Production processThere are many different processes for producing hydrogen depending on the purpose to be used, but here are the 4 most representative processes for producing hydrogen f
OVERVIEW OF HYDROGEN
Overall about Hydrogen
Hydrogen is a chemical element, symbolized as H in the periodic table of elements It is the simplest element in the periodic table and also the most abundant element in the observable universe, constituting about 75% of the total mass of the universe.
Under standard conditions, hydrogen is a colorless, odorless, and tasteless gas It has high gaseous reactivity, often existing in the form of H2 molecules Hydrogen can also exist as ions or atoms It is one of the most important elements in chemistry, participating in numerous significant chemical reactions and serving as a fundamental element in many organic and inorganic compounds Hydrogen is also a raw material for various industries, including the production of nitric acid, synthetic petroleum, and many other applications.
Chemical composition of Hydrogen
The chemical composition of hydrogen is elemental, so there are no other chemical components that form it In the periodic table of elements, hydrogen is represented by the symbol H and has an atomic number of 1 Hydrogen has one proton and one electron in its basic atomic structure Therefore, the basic chemical composition of hydrogen is one proton and one electron.
The reason to choose Hydrogen
Figure 1 Hydrogen is present in water
Under standard conditions (0°C and 1 atm pressure), hydrogen exists as a gas.
However, at very low temperatures and high pressures, hydrogen can transition into a liquid or solid state.
The density of hydrogen gas is very low, approximately 0.08988 g/L at 0°C and 1 atm pressure This makes hydrogen one of the lightest gases.
The melting point of hydrogen is -259.16°C.
The boiling point of hydrogen is -252.87°C.
This makes hydrogen one of the substances with the lowest boiling points.
The boiling point of hydrogen at one atm pressure is -252.87°C.
The dew point of hydrogen at one atm pressure is -259.2°C.
The low dew point of hydrogen can make it useful in cooling and refrigeration applications.
Hydrogen is a colorless, odorless, and tasteless gas.
It has high gasification properties, forming H2 molecules.
The properties of hydrogen vary depending on temperature and pressure.Under high pressure, hydrogen may exhibit different chemical and physical properties.
Applications of hydrogen
Hydrogen is used as a clean and efficient fuel source When burned, hydrogen produces only water and heat, with no emissions of carbon dioxide or other pollutants This makes hydrogen an environmentally friendly means of transportation for use in automobiles, trains, and other vehicles.
Hydrogen is used in the production of petroleum from hydrocarbons, as well as in the refining of oil and gas It can be used to remove sulfur and other impurities from petroleum and gas.
Hydrogen is a key raw material for the production of many important chemicals, including ammonia, methanol, and hydrochloric acid.Cooling and Cooling:
Hydrogen is used in refrigeration and cooling systems such as in the food industry, cold storage, and the air conditioning industry.
Hydrogen can be produced from many natural energy sources, including solar and wind This creates a clean and renewable energy source. Dual Gas Application:
Hydrogen can also be used in dual gas applications, as a reducing agent in steelmaking and in the production of some organic products.
Figure 2 Hydrogen Applications The table below we will see more clearly the distribution of hydrogen around the globe
Table 2 Global Hydrogen consumption by industry.
The highest density is Ammonia production with 55% and the lowest is 10%, indicating that hydrogen is not really popular for replacing traditional fuels.
Production process
There are many different processes for producing hydrogen depending on the purpose to be used, but here are the 4 most representative processes for producing hydrogen fuel as updated by the United States Department of Energy (DOE):
(Natural Gas Reforming/Gasification) - a mixture of hydrogen, carbon monoxide and a small amount of carbon dioxide produced by reacting natural gas with water vapor at high temperatures (700°C - 1,000°C) Carbon monoxide reacts with water to produce more hydrogen This method is the cheapest, most effective and most popular.
Syngas can also be produced by reacting coal, or biomass with high-temperature steam and oxygen in a pressurized gasifier This converts coal, or biomass, into gas components - a process known as gasification The resulting syngas contains hydrogen and carbon monoxide, which is reacted with water vapor to separate the hydrogen.
Natural gas reforming (NGR) is an advanced and mature production process built on the existing natural gas pipeline supply infrastructure Currently, 95% of hydrogen produced in the United States is by this technology in large factories and centers This is an important technological process for producing hydrogen in a short time.
- Reforming steam - Methane (Steam - Methane Reforming):
This is a proven production process in which high-temperature steam (700°C - 1,000°C) is used to produce hydrogen from a source of methane (such as natural gas) In reforming (simply regenerating) water vapor - methane, methane gas reacts with water vapor under a pressure of 3 - 25 bar (1 bar = 14.5 psi) in the presence of a catalyst to produce hydrogen, carbon monoxide and a relatively small amount of carbon dioxide The process of steam regeneration is endothermic - i.e heat must be supplied to the process for the reaction to take place.
Then, in what is known as the “water-gas displacement reaction,” carbon monoxide and water vapor are reacted using a catalyst to produce carbon dioxide and more hydrogen In the final process step known as “pressure oscillation adsorption,” carbon dioxide and other impurities are removed from the gas stream, leaving pure hydrogen Reforming steam can also be used to produce hydrogen from other fuels (such as ethanol, propane, or even gasoline).
Reaction of water vapor reforming - methane: CH4 + H2O (+ heat) → CO + 3H2. Water-gas displacement reaction: CO + H2O → CO2 + H2 (+ small amount of heat).
