Effect of Valve Timing and Excess Air Ratio on Torque in Hydrogen-Fueled Internal Combustion Engine for UAV

Abstract

In this study, in order to convert a 2.4 L reciprocating gasoline engine into a hydrogen engine an experimental device for supplying hydrogen fuel was installed. Additionally, an injector that is capable of supplying the hydrogen fuel was installed. The basic combustion characteristics, including torque, were investigated by driving the engine with a universal engine control unit. To achieve stable combustion and maximize output, the intake and exhaust valve opening times were changed and the excess air ratio of the mixture was controlled. The changes in the torque, excess air ratio, hydrogen fuel, and intake airflow rate, were compared under low engine speed and high load (wide open throttle) operating conditions without throttling. As the intake valve opening time advanced at a certain excess air ratio, the intake air amount and torque increased. When the opening time of the exhaust valve was retarded, the intake airflow rate and torque decreased. The torque and thermal efficiency decreased when the opening time of the intake and exhaust valve advanced excessively. The change of the mixture condition’s excess air ratio did not influence the tendency of the torque variation when the exhaust valve opening time and torque increased, and when the mixture became richer and the intake valve opening time was fixed. Under a condition that was more retarded than the 332 CAD condition, the torque decreased by about 2 Nm with the 5 CAD of intake valve opening time retards. The maximum torque of 138.1 Nm was obtained at an optimized intake and the exhaust valve opening time was 327 crank angle degree (CAD) and 161 CAD, respectively, when the excess air ratio was 1.14 and the backfire was suppressed. Backfire occurred because of the temperature increase in the combustion chamber rather than because of the change in the fuel distribution under the rich mixture condition, where the other combustion control factors were constantly fixed from a three-dimensional (3D) computational fluid dynamics (CFD) code simulation.

Effects of Compression Ratios on Combustion and Emission Characteristics of SI Engine Fueled with Hydrogen-Enriched Biogas Mixture

“…The chemical reaction mechanism used for the hydrogen-biogas combustion was based on the Arrhenius law, leading to a rate coefficient expressed as follows: (7) where A is the values of the pre-exponential coefficient, T is temperature, E a is the activation energy, and β is the temperature-dependent coefficient.…”

“…Using pure hydrogen as a fuel for the ICE could avoid many problems, i.e., low power density, high NO x emissions, and knock or backfire phenomena. This is because the absence of carbon atoms in hydrogen's composition induces lean combustion (i.e., zero emissions of CO 2 , CO, and HC) [6][7][8][9][10]. However, knock combustion is one of the disadvantages of the use of hydrogen as a fuel for ICE.…”

NOx Reduction in Diesel-Hydrogen Engines Using Different Strategies of Ammonia Injection

“…The production of NO x from oxygen and nitrogen in the air is a problem associated to the combustion of fuels, and its reduction has been investigated for a long time. As a possible solution to reduce NO x , hydrogen allows internal combustion engines to operate under ultra-lean combustion and thus under low-temperature combustion and lower NO x emissions, but at the expense of reducing efficiency noticeably [25][26][27]. Other procedures to reduce NO x emissions in internal combustion engines can be briefly summarized in primary and secondary measures.…”