Browse Topic: Adiabatic engines

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The Effects of Thick Thermal Barrier Coatings on Low-Temperature Combustion2020-01-02754/14/2020
An experimental study was conducted on a Ricardo Hydra single-cylinder light-duty diesel research engine. Start of Injection (SOI) timing sweeps from -350 deg aTDC to -210 deg aTDC were performed on a total number of five pistons including two baseline metal pistons and three coated pistons to investigate the effects of thick thermal barrier coatings (TBCs) on the efficiency and emissions of low-temperature combustion (LTC). A fuel with a high latent heat of vaporization, wet ethanol, was chosen to eliminate the undesired effects of thick TBCs on volumetric efficiency. Additionally, the higher surface temperatures of the TBCs can be used to help vaporize the high heat of vaporization fuel and avoid excessive wall wetting. A specialized injector with a 60° included angle was used to target the fuel spray at the surface of the coated piston. Throughout the experiments, the equivalence ratio, ϕ, was maintained constant at 0.4; the combustion phasing was consistently matched at 6.8 ± 0.4 deg aTDC. It can be concluded that the thick TBC cases achieved 1 to 2 percentage points improvement in combustion efficiency, and generally, a ~2 percentage points increase in indicated engine efficiency. It is also noticed that applying a dense top sealing layer to the TBC further improves the UHC emissions compared to the TBC coated piston with an unsealed surface. From the heat release analysis, it can be concluded that the TBCs have no significant impact on the heat release process and knock intensity while matching the combustion phasing; however, it reduces the intake temperature requirement by up to 20 K. The exhaust gas temperatures were expected to increase for the TBC cases, but the expected increase in exhaust temperature was not conclusive from the results observed in this study.
Yan, Ziming, Gainey, Brian, Gohn, James, Hariharan, Deivanayagam, Saputo, John, Schmidt, Carl, Caliari, Felipe, Sampath, Sanjay, Lawler, Benjamin
Experimental Evaluation of Novel Thermal Barrier Coatings in a Single Cylinder Light Duty Diesel Engine2019-24-00629/9/2019
The objective of this investigation was to improve the thermal properties of plasma sprayed thermal barrier coatings (TBC) for internal combustion engines. There is a need for further reduction of thermal conductivity and volumetric heat capacity and the negative effects on heat loss and combustion phasing of surface roughness and permeable porosity, typical for plasma sprayed coatings, should be minimized. Four measures for improvement of TBC properties were evaluated: i) modification of the coating's microstructure by using a novel suspension plasma spraying method, ii) application of gadolinium-zirconate, a novel ceramic material with low thermal conductivity, iii) polishing of the coating to achieve low surface roughness, and iv) sealing of the porous coating surface with a polysilazane. Six coating variants with different combinations of the selected measures were applied on the piston crown and evaluated in a single cylinder light duty diesel engine. The experimental data was modeled with multiple linear regression to obtain confidence intervals for the measurement results and to correct the data for variations of surface roughness, combustion phasing and compression ratio for the different pistons. The main tool for evaluation of the coating properties was cylinder pressure analysis, providing the apparent rate of heat release, indicated efficiency, wall heat loss, and exhaust loss. The new TBC microstructure from suspension plasma spraying in combination with the use of gadolinium-zirconate showed promising results with respect to indicated efficiency and heat loss reduction.
Somhorst, Joop, Uczak De Goes, Wellington, Oevermann, Michael, Bovo, Mirko
Modeling the Effect of Thermal Barrier Coatings on HCCI Engine Combustion Using CFD Simulations with Conjugate Heat Transfer2019-01-09564/2/2019
Thermal barrier coatings with low conductivity and low heat capacity have been shown to improve the performance of homogeneous charge compression ignition (HCCI) engines. These coatings improve the combustion process by reducing heat transfer during the hot portion of the engine cycle without the penalty thicker coatings typically have on volumetric efficiency. Computational fluid dynamic simulations with conjugate heat transfer between the in-cylinder fluid and solid piston of a single cylinder HCCI engine with exhaust valve rebreathing are carried out to further understand the impacts of these coatings on the combustion process. For the HCCI engine studied with exhaust valve rebreathing, it is shown that simulations needed to be run for multiple engine cycles for the results to converge given how sensitive the rebreathing process is to the residual gas state. The effect of thermal barrier coatings on the piston surface is explored using the properties of Yttria-Stabilized Zirconia (YSZ) and Gadolinium Zirconate (GdZr) top coatings with two different thicknesses. Heat flux measurements from an experimental engine with an all metal piston and YSZ and GdZr thermal barrier coatings are compared to the simulation results and the simulation is found to under predict heat transfer. Reducing the conductivity of the coating advances combustion as does increasing the thickness of the coating.
Killingsworth, Nick, Powell, Tom, O'Donnell, Ryan, Filipi, Zoran, Hoffman, Mark
A Method to Evaluate the Compression Ratio in IC Engines with Porous Thermal Barrier Coatings2018-01-17789/10/2018
The compression ratio is an important engine design parameter. It determines to a large extend engine properties like the achievable efficiency, the heat losses from the combustion chamber and the exhaust losses. The same properties are affected by insulation of the combustion chamber. It is therefore especially important to know the compression ratio when doing experiments with thermal barrier coatings (TBC). In case of porous TBCs, the standard methods to measure the compression ratio can give wrong results. When measuring the compression ratio by volume, using a liquid, it is uncertain if the liquid fills the total porous volume of the coating. And for a thermodynamic compression ratio estimation, a model for the heat losses is needed, which is not available when doing experiments with insulation. The subject of this paper is the evaluation of an alternative method to assess the compression ratio. It is based on motored cylinder pressure data like other thermodynamic methods but does not need a model for the heat losses. The validation and application of the method is done with data from experiments involving two types of porous TBCs, performed on a light duty single cylinder diesel engine. The results indicate that the proposed method accurately predicts the compression ratio for porous thermal barrier coatings.
Somhorst, Joop, Oevermann, Michael, Bovo, Mirko, Denbratt, Ingemar
Mathematical Model Validation of Experimental Results of SiC p /Al 2 O 3 Ceramic Matrix Composites Prepared by Directed Metal Oxidation of an Al Alloy2018-28-00467/9/2018
In this paper, SiCp/Al2O3 ceramic matrix composites are fabricated with specimen of dimensions measuring 70 × 70 × 20, in mm with varying volume fractions in the range of 0.35 to 0.43. The purpose of this paper is to compare experimental results namely physical properties of SiCp/Al2O3 composites with mathematical models. The model predictions were compared with the experimental data In the present paper, different mathematical models are used to comparison of physical properties such as coefficient of thermal expansion and modulus of elasticity of SiCp/Al2O3 composites with different volume fractions of SiC in the range of 0.35 to 0.43. The comparison experimental results with mathematical models provide detailed information about the results of these comparisons. The models were capable of predicting the data for some scenarios fairly well.
Malkapuram, Dr Devaiah
Coefficient of Thermal Expansion and Elastic Modulus of SIC P /AL 2 O 3 Ceramic Matrix Composites Prepared by Directed Metal Oxidation Process2018-28-00477/9/2018
The present paper, it is aimed to prepare SiCp/Al2O3 ceramic matrix composites using Directed Metal Oxidation process large enough dimension specimens for the measurement of physical properties. Continuous oxidation of an Aluminum alloy with suitable dopant along with a preform of SiC has lead to the formation of alumina matrix surrounding silicon carbide particulates. SiCp/Al2O3 ceramic matrix composites fabricated by the Directed Metal Oxidation process, possess required physical properties such as coefficient of thermal expansion (CTE) and elastic modulus, all at an affordable cost of fabrication. Al2O3 matrix composites reinforced with different volume fractions of SiC particulates were investigated for physical properties such as coefficient of thermal expansion (CTE) and elastic modulus. The composites with SiC volume fraction of 0.43 were found to possess a CTE as of as 5.0 x 10−6/K and an elastic modulus of 262 GPa.
Malkapuram, Dr Devaiah
Thermal Analysis and Experimental Investigations on the Effect of Thermal Barrier Coating on the Behavior of a Compression Ignition Engine Operated with Methyl Esters of Waste Cooking Oil2018-01-06634/3/2018
One of the globally challenging issues today is Waste Utilization. The excessive accumulation of waste has created an uncomfortable pressure on not, just the habitant but on the environment as well. As a small step forward in contributing towards minimizing waste disposal, this study attempts to address the problem raised due to the disposal of waste cooking oil. Researchers found that Waste Cooking Oil (WCO) has a very good potential as a fuel for compression ignition engine and was therefore selected for this study. In the first phase of the work, behaviour of the test engine was studied with neat WCO at different power outputs. As the first modification, neat WCO was converted in to its methyl ester and tested in the same engine. Next, combustion chamber parts like piston and cylinder head, inlet and exhaust valves were coated with Thermal Barrier Coating (TBC) and engine behaviour was studied. To make the study more interesting a thermal- stress analysis was done on the engine piston to examine the impact of coating on engine performance. Results claimed that Brake Thermal Efficiency (BTE) of the engine operated with methyl esters of WCO showed marked improvement as compared to its neat form. However, the smoke emission was found to be still on the higher range with methyl ester of WCO. Engine results with thermal barrier coating reported improved BTE as compared to the earlier case. Interestingly, all the carbon based emissions were drastically reduced at the cost of increased oxides of nitrogen emissions. It was also found from the analysis that the surface temperature of the coated surface was higher than that of the uncoated surface. Thus, this work concludes that WCO in the form of its methyl ester can be used effectively in the compression ignition engine with a slight modification of the combustion chamber parts.
