Wobble Plate Research Articles

The Potential of Wobble Plate Opposed Piston Axial Engines for Increased Efficiency

Recent announcements regarding the phase out of internal combustion engines indicate the need to make major changes in the automotive industry. Bearing in mind this innovation trend, the article proposes a new approach to the engine design. The aim of this paper is to shed a new light on the forgotten concept of axial engines with wobble plate mechanism. One of their most important advantages is the ease of use of the opposed piston layout, which has recently received much attention. Based on several years of research, the features determining the increase in mechanical efficiency, lower heat losses and the best scavenging efficiency were indicated. Thanks to the applied Variable Compression Ratio (VCR), Variable Angle Shift (VAS) and Variable Port Area (VPA) systems, the engine can operate on various fuels in each of the Spark Ignition (SI), Compression Ignition (CI) and Homogeneous Charge Compression Ignition (HCCI)/Controlled Auto Ignition (CAI) modes. In order to quantify the potential of the proposed design, an initial research of the newest PAMAR 4 engine was presented to calculate the torque curve at low rotational speeds. The achieved torque of 500 Nm at 500 rpm is 65% greater than the maximum torque of the OM 651 engine of the same 1.8 L capacity. The findings lead to the conclusion that axial engines are wrongfully overlooked and can significantly improve research on new trends in pollutant elimination.

Investigating fatigue failure of core motion mechanism for a small oil-free wobble-plate compressor

Abstract The study is driven by a recent experimental test for a small-size high-speed oil-free wobble-plate compressor, in which abrupt local fatigue failure of the wobble plate is encountered. To explore the causes, a fatigue prediction method is proposed, which involves the dynamic force calculation, stress prediction, and fatigue analysis. The dynamic forces is obtained by solving the coupled dynamic, thermodynamic and kinematic models. The dynamic stress with thermal effect is predicted, where the temperature field is calculated by solving the thermal conduction equation with the experimentally measured solid-surface temperature acting as boundary conditions, and the obtained temperature distribution is incorporated into the FEM (finite element method) prediction for thermal-dynamic stress. It is found that intensive friction heating causes the wobble plate significant local temperature rise and it is largely responsible for the structural failure. The Goodman mean stress correction method and wobble plate material S–N (Stress amplitude versus cycle Number) curves are incorporated to predict the fatigue life of wobble plate. The predicted fatigue life is comparable to the experimentally measured, which has verified the developed method. The wobble plates of 7075-T6 aluminum alloy and H62 brass alloy are compared, and the former produces a smaller dynamic stress for its smaller elasticity modulus and larger specific heat but a shorter fatigue life due to its S–N curve smaller stress amplitude.

A Novel Energy-Efficient Wobble Plate Hydraulic Joint for Mobile Robotic Manipulators

At present, mobile robotic manipulators have been greatly developed. However, these further promotions are limited by a low load capacity and short operation time. The above problems can be improved by using a hydraulic drive mode and increasing the system energy efficiency. In this paper, a novel energy-efficient wobble plate hydraulic joint is presented, which has the characteristics of having a small size, lightweight, large load capacity, and high energy efficiency. Based on the efficiency analysis in traditional robotic manipulators, this paper presents a novel hydraulic joint with a multi-chamber drive structure. Kinematics model and dynamics model are both established for the analysis of the mechanical characteristics, and the functional relationship between the input and output is depicted by numerical simulation. Based on the structural characteristics and control principle, the load matching controller is designed and specific control processes are formulated. Combined with a strategy of load matching, the servo control system is established and the energy-saving effect is verified by simulation. The result shows that the wobble plate hydraulic joint can change connections between a high-pressure circuit and different working chambers, which realizes the match between the output torque and load torque. With the load matching controller, the energy consumption of the wobble plate joint is greatly reduced, which contributes to a considerably improved energy efficiency. The research in this paper not only lays a theoretical foundation for the development of a wobble plate hydraulic joint, but also provides guidance for the improvement of the hydraulic system energy efficiency in mobile robotic manipulators.

Analysis of Kinematic Features in Non-conventional Piston Device with Wobble Board

In the case of constructing combustion engines, it is possible to use not only classical crank mechanisms, but also non-conventional mechanisms. Article deals with description of non-conventional piston mechanism with ring, which may be suitable for special applications in the engineering industry. Investigation of kinematic parameters of the machines is important step to know its basic movement behaviour, and from this, it is then possible to create the alternate dynamic model or force analysis. The aim of this analysis is to investigate the movement of several points on a wobble plate. The next section will deal with the analysis of waveforms of the piston stroke depending on connection with a specified point on wobble board.

