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Technical Paper

Adiabatic Engine Trends-Worldwide

Since the early inception of the adiabatic diesel engine in 1974, marked progress has taken place as a result of research efforts performed all over the world. The use of ceramics for heat engines in production applications has been limited to date, but is growing. Ceramic use for production heat engine has included: combustion prechambers, turbochargers, exhaust port liners, top piston ring inserts, glow plugs, oxygen sensors; and additional high temperature friction and wear components. The potential advantages of an adiabatic engine vary greatly with specific application (i.e., commercial vs. military, stationary vs. vehicular, etc.), and thus, a better understanding of the strengths and weaknesses (and associated risks) of advanced adiabatic concepts with respect to materials, tribology, cost, and payoff must be obtained.
Technical Paper

Advancements in High Temperature Cylinder Liner and Piston Ring Tribology

The high temperature tribology issue for uncooled Low Heat Rejection (LHR) diesel engines where the cylinder liner piston ring interface exceeds temperatures of 225°C to 250°C has existed for decades. It is a problem that has persistently prohibited advances in non-watercooled LHR engine development. Though the problem is not specific to non-watercooled LHR diesel engines, it is the topic of this research study for the past two and one half years. In the late 1970s and throughout the 1980s, a tremendous amount of research had been placed upon the development of the LHR diesel engine. LHR engine finite element design and cycle simulation models had been generated. Many of these projected the cylinder liner piston ring top ring reversal (TRR) temperature to exceed 540°C[1]. In order for the LHR diesel to succeed, a tribological solution for these high TRR temperatures had to be developed.
Technical Paper

Analysis and Test of Insulated Components for Rotary Engine

The two newest internal combustion engine technologies which have demonstrated the most promise in the last 25 years are the direct-injection stratified-charge (DISC) rotary engine [1] and the adiabatic diesel engine [2]. The (DISC) engine is particularly attractive for aviation applications [3] because of its light weight, multi-fuel capability and potential for low fuel consumption. However, one disadvantage with the DISC engine is the weight and size of the liquid cooling system. NASA Lewis Research Center has supported a technology enablement program to advance the DISC rotary engine for general aviation applications and recognizes the importance of improvement in fuel consumption and reductions in the coolant system weight [4].
Technical Paper

Assessment of Thin Thermal Barrier Coatings for I.C. Engines

This paper investigates theoretically the effects of heat transfer characteristics, such as crank-angle phasing and wall temperature swings, on the thermodynamic efficiency of an IC engine. The objective is to illustrate the fundamental physical basis of applying thin thermal barrier coatings to improve the performance of military and commercial IC engines. A simple model illustrates how the thermal impedance and thickness of coatings can be manipulated to control heat transfer and limit the high temperatures in engine components. A friction model is also included to estimate the overall improvement in engine efficiency by the proper selection of coating thickness and material.
Technical Paper

Ceramic Coating for Aluminum Engine and Components

The trend toward lighter vehicles for improved performance has recently introduced the use of aluminum and plastic materials for vehicle bodies and drive trains. In particular, the aluminum alloy block foar engine application is certain to reappear. The soft aluminum cylinder liner will require additional treatment before acceptance. Three possible approaches appear to solve the aluminum cylinder liner dilemma. These approaches are: 1) use of high silicon aluminum such as the 390 aluminum; 2) insert or cast steel liners into the aluminum engine block; and 3) ceramic coat the low cost standard aluminum engine block. Each has known advantages and disadvantages. It is the purpose of this paper to present the merits of option 3, the ceramic coated aluminum cylinder bore, from the standpoint of low weight, cost, and tribological effectiveness. The advantages of approaches 1) and 2) are obvious. High temperature after treatment of the ceramic engine components is not required.
Technical Paper

Ceramic Coatings for Aluminum Engine Blocks

The trend toward lighter vehicles for improved performance has recently introduced the use of aluminum and plastic materials for vehicle bodies and drive trains. In particular, the aluminum alloy block for engine application is certain to reappear. The soft aluminum cylinder liner will require additional treatment before acceptance. Three possible approaches appear to solve the aluminum cylinder liner dilemma. These approaches are: 1. Use of high silicon aluminum such as the 390 aluminum. 2. Insert or cast steel liners into the aluminum engine block. 3. Ceramic coat the low cost standard aluminum engine block. Each has known advantages and disadvantages. It is the purpose of this paper to present the merits of Option 3, the ceramic coated aluminum cylinder bore from the standpoint of low weight, cost, and tribological effectiveness. The advantages of approaches (1) and (2) are obvious. High temperature after treatment of the ceramic engine components is not required.
Technical Paper

Coatings for Improving Engine Performance

Thermal barrier coatings are becoming increasingly important in providing thermal insulation for heat engine components. Thermal insulation reduces in-cylinder heat transfer from the engine combustion chamber as well as reducing component structural temperatures. Containment of heat also contributes to increased in-cylinder work and offers higher exhaust temperatures for energy recovery. Lower component structural temperatures will result in greater durability. Advanced ceramic composite coatings also offer the unique properties that can provide reductions in friction and wear. Test results and analysis to evaluate the performance benefits of thin thermal barrier coated components in a single cylinder diesel engine are presented.
Technical Paper