During partial oxidation, methane and other hydrocarbons in natural gas react with a limited amount of oxygen (usually from the air) that is insufficient to fully oxidize the hydrocarbons to carbon dioxide and water With less than chemically balanced oxygen available, the reaction products consist mainly of hydrogen, carbon monoxide (and nitrogen, if the reaction is carried out with air rather than pure oxygen), and relatively small amounts of carbon dioxide and other compounds Then, in the water-gas displacement reaction, carbon monoxide reacts with water to form carbon dioxide and more hydrogen.
Partial oxidation is an exothermic process Typically, this process is much faster than steam reform and requires a smaller reaction vessel As can be seen in the chemical reactions of partial oxidation, this process initially produces less hydrogen per unit of input fuel than the steam regeneration of the same fuel.
Methane oxidation: CH4 + ẵO2 → CO + 2H2 (+ heat).
Water-gas displacement reaction: CO + H2O → CO2 + H2 (+ small amount of heat).
Low-cost reforming of natural gas could provide hydrogen today for fuel cell vehicles (FCEVs), as well as other applications In the longer term, the DoE expects, the production of hydrogen from natural gas will be enhanced with production from renewable energy, nuclear, coal (with carbon capture, storage) and other low-carbon domestic energy sources.
Hydrogen fuel consumption and emissions are lower than those of gasoline- powered internal combustion engines The only product from the FCEV exhaust is steam, but total greenhouse gas emissions have been halved and fuel consumption reduced by more than 90% compared to today's petrol cars.
Electric current dissociates water into hydrogen and oxygen If electricity is produced by renewable sources (such as wind, solar), then the resulting hydrogen will also be considered renewable Projects to convert energy into hydrogen are currently vibrant, using excess renewable electricity (if any) to generate hydrogen through electrolysis.
Electrolysis technology is a promising option for producing carbon-free hydrogen from renewable and nuclear energy sources This is actually the process of using electricity to split water into hydrogen and oxygen in a device called an electrolyzer Electrolyzers can range in size from small, device-sized units well suited for small-scale distributed hydrogen production to large, central production facilities that can be directly linked to renewable power sources.
Like a fuel cell, an electrolyzer consists of an anode and a cathode separated by an electrolyte Different electrolyzers work in different ways, mainly because of the different type of electrolytic material involved and the type of ions it conducts.
- Electrolyzer using polymer electrolytic film:
In Polymer Electrolyte Membrane Electrolyzers (PEMs), the electrolyte is a special solid plastic material Water reacts at the anode to form oxygen and positively charged hydrogen ions (protons) Electrons flow through an external circuit and hydrogen ions move selectively through the PEM to the cathode At the cathode, hydrogen ions combine with electrons from the outer chain to form hydrogen gas.
The alkaline electrolyte operates through the transport of hydroxide ions (OH-) through the electrolyte from the cathode to the anode with hydrogen produced on the cathode side Machines using a liquid alkaline solution of sodium, or potassium hydroxide as an electrolyte have been on the market for many years Newer methods using solid alkaline exchange (AEM) membranes as electrolytes are showing great promise at the laboratory scale.
The solid oxide electrolyzer, which uses solid ceramic materials as conductive electrolytes selectively charged negative oxygen ions (O2-) at high temperatures, produces hydrogen in a slightly different way.
The advantages of Hydrogen
When burned, hydrogen produces only water and heat, with no emissions of carbon dioxide or other pollutants This makes hydrogen a clean and environmentally friendly energy source. and it's unlimited
Hydrogen can be produced from many renewable energy sources such as solar, wind, and seawater The raw material for hydrogen production is water, which is a rich and unlimited resource.
Hydrogen can be converted into energy with high efficiency and stored easily as a fuel.
Hydrogen can be used in various fields such as fuel for automobiles, trains, aircraft, energy storage systems, and chemical manufacturing.
The production of hydrogen from renewable energy sources is still facing high costs and incomplete technology If a non-renewable energy source is used, hydrogen production can also produce carbon dioxide emissions. Filing System
Hydrogen has a low energy density and requires particularly complex and expensive storage and transportation systems It is necessary to build a safe storage system to avoid the risk of explosion.
Hydrogen is a flammable gas and if not handled carefully, it can cause safety and environmental problems.
In order to develop and deploy hydrogen energy systems on a large scale, large investments in infrastructure, including charging stations and hydrogen production stations, will be required.
Although hydrogen has many advantages as a clean and renewable energy source, it also needs to overcome some challenges to become an important part of the energy industry in the future.
Safety in use and storage Hydrogen
Safety in the use and storage of hydrogen is an important and necessary factor to ensure the safety of people and the environment Here are some measures to ensure safety when using and storing hydrogen:
Hydrogen needs to be stored at high pressure or low temperature to reduce the risk of fire and explosion Storage systems must be robustly designed and ensure there are no hydrogen gas leaks.
When using and storing hydrogen at high pressure, a pressure management system is required to ensure safety Safety valves and pressure sensors should be used to keep the pressure in the system at a safe level.
Hydrogen storage and utilization systems should be designed to prevent and control fire and explosion hazards This may include the use of fire protection and isolation systems to prevent the spread of fire and temperature.
Everyone working with hydrogen should be trained in safety measures and safe work procedures Specific instructions on how to use, store, and handle hydrogen should be provided.
Hydrogen storage and utilization systems should be periodically inspected and serviced to ensure that they are functioning properly and that there are no technical faults that could pose a hazard.
