Dynamic Performance of Conventional and Electrically Activated Engine Thermostats

This study concerns the dynamic performance of passive and active wax-actuator driven thermostats. The study is extended to wax actuator driven thermostats that have been fitted with a heating device, such that the thermostat can be actuated electrically. The thermostat valve type chosen for this study is a balanced, sleeve-type thermostat typically used in large over-the-road and industrial diesel engines. The valve operates like a spool valve to direct the flow of the engine coolant to the bypass, the heat exchanger, or partially to each. Since conventional thermostats are passive devices they lag in response to dynamic engine conditions, and under certain circumstances overheating can occur as a result of the device’s inability to respond quickly. Also, conventional thermostats are designed to protect an engine against overheating year round. Therefore, a thermostat designed to protect against overheating in the summer will often result in an overcooling condition in the winter. One possible solution to the problem is to control the thermostat electrically through the electronic engine control system, or other system, making the thermostat an active control device instead of a passive one. In this study, a mathematical model is developed to determine wax temperature, and thereby predict the thermostat operation and response. The wax temperature depends on the heat transfer from the engine coolant through the brass cup that encapsulates the wax, as well as heat transfer from the heater. The simulations are compared with measurements of temperature, thermostat position and flow at several locations around the thermostat in an experimental set-up. The outcome is used to analyze the accuracy of the methods used in the thermodynamic calculations.

Study on Wear of Piston Rings in Diesel Engines With Exhaust Gas Recirculation

The wear of piston rings in the diesel engines with EGR system is studied experimentally. In order to clarify the effect of PM on the wear, the wear of the piston rings in the test engine is measured, (1) when the non-soluble in the lubricating oil is removed by the oil filters, (2) when PM in the re-circulating gas is removed by the DPF, (3) when the carbon black is added in the lubricating oil. The experimental results are discussed with the measured time history of kinematic viscosity, total base number, total acid number, ZDTP survival rate, and carbon residual content and its particle size in the engine oil.

Analysis of Oil Film Thickness on a Piston Ring of Diesel Engine: Effect of Oil Film Temperature

This paper describes that an analysis of oil film thickness on a piston ring of diesel engine. The oil film thickness has been performed by using Reynolds equation and unsteady, two-dimensional (2-D) energy equation with a heat generated from viscous dissipation. The temperature distribution in the oil film is calculated by using the energy equation and the mean oil film temperature is computed. Then the viscosity of oil film is estimated by using the mean oil film temperature. The effect of oil film temperature on the oil film thickness of a piston ring was examined. This model has been verified with published experimental results. Moreover, the heat flow at ring and liner surfaces was examined. As a result, the oil film thickness could be calculated by using the viscosity estimated from the mean oil film temperature and the calculated value is agreement with the measured values.

A Study on Cylinder Bore Deformation of a Diesel Engine With Dry Liner Structure

The deformation of the cylinder liner of a diesel engine in actual operation have been measured by the means of a rotary piston, and the deformation has been compared with those measured statically at room temperature. As a result, it is found that the deformation of the liner in engine operation is hardly affected by the deformation at room temperature, but it follows the deformation of the cylinder block where the liner is inserted. It is also found as follows: The deformation of the liner upper portion varies according to the head bolts and the engine load, while the effect of the cylinder pressure is insignificant. The deformation at the middle of the liner changes mainly by the thermal expansion in the thrust direction, while the deformation at the lower portion is not affected by the engine speed or the load.

Relative Torsional Vibration Analysis for Crankshaft

Crankshaft torsional vibration characteristics have been studied, more often based on the results of measurement at a pulley, rather than in relation to a pulley. The results of the measurement at a pulley, however, include crankshaft torsion assuming that a crankshaft is elastic, as well as rotational speed changes due to cylinder pressure fluctuation assuming that a crankshaft is rigid. The authors recommend that relative torsional amplitude should be used in evaluating torsional vibration characteristics, rather than torsional amplitude at a pulley.

Mechanical Design of Turbine Blades With Interlocking Tip Shrouds

In contrast to the substantial body of literature regarding turbine aerodynamics and performance, there is a virtual absence of literature on the mechanical design of turbine components. As a contribution to this discipline, this paper is intended to provide an overview of a systematic approach for the mechanical design of turbine blades with interlocking tip shrouds which will result in a near-optimum mechanical and aerodynamic design for an industrial gas turbine.

Bearing Characteristic Parameters to Estimate the Optimum Counterweight Mass of a 6-Cylinder In-Line Engine

Two dimensionless relationships that estimate the maximum and average bearing load of a 6-cylinder 4-stroke in-line engine have been found. These relationships may assist the design engineer in choosing a desired counterweight mass. It has been demonstrated that: 1) the average bearing load increases with engine speed and 2) the maximum bearing load initially decreases with engine speed, reaches a minimum, then increases quickly with engine speed. This minimum refers to a critical speed at which the contribution of the inertia force overcomes the contribution of the maximum pressure force to the maximum bearing load. The critical speed increases with an increase of counterweight mass and is a function of maximum cylinder pressure and the operating parameters of the engine.

Numerical Prediction to Effects of Manifolds Configuration on Flow in Swirling Flow Exhaust Pipe System

Compared to conventional Modular Pulse Converter (MPC) system with the typical structure of symmetrical T-junction, a novel swirling flow exhaust pipe system has its advantages especially in reducing collision loss of high-speed gases near junction and having interference-free scavenging and higher energy utilization. The initial junction configuration in swirling flow exhaust system was determined with reference to T-junction in MPC. In order to analyze and compare its flow behaviors, 3D-flow fields of manifold-type junctions in swirling flow exhaust pipe system were performed with the revised KIVA II code. A non-linear algebraic Relynolds stress (ASM) model was considered in this study and comparisons were made with the standard κ–ε turbulence model. For many cases of parametric studies considered, it is found that junction’s configurations have significant influence on the velocity distribution and swirl intensity. 30° swirling flow junction is found to be unreasonable, 45° junction with oblate rectangular type contraction area is recommended in swirl flow pipe exhaust pipe system. 3D-Particle Dynamic Analyzer (PDA) measurement was introduced to measure the axial and tangential velocity components of swirling flow in main pipe. Comparisons of computed and measured velocities reveal that model predictions are in generally reasonable agreement with the measurements, indicating validity of computational code and reliability of prediction model.

Piston Slap Induced Noise Simulation Considering Elasto-Hydrodynamic Contact Conditions

Main aims in the development process for the cylinder assembly of internal combustion engines are the reduction of friction and wear due to the contact between piston and liner as well as the minimization of piston slap induced noise. In this paper, the authors extend their methodology for the simulation of structural dynamics in the area of piston and liner with the aim of predicting structure borne noise excited by the piston slap phenomenon. The simulation model uses linear, flexible bodies subjected to highly non-linear joint forces, as occurring in the piston-to-liner contact. Both, the theoretical background and the advantages of the coupled simulation procedure for such complex systems are discussed. The models are validated by comparison of measured and computed values of piston movements and modal structure behavior. The result examples focus on the effects of piston secondary movement, the resulting impact on the lubricated liner and the analysis of vibration transfer behavior in the block structure. It is shown how noise excitation and structure borne vibration transfer paths can be analyzed in order to assess engine design. Result plots show typical results on the surface of a 4 Cylinder Diesel engine and the contribution of piston slap induced noise.

Integrated Multi-Code Prediction of the Unsteady Flow Around Moving Valve and in Engine Intake Systems

Predictions of the behaviour of flow in duct system are of practical relevance in design procedure, since the performance of internal combustion engine critically depends on the gas dynamic response of the intake port and the cylinder during the induction process.