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Internal Combustion Engines
Published in Iqbal Husain, Electric and Hybrid Vehicles, 2021
Most spark-ignition engines, or gasoline engines as it is more commonly known, run on a modified Otto cycle. The air-fuel ratio used in these engines is between 10/1 and 13/1. The compression ratios are in the range of 9–12 for most production vehicles. The compression ratio of the engine is limited by the octane rating of the engine. A high compression ratio may lead to auto-ignition of the air-fuel mixture during compression, which is absolutely undesirable in a spark-ignition engine. The spark-ignition engines have been originally developed by limiting the amount of air allowed into the engine using a carburetor placed in the path of air intake. The function of the carburetor is to draw the fuel by creating a vacuum following ‘Bernoulli’s principle’. However, fuel injection, which is used for diesel engines, is now common for gasoline engines with spark ignition instead of the carburetor. The control objective for fuel injection systems is to compute the mass flow rate of air into the engine at any instant of time and to mix the correct amount of gasoline with it, such that the air and fuel mixture is right for the engine running condition. In recent years, the requirements to meet the strict exhaust gas emission regulations have increased the demand for fuel injection systems.
Internal Combustion Engines
Published in Mehrdad Ehsani, Yimin Gao, Ali Emadi, and Fuel Cell Vehicles, 2017
Mehrdad Ehsani, Yimin Gao, Ali Emadi
Proper fuel/air (or air/fuel) ratio in the fuel/air mixture is a crucial factor that affects the performance, efficiency, and emission characteristics of an engine, as shown in Figure 3.8. The mean effective pressure peaks at slightly rich stoichiometry (between φ = 1 and φ = 1.2). However, the fuel conversion efficiency decreases as the mixture is enriched above the stoichiometry (φ > 1) because part of the fuel is left after the combustion. When φ decreases, the fuel conversion efficiency increases because there exists sufficient oxygen in the cylinder to oxidize the fuel and the energy of the fuel is almost completely released as thermal energy. In SI engines, too lean mixtures will cause misfire. φ = 0.8 would be the bottom limit. With lean mixtures, the combustion produces lower temperature in the cylinder and thus results in low mean effective pressure.
Engine emission control
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
If in the interests of maximum power the air-fuel ratio is quite low and there is an excess of fuel, the quality of combustion will be poor and the emissions of both hydrocarbons and carbon monoxide will be high. These can be reduced by moving the air-fuel ratio to a region that is just rich of stoichiometry, which in fact better enables maximum power to be attained, but also incurs a penalty of increased emissions of nitrogen oxides. Should the primary aim be best economy and the air-fuel ratio moved across the dividing line to a region just lean of stoichiometry, then combustion temperatures will be raised to a maximum and produce the highest emissions of nitrogen oxides. These can be much reduced and the emissions of carbon monoxide kept to a minimum by further weakening the mixture until it comes into the ‘lean-burn’ region, which has been defined as one where the air-fuel ratios lie between 18:1 and 21:1, but the gains mentioned are bought at the expense of increased emissions of hydrocarbons and the possibility of rough running, if there is insufficient fuel for the mixture to burn properly.
Transient fuel consumption prediction for heavy-duty trucks using on-road measurements
Published in International Journal of Sustainable Transportation, 2023
Chong Peng, Yiyi Wang, Ting Xu, Yixin Chen
The CMEM is a function of vehicle power output, engine speed, and air/fuel ratio, formulated in Eq. (10). where FR is the fuel-use rate in g/s. P is engine power output in kilowatt (kW). is the engine friction factor, typically 0.2 for heavy trucks (Demir et al., 2011). is engine speed in revolutions per second. is engine displacement in L. η is a measure of the engine effective thermal efficiency, typically 0.45 (Barth et al., 2004). H is the lower heating value of a typical diesel fuel, typically 43.2 kJ/g (Barth et al., 2004). The parameter is the air/fuel equivalence ratio. The theoretical air-fuel ratio is approximately 14.6 (An et al., 1997).
Combustion and emission characteristics of light duty diesel engine fueled with transesterified algae biodiesel by K2CO3/ZnO heterogeneous base catalyst
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Jayashri Narayanan Nair, Yeditha Veera Venkata SatyanarayanaMurthy, Syed Javed
Figure 8 shows the variation of relative air – fuel ratio (λ) at different loads for ABD5, ABD10, ABD15, ABD20& Diesel fuel. Figure 8 illustrates that increase in engine load decreases the air-fuel ratio for all blends. The air-fuel ratio for all the blends and diesel fuel is greater than unity. The air-fuel ratio influences the combustion phenomenon and completeness of the combustion mostly in the lean fuel zone. Air-fuel ratio of biodiesel blend is higher compared to that of neat diesel. This trend is also reflected in bsfc graphs in Figure 2a. Similar results are also reported by Sinha and Agarwal (2005) for experiments conducted on rice bran methyl ester at variable engine speed. The air-fuel ratio for ABD15 is less than that of ABD20 in 3/4th load and full load conditions.
Performance and emissions of gasoline blended with fusel oil that a potential using as an octane enhancer
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Ahmed N. Abdalla, Omar I. Awad, Hai Tao, Thamir K. Ibrahim, Rizalman Mamat, Ali Thaeer Hammid
The air–fuel ratio is the mass ratio between air and fuel in the mixture provided to the engine. The stoichiometric air–fuel ratio illustrates the minimum amount of air wanted to complete the fuel burning. The ratio between the stoichiometric air–fuel ratio to the actual air–fuel ratio is called the lambda (ƛ). The lambda a significant impact on the engine performance, combustion, and formation of emissions. A typical lambda has a direct impact of on the brake power and brake specific fuel consumption (BSFC) of an SI engine. Highest brake power is achieved at the rich mixture (ƛ < 1) because of the higher rate of heat release. While the least BSFC is achieved at the lean mixture (ƛ > 1) due to the better combustion of fuel molecules that results in higher thermal efficiency. The general trends of formation of NOx, HC, and CO2 emissions also affected by lambda. At the lean mixture (ƛ > 1) side, the NOx and HC emission increased, while CO continues to decrease slightly (Ivanič et al. 2005).