Currently vehicles use natural gas Port fuel injection system for SI engine, and lots of research is going on for direct injection system development but still not yet achieved.
Apart from this what other challenges natural gas engines are facing ?
Gas engine need to handle rapidly changing methane numbers because the compression ratio is set high to achieve maximum efficiency and knock due to pre-ignition control is also needed. For low quality gas the maximum tolerable values for harmful substances including Sulphur, hydrogen Sulphide, chlorine and ammonia, to ensure the engine is protected from damage must be defined. Because gas engines have high cylinder pressures and high specific engine output, a minimum lubrication gap is needed to prevent mixed friction wear, the use of lubricants claiming to offer fuel economy benefits is needed. If we use gas engines for balanced energy and peak load operation, the gas engines are more flexible in load shifting than gas turbines or larger power plants, such as nuclear or coal. Multi-grade properties are desirable for engines with no lubricant preheating and, with emissions legislation tightening, and the introduction of catalysts looks unavoidable. Compared with diesel engines, modern gas engines have relatively lower emissions of NOx and CO2. However, emissions of unburnt methane, also known as ‘methane slip’, must gain some attention not only due to their cost, but also because methane is a greenhouse gas. So, focusing on combustion technologies to keep methane slip to a minimum is required. Also, the problematic nature of NG engine operation in low ambient temperatures must be considered. It was noted that such temperature changes can affect NGE output parameters; even so, the operation of engines with suitable preparation is possible. Defining the actual amount of gas in a cylinder also needs developed accurate systems.
Natural gas has less calorific value than regular diesel or petrol, which means lesser energy to push the pistons. but, in engines since air fuel ratio is measured based on mass rather than volume, this can get tricky while designing an ICE. However, currently in India, even though CNG emits lesser criteria pollutants, CH4 emissions are quite higher due to methane slip (similar to HC emissions in petrol/diesel SI's due to unburnt fuel). Engine knocking will be one of the problems that need to be answered.
Gas Engines work on Otto cycle. Natural gas should be stored in specially designed containers maintaining certain pressure. Gas leakage is a big problem as it leads to explosion to the environment and should be careful. The advantage of natural gas is cheap in cost and can be used as a fuel in various thermal equipments like engines, gas turbines etc. compared to most of the other available fuels.
Natural gas in SI as you said works fine since it requires external spark to get ignition started. But when it comes to direct injection, it is not as simple as HCCI petrol engines. Simply because fuel properties are different which I'm not going in depth. It is possible but not worth the cost from benifits it gives.
Hence Natural Gas to be working as HCCI, it needs additional fuel to get that initial ignition and get maximum performance out of it. Yes I'm talking about Dual fuel combustion system. This is what currently I'm working on. Using Diesel as pilot injection to give that initial ignition. I will be haviung ore interesting things when I'm done with the research.
Also Using Natural gas alone in engines has many problems like following
1. Power density and range.
2. Unburnt Methane is more dangerous Green house gas than CO2. It traps more heat in earth's atmosphere.(In my project I'm also analysing regeneratively produced methane that means no additional CO2).
3. Storage either as CNG or LNG.
Finally I would say Dual Fuel is an exciting topic than stand alone fuel systems especially when these Electric motors are getting more popular for no reason all of sudden like State of art technology.
Gaseous fuel is ideal in I.C. engine. These interact and mix homogeneously with air. The storage of fuel and handling of gaseous fuels is difficult and restrict their use in automobile vehicles. Improvement of design and performance of a automobile are becoming obsolete compared to liquid fuel. They can be liquefied under pressure thereby reducing the storage volume. This process is risk and expensive.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Thermodynamics