Risk assessment and design of risk control measures are necessary to ensure the safe use and storage of hydrogen Risks need to be identified and plans developed to mitigate them.
Safety regulations and standards related to the use and storage of hydrogen need to be strictly followed to ensure safety and compliance with the law.The application of these safety measures will help minimize risks and ensure safety in the use and storage of hydrogen.
Storage and transportation
As you can see, transport and storage embodiments may require changing the physical state of hydrogen from a gas to a liquid or a solid, compressing it, or chemically converting it to another carrier These modifications can make it easier to store and move hydrogen because in general, in gaseous form, hydrogen is lighter than air and is not energy dense by volume However, conversion, transportation, and storage are not without trade-offs, as each new step or form of complexity in the process adds to the cost Let's dive into the options.
There are several ways to transport hydrogen.
Hydrogen can be transported by truck in one of two ways: by liquid tanker or by
“tube trailer” with compressed air tank Trucking is a flexible option to supply hydrogen to areas where demand is still growing That's also how laboratories and other facilities that require smaller volumes receive hydrogen today However, only a limited volume can fit on a truck and of course, these trucks need their own fuel to move hydrogen on their own.
Piping is best suited to provide clean hydrogen to end users in great and stable need, such as steel mills, over long distances While we don't yet know how much pipeline capacity is needed to support the use of hydrogen as a decarbonization tool in the
US, we do know that reusing existing natural gas infrastructure for hydrogen is not necessary because hydrogen tends to degrade pipes that are not specifically designed for it Whatever the case, however, the IEA suggests that once in operation, pipelines are cost-competitive ways to transport hydrogen over distances of up to 5000 km.
Over longer distances, it may be economical to move hydrogen in some liquid form (slightly more) by ship The world's first long-haul shipment of liquid hydrogen was completed last year, potentially as a first step in building a global clean hydrogen supply chain The cost and use of energy remains high and it is far from certain that we will transport hydrogen in its pure form; the International Renewable Energy Agency estimates that nearly half of the hydrogen exchanged between countries by 2050 will be in the form of ammonia
There are still many questions about how far and in what form we need to transport hydrogen But in the short term, as we learn from our early efforts to use hydrogen in new ways, maintaining hydrogen production and use at an early stage is better because it uses less energy and costs less money That's why the Department of Energy's hydrogen scaling strategy focuses on regional centers At the end of the day, we're likely to see a combination of all of the above.
There are four main ways to store hydrogen.
Hydrogen can be stored as an underground gas in empty salt caverns, depleted aquifers, or decommissioned oil and gas fields In fact, there has been a long precedent for underground gas storage like this This method is called “geological” storage and it is an ideal option for long-term hydrogen storage, necessary for seasonal energy storage It's one of the largest and cheapest options available today, but it's not available everywhere. +Compressed air
Like any gas, hydrogen can be compressed and stored in containers But hydrogen requires very high-pressure containers and contains a limited amount of energy Whether we are talking about ground tanks or pipe trucks, compressed air is one of the most expensive and least energy-intensive options we have today, but it is also one of the simplest.
+Liquid storage and freezing (Or storage at another stage)
Hydrogen is much more energetically concentrated in liquid form The downside is that to achieve that means cooling it to near absolute zero, which requires significant energy and complex insulated containers Historically, this was meant only for space travel in the form of rocket fuel, but could be used for long-distance transportation.
As mentioned above, hydrogen can also be converted into a liquid such as ammonia , which has a higher energy density and a well-developed global infrastructure as it has been used to produce fertilizers and chemicals.
Compare the performance of hydrogen with other fuels
Table 3 Comparing hydrogen fuel with other fuel
To compare the performance of hydrogen with other fuels, we can consider a number of important factors such as cleanliness, efficiency, energy consumption, storage capacity, and environmental impact Here is a comparison between hydrogen and other fuels such as diesel, gasoline, and electricity:
Hydrogen: Hydrogen is a clean energy source that produces no carbon dioxide or other pollutants when burned It only produces water as a byproduct.
Diesel and Gasoline: The combustion of diesel and gasoline produces emissions of carbon dioxide and other pollutants, which are harmful to the environment.
Hydrogen: Hydrogen can be highly efficient in converting energy into working capacity, especially when used in hydrogen-powered vehicles.
Diesel and Gasoline: The performance of diesel and gasoline may depend on the type of engine and operating conditions, but is generally lower than hydrogen in some cases.
Hydrogen: The production of hydrogen can require large amounts of energy, especially when using methods of producing hydrogen from fossil fuels or renewable energy.
Diesel and Gasoline: The energy consumption in the production and use of diesel and gasoline can be high and cause a lot of carbon dioxide emissions. Storage Capability:
Hydrogen: Storing and transporting hydrogen requires complex and expensive systems, especially with hydrogen in gaseous form.
Diesel and Gasoline: Diesel and gasoline can be stored and transported easily in existing fuel supply systems.
Hydrogen: Using hydrogen may require the development of new infrastructure, including charging stations and hydrogen production stations.
Diesel and Gasoline: Diesel and gasoline have been widely used and are available in the existing fuel supply system.
In summary, although hydrogen has many advantages as a clean and renewable energy source, it also needs to overcome some challenges to become a popular energy source in the future.
