Hydrogen Diesel Research Articles

Decarbonisation of heavy-duty diesel engines using hydrogen fuel: a review of the potential impact on NOx emissions

Hydrogen–diesel co-fuelling may reduce NOx and PM2.5 emissions if used in lower load construction machinery and HGVs. In high load applications such as electrical generators, emissions could be higher than pure diesel, unless further abated.

Crystallization Behavior of Ammonium Chloride in High-Pressure Heat Exchanger of Hydrotreating Unit

In view of the corrosion failure of a high-pressure heat exchanger in a diesel hydrogenation unit, the formation mechanism of ammonium chloride in a multiphase flow system is investigated in this article. Numerical simulation is carried out by user defined function (UDF) on the process of adding source of mass transfer in computational fluid dynamics (CFD) solvers. The distribution characteristics of ammonium chloride are illustrated by the parameters including crystallization temperature of ammonium chloride, volume fraction of ammonium chloride, and mass transfer rates of NH3 and HCl, and the causes of corrosion cracking in the U-shaped bend of the heat exchanger are discussed. The results show that there is a great risk of ammonium chloride deposition in the heat exchanger from 4.5 m away from the outlet of the second pass. The crystallization area in the tube gradually expands from the wall to the center along the flow direction, and the crystallization rate is higher near the tube wall. The field sampling test results show that the corrosion cracking is hydrogen-induced cracking, which is due to the existence of large amount of hydrogen, high impacting force, excessive flow rate, and the risk of ammonium chloride particle erosion at the U-bend. In order to alleviate the corrosion of ammonium chloride deposition, some improvement measures are put forward, such as raising the inlet temperature of the tube side to 215 °C and increasing the water injection by 30%, which play an important role in decreasing the formation of ammonium chloride in the heat exchange system.

Risk assessment of hydrogen leakage in diesel hydrogenation process

Hydrogen, the raw material of diesel hydrofining process, is flammable and explosive. Once the leaking hydrogen is exposed to ignition sources, it will cause huge losses to people's health and property safety. In this paper, a dynamic risk assessment method of hydrogen leakage based on Dynamic Bayesian Network is proposed to analyze the uncertainty and dynamics of hydrogen leakage risk in the diesel hydrogenation process and to make up for the shortage of dynamic risk assessment of diesel hydrogenation process nowadays. Through the case study of diesel hydrogenation process, the applicability and advantages of the proposed method are proved. The dynamic changes of hydrogen leakage probability, the critical risk factors and safety barriers of hydrogen leakage accident are obtained, and possible accident consequences in two years are identified. Meanwhile, the corresponding measures which provide theoretical guidance for the safety production of petrochemical enterprises are proposed to further reduce the risk of hydrogen leakage in the diesel hydrogenation process.

Влияние регулируемых параметров рабочего процесса на образование оксидов азота в водородном дизеле

The article considers formation of nitrogen oxides in a hydrogen diesel engine with direct injection of gaseous hydrogen depending on the adjustable parameters of the working process: excess air ratio, cyclic hydrogen supply, advance angle and duration of hydrogen injection. It was found that in a number of cases the effect of these parameters on the working process and the emission of nitrogen oxides leads to results that differ significantly from those in traditional diesel engines running on hydrocarbon fuel. It is shown that by varying the specified controlled parameters, it is possible to minimize the concentration of nitrogen oxides in the exhaust gases of a hydrogen diesel engine.

Hydrogen-diesel co-combustion characteristics, vibro-acoustics and unregulated emissions in EGR assisted dual fuel engine

This work investigates the co-combustion characteristics of the hydrogen-diesel dual fuel with exhaust gas recirculation (EGR). The experiments were performed on a retrofitted duel fuel compression ignition engine for the entire engine load spectra, while the maximum hydrogen energy share in the study was 30%. Further, EGR was varied up to 10% to examine its effect on the hydrogen-diesel co-combustion and other relevant characteristics. It was found that although, hydrogen exhibit contrasting effects on the combustion at low and high loads, EGR continually degraded the peak combustion pressure. However, interestingly, the combustion’s variability improved on addition of EGR at higher loads, despite EGR’s detrimental effect on variability at lower loads. In addition, combustion noise and engine vibration were also studied with the aim to understand the effect of fuels and their combustion stability on such parameters. The relatively lower participation of hydrogen tends to reduce the vibrations, however, EGR leads to higher vibrations in the engine. The combustion noise however reduced with addition of hydrogen and EGR at lower loads. Further, the cumulative effect of EGR- hydrogen on the much unattended but harmful unregulated emissions was also investigated, and a synergy between the hydrogen addition and EGR was observed in this study. The present study showcases the key concerns as well as advantages in the EGR assisted hydrogen diesel combustion.

