Camshaft Profile Research Articles

Small-sample linear profile error uncertainty assessment based on grey system

The uncertainty assessment of the profile error of the cam profile, as defined in the national standard method, is difficult to carry out under conditions of small sample size and absence of probability distribution assumptions. This paper proposes a small-sample assessment model for the uncertainty of the profile error based on grey system. Firstly, the coordinate transformation is conducted using Vector Alignment Method to reduce systematic errors, and the non-uniform rational B-splines curve interpolation is utilized to fit the cam profile curve and perform error assessment. Subsequently, based on the error assessment results, Grey Information Measurement Model (GIMM) for the uncertainty of the profile error in small samples is established. This model employs Grey Relational Analysis to eliminate outliers and evaluates the uncertainty of the profile error by solving grey correlation coefficients. Maximum-Minimum Information Measure Method is used to assess the optimal sample size. Finally, numerical experiments and experimental tests were conducted on the uncertainty of camshaft profile error in automobiles. A total of 15 sets of profile data were compared with Guide to the Representation of Uncertainty in Measurement (GUM) and Monte Carlo Method (MCM) under different sample sizes. The results showed that GIMM achieved evaluation with only 8 sets of data samples under small sample and poor information conditions, with an uncertainty of 0.6338 μm, compared to 0.6346 μm for GUM and 0.6391 μm for MCM. The acceptance rate of GIMM reached 95.2%. This model outperforms other methods, providing a simplified and reliable assessment of cam profile error uncertainty.

Cam Profile Design of Low-Speed Marine Diesel Engine Based on the Grey Theory

The camshaft profile is one of the important parameters of the engine, the reasonableness or otherwise of its design directly influences the engine’s power output, fuel consumption, emissions, noise and reliability. However, most existing cam profile optimization designs are based on the basic software operation, profile parameter selection and tuning lack a scientific theoretical basis. In order to address this issue, this study establishes a single valve kinematic model of the gas delivery mechanism of diesel engines by using the AVL-EXCITE Timing Drive, and performs a model-based multinomial kinematic acceleration cam profile design. Subsequently, an orthogonal design method is employed to obtain the parameter combinations that can satisfy the dynamic requirements. The research investigates the influence of cam profile design parameters (C 4, p, q, r, and s) on valve fullness, maximum jerk, cam contact stress, and valve seating force through a systematic study. Lastly, based on the grey correlation theory, a thorough analysis of the performance indices of cams with different profile parameter combinations is conducted. The optimization problem of the profile parameters with multiple performance indicators is transformed into a single-objective grey relational optimization problem, resulting in the optimal cam profile parameter combination of C4 =0.1, p=14, q=20, r=28 and s=36. The optimal method proposed in the paper is straightforward to implement and is applicable to the optimum design of cam profiles of the engine, which is of great importance for the optimal design of cam fabrication processes.

Surface topography modeling and analysis of camshaft generated by swing grinding process

In conventional grinding (CG), camshafts with wide profiles suffer from poor quality and low efficiency because the large contact area between the grinding wheel and camshaft profile limits the diffusion of grinding temperature, leading to burning defects. Swing grinding (SG) can mitigate these problems as it involves a reciprocating motion along the axis of the grinding wheel; however, the lack of understanding of machined surface topography has restricted its application. Therefore, in this study, a surface topography prediction model was proposed that based on the distribution, shape, and trajectory of grains. The model was verified through experiments, and the mean error was 12% for Rax and 9% for Ray; the roughness along the grinding direction was Rax, and the roughness along the vertical grinding direction was Ray. Compared to CG, SG has a 3% lower Ray. The influence of the wheel speed and feed rate in SG is consistent with that in CG. Rax exhibited a periodic trend with an increase in the swing amplitude and a monotonically decreasing trend with an increase in the swing frequency. The variation trend of Ray with the swing amplitude was the same as that of Rax. Furthermore, Ray exhibited a nonlinear increasing trend with an increase in swing frequency.