Cummins–TARADCOM Adiabatic Turbocompound Engine Program

This paper describes the progress on the Cummins-TARADCOM adiabatic turbocompound diesel engine development program. An adiabatic diesel engine system adaptable to the use of high performance ceramics which hopefully will enable higher operating temperatures, reduced heat loss, and turbo-charged exhaust energy recovery is presented. The engine operating environments as well as the thermal and mechanical loadings of the critical engine components are covered. Design criteria are presented and techniques leading to its fulfillment are shown. The present shortcomings of the high performance ceramic design in terms of meeting reliability and insulation targets are discussed, and the needs for composite designs are shown. A ceramic design methodology for an insulated engine component is described and some of the test results are shown. Other possible future improvements such as the minimum friction-unlubricated engine through the use of ceramics are also described.
Technical Paper

Emissions Comparisons of an Insulated Turbocharged Multi-Cylinder Miller Cycle Diesel Engine

The experimental emissions testing of a turbocharged six cylinder Caterpillar 3116 diesel engine converted to the Miller cycle operation was conducted. Delayed intake valve closing times were also investigated. Effects of intake valve closing time, injection time, and insulation of piston, head, and liner on the emission characteristics of the Miller cycle engine were experimentally verified. Superior performance and emission characteristic was achieved with a LHR insulated engine. Therefore, all emission and performance comparisons are made with LHR insulated standard engine with LHR insulated Miller cycle engine. Particularly, NOx, CO2, HC, smoke and BSFC data are obtained for comparison. Effect of increasing the intake boost pressure on emission was also studied. Poor emission characteristics of the Miller cycle engine are shown to improve with increased boost pressure. Performance of the insulated Miller cycle engine shows improvement in BSFC when compared to the base engine.
Technical Paper

Exhaust Characteristics of the Automotive Diesel

The production of pollutants and an increasing need for pollution management are an inevitable concomitant of a society with a high standard of living. The automotive diesel engine is used more than any other type of engine for transporting freight over highways. Two kinds of pollution to be considered with regard to the diesel engine are the dark exhaust smoke and odor, of which the public is quite cognizant, and the less obvious but possibly toxic carbon monoxide, oxides of nitrogen, unburned hydrocarbons, and trace compounds of other toxic materials. This paper discusses sampling, measurement techniques, and established standards for exhaust smoke and odor. Examination of diesel exhaust shows it to be less offensive in terms of harmful effects than the invisible exhaust from other types of engines. The major problem is exhaust color and odor.
Technical Paper

High Pressure Fuel Injection for High Power Density Diesel Engines

High-pressure fuel injection combustion is being applied as an approach to increase the power density of diesel engines. The high-pressure injection enables higher air utilization and thus improved smoke free low air-fuel ratio combustion is obtained. It also greatly increases the injection rate and reduces combustion duration that permits timing retard for lower peak cylinder pressure and improved emissions without a loss in fuel consumption. Optimization of these injection parameters offers increased power density opportunities. The lower air-fuel ratio is also conducive to simpler air-handling and lower pressure ratio turbocharger requirements. This paper includes laboratory data demonstrating a 26 percent increase in power density by optimizing these parameters with injection pressures to 200 mPa.
Technical Paper

Improving the Fuel Economy of Insulated Engine by Matching the Fuel System

This paper deals with the analysis of heat release characteristics of an insulated turbocharged, six cylinder, DI contemporary diesel engine. The engine is fully insulated with thin thermal barrier coatings. Effect of insulation on the heat release was experimentally verified. Tests were carried over a range of engine speeds at 100%, 93%, 75% and 50% of rated torque. Fuel injection system was instrumented to obtain injection pressure characteristics. The study shows that rate of heat release, particularly in the major portion of the combustion, is higher for the insulated engine. Improvement in heat release and performance are primarily attributed to reduction in heat transfer loss due to the thin thermal barrier coating. Injection pressure at the rated speed and torque was found to be 138 MPa and there was no degradation of combustion process in the insulated engine. Improvements in BSFC at 93% load are 3.25% and 6% at 1600 and 2600 RPM, respectively.
Technical Paper

Injection Characteristics that Improve Performance of Ceramic Coated Diesel Engines

Thin thermal barrier ceramic coatings were applied to a standard production direct injection diesel engine. The resultant fuel economy when compared to the standard metallic engine at full load and speed (2600) was 6% better and 3.5% better at 1600 RPM. Most coated diesel engines todate have not shown significant fuel economy one way or the other. Why are the results more positive in this particular case? The reasons were late injection timing, high injection pressure with high injection rates to provide superior heat release rates with resultant lower fuel consumption. The recent introduction of the high injection pressure fuel injection system makes it possible to have these desirable heat release rates at the premixed combustion period. Of course the same injection characteristics were applied to the standard and the thin thermal barrier coating case. The thin thermal barrier coated engine displayed superior heat release rate.
Technical Paper

