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Compression-Ignition Engine Combustion
Published in Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong, Combustion Engineering, 2022
Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong
Diesel engines follow the same four-stroke cycle as SI engines. The primary difference is that ignition of the fuel in a diesel engine is by compression, and there is no spark plug. Some diesel engines have glow plugs for cold starting. In the ideal thermodynamic cycle, diesel combustion occurs at constant pressure, whereas combustion in the Otto cycle occurs at constant volume. In practice for both types of engines, the pressure and volume change during combustion. Diesel engines, similar to SI engines, have a higher thermal efficiency at an increased compression ratio. The compression ratio in SI engines, which burn premixed fuel and air, is limited by abnormal knocking combustion. Diesel engines, which have direct injection of liquid fuel into each cylinder, do not experience knock and thus can have a higher compression ratio than SI engines. Whereas diesel engines may have compression ratios between 12 and 18, the compression ratio in SI engines is limited to about 10. In addition, diesel engines control load (power output) by reducing the amount of fuel injected into each cylinder. By contrast, SI engines restrict the air and the fuel at part load by means of a throttle so as to maintain a stoichiometric mixture over all loads. The throttle increases the pressure loss during the intake stroke, increasing pumping loss and reducing the net thermal efficiency of the SI engine.
Road-Traffic Emissions
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Air Quality and Energy Systems, 2020
Fabian Heidegger, Regine Gerike, Wolfram Schmidt, Udo Becker, Jens Borken-Kleefeld
As previously mentioned, kinetic energy is generated in either a combustion or an electric engine. Electric engines have a higher degree of efficiency than combustion engines. A hybrid vehicle obtains its energy from an electric engine and a fuel-based engine. Combustion engines are characterized by a cyclic, non-stationary, and non-optimal combustion process (Pfäfflin 2018). For a comparable vehicle type with similar engine power, the diesel engine has an advantage in terms of fuel consumption as compared to the gasoline engine. The spark ignition of the diesel leads to a more energy-efficient yield of fuel: This combustion process results in less fuel consumption and lowers CO2 emissions; however, rising combustion temperatures lead to greater NOx emissions.
Engines
Published in Tom Denton, Alternative Fuel Vehicles, 2018
Diesel engines have the fuel injected into the combustion chamber where it is ignited by heat in the air charge. This is known as compression ignition (CI) because no spark is required. The high temperature needed to ignite the fuel is obtained by a high compression of the air charge. Diesel fuel is injected under high pressure from an injector nozzle, into the combustion chambers. The fuel is pressurised in a diesel injection pump. It is supplied and distributed to the injectors through high pressure fuel pipes or directly from a rail and/or an injector. The high-pressure generation is sometimes created by a direct acting cam on each injector, but mostly on smaller engines, by a separate pump. A range of diesel injection components is shown as Figure 5.34.
Straight vegetable oil fuel performance and exhaust emissions under turbocharged and naturally aspirated conditions
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Albert K. Sunnu, Godwin K. Ayetor, James M. Gaye
The higher oxygen content of vegetable oils associated with lower ignition delay period provides an important reduction in the CO emission by improving combustion. Moreover, the carbon/hydrogen (C/H) ratio of vegetable oil is slightly lower than that of diesel fuel, which yields lower CO emissions with the use of vegetable oil. It was experimentally determined that the TU operation causes a noticeable reduction in CO emission. Compared to NA operation, in the TU operation, the CO emissions for diesel fuel and vegetable oil are on the average 40% and 17% lower, respectively. Mean CO emissions of both vegetable oils in the TU operation are 28% lower than those in the DF-TU operation. The application of a turbocharger provides increased air to the diesel engine and enables the mixing of fuel–air easily in the combustion chamber, thereby causing better combustion and lower CO emission values.
The combined effect of multiwalled carbon nanotubes and exhaust gas recirculation on the performance and emission characteristics of a diesel engine
Published in International Journal of Ambient Energy, 2019
Anchupogu Praveen, G. Lakshmi Narayana Rao, B. Balakrishna
Environmental pollution caused by the combustion of fossil fuels has been creating an impact on the environment and human life. The contribution of the petroleum-based fuels does not meet the current demand of energy due to increased automobiles utilisation in the transportation sector (Jayed et al. 2009). Diesel engines are more advantageous because of their higher efficiency, fuel economy, reliability and durability. But diesel engines emit various pollutants (such as CO, CO2, HC, NOx and smoke emissions) into the environment, creating air pollution (Khalife et al. 2017). The NOx emissions from diesel engines create harmful effects on the environment and human health. The NOx emissions were reduced by adopting after treatment technologies like exhaust gas recirculation (EGR), Selective catalytic reduction (SCR), Lean NOx Trap (LNT) and SCR Filter (SCRF) (Devarakonda, Parker, and Johnson 2008).
A numerical study on the effect of thermal and charge stratification on the HCCI natural gas engine
Published in International Journal of Ambient Energy, 2021
Mohsen Pourfallah, Mahbod Armin, Ali Akbar Ranjbar
A glow plug is typically a thin pencil-shaped heating element that protrudes into a diesel engine combustion chamber which is used to create thermal stratification and help cold-start emissions in conventional diesel engines. In this study, the effect of glow plug temperatures on thermal stratification and combustion phasing was investigated. As shown in Figure 8, a glow plug is installed around the outlet valve on the cylinder head. The glow plug tip temperature is controlled by a variable DC voltage supply. It is desired to know the glow plug tip temperature as a function of the supply voltage. The glow plug that is used in this work is selected from Bosch company products. This type of glow plug is able to reach 1100°C in less than 3 s.