The icing of an intake pipe that might happen in an actual vehicle was numerically predicted in this study. For various operating conditions, the amount of icing was estimated, and the variables influencing the amount of icing were identified. We compared the factors that affected icing: relative humidity, air temperature, and inlet velocity. Seven RPM and load conditions, an intake temperature range of 253–268 K, and a relative humidity range of 65–85% were used for the case studies. To verify the model accuracy, wind tunnel test results from chassis dynometer tests were compared to the data from simulations. The flow analysis was performed using the numerical analytical tool ANSYS Fluent (2019 R1), while the amount of condensed water and icing was predicted using FENSAP-ICE, a program that analyzes and predicts icing phenomena under mechanical systems. The ambient temperature, relative humidity, and inlet air velocity had the biggest effects on the icing rate. The total amount of icing increased for similar BB and input air velocities. When the input air and BB velocities are the same, the variables influencing icing are the ambient temperature and relative humidity. The amount of ice was less affected by outside temperature and relative humidity when the rpm was high, and the inlet air velocity also had an impact.

In this study, we numerically predicted the icing of an intake pipe that may occur in an actual vehicle. The amount of icing was predicted for each operating point, and factors affecting icing were determined. Relative humidity, air temperature, and inlet velocity were compared as variables that affected icing. Case studies were conducted at seven operating points, an intake temperature of 253–268 K, and a relative humidity of 65–85%. The values obtained from a tunnel test were compared with simulation data to ensure the reliability of the model. The numerical analysis tool ANSYS Fluent was utilized to conduct the flow analysis, whereas the amount of condensation and icing were predicted using the icing analysis tool FENSAP-ICE. The icing was most affected by outside temperature, relative humidity, and inlet air velocity. When the inlet air and BB velocities were similar, the amount of ice increased. The factors affecting icing are the outside temperature and relative humidity when the inlet air and BB velocities are identical. With the high rpm conditions, the lesser the effect of outside temperature and relative humidity, and the velocity of the inlet air affected the amount of ice.

A Numerical study is performed for generated condensation and icing phenomenon of the intake system for diesel engines when blow-by gas discharged to the intake system in the crankcase is mixed with cold air under low and medium RPM conditions. After ensuring the model reliability by comparing the icing inside the vehicle with the wind tunnel test data and the CFD simulation data, the icing was predicted under various driving conditions. CFD simulation can be used to predict and compare the amount of icing that occurs in different operation points and analyze the key factors that influence icing formation. Flow analysis is performed numerically using ANSYS Fluent, where condensation and icing are predicted using FENSAP-ICE. The variable affecting the icing the most significantly is the outside air temperature, where a lower temperature increases the amount of icing. However, when comparing the eight operation points, the amount of icing was the lowest when the inflow air and the discharged blow-by gas velocity were similar representing the amount of icing decreases as the mixture of intake air and blow-by gas increases. Although the outside air temperature and relative humidity cannot be controlled, controlling the blow-by gas discharge rate can reduce internal icing.

The lean burn capability of spark ignition engines fueled with biogas was investigated using a one-dimensional (1D) cycle simulation and Latin hypercube sampling. The dominant variables were hydrogen contents, spark timing, and relative air fuel ratio. The fundamental effects of hydrogen were first investigated in terms of the in-cylinder temperature, heat release rate, and flame shape. To describe the combustion behavior, a user-defined combustion model was input based on the laminar flame speed of the biogas-H-2 mixture. Hydrogen acted as an enhancer of thermodynamic properties in the combustion phase by increasing the temperature and heat release rate with H-2 addition for up to 15% volume ratio. By varying spark timings, the maximum torque timing was retarded with hydrogen addition. By varying the relative air-fuel ratio, the mass fraction of the fuel burned could be enhanced in the lean burn region.

Homogeneous charge compression ignition (HCCI) is an alternative combustion strategy employed for automotive systems. It has a higher thermal efficiency with lower nitric oxides and particulate matter emissions that are below current emission requirements. However, owing to difficulties associated with combustion control, HCCI engines have disadvantages in terms of combustion instability, such as low-speed-low-load or high-speed-high-load conditions. This study investigates the effects of different parameters on HCCI engine combustion using numerical methods. The parametric study is carried out at low loads (25% part load), and a reference intake temperature of 550 K is used to preheat the air-fuel mixture. The GRI-3.0 chemical reaction mechanism involving 53 species and 325 reactions is used for 1-D simulations describing the combustion process fueled with methane and hydrogen added methane. By changing the variables, including compression ratio, excess air ratio, and hydrogen content, the combustion behavior is investigated and discussed. The results show that an increase in compression ratio resulted in a faster start of combustion and caused higher in cylinder pressure and heat-release rate. When the excess air ratio was increased, the start of combustion was delayed and lower in-cylinder pressure and heat release rate were observed. The results were similar for varying compression ratios. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

A combustion model is introduced with a 1D engine-cycle model, and a parametric study is performed by varying the hydrogen content in a heavy-duty engine with reformed-gas injection. The effect of hydrogen on the engine combustion and performance is investigated by adding hydrogen to a natural-gas-fueled engine system. The in-cylinder pressure and torque could be enhanced up to 15% in volume with the hydrogen addition. However, the nitric oxide (NOx) emissions increased slightly due to the increase in in-cylinder temperature caused by the thermal NOx formation mechanism. To suggest engine-design points, multi-objective Pareto optimization was performed by varying the valve overlap. Throughout the Pareto fronts' optimization results, conceptual engine-design possibilities were suggested by sweeping the operating parameters. Adding 15% hydrogen improved the fuel consumption; however, the resulting higher temperature caused an increase in NOx emissions. Moreover, considering the NOx emissions, it was not a good option to add hydrogen at less than 1000 rpm.