The internal combustion engine has been the workhorse of world transportation for more than a century, since innovators like Nikolaus Otto and Gottlieb Daimler developed and perfected the design in the 1870s and 1880s. But in that time, a lot of energy has been squandered. Less than one third of the energy from the fuel put into the gas tank of a car with a typical spark-ignition engine is used to move the vehicle down the road. The rest is lost, mostly as exhaust heat, due to the engine's inherent inefficiencies. Diesel engines, which use compression rather than an electric spark to ignite the fuel, are far more efficient, but researchers believe greater improvements are possible.
One promising new low-temperature combustion technology being researched is called "homogeneous charge compression ignition," or HCCI. Instead of using an electric spark to ignite the fuel, the fuel mixture is compressed until it combusts spontaneously by chemical reaction in proper phase with the piston motion. This combustion takes place at lower temperatures, higher pressures, and with a much more dilute fuel mixture than in the spark-ignition engines of most cars today. The bonus of low-temperature compression ignition is that fuel efficiency could increase by as much as 25 to 50 percent. But an HCCI engine is harder to control, and more sensitive to fuel chemistry than are conventional spark-ignition engines. Either the fuel mixture needs to be adjusted, or the temperatures in different portions of the mixture need to be stratified, or layered, to control the speed at which pressure rises in the engine. Even fuels are changing too.
Hundreds of molecules have been proposed as alternative fuels—many of them from biology. It's not practical to run them in all in comprehensive engine tests, which would require manufacturing a large amount of each proposed new fuel and fuel blend. And with many new engine designs in development, it's not clear which engine to use to test which future fuels.That's where supercomputers come in.
Scientists have turned to supercomputing power to help better understand combustion, and to model and predict the behavior of fuels by simulating the conditions found in new types of combustion engines. Using 113 million central processing unit (CPU)-hours on the Oak Ridge Leadership Computing Facility's Jaguar supercomputer, they were able to simulate fine-scale mixing-chemistry interactions in HCCI combustion with different approaches for mixture stratification that offer different options for controlling the rate of combustion in an HCCI engine.
But the calculations taxed Jaguar, even with its speed of 3.3 petaflops, or a quadrillion calculations per second. That's why scientists are looking forward to Titan, which will upgrade Oak Ridge's supercomputing power to 20 petaflops. Titan also will have energy-efficient, high-performance code accelerators called graphics processing units (GPUs). The resulting "hybrid" supercomputer, combining CPU and GPU power, will be able to run code far faster, and Chen and her team believe it will give them the ability to simulate conventional and alternative fuels of greater chemical complexity.
One promising new low-temperature combustion technology being researched is called "homogeneous charge compression ignition," or HCCI. Instead of using an electric spark to ignite the fuel, the fuel mixture is compressed until it combusts spontaneously by chemical reaction in proper phase with the piston motion. This combustion takes place at lower temperatures, higher pressures, and with a much more dilute fuel mixture than in the spark-ignition engines of most cars today. The bonus of low-temperature compression ignition is that fuel efficiency could increase by as much as 25 to 50 percent. But an HCCI engine is harder to control, and more sensitive to fuel chemistry than are conventional spark-ignition engines. Either the fuel mixture needs to be adjusted, or the temperatures in different portions of the mixture need to be stratified, or layered, to control the speed at which pressure rises in the engine. Even fuels are changing too.
Hundreds of molecules have been proposed as alternative fuels—many of them from biology. It's not practical to run them in all in comprehensive engine tests, which would require manufacturing a large amount of each proposed new fuel and fuel blend. And with many new engine designs in development, it's not clear which engine to use to test which future fuels.That's where supercomputers come in.
Scientists have turned to supercomputing power to help better understand combustion, and to model and predict the behavior of fuels by simulating the conditions found in new types of combustion engines. Using 113 million central processing unit (CPU)-hours on the Oak Ridge Leadership Computing Facility's Jaguar supercomputer, they were able to simulate fine-scale mixing-chemistry interactions in HCCI combustion with different approaches for mixture stratification that offer different options for controlling the rate of combustion in an HCCI engine.
But the calculations taxed Jaguar, even with its speed of 3.3 petaflops, or a quadrillion calculations per second. That's why scientists are looking forward to Titan, which will upgrade Oak Ridge's supercomputing power to 20 petaflops. Titan also will have energy-efficient, high-performance code accelerators called graphics processing units (GPUs). The resulting "hybrid" supercomputer, combining CPU and GPU power, will be able to run code far faster, and Chen and her team believe it will give them the ability to simulate conventional and alternative fuels of greater chemical complexity.
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