BorgWarner has developed a dual volute turbocharger specifically engineered for gasoline engines in light-duty vehicles with aggressive transient response targets. The company’s new turbocharger delivers a quicker engine response time when accelerating from low speeds. The dual volute geometry allows for the complete segregation of engine exhaust pulsations so more exhaust energy is available to the turbine wheel, compared with traditional twin-scroll turbochargers.
A turbocharger, made of a turbine and compressor, works by harnessing normally-wasted energy in the high-temperature, high-pressure exhaust flow from the engine, and then converts that energy into compressed or ‘boosted’ air to feed the engine. The dual volute turbine stage directs exhaust flow through two separate volutes (circumferential passages) of the turbine housing, each of which feed exhaust pulsations directly into one half of the turbine wheel.
Traditional twin-scroll turbochargers maintain separation of the exhaust flow to the turbine wheel by adding a divider wall to the turbine housing, creating a ‘side-by-side’ arrangement of the exhaust flow passages. However, these designs require the exhaust flow from the two passages to enter a smaller common flow channel just before entering the turbine wheel. The common channel allows some leakage of the exhaust flow and pulsation energy between the two sides, which results as a loss of energy available to the turbine wheel.
By eliminating this common flow channel and fully separating the flow passages, BorgWarner’s dual volute turbine stage is able to capture more exhaust pulsation energy than twin-scroll turbines. At low engine speeds, where there are longer periods of time between exhaust pulses and exhaust flow is more variable, the ability to harness the pulsation energy from the engine represents a significant increase in energy available to drive the turbine wheel as compared to the exhaust flow energy alone. This increase in turbine energy utilization at low engine speeds is a key to providing superior turbocharger boost response and meeting quick engine response targets in modern turbocharged engines.
Robin Kendrick, president and general Manager, BorgWarner Turbo Systems, said: “BorgWarner’s history and expertise in creating advanced engine boosting technologies enable us to take a system approach in technology development as well as support our customers in choosing the right turbocharging solution. Our engineering team recognized that a dual volute turbocharger could provide quicker engine response times for light-duty vehicles that require superior transient behavior.”
BorgWarner began developing this new generation of dual volute turbocharging technologies for gasoline engines in 2012 and is now in production with an OEM on a full-size pickup truck – its first dual volute turbocharger for the light-duty vehicle market.