Elumalai, Sangeethkumar, Mayakrishnan, Jaikumar, Nandagopal, Sasikumar, Raja, Selvakumar, Mukherjee, Sudip
Reduced Convective Combustion Chamber Wall Heat Transfer Losses of Hydrogen-Fueled Engines by Vortex-Stratified Combustion - Part 2: Numerical Analyses2017-01-928710/5/2017
In this second of two parts, the fundamentals of convective wall heat transfer losses are elucidated in the context of the desired objective toward its reduction in a direct-injected, hydrogen-fueled internal combustion engine. A comparative, transient 2D CFD analysis evaluated at 4500 RPM between a combustion chamber design representing current practice and the here-introduced “vortex-stratified combustion” process finds an approximately 50% reduction in the peak convective flux with the latter. The simulation results show that reduced heat flux of the vortex approach is driven by the combination of two effects: The first is finite-time diffusive mixing getting outpaced by the replenishment of pure air being introduced preferentially along the circumference of the combustion chamber due to the Coandă effect; this results in a distinct radial charge stratification during mixture preparation in the compression stroke, with a fuel-concentrated center and essentially pure air at the periphery. The second effect is the forced-segregation of different density reactants during the course of the combustion process caused by large body forces that result from the gravitational acceleration of the rapidly rotating charge, thereby constraining the combustible mixture and the flame to some distance from the walls. Evidence for this is observed by hot, low-density hydrogen being forced to remain near the center and cooler, heavier oxygen being inhibited from migrating from the outer periphery to react with the aforementioned hydrogen, and the distinct curvature of the radial gas temperature profile at a substantially greater distance from the wall than the thermal boundary layer thickness.
Oh, David, Brouillette, Martin, Plante, Jean-Sebastien
A New Piston Insulation Concept for Heavy-Duty Diesel Engines to Reduce Heat Loss from the Wall2017-24-01619/4/2017
To reduce heat transfer between hot gas and cavity wall, thin Zirconia (ZrO2) layer (0.5mm) on the cavity surface of a forged steel piston was firstly formed by thermal spray coating aiming higher surface temperature swing precisely synchronized with flame temperature near the wall resulting in the reduction of temperature difference. However, no apparent difference in the heat loss was analyzed. To find out the reason why the heat loss was not so improved, direct observation of flame impingement to the cavity wall was carried out with the top view visualization technique, for which one of the exhaust valves was modified to a sapphire window. Local flame behavior very close to the wall was compared by macrophotography. Numerical analysis by utilizing a three-dimensional simulation was also carried out to investigate the effect of several parameters on the heat transfer coefficient. From the observation of wall impinged flame, it was revealed that a kind of thermal boundary layer with Zirconia coating was thinner than the baseline, which could be resulted in the increase in heat transfer coefficient. Furthermore, the numerical simulation results suggested that higher wall surface temperature swing with Zirconia coating is not the main cause of thinner boundary layer, but surface roughness and/or porous structure is. To confirm the hypothesis, new pistons with different insulating structures were then experimented. Even though the heat loss was not so improved because of the limited area of insulation, the potential for BTE improvement was confirmed.
Uchida, Noboru, Osada, Hideaki
Experimental Study on the Effect of Thermal Barrier Coating on Cylinder Head of a Semi-Adiabatic Diesel Engine2017-28-19787/10/2017
The process of building the engine and its subsequent systems involves usage of metals & its compounds. The current technique is in which the fuel is burned in a combustion chamber wherein the actual combustion progression and its subsequent gases are surrounded by metallic compounds. The part of the heat energy generated in the system is forced to be removed by means of cooling to protect the structural integrity of the engine; nearly 30% of the energy is lost due to cooling. However limitation in structural behavior of metallic materials and limited resource for the production of metals and alloys with superior high temperature structural causes the search for new alternate materials like ceramics, organic synthetic plastic, etc. Thermal Barrier Coating is an attractive and promising method in providing thermal insulation for the engine components due to its good thermo-mechanical properties. Thermal insulation reduces the heat transfer from combustion chamber to the metallic materials thereby reducing the need for cooling and heat energy loss due to the same. This research has been executed on three cylinder naturally aspirated diesel engine to understand the effect of the ceramic compound coating Yttria-Stabilized Zirconia, on engine performance and emission characteristics. This investigation compares the performance & emission characteristics of two different configurations namely, Engine Build I (Baseline Engine) and Engine Build II (Ceramic coated on cylinder head (incl. valves) of the Engine). Experimental investigations have been carried out under different loading conditions where all the Engine Builds (I & II) are tested in an engine test bed for its performance and emission characteristics as per ISO 8178-4 ‘‘C1’’ 8 mode testing cycle and the test results are evaluated. Test results revels, that Ceramic coating on Cylinder head produce a reduction in fuel consumption, delivers higher performance and better emission characteristics.
Jerome, Stanley M, Sundararaj, Senthilkumar
Experimental Analysis of Performance and Emission Characteristics of Tungsten Carbide Coated Piston2017-28-19817/10/2017
Heat energy produced in the combustion chamber of an IC engine cannot be completely converted into useful work due to heat transfer losses. This leads to a fall in the performance of the engine. To overcome this, pistons have been coated with different materials like molybdenum disulphide, chromium nitrides and other materials. These thermal barrier coatings have improved the performance of the engine by preventing heat loss. In this experiment, the performance and emission characteristics of a tungsten carbide coated piston was investigated. WC was coated on the piston surface by EB-PVD Process. The WC coated piston was tested in an MK20 engine using an eddy current dynamometer. The performance of uncoated and WC coated pistons were compared and analyzed. An increase in combustion chamber temperature was obtained while using WC coated piston, which was observed by increased exhaust gas temperature. WC coated piston shows 9.89% increase in BTE than uncoated pistons, simultaneously the fuel consumption decreased, and the emissions of WC coated piston were more controlled than the uncoated piston except for oxides of nitrogen. Reduction of HC upto 10.95% and 46.9% of CO were observed with 26.9% increase in NOx at full load condition while using coated piston.
Ganapathy, Sakthinathan, Appancheal, Anand Kumar, Velusamy, Raja
An Experimental Study of a Waste Heat Recovery System Connected to a Diesel-Gen-Set2017-01-01233/28/2017
In general, diesel engines have an efficiency of about 35% and hence, a considerable amount of energy is expelled to the ambient air. In water-cooled engines, about 25%, 33% and 7% of the input energy are wasted in the coolant, exhaust gas, and friction, respectively. The heat from the exhaust gas of diesel engines can be an important heat source to provide additional power and improve overall engine efficiency. Studies related to the application of recoverable heat to produce additional power in medium capacity diesel engines (< 100 kW) using separate Rankine cycle are scarce. To recover heat from the exhaust of the engine, an efficient heat exchanger is necessary. For this type of application, the heat exchangers are needed to be designed in such a way that it can handle the heat load with reasonable size, weight and pressure drop. This paper describes the study of a diesel generator-set attached with an exhaust heat recovery system. Superheated steam was produced by using two heat exchangers. In authors’ previous study, optimizations using CFD simulations were carried out to design heat exchangers to extract the exhaust heat more effectively. Then, in this research, optimized heat exchangers were manufactured and tests were performed with water/steam as the working fluid. The optimum pressures of the working fluid were found to be 3, 5, 8 and 15 bar at 10.6, 16.1, 21.5, and 26.6 kW of engine powers, respectively. At these optimum pressures, correspondingly 0.34, 0.74, 1.78, 2.71 kW additional powers were produced. At the rated power of 26.6 kW the heat recovery system produced an additional power of 2.71 kW which reduced the brake specific consumption (bsfc) by 11.1%. However, at 40% part load, this bsfc improvement was 3% due to lower exhaust temperature.
