One-dimensional Analysis Method Research Articles

Theoretical analysis of the piston ring-pack for predicting friction and power loss in an internal combustion engine

The piston ring is considered an essential element in the operation of the internal combustion engine to improve its efficiency and reduce its emissions. It is resistant to high temperature and high-pressure gases in the combustion chamber. A one-dimensional analysis method of lubrication between piston rings and cylinder liner in mixed lubrication conditions is developed in this article by using the GT-Suite simulation software. We applied the finite difference numerical method to solve the Reynolds equation to obtain the variation during an engine cycle of the following parameters; film thickness, frictional force, and power loss. The solution results presented can be used to improve the design of the piston ring pack in internal combustion engines and is available for industry usage.

One-dimensional analysis method of pulsatile blood flow in arterial network for REBOA operations

Based on the generalized Darcy model, here we develop a linear one-dimensional (1D) composite model to predict the effects of the inserted balloon under REBOA operations on the dynamic characteristics of blood flow in flexible arterial networks. We first consider the effect of the decrease of cardiac output under different degrees of blood loss through employing the fourth-order lumped parameter model of cardiovascular system. Then, the effect of the inserted balloon is included by developing the relation between flow resistance and occlusion ratio with the neural network approach. Finally, the accuracy of the developed 1D composite model for REBOA operations, which can be solved analytically in the frequency domain, is verified by comparing to computational fluid dynamics (CFD) simulations. It is demonstrated that the 1D model is able to reproduce main features of the systemic circulation under balloon occlusion of the aorta during REBOA surgery. The 1D composite model could substantially reduce the computational time, which makes it possible to give the instant prediction of the working parameters during RABOA operations.

Low frequency sound insulation of membrane-type acoustic metamaterials with negative pressure cavity

The membrane-type acoustic metamaterial with negative pressure cavity (MAM-NPC) is designed to achieve low frequency sound insulation and tunable frequency on the duct side wall. A one-dimensional analytical method was used to discuss the sound insulation effect of MAM-NPC on the sidewall of the duct. As the negative pressure increases, the first valley of sound insulation moves to high frequency. High sound insulation can be achieved in the low frequency range. The theoretical and finite element method results are compared. The one-dimensional analysis method basically agrees with the finite element results in the low frequency band. Because only plane waves are considered in the one-dimensional analytical method.

An Experimental Investigation of Supersonic Combustion of Mildly Cracked N-Dodecane

ABSTRACT In this paper, a novel two-stage hydrocarbon fuel heating and delivery system was used to more accurately simulate the state of fuel in the cooling channel of the regenerative cooling engine. Mildly cracked (<10%) experiments of n-dodecane were conducted by using the new heating system and pyrolysis products were sampled and analyzed. The ignition delay time and laminar flame speed of the cracked products were different from those of the surrogate gas fuel. When the temperature is 1100 K, the ignition delay time of the cracked products are ~50% higher than that of surrogate gas fuel. The laminar flame speed of the cracked products is about 30% lower than that of surrogate gas fuel at the equivalence ratio of 1.0. The supersonic combustion experiments of mildly cracked and different equivalence ratios n-dodecane were also employed at Mach number 3.0 of the isolator entrance, with total temperature ~1550 K and total pressure ~1.5 MPa. The static pressure along the axis of combustor was measured, while the velocity and temperature of the airflow at the exit of combustor were also measured by the tunable diode laser absorption spectroscopy (TDLAS). The distributions of airflow velocity, static temperature, and total temperature along the combustor at different conditions were analyzed through a one-dimensional analysis method. The deviations of velocity and temperature of the airflow are less than 4% and −6%, respectively, which indicates the calculation is in great accordance with the TDLAS detections. The experimental data will be helpful for validating the simulation of supersonic combustion, and studying the influence of mildly cracked fuel on supersonic combustion characteristics.