Insulated Miller Cycle Diesel Engine

This paper investigates theoretically the benefits of the Miller cycle diesel engine with and without low heat rejection on thermodynamic efficiency, brake power, and fuel consumption. It further illustrates the effectiveness of thin thermal barrier coatings to improve the performance of military and commercial IC engines. A simple model which includes a friction model is used to estimate the overall improvement in engine performance. Miller cycle is accomplished by closing the intake valve late and the engine components are coated with PSZ for low heat rejection. A significant improvement in brake power and thermal efficiency are observed.
Technical Paper

Low Heat Rejection From High Output Ceramic Coated Diesel Engine and Its Impact on Future Design

A high output experimental single cylinder diesel engine that was fully coated and insulated with a ceramic slurry coated combustion chamber was tested at full load and full speed. The cylinder liner and cylinder head mere constructed of 410 Series stainless steel and the top half of the articulated piston and the cylinder head top deck plate were made of titanium. The cylinder liner, head plate and the piston crown were coated with ceramic slurry coating. An adiabaticity of 35 percent was predicted for the insulated engine. The top ring reversal area on the cylinder liner was oil cooled. In spite of the high boost pressure ratio of 4:1, the pressure charged air was not aftercooled. No deterioration in engine volumetric efficiency was noted. At full load (260 psi BMEP) and 2600 rpm, the coolant heat rejection rate of 12 btu/hp.min. was achieved. The original engine build had coolant heat rejection of 18.3 btu/hp-min and exhaust energy heat rejection of 42.3 btu/hp-min at full load.
Technical Paper

Lubrication of Ceramics in Ring/Cylinder Applications

In support of efforts to apply ceramics to advanced heat engines, a study was performed of the wear mechanisms of ceramics at the ring/cylinder interface. A laboratory apparatus was constructed to reproduce most of the conditions of an actual engine, but used easily prepared ring and cylinder specimens to facilitate their fabrication. Plasma-sprayed coatings of Cr2O3 and hypersonic flame-sprayed coatings of cobalt-bonded WC performed particularly well as ring coatings. Similar performance was obtained with these coatings operating against SiC, Si3N4, SiC whisker-reinforced Al2O3, and Cr2O3 coatings. The study demonstrated the critical need for lubrication and evaluated the performance of two available lubricants. SIGNIFICANT EFFICIENCY IMPROVEMENTS have been predicted resulting from the practical application of low-heat-rejection engines (1,2).
Technical Paper

Nato Durability Test of an Adiabatic Truck Engine

A previous paper (1)* described the performance improvements which can be obtained by using an “adiabatic” (uncooled) engine for military trucks. The fuel economy improved 16% to 37% (depending upon the duty cycle) and was documented by dynamometer testing and vehicle testing and affirmed by vehicle simulation. The purpose of this paper is to document a NATO cycle 400 hour durability test which was performed on the same model adiabatic engine. The test results showed that the engine has excellent durability, low lubricating oil consumption and minimal deposits.
Technical Paper

Performance Assessment of US. Army Truck with Adiabatic Diesel Engine

An investigation into the fuel economy of a U.S. Army M813 5-ton truck with an “adiabatic” (uncooled) 14 liter (855 in3) diesel engine was made with three different driving schedules. The results were used to verify a newly written vehicle simulation. This simulation was used to compare the fuel economy of an uncooled turbocharged engine, a water cooled turbocharged engine, and a water cooled naturally aspirated engine in the same vehicle. Results indicate that, depending on the duty cycle a 16% to 37% improvement in fuel economy (depending on the duty cycle) can be achieved with an uncooled engine in this vehicle.
Technical Paper

Performance of Thin Thermal Barrier Coating on Small Aluminum Block Diesel Engine

The cylinder of the aluminum engine block without iron sleeve was coated directly with thin thermal barrier coatings of zirconia and chrome oxide. The cylinder head and valve face and the piston crown were also coated. These three engine components were tested individually and together. The fuel consumption performance of this 84 x 70 mm direct injection diesel engine improved 10% with only coated cylinder bore. When the fuel injection timing of the coated cylinder bore engine was retarded by about 2°CA, emissions characteristics were approximately the same level as for the baseline engine with 8% improvement in brake specific fuel consumption compared with the baseline engine. At constant fuel flow rate to the engine, the exhaust and cylinder head temperatures were higher for the insulated bore case. One can summarize the combustion temperature must have been higher and heat release rates were faster in the insulated case.
Technical Paper

Solid Lubrication Studies for Adiabatic Diesel Engines

A new self lubricating material has been assessed in a laboratory rig simulating high temperature piston rings for adiabatic diesel engines. The material consists of a solid metallic surface containing half millimetre diameter pockets filled with solid lubricant. The friction and wear properties of conventional piston ring surfaces were assessed at 380°C versus a chromium oxide counterface. This was followed by a study of the properties of various solid lubricant formulations which were then evaluated as fillers for surface pockets. The most promising solid lubricated materials contained molybdenum disulphide or lithium fluoride plus copper.