Bari, Saiful
A Comprehensive Assessment on Combined Effect of Thermal Barrier Coating and Emulsification Techniques on Engine Behavior of a Mahua Oil Based Diesel Engine2017-01-08733/28/2017
This paper presents a comprehensive study on using MO (Mahua oil) as fuel effectively in a diesel engine by adopting emulsification and TBC (Thermal Barrier Coating) techniques. A mono cylinder diesel engine was used for the study. Initially trials were made on the engine using neat diesel (ND), Neat Mahua oil (NMO) as fuels. In the second phase, NMO was converted into its stable emulsion (called as MOE) and tested in the engine. Finally thermal barrier coating of 0.2 mm was made on the piston, valves and cylinder head of the engine using the ceramic power of Al2O3 and the engine was tested using NMO and MOE as fuels in the TBC engine. Results indicated improvement in BTE (brake thermal efficiency) with MOE as compared to NMO mainly at high power outputs in the unmodified engine. The maximum BTE was found as 31.5% with ND, 27.2% with NMO and 30.4% with MOE at the peak power output. Reduced smoke, HC (hydrocarbon), CO (carbon monoxide) and NOx (oxides of nitrogen) emissions were found with MOE mainly at high power outputs. Engine with TBC mode significantly increased the performance and reduced all the emissions (except NOx) at all power outputs with both NMO and MOE. Combustion parameters indicated shorter ignition delay and combustion duration with both NMO and MOE under TBC mode. It was concluded that combining emulsification and TBC techniques could improve the performance of a diesel engine significantly using MO as fuel at all power outputs.
Masimalai, Senthilkumar, Mayakrishnan, Jai Kumar, Ganesan, Natraj
Reduction of Heat Loss and Improvement of Thermal Efficiency by Application of “Temperature Swing” Insulation to Direct-Injection Diesel Engines2016-01-06614/5/2016
The reduction of the heat loss from the in-cylinder gas to the combustion chamber wall is one of the key technologies for improving the thermal efficiency of internal combustion engines. This paper describes an experimental verification of the “temperature swing” insulation concept, whereby the surface temperature of the combustion chamber wall follows that of the transient gas. First, we focus on the development of “temperature swing” insulation materials and structures with the thermo-physical properties of low thermal conductivity and low volumetric heat capacity. Heat flux measurements for the developed insulation coating show that a new insulation material formed from silica-reinforced porous anodized aluminum (SiRPA) offers both heat-rejecting properties and reliability in an internal combustion engine. Furthermore, a laser-induced phosphorescence technique was used to verify the temporal changes in the surface temperature of the developed insulation coating. This was found to quickly rise during the combustion stroke and then drop during the expansion stroke. Second, a SiRPA coating was formed over the entire surface of the diesel piston cavity, and the thermal efficiency and the heat-loss reduction were investigated for a single-cylinder direct-injection (DI) diesel engine with a bore of 86 mm and a stroke of 96 mm. An energy balance analysis showed that the SiRPA coating achieves heat loss reduction by means of heat rejection and an increase in not only the exhaust energy but also the piston work, which increases the thermal efficiency.
Wakisaka, Yoshifumi, Inayoshi, Minaji, Fukui, Kenji, Kosaka, Hidemasa, Hotta, Yoshihiro, Kawaguchi, Akio, Takada, Noriyuki
An Analytical Assessment of the CO 2 Emissions Benefit of Two-Stroke Diesel Engines2016-01-06594/5/2016
Two-stroke diesel engines could be a promising solution for reducing carbon dioxide (CO2) emissions from light-duty vehicles. The main objective of this study was to assess the potential of two-stroke engines in achieving a substantial reduction in CO2 emissions compared to four-stroke diesel baselines. As part of this study 1-D models were developed for loop scavenged two-stroke and opposed piston two-stroke diesel engine concepts. Based on the engine models and an in-house vehicle model, projections were made for the CO2 emissions for a representative light-duty vehicle over the New European Driving Cycle and the Worldwide Harmonized Light Vehicles Test Procedure. The loop scavenged two-stroke engine had about 5-6% lower CO2 emissions over the two driving cycles compared to a state of the art four-stroke diesel engine, while the opposed piston diesel engine had about 13-15% potential benefit. Opposed piston two-stroke engines offer the potential for even higher thermal efficiency than loop scavenged two-stroke engines. The efficiency advantages of the opposed piston two-stroke engine are mainly because of lower in-cylinder heat losses due to elimination of the cylinder head and lower surface area to volume ratio. The thermal efficiency of a loop scavenged two-stroke engine can be potentially further improved by using thermal barrier materials for incylinder surfaces to minimize heat losses. Analytical studies show that integration of thermal barrier materials and two-stroke loop scavenged engine could lead to a cost effective highly efficient diesel engine. Whether the theoretical benefit translates to actual CO2 emissions reduction will have to be verified experimentally.
Warey, Alok, Gopalakrishnan, Venkatesh, Potter, Michael, Mattarelli, Enrico, Rinaldini, Carlo Alberto
Use of an Engine Simulation to Study Low Heat Rejection (LHR) Concepts in a Multi-Cylinder Light-Duty Diesel Engine2016-01-06684/5/2016
A comprehensive analysis of engine performance and fuel consumption was carried out to study Low Heat Rejection (LHR) concepts in the conventional light-duty diesel engine. From most previous studies on LHR diesel engines, thermal-barrier coatings (TBCs) have been recognized as a conventional way of insulating engine parts; while for the cases studied in this paper, the LHR concept is realized by altering engine coolant temperature (ECT). This paper presents engine simulation of a multi-cylinder, four-stroke, 1.9L diesel engine operating at 1500 rpm with five cases having different ECTs. The simulated results have been validated against experimental data. Calibration strategy for the engine simulation model is detailed in a systematic methodology for a better understanding of this simulation-development process. The calibrated model predicts the performance and fuel consumption within tolerated uncertainties. Simulated volumetric efficiency and residual gas fraction (RGF) are in agreement with the experimental data and empirical RGF prediction model, respectively. The results indicate that increasing ECT yields improved fuel conversion efficiency, which is likely due to decreased heat rejection to the coolant. The observed variation trend of the fuel conversion efficiency is generally consistent with the existing literature on LHR engines. Because of the technical difficulties in operating a conventional production engine at higher coolant temperatures (> 120°C), the validated model can be further applied to study operating events with expanded ECTs (albeit, in extrapolation). It is noted that results shown in this paper are demonstrated for low-load case to support continued development of combining LHR with low temperature combustion; a full-scale study of LHR concept needs to be further studied at higher engine loads.
Li, Tingting, Caton, Jerald, Jacobs, Timothy
Modeling and Optimization of Organic Rankine Cycle for Waste Heat Recovery in Automotive Engines2016-01-02074/5/2016
In the last years, the research effort of the automotive industry has been mainly focused on the reduction of CO2 and pollutants emissions. In this scenario, concepts such as the engines downsizing, stop/start systems as well as more costly full hybrid solutions and, more recently, Waste Heat Recovery technologies have been proposed. These latter include Thermo-Electric Generator (TEG), Organic Rankine Cycle (ORC) and Electric Turbo-Compound (ETC) that have been practically implemented on few heavy-duty applications but have not been proved yet as effective and affordable solutions for passenger cars. The paper deals with modeling of ORC power plant for simulation analyses aimed at evaluating the opportunities and challenges of its application for the waste heat recovery in a compact car, powered by a turbocharged SI engine. A grey-box modeling approach has been applied to simulate the ORC plant components (i.e. pump, heat exchangers, scroll expander); model identification and validation have been carried out against literature experimental data, showing good agreement with published results. The ORC plant model has been integrated into a dynamic vehicle-engine model to estimate the recovered electric energy as function of hot side (exhaust gas) and cold side (ambient air or coolant) temperature as well as exhaust gas mass flow. Several simulations have been carried out to explore different driving conditions (e.g. NEDC, WLTC) and optimization analyses have been performed on ORC operating conditions and components to maximize the output power and reduce the packing. Results show that significant improvement of fuel economy can be achieved by suitable ORC operation, with average CO2 savings up to 4% on standard driving cycles for the analyzed vehicle model.
Arsie, Ivan, Cricchio, Andrea, Pianese, Cesare, Ricciardi, Vincenzo, De Cesare, Matteo
High Efficiency Diesel Engine with Low Heat Loss Combustion Concept - Toyota’s Inline 4-Cylinder 2.8-Liter ESTEC 1GD-FTV Engine -2016-01-06584/5/2016
A highly efficient new 2.8-liter inline 4-cylinder diesel engine has been developed in response to growing demand for diesel engines and to help save energy while providing high-torque performance. Engine efficiency was improved by reducing cooling loss based on an innovative combustion concept applied across the whole engine. Cooling loss was reduced by restricting in-cylinder gas flows and improving combustion chamber insulation. To prevent the restricted gas flows from affecting emissions, a new combustion chamber shape was developed that increased air utilization in the cylinder through optimizing the in-cylinder fuel distribution. Combustion chamber insulation was improved by a new insulation coat that changes the wall surface temperature in accordance with the gas temperature. This reduces cooling loss and avoids the trade-off effect of intake air heating. To adopt this combustion concept while improving power/ performance, it was necessary to adjust the characteristics of the intake and exhaust ports to emphasize high flows. This was achieved by adopting new intake ports with separated functions, optimizing the diameter and layout of the intake valve, and increasing the overall efficiency of the intake/exhaust system. Since optimizing the ports shapes required greater design freedom, a new cylinder head gasket with high sealing performance was developed, and a 92 mm-diameter bore was adopted with only four head bolts. By adopting this combustion concept across the whole engine, and incorporating various friction reduction technologies, the new engine reduces CO2 emissions by approximately 15% compared to the previous model and achieves a maximum thermal efficiency of approximately 44%.