A new method for calculating failure probability of landslide based on ANN and a convex set model

Calculating the failure probability of a landslide is important in engineering related to geological process and geomorphological evolution. Strength parameters of a soil (i.e., cohesion and internal friction angle) are regarded as uncertain-but-bounded parameters. In this study, a new method is proposed for computing the landslide failure probability based on a convex set model and artificial neural network (ANN). In the new method, ANN is used to determine the limit state function of landslide stability, and the failure probability is determined using a simple iterative algorithm. The new method was applied to calculate the failure probability of the Gufenping landslide in Nanjiang, Sichuan, China. The results calculated using a Monte Carlo simulation (MCS) method confirmed that the new method accurately and quickly obtains the failure probability of a landslide. Additionally, compared with the two-dimensional calculation method, the one-dimensional analysis method overestimates the failure probability of the landslide. The results of single factor and global sensitivity analysis indicate that the average of internal friction angle is the main factor affecting the stability of the landslide. It is easy to calculate failure probability of landslides using the novel method than using the conventional methods.

Experimental Study on Mode Transition in a Dual-Mode Scramjet Combustor

ABSTRACTAn experiment of mode transition within a supersonic combustor with a variable fuel flow rate was carried out under the total temperature of 1085 K, total pressure of 1.05 MPa and Mach number of 1.95 of the conditions of the exit of the inlet. According to the wall pressure of the combustor measured by the experiment, the distribution of other airflow parameters in the combustor was calculated by a one-dimensional analysis method. The process of the mode transition in the same test with a variable fuel flow rate was studied and the relationship between the combustion mode transition and fuel equivalence ratio was analyzed. The results show that there were a pure scramjet mode, a dual-mode scramjet mode, a dual-mode ramjet mode and a combustion state that the pressure disturbance had arrived at the entrance of the isolator with the change of the fuel equivalence ratio. During the experiment, the ratio of the peak pressure of the combustor to the total pressure of the inlet of the isolator is 0.28, 0.4, and 0.5, respectively. In addition, the study also found that the equivalence ratios converting from pure scramjet mode to the ramjet mode were a little higher than those of the opposite process.

Computational modelling of an Organic Rankine Cycle (ORC) waste heat recovery system for an aircraft engine

Escalating fuel prices and carbon dioxide emission are causing new interest in methods to increase the thrust force of an aircraft engine with limitation of fuel consumption. One viable means is the conversion of exhaust engine waste heat to a more useful form of energy or to be used in the aircraft environmental system. A one-dimensional analysis method has been proposed for the organic Rankine cycle (ORC) waste heat recovery system for turbofan engine in this paper. The paper contains two main parts: validation of the numerical model and a performance prediction of turbofan engine integrated to an ORC system. The cycle is compared with industrial waste heat recovery system from Hangzhou Chinen Steam Turbine Power CO., Ltd. The results show that thrust specific fuel consumption (TSFC) of the turbofan engine reach lowest value at 0.91 lbm/lbf.h for 7000 lbf of thrust force. When the system installation weight is applied, the system results in a 2.0% reduction in fuel burn. Hence implementation of ORC system for waste heat recovery to an aircraft engine can bring a great potential to the aviation industry.

One-Dimensional Analysis Method for Cavitation Instabilities of a Rotating Machinery

Rotating cavitation is an important problem, which makes it difficult to design reliable rotating machines. In this study, a simple analysis method that tried to evaluate the cavitation instabilities of a rotating machinery by using one-dimensional (1D) system analysis software was attempted. In this method, cavitation compliance and mass flow gain factor are distributed in each flow path of the inducer. Analysis results show that cavitation instabilities, including rotating phenomena, exist. With the evolved analysis model, effects of various parameters on the eigenvalues of the system were investigated. Analysis results agreed with inducer test results qualitatively. Furthermore, by the analysis considered whirl motion of the rotor, effects of it on cavitation instabilities were investigated.

Multi-stage turbocharger system analysis method for high altitude UAV engine

A multi-stage turbocharger system analysis method has been presented for a hydrogen fueled internal combustion engine targeted for High altitude long endurance UAV (HALE UAV), of which cruising altitude is 60000 ft. To utilize an internal combustion engine as a propulsion system of a HALE UAV, proper inlet pressure boost system such as a series of turbochargers should be ready, which makes engine performance less sensitive to flight altitude. In this study, to boost rarefied intake air pressure up to 1.7 bar to avoid early ignition of hydrogen and to produce required power from engine, we used a boost system which consists of three-staged turbocharger accompanied by intercooler to reduce compressed air temperature. To analyze multi-stage turbocharger performance at the cruising altitude, we established an explicit one-dimensional analysis method by matching required power between compressors and turbines. Then adequate turbochargers were searched for from commercially available models based on performance analysis results. One-dimensional analysis was also applied from sea level to the cruising altitude to decide turbocharger operating lines were located within each turbocharger operating ranges.

