Camless Engine Research Articles

A comparative assessment of performance, combustion, and emissions of a gasoline port and direct injection camless engine

AbstractThe lower part‐load efficiency of the spark‐ignition (SI) engine is because of the higher pumping loss during the gas exchange process. In this study, the part‐load efficiency of a port fuel injection (PFI) and gasoline direct injection (GDI) camless engines were investigated. An in‐house developed electro‐pneumatic variable valve actuation (VVA) system controls the camless engine's intake valve events. The effect of un‐throttled operation with early intake valve closings (EIVC) on performance, combustion, and emissions was analyzed. The IVC timing for GDI camless engine was found to be lower (2°–7° crank angle) than the PFI camless engine for all operating conditions due to the in‐cylinder charge cooling. Hence, the pumping mean effective pressure (PMEP) for GDI camless engine was reduced, and brake specific fuel consumption (BSFC) was improved (maximum 2.1%) compared to the PFI camless engine. The THC and CO emissions were higher for GDI camless engine due to the relatively in‐homogeneous mixture formation, whereas the NOx emission was lower for all operating conditions.

Performance enhancement of camless air engine by optimising the inlet-valve cut-off position

In the field of fuel-efficient, renewable and reduced environmental effects, air engine is the cutting edge technology. The present study is concentrated on the camless engine and specifically valvetrain timing, to maximise efficiency by reducing the excess air supply and controlling intake duration. Controlled supplied air has sufficient time for expansion and maximum useful work conversion. A prototype model was built with a novel pneumatic circuit using 3/2 direction control valve, and experimental investigation was carried out in the pressure range of 3.25–5.5 bar, and intake duration was set in the form of a crank angle from 60° to 180° to determine the optimum intake duration (cut-off position angle). A control system was developed for controlling intake duration, feedback and data acquisition system. Experimental results reveal that the engine's average efficiency increases up to 35.67% by closing the inlet valve at an optimum angle.

Effect of internal exhaust gas recirculation on performance, combustion, and emissions in a PFI camless engine

AbstractThe internal exhaust gas recirculation (EGR) into the intake manifold has a significant impact on fuel economy and emissions in the spark ignition (SI) engine. In this study, an in‐house developed novel electro‐pneumatic variable valve actuation (VVA) system was integrated on a PFI conventional engine and modified into PFI camless engine to vary the valve events independently. The potential of the developed VVA system in achieving the internal EGR by varying the intake valve opening (IVO) timings was widely investigated. The IVO timing was varied from 30° CA (crank angle) bITDC (before intake top dead center) to 40° CA aITDC (after intake top dead center). The spark timing was varied from 10° to 30° CA bCTDC (before compression top dead center). A 41% pumping mean effective pressure reduction was achieved with varying the IVO from 40° to −30° CA aITDC. It is due to the internal exhaust gas recirculation into the intake manifold that reduces the differential pressure between the manifold and combustion chamber. The entrapment of exhaust gas in the intake manifold dilutes the fresh charge, which deteriorates the combustion. However, advancing the spark timing from 10° to 30° CA bCTDC at IVO −30° CA aITDC, an 18% gas excahnge efficiency improvement was obtained. The fresh charge dilution forms an inhomogeneous mixture inside the cylinder that results in lower NOx emission. It is concluded that the developed VVA system has the potential to improve part loads efficiency by utilizing the internal EGR in a PFI camless engine.