Analysis on the corrosion failure of U-tube heat exchanger in hydrogenation unit

Unscheduled shutdown often occurs in diesel hydrogenation unit due to the corrosion leakage of heat exchanger. After a series of analyses of technological and flow processes, failure causes of the U-tube heat exchanger were investigated. The inside and outside mediums of heat exchanger tubes were hot high-pressure separation (HHPS) gas and cold low-pressure separation oil, respectively. A detailed examination shows that the corrosion occurs in shell side and was caused by under-deposit corrosion of NH4Cl. Through the numerical simulation, it is found that the leakage location is at the place where water tends to accumulate. Thus, in order to prevent the corrosion of heat exchanger, the water content carried in the cold low-pressure separation oil should be reduced.

Parametric investigation on hydrogen driven homogeneous charge compression ignition mode with advanced diesel injection using chemical kinetics based numerical model

In the present study, a numerical model based on chemical kinetics was developed to investigate the effect of different parameters on characteristics of hydrogen diesel homogeneous charge compression ignition (HDHCCI) mode. The results showed that the combustion process was retarded with diminished cool flame as increasing hydrogen energy share (HES) due to reduction of H2O2, H2O and OH radicals with hydrogen addition. Thus, it increased the indicated thermal efficiency (ITE) and decreased the indicated specific energy consumption (ISEC). The levels of NOx and soot emissions were reduced by 22% and 63% at maximum HES. A spray angle of 10° decreased the total fuel impingement compared with a spray angle of 74° because of improvement in air-fuel mixing phenomena. Incomplete combustion was recovered at HES of 25% when increasing the charge temperature or adapting the twin-pulse in HDHCCI mode, consequently the ITE was improved with a decrease in ISEC.

Regeneration and industrial application of diesel hydrogenation catalyst

Regeneration and industrial application of diesel hydrogenation catalyst

Thermodynamic Modeling of a Turbocharged Diesel–Hydrogen Dual-Fuel Marine Engine

In this work, a thermodynamic model is used to analyze the influence of some usual engine parameters such as compression ratio, ambient temperature, turbocharger compressor pressure ratio, equivalence ratio, and engine speed on the performances of a diesel–hydrogen dual-fuel marine engine. The model takes into consideration the change in the composition of the working fluid resulting from the combustion cycle as well as the reactive mixture. This model considers also the dependence of the working fluid specific heat on temperature. Results show that the increase in the equivalence ratio yields to an improvement of the brake specific fuel consumption, the brake power output, the brake thermal, and exergy efficiencies with an increase in the exhaust gas temperature. Nevertheless, it produces a drop in volumetric efficiency. The engine speed has a slight effect on the brake thermal efficiency, exergy efficiency, and the brake specific fuel consumption. The engine speed affects the engine power output mainly at higher values of the fuel–air equivalence ratio due to the reduction in heat losses and the fuel energy consumed by the engine. The increase in the turbo-compressor pressure ratio has a significant effect on the improvement of engine performance. However, it has an insignificant effect on the exhaust gas temperature. The exergy destroyed in the engine dominates. It accounts for 88.2% of the total exergy destroyed in the overall system. The remaining components (turbo-compressor, intercooler, mixer, catalytic converter, and turbine) are responsible for only 11.2%.

Comparison of the hydrogen powered homogeneous charge compression ignition mode with multiple injection schedules and the dual fuel mode using a twin-cylinder engine

The present work discusses the influence of injection schedules in hydrogen diesel homogeneous charge compression ignition (HDHCCI) mode, the experiments were carried out in three distinct diesel injection schedules like single pulse, double pulse and multi-pulse at low load operation. The maximum reachable hydrogen energy shares (HES) are 27.46%, 26.97% and 39.96% for a single pulse, double pulse and multi-pulse respectively. For almost all HES levels, the single pulse and double pulse HDHCCI mode provided ultra-low NO emission when compared with hydrogen diesel dual fuel (HDDF) mode. The multi-pulse injection increased the brake thermal efficiency (BTE) compared with single pulse and double pulse injection, since the timing of injection pulse 3 (IP3) in multi-pulse significantly altered the combustion characteristics of HDHCCI mode. Locating the IP3 in the window of 30–40 °BTDC (before cool flame) enhanced the BTE and reduced the brake specific energy consumption (BSEC) of the engine.

A comparative study of optimization models for the gas detector placement in process facilities

Gas detector network is an important layer of protection in process facilities for prevention gas leakage accidents. But traditional standards just provide basic principles for the installation of detectors. In this study, three stochastic programming (SP) models are developed and contrasted, namely minimal detection time P-Median model (MDTP), minimal leakage concentration P-Median model (MLCP), and minimal individual risk P-median model (MIRP). Meanwhile all possible leak scenarios are identified based on the combination of wind field set and leakage sources. And clustering analysis is used to filter similar scenarios and select representative leak scenarios. The leak consequences are predicted by computational fluid dynamics (CFD) method and the results are served as the input data of these SP models. A case study is carried out in a diesel hydrogenation unit.