Mode transition of fuel control test in a dual-mode combustor

Ignition combustion test in dual-mode combustor with fuel flow rate change was carried out in a direct-connected wind tunnel facility that supplied airflow with total temperature of 880K, total pressure of 8atm and Mach number of 2.0. According to the wall pressure of combustor measured through the test, the distribution of other airflow parameters in the combustor was obtained by calculating with a one-dimensional analysis method, and the mode transition process in the condition of fuel flow rate change was studied. In addition, the position that the airflow in the isolator accessed to the subsonic velocity and the location of “choked thermal throat” at the combustor downstream were determined by analyzing of pressure distribution in the combustor. The results indicated that sole hydrogen combustion brought a supersonic combustion mode, then combined combustion of hydrogen and kerosene induced a subsonic combustion mode and combustion-induced pressure disturbance had been spread to the entrance to the combustor. In cases of sole kerosene combustion and the fuel equivalence ratio being kept at 0.53 and 0.61 respectively, both were in the subsonic combustion mode. Gradual increment of the fuel equivalence ratio was accompanied by enlarging subsonic combustion area. In case of combined combustion of hydrogen and kerosene, and improving kerosene flow rate, supersonic combustion mode was transformed to a subsonic one in a gradual manner.

One-dimensional analysis for optimizing smoke venting in tunnels by combining roof vents and longitudinal ventilation

A hybrid mode that combines both longitudinal ventilation and natural roof venting is proposed for thermal and smoke control in tunnel fires. This hybrid strategy creates safe environments at the upstream side of the fire and shortens the smoke spreading distance at the downstream side, if the longitudinal ventilation and roof smoke venting are well cooperated. It is advantageous to the urban traffic tunnels that are adjacent to other underground facilities. The pressure rise of the longitudinal ventilation system and the geometrical parameters of the roof vents are the two key factors affecting the effectiveness of the proposed hybrid mode. The heat and smoke convection patterns under this hybrid mode are investigated with both a one-dimensional hydraulic analysis method and numerical simulations. The simulation results demonstrate that the smoke can be exhausted by the roof vents downstream of the fire, and thus, the gas temperatures downstream of the vents can be significantly decreased. The maximum deviation between the theoretical smoke exhaust rate and simulation result is approximately 17%, indicating the analytical model and numerical simulation results are in good agreement. The one-dimensional analysis method and the equations associated with it can be directly used to optimize the design parameters.

Parametric design and off-design analysis of organic Rankine cycle (ORC) system

A one-dimensional analysis method has been proposed for the organic Rankine cycle (ORC) system in this paper. The method contains two main parts: a one-dimensional aerodynamic analysis model of the radial-inflow turbine and a performance prediction model of the heat exchanger. Based on the present method, an ORC system for the industrial waste heat recovery is designed and analyzed. The net power output of the ORC system is 534kW, and the thermal efficiency reaches 13.5%. System performance under off-design conditions is simulated and considered. The results show that the inlet temperatures of the heat source and the cooling water have a significant influence on the system. With the increment of the heat source inlet temperature, the mass flow rate of the working fluid, the net power output and the heat utilization ratio of the ORC system increase. While, the system thermal efficiency decreases with increasing cooling water inlet temperature. In order to maintain the condensation pressure at a moderate value, the heat source inlet temperature considered in this analysis should be kept within the range of 443.15–468.15K, while the optimal temperature range of the cooling water is between 283.15K and 303.15K.

Quantification of numerically induced mixing and dissipation in discretisations of shallow water equations

The concepts of numerical mixing and numerical dissipation are developed here for one-dimensional advection-diffusion equations for velocity and a scalar tracer where depth changes due to transport divergence are considered. It is shown for the explicit first-order upwind (FOU) scheme that the numerical mixing of the scalar tracer due to the discretisation of the tracer advection (i.e., the decay of the tracer variance) can be calculated by the difference of the advected tracer square and the square of the advected tracer, divided by the time step. This method is generalised for other advection schemes. An equivalent method is introduced for the numerical dissipation which is a kinetic energy loss due to the discretisation of the velocity advection. In a one-dimensional application the performance of both analysis methods is demonstrated by comparing the numerical mixing and dissipation to physical mixing and dissipation for two advection schemes, which are the FOU and a monotone TVD scheme. It is finally discussed how the one-dimensional analysis method can be generalised for three-dimensional primitive equation models of the coastal ocean.