Measurement and modelling of a linear electromagnetic actuator driven camless valve train for spark ignition IC engines under full load condition

Camless engine valve train for gasoline engines particularly port injection engines offer major improvements over traditional system with fixed valve timing and lift, in terms of efficiency, maximum torque and power, and emissions. Electromagnetic driven valve actuators are very promising in this context, but there are significant control problems. The use of displacement sensor could add extra cost to the camless engine. In this work, a moving coil actuator driven valve train was designed and prototyped and a 1D single-cylinder internal combustion engine model was built to investigate the benefit of without throttle by adopting such camless valve train using Ricardo WAVE under full load operating conditions. A novel low-cost sensor named linear actuator position sensor (LAPS) based on flux linkage change on search coil was constructed in LabVIEW by using current, voltage and proximity sensors to detect the valve lift. The measurement of valve lift and current was reported to prove the feasibility of the camless valve train. The valve lift was used for the single-cylinder engine model and the simulation shows that the peak overall engine efficiency using camless valve train reaches 38.2% and the peak torque increases by 5 Nm compared conventional throttled engine under full load operating conditions. The LAPS model was validated by the experimental valve lift and the high accuracy indicates that the LAPS can be adopted for future development of camless valve train for spark ignition IC engines.

Bifurcation, routes to chaos, and synchronized chaos of electromagnetic valve train in camless engines

Abstract The main objects of this paper focus on the complex dynamics and chaos control of an electromagnetic valve train (EMV). A variety of periodic solutions and nonlinear phenomena can be expressed using various numerical techniques such as time responses, phase portraits, Poincaré maps, and frequency spectra. The effects of varying the system parameters can be observed in the bifurcation diagram. It shows that this system can undergo a cascade of period-doubling bifurcations prior to the onset of chaos. Lyapunov exponents and Lyapunov dimensions are employed to confirm chaotic behavior for EMV. A proposed continuous feedback control method based on synchronization characteristics eliminated chaotic oscillations. Numerical simulations are utilized to verify the feasibility and efficiency of the proposed control technique. Finally, some robustness analysis of parametric perturbation on EMV system with synchronization control is confirmed by Lyapunov stability theory and numerical simulations.

Modelling of an electro-hydraulic variable valve actuator for camless engines aimed at controlling valve lift parameters

This paper presents the mathematical modelling of an Electro-Hydraulic Valve Actuator (EHVA) prototype and its application to the design of cycle-by-cycle Valve Lift Control(VLC). EHVA is rated in the technical literature as an apparatus enabling Variable Valve Actuation (VVA) and implementation of advanced combustion concepts in future camless engines. It is, therefore, a first step towards the development of camless engines in which valve lift and timing can be freely adjusted valve-by-valve and cycle-by-cycle. Particular attention is paid to parameter identification aimed at obtaining a predictive simulation model of valve lift trajectories and valve parameters (e.g. lift, duration, area) for a wide range of system inputs. An energy loss assessment of a valvetrain based on EHVAs is described, and the results are compared with those obtained with a traditional cam-based valvetrain. The validated model is then used to build detailed numerical maps of valve parameters that are fundamental for setting up cycle-by-cycle controllers of valve parameters. Hence, the authors present the design of a cycle-by-cycle controller of maximum valve lift, the performance of which is tuned by simulations and then verified experimentally.

Experimental Investigation on the Port Timing of a Compressed Air Engine with Exhaust Predicting Technique

The air engine is one of promising propulsion system in the era of crisis of fossil fuels and demand for efficient, low emission technology. Friction due to conventional cam mechanism created a scope of research to improve the performance of the engine. Camless engine replaces the convention cam by variable valve train mechanism. Variable valve train comprises the electronics solenoid operated direction control valve and have the capability to rising cylinder pressure quick. In the air engine, compressed air entered into the cylinder requires enough time for expansion and the amount of air remains to expand reflects a higher exhaust pressure. Along with this, how quickly released expanded air and their relationship with performance is critical aspects of analysis. In this research, work-study concentrated on intake advance angle (ISA) and exhaust advance angle (EAA) which directly reflects on the amount of air entered and time required for complete expansion. Experiments conducted with the electronics control unit (ECU), predicts exhaust pressure based on expansion takes place in the cylinder. Results evidence of improvement in the performance of the engine with ISA with the controller only. Consequently, the experimental study provides a base for the design and development of self-decisive pollution-free engine system for improved performance.