HYDROGEN APPLICATIONS IN VEHICLES
The gas fuel used on the vehicle
- Natural gas, also called fossil gas or simply called gas Containing most of Hydrocarbons ( 85% of Methane ( CH4 ) and 10% of Ethane ( C2H6 ) and others chemical gases )
- Natural gas is exploited and extracted into fuels to provide about 25% of total energy for the world
- Natural gas is often described as the cleanest fossil fuel It produces 25% –30% and 40% –45% less carbon dioxide per distributed joule than oil and coal respectively and is likely to cause less pollution than other hydrocarbon fuels.
- CNG : Compressed Natural Gas contains 87% CH4 – Methane Compressed at high pressure 200-250bar Not only contributes to reducing harmful emissions, CNG compressed natural gas also saves up to 40% of fuel costs compared to gasoline and diesel Currently, the number of vehicles using CNG gas in the world has a stable growth rate of 30%/year According to statistics, since 2011, more than 14.8 million cars in the world have switched to CNG (more than 5 million cars in Asia alone) On combustion, CNG natural gas can generate a temperature of about 1954oC Has odorless, colorless, non-toxic and less polluting properties than gasoline
- LNG : Liquefied Natural Gas contains 94.3% CH4 – Methane Colorless, Odourless, Non-toxic When burning, LNG can create a flame with a very high temperature (about 1,880 degrees Celsius) and is able to burn completely without leaving residue to make equipment and machinery safer, reduce wear, less maintenance and increase life Burning LNG produces 40% less CO2 emissions than coal and 30% less than petroleum, which makes LNG the cleanest fuel compared to traditional fuels Therefore, LNG is a fuel chosen by many countries in the energy transition process, reducing greenhouse gas emissions
- CNG : Compressed Natural Gas, which is natural gas extracted from natural gas fields or as a companion gas in the process of oil and gas exploitation
- LNG : Liquefied Natural Gas is a natural gas that is liquefied when deep refrigerated to -162oC after being processed, removing impurities.
- LPG : Liquefied Petroleum Gas is a liquefied petroleum gas mixed with light hydrocarbons, with the main components of propane and butane, liquefied to facilitate storage and transportation LPG is produced from natural gas flows extracted from oil fields or through crude oil processing LPG has colorless, odorless properties.
▪ LPG is propane and butane; Natural gas is Methane
▪ LPG and natural gas are different chemicals with different formulas: LPG: Propane is C3H8 & Butane is C4H10 while natural gas – Methane is CH4.
▪ LPG is heavier than air and natural gas is lighter than air.
▪ LPG has a higher energy content at 93.2 MJ/m3 than natural gas at 38.7 MJ/m3.
▪ LPG requires a higher air/ gas to burn ratio of 25:1 to natural gas ratio of 10:1.
▪ LPG is liquefied through pressurization compared to natural gas which is cooled to liquefied natural gas – LNG.
▪ LPG is distributed in bottles and tanks compared to natural gas transported through pipelines.
LPG ▪ devices operated at a pressure of 2.75 kPa compared to natural gas devices operating at a pressure of 1.1 kPa.
LPG is not natural gas, it is generated from the processing of natural gas.
LPG is better than natural gas because it has a higher energy content, is portable and available everywhere and is cheaper in many cases.
Natural gas is better than LPG when transported by pipeline and in fact, it produces less CO2 when burned.
2.1.3 Advantages of using hydrogen gas over other gases
Clean Burning: When used in a fuel cell, hydrogen produces only water vapor and heat as byproducts This makes it a very attractive option for reducing greenhouse gas emissions and air pollution compared to fossil fuels which release harmful pollutants during combustion.
Renewable Source: Hydrogen itself can be produced from renewable sources like electrolysis using solar or wind power This creates a clean energy cycle from generation to consumption.
High Energy Density: Hydrogen packs a lot of energy by weight This translates to potentially longer range for hydrogen-powered vehicles compared to battery electric vehicles, although packaging the gas efficiently for storage remains a challenge.
Efficiency: Fuel cells using hydrogen can be highly efficient in converting chemical energy into electricity, compared to internal combustion engines which lose a significant amount of energy as heat.
Lightweight: Being the lightest element, hydrogen gas is easy to transport over long distances.
Safety: In case of a leak, hydrogen is lighter than air and disperses quickly, reducing the risk of explosions
2.1.4 Methods of using gaseous fuels to run internal combustion engines + Direct Injection
PFI is a widespread fuel delivery strategy for SI ICEs—fuel is injected during the intake stroke into the intake port upstream of the intake valve The modification of conventional PFI ICE to hydrogen involves a comparatively straightforward replacement of the injection system However, as mentioned previously, this engine combustion mode operated with hydrogen fuel can suffer from a number of issues, such as pre-ignition, knock and backfiring due to the low minimum ignition energy and quenching distance of hydrogen On the other hand, hydrogen displaces air in the intake and therefore limits engine power density PFI also increases the work needed during the compression stroke compared with late hydrogen DI These factors often lead to reduced power output and deteriorated efficiency of engines with hydrogen PFI Combustion characteristics and engine performance of hydrogen PFI engines with different ignition strategies are discussed below.
The method of dual-fuel injection, combining hydrogen and gasoline, is one of the ways to harness the benefits of both types of fuel This method is often used in research and experiments to improve the efficiency and reduce emissions of internal combustion engines Here is how this method typically works:
+Injecting hydrogen and gasoline into the combustion chamber:
In this method, both hydrogen and gasoline are injected into the engine's combustion chamber before the combustion process begins Hydrogen is usually injected earlier than gasoline to create better combustion conditions and enhance efficiency.
