Journal of Scientific & Industrial Research Vol. 77, January 2018, pp. 61-65 Improving Performance of Compressed Natural Gas Fueled Passenger Car Engine by Addition of Hydrogen A K Sehgal1*, M Saxena2, S Pandey3 and R K Malhotra4 *1Indian Oil Corporation Ltd, Faridabad, India 2Univeristy of Technology and Management, Shillong, India 3University of Petroleum and Energy Studies, Dehradun, India 4Petroleum Federation of India, New Delhi, India Received 06 October 2016; revised 05 June 2017; accepted 07 October 2017 Hydrogen is a clean fuel that can be used as sole fuel or blends with compressed natural gas (CNG) in the spark ignition engines. Blending of hydrogen in CNG improves the burning velocity and calorific value of CNG. Engine tests were carried out using CNG and optimized fuel blend of 18%HCNG for comparing the engine performance and emissions behavior. Marginal improvement in engine performance (up to 2%) and significant reduction in emissions with18%HCNG compared to neat CNG. The brake specific fuel consumption was 5% lesser compared to CNG. Replacement of methane by hydrogen in the 18%HCNG blend reduced the HC emissions by ~20% and NOx emissions was increased by ~ 10-20% compared to CNG. 18% HCNG decreased the methane emissions up to 25% compared to CNG. The investigation showed that 18% HCNG has given better performance and emissions compared to CNG. Keywords: Hydrogen, Compressed Natural Gas, Emissions, Methane Emissions Introduction produce any major pollutants such as CO, HC, SOx, Natural gas is a naturally occurring form of fossil smoke and other toxic metals except NOx. Hydrogen energy. Utilization of natural gas as fuel for internal can be produced from renewable sources such as combustion engines was almost restricted to biomass and water as well as from non-renewable stationary applications prior to World War II. sources. Hydrogen is a suitable gaseous fuel for SI Compressed natural gas is successfully utilized in and CI engines4-8. The higher self ignition temperature many parts of the world such as Argentina, Russia, of hydrogen (858 K) allows the use of higher Italy and India for transport vehicles such as taxis and compression ratios. Hydrogen can be ignited at low buses Natural gas is primarily composed of methane ignition energy (0.02mJ) compared to methane but has other hydrocarbon components in small (0.28mJ) at stoichiometric conditions. Hydrogen gas amount as well such as propane, butane and pentane, can be inducted into the engine through carburetion, and also to some extent inert components such as port injection and direct injection9-11. Addition of nitrogen and carbon dioxide. It has high hydrogen to small amount of hydrogen to natural gas (5 to 30% by carbon (H/C) ratio and high research octane number volume) improves the properties of the natural gas (RON). Due to the slow flame speed and the poor such as higher flame speed and wider flammability lean-burn capability of compressed natural gas, the limit12-13. Some studies investigated the effect of spark ignited engine running on CNG has various hydrogen ratios in HCNG (hydrogen enriched disadvantages such as large cycle-by-cycle variations compressed natural gas) fuels on combustion and and poor lean-burn capability1-3. Hydrogen is a emission characteristics of a turbocharged spark promising alternative fuel which has been receiving ignition natural gas engine at idling conditions. more and more attention all over the world in recent HCNG blends significantly reduced CH4 & CO years. Hydrogen is the least polluting fuel that can be emissions but increased NOx emissions14-16. From the used in engines. Hydrogen combustion does not literature review, it is clear that a number of research works have published using HCNG blends as fuel for —————— *Author for Correspondence dedicated natural gas engines. Limited number of E-mail: [email protected] research publications is available on the use of HCNG 62 J SCI IND RES VOL 77 JANUARY 2018 blends in a passenger car bifuel engine. We have schematic of the experimental setup is shown in conducted studies using different blends of hydrogen Figure 1. AVL Puma Open 5.0 test bed automation – compressed natural gas (up to 25% H2 in CNG) to system controls the dynamometer, fluid controlling analyse the fuel composition effects on the engine systems and emission measuring equipment is performance and emissions at our IOC R&D Centre. interfaced with the engine test bed. The test cycles are The objective of the present study is to investigate the programmed in the Puma for the automatic operation performance and exhaust emissions of the engine of test run. A combustion air system is located in the fueled with CNG and 18%CNG and operating at full plant room adjacent to the test cell and consists of