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Engine performance
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
A piston engine, also known as a reciprocating engine, is a heat engine that employs one or more pistons to release fuel energy through a combustion process and to convert it to rotating mechanical energy. Each piston is inside a cylinder, into which the air–fuel mixture is supplied, either already hot (i.e., external combustion) and under pressure (e.g., steam engine) or heated inside the cylinder (i.e., internal combustion). The combustion (ignition of the fuel–air mixture) in the cylinder is initiated either by the spark plug or by compression (i.e., diesel, where the heated air ignites fuel when injected). The combustion process generates a high-pressure gas while it increases the temperature of the gas.
Thermal Power Generation
Published in T.M. Aggarwal, Environmental Control in Thermal Power Plants, 2021
Engine-driven power plants use fuels such as diesel oil, fuel oil, gas orimulsion, and crude oil. The two types of engines normally used are the medium-speed four-stroke trunk piston engine and the low-speed two-stroke cross head engine. Both types of engine operate on the air-standard diesel thermodynamic cycle. Air is drawn or forced into a cylinder and is compressed by a piston. Fuel is injected into the cylinder and is ignited by the heat of the compression of the air. The burning mixture of fuel and air expands, pushing the piston. Finally the products of combustion are removed from the cylinder, completing the cycle. The energy released from the combustion of fuel is used to drive an engine, which rotates the shaft of an alternator to generate electricity. The combustion process typically includes preheating the fuel to the required viscosity, typically 16–20 centistokes (cSt), for good fuel atomization at the nozzle. The fuel pressure is boosted to about 1,300 bar to achieve a droplet distribution small enough for fast combustion and low smoke values. The nozzle design is critical to the ignition and combustion process. Fuel spray penetrating to the liner can damage the liner and cause smoke formation. Spray in the vicinity of the valves may increase the valve temperature and contribute to hot corrosion and burned valves. If the fuel timing is too early, the cylinder pressure will increase, resulting in higher nitrogen oxide formation. In injection is timed too late, fuel consumption and turbocharger speed will increase. NOx emissions can be reduced by later injection timing but then particulate matter and the amount of unburned species will increase.
Multi Cycle Modeling, Simulating and Controlling of a Free Piston Engine with Electrical Generator under HCCI Combustion Conditions
Published in Combustion Science and Technology, 2020
Mohammad Alrbai, Matthew Robinson, Nigel Clark
One of the first models which involved chemical kinetics in simulating the free-piston engine was presented by Goldsborough and Van Blarigan (Goldsborough and Van Blarigan 1999) from Sandia National Laboratories (SNL). They used a zero-dimensional model to represent the in-cylinder thermodynamics in their free piston engine. In their model, base parameters were calculated by an initialization scheme which required the bulk of the computational time. In their initialization scheme, the combustion process was assumed to be a constant volume process with an estimated auto-ignition point near the TDC position. The simulation scheme then started an iteration process between the chemical kinetics algorithm and the dynamic model. A Hydrodynamics, Chemistry, and Transport (HCT) software tool was used to represent the fuel species reactions. The engine cycle was completely driven by the HCCI combustion of hydrogen fuel. The published research included a basic parametric study to predict the engine performance with different equivalence ratio, scavenging efficiency, and compression ratio. The study concluded that compression ratio is significant in controlling the engine. Also, the researchers found that operation under relatively low equivalence ratios would help in reducing the NOx emissions.
Effective utilization and evaluation of waste plastic pyrolysis oil in a low heat rejection single cylinder diesel engine
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Padmanabhan Sambandam, Harish Venu, Balan Kuttinadar Narayanaperumal
The WPO utilization was investigated by measuring engine performance and emission characteristics study. The test was performed by using diesel as the baseline fuel, an 10% incremental blend of WPO with diesel used at LHR engine at the incremental load of 25% from 0% to 100%. The evaluation was made on uncoated diesel engine and coated piston engine with fuel of diesel and WPO blends. Conventionally, several types of equipment are widely used to measure the gases released during emission. The gases released from the engines that are measured include partially burned hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and smoke. Inhalation of odorless CO may initially cause headaches in individuals but can be fatal when more concentration of CO accumulates in bloodstream preventing the entry of oxygen into the body. Moreover, increased concentration of CO2 in the atmosphere causes the greenhouse effect and thereby leads to global warming. The most hazardous among all the exhaust is the HC which is released from vehicle engines.
Impact of ethanol, methyl tert-butyl ether and a gasoline–ethanol blend on the performance characteristics and hydrocarbon emissions of an opposed-piston engine
Published in Biofuels, 2020
The torque curves have convex exponential shapes. Up to peak torque value, the rising amount of air–fuel intake with increasing speed raised the torque, and all types of frictional losses as well. The bi-directional movement piston behavior in the opposed-piston engine cylinder caused the losses to increase rapidly. The highest torque value was obtained using ethanol. In ethanol usage, the torque reached its maximum value (∼125 Nm) at approximately 2000 rpm. Similar behaviors were observed for gasoline, MTBE and E85. The torque reached the maximum point (∼119 Nm) at 2000 rpm for gasoline. At MTBE, the torque curve trend is higher than that of gasoline and E85, reaching the maximum point (∼124 Nm) at 2000 rpm.