A comparative analysis of knock severity in a Cooperative Fuel Research engine using binary gasoline–alcohol blends

Today, the demand for higher output efficiencies, lower fuel consumption, and ever reduced emissions has been rising. Due to its availability, one promising alternative is the applying of hydrogen in internal combustion engines. In this study, the initial efforts concentrated on combine relationships of input and output parameters of hydrogen compressed natural gas spark-ignition engine. The quadratic regression models were conducted for all six responses: torque, carbon monoxide, brake-specific fuel consumption, methane, nitrogen oxides, and total hydrocarbon through response surface methodology and tested for adequacy by analysis of variance. The multi-objective desirability approach employed for the optimization of input variables, namely, the hydrogen compressed natural gas ratio, excess air ratio ( λ), and ignition timing ( θi). Also, two factors, that is, manifold absolute pressure and engine speed, were fixed at 105 kPa and 1600 r/min, respectively. Results indicate that the optimal independent input factors are equal to λ of 1.178, hydrogen compressed natural gas ratio of 25.98%, and θi of 18 °CA before top dead center. Also, the optimal combination of responses is as follows: brake-specific fuel consumption of 219.334 g/kWh, the torque of 395 N m, 30.189 g/kWh for nitrogen oxides, carbon monoxide equal to 5.093 g/kWh, total hydrocarbon of 0.633 g/kWh, and 0.572 g/kWh for methane. This study provided the significance of response surface methodology as an attractive technique for investigators for modeling. In this regard, the response surface methodology modeling and multi-objective desirability approach can be utilized to predict the emission and performance characteristics of the hydrogen compressed natural gas engines minutely.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical study of hydrogen addition on the performance and emission characteristics of compressed natural gas spark-ignition engine using response surface methodology and multi-objective desirability approach

Boodaghi

Etghani

Sedighi

2020

“…The use of CFR engine for experimental determination of combustion characteristics is common in literature. [8][9][10][11] However, the numerical simulation of CFR engine is sparse. Recently, Garcı´a et al 12 have developed a virtual 1-D model of CFR engine with GT Power.…”

Section: Introductionmentioning

confidence: 99%

Fuel-air mixing in motored CFR engine at research octane number (RON) relevant condition

Bhattacharya,

Keskinen,

Larmi

et al. 2023

This paper presents a three-dimensional (3-D) computational fluid dynamics (CFD) study of a motored cooperative fuel research (CFR) engine at research octane number (RON) relevant condition. The boundary conditions for 3-D simulations were generated with a one-dimensional GT-Power model. For the first time in literature, a carburetor was added to a virtual CFR engine model with 3-D CFD. Therefore, the proposed setup can simulate the fuel and thermal stratifications inside the engine cylinder with realistic detail. The transient simulations in this work were performed within the Reynolds-averaged Navier-Stokes (RANS) framework with a Realizable k-ε turbulence model. Major conclusions from the present work are: (1) The in-cylinder flow of the CFR engine is swirl-dominated due to the existence of the intake valve shroud. (2) There is a significant amount of liquid droplets entering the cylinder during the intake stroke. The maximum instantaneous amount of liquid for 50% PRF 87 (containing 87% iso-octane and 13% n-heptane (v/v)) and 50% ethanol mixture is indicated to be around 26% of total injected fuel mass. (3) The heat of vaporization (HoV) of the fuel is responsible for creating both temperature and charge stratification inside the cylinder.

“…12 Various indexes can be found to evaluate the knock content [13][14][15] but the maximum amplitude of pressure oscillations (MAPO) is one of the most common. 16,17 The MAPO is obtained by high-pass filtering the measured in-cylinder pressure trace every cycle and a threshold is traditionally determined empirically from experimental data by the user to avoid engine damage. When combustion conditions lead to unsafe operation where spontaneous auto-ignition of the end gas appears, the MAPO is detected above this limit and the cycle is considered as knocking.…”

Section: Introductionmentioning

confidence: 99%

Safe operation of dual-fuel engines using constrained stochastic control

Guardiola

Plá

Bares

et al. 2021

Premixed combustion strategies have the potential to achieve high thermal efficiency and to lower the engine-out emissions such as NOx. However, the combustion is initiated at several kernels which create high pressure gradients inside the cylinder. Similarly to knock in spark ignition engines, these gradients might be responsible of important pressure oscillations with a harmful potential for the engine. This work aims to analyze the in-cylinder pressure oscillations in a dual-fuel combustion engine and to determine the feedback variables, control actuators, and control approach for a safe engine operation. Three combustion modes were examined: fully, highly, and partially premixed, and three indexes were analyzed to characterize the safe operation of the engine: the maximum pressure rise rate, the ringing intensity, and the maximum amplitude of pressure oscillations (MAPO). Results show that operation constraints exclusively based on indicators such as the pressure rise rate are not sufficient for a proper limitation of the in-cylinder pressure oscillations. This paper explores the use of a knock-like controller for maintaining the resonance index magnitude under a predefined limit where the gasoline fraction and the main injection timing were selected as control variables. The proposed strategy shows the ability to maintain the percentage of cycles exceeding the specified limit at a desired threshold at each combustion mode in all the cylinders.