High Power Density Diesel Engine Research Articles

Study on low temperature starting strategy for high power density diesel engines

During low-temperature starting, the high viscosity and poor fluidity of diesel engine lubricating oil make it difficult to be timely replenished to the friction pair, leading to the problems of starting difficulties and wear during cold starting. To address this issue, this study completed a simulation verification work through a bench test, and carried out a transient simulation of lubricating system oil filling in the range of 1–5 s starting time and −20°C to 80°C lubricating oil temperature to obtain the transient filling characteristics of the lubrication system oil path and the friction characteristics of the bearing. The results show that extending the starting time can effectively reduce the average dry sliding speed of the bearing, thereby reducing the frictional wear of the critical friction pairs during starting; when the oil temperature is between 20°C and 30°C, the average dry sliding speed of the bearing is low and the dry sliding distance is the shortest. The research results of this study are conducive to in-depth analysis of the lubrication oil filling mechanism during cold starting, and to determine a reasonable cold starting strategy from the perspective of lubrication.

Tribological Properties of Several Surface-Modified Piston Rings Under Extreme Conditions

Abstract This article explores the performance of different commercial piston rings when matched with a boron-phosphorus (BP) alloy cast iron cylinder liner, specifically in high-power density diesel engines. The focus is on the friction, wear, and scuffing characteristics. An interrupted wear test was conducted under lean oil conditions to study the scuffing behavior of plated Cr-diamonds coating (GDC) and diamond-like carbon coating (DLC). The findings reveal that DLC coatings exhibit superior tribological properties, displaying low friction coefficients and wear loss at temperatures of 150 °C and 240 °C. In contrast, GDC coatings demonstrate relatively poor performance. Additionally, the DLC coating demonstrates excellent scuffing resistance, as no material transfer was observed for up to 77 min, even without lubrication. The interrupted scuffing test reveals that the scuffing process undergoes a stable wear stage, followed by a sudden drop and subsequent increase in friction force, ultimately resulting in scuffing when the BP cylinder is paired with GDC. On the other hand, although the frictional force of DLC initially increases after a brief decline, no significant adhesive wear is observed. This can be attributed to the formation of a tribo-chemical layer of carbides, which effectively prevents scuffing. In comparison to traditional methods of postwear morphology and analysis, our proposed interrupted scuffing tests offer enhanced capabilities for evaluating the wear condition of friction pairs at various time intervals during the oil depletion process. This novel approach introduces a new paradigm for investigating wear patterns in different friction pairs.

Surface evolution of vermicular cast iron in ultra-high temperature combustion with different single-pulsing duration

The key components in combustion chamber of high power density diesel engines are apt to be damaged rapidly under abnormal combustion. To investigate the surface damage behavior and evolution mechanism of vermicular graphite cast iron in unsteady combustion, a self-developed plasma thermal shock test method was adopted. And the effect of the single-pulsing duration (0.2, 0.5, 5, and 50 s) of combustion on reciprocating thermal shock characteristics was mainly studied. Results showed that as the sample with the longest loading duration (50 s) exhibited the highest mass gain rate (0.05 mg/s), thickness growth rate (0.096 μm/s), roughness (1.889 μm), and hardness (515 HV). The cumulative thickening and spalling of the oxide layer during the plasma impact is the main cause of the changes in ablation rate and surface roughness. And the bainite phase transformation in the heat affected zone increased the hardness of the material.

Effect of Linear Crack Size and Location Relationship to Piston Stress and Damage Tolerance

In the quantitative characterization of linear defect structure of Piston Alloy, non-destructive testing and micro-morphology of defect, shape and outline of prefabricated linear defect are used in this paper. Based on ANSYS finite element software, an experimental simulation of line defect was carried out by using the finite element software of micromechanics. The defects of piston alloy components are assigned with material parameters, the model grid is divided, the boundary condition is defined and the finite element simulation is carried out under ANSYS/Mechanical environment. The calculation of the micro-stress field of the interface with various defects is obtained. Under the service condition of high-power density diesel engine, the local stress concentration caused by line defect is less than the strength limit of alloy material. Therefore, in this location eddy current testing non-destructive testing control line defect size is 0.12 mm×0.2 mm×5 mm. It is suitable for Eddy current nondestructive testing of piston components and can ensure the material safety and work reliability of Piston components under service condition.