+Adjusting the mixing ratio: The mixing ratio between hydrogen and gasoline is often adjusted to achieve optimal efficiency This adjustment may require tight control of the fuel injection system and other operating parameters of the engine.
+Engine and fuel injection system tuning: To use this method effectively, engine and fuel injection systems may need to be tuned or improved to meet the requirements of dual fuel operation.
The benefits of this method may include improved combustion efficiency, reduced emissions, and fuel savings However, challenges such as the complexity of the fuel injection system and ensuring the safety and stability of using hydrogen in the combustion environment need to be considered.
Options for converting traditional fuel engines to hydrogen fuel
Here are some options to switch the engine from using traditional fuel to using hydrogen fuel:
This embodiment combines the use of both conventional fuels (e.g gasoline, diesel) and hydrogen fuels in one engine.
The engine is designed to operate on both fuels, providing a flexible option and minimizing dependence on hydrogen.
Advantages: Reuse of existing infrastructure; minimizing the risks of a complete conversion to hydrogen; reducing costs compared to replacing the engine completely.
Disadvantages: Performance may not be as high as complete hydrogen utilization; requires complex control systems.
Conversion of the internal combustion engine to use hydrogen:
This embodiment requires modification or redesign of an existing internal combustion engine to operate on hydrogen fuel.
This technology is being researched and developed to optimize performance and safety.
Advantages: Reuse of existing infrastructure; reduce risks of a complete transition to hydrogen.
Disadvantages: Cost and time required for engine modification; engine performance and reliability are not clearly proven.
Use of hydrogen fuel as part of a hybrid fuel system:
This embodiment combines the use of conventional fuels and hydrogen in a combined fuel system.
This can reduce dependence on traditional fuels and reduce emissions. Advantages: Minimize dependence on traditional fuels; reduce emissions.
Disadvantages: It takes the development of a complex system to manage two fuels; the efficiency may not be as high as using hydrogen entirely.
The most effective means of controlling pre-ignition and impact is to redesign the engine to use hydrogen, especially the combustion chamber and cooling system.
A disc-shaped combustion chamber (with flat piston and chamber ceiling) can be used to reduce turbulence in the chamber The disc shape helps to produce low radial and tangent velocity components and does not amplify the input vortex during compression.
Since non-flammable hydrocarbons are not a concern in a hydrogen engine, a large bore to stroke ratio can be used with this engine To accommodate the wider range of flame rates occurring over a larger range of comparable proportions, two spark plugs are required The cooling system shall be denoted to provide uniform flow for all locations requiring cooling.
Additional measures to reduce the probability of pre-ignition are the use of two small exhaust valves as opposed to a single large valve, and the development of an efficient scavenging system, that is, a means of replacing exhaust from the combustion chamber with fresh air.
-Central injection or carburetor system:
The simplest method of fueling a hydrogen engine is by means of a carburetor or central injection system This system has the advantage of a hydrogen engine First, cen- tral injections do not require that the hydrogen supply pressure be as high as for other methods Second, the central engine or carburetor is used on the gasoline engine, making it easy to convert a standard gasoline engine into a hydrogen or gasoline/hydrogen engine.
The disadvantage of the central injection is that it is more prone to abnormal combustion due to pre-ignition and backlash A greater amount of hydrogen/air mixture in the delivery tube feeds the compound with the effect of pre-ignition.
The fuel delivery system injects fuel into the fuel pump port directly into the intake manifold at each intake port, rather than drawing fuel in at a central point. Typically, hydrogen is injected into the delivery tube after the start of the loading journey At this point, the conditions are much less severe and the probability of early ignition is reduced.
When pumped into the port, air is separately pumped at the start of the filling stroke to dilute the hot residual gases and cool any hot spots Since there is less gas(hydrogen or air) in the manifold at any given time, any pre-ignition will be less severe.
The inlet supply pressure for pumping into the port tends to be higher than for carbureted or central pumping systems, but lower than for direct pumping systems.
The constant-volume pump (CVI) system uses a mechanical cam-operated device to time the hydrogen pump into each cylinder The CVI block is displayed on the far right of the image with four fuel lines exiting on the left side of the block (one fuel line per cylinder).
The Electronic Fuel Injection (EFI) system measures the hydropower for each cylinder The system uses individual electronic fuel injectors (solenoid valves) for each cylinder and is connected to a common fuel rail located in the middle of the intake manifold Whereas the CVI system uses a constant injection time and a variable fuel rail pressure, the EFI system uses a constant injection time and a constant fuel rail pressure.
The more sophisticated hydrogen engines use direct injection into the combustion cylinder during compression On direct injection, the intake valve is closed when fuel is injected, completely avoiding premature ignition during the receiving stroke Therefore, the motor cannot act backwards on the intake manifold.
The output power of a direct-injection hydrogen engine is 20% higher than that of a gasoline engine and 42% higher than that of a hydrogen engine using a carburetor.
While direct injection solves the problem of pre-ignition in the intake manifold, it does not necessarily prevent pre-ignition in the combustion chamber In addition, due to the reduced mixing time of air and fuel in the engine causing direct interference, the air/fuel mixture may be heterogeneous Studies have suggested that this may lead to higher NOx emissions than non-direct injection systems Direct injection systems require higher fuel rail pressures than other methods.
