Stringent emission regulations force the gas turbine combustor community to come up with new designs. Lean Premixed combustion (LPM) is gaining popularity to meet the emission regulations. However, lean combustion process is prone to other issues like combustion instabilities and noise.
Self-excited combustion instabilities in a gas turbine play a vital role in the lifecycle of combustor, noise generation and pollutant formation. If the instabilities in the combustor dominate at natural modes, there are risks of resonance that can lead to bursting damage to the combustors. Therefore, it is necessary to understand the combustion dynamics performance of a given lean premixed combustor. Continue reading
There’s an old project management adage that goes “Good. Fast. Cheap. Pick any two.” There are tons of websites and blogs about it. I’m particularly fond of this one about the designer’s holy triangle. Unfortunately, this holds true in the engineering simulation world. With “good” meaning “accurate,” you’re stuck with suboptimal choices: Good + fast = expensive; good + cheap = slow; fast + cheap = inferior. Product designers are stuck with good results that take too long or “directional” results fast. Good and fast just was not on the table. Continue reading
Flows around aerodynamic bodies, like aircraft wings, helicopter blades, wind turbines and turbomachinery components develop boundary layers that, to a large extent, define their performance. The boundary layers can either be laminar or turbulent depending on numerous factors, like Reynolds number, freestream turbulence levels and surface roughness, to name a few. Understanding which type of boundary layer is present, and the location of the laminar-to-turbulent transition point under varying operating conditions, is essential for accurate predictions of the performance of aerodynamic devices. Continue reading
Recently the Environmental Protection Agency (EPA) imposed more stringent emission levels from engines. These emission restrictions are expected to increase (lower levels) in the near future. As such, modern engine designs, inevitably will need to meet the goal of ultra clean combustion. Different pollutants are emitted due to incomplete combustion, like unburned hydrocarbons (UHC), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), and black carbon (BC) — also known as soot. The environmental impact of each of these pollutants is well known and can range from reduced visibility due to smog and cloud formation to cancer and premature death when inhaled by respiratory system. Continue reading
This week, I attended the American Flame Research Committee’s Combustion Symposium in Houston where I presented a paper on radiation modeling.
Most of the papers presented were about industrial flares. If you live near a process plant, you must have seen these large stacks reaching into the clear blue sky. At the end of these stacks are large flames that can be seen from a distance. For most urban area residents, these flares create a concern about public health and safety especially if there is some black smoke as well in the fireball.