Friction-optimized High Power Density Diesel Engine for the Indian Market

Friction-optimized High Power Density Diesel Engine for the Indian Market

Experimental assessment of interfacial contact thermal conductance between graphite and matrix in cast iron

ABSTRACTCast iron with good mechanical and thermal combination property is preferred material for the cylinder head of high power density diesel engine. Interface between graphite and matrix should play a key role in thermal conductivity of cast iron. However, it is difficult to measure the interfacial contact thermal conductance (ICTC) between graphite inclusion and matrix in cast iron. In this paper, a modeling experimental sample containing a macroscopic interface is designed and ICTC can be estimated with the aid of finite element (FE) calculation. At last the effect of ICTC on the thermal conductivity of cast iron is assessed according to the change of metallographic FE simulation results before and after considering ICTC. Results show that the magnitude of ICTC is between 1.0 × 105 and 2.0 × 105 W m−2·K on the whole. The interface makes the theoretical thermal conductivity of cast iron drop down 34.6%.

Technologies for High Power Density Diesel Engines

<p class="p1">The engines used in armoured fighting vehicles have to be compact, light in weight, efficient and reliable. In order to achieve a compact engine design, a complete understanding of all the factors affecting the engine performance is needed. However, it is important to note that the performance of the engine cannot be compromised in the pursuit of compactness. The aim of this paper is to classify systematically various broad areas affecting the engine’s power to weight and power to volume ratio and discuss respective current technologies available. This paper explores the possibility of size and weight reduction and efficiency enhancement of diesel engines by the use of various methods like engine friction reduction, better thermal management, high injection pressure, and turbocharging. Achieving high engine speeds and high BMEP will be the means of achieving high power density. The effects of engine configuration and technologies on compactness are also discussed. Finally, the configuration of a new engine and its design aspects, incorporating all the aforementioned concepts is discussed</p>

The effect of vermicularity on the thermal conductivity of vermicular graphite cast iron

As an ideal material for the cylinder head of high power density diesel engine, vermicular graphite cast iron (VGI) with higher thermal conductivity was received more and more attention recently. In this article, finite element (FE) software ANSYS was applied to investigate the changes of thermal conductivity of VGI with the vermicularity and the FE-models are carried out based on the real metallographic images of VGI. The results indicate that there is a big difference between the numerical simulation and the reality without the consideration of the thermal contact resistance of interface between matrix and graphite. The numerical simulation result is close to the reality when the contact thermal conductance is set at 0.1W/(m2·K). In addition, the equivalent thermal conductivity along X direction kequ,x rises from 34.437W/m·K to 38.902W/m·K and increases by 13% or so when the vermicularity is improved from 40% to 90% according to the numerical simulation.

NOx, Soot, and Fuel Consumption Predictions under Transient Operating Cycle for Common Rail High Power Density Diesel Engines

Diesel engine is presently facing the challenge of controlling NOx and soot emissions on transient cycles, to meet stricter emission norms and to control emissions during field operations. Development of a simulation tool for NOx and soot emissions prediction on transient operating cycles has become the most important objective, which can significantly reduce the experimentation time and cost required for tuning these emissions. Hence, in this work, a 0D comprehensive predictive model has been formulated with selection and coupling of appropriate combustion and emissions models to engine cycle models. Selected combustion and emissions models are further modified to improve their prediction accuracy in the full operating zone. Responses of the combustion and emissions models have been validated for load and “start of injection” changes. Model predicted transient fuel consumption, air handling system parameters, and NOx and soot emissions are in good agreement with measured data on a turbocharged high power density common rail engine for the “nonroad transient cycle” (NRTC). It can be concluded that 0D models can be used for prediction of transient emissions on modern engines. How the formulated approach can also be extended to transient emissions prediction for other applications and fuels is also discussed.

A Matching Method for Two-Stage Turbocharging System

The turbine system of a two-stage turbocharger composed of high pressure turbine (HT), low pressure turbine (LT), and by-pass valve decides distribution and utilization of exhaust gas energy and influence performance of two-stage turbocharger in whole operational conditions. Besides, characteristics of turbine is expressed by envelop line of characteristic lines in different speeds. So turbine can be conveniently selected compared with compressor with similarity theory. Therefore, two-stage turbocharger matching begins from turbine system matching in the paper. In two-stage turbocharger, cooler efficiency, cooler loss, and by-pass valve open besides turbochargers will influence turbocharging system performance and design of cooler and by-pass valve are important contents of turbocharging system matching. The paper matched intercooler, by-pass valve open, compressors, and turbines jointly. Calculation model for turbocharger matching was built, and turbine performance is get from reference turbine based on similarity theory; influence of compressor ratio distribution, cooler efficiency, and pressure drop in cooler imposing on compressor work was analyzed; and influence of turbine flow capacity and by-pass valve imposing on output working in expanding process was studied; the method for matching of two-stage turbocharging system in whole operational condition is studied. Matching analysis was made aiming at two-stage turbocharging system of a type of high power density diesel engine, and design for turbocharging system was finished. Matching result using the method is compared to matching result using traditional method. Analysis result proves that using the method matching points in different operational conditions are located in more reasonable zone of compressor MAP.

