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Please what is the difference between a standard combustor and a DLN combustion system?
i need to know please. ..thank u
i need to know please. ..thank u
Daneezy,
First of all, there are many "flavours" of DLN--and while some of them are very different they all share a common feature versus most conventional combustors (diffusion flame combustors): multiple fuel nozzles. One of the most important contributors to the formation of NOx is the temperature of the combustion of the fuel--what's called "flame temperature;" higher temperatures result in more NOx, and lower temperature result in lower NOx. So, one of the ways to lower flame temperature is to have multiple smaller diffusion flames (the bright orange/yellow flame we associate with the combustion of fossil fuels).
Another way to reduce flame temperature is to greatly increase the amount of air in the combustion mixture--called "premixing"--which results in an extremely lean air/fuel mixture which combusts ("burns") at a much lower temperature without producing the orange/yellow diffusion flame. This combustion process is somewhat unstable because it's so lean and usually requires some "pilot" diffusion flame to start and maintain the temperature required for combustion.
So, one of the functions of the many nozzles is also to "inject" the fuel into a very air-rich environment and provide the necessary conditions (pilot flame) to combust the fuel without a large diffusion flame.
The majority of conventional combustors use a single fuel nozzle (with multiple orifices) to mix the fuel with sufficient air to result in diffusion flame. But, that hot gas temperature is too hot to admit directly into the turbine section of the gas turbine, so the combustion liner has a lot of slots and holes along the body that allows cooling and dilution air to mix with the hot combustion gases before entering the turbine nozzles.
DLN combustors are very different in that they force the majority of air to the fuel nozzle area of the combustor to premix with fuel and combust at a much lower temperature that doesn't require so much cooling and dilution air before entering the turbine nozzles. There are no cooling and dilution air slots along the body of the combustor in a DLN combustor (there are very few holes to allow some air into the liner for pilot flame (small diffusion flames) combustion).
Some DLN systems also have multiple combustion zones (two, usually) and the fuel is moved ("staged") between the two zones in order to achieve premix operation. Other DLN systems operate in premix mode from very low speed/loads and have a single combustion zone.
So, again the basic differences between standard (diffusion flame) combustors and DLN combustors is that the combustion of fuel takes place at a much lower temperature in DLN combustors and this is done by premixing air and fuel so the majority of air entering the combustion liner is directed to the fuel nozzle area of the combustor. Diffusion flame combustors direct a small portion of air to the fuel nozzle area for combustion, but direct a lot more air to the cooling and dilution area of the combustor where it's used to reduce the hot combustion gas temperature before it enters the turbine nozzles.
DLN combustion systems and components are rather intricate in order to achieve the lower combustion temperatures required to reduce NOx formation. DLN combustion systems also have several fuel control valves (more than diffusion flame combustion systems have). DLN combustors may have multiple combustion zones, and usually have multiple fuel nozzles. Unfortunately, we are unable to post pictures or drawings here on control.com, so that's about as much as we can say about the differences without having pictures/drawings to help.
Hope this helps!
This topic (and many others you will likely be interested in) have been covered many times before on control.com. Cleverly hidden at the far right of the Menu bar of every control.com webpage is a 'Search' field. It's recommended to use the Search Help function because while it's a very quick and powerful search engine the context of search terms is different from what's commonly used by most Internet search engines these days. While you may not find what you're looking for on the first or second search, keep trying different terms and combinations of words and double quotation marks (as with any search engine) and you will be very happy with the search results.
And, as with many searches, you may, but likely will not, find a thread that exactly matches your question--but you will find enough information in some of the results to be of help.
First of all, there are many "flavours" of DLN--and while some of them are very different they all share a common feature versus most conventional combustors (diffusion flame combustors): multiple fuel nozzles. One of the most important contributors to the formation of NOx is the temperature of the combustion of the fuel--what's called "flame temperature;" higher temperatures result in more NOx, and lower temperature result in lower NOx. So, one of the ways to lower flame temperature is to have multiple smaller diffusion flames (the bright orange/yellow flame we associate with the combustion of fossil fuels).
Another way to reduce flame temperature is to greatly increase the amount of air in the combustion mixture--called "premixing"--which results in an extremely lean air/fuel mixture which combusts ("burns") at a much lower temperature without producing the orange/yellow diffusion flame. This combustion process is somewhat unstable because it's so lean and usually requires some "pilot" diffusion flame to start and maintain the temperature required for combustion.
So, one of the functions of the many nozzles is also to "inject" the fuel into a very air-rich environment and provide the necessary conditions (pilot flame) to combust the fuel without a large diffusion flame.
The majority of conventional combustors use a single fuel nozzle (with multiple orifices) to mix the fuel with sufficient air to result in diffusion flame. But, that hot gas temperature is too hot to admit directly into the turbine section of the gas turbine, so the combustion liner has a lot of slots and holes along the body that allows cooling and dilution air to mix with the hot combustion gases before entering the turbine nozzles.
DLN combustors are very different in that they force the majority of air to the fuel nozzle area of the combustor to premix with fuel and combust at a much lower temperature that doesn't require so much cooling and dilution air before entering the turbine nozzles. There are no cooling and dilution air slots along the body of the combustor in a DLN combustor (there are very few holes to allow some air into the liner for pilot flame (small diffusion flames) combustion).
Some DLN systems also have multiple combustion zones (two, usually) and the fuel is moved ("staged") between the two zones in order to achieve premix operation. Other DLN systems operate in premix mode from very low speed/loads and have a single combustion zone.
So, again the basic differences between standard (diffusion flame) combustors and DLN combustors is that the combustion of fuel takes place at a much lower temperature in DLN combustors and this is done by premixing air and fuel so the majority of air entering the combustion liner is directed to the fuel nozzle area of the combustor. Diffusion flame combustors direct a small portion of air to the fuel nozzle area for combustion, but direct a lot more air to the cooling and dilution area of the combustor where it's used to reduce the hot combustion gas temperature before it enters the turbine nozzles.
DLN combustion systems and components are rather intricate in order to achieve the lower combustion temperatures required to reduce NOx formation. DLN combustion systems also have several fuel control valves (more than diffusion flame combustion systems have). DLN combustors may have multiple combustion zones, and usually have multiple fuel nozzles. Unfortunately, we are unable to post pictures or drawings here on control.com, so that's about as much as we can say about the differences without having pictures/drawings to help.
Hope this helps!
This topic (and many others you will likely be interested in) have been covered many times before on control.com. Cleverly hidden at the far right of the Menu bar of every control.com webpage is a 'Search' field. It's recommended to use the Search Help function because while it's a very quick and powerful search engine the context of search terms is different from what's commonly used by most Internet search engines these days. While you may not find what you're looking for on the first or second search, keep trying different terms and combinations of words and double quotation marks (as with any search engine) and you will be very happy with the search results.
And, as with many searches, you may, but likely will not, find a thread that exactly matches your question--but you will find enough information in some of the results to be of help.