Design and Performance Analysis of a new Rotary Hydraulic Joint

To improve the driving torque of the robots joint, a wobble plate hydraulic joint is proposed, and the structure and working principle are described. Then mathematical models of kinematics and dynamics was established. On the basis of this, dynamic simulation and characteristic analysis are carried out. Results show that the motion curve of the joint is continuous and the impact is small. Moreover the output torque of the joint characterized by simple structure and easy processing is large and can be rotated continuously.

Analysis of forces in an automobile ECV using in external variable displacement swash plate type compressor for air conditioning control system

To meet the demand of improved comfort for passengers, drive ability and standard in fuel economy; external variable displacement swash (wobble) plate type compressors are used in automobile air conditioning control system because of their low energy consumption and highly efficient characteristics. It controls the compressor displacement by increasing or reducing the swash plate angle. Solenoid operated electromagnetic control valve (ECV) in the compressor controls the air conditioning system by means of a pulse width modulation (PWM) input signal supplied from an external source (controller). The mechanism changes the swash plate angle by increasing or reducing the pressure of swash plate chamber using the ECV functions. The force (solenoid) for ECV operation is important as the force directly related to the movement of the internal feature i.e. mainly plunger of the ECV which is responsible for the amount of air/refrigerant flow that results the air conditioning control procedures with various pressure ports. The research paper highlights the improved theory and equation for calculating the working force (solenoid force) in ECV and experimental analysis of 3 (three) ECV samples followed by the comparison of theoretical and experimental force results.

유량 제어 밸브 방식이 DME 고압 연료 펌프의 성능에 미치는 영향

This experimental work described the effect of flow control valve type on the performance of wobble plate type fuel pump for the stable DME fuel supply. In order to study this, different four types of flow control valves (ITV, SCV, IMV and MPROP) were installed on the wobble plate fuel pump, and fuel flow rate, torque, and temperature variation of pump were investigated under various operating conditions by using pump performance test system. It was revealed that wobble plate type fuel pump worked well with ITV and SCV control valve, and the flow rate and torque of fuel pump was in proportion to the value of valve open duty. The maximum flow rate and torque of fuel pump were achieved around the 50% duty of control valve. Temperature variation at all pump measuring points were under <TEX>$60^{\circ}C$</TEX> which is acceptable.

Analysis of Crankcase Flow of an Automobile ECV for Air Conditioning Control System

Electromagnetic control valve (ECV) controls an automobile vehicle air conditioning compressor based on a pulse width modulation (PWM) input signal that supplied from an external controller. For maintaining a suitable range of temperatures inside the vehicle, suction and crankcase port pressure controls the swash (wobble) plate at certain angle. Suction and crankcase port pressure controlled in ECV can be analyzed by experimental test by considering different technical assumptions. This research paper highlights the flow of air from crankcase port with correspondence with amount of variable supply of current to obtain the experimental test data which is important to maintain the vehicle temperature inside the compartment for passengers comfort.

Vibration Analysis and Optimization of Wobble Plate Engine

The rigid-flexible system dynamic model of wobble plate engine was created by BUSH element and so on in ADAMS software. And stiffness optimized calculation of engine rubber isolator ring and spring was done by ADAMS optimized module. By comparing the time domain and frequency domain vibration response before optimization and after optimization, the feasibility of optimized method for decreasing engine vibration and changing system response frequency range was verified. This method could provide important reference for vibration dynamic model creating of engine or analogous mechanical system. Its conclusions also could provide reference for decreasing vibration study.

Simulation Calculation Method Study on Machinery Output Torque

By analyzing the output procedure and theoretical calculation method of power machinery output torque, a kind of advisable simulation method to power machinery output torque was put forward. For example, the wobble plate engine dynamic simulation model was created by this method. And simulation calculation was done based on dynamic model. Result Comparison between simulation calculation and theoretical calculation shows that this method has high calculation precision and maneuverability. At last, some reference suggestions were put forward for application.

EC1-2: Mechanical Efficiency and Losses of Internal Combustion Engines with Cylinder Axes Parallel to Drive Shaft Axis(EC: Engines and Engine Components,General Session Papers)

Barrel engines are characterized by unconventional construction feature: cylinder axes are parallel to drive shaft axis. The rotation of the central power shaft is created from the reciprocating motion of the pistons with the use of different types of mechanisms, including wobble plate, swash plate or cam disc. Due to complex internal motion their kinematics and dynamics is completely different than that of crankshaft engine. Barrel engines are expected to have a potential to compete with currently used power units, especially in aircraft applications. The paper reviews and compares all classified types of barrel engines with conventional crankshaft engine in terms of kinematics: mechanical losses and mechanicals efficiency. Advanced computations were made for each mechanism to derive formulas describing three-dimensional movements of barrel engines' parts. Comparison of mechanisms parameters was made with the use of MatLab software. Computations methodology for mathematical description of all mechanisms' kinematics is presented as well as the results of mechanical losses and efficiency comparison. Wobble plate mechanism blocked by gear has been identified as the most promising for further analysis and research.