Kogo, Tomoyuki, Hamamura, Yoshihiko, Nakatani, Koichiro, Toda, Tadashi, Kawaguchi, Akio, Shoji, Akira
Inverted Brayton Cycle Employment for a Highly Downsized Turbocharged Gasoline Engine2015-01-19739/1/2015
The study presented in this paper aims to evaluate the performance of a new conceptual combined power system composed of a turbocharged engine and an inverted Brayton cycle (IBC). A validated 1D model of a downsized SI engine has been built in GT-power as the baseline model to quantify the performance improvement due to introducing the inverted Brayton cycle. The results show that a system performance improvement caused by adopting IBC is expected depended on the engine load, IBC turbomachinery efficiency and the bottoming expansion ratio. The maximum thermal efficiency of the combined system is achieved when both the wastegates of turbocharger and IBC turbines are closed, which is up to 6.15 percent point.
Chen, Zhihang, Copeland, Colin D.
Analysis of Engine Walls Thermal Insulation: Performance and Emissions2015-01-16604/14/2015
This paper presents an experimental analysis on the effect of thermal insulation of engine internal walls on the performance and emissions of a heavy-duty diesel engine. Some parts of the engine, like pistons, cylinder head and exhaust manifold were thermally insulated from gas contact side in order to reduce heat losses through the walls. Each component has been analyzed, independently, and in combination with others. The results have been compared with that of the original engine configuration. The analysis focuses on NOx and, smoke emissions along with brake specific fuel consumption. In order to take advantage of the engine insulation, an optimization of the air management and injection settings was finally performed, which provided the best combination for each engine configuration. The results showed that, on the one hand maintaining the same level of NOx, soot emissions is reduced using insulated cylinder head and insulated pistons, but these configurations increase the fuel consumption. On the other hand the specific fuel consumption is reduced using insulated exhaust manifolds, being this the only configuration that improves both NOx-Soot and NOx-BSFC tradeoff.
Serrano, Jose Ramon, Arnau, Francisco Jose, Martin, Jaime, Hernandez, Manuel, Lombard, Benoit
Explore and Extend the Effectiveness of Turbo-compounding in a 2.0 litres Gasoline Engine2015-01-12794/14/2015
After years of study and improvement, turbochargers in passenger cars now generally have very high efficiency. This is advantageous, but on the other hand, due to their high efficiency, only a small portion of the exhaust energy is needed for compressing the intake air, which means further utilization of waste heat is restricted. From this point of view, a turbo-compounding arrangement has significant advantage over a turbocharger in converting exhaust energy as it is immune to the upper power demand limit of the compressor. However, with the power turbine being located in series with the main turbine, power losses are incurred due to the higher back pressure which increases the pumping losses. This paper evaluates the effectiveness that the turbo-compounding arrangement has on a 2.0 litres gasoline engine and seeks to draw a conclusion on whether the produced power is sufficient to offset the increased pumping work. Furthermore, as mentioned above, the baseline engine model in this paper is not a heavy-duty diesel engine which is more appropriate to the turbo compounding mechanism for automotive application, but a small size gasoline engine. This paper also aims to explore a potential methodology for extending the operating range of the turbo compounding in light-duty petrol engine over its entire speed range under full load condition. The system models in this paper were built in GT-Power which is a one dimension (1-D) engine simulation code. Simulation results show that with the assistance of a variably driven supercharger, the output torque of the engine system is much larger (up to around 24%) at lower engine speeds. The fuel economy is also improved by up to about 8%.
Lu, Pengfei, Brace, Chris, Hu, Bo
Study of Effect of Coating of Piston on the Performance of a Diesel Engine2014-01-10214/1/2014
Insulation of pistons in engines is aimed at reducing the heat losses and thus increasing the indicated efficiency. Thermal barrier coatings (TBCs) were used to simulate adiabatic engines with the intention not only for reduced in-cylinder heat rejection and thermal fatigue protection of underlying metallic surfaces, but also for possible reduction of engine emissions. The application of TBCs reduces the heat transfer to the engine cooling jacket through the combustion chamber surfaces (which include the cylinder head, liner, and piston crown) and piston rings. The insulation of the combustion chamber with this coating, which is ceramic based, influences the combustion process and hence the performance and exhaust emissions characteristics of the engines. In the scenario of fast rising oil prices, insulation technologies are gaining importance as they help in saving fuel. A plasma sprayed thermal barrier coating was deposited on top of a piston for a Diesel engine and its effect on the engine performance is studied. It is found to increase thermal and mechanical efficiency.
Rupangudi, Suresh Kumar, Ramesh, C.S., Veerabhadhrappa, Kavadiki, V, Ram Rohit
Concept of “Temperature Swing Heat Insulation” in Combustion Chamber Walls, and Appropriate Thermo-Physical Properties for Heat Insulation Coat2013-01-02744/8/2013
The aim of this work is to investigate the possibility of heat insulation by “Temperature Swing”, that is temperature fluctuation, on combustion chamber walls coated with low-heat-conductivity and low-heat-capacity materials. Adiabatic engines studied in the 1980s, such as ceramic coated engines, caused constantly high temperature on combustion wall surface during the whole cycle including the intake stroke, even if it employed ceramic thermal barrier coating methods. This resulted in increase in NOx and Soot, decrease in volumetric efficiency and combustion efficiency, and facilitated the occurrence of engine knock. On the other hand, “Temperature Swing” coat on the combustion chamber walls leads to a large change in surface temperature. In this case, the surface temperature with this insulation coat follows the transient gas temperature, which decreases heat loss with the prevention of intake air heating, and also which is expected to prevent NOx and Soot from increasing. In our calculations, the increase of the surface temperature fluctuation, “Temperature Swing” results from the coat of lower heat conductivity and lower heat capacity. Particularly in Gasoline engines, the coat with the appropriate thickness can reduce the heat flux from the wall to the working gas during intake stroke and can avoid engine knock. Based on our calculations, it is clarified that both the prevention of intake air heating and the low heat rejection were successfully possible with the material of appropriate thermo-physical properties. In addition to the calculations, a preliminary test-piece experiment was executed. It was demonstrated that the surface temperature of a porous coat, that is a candidate of “Temperature Swing” coat, immediately follows the transient gas temperature, and also the proposed insulation coat can exactly reduce the heat flux in the single-cylinder engine.
Kosaka, Hidemasa, Wakisaka, Yoshifumi, Nomura, Yoshihiro, Hotta, Yoshihiro, Koike, Makoto, Nakakita, Kiyomi, Kawaguchi, Akio
Factors Affecting Heat Transfer in a Diesel Engine: Low Heat Rejection Engine Revisited2013-01-08754/8/2013
A large amount of the heat generated during the engine combustion process is lost to the coolant system through the surrounding metal parts. Therefore, there is a potential to improve the overall cycle efficiency by reducing the amount of heat transfer from the engine. In this paper, a Computational Fluid Dynamics (CFD) tool has been used to evaluate the effects of a number of design and operating variables on total heat loss from an engine to the coolant system. These parameters include injection characteristics and orientation, shape of the piston bowl, percentage of EGR and material property of the combustion chamber. Comprehensive analyses have been presented to show the efficient use of the heat retained in the combustion chamber and its contribution to improve thermal efficiency of the engine. Finally, changes in design and operating parameters have been suggested based on the analytical results to improve heat loss reduction from an engine.
Das, Sudhakar, Roberts, Charles E.
Development and Economic Analysis of a Two Stroke Compounded Engine Concept - the BETE-Max2013-01-02864/8/2013
Forthcoming transportation carbon dioxide and environment emission regulations favor solutions with the lowest cost of ownership in the open market. Light duty vehicles and especially those used in urban areas benefit the most from increasing electrification, but medium and heavy duty vehicles - including truck, marine, rail and aircraft - have high continuous power requirements that benefit little from electrification until energy storage costs drop significantly. This paper explores energy storage costs whose alternatives will be weighed against increasing payload fraction costs. A conceptual solution is presented that provides low cost of ownership: an engine that operates as a spark-ignited two stroke engine with compounding and light electrification. This engine (named BETE-Max) has a high thermal efficiency across its operating range and is able to meet tailpipe emissions standards with low aftertreatment costs using known technology.
Bucknell, John R.
Experimental Study of Energy Balance in Thermal Barrier Coated Diesel Engine2012-01-03894/16/2012
Energy conservation and efficiency have been the quest of engineers concerned with internal combustion engine. Approximately one-third of total fuel input energy is converted to useful work. Since the working gas in a practical engine cycle is not exhausted at ambient temperature, a major part of the energy is lost with the exhaust gases. In addition, another major part of energy input is rejected in the form of heat via the cooling system. Recently, much attention has been focused on achieving higher efficiency by reducing energy loss to coolant during the power stroke of the cycle. Thermal barrier coatings have a significant effect in the reduction of wear and abrasion failure in reciprocating and rotary engine for power generation and transportation. As operating temperature increases for improving Brake Thermal Efficiency, the wear and abrasion problem increases and becomes more challenging because lubrication in high temperature locations becomes increasingly problematic. In this study, the effect of insulated heat transfer surfaces on diesel engine energy balance system was investigated. The research engine was a four-stroke, twin cylinder vertical water cooled diesel engine. This engine was tested at different speeds and load conditions without coating. Then, combustion chamber surfaces, piston crown faces, valves, top surface of cylinder head and liners were coated with Partially Stabilized Zirconia (PSZ) attaining low heat rejection condition. Ceramic layers were made of ZrO2 and plasma coated onto base of the NiAl bond coat. The ceramic coated research engine was tested at the same operation conditions as the standard engine. The results indicate reduction in fuel consumption and heat loss to engine cooling system of the ceramic coated engine.
