First, the core principle of turbocharging technology

        Turbocharging technology can realize intake supercharging by recovering exhaust energy of diesel engine, thus improving engine performance. Its core principle is based on energy conservation and thermodynamic cycle:

        Exhaust gas driven turbine: The high-temperature and high-pressure exhaust gas discharged from the engine impacts the turbine blades and drives the turbine to rotate at high speed (the speed can reach more than 100,000 revolutions per minute).

        Compression of fresh air: the turbine drives the compressor impeller through coaxial connection to compress the outside air and send it into the combustion chamber.

        Increase intake density: The compressed air density is significantly increased (usually by 30%-50%), which makes the oxygen content in unit volume higher and provides conditions for full combustion of fuel.

        Combined with the compression ignition characteristics of diesel engine, turbocharging technology solves the problem of limited combustion efficiency caused by insufficient intake of naturally aspirated engine. Due to the high compression ratio of diesel engine (usually 16:1 to 22:1), the mixture density can be further increased and the combustion process can be optimized after supercharging.

        Second, the influence of turbocharging on the dynamic performance of diesel engine

        Greatly improve power and torque.

        Turbocharging can increase the power of diesel engine by 30%-100% and the torque by 50%-80% without increasing the displacement. For example, after a 2.0L diesel engine is turbocharged, the high power is increased from 100kW to 140kW, and the peak torque is increased from 300N・m to 400N・m. This feature makes it indispensable in heavy trucks, construction machinery and other fields, especially in plateau areas, turbocharging can compensate for the power attenuation caused by thin air.

        Improve fuel economy

        After supercharging, the engine can output high torque at a lower speed, reducing the friction loss caused by high speed. At the same time, more complete combustion can improve fuel utilization, and the fuel consumption of some models can be reduced by 10%-15%. For example, after a heavy truck is equipped with a turbocharged diesel engine, the fuel consumption per 100 kilometers is reduced from 35L to 30L.

        Optimize emission performance

        Supercharging technology can promote the oxidation of soot (PM) and reduce particulate emissions by increasing combustion temperature and pressure. However, it should be noted that turbocharging may lead to an increase in the generation of nitrogen oxides (NOx), and it is necessary to cooperate with SCR (selective catalytic reduction) and other post-treatment technologies to control emissions.

        III. Technical Challenges and Solutions

        Turbine hysteresis phenomenon

        At low speed, the exhaust gas energy is insufficient, which leads to the delay of pressurization response (usually 0.5-2 seconds) and affects the driving comfort. Solutions include:

        Variable cross-section turbine (VGT): Optimize low-speed supercharging efficiency by adjusting turbine blade angle.

        Electric auxiliary turbine: start the motor to assist the turbine to accelerate at low speed, shortening the response time.

        Thermal load and mechanical stress

        The temperature and pressure of combustion chamber increase after supercharging, which puts forward higher requirements for engine materials (such as cylinder block and piston). Adopting high strength alloy, ceramic coating and optimizing cooling system can alleviate this problem.

        Reliability and maintenance cost

        The turbocharger has a very high rotating speed, which requires high-precision bearings and high-temperature resistant lubricating oil. Changing the oil filter regularly and avoiding sudden acceleration/deceleration can prolong the service life.

        Fourth, the future development trend

        Intelligent control: The ECU monitors the intake pressure, temperature and other parameters in real time, and dynamically adjusts the supercharging strategy to achieve more accurate power output.

        Hybrid synergy: In the field of commercial vehicles, turbocharged diesel engines can be combined with motors to form a "diesel-electric hybrid" system to further improve energy efficiency.

        Hydrogen fuel adaptation: Some turbocharging technologies have been modified for hydrogen fuel engines, which can improve hydrogen combustion efficiency and explore a zero-carbon power path through turbocharging.

        tag

        Turbocharging technology is the key means for diesel engine to break through the physical limit. Through energy recovery and thermodynamic optimization, it significantly improves the power, economy and environmental protection. Despite the challenges of hysteresis and reliability, with the progress of material science and intelligent control technology, turbocharging will still be one of the core directions for the future development of diesel engines. Under the background of new energy transformation, this technology will also cooperate with other power forms to provide diversified solutions for transportation and industry.