtures, while NOx emission however was increased.

Increased compression ratio of HCNGmixture combustion led to higher thermal efficiency and lower BSFC/ BSEC. Combustive parameters at higher compression ratio while CO, HC and NOx emissions increased and CO2 emission decreased. HCNG mixtures delivered superior performance and proved to be an excellent way of moving in the direction of hydrogen economy and were compatible with present engine technology.