Application of Space-time Conservation Element and Solution Element Method in Intake and Exhaust Flows of High Power Density Diesel Engine

Abstract A one-dimensional pipe flow model of single-cylinder diesel engine is established to investigate the intake and exhaust flow characteristics of diesel engine in the condition of high power density (HPD). A space-time conservation element and solution element (CE/SE) method is used to derive the discrete equations of the partial differential equation for the intake and exhaust systems. The performance parameters of diesel engine with speed of 2100 r/min are simulated. The simulated results are in accordance with the experimental data. The effect of increased power density on charging coefficient is analyzed using a validated model. The results show that the charging coefficient is slowly improved with the increase in intake pressure, and is obviously reduced with the increase in engine speed.

The Analysis of Lubrication for HPD Diesel Engine Piston Pin Bearing

Based on the unified Reynolds equation model and fast Fourier transform (FFT) method, the lubrication performance of the piston pin bearing for high power density diesel engine was studied by numerical simulation. First of all, through the coupled solving of a unified Reynolds equation and elastic deformation equation, the orbit of journal center for piston pin bearing is investigated. The eccentricity ratio of the piston pin bearing in vertical direction of the piston stroke is smaller, however it is much larger in the downward direction of the piston stroke, which indicate that the below area of the piston pin bearing bears greater load and occurs larger deformation. This is consistent with the reality that the below area of the piston pin bearing is prone to damage and wear. Secondly, the influence of the different bearing clearances and width on the minimum oil film thickness is discussed, The results show that the minimum oil film thickness is increased, while the width of piston pin bearing is increased or the clearance of piston pin bearing is decreased.

The Analysis of the Deformation and Contact Lubrication Problem of HPD Diesel Engine Piston Pin Bearing Based on the FFT Method

Based on the unified Reynolds equation model and fast Fourier transform (FFT) method, the lubrication performance of the piston pin bearing for high power density diesel engine was studied by numerical simulation. First of all, through the coupled solving of a unified Reynolds equation and elastic deformation equation, the influence of the viscous-pressure effect on the maximum film pressure and the minimum oil film thickness for piston pin bearing are investigated. The results show that, after considering the viscosity-pressure effect, the minimum oil film thickness and the maximum film pressure of semi-floating piston pin bearings for high power density increase, and the elastic deformation decreases in greatest load position. It confirms that the bearing capability is greatly enhanced while the viscosity- pressure effect is considered. Secondly, The eccentricity ratio of the piston pin bearing in vertical direction of the piston stroke is smaller, however it is much larger in the downward direction of the piston stroke, which indicate that the below area of the piston pin bearing bears greater load and occurs larger deformation. This is consistent with the reality that the below area of the piston pin bearing is prone to damage and wear

Thermal-Structure Coupled Field Analysis of a Certain HPD Diesel Engine Cylinder Liner

Based on heat transfer theory and thermal-structure coupled in sequence method of finite element, the stress and displacement distribution of a certain high power density diesel engine cylinder liner under the action of thermal-structure coupled loads was calculated. The results showed that the highest temperature field of cylinder liner appeared on the upper part of the cylinder liner inner surface. Furthermore, the maximum stress value and displacement value of cylinder liner were obtained, which will give a gist for designing and calibrating cylinder liner in practical.

Developing of High Power Density Diesel Engine Oil

For high power density diesel engine operating characteristics and its unique compact structure, the development of new high power density diesel engine oil referred to the latest diesel engine oil standard GB 11122-2006. Through the comprehensive assessment of physical and chemical properties, the composite of poly a-olefin (PAO) and polymer esters was determined as base oil,and added high-performance additives. This oil developed has clean dispersion, antioxidation, anti-wear , anti-corrosion and other properties. the lubricating oil can well satisfy the performance requirements of high power density diesel engine.

Alternative to chrome: HVOF cermet coatings for high horse power diesel engines

High velocity oxygen fuel sprayed face coatings have shown great promise for piston rings used for high power density diesel engines. Various coatings have been tested on both wear test rigs and in an engine. A highly dense HVOF cermet coating was developed with reasonable crack resistance during service. The HVOF coated piston rings wore three to six tunes lower than chrome plating. Cylinder liner (counter face) wear was found to be one to three times higher than chrome. The HVOF coating is considered to be an excellent replacement for chrome plating. The coating process is more environmentally friendly than the chrome plating process. Also, the coating has potentially lower or equivalent production cost when compared to chrome.