Experimental study on the effects of the Miller cycle on the performance and emissions of a downsized turbocharged gasoline direct injection engine

The Miller cycle has been proven to be an effective way to improve the thermal efficiency for gasoline engines. However, it may show insufficient power performance at certain loads. In this study, the objective is to exploit the advantages of the Miller-cycle engines over the original Otto-cycle engines. Therefore, a new camshaft profile with early intake valve closure was devised, and two various pistons were redesigned to obtain higher compression ratio 11.2 and 12.1, based on the original engine with compression ratio 10. Then, a detailed comparative investigation of the effects of Miller cycle combined with higher compression ratio on the performance and emission of a turbocharged gasoline direct injection engine has been experimentally carried out based on the engine bench at full and partial loads, compared to the original engine. The results show that, at full load, for a turbocharged gasoline direct injection engine utilizing the Miller cycle, partial maximum power is compromised about 1.5% while fuel consumption shows a strong correlation with engine speed. At partial load, since the Miller effect can well reduce the pumping mean effective pressure, thus improves the fuel economy effectively. In addition, the suppression of the in-cylinder combustion temperature induced by the lower effective compression ratio contributes to the reduction of nitrogen oxide emission greatly. However, the total hydrocarbon emission increases slightly. Therefore, a combination of the Miller cycle and highly boosted turbocharger shows great potential in further improvement of fuel economy and anti-knock performance for downsized gasoline direct injection engines.

Edge states and frequency response in nonlinear forced-damped model of valve spring

This study explores the nonlinear dynamics of helical compression valve springs. To this end, the spring is mathematically modeled as a finite nonhomogenous one-dimensional mass–spring–damper discrete chain. Periodic displacement, which mimics the actual camshaft profile, is assumed at the upper end of the chain, while the other end is fixed. For the linear dynamics, the amplitudes of the periodic response are determined directly; they decrease toward the fixed end of the spring. Then, in order to meet more realistic conditions, the displacement of the upper mass is assumed to be nonnegative. This condition is realized by introducing an appropriate impact constraint. We assume that the impact is described by Newton impact law with restitution coefficient less than unity. For the case of one impact per period (1IPP) of excitation, exact periodic solutions are derived. The interplay between the nonhomogenous structure, multi-frequency excitation and nonlinearity leads to two qualitatively different states of the periodic responses; we refer to them as propagating states and edge states. The propagating states are characterized by weak localization, and the edge states—by strong localization at the forced edge. The stability of the system is analyzed using Floquet theory. Generic pitchfork and Neimark–Sacker bifurcations are observed. Analytical solutions conform to numerical simulations and experimental tests conducted on real valve springs.

Development of a new system for measuring the swirl ratio of an engine cylinder head under an unsteady flow condition

A new impulse-type swirl meter that measures the swirl ratio (Rs) and flow coefficient (Cfmean) during an intake air process for the intake port of an engine cylinder head under unsteady flow conditions was developed. The camshaft of the cylinder head was directly rotated by a step motor, allowing the valve lift to be adjusted automatically with the camshaft profile in the newly developed swirl measurement system. The measurements of the swirl ratio and flow coefficient were automated using a FPGA-DAQ board and a computer. The rotational speeds of the camshaft were held constant at steps of 90, 120, 150, 180 and 210 rpm during the measurement. As the camshaft rotation speed increased, the values of Rs tended to decrease while those of Cfmean tended to increase, implying that Rs and Cfmean depend on the engine speed. These results should be considered in the design of an intake port. With the newly developed swirl measurement system, it is possible to measure Rs and Cfmean repeatedly in a very short time. The repetitive measurement results of Rs and Cfmean were statistically processed. Through an uncertainty analysis, the values of the upper and lower bounds of Rs and Cfmean can be calculated for each camshaft rotation speed.

