Effects of hydrogen direct injection on engine stability and optimization of control parameters for a combined injection engine

As engine stability is a crucial issue for engine performance and toxic emissions, an experimental research has been conducted to analyze the effects of hydrogen direct injection on engine stability. The experiments have been divided into two parts. The first set is aimed to analyze different parameter characteristics with and without hydrogen direct injection, and the second set tries to find optimal control regions. Excess air ratios, spark timings, engine speeds and engine loads are chosen as primary parameters in the study. The results show hydrogen addition can increase brake thermal efficiency by a range from 6% to 13%, enhancing the lean burn performance. Combustion duration has been shortened to about 80% by adding 10% hydrogen mixture into gasoline. Besides, Hydrogen addition makes the mixture further insensitive to ignition timings, and narrows the optimal regions with higher excess air ratios. Under medium engine speeds, the highest CoV_IMEP locates in the low load region for pure gasoline, while this maximum value appears in the medium load region for 10% hydrogen mixture. In addition, the specific value of CoV_IMEP with 10% hydrogen is rather small compared to pure gasoline. Thus, hydrogen direct injection can significantly improve engine stability and reduce controlling difficulties.     

Experimental investigation and combustion analysis of a direct injection dual-fuel diesel–natural gas engine

A single-cylinder diesel engine has been converted into a dual-fuel engine to operate with natural gas together with a pilot injection of diesel fuel used to ignite the CNG–air charge. The CNG was injected into the intake manifold via a gas injector on purpose designed for this application. The main performance of the gas injector, such as flow coefficient, instantaneous mass flow rate, delay time between electrical signal and opening of the injector, have been characterized by testing the injector in a constant-volume optical vessel. The CNG jet structure has also been characterized by means of shadowgraphy technique.     

Investigation on the effect of injection system parameters on performance and emission characteristics of a twin cylinder compression ignition direct injection engine fuelled with pongamia biodiesel–diesel blend using response surface methodology

This study is aimed at investigating the effect of injection system parameters such as injection pressure, injection timing and nozzle tip protrusion on the performance and emission characteristics of a twin cylinder water cooled naturally aspirated CIDI engine. Biodiesel, derived from pongamia seeds through transesterification process, blended with diesel was used as fuel in this work. The experiments were designed using a statistical tool known as Design of Experiments (DoE) based on response surface methodology (RSM). The resultant models of the response surface methodology were helpful to predict the response parameters such as Brake Specific Energy Consumption (BSEC), Brake Thermal Efficiency (BTE), Carbon monoxide (CO), Hydrocarbon (HC), smoke opacity and Nitrogen Oxides (NO_x) and further to identify the significant interactions between the input factors on the responses. The results depicted that the BSEC, CO, HC and smoke opacity were lesser, and BTE and NO_x were higher at 2.5 mm nozzle tip protrusion, 225 bar of injection pressure and at 30° BTDC of injection timing. Optimization of injection system parameters was performed using the desirability approach of the response surface methodology for better performance and lower NO_x emission. An injection pressure of 225 bar, injection timing of 21° BTDC and 2.5 mm nozzle tip protrusion were found to be optimal values for the pongamia biodiesel blended diesel fuel operation in the test engine of 7.5 kW at 1500 rpm.     

Influence of injector technology on injection and combustion development – Part 1: Hydraulic characterization

An experimental study of two real multi-hole Diesel injectors is performed under current DI Diesel engine operating conditions. The aim of the investigation is to study the influence of injector technology on the flow at the nozzle exit and to analyse its effect on the spray in evaporative conditions and combustion development. The injectors used are two of the most common technologies used nowadays: solenoid and piezoelectric. The nozzles for both injectors are very similar since the objective of the work is the understanding of the influence of the injector technology on spray characteristics for a given nozzle geometry. In the first part of the study, experimental measurements of hydraulic characterization have been analyzed for both systems. Analysis of spray behaviour in evaporative conditions and combustion development will be carried out in the second part of the work. Important differences between both injectors have been observed, especially in their transient opening and closing of the needle, leading to a more efficient air–fuel mixing and combustion processes for the piezoelectric actuated injector.     