Due to the low ignition energy limit of hydrogen, hydrogen combustion is easy and gasoline ignition systems can be used At a very lean air/fuel ratio (130:1 to 180:1), the flame velocity is significantly reduced and the use of a dual spark plug system is preferred.
Ignition systems using waste ignition systems should not be used for hydrogen engines These systems power the spark every time the piston in the top dead centre dies whether the piston is on its compression stroke or its discharge stroke For petrol engines, the spark-emitting system works well and is less expensive than other systems For hydrogen en- gines, waste sparks are a source before ignition.
Spark plugs for hydrogen engines must be cold and have non-platinum plugs The cold rated plug is a button that transfers heat from the plug end to the cylinder end faster than a hot rated spark plug This means that the possibility of spark plugs burning air/fuel is reduced Heated rated spark plugs are designed to maintain a certain amount of heat so that carbon deposits do not accumulate Since hydrogen does not contain carbon, hot rated spark plugs have no useful function.
Platinum-tip spark plug tips should also be avoided as plati- num is a catalyst, causing hydrogen to oxidize with air.
The combustion of hydrogen with oxygen producing water is its only product: 2H2 + O = 2H2O2
However, hydrogen combustion with air can also produce nitrogen oxides (NOx):
High-temperature nitrogen oxides are generated in the combustion chamber during combustion This high temperature causes some ni-trogen in the air to combine with oxygen in the air The amount of NOx formed depends on:
Adjusting the Air:Fuel Ratio engine compression ratio
Engine speed ignition time whether thermal dilution is used
In addition to nitrogen oxides, traces of carbon monoxide and carbon dioxide may be present in the flue gas, due to oil seeping into the combustion chamber.
Combustion properties of hydrogen gas in internal combustion engines
Hydrogen has a wide flammability range compared to all other fuels As a result, hydrogen can be burned in an internal combustion engine with a wide range of fuel-air mixtures A significant advantage of this is that hydrogen can run on poor mixtures A poor mixture is one in which the amount of fuel is less than the ideal, chemically or theoretically balanced amount required for combustion with a given amount of air This is why starting the engine with hydrogen is quite easy.
In general, more fuel economy and more complete combustion response when vehicles run on poor mixtures In addition, the final combustion temperature is usually lower, which reduces the amount of pollutants, such as nitrogen oxides, emitted in the flue gas There is a limit to the level of poor mixed operation of the engine, as it can significantly reduce the output power due to a decrease in the volumetric heating value of the air/fuel mixture.
Hydrogen has a very low ignition energy The amount of energy required to burn hydrogen is about one order less than the energy required for gasoline This allows the hydrogen engine to ignite the poor mixture and ensures rapid ignition.
However, low ignition energy means that hot gas and hot spots on the cylinder can serve as ignition sources, creating early ignition problems and backfires and detonations Preventing this is one of the challenges associated with operating a hydrogen-powered engine The wide flammability range of hydrogen means that almost any mixture can be ignited by the hot spot.
Hydrogen has a small extinguishing gap, smaller than gasoline Therefore, hydrogen flames move closer to the cylinder wall than other fuels before they go out Therefore, it is harder to extinguish a hydrogen fire than a gasoline fire A smaller extinguishing distance may also increase the counterproductive tendency due to the flame from the hydrogen-air mixture readily passing through the intake valve being almost more closed than the flame of the hydrogen-carbon-air mixture.
Hydrogen has a relatively high autoignition temperature This has important implications when compressing the hydrogen-air mixture In fact, self-ignition temperature is an important factor in determining the compression ratio that the motor can use, since the temperature increase during compression is related to the compression ratio The temperature rise is shown by Eq.
V1/V2: Compression ratio T1: initial absolute temperature T2: final absolute temperature γ: specific heat capacity ratio
The temperature shall not exceed the self-ignition temperature of hydrogen without causing premature ignition Therefore, the absolute end temperature limits the compression ratio The high autoignition temperature of hydrogen allows a greater compression ratio to be used in a hydrogen engine than in a hydrocarbon engine.
This higher compression ratio is important as it relates to the thermal performance of the system Hydrogen, on the other hand, is difficult to ignite in a compression ignition configuration or a diesel engine, as the temperatures required for those ignition types are relatively high.
Hydrogen has a high flame rate at a chemical equilibrium ratio Under these conditions, the hydrogen flame rate is almost as high (faster) than gasoline This means that the hydrogen engine can get closer to the ideal engine cycle thermodynamically However, in thinner mixtures, the flame velocity is significantly reduced.
Hydrogen has a very high diffusion potential This ability to disperse in air is significantly greater than gasoline and is beneficial for two main reasons First, it facilitates the formation of homogeneous mixtures of fuel and air Second, if a hydrogen leak develops, the hydrogen will disperse rapidly Therefore, unsafe conditions can be avoided or minimized.
Hydrogen has a very low density This leads to two problems when used in internal combustion engines First, a very large volume is required to store sufficient hydrogen to provide the vehicle with a suitable operating range Second, the energy density of the hydrogen-air mixture, and therefore, the output power is reduced.