Testing and modelling of an automotive wobble plate compressor

Wobble plate compressors are well used in air conditioning for high-class automobiles. They allow continuous control by automatic adjustment of the piston stroke, to keep the low pressure above a certain limit. Here an externally controlled wobble plate compressor is analyzed experimentally through its isentropic and volumetric effectivenesses and control characteristics. Compressor effectivenesses depend mainly on the compressor speed and pressure ratio: there is obtained, for example, isentropic and volumetric effectivenesses of 0.65 and 0.8 for a pressure ratio of 4 at 1000 rpm and 0.4 and 0.35 for the same pressure ratio at 4000 rpm. This degradation is attributed to the increasing of the supply pressure drop. The “lubricant” (oil + dissolved refrigerant) mass flow rate is obtained by minimization of the residuals of the thermal balances on the compressor, condenser and evaporator. Here an important oil-flow circulation is obtained: between 9.5% and 12.5% of the refrigerant flow rate. A special displacement sensor is used to measure instantaneous piston stroke and to relate it to overall compressor performance. This measurement is then compared with the results obtained with a semi-empirical model, which is able to predict, in part load, the compressor displacement. The model predicts the displacement ratio with deviations that vary between −14.5% and +8.1%.

A mathematical model of variable displacement swash plate compressor for automotive air conditioning system

A mathematical model of control mechanism used in the variable displacement swash plate compressor (VDSC) is developed firstly based on the force balance equation, mass and energy conservation equation. The model of moving components dynamics is developed then by analyzing the forces and force moments acting on the pistons and the swash plate. The compression process model is obtained by fitting the data from our experiments. And finally, the steady-state mathematical model of VDSC is developed by combining the three sub-models above. In order to verify the mathematical model, a test bench for control mechanism and the test system for VDSC have been established, and the simulated results agree well with the experimental data. The simulation results show that, like the variable displacement wobble plate compressor, there are four operation modes for the VDSC, i.e. constant rotary speed and constant piston stroke length (PSL), variable rotary speed and constant PSL, constant rotary speed and variable PSL, variable rotary speed and variable PSL, which have included almost all operation modes of the refrigeration compressor in common use. And there is a hysteresis zone and multiple-valued relationship between the compressor parameters when PSL changes.

Instability of automotive air conditioning system with a variable displacement compressor. Part 1. Experimental investigation

A test system is built first in order to investigate the instability of the automotive air conditioning (AAC) system with a variable displacement compressor (VDC), and hunting phenomena caused by the large external disturbance in the AAC system with a VDC and a thermal expansion valve, and in the AAC system with a VDC and a fixed-area throttling device are investigated experimentally in part 1 of this paper. The experimental results indicate that there also exist the hunting phenomena in the AAC system with a fixed-area throttling device. The system stability is found to be dependent on the direction of the external disturbance, and the system is apt to cause hunting when the condensing pressure decreases excessively since it may cause two-phase state at the throttling device inlet and make a large disturbance to the system. The piston stroke length will oscillate only when the oscillation amplitudes of forces acting on the wobble plate are great enough, otherwise the piston stroke length will be kept invariable, and then the system instability rule is also suitable for the AAC system with a fixed displacement compressor. From the experimental results, it is concluded that the two-phase flow at the throttling device inlet or at the evaporator outlet is the necessary condition but not sufficient condition for system hunting. Finally, a new concept, conservative stable region, is proposed based on the experimental results and theoretical analysis.

Numerical Analysis on the Performance of Control Valve in Variable Displacement Wobble Plate Compressor

The performance of control valve is analyzed in this paper in order to study characteristics of the variable displacement wobble plate compressor. The forces acting on the control valve are analyzed and the mathematical model to analyze its performance is developed. A test bench is set up to get the steady and dynamic performance of control valve. The steady-state performances predicted by the mathematical model agree well with the experimental data while the predicted dynamic performances agree with the experimental results qualitatively. With the mathematical model, the steady-state performances of the control valve with four different preset control points and three different effective areas of the evacuated bellows have been analyzed, and the dynamic behavior of one type control valve has been studied. It is shown that: (1) the suction pressure at preset control point is inversely proportional to the discharge pressure; (2) the larger the starting force of spring in control valve or the smaller the effective area of evacuated bellows, the larger the suction pressure at preset control point; and the larger the starting force of spring in control valve and the smaller the maximum opening of ball valve, the more quickly the crankcase pressure changes and the smaller mass flow rate of control valve; the slope ratio of crankcase pressure to suction pressure cannot be influenced by the starting force of spring in control valve but can be influenced by the effective area of evacuated bellows; (3) the transition time of the crankcase pressure is about 1 s and can be neglected when working condition changes.