Investigation on the effect of injection schedule and EGR in hydrogen energy share using common rail direct injection dual fuel engine

In this research work, four different diesel injection schedules have been experimented at a BMEP of 2 bar (Low load) in hydrogen diesel dual fuel (HDDF) mode, which are namely single pulse, double pulse phase-1, double pulse phase-2 and multi-pulse. The maximum possible hydrogen energy shares (HES) for single pulse, double pulse phase-1, double pulse phase-2 and multi-pulse injection schedules were 73.99%, 48.98%, 34.46% and 24.39% respectively. Over the injection schedules, double pulse phase-2 improved the brake thermal efficiency (BTE) from 19.50% (single pulse) to 21.61% with a penalty in NO emission. On the other hand, multi-pulse moderately increased the BTE with significant reduction in NO beside rise in smoke emission. At a BMEP of 5 bar (Medium load) operation, there was a considerable reduction in NO emission at maximum range of HES level with 18.21% of EGR, moreover the engine stability was improved with minor increase in smoke emission.

Optimization of gas detector placement considering scenario probability and detector reliability in oil refinery installation

Gas detection system is a critical layer of protection in process safety. Leak scenario probability and detector reliability are two key factors in the optimization of gas detector placement. However, they are easily neglected in previous studies, which may lead to an inaccurate evaluation of the optimization solutions. In this study, a stochastic programming (SP) optimization method is proposed considering these two factors. In order to quantitatively represent the probability of leak scenarios, a complete accident scenario set (CASS) is built combining leak sources and wind fields. Then, the computational fluid dynamics (CFD) method is adopted for consequence modeling of gas dispersion. The Markov model is developed to predict the detector reliability. With the objective of minimal cumulative detection time (MCDT), the SP formulation considering scenario probability and detector reliability (MCDT-SPR) is proposed. By introducing the particle swarm optimization (PSO) algorithm, the optimization formulations can be solved. A case study is investigated on a diesel hydrogenation refining unit. Results validate this approach is promising to improve the detection efficiency. This method is more practical and matching with the actual industrial environment, where the leak scenarios and the detector reliability can change dynamically in real process setting.

A data‐driven approach for flow corrosion characteristic parameters prediction in an air cooler

AbstractA data‐driven soft measurement method based on a multiunit back propagation neural network (MBPNN) is presented in this study. This model aims to estimate the characteristic parameters that can reflect the flow corrosion of the reactor effluent air cooler (REAC). Flow corrosion failure during the hydrogenation process presents a serious concern to the petrochemical industry. In this paper, a safety evaluation of flow corrosion failure for a petrochemical diesel hydrogenation unit is first carried out. During the investigation, it is found that there is a risk of NH4Cl crystallization at around 187°C. Then, considering flow‐induced corrosion and ammonium salt deposition, main characteristic parameters are determined, including NH4Cl crystallization temperature (TC), air cooler tube bundle minimum and maximum flow rate (VminandVmax), air cooler inlet liquid water content (CW), and NH4HS concentration (CA). Finally, the data‐driven model based on a multiunit back propagation neural network (MBPNN) is constructed. An improved particle swarm optimization (PSO) approach is employed to initialize the main parameters of the model. Compared with a multioutput back propagation neural network (BPNN) model and MBPNN model without an optimization algorithm, the presented data‐driven model is proved to have high accuracy, a fast convergence rate, and high reliability.

Removal of hydrocarbons and recovery of hydrogen from hydrogenation tail gas via hydrates formation using reverse thinking: Cast a small fish for a big one

We conducted the removal of hydrocarbons and concentrating of H2 from the tail gas of diesel hydrogenation (tail gas for short) using hydrate separation method. Based on the preliminary separation results, it is necessary to apply hydrate thermodynamic promoter to further improve the separation efficiency. In order to avoid the introduction of new impurity, we added propane (C3H8), one component of tail gas, in the feed gas as the hydrate promoter by reverse thinking, because it runs counter to the hydrocarbons removal from tail gas. The formation equilibrium conditions of tail gas hydrates were measured, and the enthalpy of hydrates equilibrium dissociation was calculated by the Clausius–Clapeyron equation. The results show that the addition of C3H8 significantly decreases the formation equilibrium pressure of tail gas hydrates at the same temperature. It indicates that C3H8 indeed performs as a thermodynamic promoter for tail gas hydrates. Consequently, the driving force for hydrates formation increases, and more hydrates form at the equilibrium state. As a result, the total removal rate of hydrocarbons and the recovery rate of H2 are both increased, while the concentration of H2 in equilibrium gas almost keeps unchanged. The results demonstrate that the addition of C3H8 behaves as an inducer to enclose relatively more hydrocarbons into hydrate phase, and it also accelerates the hydrates formation rate at the same time. This work presents a new research idea, i.e., cast a small fish for a big one, for the flexible and optimum application of hydrate separation technology.