Modi, Ashish Jashvantlal
Modelling of the Warm-up of a Spark Ignition Engine: Application to Hybrid Vehicles2011-01-17478/30/2011
One of the main advantage of a hybrid thermal-electric vehicle is that the internal combustion engine (ICE) can be shut down when not needed anymore (Stop&Start system, propulsion with full-electric mode), thus reducing fuel consumption. But this use of the ICE impacts its thermal behavior because of a lack of heat source and thermal losses. Furthermore, the ICE is sometimes used with higher load in order to charge the batteries that increases the total heating power produced by the combustion. Therefore, the simulation of hybrid vehicles becomes really interesting to evaluate the effect of different control strategies (energy repartition between the engine and the electric motor) on the fuel consumption. However, in most of actual hybrid vehicles simulation tools, for calculation speed reasons, the thermal phenomena are either not taken into account, or their calculation is not based on physical equations (empirical formulas). Their predictive capability is then limited. The global aim of this study is the development of a simulation tool (using the Amesim® software) for hybrid electric vehicle which takes into account most of the thermal phenomena occurring in the various components and between them without increasing the calculation time. In this paper, we first focus on thermal phenomena occurring in the spark ignition ICE. The coupling of a combustion model with a thermal model of the engine cooling system and its metal parts allows a simulation of its warm-up after a cold start. The thermal transfers between the different thermal inertia are computed and their dependence with different parameters like speed or load is evaluated. Research about the heating speed of the cooling water and the lubricating oil (due to the viscous friction and dependent of the global thermal state of the ICE) are interesting in order to find the best use of the ICE and therefore reducing the fuel consumption. Finally, the model of the engine including the thermal transfers is integrated in a simulation of the whole vehicle. The thermal behavior of two vehicles (a conventional and a parallel hybrid electric) using the same spark ignition engine is finally presented. The first results show that the thermal phenomena have a significant impact on the final consumption of the vehicles.
Dubouil, R., Hetet, J. F., Maiboom, A.
CFD Investigation of Heat Transfer in a Diesel Engine with Diesel and PPC Combustion Modes2011-01-18388/30/2011
In this study, an investigation was made on a heavy duty diesel engine using both conventional diesel combustion mode and a partially premixed combustion (PPC) mode. A segment mesh was built up and modeled using the commercial CFD code AVL FIRE, where only the closed volume cycle, between IVC and EVO, was modeled. Both combustion modes were validated using experimental data, before a number of heat flux boundary conditions were applied. These conditions were used to evaluate the engine response in terms of engine performance and emission levels for the different percentage of heat rejection. The engine performance was measured in terms of specific fuel consumption and estimated power output, while the calculated net soot and accumulated NOx mass fractions were used for comparing the emission levels. The results showed improved efficiency for both combustion types, but only the PPC combustion mode managed that without increasing the production of NOx emissions severely.
Fridriksson, Helgi, Sunden, Bengt, Hajireza, Shahrokh, Tuner, Martin
High Efficiency Internal Combustion Stirling Engine Development2011-01-04104/12/2011
A unique engine, based on the regenerative principle, is being developed with the goal of achieving high brake efficiency over a wide power range. It can be characterized as an internal combustion Stirling engine (ICSE). The engine is a split-cycle configuration with a regenerator between the intake/compression cylinder and the power/exhaust cylinder. The regenerator acts as a counter-flow heat exchanger. During exhaust, the hot gases are cooled by the regenerator. The regenerator stores this heat. On the next cycle, compressed gases flow in the opposite direction and are heated by the regenerator. The gases coming from the regenerator into the power cylinder are very hot (~900°C), which provides the necessary gas temperature for auto-ignition of diesel and other fuels. A simplified Air Cycle analysis of the ICS engine is presented to validate the concept thermodynamics and to show the inherent difference between the ICS and conventional internal combustion engine (ICE) indicated efficiency. The ICE engine indicated efficiency increases with increasing compression ratio and is insensitive to peak temperatures, whereas in the ICS engine indicated efficiency increases with decreasing compression ratio and increasing peak temperature. This engine concept is a candidate for application of adiabatic engine technology which has been explored for many years. With materials that can withstand high temperatures, brake efficiencies of 60-70% are possible. Low heat transfer is important to the proper operation of the engine. A multi-step cycle computer indicated thermodynamic and fluid flow model of the ICS engine of increasing detail was used during the engine development. Finally, detailed perturbation studies were conducted to fully understand the ICS design sensitivities. An engine friction model was added to the computer model to be able to compare estimates of ICSE BSFC and BMEP with ICE engines. Important ICS engine innovations include elimination of throttling losses, low friction due to low compression ratio, and very high air cycle efficiencies (~80%) combined with low compression ratio. The engine is designed for the highest possible efficiencies. In addition to these advantages, the engine has nearly constant pressure combustion, which should help reduce NOx formation. The major findings were: the ICS engine is more efficient than either gasoline or diesel engines over the entire operating range especially at part power. At wide open throttle, an ICS engine is more efficient than either a gasoline or a diesel engine. This advantage increases at part power. On the negative side, the ICS engine has inherent low power density (volumetric efficiency) because of low compression ratio, late air intake and late combustion. A prototype engine and a modest engine test dynamometer and instrumentation are nearing completion to demonstrate the P&B Enterprises, Inc. (PBEI), ICSE concept. The prototype is a retrofitted two-cylinder diesel engine. The prototype uses the existing engine block, and the crankshaft and camshaft fit into existing spaces in the block. Anticipated problems to be addressed with the prototype engine are starting, combustion characteristics, regenerator temperature control and high turbocharging ratios to achieve reasonable power density.
Patton, Richard, Bennett, George
The Effect of Ceramic Thermal Barrier Combustion Chamber Coatings on the Performance and Efficiency of a Small Diesel Engine2010-32-00909/28/2010
This study considers the relatively high fuel consumption of small-displacement Diesel engines and seeks to improve it through thin ceramic thermal barrier coatings. A small displacement (219 cc) single-cylinder direct-injection production Diesel engine is utilized. A Ricardo WAVE simulation is developed and suggests that through simultaneous application of the coatings and reduction of compression ratio, the fuel consumption can be improved through a reduction in thermal losses. At the stock compression ratio, the application of thermal barrier coatings does not improve fuel consumption unless injection timing is carefully controlled. When injection timing is also adjusted, fuel consumption can be improved by up to 10%, particularly at low loads, with application of the thermal barrier coatings. The data show higher rates of energy release, higher peak pressures, leading to the lower fuel consumption. When coatings are combined with simultaneous reduction in compression ratio and injection timing adjustment, fuel consumption remained similar at low loads but increased at high loads due to delayed combustion phasing and increased exhaust sensible enthalpy loss. However, these data suggest that an engine with lower compression ratio could achieve similar fuel consumption with thermal barrier coatings, thus allowing a smaller and lighter engine to be utilized, which enhances mobility of these small diesel power plants.
Arment, Tyrell, Cowart, Jim, Caton, Pat, Hamilton, Leonard
Experimental Study on Thermal Barrier Coated Diesel Engine Performance with Blends of Diesel and Palm Biodiesel2010-01-15195/5/2010
Energy conservation and efficiency have been the quest of engineers concerned with internal combustion engine. Theoretically, if the heat rejected could be reduced, then the thermal efficiency would be improved, at least up to the limit set by the second law of thermodynamics. Low Heat Rejection engines aim to do this by reducing the heat lost to the coolant. For current work a ceramic coated twin cylinder water-cooled diesel engine using blends of diesel and palm biodiesel as the fuel was evaluated for its performance and exhaust emissions. In recent years, Considerable efforts were made to develop and introduce alternative renewable fuel, to replace conventional petroleum-base fuels. Here, the diesel engine was insulated by Partially Stabilized Zirconia (PSZ) as ceramic material attaining an adiabatic condition. The cycle average gas temperature and metal surface temperature are higher in adiabatic engine. For the present study the biodiesel was prepared in laboratory from non-edible vegetable oil (Palm oil) by transesterification process with methanol, where potassium hydroxide (KOH) was used as a catalyst. An experimental investigation of the performance of a ceramic coated engine was carried out with palm bio-diesels and its blends, the results were compared to the experiment done with the conventional petroleum diesel. Multi cylinder vertical water cooled self-governed diesel engine, piston, top surface of cylinder head and liners were fully coated with Partially Stabilized Zirconia (PSZ). Experimental test set-up was developed in laboratory. The stationary diesel engine was run in laboratory at a medium speed, variable load condition experienced in most urban driving conditions and various measurements like fuel flow, exhaust temperature, exhaust emission measurement and exhaust smoke test were carried out. The results indicate improved fuel economy and reduced pollution levels for the Thermal Barrier Coated (TBC) engine. The fuel properties of biodiesel such as kinematic viscosity, calorific value, flash point, carbon residue and specific gravity were found. Results indicated that Bio-diesels had lower brake thermal efficiency mainly due to its high viscosity compared to diesel. For biodiesel fuel, the exhaust gas temperature increased with increase in power and amount of biodiesel. However, during performance test it showed reasonable efficiencies, lower smoke, SO2, PM (particulate matter) and CO with some increase in emission of oxides of nitrogen. Biodiesel also increased efficiency in reducing particulate emissions. Regulated emissions and performance data were generated, and a detailed emission was performed. Fuel properties were close to the standard limit for diesel fuel. The use of palm biodiesel resulted in lower emissions of unburned hydrocarbons, carbon monoxide, and particulate matter, with some increase in emissions of oxides of nitrogen.