throttle conditions for different speed conditions. an AVL ACS1200 unit and an air dryer to control the humidity of the incoming air. The controlled Experimental setup temperature air enters the engine intake system The engine transient dynamometer test bench is through the ABB make air mass measuring installed in a climate controlled test cell which is equipment. The system is equipped with a coolant capable of maintaining the test cell temperature and oil temperature control systems which are ranges between -5 to +45 °C. The test bench consists capable of maintaining the coolant temperature of of a 4 cylinder, MPFI gasoline engine, 120 kW 70 to 120°C and oil temperature of 70 to 140 °C. asynchronous dynamometer and fluid conditioning A gas mass flow meter is used to measure the mass of systems, and gas emission measuring equipment. The gaseous fuel entering the engine. Horiba 7100 test engine specification is given in Table 1 and the DEGR is an integrated gas analyzer that combines Table 1 — Engine Specification various emission detectors together by using the same sample point and is used for gaseous Engine Type Gasoline / CNG Engine emission measurement. A thermally insulated Fuel system Multi point fuel injection sample probe is installed ahead of the after treatment Engine size 1196 cc devices to avoid condensation of particulates during No. of cylinders × valves / 4 × 4 measurement. cylinder Test fuel Compression ratio 9.9 Gas chromatography is used to analyse the Maximum torque 101 Nm @3000 rpm composition of test fuels. The compositions of test Maximum power 54 kW @ 6000 rpm fuels of CNG and 18% HCNG are given in Table 2. Fig. 1 — Schematic of the experimental setup MALHOTRA et al.: IMPROVING PERFORMANCE OF CNG FUELED PASSENGER CAR 63 Test methodology 60 second measurement data is used for the analysis Engine tests were carried out at full throttle (Table 3). opening condition using CNG and 18%HCNG HCNG on the gasoline engine at 25 °C ambient conditions in Results and Discussions the weather controlled test cell. The engine test bed Engine performance control parameters for the test are given in Table 3. Figure 2 shows the plot of the power, torque and Throttle position is maintained at 100% opening brake specific fuel consumption of the engine at (WOT) and speed increased from 1000 to 6500 rpm at different speeds at full throttle conditions. It is a regular interval of 1000 rpm. The engine observed that the measured power for 18%HCNG are performance parameters such as power, torque & fuel up to 2.0% higher compared to CNG over the entire consumption, and emission parameters such as CO, speed range. Higher flame speed of hydrogen compared to CNG improved the combustion THC, NOx & CH4 were measured. The average of characteristics of CNG and thereby improved the Table 2 — Composition of HCNG blends power. The BSFC of the engine decreased till 3000 S.No Type of compounds CNG 18% HCNG rpm and further it increased. The similar trend was observed for the both test fuel. The BSFC of the engine 1 Hydrogen 0.2 17.8 for the 18%HCNG blend is lower than neat CNG for 2 Methane 90.1 73.4 the all speed conditions. The 18% HCNG blend 3 CO2 2.9 3.2 decreased the BSFC 5.0% in comparison with CNG. 4 Nitrogen 2.2 1.3 This is due to higher calorific value of the blends and 5 Oxygen 0.1 0.1 improved combustion efficiency. The combustion 6 Ethane 3.2 3.1 efficiency is directly dependent on the C/H ratio; more 7 Propane 1.0 0.9 hydrogen per carbon lowered the oxidation state of the 8 i-Butane 0.1 0.1 fuel thus releasing more energy during combustion resulting in comparatively higher temperatures. 9 n-Butane 0.2 0.1 Engine exhaust emissions Table 3 — Test conditions Figure 2 depicts engine exhaust emissions of the Engine parameters Value engine for the various speed conditions at full throttle Test cell temperature 25±1 °C conditions. Reduction in HC emissions with increase Intake air temperature 25±1 °C in speed was observed for the all test fuels. Coolant temperature 90±1 °C The quenching gap of hydrogen is 0.064 mm whereas Oil temperature 95±1 °C 0.25 mm for methane which enables more complete Relative Humidity 50±1 % combustion of fuel air mixture adjacent to cylinder Fig. 2 — Engine performance 64 J SCI IND RES VOL 77 JANUARY 2018 Fig. 3 — Engine exhaust emissions walls and crevice volumes thus further reducing HC 10 -20% increase in NOx emissions with 18% emission. Moreover, the addition of hydrogen in CNG HCNG compared to CNG increased the laminar flame speed and that decreased 18% HCNG decreased the methane emissions up the amount of unburned hydrocarbons in the exhaust. to 25% compared to CNG All these factors reduced the CO and HC emission The 18% HCNG blend has shown better with 18% HCNG blends compared to that of CNG.