Experimental study on combustion characteristics of diesel–hydrogen dual-fuel engine

As a clean and sustainable energy source, hydrogen is widely considered as an engine fuel by top researchers. In view of the fact that the uneven fuel mixture of diesel fuel deteriorated the combustion and emissions process, it is expected to adopt diesel and hydrogen dual-fuel combustion technology to optimize combustion and heat release of diesel engine. In this study, experiments are carried out on a diesel engine and the combustion characteristics of the engine with different hydrogen ratios (RH) are compared. It has been found that hydrogen addition is conducive to accelerate the heat release rate and improve the thermal efficiency. Specifically, compared with pure diesel conditions, the peak pressure increased by 7.7% and the cumulative heat release rate increased by 3.7% under the condition of RH of 20%. Moreover, although the effect on the ignition delay period is not clear, the higher RH brings about earlier heat release center and more cumulative heat release while enhancing the heat release of premixed combustion reducing the diffusion combustion and post-combustion.

Effect of Hydrogen Energy Share on a Hydrogen Diesel Dual Fuel Mode using a Common Rail Direct Injection System

This research work was aimed to investigate the maximum possible utilization of hydrogen energy in CI engine with diesel fuel replacement on energy share basis in hydrogen diesel dual fuel (HDDF) mode using common rail direct injection diesel engine. In HDDF mode, experiments were performed at two load conditions such as 3 and 5 bar of brake mean effective pressures (BMEPs). At a BMEP of 3 bar, the maximum hydrogen energy share (HES) could be reached to 50.1% without erratic engine operation, the level of NO, HC, CO and CO2 emissions were decreased up to 18%, 62%, 56% and 45% as compared with neat diesel case. However, there was no significant change in brake thermal efficiency (BTE) and smoke at high HES. At a BMEP of 5 bar, the maximum possible hydrogen energy share was nearly 40%, beyond this energy share severe knocking was noticed. NO emission was raised by 48%, whereas smoke and CO2 emission were decreased up to 20% and 24%. The brake specific HC emission was increased by 42% and there was no significant variation in CO emission with HES.

Local Heat Transfer in the Combustion Chamber of a Hydrogen Diesel

By three-dimensional modeling, the local heat transfer in the combustion chamber of a traditional diesel is compared with that in a promising hydrogen diesel, which is based on the direct injection of gaseous hydrogen. The local heat transfer in the combustion chamber of a hydrogen diesel is analyzed, because it must be taken into account in the conversion of mass-produced diesel engines.

Computational investigation of diesel injection strategies in hydrogen-diesel dual fuel engine

This paper deals with the numerical study of hydrogen-diesel dual fuel engine characteristics under various diesel injection strategies. Here, CONVERGE CFD software package is used to simulate a hydrogen diesel dual fuel engine, under split injection of diesel. The combustion and spray is modeled using coupled solution of chemical kinetics and fluid mechanics (CFD) equations. The study was performed at four strokes direct injection compression ignition engine. The engine speed (1500 rpm) and compression ratio (19.5:1) remain constant throughout the study. The developed model was validated against already published experimental data of 18.5% hydrogen energy share. The simulation result showed that 8° bTDC was optimum injection timing for single injection case and 16° bTDC was optimum injection timing for pilot fuel injection and 10% pilot mass was optimum pilot mass amount for minimum NOx, soot, CO and HC emissions and higher gIMEP.

Effect of hydrogen fumigation on combustion stability and unregulated emissions in a diesel fuelled compression ignition engine

The automotive pollution norms throughout the world are getting increasingly stringent, which has made achieving the emissions regulation significantly challenging for the automakers. Additionally, energy security remains a matter of concern for all the economies due to depleting fossil fuels and fluctuating crude oil prices. These factors have motivated researchers to invest resources in the exploration of alternative fuels. Hydrogen has been consistently pitched and researched upon as a viable fuel for the future, meeting all these requirements. In this context, the presented work explores the dual fuel mode combustion in a single-cylinder constant speed engine. Under variation of engine load (25, 50 and 75%) different levels of hydrogen energy substitution are investigated. This study examines the combustion performance of hydrogen diesel dual-fuel through peak pressure location, cycle to cycle variability and combustion noise. The detrimental effects of hydrogen substitution at lower and mid loads are observed on the stability of combustion as cycle to cycle variability of combustion metrics show an increase. Additionally, the effect of hydrogen energy substitution on unregulated emissions like aldehydes and aromatics is reported. These unregulated emissions at these operating conditions are relatively unexplored despite being reported as carcinogens and precursors for soot formation.