Effect of different strut + wall injection techniques on the performance of two-strut scramjet combustor

The two-dimensional Reynolds-Averaged Navier–Stokes (RANS) equations coupled with the two equation Shear stress transport k–ω turbulence model as well as the finite-rate/eddy–dissipation reaction model have been employed to numerically simulate the flow field structures in a typical two-strut based scramjet combustor. Here all the computations have been performed by using ANSYS 14-FLUENT code. Additionally, validation has been completed for the single strut scramjet engine by comparing its outcome with the open, experimental data. The computational results show reasonable agreement with the experimental schlieren image, and the velocity, pressure and temperature variation graph available in the open literature. The introduction of two-strut improves the combustion and mixing efficiency of the combustor appreciably when compared with single strut engine. Further, investigations have been carried out on the effect of different strut + wall injector on the combustion as well mixing performance of two-strut scramjet combustor. The obtained results show that the combination of two-strut + wall 1 + wall 2 injectors provide better air–H₂ mixing as they lead to a higher penetration depth out of the other strut + wall injection techniques. Thus the combustion as well as mixing efficiency of two-strut + wall 1 + wall 2 injection technique is found to be higher as compared to remaining strut + wall injection techniques but lower than that of the two-strut injection.     

Effect of organoclay on the mechanical/thermal properties of microcellular injection molded PBT–clay nanocomposites

An organically modified montmorillonite (MMT) was compounded with polybutylene terephthalate (PBT) in a twin-screw extruder. The organoclay PBT nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content, organoclay size (8 and 35 μm), and speed of the screw (80 and 100 rpm) on the mechanical and thermal properties were investigated.     

Combustion and emissions behaviour for methanol–gasoline blended fuels in a multipoint electronic fuel injection engine

The purpose of this study is to experimentally investigate the performance, combustion and pollutant emissions of a multipoint electronic fuel injection gasoline engine using methanol–gasoline blends. The results indicated that, with the increase in methanol (CH₃OH) content in the blends, the maximum engine torque and power are slightly decreased, the brake specific fuel consumption is evidently increased and brake thermal efficiency remains almost identical. At low engine loads and speeds, gasoline is observed to have faster combustion velocity, but the blends are faster at high engine loads and speeds. The carbon monoxide of the blends is slightly lower, hydrocarbon is slightly higher at high engine loads and nitrogen oxide is lower for M10 at low engine loads. The emissions of formaldehyde are evidently higher with the increase in CH₃OH content, but CH₃OH and acetaldehyde emissions of the blends show little variation.     

When does decentralized production of biogas and centralized upgrading and injection into the natural gas grid make sense?

The production of biogas through anaerobic digestion is one of the technological solutions to convert biomass into a readily usable fuel. Biogas can replace natural gas, if the biogas is upgraded to green gas. To contribute to the EU-target to reduce Green House Gases emissions, the installed biogas production capacity and the amount of farm-based biomass, as a feedstock, has to be increased. A model was developed to describe a green gas production chain that consists of several digesters connected by a biogas grid to an upgrading and injection facility. The model calculates costs and energy use for 1 m³ of green gas. The number of digesters in the chain can be varied to find results for different configurations. Results are presented for a chain with decentralized production of biogas, i.e. a configuration with several digesters, and a centralized green gas production chain using a single digester. The model showed that no energy advantage per produced m³ green gas can be created using a biogas grid and decentralized digesters instead of one large-scale digester. Production costs using a centralized digester are lower, in the range of 5 €ct to 13 €ct per m³, than in a configuration of decentralized digesters. The model calculations also showed the financial benefit for an operator of a small-scale digester wishing to produce green gas in the cooperation with nearby other producers. E.g. subsidies and legislation based on environmental arguments could encourage the use of decentralized digesters in a biogas grid.     

Effects of heat transfer on MHD suction–injection model of viscous fluid flow through differential transformation and Bernoulli wavelet techniques

In this study, a numerical solution of the velocity and heat transfer on the magnetohydrodynamic suction–injection model of viscous fluid flow has been studied. We use the differential transformation method and Bernoulli wavelet method to solve the highly nonlinear governing equations; applying appropriate similarity transformations and reducing governing equations to highly nonlinear coupled ordinary differential equations. The objective of this analysis is to determine how the suction parameter, Hartmann number, squeeze number, thermophoresis parameter, and Prandtl number affect the velocity and temperature profiles. When the current findings are compared with those that have already been published in the literature, confident suppositions are made, and it is discovered that there is considerable agreement. Graphs have been used to discuss the influence of nondimensional characteristics on velocity and temperature.     