Effect of injection timing on performance and emissions characteristics of a single cylinder diesel engine fuelled with waste plastic oil

This research was aimed to study the effect of injection timing on performance and emissions characteristics of a single cylinder diesel engine using waste plastic oil as an alternative fuel. The injection timing was set up to 15°, 20° (factory default) and 25° CA bTDC position by directly adjusting the camshaft profile angle. The engine was loaded at 50%, 75% and 100% of full load with constant engine speeds of 3,600 rpm. The experimental results showed that retarding the fuel injection led to the improvement of brake specific fuel consumption and NOx emissions when the engine was operated with waste plastic oil at all engine operating loads tested. The slightly reduction in the maximum brake power was obtained by the use of waste plastic oil with respect to diesel fuel. To meet benefits of using waste plastic oil as a feasible alternative for next generation fuels in compression ignition engines, the retard of fuel injection was recommended to adjust the injection timing of the engine operated with waste plastic oil.

Methodology to parametric design of cam profile for electronic unit pump

As to the fuel injection system of electronic unit pump, of which fuel supply principles mainly be influenced by fuel supply camshaft. Due to the requirements of the diesel engine for the fuel supply system, a new method is presented to design the constant pressure injection fuel supply cam profile. First, design principles of the fuel supply camshaft profile according to the diesel engine combustion requirement are proposed and then the parametric equation for the camshaft profile can be obtained by the proposed principles which are analyzed through math method. At last, after the prediction and comparison of the designed camshaft profile, the conclusion shows that the fuel injection system designed by the proposed principle can satisfy the injection requirements of the diesel engine. Meanwhile, the parametric equations simplify the design process of camshaft profile so as to improve the reliability and the injection performance of the fuel supply system.

Different camshaft profile analyses for natural gas engine performance and emission

Recently, the environmental crisis and the negative influence of gasoline and diesel fuels on it, together with these fuels high cost persuaded manufacturing companies to use natural gas as substitute fuel. Considering the same volumetric efficiency and fuel penetration, natural gas needs more space because of its much lower density in comparison to liquid fuels. In this regard, the Miller cycle as the fifth-thermodynamic cycle in internal combustion engines is discussed. Increasing the expansion ratio along with the compression by changing in the intake valve closure is the main characteristic of this cycle. In this study, AVL FIRE software is used to simulate D87 gas engine. Since the close cycle cannot examine valve lifting effectively as well as turbo charging, one-dimensional simulation by GT Power software is used. After their parallelism with each other, four camshaft timing was used as well as Otto cycle. Results show that there is a reduction in the maximum pressure and temperature with slight increment in power. Also due to decrease in peak temperature, NOx diminishes obviously.

The dry wear profile of cam shaft

In this study, the variation of the wear mechanism and the worn surface profile of the cam shaft were investigated under the dry wear conditions. The samples which were made of AISI 1040 were hardened by induction. The counter body material was AISI 1020 borided steel. The wear was determined as weight losses of the samples as a function of wear test duration and loads. The variation of camshaft profile was captured by a level sensor during the wear. The profile variation was continuously monitored on the computer screen throughout the tests. It was found that the wear mechanisms of the cam surface change along the contact surface. The maximum wear value was obtained just to cam tip.

Kinematics and Lubrication of Camshaft Roller Follower Mechanisms

This study provides a theoretical treatment of the lubrication of a camshaft in rolling contact with an oscillating roller follower. The rocker arm motion was specified as a function of the camshaft angle of rotation. The method of kinematic coefficients was used to determine the camshaft profile and the radius of curvature of the camshaft at the contact interface. The vector loop approach was used to calculate the lubricant entraining velocity. A numerical model for the dynamic elastohydrodynamic lubrication of rolling line contact was developed. This model uses as input the kinematics of the camshaft and roller follower mechanism. The one-dimensional Reynolds and elasticity equations were simultaneously solved using the multigrid multilevel technique to obtain the pressure and film thickness distributions within the lubricant film as a function of time. The time-dependent pressure and film thickness distributions for different loadings and camshaft angular velocities are presented. Presented at the 49th...