Modi, A. J., Gosai, D. C.
Potentiality for Optimizing Operational Performance and Thermal Management of Diesel Truck Engine Rankine Cycle by Recovering Heat in EGR Cooler2010-01-03154/12/2010
Further reduction of brake specific fuel consumption (bsfc) in heavy-duty diesel engines, which are used for vehicle applications, is of utmost importance due to high fuel prices, global warming issue (CO₂ emissions) and continuously stringent environmental regulations. Specifically, the necessity for further reduction of specific diesel oil consumption and increase of vehicle mileage, respectively, is more pronounced in large haul diesel trucks due to technical, environmental and economical reasons. Heavy-duty (HD) direction injection (DI) diesel engines are used in these vehicles, which indicate a rather high power output in the range of 200-400 kW. During recent years, various measures have been proposed from engine manufacturers and researchers for improving combustion process and through that, increasing the fuel economy of diesel engines. However, the implementation of all these measures showed that the brake specific consumption of HDDI diesel engines cannot be significantly reduced, unless new ideas or techniques are employed. A promising technique is the exhaust heat utilization from diesel truck engines for power production since approximately 30-40% of fuel supplied energy is rejected to the ambient. In the past, various attempts have been made to utilize exhaust heat from diesel engines using bottoming cycles. However, no serious long-term investigation has been conducted at that time since the fuel cost has not yet become an issue of primary concern. In addition, there is a lack of information concerning the potential ways of improving exhaust gas heat recovery from heavy-duty diesel engines. For this reason, a theoretical study is conducted herein using a newly developed simulation model to examine the potentiality of improving the overall efficiency of a heavy-duty truck diesel engine using a steam Rankine bottoming cycle. The diesel engine is equipped with an exhaust gas recirculation (EGR) system. Hence, rejected heat is also recovered from the exhaust gas stream when it flows through the EGR cooler. Specifically, heat rejected from EGR cooler is utilized to superheat and/or partially evaporate the working media of the bottoming cycle. A thermodynamic simulation model of the Rankine cycle has been developed for calculating the performance parameters of the bottoming cycle with and without EGR cooler. The proposed bottoming cycle model takes into account the effect of the pressure drop in the exhaust gas heat exchanger on the variation of engine back-pressure. Volume and weight constraints of exhaust gas and EGR heat exchangers are also taken into consideration by the thermodynamic model. A parametric study is performed using the developed model to examine the effects of varying high pressure of the steam Rankine cycle on the thermal performance parameters of the installation when either recovering or not heat from EGR cooler. Predictions were generated for several operational parameters of the heat recovery installation such as the relative bsfc improvement, the cycle power output and the steam temperature and mass flow rate at 1700 rpm engine speed and at various engine loads. The criteria for selecting the optimum high pressure value of the Rankine cycle are two-fold: The first is the maximization of cycle power output and the second is the minimization of the total amount of heat rejected to the ambient. The analysis of the preliminary results indicate that the steam Rankine cycle may operate efficiently at higher values of vaporization pressure reducing at the same time the heat rejected to the engine radiator due to EGR cooler heat recovery.
Katsanos, Christos, Hountalas, Dimitrios, Zannis, Theodoros, Yfantis, Elias
Experimental Assessment of Instantaneous Heat Transfer in the Combustion Chamber and Exhaust Manifold Walls of Air-Cooled Direct Injection Diesel Engine2008-01-13264/14/2008
An experimental analysis is carried out to investigate several heat transfer characteristics during the engine cycle, in the combustion chamber and exhaust manifold walls of a direct injection (DI), air-cooled, diesel engine. For this purpose, a novel experimental installation has been developed, which separates the engine transient temperature signals into two groups, namely the long-and the short- term response ones, processing the respective signals in two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object-oriented, control code for fast data acquisition have been designed and applied. Experimentally obtained cylinder pressure diagrams together with semi-empirical equations for instantaneous heat transfer were used as basis for the calculation of overall heat transfer coefficient. On the other hand, one-dimensional heat conduction theory with Fourier analysis techniques combined with an iterative procedure between calculated and measured temperature data are implemented, in order to calculate the instantaneous local engine cylinder heat transfer coefficients in the cylinder head surfaces. For the exhaust manifold, the local gas temperature was calculated based on a thermal-zone model approach developed. Analysis of experimental results revealed significant differences between the overall and local peak heat transfer coefficient values in the cylinder head surface. The effect of engine speed and load as well as the effect of air-swirling motion on cylinder head heat transfer coefficient variation are presented and quantified, revealing the significant influence of turbulence on local heat transfer conditions. The effect of valve motion on instantaneous heat transfer is also depicted and quantified. Analysis of the results for the instantaneous wall temperatures and heat transfer coefficient on the exhaust manifold reveals interesting details regarding the flow of exhaust gases, both in the blowdown and displacement phases of the engine exhaust stroke. From the results it is concluded that the instantaneous heat transfer coefficient variation for engine combustion chamber is highly non-uniform, unlike its values calculated from standard correlations that assume spatial uniformity. This is very important, since especially for air-cooled diesel engines limited relevant information seems to exist in the literature.
Mavropoulos, G. C., Rakopoulos, C. D., Hountalas, D. T.
Heat Release Comparison Between Optical and All-Metal HSDI Diesel Engines2008-01-10624/14/2008
Experiments are performed in optical engines in order to understand the combustion process in standard engines. In spite of this, little work has been done to verify that the results from optical engines are representative for a standard engine. The wall heat losses in optical engines are lower than in all-metal engines due to the lower heat conductivity of optical parts and a less efficient cooling system. Furthermore, optical engines often have larger crevice volumes due to a lower position of the piston rings. The present investigation studies how these differences affect the heat release and emissions in optical HSDI diesel engines. Five different engine configurations are studied: an optical engine of Bowditch design with two different squish heights, the same engine fitted with a metal piston, the same engine with all quartz parts replaced with metal components and, finally, a standard diesel engine. It is found that the use of optical parts affect the combustion process. The effects can be seen both in the heat release and in the exhaust emissions. They are explained by differences in heat conductivity between the wall materials of the engines investigated. It is shown that the differences can be compensated for by adjusting the inlet temperature.
Aronsson, Ulf, Chartier, Clement, Horn, Uwe, Andersson, Öivind, Johansson, Bengt, Egnell, Rolf
Study of Optical Parameters of Semitransparent Materials for Heat-Insulating Coatings of Combustion Chamber2007-24-00669/16/2007
A new approach to evaluate optical parameters of new semitransparent materials which can be used for heat-insulating coatings of combustion chamber (chamber ([[illegible]]) is discussed. Theoretical predictions and experimental estimations of the parameters are analyzed with particular attention to those of model samples based on granulated powder of the stabilized zirconium oxide (ZrO2 + 10% Y2O3). A setup is described designed to measure the reflection and transmission coefficients of the flat samples semitransparent materials. Possible applications of the semitransparent ceramic heat-insulating coatings in CC are outlined.
Merzlikin, V., Sidorov, O., Ojeda, M. Gutierrez, Amelenkov, A., Sutugin, V.