Modeling Flash Diffusivity Experiments in Two Dimensions for Thick Samples

The laser flash method for measuring thermal diffusivity is well established and has been in use for many years. Early analysis methods employed a simple model, in which one-dimensional transient conduction was assumed, with insulated surfaces during the time subsequent to the flash. More recently, models of greater sophistication have been applied to flash diffusivity experiments using nonlinear regression. The advanced models have achieved highly accurate agreement with experimental data taken from thin samples, on the order of 1 mm in thickness. As samples become thicker, models that neglect edge losses can lose some conformity to the experimental data. The present research involves the application of a two-dimensional model, which allows for penetration of the laser flash into the sample. The accommodation of the flash penetration is important for porous materials, where the coarseness of the porosity is more than 1% of the sample thickness. Variability of the area of incidence of the flash is also investigated to determine the effect on the model and the results. Statistical methods are used in order to make a determination as to the validity of the two-dimensional model, as compared with the one-dimensional analysis method.

Two-dimensional simulation and critical efficiency analysis of high-temperature steam electrolysis system for hydrogen production

High-temperature steam electrolysis (HTSE) is a promising method for highly efficient large-scale hydrogen production. The HTSE process not only reduces the amount of thermodynamic electrical energy requirement but also decreases the polarization losses, which improves the overall efficiency of hydrogen production. In this paper, a two-dimensional simulation method of the efficiency of the HTSE system integrated with high-temperature gas-cooled nuclear reactor (HTGR), which changes two parameters simultaneously in a reasonable range while keeping one parameter constant, was presented. Compared with one-dimensional analysis method, the effects of electrical efficiency ( η el), electrolysis efficiency ( η es,), and thermal efficiency ( η th) on overall efficiency ( η overall) were investigated more objectively and accurately. Moreover, the critical concepts of η es and η th were put forward originally, which were very important to determine the optimum electrolysis voltages and operation temperatures in the actual HTSE processes. The calculated critical value of η es was Δ G( T)/Δ H( T) and the actual η es should be higher than the theoretically calculated one in order to maintain the high hydrogen production efficiency of HTSE system. Also, it was very interesting to find that the critical η es was the theoretical maximum efficiency in SOFC mode. Furthermore, the critical value of η th was equal to the value of η el, which means the overall efficiency decreases with the η es increasing if the η th in the actual HTSE process is less than the critical value of η th. Therefore, it is very important to control the η th higher than the critical value in the actual HTSE process to get high overall system efficiency.

Numerical analysis of turn-off characteristics for a gate turn-off thyristor with a shorted anode emitter

Turn-off current waveform for a gate turn-off thyristor (GTO) with a shorted anode emitter has been calculated numerically by solving the semiconductor basic equations in an equivalent one-dimensional model device. This model is derived from the analysis of current and carrier distributions obtained by a two-dimensional calculation of the on-state of GTO. A calculated turn-off current waveform agrees well with the experimental waveform. The computational time of one case is about 2 min. It is shown that this one-dimensional analysis method is useful for the calculation of the turn-off time. Using this one-dimensional model during the turn-off process and the two-dimensional model in the on-state, the relation between turn-off time and the forward voltage drop can be obtained in relation to the shorted emitter structure. It is shown that the shorted emitter structure is useful to improve this tradeoff relation.

A Numerical Method of Unsteady Flow Analysis in a Duct with Junction

The method of characteristics based on Benson's technique has been widely used for the analysis of unsteady flow in the exhaust system of internal combustion engines. But, being a one-dimensional analysis method, this method cannot be applied to a junction directly, and some assumptions or experimental data are used for the analysis of this part. The authors have been requested to increase the accuracy of this analysis for a long time, and one of them has recently developed a numerical technique that can be applied to two-dimensional compressible flow of any boundary shape, which is named " Modified FLIC Method". This paper presents the applicability of the Modified FLIC Method to unsteady flow analysis at a junction of the exhaust system by comparison with experimental results.