Electro-pneumatic variable valve actuation system for camless engine: Part II-fuel consumption improvement through un-throttled operation

Pumping loss during the gas exchange process becomes severe at low load operation in the conventional cam operated spark-ignition (SI) engine. In this study, the throttle body and conventional cam operated valve actuation mechanism of a single cylinder SI engine were removed. A novel in-house developed electro-pneumatic variable valve actuation system (VVA), as discussed in Part-I, was integrated and modified the conventional engine into camless engine. Air flow rates were varied using a throttle valve in the conventional engine. Whereas, for camess engine, air flow rates were varied by low intake valve lift and early intake valve closing (EIVC). It was found that the developed electro-pneumatic camless engine can inhale the same amount of air as compared to the conventional engine. The un-throttled operation in camless engine reduced the pumping loss at low engine speed and low load conditions, which helps in reducing the brake specific fuel consumption (BSFC) as compared to the conventional engine.

Electro-pneumatic variable valve actuation system for camless engine: Part I-development and characterization

The intake and exhaust valves lift, timing, and duration influence the performance, combustion, and emissions of an internal combustion engine. In this study, an electro-pneumatic variable valve actuation (VVA) system was developed for independent control of the valve motion. The Shadowgraph technique was used to characterize the valve motion, and a high-speed camera was used to capture the valve images. It was observed that by controlling the airflow rate into the pneumatic actuator, different valve lifts were achieved successfully. However, the valve velocity at the end of backward stroke was so high that valve hits the valve seat. Therefore, pneumatic damping was introduced towards the end of backward stroke and valve velocity was reduced when valve comes in contact with the valve seat. Multi-cycle analysis for valve lift and velocity profiles were performed to evaluate cycle-to-cycle variations of the developed actuation system. The results show that the system performs well for both part and full lift conditions with coefficient of variation below 1% and has an acceptable valve seating velocity control. The developed VVA system will be used in Part-II and the effect of un-throttled operation on fuel consumption improvement in a camless engine will be investigated.

AN OPTIMAL FEEDBACK LINEARIZATION APPROACH FOR SOFT LANDING OF ELECTROMECHANICAL VALVE ACTUATOR IN CAMLESS INTERNAL COMBUSTION ENGINES

The fuel efficiency, maximum torque and power, and pollutant emissions of internal combustion engines have improved rather than conventional crankshaft system. These improvements are the result of replacing the crankshaft with a camless actuation technology. Soft landing, tracking the desired trajectory, valve seating in a low velocity and having a small time for valve opening and closing are some of the main conflicting objectives in camless engines. Due to the nonlinear model of the system, feedback linearization control is presented for dealing with the system challenges in this paper. Moreover, to optimize the system response, the concept of feedback linearization control is incorporated into the linear quadratic tracker and makes the proposed structure named FLQT. The simulation results indicate the optimal feedback linearization controller has a good performance in the realization of desired goals of the system.

Modeling Analysis on Improving Cylinder Balance in A Gasoline Engine Using Electromagnetic Valve Train

For the multi-cylinder gasoline engine, the consistency among cylinders is an important index to affect the engine emission and the engine power. In this paper, an individual cylinder air-fuel ratio (A/F) control method for a fourcylinder camless engine with the electromagnetic valve train (EMVT) was proposed to reduce the imbalance of engine torque. An individual cylinder A/F estimation algorithm with a single universal exhaust gas oxygen (UEGO) sensor based on fading Kalman filtering was introduced. Four proportional-integral feedback controllers were built to regulate the individual A/F by adjusting the intake valve closing (IVC) timing of each cylinder independently based on the EMVT. The effectiveness of the proposed estimation and control approach was validated by co-simulation of GT-Power and Simulink. The results showed that the proposed estimation method could accurately estimate the individual cylinder A/F, and the maximum estimation error under steady state condition was less than 1 %. With the feedback control, both the individual A/F imbalance and the cylinderto- cylinder torque generation imbalance were decreased.

