Optimal Degree of Hybridization for Spark-Ignited Engines with Optional Variable Valve Timings

The electric hybridization of vehicles with an internal combustion engine is an effective measure to reduce CO2 emissions. However, the identification of the dimension and the sufficient complexity of the powertrain parts such as the engine, electric machine, and battery is not trivial. This paper investigates the influence of the technological advancement of an internal combustion engine and the sizing of all propulsion components on the optimal degree of hybridization and the corresponding fuel consumption reduction. Thus, a turbocharged and a naturally aspirated engine are both modeled with the additional option of either a fixed camshaft or a fully variable valve train. All models are based on data obtained from measurements on engine test benches. We apply dynamic programming to find the globally optimal operating strategy for the driving cycle chosen. Depending on the engine type, a reduction in fuel consumption by up to 32% is achieved with a degree of hybridization of 45%. Depending on the degree of hybridization, a fully variable valve train reduces the fuel consumption additionally by up to 9% and advances the optimal degree of hybridization to 50%. Furthermore, a sufficiently high degree of hybridization renders the gearbox obsolete, which permits simpler vehicle concepts to be derived. A degree of hybridization of 65% is found to be fuel optimal for a vehicle with a fixed transmission ratio. Its fuel economy diverges less than 4% from the optimal fuel economy of a hybrid electric vehicle equipped with a gearbox.

Design of an Electromagnetic Variable Valve Train with a Magnetorheological Buffer

In this paper, an electromagnetic variable valve train with a magnetorheological buffer (EMVT with MR buffer) is proposed. This system is mainly composed of an electromagnetic linear actuator (EMLA) and a magnetorheological buffer (MR buffer). The valves of an internal combustion engine are driven by the EMLA directly to open and close, which can adjust the valve lift and phase angle of the engine. At the same time, MR buffer can reduce the seat velocity of the valve and realize the seat buffer of the electromagnetic variable valve. In this paper, the overall design scheme of the system is proposed and the structure design, finite element simulation of the EMLA, and the MR buffer are carried out. The electromagnetic force characteristics of the EMLA and buffer force of the MR buffer are measured, and the seat buffering performance is verified as well. Experiments and simulation results show that the electromagnetic force of the EMLA can reach 320.3 N when the maximum coil current is 40 A. When the current of the buffer coil is 2.5 A and the piston’s motion frequency is 5 Hz, the buffering force can reach 35 N. At the same time, a soft landing can be realized when the valve is seated.

High Efficiency Diesel Engine Concept With Variable Valve Train and Cylinder Deactivation for Integration Into a Tractor

The objective of current research on internal combustion engines is to further reduce exhaust emissions while simultaneously reducing fuel consumption. The resulting measures often mean an increase in complexity of internal combustion engines, which on one hand increases production cost and on the other hand increases the susceptibility of the overall system to defects. It is therefore necessary to develop technologies which can generate an advantage for the consumer despite increasing complexity. Within the scope of the project “High Efficiency Diesel Engine Concept” (“Hocheffizientes Diesel-Motoren-Konzept” HDMK), funded by the Federal Ministry of Economic Affairs and Energy with TÜV Rheinland as project management organization (funding code: 19U15003A), two engine concepts were investigated and combined on a John Deere four-cylinder inline engine. On the one hand, a new cylinder activation concept (“3/4-cylinder concept”) was implemented with the aim of reducing fuel consumption. On the other hand, a fully variable valve train was developed for this engine, which both improves the functionality of the 3/4-cylinder concept and can have a positive influence on exhaust emissions through internal exhaust gas recirculation. A comparison of this engine concept with its series reference based on measurement data showed a fuel economy advantage of up to 5.2% in the low load field cycles of the DLG PowerMix. The maximum fuel consumption benefit in the low load engine regime exceeded 15% in some of the operating points. As a final step, the engine was modified for the integration into an existing and working tractor, maintaining the available installation space of the powertrain.

Modeling and Analysis of an Electromagnetic Fully Variable Valve Train with a Magnetorheological Buffer

Electromagnetic fully variable valve train (EMVT) technology promises to improve the fuel economy and optimize the engine performance. A novel EMVT equipped with a magnetorheological buffer (EMVT with MR buffer) is proposed to suppress the valve seating impact in this paper. The magnetorheological buffer can adjust the damping characteristics of the whole system in the seating process. Valve precise motion control and better seating performance can be achieved through the coordinated control of electromagnetic linear actuator (EMLA) and MR buffer. For better analysis of system performance, establishing an accurate system dynamic model is the basis of the coordinated control system. A high-order nonlinear precise model integrating dynamics, electromagnetism, and fluid mechanic was established. Then, the Jacobi linearization model is carried out at the equilibrium seating point to build a control-oriented linearized model. The correctness and accuracy of the linearized model is verified. Experiments and simulations show that the valve precise motion can be well controlled to achieve fully variable actuation. And the valve soft landing can be completed under collaborative control.