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<div class="section abstract"><div class="htmlview paragraph">In India, , as per mandate of hon'ble Supreme Court of India for reduction of emission due to vehicles, compressed natural gas (CNG) powered city buses and passengers cars are in use since 2000. Their usage is limited to metropolitan cities like Delhi, Mumbai, Bangalore etc. due to limitation of CNG storage and dispensing infrastructure along with low energy density storage. High energy density liquid form of natural gas storage (LNG) can overcome these difficulties and promising in near future. Simultaneously, there is a need for development of efficient fuel storage system, fuel supply system, engine optimization &amp; calibration, engine lubricant etc. suitable for implementation of LNG for automotive application. In this background, the present work is aimed at the framework of engine testing facility, development of dedicated lubricant and performance of the engine for LNG application.</div><div class="htmlview paragraph">This paper describes LNG engine test lab standard operating procedure developed during the LNG internal combustion engine dynamometer testing programme. Due to safety requirement, it is neither advisable nor permissible to connect large LNG cryogenic tankers to engine test bench. Hence, state of the art small &amp; portable cryogenic LNG tank (450 Lit water capacity (WC)) comprised of vacuum and super insulated layered configuration manufactured as per International Organization for Standardization (ISO) 21029-1 and type tested according to ISO-12991 was designed as horizontal tank to transport LNG from large LNG cryogenic tanker to engine testing site. Bharat Stage (BS) VI emission standard complied LNG engine testing facility was developed and forced convection heat transfer methodology applied for avoiding icing at re-gasified liquefied natural gas (RLNG) fuel line.</div><div class="htmlview paragraph">This paper presents the development of dedicated lubricant for LNG fuelled heavy duty (HD) engine and establishment of oil drain interval and evaluation was done on 6-cylinder HD engine using LNG fuel. The engine was optimized for using LNG fuel. Initial performance of the engine using LNG was compared vis-à-vis CNG and, thereafter, the engine was subjected to endurance test of 1500 hours as per engine simulated driving cycle that closely represents road drive conditions to validate the technology and to establish the drain interval of lubricant. Further, to access the actual performance, limited field trials of 30,000 Km with LNG fuelled busses have been completed. It has been observed that LNG shows reduction of CO, THC and CH4 emissions and NOx emissions increased as compared to CNG. However, these values meet the BS VI emission norms. Oil sampling and analysis were undertaken after completion of every 100 hrs along with performance of the engine i.e. Power (kW), Torque (Nm) and brake specific fuel consumption (BSFC) (g/kWh) and emission characteristics. Engine performance was found satisfactory during endurance test. Developed engine oil demonstrated excellent behavior with LNG fuel and used engine oil physicochemical properties i.e. Kinematic viscosity@100°C, Total Base number (TBN), Total acid number (TAN), oxidation, nitration and wear elements (Iron (Fe), Copper (Cu), Aluminum (AL), Lead (Pb)) were reported well within the permissible limit. The study shows that the lubricant can be used for LNG application.</div></div>

Diesel engines have been powering a range of commercial vehicles for a many years. Considering air pollution, there is a thrust on use of natural gas (NG). Thereafter, natural gas engines for commercial vehicles have been subject of development, particularly to meet drivability demands and emissions requirements. Bus used for intra-city mass transportation of passengers is probably the most common form of natural gas commercial vehicle. Considering typical city applications, such vehicles is characterized by low speeds, frequent gear changes, start-stops, traffic conditions etc. For better drivability, they need higher traction at low engine speeds. This study captures few means of torque enhancement and motive is to integrate a selective ones as not much research is available mentioning enhancements specifically at low engine speeds. Turbocharging of natural gas engine is complicated due to high exhaust temperatures. As most turbocharger manufacturers cater to requirements of diesel engine, turbochargers for natural gas are simply not available. Many compromises are thus to be made. Under this study, four different turbochargers and one supercharger shall be simulated for experimenting and optimizing to enhance torque at low engine speeds. A virtual model of reference, naturally aspirated engine is built in appropriate software and its output is verified against test bed performance, to establish model faithfulness. Next, simulation runs with different turbochargers and superchargers are carried out. Various parameters are recorded and compared. Findings are recorded and it is noted that there is room for enhancement based on different hardware capabilities.

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