IC ENGINE PERFORMANCE LAB REPORT
Introduction
This experiment examines different characteristics of petrol and diesel engine. It was done with three main objectives: to understand the operational and design characteristics of both petrol and diesel engines, to determine the full-throttle torque and power as well as fuel consumptions attributes, and to experimentally determine the mechanical efficiency of diesel and petrol engines alike. While petrol engines are applied in petrol ICEs, diesel engines can be applied in both heating systems and Diesel ICEs. Diesel engines are known to exhibit more torque at low speed while petrol engines run at high revolutions per minute with reduced torque.
According to Schilling, ICE can be defined as a mechanical device that is used to transform the energy stored in different forms of fuel into torque and power (2010). The engine block houses various parts which operate in synch to produce and extract rotating power for fuel. The engine is made up of four major parts including a cylinder, pistons, crankshaft and the connecting rods. The connecting rods are used to connect the piston and the crankshaft. On the other hand, the crankshaft shafts with the offset to which the connecting rods are linked (Kobayashi, 2015). The piston is fitted inside the cylinder and prevents air from leaking while combustion occurs inside the cylinder.
Diesel and petrol engines exhibit full load performance figures regarding thermal, power output and mechanical efficiencies. However, the two engine types demonstrate differences. As compared to Petrol engines, diesel engines are more quantity governed whereas petrol engines are quality governed. Additionally, petrol engines are designed to be light in weight. For this reason, petrol engines are more suitable to function and operate at conditions that require comparable higher revolutions per minute as compared to diesel engines (Murugesan et al., 2009). A better fuel economy is highly demonstrated in the diesel engine as compared to the petrol engine. Furthermore, diesel engines exhibit improved thermal efficiencies at various speeds and load conditions.
Procedure
Since the data of the petrol engine is given, the diesel engine will be tested at its maximum torque output. The obtained results were compared with the presented petrol engine at full throttle. The measurements of the revolutions per minute, torque and fuel flow was used to determine Torque/speed characteristics and power/speed characteristics and fuel economy. The diesel engine was run at a set speed to determine its mechanical efficiency. The Willians Line Method was used to test the mechanical efficiency of the engine. The results of the petrol engine tested using the Morse method.
Results
Petrol Engine
Presentation
GRAPH 1 Torque and shaft power against RPM
Figure 1: A graph showing the relationship between torque and shaft power against speed(RPM) for both diesel and petrol engine.
GRAPH 2: BSFC against shaft power
Figure 2: A graph showing the relationship between nth and shaft BSFC against shaft power for both diesel and petrol engine.
Calculations
Mechanical efficiencies
Diesel engine (Willian Line Method)
Mechanical efficiency in diesel engines is determined through Willian Line Method which entails constructing a curve of fuel flow against the torque produced by the engine.
Petrol engine
Output power = Indicated power – Friction power
Indicated power= torque x speed
Cylinder 1 out: 500000
Cylinder 1 out: 525000
Cylinder 1 out: 520000
Cylinder 1 out: 512500
IP= 4W-ΣW-
= 4X728750 -2057500
=2915000-2057500
= 85,7500
Observation
It was noted that as compared to the petrol engine, diesel engine demonstrated lower torque at the same revolutions per minute. Torque in petrol engine is commonly advanced than that in diesel engines. Additionally, the fuel utilization rate of both engines increased with increased speed and torque. Nonetheless, the petrol engine guzzled more fuel at a higher rate than the diesel engine.
Discussion
As noted by Woodyard, the performance relationship of BMEP against revolutions per minute can be generated for the various characteristics of these engines (2009). The maximum permissible power, the availability of air and torque of the engine highly determines the function and behavior brake mean effective pressure. In other words, the engine's aptitude to do work and rating is highly affected and limited by both the availability of air, maximum permissible power as well as the maximum permissible torque (Kobayashi, 2015). Additional factors and conditions that affect the performance and engine characteristics include the density of air at the start of compression, the ability of the engine to trap air, the effectiveness of the gas exchange process within the engine and the quality of fuel and combustion, hence thermodynamic cycles and combustion processes.
Conclusion
According to the fuel economy (the relationship between the time is taken to consume the set amount of fuel and the speed of the engine), the rate of fuel consumption in petrol engine increases drastically as compared to the diesel engine. This indicates the diesel engine has a better fuel economy than the petrol engine. Both engines experience a plateau phase in fuel consumption rate between the speed of 2000 and 3500. Power output and fuel efficiency evaluation of the two engines indicates a significant factor which can be used to distinguish the quality of petrol and diesel engines. The petrol engine is more fuel efficient as well as powerful than diesel engines. At low torque, petrol engine produces more revolutions per minute than diesel engines.
References
Kobayashi, S. and Harada, T., Toyota Jidosha Kabushiki Kaisha, 2015. Internal Combustion Engine. U.S. Patent 20,150,252,749.
Mollenhauer, K., & Tschöke, H. (Eds.). (2010). Handbook of diesel engines. Springer Science & Business Media.
Murugesan, A., Umarani, C., Subramanian, R., & Nedunchezhian, N. (2009). Bio-diesel as an alternative fuel for diesel engines—a review. Renewable and Sustainable Energy Reviews, 13(3), 653-662.
Schilling, J. C. (2010). U.S. Patent No. 7,694,505. Washington, DC: U.S. Patent and Trademark Office.
Woodyard, D. (2009). Pounder's marine diesel engines and gas turbines. Butterworth-Heinemann.