Fuel air ratio
The theoretical combustion or chemical equilibrium of hydrogen and oxygen is given as follows: 2H2+O2=2H2O
Number of moles H2 fully burned = 2 moles
Number of moles of O2 for complete combustion = 1 mole
Because air is used as an oxidizer instead of oxygen, nitrogen in the air needs to be included in the calculation:
N2 moles in air = O2 moles x (79% N2 in air / 21% O2 in air)
=1 mole of O 2 x (79% N 2 in air / 21% O 2 in air) = 3,762 moles of N 2
Air moles = O2 moles + N2 moles = 1 + 3,762 moles =4,762 moles
The chemical equilibrium air/fuel ratio (A/F) for hydrogen and air is:
A/F based on mass = air mass/fuel mass = 137.33 g / 4 g = 34.33:1
A/F based on volume = volume (mol) air/volume (mol) fuel = 4,762/2 = 2.4:1Percentage of combustion chamber occupied by hydrogen for a chemical equilibrium mixture:
= volume H2/(volume of air + volume H2)
As these calculations show, the chemically correct or chemically balanced A/F ratio for the complete combustion of hydrogen in air is about 34:1 by mass This means that for complete combustion, 34 kg of air per kg of hydrogen is required This ratio is much higher than the 14.7:1 A/F ratio required for gasoline
Since hydrogen is a gaseous fuel at ambient conditions, it occupies more space in the combustion chamber than liquid fuel Therefore, the combustion chamber may be occupied by less air At chemical equilibrium, hydrogen accounts for about 30% of the combustion chamber volume, compared to about 1 to 2% for gasoline The figure above compares the volume of the combustion chamber and the energy content of the gasoline and hydrogen fueled engines.
Depending on the method used to measure the amount of hydrogen for the engine, the output power relative to the gasoline engine can range from 85% (spraying through the intake manifold) to 120% (high pressure spraying).
Due to the wide ignition range of hydrogen, the hydrogen engine can run at an A/F ratio anywhere from 34:1 (chemical equilibrium) to 180:1 The A/F ratio can also be expressed in an equivalent ratio, denoted as phi (Φ) Phi equals the chemical equilibrium A/F ratio divided by the actual A/F ratio For a chemically balanced mixture, the actual A/F ratio is equal to the chemically balanced A/F ratio and thus Φ is in units (one) For a poor A/F ratio, phi will be a value of less than one For example, Φ 0.5 means that there
Figure 12 Comparison of combustion chamber volume is only enough fuel in the mixture to oxidize with half the available air Another way of saying this is that there is twice as much air to burn as theoretically required.
Application of hydrogen fuel to 1zn-fe engine and comparison with other fuels
The principle of operation between gasoline engines and hydrogen engines seems to be quite similar Hydrogen engine has 4 strokes: Load – Compress – Explode – Discharge Hydrogen engines still have 2 types, one uses fuel injected directly into the combustion chamber, the second is fuel mixed in the intake pipe and then into the combustion chamber.
In essence, a hydrogen engine is like an internal combustion engine However, deep inside those natures are still things that cannot be the same.
A huge difference of the hydrogen engine when it is mentioned is the eco- friendliness We will be mistaken that the hydrogen engine does not pollute the environment at all, and it can even replace electric cars It was not right The fact is that hydrogen engines do not emit CO2 into the environment On the other hand, hydrogen is still burned at high temperatures due to the presence of nitrogen oxides (NOx), which is considered one of the environmental pollutants that internal combustion engines are still doing every day.
Due to the low ignition energy limit of hydrogen, it is easy to burn hydrogen and a gasoline ignition system can be used At the air / fuel ratio (34:1 to 180:1), the flame rate is significantly reduced Attention: For complete combustion, 34 pounds of air per pound of hydrogen are required This is much higher than the 14.7: 1 A/F ratio required for gasoline.
At equilibrium conditions, hydrogen makes up about 30% of the combustion chamber, compared to about 1 to 2% for gasoline Therefore, it is very easy for a hydrogen engine to start the engine while it is cold But there are two sides to everything, the high mixing ratio means that the car will use less fuel to burn And using less fuel, the car will not be as powerful as a car using gasoline Since less fuel is used for combustion, the hydrogen engine will therefore emit less NOx than the internal combustion engine.
It is possible to compare the maximum average indication pressure of a hydrogen engine with the maximum average indication pressure of a gasoline primitive engine and to compare the thermal efficiency of two engines at the same rated speed of 6000 v/p and the same average indication pressure in load modes with air residue coefficient =1 and optimal early ignition angle The simulation model prepared above allows calculating all parameters of the engine's duty cycle when using gasoline and when using hydrogen, thereby calculating the average indicator pressure and thermal efficiency of the engine. The calculation results show that, in fully open throttle mode, the optimal early ignition angle of a hydrogen engine is 5 degrees, which is 14 degrees less than the optimal early ignition angle of a gasoline engine due to the greater rate of combustion of hydrogen than that of gasoline In this mode, the average indication pressure of the gasoline engine is 11.02 bar while that of the hydrogen engine is 9.81 bar, 11% lower than that of the gasoline engine This is completely explainable because the hydrogen is light, has a much larger specific volume than gasoline, so it occupies the air volume of the intake air is larger.
The study was carried out by modeling hydrogen engines on the basis of the 1NZ-
FE indirect gasoline injection engine installed on Tyota Vios vehicles.
Figure 13 Combustion of gasoline and hydrogen
Table 4 1NZ-FE engine parameters.