Recovering Energy from the Diesel Engine Exhaust Using Mechanical and Electrical Turbocompounding2007-01-15634/16/2007
Considering future emission legislation and the global thermal problem, two are the main issues that are of specific concern for the future of the diesel engine, specific gaseous pollutants and CO2 emissions. Both parameters are related to engine bsfc consumption directly or indirectly. The last is becoming even more important considering current fuel prices and the projection for the future indicating a trend for increasing fuel prices. The last decade significant improvement have been accomplished in the field of diesel engine efficiency that has resulted to considerable reduction of engine bsfc. It is obvious that despite improvements in diesel engine efficiency still a considerable amount of energy is rejected to the environment through the exhaust gas. Approximately 30-40% of the energy supplied by the fuel is rejected to the ambience. Therefore, it appears a possibility for further considerable increase of diesel engine efficiency with the utilization of exhaust gas energy and its conversion to mechanical energy. In this case, the following technological solutions exist: turbocompounding, bottoming cycles (i.e. Rankine with various working media) and use of thermoelectric generators. An attractive technological solution concerning applicability appears to be turbocompounding. In the present work, a thorough investigation is conducted using modeling to estimate the potential of energy recovery from the exhaust of a heavy-duty diesel engine using turbocompounding and its variation with engine operating conditions and exhaust manifold pressure. Two turbocompounding techniques are examined theoretically, mechanical and electrical turbocompounding. The produced results are evaluated comparing engine performance and especially bsfc with the one corresponding to normal diesel operation on the entire engine operating range i.e. speed and load. Results are derived concerning the effect of both technologies on exhaust manifold pressure and temperature that can be a problem especially for future downsized engines. Using the produced data, the two technological solutions are comparatively evaluated. Finally, indicative results are derived concerning the effect of each technology on specific engine out emissions.
Hountalas, D.T., Katsanos, C.O., Lamaris, V.T.
Study of the Transient Operation of Low Heat Rejection Turbocharged Diesel Engine Including Wall Temperature Oscillations2007-01-10914/16/2007
During the last decades, a vivid interest in the low heat rejection (LHR) diesel engine has arisen. In a LHR engine, an increased level of temperatures inside the cylinder is achieved resulting from the insulation applied to the combustion chamber walls. The steady-state LHR engine operation has been studied so far by applying either first- or second-law balances. However, very few works have treated this subject during the very important transient operation, with the results limited to the engine speed response. For this purpose, an experimentally validated simulation code of the thermodynamic cycle of the engine during transient conditions is applied. This takes into account the transient operation of the fuel pump, the development of friction torque using a detailed per degree crank angle sub-model, while the equations for each cylinder are solved individually and sequentially. In this work, two common insulators of various thicknesses are considered for the engine in hand, viz. silicon nitride and plasma spray zirconia. The transient response of various engine (e.g. speed, volumetric efficiency, fuel pump rack position, brake mean effective pressure and specific fuel consumption) and turbocharger variables is depicted and analyzed, with the results compared to the non-insulated transient and the insulated steady-state operation. For a more in-depth analysis of transient engine heat transfer, the interesting phenomenon of the short-term temperature (cyclic) oscillations in the combustion chamber walls during transients needs to be studied. To this aim, the thermodynamic model of the engine is appropriately coupled to a wall periodic heat conduction model, which uses the gas temperature variation as boundary condition throughout the engine cycle after being treated by Fourier analysis techniques. The evolution of many variables during the transient engine cycles, such as the amplitude of oscillation or gradient of temperature swing is thus illustrated. Moreover, the simulation code is expanded in a way to include the second-law balance, as this may prove an interesting alternative to the first-law analysis. It is revealed that after a ramp increase in load, the second-law values unlike the first-law ones are heavily impacted by the insulation scheme applied. Combustion and total engine irreversibilities decrease significantly (up to 24% for the cases examined) with increasing insulation. Unfortunately, this decrease is not transformed into an increase in piston work but rather increases the potential for extra work recovery owing to the higher availability content of the exhaust gas.
Rakopoulos, Constantine D., Giakoumis, Evangelos G.
New Selectively Absorbing and Scattering Heat-Insulating Coatings of the Combustion Chamber for Low-Heat-Rejection Diesel2007-01-17554/16/2007
This work is about heat-insulating coatings (HIC) used for combustion chambers (CC) of Low-Heat-Rejection Diesel Engines. These semitransparent coatings provide the necessary thermal regime to boundary walls and elements of CC, generation make up 50% of the radiant heat flow component. For this purpose model samples of porous ceramic materials based on powders of zirconium, silicon, aluminum oxides were offered as selectively absorbing and scattering coatings. These materials have transparent bands within the range of radiation wavelengths of an ignited gas mixture in CC of high-speed diesel engines. Simulation results show that there is a subsurface temperature maximum for ceramics under intensive visible and short-range infrared radiation. Internal CC walls do not achieve these extreme temperatures using these coatings. This allows us to provide an optimum temperature mode for CC which limits formation of toxic nitrogen oxides and increases the engine efficiency.
Merzlikin, V., Timonin, V., Ojeda, M. Gutierrez, Sidorov, O.
Diesel Engine Cylinder Bore Coating for Extreme Operating Conditions2007-01-14394/16/2007
Adiabatics, Inc., with the support of the U.S. Army Tank Automotive Research & Development Engineering Center (TARDEC) has developed a low cost, durable ceramic composite cylinder bore coating for diesel engines operating under severe conditions. This bore coating is a ceramic composite consisting primarily of Iron Oxide, Iron Titanate and Partially Stabilized Zirconia. It is applied by unique chemical thermal bonding technology developed at Adiabatics, Inc. and is referred to as Low Temperature Iron Titanate (LTIT). This coating has been tested against a wide range of cylinder bore treatments ranging from hard chrome plate to hard Nickel Silicon Carbide (NikaSil) and found to provide a superior sliding wear surface. It is superior because it is compatible against most common piston ring materials and coatings. As compared to other liner treatments, it displays superior running in or break in performance of the ring against the cylinder liner and yields significantly better wear rates under high wear extreme loading engine operating conditions. These conditions include top ring reversal temperatures exceeding 700°F and 320 psi bmep over the entire range of engine speed and loads. Current work is being performed to bring this cylinder liner coating to the commercial marketplace.
Kamo, Lloyd, Saad, Philipe, Saad, Dorsaf, Bryzik, Walter, Mekari, Milad H.
Simulation and Experimental Studies on Combustion and Performance Characteristics for a Turbocharged and Naturally Aspirated Multi-Cylinder Compression Ignition Engine2006-01-348710/31/2006
The paper discusses the potential of a conventional light duty indirect injection diesel engine for operation under naturally aspirated and turbocharged conditions. An exhaust gas New Garret air turbocharger with waste-gate control was used for the present investigations. The results of an extensive experimental programme using an 2.4 liter in-line four-cylinder engine are presented to predict the pressure crank angle diagram, brake power output, brake specific energy consumption, delay period, rate of pressure rise, volumetric efficiency, peak cylinder pressure, exhaust gas temperature and coefficient of variation. The paper also presents some numerical results and a comparison between computed and experimental pressure crank angle diagram for turbocharged diesel engine. The overall analysis of the results shows a 17 percent increase in power output, 12 percent increase in volumetric efficiency and 20 percent improvement in brake specific energy consumption compared to base line engine.
Ahmad, Nafis, Gajendra Babu, M. K.
Numerical Modeling of Charge Stratification for the Combustion Control of HCCI Engines2005-01-372210/24/2005
Numerical modeling is used to estimate the realizable potential of combustion control and burn duration extension in homogeneous charge compression ignition (HCCI) engines using in-cylinder charge stratification. Parametric analyses of several fuels using a range of operating conditions illustrate the potential physical variables have on ignition timing and burn duration. The detailed stratification model utilizes a one-dimensional CFD gas dynamics representation of radial gas motion in an engine cylinder with time-varying chamber volume and detailed combustion chemistry of n-pentane fuel. This approach provides the ability to incorporate the effects of in-cylinder temperature and species concentration non-uniformities while remaining sufficiently tractable to include a detailed kinetic model of combustion chemistry. A parametric set of conditions was studied to determine the effect of stratified temperature, equivalence ratio, and EGR on the ignition timing and burn duration of a representative HCCI engine. The assumption of adiabatic engine operation was made to assess the potential of combustion control mechanisms separate from heat transfer effects. The results demonstrate that moderate and potentially achievable amounts of in-cylinder charge stratification result in extended heat release durations relative to homogeneous conditions. The use of combined temperature, equivalence ratio, and EGR variation in a conceptionally achievable configuration is shown to provide the largest benefit. A series of path forward research directions are also discussed.
Grenda, Jeffrey M.
On the Potential of Low Heat Rejection DI Diesel Engines to Reduce Tail-Pipe Emissions2005-01-09204/11/2005
Heat transfer to the combustion chamber walls constitutes a significant portion of the overall energy losses over the working cycle of a direct injection (DI) diesel engine. In the last few decades, numerous research efforts have been devoted to investigating the prospects of boosting efficiency by insulating the combustion chamber. Relatively few studies have focused on the prospects of reducing emissions by applying combustion chamber insulation. A main purpose of this study is to assess the potential of reducing in-cylinder soot as well as boosting aftertreatment performance by means of partially insulating the combustion chamber. Based on the findings from a conceptual study, a Low Heat Rejection (LHR) design, featuring a Nimonic 80A insert into an Aluminum piston, was developed and tested experimentally at various loads in a single-cylinder Hatz-engine. The piston wall temperature, which was measured using an infrared pyrometer technique, was approximately 250 K higher using the Nimonic-insert compared with the conventional aluminum piston. For various EGR levels combustion in the tested low heat rejection engine was characterized by a shorter ignition delay followed by a prolonged diffusion burn. Replacing the conventional piston with the low heat rejection one, IMEP was slightly improved, emissions of CO and NOx were generally reduced, whereas the trend for soot and hydrocarbons was found to be more complex. In order to realize the full potential of the developed Low Heat Rejection concept, a re-optimization of the combustion system has to be undertaken.