Overview Study of Camless Combustion Engines

The internal combustion engine (ICE) finds its place in the market with latest design modifications in various components to improve efficiency, economy and overall performance. However, one component has remained unchanged in the internal combustion engine development i.e., the camshaft, has been the primary means of controlling the valve actuation and timing, and therefore, influencing the overall performance of the vehicle. Camless technology is capturing the future of internal combustion engines. It has been known to man that if valves could be controlled independently in an Internal Combustion Engine then there would be benefits like increased power, reduced emissions and increased fuel economy. In the camless technology valve motion is operated by valve actuators of electro-mechanical and electro-hydraulic type. In this paper we compare camless valve operation with conventional valve operation and we deal with the valve actuating mechanisms of camless engine by considering the electromechanical and electrohydraulic actuators as the important types of actuating valves in camless engines.

An Overview Study of Camless Combustion Engines

The internal combustion engine (ICE) finds its place in the market with latest design modifications in various components to improve efficiency, economy and overall performance. However, one component has remained unchanged in the internal combustion engine development i.e., the camshaft, has been the primary means of controlling the valve actuation and timing, and therefore, influencing the overall performance of the vehicle. Camless technology is capturing the future of internal combustion engines. It has been known to man that if valves could be controlled independently in an Internal Combustion Engine then there would be benefits like increased power, reduced emissions and increased fuel economy. In the camless technology valve motion is operated by valve actuators of electro-mechanical and electro-hydraulic type. In this paper we compare camless valve operation with conventional valve operation and we deal with the valve actuating mechanisms of camless engine by considering the electromechanical and electrohydraulic actuators as the important types of actuating valves in camless engines.

Novel Design and Modeling of Shutter Valves for Camless Engines

For the intake of air fuel mixture and exhaust of gases camshaft operated valves are mounted on the cylinder head. In this paper, we have proposed a novel physical model of a shutter valve to replace the traditional camshaft operated valve resulting in a camless four–stroke engine. The lift control for the opening and closing of the intake and exhaust valves are monitored traditionally by a camshaft which is a mechanical component having a fixed shape. A camless engine replaces the camshaft by allowing the control of valves through the Electronic Control Unit (ECU). The already developed valves have limitations in terms of lift, life expectancy or higher costs. This research work proposes a novel shutter valve design instead of a poppet valve for intake and exhaust of four– stroke engines. These valves are then operated directly by an ECU and controlled through pulse width modulation. The proposed variation in shutter valve design optimally adjusts and controls the fuel intake amount and the flow of exhaust gases in and out of the cylinder respectively. The opening of the valve can be set to maximum or at the desired angle so that the engine can run according to the driver’s requirement. The novel design of the shutter valve will reduce the engine cost and will improve the fuel economy. At the same time, providing complete control to the driver’s performance preferences.

Stepping Valve Actuator Algorithm for a Camless IC Engine

Abstract Camless Engines offer many advantages over poppet valve systems. However, they suffer from air/hydraulic leakages and piston-valve interactions. In addressing the situation, the stepping valve rotates perpendicularly to the piston motion with no interactions. In this case, the valve events will be flexible enough to allow engine cranking without the mechanical starter. For this study, a 3-phase, 12-coil Stator rated at 3Amp 12V DC and a Stepping Valve were used. To avoid friction against its seat, the Stepping Valve is lifted up by 1mm in 2mS. Then it steps to a new Valve State Position in 2mS before gently landing back on its seat in 4mS. The Valve Event Algorithm has been designed, simulated and successfully programmed onto an Altera Programmable Device using Max Plus II Design Environment. The overall aim of this study is to have the three components required for ignition: fuel, spark and air, entirely controlled in software to maintain engine efficiency for the entire RPM range.

