Computational studies of the influence of variable valve timing on the performance of a gas engine with Miller’s thermodynamic cycle

Current development trends in the field of internal combustion engines aim at regulating all processes of the engine and individual units. A converted diesel to gas engine with Miller thermodynamic cycle is more energy efficient at partial loads than a gas engine with Otto thermodynamic cycle. The Miller cycle engine with variable valve timing and valve lift has been investigated to improve performance and energy efficiency across the load range. The aim of the work is to study the influence of the displacement of the valve timing phases of the intake and exhaust camshafts and the valve lift height on the performance of the gas engine with the Miller cycle. Computer modelling was based on data obtained from the full-scale experiment on the gas engine with the Miller thermodynamic cycle.

Flow Field Parametric Interpolation Using a Proper Orthogonal Decomposition: Application to the Variable Valve Timing Effect on a Tumble In-cylinder Miller Engine Mean Flow

The current article presents a method to reconstruct the mean velocity field of a cyclic flow for an input parameter value that has not been measured, allowing for the number of tests to be reduced. It is applied to the tumble flow of a gasoline engine following a Miller cycle. New engines often include variable valve timing (VVT) systems to maximize the efficiency of such over-expanded cycles for different operating points. The reconstruction was thus carried out using different offset values of the intake valve lift timing. Experimental data were collected from a transparent engine in an early intake valve closing (EIVC) configuration using particle image velocimetry (PIV). The mean velocity field reconstruction was based on the interpolation of the proper orthogonal decomposition (POD) coefficients. The accuracy of the method was evaluated at different points by comparing the interpolated and the measured flow fields. The accuracy was estimated by calculating the error in the rotation rate of the tumble and the position of its center of rotation. The new mean velocity field set allowed for the position of the tumble’s center of rotation to be closely tracked according to the input parameter and a rotation rate map to be made. Some results on Miller’s cycle could thus be found and the data generated could guide future developments.

Study on Non-Axisymmetric 3D Curved Surface Turning by Driven-Type Rotary Tool Synchronized With Spindle

Since shifting to electric vehicles as a countermeasure against global warming is not always easy to complete, the hybrid car has been considered as another possible solution. However, based on the calculation of total CO2 emissions, all hybrid cars which will constitute 90% of all cars are expected to be equipped with an internal combustion engine even after 2030. Therefore, further efficiency improvement of the internal combustion engine is necessary. One of the key factors is the variable valve timing and variable lift with the 3D cam mechanism. Since conventional technology uses a complicated link mechanism and servo motor control, this leads a problem to set into small cars or motorcycles because they cannot afford to install the variable valve timing and variable lift with cam mechanism. To solve this problem, a cam shape with a three-dimensional curved surface has been proposed. In order to create this shape, the machining method for non-axisymmetric curved surface turning (NACS-Turning) is required. To build the new system, our research group has proposed a new machining method using a driven type rotary tool and a linear motor driven moving table to enable to achieve NACS-Turning. In this new system, a new tool rotation axis (B axis) is adopted to synchronize its rotational position with the rotational position of the spindle (C axis) holding the workpiece, the X1-, X2-, and Z-Axis positions in total. In this paper, the new hardware configuration is proposed to overcome the present machining accuracy.

Analisis Perbandingan Teoritis Performansi Daya Mesin Mobil dan Konsumsi Bahan Bakar Spesifik Berteknologi VVT-i dan Non VVT-i

Mesin berteknologi VVT-i (Variable Valve Timing with Intellegence) pada dasarnya bekerja mengoptimalkan torsi mesin pada setiap kecepatan serta kondisi mengemudi. Mekanisme tersebut akhirnya akan membuahkan konsumsi BBM menjadi lebih efisien serta emisi gas buang menjadi lebih rendah. Cara kerja teknologi VVT-i cukup sederhana, yaitu untuk menghitung waktu buka tutup katup (Valve Timing) yang optimal, ECU (Electronic Control Unit) akan menyesuaikan dengan kecepatan mesin, volume udara masuk, posisi throttle dan temperatur air. Agar target valve timing senantiasa terwujud, sensor posisi crankshaft memberikan sinyal yang menjadi respon koreksi. Sistem VVT-i ini akan mengoreksi valve timing atau jalur keluar masuk bahan bakar dan udara. Disesuaikan dengan pijakan pedal gas dan beban yang ditanggung untuk menghasilkan torsi optimal di tiap putaran dan beban mesin. Teknologi ini juga diklaim memiliki kelebihan tenaga yang jauh lebih optimal dan hemat konsumsi bahan bakar, serta ramah lingkungan.

Variable Valve Timing (VVT) Modelling by Lotus Engine Simulation Software

Variable valve timing (VVT) is an advanced modern technique applied in internal combustion engines by altering the valve lift event timing. This work aims to contribute to the continuing industrial VVT development to improve engine efficiency, fuel consumption and performance. To observe the influence on the spark-ignition (SI) engine’s performance, four valve timing strategies are selected carefully by varying the intake and exhaust valve timing. Lotus Engine Simulation, a simulation engineering software, is adapted in this study. The engine characteristics used in this modelling are spark engine, multicylinder, four strokes, port injection fuel system and constant compression ratio. A comparison between a conventional standard exhaust/intake valve timing and three other different timing cases is carried out. Results reveal that the overlap case of 98° showed a good brake-specific fuel consumption by approximately 3% less than the conventional case. An improvement of 6.2% for volume efficiency and 2.9% in brake thermal efficiency is also reported.