TI Automotive, the world’s leading supplier of fluid storage and delivery systems, is applying a unique combination of technologies to develop the next generation of injection tubes for high-pressure diesel injection (HPD) engines. Electronically controlled HPD injection has dramatically increased the fuel efficiency of diesel engines while also helping to reduce emissions and make the engines quieter and smoother for passenger car applications.
To achieve these results, HPD injection systems must operate at extremely high pressures – up to 33,000 psi for cars and 40,000 psi for large truck engines.
TI Automotive employ rigorous processes and technologies to design, test and manufacture fuel tubing to withstand high system pressures.
“The benefits of HPD are overwhelming in terms of efficiency, power and emissions reduction, but developing fuel systems to withstand the extreme pressures over the lifetime of the vehicle is a tough engineering challenge,” said Joachim Burkhardt, president of TI Automotive’s Global Fluid Carrying Systems division. “The tubes must be made out of specialty steel, with a special treatment, called autofrettage, on the inner surface of the tube for added strength and durability, plus customized corrosion protection on the outside. At TI Automotive we are using methods such as finite element analysis and computerized x-ray testing to assure that the tubing will remain durable and dependable under such difficult conditions.”
TI Automotive has more than 20 years experience in delivering injection solutions as system pressures have increased from 10,000 psi up to today’s maximum of 40,000 psi.
The extreme pressures generated by HPD injection systems require great precision and expertise in the design and application of the components. The company uses sophisticated three-dimensional vibration and impulse pressure fatigue testing to assure lifetime performance of the parts.
Production equipment is optimized to achieve the accuracy and cleanliness the system design requires. Specially designed robotic machines perform the autofrettage process, a sophisticated method of strengthening the injection tubing for long-term reliability.
Benefits of HPD injection
The combination of HPD’s high pressures and multistage injection serves as an important tool for increasing combustion efficiency, which helps reduce emissions and improve fuel economy. Higher pressures create smaller fuel droplets and higher injection velocity to promote more complete burning of the fuel, which maximizes power and minimizes pollution. By injecting precise amounts of fuel in a shorter time frame, a high pressure system can supply multiple injection events during each combustion cycle, allowing the engine control software to optimize combustion for particular conditions.
For passenger car applications, the engine’s electronic control unit can help lower engine noise by injecting a small amount of fuel just before the main injection event (“pilot” injection), reducing its explosiveness and vibration, and optimizing injection timing and quantity for changing conditions and loads. Some advanced HPD fuel systems perform as many as five injections per stroke.