A modified diesel engine for natural gas operation: Performance and emission tests
Highlights
► A diesel engine for natural gas operation to optimize performance using gaseous fuel. ► A variation of combustion ratios (CR) was utilized to evaluate engine performance and emissions. ► CR of 9.5:1 had the highest thermal efficiency and the lowest SFC. ► CR of 10:1 showed a high torque at low speed. ► THC and NOx emissions were directly proportional to the CR.
Introduction
Over past decades, increased energy demand has resulted in higher fossil fuel consumption and, consequently, higher emissions. Presently, it is estimated that combustion of fossil fuels releases greenhouse gases, especially CO2, at a rate of about 7 billion tons each year [1]. Modifications have been developed and mandated to reduce emissions; examples include the improvement of energy-conversion efficiency, technology innovations, uses of renewable energies, etc.
In many countries, including Thailand, diesel consumption is much higher than that of other fuels due to its use as the main fuel for mass transportation. Due to its combustion characteristics, the diesel engine shows higher thermal efficiency than the gasoline engine. However, the exhaust emissions from the diesel engine are higher. Several studies have been published showing the reduction of diesel consumption and emissions; blending diesel with biodiesel [2], [3], [4], [5], ethanol [6], ethers [7], and dual injection with natural gas [8], [9], [10], [11]. The results from these studies show less emissions at constant power output.
Natural gas offers several advantages such as clean combustion, high octane number (approximately 120), high availability, and attractive price. Additionally, its relatively high auto-ignition temperature is suitable for higher compression engines [9], [10]. For these reasons, natural gas is expected to find wide spread use in locomotive engines. Previous studies investigated the characteristics of dual fuel operation in unmodified or minor-modified gasoline engines [12], [13] and diesel engines [8], [9]. Dual injection of natural gas in gasoline engine leads to lower unburned hydrocarbon and carbon monoxide (CO) emissions, at the cost of reduced horse power and thermal efficiency. The combustion characteristics of diesel engine with natural gas/diesel fuels showed positive effect on thermal efficiency, total brake-specific fuel consumption, soot and NO emissions [8], [9]. However, the reports indicated that such dual operation system could not reach high speed operation as it could be gained while using only diesel engine. Therefore, the modification of the engine may offer an alternative way to trade off these effects.
The main objective of the present work is the modification of a diesel engine for natural gas operation to maximize output using gaseous fuel. The variation of combustion ratios was conducted to evaluate engine performance and emissions from the same engine. Engine performance includes brake torque, brake power, specific fuel consumption (SFC), and brake thermal efficiency. Emissions testing included total hydrocarbon (THC), nitrogen oxides (NOx), and carbon monoxide (CO) measurements.
Section snippets
Experimental
As previously stated, the primary purpose of this experimental investigation was to compare engine performance and emissions between a standard diesel engine and a modified one which used natural gas as the main fuel. The basic properties of the fuels used are given in Table 1, Table 2. The engine used in the present study was Daedong indirect injection diesel engine. The detailed specifications of this engine are shown in Table 3. The engine was loaded by a 130-kW Hwanwoong eddy current
Comparison of the diesel and natural gas engines
Engine outputs including engine brake power, brake torque, SFC and thermal efficiency of the diesel and natural gas engines are showed in Fig. 2, Fig. 3, Fig. 4, Fig. 5. Fig. 2 shows the influence of engine speed on the brake torque for both engines. As the engine speed increases, the brake torque continuously decreases as a result of a decrease in volumetric efficiency [14]. Compared to a diesel engine at the same engine speed, the natural gas engine shows higher brake torque. The difference
Conclusion
The modification of a diesel engine for natural gas operation was studied. A range of combustion ratios was used to evaluate engine performance and emissions using a natural gas fuel. The following are this study’s conclusions:
- 1.
Using the same engine, natural gas showed improved performance over the diesel engine, approximately 5.67%–13.07%.
- 2.
For CRs ranging from 9:1 to 10.5:1, a CR of 9.5:1 had the highest thermal efficiency at speeds between 1500 and 2500 rpm.
- 3.
CR of 10:1 showed a high torque at
Acknowledgment
The authors gratefully acknowledge the contribution of the College of Industrial Technology, King Mongkut’s University of Technology North Bangkok for the financial support.
References (17)
- et al.
Interest of combining an additive with diesel-ethanol blends for use in diesel engines
Fuel
(2001) - et al.
Effects of ethanol addition on performance and emissions of a turbocharged indirect injection diesel engine running at different injection pressures
Energy Conversion and Management
(2004) - et al.
Experimental investigation concerning the effect of natural gas percentage on performance and emissions of a DI dual fuel engine
Applied Thermal Engineering
(2003) Pressure–time characteristics in diesel engine fueled with natural gas
Renewable Energy
(2001)- et al.
Evaluation of the maximum horsepower of vehicles converted for use with natural gas fuel
Fuel
(2006) - et al.
Experimental study on combustion characteristics of a spark-ignition engine fueled with natural gas–hydrogen blends combining with EGR
International Journal of Hydrogen Energy
(2009) - et al.
A plan to keep carbon in check
Scientific American
(2006) - et al.
Performance of a constant speed CI engine on alcohol-diesel micro emulsion
Applied Engineering in Agriculture
(2004)
Cited by (54)
A review of the development and application of soot modelling for modern diesel engines and the soot modelling for different fuels
2023, Process Safety and Environmental ProtectionLife cycle assessment of alternative marine fuels for super yacht
2022, Regional Studies in Marine ScienceEffects of various discharge strategies on ignition and combustion of lean natural gas mixture under the static and turbulent conditions
2022, Experimental Thermal and Fluid Science