The results of calculating the engine cycle parameters corresponding to 2 types of fuel at the same speed and average indicator pressure are shown on the graphs Figure 1 to Figure 8 The ignition timing is chosen optimally for each type of fuel Figure 1 compares the public graph and Figure 2 compares the combustion law of gasoline engine and hydrogen engine at 6000v/p, indication pressure pi=9.81 bar It can be seen that the hydrogen engine has a higher peak pressure than the gasoline engine due to the faster combustion rate, shorter combustion time The early ignition angle of the hydrogen engine is adjusted so that the moment of fire occurs later than that of the gasoline engine to ensure the best combustion The gaseous pressure of the hydrogen engine decreases faster at the expansion period (the pressure line of the hydrogen engine is below the pressure line of the gasoline engine) because at this stage the gaseous temperature of the hydrogen engine is lower than that of the gasoline engine(Figure 3).
Figure 4 compares the work, cycle heat loss and Figure 5 compares the useful heat ratio (thermal efficiency), ratio heat loss rate of gasoline engine and hydrogen engine at 6000v/p, indication pressure pi=9.81 bar. hydrogen engine are both smaller than that of the gasoline engine This is because the gaseous temperature of the hydrogen engine , the temperature and the exhaust volume of the hydrogen engine are both less than the corresponding values of the gasoline engine Therefore, the thermal efficiency of the hydrogen engine is greater than that of the gasoline engine (greater than 3.9% in terms of efficiency value, while in terms of relative increase value, it is nearly 9%).
Compares heat loss due to heat transfer to the fire chamber wall and to the takeaway flue gas of the dynamic gasoline engine to use completely hydrogen supplied to the intake line without any change in the engine structure, the efficiency of the engine gasoline engine and hydrogen engine at 6000v/p and different load modes It can be seen that over the entire load range (each load mode corresponds to an average indicator pressure), the heat loss due to heat transfer to the combustion chamber wall and the heat loss due to takeaway exhaust of the hydrogen engine are all smaller than the corresponding figures of the gasoline engine As a result, the total heat loss is smaller, so the hydrogen engine has a higher thermal efficiency than the gasoline engine at the same average indicator pressure, i.e at the same power, the hydrogen engine has a higher thermal efficiency, in other words, the hydrogen engine is more economical than the gasoline engine Thus, when transferring current through the mean indication pressure) decreased by about 11% but the thermal efficiency of the engine increased by3.9% in terms of efficiency value.
It is clear that, for the same cycle the heat loss for the combustion chamber wall and the heat loss due to the carry-away exhaust of the hydrogen engine are both smaller than that of the gasoline engine This is because the gaseous temperature of the hydrogen engine the temperature and the exhaust volume of the hydrogen engine are both less than the corresponding values of the gasoline engine Therefore, the thermal efficiency of the hydrogen engine is greater than that of the gasoline engine (greater than 3.9% in terms of efficiency value, while in terms of relative increase value, it is nearly 9%).Figure 6 compares heat loss due to heat transfer to the fire chamber wall and due to the takeaway exhaust of the gasoline engine and the hydrogen engine at 6000v/p and various load modes It can be seen that over the entire load range (each load mode corresponds to an average indicator pressure), the heat loss due to heat transfer to the combustion chamber wall and the heat loss due to takeaway exhaust of the hydrogen engine are all smaller than the corresponding figures of the gasoline engine As a result,the total heat loss is smaller, so the hydrogen engine has a higher thermal efficiency than the gasoline engine at the same average indicator pressure i.e at the same power,the hydrogen engine has a higher thermal efficiency, in other words, the hydrogen engine is more economical than the gasoline engine Thus, when the gasoline engine is converted to use completely hydrogen supply into the intake line without any change in the engine structure, the efficiency of the engine (shown by the average indicator pressure) decreases by about 11% but the thermal efficiency of the engine increases by3.9% in terms of efficiency value.
Conclusion: The paper has developed a model that simulates the 1NZ-FE automobile gasoline engine using gasoline and using hydrogen The model was built for two fuels on the same engine, so even though it has not been tested experimentally, it is still significant to use to evaluate the change in the performance of the engine when switching from using gasoline to using hydrogen fuel The research results show that when converting the engine from gasoline to fuel H into the intake line without2 changing the engine structure, the average indication pressure is reduced by 11% but the thermal efficiency is significantly increased At the same speed and pressure mode only on average, the thermal efficiency of a hydrogen engine is 3.9% higher than that of a gasoline engine in terms of efficiency value and the relative amount of increase is8.8- 11.5% of the primitive engine efficiency value This result can confirm that in terms of working characteristics, current gasoline engines can completely switch to using hydrogen without having to change the engine structure The conversion motor has a slightly reduced efficiency (power) but a significantly improved economy(efficiency) However, it is necessary to equip the engine with back fire safety equipment and hydrogen filling station system to ensure explosion safety.
CONCLUSION
A hydrogen economy will emerge as the oil and gas economy has emerged, forcing radical changes in the infrastructure of the fossil economy and human activities The method of producing new energy sources is no longer searching, exploring, and exploiting; Methods of storing, transporting, and supplying hydrogen for consumption needs will require the structure and construction of new infrastructure The engine will be built according to new principles suitable for hydrogen energy sources, of course it will be different from gasoline and diesel engines
Technical standards, safety regulations, and legal laws when using new energy sources will have to be rebuilt Education, training, and scientific research to serve the hydrogen economy will require new content and new facilities, completely different from the current fossil economy The problems of environmental pollution caused by the use of hydrogen energy will no longer be a research topic that consumes money and labor for scientists, nor will it be the topic of ongoing international conferences about global climate change as when using fossil energy.
All of these changes show that this is truly a profound revolution in the development of human society, and has been assessed to have as great significance as the previous industrial revolution, when Invented the steam locomotive using coal fuel.
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