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Technical Paper

Thermal Barrier Coatings for High Output Turbocharged Diesel Engine

2007-04-16
2007-01-1442
Thermal barrier coatings (TBC) are perceived as enabling technology to increase low heat rejection (LHR) diesel engine performance and improve its longevity. The state of the art of thermal barrier coating is the plasma spray zirconia. In addition, other material systems have been investigated for the next generation of thermal barrier coatings. The purpose of this TBC program is to focus on developing binder systems with low thermal conductivity materials to improve the coating durability under high load and temperature cyclical conditions encountered in the real engine. Research and development (R&D) and analysis were conducted on aluminum alloy piston for high output turbocharged diesel engine coated with TBC.
Technical Paper

Development of a Zero-Dimensional Heat Release Model for Application to Small Bore Diesel Engines

2002-03-04
2002-01-0073
A zero-dimensional heat release model has been formulated for small bore, automotive-type, direct injection diesel engines and compared with high-speed data acquired from a prototype single-cylinder engine. This comparison included a significant portion of the full-load torque curve and various light-loads with variable speed, injection timing sweeps, and injection pressures. In general, the agreement between the predicted net heat release rate profiles and the experimentally, indirectly-determined profiles was acceptable from a mean cylinder pressure point-of-view while employing a single constant for the turbulent mixing dissipation rate. The proposed model also revealed that moderate swirl rates included in this study had little impact on the gross fuel burning rate profile especially at higher load conditions.
Technical Paper

Combat Vehicle Engine Selection Methodology Based On Vehicle Integration Considerations

2005-04-11
2005-01-1545
Past experience has shown that the power density of an engine itself is not a sufficient guide to determine whether it will meet the power density needs of the intended combat vehicle application. The real need is for the complete propulsion system to be power dense. Here the definition of the propulsion system includes the engine, transmission, cooling system, air filtration system, intake and exhaust ducting, controls, accessories, batteries, fuel system and final drives. The power pack is a subset of the propulsion system and consists of that part of the propulsion system that would be lifted out of the vehicle for service or replacement and would typically consist of at least the engine, and transmission, cooling system, and power pack controls and ideally would also include the air filtration system and accessory drives. Engine operating characteristics will directly impact power density for some propulsion system items.
Technical Paper

Advancements in High Temperature Cylinder Liner and Piston Ring Tribology

2000-03-06
2000-01-1237
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

High Pressure Fuel Injection for High Power Density Diesel Engines

2000-03-06
2000-01-1186
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

NATO Qualification Test of Detroit Diesel 8V71-TA Engine at 530 BHP with Advanced Ceramic Components

2000-03-06
2000-01-0524
Objective: This paper documents the 400 hour NATO qualification endurance test for the Detroit Diesel Corporation (DDC), 8V71TA/LHR (turbocharged, aftercooled/low heat rejection) diesel engine rated at 395 kw (530 bhp) at 2500 RPM for potential M109 Self-Propelled Howitzer (SPH) application. The engine was developed under the DARPA (Defense Advanced Research Projects Agency) Advanced Ceramic Technology Insertion Program, managed by U.S. Army TACOM (Tank-automotive and Armaments Command). The test was performed by DDC in accordance with the standards set forth in NATO AEP-5 (Allied Engineering Publication). The ACTIP program objective was to demonstrate the production viability of selected ceramic engine components and investigate the manner in which the ceramic technology integration would enhance the engine's performance and durability. Effects on performance and durability are reported herein. Four engine systems were developed with ceramic components for the ACTIP program.
Technical Paper

Direct Visualization of High Pressure Diesel Spray and Engine Combustion

1999-10-25
1999-01-3496
An experimental study was carried out to visualize the spray and combustion inside an AVL single-cylinder research diesel engine converted for optical access. The injection system was a hydraulically-amplified electronically-controlled unit injector capable of high injection pressure up to 180 MPa and injection rate shaping. The injection characteristics were carefully characterized with injection rate meter and with spray visualization in high-pressure chamber. The intake air was supplied by a compressor and heated with a 40kW electrical heater to simulate turbocharged intake condition. In addition to injection and cylinder pressure measurements, the experiment used 16-mm high-speed movie photography to directly visualize the global structures of the sprays and ignition process. The results showed that optically accessible engines provide very useful information for studying the diesel combustion conditions, which also provided a very critical test for diesel combustion models.
Technical Paper