Development and Control of a Camless Engine Valvetrain

Abstract This paper presents an innovative application of an electromagnetic actuator for a future camless engine valvetrain. The actuators are designed for small gasoline engine. The design method is inversed to create a control-oriented model. The control architecture is designed for a robust control of the actuator. An experimental test bench is built for the correlation of the control model with experimental measures. Control strategies are developed and the performance indicators of the actuators are evaluated. The robust controller method uses CRONE system design methodology. The investigations show that the design of the innovative actuator and of its controller provide very good dynamic performances.

Absolute stability analysis of nonlinear active disturbance rejection control for electromagnetic valve actuator system via linear matrix inequality method

Nonlinear active disturbance rejection control is much more effective than linear active disturbance rejection control in tolerance to uncertainties and disturbances. However, it brings a great challenge for theoretical analysis, especially the stability analysis. This article proposes a linear matrix inequality method to analyze the absolute stability of generalized nonlinear active disturbance rejection control form which contains multiple nonlinearities with different parameters in both extended state observer and control law for single-input single-output systems. The generalized nonlinear active disturbance rejection control algorithm and the single-input single-output system are transformed into a direct multiple-input multiple-output Lurie system. A sufficient condition to determine its absolute stability based on linear matrix inequality method is given. The Lyapunov function of the Lurie system exists when the group of linear matrix inequalities is feasible. The free parameters and coefficients in Lyapunov function are given by the solution of these linear matrix inequalities. The electromagnetic valve actuator system in camless engine is presented as an application to illustrate how to perform the proposed method for absolute stability analysis and the stable region of parameter perturbations is obtained via the method. Simulation results show that the linear matrix inequality–based method is convenient and effective to determine whether the closed-loop system is absolutely stable.

Design and Performance Evaluation of an Electro-Hydraulic Camless Engine Valve Actuator for Future Vehicle Applications.

This paper details the new design and dynamic simulation of an electro-hydraulic camless engine valve actuator (EH-CEVA) and experimental verification with lift position sensors. In general, camless engine technologies have been known for improving fuel efficiency, enhancing power output, and reducing emissions of internal combustion engines. Electro-hydraulic valve actuators are used to eliminate the camshaft of an existing internal combustion engines and used to control the valve timing and valve duration independently. This paper presents novel electro-hydraulic actuator design, dynamic simulations, and analysis based on design specifications required to satisfy the operation performances. An EH-CEVA has initially been designed and modeled by means of a powerful hydraulic simulation software, AMESim, which is useful for the dynamic simulations and analysis of hydraulic systems. Fundamental functions and performances of the EH-CEVA have been validated through comparisons with experimental results obtained in a prototype test bench.

Design of a hybrid magnetomotive force electromechanical valve actuator

We propose a novel axis-symmetric modified hybrid permanent magnet (PM)/electromagnet (EM) magnetomotive force actuator for a variable valve timing camless engine. The design provides a large magnetic force with low energy consump-tion, low coil inductance, PM demagnetization isolation, and improved transient response. Simulation and experimental results confirm forces of about 200 N (in the presence of coil current) at the equilibrium position and 500 N (in the absence of coil current) at the armature seat. We compared our proposed design with a double solenoid valve actuator (DSVA). The finite element method (FEM) designs of the DSVA and our proposed valve actuator were validated by experiments performed on manufactured prototypes.

An Adaptive Resonance Regulator Design for Motion Control of Intake Valves in Camless Engine Systems

This paper deals with an adaptive control strategy based on the resonance concept to minimize the regulation energy of a new generation of actuators for intake valves of camless engines. The new actuator contains different parts, but basically it consists of a piezo part and a hydraulic one. Even though this work considers a particular application, the solutions proposed in the paper are quite general. The regulator consists of a cascade structure which combines feedforward actions with an external resonance controller strategy. These controllers guarantee that each single part of the actuator works at the frequency given by the velocity of the revolution of the engine. The parameters of the valve controller and of its feedforward action change adaptively in accordance with any change in the velocity of the revolution of the engine. Real measurements on an intake valve of a camless engine are shown.