Hergart, Carl-Anders, Louki, Abdelilah, Peters, Norbert
Innovative Engine Cooling Systems Comparison2005-01-13784/11/2005
In order firstly to reduce weight, packaging and cost of engine cooling system and secondly to reduce fuel consumption and pollutants in the exhaust we have seen, over the last twenty years, several innovative engine cooling system offers. These innovative engines cooling were: Nucleate boiling engine cooling, THEMIS™ cooling system, Precision cooling system, Intelligent cooling System, …, CoolMaster™ UltimateCooling™ For each cooling system several vehicles were tested in the climatic wind tunnel, on road in real conditions and on fuel consumption and pollution facilities. The comparison of these innovative engine cooling systems will be presented in this paper, in terms of: System weight, packaging and cost, Fuel consumption and pollutants in the exhaust, Thermal comfort, Heat performance of engine cooling system.
Ap, Ngy-Srun, Tarquis, Michelle
Predictions of Diesel Engine's Performance by the DESP Program with the Combustion Chamber Coated with Metals or Ceramics2004-01-269710/26/2004
In the past decades, the diesel engines are considered as the major power source, not only because of their high thermal efficiency, high torque output, and easy maintenance; but also due to the improved exhaust emissions reduction technology. In order to increase the thermal efficiency, the low heat rejection ceramic coating engine is one of the possible solutions for future engine manufacturing. Due to the thermal insulating effects of the ceramic material (low thermal conductivity), the cylinder charge and engine components' temperatures are substantially increased. However, the thermal impact problem and the possible high friction characteristics of the new coating material can be deadly to the engine's lifetime. Various non-ceramic and ceramic materials are tested in this research to decide their thermal insulating effects on the engine performance and their downside on the friction and thermal impact problems. The characteristics of the cylinder charge pressure against the crank angle is very important for analyzing the engine combustion pattern. The heat release calculated according to the pressure profile (differentiated by time) can tell us in details what actually happen within the combustion chamber. Thus, a good methodology to predict the cylinder charge pressure is essential in this study. The DESP (Diesel Engine Simulation) program is thus used in this research to study the effects of thermal insulation effects by coating the cylinder liner and piston surface with a thin non-ceramic (Nickel or Chrome) material or a thin ceramic (ZrO2 or Al2O3+TiO2) material. The comparisons between the non-ceramic and ceramic coatings on the engine performance are also conducted under various engine speeds and loads. The equivalence ratio (ϕ) is used in this study instead of engine load.
Shih, Leonard Kuo-Liang, Hsu, Tien-Chou
A Wall-Modified Flamelet Model for Diesel Combustion2004-01-01033/8/2004
In this paper, a wall-modified interactive flamelet model is developed for improving the modeling of Diesel combustion. The objective is to include the effects of wall heat loss on the transient flame structure. The essential idea is to compute several flamelets with several representative enthalpy defects which account for wall heat loss. Then, the averaged flamelet profile can be obtained through a linear fit between the flamelets according to the enthalpy defect of the local gas which results from the wall heat loss. The enthalpy defect is estimated as the difference between the enthalpy in a flamelet without wall heat loss, which would correspond to the enthalpy in the gas without wall heat loss, and the gas with wall heat loss. The improved model is applied to model combustion in a Diesel engine. In the application, two flamelets, one without wall heat loss and one with wall heat loss, are considered. Results are shown from computations for the cases without heat loss and with wall heat loss in the flamelet. Effects of spray angle on engine emissions are investigated. The computed emissions from the engine for different spray angles are compared to measurements. It is shown that the wall-modified interactive flamelet model is able to reproduce the trends more accurately.
Song, Lijun, Abraham, John
The Status of Experimental Investigations on Low Heat Rejection Engines2004-01-14533/8/2004
Energy conservation and emissions have become of increasing concern over the past few decades. As automobiles are one of the major sources of energy consumption and urban emissions, engineers concerned are under significant pressure to improve their energy efficiency and reduce exhaust emission levels. While tremendous effort has been devoted in improving performance and reducing emissions of current engines, new technologies are also getting attention. One example is the Low Heat Rejection Engine (LHRE). A technological thrust is currently in progress to develop insulated, low heat rejection engines which exhibit higher thermal efficiency and improved exhaust emissions. The low heat rejection engine concept is not new. For the past two decades many have conducted experiments on low heat rejection engines. Although promising, the results of the experimental investigations have been somewhat mixed. Many have shown that insulation reduces heat transfer but none have shown substantial gains in efficiency, performance and emissions. Some investigators even concluded that insulation increases heat transfer and degrades the performance of the engine. This paper presents a general overview about the previous experimental research efforts into low heat rejection engine concept. This paper explains in detail the engine used, test conditions and constraints, insulation materials used, degree of insulation and results obtained by different researchers in their experimental investigation. The factors that affect thermal efficiency, other performance parameters and exhaust emissions were deduced and their influences discussed.
Jaichandar, S., Tamilporai, P.
Alternative Cars in the 21st Century, Second EditionR-22710/17/2003
The rapidly changing landscape of alternative car technologies created the need for the second edition of Alternative Cars in the 21st Century: A New Personal Transportation Paradigm. This essential publication provides an abundance of critical knowledge for engineering professionals and consumers alike, offering a brighter alternative future through better alternative cars.
Riley, Robert Q.
Development of an Adiabatic Engine Installed Energy Recover Turbines and Converters of CNG Fuel2003-01-22656/23/2003
In order to improve the fuel consumption and control exhaust emissions in a heat insulation engine, fuels reformed CH4 by CO2 and steam were used. Porous metal plate coated Li2ZrO3 was used to make CO2 separate from the exhaust gas of the engine. CH4 and CO2 gas are supplied to the catalytic converter and reformed CO and H2gas increased to 30% on kinetic energy are supplied to the engine as well as gas and steam turbine is installed to recover the exhaust gas energy. As the result the thermal efficiency of the engine systems will be improved to about 57.5% compared with 42% of conventional diesel engine.
Kawamura, Hideo, Akama, Mitsuru
A Parametric Study of HCCI Combustion - the Sources of Emissions at Low Loads and the Effects of GDI Fuel Injection2003-01-07523/3/2003
A combined experimental and modeling study has been conducted to investigate the sources of CO and HC emissions (and the associated combustion inefficiencies) at low-loads. Engine performance and emissions were evaluated as fueling was reduced from knocking conditions to very low loads (ϕ = 0.28 - 0.04) for a variety of operating conditions, including: various intake temperatures, engine speeds, compression ratios, and a comparison of fully premixed and GDI (gasoline-type direct injection) fueling. The experiments were conducted in a single-cylinder engine (0.98 liters) using iso-octane as the fuel. Comparative computations were made using a single-zone model with the full chemistry mechanisms for iso-octane, to determine the expected behavior of the bulk-gases for the limiting case of no heat transfer, crevices, or charge inhomogeneities. Experimental results show that as fueling is reduced to equivalence ratios (ϕ) below 0.20, CO emissions begin to increase substantially, reaching levels corresponding to more than 60% of all fuel carbon at idle loads (ϕ = 0.1 - 0.12). As this occurs, combustion efficiency falls from 94% to less than 55%. These high CO levels are in very good agreement with those predicted by the model, indicating that the high CO emissions and the associated combustion inefficiencies are due to incomplete bulk-gas reactions. HC emissions also rise, but the increase does not become pronounced until ϕ < 0.14. In addition, the model indicates that significant emissions of oxygenated hydrocarbons (e.g., formaldehyde) should occur as bulk-gas reactions become less complete. This prediction is supported by the experimental exhaust carbon balance. Intake temperature significantly affects the onset of incomplete bulk-gas combustion; however, engine speed and compression ratio have only small effects for the fuel studied here. Fuel stratification by late GDI injection was investigated and found to have good potential for improving combustion efficiency at low loads.
Dec, John E., Sjöberg, Magnus
Low Heat Rejection Engines – An Overview2003-01-04053/3/2003
This paper presents a general overview about the previous research efforts into Low Heat Rejection Engine (LHRE) concept. The purpose of this paper is to explain the effect of insulation on engine performance, heat transfer characteristics, combustion and emission characteristics. Many researchers have carried out a large number of studies on LHRE concept. Some of them are experimental work and many are theoretical studies. In the case of LHR engines almost all theoretical studies predict improved performance but many experimental studies show different picture. This paper analyzes the reason for this deviation. The operating conditions, under which the experimental and simulation studies are carried out, have been clearly discussed. The factors, which affect thermal efficiency, combustion, and exhaust emissions in LHR engine, are deduced and their influences discussed. Effect of fuel injection characteristics on LHR engine performance is also reviewed. It is concluded that much more research is needed to overcome the practical problems before LHR engines can be put into production.
Jaichandar, S., Tamilporai, P.
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