Ceramic Coatings for Aluminum Engine Blocks

1991-09-01
911719
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

Starting Low Compression Ratio Rotary Wankel Diesel Engine

1987-02-01
870449
The single stage rotary Wankel engine is difficult to convert into a diesel version having an adequate compression ratio and a compatible combustion chamber configuration. Past efforts in designing a rotary-type Wankel diesel engine resorted to a two-stage design. Complexity, size, weight, cost and performance penalties were some of the drawbacks of the two-stage Wankel-type diesel designs. This paper presents an approach to a single stage low compression ratio Wankel-type rotary engine. Cold starting of a low compression ratio single stage diesel Wankel becomes the key problem. It was demonstrated that the low compression single stage diesel Wankel type rotary engine can satisfactorily be cold started with a properly designed combustion chamber in the rotor and a variable heat input combustion aid. A 10.5 compression ratio rotary Wankel-type engine was started in 15 secs at −10°C inlet air temperature. High cranking speeds and white smoke were the biggest drawbacks of this design.
Technical Paper

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

1995-02-01
950980
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

Design of High Temperature Engine Components

1995-02-01
950982
The successful design of engine components for high temperature applications is very dependent on the use of advanced finite element methods. Without the use of thermal and structural modeling techniques it is virtually impossible to establish the reliable design specifications to meet the application requirements. Advanced modeling and design of two key engine components, the cylinder head thermal insulating headface plate and the capped air gap insulated piston, are presented. Prior engine test experience contributes to further understanding of the important factors in recognizing successful design solutions. It has been found that the modeling results are only as good as the modeling assumptions and that all modeling boundary conditions and constraints must be reviewed carefully.
Technical Paper

Insulated Miller Cycle Diesel Engine

1996-02-01
961050
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

Coatings for Improving Engine Performance

1997-02-24
970204
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

Combined Cycle Diesel-Stirling Heat Engine

1985-09-01
851521
A new concept is described for a combined cycle Diesel-Stirling engine that promises to achieve an extraordinarily high thermal efficiency. The two basic cycles are coupled together in series, the high temperature exhaust gases from an adiabatic Diesel engine are fed into a high efficiency Stirling engine in such a way that both engines produce mechanical power. The whole combined cycle is highly turbocharged in order to get the desired power density, favorable heat transfer conditions and energy saving regeneration of exhaust gas heat. The problems posed by such a combined cycle are examined and calculation results are presented and discussed using a mathematical model developed as a preliminary effort of optimization and evaluation.
Technical Paper

Solid Lubrication Studies for Adiabatic Diesel Engines

1985-02-25
850508
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.
Technical Paper

Cummins–TARADCOM Adiabatic Turbocompound Engine Program

1981-02-01
810070
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

Tribological Investigations for an Insulated Diesel Engine

1983-02-01
830319
A Minimum Cooled Engine (MCE) has been successfully run for 250 hours at rated condition of 298 kW and 1900 rpm. This engine was all metallic without any coolant in the block and lower part of the heads. Ring/liner/lubricant system and thermal loading on the liner at top ring reversal (TRR) as well as on the piston are presented and discussed. Ring/liner wear is given as well as oil consumption and blow-by data during the endurance run. Another engine build with a different top ring coating and several lubricants suggested that a 1500 hours endurance run of MCE is achievable. Rig test data for screening ring materials and synthetic lubricants necessary for a successful operation of a so-called Adiabatic Engine with the ring/ceramic liner (SiN) interface temperature up to 650°C are presented and discussed.
Technical Paper

TACOM/Cummins Adiabatic Engine Program

1983-02-01
830314
This paper discusses the goals, progress, and future plans of the TACOM/Cummins Adiabatic Engine Program. The Adiabatic Engine concept insulates the diesel combustion chamber with high temperature materials to allow hot operation near an adiabatic operation condition. Additional power and improved efficiency derived from this concept occur because thermal energy, normally lost to the cooling and exhaust systems, is converted to useful power through the use of turbomachinery and high-temperature materials. Engine testing has repeatedly demonstrated the Adiabatic Engine to be the most fuel efficient engine in the world with multi-cylinder engine performance levels of 0.285 LB/BHP-HR (48% thermal efficiency) at 450 HP representative. Installation of an early version of the Adiabatic Engine within a military 5 ton truck has been completed, with initial vehicle evaluation successfully accomplished.
Technical Paper

Adiabatic Engine Trends-Worldwide

1987-02-01
870018
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

100 Hour Endurance Testing of a High Output Adiabatic Diesel Engine

1994-03-01
940951
An advanced low heat rejection engine concept has successfully completed a 100 hour endurance test. The combustion chamber components were insulated with thermal barrier coatings. The engine components included a titanium piston, titanium headface plate, titanium cylinder liner insert, M2 steel valve guides and monolithic zirconia valve seat inserts. The tribological system was composed of a ceramic chrome oxide coated cylinder liner, chrome carbide coated piston rings and an advanced polyolester class lubricant. The top piston compression ring Included a novel design feature to provide self-cleaning of ring groove lubricant deposits to prevent ring face scuffing. The prototype test engine demonstrated 52 percent reduction in radiator heat rejection with reduced intake air aftercooling and strategic forced oil cooling.
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