Transient behavior evaluation of an automotive air conditioning system with a variable displacement compressor

In order to simulate the transient behavior of the automotive air conditioning (AAC) system with a variable displacement wobble plate compressor (VDC), a dynamic model which is consisted of a VDC, a finned tube evaporator, a parallel flow type condenser, a cross and absorptive charge H type thermal expansion valve, and a suction pipe is developed. Both the simulation results of control valve and experimental data of VDC indicate that transient process inside VDC can be ignored and the steady state model of VDC can be used in the dynamic simulation of AAC system. The method to calculate the variation of piston stroke length is proposed in the numerical solution procedure for dynamic simulation of AAC system. A test system is built with original components from an actual AAC system and the dynamic simulation results are compared with the experimental data. It is shown that the predicted results with the dynamic model agree well with the experimental data. Further simulation results show that: (1) whether the piston stroke length changes or not is determined by not only the changing values but also the changing direction of external parameters in the AAC system; (2) the variation of piston stroke length usually has a time lag when the external parameter varies; (3) there is a greater counter-regulation for the refrigerating capacity and compressor power consumption when the compressor rotary speed changes suddenly due to the adjustment of piston stroke length, which is different from the AAC system with a fixed displacement compressor.

Experimental investigation on the steady-state performance and piston stroke length control of a variable displacement wobble plate compressor

The aim of this paper is to find out the steady-state performance and piston-stroke-length control behaviour of a variable displacement wobble-plate compressor for an automotive air-conditioning system by experimental investigation. First, a new method and device to measure the piston stroke length of the variable displacement compressor has been developed, with which the test bench for the variable displacement compressor has been set up. Second, the steady-state performance of the variable displacement compressor, such as the relative volumetric efficiency and the relative isentropic efficiency at partial piston stroke length, has been obtained. The influence of the work condition and compressor rotary speed on the relative volumetric efficiency can be neglected according to the test data. Finally, the critical wobble-plate case pressure is proposed in this paper to judge whether the piston stroke length will change or not. The critical wobble-plate case pressure when the piston stroke length decreases is greater than that when the piston stroke length increases, which is less influenced by the piston stroke length itself from the test data. The higher the compressor discharge pressure or rotary speed, the greater the critical wobble-plate case pressure. The piston stroke length can be adjusted automatically along with the air-conditioning load when the compressor rotary speed or air conditioning load changes.

A mathematical model of variable displacement wobble plate compressor for automotive air conditioning system

Based on the force balance equations, mass and energy conservation equations, a mathematical model of control valve used in the variable displacement wobble plate compressor (VDC) is developed firstly. The dynamic model of the moving components is developed then by analyzing the forces and force moments acting on the piston, piston rod, wobble plate, rotating journal and shaft sleeve. The compression process model is obtained by fitting the data from our experiments. And finally the steady-state mathematical model of VDC is developed by combining the three models above. In order to verify the mathematical model of compressor, a test bench for the control valve and the test system for the VDC have been established, and the simulated results agree well with the experimental data. The simulation results show that there are four operation modes for the VDC, i.e. constant rotary speed and constant piston stroke length (PSL), variable rotary speed and constant PSL, constant rotary speed and variable PSL, variable rotary speed and variable PSL, which have included almost all operation modes of the refrigeration compressor in common use.

Displacement control and kinetic analysis of a novel variable displacement compressor for automotive air conditioner

A novel variable displacement compressor (VDC) for automotive air conditioner (AAC) is introduced, which inherits the advantages of common wobble plate type VDC. It has fewer parts and makes less noise, and inst ead of pneumatic valve the displacement is controlled by electronic control valv e. In order to know the control mechanism well and get a good control effect, a mathematical model for the variable displacement mechanism is developed accordin g to the geometrical and kinematical information of the compressor. Using the mo del, the effect of relevant parameters on variable displace control is estimated . It is helpful to make the optimum decision in the flow control of AAC. As the novel displacement control device, the structure and control rule of electronic control valve is introduced. It can get better effect than the conventional pneu matic valves. And by using this new electronic control device, the optimum syste mic control of AAC is available.

A study on capacity control of a vane type rotary compressor for automotive air conditioners.

Since a compressor used for an automotive air conditioner is driven by an engine, refrigerating capacity will change according to the speed of the engine. While wobble plate compressors achieve continuous capacity control by changing the slope of the wobble plate, rotary compressors can perform only a few stage capacity control by opening or closing bypass ports. We developed a rotary compressor with a continuous capacity control mechanism which is activated by rotating a bypass port in a front plate, and evaluated its performance. The experimental compressor showed a high coefficient of performance under operating conditions which simulated practical conditions of automotive air conditioners, though its performance slightly decreased due to the re-expansion loss with the increase of the rotating angle of the bypass port.