The effect of hydrogen injection parameters on the quality of hydrogen–air mixture formation for a PFI hydrogen internal combustion engine

To research the quality of the hydrogen–air mixture formation and the combustion characteristics of the hydrogen fueled engine under different hydrogen injection timings, nozzle hole positions and nozzle hole diameter, a three-dimensional simulation model for a PFI hydrogen internal combustion engine with the inlet, outlet, valves and cylinder was established using AVL Fire software. In the maximum torque condition, research focused on the variation law of the total hydrogen mass in the cylinder and inlet and the space distribution characteristics and variation law of velocity field, concentration field and turbulent kinetic energy under different hydrogen injection parameters (injection timings, nozzle hole positions and nozzle hole area) in order to reveal the influence of these parameters on hydrogen–air mixture formation process. Then the formation quality of hydrogen–air mixture was comprehensively evaluated according to the mixture uniformity coefficient, the remnant hydrogen percentage in the inlet and restraining abnormal combustion (such as preignition and backfire). The results showed that the three hydrogen injection parameters have important influence on the forming quality of hydrogen–air mixture and combustion state. The reasonable choice of the nozzle hole position of hydrogen, nozzle hole diameter and the hydrogen injection time can improve the uniformity of the hydrogen–air mixing in the cylinder of the hydrogen internal combustion engine, and the combustion heat release reaction is more reasonable. At the end of the compression stroke, the equivalence ratio uniform coefficient increased at first and then decreased with the beginning of the hydrogen injection. When hydrogen injection starting point was with 410–430°CA, equivalence ratio uniform coefficient was larger, and ignition delay period was shorter so that the combustion performance index was also good. And remnant hydrogen percentage in the inlet was less, high concentration of mixed gas in the vicinity of the inlet valve also gathered less, thus suppressing the preignition and backfire. With the increase of the distance between the nozzle and the inlet valve, the selection of the hydrogen injection period is narrowed, and the optimum hydrogen injection time was also ahead of time. The results also showed that it was favorable for the formation of uniform mixing gas when the nozzle hole diameter was 4 mm.     

Investigations on the influence of ethanol and water injection techniques on engine's behavior of a hydrogen - biofuel based dual fuel engine

This work explores the influence of hydrogen and ethanol on improving engine's behavior of Maduca longifolia oil (MO) based dual fuel diesel engine. A mono cylinder diesel engine was tested in dual fuel mode of operation at the rated power output of 3.7 kW under variable hydrogen energy shares from 0 to the maximum allowable limit (until severe knocking i.e. upto 20%). The knock limit was further extended by injecting water and ethanol at the intake manifold and the engine's performance, emission and combustion characteristics were analyzed. In addition ethanol was also injected and introduced along with the intake air for comparison with hydrogen dual fuel mode. Dual fuel operation increased the BTE from 25.2% with neat MO to a maximum of 28.5% and 30% respectively with hydrogen and ethanol for the energy share of 15% and 38% where as the BTE was 30.8% with ND. The smoke opacity was reduced from 78% with neat MO to 58% for the hydrogen energy share of 15% which is the MEP (maximum efficiency point) whereas the smoke emission was noted as 51% with ND operation. However, hydrogen induction increased the NO (nitric oxide) emission. Injection of water and ethanol at the inlet was observed to extend the knocking limit with improved BTE. The BTE reached a maximum of 30.1% with 5% water and 30.8% with 10% ethanol injection. The MEPs were arrived as 31% and 30% hydrogen energy shares respectively with 5% water and 10% ethanol injection. It was concluded that hydrogen induction can be very effective in improving the diesel engine's performance when using MO as base fuel when operating on dual fuel mode. The performance could be improved by extending the knock limit by injecting ethanol and water along with hydrogen.     

Modeling gas flow in PEMFC channels: Part I – Flow pattern transitions and pressure drop in a simulated ex situ channel with uniform water injection through the GDL

The two-phase flow in the gas channels of a proton exchange membrane fuel cell (PEMFC) is studied with an ex situ setup using a gas diffusion layer (GDL) as the sidewall of the channels. Air is supplied at the channel inlet manifold and water is supplied continuously and uniformly through the GDL along the length of the channel. This is different from the simultaneous air and water introduction at the inlet of the channel as studied by previous two-phase flow researchers. The GDL is compressed between the gas channels and the water chambers to simulate PEMFC conditions. The superficial velocity for air and water ranged from 0.25 to 34.5 m/s and 1.54 × 10⁻⁵ to 1.54 × 10⁻⁴ m/s, respectively. The ex situ setup was run in both vertical and horizontal orientations with two GDLs, – Baseline (Mitsubishi Rayon Co. MRC 105 with 5 wt.% PTFE and coated with an in-house MPL by General Motors) and SGL 25 BC – and three channel treatments – hydrophobic, hydrophilic, and untreated Lexan, with contact angles of 116°, 11° and 86°, respectively. No appreciable effect was noted because of the orientation, GDL type or channel coatings. The flow regime is observed at different locations along the channel and is expressed as a function of the superficial air and water velocities. Flow regime criteria are developed and validated against the range of ex situ data observations. A new variable water flow rate pressure drop model is developed in order to account for the variation of water entering the channel at multiple locations along the flow length. Pressure drop models are developed for specific flow regimes and validated against experimental data. The models are able to predict the experimental pressure drop data with a mean error of less than 14%.